XLI Ibero-Latin American Congress on Computational Methods in Engineering

Approximate solution of the wave equation using the Multigrid Method

Maicon F. Malacarne, Marcio A. V. Pinto, Sebastiao R. Franco — Tue, 02 Jul 2024 00:00:00 +0000

In order to obtain the solution of the wave equation, the problem is discretized using the Finite Difference
Method (FDM). The discretization of the temporal direction is performed using the Time-Stepping Method. Thus,
it is a system of equations that involves spatial variables and is solved at every step of the time, which in real
problems, is usually a big variation. Using a conventional solver, such as Gauss-Seidel, to obtain the solution of
such systems, convergence factors are very close to the unit, which often implies a very high computational time.
To accelerate the convergence and decrease the computational time, it was proposed to use the Multigrid Method
to obtain the solution of the system of equations. Multigrid was initially proposed for elliptical problems, but it
has been used successfully in some parabolic and hyperbolic problems. This work deals especially with waves in
strings (1D), where a new approach is proposed to solve this class of problems.

Approximate solution of the wave equation using the Multigrid Method

Maicon F. Malacarne, Marcio A. V. Pinto, Sebastiao R. Franco — Wed, 03 Jul 2024 00:00:00 +0000

Transient hyperbolic analyses considering a fully adaptive explicit time- marching formulation

Lucas Ruffo Pinto, Delfim Soares Jr., Webe Joao Mansur — Wed, 03 Jul 2024 00:00:00 +0000

This work presents an explicit formulation with adaptive time integrators, enhanced by sub-cycling, for
time domain analyses of hyperbolic models. The method is based on single-step displacement-velocity relations,

describing a truly self-starting, easy to implement technique. Its stability limit is the same as of the central differ-
ence method and it provides adaptive controllable numerical dissipation. Since the technique is explicit, it does

not need to consider any solver routine, standing as a very efficient methodology. Subdomain decomposition pro-
cedures, associated to multiple time-steps and sub-cycling, are also considered herein to improve the performance

of the formulation. In this case, a generic methodology is discussed, in which subdomain divisions and local time-
step values are automatically evaluated. At the end of the paper, numerical results are presented in comparison to

those of the central difference method and the explicit generalized α method, illustrating the effectiveness of the
discussed approach.

L-BFGS BASED LEAST-SQUARES REVERSE TIME MIGRATION FOR REFLECTIVITY IMAGING

Wed, 03 Jul 2024 00:00:00 +0000

Assuming kinematic accuracy on the migration velocity model, seismic least-squares migration seeks to
overcome the drawbacks of traditional migration algorithms by approximating the inverse imaging operator within
a linear inversion framework. In this paper, we combine reverse-time migration and the L-BFGS optimization
method to iteratively reconstruct the true subsurface reflectivity model from seismic reflection measurements. In
each iteration, the initial model is first demigrated using the Born approximation of the acoustic wave equation to
generate the predicted seismic data. Then, the reflectivity is updated by minimizing the least-squares misfit function
in the data domain. Furthermore, to speed up the convergence of the inversion algorithm, we preconditioned the
gradient by the illumination compensation operator. Numerical examples demonstrate that, even in the presence
of salt bodies, the inverse operator of the imaging problem can be used to obtain improved migrated sections with
reduced artifacts, better resolution, and reflectors with more balanced amplitudes.

Enhancing Reverse Time Migration: Hybrid Parallelism plus Data Compression

Carlos Henrique S. Barbosa, Alvaro L. G. A. Coutinho — Wed, 03 Jul 2024 00:00:00 +0000

Migration techniques like the Reverse Time Migration (RTM) are time-consuming and data-intensive.
RTM is time-consuming due to the computational cost associated with the stability and dispersion conditions in
the discrete two-way wave equation. On the other hand, RTM is data-intensive because of the number of input
seismograms to be loaded and the need to store temporary files, such as the forward propagated wavefields, to build
the migrated seismic images and partial migrated images before stacking. Thus, to overcome the time-consuming
problem, we implement a Reverse Time Migration algorithm that explores the Message Passing Interface (MPI)
library and the OpenMP+vectorization to explore parallelism in hybrid architectures. On the other hand, we
implement compression techniques to reduce storage and to improve network data transfer. The data compression
can be used to reduce the storage of seismograms, model parameters, migrated seismic images, and temporary files.
Results show that an MPI/OpenMP+vectorization strategy is efficient in hybrid multi-core machines. Besides, high
levels of data compression suggest that its use does not hamper the final migrated seismic images.

Finite Elements Method use for displacement calculus in trusses

Chiquesi P. L. Amós, Pegoretti dos S. Thaís — Wed, 03 Jul 2024 00:00:00 +0000

The Finite Element Method (FEM) is a numerical procedure for analyzing structures and
continuous media. It is a technique used to obtain approximate solutions of differential equations. Trusses are
rigid elements whose definition is based on loads applied only to moorings (knots). This project proposes the use
of the FEM in trusses in order to discover displacement values and the intensity of the tensile and compression
forces in each element of the structure. Initially, the bar was studied and implemented, then the beam. In this
work, one example is presented to illustrate the application of the FEM, for the case of a static analysis of a truss,
using one-dimensional bar elements including bibliographic results.The stiffness matrixes of each element are
presented and the global matrix assembly is developed. To compare the results of the example with a simulation,
oneFtool® model is constructed and both results are compared. This project is able to expand the student's
understanding of FEM, modelling and results interpretation.

Reliability assessment of existing transmission line towers considering mechanical model uncertainties

Wed, 03 Jul 2024 00:00:00 +0000

Recent studies have shown the importance of the bolt slippage effect on the structural behavior of
transmission line (TL) towers (CIGRE-187 (2009), Ramalingam e Jayachandran (2016), Jiang et al. (2017), just
to name a few). However, these effects are not included among the studies regarding the structural reliability of
these structures considering model uncertainties. Additionally, the bolt slippage effect has also been disregarded
in the structural design, which is carried out through commercial computational packages that employ a linear or
geometrically nonlinear elastic analysis. Moreover, the magnitude of these effects is highly dependent on the tower
topology, a definition influenced by the engineer experience. Thus, neglecting those effects can lead to a wrong
choice of topology configuration. In these cases, the tower elements that are originally designed to resist to axial
forces determined through structural analysis procedures that do not include the bolt slippage effect, indeed, can be
actually subjected to higher values due to this inaccurate modeling (i.e., they present smaller cross sections that
they should have). This fact is even more relevant when old structures are considered, which were designed when
studies on this subject were not well established. Consequently, these structures are especially prone to present
topologies which increases the influence of the bolt slippage effect, resulting on a structural behavior further away
from a linear elastic hypothesis, originally employed on its design. Therefore, given the high number of old towers
still operating in Brazil and its relevance for the entire electric system, the main goal of this paper is to assess the
structural reliability of existing transmission towers considering mechanical model uncertainties, on a design region
(for pre-collapse loads). For this, the behavior of the connections and modeling assumptions are be considered as
uncertainties. Thus, allowing, for example, to analyze the reliability of these structures considering different levels
of modeling complexity.

Comparative analysis between the shear resistance of the Truss Type shear connector and stud bolt

Jerfson M. Lima, Luciano M. Bezerra, Jorge Bonilla — Wed, 03 Jul 2024 00:00:00 +0000

Shear connectors are extremely important in the functioning of composite steel-concrete structures, as
they are responsible for carrying out the transmission of forces between the steel beam and the concrete slab. The
Truss Type shear connector is an alternative connector that aligns efficient structural behavior, agility of execution
and low cost of production when compared to conventional shear connectors (stud bolt, for example) applied in
composite structures. However, due to the short time of existence, there is still a lack regarding the understanding
of the mechanical behavior of the Truss Type connector. Thus, this study aims to perform a comparative analysis
between the shear resistance of the Truss Type connector and stud bolt. This study was conducted from the
development of a non-linear three-dimensional finite element numerical model for simulating push-out tests with
Truss Type connector. The results showed that the Truss Type connector has a strong capacity and a higher
load/cross section ratio than stud bolt, even when manufactured with materials with identical properties.

Theoretical and experimental study of the behavior of composite beam-columns using double I section filled with reinforced concrete

Wed, 03 Jul 2024 00:00:00 +0000

Composite beam-columns are cost-effective structural systems for buildings and warehouses. They can
be pre-cast with reduced formwork or can be cast in-place in order to reduce crane usage. This paper reports the
structural behaviour of a pre-fabricated composite system based on a theoretical and experimental study. The
structural model is composed of a double rolled I section constituting a built-up member by means of I-section
web connectors, then filled with reinforced concrete. A theoretical study based on linear and nonlinear static
analysis through the Finite Element Method was carried using ABAQUS software. Based on this study, an
experimental programme was developed to test full-scale members submitted to flexural tests in order to validate
the numerical results. The experimental results were compared to the numerical results and the design
recommendations of Brazilian standard. Lastly, the economic conditions for the implementation of the system
were evaluated and the structural efficiency was analysed for an industrialized construction method.

NUMERICAL ANALYSIS OF THE BEHAVIOR OF CONCRETE COLUMNS CONFINED WITH CFRP USING THE CONSTITUTIVE MODEL CONCRETE DAMAGED PLASTICITY

Matheus de Santana Santos, Tereza Denyse Pereira de Araujo — Wed, 03 Jul 2024 00:00:00 +0000

The use of carbon fiber reinforced polymers (CFRP) in the reinforcement of concrete structures was
consolidated in civil construction due to its excellent mechanical properties and low specific weight. In this context,
this article aims to present numerical simulations in finite elements of columns reinforced externally to the CFRP,
submitted to centralized compression. The simulations were developed considering the physical non-linearity of
the concrete through the constitutive model Concrete Damaged Plasticity (CDP), based on plasticity and damage
to the material. The numerical models were calibrated with data from experimental tests and indicated good
compatibility of forces and axial displacements. The distribution of the compression stresses indicated that for
the case of centered force the circular columns present uniform confinement, while in the prismatic columns the
confinement is concentrated close to the rounded corners. The reinforcement efficiency in the resistance gain for
different column cross sections was proven.

Numerical simulation of full-scale tests in transmission line towers

Rafael R. Roman, Leandro F. F. Miguel, Fabio Alminhana, Joel Pimenta — Wed, 03 Jul 2024 00:00:00 +0000

Transmission line towers are structures designed to carry electrical energy from generating stations
to consuming centers. Full-scale tests are traditionally employed in designing verification of transmission line
lattice tower structures. Due to the cost of these tests, an alternative is to evaluate their structural behavior using
numerical methods. In the present work, a nonlinear analysis method is presented for predicting the ultimate
structural response of two steel lattice towers under static load conditions. In the proposed technique, each tower
is modeled as an assembly of beam-column elements. The solution scheme consists of an incremental-iterative
predictor-corrector strategy based on the arc-length method. Linear, geometric and plastic matrices are used to
describe the structure behavior in an updated Lagrangean framework. A lumped plasticity approach coupled with
the concept of yield surfaces and plastic hinges is adopted for modelling material nonlinearity. Based on the results,
it was verified that the proposed model can produce accurate results to simulate load and failure modes of steel
lattice towers. However, some inaccuracies may arise in predicting the collapse load when failure occurs due to
elastoplastic buckling of the members.

Influence of distance between outer tubes in bolted sleeve connections under compression

Wed, 03 Jul 2024 00:00:00 +0000

The sleeve connection with circular hollow sections(CHS) allows a harmony in the continuity of tubular
profiles, becoming a discreet connection in the real structure and contributing to a new aesthetic identity for
connections between these steel profiles. This connection was proposed to facilitate the execution and
maintenance, reduce costs and enable other projects of the structures formed by CHS. This work presents a
numerical study about the influence of distance between outer tubes in sleeve connections, with aligned bolts,
under compression. Possible failure modes and the values necessary for the efficient operation of the connection
without the possibility of outer tubes touching, changing the behavior of the connection, were evaluated. The study
was carried out by a numerical analysis using the finite element method (FEM) in a commercial software, allowing
the geometric parameters variations. With the study results, it was possible to evaluate the behavior of sleeve
connection and to define a minimum distance between the outer tubes, contributing to the dimensioning and
assembly of the connection in truss systems.

ESTUDO DO COMPORTAMENTO ESTRUTURAL DE VIGAS CASTELADAS DE AÇO EM PADRÃO LITZKA COM ABERTURAS HEXAGONAIS E OCTOGONAIS

Manuella M. de Lima, Washington B. Vieira, André L. R. Brandão — Wed, 03 Jul 2024 00:00:00 +0000

Castellated steel beams (CSB) are manufactured from the zigzag cut of the web of the I-sections, whose
halves are displaced and welded, making the beam expand in height, without changing the profile mass. Changing
dimensional cutting parameters makes it possible to create several geometric patterns of castellated beams. The
study in question addresses the addition of expansion plates to the Litzka CSB, further increasing the height of the
profile, and consequently the moment of inertia and the stiffness of the section, thus enabling the execution of
larger spans. The CSB has an architectural and functional appeal, due to their light appearance and the possibility
of passing ducts through the alveoli. In order to compare the results obtained, the cross section was varied, ranging
between supports, types of loading and the size of the expansion plate for performing numerical analysis using the
finite element method. The numerical model considers the initial geometric imperfections, residual stress and
physical nonlinearities derived from the manufacturing process. The results show the comparison of the structural
behavior and the resistant capacity of CSB with different characteristics.

RECON: PROGRAM IN PYTHON FOR CALCULATING REINFORCED CONCRETE BEAMS

Joao Vítor Jesus, Janaina Gomide, Esdras Oliveira — Wed, 03 Jul 2024 00:00:00 +0000

The utilization of programs for making structural analysis of reinforced concrete is usual in civil en-
gineering. Structural analysis is a fundamental step in buildings project where internal forces, dimensions and

structural members design are defined, such as beams, columns and slabs. The used parameters, as well as the

considerations and equations are specified at the ABNT NBR 6118/2014 – “Design of concrete structures — Pro-
cedure”. The goal of this paper is to present ReCon1

, a Web application for calculating reinforced concrete beams.

It was made to perform the design according to the specifications of the Brazilian standard. It has a friendly inter-
face and it brings two advantages: it is free and open-source and was designed also to be used as an educational

tool. The achievements obtained by ReCon have been compared to some examples of already solved exercises
in the current literature about reinforced concrete. These comparisons have shown excellent results which prove
ReCon as trustful program. Moreover, students of civil engineering have used ReCon in order to compare theirs
experience solving exercises using this program to what they usually do in class. They have mentioned about the
friendly interface and found a good educational tool to add in class.

A comprehensive model of fatigue for steel beams

Deborah C. Nardi, Yongtao Bai, Ricardo A. Picón, Julio Flórez-López — Wed, 03 Jul 2024 00:00:00 +0000

Steel beams may be subjected to cyclic loads and consequently damaged by the fatigue phenomena.
Concerning to identify and to monitor the crack initiation, the crack evolution and the subsequent failure of this
structures, in this paper it is proposed a model that allows the study of the fatigue phenomena, either for ultralow
and low cycles and high and ultrahigh cycles, considering both stationary and non-stationary fatigues. A new state
variable for the identification of the beginning of the crack propagation is introduced for each plastic hinge, which
is called the pre-damage variable. Its evolution law is based on Manson-Coffin law and also on the Basquin law.
Fundamental concepts of the Lumped Damage Mechanics (LDM) are also included. It allows the consideration of
the damage variable itself and its influence in the constitutive relationships. A new damage law is settled and takes
into consideration effects from both different types of fatigues. Appropriately, the crack closure effect is used
through the unilateral damage assumption. Finally, the accuracy of the model is its validation is done by a finite
element analysis (FEA) to predict the experimental behavior of tests of steel beam-column that are available in the
literature.

An elastoplastic model with damage based on the Thermodynamics of Frames

Deborah C. Nardi, Julio Flórez-López, Ricardo A. Picón — Wed, 03 Jul 2024 00:00:00 +0000

The representation of the mechanical behavior of reinforced concrete structures aims to describe the
physical reality as accurately as possible, which for there are many available theories. Besides that, to go further
in those researches of physical representation, there are postulated formulations based on the science of
thermodynamics, which link the influence of mechanical behavior in the development of physical phenomena and
vice versa, through a systematic procedure that allows the determination of thermodynamic forces associated with
the state variables, which are able to represent these phenomena. Therefore, the model here presented is
underpinned on thermodynamic models that describe physical phenomena of reinforced concrete structures and
proposes a new damage law that allows the observation of the cracking evolution. A new cracking resistance
function that describes the energy release rate during the damage evolution is established since this new damage
law comes now from Gibbs Free Energy. Finally, in order to evaluate the accuracy of the new model, the results
obtained by the proposed model are compared with those given by the Lumped Damage Mechanics theory, which
presents itself as an efficient tool to describe the cracking appearance and evolution, for both analysis and
computational implementation.

Numerical analysis of compressed end-flattened steel bars of three- dimensional trusses

Henrique de A. R. Cruz, Welington V. da Silva, Luciano M. Bezerra — Wed, 03 Jul 2024 00:00:00 +0000

On the field of steel structures, one of the most commonly used types of structural systems is the
three-dimensional truss. It is applied in a wide range of sizes and shapes, with its constituent elements usually
prescribed as hollow circular cross-section bars. In order to assemble them in a practical and efficient way, one
alternative often chosen by designers is to flatten their ends and attach these bars in bolted connections.
Although such constructive method has notorious advantages and is already present in a large number of
engineering projects in different countries, it is still necessary to conduct more studies that analyze its singular
structural behavior and thereby contribute to the establishment of forthcoming normative criteria. In this sense,
this work presents an association of numerical analysis and empirical data of an example of end-flattened steel
bar, especially regarding the variation of the stress field developed along the structure subjected to different
levels of load. The results obtained provide a better understanding of the consequences of the reduction of
stiffness due to the flattening process of the bar ends.

Estabilidade de edifícios de múltiplos andares em aço: uma comparação entre metodologias de análise

Rafael Eclache Moreira de Camargo, José Jairo de Sáles — Wed, 03 Jul 2024 00:00:00 +0000

Este trabalho apresenta uma análise comparativa dos efeitos de segunda ordem em um edifício de 20
pavimentos. O modelo apresentado foi dimensionado pelos princípios do método da análise direta, presente na
ABNT NBR 8800:2008. O método da amplificação dos esforços solicitantes (MAES) foi usado para se obter os
esforços atuantes nos elementos do edifício considerando os efeitos locais e globais de segunda ordem. A
incidência do vento foi simulada sem e com excentricidade devida aos efeitos de vizinhança, de acordo com a
ABNT NBR 6123:1988. Todas as análises numéricas foram repetidas usando o método simplificado de segunda
ordem conhecido como P-Delta. Por meio dos resultados obtidos, foi observado que os esforços solicitantes
determinados pelo método P-Delta ficaram bastante semelhantes àqueles calculados pelo MAES, com desvios
desprezíveis. O MAES, por sua vez, mostrou-se bastante trabalhoso, pois exige a modelagem de diferentes tipos
de estruturas para a determinação dos esforços. No que diz respeito aos efeitos de vizinhança, observou-se que sua
maior influência está no aumento dos momentos fletores e dos deslocamentos da estrutura.

Estudo numérico do efeito Shear Lag em perfis de aço com seção transversal do tipo U

Wed, 03 Jul 2024 00:00:00 +0000

Barras de aço tracionadas são amplamente empregadas em sistemas estruturais, tais como treliças de
cobertura, torres de transmissão, sistemas de contraventamento e outros. Dentre os perfis mais utilizados, tem-se
o tipo U, que pode ser conectado por meio de uma ou mais partes da seção transversal, por exemplo, conexão a
partir do elemento da alma. Nesses casos, a distribuição de tensões se torna não uniforme ao longo da seção do
perfil, tendo maior intensidade nas regiões conectadas. O efeito proveniente da concentração dessas tensões em
uma área reduzida é conhecido como shear lag e tem como consequência a redução na capacidade resistente. Esse
efeito é contemplado pelas normas ABNT NBR 8800:2008, ANSI/AISC 360-16 e EN 1993-1-1:2005 com
simplificações gerais. Na literatura encontram-se estudos mais abrangentes para perfis cantoneira e ligações
parafusadas. Sendo assim, realizou-se um estudo numérico por meio do método dos elementos finitos (MEF) de
ligações de perfis U tracionados com ligações soldadas, considerando a influência da presença ou não de solda
transversal em conjunto com a longitudinal, comprimento da barra e da ligação para seções com geometrias
diferentes. Os resultados foram confrontados com a literatura, indicando comportamento menos conservador dos
modelos.

A numerical methodology for the cross-sections analysis of steel-concrete composite beams with partial shear connection

Wed, 03 Jul 2024 00:00:00 +0000

The present work aims at the implementation and validation of a numerical formulation based on the
Strain Compatibility Method (SCM) for the calculus of the cross-section’s resistance capacity of steel-concrete
composite beams with partial shear connection. It is developed, here, a strategy for capturing the longitudinal
deformations at all cross-section’s points. Thus, the section’s discretization, isolating the steel profile from the
concrete slab, is necessary. In this context, the classic SCM is modified by the insertion of one explicit degree of
freedom at the steel-concrete interface, corresponding to a discontinuity on the deformations field, allowing the
longitudinal sliding between the steel profile and the concrete slab. Therefore, the axial force dismemberment is
done, on which a part is absorbed by the profile and the other part by the slab. By equilibrium, the difference
between the slab’s and profile’s forces generates a shear force at the connection and, using the Ollgaard’s model,
the longitudinal sliding at the contact point, is found. Assuming the plane cross-section theory, a single curvature
is assigned to both constituents of the section. Thereby, it is done the construction of the moment-curvature
relationship using the standard Newton-Raphson method combined with continuation strategies aiming to capture
the hardening and softening of the materials over the loading historic of the section. However, in order to implement
the analysis, exclusively, in the cross-section, a fixed degree of freedom is assigned to it. For the validation of the
proposed numerical formulation, the obtained results are confronted with numerical data available in the literature.

Concentrated plasticity-based second order formulation for analysis of semirigid steel-concrete composite frames and beams with partial shear connection

Wed, 03 Jul 2024 00:00:00 +0000

The present work aims at the implementation and validation of a displacement-based two-dimensional
numerical formulation including several sources of non-linearities in steel-concrete composite frames, such as:
second order effects; plasticity; beam-to-column semi-rigid connections; and partial shear connection on beams.
The finite element method is used together with the co-rotational approach in order to allow large displacements
and rotations in the numerical model. The degradation of axial and flexural stiffness is determined exclusively at
the nodal points of the finite element mesh, characterizing the concentrated plasticity. In cross sections, the Strain
Compatibility Method (SCM) is used to capture the axial strains in the components of the section and also the
slip in the steel-concrete interface. Sliding is considered by introducing a degree of freedom at the steel-concrete
interface in the analysis of the cross section. In this way, the constitutive models of the materials and the shear
connection elements are described by continuous functions. The semi-rigid connections are simulated by means
of zero-length pseudo springs that are introduced at the finite elements ends, making them hybrid. To validate the
proposed numerical formulation, the results obtained are compared with numerical and experimental data available
in the literature. Since the model proposed here starts from the concentrated simulation of nonlinear effects, a study
of the finite element mesh refinement is also carried out.

Non-linear analysis of steel-concrete composite frames via RPHM consid- ering cracking and partial shear connection

Wed, 03 Jul 2024 00:00:00 +0000

The present work aims at the implementation and validation of a two-dimensional numerical formulation
for the simulation of steel-concrete composite frames. Geometric and material nonlinearities are considered. A
corotational approach is used to simulate second order effects. In the case of material nonlinearity, zero-length
pseudo springs are used at the finite elements ends, where the gradual loss of flexural stiffness is determined by the
combination of normal and flexural efforts (NM) at the nodal points, exclusively. The limits of the non-cracked,
elastic and plastic regimes of the section are made in the NM interaction diagram. This diagram is obtained from
the Strain Compatibility Method (SCM), where the non-linear analysis of the cross section is made. The cracking
of the concrete is explicitly simulated with the effective moment of inertia proposed by NBR 6118 (2014). For
steel-concrete composite beams, the possibility of longitudinal sliding between the concrete slab and the steel
profile is considered, with the degradation of inertia being addressed as prescribed in NBR 8800 (2008). The
results obtained are compared with numerical and experimental data available in the literature.

Numerical study of thermal-mechanical behavior of 2D composite steel-concrete frames

Rafael C. Barros, Dalilah Pires, Ricardo A.M. Silveira, Ígor J.M. Lemes — Wed, 03 Jul 2024 00:00:00 +0000

The purpose of this study is to apply the advanced numerical methodology developed and implemented
in the CS-ASA/FA (Computational System for Advanced Structural Analysis/Fire Analysis) and CS-ASA/FSA
(Fire Structural Analysis) to understand the thermal-mechanical behavior of 2D composite steel-concrete frames
in fire situation. The analysis is carried out on two-level approaches, the first referring to the structural element
cross-section. In this step, the temperature field is calculated using a transient heat transfer model, from where the

degradation of stiffness and strength parameters are obtained when the materials are exposed to fire. The second-
level stage is related to inelastic second order analysis (ISOA) of the composite steel-concrete structural system

under high temperatures. In the ISOA context via finite element method (FEM), a co-rotational formulation is used
to follow the large displacements and rotations of the structural model, and the material elasto-plastic behavior is
simulated through the Refined Plastic Hinge Method (RPHM) and Strain Compatibility Method (SCM) coupling.
Finally, the structural modeling studied seeks to validate the proposed numerical strategy using the results found
in literature.

Advanced numerical analysis of shallow and deep steel arches under fire condition

Wed, 03 Jul 2024 00:00:00 +0000

The arches are structures used to overcome large spans, since their curvature can guarantee strength
gains. However, such systems exhibit strongly nonlinear behavior, and therefore, for a more realistic modeling, it
is necessary that numerical formulations consider several sources of nonlinearity, such as geometric and material.
In a fire situation, the analysis is usually more complex, since the materials physical and mechanical properties are
significantly affected by temperature. Therefore, this work aims to study the thermal-mechanical behavior of
shallow and deep steel arches under high temperatures using the CS-ASA/FSA module (Computational System
for Advanced Structural Analysis/Fire Structural Analysis). Basically, the analysis will be developed in two-level
approaches: the first refers to the temperature field calculation in any cross-section, where, as consequence of fire
exposition, the materials properties degradation are obtained; the second stage is intended to carry out an inelastic
second order analysis (ISOA) of shallow and deep steel arch in a fire situation. A co-rotational finite element
formulation is used to follow the large displacements and rotations of the structural model, and the material
inelastic behavior is simulated with the Refined Plastic Hinge Method (RPHM) and Strain Compatibility Method
(SCM) coupling. The numerical thermal-structural results obtained here will be validated by comparison with
responses available in the literature.

Simulação numérica de uma estrutura tridimensional considerando a interação solo-estrutura

Wed, 03 Jul 2024 00:00:00 +0000

The dynamic behavior in the study of Soil-Structure Interaction (SSI) has attracted intense interest
among researchers and engineers from diverse areas, as it is a fundamental principle to ensure the safety and
structural stability of buildings that are increasingly slender and flexible. However, problems associated with the
practical application of SSI are harmed by complex literature, in addition to codes and standards with limited
guidelines and practical examples with scarce applications. Thus, the present study proposes to numerically
analyze the SSI of a three-dimensional (3D) structure based on the modal response. The model is discretized in an
equivalent mass-spring-dampener system, the structure is a system of concentrated masses and soil represented by
a system of springs and dampeners calculated through impedance coefficients. Posteriorly, the geometry is
modeled and the SSI is coupled with the structure receiving excitation from the base. For such, the finite element
method and the ANSYS software are used. The results showed the vibration modes and the harmonic and transient
response of the structure with the greatest displacement occurred on the third floor at a frequency of 1.1417 Hz.
Therefore, the study made possible to identify the dynamic behavior of the structure before external action at the
base.

Dynamic analysis of highway bridges considering a progressive pavement deterioration model

Wed, 03 Jul 2024 00:00:00 +0000

Highway bridges are subjected to random traffic loads along their lifecycle and also subjected to
relevant impact dynamic loadings. The road-roughness of asphalt pavements represents a key issue to the
significant increase of the displacement and stress values on the highway bridge decks. Considering this fact, the
aim of this research work is to develop an analysis methodology to evaluate the displacement and stress values
of a steel-concrete composite highway bridge, including the dynamic actions due to vehicles convoy and also the
effect of the progressive deterioration of the pavement, taking into account the road surface damages. The
analyzed structural model corresponds to a typical steel-concrete composite highway bridge deck, with straight
axis, simple supported and spanning 13.0m by 40.0m. In this investigation, the numerical model developed for
the dynamic analysis of the steel-concrete composite bridge, adopted the usual mesh refinement techniques
present in Finite Element Method (FEM) simulations implemented in the ANSYS computational program. The
main conclusions of this study focused on alerting structural engineers to the significant distortions associated to
the bridge dynamic structural response, when subjected to dynamic actions produced by vehicles convoys on the
irregular pavement surface.

Human-induced vibration analysis and human comfort assessment of pedestrian footbridges

Irwing Aguiar Ribeiro da Silva, José Guilherme Santos da Silva — Wed, 03 Jul 2024 00:00:00 +0000

The design of pedestrian footbridges has always been challenging. Essentially, this type of structure
presents long spans and, due to more resistant materials, the structural elements slenderness has been
considerably increased. Consequently, the excessive vibration problems become more evident and may cause
discomfort to the pedestrians or even structural risk. Therefore, aiming to predict the dynamic structural response
of footbridges induced by human walking, two mathematical models were used: single force model and
biodynamic models. Based on the use of the two loading models, an extensive parametric study was carried out
considering the pedestrian step frequencies, the pedestrian-footbridge mass ratios and the structural damping
rate. The results obtained along this investigation shows that the influence of the human walking depends on the
relationship between the mass of the pedestrians and the footbridge, and the pedestrian-footbridge dynamic
interaction effect can be irrelevant for small mass ratios. On the other hand, the human walking can, without any
doubt, provoke higher dynamic structural responses, especially when the footbridge fundamental frequency is
close to the pedestrian step frequencies’ range. In this situation, the structural system can reach high vibration
levels that can compromise the footbridge user’s comfort.

Dynamic structural analysis and fatigue assessment of wind turbine towers

Wed, 03 Jul 2024 00:00:00 +0000

The wind energy has been very promising because it is inexhaustible energy of low environmental
impact. Based on the increasing demand on renewable and clean energy, the wind turbine design has advanced
significantly in terms of its size and type. In Brazil, considering this advance, the conventional conical steel
tower is a predominant type of supporting structure. Proper consideration of all the aspects before mentioned
pointed out our team to develop an analysis methodology with emphasis to evaluate the stresses through a
dynamic structural analysis of a typical wind turbine supporting steel tower, including the nondeterministic wind
actions. Thus, this research works aims to study the dynamic non-deterministic structural response and evaluate
the service life of a steel tower to be used as a support for a wind turbine model type MM-92 from Repower. In
this investigation, the numerical model developed for the structural analysis of the tower adopted the usual mesh
refinement techniques present in Finite Element Method (FEM) simulations and implemented in the ANSYS
program. The analysis of the non-deterministic dynamic response of the tower is performed for several wind
velocities, having in mind a critical evaluation about the maximum values obtained for the Von Mises's stresses
and the service life of the investigated structure. Finally, the results obtained along this study are evaluated and
compared with the limit values recommended by international design codes and recommendations.

Structural integrity assessment of storage tanks based on damaged surface reconstruction and finite element modelling

Wed, 03 Jul 2024 00:00:00 +0000

This research paper aims to discuss an analysis methodology developed for structural integrity
assessment of storage tanks. Such methodology is based on the assessment of the damaged structure, considering
the pre-deformed geometry, via stresses analysis. Then, a finite element model is generated, based on the
deformed surface of the structural system, through laser scanning technology. This way, it is possible to detect
the real geometry that explicitly includes the damages present on the studied storage tank. This way in this work,
a real case study is investigated having in mind an Atmospheric Storage Tank (AST) located in an industrial
floor related to the oil and gas industry. The equipment object of this analysis presents a cylindrical geometry
with approximately 45 m diameter and a 14.63 m height and is utilized for diesel oil storage. The storage tank

presents deformations on its shell (cylindrical surface of the structure), and in order to evaluate its Fitness-For-
Service (FFS), i.e. evaluate whether the equipment is suitable to continue in operation, with existing damages, a

laser scanning was performed on the storage tank shell. In sequence, the stresses analysis methodology provided
by API (American Petroleum Institute) design codes was adopted to the assessment of the structural response.
The results obtained along this research work show that the developed analysis methodology used for the
evaluation of the damaged storage tank is very effective and also can reduce maintenance costs as well as losses
due to the time that the structure needs to be out-of-operation.

Dynamic experimental monitoring and numerical analysis of floors subjected to human activities

Wed, 03 Jul 2024 00:00:00 +0000

The present work aims to evaluate the dynamic structural behaviour of a reinforced concrete floor
located on the eighth story of the State University of Rio de Janeiro (UERJ). The investigated floor is currently
used for rhythmic human activities (gym activities). In some situations, such rhythmic activities produce a high
degree of synchronization, which on some occasions can stimulate high levels of vibrations that may cause
discomfort to the users. This way, the investigated structural model consists of a reinforced concrete floor with
dimensions of 16 m by 35 m and total area of 560 m2. Initially, a dynamic experimental monitoring of the floor
was performed aiming to determine the dynamical properties (natural frequencies and structural damping). After
that, a numerical model was developed to represent the studied floor, based on the use of usual mesh refinement
techniques present in the Finite Element Method (FEM) simulations and implemented in ANSYS program. In
sequence, the experimental and numerical dynamic structural responses were compared and the finite element
model of the reinforced concrete floor was properly calibrated. Finally, the floor was subjected to rhythmic
human activities (gym activities) and the dynamic response was investigated based on the use of biodynamic
models. The current outcome of this research paper enabled a complete structural dynamic assessment of the
concrete floor in terms of human comfort and its associated vibration serviceability limit states. The results show
the relevance of the dynamic analysis in the structural design of buildings, considering the human activities that
take place and influence the structure.

Assessment of the human comfort of steel-concrete composite floors

Wed, 03 Jul 2024 00:00:00 +0000

This research work aims to investigate the dynamic structural response of steel-concrete composite
floors from the point of view of human comfort, when subjected to human walking. This way, the investigated
structural model is associated to a steel-concrete composite floor building which is composed of a hot-rolled
framing system, with a total area equal to 1300 m2. The floor system is used for normal school occupancy and is
supported by steel-concrete composite columns with a ceiling height of 3.40m. The proposed numerical model,
developed for the floor building dynamic analysis, adopted the usual mesh refinement techniques present in the
Finite Element Method (FEM) simulations and implemented in the ANSYS program. In this numerical model,
the steel-concrete composite floor girders were represented by three-dimensional beam elements, where flexural
and torsion effects are considered. On the other hand, the concrete slab was represented by shell finite elements.
Both materials (steel and concrete) present an elastic behavior. The complete interaction between the concrete
slab and steel beams was considered in the analysis, i.e., the finite element model coupled all the nodes between
the steel beams and concrete slabs, in order to prevent the occurrence of any slip. Regarding the structural

behavior of the connections present in the investigated structure, the beam-to-beam connections and the beam-to-
column connections were considered as rigid joints. After that, having in mind to determine if the investigated

floor framing system satisfies the human comfort criterion for walking vibration, the dynamic structural response
of the investigated floor was analysed based on the peak accelerations values. These values were calculated and
classified according to several human comfort criteria, considering situations of the current design practice.

Fixed offshore platform: assessment on the possibility of reuse of the jackets for offshore wind farms

Vencislau Manuel Quissanga, José Guilherme Santos da Silva — Wed, 03 Jul 2024 00:00:00 +0000

This paper focuses on the possibility of reusing (or not) a fixed offshore platform, with the purpose to
understand whether the removal of the deck from the platform (partial decommissioning) would be considered
including the replacement for a wind tower. Thus, the present research aims to verify the structural behaviour of
a fixed offshore platform (jacket) when subjected to the loading of a 10 MW wind tower. However, in addition
to the static loading coming from the wind tower, the environmental forces (variable loads) related to the waves
and wind acting on the platform were pondered. The loading related to the 10MW wind tower was considered
and distributed on top of the four legs of the jacket. The investigated structural system presents a 26 m height
jacket (from the mudline); the lower area presents dimensions of 9.97 m x 9.97 m and the upper area 6.10 m x
6.10 m. The structure presents eight legs and three deck elevations between the upper and lower deck. The
numerical model was developed based on the use of the SACS V12.0 computational software, and via the use of
the Finite Element Method (MEF). Therefore, the resistance analysis is performed on the fixed offshore platform
(jacket) considering the influence of the static and variable loadings in order to assess the current structural
behaviour.

Human comfort assessment of buildings considering the modelling of masonry infills and the soil-structure effect

Jean Carlos Mota Silva, José Guilherme Santos da Silva — Wed, 03 Jul 2024 00:00:00 +0000

In the last decades, the urban verticalization in Brazil has been remarkable, and even in medium-sized
cities, the project and construction of high buildings is growing exponentially. However, the architectural dareness
and also the increasing in the building project’s slenderness have been crucial to reducing the natural frequency
values of these structures, and in some situations, these facts could induce excessive vibration problems. On the
other hand, important aspects, generally disregarded in the current design practice are related to the effects of the
masonry infills and the soil-structure interaction. This way, this research work aims to develop an analysis
methodology aiming to evaluate the structural behaviour and assess the human comfort of buildings subjected to

the wind nondeterministic dynamic actions, including in the analysis the effects of the masonry infills and the soil-
structure interaction. This way, the dynamic structural behaviour of a 16-storey reinforced concrete building, 48

m high and dimensions of 15.0 m by 14.2 m is investigated. Thus, numerical models were developed to obtain a
more realistic representation of the system, based on the Finite Element Method (FEM), through the use of the
ANSYS program. The results obtained along this investigation have indicated relevant quantitative differences
when the dynamic structural response of the building was analysed, such as the reduction of the horizontal

translational displacements and peak acceleration values, when the effects of the masonry infills and the soil-
structure interaction were considered.

Structural assessment of lattice steel towers used in power transmission lines

Mariana Souza Rechtman, José Guilherme S. da Silva — Wed, 03 Jul 2024 00:00:00 +0000

The lattice steel towers have been widely used as supports for overhead power transmission lines.
These towers have become essential elements to the transmission systems and their stability contributes to a
better functioning and electrical safety. In this research work, a three-dimensional latticed structural system,
composed by primary and redundant members was adopted to represent the steel towers. In current design
practice, redundant members are not included in the finite element models and a linear analysis is performed for
the structural design. Considering this methodology, several design recommendations indicates that the forces
acting on the redundant members can be up to 2.5% of the forces on the primary elements (main elements).
Therefore, the main objective of this investigation is to develop an analysis regarding the redundant member’s
structural behaviour of lattice steel towers used in power transmission lines, having in mind the assessment of
the forces, as well as the design on these elements. Hence, five different steel towers associated to a 500 kV
transmission line were investigated and a nonlinear analysis was performed aiming to determine the forces
values acting on the redundant members and comparing with those calculated according to the design standards
(linear analysis). The global structural behaviour related to the redundant elements failure was also studied, as
well as the influence of the angle between the members, having in mind the forces values. The results obtained
along this analysis have shown relevant quantitative differences between the forces values established by the
design standards and those calculated through a nonlinear analysis based on finite element models.

BIM aplicado a projetos de engenharia, com foco em incompatibilidades – Estudo de caso

Wed, 03 Jul 2024 00:00:00 +0000

Durante muito tempo a elaboração de projetos de engenharia consistiu na utilização de diferentes
plataformas, utilizando-se para a elaboração das plantas baixas, desenhos auxiliados por computador (CAD), de
softwares estruturais, para dimensionar as estruturas e planilhas eletrônicas, para quantificar os materiais.
Entretanto, a não centralização dos projetos e quantitativos acaba ocasionando a perda ou o aumento de
informações durante o processo de quantificação, culminando no excesso ou na falta de material durante o processo
construtivo. Além disso, devido aos projetos complementares não serem executados dentro de uma mesma
plataforma diversos problemas quanto a compatibilidade entre os projetos surge durante a execução das obras.
Como forma de gerar dados cada vez mais precisos as ferramentas de Modelagem/Modelação da Informação da
Construção (BIM) surgem com um ambiente ideal para a modelagem de projetos e checagem de
incompatibilidades. Neste trabalho será utilizada uma plataforma BIM, o Autodesk Revit®, para realizar um
estudo de caso dos desenhos arquitetônicos e complementares de uma residência unifamiliar feito no Autodesk
AutoCAD®, juntamente com o Autodesk Neviswork® para checagem das incompatibilidades entre os projetos.
Comparando com os projetos já realizados de maneira convencional foi possível encontrar incompatibilidades
entre elementos estruturais, instalações e estrutura.

Finite element analysis of cellular beam by load control method

L. Madeira, G. S. Vieira, J. G. Ribeiro Neto, L. R. Cruvinel — Wed, 03 Jul 2024 00:00:00 +0000

Cellular beams are of great interest due to their great flexural rigidity, high section modulus, excellent
height/weight ratio, economical and eco-sustainable construction, possibility of services through the openings of
the web and architectural aesthetic appearance. This study perform an approach to the processes of numerical
implementation via Finite Elements Method in cellular beams evaluating their elastoplastic behavior with focus
on the Vierendeel mechanism. The numerical model was calibrated against the experimental results of Warren [1]
and a comparative study is carried out with respect to the physical properties of the steel, allowing to understand
the advantages that high-strength steel can promote in this kind of structure.

Analysis of the distortional buckling curves of cold-formed steel beams through GBTUL and DSM

L. Cruvinel, G. Vieira, E. Silva — Wed, 03 Jul 2024 00:00:00 +0000

Due to the wide variety of cross-section as well as their good mass/strength ratio, cold-formed steel
(CFS) components are gaining prominence among metal structures. However, this material is more susceptible to
local, distortional, and global buckling. The Direct Strength Method (DSM) requires obtaining the buckling critical
loads and applying these data in conjunction with a series of resistance curves to determine the final cross-section
strength. This study aims to investigate the behavior of distortional buckling mode for a CFS simply supported

beam, and to compare the results obtained through DSM and GBTUL (software responsible for numerical compu-
tational analysis). To obtain the data, the GBTUL was used, which, in turn, uses the geometries and flow stresses.

For this analysis, a cold-formed, non-drilled, multi-dimension section was chosen. From the analyses presented
in this paper, it was noticed that the distortional curves available in the Brazilian standard do not overestimate the
final strength of the CFS beams simply supported when subjected to uniform bending.

Shape optimization of cold-formed steel columns using generalized beam theory and genetic algorithms

M. Neves, C. Baságlia — Wed, 03 Jul 2024 00:00:00 +0000

The search for lighter and more efficient design has put thin walled steel structures on the center of the
attention from civil engineers. Furthermore, with the necessity to fight its slenderness and improve its structural
worth we have a need to find its best optimal cross section. The newest way to achieve such is to wed both
Generalized Beam Theory (GBT) and Genetic Algorithms (GA) for an improved analysis that takes short periods
of processing times. Enhancing structural elements to endure local and distortional failures with longitudinal
stiffeners is not something new to engineers although could be even more efficient for a computer to do it. The
pursuit for the best stiffener geometry and its location based on the knowledge of the local and distortional
responses from multiple elements could save an abundance of resources and time. The goal of this work is to
implement a computational calculation using a genetic algorithm to find the most suitable solution within a limit
range of parameters for an optimal cross section design for channel and zed compressed columns. Genetic
Algorithms are a heuristic search that mimics natural evolution events. Learning by evolving generations populated
with random elements and combinations of the best cross sections the algorithm sets its goal to find the optimal
solutions for distortional and local strengths separately. After its goals are met is its job to try to cross both solutions
to turn into an optimal cross section design. With the local and distortional critical loads, the element could be
analyzed using the Direct Strength Method (DSM) that has been widely used to design Cold-Formed Steel (CFS)
elements. This implementation will be used in the future to accomplish the same on different structural elements
composed of CFS and improve the way these elements are fabricated thus resulting in better and lighter overall
structures.

Finite element simulation of composite steel-concrete castellated and cellular beams: effect of the web openings

Matheus E. Benincá, Inácio B. Morsch — Wed, 03 Jul 2024 00:00:00 +0000

Composite castellated or cellular beams consist of a concrete slab linked with castellated or cellular
steel profiles through shear studs. Particularly, for simply supported beams, it results in an optimized structural
solution. However, designing a composite alveolar beam is not a simple task, since Brazilian and international
standards do not specify criteria for its analysis and design. Therefore, advances in numerical simulations are
important for a better understanding of their complex structural behavior, which involves different failure modes.
This work continues the research presented in the latest edition of CILAMCE, in which a finite element model
was developed and validated, using ANSYS software. This model was used in this paper to study the effects of
the web openings on the structural behavior of composite beams. For this purpose, firstly two composite cellular
beams experimentally tested in previous works were numerically simulated, considering the cases with and without
web openings. Secondly, it was proposed an example of a beam with a larger span (11 m) subjected to a uniformly
distributed load, and a numerical study was carried out considering both the original steel profile, without holes,
and the expanded profiles, with different opening patterns. It was concluded that the web-post buckling may limit
the structural gains on load capacity, so it is important to adopt opening patterns that enhance the resistance of the
beam to this mode of failure. On the other hand, when the failure mode is the formation of a flexural mechanism,
it was verified that the load capacity gain is influenced by the expansion ratio and the tee-section height.

Desenvolvimento de software de análise, dimensionamento e verificação de lajes retangulares de concreto armado

Aaron Farah Nolasco, Ana Waldila de Queiroz Ramiro Reis, Rodrigo Bird Burgos — Wed, 03 Jul 2024 00:00:00 +0000

The progress of theoretical knowledge and computational technology has enabled the development of
several methods for the analysis and design of structures. Reinforced concrete is still widely used today in several
structures, from bridges to buildings. Even in so-called composite structures (steel-concrete), slabs in reinforced
concrete are still used, since the material is the best choice in terms of plate behavior. In this way, the design of
slabs is still a current issue, and this procedure must guarantee that the final structure is safe from both the ULS
(Ultimate Limit State) and SLS (Service Limit State) points of view. In the context of slabs design and to assist
civil engineering students and newly graduated engineers, this work presents the development of computer
software for the design of reinforced concrete slabs, based on Visual Basic programming language for the
Windows operating system. This software uses design tables for obtaining internal forces in thin plates (Kirchhoff
theory), allows the design and verification of reinforced concrete two-way slabs in a fast and practical way. Such
implementations are confronted with classical examples, in order to prove the validity of the results obtained by
the software. Finally, the user can export these solutions to a text document, so that it can be easily interpreted and
manipulated. It should be noted that the design and verification procedures implemented in the software are in
accordance with criteria established by the Brazilian Standard NBR 6118:2014.

GBT-Based buckling analysis of cold-formed steel purlin-sheeting systems using restrained deformation modes

Heitor de F. Araujo, Cilmar Basaglia — Wed, 03 Jul 2024 00:00:00 +0000

In Generalized Beam Theory (GBT), which incorporates genuine plate theory concepts, the cross-
section displacement field is expressed as a linear combination of deformation modes, making it possible to write

the equilibrium equations in a very convenient format. In practical applications, thin-walled steel members are
often continuously braced along their lengths - e.g., cold-formed steel purlins restrained by sheeting. In order to
incorporate such bracing in a GBT analysis, two approaches can be followed: (i) incorporate the restraints only at
the member analysis stage, which means that the deformation modes are obtained for the unrestrained cross-section
(conventional approach) or (ii) incorporate the restraints at the cross-section analysis stage, which means that the
deformation modes already take them into account (restrained cross-section analysis approach - proposed in this
work).This paper reports the results of an investigation on improving the GBT buckling analysis of continuously
braced cold-formed steel purlins by including the displacement/rotation restraints at the cross-section analysis
stage, i.e., during the determination of the cross-section deformation modes and calculation of the associated modal
properties - the end product of this procedure are “restrained deformation modes”. After describing, the procedures
involved in the determination of such restrained deformation modes, the paper illustrates the advantages of their
use in the GBT-based buckling analysis of cold-formed steel purlins restrained by sheeting. For validation and
assessment purposes, some GBT-based results are compared with values provided by the codes GBTUL2.0

(conventional GBT approach) and Finite Strip Method (FSM) analyses. It is still worth noting that restrained cross-
section analysis makes it possible to obtain semi-analytical solutions to determine critical buckling loadings in

purlins restrained by sheeting - such solutions are based on one or two restrained deformation modes.

Strength analysis of steel columns under influence of residual stresses and geometric imperfections

Jefferson A. Ferreira, Giovani V. Costa, Harley F. Viana, Renata G. L. Silva — Wed, 03 Jul 2024 00:00:00 +0000

Knowledge about the behavior of structures is of great importance for the correct design of a structural
project. Generally, it is desired to obtain lighter and slender structures, which, in addition to providing cost savings,
present a good performance in face of the requesting efforts. In addition, improvements in computational methods
for advanced analysis have favored the achievement of results closer to the structure’s real behavior. In this sense,
the objective of this article is to evaluate the influence of residual stresses and geometric imperfections on steel
columns subjected to bending around weak-axis, especially in columns with intermediate slenderness (40 ≤ l / r ≤
120). For this end, it is used the data obtained by a non-commercial software, called PPLANLEP program, which
is based on the Finite Element Method and is capable of considering the physical nonlinearity, modeled by the
distributed plasticity approach, and the geometric nonlinearity. In the analyses, residual self-balanced stresses due
to material manufacturing process are considered with different magnitudes and distributions on the flanges and
web for an I-type cross section. In addition, this factor is combined with different configurations of initial
geometric imperfections. Finally, the resistance curves of the columns are compared with the curves proposed by
the Brazilian standard ABNT NBR 8800: 2008 and European standard EN 1993-1-1: 2005. It is verified an
inadequacy in the use of the single buckling curve, adopted by the Brazilian standard, for flexural buckling about
minor axis. In addition, it is observed that the use of the buckling curve “c” proposed by the European standard is
more assertive for the design of columns subjected to bending around the weak-axis.

GBT-based buckling analysis of composite steel-concrete beams

Carlos M. Andrade Júnior, Cilmar D. Basaglia — Wed, 03 Jul 2024 00:00:00 +0000

Continuous restrained I-section beams may be subject to lateral-distortional buckling and web lateral
buckling in regions of negative bending. Buckling analysis of restrained beams demands time-consuming Shell
Finite Element Method (SFEM) models. SFEM is an important unquestionable tool to solve eigenvalue problems,
however, it requires models involving several degrees of freedom and substantial engineering judgment. This fact
explains why assessing the structural response of such structural systems constitutes a complex task. One very
promising route that has been explored in the last decade is the use of Generalized Beam Theory (GBT) − a beam
theory that incorporates genuine folded-plate concepts. In this context, a GBT-based analytical solution for the
distortional buckling is proposed. First, the continuous elastic torsional restraint is incorporated in the cross-section

distortional deformation mode. Next, a kinematic assumption comprising the null shear strain in each wall mid-
plane is imposed to determine the distortional displacement field. Finally, the buckling stress is derived from an

energy method. The accuracy of the solution is validated by numerical solutions provided by the 2.0 release of the
software GBTUL.

Numerical study of CHS-SHS and CHS-RHS T-joints with chord web failure

Wed, 03 Jul 2024 00:00:00 +0000

Hollow steel sections have properties that enable their use in large span structures and trusses, in which
the design of joints between chords and braces with hollow steel sections are composed of circular (CHS),
rectangular (RHS) or square (SHS) cross-sections. However, the current design prescriptions do not contemplate
the design of T-joints with containing slender cross-sections. In this work, CHS-SHS and CHS-RHS T-joints with
brace-to-chord ratios equal to one and composed of chords with slender sections were analysed through a
numerical analysis using a commercial software. A brace axial load of compression was applied, and the normal
tension distributions, the joint resistance and the load-displacement behaviour were examined. The numerical
results were compared with a design equation from a normative prescription. Chord web failure was observed in
all the joints analysed. Thus, the joints outside the current validity ranges of the normative prescriptions – that is,

with slender sections – presented the same predicted failure mode for joints with compact or semi-compact cross-
sections. The comparison between numerical and analytical joint resistances showed that current design equation

does not adequately predict the joint behaviour of joints with slender chords.

Análise experimental de uma viga de concreto armado reforçada com barras externas protendidas

Wed, 03 Jul 2024 00:00:00 +0000

A degradação do concreto é uma condição natural que deve ser avaliada em cada caso. Na análise
estática, a avaliação pode ser feita por meio de deslocamentos em um determinado intervalo de tempo. Na
análise dinâmica, essa avaliação pode ser feita por meio da análise modal, que permite a identificação de
frequências naturais, formas modais e taxas de amortecimento. As técnicas de armadura são soluções que
produzem ganho de rigidez na recuperação estrutural, neste sentido, a utilização de barras externas protendidas
em elementos danificados tem se mostrado bastante adequada, de forma que sua execução possa ocorrer sem
maiores interferências destrutivas. Assim, para verificar a eficácia da utilização desta técnica, foi dimensionado e
produzido um protótipo de viga de concreto armado que, posteriormente, foi submetido ao ensaio de flexão e ao
ensaio de captura de frequências naturais com o software Sonelastic®. Com base nos resultados das análises,
constatou-se que o sistema de barras externas protendidas pode ser eficiente na recuperação estrutural.

Modelagem Numerica de Vigas de Aço Constituídas por Perfis Formados a Frio

Gregorio Sandro Vieira, Jerfson Moura Lima — Wed, 03 Jul 2024 00:00:00 +0000

Os sistemas estruturais que utilizam perfis de ac ̧o formados a frio tem aumentado sobremaneira sua ˆ
parcela no Mercado. Apesar disto, os estudos dos comportamentos destes perfis quando submetidos aos mais
diferentes tipos de carregamentos, nao tem acompanhado na mesma proporc ̧ ̃ ao esta utilizac ̧ ̃ ao. Neste trabalho ̃
foi apresentado um estudo numerico feito em vigas compostas por dois perfis met ́ alicos formados a frio do tipo ́
“U” simples unidos por suas almas formando uma sec ̧ao do tipo “I”. O objetivo principal deste estudo foi desen- ̃
volver um modelo numerico tridimensional e n ́ ao-linear capaz de simular o comportamento de vigas constitu ̃ ́ıdas
por perfis formados a frio. Para o desenvolvimento do modelo numerico foi utilizado o programa computacional ́
ABAQUS, baseado no Metodo dos Elementos Finitos. O modelo num ́ erico foi calibrado e validado com os resul- ́
tados experimentais da literatura. Os resultados numericos obtidos foram concordantes com os resultados experi- ́
mentais.

Proposta para obtenção do momento de inércia efetivo aplicado à laje mista de aço e concreto

Wed, 03 Jul 2024 00:00:00 +0000

A análise do comportamento e da resistência de lajes mistas de aço e concreto abrange vários parâmetros;
nesse viés, a curva carga versus flecha no meio do vão consiste em uma importante relação para a verificação dos
deslocamentos. Em relação ao cálculo da flecha, geralmente, as normas técnicas recomendam que o momento de
inércia da seção mista seja dado pela média simples dos momentos de inércia das seções não-fissurada e fissurada.
Porém, investigações experimentais mostram que esse procedimento não representa adequadamente o
comportamento das lajes mistas de aço e concreto, levando a uma estimativa inadequada do momento efetivo de
inércia e resultando em menor flecha, principalmente quando submetidas a cargas maiores. Utilizando os
resultados de pesquisas realizadas no Departamento de Engenharia de Estruturas da UFMG, este trabalho tem
como objetivo apresentar uma proposta para determinar o momento de inércia efetiva em lajes mistas que
representa adequadamente o comportamento durante a fase de carregamento.

Numerical analysis of the structural behavior of flat plates under tension loads

K. Rocha, J. G. R. Neto, B. S. Rocha — Wed, 03 Jul 2024 00:00:00 +0000

Based on the guidelines provided by the ABNT NBR 8800 [1], the present study analyzes the
prescription for determining the strength of cross-sections with holes arranged straight or zigzag for elements
subject to tensile load. In case of misaligned holes, these calculations are performed by a semi-empirical parameter,
defined by the Cochrane equation. This additional parameter covers an increase of resistance from an additional
equivalent portion of the cross-sectional area. In this work, it is intended to simulate numerically the structural
behavior of flat steel plates under tensile stress through a finite element modeling processed by Ansys 16.0 and
verify the compatibility with the analytical methods prescribed by the code. Three plates were modelled according
to the study by Oliveira and Wietzikoski [2] to attest the collapse modes, rupture profile, and resistance obtained
experimentally and validate the analytical prescriptions from the results of the numerical modeling.

DIMENSIONAMENTO E ANÁLISE COMPUTACIONAL DE UM GALPÃO METÁLICO UTILIZANDO O SOFTWARE SAP 2000

Bianca Saldanha Pinheiro, Salete Souza de Oliveira — Wed, 03 Jul 2024 00:00:00 +0000

O presente trabalho apresenta um tutorial do SAP 2000 v.16 - Structural Analisys Program, para
modelagem, dimensionamento e análise estrutural de um galpão com estrutura em perfis metálicos. O SAP 2000
é um software para análise estrutural que utiliza o método dos elementos finitos, desenvolvido pela empresa
americana CSI – Computers&Structures Inc. e comercializado no Brasil pela empresa Multiplus Softwares
Técnicos in. O software é vastamente utilizado para analisar edificações de pequeno, médio e grande porte, no
entanto, apesar de ser uma importante ferramenta de análise e dimensionamento, nota-se a dificuldade dos alunos
de engenharia civil em aprender a usá-lo, assim como a escassez de material em português apresentando,
didaticamente, tutoriais para auxiliar na utilização do programa, visto que, com a evolução das estruturas, que
estão se tornando cada vez mais complexas, tornou-se, em grande parte das situações, inviável a resolução por
meio de cálculos analíticos. Desta forma, o presente trabalho visa contribuir para diminuir estas dificuldades,
apresentando um manual de modelagem, dimensionamento e análise de uma estrutura metálica, a fim de gerar o
perfil adequado para cada barra, assim como os diagramas de esforços, deflexões, momentos, cisalhamento,
reações e deformadas.

Comparative Optimization Study of an Isogrid Structure Using Sunflower Optimization and Genetic Algorithm

Wed, 03 Jul 2024 00:00:00 +0000

Isogrid structure emerged in the early 1970s due the need for lightweight and high-performance model
in the aeronautical industry, however, over the years, several other branches that also need these characteristics
began to use this type of components. The present work aims to find the optimal design parameters for the lattice
structure in order to minimize the Tsai-Wu failure index and the mass of the structure under compression loads by
using two different metaheuristics algorithm: Genetic Algorithm (GA) and Sunflower Optimization (SFO). A
Response Surface Methodology (RSM) was used for the purpose of setting up a series of experiments for adequate

predictions of the responses and the generated models were used as objective functions for single and multi-
objective optimizations. Finally, the results of both algorithms were compared with finite element method and the

performance of the new meta-heuristics algorithm SFO was evaluated.

Tri-objective truss structural optimization considering sizing design variables

Wed, 03 Jul 2024 00:00:00 +0000

Structural multi-objective optimization problems are common in the Engineering field’s real-world
problems where one or more objective functions, in general conflicting, may be considered to be optimized, leading
to complex optimization problems. Two objective functions problems represent the great majority of formulations
in this context where Pareto fronts can be easily represented and provided to the Decision Maker (DM). For
instance, in the trusses’ structural optimization, these conflicting objective functions may be the weight and the
maximum nodal displacements to be minimized. This paper presents the formulation of multi-objective truss
structural optimization problems considering three objective functions, such as the weight, the maximum nodal
displacement, and the first natural frequency of vibration. The constraints refer to the allowable axial stresses
in the bars. Several experiments inspired in the benchmark mono-objective optimization are analyzed in this
paper, presenting their Pareto surfaces showing the non-dominated solutions. The structural optimization problems
consider sizing and shape design variables simultaneously, and they can be continuous, discrete, or mixed. The
search algorithm adopted to solve these problems is a modified version of the Differential Evolution called Third
Evolution Step Differential Evolution (GDE3). One of the most important steps, after obtaining the Pareto surfaces,
is the definition of which solution or solutions will be chosen by the decision-maker (DM), a non-trivial task. A
Multi-Tournament Decision method, commonly used in bi-objective optimization, is adapted in this paper to extract
the solutions from the Pareto surfaces based on DM preferences.

Uso da Otimização por Colônia de Formigas (ACO) na determinação trajetória de pulsos ultrassónicos em elementos de concreto

Vinícius M. Giglio, Vladimir G. Haach — Wed, 03 Jul 2024 00:00:00 +0000

Os ensaios nao destrutivos t ̃ em se mostrado eficientes na detecc ̧ ˆ ao de heterogeneidades do concreto, se ̃
firmando como uma alternativa menos invasiva e com menor variabilidade estat ́ıstica. Dentre estes, o ensaio de
ultrassom tem se desenvolvido bastante. E poss ́ ́ıvel combina-lo com a t ́ ecnica de tomografia computadorizada para ́
gerar imagens do mapa de velocidades do pulso ultrassonico em sec ̧ ˆ oes transversais de estruturas. No entanto, para ̃
calcular essas velocidades, e necess ́ ario que se assuma uma hip ́ otese a respeito da trajet ́ oria seguida pelos pulsos. ́
O presente artigo tem como objetivo determinar a trajetoria de pulsos ultrass ́ onicos em elementos de concreto ˆ
utilizando a otimizac ̧ao por col ̃ onia de formigas na variac ̧ ˆ ao ACS ( ̃ Ant Colony System). Para isso, um modelo
do algoritmo foi implementado no software de gerac ̧ao de imagens tomogr ̃ aficas em estruturas TUSom. A fim de ́
comparar os parametros tempo de processamento e qualidade das soluc ̧ ˆ oes fornecidas, o ACS foi comparado com o ̃
algoritmo determin ́ıstico de Dijkstra em um exemplo de sec ̧ao de concreto com defeitos simulados. Os resultados ̃
demonstraram que Dijkstra apresentou melhor desempenho em problemas pequenos (ate 150 n ́ os), enquanto o ́
ACS se mostrou muito superior conforme a malha cresce, se firmando como uma alternativa mais rapida para ́
solucionar o problema das trajetorias. ́

Static Analysis and Optimization of stiffened plates under pressure loading

Wed, 03 Jul 2024 00:00:00 +0000

In this work, the Exhaustive Search Method (ESM) was used to optimize a plate structure with stiffeners.
The main goal is to establish a numerical simulation procedure in order to identify the optimal geometry for
stiffened steel plates, where the objective function to be minimized is the maximum displacement, keeping the
total reference volume constant. The search process is allowed to vary the number, thickness, and height of the
stiffeners. The optimization and analysis of mechanical behavior were performed by ESM combined with ANSYS
Mechanical APDL software which is based on the Finite Element Method (FEM). The stiffened plates were
calculated to transform 40% of the total volume into stiffeners. The optimal geometry resulted in a reduction of
98.34% in the maximum displacement if compared to the reference plate showing the good results obtained by the
proposed methodology.

OTIMIZAÇÃO DE VIGAS CASTELADAS DE AÇO

Mateus P. Pauletto, Moacir Kripka — Wed, 03 Jul 2024 00:00:00 +0000

Due to the increasing competition, associated to growing concerns about the environmental impacts
caused by construction, it is important the rational use of structural materials. In this sense, optimization techniques
can be seen as valuable tools to improve the design efficiency. This work presents the application of optimization
to design of castellated steel beams, aiming the weight minimization. To achieve this goal, both the dimensions of
the profile and of the holes were taken as the design variables. The constraints, related to ultimate and limit states,
were considered according to Brazilian standards. The optimization was performed through the usage of Simulated
Annealing Method, a meta-heuristic developed upon the analogy of the annealing of metals. Based on the
formulation implementation, some structures were analyzed in order to verify the efficiency of the proposed
procedure. In addition, welded and laminated optimized steel beams were compared, aiming to ide notify the
relative economy obtained.

Dimensionamento otimizado de vigas de aço e de concreto armado: estudo comparativo

Joel M. Ozimboski, Zacarias M. C. Pravia, Moacir Kripka — Wed, 03 Jul 2024 00:00:00 +0000

This work presents a study related to the optimization of reinforced concrete beams and steel beams.
Initially, formulations to optimize reinforced concrete beams of rectangular section and “I” welded steel beams
were developed, aiming to minimize the total cost. For both structural materials, cross-sectional dimensions were
considered as discrete design variables. To the constraints, related to serviceability and ultimate limit states,
Brazilian Standards NBR6118/2014 and NBR8800/2008 were adopted, respectively to reinforced concrete and to
steel beams. The developed formulations were computationally implemented by the usage of Simulated Annealing
optimization method. From a parametric study considering different spans and loads, simply supported beams
were analyzed in order to obtain the optimized costs and their corresponding cross-sectional dimensions. The
comparison of concrete and steel beams aimed to clearly identify the advantages of each structural material to a
given span in terms of cost, height and self-weight.

A tri-objective truss design optimization using a Multi-objective Craziness based Particle Swarm Optimization

Wed, 03 Jul 2024 00:00:00 +0000

Recently there has been a growing interest in evolutionary multi-objective optimization algorithms
due to its applicability in problems from several fields, especially those of applied engineering and mathematics.
In this context, there are many of algorithms applied to these types of problems, such as differential evolution,

genetic algorithms, particle swarm, among others. This paper deals with a multi-objetive sizing, discrete or con-
tinuous, strucutural optimization problem with respect to: i) the minimization of the mass of truss structures; ii)

the maximization of the first natural frequency of vibration and iii) the minimization of the maximum displace-
ment, considering stress constraints. A multi-objective particle swarm algorithm called Multi-objective Craziness

based Particle Swarm Optimization (MOCRPSO) is the search algorithm adopted here and an Adaptive Penal-
ization Method (APM), which has been successfully applied to solving mono-objective optimization problems, is

used to handle the constraints. Some computational experiments are analyzed, presenting very interesting results
providing pareto fronts between the objectives.

Optimal Search Space for Topological Optimization of Transmission Line Towers

Gabriel P. Alves, Leandro F. F. Miguel, Joel V. Pimenta — Wed, 03 Jul 2024 00:00:00 +0000

Due to the vast territorial extension of Brazil and its hydroelectric potential, many power plants are built
far from consumption centers and in order to deliver electricity to these centers, extensive transmission lines (TL)
are needed. One of the main components of these lines are the steel lattice towers, which end up being repeated
several times in a TL. For this reason, an opportunity to reduce costs presents itself through the optimization of

these structures, especially when the dimension, geometry and topology of the tower are optimized simultane-
ously. However, with the inclusion of topological variables an uncertainty arises due to the definition of the search

space for the process of optimization. On one hand, if many variables are considered, the convergence may be
impaired. On the other hand, if just a few variables are chosen, great possibilities of mass reduction might be left
aside. Hence, the present work aims to relate the structure mass and its search space, finding a general rule for
templates selection by analyzing the optimization results of eight towers with three design spaces for each, where
the difference between these is the number of templates considered.

Optimization of transmission line towers considering the family concept

Alexandre Deichmann, Leandro F. F. Miguel, Rafael H. Lopez, Joel V. Pimenta — Wed, 03 Jul 2024 00:00:00 +0000

Transmission line towers (TLTs) are responsible to support the cables of overhead transmission lines
(TLs). Because these structures are repeated several times in a line, the application of optimization procedures is
highly recommended. In the design of a line, towers with different heights and leg combinations are necessary.
However, it would be difficult to individually design or produce these supports. Therefore, for the ease of design,

industrial production and erection processes, a TLT can be separated in main parts, such as basic body, body ex-
tensions and legs. The so-called tower family is the combination of these minor components in order to obtain the

different supports. The present work aims to apply this concept into a size, shape and topology optimization pro-
cedure of TLTs. The developed optimization procedure is an extension of the methodology proposed by de Souza

et al. [1]. A self-supported 138 kV double circuit tower family composed by tower body, one body extension
and two different tower legs was evaluated. The sizing of redundant members and each bolted connection are
considered. The final solution is around 9% lighter than the original family design, showing the efficiency of the
proposed optimization procedure.

A Comparative analysis of structural optimization of spatial steel frames considering different bracing systems

Wed, 03 Jul 2024 00:00:00 +0000

In tall steel buildings, aspects related to natural frequencies of vibration, global stability, and horizontal
displacements due to wind pressure become more relevant when compared to sizing strength constraints. In this
sense, the bracing systems may be crucial to improve the dynamic behavior increasing the structure stiffness. This
paper shows a comparative analysis between four bracing systems used in six-story spatial steel frames subjected to
weight minimization. This study shows which bracing system is most suitable for the final design of the structure.
The constraints imposed in the structural optimization problem are the first natural vibration frequency, the critical
load factor concerning to global stability, and horizontal displacements. The search algorithm is the Differential
Evolution (DE) coupled with an Adaptive Penalty Method (APM) to handle the constraints.

Global stability and natural frequencies of vibration in multi-objective op- timization of 3D steel frames.

Wed, 03 Jul 2024 00:00:00 +0000

In a structural optimization problem, it may be desired not only to minimize the cost of the final design
but also to enhance its performance. In this sense, aspects concerning the first natural frequency of vibration
and the critical load factor concerning global stability may be desired to be maximized. Also, for instance, the
displacements are to be minimized, leading to conflicting objective functions. This paper analyses multi-objective
structural optimization of 3D steel frames considering the weight minimization of the structure with the first natural
frequency, the critical load factor, and the maximum horizontal displacement in three different multi-objective
problems. The analysis presents their Pareto-fronts showing the non-dominated solutions, leaving the task of
defining which solution or solutions to be extracted from these curves to a Multi-Tournament method based on the
preferences of the decision-maker. The search algorithm adopted is the Third Step Differential Evolution (GDE3)
coupled with an Adaptive Penalty (APM) Method to handle the constraints.

Fatigue Curves in Steel Railway Generated by Genetic Algorithm

Maria Rafaela B. de M. Ribeiro, José Antônio F. Santiago, Ritermayer M. Teixeira — Wed, 03 Jul 2024 00:00:00 +0000

Genetic Algorithms (GA) are global optimization, based on natural selections and genetic mechanisms
for which structured and random search strategies are geared by reinforcing the search for high amplitude points
in which the function to be minimized (maximized) has relatively low (high) values. This work deals with a study
on the Genetic Algorithm application to estimate parameters inherent to S-N-p Curves generated for typically
structural details of the metal railway bridges applying together with The Maximum Likelihood Method to infer
runout data, such as censored data for failure probability functions. MatLab software is employed to develop the
computational program. To compare the obtained results, the Interior Point Algorithm is also presented, due to its
wide use in problems involving linear and nonlinear quadratic programming.

A Dynamic Treatment Criterion of Population Sizes in PSO

Wed, 03 Jul 2024 00:00:00 +0000

Populational algorithms are strongly dependent on parameters, and among them, the size of the pop-
ulation directly impacts the search for optimized solutions and computational cost. As the population grows, the

slice of the inspected search space also tends to expand, allowing new optimums to be discovered. However, the

increase in this population also implies an increase in the objective function calls, consequently increasing the al-
gorithms’ computational effort and execution time. When the objective function calls are the execution bottleneck,

the number of individuals observed at each iteration is decisive for the weight given to exploration and exploita-
tion. In general, the choice of population size happens empirically, through the user’s experience. However, the

dynamic treatment of population size can be a more interesting choice. In optimization problems that require a
simulator, such as optimization in mechanical and structural engineering, the decrease in computational cost is

very significant. Moreover, many simulations have high computational costs, motivating the study of a less empir-
ical approach in population size choosing. Here we propose and study an approximation metamodel in the form

of a criterion for dynamic treatment of the population size of a Particle Swarm Optimization algorithm applied to
mechanical engineering optimization problems. This metamodel considers that particles that are very close and
with similar speeds will have similar behavior, tending to the same solution, thus allowing one of the particles to
be eliminated. Comparative results are presented using the proposed strategy, showing that it achieved the desired
expectations.

A Dynamic Treatment Criterion of Population Sizes in PSO

Wed, 03 Jul 2024 00:00:00 +0000

slice of the inspected search space also tends to expand, allowing new optimums to be discovered. However, the

Comparison of the performance of different metaheuristic optimization algorithms

Otávio A. P. de Souza, Letícia F. F. Miguel — Wed, 03 Jul 2024 00:00:00 +0000

Metaheuristic algorithms are powerful tools for solving optimization problems. With the advancement
of computational technology, many metaheuristic algorithms were developed to solve optimization problems
quickly and accurately. Within this context, in this paper five of the main metaheuristic optimization algorithms
developed in recent decades – Particle Swarm Optimization (PSO), Harmony Search (HS), Firefly Algorithm (FA),
Search Group Algorithm (SGA) and Whale Optimization Algorithm (WOA) – had their performance compared in
the solution of problems involving the optimization of benchmark functions and the optimization of trusses in
which the design variables are the cross-sectional areas. Each algorithm was evaluated in terms of precision,
computational time of operation and standard deviation among the results obtained after many executions. With
the results obtained, the effectiveness of the five algorithms has been proven, although the older algorithms have
a slightly lower performance. In most problems, the best results were achieved through the WOA or the SGA.

Optimización de armaduras con un algoritmo de evolución diferencial a través de control de parámetros

Oscar. Contreras-Bejarano, Jesús D. Villalba-Morales — Wed, 03 Jul 2024 00:00:00 +0000

In recent decades, numerical tools have been to improve the design process of civil structures. Among
them, it is possible to find the evolutionary algorithms, which are based on analogies with the evolutionary process.
Among the main limitations observed in the literature for its implementation is the need to enter the algorithm
parameters for a problem in study by the user. There exist some parameters own of each algorithm that control the
success level. This paper presents the application of an adaptive differential evolution algorithm (ADEA) to the
optimization of planar steel trusses. In ADEA is necessary that the user to set the population size and the
coefficients cF and cCR. To show the performance of the proposed methodology, two cases obtained in the literature
are presented for comparison, which is done in terms of quality of the objective function, robustness and
convergence. It is expected that with this type of work, the results required in structural optimization problems can
be improved through implementing the differential evolution algorithm.

Optimization Algorithm and the Inverse Problems Applied to the Structural Damage Identification in Steel Beams with the use of FEM and Experimental Data

Brunno E. Sobrinho, Gilberto Gomes, Ramon S. Y. R. C. Silva — Wed, 03 Jul 2024 00:00:00 +0000

Optimization problems in academia and industry are recurrent, in addition the structural elements
conditions over their lifetime when in use acquired differents damages from their natural deterioration or even
because of the exceptional causes that can cause these different magnitudes of damage. In this sense, to combine
the damages identification through optimization processes in the continuous search for more adequate means and
consequently the improvement of the available informations that characterizes the problems under essential study,
and constitutes one of the current engineering requirements, considering the evolutionary state of the structural
elements when in use. In this work, it is proposed the adjustment of experimentally steel beams structures tested,
from a static analysis by the Finite Element Method (FEM) using ANSYS© to obtain displacements, with the use
of inverse problems and an optimization method. From the adjusted models, damages in the structures are
simulated (elements stiffness properties reduction) and then an optimization technique and damage identification
are applied through the Differential Evolution Method. The modelled and experimentally steel beams structures
tested showed mostly consistent results and the DE technique showed good potential for solving damage
identification problems using Inverse Problems, achieving convergence in almost all cases.

Structural Optimization of Reinforced Concrete Beams using GA method.

Guilherme Adriano Weber, Alana Paula Costa Quispe, René Quispe Rodríguez — Wed, 03 Jul 2024 00:00:00 +0000

In the civil construction sector, especially in the structural area, the search for optimized designs that
satisfy architectural, constructive, safety criteria, being at the same time economic viable are the challenges
experienced by designers, who are constantly looking for tools and methods to find the ideal structure. In reinforced
concrete structures, beams are elements designed to support and distribute the loads, generally from slabs, to the
columns and correspond to a significant portion of the structural design. Therefore, the search for optimal beams
can be advantageous, since the final cost can be positively impacted. The main objective of this work is the
optimization of cross sections of reinforced concrete beams, having as an objective function the final cost of
reinforced concrete inputs. For computational implementation of routines for dimensioning longitudinal and
transverse reinforcement, the programming language Matlab was used. The dimensioning process of longitudinal
and transverse reinforcement areas were implemented using the commercial software Matlab. This process, as
well as all imposed constraints are in accordance with the Brazilian standard NBR6118/2014. The optimization
was achieve using the heuristic method GA (Genetic Algorithm). Diverse situations were analyzed as variations in
spans and loads, having the height of the section, the resistance of the concrete (Fck) and the area of the transverse
and longitudinal reinforcements as design variables.

Topology Optimization of Continuum Elastic Structures through the Progressive Directional Selection Method

Luiz C. L. Véras, Márcio A. A. Cavalcante — Wed, 03 Jul 2024 00:00:00 +0000

The present work deals with a new approach for Topology Optimization (TO) of two-dimensional
continuum elastic structures through the Progressive Directional Selection (PDS) method. To achieve the best
topology of a structure, a typical goal is to define the best material distribution in a domain, considering an
objective function and mechanical constraints. In general, most of the studies address the compliance minimization
of structures. Numerical methods for TO of continuum structures have been investigated extensively. Most of
those methods are based on finite element analysis, where the design domain is discretized into a fine mesh of
elements. In such a setting, the optimization procedure is to find a structure's topology by determining for every
point in the design domain if there should be material (solid element) or not (void element). To control the process
of inserting or removing finite elements without forgotten the continuum representation, standard algorithms as
Homogenization, Solid Isotropic Microstructure with Penalization (SIMP), and Evolutionary Structural
Optimization (ESO) are applied in many studies. The latter approach is based on the simple concept that the
optimal design can be achieved by gradually removing inefficient material (elements) from the design space. The
ESO algorithms are easy to understand and implement. However, ESO is heuristic, and there is no proof that an
optimum solution can be achieved by element elimination and admission. The original scheme is inefficient once
it needs to find the best solution by comparing several intuitively generated solutions. To avoid this problem but
taking advantage of ESO's simplicity, the PDS method, which is inspired by natural selection observed in biology,
applies a strategy to minimize the strain energy of a discretized analyzed domain with a volume restriction. Based
on the performance criteria adopted for the problem, the selected population is reached through an iterative process
that converges when the optimal topology does not evolve anymore, i.e., there is no change in the final set of
selected elements. An instructional problem that shows the essence of PDS for a rigid body problem and one
example of topology optimization of a classical problem found in the literature are investigated.

Mechanical Project of an Automotive Part Using Numerical Analysis-Based Reverse Engineering

Hiram Y. Shirata, Rosicley J. R. Rosa, Rodolfo A. K. Sanches — Wed, 03 Jul 2024 00:00:00 +0000

In the diverse areas of mechanical industry, sometimes it is difficult to find specific reposition parts.
In such cases, it is necessary to manufacture a single part, which must have its mechanical properties similar
to the original one. In this work, we develop a technique to design a replacement part based on finite element
simulations and optimization techniques, seeking to produce a new part with optimal similarity to old one regarding
mechanical properties, even if material, geometry and manufacturing process are not the same as in the original
context. This is done by considering that there is no previous knowledge about the design loads, being known just
the material and geometry. The mechanical analysis is based on triangular isoparametric finite element with cubic
approximation for plane stresses elasticity. In order to perform shape optimization, we employ an evolutionary
algorithm. The developed technique is applied to a lower control arm of a vehicle that is no longer under production
as a replacement strategy.

Modeling and Model Predictive Control (MPC) of an Underwater Double Inverted Pendulum (UDIP)

Wed, 03 Jul 2024 00:00:00 +0000

The Inverted Double Pendulum (IDP) is a classical nonlinear and unstable mechanical system used as
a benchmark model for the application of innumerous control techniques. However, such a model was never treated
in an off-the-self environment, which represents a gap in its applications range since the demand for underwater

robotics is increasing together with the ocean engineering activities. Thus, to fill this gap and build a new bench-
mark model for the control development of underwater robotics, this paper presents the modeling and control of

an Underwater Double Inverted Pendulum (UDIP). The dynamic model is formulated using the formalism of An-
alytical Mechanics and considering the pertinent hydrodynamic and hydrostatic effects. To keep straight with the

control techniques trends, a Model Predictive Control (MPC) is designed for the UDIP. This controller is tested
through numerical simulations in MATLAB/Simulink© environment considering two scenarios: 1) in the absence
of disturbances, and 2) in the presence of a time-varying water current. The obtained results for the disturbances
case reveal an increase in the control effort in comparison with the case without disturbances. In such a way, this
reflect the difficulty associated to the control of underwater robots in unstructured environments.

Vibration control of slender structures under base motions by pendulum TMD’S

Wed, 03 Jul 2024 00:00:00 +0000

The technological progress has been making possible the building of slender constructions, but very
susceptible to unwanted vibrations. To control that, it has been advised the use of TDM’s, that can decrease
considerably the dynamic responses. Following that line, the present work aims to realize a dynamic analysis of a
tall slender tower, exposed to support motions but with a pendular TDM installed to damp out the dynamic effects.
In this work a finite elements model of a 90m tall slim tower without damper is modeled in the Scia Engineer
software, to achieve the natural vibration frequencies, the structure’s equivalent stiffness and mass in the top end.
With those values, a mathematical model with two degrees of freedom is built: the horizontal movement of the top
end of the tower (q1) and the pendulum’s vertical angle (q2). The equations that govern the movement of the
system are derived by the Lagrange Equations. From that model, a program in the Matlab software is introduced
to calculate the structural displacement with and without a tuned pendular mass damper, to verify the dynamic
damper effects, and the displacement limit according to international standards.

Theoretical study of Sommerfeld effect in flexible rotor shaft on structural model with two degrees of freedom

Sara Prates Lima, Reyolando Manoel Lopes Rebello da Fonseca Brasil — Wed, 03 Jul 2024 00:00:00 +0000

This paper address nonlinear dynamical analysis of a foundation structure for a flexible rotor machine.
The residual unbalance will always be present in rotating equipment systems. This aspect is often not considered
during the design steps, although all real motors are non-ideal power sources. Thus, the interest in further studying
the machine-foundation and soil-foundation interactions.
Our mathematical model considers this system as non-ideal, subjected to the Sommerfeld effect, which may
manifest close to the low power machine’s resonance, with possible jumps from lower to higher frequency rotation
regimes without intermediate stable solutions. The model proposed is defined by two degrees of freedom, vertical

and horizontal translations, and an additional one associated with the rotation of the rotor shaft (intrinsic to the so-
called non-ideal systems).

The mathematical model that describes the system’s motion is derived via Lagrange equations. The solution of
this system of differential equations can in principle be solved analytically, but this can be difficult or even
impossible in some cases, particularly when these equations are nonlinear, such as the proposed model. The
numerical solution adopted here will be implemented in the Matlab®. This paper aims to analyze a little studied
problem of practical importance.

Calculo da velocidade de flutter de uma asa retangular considerando incertezas paramétricas

Wed, 03 Jul 2024 00:00:00 +0000

No contexto da aeroelasticidade, a velocidade de flutter pode ser calculada pelo o metodo doublet lattice ́
(DLM) em conjunto com o metodo dos elementos finitos (MEF) e o m ́ etodo pk. Os referidos m ́ etodos, apesar ́
de bastante consolidados, sao determin ̃ ́ısticos, e nao consideram assim o efeito de variac ̧ ̃ oes nos par ̃ ametros de ˆ
entrada que possam existir na pratica. Assim, o objetivo deste trabalho ́ e o de verificar a influ ́ encia da incerteza ˆ
inerente as vari ` aveis de projeto geom ́ etricas sobre a velocidade de flutter de uma asa retangular. Com essa fi- ́
nalidade, empregou-se o metodo de Monte Carlo, considerando o comprimento, largura e espessura da asa como ́
variaveis aleat ́ orias, todas com distribuic ̧ ́ ao gaussiana. Conclui-se que a velocidade de flutter ̃ e sens ́ ́ıvel as variac ̧ ` oes ̃
geometricas, variando 25,5% para 10% de incerteza nas dimens ́ oes avaliadas, apresentando uma distribuic ̧ ̃ ao apro- ̃
ximadamente gaussiana.

Spectral characterization of the electron drift instability in a Hall thruster

Rodrigo A. F. Alves, Rodrigo A. Miranda — Thu, 04 Jul 2024 00:00:00 +0000

The Hall thruster is an electric propulsion device commonly used for station-keeping purposes in satel-
lites and in deep-space missions since 1971. This device generates thrust from the interaction between a plasma and

electromagnetic fields. Several aspects of this interaction and the thruster operation are still not well understood.
Recently, numerical simulations and experimental measurements have shown the occurence of a high-frequency,
low-wavenumber instability known as the E × B electron drift instability. This instability modifies the electron
cross-field mobility in the plasma and can affect the thruster efficiency.
In this study we perform numerical simulations of a SPT-100 Hall thruster using the particle-in-cell method.
We describe a two-dimensional model in cylindrical coordinates in which the axial and azimuthal directions are
kept, neglecting variations in the radial direction. Our numerical simulations show that the instability induces a

large-amplitude wave in the azimuthal electric field and the ion density, as expected. We proceed by character-
izing the frequency and wavenumber of this instability using a spectral analysis, and compute power-laws in the

resulting power spectra. Our results demonstrate that the plasma in a Hall thruster displays a turbulent behavior
with an energy cascade induced by the E × B electron drift instability. We also show that the microturbulence is
characterized by an inertial subrange which extends to scales smaller than 1 mm.

Final results of topology optimization of a stringer using MATLAB program and comparison with Ansys software.

Da Silva Maschietto. Julia, Araujo da Silva. Marcelo — Thu, 04 Jul 2024 00:00:00 +0000

Esta pesquisa tem como intuito apresentar o resultado final das otimizações realizadas nos softwares
Ansys® e MATLAB. Calculou-se as tensões máximas e mínimas em ambos os softwares a fim de realizar
otimizações a partir de dois métodos: redução de energia e espessura comparando-as com a Otimização Topológica
do software Ansys Mechanical e otimização paramétrica do software Ansys AIM. Após a coleta dos resultados,
os resultados serão apresentados e por fim, a apresentação de sugestões para trabalhos futuros.

Paulistinha Design Review

De Aguiar, J.B, Gagliardi, G, De Aguiar, J.M — Thu, 04 Jul 2024 00:00:00 +0000

Paulistinha was the first airplane developed and constructed in industrial form in Brazil. It was inspired
in the initial designs of the Taylor Cub in US, having however several differences, to accommodate local
technological possibilities, mostly. It resulted from a semi-empirical approach, having suffered many changes
during its long maturation life, from its start in Ipiranga, São Paulo in the 1930 ́s up to the end of its serial
fabrication in Botucatu, in the late 1970 ́s. In this research starting, from the drawings of the airplane, a model
of the structure is constructed. Wings and fuselage are compiled to detail, from local measures in a real airplane.
A model is then developed in computer, from the drawings, to ascertain aerodynamic and structural
characteristics. Finite element procedures are used in the analysis. Results show large safety values and therefore
margins for improvements with the model. Its concept may be extended to new planes using alternative
propulsion, construction materials and applications including the much required versatility of hydroplanes.

Smooth Second-Order Sliding Mode Flight Control of an Ellipsoidal Multirotor Airship

Jorge A. Ricardo Jr, Davi A. Santos — Wed, 03 Jul 2024 00:00:00 +0000

This work is concerned with the robust attitude and position tracking control of a multirotor
airship subject to a smooth model uncertainty representing unknown aerodynamics coefficients and added
mass. The vehicle is assumed to be full-actuated. To tackle this problem, we present a multi-input
formulation of a smooth second-order sliding mode control strategy with stability guaranteed on the basis
of vector field homogeneity. The method is evaluated using numerical simulation and shows effective.

Suboptimal Control on Nonlinear Satellite Simulations using SDRE and H-infinity

Alessandro Gerlinger Romero, Luiz Carlos Gadelha de Souza — Thu, 04 Jul 2024 00:00:00 +0000

The control of a satellite can be designed with success by linear control theory if the satellite has slow
angular motions. However, for fast maneuvers, the linearized models are not able to represent all the perturbations
due to the effects of the nonlinear terms present in the dynamics which compromises the system’s performance.

Therefore, a nonlinear control technique yields better performance. Nonetheless, these nonlinear control tech-
niques can be more sensitive to uncertainties. One candidate technique for the design of the satellite's control law

under a fast maneuver is the State-Dependent Riccati Equation (SDRE). SDRE provides an effective algorithm for
synthesizing nonlinear feedback control by allowing nonlinearities in the system states. The Brazilian National

Institute for Space Research (INPE, in Portuguese) was demanded by the Brazilian government to build remote-
sensing satellites, such as the Amazonia-1 mission. In such missions, the satellite must be stabilized in three-axes

so that the optical payload can point to the desired target. Although elsewhere the application of the SDRE tech-
nique has shown to yield better performance for the missions developed by INPE, a subsequent important question

is whether such better performance is robust to uncertainties. In this paper, we investigate whether the application
of the SDRE technique in the AOCS is robust stable to uncertainties in the missions developed by INPE. Moreover,
in order to handle such uncertainty appropriately, we propose a combination of SDRE with H-infinity based on a
left coprime factorization. In such a way that the attention is moved to the size of error signals and away from the
size and bandwidth of selected closed-loop transfer function. The initial results showed that SDRE controller is
robust to 5%, at least, variations in the inertia tensor of the satellite.

Effects of Geometric Nonlinearities on the Dynamic Characteristics of Portal Frames

Paulo E S Santos, Reyolando M L R F Brasil — Thu, 04 Jul 2024 00:00:00 +0000

In this paper, we present a study of the effects of the presence of large compressive axial forces applied
to members of portal frames on their vibration frequencies. It is a well-known fact that axial forces in structural
members may affect the so-called geometric stiffness. If they are compressive, the overall stiffness will decrease,
and, as a consequence, the vibration frequencies also.
Our structural model is a simple portal frame composed of two upright columns fixed at their bases supporting a
horizontal beam pinned at both ends. We suppose a motor to be mounted at the beam mid span. The natural
frequencies of vibration of the structure will usually be set far away from the machine nominal operational speed
to avoid possible resonance due to motor unbalance. But if large axial forces are applied to the portal frame
members changing their geometric stiffness and frequencies, unexpected resonances may occur, potentially
dangerous.
Two analysis are carried out. First, a simplified mathematical model is derived using simple Rayleigh’s Method
considerations. Next, a more refined Finite Element model is implemented. Results agree reasonably well.

Passive Control of HALE Aircraft Wings with Tuned Mass Dampers

Victor Casulli de Oliveira, Reyolando M. L. R. F. Brasil — Thu, 04 Jul 2024 00:00:00 +0000

In this paper we study the control of vibrations of a HALE aircraft wing using TMD devices. The
structure was modeled using a commercial structural analysis software. The wing profile and material
characteristics used were provided in available literature. Aerodynamic loads of random nature are simulated.
When the first natural frequencies of the structure are close to the aerodynamic loads frequencies it can lead to
unsafe flying conditions due to resonance. In addition, it can shorten the frame life due to material fatigue and
further maintenance may be required. Processing suggests the presence of accelerations above the desired or
anticipated by several international standards on the subject. To mitigate them, passive vibration absorber (TMD's,
Tuned Mass Dampers) control is proposed for vertical and lateral vibrations.

Dynamic Effects of Moving Loads on Structures

Baddyo K. S. P. Silva, Reyolando M. L. R. F. Brasil — Thu, 04 Jul 2024 00:00:00 +0000

This study presents a computational analysis of the dynamic behavior of a cantilever steel beam
subjected to a moving mass and corresponding load that travels along its entire length. It aims to understand the
behavior of such a structure and to determine dynamic impacts on displacements. Present methods for structural
analysis usually consider acting forces as static. However, structures subjected to masses whose position change
considerably in time need to be more carefully considered. It is essential to ensure the safety of the structure, the
proper functioning of equipment and the comfort and safety of users. Consideration of the dynamic behavior of a
structure allows to evaluate the results with greater reliability, since it brings the model closer to reality, as the
actual masses and corresponding loads vary with time and, therefore, produce dynamic effects. Advances in
computational power and in the development of computational methods allow the design of these structures to
include dynamic analysis, which promotes more realistic results in engineering design. Here, a discretized model
was developed, based on the Finite Element Method, using numerical integration by Newmark’s Method for the
solution of the nonlinear 2nd order ordinary differential equations and obtaining the displacements of the structure
in the time domain, to evaluate its behavior due to moving masses and loads.

Vibration analysis of the CubeSat SPORT boom’s through a flexible multi- body model

Lorenzzo Q. Mantovani, Willer G. dos Santos, Flavio L. Cardoso-Ribeiro — Thu, 04 Jul 2024 00:00:00 +0000

SPORT (Scintillation Prediction Observation Research Task) is a 6U CubeSat being developed in a part-
nership among NASA, Aeronautics Institute of Technology (ITA), National Institute for Space Research (INPE)

and several U.S. universities, with its launch planned for 2021. SPORT’s scientific mission is the study of the

pre-bubble conditions in space weather, which induce the formation of plasma bubbles; hence it has several instru-
ments, with five of them positioned in four booms around the satellite. The boom’s opening occurs through spring

mechanisms soon after its ejection from the International Space Station (ISS). These same springs keep the boom’s
final position perpendicular to the satellite body since there are no mechanisms to lock the booms in place. Thus,
periodic calibration maneuvers performed by the SPORT may induce vibration in both rigid and flexible modes of
these booms, which can lead to interferences in the control system. These interferences can reduce the pointing
accuracy of the satellite or even make the control system unstable, which supports the need to analyze them. This
paper presents the modeling of the SPORT as a rigid body and its mechanisms as flexible bodies using a multibody
approach, which allows simulating the boom’s behavior in the space environment.

Use of Third-Order Piston Theory in Panel Flutter Analysis on Composite Laminated Plates with NASTRAN

Victor S. dos Santos, Helio A. Pegado — Wed, 03 Jul 2024 00:00:00 +0000

Panel Flutter is an aeroelastic instability of plates and shells of aerospace vehicles. The phenomena have

recently grown of interest as the increased efforts to make supersonic and hypersonic flight viable in the upper lay-
ers of the atmosphere. Many results are available in the literature using customized programs to study panel flutter

with non-linear structural and aerodynamics models. In this work, the third-order Piston Theory is used in the su-
personic panel flutter analysis and an evaluation of the NASTRAN capabilities. Later, the mesh convergence study

and, subsequentially, the flutter analysis of a metallic and a composite laminated plate is performed. The obtained
results show a good agreement with the literature and, therefore, demonstrate the capability of the methodology
for the cases developed in this work.

Lumped Element Multibody Modeling Approach for Very Flexible Aircraft

Marko A. Rempel, Flavio L. Cardoso-Ribeiro, Fernando J. O. Moreira — Thu, 04 Jul 2024 00:00:00 +0000

This paper presents a modeling approach using lumped element multibody systems to describe aeroe-
lastic dynamics of aircraft. The model is shown to describe geometric nonlinearities arising from large structural

displacements and oscillations such as that of a very flexible wing bending under aerodynamic loads. The pre-
sented approach is applied to a Goland’s wing to determine the flutter speed resulting from coupling the multibody

structure to a quasi-steady aerodynamic model. Flutter velocities are comparable to those obtained using modal
representations for structural dynamics. Finally, the modeling appoach is shown to be scalable, parametrized and
modular, all of which could make it valuable in iterative environments such as during conceptual design phases of
very flexible aircraft.

Análise de sistemas aeroelásticos em regime subsônico: efeito do amortecimento viscoelástico

G.F. Diniz, A.M.G. de Lima, M.A.D. Filho, D.M. Borges — Thu, 04 Jul 2024 00:00:00 +0000

Fenômenos aeroelásticos estão presentes em várias aplicações de engenharia. O flutter é um fenômeno
aeroelástico que surge da interação fluido-sólido e causa instabilidades em estruturas aeronáuticas. A aplicação de
novos materiais e técnicas de construção estrutural vêm sendo utilizadas de forma conjunta para o controle de
instabilidades aerodinâmicas em estruturas flexíveis, onde modelos aerodinâmicos não estacionários são
utilizados. Nesse sentido, o Doublet Lattice Method (DLM) se destaca por sua confiabilidade e eficácia nos
estágios iniciais do desenvolvimento de aeronaves para análises aeroelásticas. Os materiais viscoelásticos são
amplamente utilizados como mitigadores de vibrações e, portanto, no controle aeroelástico, uma vez que atuam
incluindo um amortecimento adicional na estrutura. Com base nisso, o presente trabalho analisou o efeito do
amortecimento viscoelástico no controle aeroelástico de estruturas tipo plate like wing engastada livre. A
modelagem do problema aeroelástico foi realizada em ambiente Matlab®, onde o comportamento aerodinâmico,
modelado via DLM, foi acoplado ao comportamento estrutural modelado em elementos finitos (MEF). A presença
de material viscoelástico alterou a dinâmica do sistema através da adição de massa, rigidez e a presença do efeito
dissipativo inerente ao material. Houve aumento na frequência e velocidade crítica da vibração da placa tratada,
demonstrando numericamente a eficiência do tratamento viscoelástico na mitigação da instabilidade.

Wing Structural Optimization for Electric Distributed Propulsion Aircraft using Genetic Algorithm

Bruno Amaral de Oliveira, Hélio de Assis Pegado — Thu, 04 Jul 2024 00:00:00 +0000

The search for less polluting means of transport has been stimulating the development of batteries
with higher energy densities and electric motors that are more efficient. These advances have made possible the
emergence of several all-electric aircraft, which make use of multiple rotors. In this sense, there was a need to
create a methodology to be followed in the conceptual design phase, focused on aerodynamic and structural issues
that change in this type of aircraft. These changes, such as the lack of a Gravity Center shift and the need for a
greater number of engines and rotors, alters the spar, the aerodynamic flow, the number of ribs and the stiffness of
the wing itself. In this study, the engines are distributed along the wing, aiming greater traction and less variation
in the angle of attack along the wingspan. An aerodynamic model was created with these requirements, based on
the lift line theory, in order to calculate the flight load. Finally, using these values, employing routines of genetic
algorithms, the structure was optimized, adopting the spar geometry and thickness as design variables, with the
objective of minimizing weight, following the Tsai-Wu criterion and the impossibility of buckling.

Dynamic modeling of a liquid rocket engine turbo pump rotor

Sâmela Fernandes Pereira de Lima, Carlos d’Andrade Souto — Thu, 04 Jul 2024 00:00:00 +0000

Liquid propelled rocket engines present many advantages over its solid propelled counterpart: the
possibility of shutdown and re-ignition in flight and the fact that they are more efficient (greater specific
impulse). For these reasons, they are used in most satellite launching rockets. In a liquid propellant rocket
engine, the oxidizer and fuel must be injected under high pressure into the combustion chamber. This can be
achieved by using pressurized tanks. This solution is technologically simpler and less costly but significantly
limits the injection pressures of propellants. To obtain more powerful engines, propellants must be injected at
higher pressures into the combustion chamber. This is done using a turbo pump, a high-capacity pump powered
by a gas turbine. Turbo pumps operate at high angular speeds (tens of thousands of rpm) and undergo intense
dynamic loads in flight, in addition to the dynamic loads intrinsic to the operation of rotating machines.
Therefore, the dynamic behavior of this type of system must be evaluated at the design stage. In this work, the
transverse displacements of a turbo pump rotor are analyzed using routines developed in the numerical
computation software Octave. The mathematical model developed considers the rotor shaft flexible and rigid
disks. The axis is modeled using finite elements and point masses and inertias are used to represent the disks.
Campbell’s diagram, response to unbalance and forces applied on bearing are obtained. The influence of
bearings positioning on the rotor unbalance response is studied.

Impact of falling cables on bulkhead beams

Thu, 04 Jul 2024 00:00:00 +0000

In this work, 585.95 meters long falling cable will be analyze to compute its impact on a steel beam.
The beam is lifted by two cranes and used as a shield to protect structures under the cables, during its installation.
Using energy conservation concepts, it is possible to find the impact force on the beam, and with that, dimension
which is the ideal metallic profile to support such impact. A model was also developed using the STRAP software,
via Finite Element Method, to perform a more refined analyze and check the design of the metal beam.

Regulador Linear Quadrático iterativo para Controle de Atitude de um Quadricóptero

Iago S. Vieira, Aniel S. Morais — Thu, 04 Jul 2024 00:00:00 +0000

The quadrirotor is an aircraft which has a vertical takeoff and landing. Due to the mechanical simplicity
many papers have been published recently, proposing numeric methods to increase the reliability on flights. This
work presents the development of a dynamic model of a quadcopter that was obtained from the Newton-Euler
formalism and also the development of a control system using iLQR (iteractive Linear Quadratic Regulator) with
a time variant system considering the gyroscopic effect generated by the angular velocity from the frame. The
method must be able to stabilize and act on the trajectory compliance of a quadcopter. The model was built in
SolidWors to extract the moments of inertia required for the mathematical model and the prototype was built by
hand using aluminum profiles and brushless motors A simulation was developed on the MATLAB®️ platform from
the model obtained to check the proposed control, and then analyze the experimental flights, where the
simplifications on the mathematical model will be verified..

Nonlinear Receding Horizon Guidance of a Thrust-Vectoring Quadrotor Under Control Allocation Constraints

Jose Agnelo Bezerra, Davi A. Santos — Thu, 04 Jul 2024 00:00:00 +0000

The present work deals with the guidance of a pre-stabilized thrust-vectoring quadrotor, which is re-
quired to be steered from its initial condition to a given state-based wayset. To tackle this problem, we adopt a

receding horizon strategy based on a constrained nonlinear programming, whose crucial constraints are the control
mapping equation and the actuator limits. The online optimization solution is calculated using sequential quadratic
programming. The proposed method is evaluated using computer simulation, which shows its effectiveness.

Attitude Tracking Control for a Quadrotor Aerial Robot Using Adaptive Sliding Modes

Jorge A. Ricardo Jr, Davi A. Santos, Tiago Roux de Oliveira — Thu, 04 Jul 2024 00:00:00 +0000

This work is concerned with the design and analysis of the attitude control law for a quadrotor aerial
vehicle, under bounded external disturbances and model uncertainties with unknown bounds. First, the vehicle

rotational kinematics and dynamics are modeled in terms of well-defined Gibbs vector and angular velocity rep-
resenting the control errors. To tackle the problem, we propose a first-order multi-input adaptive sliding mode

control strategy based on an adaptation law for the switching gain matrix. This adaptive gain matrix is proved

to converge to its maximum bound and the existence of an ideal sliding mode is guaranteed. The main contribu-
tions are: 1) the geometric dynamic modeling in SO(3) for the attitude control error using Gibbs vector; and 2)

the extension of a switching gain adaptation law originally proposed for single-input systems to a more general
multi-input formulation. The method is evaluated by numerical simulations, using IMAV-M, which is a recently
deployed open-source flight control simulator for multirotor aerial vehicles (MAVs). In an ideal scenario, without
measurement noise (or estimation errors) and small sampling time, the method shows to be effective and easy to
implement and tune.

Adaptive Universal Integral Regulator For Flight Control - A Preliminary Study

Thu, 04 Jul 2024 00:00:00 +0000

This article proposes a new treatment for the design of the Universal Integral Regulator (UIR). The UIR
is a non-linear control technique based on sliding mode control with the inclusion of a Conditional Integrator (CI).
The main tuned gain of this control law is constant in the original approach, in the present work we propose to make
this gain dependent on the tracking error (adaptive gain). The performance of this change will be demonstrated in
a flight control case, performance indexes will allow to quantitatively compare its performance with the original
one. Simulations results show a superior performance of the UIR after the proposed gain modification, called at
this work as Adaptive UIR (AUIR)

Influência da Flambagem Termomecânica na Otimização de Rotas de Dutos Submarinos

Thu, 04 Jul 2024 00:00:00 +0000

The planning of subsea pipeline routes has great relevance for exploration and production projects,
as they ensure a safety operation of subsea systems. With the advance of oil exploration in deep and ultra-deep
waters, which means a rise in the operation severity, where the equipment works in an environmental with high
pressure and temperature levels. These factors can lead the large vertical or lateral displacement in the pipeline
initial condition (as laid), that is because the temperature variations leading to the occurrence of the phenomenon
of thermomechanical buckling. The aim of this work is to study the weight of buckling in pipelines submitted by
HT / HP (high temperature / high pressure) flow in the penalty criteria on submarine pipeline route synthesis and
optimization tools, using evolutionary algorithms. In ways to do a better representation of buckling, the pipelines
are assumed laid on the seabed, subjected to environmental loading as current and passive soil resistance due
the soil mobilization around the pipe, with or without thermal coating, and also with a hot internal fluid. Once the
classic formulation of pipeline buckling proposed by Hobbs is based in an infinite rigid soil, in this work a modified
Hobbs formulation is considered, so this secure that the resistance and all intrinsic penetration soil properties are
represented. Thus, a safety factor indicated in the practical recommendation of DNV-OS-F101 and DNV-RP-F110
is calculated and compared with the limit safety factor pre-established in the project. With the results obtained
by the pipeline section defined in the project, a depth profile graph is generated showing the critical sections
considering the buckling. In this way, the tool assists the designer in the assessment of submarine pipeline routes
considering thermomechanical criteria and environmental factors.

Evaluation of Composite Hull for Subsea Separator

Thu, 04 Jul 2024 00:00:00 +0000

The subsea separator is one of the most important equipment to subsea processing, since it is responsible
for separating the fluids extracted from the reservoir. The separation module may be composed by injection bombs
and several other equipment, besides the separator tank, which makes it a huge structure. Since it is made of steel,
the separator hull is extremely heavy and expensive, requiring very specific and expensive crane vessels for
installation. Composite materials made of polymeric resins and fibers usually have very low density compared to
steel, good mechanical properties, which make them a feasible alternative to weight reduction without losing
structural safety. Therefore, it is important to evaluate its mechanical properties under the operational conditions
to validate the proposed application. This work evaluated salt water absorption of composite plates under
conditions of 3000 psi of external pressure and temperature of 4oC. Tensile and shear tests were performed to
assess the influence of water absorption on the resistance and elastic and shear moduli of the material. A numerical
model was also developed to evaluate the behavior of the structure under different levels of external pressure and
to compare a metallic with a composite hull. It was possible to conclude that the absorption did not cause
significant changes on the elastic and shear moduli nor on the tensile strength of the material. In addition, the
numerical results showed that, for the same external pressure, the composite hull has a thicker wall and a lower
mass when compared with a metallic one.

Design and fatigue assessment of gravity base foundations for offshore wind turbines

Gabriel Nogueira, Fellipe A. Gomes, Eduardo Dorscheidt, Gilberto B. Ellwanger — Thu, 04 Jul 2024 00:00:00 +0000

In this work, a gravity base foundation (GBF) was designed to support the DTU’s 10 MW wind turbine.
Recently, the industry is considering GBFs as a potential solution to the difficulties of driving monopile
foundations in certain types of soil. Also, checking their feasibility in greater water depths is a pivotal question
since these concrete structures might be cheaper than the steel monopile alternative. Thus, in a 40 meters water
depth, the proposed model is checked for its geotechnical capacity and the resistance of critical points under
extreme loads. The foundation is designed with a natural frequency that avoids excessive fatigue damage due to
the action of Brazilian environmental loads and rotor operation frequencies. This paper discusses the most
influential factors in these analyses. Palmgren-Miner rule assessed the fatigue damage in association with the
widely employed S-N curves for concrete. SIMA-RIFLEX’s dynamic analysis module generated the stress time
series. Rainflow method, combined with the Markov matrix, is utilized for counting stress cycles.

Numerical model for analysis of the load attenuation on mooring lines in catenary system

Eduardo. G. Rosa, Marcelo. M Rocha — Thu, 04 Jul 2024 00:00:00 +0000

With the advancement of oil exploration at greater depths, the solution to maintain offshore platforms
in place has changed from a traditional rigid system to a flexible system formed by mooring lines. Usually, a
mooring line consists of an anchor chain attached to the floating unit in the upper end and the anchor or foundation
element at the lower end, which implies that, along its length, the chain is not only submerged in water but also
embedded in soil. Experimental investigations conducted on reduced scale have shown that the load applied at the

embedment point located on the seabed surface does not reach the same magnitude at the anchoring point. The so-
called “load attenuation” is related to the inverse catenary shape developed by the mooring line embedded in the

soil, providing a transversal reaction force and longitudinal friction force in the soil-chain interface. In order to
evaluate the problem from a numerical point of view, an initial 3D finite element model of the anchor chain
embedded in marine soil was built in the ANSYS software. As a starting point, the anchor chain behavior is adopted
as elastic, the soil is considered perfect elastoplastic with Drucker-Prager yield criterion and the contact interface
is simulated by Coulomb’s law of friction. The load attenuation levels obtained for several cases are compared to
reference results, both experimental and numerical, and the stress disturbance in soil is presented in terms of von
Mises equivalent stress.

UNVEILING PATTERNS IN THE INTERACTION BETWEEN RISERS AND SEABED

Edgar Stonyo B. Micolo, Anderson Barata Custódio — Thu, 04 Jul 2024 00:00:00 +0000

Risers play an important role in offshore production systems by conveying oil, gas and other fluids from
subsea wells to floating production units (FPU) or vice versa. Free hanging (catenary) risers using flexible pipes
have been the most conventional configuration in Brazilian production assets, but the participation of steel catenary
risers has long been fostered by oil companies and their technological partners. The most challenging sections of
free hanging risers are the vicinity of their top end and the touchdown zone (TDZ). This investigation focuses on
the latter section, by examining the static interaction between riser and seabed, which is described by Skempton’s
backbone curve. Besides the external pressure and possible wall compression, the curvatures often impose the
strongest constraints to the riser design space. Parametric studies using finite element methods, non-dimensional
analysis and statistics seem to be promising route to assess the riser response. The results documented herein are
limited to static response with no marine current or wave loads, focusing on the maximum curvature along the
TDZ, and they supply zero-order approximations to studies which aim at describing the dynamic response using
asymptotic approximation techniques.

Fatigue analysis of gravity-based foundation supporting a 10 MW OWT considering small-strain stiffness of soils

Eduardo Dorscheidt, Fellipe A. Gomes, Gabriel Nogueira, Gilberto B. Ellwanger — Thu, 04 Jul 2024 00:00:00 +0000

In the past few years, gravity-based foundations (GBF) proved to be an advantageous solution for
supporting offshore wind turbines (OWT) when soil conditions represent a hindrance to deep foundations as
monopiles. In this type of support structure, soil-structure interaction (SSI) interferes directly in system stiffness.
The available standard formulations are still based on the Theory of Elasticity and do not contemplate some soil
properties, as its hardening effects when subjected to plastification. This paper aimed to investigate the influence
of an elasto-plastic soil model such as HSS (Hardening Soil with Small-Strain Stiffness) in a coupled fatigue
analysis of concrete, a critical point of GBF structural design, considering a 10 MW OWT. The results of the
proposed analysis showed low influence of small-strain stiffness, but a significant role of plasticity and hardening
effects.

Post-failure behavior of long wires under dynamic pulse buckling

Thu, 04 Jul 2024 00:00:00 +0000

The phenomenon of dynamic pulse buckling, which can appear with the failure of long slender structures
under tension, as offshore structures such as risers, has drawn the attention of the interest of researchers due
to accidents and the damage they can cause to the environment. The risers connect floating units to flowlines
and other equipment on the seabed and are used for drilling and exploration of oil and gas. Experimental and
numerical researches have been conducted in reduced wire models to study post-failure behavior, mainly after the
compressive elastic unloading wave reaches the fixed end, being reflected and giving rise to a buckling located
near this end. This work addresses the finite element modeling and simulation of dynamic pulse buckling in
wire failure tests. An elastoplastic model with linear hardening is adopted for the material behavior. Explicit and
implicit integration algorithms are used for nonlinear dynamic analysis considering 2D and 3D beam elements with
large displacements and strains. The effects of the finite element type, mesh discretization, integration algorithm,
geometric imperfections, numerical damping, wire length, and time step in the post-failure behavior are assessed
and the implications of these results for the simulation of post-failure analysis of marine risers are discussed.

USING METAMODELS TO PREDICT CUTTING FORCES IN BOP

Nikolas Lukin, Larissa Driemeier — Thu, 04 Jul 2024 00:00:00 +0000

Cutting drill string inside BOP (BlowOut Preventer) may be required if Dynamic Positioning System
fails to maintain an offshore drilling platform at a fixed point in the ocean. The required force to cut the string is
traditionally determined by analytical models and commissioning tests, which can be far from the real situations.
Depending on boundary conditions of this tubular, the BOP may fail to cut it, which can lead to catastrophic events.
In this way, the proposed work aims to define a metamodel to predict required forces for BOP to cut API S-135
6.63’’ 40.87 ppf drill pipes, with different boundary conditions. Simulations were performed using FEM, with
material and failure modelled according to Johnson-Cook model (1986), with parameters obtained from literature.
Different simulations in combined conditions, including initial traction and torque, pipe decentralization and ram
offsetting, were performed in order to find the required force in indentator to cut the pipe. Such data were used to
develop a metamodel using feed a machine learning algorithm and its results were validated with real test data.
Situations with more realistic boundary conditions concludes that current BOP cutting models may underestimate
the required force.

Investigation of Soil Effects on the Fatigue Behaviour of an Offshore Wind Turbine

Fellipe A. Gomes, Gilberto B. Ellwanger, Jose R. M. de Sousa — Thu, 04 Jul 2024 00:00:00 +0000

Fatigue is a governing limit state for the design of an offshore wind turbine (OWT). The fatigue loads
are not only strongly dependent on the action of waves and wind but also on the site-specific soil properties. The
present article is aimed at investigating the effects of cohesive and non-cohesive soils on the fatigue damage of
a monopile foundation in water depth of 20 meters, using SIMA-RIFLEX for coupled aero-hydro-servo-elastic
simulations and TurbSim for spatio-temporal stochastic wind speed generation. The turbine model is based on the
5-MW reference wind turbine described by NREL (National Renewable Energy Laboratory) and the soil-structure
interaction is simulated by applying p-y curves proposed by API-RP-2GEO (2011) and DNVGL-ST-0126 (2016).
Fatigue damage is estimated with use of rainflow counting (RFC) method, which is used in combination with
Palmgreen-Miner rule and S-N curve proposed by DNVGL-RP-C203 (2016). It was identified that, depending on
the soil type, the degree of fatigue damage can vary as well as the critical region along the monopile.

NUMERICAL ANALYSIS USING DIFFERENT LEVELS OF COMPLEXITY AND DETERMINATION OF ULTIMATE LIMIT STATE FOR RISER CONNECTION DEVICE

Bruno C. Vieceli, Filipe P. Geiger, Ignacio Iturrioz — Thu, 04 Jul 2024 00:00:00 +0000

In this work, it is presented two methodologies to analyze the Ultimate Limit State (ULS) of a
commonly adopted riser connection device named bell mouth (used to decrease the loads that cause excessive
bending in the riser) as well as numerical models of said structure, which are compared to a benchmark model.
The assessment of the ULS is performed by a standard applicable to steel structures (but not offshore structures)
with two different approaches – a traditional one and a, not commonly used, hybrid methodology. The numerical
models employ the Finite Element Method with different levels of complexity considered, including elastoplastic
behavior, finite deformations and contact formulations (between the bell mouth and cap). Results show an good
agreement between the two different ULS approaches. The numerical models provide acceptable similarity with
the benchmark model, given its simplicity and low computational cost. It is concluded that the combination of
both ULS and numerical analysis may bring a good first iteration in the bell mouth design process.

TOWARDS A METHODOLOGY FOR THE OPTIMAL DETERMINATION OF SAFE OPERATIONAL REGIONS FOR OFFSHORE DRILLING OPERATIONS

Thu, 04 Jul 2024 00:00:00 +0000

Na industria para a produc ̧ ́ ao de ̃ oleo ́ offshore, o projeto do sistema de perfurac ̧ao e completac ̧ ̃ ao de ̃
poc ̧os atraves de Unidades M ́ oveis para Perfurac ̧ ́ ao ̃ Offshore (MODU – do inglesˆ Mobile Offshore Drilling Units)
normalmente envolve analises computacionais baseadas em simulac ̧ ́ oes num ̃ ericas. Um desses tipos de an ́ alise, ́
conhecida como “analise de operabilidade”, tem como objetivo indicar a regi ́ ao segura e oper ̃ avel para o sistema, ́
com base na avaliac ̧ao de um conjunto de crit ̃ erios a serem atendidos durante a operac ̧ ́ ao. A an ̃ alise considera um ́
conjunto de posic ̧oes que o equipamento pode assumir durante a atividade, sob um conjunto de valores de pr ̃ e- ́
trac ̧ao no ̃ riser. Cada posic ̧ao assumida sob cada trac ̧ ̃ ao no ̃ riser, que pode chegar a centenas ou milhares, requer
a simulac ̧ao do comportamento do sistema para avaliac ̧ ̃ ao dos crit ̃ erios. Desta forma, uma das caracter ́ ́ısticas da
analise de operabilidade ́ e o seu alto custo computacional. Com o objetivo de reduzir o custo computacional, este ́
trabalho propoe uma estrat ̃ egia para reduzir o n ́ umero total de avaliac ̧ ́ oes necess ̃ arias para encontrar os limites da ́
regiao oper ̃ avel, empregando o m ́ etodo da bissec ̧ ́ ao para selecionar as simulac ̧ ̃ oes a serem executadas com base ̃
nos resultados obtidos de simulac ̧oes anteriores. ̃

POST-FAILURE SIMULATION OF LAZY-WAVE RISERS

Thu, 04 Jul 2024 00:00:00 +0000

Even with great advances in methods for analysis and design of marine risers, structures still fail,
resulting in their rupture and fall on the seabed. The fall can cause high environmental and economic costs,
compromising the lifespan of other neighboring structures, such as other risers, anchoring systems, and submarine
equipment. Therefore, this work aims to study the fall of flexible lazy-wave risers. The influence of the integration
algorithm and the time step in the accuracy and efficiency will be studied, as this work deals with the computational
modeling of the post-failure phenomenon, focusing at describing an effective way of assessing the fall trajectory,
fall time, and the riser accommodation on the seabed. These are important outputs to better understand the fall
phenomenon, generating important results aiming at mitigating damage in the case of accidents in future riser
projects.

CASE STUDY ANALYSIS OF A PELAMIS WAVE-ENERGY CONVERTER

Thu, 04 Jul 2024 00:00:00 +0000

Having in mind the objectives defined by the UN 2030 agenda, researches such as those resulting from
the ondomotriz principle grew in importance. Therefore, this work aims to evaluate the potential energy conversion
provided by a Pelamis device in a study case for Rio Grande - RS. The development of the research is made through
parameterized numerical simulations, which were performed using ANSYS AQWA software. Specific issues were
necessary about verification of mesh refining convergence, time step definition and application of monochrome
waves belonging to the study area sea state. Relative to the anchorage system, the catenaries composition was
determined through an iterative routine using the MATLAB software. The simulations returned data about the
movement of the cylinders, which were processed in MATLAB aiming to quantify, plot and evaluate the rotation
in the joint between the cylinders. Thus, the stability of the mechanism and the possible power generation potential
is evaluated. The study demonstrates an important relationship between the structure length and the wavelength.
Finally, from the analysis of the results, the study suggests the best parameters combination for the researched
location.

Application of fuzzy logic for stuck pipe prevention purposes on oil wells drilling operations

Victor S. M. Siqueira, Marco A. S. L. Cuadros, Gustavo M. Almeida — Thu, 04 Jul 2024 00:00:00 +0000

The drilling of oil wells represents one of the most challenging activities in the oil and gas industry. In
an environment surrounded by uncertainties, one of the most common problems is the stuck pipe, which results in
increases in the cost of building the well and in non-productive time. Considering that factors such as safety and
costs are directly related to the decisions made during operations, the adoption of tools that help the operator to
make the best decisions is highly desirable. In addition, the large amount of information available to the operator
requires its due analysis in real time in order to offer the diagnosis of anomalies. Artificial intelligence techniques
such as artificial neural networks, decision trees and support vector machines have been used to detect stuck pipe.
These strategies, however, have efficiency conditioned to the specific characteristics of the available data set.
Alternatively, this work presents an algorithm for preventing stuck pipe using fuzzy logic. Throughout the paper,
the stuck pipe problem and its impacts will be presented, the characteristics of fuzzy logic and its application to
the case under study, the results obtained from the application to an oil well data and, finally, the job conclusions.

Comparison between empirical forecast methods of resistance to advance and propulsive design of a container ship

Huascar B. Feijó, Jasmim L. C. de Oliveira — Thu, 04 Jul 2024 00:00:00 +0000

Estimating the resistance to advancement and the necessary power of ships ́ engines has a vital
importance in the design and construction of any marine vehicle. However, performing this task is not simple and
can be done by different methods. So far, the main ways of predicting ship dragging are restricted to computational
fluid dynamics methods (CFD), testing on ship models (small scale), and systematic series. The series, in turn, are
empirical approaches originating from tests performed systematically on model ships. In order to verify the
applicability of these series, this study presents a comparison between the approach proposed by Holtrop and
Mennen and the method proposed by Hollenbach. For this, a container ship was subjected to both methods and the
expected resistance values were compared. The second stage of this work consists of the optimization of the
propulsive system using the Microsoft Excel Solver tool, which allowed to find parameters in their ideal forms,
such as: propeller rotation and maximum propeller efficiency. The Wageningen B-Series propeller series was used
in this last stage.

Prediction of dynamic response in a cantilever beam using a smoothed version of the experimental modal matrix

Thu, 04 Jul 2024 00:00:00 +0000

It is not economically viable, nor technically interesting the installation of accelerometers in all locations
of interest in a given machine or structure. To estimate vibration responses in non-instrumented locations, a
smoothed and expanded version of the experimental modal matrix can be employed. For this, a finite element
model and operational modal analysis can be used. In this work, we used a smoothed version of the experimental
modal matrix of a cantilever rectangular aluminum beam, to estimate vibration responses. Impact test and the
EFDD method were used for modal parameter identification. The SEREP reduction technique was used to match
numerical DOFs with the measured ones. Then, the local correspondence principle (LC) was used to smooth the
measured DOFs in the experimental modal matrix. Finally, the smoothed version of the experimental modal matrix
was used to estimate the acceleration signal in DOF no.5 and results showed high accuracy between the measured
and the estimated signals.

Theoretical-Experimental Analysis of Corrosion-Cracking Coupling in Reinforced Concrete Structures

Samanta A. Klering, Thiago A. Bertuzzo, Edna Possan, Julio Flórez-López — Thu, 04 Jul 2024 00:00:00 +0000

The corrosive process is not a recent problem, however, even nowadays it is one of the most common
problems on reinforced concrete structures, whether by execution inconveniences, by the high relation
water/cement of concrete or even by the negligence in the project stage of consideration of an adequate covering
which attends the corresponding aggressiveness of the class. Therefore, the previous determination of the evolution
of the corrosion along time shows itself as an allied tool in the reduction of costs with maintenance and/or repairs.
In this context, the following paper aimed to identify experimentally, in beams, the influence of the corrosion
evolution by chloride ions in the advance of degradation from the elements of reinforced concrete. A process of
acceleration of the corrosion was used through the sprinkling of a sodium chloride solution (NaCl) via a sprayer,
simulating the effect of wetting/drying in the breams. Simultaneously, the beams were under mechanic
solicitations, so as the experiment advanced the deflections, cracking and especially the corrosion potential in the
rebars were evaluated. Later, after this identification, the experimental analysis was combined with thermodynamic
models based on the Lumped Damage Mechanics to analyze reinforced concrete structures that are subject to
chemical action in addition to mechanical stresses. It was found that all beams subjected to the spraying of
chlorides showed a greater than 90% probability of being under corrosion and the highest values of corrosion
potential were concentrated in the central region of the beam, where the damage was also higher. Furthermore, the
presence of corrosion increased the values of damage and plastic rotations in the beams, and this increase, in turn,
contributed to the increase in corrosion rates. However, the presence of moisture due to the NaCl solution affected
the creep and consequently, the displacements suffered over time.

Using Multivariate Energy Distance on Frequency-based Damage Detection

Horacio V. Duarte, Lázaro V. Donadon — Thu, 04 Jul 2024 00:00:00 +0000

The Frequency-based Damage Detection Method using FRFs (Frequency Response Functions)
in a high-frequency range can identify a structural failure of about 0.16% and 0.34% of the total mass.
These results demonstrate the effectiveness and reliability of the method to track the problem in its

initial stage. The Robust Singular Value Decomposition algorithm (RSVD) is employed in Frequency-
based Damage Detection Method to find out a damaged subset from a set composed by reference and

damaged data. Although effective, this procedure has some drawbacks, it is time consuming and the
method performance is linked to optimum singular value basis reduction. The main objective of this
work is to select an algorithm to overcome these less acceptable features. In order to achieve this goal
there are a short review of the main methods employed in data classification, parameter extraction. The
selection criteria is to pick out those that present simple algorithms and that are based on metric distances.
From those review the Multivariate Energy Distance Correlation was selected. Using experimental data
this Energy statistic method are compared with Robust Singular Value Decomposition (RSVD).

Application of low-cost instrumentation and output-only modal identification techniques for the structural health monitoring of mechanical systems

Sidney Bruce Shiki, Vitor Ramos Franco — Thu, 04 Jul 2024 00:00:00 +0000

Monitoring systems are becoming more relevant to maintain the structural integrity of engineering
structures. Structural Health Monitoring (SHM) tools are getting even more important nowadays due to the need
of sustainable long-living structures. However, it is safe to say that the large costs involved on the hardware and

sensors used to apply SHM techniques are prohibitive for a large scale adoption of these tools. With the populariza-
tion of fast prototyping electronic platforms and MEMS sensors, new opportunities are showing up for industrial

applications. In this paper, an Arduino Mega 2560 board was used with ADXL335 vibration sensors in order to
monitor the structural state of a simple benchmark structure representing a two-storey building. The frequency
domain decomposition (FDD) was used to extract the mode shapes and natural frequencies of the structure by

measuring the accelerations in different locations. Damage indexes based on natural frequencies revealed the pres-
ence of the damage and its propagation. The results showed the viability of using low-cost instrumentation and

output-only modal identification techniques as alternative for the SHM of simple mechanical structures.

DAMAGE DETECTION IN SIMPLE SUPPORTED PIPE CONVEYING FLUID USING AN ADDITIONAL MOVING MASS

Thu, 04 Jul 2024 00:00:00 +0000

This paper investigated the dynamic behavior a cracked simple supported pipe conveying fluid due to
the application of an additional roving mass along the structure. First, a difference finite model of a simple
supported Euler-Bernoulli beam conveying fluid experimental was developed to obtain natural frequencies of
damped modal analysis. The results are compared to literature. In addition, the frequency shift technique is applied
for an undamaged simple support pipe conveying fluid. Last, it was identified a cracked simple supported pipe
using a frequency shift technique for different fluid velocity.

Desenvolvimento de aplicativo para um sistema de manutenção de pontes de aço

Verissa P. M. Queiroz, Gabriel V. Santos, Elisa D. Sotelino — Thu, 04 Jul 2024 00:00:00 +0000

Highway bridges are structures subject to fatigue and corrosion effects. In this sense, this work aims to
develop a steel bridge maintenance system tool based on the use of a neural network model and a reliability
analysis, using languages such as Python, HTML, CSS and Javascript. The system prototype considers the
corrosion-fatigue effects and some maintenance activities to estimate the structure’s lifetime. According to the
simulations carried out on a steel bridge designed according to the AASHTO American code, it was found that the
increase in the traffic volume and in its growth rate can cause a reduction of up to 66% in the structure’s lifetime,
while the presence of maintenance activities can increase its lifetime by up to 71% depending on the traffic
parameters.

SSI-COV method applied to ambient vibrations of a concrete block of a dam: Uncertainty of modal parameters

Yeny V. Ardila, Ivan D. Gómez, Jesus D. Villalba, Luis A. Aracayo — Thu, 04 Jul 2024 00:00:00 +0000

Due to advances and automation in operational modal analysis (OMA) methods, it is possible to extract
modal parameters (natural frequencies, damping ratios and vibration modes) in a quick and easy way solely from
data collected during operation. However, one of the shortcomings of these methods lies in the assessment of the
accuracy of the information obtained. In this work, the uncertainty in the identified modal data is quantified by
calculating confidence intervals using the Bootstrap technique. The modal parameters of a concrete block of a dam
are identified through the application of the SSI-COV method to acceleration measurements from a triaxial sensor
installed in the block. Then, the bootstrap technique is applied and a comparison is made between three common
methods of resampling the time series based on nonrandom as well as random block lengths.

Application of peridynamics in the simulation of acoustic emission in quasi-brittle materials

Pricila Cottica, Leandro Friedrich, Ederli Marangon, Ignacio Iturrioz — Thu, 04 Jul 2024 00:00:00 +0000

The acoustic emission (AE) technique consists in capturing the internal mechanical waves produced by
materials due to changes such as chemical reactions, cracks, dislocations, among others, that propagates for the
surfaces of the structure and are captured by sensors distributed on these surfaces generating the AE events. This
methodology has been used to monitor the damage of real structures, allowing predicting when an event of greater
magnitude could mean the imminence of a total or partial collapse. In addition, the technique of acoustic emission
allows extracting information from structures formed by quasi-brittle materials where the succession of
instabilities has a pattern of behavior can be established. The interpretation of acoustic emission tests is not trivial
and the simulation of this type of test can complement the information about the experimental test performed.
Aligned with the topic mentioned here, in the present work, an acoustic emission test on concrete specimens is
simulated. To perform the numerical simulations, a version of the discrete element method called peridynamics
was used. The results show that the peridynamic theory is a powerful tool and can be used to help in the planning
and interpretation of experimental results from the monitoring of structures.

Optimization of the concrete material parameters in numerical simulation of RC beams under shear failure by artificial neural networks

Thu, 04 Jul 2024 00:00:00 +0000

Three-dimensional nonlinear constitutive models for reinforced concrete (RC) often require an
extensive number of material parameters. Some of these are evaluated through experimental tests, but most of
them are estimated from empirical or semi-empirical expressions. The inherent limitations of representing real
structures with mathematical models may introduce different constraints on the parameter calibrations that
originally adjusted those expressions. That is one of the main reasons that lead to divergences between nonlinear
finite element analysis (NLFEA) and reliable experimental data. In this study, we employ a method that adopts an
artificial neural network (ANN) and Levenberg-Marquatd backpropagation method for calibrating material
parameters in a numerical model of an RC member. The simulated experiment is an RC beam under a three-point
bending scheme with shear failure. Finite element computations are carried out in ATENA software, and the goal
of the calibration is to find the best adjustment of the experimental load-deflection curve at the center of the beam.
The algorithm shows an excellent capability to fit the numerical curves, and it successfully automates a task that
customarily would take several analyses and trial-and-error process to achieve the best fitting.

Numerical analysis of the influence of welding speed on cylindrical pressure vessels

Fernanda F. Santos — Thu, 04 Jul 2024 00:00:00 +0000

This work aims to determine the residual stresses of cylindrical pressure vessels subjected to weld
repairs via numerical analysis . In welding repair , a glove is attached to the pressure vessel through two
longitudinal welds and two circumferential welds . Was performa modeling of the pressure vessels , the repair and
the welds acoording to the standart . The parameters of the weld bead will be adopted on the basis of what happens
in practice , and this will be done the analyzes of the residual stresses varying the speed of the weld bead . From
this , will be analyzes the residual stresses in the regions of the weld to verify the behavior of the results after the
cooling period by the Finite Element Method .

A model-based damage detection approach using genetic algorithm optimization

Thu, 04 Jul 2024 00:00:00 +0000

The identification of structural damages based on numerical model updating has been of increasing
interest in several areas of engineering, and basically consists on an optimization process relying on the
minimization of the residuals between the measured and estimated numerical responses. Most of the existing
studies using this methodology are applied to simple structures such as beams, frames and trusses, existing a scarce
of studies applied to large and complex structures. In this context, this article aims to evaluate the performance of
this methodology using genetic algorithms with application to a case study of a real railway bridge, to assess its
performance when applied to complex and large-scale structures. The results obtained proved the reliability of the
proposed methodology in detecting, locating and quantify multiple damages, with a considerable number of
updating parameters and scarce number of target responses.

Sistema de medição de deslocamentos com recurso a veículos aéreos não tripulados

R. Cabral, D. Ribeiro, A. Mourão, J. Correia, R. Calçada — Thu, 04 Jul 2024 00:00:00 +0000

Este artigo descreve uma metodologia inovadora para estimar deslocamentos em estruturas de Engenha-
ria Civil baseadas em sistemas de vídeo integrados em Veículos Aéreos Não Tripulados (VANTs). Dado que a

estrutura e o VANT estão ambos em movimento, a estimativa dos deslocamentos envolve, inicialmente, a avalia-
ção dos deslocamentos relativos entre o VANT e a estrutura, com base no rastreio de um alvo, e, posteriormente,

na compensação dos movimentos VANT com base nos dados de uma Unidade de Medição Inercial (IMU). Para o
efeito, foram desenvolvidas ferramentas de processamento heurístico de imagem para o rastreio do alvo, para além
da implementação de uma estratégia de integração numérica para o processamento de dados da IMU. A validação
da metodologia baseou-se em um teste dinâmico exploratório realizados em campo. A metodologia desenvolvida
demonstrou eficiência e robustez na estimativa de deslocamentos absolutos e com potencial de integração em
sistemas de monitorização da integridade estrutural (SHM).

Damage Models for Micromorphic Continuum

Pamela D. Nogueira, Roque L. S. Pitangueira, Leandro L. Silva — Thu, 04 Jul 2024 00:00:00 +0000

Numerous materials, although they appear macroscopically homogeneous, usually present a heteroge-
neous microstructure that directly influences the structural behavior. The phenomenological approach followed by

the classical continuum mechanics does not individually accounts for this influence, which can be significant, for
example, in cases where the structure or the specimen under analysis is small compared to its microstructure or
when the material media has a complex microstructure. Within the framework of continuum mechanics, so-called

generalized continuum theories are particularly suited to deal with the above issues incorporating the microstruc-
tural behavior on the formulation. The micromorphic theory is included in this general class of generalized con-
tinua and, more specifically, in the group that incorporates additional degrees of freedom to the material particles.

Another aspect of generalized continua is its ability to address the issue of localization in quasi-brittle materials
modeled as elastic-degrading media as a result of its non-local character. In order to allow the representation of
quasi-brittle media with the micromorphic continuum theory, this work presents a formulation for scalar-isotropic

damage models for a micromorphic continuum in the constitutive models framework of the INSANE system, ini-
tially conceived for classical media and later expanded for the micropolar continuum. This implementation is based

on the tensorial format of a unified constitutive models formulation and homogenization techniques to obtain the
micromorphic constitutive relations.

ESTUDO DA INFLUÊNCIA DA VARIAÇÃO DA FRAÇÃO VOLUMÉTRICA DA INCLUSÃO NO COMPORTAMENTO ELÁSTICO DAS PROPRIEDADES MECÂNICAS DE UM COMPÓSITO DE INCLUSÃO ESFÉRICA POR MEIO DO SWIFTCOMP ACOPLADO A UM SOFTWARE DE ELEMENTOS FINITOS

Thu, 04 Jul 2024 00:00:00 +0000

Análises multiescala foram realizadas com o auxílio do ANSYS e do SwiftComp, este último trabalha
com o conceito de Mecânica das Estruturas Genoma (MEG), proposta por Wenbin Yu e trata-se de uma abordagem
unificada para determinação de modelos constitutivos para estruturas 3D, vigas, placas e cascas, em diversos níveis
de escala. Esta técnica é baseada no conceito de genoma da estrutura (SG) e possibilita a união da análise
micromecânica de uma determinada microestrutura à análise estrutural de uma estrutura macroscópica. Almeida e
Lourenço (2019) publicaram o primeiro artigo sobre a técnica da Mecânica das Estruturas Genoma (MEG) em
língua portuguesa onde os mesmos utilizaram a MEG para homogeneização elástica de alvenaria. Definimos um
SG de um compósito com inclusão esférica de Carbeto de silício e matriz de alumínio. Houve variação da fração
volumétrica da inclusão, em um intervalo de 0% a 20%, a fim de verificar o comportamento elástico das
propriedades mecânicas. Frações volumétricas maiores tornaram o material mais rígido, ou seja, com o aumento
da fração volumétrica ocorria também um aumento no Módulo de Young. O módulo de elasticidade transversal
também apresentou comportamento crescente com a elevação dos níveis de fração volumétrica da inclusão. Com
relação ao coeficiente de Poisson, o aumento dessa fração volumétrica gerava um decrescimento nesta propriedade.
Os resultados obtidos com a simulação numérica foram comparados com outros adquiridos através da
micromecânica dos campos médios, apresentando conformidade entre ambas as técnicas.

Time-dependent effective behavior of jointed materials

Cássio B. Aguiar, Rodrigo Rossi, Samir Maghous — Thu, 04 Jul 2024 00:00:00 +0000

Inspections carried out on materials used in engineering often reveal the presence of discontinuities in
different shapes and scales. Discontinuities are one of the main forms of physical-mechanical degradation of the
material’s properties. More specifically, joints are a particular type of discontinuity whose geometry is plane and
have the mechanical capacity to transfer efforts along their opposite faces. Most works that aim to determine the
properties of jointed materials tend to neglect differed deformation components, which are fundamental in several
engineering fields. In this context, this work aims to propose a constitutive law that describes the effective behavior
of viscoelastic jointed materials, without disregard aging effects. Backed by laboratory tests, the joints are modeled
as interfaces whose mechanical behavior relates the stress vector to the displacement jumps on the joint’s faces.
Coupling the viscoelastic behavior of the constituents (solid matrix and joints) to micromechanical relationships,
the homogenized creep tensor was analytically formulated, being written as the creep tensor of the solid matrix
added to a fourth-order tensor related to the joints’ properties. Classic cases of rock mechanics are derived, which
show that particular distributions of joints families can cause anisotropy in the effective behavior of the material.

A study on the coefficients of thermal expansion of periodic unidirectional fiber reinforced composites

Eduardo N. Lages, Severino P. C. Marques — Thu, 04 Jul 2024 00:00:00 +0000

Composite materials have become an attractive alternative to traditional materials because of their
advantages of high strength and stiffness combined with low density, excellent durability, and design flexibility.
In many applications, the composites are subjected to temperature gradient that can produce critical thermal
stress or strain fields. Then, the coefficients of thermal expansion of fiber reinforced composites are very
important parameters for the design and analysis of composite structures. In this work, the effective coefficients
of thermal expansion of periodic unidirectional fiber reinforced composites are studied using a micromechanical
model based on the Levin’s formula. The necessary effective elastic properties of the composites are evaluated
through an analytical procedure based on the Eshelby equivalent inclusion method and expressed in terms of
Fourier series. Numerical examples involving thermal expansion of traditional advanced composites are
analyzed. The results provided by the model are compared with predictions obtained using finite element
procedures and analytical simplified methods, as well as available experimental data. These comparisons
demonstrate a very good performance of the presented micromechanical model.

Micromechanics Approach to the Effective Permeability of a Jointed Rock

Augusto Bopsin Borges, Samir Maghous — Thu, 04 Jul 2024 00:00:00 +0000

The use of macroscopic models in numerical approaches for studying subsurface flow has become
common practice in hydrogeology and petroleum engineering since the late 1960’s. Particularly in rock masses,
where the presence of joints constitutes a key weak point along which the mechanical, physical and hydraulic
properties of rock matrix degrade, the presence of discontinuities, at different scales, represent a fundamental
component of transport of fluid or contaminants through rock masses. However, one of the major questions that
still poses a problem is what parameters to introduce into the models. From a transport properties viewpoint, joints
within rock masses represent preferential channels for fluid flow and, as such, may be contributors to rapid transport
of fluid and contaminants through rock masses, particularly when the permeability of the rock matrix is low. This
article aims to present a micromechanical approach to the derivation of jointed rock permeability. Several examples
are present for different numbers of joint sets crosscutting rock masses, showing the flow anisotropy introduced by
their presence.

Estimation of absolute permeability in microCT images of highly heterogeneous carbonate rocks

Thu, 04 Jul 2024 00:00:00 +0000

Carbonates rocks contain more than 50% of the world’s oil prove reserves. Hence, to consider proper
strategies in oil recovery methods, the understanding of how fluid flows in such porous media has fundamental

importance. Advances in X-ray microCT enable us to retrieve not only most of the details of the internal struc-
ture of rocks, but also simulated petrophysical properties. However, one single microCT image can be unable to

sufficiently describe the wide range of pore sizes of carbonate rocks, specially the sub-resolution porosity (mi-
croporosity). To address this problem, we propose a study to assess the influence of the sub-resolution porosity

on the fluid-flow and in the intrinsic permeability values, obtained from carbonate core-plug subsamples microCT
images. Brinkman equation is used to model the fluid flow in the entire domain, covering the pores governed by
the Stokes equation and the regions of the microporosity governed by Darcy flow (solved using the Finite Volume

Method). Simulation results show that when connectivities among the voids are present and microporosity is con-
sidered, the value of permeability increases, but remains between the limits, i.e. when consider only the voids and

the microporosity as voids. Furthermore, when the pore connectivity place through a microporosity’s region, it has
an important role to estimate permeabilities.

Analysis of the elastoplastic behavior of porous microstructures under volumetric strains through a computational homogenization procedure

Wanderson F. Santos, Ayrton R. Ferreira, Sergio P. B. Proença — Thu, 04 Jul 2024 00:00:00 +0000

The rupture processes in ductile materials such as metals and alloys occur by concentration of plas-
tic strains around impurities in the microstructure. Therefore, the formulation of realistic constitutive models for

these materials requires consideration of the effects of this heterogeneity on the distribution of stresses and strains
at the microscale. These impurities are generally considered as voids due to the tendency of detaching from the
surrounding matrix during the deformation process towards rupture. Moreover, different simplifications of the
morphology of both void and matrix portion around it may imply different constitutive responses for identical load
situations. Constitutive responses of porous materials can be constructed through computational homogenization
procedure considering the behavior of representative volume elements (RVE). In this context, the present paper
examines three different geometric configurations of ductile porous media RVE’s subjected to volumetric strains.

The matrix of each RVE is considered to be perfectly elastoplastic undergoing small strains regimes. The homog-
enized constitutive responses of the RVEs are obtained by averaging the stress and strain fields computed by Finite

Element Method (FEM) analyses. The results hereby presented emphasize the determinant influence of the studied
morphologies on the constitutive responses as the load level approaches the rupture regime.

Análise comparativa entre modelos da micromecânica e valores experimentais das propriedades de materiais compósitos reforçados por fibras longas unidirecionais

Thu, 04 Jul 2024 00:00:00 +0000

Uma das limitações na aplicação dos materiais compósitos está na determinação com exatidão de suas
propriedades, devido, principalmente, às diversas variáveis consideradas nos procedimentos experimentais. Diante
disso, a análise micromecânica surge como forte aliada na elaboração de projetos que envolvam materiais
compósitos, servindo como estudo prévio e norteador. Este trabalho tem como objetivo realizar uma análise
comparativa entre valores teóricos obtidos através dos modelos da micromecânica e valores experimentais das
propriedades mecânicas efetivas de material compósito reforçado por fibras longas unidirecionais. Os modelos da
micromecânica estudados foram: Modelo baseado em Resistência dos Materiais, Modelo de Três Fases, Método

de Mori-Tanaka, Método Auto-Consistente e Esquema Diferencial (Eshelby) e Esquema Diferencial (Mori-
Tanaka). Para a realização da análise comparativa, os valores experimentais das propriedades mecânicas dos

compósitos e seus constituintes foram coletados na literatura. Foram construídos gráficos para o comportamento
das propriedades mecânicas do compósito em função da fração volumétrica de fibras e, posteriormente, foram
adicionados os correspondentes valores experimentais. A análise dos gráficos permitiu avaliar quais os modelos
que apresentaram as melhores aproximações em relação aos dados experimentais. Por fim, o artigo apresenta um
papel fundamental na produção do conhecimento acerca da análise micromecânica de materiais compósitos
reforçados por fibras longas unidirecionais.

QUANTIFICATION OF UNCERTAINTIES OF RANDOM DISCRETE VIBRA- TIONS SYSTEMS USING POLYNOMIAL CHAOS

Thu, 04 Jul 2024 00:00:00 +0000

The quantification of uncertainties consists in exploring how much the uncertainties in initial data
can propagate and change the final results. One of the most used methods is the Monte Carlo Simulation

Method. Despite it’s simplicity and versatility for engineering problems, this method presents high compu-
tational costs for complex problems, which might render it inapplicable. The Polynomial Chaos is an efficient

alternative for Monte Carlo Simulation Method because of its orthogonal properties and convergence. This

work approaches the quantification of uncertainties of discrete dynamic systems using generalized Polyno-
mial Chaos. The discrete system will be a general model of mass-spring-damper and the uncertainties will be

related to the initial conditions. This method will be validated by comparison with results obtained by Monte
Carlo Simulation.

Robust Optimization with Reliability Constraints considering Approximate Models

Jacqueline C. M. do Nascimento, Silvana M. B. Afonso, Renato S. Motta — Fri, 05 Jul 2024 00:00:00 +0000

Reliability-Based Robust Design Optimization (RBRDO), where random variables are statistically
treated, have been gaining space in practical engineering since it allows to compute the structural probability of
failure associated with a design criteria. The mathematical formulation for robust optimization can falls into a
multiobjective optimization (MO) problem involving as objectives the mean and the standard deviation of a given
function. The most appropriate approach to solve these problems is through a class of strategies based on the Pareto
concept. The uncertainties in the optimization process to obtain robust and reliable projects will be considered
both in the objective function and in the constraints. Robustness measures required by objective functions are
computed by Monte Carlo simulation (MC). For reliability constraints two approaches will be used: RIA
(Reliability index approach) and PMA (Performance Measure Approach). The process of reliability analysis and
optimization requires multiple function evaluations. When applied to real engineering problems it involves
numerical simulations, resulting in a high computational cost procedure. Alternatives to overcome that here is
through two distinct strategies for metamodels: the use of data fitting approximation and a reduced order model.
For the application of the above process, a reinforced concrete frame with three floors will be used.

New Equation for Failure Pressure Estimation on Curved Pipelines

João L. A. Nepomuceno, Renato de S. Motta, Silvana M. B. Afonso — Fri, 05 Jul 2024 00:00:00 +0000

The present work aims to assess the influence of the curvature of the axis of corroded pipelines in
their failure pressure. Corrosion is one of the major causes of incidents in pipelines, whose integrity is usually
assessed through semi-empirical methods. When corrosion occurs in curves of pipelines, the literature on the
influence of the pipeline curvature in the remaining pipeline strength is very limited. The use of curved pipelines
arises from the need to overcome topological obstacles, being a solution commonly used to implement
adjustments to segments of pipelines. The use of curves in pipelines is even more evident on off-shore pipelines,
in which the installation process causes bending and curvature to the originally straight pipeline. The present
study will simulate and obtain failure pressure in curves of corroded pipelines using Finite Element Analysis
(FEA) provided by the PIPEFLAW software developed by PADMEC research group from UFPE. The results
obtained will be compared to those found by using Lorenz Factor (LF) and Nepo Factor (NF), a newly proposed
alternative factor to Lorenz Factor for failure pressure estimation on curves of corroded pipelines.

A unified framework for local sensitivity analysis of probability of failure

Andre Jacomel Torii, Leandro Fleck Fadel Miguel, Rafael Holdorf Lopez — Fri, 05 Jul 2024 00:00:00 +0000

In this work we present a unified framework for sensitivity analysis of probability of failure with respect
to design variables (i.e. local sensitivity). Local sensitivity analysis is generally classified in two cases. In first
case, the design variables do not affect the probability distribution. In the second case, the design variables do
affect the probability distribution (e.g. expected values). Equations for sensitivity analysis for each one of these
two cases were developed in the past. However, in this work we demonstrate that the first case (i.e design variables
that do not affect the probability distribution) can be viewed as a limit of the second case (i.e. design variables that
affect the probability distribution). This unifies the theoretical background of the problem and leads to a single set
of equations for both cases. This development is important from the theoretical point of view, since it allows an
easier mathematical analysis of the problem. From the computational point of view, it demonstrates how routines
developed to address the second case (i.e. design variables that affect the probability distribution) can be adapted
to address the first case (i.e design variables that do not affect the probability distribution).

Assessment of failure probability of planar steel frames to plastic collapse by advanced structural analysis

Fri, 05 Jul 2024 00:00:00 +0000

The current advanced analysis techniques for steel frames generally use structural analyses with
geometric and material non-linearities to capture the collapse strength of the steel frame. Advanced analysis has
the potential to result in more efficient designs, due to more accurate predictions of true strength of the structural
system. Unfortunately, even with the advanced nonlinear structural analysis method, the true strength of a steel
frame cannot be predicted with certainty because of ever-present uncertainties of the most significant design
variables, which are the properties of the material, the applied external loads and the geometric properties of the
cross sections of the steel profiles. Reliability methods allow the evaluation of the safety level of structures in
probabilistic terms, by the direct evaluation of the failure probability of the structural system. In the present
work, the First Order Reliability Method (FORM) was used to calculate the probability of failure of planar steel
frames to plastic collapse. The advanced analyses were performed using the program MASTAN2 and considered
the geometric nonlinearities and the inelasticity of the steel. The failure probabilities of numerical examples of
planar steel frames were evaluated and compared to other authors. The results of the numerical examples showed
that it is essential to obtain the probability of failure as part of the structural design to account for uncertainties
inherent to design variables in order to obtain safer structures.

Structural optimization of a continuous reinforced concrete beam considering risks and progressive collapse

Lucas da Rosa Ribeiro, André T. Beck — Fri, 05 Jul 2024 00:00:00 +0000

Current normatives that guides the structural design against progressive collapse adopts a damage-
tolerant approach, where the system is design to withstand the loss of individual vertical elements due to abnormal

load conditions. However, the actual guidelines consider this individual element loss in a deterministic manner,
which can overestimate the damage occurrence and substantially increase the total expected costs. Aiming to
analyze how the optimal design of usual structural systems is affected by a column removal scenario, a Risk
Optimization is performed on a continuous beam of reinforced concrete subjected to the loss of the internal support,
which is considered by means of a latent probability of failure. In order to increase the efficiency of the
optimization process, an adapted system single loop approach to the risk optimization is employed herein, allowing
a very fast convergence to the optimal design. Considering the steel rebar areas as the optimal parameters, it is
found that the latent probability of failure substantially increases the steel rebar area directly affect by the internal
column loss when compared to the semiprobabilist design presented by the current normative. When the smallest
latent probability is considered, the optimal steel rebar area is identical to when this probability is null, however,
when the target reliability is over the reliability of the reference design, this area increases very fast. It is also
identified evidences of a threshold column loss probability, but only for the rebar area not affected by the column
loss removal, meaning that its design is indifferent to the objective consideration of the column loss.

PERFORMANCE BASED ANALYSIS OF COLD-FORMED STEEL COLUMNS UNDER FIRE CONDITIONS WITH RESTRAINED THERMAL ELONGATION

Breno de Moraes Dorta, Saulo Jose de Castro Almeida, Luiz C. M. Vieira Jr. — Fri, 05 Jul 2024 00:00:00 +0000

In the present paper a performance based approach is developed for assessing the fire resistance of single
and built-up cold formed steel (CFS) columns at elevated temperature restrained to thermal elongation subjected
to axial compressive loading using finite element models and the Reliability Based Design (RBD). In the first
studies Monte Carlo simulation was selected and the analyzed variables were the material’s mechanical properties,
Young’s module (E) and yield stress (fy), and the level of stiffness of the surrounding structure (K). According
to the results from the preliminary studies the use of high computational resources would be a limitation. As an
alternative to work around this problem the Latin Hypercube Sample (LHS) method was chose. In the sequence
of this work the results obtained from the performance based approach was compared to that obtained using the
simplify method proposed by the ABNT NBR 14323:2013 to determine the axial compression resistance force of
CFS columns in fire situation. Finally, was evaluate among other aspects the probability of failure associated with
each method.

An approach to solve structural reliability problems combining the weighted average simulation method and Kriging

Mariana O. Milanez, Marcela A. Juliani, Wellison J. S. Gomes — Fri, 05 Jul 2024 00:00:00 +0000

Reliability analyses of structural systems remain a challenge due to the number of performance function
calls, associated with the considerable computational efforts necessary for the evaluation of some mechanical
system models. Recently, Kriging surrogate models have been employed to provide predictions of the limit state
function, in order to reduce the number of required evaluations. However, the accuracy of the results depends on the
sample points used to build the surrogate model. Over the last few years, several developments based on learning
functions have been done to choose the appropriate sample points. The aim of this paper is to combine Kriging and
the weighted average simulation method (WASM) and analyze the performance of three learning functions from
the literature, i.e, the U, EFF and UWS functions. The methodology is applied in several examples and the results
are compared taking the evaluation of failure probabilities by WASM as a reference. Results show that all active
learning functions lead to accurate solutions in terms of failure probabilities. In addition, it was observed that the
UWS-function requires a fewer number of sample points to achieve the convergence.

A hierarchical Bayesian framework for model updating regarding structural systems

Matheus Silva Gonçalves, Rafael Holdorf Lopez — Fri, 05 Jul 2024 00:00:00 +0000

The inherent variability of parameters that define engineering systems result in uncertainties for the
predicted response. This scenario is even more noticeable for civil engineering structures, where environment
effects, acting along the whole lifespan of the system, can accelerate the structure deterioration process. In this
context, the structure can reach a safety level lower than the acceptable minimum and, if no corrective actions be
taken by responsible authorities, catastrophic scenarios could occur. Thus, for such responsible authorities, it is of
paramount interest that a reliable bound of the current safety level be available. In this context, the present work
proposes the application of a hierarchical Bayesian framework to perform model updating regarding structural
engineering. By this approach, it is enabled the estimate of the inherent variability of the own parameter to be
updated, avoiding the underestimation of its total uncertainty. In order to assess the suitability of the proposed
approach, it is compared with the classical Bayesian approach in a set of numerical simulations regarding the
response of a cantilever beam due to a point load. Results showed that the hierarchical Bayesian approach is able
to provide more reliable estimates for the total uncertainty regarding the parameter of interest.

Reliability analysis of perforated cold-formed steel members in compression

Roberta L. F. Jardim, Marcílio S. R. Freitas, André L. R. Brandão — Fri, 05 Jul 2024 00:00:00 +0000

Cold-formed steel (CFS) members have been widely used in residential, industrial and commercial
buildings as primary load bearing structural elements due to their advantages such as higher strength to weight
ratio over other structural materials such as hot-rolled steel and concrete. CFS members are made of thin steel
sheets and hence they are more susceptible to various buckling modes. CFS with perforations are commonly used
in construction industry for example in residential construction and also low-rise buildings. This paper shows a
study of the level of reliability of perforated CFS members, based on AISI code, in order to adapt Brazilian code.
The aim of this study is the assessment of the reliability index β for a variation of the nominal live-to-dead load

ratios as well as comparison of the value found considering different load combinations. A test database of cold-
formed steel columns concentrically loaded was assembled and test-to-predicted statistics were obtained for the

Direct Strength Method (DSM). The first order reliability method (FORM) is used to calculate the reliability index
β. Based on the results of the reliability index, it was found that the required safety level was not reached when the
target reliability index of 3.0 was established.

Optimal design of regular frames considering column removal

André T. Beck, Lucas da Rosa Ribeiro, Marcos Valdebenito — Fri, 05 Jul 2024 00:00:00 +0000

Designing a frame to withstand the loss of columns has a great impact over the construction costs, and
it may not be viable since not all buildings are likely to be subjected to extraordinary events that might remove
these supporting elements. In view of that, this paper employs a formulation for the optimal design of framed
structures in the design of a continuous beam. This formulation allows independent column loss probability, and
combines the intact structural condition with all the column loss conditions in one objective function. It is shown
a threshold column loss probability for with the optimal design becomes indifferent to the objective consideration
of column loss. Such threshold varies for different structures, column loss scenarios, and the cost multipliers
employed. It is also found that designing by a discretionary column removal is only beneficial if the column loss
probability is higher than this threshold.

On the Applicability of Time-Series Models for Structural Reliability Analysis

Henrique M. Kroetz, Eduardo M. de Medeiros, Andre J. Torii — Fri, 05 Jul 2024 00:00:00 +0000

The assessment of time-dependent reliability problems is still a challenging task. Besides the difficulty
to characterize a problem from real-world data, most of known solutions rely on approximations suitable only

for specific cases or on burdensome simulation approaches. This is due to the difficulty in working with gen-
eral stochastic processes, particularly for situations of non-ergodicity. A time-series model is a particular case of

stochastic process that operates in continuous state space and discrete time set. Such models can be used to repre-
sent a wide range of random phenomena that spans through time, usually with simpler formulation. They are also

relatively simple to build from data tables, which are usually all the information available about time-dependent

behavior of random engineering systems. This work presents a preliminary study where data generated from con-
tinuous stochastic processes commonly used in structural reliability are used to build different time-series models,

which are then used to replace the original stochastic process in reliability analysis. Auto Regressive, Moving Av-
erage and Auto Regressive Moving Average models are considered. The same time-dependent reliability problem

is solved considering each case, and details about the solutions are addressed.

Cálculo de deformações em Estruturas em Balanços Sucessivos aplicando incerteza nas variáveis de projeto com distribuição estatística através do método de Monte Carlo

Fri, 05 Jul 2024 00:00:00 +0000

Na análise de projetos, as características da estrutura podem solicitar verificações adicionais. Para as
construções pelo método dos balanços sucessivos, cada novo trecho é executado a partir do anterior suportando
as novas cargas de construção e aumentando as deformações à medida que a obra prossegue. Essas deformações
são controladas com a aplicação de contra flechas compensando os deslocamentos para atingir o perfil de
projeto. As contra flechas aplicadas são obtidas com o valor das deformações previstas em modelos
computacionais de análise estrutural. Essas obras apresentam inúmeras variáveis de projeto que influenciam no
comportamento estrutural. No desenvolvimento de projetos de estruturas, as metodologias determinísticas
utilizam fatores de segurança para indiretamente considerar a incerteza das variáveis nos problemas. Este
trabalho difere dos métodos convencionais para o cálculo das deformações, utilizadas para determinar as contra
flechas, pois com o auxílio de um programa desenvolvido para as análises estruturais, considera a fluência em
cada etapa executiva e as incertezas das variáveis. Com a simulação de Monte Carlo é obtido um conjunto de
amostras das variáveis para realizar uma análise estocástica. As repetidas simulações são obtidas com a
distribuição de probabilidade e os parâmetros estatísticos obedecem às orientações do JCSS e de estudos
estatísticos empíricos e com dados de campo. Assim, é permitido encontrar uma melhor representação das
propriedades do material aplicado na obra e sua estimada deformação.

COMPARATIVE ANALYSES BETWEEN MONTE CARLO AND KER- NEL SMOOTHER METHODS TO EVALUATE STRUCTURAL RELIABILITY

Fri, 05 Jul 2024 00:00:00 +0000

Among the methodologies widely used for structural reliability, some of them can be highlighted. The semi-
probabilistic approach, for example, considers the structure in a failure scenario, taking into account purely deter-
ministic variables and safety coefficients established by standards, without calculating the probability of failure.

Numerical methods, such as First-order reliability method (FORM), Second-order reliability method (SORM), and

First-order second-moment method (FOSM), calculate the probability of failure from the limit state equation consi-
dering stochastic factors. On the other hand, observational methods, such as Monte Carlo, simulate pseudo-random

scenarios and estimate the probability of failure by counting collapse occurrences. To guarantee the convergence of
this method, a sufficiently large number of simulations must be carried out, increasing the required computational
effort. Alternatively, the Kernel Smoother obsevational method may be used to calculate the probability of failure
(PoF) of structural systems demanding a computational effort considerably smaller than Monte Carlo. In that way,
the purpose of the present work is to establish a comparison between Monte Carlo and Kernel Smoother methods
by evaluating PoFs and reliability indexes calculated for numerical applications, by using both methodologies.

A new strategy to evaluate the collapse probability and robustness index using Monte Carlo simulation

Aristides P. Orlandi, Flávio de S. Barbosa, Alexandre A. Cury — Fri, 05 Jul 2024 00:00:00 +0000

This paper proposes a new strategy to evaluate the collapse probability and its respective robustness
idex through the construction of an event tree using Monte Carlo simulations. This event tree expresses - in
chronological order - the failure that must occur in different structural elements so that the entire building
collapses, characterizing a progressive collapse. Moreover, the possibility of elements failing simultaneously is
also considered. The results obtained so far are promising since they have achieved all the proposed objectives
and provided a method for assessing progressive collapse. The collapse probability of the structure can be
obtained directly in the model or through the application of the theoretical relationship between elements (series
or parallel), reaching the same results for both cases.

Confiabilidade estrutural aplicada a um modelo de bielas e tirantes para consolo curto de concreto

Fri, 05 Jul 2024 00:00:00 +0000

Os consolos de concreto sao elementos estruturais que se projetam de pilares ou paredes para servir de
apoio a outras partes da estrutura, tendo a importante func ̧ao de redistribuir os esforços entre os elementos consti-
tuintes do sistema. Assim, visando uma adequada modelagem de seu comportamento mecanico, a confiabilidade ˆ
estrutural surge como uma importante ferramenta, permitindo uma estimativa, a priori, da probabilidade de falha,
ainda na fase de projeto. Incertezas associadas aos parametros de resistência e carregamento são incorporadas ao
modelo a partir da descrição estatística das variaveis de projeto. Apresenta-se um estudo associado a quatro me-
canismos de falha em um consolo, relacionados com esforços de tração e compressão avaliados em um modelo de
bielas e tirantes, por meio dos metodos de confiabilidade FOSM, FORM e Monte Carlo. A representação estatística
das dimensoes do consolo, das propriedades dos materiais, e dos carregamentos atuantes e feita a partir de dados
disponíveis na literatura. Os resultados indicam que o modo de falha governante e devido ao esforço secundário
horizontal de tração no tirante. Na análise dos cenários de tração, a carga permanente e o limite de escoamento
do aço se mostram mais importantes na composição do valor de probabilidade de falha obtido, enquanto que, nos
cenarios de compressão, a resistência do concreto se mostra como variável aleatória dominante. Por fim, faz-se
uma analise da interação entre os modos de falha, através de sua combinação segundo a teoria de confiabilidade de
sistemas. Entende-se que o uso de modelos probabil ́ısticos contribui significativamente com a avaliação do nível
de segurança estrutural, de seu balanço com o custo da estrutura, auxiliando o projetista no processo de tomada de
decisao.

Reliability Assessment of Pipelines with River-Bottom Corrosion Profile

Fri, 05 Jul 2024 00:00:00 +0000

The structural integrity assessment of pipelines can be performed through inspection, standards, and
computer simulations. Although these methodologies are widely used, the data used for the evaluations have some

uncertainties and these must be taken into account by the pipeline engineers. Based on inspection data, of the river-
bottom corrosion profile, eleven specimens taken from a brazilian pipeline will be analysed. The present work will

make a comparison between the use of different semi-empirical standards for the evaluation of structural integrity
of corroded pipelines, using First Order Reliability Method (FORM) for reliability analysis. The problem of
reliability analysis of corroded pipelines with idealized defects has been extensively addressed in the literature, but
there are still few studies considering complex corrosion profiles. In this work, we will apply some semi-empirical
equations found in international standards such as DNV RP F101, ASME B31G, modified ASME B31G, and
RSTRENG Effective Area (river-bottom profile). The results of the probability of failure will be compared with
each other, presenting the main conclusions in the use of each standard. To speed up the computation of failure
pressures, parallel programming in GPU (Graphics Processing Units) is used.

RBDO MODEL APPLIED TO WELL CASING SELECTION CONSIDERING RANDOM LOAD SCENARIOS

Fri, 05 Jul 2024 00:00:00 +0000

This paper addresses the coupling of reliability-based models with optimization routines in the
selection of casing tubulars, regarding the failure modes defined in API/TR 5C3 code. The casing system has
great relevance in the construction and operation of oil and gas wells, considering the high costs associated with
its material selection and execution. In this context, regulatory agencies have become more rigorous and are
moving towards the adoption of probabilistic criteria for well integrity evaluation. Methodologies based on
structural reliability, taking into account uncertainties associated with the design variables, have been
disseminated in normative documents and adopted in the industry, with a positive impact on the design practice.
The proposed solution comprises integer programming routines combined to a probabilistic casing design model,
dealing with uncertainties associated with the tube manufacturing, as variations in geometrical and mechanical
properties, and the variability in load parameters, as pore pressure gradient and fracture gradient. The First Order
Reliability Method (FORM) is applied to the reliability index evaluation. The case study presented shows that
the probabilistic optimization strategy can provide interesting solutions on the composition of casing strings,
saving investments but complying with the casing integrity for the relevant load scenarios.

Computation of Axial Forces-Bending Moments Interaction Diagrams for Reinforced Concrete Polygonal Cross Sections

Fri, 05 Jul 2024 00:00:00 +0000

This study aimed to calculate the generalized stress (axial forces and bending moments) and their
respective interaction diagrams for reinforced concrete cross sections. Most of the approaches to compute the
generalize stress are restricted to particular cases, such as rectangular cross sections and simplified stress-strain
diagrams. The adopted methodology allows to calculate the generalized stress for any polygonal cross section, and
it is also flexible with respect to the choice of the stress-strain diagram of the materials. The main contribution of
the present study is to extend such methodology to calculate not only the ultimate axial forces-bending moments
interaction diagram, but also the interaction diagrams defined by the yielding of the reinforcements and cracking
of the concrete. Such diagrams are important in applications of non-linear analysis of reinforced concrete elements
by the lumped damage mechanics for the definition of yielding functions and evolution laws.

Matching numerically a rheological model to the Eurocode creep through dynamic analysis

Alexandre de Macêdo Wahrhaftig, Kaique Moreira Matos Magalhães — Fri, 05 Jul 2024 00:00:00 +0000

A dynamic analysis of vibration for considering a three-parameter rheological model to fit the same
results as predicted for creep by the Eurocode (EN 1992) criteria is performed based on the adjustment of its
parameters. The use of a rheological model of three parameters as a valid alternative for real problems brings a
huge facility for mathematical implementation and manipulation due the simplicity of the solution. For adjustment
of the elastics and the viscous parameters, a numerical simulation to calculate the fundamental frequency of an
actual reinforcement concrete pole is carried out in comparison with the standard Eurocode criteria. In this
determination, the geometry variation, a concentrated force present at the free end of the structural element, and
the self-weight of the structure are considered.

NONLINEAR CYCLIC ANALYSIS WITH UNLOADING-RELOADING LAWS BASED ON MOVING FOCAL POINT

Lívia Ramos Santos Pereira, Samuel Silva Penna — Fri, 05 Jul 2024 00:00:00 +0000

Constitutive models are mechanical-mathematical formulations that describe the behavior
of a material. For a complete representation of the medium, these models must be able to reproduce
the processes of loading, unloading and reloading. Usually, models for quasi-brittle materials present
deterioration of the elastic modulus, while residual strains are not verified. Models for ductile materials,
although, have their elastic modulus preserved during unloading and that results in permanent strains. In
real materials analysis what is observed is a composition of these two behaviors. The literature presents
analytical models to incorporate both hypotheses, developed from the concept of focal point. Traditional
formulations usually work with a fixed focal point. Thus, in order to expand existing formulations,
this work presents an elastic degradation model associated with cyclic stress-strain laws according to a
moving focal point, which varies depending on the deterioration of the material medium.

Probabilistic analysis of the corrosion initiation in concrete structures subjected to chloride ingress using the Boundary Element Method

Vinícius de B. Souza, Edson D. Leonel — Fri, 05 Jul 2024 00:00:00 +0000

Reinforcement’s corrosion is the main cause of durability reduction in reinforced concrete structures.
Besides, the chloride ingress is the main agent in this problem. The reinforcement’s corrosion process occurs in
two stages: in the first, known as the initiation period, chloride ions penetrate into concrete pores and accumulate
at the concrete/reinforcement interface, which lead to the depassivation when the threshold concentration is
reached. After the depassivation, the propagation period starts, which triggers the reinforcement’s corrosion and
the structural collapse. Because of the faster structural safety reduction observed in the latter stage, the initiation
period is often adopted as structural service life. In this regard, this study applies the two-dimensional transient

formulation of the Boundary Element Method (BEM) for the chloride diffusion modelling. Because of the non-
requirement of the domain mesh, the chloride concentrations at the domain are accurately assessed. Moreover, this

problem is properly analysed solely in the probabilistic context because of the huge randomness over the governing
variables. The Monte Carlo Simulation assesses the probabilities of failure herein, which accounts for the failure
scenarios described by the BEM. In addition to the phenomenological random variables, cracks positioned at the
cover account for the inherent concrete cracking and describe preferential ingress paths.

Computational modeling of steel fiber reinforced concrete

Victor Sloboda, Roberto Dalledone Machado, Ricardo Pieralisi — Fri, 05 Jul 2024 00:00:00 +0000

New building technologies are developed with the goal of improving structural performance. One very
promising technology is the steel fiber reinforced concrete (SFRC), in which steel fibers are added in the concrete

mixture. Concrete is a fragile material whose tensile resistance is very lower than compressive. Steel reinforce-
ment, as well as steel fibers, improves the tensile behavior, grants more ductility to concrete and increases cracking

and spalling resistance. Although SFRC is considered promising, there are still a few reliable computational mod-
els to analyze and predict the behavior of SFRC. The modeling is difficult because of the random distribution of

fibers and the consequent anisotropy. A numerical and computational approaching, using numerical methods, is

used to develop this work. Different constitutive models are analyzed and the results are compared with experimen-
tal data obtained from flexural tests. This work aims to extend the application of the SFRC in various situations,

for example the precast structures.

Finite element modeling the structural effects of chloride corrosion in concrete cover

Éverton S. Ramos, Matheus G. Tavares, Rogério Carrazedo — Fri, 05 Jul 2024 00:00:00 +0000

As the construction industry grows, corrosion-related pathologies in reinforced concrete members inten-
sified. These pathologies evolve from the ingress of chloride ions, decreasing structural elements safety. Formation

of pitting in the steel bars characterizes this phenomenon, which non-uniformly corrodes the cross section of the
reinforcements. The main objective of this study is to develop a computational tool to evaluate the corrosion of
concrete structures due to the action of chloride ions. We use a total Lagrangian description of the equilibrium with

the Positional Finite Element Method (Positional FEM). Two-dimensional finite elements with cubic approxima-
tion using Mazar’s damage criterion has been used to model the concrete matrix, while two-dimensional (particles)

finite elements has been used to model the steel bars, coupled by the embedded technique. A deterministic appro-
ach is adopted to evaluate the harmful effects of the corrosion propagation on cross section of reinforced concrete

elements, in particular, the non-uniform stresses generated by the advance of the rust layer. Finally, a numerical
example is presented to demonstrate the efficiency of the developed code and its applicability in evaluating of
non-uniform corrosion.

Numerical analysis of reinforced concrete structures considering coarse aggregates

Éverton S. Ramos, Rogério Carrazedo — Fri, 05 Jul 2024 00:00:00 +0000

Reinforced concrete is the most used material in the civil construction sector, providing high resistance
to mechanical stresses and contributing to the durability of structural systems. Its application allows the design of
structural components with the various formats, motivating its use in the bold and functional architectural designs
required by contemporary society. In order to predict the behavior of reinforced concrete structures according
to the project stresses, the development of numerical tools is essential. The main objective of this study is to
present a numerical approach for modeling reinforced concrete structures considering the presence of particulate
inclusions (coarse aggregate). Geometric non-linearity is considered naturally by the positional formulation of the
Finite Element Method (Positional FEM), while the physical non-linearity of concrete is considered using Mazar’s
damage criterion and of steel using an elastoplastic model. Two-dimensional triangular finite elements were used
to model the cement matrix and coarse aggregates (particles), while one-dimensional finite elements were used for
steel bars (fibers). The kinematic coupling between the domains is performed by the embedded technique, which
allows the generation of independent meshes for the matrix and reinforcement. The computational formulation
and implementation are validated using experimental and numerical results available in the literature. The results
obtained demonstrate the robustness and applicability of the model developed.

Numerical simulation of the service life of reinforced concrete structures subject to pitting corrosion

Éverton S. Ramos, Rogério Carrazedo — Fri, 05 Jul 2024 00:00:00 +0000

Chloride corrosion is the most severe deterioration mechanism that affects reinforced concrete struc-
tures, especially in regions with a marine atmosphere. Electrochemical reactions begin when the critical chloride

ion content is reached on the surface of the bar, promoting the depassivation of the steel. In this work, a two-
dimensional numerical model based on the Finite Element Method (FEM) is proposed to analyze the service life

of reinforced concrete beams subjected to pitting corrosion. Two-dimensional triangular elements with Mazar’s
damage criterion were used for the concrete matrix and truss elements with elastoplastic behavior were used for
the reinforcements, coupled through the embedded technique. The period of initiation of the corrosive process is
determined considering exclusively the mechanism of diffusion of chloride ions, using Fick’s laws. Deterministic
models based Faraday’s laws available in the literature are used for the analysis of the propagation phase, simulated
by reducing the cross section area of the reinforcement over time. Service life is estimated by the crack opening

limit state, according to the Brazilian standardization ABNT NBR 6118:2014. Numerical applications are presen-
ted to demonstrate the robustness of the implementations carried out, revealing the importance of the thickness of

the concrete cover and the water / cement ratio in the service life of the structural element.

Mesoscale analysis of crack propagation in reinforced concrete via positio- nal FEM using interface elements

Welington H. Vieira, Rodrigo R. Paccola, Humberto B. Coda — Fri, 05 Jul 2024 00:00:00 +0000

This work presents an alternative of mesoscale analysis of propagation of cracks in conventional reinforced
concrete structures. The equilibrium of the structure was achieved through the position-based formulation of
the Finite Element Method (FEM), which is naturally non-linear geometric. For mesoscale representation, the
concrete was considered a heterogeneous material composed of the matrix (mortar), the coarse aggregate and the
interfacial transition zone (ITZ). The rebar was represented by truss elements without adding degrees of freedom
to the problem. To represent the beginning and propagation of cracks, interface elements were created between
the matrix elements and between matrix and aggregate. The results obtained were compared with an experimental
work from the literature, for the crack path and for the load-displacement curve. It was possible to show results
close to the real ones, without using overly complex techniques.

Thermal Diffusion over a Portland Cement Concrete Gravity Dam

E.L. Madureira, G.B. Spinola, E. M. Medeiros, A. L. A. Silva — Fri, 05 Jul 2024 00:00:00 +0000

Temperature and its oscillations can influence some physical phenomena progress in concrete structures
as the alkali-aggregate reaction swelling effect, the Creep volume variations, and the Shrinkage, and, consequently,
affect its mechanical performance. The temperature distribution analysis drops over the Thermal Diffusion Theory
that culminates in the Heat Diffusion Differential Equation. It is already known, at present, that the Finite
Difference Technique represents as modest formulation, however it may be used to support the computational
tools applied to the numerical analysis expeditiously, suitable to the endorsement of studies and designs. Its widely
known in the Civil Engineering ambit the hot release due to the cement Portland hydration chemical reaction in
concrete mass structures. The subject of this work is the numerical simulation of the thermal diffusion across
concrete gravity dam focusing, specially, over the temperature fields evolution by time in its continuous solid
mass. Such a subject will be hit from the implementation and application of one-dimensional and two-dimensional
thermal diffusion models using an automatic language translated algorithm through the Finite Difference Approach
on the Heat Diffusion Differential Equation. According the obtained results, the numerical modelling adopted in
this paper simulates, in a suitable way, the dam behavior in face of the thermal diffusion, so that it represents
strategically promising tool to perform similar tasks.

Geometrically nonlinear buckling analysis of cement-based structures with thermoelastic effects and material damage

Henrique C. F. Curci, Eduardo M. B. Campello, Henrique C. Gomes — Fri, 05 Jul 2024 00:00:00 +0000

This work presents a geometrically nonlinear formulation for the analysis of buckling problems
involving cement-based structures susceptible to thermoelastic effects and progressive material damage.
Particularly, we are interested in simulating bifurcation and snap-through phenomena of columns and shallow
arches under such conditions. The thermoelastic material implementation is based on a multiplicative
decomposition of the deformation gradient, wherein the temperature field is assumed to be known (given). Damage
effects, in turn, are taken into account based on a simple (yet representative) nonlocal continuum damage
mechanics (CDM) mode ocality of which is ensured by means of a
homogenization of the elastic equivalent deformation field. The formulation is implemented in an in-house finite
element code developed by the authors including tools for solving two-dimensional plane strain problems. The
model is solved within an iterative, fully consistent Newton-Raphson scheme. A numerical example is provided
to validate our model and illustrate its capabilities against known results from the literature.

Estudo de caso de edifício de alvenaria estrutural em situação de incêndio por meio de simulação numérica

Danilo de F. Barbosa, Vladimir G. Haach — Fri, 05 Jul 2024 00:00:00 +0000

Muitas pesquisas estão sendo desenvolvidas buscando melhor entender o comportamento da alvenaria
estrutural submetida a temperaturas elevadas. Devido às diversas limitações para esse tipo de ensaio, os elementos
submetidos a esses experimentos geralmente são prismas e pequenas paredes, nos quais a análise geralmente
abrange seu comportamento térmico ou termomecânico. No entanto, pensando na análise estrutural de um edifício
de alvenaria submetido a condição de incêndio, deve-se considerar não apenas a perda de rigidez das paredes
individualmente, mas incluir a capacidade de redistribuição de esforços entre os demais elementos estruturais.
Nesse contexto, esse trabalho tem como objetivo realizar uma análise mecânica de um edifício usual de alvenaria
para um cenário de incêndio adotado. Dessa forma, com o auxílio do software DIANA®, foram simulados alguns
modelos para considerar a perda de rigidez gradual dos elementos do cômodo onde ocorre o sinistro. Com os
resultados obtidos, foi possível observar a grande reserva de capacidade resistente dessa tipologia de edificação,
além da grande capacidade de redistribuição de esforços nas paredes estruturais conforme a ocorrência do incêndio,
o que permitiu contemplar a importância da compartimentação como medida protetiva de combate ao incêndio.

Aplicação dos Elementos Finitos Semi-Embutidos na Simulação de Vigas de Concreto Protendido

Jordana F. Vieira, Raul D. Durand Fárfan — Fri, 05 Jul 2024 00:00:00 +0000

This article deals with the application of the semi-embedded method in prestressed concrete beams in
modeling based on the Finite Element Method. In the case of prestressed concrete structures, their computational
representation must consider the heterogeneity of the materials that constitute the structure and the way these
materials interact. Thus, the objective of this paper is to present the formulation of the semi-embedded method
used as an alternative for the numerical simulation of prestressed concrete beams and apply the formulation in a
simply supported beam with available experimental data . In the semi-embedded method, unlike the other methods,
the reinforcement is discretized into bar elements and thus, the boundary conditions can be applied to each bar
node, allowing a more realistic approach. Three analysis for different concrete models were performed using the
Mazars model, Drucker-Prager model, and the Damage model. In the comparison, it is noted that the numerical
results are fairly agree with the experimental data, thus concluding that it is possible to represent prestressing in
concrete beams using the semi-embedded method.

Computational analysis of concrete slabs subjected to perpendicular loads

Luiz E. G. de Mattos, Cosmo D. Santiago, Rodolfo K. Tessari — Fri, 05 Jul 2024 00:00:00 +0000

The objective of the present paper is the analysis of the behaviour of concrete slabs when subjected to
loads normal to the plane. The mathematical model is governed by the Lagrange’s Equation in the two-dimensional
plane. The differential equation is discretized by the Finite Difference Method in uniform grid with Neumann’s
boundary condition at the support positions. The system of algebraic equations is solved by the Gauss-Seidel
method. Two case studies with distinct geometry, boundary conditions and loading are carried out. The first
case is a simply supported triangular slab subject to uniformly distributed load. The second case simulates the
hydrostatic loading on a reservoir wall or the earth thrust on a retaining wall. Through the computational analysis
it was possible to capture displacements and internal forces (shear forces and bending moments) over the whole
slab domain, which is crucial for designing such structural element. Numerical results also showed excellent
agreement with analytical results extracted from the literature, validating the use of the proposed computational
code.

Computation of stay cable forces in Segmental Construction of Concrete Cable-Stayed Bridges

Beatriz Montelato, Rui N. Oyamada, Eduardo M. B. Campello — Fri, 05 Jul 2024 00:00:00 +0000

Concrete deck cable-stayed bridges are complex, highly hyper-static nonlinear structures. Design of
such structures must consider not only these aspects but also time-dependent effects (such as creep, shrinkage and
varying stiffness) of the concrete deck. Determination of the stay cables installation forces is highly influenced by
these effects, as well as by the construction method. Since these types of bridges are mostly constructed in phases,
these effects become even more pronounced. This work presents a methodology, using computational methods, to
compute stay cable forces in such bridges taking into account the construction method and time-dependent effects.
We also assess the distribution of internal (i.e., cross-sectional) forces of the deck as influenced by these effects.
The methodology will be applied to a case study consisted of the cable-stayed railway bridge over the Ayrton
Senna and Hélio Smidt freeways that give access to the André Franco Montoro International Airport in the city of
Guarulhos, São Paulo, Brazil. A thorough discussion of results, and comparisons between techniques, are provided.

Finite element model for pretensioned concrete beams using partial interaction theory

Joao Batista M. Sousa Jr., Evandro Parente Jr., Eduardo F. Morais — Fri, 05 Jul 2024 00:00:00 +0000

Pretensioned beams are an efficient load-carrying structural system, and are usually precast. Tendons
are pretensioned on a pretensioning bed, and the concrete is cast in contact with these tendons. After curing, the
tendons are cut resulting in a self-equilibrating system with improved mechanical properties. The bond and slip
between tendon and concrete may be simulated in different ways depending on the purposes of the model. Recent
works have employed partial interaction assumptions on the modelling and simulation of pretensioned concrete
beams. Analytical results have been provided giving some insight as to how a numerical modeling by the finite
element method (FEM) should be developed. in this paper, a FE formulation for the linear analysis of pretensioned
concrete beams is described, developed and tested. The bond-slip relationship is taken identical to the form which
is used in partial interaction composite beam analysis, frequently associated to steel-concrete or other bimaterial
beams. The relative merits of the ensuing formulations, the ocurrence of locking and the precision of the numerical
schemes are addressed with respect to analytical solutions.

THERMO-CHEMO-MECHANICAL ANALYSIS OF CONCRETE STRUCTURES CONSIDERING AGING AND DAMAGE

Fri, 05 Jul 2024 00:00:00 +0000

This paper will present Finite Element models to study the thermo-chemo-mechanical behaviour of
concrete structures taking into account both aging and damage. The analysis is composed of two separated models,
namely: thermo-chemical and thermo-mechanical with damage. First, the thermo-chemical model will be briefly
presented. Then, the thermo-mechanical model with damage will be developed and the need for an incremental
constitutive equation for modeling aging of concrete will be discussed. In order to avoid mesh-dependency due to
strain localization, a nonlocal integral-type technique will be employed with few changes on the logical scheme
of the Finite Element model. Finally, the thermo-chemo-mechanical analysis will be presented for a theoretical
example: a concrete specimen. The results will show that residual stresses will take place due to both concrete
aging and thermal strains. This, in turn, might lead to the premature collapse of the structure.

Análise numérica da punção em lajes lisas de concreto armado pelo método dos elementos finitos

Mateus G. M. Pereira, Bruno R. Amorim, Jerfson M. Lima — Fri, 05 Jul 2024 00:00:00 +0000

O sistema de lajes-lisas, onde não há presença de vigas, é bastante utilizado atualmente, contudo seu
comportamento é bastante complexo devido ao surgimento de elevadas tensões cisalhantes nas regiões de ligação
entre laje e pilar, possibilitando uma ruptura por punção. Essa ligação deve ser corretamente dimensionada, para
evitar a ocorrência de rupturas frágeis e, em grande parte, com possibilidade de colapso progressivo da estrutura.
Embora muitos métodos teóricos tenham sido propostos, não se obteve ainda um modelo exato aceito pelo meio
técnico-científico capaz de estimar com precisão a resistência à punção dessas ligações. O presente estudo tem
como principal objetivo analisar, através do Método dos Elementos Finitos (MEF), a ligação laje-pilar no sistema
de lajes lisas de concreto armado submetidas a carregamento uniforme, buscando fazer um comparativo da
capacidade resistente de lajes lisas entre os resultados numéricos e os ensaios experimentais de Palhares [1]. Para
isso, será desenvolvido um modelo tridimensional não-linear, levando em consideração o Concrete Plastic Damage
Model (CPDM) como modelo constitutivo do concreto e um modelo elástico-plástico para o aço.

Estudo Analítico e Numérico via Método dos Elementos Finitos da Rigidez dos Pilares de Pontes em Concreto Armado

Fri, 05 Jul 2024 00:00:00 +0000

As obras de concreto armado prevalecem na construção civil mesmo com uma demanda para a utilização do

concreto protendido e da estrutura metálica. A escolha do material sempre incide no menor custo técnico-
econômico e nas condições de infraestrutura, até que haja uma preferência relativa ao sistema estrutural ou aço

de maior resistência. Na engenharia para que a influência da flambagem seja avaliada de forma correta, deve-se
associar ao comportamento da estrutura, além da não linearidade geométrica, a não linearidade física. A rigidez
flexional EI é significativamente sensível aos níveis de esforços internos atuantes nas peças de concreto armado.
Desta forma, esta pesquisa teve como objetivo fazer, por meio de modelos analítico e numérico utilizando o
programa ABAQUS via Método dos Elementos Finitos (MEF), com proposito de observar as perdas de rigidez
em pilares de pontes, a fim de elaborar novas curvas com rigidez flexionais com a finalidade de verificar os
deslocamentos devido ao acréscimo do carregamento. Os resultados numéricos encontrados mostraram
convergência com os obtidos analiticamente.

Estudo Analítico e Numérico da Armadura Longitudinal Retangular para Vigas de Concreto Armado

Fri, 05 Jul 2024 00:00:00 +0000

No presente trabalho, será apresentado um modelo de viga onde a armadura longitudinal terá seção transversal
retangular sendo que a base sempre será menor que sua altura, para que seja atingido um maior momento de
inércia nessa armadura aumentando consequentemente sua resistência à deformação da peça, quando uma tensão
for aplicada. Antes de aplicar o experimento, será realizado um análise computacional e numérica da viga
convencional (armadura com seção transversal circular) e da viga com armadura cuja seção transversal será
retangular, sendo os dois modelos com as mesmas dimensões. Trabalhando os resultados da análise, o objetivo
maior é que o novo modelo de viga obtenha uma maior resistência à deformação que o modelo convencional,
podendo reduzir a área de concreto e também a quantidade de ferro utilizado na confecção de estribos de
maneira que, mesmo com a redução de materiais a resistência de uma seja equivalente à outra, reduzindo custos
na construção e indiretamente preservando o meio ambiente.

Análise de uma metodologia de modelagem proposta para lajes lisas de concreto armado sem e com armadura de cisalhamento

Frederico P. Maués, Lucas N. Andrade, Maurício P. Ferreira — Fri, 05 Jul 2024 00:00:00 +0000

Este artigo tem como objetivo discutir a precisão dos resultados obtidos através de uma metodologia de
modelagem computacional, feita no programa ATENA, para o problema da punção. Buscou-se definir uma malha
de elementos finitos e calibrar as propriedades do concreto com base em um ensaio de referência realizado em
laboratório por RUIZ [1] e que também serviu como referência de laje sem armadura de punção para a série de
LIPS [2]. Os parâmetros de calibração do concreto foram a resistência à tração, o módulo de elasticidade e a
energia de fratura – todos derivados da resistência à compressão, utilizando-se equações de normas vigentes.
Além disso, foi avaliado o modelo de fissura a ser usado e o tamanho dos elementos da malha. Em seguida, foi
modelada uma laje de LIPS [2] com armadura de cisalhamento para avaliar a melhor forma de implementar
essas armaduras. As definições finais dos modelos de referência foram usadas para a modelagem de dois
espécimes de FERREIRA [3], os quais apresentavam resistência do concreto e geometria diferentes da laje de
referência. Foram determinados comportamento carga vs rotação nos modelos e comparados com as respostas
experimentais para a validação da estratégia de modelagem, aonde foi obtida boa correlação.

Numerical Modeling of Post Tensioned Concrete Slab

Matheus S. V. Fernandes, Maria Elizabeth T. da Nóbrega, André Tenchini da Silva — Fri, 05 Jul 2024 00:00:00 +0000

The fragile failure of concrete is a complex problem where reinforcement steels are
employed at regions subjected to tension. The other important solution in order to improve the
structural behavior corresponds to inclusion of prestress steel reinforcement in concrete. This
introduces a precompression avoiding cracks during service lifetime. Nowadays, post-tensioned
concrete remains not fully controlled where the numerical modeling plays a relevant role to improve
the knowledge concerning to structural behavior. Therefore, this paper focus on numerical evaluation
of the post tensioning influences on the global behavior of concrete slabs. The numerical model has
been created taking into account the experimental results. In details, it was modeled one simple
support concrete slab that was carried out up to its ultimate loading. This test measured important
aspects, such as deflections, yield lines, and cracks development. The specimen has a square geometry
and uses straight prestressing wires. The numerical model has been developed using the Abaqus
software. It is known that the standard solver could not advance much after cracking load because of
many nonlinearities introduced. The viscosity parameter on the concrete damaged plasticity model
was the only way to pass through this point, but this technique weakens the results and raises doubts
about it. An attempt with explicit solver has been used to overcome those nonlinearities during the
analysis and showed good results. Contact problems between concrete and steel wires, concrete
damage plasticity modeling, and explicit analysis require to scrutinize many topics during pre- and
post-processing analysis. This paper presents the whole process of modeling a post-tensioned concrete
slab using Abaqus Explicit taking into account its applicability, advantages, disadvantages and the
validation procedure. This paper presents a method to identify the cracking load in an Explicit analysis
based on the plastic deformation energy.

Parametric analysis of prestressed beam variation force with nonlinear feature through nonlinear finite element analysis

Marcos N. Rabelo, Werley R. Silva, Wanderlei M. Pereira Junior. — Fri, 05 Jul 2024 00:00:00 +0000

Prestressing concrete has been used as a good options to beams and plates mainly those structures
which has enough strength to support large loads and distance. Parameters like fields strain and tension must
be considered in the mathematical models to design structures and predicts its behavior. In this article the main
goal is to analyze the relationship between loads and displacement of prestressing concrete structures with bound.
The approach taking into account the methods of nonlinear finite elements to describe the equations of tensor
fields regarding the strain/tension tensor fields. In order to analysis physical nonlinearities constitutive models are
assumed. On the other hand the geometrical nonlinearities are analyzed by means of a beam supported in both
ends with rectangular transversal section. The strain of the beam is given by the Euler-Bernoulli theory. In addition
the prestressing tendon is modeled as truss element. With analytical techniques based on nodal equilibrium forces
are employed to predict its mechanical behavior. A huge amount of results coming from literature is performed
in order to get news insights regarding the displacements in cables. The equilibrium conditions are obtained by
means of the equations regarding the nodal displacements. Thus the tangent stiffness matrix is assembled. Finally
the article is closed by comparing the numerical with experimental results.

Computational model for crack simulation in concrete beams using interface elements

Eduarda M. Ferreira, Flavio S. Barbosa, George O. Ainsworth Junior — Fri, 05 Jul 2024 00:00:00 +0000

The study of damage in concrete structures plays an essential role in evaluating its useful life and
integrity, preventing disasters, and defining the need for maintenance or reinforcement in the structure. Among
the common pathologies that occur in reinforced concrete structural elements, there is cracking. Despite being
unavoidable due to the concrete’s low tensile strength compared to its compressive strength, it is essential to know
the behavior of the material before and after cracking starts, investigate its causes, limiting the level of crack
opening to guarantee a good performance of the structure. Therefore, the present work aims to study cracked
concrete beams modeled as a plane stress state, submitted to different loading and boundary conditions situations.
A computational crack model was developed based on the Finite Element Method with conventional quadrilateral
isoparametric elements and interface elements with five springs extracted from the literature. These interface
elements allow the simulation of cracking opening in regions where the tensile stresses are higher than the concrete
strength. The constitutive model for the interface element depends on a penalty parameter empirically inserted to
simulate the reduction of material stiffness when subjected to tensile stresses. To avoid shear-locking, reduced
integration was adopted together with techniques for controlling the hourglass modes in such under-integrated
elements. This model has been implemented using the software MATLAB and the results were validated by
comparing with the ones of other authors, showing good agreement.

NONLINEAR ANALYSIS OF REINFORCED CONCRETE BEAMS WITH SECANT METHOD

Gabriel F. de Melo, Paula M. A. Gracite, André J. Torii — Fri, 05 Jul 2024 00:00:00 +0000

This work aims to develop and implement a model to perform structural analysis of reinforced con-
crete beams using the Finite Element Method, considering the physical nonlinear behavior of materials using

moment-curvature diagrams calculated before structural analysis. A finite element model for nonlinear analysis
of reinforced concrete beams based on moment-curvature relationships was developed and implemented, adopting

the Euler-Bernoulli beam element and using the iterative secant method for solving the resulting system of non-
linear equations. This model was implemented through computational routines and validated by comparisons with

results from numerical and experimental examples in the literature. With the results obtained in the examples, it
was concluded that the computational routines for nonlinear analysis of reinforced concrete beams proved to be
accurate and efficient, and can be used to verify the deformations in service and analysis in ultimate limit state
of reinforced concrete beams under bending, provided a finite element mesh sufficiently refined at the points of
maximum effort is employed.

Formulação numérica para simulação de sistemas de pós-resfriamento em estruturas de concreto massa

Igor A. Fraga, Ana B. C. G. Silva, Eduardo M. R. Fairbairn — Fri, 05 Jul 2024 00:00:00 +0000

Due to the high costs and safety requirements of construction and infrastructure works, thermal cracking
of young concrete has been a concern of the engineering community since the first applications of mass concrete.

The heat generation during hydration and the consequent increase in the temperature of the concrete are very im-
portant, not only because they can generate thermal gradients in space and time, responsible for the appearance of

high initial stresses, but also because deleterious phenomena such as the formation of delayed etringite formation
(DEF) have been shown to be associated with the existence of thermal fields in the early ages of cementitious
material. In this way, many actions can be taken to minimize the appearance of undesired stresses, such as: (i)
decrease in construction speed; (ii) reducing the casting temperature of the concrete; (iii) lowering the temperature
using a post-cooling system; (iv) choice of a low heat hydration composition. This work will discuss the numerical
implementation of a concrete post-cooling model, in which the temperature of the concrete during hydration is
reduced by the circulation of water or air in pipes embedded in the formwork (postcooling systems). Numerical
modeling of the post-cooling of concrete allows significant savings in the construction of large structures. Thus,

developing a predictive cracking model, which incorporates concrete cooling in the early ages, is extremely impor-
tant to minimize the appearance of stresses that exceed the resistive capacity of the element and future pathologies.

In this work, a numerical formulation is presented for a simulation model of the cooling system with tubes in mass
concrete structures, on a mesoscopic scale, to be implemented and coupled in a DAMTHE finite element model,
developed in FORTRAN programming language, by PEC / COPPE / UFRJ.

Neural Networks with Backpropagation in Engineering

Caio Fernando L. Saud, Ana Carolina Cellular, Gustavo Coquet Braga — Fri, 05 Jul 2024 00:00:00 +0000

Nowadays, with the amount of data increasing continuously in online networks there is the possibility
to use artificial intelligence to analyze large databases. The Artificial Neural Network is a very utilized tool to
find patterns in data to optimize the time and efficiency of analysis. Concrete is the most used structural material
in Brazil in civil construction. Its resistance depends on the proportion of the materials used in its fabrication. To
quantify each material to reach the required resistance for a particular need of a structure is a challenge found by
engineering. This article aims to elicit how an Artificial Neural Network is capable of processing data and
understanding patterns that are necessary to develop a coherent formula for the concrete based on obtained data
in mechanical tests. The program is capable of making interactions among the data in a process of training and
learning and it is also capable of finding acceptable solutions. It used a feedforward neural network with
backpropagation algorithm to find the resistance of the concrete. The input data were the material used in a 1m3
construction of adensed concrete with different types of traits and tests and the output data, its resistance.

Study of the Behavior of SFRC Tunnel Segments using a Multiscale Model

Fri, 05 Jul 2024 00:00:00 +0000

Considering the recent increase of investments in underground infrastructure, progress and innovations
are needed to build in a safe, efficient, and economical way. This paper aims to contribute to the state of the art on
the numerical modeling of hybrid tunnel segments for mechanized tunneling constructed with Tunnel Boring
Machines (TBMs). In this way, a 2D multiscale model was applied to predict the mechanical behavior of individual
segmentsreinforced partial- or fully with steel fibers in a three-point bending setup. The multiscale model proposed
presented good accuracy to represent the nonlinear post-cracking behavior, propagation of fracture and interaction
between reinforcement and concrete. Finally, the results demonstrate that the application of the numerical strategy
adopted for modeling the mechanical behavior of reinforced tunnel segments is highly promising.

NUMERICAL MODELING OF LOSS OF PRESTRESS IN CONCRETE BEAMS

Matheus de Godoy Tavares, Éverton Souza Ramos, Rogério Carrazedo — Fri, 05 Jul 2024 00:00:00 +0000

The correct estimation of prestressing losses has fundamental importance for preventing damage and
improving the design of prestressed structures. In prestressed concrete beams the level of prestressing force
initially applied is reduced instantly and over time. The progressive prestressing losses constitute an important part
of the total loss and are related to shrinkage, creep of the concrete and the relaxation of the prestressed steel.
Thereby, this work aims to develop a computational tool using the positional approach of the finite element method
to evaluate the mechanical behavior of bonded prestressed concrete structures. The concrete matrix is represented
by plate finite elements with cubic approximation, whereas, for reinforcement, one-dimensional finite elements
are considered. The coupling between matrix and reinforcement is performed by means of the embedded
technique, without adding degrees of freedom to the problem. The prestressing loss due to shrinkage and creep of
the concrete are determined by the model B4 (WENDNER; HUBLER; BAŽANT [1]). The loss by relaxation of
prestressed steel is calculated using the model proposed by Model Code 10 (CEB-FIB [2]). The numerical
applications performed demonstrated the accuracy of the developed model, evidencing its capacity in the analysis
of prestressing loss in bonded prestressed concrete elements.

Modelagem numérica do processo de formação e propagação de fissuras em CRFA utilizando uma abordagem de aproximação contínua

Bruno T. de Vasconcelos, Luís A. G. Bitencourt Jr. — Fri, 05 Jul 2024 00:00:00 +0000

Este trabalho propoe um modelo numérico para simular o processo de formação e propagação de fis-
suras em Concreto Reforc ̧ado com Fibras de Aço (CRFA). A Aproximação Contínua de Descontinuidades Fortes
(ACDF) e aplicada utilizando um enriquecimento elementar (E-FEM), cujo comportamento na regiao descontínua
e descrito por um modelo de dano à tração para simular o processo de falha na matriz de concreto. As fibras de aço
sao representadas por elementos finitos unidimensionais com dois nós (elementos de treliça), e comportamento ́
descrito por um modelo constitutivo elastoplastico unidimensional. As fibras de aço e o concreto são discretiza-
dos inicialmente em malhas de elementos finitos independentes. Em seguida, elementos finitos de acoplamento
(EFA) sao inseridos para descrever as interações entre eles empregando um modelo constitutivo de dano contínuo
apropriado. Os exemplos numericos demonstram que a metodologia proposta ́ e promissora e consegue descrever ́
apropriadamente o processo de formação e propagação de fissuras em CRFA.

SIMULAÇÃO NUMÉRICA DE VIGA DE CONCRETO PROTENDIDO EM DUPLO BALANÇO UTILIZANDO UM MODELO PROBABILÍSTICO MACROSCOPICO

Fri, 05 Jul 2024 00:00:00 +0000

The Double Cantilever Beam (DCB) test has been used in many studies, generally in the framework of Frac-
ture Mechanics, in order to characterizing the concrete fracture under tensile loads. This test provides information,

such as, the critical stress intensity factor and the critical energy release rate, that allows evaluating the toughness

of the material. In this work, a numerical simulation of a prestressed DCB was carried out based on a macrosco-
pic probabilistic model. The macroscopic probabilistic approach is developed in the context of the finite element

method (FEM) and considers that each finite element is represents of a heterogeneous material volume. The proba-
bilistic aspect is introduced in the model by considering random distributions of tensile strength and local cracking

energy at the local scale of the material. That states the cracks are created within the concrete with different energy
dissipation depending on the spatial distribution of constituents and initial defects. To furnish consistent statistical
results, the Monte Carlo procedure is used. Promising results in terms of global behaviour and macrocracking
information in a very large prestressed DCB specimen are presented.

Numerical approximation of the classical solutions for plates

Matheus S. Carvalho, Jorge C. Costa — Fri, 05 Jul 2024 00:00:00 +0000

This article proposes a solution, obtained by line adjustment, to the problem of bending of thin plates
with small deflections. The aim of this solution is to make the programming and manual calculation of bending
moments and deflections easier than classical method equations and calculation tables. The values to make the fit
was obtained by programing the Levy’s classical method in MATLAB® and the results were close to the values
given by Timoshenko e Goodier (1959). The line adjustment was made in MATLAB® and the shape function was
a polynomial equation of third degree with four variables. Furthermore, the values obtained numerically was
compared with the coefficients in Chust and Figueiredo’s (2014) calculations table. It was verified that the
tabulated values were not the maximums because they were always obtained in the middle of the plate. Therefore,
a new calculation table for each kind of plate with the maximum values is proposed along with closed form
approximations. The analyses were carried out for rectangular plates with clamped or simply supported edges.

Multi-scale meshing for 3D discrete fracture networks

Pedro Lima, Philippe R.B. Devloo, Jose Villegas — Fri, 05 Jul 2024 00:00:00 +0000

The geometric description of a Discrete Fracture Network (DFN) in the context of multi-scale meth-
ods, involves the ability of inserting multiple fractures in a predefined coarse mesh, while building volumetrical

elements of smaller scale around the surface of these fractures in order to create sub-meshes inside the coarse
elements. This paper presents an approach for automatic finite element meshing of fractured reservoirs suited to
Multi-scale Hybrid-Mixed methods (MHM). The code is written in C++ and largely relies on two open source

finite element libraries: NeoPZ and Gmsh. The main steps to the method involve: locating intersections and re-
fining elements at those points, building a data structure that associates each element of a fracture surface to the

coarse volume that encloses it, and then generate a sub-mesh of fine elements around the fractures to fill these
coarse elements, without altering originally defined nodes in the coarse mesh. In order to improve the quality of
geometrical elements to be generated, strategies of moving intersection points and features simplifications are also
presented. Results show that the proposed technique can efficiently construct adequate 3D meshes. While relying

on neighbourhood information and consistent element topologies available from NeoPZ’s geometric meshes, en-
ables optimization of multiple algorithms of geometric search that would, otherwise, require a considerable amount

of floating-point operations.

SIMULAÇÃO NUMÉRICA DE TRAÇADORES APLICADOS EM MEIOS POROSOS UTILIZANDO UM MÉTODO DE VOLUMES FINITOS DO TIPO MULTIPOINT FLUX APPROXIMATION QUASI-LOCAL (MPFA-QL)

Fri, 05 Jul 2024 00:00:00 +0000

Numerical simulation of solutes (e.g.: tracers and contaminants) in porous media remain a challenge
for numerical analysts, particularly due to the complex geological characteristics of the medium. The use of
tracers allows to characterize hydrodynamically the porous media covered by a certain volume of fluid
previously marked by these substances. The mathematical model that determines the concentration of tracers in
porous medium is given by the advection-dispersion-reaction (ADR) equation. The numerical solution of this
equation is usually obtained by the finite difference method, therefore, there are limitations to treat problems
with anisotropic tensors, and it is not suitable for the use of unstructured meshes. On the other hand, an
alternative solution is the use of Galerkin finite element method, however, this method in the most classical form
does not produce locally conservative solutions, which can be a serious problem for numerical modeling
involving conservation laws. In this context, the present work presents a finite volume method (FVM) to

discretize the ADR equation, where the discretization of the advective-dispersive term is performed using a non-
orthodox FVM, known as multipoint flux approximation quasi-local (MPFA-QL), that was originally used to

solve diffusion problems with heterogeneous and anisotropic coefficients on unstructured and distorted meshes.

On the equivalent permeability of fractured porous media

Ismael R. Vasconcelos Neto, Cristian Mejia, Deane M. Roehl — Fri, 05 Jul 2024 00:00:00 +0000

Fractured porous media are present in different geological formations, such as rock masses and oil
reservoirs. The proper modeling of these fractured systems is of high relevance to the permeability assessment and
production management of the reservoirs. The fracture networks present in these media have a significant
contribution to fluid flow, once they create preferential paths for fluid transport. This work discusses the influence
of the fracture geometry on the equivalent permeability of fractured porous media. A generalized dual
porosity/dual permeability (DPDP) model is adopted to incorporate the fracture sets implicitly into the porous
matrix. This formulation was implemented into an in-house multiphysics framework called GeMA. Due to the
ease to simulate fractured porous media using DPDP, the influence of several parameters such as fluid viscosity,
matrix permeability, and fracture opening, spacing and orientation, are simulated generating a large number of
models. For each model, the horizontal and vertical equivalent permeabilities were estimated by applying a
horizontal and vertical pressure gradient, respectively. The numerical results showed that the fracture geometric
characteristics have a significant influence on the equivalent permeability and the dual porosity/dual permeability
model is a powerful approach to represent the behavior of fractured porous media.

A Multipoint Flux Approximation Method Based on Harmonic Points (MPFA-H) for the Numerical Solution of the Stokes-Brinkman Equations in Carbonate Petroleum Reservoirs

Fri, 05 Jul 2024 00:00:00 +0000

In this work, our main purpose is to present a cell-centered finite volume scheme for the simulation
of fluid flow on carbonate petroleum reservoirs using an unstructured polygonal mesh. The governing equations

are solved using two different aproaches, a monolythical and segregated, the latter employs the SIMPLEC (Semi-
Implicit Method for Pressure Linked Equations-Consistent), where the Stokes Brinkman’s equations are discretized

using a Multipoint Flux Approximation method based on harmonic points (MPFA-H) that can handle highly het-
erogeneous and anisotropic media. Furthermore, to assure the coupling between the variables, a modification of

the Rhie-Chow’s interpolation method given by Zhang et al. [1]. is used. The proposed methods are tested and the
differences between these two approaches are discussed.

Primal HDG Methods for Elliptic Problems on Curved Meshes

Ismael de Souza Ledoino, Abimael Fernando Dourado Loula — Fri, 05 Jul 2024 00:00:00 +0000

This work addresses stability and locking of three classes of hybrid methods for elliptic problems on
straight and curved meshes in 2d. We consider here modifications of the hybrid methods presented in [1] and [2],
and compare them with the hybrid high order method discussed in [3]. For straight meshes, the approximation
order for polynomial spaces over edges can either be equal or one order smaller than the approximation order for
polynomial spaces in the interior. However, having one order smaller for edges is actually mandatory for obtaining
locking-free estimates from our modification of the primal method introduced in [1] on straight meshes (except
for triangles, where the approximation spaces are divergence-free). The other two hybrid methods are locking-free
whenever they are stable. In the case of curved meshes, we verify that all three methods are unstable if one chooses
approximation orders for the edges one order smaller than the interior. However, we also verify numerically that
all three methods are locking-free in curved meshes if these polynomial orders are equal.

Fluid Flow Simulation in Porus Media with Deformation Bands

Fri, 05 Jul 2024 00:00:00 +0000

Deformation bands are one of the most common structures in fault zones formed in porous sandstone
rocks. They are characterized by tabular format, with millimeter to centimeter thickness and reduced permeability

and porosity in relation to the host rock. Due to this, deformation bands can affect the rock flow patterns and com-
partmentalize rocks. Since they represent a small-scale heterogeneity, their incorporation on reservoir simulation

is associated with high computational cost when deformation band explicit discretization is needed. As an alter-
native, this work proposes to incorporate this discontinuity in an implicitly way using finite element method with

embedded discontinuities. This method was tested in synthetic scenarios with differentes configurations of posi-
tion, permeability values and number of deformation bands in order to analyze the effects of them on equivalent

permeability and pressure distribution. The adopted approach was able to capture the resulting pressure field dis-
continuity. Furthermore, in the shown cases it was observed that deformation bands were able to compartmentalize

the domain, behaving as barriers to the fluid flow.

An Adaptive Algebraic Dynamic Multilevel (A-ADM) and Multiscale Method with Enriched Basis Functions for the Simulation of Two- Phase Flows in Highly Heterogeneous Petroleum Reservoirs

Fri, 05 Jul 2024 00:00:00 +0000

Classical Multiscale Finite Volume (MsFV) methods can produce highly oscillatory pressure solutions
(i.e. non-monotonic) for high permeability contrasts. This can be a serious problem as it can produce spurious gas
throughout the reservoir when the pressure erroneously falls below the bubble point pressure and it can
substantially increase the computational cost to solve the problem due to the necessity of extensive use of iterative
procedures in order to obtain a low-recirculation velocity field. In this paper, we propose an adaptive flow based
agglomeration strategy for correcting the non-physical terms present in the coarse transmissibility matrix by means
of a preprocessing local step. This is done by using a local recalculation of the basis functions in a patch defined
by a judicious grouping of dual coarse volumes that eliminates the spurious oscillations. Classical multilevel and
multiscale methods define a uniform level at each coarse control volume, i.e., the same mesh level is used at each
coarse control volume. As a result, it generates, in multiphase transport problems, the necessity of the inclusion of
volumes that do not contain the saturation front in the high-resolution level. In this context, we present a framework
to deal with non-uniform levels at each coarse control volume, which allows the use of fine-scale control volumes
only where it is strictly needed, in order to produce smaller coarse scale matrices than those from classical
multilevel multiscale methods.

Some Results on the Accuracy of a Classical Upscaling Technique Using an Intuitive Multilevel Preprocessor for Smart Simulation

Fri, 05 Jul 2024 00:00:00 +0000

The progress in geology has allowed the creation of high resolution reservoir models, however hard-
ware limitations turn multiple simulations using these models unfeasible. To overcome this problem, upscaling

techniques were developed allowing fine scale information to be projected onto a coarse scale discrete domain,
through homogenization of petro-physical parameters, decreasing the amount of processing and storage needed,
and so turning the simulation feasible. Different upscaling techniques were developed in order to improve the
tradeoff between accuracy and computational performance for different boundary conditions, so studies to identify
appropriated approaches and coarsening ratios to certain types of problems are important to industry, raising up the
necessity of suitable tools to perform these tests. In this context, the IMPRESS (Intuitive Multilevel Preprocessor

for Smart Simulation) has been developed to simplify multilevel simulations, such as those in the family of upscal-
ing techniques. In this article, we demonstrate an application of the IMPRESS that integrates a classical upscaling

technique with a commercial petroleum reservoir simulator, the IMEX. Results are presented on the second model
of the 10th SPE Comparative Solution Project (10th CSP-SPE).

An iterative MsCV method coupled to the high-resolution CPR approach via different solution smoothers for the simulation of oil-water flows in 2D petroleum reservoirs on unstructured grids

Fri, 05 Jul 2024 00:00:00 +0000

The use of very high-order schemes to solve the transport problem, together with multiscale methods
applied to multi-phase flows in petroleum reservoirs has not been explored in literature. In this work, the Multiscale
Control-Volume (MsCV) method is used to solve the elliptical pressure problem while the hyperbolic saturation
equation is solved using the high-resolution nodal Correction Procedure via Reconstruction (CPR) approach. In
order to properly couple the previous set of equations, we use the Implicit Pressure Explicit Saturation (IMPES)
strategy and a velocity reconstruction operator based on the lowest order Raviart–Thomas shape functions. In
addition, a hierarchical Multidimensional Limiting Process (MLP) is employed in the reconstruction stage of CPR
approach to suppress numerical oscillations. To properly couple the MsCV method with the CPR approach an
adequate velocity reconstruction throughout all control volumes (CVs) is necessary to assure the accuracy of the
high-order method. Thus, the velocity field must present a proper degree of accuracy that, in general, is not handed
by multi-scale methods. To deal with this issue and to remove the high-frequency components of the error, we
have studied several smoothers. Hence, the aim of this paper is to describe the coupling of the MsCV method
with CPR for the first time in literature and to analyze the behavior and efficiency of different smoothers applied
to the elliptical problem in order to produce accurate velocity field and so proper two-phase flow results. Finally,
through two representative problems, which were solved to evaluate the accuracy, efficiency, and shock-capturing
capabilities of our new numerical methodology, we concluded that, for the same level o accuracy, our high-order
proposed methodology reduces the computational effort.

A new approach for modeling of fluid flow in naturally fractured porous media

Fri, 05 Jul 2024 00:00:00 +0000

It is important to consider the distinct hydraulic properties of the discontinuities and porous matrix in
the numerical simulation of fluid flow in fractured porous medium. In this sense, many researchers have been
proposed numerical models in the context of discrete fracture approaches. In general, numerical models with a
discrete fracture representation present a large number of degrees of freedom to adequately represent the
discontinuities, and as a consequence, requires high computational cost to solve the problem, even with a small
number of fractures. The present work introduces an approach based on the use of coupling finite elements to
consider the effect of the fractures in the simulation of steady-state fluid flow in fractured porous media. This
scheme allows the independent discretization of fractures and matrix (overlapping non-matching meshes) without
increasing the total number of degrees of freedom of the problem. Two examples are performed to demonstrate
the versatility of the proposed model.

Upscaling Numérico Baseado em uma Metodologia Multiescala para a Simulação de Escoamentos em Reservatórios de Petróleo Heterogêneos e Anisotrópicos

Fri, 05 Jul 2024 00:00:00 +0000

This work aims to develop a scale transfer methodology in highly heterogeneous and anisotropic
porous media, that makes it possible to solve elliptical problems with accuracy and low computational cost. A
scale transfer method is developed that uses the Multiscale Finite Volume Method (MSFVM) to perform a flow
based numerical upscaling of absolute permeability. The transmissibility matrix was built in the coarse mesh
over the projection and restriction operators obtaining permeability in the coarse scale. This allows to solve only
local problems in the coarse mesh volumes and to use pressure multiscale solution in the fine mesh. The
permeability field can be obtained by different strategies, and enabling simulations directly on the coarse mesh,
controlling the accuracy of the solutions and also with the possibility of updating the permeability field over the
recalculated locally conservative multiscale solution.

LSTM Ensemble Approach for Demand Forecasting in Supply Chain Management

Paulo J. D. A. Barbosa, Daniel C. Cavalireri — Fri, 05 Jul 2024 00:00:00 +0000

Perishable product handling represents great challenge to supply-chain management. These items
have shorter shelf-life and most of them have special needs for transportation, storage and display. Inappropriate
treatment of these products, as well as the inability of the retailer to sell them within its shelf-life leads to waste
of products that affects the entire supply chain, society and environment. The trouble to manage these products is
to match the stock replenishment with its future demand and retail profits are significantly affected by perishable
losses. This paper proposes an approach of an one-step ahead forecasting for single time series using LSTM
Ensemble. The forecasts obtained by the proposed method yielded smaller forecasting error compared to the best
single LSTM, best single ARIMA and to the 12-month average sales - method commonly used by retail.

Automação na avicultura de corte: Desenvolvimento de um sistema de identificação, monitoramento e predição do peso de aves com uso de visão computacional

Andre E.P. Freitas, Lucas D. Fonseca, Thiago M.R. Dias — Fri, 05 Jul 2024 00:00:00 +0000

Na ultima década, o setor agroeconômico avícola brasileiro cresceu 112%, posicionando o Brasil como
l ́ıder em produção e comercialização da carne de frango, sendo hoje o maior exportador e o segundo maior produtor
mundial. A implementação de tecnologias que possibilitem melhor organização, capacidade gerencial e inovações
no processo se fazem necessarias para aprimorar a produtividade, controle e qualidade do produto fornecido pelas
plantas avícolas brasileiras, disponibilizando ao setor melhores condições para atender a demanda mundial. No
contexto tecnologico, a Visão Computacional já se estabelece como importante e abrangente tecnologia de senso-
riamento aplicado a sistemas de automac ̧ao, buscando reproduzir a visão humana e podendo ser implementada em
diversas areas e processos produtivos. Desta forma, imagens podem ser utilizadas para gerar fluxos de execuções
em sistemas computacionais. A observação desses dois fatores motivou o desenvolvimento deste projeto, que re-
sultara em um sistema capaz de detectar, identificar e monitorar o desenvolvimento de lotes de aves presentes em
um aviario, integralizando conceitos de Modelagem e Controle de Processos e de Programação de Computadores
e Computação Aplicada, para o processamento das imagens e para a análise, armazenamento e exibic ̧ ́ ao dos dados,
respectivamente. O sistema sera desenvolvido em linguagem Python, implementando técnicas de visão compu-
tacional, com auxílio da biblioteca OpenCV, utilizando a plataforma Raspberry Pi, com o objetivo de processar
imagens obtidas por uma camera de vídeo in loco afim de monitorar atraves de uma aplicação web a distribuição
do perfil de peso dos lotes de aves presentes em um aviario, de forma não invasiva, autonoma e de baixo custo.

Aplicação de microcontroladores de baixo custo para o desenvolvimento de um analisador modular – módulo de análise de vibrações

Sávio M. F. Pessoa, Richard Senko — Fri, 05 Jul 2024 00:00:00 +0000

Para as indústrias se manterem competitivas atualmente, é necessário que seus equipamentos estejam
em pleno funcionamento, logo, setores de manutenção industrial precisam ter acompanhamento diário sobre a
situação do maquinário. Porém, o alto custo de equipamentos para auxiliar estes setores na aplicação da
manutenção preditiva, faz com que pequenas e médias indústrias tenham dificuldades para elevar o padrão de
conservação e produção. Assim, apresentam-se como opções os microcontroladores de código aberto. Os objetivos
deste artigo são avaliar e definir a melhor plataforma de prototipagem para construção de um analisador modular
de baixo custo, iniciando pelo módulo de análise de vibrações, para aplicação na manutenção preditiva. Para avaliar
a viabilidade das plataformas, considerou-se aspectos como: processamento, memória, interface, modularidade e
preço. Primeiramente, realizou-se teste de amostragem e ruído em um sistema vibratório utilizando um
acelerômetro, para seleção da plataforma ideal. Posteriormente, utilizou-se o microcontrolador selecionado,
implementando o módulo de análise de vibrações testando-o num sistema rotativo. Neste trabalho, possibilitou-se
definir que o microcontrolador Raspberry Pi 3 B+ seria a mais indicada, pois apresentou; maior taxa de
amostragem, possibilitando detecção de sinais de maior frequência; maior relação sinal ruído e alto poder de
processamento; características ideais para uma aplicação modular.

Algoritmo de Rastreamento de Trajetória Veicular

Lucas D. Fonseca, Thiago M.R. Dias — Fri, 05 Jul 2024 00:00:00 +0000

O surgimento de carros autonômos e tecnologias de direção assistida torna essencial o desenvolvimento
de tecnologias capazes de agregar valor e auxiliar na execução de trabalhos. A aplicação de softwares baseados
em visao computacional possibilita uma série de aplicações em termos de monitoramento de tráfego, auxílio de
dirigibilidade e direção autônoma. Nesse contexto, o presente trabalho busca o desenvolvimento de um algoritmo
para rastreamento da trajetoria de veículos em imagens digitais. Atraves do uso da biblioteca OpenCV e da ́
linguagem de programação Python, foi possível a implementação de um algoritmo capaz de reconhecer veículos
em imagens e, por meio da analise de sucessivos frames, identificar a trajetória destes. Para elaborar uma relação
matematica que descreva a presença de um automóvel na imagem analisada, são realizados testes empíricos. Apos
a determinação da referida relação, e possível a construção de um método que reconhece os parâmetros necessários
para o rastreamento do veiculo e retorna sua posição relativa no instante em que o frame e processado. A aplicação
de metodos numéricos e técnicas para análise e processamento de imagens permite a extração de dados em tempo
real para analise e tomadas de decisões. O uso de rotinas computacionais e indispensável para a obtenção de
resultados mais apurados e confiaveis do algoritmo desenvolvido. Por fim, e elaborado um software capaz de
encontrar, em tempo real, veıculos em movimento e calcular suas posições, velocidades e acelerações relativas ao
ponto de captura da imagem.

Identificação e Análise dos Principais Tópicos de Pesquisas em Engenharias no Brasil

Jether Gomes, Thiago M. R. Dias, Gray F. Moita — Fri, 05 Jul 2024 00:00:00 +0000

A ciência apresentou um crescimento impressionante nas últimas décadas quanto ao número de
publicações de artigos científicos. Consequentemente, nota-se um esforço global de todas as áreas do
conhecimento, negócios e fundações interessados em entender o patamar científico para, por exemplo, servir de
base na construção de políticas científicas ou impulsionar grupos de pesquisas. Neste contexto, o objetivo deste
trabalho é identificar e analisar temporalmente os principais tópicos de pesquisa publicados durante a trajetória da
ciência brasileira por pesquisadores doutores que possuem currículos cadastrados na Plataforma Lattes e tem as
Engenharias como grande área de atuação. Para isso, após a aquisição dos currículos, foi desenvolvido um
arcabouço de componentes responsável por filtrar, tratar e consolidar separadamente os dados das publicações
científicas a serem analisadas por métodos bibliométricos. Dentre estes dados, estão todas as palavras-chave de
artigos publicados em periódicos entre 1997 e 2016, que são ranqueadas através da aplicação de uma medida de
popularidade de tópico (TF.FI) proposta, que considera tanto as características quantitativas das palavras-chave
dos artigos quanto qualitativas dos periódicos em que tais artigos foram publicados.

MODELING AND SIMULATION OF A TANK SYSTEM USING PREDICTIVE CONTROLLERS

Luiz G. C. Costa, Mário S. C. Filho, Luiz C. Oliveira, Emerson de S. Costa — Fri, 05 Jul 2024 00:00:00 +0000

The study and application of PID controllers -Proportional, Integral and Derivative- represents
a great advance in productivity to the automation, being this one the most used for control of dynamic
systems. However, despite the robustness and ease of use of PID, we have more efficient options for
nonlinear processes or with dominant delay time. Among them, it should be emphasized that studies
are developed on predictive controllers based on model or MPC-Model Predictive Control-. The present
work aims to simulate a tank system with the objective of studying and evaluating the applicability of
MPC implemented in PLC - programmable logic controller. The PLC was chosen as one of the main
industrial automation tools, showing robustness to applications in adverse environmental conditions and
is widespread in the sector. Allied to the PLC, a supervisory software was developed that is responsible
for receiving information via the MODBUS protocol and storing it in a database. Such automation tools
as PLC and supervisory software stand out, for their ease, simplicity and robustness. The information
obtained by the process sensors will be used to construct the dynamic model of the system. Among
the steps, it was initiated by the instrumentation of the system, construction of the sensor, calibration
and connection to the PLC. The logical controller, in addition to sending information for presentation
and storage, will be the tool used to interpret the process signals and then execute the predictive control
algorithms. Thus, MPC presents dependency on the model for its construction and performs iterative
optimizations based on constraints that can be imposed on the cost function. Therefore, it is observed
that the construction of its algorithm is more complex when compared to the PID. It then becomes an
advantage to develop process simulations and use for MPC controller tuning. The construction of the
simulated model will allow to adjust parameters of the predictive controller and the cost function of the
optimization algorithm and after we can check that MPC was able to run in PLC and with results based
on control performance index.

Extensions and Improvements of the Extreme Learning Machine (ELM) Applied to Face Recognition

Fri, 05 Jul 2024 00:00:00 +0000

Considering data science popularization in recent years, there has been an increase in using machine
learning methods, such as artificial neural networks, in several research fields. The Extreme Learning Machine
(ELM) method is a single-hidden layer feedforward network that stands out for its computational efficiency. It is
reached mainly by adopting random weights initialization between the input layer and the hidden layer, as well as

for the hidden neuron bias. This initialization allows the weights between the hidden and output layers to be deter-
mined analytically by calculating the pseudoinverse, avoiding the use of an iterative algorithm based on gradient

descent. This work seeks to evaluate the performance of more sophisticated strategies for initializing the weights

and fitting the machine’s internal parameters. We proposed a performance analysis when replacing the pseudoin-
verse resolution step with the non-linear dual version of the linear least squares (LSDual), still little explored in

the literature. We performed tests over face recognition databases in a classification approach. The results support
the construction of an ELM model with a higher level of robustness regarding the quality of prediction. The use of
more sophisticated random initialization coupled with LSDual solution reduced the testing error in all scenarios.

INTELIGÊNCIA ARTIFICIAL PARA AUTOMATIZAR A TRIAGEM DOS EXAMES DE RAIO-X DE TÓRAX DE PACIENTES SUSPEITOS DE COVID-19

Fri, 05 Jul 2024 00:00:00 +0000

Em 11 de março de 2020 a Organização Mundial da Saúde (OMS) decretou pandemia da Covid-19,
doença causada pelo novo coronavírus (Sars-Cov-2) e no o Brasil o primeiro caso foi registrado em 26 de fevereiro
de 2020. Depois disso, os números cresceram e continuaram a aumentar. Em casos mais graves essa enfermidade
causa uma espécie de fibrose pulmonar que é caracterizada pela formação excessiva de tecido que engrossa as
paredes dos tecidos pulmonares prejudicando a elasticidade e a troca gasosa do pulmão. Isto posto, recomenda-se
a realização do raio-x de tórax ou de tomografia computadorizada (TC) para os casos mais graves dessa patologia.
Como o exame de raio-x tem um custo menor do que o de TC, seu acesso é mais amplo, sendo encontrado em
grande parte das unidades de saúde. Diante disso, com o intuito de apoiar e automatizar o trabalho dos profissionais
da saúde, esta pesquisa tem como objetivo utilizar a linguagem de programação Python para desenvolver um
algoritmo de Redes Neurais Convolucionais (RNC) para agilizar a triagem dos exames de raio-x de tórax de
pacientes suspeitos de Covid-19. Em testes iniciais constatou-se uma acurácia de 98%.

Aplicação de Inteligência Artificial na Identificação do Uso de Máscara na Prevenção da Covid-19

Fri, 05 Jul 2024 00:00:00 +0000

Em dezembro de 2019 constatou-se o primeiro caso de Covid 19 em Wuhan, na província de Hubei,
República Popular da China. Essa doença é causada pelo SARS-CoV-2, vírus que se espalhou no mundo todo e
assim causou uma pandemia. Segundo as orientações da Organização Mundial da Saúde (OMS) medidas como
lavar as mãos frequentemente, evitar aglomerações e utilizar máscara devem ser tomadas para prevenção da
doença. A utilização de máscaras deve ser feita por todos sempre que houver a necessidade de sair de casa.
Sendo correto a utilização de máscara cirúrgica ou de pano dupla face, a qual deve cobrir todo o queixo, boca e
nariz de forma ajustada ao rosto. Em alguns países como o Brasil, a não utilização de máscara foi decretado
como infração e pode acarretar na cobrança de multa em algumas cidades. Pensando nesta problemática, este
trabalho tem como objetivo desenvolver um algoritmo de Redes Neurais Convolucionais (CNN) que identifica se
a pessoa está ou não utilizando a máscara. Esse programa poderá ser usado como uma triagem que alertará o não
uso da máscara para impedir a entrada em locais de acesso públicos. Em testes iniciais constatou-se uma
acurácia de 97%.

FORECASTING THE SPOT PRICE BEHAVIOR IN THE BRAZILIAN ENERGY MARKET WITH STATISTICAL TOOLS

Fri, 05 Jul 2024 00:00:00 +0000

Electricity in the short-term market, or spot market, is traded according to the Difference Settlement
Price PLD, whose calculation follows a complex and computationally demanding procedure. The present work
proposes the use of statistical methods to forecast PLD values and trends in order to mitigate uncertainty in the
decision making of market agents. Inputs for the proposed models are the affluent natural energy, the stored energy,
the hydroelectric, thermal and wind generations, and the demand for electric energy, publicly disclosed by the
system operator ONS, in addition to the historical series of the PLD itself, disclosed by Electricity Trading
Chamber CCEE. One week ahead forecasts for the southern Brazilian submarket under heavy demand are
proposed, based on time series and regression models for a 2015-2020 historical data. The best PLD forecast
accuracy is achieved with the simple exponential smoothing time series model, with average errors of 17.91 %
and 28.01 R$/MWh. The best trend forecast, of 64.77 %, is obtained by both time series exponential smoothing
models.

Classification of Sleep Stages using Neural Networks

Fri, 05 Jul 2024 00:00:00 +0000

Sleep stages are considered important indicators for diagnosing neurological and psychiatric illnesses,
so sleep disturbances have a major impact on a person's well-being. However, many sleep status analyzes are done
visually by professionals in the field, which can be a slow task. For this reason, studies on sleep states automatically
are of great importance in diagnosing neurological disorders quickly. In this article, an approach using the variance
of the electroencephalogram (EEG) as an input to a multilayered neural network was used to classify sleep states.
The EEGs were obtained from the Sleep-EDF Database Expanded database, obtained from two healthy patients,
the first containing 7,950,100 records (22 total hours), and the second 8,490,100 (23 total hours), being extracted,
filtered and subsequently classified automatically into five sleep states. A neural network used was fully connected

with two intermediate layers and 12 neurons in each layer, with a learning rate of 0.01. The accuracy of the five-
stage classification was 94.3%. These results showed that the proposed algorithm is favorable to obtain a

classification of the stages with good precision in comparison to the other results found in the literature.

iagnosis of breast cancer using Artificial Neural Network

Fri, 05 Jul 2024 00:00:00 +0000

Breast cancer is a common invasive cancer in women, affecting more than 10% of the world's female
population, being one of the main causes of death in the world. The analysis of the biopsy procedure carried out
by a qualified professional, still appears as the most effective method in the diagnosis of cancer in general, if

diagnosed and treated prematurely, the patient has great chances of cure, however the process can be time-
consuming and the diagnosis is not it's always assertive. In this context, automatic breast cancer classification

algorithms appear, using machine learning algorithms in search of an efficient result for the final diagnosis.
However, it is still necessary to establish methodologies with greater precision to guarantee the assertive result.
Here, we use a multilayer artificial neural to classify breast cancer in two stages: malignant and benign. To test
the proposed methodology, a Breast Cancer Wisconsin (Diagnostic) Data Set database was used, where feature
extractions were made from digitalized images of breast masses. Several architectures of the neural network
have been proposed. And a cross-validation was implemented with 10 k-fold. The result showed an average
accuracy of 92%. Thus, with this result, a tool can be made that can expedite the diagnosis of the patient in a
precise way and, consequently, enable an early treatment increasing the chances of cure.

STOCK MARKET PREDICTION USING NEURAL NETWORKS

Bianca V. L. Pereira, Marta de O. Barreiros — Fri, 05 Jul 2024 00:00:00 +0000

Trading on the stock exchange is a fundamental part of a country’s economic development, resulting
in profits directly or indirectly from market transactions. However, the stock exchange is highly dynamic, stocks
rise and fall as a result of changes in various parameters. Some techniques have already been used to try to predict
these changes in the market, but there is still a need for improvements to ensure greater accuracy in the market’s
bets, as most of them are high risk. Predicting an asset’s closing value is a difficult task because the asset’s value
is constantly changing and has a variety of parameters that influence its increase and decrease. In this work, an
algorithm based on Multilayer Perceptron Neural Network (MLP) was implemented to estimate the price of assets,
predicting the closing value of the stock market shares. The proposed network architecture was modeled with two
hidden layers, containing six neurons in the first layer and four neurons in the second layer and one neuron in
the output. In this case, MLP considerably closed the closing of all the proposed shares (EQTL, PETR4, IBM,
ABEV3, BBAS3, CIEL3, COGN3, LAME4, OIBR3 and VALE3) in the period of 10 consecutive years, forecasting
an average of 93.60% of the value of the actions in the year following the training of the network.

Monitoramento de Falhas em Maquinas Elétricas Rotativas Usando Sinais de Vibração e Machine Learning

Lucas de O. Soares, Diego A. Lobao, Luiz A. Pinto — Fri, 05 Jul 2024 00:00:00 +0000

Rotating electrical machines are essential components of modern production systems. Due to their
structural characteristics, as, small gaps between fixed and moving parts, and by operating at high rotational speeds,
a local incipient failure can spread out through the entire equipment, leading to system and production shutdown. In
view of this, an efficient maintenance strategy becomes necessary to ensure the availability and safety of equipment,
facilities, and operators. This work presents the development stages of a system to detect and diagnose failures
in rotating equipment, through vibration signals analysis from the data set Mafaulda. For failure detection and
diagnosis, a fusion of descriptors in both time and time/frequency domains is used. In the classification stage, the
following Machine Learning algorithms are applied: Support Vector Machine (SVM), Artificial Neural Networks
(ANN) and Random Forest (RF). The obtained results, considering the accuracy (98,63%) with RF, in diagnosing
failures such as shaft misalignments, structural unbalances, as well as bearings failures, indicate that the use of
intelligent systems in detecting and diagnosing failures in rotating machines, in fact, improves the availability and
reliability of production systems, reducing untimely stops for corrective maintenance.

Projection of Covid-19 in state of Minas Gerais using artificial neural network

O. Fernanda, M. Camila, O. Filipe, Edyene Oliveira — Fri, 05 Jul 2024 00:00:00 +0000

Coronavirus is a disease that, since the end of 2019, has been contaminating people in all
countries and continents. As a result of its appearance, scientists and researchers around the world are
conducting studies and disseminating information from data on virus behavior in the human body to data
on contagion and prevention. These research fhave been decisive in the fight against Covid-19, because
according to WHO (World Health Organization) the tendency is that the virus continues to circulate for
some years. Therefore, the exhibition of auxiliary information helps people and governments to take actions
to reduce Contagion. Thus, the present work aims to project the impact of the pandemic in the State of
Minas Gerais, considering the government data to try control the pandemic, such as periods when there was
social isolation and social flexibility. For the realization of this project, the use of Artificial Neural
Networks (ANN) was made. To train the ANN, data from public government databases, both national and
international, were used. This data was pre-processed using Python and Matlab programming language. In
addition, they were carried out in the comparative project between the ANN algorithms, aiming to find the
best performance among them.

DATA-DRIVEN IDENTIFICATION OF OPERATING PATTERNS IN A THERMAL POWER PLANT BY CLUSTERING METHODS

Fri, 05 Jul 2024 00:00:00 +0000

Thermal power plant operation depends on the knowledge of a wide range of complex and cross de-
pendent parameters. Information is usually captured through Distributed Control Systems (DCS) which allow to

access up to date data but also long periods of recorded operation. Large and available data sets are decisive for
plant operation, but they must be properly used and interpreted to achieve effectiveness. The purpose of the present
paper is to present an identification of operational patterns from historical data from an actual thermal power plant
based on unsupervised machine learning methods. The proposed methodology is applied to a long term data series

from the 360 MW Brazilian coal-fired Pecem power plant, for 29 selected parameters, concerning its steam gen-
erator and associated mills. Dataset size and redundancy is treated by the Principal Component Analysis (PCA)

approach, which defines a lower dimensional space, proper for clustering while preserving most of its variance.

The K-means clustering method identifies operating point groups according to their degree of similarity. The ap-
propriate cluster number is defined by means of the average silhouette coefficient, which measures the clusters

consistency. Cluster parameter values and distribution are evaluated to verify result consistency. The assessment

with the 29 parameters from the steam generator and mills system is presented, and the results show that the op-
eration may be described globally by a 2 clusters analysis or, for refined observations, by a 10 clusters analysis.

The different patterns encountered facilitate an understanding of the parameters arrangement and resulting perfor-
mance, enabling the identification of low efficiency operation conditions and supporting practices to improve the

plants operation.

Comparative analysis of the performance of a enriched mixed finite ele- ment method with static condensation for Poisson problems

Fri, 05 Jul 2024 00:00:00 +0000

The enriched mixed method is a variant of the mixed finite element method, obtained through a selection
and appropriate configuration of the shape functions in the space of flux approximation, increasing the order
of approximation just inside the elements, taking care of the balance with the space of approximation of the
potential. The purpose of this paper is to analyze this method in the context of the Poisson equation. For spaces
of approximation of various orders, we carry out numerical simulations considering two model problems: smooth
(low oscillation and low gradient) and strongly oscillatory, in quadrilateral meshes. We conclude that the enriched
mixed method of order p achieves a precision practically equivalent, with lower computational cost, to the mixed
method of order p + 1.

Machine Learning models to predict nonlinear simulations of net section resistance in steel structures

Raí L. Barbosa, Francisco Evangelista Junior — Fri, 05 Jul 2024 00:00:00 +0000

This paper applies Machine Learning techniques to predict computer simulations of net section
resistance in bolted cold-formed steel connections of steel structures. Support Vector Regression (SVR) and
Gaussian Process Regression (GPR) techniques where chosen to be used for the analysis due to their good
performances on high dimensional data problems. One of the goals is to construct an efficient machine learning
model with minimal training to the uncertainty quantification of the net-section resistance. The algorithms were
trained using data set from expensive nonlinear finite element simulations where the resistance depends on the
cross-section geometry, connection eccentricity and connection length. The finite element simulations were
considered nonlinear due to the elastoplastic behavior of the steel. SVR and GPR were then compared by using
standardized statistics measures with different cross-validation strategies. The results showed that SVR had a
slightly better performance. In addition to that, it was possible to identify the best covariance function of each
technique for this specific problem.

Support method for the diagnosis of Atrial Fibrillation using Machine Learning.

Luis Fillype da Silva, Jonathan Araujo Queiroz, Allan Kardec Barros — Fri, 05 Jul 2024 00:00:00 +0000

The electrocardiogram is an examination that provides a graphical representation of the electrical
activity of the heart. Through it, it is possible to observe the rhythm of heart beats, the number of beats per
minute, in addition to enabling the diagnosis of various arrhythmias. This article aims to develop a classification
model based on the beats of two groups of individuals, healthy and Atrial Fibrillation. The methodology for the
extraction of characteristics based on the morphology of the cardiac signal was adapted to classify Atrial
Fibrillation. Classifications were performed in two-dimensional and three-dimensional space, obtaining accuracy
from 95% to 100%.

Classification of Intra Cardiac Atrial Fibrillation using High Order Statistics and Machine Learning.

Luis Fillype da Silva, Jonathan Araujo Queiroz, Allan Kardec Barros — Fri, 05 Jul 2024 00:00:00 +0000

The electrocardiogram is an exam that quantifies the electrical activity of the heart, allowing the
detection of the heart rhythm, the number of beats per minute and the diagnosis of various cardiac pathologies.
This article aims to obtain a classification model based on the beats of two groups of individuals: healthy and
unhealthy. The feature extraction methodology was used and adapted for the classification of atrial fibrillation.
Classifications were performed in two-dimensional and three-dimensional space in the database, obtaining an
accuracy of 97% to 100%.

Prediction of Covid-19 contagion in the State of Maranhão using Neural Networks and the SIR epidemiological model

Sat, 06 Jul 2024 00:00:00 +0000

Coronavirus disease 2019 (COVID-19) is a public health emergency of international interest, being
declared by the World Health Organization (WHO) as a pandemic, and has instituted essential measures for
prevention and confrontation. Because it has high rates of transmission and rapid dissemination around the world,
medical authorities worldwide have realized its potential danger and the possible collapse of the Health Systems

of the affected countries. Therefore, specific predictive methods are urgently needed to predict the risk of COVID-
19 and to assist in the decision-making process in the control of epidemics and / or pandemics. Here, the number

of cases for the State of Maranhão in the period from 27/03 to 27/05 of this year was estimated, with observations
up to the Lockdown decree using the epidemiological model SIR (Susceptible-Infected-Recovered) and a neural
network Multilayer Perceptron (MLP). The samples were obtained through Kaggle, collected from the Ministry
of Health. In order to compare the algorithms, the population was divided into three groups: susceptible, infected
and recovered. MLP averaged 5507.95 cases, while the actual number was 5787.56. An epidemiological
mathematical model estimated the number of cases with a larger lag (about 1.8 million cases). The results obtained
by the proposed method can be used to support COVID-19 decision making. The neural network has shown to
have more reliability in the results and is closer to the real cases disclosed until May 17, 2020.

ANÁLISE DE SINAIS ECG POR MEIO DA DECOMPOSIÇÃO EMPÍRICA DE MODO E ALGORITMO DE PAN E TOMPKINS

Sat, 06 Jul 2024 00:00:00 +0000

A análise automática computadorizada de sinais fisiológicos tem sido um grande campo de interesse
desde as últimas décadas. O sinal do eletrocardiograma representa a atividade elétrica do coração e é caracterizado
por um comportamento periódico ou semiperiódico. O estudo detalhado e a análise metódica de ondas, intervalos
e segmentos são tipicamente compostos de três ondas significativas chamadas; Onda P, complexo QRS e onda T.
Essas ondas são registros do comportamento do coração e são estudadas, analisadas e interpretadas para o
diagnóstico de anormalidades cardíacas. O complexo QRS possui aspectos dominantes em relação aos outros
componentes do sinal de ECG. A aquisição e o pré-processamento de sinais fisiológicos são frequentemente
seguidos pela extração de parâmetros de importância clínica. No caso do sinal do eletrocardiograma (ECG), o
complexo QRS é um dos parâmetros mais significativos para o diagnóstico de arritmias cardíacas. Neste trabalho,
a detecção de frequências cardíacas é proposta com a adição de dois algoritmos: o método de decomposição em
modo empírico (EMD) e o algoritmo de Pan e Tompkins, utilizado no pré-processamento dos sinais. O EMD visa
decompor de forma adaptativa os sinais não lineares e não estacionários em uma série de sinais modulados em
amplitude e frequência, denominados funções de modo intrínseco (IMF). O algoritmo foi testado em sinais do
banco de dados do MIT / BIH (Massachusetts Institute of Technology - Beth Israel Hospitalar). Os resultados
obtidos foram promissores, o algoritmo mostrou -se eficiente na detecção do complexo QRS e por conseguinte a
frequência cardíaca, possibilitando a detecção de arritmias.

Financial Market Shares Prediction Using LSTM Networks

Clauber Martins, Marta Barreiros — Sat, 06 Jul 2024 00:00:00 +0000

The financial market provides economic growth, as it is very efficient in capturing savings and other
resources for more productive activities. Stock investment is seen as a challenge even for specialist shareholders
with many years of experience, in which the results for this type of investment are quite variable, as they are based
on different macroeconomic factors with highlights in political events, bank rates, expectations investors, financial
conditions in general, among others. Therefore, accurately predicting the variation of these prices is quite
challenging, thus making it of great interest to investors to minimize this problem. Thus, artificial intelligence
techniques are quite favorable to predict stocks in the financial market. To predict stocks on the stock exchange,
we propose a methodology based on a recurring artificial neural network, the Long Short Term Memory (LSTM).
This type of neural network, designed for time series, takes time and sequence into account, giving a feedback
loop connected to your previous decisions, being quite appropriate for predicting data such as the stock exchange.
The input data of the LSTM network were shares on the Petrobras stock exchange, in the period from January
2014 to December 2017 to make a projection of a future month which is the month of January 2018 based on the
previous data, the operations were simulated in this action, obtaining the forecast of the stock's share with a
difference of 0.03 and 0.23 cents.

Estimating drought indexes from three satellite-based retrieval algorithms over the São Francisco River basin

Sat, 06 Jul 2024 00:00:00 +0000

The prediction of droughts in the São Francisco River Basin (SFRB) plays an imperative role for
environmental and socioeconomic studies as it can provide estimates of short-, mid- and long-term water supply
in the basin. However, in smaller and more remote areas, the availability of a network of rain gauges is
compromised. Thus, satellite-based rainfall products become the only source of estimates of rainfall for much of
the regions in the SFRB, especially the more remote and underdeveloped ones. This study presents drought
indexes as calculated from estimates of rainfall from three satellite-based retrieval algorithms: TRMM,
PERSIANN and CHIRPS. Drought indexes are averaged for the whole SFRB and presented as time series for as
long as the estimates of rainfall from each algorithm spans. For this work, droughts were measured as a function
of the SPI (Standardized Precipitation Index). Estimates of SPI values indicated that 22, 18, 10 out of 252
months were from moderate to extreme droughts from TRMM, PERSIANN and CHIRPS, respectively.

Predicting effective constitutive constants for woven-fibre composite materials

Jonas T. da Rocha, Tales V. Lisboa, Rogerio J. Marczak — Sun, 07 Jul 2024 00:00:00 +0000

A meso-scaled finite element model is developed aiming at the study the mechanical properties of woven-
fibre composites regarding different weave pattern. A Representative Volume Element (RVE) is constructed and

the Uniform Displacement Boundary Conditions (UDBC) are applied in order to obtain the stiffness tensor of

such composites. Two different types of woven-fibre composites are evaluated by the introduced model - E-
glass/Vinylester plain-weave and 2/2 Twill E-glass/Epoxy. The results from computational homogenization are

compared to both experimental and numerical works from literature, showing good agreement. It is verified that
the boundary conditions applied to the RVE play a significant role in the homogenization results.

Computational algorithm for geometrically nonlinear analysis of laminated composite frames with zig-zag enhancement of the transverse strain field

Caio C. L. G., Humberto B. Coda, Rodrigo R. Paccola — Sun, 07 Jul 2024 00:00:00 +0000

Laminated composite materials are widely used in engineering applications due to the high control
and flexibility over the design of its mechanical properties. It is known, however, that when subjected to loads,
structural elements made of laminated composites display a zig-zag pattern on their strain field in the transverse
direction, behaving differently from the usual assumption that considers transverse sections as planes after the
load application for calculation purposes. Therefore, this work proposes the implementation of a finite element
method computational algorithm, based on positions, that numerically solves laminated composite frames by
enhancing the strain field in the transverse direction. The first order shear deformation theory (FSDT) adapted

for generalized vectors is used as the basic kinematic assumption, and then enhanced by a normalized zig-zag-
shaped function multiplied by an amplitude factor, which is a new nodal degree of freedom. In addition, the

cross section direction and height variation are represented by generalized vectors, which are also nodal degrees
of freedom. The developed formulation is total Lagrangian, comprising large displacements and rotations, and
uses the Saint-Venant-Kirchhoff constitutive law, which allows moderate strains.

Experimental and Finite Element Analysis of Pullout Test on GFRP Rebars

Sun, 07 Jul 2024 00:00:00 +0000

Rebars with fiber glass reinforced polymer (GFRP) are a viable option in highly aggressive environ-
ments. They also make the structure lighter, more sustainable and have high corrosion resistance. In this article,

an experimental program was carried out to verify the maximum pullout force, in addition to a numerical analysis
and computational simulation. The finite element method was used for the computational simulation of concrete

reinforced with GFRP. A constant tractive force was applied at the end of the rebar, from which the strain and max-
imum principal stresses were analyzed. The displacements and concrete-GFRP adhesion were verified through the

Hertz contact theory and Coloumb friction theory, in the ABAQUS software. The results showed that the incorpo-
ration of epoxy resin had little influence on the pullout force. The experimental and numerical analysis showed an

increase of about 20% in the pullout force of the GFRP bars, although this should not be the only limiting factor
for the use of GFRP rebars in civil construction.

Inverse analysis of constitutive models applied to steel fiber reinforced concrete

Leticia C. D. Santos, Alejandro Nogales, Ricardo Pieralisi — Sun, 07 Jul 2024 00:00:00 +0000

Steel fiber reinforced concrete (SFRC) structures are increasingly being inserted in engineering, mainly
due to the good properties of the material to the tensile stresses. To represent the behavior of these structures, there
are several constitutive models in the literature, in which the stress x strain diagram of the material is derived from
laboratory tests, such as the flexural test EN 14651. The simplicity of obtaining the stress x strain diagram of these
constitutive models is one of its main advantages, however, they do not always represent the real behavior of the
material. In this paper, the modeling strategies developed to simulate the EN 14651 three point bending test are
presented, where the constitutive models of 2010 fib Model Code (MC 2010) and 2008 Instrucction de hormigón
structural (EHE 08) are inserted. Through a quasi - static analysis of the Abaqus software, the divergences and
similarities between the two models and existents experimental results are discussed. An adaptation of the stress
x strain diagram is suggested through an inverse analysis, where it was possible to perceive that the complex
mechanical behavior of the SFRC needs adjustments to be better represented.

PARAMETRIC STUDY ON FRACTURE ANGLE SEARCH ALGORITHM FOR PUCK’S 3D MATRIX FAILURE CRITERION

Kayque Andson S. Ximenes, Marcelo S. Medeiros Jr., Evandro Parente Jr. — Sun, 07 Jul 2024 00:00:00 +0000

The Puck’s failure criteria is one of the most successful models for assessing the onset of
damage in unidirectional (UD) laminate composites. However the original algorithm proposed for matrix
fracture plane angle search is based on brute-force approach where all the angles between −90o
to 90o
, in

increments of 1

o ought to be evaluated. This work presents an enhanced method to expedite the detection
of inter-fiber fracture (IFF) angle in UD laminate composites. A series of numerical optimisations and
enhancements were made to reduce the computational cost of the fracture angle search.

STRUCTURAL ANALYSIS OF A COMPOSITE WING SPAR OF A LIGHT SPORTING AIRCRAFT

Sun, 07 Jul 2024 00:00:00 +0000

Este artigo tem como objetivo examinar o comportamento mecânico-estático de uma longarina
compósita projetada para uma aeronave esportiva leve através de investigações numéricas, empreendidas em
software (ANSYS Release 19.2) comercial de elementos finitos. Diferentes seções transversais foram testadas
numericamente para se determinar suas respectivas tensão equivalente e deslocamentos finais alcançados. Para
avaliar os efeitos tridimensionais, modelos com a capacidade de simular uma viga em balanço, onde uma
extremidade foi engastada enquanto a outra sofre flexão devido a sustentação, foram desenvolvidos cumprindo
etapas de definição geométrica, geração de malha e aplicação de carregamento. As simulações revelaram que os
fatores analisados, assinalaram os efeitos dos picos resultantes de tensão na sobrecarga sob a região engastada,
simultaneamente, destaca que uma opção de perfil se sobrepõe com deslocamentos inferiores a 10 % em relação
aos outros, assim como tensões equivalentes variando 17 até 75 % inferiores ao que foi desenvolvido em outros
espécimes. Por fim, a partir dos resultados verificou-se a presença de pontos críticos e locais de baixa solicitação,
mantidos dentro de especificações de projeto, o que evidencia a versatilidade da análise por elementos finitos,
podendo evitar equívocos desconsiderados em análises empíricas, imprimindo celeridade ao processo de
investigação.

Allowable Load Assessment in Metal-Composite Double-Lap Joint

Helio de Assis Pegado, Rafael Felipe de Souza Almeida, Rodrigo de Sa Martins — Sun, 07 Jul 2024 00:00:00 +0000

This work consists of evaluating the tensile and compression static allowable stress of a hybrid (metal
-composite) riveted joint. The analyzed joint is composed by two sheets of 2014 – T6 aluminium alloy and a
T300/5208 Graphite/Epoxy quasi-isotropic laminate, which were joined by twelve Lockbolt Swaged Collar rivets
titanium alloy Ti–6Al–4V annealed. The joint was analyzed through a computational model developed using the
Finite Element Method (FEM), with the fasteners modelled through the Multi - Springs technique. This method
was widely used to simulate the mechanical behaviour metal-metal and composite-composite parts of the joint.
It is validated comparing its results with analytical results of metallic joints available in the literature. Through
this model, both the allowable load and its distribution in the fasteners of the joint were determined. Since the
evaluated joint is subjected to double shear and, therefore, has no eccentricities, the presence of secondary bending
was not observed, the bearing and bypass loads were the most relevant in evaluating the allowable loads of the
joint. The load distribution in the joint and its components’ safety margin was determined, with the laminate being
the limiting component of the allowable load.

Investigation of Concrete Damaged Plasticity for steel fiber reinforced concrete through numerical analysis

Matos C.C.D., Barboza A. da S. R. — Sun, 07 Jul 2024 00:00:00 +0000

The use of reinforced concrete with steel fibers (SFRC) in conventional structures has grown in civil
construction due to its mechanical characteristics, which have advantages when compared to conventional concrete
as better responses to tensile stresses and post-fissuring behavior. These factors lead researchers to deepen their
studies on properties and computational models in order to obtain better predictions for the structures built with this
composite. This work then has the main objective compare the Concrete Damaged Plasticity (CDP) parameters
suggested by Chi et al. [1] to the default used for plain concrete, simulating the SFRC as homogeneous material.
The presented analysis is performed using the finite element method (FEM), using the ABAQUS software as a
processing environment. Uniaxial tensile and compressive test parameters are used as input to calculate the CDP
parameters for SFRC. Beam models are tested according to the proposed test parameters EN-14651 using the
parameters suggested by Chi et al. [1] and default values for concrete. The model showed resistance, within the
acceptable margins, consistent with the experimental ones. However, these changes in CDP parameters showed
a little impact on mechanical response and curve shape. This process of obtaining the constitutive behavior for
SFRC proved to be acceptable from the practical point of view since it uses the results of tests of easy execution
as input parameters, but a few adjustments need to be done in order to obtain reliable results.

Análise Numérica de um Compósito Híbrido Através do MEF

Everton C. Silva, Avelino M. S. Dias, Raimundo C. S. Freire Júnior — Sun, 07 Jul 2024 00:00:00 +0000

A constante evolução da tecnologia vem gerando uma necessidade de produzir novos materiais que
solucionem requisitos cada vez mais particulares. Com a recente tendência da utilização de compósitos laminados,
logo tem sido estudado compósitos híbridos, somando assim, uma série de materiais com características mecânicas
mais específicas. De forma análoga aos laminados, tais materiais compósitos híbridos requerem novos estudos
referentes à caracterização de seu comportamento mecânico. Atualmente, um aliado nos estudos destes compósitos
tem sido a análise numérica, através do MEF. O principal objetivo deste trabalho foi a análise do comportamento
mecânico de um material compósito híbrido confeccionado com fibras de carbono e de vidro por meio do MEF.
Desta forma, foram analisados os resultados numéricos do ensaio de tração de materiais compostos por uma lâmina
de compósito híbrido e comparado os resultados obtidos experimentalmente, onde foram laminados os compósitos
híbridos trançados com fibra de carbono inicialmente na direção do carregamento e fibra de vidro orientado na
direção perpendicular à fibra de carbono. Para as análises computacionais, as amostras foram modeladas como
materiais ortotrópicos com sentidos da fibra de carbono a 0o, 30o, 45o, 60o e 90o. Introduziu-se também ao estudo
a análise de concentradores de tensões nos compósitos, os quais foram modelados como sendo uma placa com
furo central. Foram obtidos valores de diferença entre as tensões médias experimental e numérica para corpo de
prova sem descontinuidade de 1,71% para fibras à 0°; 21,83% para fibras à 30°; 12,79% para fibras à 45°; 39,77%
para fibras à 60° e 7,69% para fibras à 90°. Nas amostras com descontinuidade, obtiveram diferença de tensão
média de 19,62% para fibras à 0°; 10,94% para fibras à 30°;17,72% para fibras à 45°;15,51% para fibras à 60° e
116,10% para fibras à 90°.

Computational implementation of constitutive models of mortar joints for the analysis of masonry panels in ANSYS

Carolina R. F. Silva, Maria F. F. de Oliveira — Sun, 07 Jul 2024 00:00:00 +0000

The modeling of a masonry panel may be a complex task due to the anisotropic behavior of the
composite material. Deformation and failure properties depend on both the stress orientation and the joint
direction, since the mortar-unit interfaces act as weak surfaces. The simplified micro-modeling approach is one of
the several strategies that have been proposed for the numerical analysis of masonry panels in the frame of the
Finite Element Method. This approach makes use of zero-thickness interface elements to represent mortar joints
and simulate their sliding and opening behavior with appropriate constitutive models. This work analyzes the
behavior of structural masonry panels by using the simplified micro-modeling approach with the application of
the Finite Element Method software ANSYS. Two plasticity constitutive models for the mortar joints could be
investigated: a Mohr Coulomb envelop with tension cut-off and compressive cap with hardening, and a Mohr
Coulomb envelop with tension cut-off and bilinear damage. The corresponding algorithms were implemented into
an ANSYS user material subroutine by employing an implicit scheme using the return mapping algorithm.
Numerical results were compared to some experimental results available in literature.

VIRTUAL ELEMENT METHOD PRE-PROCESSOR SOFTWARE

Paulo Akira Figuti Enabe, Rodrigo Provasi — Sun, 07 Jul 2024 00:00:00 +0000

The Virtual Element Method (VEM) is a relatively recent method where it is possible to have non-
polynomial functions inside the virtual elements (virtual elements are the equivalent of finite elements for VEM),

while requiring them to behave like polynomials only at the frontier of the virtual elements. The “virtual” term
comes from the fact that the shape functions are computed implicitly using an optimal set of degrees of freedom
leading to a stiffness matrix that heavily depends on the choice of the degrees of freedom.
Geometry parameters like coordinate of vertices, polygonal diameter and area are fundamental quantities
in VEM because they are related to the choice of the degrees of freedom and, consequently, the stiffness matrix
calculation. In this work, a graphical user interface to VEM focused on the two-dimensional case is developed in
order to ease input data and guarantee VEM performance by ensuring the optimal choice of the degrees of freedom.
The interface is responsible to generate the geometry from a set of coordinates, calculate the area, centroid, and
polygonal diameter.
As the main goal of the interface is to make the use o VEM less abstract, a set of requirements were defined
for the graphic tool development. Among them, two are crucial: the interface must be user-friendly, guaranteeing
that user with no prior experience of the method can use it, and data input must be simple. To keep data input
simple, a text file with the coordinates of vertices are used. And to guarantee that the graphic tool is user friendly,
C# programing language is employed in a very intuitive and clear construction.
Throughout the article, the requirements and the interface are shown, explaining the choices made during

the project phase related to programming language and libraries. To exemplify its use, a simple case of a two-
dimensional problem using VEM is done. More specifically, the computation of a local stiffness of a polygon with

more than 4 sides is shown.

On the numerical integration in G/XFEM analysis for physically nonlinear problems and cohesive crack propagation

Bruna C. Campos, Felício B. Barros, Samuel S. Penna — Sun, 07 Jul 2024 00:00:00 +0000

This work presents a novel methodology to deal with some drawbacks related to crack propagation
in physically nonlinear problems in the context of the Generalized Finite Element Method (GFEM). The GFEM
associates Finite Element Method shape functions to local approximation functions that describe, for example,
the discontinuity from Fracture Mechanics cohesive crack problems. In this case, numerical integration must be
adapted for properly dealing with the non-polynomial integrand of the weak form of the boundary value problem.

A common alternative to consider the discontinuity is the employment of the subdivision of elements, in the inte-
gration points are changed according to the cited strategy. Although a very efficient procedure in linear problems,

it leads to the loss of the state constitutive variables history, responsible for indicating the degradation level in
physically nonlinear materials. A new strategy is here proposed, based on the nonlocal approach to recover the

evolution of the state constitutive variables in the integration points. A numerical example is provided to vali-
date and prove the efficiency of the proposed methodology. The computational implementation and analysis are

performed in the open source software INSANE (Interactive Structural Analysis Environment), developed by the
Structural Engineering Department of Federal University of Minas Gerais.

An adaptive and selective generalized finite element method for free vibration of trusses

Sun, 07 Jul 2024 00:00:00 +0000

The ability to support large loads over a great span makes trusses structural systems with a variety of
applications in engineering. In regards to dynamic analysis, such structures do have few known analytical solutions
and, thus, are usually analyzed through approximated methods such as the Generalized Finite Element Method
(GFEM). The GFEM is based on the Partition of Unity Method and uses previous knowledge of the problem’s
solution to expand the traditional Finite Element Method (FEM) approximation space. In previous literature an
adaptive GFEM has been proposed for the free vibration problem of bars and trusses and has led to excellent
results. This method consists of an iterative process that incorporates in the enrichment an approximated natural
frequency result in each step. On the other hand, another technique found in literature is the use of the Friberg
error indicator to identify which elements of a mesh have greater impact on the solution in an enrichment process.
The indicator has already been shown to be applicable in GFEM analysis. The selective technique aims to reduce
the number of degrees of freedom necessary in obtaining good approximations of a determined natural frequency.
In this paper a selective adaptive technique is proposed. The Friberg indicator is used to define which bars of the
truss will be enriched and the adaptive process is used to improve the accuracy of the solution. Thus, combining
the advantages of both methods leads to results with low error and reduced number of degrees of freedom when
compared to the traditional GFEM approach. The results obtained by the proposed technique are compared with
reference solutions found in literature.

Virtual element method: who are the virtual functions?

Tiago Fernandes Moherdaui, Alfredo Gay Neto — Sun, 07 Jul 2024 00:00:00 +0000

The Virtual Element Method (VEM) is a generalization of the Finite Element Method (FEM). It
proposes approximations to fields of interest on elements of almost any shape, by employing a function space
containing a full polynomial space of arbitrary degree, for its convergence properties, along with additional
suitable functions. The degrees of freedom of the element are designed such that these additional functions can
remain unknown while solving the discretized version of the problem. A term containing the projection of the
approximate solution onto the polynomial functions space guarantees the method’s consistency, while a term with
projection’s residual has to be approximated to ensure stability. The approximation for the latter term is still an
open problem for many applications. The objective of this paper is to show a procedure to solve for these virtual
functions, their projection onto the polynomial space and its residual. This is proposed for the 2D Poisson problem,
by presenting the functions as solutions, and solving for them via FEM. Then, finding their polynomial projection
and the residual of the projection. From this, the stabilization term can be approximated up to the error of the FEM
solution. This procedure may be a clue to visualize the virtual functions behavior and, in future, to help on
proposing stabilization schemes.

Cohesive crack propagation simulated by different SGFEM strategies

Thaianne S. de Oliveira, Felício B. Barros, Bruna C. Campos — Sun, 07 Jul 2024 00:00:00 +0000

The present work aims to evaluate the performance of the Stable Generalized Finite Element Method
(SGFEM), a relatively new approach that derives from a simple modification of enrichment functions used in
Generalized/eXtended Finite Element Method (G/XFEM), in the analysis of a three-point bending test. For this,

different crack propagation simulations are performed using the standard Heaviside Function, its linear modifica-
tion as proposed by Gupta et al. [1] and a version that employs a stabilization parameter, presented in Wu and

Li [2]. A cohesive crack model is considered and linear elastic material is assumed for the numerical experi-
ments. Equilibrium paths, as well as the scaled condition numbers (SCNs), calculated at each step, are evaluated

by SGFEM and compared with the results obtained by G/XFEM. This work is related to a proposal of expan-
sion of the INSANE (INteractive Structural ANalysis Environment) system, an open source project developed at

the Structural Engineering Department of the Federal University of Minas Gerais. This platform has enabled the
resources that allowed the analysis and discussions carried out in this work.

A study about SIF estimation using XFEM

Eduardo Nantes Serenza, Oscar Alfredo G. de Suarez, Rodrigo Rossi — Sun, 07 Jul 2024 00:00:00 +0000

The numerical approach to fracture mechanics has been a challenge in recent decades, especially for the
aeronautical and naval industry. In general, these problems involve discontinuities, singularities and high
gradients, becoming impracticable for being addressed by the classical finite element method (FEM) where one
faces significant precision losses and excessive remesh in the vicinity at the crack tip. In order to overcome these
difficulties, the eXtended Finite Element Method (XFEM), has been developed to enhance the modeling of
discontinuities such as jumps, singularities and other non-smooth features. XFEM is a numerical technique that
extends the classic FEM, enriching the approximation space with information coming from asymptotic and other
solutions knowledge of the physics of the problem. The main objective of this work is to investigate the features
of the application of XFEM for LEFM problems in plane elasticity problems by numerical calculation the stress
intensity factor (SIF) using an approximate approach to obtain the J integral and then compare the stress intensity
factors with those available in the literature. For classic cases numerical results are close to the solutions available
in the literature.

Proper Generalized Decomposition (PGD) applied to heat conduction prob- lem in heterogeneous materials

Paulo de Tarso R. Mendonça, Vinícius Gregory Gonçalves — Sun, 07 Jul 2024 00:00:00 +0000

In order to reduce processing time in complex simulations, several order reduction methods have been
developed. One of these methods is the Proper Generalized Decomposition (PGD). The PGD method is based

on the decomposition of unknown fields in each of the coordinates. PGD is used to solve sequences of one-
dimensional problems of the finite element method. Throughout the iterations, the spatial variables are separated

via the PGD method, resulting in an iterative sequence of global solutions, even in a linear problem. The present
work aims to evaluate the PGD method in heat conduction problems using heterogeneous materials.

Revisiting the topological enrichment pattern in the linear elastic fracture modeling via GFEM / XFEM

Diego Amadeu F. Torres — Sun, 07 Jul 2024 00:00:00 +0000

The way of performing special enrichment to model crack tip singularities, in the linear elastic fracture
analysis via Partition of Unity (PoU) based methods, has been an issue of concern over the past two decades.
One aspect of significant importance is to alleviate the mesh dependences to assure convergence rates do not be
adversely affected by the discretization h-parameter reduction. The geometric enrichment pattern emerged as the
preferable strategy to reach such a goal. Additionally, the PoU regularity has been identified as a feature of great
impact in the ansatz’s capability of capturing the singularity of such especial enrichments, as shown in recent results
in the context of C
k
-GFEM. Thus, once lower dependence on the enrichment zone size has been found in the case
of using smooth PoU functions, the enrichment strategies which lead to a smaller increment in the amount of DOF
become attractive again. This work aims to study how the topological pattern of enrichment performs in the case
of the C
k
-GFEM if compared to the conventional XFEM / GFEM. Different schemes of polynomial enrichment
are also considered trying to enlighten some blending / transition effects. The approximations performances are
assessed by crack severity parameters computation using the material forces method.

Isogeometric analysis using Bezier elements

Francisco D. P. Silva, Elias S. Barroso, Evandro Parente Jr. — Sun, 07 Jul 2024 00:00:00 +0000

Isogeometric Analysis (IGA) is a numerical analysis approach that integrates the concepts of CAD
(Computer-Aided Design) and CAE (Computer-Aided Engineering). It uses the same basis functions employed
by CAD systems to describe the model geometry (e.g. Bezier and NURBS surfaces) to approximate the solution ́
field (e.g. displacement or temperature). Therefore, the geometry of the models is exactly represented for any
level of discretization. The use of well-known geometric modeling algorithms (e.g. knot insertion and degree
elevation) simplifies the model refinement procedure, allowing an easy application of discretization schemes while
preserving the initial geometry. The modeling paradigm adopted in CAD systems uses boundary models that
cannot be directly used by CAE. The use of Bezier elements is a good alternative, as it facilitates the connection ́
between the geometric model, based on a Boundary Representation (B-Rep), and the isogeometric analysis model.
High-order mesh generation techniques are used to discretize geometric models through rational Bezier elements, ́

preserving the exact geometry and creating a suitable analysis model. This paper discusses the definition of two-
dimensional triangular Bezier elements and their performance in numerical analysis. The numerical results are ́

compared with an analytical solution, where the convergence rate of the Bezier elements is assessed in linear ́
elasticity problem.

Multiscale analysis of solids with a spaces of functions blending method

Rosicley J. R. Rosa, Rodolfo A. K. Sanches, Humberto B. Coda — Sun, 07 Jul 2024 00:00:00 +0000

Many engineering problems deal with localized effects in a larger domain, such as cracked solids,
localized plastic strains and discontinuities like holes or stiffeners. The proper analysis of such problems require
techniques that allow to accurately represent the mechanical fields of the problem at different scales. In this study, a
space of functions blending technique is applied for two-dimensional solids, under a position-based finite element
formulation for large displacements dynamic and static problems. The multiscale analysis consists of overlapping
a local finite element discretization, able to capture the localized effects, to an isogeometric global discretization.
In a region of the local discretization, close to its outer boundaries (blending zone), the fem and isogeometric
spaces of shape functions are weighted by functions specially designed to avoid a linear combination and added
generating the blended space of functions. With this approach, no additional degrees of freedom are introduced to
enforce continuity between models. Numerical examples are simulated, considering plane strain and plane stress,
with results compared to the literature in order to verify the proposed method and assess its accuracy and efficiency.

ON GENERALIZED FINITE ELEMENT METHOD’S NUMERICAL STABILITY PRESERVATION

Daniel C. Sales, Sergio P. B. Proença — Sun, 07 Jul 2024 00:00:00 +0000

The Generalized Finite Element Method (GFEM) proposes the expansion of FEM’s approximation

space by combining Partition of Unity (PU) functions with enrichment functions. Such combination provides lo-
cally better capacity to approximate the desired solution. PU functions combine local approximations, forming

the corresponding global approximation. The Galerkin method is employed, leading to a system of equations to
be solved for global nodal parameters. However, it is important that the extended approximation space is linearly
independent, as to not jeopardize GFEM’s system’s conditioning which could lead to inaccurate results. Recent

developments propose alternatives for preserving the solving system’s linear independence, improving its condi-
tioning. This work offers new contributions in two manners. On one hand, a new set of PU functions to compose

the enriched space is explored. On the other hand, the Singular Value Decomposition (SVD) methodology is ex-
plored to obtain adequate solutions even in the presence of linear dependencies. Examples that normally lead to

dependencies are explored, emphasizing the advantages of the strategies. It is shown that GFEM’s system’s condi-
tioning is close to FEM’s while employing the new PU. Also, SVD’s efficiency for solving the system disregarding

its dependencies is demonstrated, adding robustness to the most conventional versions of the method.

Classical transient pipe flow analysis with SPH method

José Fernandes Júnior, Joel R. G. Vasco, Alexandre K. Soares — Sun, 07 Jul 2024 00:00:00 +0000

The main purpose of this paper is to analyze the applicability of the Smoothed Particle Hydrodynamics
(SPH) method in water hammer modeling, a transient pipe flow problem. A reservoir-pipe-valve system with
steady friction losses was chosen to implement the method. In order to suppress the limitations of the method due
to boundary conditions and numerical instability, numerical corrections were applied to the SPH. The applied
corrections are found in the kernel function (CSPH) and in the use of artificial viscosity. Furthermore, the method
is validated by comparing the numerical results obtained with SPH and the numerical solution obtained by the
Method of Characteristics (MOC).

A preliminary study of selected integration methods in XFEM

Jamile M. A. Tavares, Erik R. Rodriguez, Oscar G. A. de Suarez, Rodrigo Rossi — Sun, 07 Jul 2024 00:00:00 +0000

In this paper, we conduct a preliminary study of some numerical integration strategies employed in the
modeling of weak discontinuity interfaces inside the context of XFEM, such that used as enrichment to model
interfaces bi-materials. The first integration strategy considered is the standard Gauss quadrature method. The
second uses sub-elements conformed to the discontinuity, which are generated by the Delaunay triangularization.
In this case, the Gauss points are applied to the triangular sub-elements and transformed into the quadrilateral
element domain. The third technique replaces the discontinuity by an equivalent polynomial that eliminates the
use of sub-elements applying directly the standard Gaussian quadrature. A numerical example is carried out in
order to draw the very first impressions of the integration strategies.

Nonlinear analysis of three-point bending notched concrete beams via global-local Generalized Finite Element Method approach

Sun, 07 Jul 2024 00:00:00 +0000

The Generalized Finite Element Method (GFEM) was developed in order to overcome some limitations
inherent to the Finite Element Method (FEM), related to the defects propagation, presence of large deformations
or even in the description of high gradients of state variables. The GFEM enriches the space of the polynomial
FEM solution with a priori known information based on the concept of Partition of Unit (PoU). Certain obstacles of
nonlinear analysis can be mitigated with the GFEM, and damage and plasticity fronts can be accurately represented.
In this context, the global-local approach to the GFEM (GFEM global-local) was proposed. The success of its
application to problems of Linear Elastic Fracture Mechanics is already proven, but its extension to the simulation
of collapse of structures made of quasi-brittle media is still a vast field to be researched. Here, a coupling strategy
is presented based on the global-local GFEM to describe the deterioration process of quasi-brittle media, such
as concrete, in the context of Continuous Damage Mechanics. The numerical solution used to enrich the global
problem, represented by a coarse mesh, is obtained through physically nonlinear analysis performed only in the
local region where damage propagation occurs, represented by constitutive models. The linear analysis of the
global region is performed considering the incorporation of local damage through the global-local enrichment
functions and damage state mapped from local problem. Numerical examples of three-point bending notched
concrete beams have been presented to evaluate the performance of the proposed approach and the obtained results
were compared with the experimental results and with the ones obtained with standard GFEM. Two constitutive
models were applied to represent the concrete in the local region: smeared crack model and microplane model.

Numerical implementation of the Stokes-Couette flow using the SPH method

Charleston J. S. Roice Filho, Jose Fernandes Júnior, Joel R. G. Vasco — Sun, 07 Jul 2024 00:00:00 +0000

This article uses the Lagrangian numerical method SPH (Smoothed Particle Hydrodynamics) to solve
the Stokes-Couette flow. The laminar flow is created by horizontal oscillation of the lower plate while the upper
plate remains stationary. Stokes-Couette flow can be used as a benchmark to test codes using the meshfree SPH
method since this phenomenon is governed by the one-dimensional classical heat equation. The newtonian fluid
domain between the flat plates is discretized by particles in a vertical column, which would be free to move
according to the forces acting on the particles. Boundary conditions are treated with ghost particles, created outside
the physical domain to keep the number of neighbors of each particle constant. The initial condition considers the
fluid at rest. The heat equation is then solved for each particle inside the domain and the horizontal velocity profile
is obtained from the integration over time. The variation in time of the velocity profile from the oscillatory point of
view (non-zero oscillation frequency) and the evolution in time of the velocity profile (zero oscillation frequency)
are evaluated. The numerical solution of the SPH method reproduces the Stokes-Couette flow, which can be used
as a benchmark for more complex SPH-based codes.

A MLPG Formulation for Plane Stress Problems

André L. A. Silveira, José A. F. Santiago, Edmundo G. de A. Costa — Sun, 07 Jul 2024 00:00:00 +0000

This paper presents an analysis of plane stress problems using the first variant of the Meshless Local

Petrov-Galerkin (MLPG) method designed in the literature by MLPG-1. In this method, the Moving Least-
Squares (MLS) is used as approximation function, and an integration scheme is proposed for avoiding the

numerical errors associated to the points of integration located outside of the global domain of interesting. An
example is presented in order to assess the accuracy and the stability of the proposed formulation by comparing
its numerical model with a reference model based on the Boundary Element Method (BEM) formulation.

SIMULATION OF A MATHEMATICAL MODEL OF TUMORAL GROWTH

Sun, 07 Jul 2024 00:00:00 +0000

The work presents a study of the non-linear mathematical model of tumor growth, proposed by Kolev
and Zubik-Kowal [1]. The model is described by a system composed of four partial differential equations that
represent the evolution of the density of cancer cells, density of the extracellular matrix (ECM), concentration of

matrix-degrading enzyme (MDE) and concentration of tissue metalloproteinase inhibitors. For numerical simu-
lations, the finite difference method is used, in which the temporal terms of the equations are discretized using a

two-stage method. In spatial terms, finite central differences are used. A study of numerical convergence for the

proposed scheme is presented, using analytical solutions manufactured in a rectangular geometry. Finally, simula-
tions of the tumor growth model are performed, using a non-regular mesh that represents the geometry of a female

breast. To simulate the model in non-regular geometry, the technique used is to approximate the contour of the
physical domain by mesh segments. The simulations showed that the model has important characteristics of the
interactions between tumor cells and the surrounding tissue.

Study of mechanical potentials to describe the biphasic mechanical behavior of fiber-reinforced soft tissues

Jonatas S. Fagundes, Jakson Vassoler — Sun, 07 Jul 2024 00:00:00 +0000

Soft tissues have a considerable percentage of their weight constituted of fluid, which directly impacts
its mechanical behavior. An appropriate formulation for describing this type of material is found in the biphasic
theory. However, although the mechanical potentials used in the literature have no difficulties in reproducing
the force response of the tissue, these potentials may also contradict experimental observations about the volume
change and fluid flow in traction. This work investigates a biphasic framework with an anisotropic hyperelastic
model in which the volumetric deformations are related to the extension of the fibers in the tissue through the
control of the Poisson’s ratio. In order to highlight the characteristics of this model, a experimental relaxation
test of tendon is adjusted using the force and Poisson ratio as variables, and a comparison using a viscoelastic
model is made. The results demonstrate the ability of the studied potential, together with a biphasic framework, to
represent volumetric, dissipative and fluid flow characteristics in the tendon. The results also show that the classic
viscoelastic model may not be appropriated in these aspects, demonstrating that characterization of the tissue using
only the force response may not guarantee an adequate characterization.

ESTUDO NUMÉRICO-EXPERIMENTAL DO EFEITO DA ABSORÇÃO DE ÁGUA SOBRE O COMPORTAMENTO VISCOELÁSTICO DO POLÍMERO POLIAMIDA 6 NO DOMÍNIO DO TEMPO E FREQUÊNCIA

Lucas Casagranda, Jakson Manfredini Vassoler — Sun, 07 Jul 2024 00:00:00 +0000

Polímeros vem ganhando cada vez mais espaço em aplicações estruturais tornando-se cada vez mais
essencial entender os efeitos sobre estes materiais de fatores ambientais, como temperatura, pressão e absorção de
água. Aplicações biomecânicas, como placas poliméricas e parafusos para implantes, estão sujeitas a condições
ambientais não padronizadas. Devido ao comportamento mecânico bastante complexo desses materiais, é
necessário o uso de modelos matemáticos apropriados, que capturem tais fatores ambientais, para sua simulação
numérica. Neste trabalho, polímeros termoplásticos sujeitos à absorção de água foram estudados e uma
caracterização numérico-experimental de seu comportamento viscoelástico é apresentada. O material foi
caracterizado experimentalmente através de análise dinâmico-mecânica para diferentes relações de absorção de
água. Por meio de um princípio de superposição análogo ao de “tempo-temperatura”, a função de translação
proposta pelo modelo Williams-Landel-Ferry foi usada para levar em consideração a absorção de água em modelos
viscoelásticos clássicos. Diferentes metodologias numéricas foram adotadas e seus resultados comparados para
avaliar o fenômeno de absorção de água. Com essa abordagem, foi possível representar o comportamento
mecânico do termoplástico com diferentes taxas de absorção de água.

Hybrid multiscale modeling of tumor growth with chemotherapeutic drug dispersion

Gustavo T. Naozuka, Heber L. Rocha, Regina C. Almeida — Sun, 07 Jul 2024 00:00:00 +0000

Cancer is a group of diseases characterized by complex phenomena across multiple temporal and spa-
tial scales. Comprehending its growth dynamics is a challenge and may improve the understanding of underlying

mechanisms, and suggests more effective therapy protocols. In this context, mathematical and computational
modeling may provide insights into tumorigenesis, cancer growth, and response to drug treatments. In this work,
we develop a hybrid discrete-continuum model describing the avascular phase of cancer growth and incorporate
chemotherapeutic drugs acting in different phases of the cell cycle. The growth phenomenon occurs at three scales:
(i) at the tissue scale, partial differential equations model oxygen, drug, and growth factor dispersion; (ii) at the

cellular scale, an agent-based model describes transitions among phenotypic states of each tumor cell and mechan-
ical interactions among cells and the microenvironment; (iii) at the molecular level, ordinary differential equations

represent signaling pathways that regulate cellular metabolism, cell cycle, and cell proliferation. Computational

experiments demonstrate that the proposed modeling framework can be instrumental in the development of inno-
vative new treatments for cancer patients.

A comparative analysis between different approaches for simulating the bone remodeling

Sun, 07 Jul 2024 00:00:00 +0000

Bones can replace old and damaged tissue with healthy new tissue in a process called bone remodeling.
This process is biologically described by coordinated activity between bone formation (osteoblasts) and bone
resorption (osteoclasts) by following stages of activation, resorption, and formation. From a mechanical point of
view, there is formation (resorption) where there are high (low) levels of mechanical stimulus. The literature
presents several models for bone remodeling simulation, which can be classified as phenomenological, biological,
mechanobiological and chemomechanobiological, among others. Thus, this work aims, through numerical
simulations, to compare phenomenological and mechanobiological bone remodeling models. With the
phenomenological model, the objective is to obtain the density distribution that characterizes a human femur. In
turn, the mechanobiological model simulates the behavior of bone tissue by evaluating the biological feedback due
to different levels of external stimulus applied. It should be emphasized that in this second approach, simulation
time has real physical meaning. In the end, the bone tissue behavior was simulated using both approaches. The
mechanobiological model provided a distinct behavior for cortical, trabecular, and osteoporotic bones under
different load conditions. This was not visualized when we used the phenomenological approach. However, the
phenomenological model characterized the femoral density distribution that qualitatively represents a radiography.

Incertezas no campo de orientação das fibras cardíacas e os efeitos na eletrofisiologia cardíaca utilizando a expansão Karhunen-Loève `

Berilo O. Santos, Rodrigo W. Santos, Bernardo M. Rocha — Sun, 07 Jul 2024 00:00:00 +0000

O estudo da atividade eletrica cardíaco humana e crucial para analisar perturbações e distúrbios que
podem levar ao obito. O uso de simulações computacionais pelo método dos elementos finitos tem se tornado
uma alternativa para o estudo e entendimento da atividade eletrica cardíaca. Porem, para que as simulações com-
putacionais sejam confiaveis a ponto de serem relevantes em aplicações clínicas, ainda e necessário identificar
quais parametros do modelo precisam de maior precisão durante a calibração e como eles afetam as previsões do
modelo. Neste trabalho, e realizado um estudo de quantificação de incerteza sobre propriedades de orientação das
fibras no tecido cardíaco considerando a orientação das fibras como um campo aleatório através usando a expansão
de Karhunen-Loeve. O objetivo deste trabalho é estudar o impacto das incertezas na orientação das fibras na velo-
cidade de propagação da onda de ativação elétrica. Os experimentos indicam o quanto a velocidade de propagação
e afetada e mostram que a expansão de KL e uma ferramenta fundamental no estudo de campos aleatórios.

Computational fluid dynamics of biomaterial inks flowing through extrusion nozzles in bioprinting of substitutes for cartilaginous tissues

Isabela M. Poley, Patrícia M. de Oliveira, Estevam B. Las Casas — Sun, 07 Jul 2024 00:00:00 +0000

Computational fluid dynamics (CFD) can be useful to predict the behavior of biomaterials in
bioprinting in order to avoid clogging of extrusion nozzles and, in case of cell embedded biomaterials, to avoid
wasting cells. In bioprinting, cells are exposed to high shear stresses when in contact against the printing needle
walls. If the stresses exceed a limit value, cell membranes may disrupt. Biomaterial inks specially formulated for
bioprinting of substitutes for cartilaginous tissues were characterized for their rheological properties, and the
obtained data were used in fluid dynamics simulations of the flow through extrusion nozzles. Some compositions
contained powdered extracellular matrix derived from devitalized cartilage (DVC), added to give the
biochemical complexity necessary for the bioprinted material, and others contained polycaprolactone (PCL),
added to give greater mechanical resistance. The simulations indicated very high shear stresses (greater than 4
kPa) during extrusion for compositions containing PCL, which could cause cell disruption in high extent. It is
concluded that, for those compositions, the addition of cells to the scaffolds should be done preferably after
bioprinting, instead of using a cell embedded biomaterial, because cell viability after extrusion tends to be low.

A model extending from Goldstein-Kac Telegraphic Equation that describe numerically the population dynamics problem

Pedro H. V. Godoi, Eliandro R. Cirilo, Paulo L. Natti, Neyva M. L. Romeiro — Sun, 07 Jul 2024 00:00:00 +0000

In this work we consider a particles motion modeling into 2D domain. The motion happens by par-
ticles’ decision which is modeled from parameters like territorial occupation and populational value, both at the

domain. We used an equations’ system to create our model from extending the well-known Goldstein-Kac tele-
graphic equation. Specifically, the particles could be animals, virus, cells, the property concentration and anything

of engineering as well. This model describes the population’s density behavior at the space and time in a two

dimensional space. Also, the model lets the particles to have different spreading properties in each dimension. Be-
sides, the model is solved by quasi linear numerical method (QLNM). The QLNM is a novel smart finite difference

technique that solves complex nonlinear partial differential equations. The quality of solutions is guaranteed by
numerical

A comparative analysis between different approaches for simulating the bone remodeling

Sun, 07 Jul 2024 00:00:00 +0000

Uma abordagem computacional de porohiperelasticidade aplicada a análise de tecidos biológicos

Bruno Klahr, Thayller W. Barp, Thiago A. Carniel, Eduardo A. Fancello — Sun, 07 Jul 2024 00:00:00 +0000

O presente trabalho aborda a formulação de um modelo bifásico submetido a deformações finitas. Neste
caso, o meio poroso e considerado homogeneizado, no qual as fases materiais são assumidas como um único meio
contínuo, nao havendo distinção entre as fases fluida e sólida. A solução das equações de governo e realizada
atraves do método de elementos finitos empregando um procedimento escalonado para os campos de deslocamen-
tos e pressoes. Além disso, emprega-se um método de integração temporal implícito de primeira ordem. Visando
demonstrar a eficacia da abordagem proposta, um estudo de caso de compressão confinada foi realizado e compa-
rado com resultados obtidos de um software comercial de elementos finitos. Em vista disso, os resultados obtidos
demonstram que a abordagem computacional proposta consiste em uma ferramenta promissora para a investigação
do comportamento mecanico de tecidos biológicos moles.

Analise Mecânica da cartilagem na articulação coxofemoral por escaneamento óptico e simulação 3D via Abaqus®

Sun, 07 Jul 2024 00:00:00 +0000

A osteoartrite e uma doença causada pelo desgaste da articulação, causando dores e perdas das funções
articulares. Esta ainda pode ser adquirida por causas geneticas, obesidade ou por esforço extremo das articulações.
Uma das articulações mais acometidas e a do quadril. Modelagem computacional e simulação numérica tem
sido amplamente utilizadas para estudar as causas dos desgastes nas articulações. No ambito da biomecânica
computacional, e possível gerar um modelo geometrico tridimensional que representa o osso do quadril. Este
trabalho consiste em uma analise mecânica dos esforços de contato submetidos pelo fêmur a cartilagem localizada `
no acetabulo. É desenvolvido um modelo computacional, a partir de escaneamento óptico dos ossos do quadril:
femur e pelve. Após a execução de vários protocolos em programas de modelagem geométrica para suavização
e correção de malhas, bem como alinhamento dos ossos em questão, busca-se no software Abaqus®.

simular
o contato na junta do quadril, a fim de encontrar as pressoes de contato submetidas ̃ a cartilagem saud ` avel de um ́
indiv ́ıduo, a partir do qual sao analisados dois cen ̃ arios: a posic ̧ ́ ao ortost ̃ atica (neutra) e com 10 ́o de flexao. Para tal,
dois steps (ou passos de analise) são levados em consideração. A estratégia aqui utilizada é impor um deslocamento
prescrito para a efetivação do contato de modo que a pressão de contato resultante seja compatível com resultados
disponíveis na literatura. Neste contexto, verifica-se que os resultados apresentados foram satisfatorios, sendo a
pressao obtida de 5,799 MPa.

Modelo bidimensional para avaliação de guia cirúrgica no procedimento de osteotomia periacetabular através de simulação no ABAQUS® e otimização usando Algoritmo Genético

Gustavo S. O. Marques, Marcus V. S. Ferraz, Flavia S. Bas, Bruno G. S. e Souza — Sun, 07 Jul 2024 00:00:00 +0000

O presente artigo tem por objetivo avaliar a viabilidade de uma guia cirurgica no procedimento de osteotomia periacetabular, que apresenta elevado grau de complexidade e e utilizado na correção da displasia. A
função da guia consiste em definir em quais locais deverão ser realizados os cortes no osso, a fim de proporci-
onar uma orientação mais precisa, contudo, durante a cirurgia o ortopedista realiza diversos esforçoss que podem
danificar a guia. Neste trabalho, verifica-se se a guia resiste as tensões exercidas durante o procedimento e quais
parametros tornam seu uso viável, utilizando o software ABAQUS® para modelagem e simulação do problema
em conjunto com o Algoritmo Genetico, que irá realizar a parte de otimização. O modelo aqui proposto e bidi-
mensional e baseia-se em uma analise estática e preliminar, usando geometrias simplificadas a fim de reduzir o
custo computacional. Busca-se otimizar alguns parametros construtivos (espessura da guia e raio do parafuso que
fixa a guia no osso) de maneira que a tensao máxima encontrada na guia seja a mínima possível (função objetivo).
Verificou-se que os resultados que suportaram melhor as tensoes foram aqueles com 11 mm de espessura e 3 mm
de raio, respectivamente. Uma proposta para analises futuras e levar em consideração outros aspectos geométricos
e construtivos (estudo tridimensional), alem de avaliar novos parámetros no Algoritmo Genético.

Constitutive modeling of viscoelastic materials: A quantitative comparison between classic and fractional models

M. E. W. Costa, J.-M. C. Farias, L. B. P. de Faria, E. A. Fancello — Sun, 07 Jul 2024 00:00:00 +0000

Thermoplastic polymers are widely used in biomedical applications, such as knee and hip prosthetics.
The development of optimized orthopedic implants is strongly related to the performance of experimental tests and

computer simulations that approximate the behavior in situ of the material used. The literature indicates the possi-
bility of applying fractional viscoelastic constitutive models as an alternative to the classical integer order models.

However, it is not common to compare quantitatively the results obtained using both approaches. Therefore, the
predictive capabilities of some fractional and classical viscoelastic models with infinitesimal and finite kinematics
are compared in this work. The study is conducted using cyclical and creep-recovery experimental tests at two
strain and stress rates. First we present the individual fittings of the cyclical and creep-recovery experimental data.
Then, these tests are fitted simultaneously. The parameter fitting is made using a hybrid optimization procedure,
using a heuristic method for global search and another based on gradients for local search. In the context of the
experimental conditions evaluated, the results indicated that the use of the fractional models tested did not result in
a significant improvement when the assessment are made using individual experimental data. On the other hand,
for the the simultaneously parameter fitting, the fractional models showed a slight improvement. However, none
of the models used was able to represent satisfactorily the cyclic and creep-recovery data used, this fact may be
related to the presence of nonlinear phenomena not taken into account in the present work.

Estimativa das forças exercidas pelos segmentos musculares utilizando diferentes restrições

Sun, 07 Jul 2024 00:00:00 +0000

A great number of musculoskeletal models have been developed over the last few decades, allowing
non-invasive prediction of parameters that cannot be measured in vivo, such as individual muscle forces and joint
reaction forces. Estimation of these parameters can contribute to improved diagnosis of pathologies and
development of treatment techniques. On computational models it is not always possible to account all the
variables that influence the force generation of a muscle and simplifications are made, such as the representation
of the muscles as bundles of frictionless, massless and elastic cables. The objective of this study is to analyze how
a constraint on the force amplitude generated by muscle segments influence the muscle force estimation and the
joint reaction force of the glenohumeral joint. For this purpose, a previously developed shoulder model was used,
and two cases were studied: with and without constraints. Results show that the joint reaction force is greater on
the model with constraints and that there are differences between the forces exerted by the segments of the same
muscle group when the constraint is removed. The presence of constraints on models similar to the one used is
necessary to simulate an adequate muscle physiology, however, studies are still necessary to define how to apply
these constraints.

Abordagem FEMU para investigar a representação de modelos bifásicos aplicados a tecidos biológicos anisotrópicos

Sun, 07 Jul 2024 00:00:00 +0000

A caracterização mecânica dos tecidos biologicos moles pode ser útil em diversas aplicações, como por
exemplo no auxílio de escolha de tecnicas de tratamento individualizadas, prevenção de lesões, e no desenvol-
vimento da engenharia de tecidos. Modelos computacionais tem sido desenvolvidos para atender estes escopos,
principalmente na investigação de sistemas biomecanicos complexos. Nestes casos, as ferramentas numéricas
devem ser capazes de representar as respostas mecanicas do tecido de interesse com certa acuracia. A maioria
dos trabalhos encontrados na literatura geralmente utilizam modelos fenomenologicos apenas considerando a fase solida, apesar da evidente presenc ̧a de fluido em seu interior. Neste contexto, modelos bifásicos tem atraído par-
ticular atenção pois incorporam efeitos de um fluxo de fluido (fase fluida) dentro de uma matriz porosa sólida

(fase solida), assim como ocorre fisiologicamente nos tecidos biológicos. Nesta abordagem, ainda existem muitas
dificuldades associadas a identificação da contribuição de cada fase na resposta mecânica, principalmente quando
estes materiais podem estar submetidos a campos de velocidade ou deformação heterogêneos. Portanto, o obje-
tivo do presente trabalho e propor uma metodologia para estudar a capacidade representativa de modelos poro- ́
hiperelasticos em tais condições. Para isto, propõe-se a utilização da técnica FEMU (Finite Element Method ́
Updating) com respostas mecanicas experimentais da fase fluída, por meio do volume de fluído exsudato, e da fase
solida, por meio dos hist ́ oricos de força e deslocamentos em diferentes modos de compressão. Casos numéricos
preliminares sao apresentados com a combinação de diferentes modelos constitutivos para as fases sólida e fluida, usando dados experimentais extraídos de literatura. Os resultados preliminares demostram que a proposta tem po-
tencial para estudos de identificalçao de parâmetros de modelos poro-hiperelasticos anisotropicos, utilizando dados experimentais relacionados a contribuição de cada fase do modelo bifásico.

Computational modeling of the growth of breast tumors with chemotherapy administered in cycles

Sun, 07 Jul 2024 00:00:00 +0000

Breast cancer is a disease caused by the disordered multiplication of breast cells. It is the most frequent
cause of death from cancer among women in the world, affecting 2.1 million women each year. Considering
the impact of breast cancer on global health, it is necessary to develop mathematical models that simulate the
growth of breast tumors in response to treatment factors. Several methods have been used, such as those based on
differential equations. Because of the complexity of tumor kinetics, some mathematical models seek to understand
their behavior through application of laws that assist the study of chemotherapy treatment regimens and the action
of drugs. This paper presents a model based on ordinary differential equations (ODE) to simulate breast tumor
growth in two chemotherapy treatment regimens, executed in cycles, to analyze the effects of drugs on tumor and
healthy tissue. To solve the ODE system, the fourth-order numerical Runge-Kutta method was used, implemented
in MATLAB. The results show that chemotherapy treatment regimens comprised of two or more drugs (AC and
FAC protocols) are more effective than only administering cyclophosphamide. The two protocols caused greater
reduction of tumor cells and less destruction in healthy tissue.

Computational analisys of the Anterior Cruciate Ligament when climbing a step

Ing. C. Díaz-Cuadro, Dr. Ing. H. Figueredo, MSc. D. Santos — Sun, 07 Jul 2024 00:00:00 +0000

The human body is a complex mechanic structure and the knee joint (KJ) is one of the most complex and
demanded joint due to it has to carry very high loads and his structure must to enable triaxial movements without
lose both, the stability and the control motor. In addition, the Anterior Cruciate Ligament (LCA) deficiency is
one of the most common injuries of the KJ and affect about one of 3000 people in US every year. Moreover, a
LCA deficiency commonly leads to more than one causes that produces articular surfaces damage or osteoarthritis.
Many studies about the KJ had been carried out in both in-vivo and in-vitro and it showed a high variability by
both person and age.
The aim of this work is to take a first step towards developing a procedure to quantify the subject specific
LCA health with a non-invasive technique. This procedure is based on two steps, the motion capture and then the
numeric simulation with the finite element method. For the motion capture we designed an experiment of climbing
a step, to record the movements of the KJ with stereophotogrammetry using the well-known protocol Plug-in Gait
developed by Vicon Motions Systems. We record the trajectories of the markers placed over the skin of the patient

lower limb and extracted the curves of the knee kinematics. This data was transform to extract both, the flexion-
extension an internal-external rotation curves, to use as boundary condition for the finite element model of the

patient’s tibiofemoral joint.
On the second part, we developed a 3D finite element model of the KJ starting from the model released by
the OpenKnee project to run on FEBio. With this model we analyze the resulting joint kinematics and its changes
when using, another constitutive models for the ligaments or different the mesh densities for de ACL. Moreover,
we determine the kinematics of the LCA and the stress and strain distribution on this complex structure when
climbing a step. The obtained results were compared against available data from literature and showed a good
agreement. Furthermore, this procedure enable to work on the study of specific mechanic properties of soft tissues
for each patient with this protocol as starting point in order to obtain more reliable results.

Tension analysis in a knee prosthesis model under different loading conditions using the finite element method

Sun, 07 Jul 2024 00:00:00 +0000

Given the fundamental importance that collaborative and interdisciplinary developments have for
scientific knowledge, this work brings an approach focused on the stress distribution presented by a knee prosthesis
prototype, to assess the impact of the prosthesis geometry in the intervention regions. Quantitative analysis was
performed using the Finite Element Method. 3D digital models of the prosthesis were made, based on the catalogs
of commercial prostheses, and of the bones, based on radiographic images and anatomy literature. Subsequently,
the bone models were segmented, seeking to approximate the model geometry to the intervention performed in the
real case, based on the procedure described by the American Academy of Orthopedic Surgeons. In this model, a
numerical simulation was performed, considering the uniform weight distribution and different positions that
occurred during a gait, that is, the way human walk. From these results, it is possible to observe that, despite the
great variability of geometries involved, there are concentrations of stresses at specific points of intervention to
support and fix the prosthesis to the bones. Thus, to reduce impacts on bones, these points must have geometries
that reduce these stress concentrations.

Numerical modeling of cable-rigid-body structural systems using the NP-FEM method

Mateus Guimarães Tonin, Alexandre Luis Braun — Sun, 07 Jul 2024 00:00:00 +0000

This work presents a numerical formulation based on the Finite Element Method (FEM) to solve non-
linear dynamic problems involving cable-rigid-body structural systems. The Nodal Position Finite Element

Method (NP-FEM), used for cable modeling, is a simple and robust method that resolves directly the position of
cable nodes instead of indirectly using displacements. In this way, a polar decomposition of the cable elastic
deformations and rigid body rotations are not necessary, eliminating errors in the incremental approximations
existing in classic FEM formulations. The method is suitable for simulating cables with large rigid body
rotations and small elastic axial deformations. The body linked to the cable is treated as a rigid body with six
degrees of freedom and the cable-rigid-body coupling is done by creating an extra, massless, cable element with
a very large axial rigidity to simulate the rigid link between the cable free end and the center of gravity (CG) of
the rigid body. The algorithm is verified through comparisons with other authors, using their own numerical
codes or commercials software, and experimental predictions. Results are very close to those of the references
and proved that the formulation proposed here is quite efficient, reliable and stable for the examples simulated.

Dynamic analysis of the action of the wind acting in a standardized tall building

Sun, 07 Jul 2024 00:00:00 +0000

Buildings are increasingly tall and slender, which requires greater attention to ensure comfort and
safety for users. From a structural point of view, special attention should be paid to the dynamic effects caused
by the wind. Considering such effects in the design of a building, today, is facilitated by computational tools
that provide values of basic parameters such as amplitude and frequency. In this work, dynamic analysis was
performed through numerical simulation using the SAP2000 v.15 program for modeling the CAARC Standard
Tall Building. Different scenarios were considered, where the drag force calculated according to ABNT NBR
6123:1988 was applied. Such efforts were calculated for the 0
o
and 90o directions in relation to the building axes,
each being applied in two ways: on the building axis and with the eccentricity determined by rule to consider the
torsion effects on the building. The results regarding the top displacement, frequency and period were analyzed.
It was noted that the 90o

efforts applied off-axis resulted in the greatest displacements and frequency. From this
analysis it is demonstrated the importance of analyzing the dynamic effects in the considerations of eccentric
performance of the wind because, this can represent the most critical situation and, therefore, necessary for the
structural dimensioning of the building.

Richardson Error Estimator and Convergence Error Estimator applied in a buckling analysis by Finite Difference Method (FDM)

Beatriz F. Souza, Daniel O. Fernandes, Carla T. M. Anflor, Marcus V. G. Morais — Sun, 07 Jul 2024 00:00:00 +0000

In order to reduce the numerical error caused by discretization errors, the Richardson Extrapolation and
Convergence Error Estimator were used. The main goal relies on estimating and reducing the numerical error in
the analysis of a simply-supported stepped column. The estimate of the discretization error followed the
approach proposed by Marchi and Silva [1-2]. The variable of interest was the critical buckling load obtained
through the Finite Difference Method (FDM). The main concern regards the verification of the order of
convergence for a buckling problem of continuous and stepped columns. The equivalent moment of inertia is
determined at the node where the sudden cross-section variation occurs. Different ratios between moments of
inertia of the cross-sections were considered. The use of the equivalent moment of inertia in the modeling
reached the order of convergence 2 for Richardson Error Estimator and the convergence order 4 using
Convergence Error Estimator.

ERROR INTERPOLATION FOR REFERENCE VALUE CHARACTERIZATION FOR COMPLEX COLUMN BUCKLING PROBLEMS

Sun, 07 Jul 2024 00:00:00 +0000

For convergence verification of the column buckling problem it is necessary to obtain a good
reference value to compare the values obtained during the numerical process, in most cases the reference value
used is given by an experimental data or the result obtained by an analytical solution. In this way, the purpose of
the present study is to analyze a critical load buckling problem in a continuous beam that have analytical solution
and compared with curve fitting reference value obtained by Finite Element Method. The methodology applied
seen to be reliable and applicable to problems that does not have analytical solution.

A PARAMETRIC STUDY OF FOOTBRIDGE VERTICAL BENDING RESPONSE CONSIDERING HUMAN-STRUCTURE INTERACTION

Igor Braz N. Gonzaga, Michèle S. Pfeil, Wendell D. Varela — Sun, 07 Jul 2024 00:00:00 +0000

The effect of human walking in slender footbridges have been experimentally observed by many authors
such as changes in the modal properties of the coupled human-structure system, especially damping ratio, which
is responsible for the attenuation of the structural vibration oscillations. To simulate the pedestrian - structure
dynamic interaction biodynamic models have been used to represent human walking effects (in contrast to the live
load traditional model). The structural response is then governed by the modal parameters of the biodynamic
models in addition to those of the structure itself. This paper presents a parametric study of footbridge vertical
bending response considering the modal properties of a single degree of freedom spring-mass damper biodynamic
model coupled to the structure within a mathematical model of the human-structure interaction. The results
highlight the important role played by the frequency of the biodynamic model in addition to that of the walking
frequency in relation to the frequency of the structure.

Path-following strategy in bifurcation problems of thin-walled members by positional Finite Element Method

Henrique B. Soares, Rodrigo R. Paccola, Humberto B. Coda — Sun, 07 Jul 2024 00:00:00 +0000

In the present study, a computational framework is developed to the determination of thin-walled profi-
les’ equilibrium paths. These developments apply a geometric nonlinear formulation of the Finite Element Method

(FEM) based on the Total Lagrangian description of equilibrium. Besides, the mesh is composed of positional shell

finite element, in which the nodal degrees of freedom are positions, generalized vectors and linear rate of thick-
ness variation. The material’s behavior is represented by the Saint-Venant-Kirchhoff constitutive law. Moreover,

the precisely obtaining of the fundamental equilibrium path is executed by the Arc-Length strategy coupled with
the nonlinear solution technique based on the Newton-Raphson method. In this sense, the main purpose of the
present study is to obtain the multiple equilibrium paths starting from the same bifurcation point. Therefore, a

path-following approach is developed to induce the search for the requested path. The strategy consists of impo-
sing a perturbation on the current configuration, which is related to the eigenvector of the required mode. This

eigenvector is computed by means of a buckling analysis performed on the current configuration. The perturbation

is imposed as an external force, being applied close to the bifurcation point and removed as soon as it enters the de-
sired path. In this way, the equilibrium paths that present a bifurcation point can be completely determined without

the consideration of imperfections on the initial configuration, as it is traditionally done. Finally, one example are
compared against data available in literature, in which the accuracy, robustness and applicability of the proposed
formulation are demonstrated.

VIBRATION AND STABILITY OF A HYPERELASTIC NEOHOOKEAN TRUSS

Antônio A. L. dos Santos, Renata M. Soares — Sun, 07 Jul 2024 00:00:00 +0000

Trusses are structural elements that present multi-stability, even under characteristic conditions of
geometry, contour and rigidity. Metamaterials, on the other hand, have been an increase motivation for studies
recently and their characteristics can be represented by hyperelastic constitutive models together with a
geometric shape of trusses. Thus, in this work, the behavior, linear and non-linear, of the stability and vibrations
of a hyperelastic neo-Hookean truss exhibiting Multistable behavior is investigated. For this, it is considered a
plane truss with two bars and geometric imperfections First an energetic formulation, considering large
displacements, is presented and the nonlinear equations of motion for a nodal load applied at the top node are
derived. Based on this formulation, the parametric buckling analysis of the truss under static load as a function of
the load and geometric imperfections. Then, the fundamental vibration frequency, nonlinear frequency–
amplitude relations and time history are obtained as a function of the static preload.

Nonlinear analysis of viscoelastic rectangular plates subjected to harmonic in-plane load compression

Phablo V. I. Dias, Zenón J. G. N. del Prado, Renata M. Soares — Sun, 07 Jul 2024 00:00:00 +0000

In this work, based on Kelvin-Voigt mechanical model, the viscoelastic damping on the dynamic
instability of axially loaded rectangular plates is studied. A thin stainless-steel rectangular plate with linear
rotational springs at the edges is considered. The non-linear Von-Kármán relations are used to describe the
deformation relations of plates and the system of non-linear dynamic equilibrium equations is found through the
Hamilton principle by application of the Rayleigh-Ritz method, which are in turn, solved by the fourth-order
Runge-Kutta method. The bifurcation diagrams, the phase portraits and the Poincaré maps are obtained for the
principal and secondary instability regions. For lower values of axial loading, the non-trivial solutions analyzed
in the secondary region of dynamic instability are characterized by two periodic responses of period 1T, at the
principal instability region, a periodic solution of period 2T is observed. When the plate is analyzed with higher
levels of axial loading, this response may have periods of high order, and quasi-periodic and chaotic responses
are also found.

Physical and geometric parameters uncertainty effect on the nonlinear dynamics of cylindrical panels

Anna Elizabete Fonseca Palla, Frederico Martins Alves da Silva — Sun, 07 Jul 2024 00:00:00 +0000

Some physical and geometric characteristics of a structure such as radius, thickness and Young’s might
present, within a small margin of error, a value different from the nominal value considered in the project.
Therefore, the objective of this work is to investigate the influence of the randomness of these characteristics on
the nonlinear dynamic behavior of a simply supported cylindrical panel subjected to a time-dependent loading.

The nonlinear equations of motion of the panel are deduced from its total potential energy and the strain-
displacements relationships proposed by Donnell's nonlinear shallow shell theory. The physical and geometric

parameters mentioned above are inserted individually as random variables in the partial differential equation of
motion and the problem becomes stochastic due to the presence of randomness. Thus, the partial stochastic
equations of motion of the cylindrical panel are discretized by the Galerkin Stochastic method combined with the
Legendre-Chaos Polynomial and integrated over time by the fourth order Runge Kutta method to obtain several
results to forced nonlinear vibrations of the panel for a given load. These results are compared with those obtained
by the Monte Carlo simulation performed with the deterministic equations, showing the Legendre-Chaos
Polynomial as a good tool for obtaining the statistical responses of the present stochastic system without the need
for a sampling process.

Ftool 5.0: Nonlinear, stability and natural vibration analyses

Rafael L. Rangel, Luiz Fernando Martha — Sun, 07 Jul 2024 00:00:00 +0000

This work presents a new version of Ftool, a program for structural analysis of two-dimensional frame
models. This new version has two new analysis modes: nonlinear analysis and eigenvalue analysis. The former
currently considers geometric nonlinearity, allowing users to perform numerical simulations of structures with
large displacements and rotations, but small deformations. The latter considers two types of general eigenvalue
problem to analyze the stability and the natural vibration of structures. The stability analysis provides the critical
loads and the buckling modes of the structure while the natural vibration analysis provides the natural frequencies
and the vibration modes. Several options are available to perform these new types of analysis and to check the
results. These options are explained and exemplified throughout this paper.

Nonlinear dynamic analysis of a partially fluid-filled tank

Ericka L. M. B. Hansen, Frederico M. A. Silva — Sun, 07 Jul 2024 00:00:00 +0000

The nonlinear dynamic analysis of a partially fluid-filled tank is proposed considering the coupling
between the sloshing phenomena and the flexible tank. Donnell non-linear shell theory is considered to describe a
simply supported cylindrical tank while the fluid is based on the velocity potential theory that describes an inviscid,
irrotational and incompressible fluid. As the fluid is linear, it is possible to consider the velocity potential in two
parts: the first one that describes a flexible cylindrical tank without the sloshing and the second one that considers
the effect of the sloshing in a rigid tank. These hypotheses are guaranteed with a convenient choice of expressions
for the velocity potentials that obey boundary conditions equivalent to these considerations. The equivalent
hydrodynamic pressure is obtained by the velocity potential and applied in the equations of the cylindrical tank as
an external force while the free surface equilibrium equation must also be considered together with the cylindrical
tank’s equation. The set of the final discrete equations to be solved is obtained applying the standard Galerkin
method in the tank’s equations and in the free surface equation, creating a coupled system. First of all, the linear
problem is considered to obtain the natural frequencies for the cylindrical shell (bulging modes) and the sloshing.
Afterward, the dynamic nonlinear analysis takes place with the special attention to the frequency-amplitude
relations, phase-portraits and resonance curves that they evaluate the nonlinear oscillations of the cylindrical tanks.

Influence of circumferential discontinuity of an elastic foundation on the nonlinear dynamics of cylindrical shells with functionally graded material

Jonathas K. A. Pereira, Renata M. Soares, Frederico M. A. Silva — Sun, 07 Jul 2024 00:00:00 +0000

In this paper we analyze the nonlinear vibrations of cylindrical shells, composed by functionally
graded material, on an elastic foundation with circumferential discontinuity. The equilibrium equations are
obtained from Donnell nonlinear theories and the elastic foundation is represented by Winkler model. The
standard Galerkin's method was applied to discretize the differential partial equations and the perturbation
method is used to describe the modal coupling of the solution that will be used in analysis. The nonlinear
vibration of the shell will be studied through the frequency spectrum and frequency-amplitude relation,
investigating the influence of some system parameters and the proposed modal solution for the transverse
displacement field. Resonance curves for nonlinear forced vibrations and phase portrait are also evaluated,
showing the complex behavior of nonlinear oscillations of shells with discontinuity of the elastic foundation.

Lipped Channel, Hat, Zed and Rack Cold-Formed Steel Columns Under Local-Distortional Buckling Interaction

Gustavo Yoshio Matsubara, Eduardo de Miranda Batista — Sun, 07 Jul 2024 00:00:00 +0000

Cold-Formed Steel (CFS) are usually thin-walled structural members, susceptible to several individual buckling
phenomena, namely local (L), distortional (D), global (G) (flexural or flexural-torsional) or interaction buckling

behavior, denominated local-distortional (LD), local-global (LG), distortional-global (DG) and local-distortional-
global (LDG) interactive buckling modes. The currently codified design approaches are able to handle single local

(L), distortional (D) and global (G) modes, as well as local-global (LG) interaction buckling failure. The buckling
mode interaction may conduct to erosion of the column strength, if compared to isolated single modes, and must
be taken into account in the structural design practice. The present work is aimed to propose a design approach for
CFS columns undergoing LD interaction, condition not considered by the Brazilian code ABNT NBR14762:2010.
The authors’ developed equations for LD design approach for CFS lipped channel columns were tested for other
CFS shapes, in order to expand its validity to usual CFS geometries, as zed, hat and rack. The obtained results and
the validation of the proposed solution proved to be easy to apply and reliable in predicting the column strength
of the most usual CFS.

Formulação do coeficiente de flambagem local da seção completa para perfis formados a frio do tipo Rack

Sun, 07 Jul 2024 00:00:00 +0000

A grande flexibilidade de fabricação e montagem atribuída aos Perfis Formados a Frio (PFF’s) possibilita
a composição de uma variedade de seções transversais, o que facilita seu emprego em diversas aplicações na
construção civil. Devido a sua concepção esbelta, os PFF’s tornam-se mais leves e econômicos, porém, essa
característica torna o elemento susceptível à instabilidade e redução gradativa de sua rigidez. O dimensionamento
desses perfis é descrito na ABNT NBR 14762:2010, sendo que um dos procedimentos de cálculo adotado é o
Método da Seção Efetiva (MSE), que considera a flambagem local por meio de propriedades geométricas efetivas
da seção transversal completa das barras. Na formulação proposta por esta norma brasileira, o perfil Rack é
considerado apenas com abas retas. Nesse trabalho, apresenta-se um estudo para a obtenção da formulação do
coeficiente de flambagem local que também aborde o perfil Rack com abas inclinadas submetido à compressão
uniforme. Para isso, uma simulação numérica e paramétrica do perfil em questão foi desenvolvida por meio do
software de elementos finitos ABAQUS, de forma a determinar a tensão crítica de flambagem local. A partir da
análise numérica, foi também realizado um estudo comparativo do perfil Rack consoante à norma brasileira, de
modo a verificar a consistência da aplicação desta formulação ao perfil Rack.

Influência da geometria nos modos de flambagem de perfis formados a frio com seção transversal do tipo Rack

Sun, 07 Jul 2024 00:00:00 +0000

Os Perfis de aço Formados a Frio (PFFs) são fabricados em diversas seções transversais e amplamente
utilizados na construção civil, proporcionando soluções eficientes e abrangentes tanto no aspecto econômico
quanto em aproveitamento. Quando submetidos a tensões de compressão, se tornam suscetíveis à ocorrência de
fenômenos de instabilidade apresentando diferentes modos de flambagem. Dentre eles, tem-se os modos globais
(flexão, torção pura e flexo-torção), os modos locais (flambagem local e distorção) e o modo misto, que representa
a interação dos modos local e global. A flambagem é um fenômeno que causa redução da rigidez das barras e
conduz a um comportamento pós-crítico instável. Esses modos são influenciados pelo comprimento e dimensões
da seção transversal do PFF. É comum usar métodos numéricos como alternativas viáveis para estudar o
comportamento de estruturas. Portanto, o presente estudo tem como objetivo avaliar a influência do comprimento
das barras e de diferentes dimensões na seção transversal nos modos de flambagem para o perfil Rack com
enrijecedor reto e inclinado, submetido à compressão pura. Para tanto, são utilizados os softwares ABAQUS e
CUFSM, os quais são baseados no Método dos Elementos Finitos (MEF) e Método das Faixas Finitas (MFF),
respectivamente.

Influência da geometria nos modos de flambagem de perfis formados a frio com seção transversal do tipo Rack

Sun, 07 Jul 2024 00:00:00 +0000

Influência da geometria nos modos de flambagem de perfis formados a frio com seção transversal do tipo Sigma

Sun, 07 Jul 2024 00:00:00 +0000

Os Perfis de aço Formados a Frio (PFF’s) têm sido cada vez mais utilizados na construção civil, visto
que apresentam um ótimo aproveitamento no aspecto econômico, além de ampla variedade de formas de seções
transversais. Quando submetidos à compressão, seus elementos ficam susceptíveis à instabilidade, que se
manifesta por meio de diferentes modos de flambagem influenciados pelas dimensões da barra e da seção
transversal. Dentre os modos de flambagem, têm-se os modos globais (flexão, torção pura e flexo-torção), modos
locais (flambagem local e distorção) e modo misto, que representa a interação dos modos local e global. Nesse
contexto, para o estudo do perfil Sigma, o presente trabalho utiliza a simulação numérica para avaliar a influência
do comprimento e das dimensões da seção transversal no comportamento dos perfis quando comprimidos. Para
tanto, utilizou-se o programa ABAQUS, baseado no Método dos Elementos Finitos (MEF), para obtenção dos
modos de flambagem de diferentes configurações do perfil Sigma. Em seguida, para a validação e comparação
dos dados, o perfil principal foi modelado no programa CUFSM, baseado no Método das Faixas Finitas (MFF).

Nonlinear Analysis on the Distortional-Global Couple Phenomenon in Cold-Formed Steel Lipped Channel Columns

Joao Alfredo De Lazzari, Eduardo de Miranda Batista — Sun, 07 Jul 2024 00:00:00 +0000

The objective of this work is to understand the distortional-global (DG) buckling interaction of cold-
formed steel (CFS) lipped channel (LC) columns in its post buckling structural behavior and strength. There are a

few studies conducted on this topic in the literature, and the present study can be a motivation to encourage new
design procedures for CFS structures. The research program included the development of a FEM model, which
allowed detailed study of the DG buckling interaction and the comparison of the obtained results with usual design
procedures. In order to perform elastic buckling analysis, a software entitled FStr Computer Application was
developed, based on the finite strip method. The developed computational program is able to generates the
buckling mode geometry to be inserted as the initial geometric imperfection (IGI) in the shell finite element model.
Furthermore, the nonlinear analysis carried out stability paths for different combination of IGI of global and
distortional buckling modes. This IGI combination helps to understand the DG buckling interaction in a wide range
of cases. A parametric study varying the column’s length has demonstrated that the nominal column strength
equation for global buckling, presented in ABNT NBR 14762:2010, is enough to cover the DG interaction.

The Hierarchical Finite Element Method applied to dynamics analysis of Kirchhoff-Love plates

Bruno C. Kowalczuk, Marcos Arndt — Sun, 07 Jul 2024 00:00:00 +0000

The theoretical model proposed by Kirchhoff-Love, also referred to as the thin plate model, once applied
to the dynamic analysis, is useful on several problems in Engineering, such as seismic effects on slabs, dynamic
impacts of aircraft on airport runways and industrial floor structures subject to machinery activities. There is a lot
of numerical methods that intend to provide an approximate solution for this problem, for an example the
conventional Finite Element Method (FEM), the p-Fourier Method and the Hierarchical Finite Element Method
(HFEM). The aim of this paper is to evaluate the efficiency of the HFEM applied to free vibration analysis of thin
plates. The HFEM improves the accuracy of the solution by adding hierarchical shape functions of higher order.
This does not require a change in the mesh and in the number of element nodes, which would be necessary in the
conventional FEM. The results obtained by HFEM are compared to reference analytical solutions found in
literature and to other numerical methods, such as the conventional FEM and the p-Fourier Method.

Nonlinear analysis in FTOOL with semi-rigid connections: a partial development

Christian L. Dias, Rafael L. Rangel, Luiz Fernando Martha — Sun, 07 Jul 2024 00:00:00 +0000

FTOOL is an interactive graphic software used worldwide by students and engineers for analysis of
two-dimensional frame models. The main objective of this work is to present the partial development of a new
version of FTOOL, incorporating semi-rigid connections in the analysis. The new version simulates a semi-rigid
connection by inserting a rotational spring finite element with linear-elastic or nonlinear behavior, allowing a
physically nonlinear analysis. An important characteristic of this implementation is that the stiffness matrix of a
connection finite element is not condensed to the beam element that contains the join, as it is usually done. Instead,
a fictitious node with only one additional rotational degree of freedom is created for each semi-rigid connection in
the planar case. The advantages of this approach are that the physically nonlinear behavior is isolated from the
elastic behavior of the beam elements and that the stiffness matrix of a nonlinear connection fictitious element is
assembled to the global stiffness matrix independently. The numerical algorithms to compute the nonlinear
solution of the structure are based on a geometric nonlinear analysis implementation of FTOOL, adapted to
physically nonlinear analysis. The resulting version will incorporate geometric and physical (from semi-rigid
connections) nonlinear analyses.

Periodic Signal Generation using an Approximation to the Analytical Wave Equation Solution

Santiago, A. G., Mello, S. G., Sims, J. A. — Sun, 07 Jul 2024 00:00:00 +0000

A major issue in analysing wave propagation problems is the geometric and time domain discretizations,
which if it is not properly performed, may lead to poor results or computational issues such as memory overflow.
Ideally, an analytical solution for the Partial Differential Equation is desired since it may provide results for any

given pair (~x, t) independently of mesh size, time step and without any previous iteration. In this paper, an approx-
imate analytical solution of the wave equation is used in order to simulate the behavior of any periodic signal in

one dimensional domains. The periodic signal is approximated using Fourier series with the sine and cosine terms
evaluated analytically and their respective coefficients evaluated numerically using Gauss-Legendre integration
rule. A Python 3.7 Application Programming Interface was developed using an object oriented approach, allowing
user defined periodic input function, spatial domain size, time range, number of Fourier terms used and static and
dynamic solution plotting. Dirichlet Boundary Conditions defined as time periodic functions are considered and
three different functions, rectangular pulse, sawtooth wave and Gaussian pulse, are evaluated and their respective
results compared with the corresponding Finite Difference Method solution presenting a mean-squared-errors of
order 10−3
.

Comparison between Spectral Modal Dynamic Analysis and Equivalent Static Seismic Analysis

Sun, 07 Jul 2024 00:00:00 +0000

The study consists of analyzing and comparing the equivalent static behavior and the dynamic behavior,
under seismic excitation, of a structure located in the city of Portoviejo (Republic of Ecuador). The building was
designed for office occupancy, having five floors and being irregular in plan. The equivalent static analysis uses
the Ecuadorian seismic code that defines the maximum acceleration of the soil on the construction site, the soil
amplification coefficients, the type of importance of the building, the types of construction irregularity and the
factor of reduction of the seismic resistance. In the dynamic analysis of the structure was used the modal analysis
and to represent the seismic force, the response spectrum for accelerations. Additionally, a nonlinear static analysis
(Pushover) was used to determine the behavior of the structure after overcoming the elastic regime going until the
collapse. The results show the values of the basal shear forces, both for the equivalent static analysis and in the
spectral modal analysis, demand/capacity curves and transverse displacements in the structure.

Local buckling coefficient for cold-formed steel Sigma sections

Sun, 07 Jul 2024 00:00:00 +0000

Cold formed steel profiles (CFS’s) allow the use of a variety of cross-sections, due to the flexibility of
manufacture and assembly. The use of CFS’s is generally associated with slender structural designs, with a large
ratio between the width and thickness of the members that compose its cross-section, which makes the profiles
lighter and more economical. CFS's are susceptible to instability due to the slenderness. This phenomenon induces
problems such as the local buckling of their members when subjected to compression. The design of these profiles
is approached by the Brazilian standard, and one of the calculation procedures presented is the Effective Section
Method (ESM), which considers local buckling through effective geometric properties of the cross-section. For
this purpose, the standard defines the buckling coefficient of the complete section by means of formulations for
specific profile types. In order to define a specific formulation for different cross-sections, it is necessary to
perform particular analyzes, such as numerical simulations using Finite Element Methods (FEM) or Finite Strip
Methods (FSM). Therefore, this work aims to define a formulation for the buckling coefficient of the complete
section of a Sigma profile, which is not defined in the scope of the Brazilian standard. For this, a numerical analysis
was developed using the ABAQUS finite element software. A parametric study was conducted through a range of
several Sigma profile's dimensions submitted to uniform compression. Based on the determinations of critical
buckling stresses from numerical analysis, a satisfactory formulation was developed. Furthermore, relevant data
about the study of local buckling behavior of Sigma-type has been determined and can be useful for their design.

ANÁLISE DA INTERAÇÃO ENTRE OS MODOS DE FLAMBAGEM LOCAL E DISTORCIONAL EM PERFIS DE AÇO FORMADOS A FRIO COM SEÇÃO RACK

Sun, 07 Jul 2024 00:00:00 +0000

Buckling modes interaction is a quite frequent behavior of cold-formed steel members, conducting to
structural strength reduction. Local, distorcional and global buckling modes are considered in design standard and
code procedures of steel cold-formed members, according with widely accepted rules, as those included in the
direct strength method, DSM, and the effective section method, ESM. The former has been incorporated by
different standards in many countries and the latter is part of the Brazilian code NBR 14762:2010. Anyway, the
design rules available in these standards offer solution only for local-global buckling interaction.
The local-distortional buckling interaction, LD, is the focus of the present research, addressed to the particular
case of rack section columns, usually applied in storage rack systems. The investigation takes into account previous
results for LD buckling interaction for lipped channel columns available in the literature, including the results of
recent researches developed by the Thin-Walled Structures research group from COPPE-UFRJ. The present study
is based on (i) the development of a shell finite element method numerical model, calibrated with the help of
experimental results available from previous investigations; (ii) development of parametric analysis covering LD

interaction of CFS rack columns with wide variation of geometry and slenderness; (iii) examining proposed DSM-
based formulations in the literature to predict CFS lipped channel columns strength, and its applicability to rack

sections. Based on the results obtained through FEM modeling of 210 columns, it was found that the DSM
approaches proposed for lipped channel columns lead to appropriate and accurate results in the case of rack
sections.

Subsidies for the generation of artificial accelerograms

André de F. Stabile, Selma H. S. da Nóbrega, Petrus G. B. da Nóbrega — Sun, 07 Jul 2024 00:00:00 +0000

Despite an evident relatively low seismic activity, Brazil is not free of earthquakes and the correct
techniques must be used in order to design civil structures and to assess their seismic risk. NBR 15421:2006 is
the Brazilian standard code for the design of seismic resistant structures and it defines four different methods for
the structural analysis, depending on building location site: a simplified procedure, the equivalent horizontal
forces method, the spectral method and the time-history analysis procedure. In fact, it is important to ensure
strength to the structure as well as an adequate performance, what can be evaluated, for example, by the fragility
curves results from the time-history analyses. However, NBR 15421 code presents only a design response
spectrum and defines that input accelerograms should be compatible to this response spectrum. This paper
presents an iterative computational procedure, based on stochastic structural dynamics concepts, to generate
artificial accelerograms compatible with response spectra. After the methodology exposition, some applications
highlighting the influence of important parameters and an example of time-history response are describe. A
contribution to the technical discussion about this topic is important because the NBR 15421 revision process is
coming soon.

Physical Non-Linear Analysis Using the Finite Element Method One- Dimensional by Iterative Potra-Pták Method

Sun, 07 Jul 2024 00:00:00 +0000

In recent years, structural analysis has has gained a notoriety due to the technological advance. The
structures that require a non-linear analysis, require the execution of a large number of calculations, with large
and sparse matrices, requiring the use of iterative methods to solve the problems. This context, there is a need to
search for more efficient solution methods or those that are adapted to the needs of advances in Civil
Engineering analysis. Within the process of structural analysis, different analyzes have to be done in order to
achieve structural security. Physical non-linear analysis considers a non-linear constitutive relationship, which
when added to the analysis of the structure increases the use of the resistant capacity of the materials, in addition
to making it more realistic. Currently, frameworks are used in many practical engineering applications from
simple to more complex structures. Increasing the resistant capacity of these new materials can produce more
economical structures. Structures that have plastic behavior only after the yelding was modeled using a
parameter for hardening module. The current work aim is compare the solution methods Newton-Raphson,
Modified Newton-Raphson and Potra-Pták. To analyses the performance of the methods, frameworks problems
with physical non-linearity are analyzed by algorithms using Finite Element Methods developed in Fortran90.
The both Newton-Raphson methods are largely used in non-linear analysis and have quadratics convergence and
the Potra-Pták is a new method that has cubic convergence. According with the result, the Potra-Pták method
become an advantageous comparing to others iterative methods.

Análise probabilística de modelo biodinâmico para representar a ação de pedestres sobre passarelas

Sun, 07 Jul 2024 00:00:00 +0000

O uso recente de novos materiais e ideias inovadoras em projetos de passarelas têm resultado em
estruturas com baixas frequências naturais sujeitas a problemas de vibração excessivas, exigindo análise criteriosas
na fase de projeto. No presente trabalho, foram realizadas análises dinâmicas considerando modelos de
carregamento com duas formulações: modelo de força por Série de Fourier e modelo biodinâmico, sendo este
último para avaliar a relevância da interação pessoa-estrutura na resposta oscilatória. Para simular a aleatoriedade
típica do passo humano, um modelo probabilístico também foi considerado. A pesquisa reflete uma evolução desse
modelo, onde se buscou representar o movimento de um pedestre de forma ainda mais realista em sua lógica de
programação, utilizando o método de Random Walk (MRW). Com o auxílio de um modelo tridimensional de uma
passarela localizada no Rio de Janeiro, foram feitas correlações entre resultados experimentais e simulações para
uma e seis pessoas caminhando em ressonância com a estrutura. A melhor correlação entre os resultados teóricos
e experimentais foi obtida para o modelo probabilístico com parâmetros de carregamento que consideram a
formulação biodinâmica.

Analysis of the Vibrations in Walk Bridges

Pamela Paulino Carvalho, Marcelo Araujo da Silva — Sun, 07 Jul 2024 00:00:00 +0000

This report looks for to present a research carried out, related to the area of analysis of vibrations
in structures taking into account the importance of these in our daily lives. The dynamics of the structures bring
about the movement of people, which cause harmful vibrations for the structure and unpleasant for users. We call
this dynamic of rhythmic movements, taking into account the frequency with which they are performed. Each
structure has expected rhythmic movements and its corresponding frequency, which is taken into account at the
time of its projection, thus being adapted for each function it supports. It is worth mentioning that users, as soon
as they perceive this frequency, tend to synchronize themselves accordingly, intensifying the submitted vibrations,
making their effects more intense.

Dynamic analysis of soil-structure interaction problems using hexahedral finite elements with reduced integration

Michael. R. M. Visintainer, Alexandre L. Braun — Sun, 07 Jul 2024 00:00:00 +0000

In the present work, a numerical simulation is performed to obtain the soil influence on the dynamic
response of structures under cyclic loading. The spatial discretization of the soil and the structure is carried out
here by employing hexahedral isoparametric elements with reduced integration and an efficient technique is
employed for controlling the so-called hourglass modes. The load transfer between the soil and the structure is
performed by a three-dimensional contact algorithm based on the penalty method formulation, where small
interpenetrations can occur between the deformable bodies in contact. A corotational approach at element level
is used to deal with physically and geometrically nonlinear analysis, where the physical nonlinearity is due to the
elastoplastic behavior of the materials employed. Dynamic equilibrium equation is solved using the Newmark’s
method and the Generalized-α method. Numerical examples are performed and compared with predictions
obtained by the software ANSYS in order to verify the present algorithm.

Search for Improved Steel Cold-Formed Lipped Channel Beams

Amanda I. de Campos, Eduardo de M. Batista, Juarez M. S. Franco — Sun, 07 Jul 2024 00:00:00 +0000

Cold-formed steel (CFS) members are light-weight structural elements with high strength-weight ratio,
usually applied in many industrial applications. The CFS sections are frequently classified as thin-walled
structures, which means high sensitivity to buckling behavior associated to the buckling modes: local, distortional
and global. In order to improve the structural capacity of the CFS members, one may design thin-walled sections
including intermediate stiffeners, providing quite improved structural behavior. The main purpose of the
investigation is the development of a search procedure for stiffened lipped channel beams, performing the highest
critical buckling moment and flexural strength. For this, the point of departure is a 600 mm width and 1.0 mm
thick steel sheet, originated from a steel coil, which will be designed to produce lipped channel CFS with the
following possibilities of intermediate stiffeners: (i) type of stiffener; (ii) number of stiffeners in a single element;
(iii) stiffeners distribution in the flanges and the web; (iv) stiffener dimensions. As all the CFS’s candidates will
be created from the same initial coil (600 x1.0 mm), all will have the same cross-section area and weight. In this
condition, the search process is restricted to the geometric organization of the cross-section dimensions and choice
of the stiffeners geometry, dimensions and distribution, in order to display the most efficient section for simple
bending loading (in the major axis). After the generation of the possible CFS’s, the corresponding beam members
were submitted to elastic buckling analysis with the help of the finite strip method computational program
CUFSM, for the determination of the critical buckling bending moment. The obtained results are applied for the
calculation of the flexural strength of the beams, on the basis of the Direct Strength Method (DSM) rules included
in the Brazilian standard NBR 14762:2010. A shell FEM model was implemented via Ansys computational
package, in order to confirm the accuracy of the DSM results in terms of the beam strength. Finally, it was
concluded that (i) the presence of intermediate stiffeners may bring remarkable structural performance
improvement (up to 60% in some cases) and (ii) that the combination of the FSM and the DSM proved to be an
optimal tool for determining the most efficient geometry for a CFS cross section from any steel coil indicated as
input data.

Projetos de Passarelas de Materiais Compósitos com Diferentes Vãos.

João M. Ribeiro, Eliane M. L. Carvalho, Janine D. Vieira, Wendell D. Varela — Sun, 07 Jul 2024 00:00:00 +0000

A análise dinâmica de passarelas sob a ação do caminhar humano envolve muitas variáveis com
influência no comportamento da estrutura. Tendo isto em vista, este trabalho analisou as respostas de passarelas
de material compósito com diferentes concepções estruturais submetidas a uma mesma carga dinâmica com intuito
de aferir o impacto de cada concepção na resposta dinâmica da estrutura. As análises estáticas e de vibração livre
foram feitas por meio de modelos tridimensionais 3D utilizando um programa comercial baseado no Métodos dos
Elementos Finitos. As respostas da estrutura no domínio do tempo foram obtidas através de um programa de
computador desenvolvido em linguagem de programação Python para integração das equações diferenciais de
equilíbrio utilizando as propriedades dinâmicas obtidas do modelo 3D.

Behavior assessment of asymmetrical building with concrete damage plasticity (CDP) under seismic load

Sun, 07 Jul 2024 00:00:00 +0000

According to the research conducted, the asymmetric multi-storey buildings are complex and suffer
from severe damage caused by increased torsional response. This paper addresses the behavior assessment of

setback building with irregularity in the plan under severe seismic event such as Kobe earthquake. Using three-
dimensional model, the structure issubjected to seismic waves in the three directions through ground accelerations.

Nonlinear dynamic procedures have been used by means time-history analysis method. The mechanical model
describes physical nonlinear behavior with damage and plasticity showing the regions of cracking propagation,
mainly the columns-beams connections and the whole column as well, corroborating the weak column and strong
beam concept. The slabs did not present significant failures despite indicating damage regions on the borders of
the first floors.

Flutter analysis of a tip-mass-wing using Rayleigh-Ritz by hierarchical polynomials

Thais Cardoso Franco, Flavio Luiz Cardoso Ribeiro — Sun, 07 Jul 2024 00:00:00 +0000

In an attempt to reduce fuel consumption and noise, aircraft designers try to minimize structural weight
and maximize the wing aspect ratio. Both constraints lead to an increase in structural flexibility. Consequently,
aeroelastic effects, as flutter, must be researched extensively from conceptual design stages. In order to avoid
flutter, several studies have been conducted seeking to use active control techniques using piezoelectric materials.
This paper proposes to analyze the vibration frequencies and flutter velocities of a wing model described as a
clamped-free beam with bending and torsion movements with mass at its tip. A second model, the Goland wing,
whose flutter speeds are widely reported in the literature, is used to validate the results of flutter velocity obtained
for the propose model. To compare the accuracy of the results obtained and the computational cost, approximate
methods are used to obtain the discrete structural equations: Rayleigh-Ritz with hierarchical standard and Bardell

polynomials. The complete aeroelastic model is developed applying the Peters aerodynamic model, which approx-
imates the effects of the unsteady incompressible flow using a state-space approximation. Thanks to the use of

hierarchical polynomials, a low-order and computationally cheap numerical model is obtained. This model can be
used for optimization in conceptual design stages, as well for feedback control design.

DISCUSSÃO SOBRE AS METODOLOGIAS DE MODELAGEM DE PILARES DE CONCRETO ARMADO REVESTIDOS COM PRFC E SOLICITADOS POR CARGA EXCÊNTRICA

Savina Laís Silva Nunes, Tereza Denyse Pereira de Araújo — Sun, 07 Jul 2024 00:00:00 +0000

Studies have currently increased about evaluating the application of carbon fiber reinforced polymers
(CFRP) in the confinement of degraded reinforced concrete pillars. CFRP is a material that has stood out due to
its excellent mechanical properties and its specific low weight. Performing a structural evaluation is essential,
which can be through laboratory tests or computational modeling. Several numerical methods can be used,
especially the Finite Element Method. In this case, several types of carbon fiber modeling can be done using shell
elements, which can be considered isotropic, orthotropic, or lamina and cross-section considered as composite or
homogeneous. This work aims to evaluate the various modeling of the CFRP in reinforced concrete pillars
submitted to the eccentric axial load. For this, the ABAQUS® software is used, where the nonlinear concrete
material is modeled through the constitutive model Concrete Damaged Plasticity (CDP). Examples from the
literature are used, where the results are compared with those of experimental tests. Thus, the use of orthotropic
shell elements provides solutions much closer to those of reference, and the section configured as composite is the
one that provides the best results.

CONTRIBUIÇÃO PARA ANÁLISE NÃO LINEAR DE PÓRTICOS PLANOS DE EDIFÍCIOS UTILIZANDO O P-DELTA COM A TÉCNICA DAS CARGAS LATERAIS FICTÍCIAS

Bruno Correia de Araújo Moura, João Carlos Cordeiro Barbirato — Sun, 07 Jul 2024 00:00:00 +0000

Estruturas de concreto armado são frequentemente utilizadas em edificações no Brasil, devido à
abundância de matéria prima e facilidade construtiva. As cidades estão cada vez mais se constituindo em
aglomerações verticalizadas, edificações altas em terrenos relativamente pequenos. Quando se trata de edificações
esbeltas, além de ser feita uma análise dos esforços de maneira linear, deve-se analisar a estrutura considerando os
efeitos de segunda ordem provenientes da não-linearidade geométrica, por exemplo. Neste contexto, o presente
trabalho traz uma contribuição ao estudo na área da estabilidade estrutural, e apresenta um programa
computacional de análise de pórtico plano não somente no comportamento linear, mas também no comportamento
não-linear da estrutura, a partir do processo P-Delta. Foi escolhida e implementada a técnica da carga lateral
fictícia, um de seus métodos aproximados, para considerar os efeitos de segunda ordem da estrutura analisada.
Isso é feito a partir de iterações na aplicação do processo até que haja a convergência nos resultados a valores
definitivos de esforços e deslocamentos da estrutura. O resultado final de cargas, portanto, foi utilizado na
configuração dos esforços internos e nos deslocamentos. O código computacional foi implementado na linguagem
de programação PYTHON, com uso o método da rigidez direta, adicionalmente considerando a implementação de
um operador tangente, onde é possível obter o valor final de deslocamentos utilizando apenas os valores obtidos
na análise linear e na primeira iteração P-Delta. São apresentadas aplicações para comprovar a eficácia da
formulação escolhida.

ESTUDO ANALÍTICO SOBRE VELOCIDADE DE VIBRAÇÃO DE SOLOS PRÓXIMOS A LINHAS FERROVIÁRIAS

Celso Gabriel Barroso Filho, Tereza Denyse P. de Araújo — Sun, 07 Jul 2024 00:00:00 +0000

Os edifícios estão sujeitos a vibrações provocadas pelo ambiente, tais como as provenientes da indústria,
construções, tráfego de veículos, dentre outros. Estas vibrações podem danificar o edifício com o tempo ou gerar
desconforto em seus usuários. A construção de edifícios próximos as linhas férreas está se tornando cada vez mais
comum nas grandes e pequenas cidades, ao redor do mundo. O presente trabalho mostra uma metodologia analítica
para a previsão das vibrações no solo, causadas pela passagem dos trens, que atingem as edificações, pessoas ou
benfeitorias próximas. Utilizando um exemplo da literatura, pretende-se validar estas equações matemáticas, bem
como discutir as vibrações físicas e os ruídos, que o tráfego de trens gera. O objetivo é a segurança estrutural e o
melhor aproveitamento das regiões próximas às linhas de férreas. São verificados vários tipos de solo, a fim de
avaliar sua influência na propagação da velocidade instantânea de vibração induzida no meio. Outros parâmetros
também são analisados, tais como a distância da linha férrea, velocidade e carga do trem e o tipo de trilho. Essas
análises são feitas utilizando um programa matemático. Dessa forma, espera-se contribuir para a normatização de
critérios de construções de edifícios próximos a linhas férreas.

Static and dynamic buckling of deep beams with plate finite elements

Felipe S. Brandão, Raul R. Silva — Sun, 07 Jul 2024 00:00:00 +0000

The main objective of this paper is to present results on the lateral buckling of beams using finite
elements based on Kirchhoff and Mindlin-Reissner Plate theories, merged with membrane elements in order to
include the analysis of shells. A MATLAB code was developed to calculate static and dynamic critical loads,

buckling modes, frequencies, and vibration modes of thin and thick plates subjected to conservative and non-
conservative (also called follower or circulatory) loads using a so-called geometric matrix. In case of displacement-
dependent applied forces, it is necessary to implement a matrix that will correct the loads, designated as load

matrix. In the case of conservative forces, the load matrix is symmetric, and in the case of non-conservative forces,
it is non-symmetric. In the latter case, the critical load usually will correspond to dynamic behavior designated as
flutter. Different boundary conditions and loads are considered and several cases of lateral buckling are
investigated. Theoretical values when found in the literature or in national and international rules are compared
with values determined by Finite Element Method (FEM). The lateral instability of slender beams is very important
in practice, because in some situations it may occur prior to ultimate plastic limit state in bending.

Dynamic Modal Analysis by Craig-Bampton Method Applied Reticulated Structures

Sun, 07 Jul 2024 00:00:00 +0000

The Craig-Bampton method reduces the number of internal degrees of freedom of substructures by
approximations, using a set of truncated vibration modes. This is useful for large/complex structures projects. This
work aims to develop dynamic substructuring through the Craig-Bampton method for free vibration analysis on
reticulated structures. The reduction in the number of equations provided by the method is demonstrated for the
numerical examples considered. The accuracy of the method was verified through structural analyzes performed
in the SAP 2000 software.

Buckling and vibration of slender rings and pipes on an elastic foundation

Mariana Barros dos Santos Dias, Paulo B. Gonçalves — Sun, 07 Jul 2024 00:00:00 +0000

It is well known that thin-walled elastic rings and pipes are prone to buckling instabilities when under
external pressure. A particularly interesting example is the buckling of a thin, elastic ring under hydrostatic
pressure. The buckling load is strongly influenced by the follower force nature of the pressure and, if this effect
is neglected, the prediction of the critical buckling load can be as much as 50% for very thin rings. This work
studies, using a variational nonlinear formulation, the buckling and vibration characteristics of rings and pipes
resting on an elastic Pasternak foundation. First the equation of motion of the pre-loaded ring is derived and the
analytical solution of the eigenvalue problems are obtained. The parametric analysis shows the influence of the
geometric and physical parameters on the critical load, natural frequencies and load-frequency nonlinear relation,
considering the follower force effect of the hydrostatic pressure.

A comparison of geometric integrators for nonconservative and nonholonomic systems

Elias Maciel, Inocencio Ortiz, Christian E. Schaerer — Sun, 07 Jul 2024 00:00:00 +0000

In this paper, we incorporate nonholonomic constraints to the contact integrator obtained from the Her-
glotz’ variational principle. This results in a geometric integrator which is suitable for nonconservative, nonholo-
nomic systems. We compare this integrator with the more traditional one obtained from the Lagrange-d’Alembert

principle. The comparison is performed using numerical simulations on both holonomic and nonholonomic cases.
For the holonomic case, in addition to the numerical simulations we present a recently developed backward error
analysis.

Effect of uncertainties and noise on the nonlinear vibrations of a slender beam

Kaio. C. B. Benedetti, Paulo B. Gonçalves — Sun, 07 Jul 2024 00:00:00 +0000

Uncertainty analysis is fundamental in structural engineering in order to incorporate imprecise
information, errors, and limitations into theoretical models. Various techniques have been developed over the years
to access the uncertainty, with advances regarding semilinear boundary value problems to correctly represent the
probability spaces, namely spectral decomposition and collocation. However, the analysis is continuously
improving for initial value problems, and nonlinear problems in general since the methods developed to decompose
the probability spaces do not behave well in such cases. When uncertainties are given in spaces of distributions,
such as white noise processes, the applicability of those techniques is even more limited, leaving the Monte Carlo
sampling strategies as the final and, in various cases, the only choice of analysis. We consider a planar nonlinear
beam equation under an additive white noise excitation and imperfections to exemplify these limitations. To obtain
the dynamics of such a system, we spatially discretize the problem using the first linear vibration mode and analyze
the resulting differential equation by varying the uncertainty parameters. A stochastic differential equation of Itô
type is derived to verify the white noise excitation. We demonstrate the global dynamics through the generalized
cell mapping, which is used to construct both the Perron-Frobenius and the Koopman operator of the differential
equations. This example shows the effects of noise on the resonant solutions of nonlinear dynamic problems,
stabilizing the nonresonant solution. Also, the mutual impact of noise with imperfections demonstrates the
correlation of parametric uncertainty with random vibrations.

On the dynamic analysis and design of pultruded GFRP I-beams

Sun, 07 Jul 2024 00:00:00 +0000

Pultruded Glass Fiber Reinforced Polymer (pGFRP) members are increasingly used in civil engineering
applications, such as pedestrian bridges and floor systems. Published research indicates gaps in the analysis and
design of pGFRP profiles under dynamic loads. Due to their low modulus of elasticity (about 1/10 that of steel)
and lightweight, dynamic behavior is an essential aspect on the structural response of pGFRP members. This paper
presents results of numerical and analytical investigations on the structural dynamic behavior of pGFRP I-beams
through a parametric analysis that evaluates the influence of the useful height and cross-sections geometry in the
natural frequency variation. Numerical analysis has been carried out in the linear elastic field through Finite
Element Model to determine the modal shapes and related natural frequencies. For this analysis, the structural
elements made of a homogeneous material with elastic properties obtained experimentally are considered. The
results were discussed comparing the analytical predictions provided by different design approaches. Finally, the
analytical dynamic response of pGFRP I-beams was compared with those obtained for steel elements. Performed
investigation shows that pGFRP members are suitable for different human-induced vibrations applications.

Different methodologies for shear-building impact analysis

Sun, 07 Jul 2024 00:00:00 +0000

In structural analysis, the great important topic concerns the safety and stability of the structure when it
is subject to an impact load. The science of mechanical shock used to be a complex analysis in structural dynamics
area. Thus, it is proposed to investigate different methodologies of impact analysis in a shear-building. The
modelling of the problem consists of applying a short load and linear solid finite elements with 3 degrees of
freedom per node. Before, to validate the computacional analysis, one beam was evaluated. The results were also
compared with the analytical calculation. The response history shows a good agreement and some of the
advantages and disadvantages of each numerical method were highlighted.

Avaliação da influência da espessura de almas e comprimento da barra em elementos de aço comprimidos de seção I

Sun, 07 Jul 2024 00:00:00 +0000

Barras de aço comprimidas de seção transversal I estão presentes em sistemas estruturais como vigas,
pilares, treliças e contraventamentos. Podem apresentar como modos de falha uma instabilidade global, flambagem
local ou plastificação da seção. Normas técnicas como a brasileira ABNT NBR 8800:2008 e a americana
ANSI/AISC 360-16 estabelecem o dimensionamento desses elementos à compressão, fazendo considerações sobre
as imperfeições geométricas, as tensões residuais, a instabilidade e a flambagem local, de modo a garantir a
segurança das estruturas. O objetivo desse trabalho é realizar um estudo acerca da força crítica e última de barras
de seção transversal I por meio das normas ABNT NBR 8800:2008 e ANSI/AISC 360-16 e do programa
computacional ABAQUS, baseado no Método dos Elemento Finitos. Para tanto, foram utilizadas barras com
diferentes espessuras da alma e com comprimento variado, de modo a avaliar a influência desses parâmetros no
comportamento da estrutura. Por fim chegou-se a um modelo que levou a resultados similares aos normativos,
reproduzindo o comportamento de instabilidade de perfis do tipo I.

Dimensionamento via Método da Resistência Direta de Colunas de Aço Formadas a Frio com Seção em U

Elisa L. Cerqueira, Alexandre Landesmann — Sun, 07 Jul 2024 00:00:00 +0000

Recentemente, Dinis et al.[1] demonstraram que as curvas propostas por eles baseadas noMétodo da Resistência
Direta (MRD) subestimam a resistência de colunas de aço em perfil formado a frio sob interação global-global (flexão e
flexo-torção). O objetivo deste trabalho é estender o escopo do estudo anterior, considerando-se geometrias adicionais,

cuidadosamente selecionadas em seção-transversal U (simples), para o desenvolvimento de análises numérica-
computacionais de colunas (engastadas) com diferentes níveis de proximidade entre as tensões de flambagem da

coluna �!" e �#.%& (�'). Os resultados apresentados e discutidos consistem em forças críticas e respectivos modos de
flambagem, trajetórias de equilíbrio e resistências últimas (modos de colapso), obtidos via MEF, com auxílio do código
comercial ANSYS [2], segundo análises não-lineares com elementos de casca. As colunas analisadas exibem (i) seções
transversais e comprimentos que garantem esbeltezes altas e moderadas, (ii) diferentes tensões de escoamento (para cobrir
uma ampla faixa de esbeltez) e (iii) sob falha flexo-torcional. O trabalho explora o comportamento pós-crítico das colunas
selecionadas e as forças últimas compiladas que, juntamente com anteriormente reportadas, são usadas para avaliar as atuais
curvas propostas por Dinis et al. [1].

STATIC AND DYNAMIC ANALYSIS OF SUBMARINE OUTFALL STRUCTURE

Camila Brito da S., Ana Carolina Cellular, Mauricio A. P. dos Santos — Sun, 07 Jul 2024 00:00:00 +0000

Submarine outfalls are composed of an oceanic disposal system, represented by a tube that transports
domestic effluents to the sea. The discharge of sewage by underwater outfalls is shown as an efficient alternative
for the final destination of sanitary effluents since it has a high capacity to disperse and purify organic materials
in the marine environment. To design a submarine outfall as a method of disposal of effluents is necessary to
evaluate several factors that can influence the behavior of the structure, such as the forces due to sea currents.
Therewith, the study presents, through numerical modeling in SAP2000 software based on the finite element
method, a comparison between static and dynamic model, in a submarine outfall. The hydrodynamic forces were
applied by Morison’s equation for two load case, multi-step static parameters were employed in the static model
and the time history was putted in the dynamic model. The results were analyzed by means of the displacement of
the structure by varying the height and period of the waves. The analysis presents significant differences in relation
to the static and dynamic of structure comparison, mainly in the peak of the resonance.

Implementation of a consistent co-rotational nonlinear dynamic formulation and application to modeling overhead transmission lines

M.C. Vanzulli, J.B. Bazzano, G. Usera, J.M. Perez Zerpa — Sun, 07 Jul 2024 00:00:00 +0000

The overhead transmission lines are frequently affected by severe climate events such as thunderstorms
or heavy snowfalls. Such events might cause the disconnection of the line, with potentially severe consequences. In
the period of 2000- 2007, more than twenty events of disconnection were registered in one of the main transmission
lines in Uruguay. Given the particular features of local winds and temperatures, solutions applied in other countries
might not be applicable. This demonstrates the necessity to develop numerical models to enhance the prediction
capabilities of these events, guaranteeing in that manner a continuous supply of energy.
The Universidad de la Republica (UdelaR) counts with research groups working on this problem. The Com- ́
putational Fluid Mechanics Group (GMFC) is working, since 2004, in the development of computational models
of tridimensional fluxes for various applications. The main code developed is called caffa.3d.MBRi and it’s based
on the Finite Volume Method, using MPI parallelization. The group called Modelling and Identification in Solids

and Structures (MISES) is committed, since its creation in 2018, to the development of numerical codes for struc-
tural analysis. The main code developed is called Open Non-linear Structural Analysis Solver (ONSAS) and it is

publicly available.
In this work a reference formulation for consistent non-linear dynamic analysis of beam structures using a

co-rotational approach is implemented in the ONSAS code. The authors are not aware of any other open imple-
mentation of this formulation available. The implementation is validated using reference problems and also applied to the modelling of high voltage transmission lines considering realistic geometries and loadings.

Structural optimization of plane frame and analyze of the static effect of the wind

Sun, 07 Jul 2024 00:00:00 +0000

Structural optimization is used in engineering in order to find elements with optimal characteristics,
such as the size of the cross-sections. From this determination it is possible to obtain the weight of the structure,
and to find the optimal results it is necessary that some constraints are met, such maximum stresses and
displacements. The teaching-learning based optimization method (TLBO) can be used to solve structural problems,
making a correlation with a class of students. In this case, students' performance is measured through grades, where
in the structural system the grades correspond to weight. The consideration of wind forces in a structural design is
essential, as these loads can generate high efforts and require larger dimensions for the elements. The Brazilian
standard NBR 6123:1988 regulates the application of wind forces in buildings, both for static and dynamic
analysis. Thus, this work aims to analyze a building with application of forces due to static wind loads, as well as
the structural optimization of a plane frame. The teaching-learning based optimization method will be used in
order to determine the areas of the cross sections, being developed through the Matlab software based on the Finite
Element Method.

Efeito de vizinhança relacionado ao desempenho e confiabilidade

Matheus N. Reis, Thiarly F.A. Lavôr, João C. Pantoja, José L.V. de Brito — Sun, 07 Jul 2024 00:00:00 +0000

Mudanças causadas nas pressões e forças do vento devido à presença de estrutura vizinha associam-se
também a mudanças de deslocamento e aceleração, podendo afetar o conforto dos usuários em um edifício. A
adoção de confiabilidade estrutural referente à ação dinâmica do vento permite a aplicação de incertezas e um
melhor controle de suas consequências. Este estudo objetiva avaliar a confiabilidade estrutural de um edifício alto
padrão, denominado modelo CAARC, sujeito a ação dinâmica de vento, relacionando como a presença de
vizinhança pode afetar os estados limites de serviço, mediante deslocamentos e acelerações no topo. Com a
determinação das pressões obtidas em ensaios com e sem vizinhança, realizados no túnel de vento da UFRGS,
adotando diferentes direções para o CAARC, é utilizada a técnica numérica de integração de pressão de alta
frequência (HFPI) para determinar os deslocamentos e acelerações do modelo. Para realizar a análise de
confiabilidade, foram modeladas funções de falha, considerando deslocamentos e acelerações excessivos como
modos de falha. Em seguida, foram determinados índices de confiabilidade pelo método de Monte Carlo, tanto
para o modelo isolado quanto para a situação com vizinhança. Enfim, esses índices são avaliados em relação ao
índice de confiabilidade alvo preconizado em normas internacionais.

ESTUDO EM OTIMIZAÇÃO DE TERÇAS METÁLICAS EM GALPÕES LEVES UTILIZANDO PERFIL Z ENRIJECIDO FORMADO A FRIO

Marco Aurélio S Bessa, Yago S R M de Godoi, Lenildo Santos da Silva — Sun, 07 Jul 2024 00:00:00 +0000

Este trabalho visa otimizar perfis formados a frio empregados como terças em galpões leves,
tendo suas dimensões previamente definidas. Utilizou-se como variáveis a inclinação, o vão e o
espaçamento entre as terças para determinar os menores pesos possíveis para cada combinação. Foi adotado
o método dos estados limites para o estudo, fazendo análises que verificam e consideram unicamente a
terça, apontando os vãos e espaçamentos mais viáveis para a estrutura de um galpão leve, de acordo com
sua inclinação, além de fazer um comparativo entre as inclinações estudadas. As análises e cálculos foram
feitos embasados em normas nacionais e internacionais referentes a estruturas metálicas, em conjunto com
softwares e planilhas eletrônicas geradas no decorrer do estudo. Como esperado percebeu-se um
comportamento não linear ao relacionar o peso dos perfis com as inclinações propostas, vãos maiores que
7 metros necessitam de perfis muito grandes para vencer seus vãos; e, espaçamentos menores que 1,25
metros, ocasionam em mais peso por metro quadrado. Também se notou a necessidade de travamentos
horizontais em diferentes vãos a fim de otimizar e aumentar a precisão das equações encontradas.

Estudo numérico de vigas casteladas em flexão pura quanto à interação entre os modos de flambagem global e local

Christovam M. Weidlich, Daniel C.T. Cardoso, Elisa D. Sotelino — Sun, 07 Jul 2024 00:00:00 +0000

Esse trabalho investiga a interação entre os modos de flambagem lateral com torção (FLT) e flambagem
local da seção “tê” comprimida (FT) de vigas casteladas por meio de análises numéricas. São realizadas análises
lineares de flambagem elástica e não lineares de material com imperfeições geométricas iniciais pelo método dos
elementos finitos (MEF). São modeladas 12 vigas casteladas com diferentes especificações geométricas
comerciais e variando em suas tensões de escoamento dos aços. Os modelos das vigas são biapoiados com as
mesas livres sob flexão pura e as técnicas de modelagem são validadas com teste experimental de referência.
Assim, são computados os momentos críticos de flambagem global e local, através das análises de autovalor, bem
como as correspondentes esbeltezes relativas. A carga última resistente é obtida por meio das análises não lineares
e comparada com a previsão da normatização para vigas casteladas quanto à flexão. Tendo em vista os resultados
obtidos, é possível notar que quando o modo de falha predominante é o de plastificação, a normatização consegue
realizar uma boa aproximação do momento último resistente. Entretanto, quando ocorre a interação entre os
modos, e/ou o modo local é o dominante, a diferença entre a resistência prevista e as obtidas nas análises numéricas
é acentuada, chegando até a 40%. Foi possível constatar a queda na capacidade resistente das vigas em função da
interação entre os modos, de forma que quanto maior a interação, maior a queda de resistência. Vigas com FLT
como modo de falha dominante apresentaram diferenças inferiores a 10%, porém a normatização sobrestima suas
resistências.

Analysis of the progressive collapse of a reinforced concrete structure using the finite element method

José Guilherme Porto Oliveira, Luiz Carlos Wrobel — Sun, 07 Jul 2024 00:00:00 +0000

The loss of a load support element due to an extreme event can result in the progressive collapse of an
entire building. There is a great complexity involved in modeling the behavior of a structure subject to this type
of event, which makes it difficult for designers to access it. This work realized successive analysis of structural
models of a reinforced concrete building, adopting a progressive complexity to each of them, using the alternative
path method. At the end, the effectiveness and importance of each of the analysis steps employed were analyzed.

Implementação da norma brasileira de aço em um programa MATLAB orientado a objetos

Sun, 07 Jul 2024 00:00:00 +0000

The complexities in designing structures require that engineers be experts in the use of structural
design software. However, many of these programs have complex user interfaces and closed codes. For this
reason, it is often difficult for engineering students to use such programs as educational tools. In this regard, the
Tecgraf/PUC-Rio Institute is developing an interactive graphics open-source tool on MATLAB for structural

analysis of 3D frame structures: the LESM program, which has an intuitive graphical user interface and well-
structured code based on the Object-Oriented Programming (OOP) paradigm. This work describes an extension

of LESM for the design of steel structures based on the Brazilian standard NBR8800:2008. The code
architecture was conceived with modularity, in an abstract OOP fashion, making it possible to extend the
program to handle different steel design codes. The definition and organization of the OOP classes and methods
that were added to the program are presented, in addition to a demonstration of the usability of the software.

Integrated design of reinforced concrete buildings in a BIM environment

Matheus L. Peres, Elisa Sotelino, André Fregolente — Sun, 07 Jul 2024 00:00:00 +0000

A lean solution demands that not only the final result must be efficient, but the whole process also needs
to have its efficiency improved. The collaboration between engineers and architects in the design process within
BIM methodology is a way of achieve this objective. However, much of the research effort has focused in the
development and usage of 3D modeling software packages rather than in the direction of integrating the design
teams. In this work, a design process is proposed to facilitate the integration between the structural and the
architectural designs at early stages of the process. To help the implementation of the proposed process an
Autodesk Revit plugin, named ConDA, was developed. It allows the architect to perform preliminary verifications
of reinforced concrete structures at an earlier stage in the design process, which avoids the conception of unfeasible
structures and facilitates the communication between architects and structural engineers. Introducing ConDA to
the design workflow has the potential to reduce the number of design reviews and, consequently, the time spent
during design.

Concrete compressive strength prediction with machine learning

Pedro B. A. Moreira, Victor M. Silva — Sun, 07 Jul 2024 00:00:00 +0000

Compressive strength is the main characteristic of concrete. The correct prediction of this parameter
means cost and time reduction. This work built predictive models for 6 different ages of concrete samples. A set
of 1030 samples from previous studies was used, with 9 variables. Another 6 variables were added to represent
the proportions of the main ingredients in each sample. The predictive models were developed in R language,
using the Parallel Random Forest algorithm and repeated cross-validation technique to optimize the parameters.
The results were compatible with other studies using the same data set. The most important model, 28 days old,
obtained a root mean square error (RMSE) of 4.717. The 3-day model obtained the best result, RMSE of 3.310.
The work showed that the compressive strength of concrete can be predicted. The choice of creating a model for
each age allowed to get compatible results with the available data at each age. It was a promising alternative since
good results were achieved by training with just one algorithm. This work facilitates exploration and new efforts
to predict the compressive strength of concrete, it can be used as a baseline to predict with different algorithms or
the combination of several.

Numerical Simulation Of Pull Out Tests In Steel Checkered Plates

Sun, 07 Jul 2024 00:00:00 +0000

Steel-concrete solidary behaviour in composite structures can be obtained through shear connectors.
Most of the used connectors do not allow a uniform shear stress distribution between these materials, contributing
to the stress concentration and the development of cracks, which can decrease the systems’ durability. Connections
by adherence (CA) appear as an alternative. In this type of connection, the steel-concrete interaction is achieved
through a linear connector, which consists of a steel plate with checkered grooves, that favors the transfer of stress
through the friction between the interfaces that will be in contact. In this way, the connection’ performance is
influenced by interfaces’ behavior and steel-concrete interaction. In the case of CA, the resistance to pull a steel
plate from a concrete element can be investigated employing Pull Out tests, in a similar way to that developed with
bars. Therefore, this paper aimed to model Pull Out tests of steel plates, using ABAQUS®, which were calibrated

from literature’s experimental results. A parametric study was developed to investigate the influence of the steel-
concrete contact area and the interface’s stiffness in the adherence of the plates. The results showed that rougher

interfaces, with greater stiffness and greater steel-concrete contact area, developed better results.

Numerical analysis of truss elements on a sustainable bamboo bridge

Fernando Oliveira, Tiago Oliveira — Sun, 07 Jul 2024 00:00:00 +0000

This paper is concerned with a numerical comparison of truss elements between a steel bridge and
a bamboo bridge, both designed for pedestrian traffic. For this purpose, an existing steel bridge in Brasilia was
considered and later numerically modeled using the Finite Element Method (FEM). In order to show the efficiency
and feasibility of the bamboo as a structural material, another FEM model was considered changing steel elements
with sustainable bamboo elements. It was demonstrated that both bridges have satisfactory stiffness and load
carrying capacity under the Brazilian standards. Based on the results and the analysis, the sustainable bamboo
bridge proved to be lighter and cheaper than the real steel bridge with equal load carrying capacity.

Numerical Analysis of the Structural Design of the Museum of Modern Art of Rio de Janeiro - MAM

Sun, 07 Jul 2024 00:00:00 +0000

In 1958 the definitive headquarters of the Museum of Modern Art of Rio de Janeiro - MAM was
inaugurated, a project by Affonso Reidy between 1952 and 1953. MAM ́s building is an architectural and
historical landmark for Brazil, its importance is not limited to its function, like any important museum, its
relevance goes beyond the limits of simple purpose and becomes an icon of an era, and of Rio de
Janeiro. MAM is a symbol of both the evolution of museums in Brazil and the main representative of the
“Carioca school” of modern architecture. The whole of the complex is formed by 3 blocks. The School
Block, first to be opened in 1953; the Main Body, where is the exhibition gallery, object of study of this
work, built in 1967; and finally the Theater, opened at the end of 2006. The area occupied by the
Museum is 40 thousand square meters, surrounded by the sea and the gardens of Burle Marx at “Aterro
do Flamengo”. Affonso Reidy was concerned, throughout the project process, not to influence the
landscape of the place, leaving large open spaces on the ground floor and giving the building a lot of
transparency. He also made natural use of the chosen materials, such as the concrete of the main block
structure, which is structured by 12 reinforced concrete frames and 2 concrete gables at the ends,
spaced every 10 m, overcoming spans of 26 m. Pillars that follow a striking architectural form, consistent
with the needs of the efforts, form these porches. The objective of the present study is, by means of
computational tools such as the SAP 2000 program, to understand the efforts to which the structure is
subjected, verifying the constructive and aesthetic justifications of the structural solution and highlighting
the importance of the structural system adopted for the architectural result.

Análise comparativa de diferentes sistemas de cobertura em estrutura de aço

Marco A. S. Bessa, Filipe P. Battisti, Matheus N. Reis — Sun, 07 Jul 2024 00:00:00 +0000

O uso de estruturas metálicas tem se intensificado no Brasil, pois se apresenta como uma alternativa
moderna e prática na construção, mostrando perspectivas de crescimento nesse nicho de mercado. Este estudo tem
como objetivo avaliar comparativamente o desempenho de diferentes sistemas estruturais de coberturas de galpões
industriais de uso geral, considerando o menor custo e deslocamentos. Os modelos de telhado estudados são
inteiramente em estrutura metálica de diferentes topologias, com perfis formados a frio. O cálculo e a análise das
estruturas em questão são baseados em normas brasileiras e internacionais de construção em aço, juntamente com
o uso de software e planilhas desenvolvidas. Os resultados e as estimativas de custo obtidos em projeto podem ser
afetados por algumas variáveis, como a geometria e inclinação adotada para o telhado de treliça. Apesar dessa
sensibilidade, a análise das estruturas mostra que a de pórtico de banzos paralelos (PBP) é mais econômica no final
do projeto, de modo geral, e a treliça de banzos paralelos inclinados sofre menores deslocamentos.

A implementação BIM em projetos replicáveis em escala considerando elementos estruturais pré-fabricados.

Alessandra S. R. D. San Secondo, Elisa D. Sotelino, Alexandre S. Cruz — Sun, 07 Jul 2024 00:00:00 +0000

The employment of standardized structural elements manufactured off-site construction, such as
structural precast element, is considered a valid practice to achieve this purpose. Building Information Modeling
(BIM) methodology provides a promising environment for the exchange of information between those involved
in the development of a project. In addition, it is possible to incorporate planning analyzes during the design phase
to support decision making. This has great potential in the context of replicable building projects. An experiment
of a school complex was developed to simulate the planning analysis and interpretation in the project phase. The
results indicated that the consideration of precast concrete elements does not always contradict economic, practical
and aesthetic interests. Moreover, the inclusion of the planning analysis proved to be an important parameter in
decision making, improving the identification of opportunities for improvement in the project and enhancing the
work efficiency at the construction site.

Computational routine for the generation of artificial earthquakes through the Kanai-Tajimi spectrum and dynamic analysis using the Newmark method

Igor A. A. Kirchner, Letícia F. F. Miguel — Sun, 07 Jul 2024 00:00:00 +0000

The dynamic analysis of structures becomes each day more important, due to the constant cases of
earthquakes around the world, which compromises the stability of buildings. In this context, the present study aims
to develop and validate a tool that allows analyzing the behavior of structures facing different earthquakes. This
tool was developed in the form of a computational routine in the MATLAB® software, through the implementation
of a code based on the generation of an artificial earthquake to obtain an artificial seismic accelerogram, by
applying the Kanai-Tajimi filter [6] and [7], and a routine with the Newmark method developed to solve the
dynamic motion equation. Then, the code was validated through results available in the literature, being them a
ten-story shear building by Mohebbi et al. [9] and a six-story shear building by Miguel et al. [10]. The results

obtained with the program allow dynamic analysis of any building, important for the dimensioning of energy-
dissipation devices. From the literature results, it was possible to validate and prove the employability of the

computational routine developed, since the results obtained in the present code converged to the literature reference
values, with some variations due to the randomness of the earthquake.

Analysis of modal frequencies of beams by a numerical and analytical approach

Sun, 07 Jul 2024 00:00:00 +0000

While static loads are more predictable and commonly applied in a project, dynamic ones are more
complex due to its irregularity and its dependency on time. But the importance of knowing how the structures are
affected and behave when dynamic loads are applied is essential to a building. Into the dynamic analysis, the
natural frequency is one of the modal parameters vastly used to describe the comportment and the problems that
the dynamic loads cause, such as resonance that induces to higher deflections. Thus, this paper will perform modal
analysis of a steel beam, undamaged and damaged, through two different calculus approaches: analytical and
numerical. The analytical approach data used in the modal analysis was calculated based on three generical
equations; for the numerical study, ABAQUS software based in the finite element method was used. The numerical
model was created in 1D, 2D, and 3D for the undamaged beam to compare the results with the parametric ones,
and in 2D for the damaged beam. The natural frequencies obtained by all method was satisfactory, and this
outcome might be useful for more complex research as composite structures composed by a steel beam and a
concrete slab.

Application of strut-and-tie model in overhanging beams using CAST program

Philipe Q. Rodrigues, João C. Pantoja — Sun, 07 Jul 2024 00:00:00 +0000

The strut-and-tie model has been useful to solve problems involving D-regions (holes, dapped end
beam) in reinforced concrete. On this approach, overhanging beams supported by pile foundation has been found
frequently in building on the limit of land although its study does not follow the same intensity. This work aims to
compare the performance of some struts and tie topology for a beam under predefined load through CAST based
on Brazil Codes. The tool allows users an iterative process verifying each truss element. Nevertheless, there isn’t
automatic optimum topology generation thus requiring an experience by the designer to choose the best model. It
was proposed six varied layouts for a beam with constant geometric and materials properties, applying equal failure
load to all models. Reduced the load in order to obtain in stress ratio bellow and near to 1.0 in each model. The
results are presented comparing their reinforcement and limitations of layout. Some models reached equal
maximum load working different members. From the results, it was possible to define the beam with reasonable
performance and their applicability in practical design. It was discussed the potentials of the program like teaching
the strut-and-tie model and also automation in node verification.

ANALÍSE DE ESTRUTURAS DE CONCRETO USANDO BIM PARA MANUTENÇÃO

Sun, 07 Jul 2024 00:00:00 +0000

Estruturas de concreto armado para se ter um melhor desempenho para o usuário dentro da vida útil
definida em projeto deve se ter manutenções periódicas, e para se prever e identificar os elementos a serem
manutenidos há várias metodologias visuais. Um fator que deve ser considerado é a analise estrutural buscando
representar em um modelo estrutural a degradação da estrutura com o passar do tempo quanto mais antiga a
estrutura mais cuidado deve se ter com a mesma. Por meio desse trabalho apresenta uma metodologia para fazer a
análise de estruturas existentes associando a metodologia GDE/UNB com ferramentas BIM que irão auxiliar no
controle da manutenção de estruturas de concreto armado. A metodologia proposta é aplicada em um estudo de
caso no prédio da faculdade de Tecnologia da Universidade Brasília visando verificar a utilidade e aplicabilidade
da metodologia proposta e da possível replicação para analises de estruturas existentes.

State of the art and numerical simulation of high voltage towers against high-intensity winds

Agustin Teliz, Mauricio Vanzulli — Sun, 07 Jul 2024 00:00:00 +0000

High-intensity winds, such as downburst storms, generally do not follow the pattern and characteristics
of normal synoptic extreme winds. Therefore, the winds produced by downburst storms must also be taken into
account when designing large structures, particularly in Uruguayan territory where they are frequent. In this paper,
a bibliographic review of synoptic winds is presented, making comparisons with the Uruguayan wind standard
UNIT 50:84 and specific high-intensity winds studies. On the other hand, a numerical simulation of a high-voltage

tower loaded by winds from a downburst storm, neglecting the oscillation of the cables. For the simulation, a non-
linear dynamic model using Finite Element Method (truss elements) was used. For dynamic analysis, the HHT

method provided by the ONSAS software was applied. For the period simulated, the safety factor of the structure
was obtained taking into account the creep of the tensile bars and elastic instability. Also it is verified the criteria
of AISC 360-16 Standard. Finally, the first five natural frequencies of the structure were found and the first four
modes are illustrated. The numerical simulations were carried out with codes developed in MATLAB together
with the ONSAS software. They are open and free codes and the link that contains the codes is presented in the
article.

Avaliação probabilística do nível de segurança e durabilidade de estruturas existentes em concreto armado com base em inspeções

Naiara G. O. Porto, João da C. Pantoja, Hugo P. Rodrigues — Sun, 07 Jul 2024 00:00:00 +0000

O estudo de estruturas existentes é um desafio, visando fornecer técnicas de análise e cálculo que estejam
próximos ao real contexto do desempenho que a estrutura e seus componentes se encontram. Este artigo aponta
uma metodologia probabilística que associa uma análise de confiabilidade a um processo de inspeções e avaliações
em estrutura existente de concreto armado. A investigação dos danos presentes nos elementos da estrutura acontece
em fases, chegando-se a um nível de degradação para a realização de uma avaliação estrutural. Primeiramente
deve ser feita uma inspeção visual com registro das condições de uso da estrutura e das patologias existentes. Para
complementar os dados da inspeção, ensaios in situ ou em laboratório devem ser realizados. Através de uma
metodologia, avalia-se a gravidade dos danos na estrutura e seu processo de degradação. Assim, é proposto um
acoplamento dos níveis de segurança da estrutura, por confiabilidade, à um modelo de integridade de sua
deterioração. A metodologia proposta, viabiliza um diagnóstico dos processos de degradação e indica o nível de
segurança da estrutura e seus componentes. Logo, é possível entender o funcionamento do sistema e prever
possíveis comportamentos da estrutura. Um reservatório em concreto armado será utilizado como exemplo.

Estudo numérico e térmico em prismas de alvenaria estrutural com blocos de concreto e cerâmico submetidos a elevadas temperaturas

Alana P. C. Quispe, Rogerio C. A. de Lima, Rene Q. Rodriguez, Guilherme A. Weber — Sun, 07 Jul 2024 00:00:00 +0000

Nos ultimos anos, a difusão da alvenaria estrutural no Brasil acarretou na evolução de pesquisas relacio-
nadas ao comportamento do sistema em situação de incêndio, com o intuito de compreender melhor o desempenho
dos materiais e, consequentemente, do conjunto. Este trabalho tem como objetivo principal analisar, por meio
de simulações numéricas, a influência da geometria dos blocos cerâmicos quando expostos a elevadas temperatu-
ras. Foram analisados prismas de blocos ceramicos com diferentes configurações de revestimento de argamassa
e geometria e prismas de blocos de concreto com diferentes configurações de revestimento de argamassa. A
representação do ar nas cavidades dos blocos foi realizada mediante uma interação fluido-estrutura. As proprie-
dades termofísicas necessarias para calibração dos modelos foram obtidas na literatura e de normas técnicas. A
analise foi feita utilizando o Método dos Elementos Finitos (MEF), por meio do software comercial ABAQUS.
Neste artigo foram realizadas simulações puramente térmicas, avaliando o critério de isolamento térmico na face
nao exposta ao incêndio, definido pela ABNT NBR 5628:2001. Os resultados obtidos mostram a importância do
uso de revestimento, assim como da escolha do material, no desempenho termico em prismas expostos a altas
temperaturas.

Behavior of a RC infilled frame applying the classic equivalent strut macro-model

Alessandro O. Rigão, Gerson M. S. Alva, João Kaminski. Jr, Marco A. S. Pinheiro — Sun, 07 Jul 2024 00:00:00 +0000

There is knowledge of contribution to the gain of stiffness, stress changing in structural elements and
dynamic response provided by infill walls. However it is unusual to consider the masonry in frame structures
because of the complex behavior of the panel-frame and the dependence of mechanical and geometric variables
of the structure and masonry. A simple macro-model to simulate the contribution of the infill walls is the
replacement by equivalent single struts. The most methods are applicable to particular cases. The adjustment for
multi-storey buildings shall be at the charge structural designer. The purpose of this paper is to verify the lateral
stiffness and dynamic response via modal analysis of a three-story reinforced concrete frame. Two classic
macro-models are used which are mentioned by most standards that approach the theme. In addition to these
models, a macro-model with calibrated lateral stiffness was used. Some mass arrangements between masonry
and boundary beams are simulated, in order to obtain closer frequencies to the numerical model more refined.
The results are compared with the more refined plane model using FEM, including the contact effect between
masonry and the frame.

Computational Code for guide the decision on the type of structure: Steel, Wood or Concrete

Lays R.A. Costa, Hidelbrando J.F Diógenes, Andrea B. Silva — Sun, 07 Jul 2024 00:00:00 +0000

In views of rationalization in the civil construction, the knowledge about the properties of materials,
such as steel and wood, it’s necessary to compare their properties, in financial and structural terms with concrete.
Thus, the objective of this study was to compare the structural and financial conditions obtained for beams, from
the development of software in the Visual Basic programming language. The study was carried out from the
adoption of fixed calculation parameters for the materials, with variation only in the span length of the beam to
analyze each material performance. It was found that for the small spans, up to 5 meters, there were no significant
variations in the values found for the materials. Above this interval, the advantage of using concrete beams was
found, when only the cost of the reinforced concrete was considered. When the possibility of reducing the height
and weight of the building elements was considered, the steel beams proved to be more advantageous. The analysis
considered isolated parameters, and additional studies regarding the buildings’ execution time, expenses with the
materials’ maintenance, and resistant properties are necessary to achieve the best parameter and adoption of the
construction system that fits the requirements of each construction.

Metodologia prática para determinação de cablagem em vigas de pontes isostáticas

Huber R.Tokunaga, Paulo C. de R. Martins, Willian T. M. Silva — Sun, 07 Jul 2024 00:00:00 +0000

Structural design, in essence, involve choices and definitions among combinations of various
possibilities. They become iterative processes. Thus, an efficient design process will be the one with the least
number of iterations. In this sense, this paper aims to develop a practical methodology for determining the tendons
in prestressed bridge beams. In general, in Brazil, the tendons are defined by methods based on iterative processes,
highly dependent on the experience of the designer. Basically, the process involves the definition of tendons and
section checking. If the expected results are not achieved, the process is repeated. The proposed methodology will
include the determination of the tendons using Magnel diagrams and the definition of the feasible domain, as well
the definition of the limit zone for the prestressing steel, considering isostatic structures. This article refers only to
a methodology for cases of isostatic bridges. The developed proposal can be applied in manual calculations or
inserted in automated routines, in the framework of an application for practical design process as in theoretical
studies.

Topology optimization tools applied to the design of anchor systems in offshore structures

Gabriel R. Domingos, Adeildo S. Ramos Jr — Sun, 07 Jul 2024 00:00:00 +0000

The design of anchor systems in offshore structures consists in three general steps: conceptual design,
sizing and analysis, and verification. In this work, the topology optimization is applied on the first step, as an
effort to support the design of new anchor lines topologies. There are demands on the oil and gas industry that
seek to minimize the anchor radius of a production unity, which is the horizontal projection of the line connecting
the platform and the anchor point, and to maximize the anchor pattern, which is the angle between the last anchor
line of a cluster and the first anchor line of the neighbor cluster, for example. Topology optimization formulations
can incorporate these demands in order to achieve better (more economic) solutions to be used in the conceptual
design of new production unities. In this work, we use a discrete topology optimization formulation with multiple
load cases and box constraints with a cable constitutive model. Results show that our approach has the potential of
producing innovative topologies unlocking the creativity of the designer and new conceptual designs.

Design of a conveyor belt idler roller using a hybrid topology/parametric optimization approach

Rodrigo de Sa Martins, Joao Pedro Ceniz, Marco Antonio Luersen, Tiago Cousseau — Sun, 07 Jul 2024 00:00:00 +0000

A significant part of iron ore cost is due to transportation. Around 30% of this cost consists in replacing
idlers in conveyor belts. Thus, a proper design of the idler is of great economic importance. Another crucial
aspect is the ergonomics related to idlers replacement due to its weight and logistics. Having this in mind, the
usage of a robust optimization methodology for the conveyor belt idlers becomes essential to reduce the cost
of the mining process and improve idler replacement conditions. Polymeric materials have a great potential to
reduce idlers weight due to their low density. However, polymers have lower Youngs’s modulus when compared
to metals, making a hybrid design (metal + polymer) a very suitable option for the idler. Polymers can be easily
molded by additive manufacturing, thus, a great range of different shapes can be obtained. In this case, topology
optimization methods are suitable to obtain an optimum manufacturable design. However, the steel part (shaft)
has less flexibility in the design. Its topology and shape being fixed, levaves only a few parameters to define the
part design. In this case, a parametric optimization is applicable. This paper presents a systematic procedure that
combines both parametric and topology optimization to obtain an optimum design for a conveyor belt idler. The
topology optimization scheme is used within the parametric optimization iterations with different combinations of
the geometric parameters of the shaft to build a surrogate model. Then, the surrogate model is optimized using an
improved sequential least-squares quadratic programming (SLSQP) method.

BESO-LS: otimização topológica estrutural combinando os métodos BESO e de representação de domínio por função level-set

Diego S. Duarte, Marcel D. Xavier, Antonio A. Novotny — Sun, 07 Jul 2024 00:00:00 +0000

Nos ultimos anos, o campo de otimização topológica estrutural acumulou vasta contribuição científica,
principalmente envolvendo os metodos SIMP, BESO e da derivada topológica. Há interesse específico na solução
de problemas complexos de engenharia, como os multifísicos e nao-lineares, que podem ter abordagem simplifi-
cada com tecnicas cuja análise seja puramente discreta, como no caso do BESO. Mais recentemente, a penalização
material do SIMP e o metodo phase field foram incorporados ao BESO, conduzindo a resultados bastante satis-
fatorios. Sendo assim, nesse trabalho, um método alternativo de otimização topológica e proposto com o intuito
de utilizar tal benefício de analises discretas, adaptando a sensibilidade da nova versão do BESO ao método de
representação de domínio por função level-set (LS). Nesta proposta, denominada BESO-LS, a sensibilidade do
BESO e utilizada para guiar a função level-set em direção a um mínimo local do problema de otimização to-
pologica. A presente técnica se destaca por enriquecer o método BESO com o critério de otimalidade advindo
da level-set, cujo algoritmo e extremamente simples e bastante eficiente. A aplicabilidade do método BESO-LS é
demostrada atraves da realização de exemplos numéricos no contexto de minimização da complacência estrutural, ˆ
bem como na síntese de mecanismos flexíveis.

On interpolation methods for modeling low-density elements in topology optimization of geometrically nonlinear structures

Vinicius O. Fontes, Andre X. Leitão, Anderson Pereira — Sun, 07 Jul 2024 00:00:00 +0000

Modeling void regions is one of the main challenges in topology optimization of geometrically nonlinear
structures due to the excessive distortions of low-density elements. Several solutions to this problem have been

suggested in the literature, including interpolation methods such as the Energy Interpolation scheme and the Addi-
tive Hyperelasticity technique. These methods consist in interpolating each element’s model between the original

material for solid elements and a less stiff model for the low-density ones. In this work, we introduce the gen-
eral framework for topology optimization that handles several hyperelastic materials. Both interpolation methods

are explored in the solution of classic compliance-minimization problems under the assumption of plane strain
conditions with numerical results for two benchmark topology optimization problems being provided.

Topological Optimization of three-dimensional Structures using the methods of moving asymptotes and optimality criteria

Sun, 07 Jul 2024 00:00:00 +0000

In structural optimization, one of the most fascinating fields is Topological Optimization (TO). In this
article, the evolutionary topological optimization methods Smoothing Evolutionary Structural Optimization (SESO)
and Sequential Element Rejection and Admission (SERA) are used to minimize the growth of compliance using the
Method of Moving Asymptotes (MMA) and the Optimality Criteria (OC) that applies the deterministic procedure
with lagrangian multipliers. The effect of changing asymptotes is to control the generation of subproblems, which can
both stabilize and accelerate the convergence of the overall process. The three- dimensional topological optimization
of the cantilever beam is performed. Therefore, to optimize the computational solution, such as cost and excess
memory, which occur in these types of problems, a Preconditioned Conjugated Gradient Method (PCG) is used as an
iterative solver. The results obtained are compared with the Solid Isotropic Material with Penalization (SIMP) that
uses for convergence the OC.

Structural Topology Optimization Applied to Scarifier Subsoiler

Artur F. de Vito Jr., William M. Vicente — Sun, 07 Jul 2024 00:00:00 +0000

The subsoiler is one of the most used tools in tillage, mainly in the subsurface layers, helping in the
availability of nutrients for the plants and reducing soil compaction. In some cases, this tool is oversized due
to the lack of engineering tools and technical knowledge. In this aspect, this work aims to apply the topology
optimization method to the shank of a subsoiler to decrease the consumption of raw material while maintaining
performance during tillage. It was used Ansys, to solve the finite element analysis, in parallel with Matlab based

in Bi-directional Evolutionary Structural Optimization (BESO) scheme for the compliance minimization and con-
sidering the volume as the constraint. The three-dimensional model of the subsoiler shank was generated on 3D

Computer-aided design (CAD). MatLab reads the set parameters, builds an Ansys input file, and sends it to Ansys
to perform the finite element analysis. Ansys exports geometry details and elemental strain energy necessary to
perform the topology optimization. As a result, the topology optimized subsoiler shank is is 25% lighter than the
original part with a 8% increase in the mean compliance . An adaptation of the final geometry was implemented
so that the subsoiler could be more easily manufactured after applying the topological optimization method.

TOPOLOGICAL OPTIMIZATION OF THE STRUCTURAL OF A STEERING KNUCKLE FOR THE PUSHROD AUTOMOTIVE SUSPENSION SYSTEM

Álvaro Barbosa da Rocha, Felipe Silva Lima, Wanderley Ferreira de Amorim Júnior — Sun, 07 Jul 2024 00:00:00 +0000

The steering knuckle is a fundamental part of automobiles, being responsible for the direct integration
of the scrolling, steering, braking and suspension systems into the vehicle's chassis. Pushrod type suspension
incorporates a double arm system overlapped with rods to activate the damping system, favoring the approximation
between the vehicle's center of gravity and the ground, improving the vehicle's performance at high speeds. The
knuckle undergoes severe efforts under conditions of use, and catastrophic failures can occur in certain cases. This
paper present a static structural analysis of the knuckle under impact loads, maneuver in short radius curves and
maneuver in long curves followed by a topological optimization aiming to improve the stress distribution,
minimizing the weight of the structural component for critical conditions of use. The topological optimization
performed on the knuckle employed a generic CAD model, made of aluminum alloy Al7075-T6, which allowed
the mass to be reduced by 35,439%, minimizing the stress gradient by 34,614%, the maximum stress of which was
186.65MPa

Applying a topology optimization projection scheme for structures under free and forced vibration

Lucas O. Zúñiga, Renata M. Soares, Sylvia R. M. de Almeida — Sun, 07 Jul 2024 00:00:00 +0000

This work addresses topology optimization applied to structures under free and forced vibrations using
the density approach. A SIMP-like model is used to penalize the stiffness and the mass distribution. The density
approach applied to structures under vibration is prone to intermediate densities in the final solution and to
numerical instabilities on a larger scale than the static approaches. In this paper a projection scheme is applied to
overcome the numerical instabilities characteristic of this type of approach using a Heaviside projection function
is applied in both cases. The Heaviside function also reduces de intermediate densities in the final solution when
compared both to the linear function and to the application of the classical sensitivity filter. Numerical examples
are presented to illustrate the application of the projection-based technique applied to free and forced vibration
problems.

Inverse and direct projection schemes for topology optimization using polygonal elements

Lorran F. Oliveira, Daniel L. Araújo, Sylvia R. M. de Almeida — Sun, 07 Jul 2024 00:00:00 +0000

Projection schemes are used in topology optimization to provide minimum length scale on structural
members in topology optimization solutions. On the other hand, inverse schemes provide control over the
minimum size of holes in the resultant topology. Literature provide several applications of both schemes associated
to regular meshes using quadrilateral finite elements to discretize the design domain. Besides, in the last decade
polygonal element has been applied to solve topology optimization problems, providing better representation for
the contour of the design domain. This paper applies the concepts of both direct and inverse schemes to
unstructured polygonal finite element meshes. Each projection is made via mesh independent functions based upon
the minimum length scale for either structural members or holes. A linear and a Heaviside projection function are

applied to both schemes. Numerical examples are presented to demonstrate the various features of the projection-
based techniques.

A von Mises stress-based topology optimization applying the standard finite-volume theory for continuum elastic structures

Sun, 07 Jul 2024 00:00:00 +0000

Topology optimization algorithms want to establish the best material distribution inside of an analysis
domain. In those optimization problems, usually there are some numerical problems to be overcome, such as the
checkerboard pattern, mesh dependence, local minima, and occurrence of gray regions. This paper addresses a
new topology optimization technique, where the objective is to minimize the equivalent average von Mises stress
subject to a volume constraint and to apply the standard finite-volume theory for elastic stress analysis. The solid
isotropic material with penalization (SIMP) approach is employed to avoid discrete optimization problems. The
proposed optimization problem has shown efficiency, avoiding the occurrence of numerical instabilities, such as
checkerboard pattern, mesh dependence, and local minima, when a sensitivity filter is employed. In the absence
of filtering techniques, the proposed approach has shown efficiency by producing checkerboard-free optimized
topologies with fewer bars, more robust bars, and well-defined “black and white” designs.

Use of an improved fractional derivative model for transient analyses of viscoelastic systems

Erivaldo P. Nunes, Gabriella F. Garcia, João P. Sena, Antônio M. G. de Lima — Sun, 07 Jul 2024 00:00:00 +0000

Vibration control is an important field in the study of structures. One of the ways commonly used to
mitigate structural oscillations is passive control using viscoelastic materials. The properties of these materials are
strongly dependent on environmental factors, mainly on the temperature and frequency of excitation, so that the
models for the characterization of their dynamic behavior must be able to represent this dependence. In this sense,
this work presents the modeling of a sandwich beam treated with viscoelastic material and subjected to dynamic
loading. For this, a viscoelastic fractional model is presented, the kinematic relations between the layers were
obtained, and, applying the variational principles of mechanics the equation of motion of the system was found
and evaluated using finite element method. Through this procedure it was possible to represent the transient
behavior of the sandwich beam and compare it with the response of the structure with no viscoelastic treatment.

Multi-Modal Dynamic Vibration Absorber Design for Aerodynamic Surfaces Using Optimization

Sun, 07 Jul 2024 00:00:00 +0000

Dynamic Vibration Absorbers (DVAs) are devices that aim to reduce the vibration amplitudes of systems
subjected to external forces. When a DVA is coupled to a primary system, it promotes the reduction of vibration at
a certain frequency of operation. The aerodynamic surfaces of aircraft, such as wings, are subject to problems, for

example, those caused by the Flutter effect, dangerous phenomenon found in flexible structures subject to aerody-
namic forces such as aircraft, buildings, bridges, among others. This phenomenon is characterized by the coupling

of two oscillations, flexion and torsion, which occurs due to the interactions between aerodynamics, low stiffness
and inertial forces in a structure. In order to simultaneously mitigate the amplitudes of vibration in the vicinity
of both oscillations in the wing, this work proposes the design and optimization of a passive MultiModal DVA
(MMDVA) whose main feature is the ability of reducing vibration at the vicinity of various resonance frequencies
of a primary structure. This justifies why it is used in the current application. However, it is not easy to determine
the optimum constructive parameters of these MMDVAs and therefore it is necessary to use optimization methods
to guarantee that they are tuned to the wing frequencies (flexional and torsional). The global optimization heuristic
Genetic Algorithms (GAs) was used for this purpose and demonstrated to be efficient.

Aplicação De Amortecedores Para Controle De Vibrações Em Estruturas Metálicas

Andressa B. Miranda, Renato A. Maia — Sun, 07 Jul 2024 00:00:00 +0000

Diante do cenário atual da construção civil composto cada vez mais por estruturas esbeltas e susceptíveis
a choques e vibrações, têm sido desenvolvidas alternativas de amortecimento e controle das vibrações excessivas.
No presente trabalho, o dispositivo de controle a ser aplicado trata-se do AMS (Amortecedor de Massa
Sintonizada). Para se alcançar a efetividade do sistema de controle, é necessário que os parâmetros do dispositivo
(massa, rigidez e amortecimento) estejam adequados aos procedimentos ótimos de projeto expostos pelo
pesquisador Den Hartog [1]. Neste artigo será apresentada a simulação da aplicação do dispositivo de acordo com
os parâmetros ótimos de projeto utilizando o software de análise estrutural SAP 2000, pelo qual obtiveram-se as
respectivas respostas dinâmicas para a modelagem numérica realizada, onde foi feito um comparativo entre os
resultados obtidos.

Vibration control of coupled wind tower-nacelle-blade system

Sun, 07 Jul 2024 00:00:00 +0000

In this work, the vibration control of a coupled wind tower – nacelle – blades system subjected to
external lateral loads and rotating blades is studied. To model the tower and blades, the non-linear Euler-Bernoulli
beam theory and the linear Euler-Bernoulli beam, respectively, are considered. The structural control device
studied is an inverted pendulum tuned mass damper (IPTMD) located at the top of the tower. The Rayleigh-Ritz
method, together with Hamilton principle, is applied to obtain a set of nonlinear ordinary differential equations of
motion which are, in turn, solved by the Runge-Kutta method. First, the dynamic instability is studied when
rotating blades are considered, where it is possible to observe veering phenomena. In addition, the optimum
parameters of the IPTMD are obtained. The results show a good performance achieved by the vibration control
adopted to the dynamical behavior.

Centrifugal Pendulum Dynamic Vibration Absorber for Helicopter Blades

Sun, 07 Jul 2024 00:00:00 +0000

A large part of the engineering problems in rotating machines are related to vibration. This shortcoming
causes discomfort, wear and fatigue, leading to structural failures if they are not properly controlled. The main
techniques used to reduce the amplitudes of vibration include the installation of Dynamic Vibration Absorbers
(DVAs) which vary roughly from passive, semi-passive, semi-active and active, differing mainly in two aspects: i)
frequency range where it is effective and ii) external energy consumption. In rotating machines such as helicopter
blades, a type of DVA historically used is the Centrifugal Pendulum DVA (CPDVA), the use of this passive DVA
is justified due to the frequency of rotation of the helicopter rotor remains almost constant during its operation and
for the complexity of installing an active system on the blade. In this work, we will design a numerically passive
CPDVA. The blade and the absorber are modelled as beams using Finite Element Method (FEM) and validated
with analytical previous studies. Results show a good agreement with reality and theoretical expected behaviour,
the CPDVA attended the function it was designed.

Aplicação de um amortecedor de massa sintonizado para o controle de vibração de uma viga engastada

Sun, 07 Jul 2024 00:00:00 +0000

The concern with dynamic structural behavior has been increasingly relevant. The constant development
of civil construction, combined with the growth of the regions and the increase in the population, has been forcing
a continuous verticalization of the structures. Due to this verticalization, the structures were designed and built
increasingly thin and with larger spans. However, due to their high flexibility, they are vulnerable to excessive
vibrations that can cause discomfort to users and compromise the safety of the building. One of the control systems
that can be used to reduce these oscillations is the Tuned Mass Damper (TMD), a device that, when coupled to the
primary structure whose vibrations are to be controlled, is able to absorb vibratory energy at the connection point.
In this study, a numerical simulation will be performed using the Finite Element Method (FEM), for a system
formed by a cantilever beam at one end and free at the other. From the dynamic characteristics of the system, a
TMD will be modeled and coupled to the structure, so that the first frequency of the system is attenuated. The
results show a reduction of 77.8% for the displacement of the beam considering a mass ratio equal to 0.005 and a
TMD damping factor of 0.043.

Hysteretical Behavior of Steel Slit Dampers Subject to Geometric Changes

Mendoza C. Angie, Begambre C. Óscar, Villalba-Morales Jesús D. — Sun, 07 Jul 2024 00:00:00 +0000

In the last decades several alternatives to obtain buildings that present a more efficient behavior to
seismic events have been developed, one of these alternatives is the implementation of passive energy dissipation
systems that modify the dynamic characteristics of the structure thus controlling its deformation and subsequent
damage. Particularly, steel slit dampers are an inexpensive alternative and they have proved reliable and easy to
install and maintain. This paper evaluates the hysteretic behavior of metallic dampers subject to cyclic load. The
amount of energy that a steel slit damper can absorb is determined numerically by means of a finite element model
and a comparative analysis of sensitivity to changes in shape and distribution of holes, thickness and width-height
ratio of the plate is presented.

Influence of the Shape of Slit of a Circular Hollow Steel Damper on its Energy Dissipation Capacity

Diego H. Leon, Letícia F. Fadel Miguel, Jesús D. Villalba — Sun, 07 Jul 2024 00:00:00 +0000

This research studies the effect that the shape of slits of a circular hollow steel (CHS) damper has
on its EDC, whose computation is raised in a hysteresis diagram obtained from a tridimensional non -linear
dynamic element finite analysis in Abaqus. A cyclic displacement protocol attending inte rnational normative is
used to induce cyclic displacement in the upper part of the device while the bottom part is considered fully
restrained. The model considers the presence of large deformations in the device as a result of the yielding in the
material. Only one configuration for the geometry (predefined thickness and external diameter) the CHS is
analyzed, but a total of 5 different shapes for the slits are considered (horizontal, vertical, circular, square and

triangular shapes). All the slits configuration presents the same void area in order to obtain a fair comparison. A-
36 steel is used for the damper as present good ductility characteristics. Finally, the performance of each CHS

damper configuration is analyzed from the characteristics of their hysteresis diagram, the stress distribution
through the damper and their EDC. It was concluded that the model with circular slits was the one that presented
the highest dissipation capacity, since this type of groove favors the distribution of stresses in its contour, unlike
the others whose vertices generate stress concentrators.

Bayesian statistics of uncertainty quantification attenuation bands of three-dimensional phononic lattices

L. H. M. S. Ribeiro, V. F. Dal Poggetto, D. Beli, A. T. Fabro, J. R. F. Arruda — Sun, 07 Jul 2024 00:00:00 +0000

Phononic crystals are periodic structures that may present Bragg scattering and wave coupling band

gaps, which are frequency ranges where waves cannot propagate freely. In this work, it is proposed a three-
dimensional frame structure that can be used to support and isolate vibrations of a rigid payload. This structure is

a 3D lattice made of frame elements. Firstly, one frame presenting the intersection of longitudinal, flexural, and
torsional band gaps were proposed. The resulting unit cell is modeled via the spectral element method (SEM).
The three-dimensional structural model includes constraints and inertial characteristics of a rigid body attached
at its top. Pseudo experiments are performed using mechanical property values sampled from previously defined
statistical distributions. A Markov chain Monte Carlo (MCMC) algorithm is used to estimate posterior distributions
of mechanical properties considered as statistical variables. Prony’s method is used in the MCMC algorithm to
improve its precision. The Monte Carlo method is used to infer about the stochastic wavenumber. Two robust and
complete attenuation bands related to the considered variability are observed, which are shown on the dispersion
diagram of the 3D structure for some observations along the contours of the irreducible Brillouin zone (IBZ). Such
attenuation bands can also be observed on the forced response of the rigid payload subjected to base excitations.

Vertical Dynamics of a Half-car Computational Model

L. T. Matos, N. S. C. Seguins, V. S. Pereira, D. I. G. Costa — Sun, 07 Jul 2024 00:00:00 +0000

Vertical dynamics studies of a vehicle can be used to obtain responses to imperfections of a track.
Closely related to comfort issues, this analysis is affected mainly by the vertical movement (bounce) and alternating
oscillations such as roll and pitch. An off-road vehicle model for student competitions, such as SAE Mini-Baja,
aims to challenge students to design and build vehicles that will be put to test in tracks with critical conditions.
The main goal of this work is to analyze the vertical dynamics of an off-road vehicle prototype, using dynamic
modeling and numerical simulation. A half car 2-D vehicle model is presented in this paper. An analysis of the
system’s damped forced vibration was performed using a track function as input, simulating the disturbances that
the vehicle’s suspension suffers during competition. From this type of analysis, it was possible to obtain important
data, linked to safety, handling, driver comfort and car structure. The results revealed that factors such as stiffness
and damping of the suspension set can generate unwanted vibration frequencies, discomfort to the pilot, in addition
to compromising the structure and stability of the vehicle. Additionally, the results obtained are in accordance with
the literature.

A COMPARISON OF A NON-LINEAR PENDULUM ABSORBER 2D AND 3D

Igor Braz N. Gonzaga, Wendell D. Varela, Ronaldo C. Battista — Sun, 07 Jul 2024 00:00:00 +0000

Designed to reduce the vibrations amplitudes in the horizontal direction of slender structures and
industrial components subjected to dynamic excitations, such as wind and earthquakes, a non-linear pendulum
control system is assessed in this paper. Firstly, 2D and 3D mathematical models are developed based on the
Lagrange’s energy equations. The system of non-linear differential equations of motion is numerically solved in
time domain. Some parametric studies are performed to understand the role of some key physical characteristics
of the control device in its effectiveness in controlling the vibration amplitudes of a structure under certain load
scenarios, including the pendulum mass, damping ratio and length. Finally, the results obtained with two
perpendicular 2D simplified pendulum model is compared to the results obtained with the 3D pendulum model in
order to evaluate the performance in the use of the simplified approach to design this type of passive control
system.

Optimal Tuned Mass Damper Properties to Reduce the Response of Floors Subjected to Rhythmic Induced Loads

C.A.N Silva Jr, F.A.C. Monteiro — Sun, 07 Jul 2024 00:00:00 +0000

Building floors designed for gyms can present high level of vibration due to human induced dynamic
load during rhythmic activities. This problem can be solved by increasing the structural stiffness and damping, or
by using passive energy dissipation devices known as tuned mass damper (TMD). This paper analyses a steel-deck
slab subjected to dynamic load due to rhythmic activities and relates the maximum acceleration of the model with
the material damping ratio. Four material damping combinations are analyzed and a two-dimensional equivalent
orthotropic plate is proposed to represent the slab tridimensional behavior. A parametric study is performed, where
an optimization process is employed to find the best combination of stiffness and mass of a tuned mass damper
that minimizes the mass required to achieve a given vibration reduction. The vibration attenuation ranges from
10% up to 80% reduction of maximum acceleration of the reference model without any damping absorbing device.
The results showed that the structure with lowest structural damping ratio is the most sensitive to the presence of
the tuned mass dampers. Moreover, increasing in the TMD damping ratio can significantly reduce the total mass

required to achieve a certain main structure vibration reduction, proving that this solution can be a great cost-
effective approach to mitigate structural unwanted vibrations.

Analysis and Design of Base Insulators Applied to the Helipad of the Hospital Structure

Sun, 07 Jul 2024 00:00:00 +0000

In catastrophic situations, rescue cannot be carried out via ground ambulances, which makes helicopters
a very common solution to locate and transport patients to hospitals. However, due to the small areas in urban
centers, hospitals choose to build landing areas on the rooftop, optimizing the space available. The main problem
of this proposal is the transmissibility of vibration caused by the helicopter landing and takeoff, affecting
employees, patients and equipment inside. In general, construction in hospitals, especially when they are still in
operation, require simple, fast and effective solutions. For this, metallic structures and passive insulation are widely
used in elevated hospital heliports. For passive isolation, some indicators are necessary for an efficient reduction,
such as, applied loading, type of material and degree of transmissibility. For this study, analytical and numerical
calculations are necessary, each of which is extremely important to assess whether the vibrations transmitted to
the building will be negligible or whether it is necessary to add something for reduction.

Coupling technique between adjacent structures for vibration control using inerter element

Augusto de Souza Pippi, Suzana M. Avila, Graciela Doz — Sun, 07 Jul 2024 00:00:00 +0000

Vibration control techniques in structures are widely studied as a way to guarantee reliability and
comfort for its users. In addition, structural control techniques ensure that complex structures, with a high degree
of vibration restriction, can be designed. A technique that has been gaining space in recent years is of the so called
structural coupling. In this technique, adjacent structures are connected by control devices, whether passive, active,
semi-active or hybrid. Thus, one structure exerts forces of control over the other, reducing the amplitude of
vibrations of each individual structure and the coupled system. Studies on structural coupling as proposed by Pérez
Peña [1] use viscofluid and viscoelastic dampers (passive systems) in the connection between buildings and
demonstrate the efficiency of this technique. As an alternative to these dampers, more recently, the inert elements
have appeared. The use of inertial dampers, which use inertial mass rotating forces, emerged in the early 2000s,
when Smith [2] defined the term “inerter” as a mechanical two-node (two-terminal) and one-port device with the
property of that the equal and opposite force applied at nodes is proportional to the relative acceleration between
the terminals. In the structural coupling technique, the inerter devices are still little explored. Thus, the aim of this
work is to verify the efficiency of the application of inerter devices in the connection between adjacent buildings.
The buildings are modeled as shear frame structures. The position, quantity and mechanical properties of the
connection devices are optimized by the particle swarm optimization algorithm. The initial results indicate that the
use of inerters in the connection between adjacent buildings requires caution, since the addition of inertia to the
system decreases its natural frequencies, which can be harmful to the coupled system.

The nonlinear modal analysis of a barge-type offshore wind turbine

Elvidio. Gavassoni, Paulo D. G. Zwierzikowski — Sun, 07 Jul 2024 00:00:00 +0000

Wind turbine use is increasing all over the world. At depth-water greater than 50 m floating support

platforms will be the most economical type of support structure to use. Among the numerous floating support-
platform configurations possible for the use with offshore wind turbines one may cites the barge, whose static

stability in pitch and roll is achieved using a large waterplane area. Such structures can exhibit large displacements
when vibrating. This scenario demands a nonlinear dynamic analysis of the problem. The main goal of this study
is to use reduced order models, based on the nonlinear normal modes, to identify and to analyze the nonlinear
dynamic behavior of a reference turbine of 5 MW supported by a barge floating structure. Free and forced
vibrations are studied. The existence of multiple solutions, unstable solutions and bifurcations are detected. The
use of the Mathieu’s chart allows the study of the stability of the solutions. The results show that the nonlinear
normal modes are an efficient tool to capture some important behavior and to perform fast parametrical studies.
The reduced order model results are compared to the numerical integration of the equations of motion and a good
agreement between both results is found.

Sensitivity analysis of a Small-Scale Darrieus vertical axis wind turbine

Pedro Henrique M. Barros, Leandro O. Salviano — Sun, 07 Jul 2024 00:00:00 +0000

Demand for alternative and renewable energy sources has grown substantially in recent years as a result,
inter alia, of economic and environmental aspects of conventional sources such as oil and its derivatives. In this
context, wind energy has emerged as attractive renewable source. The growth of wind energy in Brazil and in the
world envision the possibility of developing new technologies and more efficient equipment that meet energy
needs. Thus, the objective of this work is to contribute to the development of Small-Scale Darrieus Vertical Axis
Wind Turbine (VAWT) that can be employed in decentralized electrical generation through computational fluid
dynamics (CFD), operating at low tip speed ratio λ (TSR). A 2D numerical modeling is performed considering an
unsteady-state and turbulent flow. Mesh density analysis is ensured by Grid Convergence Index (GCI)
methodology and the numerical robustness is verified through experimental comparison. The geometric
parameters of the VAWT analyzed are: profile camber (m), camber position (p), aerodynamic profile thickness
(t), profile chord (c) and blade incidence angle (α), the first three being based on the NACA-4 digit
parameterization. These five parameters, associated with the operational parameters, are submitted to a sensitivity
analysis using the Smoothing Spline ANOVA algorithm in order to predict the influence of each one of these on
the power coefficient (Cp) of Darrieus VAWT. With a Design of Experiments (DoE) containing 100 possible
configurations of the Darrieus turbine generated using the Uniform Latin Hypercube Sampling (ULHS) method,
it was possible to evaluate which parameters and interactions of them have the most influence on the power
coefficient. The main finds showed that the contribution index of the angle of incidence (α) on the power
coefficient was the highest among the others, with a contribution of 73%. Another significant contribution is the
combination of angle of incidence parameter (α) and the profile chord (c), presenting an index of 16%. Therefore,
the impact of NACA-4 digit parameterization on the power coefficient is small. Moreover, the sum of the
contribution of the parameters inherent to the parameterization is only 4%.

Finite element models for analysis of structural integrity of onshore wind turbine foundations with embedded rings submitted to static and dynamic loads.

Thaís Tenório Dourado, Windson Bezerra de Aguiar, Paulo Marcelo Vieira Ribeiro — Sun, 07 Jul 2024 00:00:00 +0000

Wind turbines’ share in the energy industry continues to grow, its status of renewable energy source
deeming it attractive due to environmental policies established worldwide. Most of these turbines are onshore
installations and are supported by steel towers connected to reinforced concrete foundations through embedded
rings (or insert rings), a type of structure with reported damages to the tower-foundation interface. This study
presents simulation procedures for this kind of foundation concerning their structural behavior. Emphasis is given
on the development of finite element models with the aid of the finite element software Abaqus. First, a linear 3D
model considering only equivalent static loads transferred through the embedded ring. Then, after estimation of
aerodynamic loads, a linear dynamic analysis. This methodology provides a valuable resource since the knowledge
of the model’s response to different load scenarios can be used to prevent deterioration in embedded ring
foundations, and future advances can guide maintenance and rehabilitation plans on existing wind turbine farms.

A layup optimization approach of laminated composite wind turbine blade for improved power efficiency

Danilo G. Dellaroza, Claudio Tavares da Silva, Marco A. Luersen — Sun, 07 Jul 2024 00:00:00 +0000

Wind turbine blades are usually made of composite materials. Their stiffness and behavior affect the
turbine performance, on the other hand, the material and layup orientation influence the blade stiffness. By taking
advantage of the bend-twist coupling that is a consequence of layup sequence, it is possible to produce a passive
control of the pitch angle which aims to improve the blade performance. The purpose of this work is finding the
best layup sequence of a wind turbine blade made of laminate composite materials using metamodeling based
optimization. For this, the finite element method is used to obtain the structural response of the wind turbine blade.
From this numerical simulation responses, a surrogate model based on Kriging approach is generated. Ply
orientations are adopted as input parameters, and the power coefficient of the wind turbine as output. Then, an
optimization process is carried out. The optimized layup sequence is compared with other layup configurations
and the surrogate model responses with the finite element model itself. Using this methodology is possible to reach
a significant improvement in turbine power coefficient. For instance, at wind speed of 20 m/s, the power coefficient
between layups achieves 8.2% of variation.

Evaluation of the behavior of a horizontal axis wind turbine subjected to wind loading

Vanessa Lanziere Neves Carvalho, Luiz Carlos Wrobel — Sun, 07 Jul 2024 00:00:00 +0000

Due to the advances in wind energy, it became necessary to better understand the structural and
mechanical behavior of wind turbines. This work presents the modeling of the 5 MW baseline wind turbine,
developed by the National Renewable Energy Laboratory (NREL) in the USA, considering an onshore structure
with 3 blades. Through the SAP2000 structural model, it was obtained the natural frequencies and modes of
vibration, while the dynamic response of the structure, when submitted to wind cases asIEC 61400-1, was obtained
through the software FAST.

Discrete Model Identification of a wind turbine: a case study of Nordtank NTK 330F

Sun, 07 Jul 2024 00:00:00 +0000

The renewable energies are in constant evolution for the sake of the necessity of finding alternatives to
fossil fuels derived energy. One of these alternatives are the wind farms, offshore and/or onshore, that provides
electricity through the wind force. The horizontal axis turbines are commonly seen on this farms, usually with 3
blades, because of its cost-benefit. However, even though there are equations well defined regarding the behavior
of this machines, some environmental variables (such as terrain, height and wind wakes) can add a nonlinear and
random factor to the energy conversion. Thereby, the use of system identification shows itself useful to forecast
the behavior of this system. In this work, a database from Nørrekær Wind Farm, located on Denmark, is exploited
by identification techniques, in order to estimate nonlinear auto-regressive with exogenous inputs (NARX) and
auto-regressive with exogenous Inputs (ARX) models. To calculate them properly, three methods will be used

and compared: Classical Gram-Schmidt (CGS), Modified Gram-Schmidt (MGS) and Householder-based QR-
Decomposition with Column Pivoting. All the methods provided results closer to real data, although MGS and HT

models were slightly more accurate.

Comparison of the natural frequencies of a reference wind turbine blade using the finite element method with Euler-Bernoulli and Timoshenko beam formulations

João Pedro Tavares Pereira dos Santos, Guilherme Ribeiro Begnini — Sun, 07 Jul 2024 00:00:00 +0000

The development of horizontal axis wind turbines brought longer blades and taller towers, which incurs
in structures more susceptible to vibration problems. The vibrational behavior of the blades and the tower are
studied separately at a first stage and each structure is typically modeled as a cantilever beam, with the aid of the
finite element method. The most common beam models are the Euler-Bernoulli Beam Model and Timoshenko
Beam Model, both used on this work. The key differences between those two models are that the shear stress and
the rotatory inertia effects are ignored on the first one, which generate some discrepancies among the results. In
the present work, a finite element method code is implemented for both beam formulations to determine the natural
frequencies of a reference wind turbine blade, whose properties were obtained in the literature. The code was first
validated by comparing the computed and theoretical results for a cantilever beam with rectangular cross section,
and then applied to the wind turbine blade. For both structures analyzed it is shown that the natural frequencies
obtained with Timoshenko model are lower than the ones obtained with Euler-Bernoulli model, and that the
magnitude of difference increases with mode order.

Vibration control of a wind turbine with a hybrid mass damper

Pedro H. Q. Rocha, Suzana M. Avila — Sun, 07 Jul 2024 00:00:00 +0000

It is studied the application of structural control in the protection of wind turbines subjected to external
loads, such as wind and earthquake, which can compromise the safety and integrity of the structure with excessive
vibrations. Structural control can be classified as passive, active, hybrid or semi-active control. The structural
control device used is the hybrid mass damper (HMD), which is the combination of a tuned mass damper (TMD)
with an active controller. It is a more robust and reliable control when compared only to active and passive
dampers. The objective of this research is to numerically analyze the behavior of a dynamically loaded wind
turbine and apply a hybrid control system. A comparative study of the performances obtained by different
controllers is presented, such as proportional integral derivative (PID) and linear quadratic regulator (LQR).
Numerical simulations are performed using the Matlab computational package and its Simulink control toolbox.
A wind turbine tower has been analyzed using the technique of reducing tall towers to a single degree of freedom.
The results showed that the HMD was efficient in controlling the dynamic response of the tower.

Parametric structural optimization of conveyor idler rollers

João Pedro Ceniz, Rodrigo de Sá Martins, Marco Antônio Luersen, Tiago Cousseau — Sun, 07 Jul 2024 00:00:00 +0000

Conveyor rollers are widely used in the mining industry for ore transportation. However, due to the
severe operating conditions, these components may fail prematurely and thus cause high maintenance costs. The
failure of these rollers is usually directly related to the service life of their bearings. This service life is greatly
influenced by the angular deflection of the bearings. Within this context, this work presents an optimization
study of a metallic conveyor roller. The purpose is to find a roller with lower mass, however, maintaining the
angular deflection of the bearings in an acceptable range of operation, without significant changes in the roller's
shape to do not affect the current manufacturing processes. To define the optimization design problem, the study
is based on a Brazilian standard, where factors such as: type of roller, load, allowable stresses and angular
deflections are defined. The optimization algorithm is coupled to a radial basis functions (RBF) metamodel
which predicts the structural response of the roller. The RBF metamodel is built, and iteratively refined, through
finite element analyses performed in the commercial code Ansys. The optimization results indicate the
possibility of obtaining a roller design with lower mass and higher stiffness than those manufactured nowadays.

SURROGATE BASED OPTIMIZATION OF FUNCTIONALLY GRADED PLATES USING PSO AND DE

Sun, 07 Jul 2024 00:00:00 +0000

Optimization procedures are often employed in the design of functionally graded structures to achieve
a superior efficiency. Thus, this paper aims at comparing the Particle Swarm Optimization and the Differential
Evolution algorithms when applied to the optimization of FG plates. The optimization is carried out using the
Isogeometric Analysis to evaluate the structural responses and Radial Basis Functions are used as a surrogate
modeling technique to lower the computation cost. A Sequential Approximate Optimization approach is used
to improve the surrogate model during the optimization process. The two optimization algorithms will also be
compared in terms of accuracy and computational efficiency.

DEVELOPMENT OF A WOODEN TRUSS OPTIMIZATION SOFTWARE BY THE HARMONY SEARCH METHOD

Fernando L. T. Junior, Guilherme F. Medeiros — Sun, 07 Jul 2024 00:00:00 +0000

The optimization algorithms are efficient tools for structural design, reaching optimal solutions for a
given problem through a systematic search method. In this way, the engineer is able to design technically viable
structures that have the lowest cost, regardless of their previous experience. The Harmony Search method is a
heuristic that makes an analogy to the musical improvisation of jazz, where musicians generate from their own
memory new combinations of notes among instruments, looking for the perfect harmony. This paper shows the
development of a software in C# that perform the structural analysis of isostatic plane trusses and, thereafter, the
parametric optimization of the structure, using the Harmonic Search process. In order to reduce the cost, the
objective function is the truss weight, which should be minimized by determining the optimum base dimensions
and height of the cross section. To ensure that the solution is feasible, the constraints imposed by the revision
version of Brazilian code ABNT NBR 7190/2013 must be met. The parameters of the optimization algorithm were
studied, seeking a better calibration to the specific problem of this research. To validate the program, wooden
gable roof structures are tested.

Optimization of post tensioned unidirectional flat slabs

Sun, 07 Jul 2024 00:00:00 +0000

The structural solution for slabs of a building is a very important factor and significantly affects the
total construction cost. The use of prestressed tendons, in particular its unbonded type, has become increasingly
popular, as well as its application to flat slabs because it allows larger spans, greather architectural flexibility
and construction speed and less labor required. Although the prestressed flat slabs have a higher consumption of
concrete in relation to ribbed slabs, they are an attractive solution due to their simple formwork. For an efficient
design, it is necessary to pay attention to the thickness of the slab, the number and layout of the tendons. In this
sense, numerical optimization techniques are appropriated tools to search for an optimal design of flat slabs. This
work presents an optimization model for post tensioned unidirectional flat slab with unbonded tendons according
to the recommendations of NBR 6118:2014, seeking the minimization of material and labor costs. The design
variables are the slab thickness, the number of tendons and the eccentricities that characterize their profiles in
both directions, all of them are of the discrete type. A grid model is applied in the structural analysis, where
the prestressed tendons are treated as equivalent loads. The optimization problem is solved using an open source
genetic algorithm, which is successfully applied to discrete structural optimization problems. The results of the
proposed optimization model are compared with others obtained using the conventional design approach found in
the literature and show an excellent cost reduction.

OPTIMIZATION OF FLAT ARCHES UNDER UNIFORMLY DISTRIBUTED LOAD CONSIDERING IN-PLANE BUCKLING

Francisco G. Chaves Neto, Antônio M. C. de Melo — Sun, 07 Jul 2024 00:00:00 +0000

The optimization of shallow two hinged arches is studied in this work. Specific problem investigated
are sinusoidal or segmental arch, with an arbitrary section, under uniformly distributed load. Arches resist general
loading by a combination of axial compression and bending actions and an arch which is braced by lateral restraints
that prevents lateral buckling, nevertheless, may still suffer in-plane buckling. Shallow arches stability is studied
under an energy method to establish the critical load, considering the shortening of its center line, but simplifying
the curvature change. Approximations to the symmetric buckling of shallow arches are demonstrated. Analytical
solutions for buckling loads and the compressive stress on the section under an uniaxial stress state are reviewed
and used for efficiently evaluation of the constraints in the optimization problem. In a volume minimization model
of the arch the design variables are continuous, consisting of the section dimensions and arch rise. Three types of
sections are investigated: circular, rectangular and I-shaped. Others shapes can be considered but constraints to
prevent local buckling must be applied, as in the case of the I-section. Results for the optimal section dimensions
and arch rise are obtained using Microsoft Excel's Solver tool.

Assessment of penalty parameters in density-based topology optimization

João Pedro Furrier Rosa Pacheco, Jéderson da Silva, João Luiz do Vale — Sun, 07 Jul 2024 00:00:00 +0000

The present paper discusses two penalty parameters — the penalty parameter of intermediate densities
(PPID) and the penalty parameter of the density field gradient (PPDFG) — in the context of density-based topology
optimization problems considering a Solid Isotropic Microstructure with Penalization (SIMP). Both parameters
aim to control the influence of functional terms added to the cost functional to regularize the optimization problem.
PPID aims to the reduction of intermediate densities regions and, consequently, finding out a better definition of
the material contour. PPDFG, in its turn, has as its purpose to mitigate the checkerboard phenomenon.
Displacements, strains, and stresses are obtained via the Finite Element Method, with relative densities defined at
element nodes. The mathematical solution of the optimization problem is carried out taking into account the
Augmented Lagrangean Method. The numerical experiment planning consisted of performing a series of
combinations between the penalty parameters and different finite element meshes, to check their influence on the
checkerboard phenomenon, mesh dependence, intermediate densities regions extension, structural topology, and
values of the cost functional. In particular, the optimization problem aims to minimize the compliance of the
structure with a constraint on the material volume. From the results obtained in this work, it is possible to verify
that PPGDF can mitigate or inhibit the mesh dependence, avoid coarse contours, and the occurrence of the
checkerboard phenomenon — conversely, for high values, extensive intermediate densities regions appear, causing
a sharp increase in the structure compliance. In addition, PPGDF has a greater influence than PPID, which, for the
optimization problem presented, exerted little variation in the compliance of the structure.

Investigation of different interpolation functions for a newly developed framework for sequential coupling of the reservoir, wells, and surface facilities

Sun, 07 Jul 2024 00:00:00 +0000

The development of numerical software which can simultaneously simulate reservoir, well and surface
facilities is becoming a remarkable research topic for both academia and industry. Previously, we developed a
numerical algorithm for our in-house compositional simulator, UTCOMPRS, to couple the simulator with surface
facilities. The information for well and surface facilities is produced by a commercial simulator and included
within the UTCOMPRS through two sets of tables named simplified and advanced flow tables. By introducing a
new class of flow tables named commercial flow tables, for well modeling, this work presents three main
objectives: 1) introducing a newly developed framework for commercial flow tables, 2) introducing a new feature
for controlling the injecting well, 3) investigation of different interpolation functions, such as gas-liquid ratio,
water-oil ratio, liquid rate, and wellhead pressure for the validation of the newly developed framework with a
commercial simulator. Also, we present the results of two case studies. They show that the developed framework
was successfully designed and validated. Also, the values of bottom hole pressure, wellhead pressure, water-oil
ratio, gas-oil ratio, the pressure of injector, oil, gas, and water rates were in good agreement with both UTCOMPRS
and commercial simulators. The outcomes of this research study increase the applicability of our simulator for
modeling more complex models through the sequential coupling of the reservoir, well, and surface facilities. Also,
these new functions are designed in a way that can be used for our future studies, which are concentrated in
application for fully-coupling frameworks.

Development of an objective function to measure the dissimilarity between data observed in wells and results of Stratigraphic Forward Models-SFM

Sun, 07 Jul 2024 00:00:00 +0000

In the area of oil production investment decisions and production planning depend on oil production
predictions, which are made using reservoir simulation techniques. Simulations reproduce the flows of
hydrocarbons in the reservoirs, described through a geological model. Geological models integrate data (well,
seismic) and geological interpretations. Stratigraphic Forward Models (SFM) consists in modeling geological
processes that considers the principles of conservation of mass, energy and reproduces processes in the study
domain (sedimentary basin). SFM provides the facies distribution in the sedimentary basin, resulting from the
geological processes. Once the SF modeling has been carried out, it is necessary to evaluate the results obtained
and apply a calibration since the results do not honor information from the well data. In order to solve the inversion
problem, several authors have developed different methodologies. These approaches provide numerous
contributions of extreme relevance, but none of them presents a possible solution for operational application due
to an incomplete or inadequate configuration of the objective function (generally not sufficiently geologically
representative). Therefore, this work describes a possibility more adequate objective function that clearly and
quantitatively translates the degree of similarity between the numerical results and the data is one of the main keys
of a successful inversion. The proposed objective function was developed based on previous work, which used an
approach originated from automated well correlations. Some modifications of this method were proposed to make
the objective function more adapted to SFM calibration. Among these modifications are the fact that the objective
function can now compare SFM results whose resolution differ greatly from the resolution of the calibration data.

Optimization of a vehicle’s electric fan parameters through evolutionary algorithms aiming a higher energy efficiency

Felipe A. R. D. Silva, Frederico G. Guimaraes, Ricardo P. M. Ferreira — Sun, 07 Jul 2024 00:00:00 +0000

In current automotive projects, the presence of new technologies aimed to maintain a better energy
efficiency and, consequently, a reduction in fuel consumption is very common. Most of these technologies need a
specific calibration, in order to increase the efficiency of the component, keeping its performance within acceptable
limits. Regarding cooling system components, the electric fan driven by Pulse Width Modulation (PWM) is an
example of technology used to enhance the vehicle’s energy efficiency with less demand from the alternator and,
consequently, less engine torque. Its calibration, however, is often performed in an experimental way, and many
tests are performed until satisfying values are found for the calibrated parameters. The present work aims to use a
computational model of the cooling system to adjust the fan control parameters of a vehicle controlled by a Fuzzy
Logic based strategy. The optimization of the control parameters is performed through three different genetic
algorithms - Standard Genetic Algorithm (SGA), Differential Evolution (DE) and Particle Swarm Optimization
(PSO) - which are compared with each other and with the Nelder Mead algorithm (considered as a reference
for comparison, since it is the algorithm used in previous works). The main purpose is to show a comparison
of the coolant temperature, the percentage of the Duty Cycle and the energy spent by the electric fan, using the
computational model, with each of the optimization algorithms discussed, being the energy the main parameter
to be considered in the comparison. The results demonstrate a reduction of energy spent by the electric fan in
relation to the reference for all the studied genetic algorithms, being the PSO and DE algorithms presenting the
better results, with an energy reduction percentage of the order of 15%, followed by SGA algorithm, that presents
an energy reduction percentage of the order of 12%.

Comparison of Kriging and Radial Basis Function surrogate models applied to a global optimization framework

Marcela A. Juliani, Wellison J. S. Gomes — Sun, 07 Jul 2024 00:00:00 +0000

A literature survey reveals that many optimization problems present objective and/or constraints func-
tions that demand high computational effort. Optimization algorithms which are able to solve these problems with

just a few evaluations of such functions become necessary, in order to avoid prohibitive computational costs. In

this context, there are a lot of surrogate models that can be employed to replace objective and/or constraints func-
tions whenever possible, which are much faster to be evaluated than the original functions. In the present paper, a

global optimization framework based on surrogate models is investigated, and two different surrogate models are
considered: Radial Basis Function and Kriging. The framework consists of three search strategies, which may take

place in each iteration of the optimization process: a local search, a global search and a refinement step. This opti-
mization procedure is applied in benchmark problems from the literature and the results obtained by each surrogate

model are compared. As a result, the framework was found to be considerably stable and to achieve satisfactory
responses with both surrogates. Overall, among the cases analyzed, the framework based on Radial Basis Function
showed better performance.

PREDICTING THE CONCRETE COMPRESSION STRENGTH BY THE APPLICATION OF SUPPORT VECTOR MACHINES

Vanderci F. Arruda, Gray F. Moita, Priscila F. S. Silva — Sun, 07 Jul 2024 00:00:00 +0000

The compressive strength of concrete is one of the most used parameters in structural
engineering. In this study, the concrete compression strength is characterized by the presence and
quantification of the following components: cement, blast furnace slag, fly ash, water, superplasticizer
content, coarse aggregate, fine aggregate and age. This resistance is usually defined through destructive
experimental tests, a process that requires time and money. Another way to obtain this parameter is to rely
on computational intelligence techniques, especially with the use of an intelligent system. This study
proposes the determination of the compressive strength of concrete with a computer science concept entitled
support vector machines (SVM). SVMs technique is a machine learning method that has been used for
pattern recognition and regression analysis, which is the current case. The database used in the study is
obtained from the established and widely used studies by Yeh [1]. As performance parameters of the
method, MSE and R2

are used. The main objective of this investigation is to obtain an analytical equation
relating the constituents to the compressive strength of concrete by means of an intelligent system.

Lagrangian Relaxation Applied to Combinatorial Reverse Auctions for the Electricity Sector: Variation of Sub-gradient Method Parameters

Rafael E. Albieri, Laura Silva G., Paulo B. Correia, Kelly C. Poldi — Sun, 07 Jul 2024 00:00:00 +0000

Some optimization problems are N P-hard and they can be intractable when solving for big instances
exactly. However, if most of the set of constraints has proper structure, then Lagrangian Relaxation can be a
suitable approach. Anyway, the duality gap for the non-convex problem can remain large, if no good upper-bound
for the objective function can be found. This paper presents a Lagrangian Relaxation which deals with some
problem parameters to provide better objective function bounds, by improving the sub-gradient algorithm. It is
applied to solve the Winner Determination Problem (WDP) of a Combinatorial Reverse Auction (CRA) for the
Brazilian Electricity Sector, an auction that allows bids on packages of generation power plants. The WDP is
formulated as an Integer Optimization Problem to allocate the packages that minimizes the sum of accepted bids.
Besides, packing rules are applied to ensure a totally unimodular matrix for the relaxed sub-problem constraints,
which is solved by a linear optimization method.

A Computational Method to Predict the Concrete Compression Strength Using Decision Trees and Random Forest

Priscila F. S. Silva, Gray F. Moita, Vanderci F. Arruda — Sun, 07 Jul 2024 00:00:00 +0000

The engineering properties of concrete made structures depend on various parameters such as
the properties of the mixture of concrete, including its nonhomogeneous nature. A clear understanding of
such complex behavior is needed to use these materials successfully in various engineered structures.
Recently, the advancement of machine learning techniques has managed to propose different optimum
solutions to general engineering applications. This study aims to predict concrete compression strength by
employing methods such as Decision Trees (DTR) and Random Forests (RFR) using the database available
in Yeh [1]. The model used in this study considers the effect of eight contributory factors, i.e., cement, blast
furnace slag, fly ash, water, superplasticizer, coarse aggregate, fine aggregate and age to predict the concrete
compressive strength. Computational methods like DTR and RFR are used to develop a predictive model.
A tuning method called GridsearchCV is also used to automate the process of adjusting the algorithms. The
study also compared the performance of the algorithms concerning their predicting abilities. The divergence
of the root means square error (RMSE) and R2 between the output and target values of the test set was
monitored and used to establish a better solution.

Application of Natural Language Processing to Search for Business Opportunities for the raw Glycerol in Biodiesel Production

Sun, 07 Jul 2024 00:00:00 +0000

Recently, in Brazil, the level of biodiesel added to oil diesel fuel has expanded because of compulsory rules. The
increase of biodiesel production has provided an excess of crude glycerol which is its primary co-product. This
paper intends to search business opportunities for the excess of crude glycerol by a Natural Language Processing
Approach. This process of exploring and analyzing unstructured data was performed by text mining thousands of
recovered abstracts from the scientific literature available on online research platforms over ten years. The
methodology involved the information retrieval and compilation of a database for the textual content analysis and
the use of word embedding concepts including Word2vec and Bert. The results indicated the tendencies for
producing value-added substances from crude glycerol over ten years of research.

In core fuel management in PWR reactors using genetic algorithms

Pedro H. S. Rodrigues, José R. Maiorino, Roberto Asano Jr., Patrícia T. L. Asano — Sun, 07 Jul 2024 00:00:00 +0000

This work presents a methodology applied to perform an in core fuel management (ICFM) in pressurized
water reactors (PWR) using genetic algorithms (GA’s). The ICFM consists of defining a recharge pattern during
the reactor's operational cycles, that is, finding the best arrangement of fuel elements (FEs), new and partially
burned, which optimizes the reactor's performance, meeting its safety criteria. The proposed methodology is based
on developing an interface in which the GA can interact with the reactor physics simulation code, which has the
neutronic characteristics of each FE and must be reliable and fast. Then, it was necessary to develop, using a
technique already consolidated in the literature, a coarse-meshed nodal code that numerically solves the multigroup
diffusion equation for two energy groups, fast and thermal neutrons, in two dimensions. In this type of code, each
FE, represented by a node, must be homogenized and represented by its multigroup constants, for each reactor
burn step. The SCALE system, developed by The Reactor and Nuclear Systems Division (RNSD) of the Oak
Ridge National Laboratory (ORNL), was used to calculate these constants. All qualification and validation of the
results obtained from the homogenization of the EC's by SCALE together with the nodal code were carried out
comparing them with the benchmark of Central Nuclear Almaraz II provided by the International Atomic Energy
Agency (IAEA).

Uma estratégia para seleção de portfólios baseada em reversão a média com controle de risco

Joao D. M. Yamim, Igor M. S. Leite, Carlos C. H. Borges, Raul F. Neto — Sun, 07 Jul 2024 00:00:00 +0000

O problema de seleção de portifolio e, sem dúvida, um dos tópicos mais desafiadores da área financeira.
Desde a contribuição inicial de Markowitz, várias técnicas e modelos aplicáveis foram propostos. Com o desen-
volvimento de metodos de otimização online, ou seja, os algoritmos de aprendizado dinamico, tem se mostrado como uma abordagem eficaz para a criação de portifolios eficientes. Algoritmos amplamente utilizados no con-
texto da seleção de portifolio online concentram-se no uso de informações sobre o retorno dos ativos para tomada
de decisao, embora as informações sobre a variância também tenham se mostrado eficientes. Além disso, estudos
como Li, Bin, et al [1] mostram que os preços relativos das ações podem seguir a propriedade de reversão a média,
que ainda nao foi totalmente explorada pelas estratégias atuais. A reversão a média modela a distribuição dos
retornos dos ativos como uma distribuição gaussiana, analisando os preços de curto prazo sobre os preços médios
de longo prazo, possibilitando decisoes de compra e venda com base na avaliação do preço do ativo referente à

cotação histórica. Neste trabalho, implementa-se uma variação da estratégia de selção de portifolio online denom-
inada Reversao da Média Ponderada pela Confiança (CWMR - sigla em inglês para ˆConfidence Weighted Mean

Reversion), para que informações importantes sobre o risco das ações sejam consideradas na etapa de projeção
do algoritmo. Para controlar o risco de cada estrategia de investimento, usamos o modelo CAPM (Capital Asset

Pricing Model) com Beta variante no tempo. As carteiras construídas foram comparadas com a Uniform Con-
stant Re-Balanced Portifolio (UCRP) e o índice BOVESPA. Utilizamos dados da BOVESPA de janeiro de 2000 a

dezembro de 2017 com observações diárias.

Brazilian Multiplex Airline Networks in the context of privatization

Fernanda S. Toledo, Nelson F. F. Ebecken — Sun, 07 Jul 2024 00:00:00 +0000

Multiplex networks are a particular set among multilayer systems, which is represented by multiple
layers and each layer consists of a network with one type of interaction. Many real-world systems would be better
described as a multiplex network rather than a single-layer network. Air transportation is an example of a complex
infrastructure system and the introduction of the weight of interactions and multilayer aspect make their description
even more detailed. The concession of main Brazilian airports (a type of privatization) started in 2011, currently,
22 airports are in concession and after the sixth round this number will be doubled. The firsts contracts had
problems with huge mandatory investment not compatible with demand, therefore the current and next contracts
need to be adjusted, also considering an evaluation of the airports’ role in the network to enhance its robustness.
This paper aims to characterize structural properties using topological analysis of the Brazilian multiplex Air
Transportation Network, comparing the network of 2019 (after the fifth concession round) and 2011 network
(before the first concession started) to measure the granted airports versatility and its variation after the private
management. The multilayer approach is also compared with an aggregated approach, where airlines compose the
multiple layers. Data related to domestic and international passenger traffic of both years were collected at ANAC
database and processed using MuxViz software. The proprieties obtained are used to network characterization
including node centrality measures, multiplexity, degree and strength. Results show a network concentration
during this period, with a demand increase but half operating airlines and less available routes, increasing the
demand for larger aircraft. Results can provide an understanding of the versatility of airports, giving an insight
into the new investments to consider the airports’ network role in the next years.

A multi-agent approach to simulate contamination with the new Coronavirus

Victor Geraldo Gomes, Gray Farias Moita — Mon, 08 Jul 2024 00:00:00 +0000

We are currently experiencing a severe Coronavirus pandemic. Understanding the movement of crowds is of
vital importance for planning and decision making, not only to define strategies for loosening or tightening the quarantine,
but also for the allocation of health professionals or funds to more impacted locations, the definition of new needs and the
necessity of hospital beds for each city, among others. As we have witnessed, modeling and empirical studies of crowd
behavior are critical to supporting governments and health agencies. To try to provide quality information, a mathematical
model was developed where a multi-agent system simulates the movement of people and the risk of contamination
according to some situations. In this work, we are simulating scenarios where there is loosening of the quarantine and more
people on the street, situations where there is stricter social isolation and the risk of contamination for these scenarios. A
system was developed where the interface shows the movement of people and the moment of contagion. The preliminary
results show the great difference in the time of contamination of the population in each scenario and the moment when the
health system is overloaded, that is, there are no more beds for the admission of new patients. The objective of this work is
to add to the studies already in progress, with more data and information that can help to improve the policies and actions
to combat the pandemic.

SHUNT CONTROL ON CANTILEVER BEAM BY NEURAL NETWORK: OBJECTIVE FUNCTION

Venicio S. Araujo, Guilherme S. Prado, Cayo C. Silva, Heinsten F. L. Santos — Mon, 08 Jul 2024 00:00:00 +0000

Piezoelectric materials have been extensively studied in recent years for the development of electrome-
chanical harvesting devices. Usually connected to a structure, these kinds of materials convert kinetic energy into

electric energy, and your electronic parameters interact directly to the vibrations of the system they are coupled
on. Therefore, this work aims at comparing the use of genetic algorithms and artificial neural network techniques
in the implement of shunt control in a structural set of a cantilever beam coupled to a piezoelectric layer in the

piezo-beam configuration. For the architecture of the genetic algorithm and the neural network, was used a soft-
ware with finite element model implemented and the comparisons were made analyzing the computational demand

of the algorithms and their respective responses when both of them were defined on the task of finding the best
combination between the parameters of resistance and inductance of the piezoelectric patch that result in the best
damping to the structure. The comparison between the techniques had a focus on the use of the objective function

of the system by them, parameter used as a metric to gauge the aggregate computational demand, and the damp-
ing provided with the respective configurations suggested by the two techniques.The results show that the neural

network after training completes your execution in order of 102 seconds, much faster than the genetic algorithm,
presenting a response with an average gain in damping of 23,24dB, but, even though faster, this technique demands
much more iterations than the genetic algorithm, due to its nature of parallel computations, and additional care for
the input data, that need a pre-processing not seen in the genetic algorithm technique.

Identification of real estate submarkets by detecting communities in graphs

Barros P., Espíndola R.P. — Mon, 08 Jul 2024 00:00:00 +0000

The identification of submarkets plays an important role in the context of real estate mass appraisal, to
eliminate spatial autocorrelation, or the heteroscedasticity of residues in linear models, making statistical inference
more reliable and allowing a better interpretation of the formation of property prices. Traditionally carried out
empirically, by grouping techniques or by spatial residual modelling applied to hedonic data from properties in a
specific region, studies indicate that the use of data mining models has obtained promising results to carry out this
task automatically. In this work, considering a regionalized and not individual view of the real estate unit, it is
proposed to discover submarkets based on the detection of communities in graphs formed by the neighborhoods
of a city. From the socioeconomic and locational information of the city of Rio de Janeiro, a complex network of
neighborhoods is formed, and communities are identified based on this network's modularity. The hierarchical
approach to obtaining the community structure used here allows different scenarios for understanding the
submarkets, an important aspect for decision makers in an area of knowledge so susceptible to uncertainty.

Hybrid Method for Adjusting Models of Nonlinear Regression

Mon, 08 Jul 2024 00:00:00 +0000

Regression analysis is widely applied in many fields of science and engineering to predict any variable
that is difficult to determine. Generally, Nonlinear regression models are more complex than linear regression.
More traditional models require initial parameters to be adjusted, and the procedure for estimating these values is
not simple. In this paper, a hybrid method is proposed to meet nonlinear needs. The proposed method consists
of two steps. In the first one, two genetic algorithms (GA) were applied for automated parameter prediction. The
second step consisted of applying the Levenberg-Marquardt algorithm (GALM) to obtain the appropriate values.
The T LBO and Differential Evolution algorithms were tested to estimate the initial parameters. The model selected
for the study concerns the population analysis of individuals; and the database describes the forest inventory of the
Tectona Grandis planting in southern Minas Gerais. The results showed that both genetic algorithms were efficient
to estimate the initial parameters, with equivalent square mean error. Therefore, it is concluded that the proposed
hybrid method is effective for estimating the initial parameters.

Comparative study of the performance of different bio-inspired algorithms using the same cost function

Pedro Henrique Nunes — Mon, 08 Jul 2024 00:00:00 +0000

Evolutionary computing is a computational intelligence tool widely used for data analysis and cost

functions. In addition to being accessible in different languages, there are different types of techniques and con-
cepts that can be used for different types of functions. One of these techniques is the bio-inspired algorithms,

which have this name due to the fact that they are inspired by phenomena occurring in nature to search for results.
One of the situations where this type of algorithm is generally used is in minimizing or maximizing a value of
a cost function. There are several types and models of bio-inspired algorithms in the literature, each inspired by
a phenomenon and which works best on a certain type of problem. This work aims to explore different types
of these algorithms and thus perform a comparative study of which has the best performance for a function-cost
minimization problem, here represented by the function called Matyas, which has two dimensions and has no local

minimums , only the global. For this, 7 different types of algorithms were designed, which are: Simple Differen-
tial Evolution, Differential Evolution with Variant, Differential Evolution with Opposition, Simple PSO, PSO with

Constriction Factor, PSO with Inertia Factor and CLONALG. The results showed that, for the chosen optimization
cost-function, as the objective was to minimize the value of the variable, the Differential Evolution algorithms
obtained more satisfactory results in relation to the PSO and CLONALG algorithms, especially with opposition
learning.

Study of the Evaluation Functions of PSO for Reconfiguration of Electrical Power System

Tarcísio R. dos Santos, Alessandra F. Picanco — Mon, 08 Jul 2024 00:00:00 +0000

This paper proposes the analysis of Sigmoid, Hyperbolic Tangent and Elliot functions in the PSO
algorithm for reconfiguration of electrical system. The aim of reconfiguration is to reduce losses in the electrical
system. The optimization algorithm used the binary PSO heuristic method and was developed in MATLAB©
software using the MATPOWER toolbox to solve the power flow. The reduction of real losses is the objective
function, where each particle is the state of the branch switch, open or closed. The methodology was applied to
the IEEE-30 Bus, IEEE-118 Bus and to a Planned Example Case of a Brazilian Power Distribution Company. It
was observed that the Hyperbolic Tangent and Elliot function performed well in optimizing the power system
reconfiguration to reduce losses in the IEEE-30 bus, IEEE-118 bus and 138 kV planned example case.

Gaussian process models applied for monthly forecast coal price mineral : a case study of Mozambique

Alfeu .D. Martinho, Leonardo Goliatt, Henrique Hippert — Mon, 08 Jul 2024 00:00:00 +0000

The search for models capable of predicting price movements and economic variables is recurrent in the
finance literature. The understanding of these prices’ behavior is essential for proper inflation control and planning
of production in exporting countries. Although the research in this regard is relatively vast, presenting studies
on statistical or econometric learning models of time series. Some approaches have deserved greater prominence
in modeling and their prediction, such as moving averages methods, exponential smoothing, seasonal ARIMA,
Autoregressive Vector (VAR), and ARCH or GARCH, among others. However, due to the peculiar characteristics
of the commodities market, such series often describe movements such as randomness, changing levels, explained
by various market factors and exogenous aspects. Linear models, as previously mentioned, may not be entirely
appropriate for capturing this nonlinear behavior and therefore requiring other modeling forms. This work is
part of this context since it proposes the application of Gaussian process models as an alternative for modeling
and forecasting the behavior of the monthly prices of mineral coal in Mozambique. The time series refers to
the monthly sales of coal mineral between 2011 to March 2020. The data were collected on the website of the
bank of Mozambique, in the external sector database. The proposed model is compared to the other models using
proper metrics. Our findings show that the Gaussian processes model presented promising results in the forecast
one month ahead. The results obtained of this research can provide useful predictions for the coal prices that
can assist the treasury managers in previewing the economic performance and potentially improve Mozambique’s
performance on the global commodities market.

NEURAL NETWORKS FOR DATA ASSIMILATION IN THE METROPOLITAN AREA OF RIO DE JANEIRO

Mon, 08 Jul 2024 00:00:00 +0000

The use of neural networks for data assimilation in the terminal area of Rio de Janeiro - emulating the
3D-Var method as implemented in the Weather Research and Forecasting Data Assimilation module - is explored
here. Surface and upper-air data (air temperature, relative humidity and wind speed and direction) from airport
stations and 6-hour forecast from WRF are used as input for the model and the 3D-Var analysis for each grid
point is used as target variable. Periods of 168h from 2014 and 2015 are used with 6h and 12h assimilation cycles
for surface and upper-air data, respectively. The neural network model was built using two different approaches:
multilayer perceptron with static topology in Weka and a metaheuristic called Multi-Particle Collision Algorithm,

where different topologies are tested until the optimum solution is found. Results show that Weka-NN and MPCA-
NN are able to emulate the 3D-Var method with negligible differences in comparison of the magnitude of the

assimilated data. Also, the neural networks are able to speed up the data assimilation process. In this study, neural
network models were able to run from 70 to 100 times faster than the conventional method (3D-Var analysis) under
the same hardware configurations. This time reduction enables the execution of data assimilation methods using
less CPU time and using personal computers.

A Particle Swarm Optimizer with Sensitivity Analysis for the Optimal Placement and Sizing of Distributed Generators in Radial Distribution Systems

Mon, 08 Jul 2024 00:00:00 +0000

In recent years, the penetration of Distributed Generation (DG) has rapidly increased worldwide, mainly

due to the liberalization of electricity markets, restrictions on system expansion and environmental concerns. Tech-
nological advances in small generators and energy storage devices have also accelerated the process. This paper

proposes a methodology based on Particle Swarm Optimization (PSO) and Sensitivity Analysis (SA), namely
(PSO-SA), to identify the optimal placement and sizing of DG in radial distribution system (RDs). For improved
efficiency, a limited set of candidate buses for placement is defined through SA on the Lagrange multipliers. A
comparison against a regular PSO and other similar approaches is made. Numerical results show the effectiveness
and robustness of the method in providing good solutions with reduced power losses, when compared to other
techniques.

The Usage of Neural Network on Prediction of Covid-19 on Brazil

Mon, 08 Jul 2024 00:00:00 +0000

The development of smart dynamic systems through computational models has been used extensively in

recent years to predict behaviors, gaining prominence in the field of medicine with regard to the diagnosis, identifi-
cation and spread of diseases. Usually associated with a probabilistic or classificatory model, these algorithms gain

prominence in image diagnostics, acting in the identification of tumors, and in the prediction of dynamic behavior,
such as virus propagation, due to their computational demand and easy data acquisition. Therefore, this work aims
to use techniques of artificial neural networks to analyze the propagation behavior of COVID-19 in Brazil. For the
architecture of the algorithm, a matrix calculation software implemented with neural network algorithms was used
and the prediction model was built by reading data from infected, recovered and deaths from the initial days, with
limited temporal sampling of the infection in the world. The neural network used follows the Feed-Foward model,
trained with backpropagation through the Levenberg-Marquardt equation and was adjusted to predict the number
of infected, recovered and deaths over the days using a pattern of behavior analysis based on the respective rates of
infection, recovery and deaths. The results obtained for the forecast were validated through the conference with the
data presented by the health departments for the days for which the network was configured to forecast, showing
considerable precision, which increases as new data are inserted, thus showing a practical model for recurrence
and analysis.

FPA applied to the resolution of the economic dispatch problem with operational limits of maximum and minimum power of the generating units

Mon, 08 Jul 2024 00:00:00 +0000

This paper presents an application analysis of a computational intelligence (CI) technique based on
flower pollination (FPA - Flower Pollination Algorithm) to solve an Economic Dispatch (ED) problem, aiming to
minimize the total generation costs, considering operational restrictions of maximum and minimum generation
power and the power balance. The algorithm will be tested, in two systems the first one with three generating units
and the second with fifteen generating units. Both studies are available in the current literature. Finally, the
obtained data will be compared with others already released, where the authors applied a Directional Search
Genetic Algorithm (DSGA) to solve the problem. The good results achieved demonstrate the applicability of the
proposed technique.

A Mathematical Programming Approach for Optimization of Distribution Networks with Photovoltaic Sources

Mon, 08 Jul 2024 00:00:00 +0000

This paper presents a mathematical formulation for minimizing the active losses of the electric power
distribution network with photovoltaic (PV) generation sources. The modeling considers the distribution network
reconfiguration (DNR) and the adjustment of the photovoltaic inverter power factor (fppv). Depending on the used
technology, the PV inverters can inject active and reactive power by adjusting its fppv, controlling the voltage
profile, and minimizing network losses. Another way to minimize losses and improve the voltage profile is by
performing the DNR. The DNR is performed by opening/closing switches to form a new network structure,
reducing power losses while satisfying operation constraints, and improves the voltage profile. This mathematical
formulation involves continuous and discrete variables, constraints, nonlinear, and non-convex objective
functions. To solve this problem, the use of a mathematical programming approach was proposed. The problem
aims to find the network configuration and the fppv of the PV inverters adjustment that minimize the losses of
active power and improve the voltage profile. The tests were performed in the 33-bus modified system using
AMPL software and Knitro solver. The results showed that the methodology is effective and the combination of
PV inverters control and DNR can reduce network losses by more than 85% in some situations of load and
generation.

A high surge impedance loading technique approach for uprating transmission lines

Vinicius A. Goncalves, Andre L. Paganotti, Marcio M. Afonso, Rodney R. Saldanha — Mon, 08 Jul 2024 00:00:00 +0000

This paper presents a study involving a viable unconventional transmission line (TL) uprating concept,
named High Surge Impedance Loading (HSIL). This technique is based on the understanding of the variation
of the electric field produced by the TL, regarding the geometric position of the conductors. It proposes the
adoption of unconventional geometric bundles design, by reducing the distance between phases and increasing the
distance between conductors of the same phase. An analytical model for transmission lines is developed for the
soil effect determination on the estimate of electric field magnitude at ground level and at the conductors’ surface
of TLs. The model is submitted to a stochastic evolutionary optimization technique called Differential Evolution,
aiming at maximizing the Surge Impedance Loading. However, many constraints as minimum distances among
TL components and soil determined by NBR 5422 are considered, as well as the magnitude of the electric fields
for human exposure of the general public at ground level, established by NBR 25415. Also, using altimetry
data supplied by the Brazilian Geodetic System, maximum levels of the surface electric field are determined and
compared with the values of the critical electric field, from which the Corona effect occurs. The results acquired
from the developed computational tool suggested new bundle geometric configurations for an existing transmission
line, with enhanced surge impedance loading and with electric fields at ground level and at conductors’ surface
below the thresholds values and defined by the norm.

Coordination of power reactive management considering variations in wind speed from wind farms and power transmission limits

Mon, 08 Jul 2024 00:00:00 +0000

This paper presents a methodology that allows performing the optimized and coordinated management
of reactive power injection in power systems with wind farms and other sources of reactive injection, such as
capacitor banks or static voltage compensators, minimizing the losses in the transmission power system. The
variation in wind speed is characterized by the Weibull distribution. The values of this distribution are used as
input data for the optimal power flow model whose output provides a sample of values for defining the
confidence intervals of the injected reactive power, as well as the voltage values in each bus of the electrical
system. The proposed methodology was tested using a real 140 buses system to determine the dispatch of
reactive sources available in the power system. The results found by the proposal can help to make a better
management of the available reactive sources in the real-time operation.

Surrogate modeling approach to standardize a steam generator operation – a case study of the PECEM power plant

Mon, 08 Jul 2024 00:00:00 +0000

Coal-fired power plants provides about 40% of electricity worldwide and should be in line with the strin-
gent environmental control requirements and continuous efficiency enhancement. Actions towards high-quality

operation can be supported by the fine modeling of plant systems in order to aid field operation. The present work

proposes the standardization of operation through surrogate models to represent the assembly of the steam gener-
ator and its mills, based on the system simulation by the EBSILON commercial software. A methodology for the

construction of a surrogate model to a coal-fired power plant in operation is proposed and applied to the case study
of the PECEM power plant. Design of Experiments (DoE) and Response Surface Methodology (RSM) are used to
identify the model main controllable parameters and interactions to then rank them by order of importance. The
surrogate model based on the commercial software is built to simulate the system efficiency with seven controllable
input parameters: primary airflow, pulverized coal outlet temperature, stoichiometry, excess O2, secondary, and
primary air crossover duct pressure, ranked by descendent significance. The maximum relative deviation of that
surrogate model compared to the software simulation is 0.0172. The best operating ranges by each controllable
parameter are proposed.

Redes Neurais na gestão das águas em reservatórios hidrelétricos: um estudo de caso na Hidrelétrica Itaipu (Brasil)

Mon, 08 Jul 2024 00:00:00 +0000

A geração de energia elétrica a partir da água é muito promissora no Brasil. No entanto, em reservatórios
hidroelétricos, processos de eutrofização podem ocasionar alterações, prejuízos e comprometer a operação da
usina. Nesse cenário, o uso de comunidades biológicas fitoplanctônicas é uma importante ferramenta no
biomonitoramento, principalmente pela presença e/ou ausência delas serem um importante elemento para
avaliação das condições ambientais. Esse artigo teve como objetivo utilizar Algoritmos Genéticos (AGs) para
identificar variáveis físico-químicas relacionadas à densidade de fitoplâncton nas águas do reservatório da Usina
de Itaipu e desenvolver um modelo preditivo para a densidade fitoplanctônica utilizando Redes Neurais Artificiais
(RNAs). O AG indicou que as variáveis mais importantes para predição de fitoplâncton foram: concentrações de
nitrato, nitrogênio amoniacal, oxigênio dissolvido e Demanda Química de Oxigênio (DQO). As previsões da RNA
foram coerentes com outros estudos e com os dados reais utilizados no teste da RNA e sustentam a possibilidade
de que o modelo pode ser implementado na usina hidrelétrica para auxiliar na gestão das águas no reservatório ao
permitir o monitoramento da qualidade da água em intervalos temporais menores que os atuais.

A comparative study of Singular Value Decomposition (SVD) and Discrete Cosine Transform (DCT) techniques for image compression applications

Mon, 08 Jul 2024 00:00:00 +0000

The demand for methods capable of extracting knowledge from data and organizing large amounts of
information has been growing in recent decades. Images are present in several applications in biomechanics and
biomedicine, and usually require the use of computational methods to reduce complexity without compromising
quality. This paper proposes the application of computational methods for image compression, considering data

storage and transfer issues. In particular, we present a comparative study between the Singular Value Decompo-
sition (SVD) and Discrete Cosine Transform (DCT) techniques for image compression. We use a referencial way

of obtaining some metrics for compression without excessive loss of information. The computational experiments

in this work consisted of fixing compression metrics and evaluating the performances of DCT and SVD. The re-
sults demonstrate that DCT presents, in most tests, better performance in reducing memory usage in compression

compared to SVD, despite resulting in lower image quality.

APPLICATION OF DEEP LEARNING FOR ANALYSIS OF CRACKS IN PELLET FALLING TESTS

Mon, 08 Jul 2024 00:00:00 +0000

Iron ore pellets are a prime input for iron production. Therefore there is a need for a rigorous control of
the quality of the pellets to apply them in the industrial process. The pellets are degraded due to impacts caused
by their handling or transport systems. As a result of these degradations many pellet shipments reach the customer
with a proportion of cracks. Laboratory drop test trials are required on wet raw pellets to assess their resistance to
the various drops they suffer in the industrial process. Currently the drop test is performed manually, where the
whole test process, from pellet manipulation and data collection, depends on human action. The present work aims
at the application of Deep Learning to carry out the analysis of pellet cracks, pellet segmentation is initially
presented in this article. A network of light deep learning was designed, generating a data set of the pellet drop
test for training the network for pellet classification. This network will be applied in the autonomous prototype for
the drop test, a technological innovation that is being developed by the Research and Automation Group (GAIn),
of the Federal Institute of Espírito Santo, located in the Municipality of Serra, for the analysis of cracks in the
pellets.

RESTORATION OF ASTRONOMICAL IMAGES BY WAVELET TECHNIQUES

Vinicius S. Monego, Alice J. Kozakevicius, Haroldo F. Campos Velho — Mon, 08 Jul 2024 00:00:00 +0000

Image restoration, an important application of inverse problem techniques, is relevant for remote
sensing, surveillance and security, medicine, material science, research on biology, entertainment industry, and

more recently for aerial drone autonomous navigation. Our focus is on astronomical images. Indeed, observa-
tional astronomy is fully dependent on image interpretation. Therefore, image restoration techniques applied to

astronomy is a relevant research topic in this field. Here, Several wavelet schemes are applied for astronomical
images restoration, ranging from the orthogonal wavelets, including Haar, Daubechies, and Symlet families, to

biorthogonal wavelets. Different thresholding schemes are assumed to analyze the resulting wavelet decomposi-
tion, assuming as input data RGB images with high noise levels. The results are evaluated by using structural

image similarity as the comparative metric for different schemes to image restoration.

Detection and segmentation of pig iron slag scrapers using Mask R- CNN for wear control

Mon, 08 Jul 2024 00:00:00 +0000

The steel industry presents a vast list of problems and opportunities for improvement, ranging from the
factory floor to levels of business management. Operating procedures are revolutionized every day to decrease
failures, create reliable parameters and increase equipment reliability, and with the continuous and accelerated
advance of innovations in industrial processes, computer vision is increasingly present and is necessary for the
automation of new systems or of systems that need an update in their way of operating. This project aims to
segment and detect, through convolutive neural networks, the shovels of the slag scrapers in pig iron pans in a
Kambara Reactor of a steel plant. Aiming at detecting the wear of the shovels to control their use and replacement
using Mask R-CNN for instance segmentation and pixel count for wear control.

COMPUTATIONAL MODEL FOR A POLYMER EXTRUDER SCREW

Matheus Rocha Ferrari, Dianne Magalhaes Viana, Adriano Possebon Rosa — Mon, 08 Jul 2024 00:00:00 +0000

The most adequate process for an extrusive screw is the condition of operation. That involves the type of
polymer, the flow rate, mixture devices, temperature control and die. In view of productivity demands, e.g. flow
speed and filament homogeneity, it is deemed necessary a detailed study on the behaviour of the polymer along
the screw. This work aims at the development of a computational model, a tool which will be used on the design
of the screw of the extruder machine. Our model seeks to simulate the behavior of the material, providing enough
information for an adequate design for the screw, which is necessary in order to define the parameter for a viable
production.
The implemented model is based on the conservation of energy and moment equations, for which numerical
solutions are obtained through a projection method, where different boundary conditions are used for distinct stages
of the processes - feeding, metering and dosage. We simplify the process by considering a steady state regime on
a bi-dimensional domain. This characterizes a classical cavity problem. Since a rise of root diameter along the
axis is observed on most of commercial screws, this was the standard geometry adopted for the model. After
numerically solving the 2D Navier-Stokes equations, the pressure and velocity of the flow, which are obtained for
every stage, allow us to assess the efficiency of the process for the given geometry.

Pore size distribution characterization in carbonates by correlating NMR, MICP and micro-CT data

Horrara Diógenes, Austin Boyd, Paulo Couto — Mon, 08 Jul 2024 00:00:00 +0000

From laboratory tests on pre-salt plugs, it is possible to obtain information such as pore body and pore
throat size distributions, that may indicate the storage capacity and potential for extraction of fluids from a
reservoir. This paper correlates data from NMR, MICP and micro-CT tests in order to characterize the pore body
to pore throat ratios (BTR) for coquinas from Morro do Chaves Formation, in the Sergipe-Alagoas Basin. MICP
data was converted to pore throat size distributions using Washburn equation and compared with pore body sizes
computed from micro-CT data analyzed with image processing software. The comparison between MICP and
micro-CT data yields the pore body to throat ratios, which are known to vary considerably in carbonates due to
the heterogeneity of the pore structure. Next, the NMR T2 distributions were scaled to pore size distributions using
the surface relaxivity parameter (ρe) and compared to both MICP pore throat size distributions and micro-CT pore
body size distributions. The results indicate a good correlation between MICP pore throat distributions and T2
distributions, but when comparing T2 distributions with micro-CT distributions, allowance must be made for the
low resolution limit of the micro-CT (20 microns) and the effect of bulk relaxation on larger pores.

Monitoring of the oxygen lance, in the steel fabrication process by LD conveter, using a Mask R-CNN deep learning network

Mon, 08 Jul 2024 00:00:00 +0000

A critical problem in the manufacture of steel by converting pig iron into a Linz-Donawitz (LD) con-
verter is the accumulation of skull, a mixture of slag and steel, in the body of the lance used for oxygen injection.

This accumulation of skull can cause serious problems, among them prevent the movement of the lance through
the flanges located in the converters. Currently, in the steel industry, monitoring is done manually, based on an
operator’s experience. Traditional computer vision methods are not effective due to the hostile environment of the
steelmaking process, due to its object detection algorithm. Problems such as light, smoke, and others, hamper the

task of image recognition. To overcome these deficiencies, this article proposes a method to monitor and mea-
sure, in real time, the thickness of the skull on the lance using deep learning, more specifically a Mask R-CNN

framework. Our method consists of installing a high resolution camera to monitor the lance in real time, sending
images to a computer, equipped with a Mask R-CNN framework already trained to identify and measure the skull
deposited on the lance. The results of the experiments performed show the feasibility of using the system to assist
the operator in monitoring of lance skull.

UAV autonomous navigation with thermal infrared camera

Mon, 08 Jul 2024 00:00:00 +0000

Image processing approach has been employed as an alternative to the global navigation satellite system
(GNSS) signal for the unmanned aerial vehicle (UAV) autonomous navigation. The UAV image is caught during
the fly. A supervised artificial neural network is configured to be an image edge extractor. Two images are
employed to the UAV positioning: a satellite georeferenced image, and image from the UAV. The image processing
procedure consists to extract edges from the images, and to apply a correlation operator on the two segmented
former images. The maximum correlation coordinate will be to indicate the UAV position. A low cost thermal
infrared camera of type FLIR (Forward Looking Infrared) Duo is coupled to two UAVs (DJI Phantom 3 Standard,
DJI Matrice 600 Pro) for two experiments, during daytime and nighttime. The algorithm is also implemented in
Raspberry Pi and its processing time was evaluated. The results have shown good results for the UAV autonomous
navigation using the low cost thermal infrared camera

Classification of coffee beans using Deep Learning

Igor G. Lube, Gustavo M. Almeida — Mon, 08 Jul 2024 00:00:00 +0000

The global agribusiness of coffee includes, annually, resources that reach 91 billion dollars and involves
half a billion people. The coffee market is characterized by a set of activities of enormous complexity, dynamism,
and a growing level of demand from consumers regarding the quality of the drink. This imposes high quality
control on producing, consuming, and exporting countries. Currently, the definition of the quality and therefore
the value of coffee is based on manual classification, that is, a person plays the role of a trained (certified) classifier
to qualify coffee samples. Thus, the current classification process suffers from the subjectivity of the classifiers
and a great difficulty in standardizing the process due to possible inconsistencies in the process. Given this
scenario, the present work proposes to develop a system for classifying coffee samples considering shape and
imperfections. The classification process will be done by using computer vision through Deep Learning and
regional convolutional networks (R-CNN) where the intrinsic defects present in the sample will be identified.
Among the benefits of automating the coffee classification process, the following stand out: Cost reduction, agility
and standardization of the classification.

Detection of Breast Cancer in Thermal Images Using Convolutional Neural Network

Mon, 08 Jul 2024 00:00:00 +0000

Worldwide, breast cancer is the most commonly diagnosed cancer in women. Early detection of this
type of cancer can help women to have a more appropriate treatment and, consequently, reduce the mortality rate.
Today, there are several techniques and algorithms for the diagnosis of breast cancer, but techniques that provide
greater agility in diagnosis and precision in results are still widely studied. Thermography is a recent technique to
record the image of the breast, measuring the temperature based on infrared radiation, and has been an attraction
for research. In this context, a Convolutional Neural Network (CNN) was set up to process a data set of thermal
breast image inputs in order to classify healthy and breast cancer patients with good accuracy. The data were
obtained from the Mastology Database (DMR), with a total of 5,602 images divided into 80% for training and
20% for validation. The CNN architectures used in the experiments were Xception, ResNet101, ResNet101V2,
MobileNet, MobileNetV2, DenseNet201 and InceptionV3. Each architecture had the same configurations, with a
learning rate of 0.001, using SGD and a maximum of 20 times. The results found showed that the best proposed
CNN architecture was Xception with an accuracy of 95.89%, while InceptionV3 obtained an accuracy of 94.73%
and DenseNet201 had an accuracy of 93.22%.

Recyclable Waste Classification Using a Deep Learning Vision System

Rafael Meneguelli, Daniel C. Cavalieri, Cassius Z. Resende — Mon, 08 Jul 2024 00:00:00 +0000

One of the biggest environmental problems that humanity have been facing is the amount of waste
generated. The disorderly growth of large cities combined with consumption and industrialization are substantially
increasing the amount of solid waste generation. Recycling is an essential resource for sustainable development of
societies whereas, as it reuses waste and decreases the accumulation of garbage. Brazil is one of the countries in
the world where most generate solid urban waste and which has one of the largest numbers of people who separate
this waste manually, many times in deplorable working conditions. Selective waste sorting basically consists of
segregation of recyclable waste. However, when performed manually, the practice of segregation may not be
followed evenly. The use of automated systems are an alternative to make the waste segregation more efficient
and safer. This paper describes the use of a computer vision-based method to detect 4 main types of solid waste:
glass, metal, paper and plastic. To classify and detect each type of solid waste was used a Convolutional Neural
Network Based on the Mask Region (Mask R-CNN). The classification generates a mask and bounding box. After
training the model using TrashNet dataset was achieved 0.80 for mAP. The use of those information can provide
the position of the objects at the scene and robotic arms can make the automatic waste sorting.

METHODOLOGICAL PROPOSAL OF IMAGE PROCESSING WITH FREE SOFTWARE TO EVALUATE THE ROUGHNESS OF MASONRY PIECES

Florentino M. Jose, Sanchez T. Sulpicio — Mon, 08 Jul 2024 00:00:00 +0000

Masonry is widely used in a large number of constructions around the world. However, these register
severe damages in seismic areas. An important parameter to guarantee adequate structural behavior is the adhesion
between the piece and the mortar, which has two origins: a) chemical, b) mechanical. The latter is related to the
fineness of the mortar components and the roughness of the piece. Under this consideration, a proposal is presented
to calculate the roughness of the faces of a concrete masonry block made with cement and fine sand, using
photographs taken with a 24 megapixels camera capacity and processed with three free software applications. The
procedure has four steps: a) calibration of the camera and taking of photographs, b) three-dimensional
reconstruction of the piece using the Visual SFM software, c) obtaining the points of both faces with the Meshlab
software from the three-dimensional model, d) construction of a point cloud using the CloudCompare software,
where it is possible to visualize the crests and valleys of the faces, and therefore it is possible to measure the
average roughness. For the piece under study, 25 images were taken and processed for each face, the average
values of roughness were 0.06 mm and 0.23 mm for the smooth and rough faces, respectively; the references show
values of 0.08 and 0.32 mm measured in red clay brick. For the lightweight concrete block and the same order,
there are references of 0.45 and 0.77 mm. In the case of concrete, average values of 0.3 mm on smooth surfaces
and between 0.3 -1.0 mm on standard surfaces are reported. The proposed methodology, in the experimental phase,
provides values of roughness in the range defined in other investigations of similar materials with two additional
advantages: it does not require special equipment, and the computer applications are free software. This tool can
be used to evaluate the influence of the roughness of masonry faces on the resistance to lateral loads generated by
earthquakes.

Use of computational vision to estimate the weight of steel slab places on the rolling mill reheating table

Josceley C. da Silva, Leonardo A. Scardua, Gustavo M. de Almeida — Mon, 08 Jul 2024 00:00:00 +0000

The fuel consumption of the slab rolling reheating furnace is one of the largest expenses of the hot
rolling mill production process. Decreasing the time between slab leakage and creation is the scenario to be
achieved. It is then desired to ensure conditions for the slabs to be hung increasingly hot by eliminating a “toll” in
this process, which is the weighing of the slab at the oven inlet. In a continuous hot hanging process, weighing
may cause a loss of 150 ° in the temperature of the slabs. The purpose of this paper is to present a new proposal
for the detection of steel slab dimensions in the hanging table using computational vision and convolutional neural
networks. To achieve this goal, the Convolutional Neural Networks regression technique will be used. The
regressive technique is able to identify a numerical value from a set of information, in the case of images. Networks
recognized in this application will be used, such as: VGG16, DenseNet, InceptionV3, etc., in addition to networks
built and trained for this process, with existing datasets and generated in this production process. At the end of the
work, we want to have an intelligent system capable of detecting the width, length and thickness of the slabs in
order to obtain the weight of the material, eliminating the need for other forms of dimensional measurements.

A Bag of Visual Words-Based Approach to Identify Scenarios Suspected of Being Breeding Sites of the Aedes aegypti Mosquito from Aerial Images Acquired by UAVs

Gustavo A. Lima, Daniel T. Bravo, Sidnei A. de Araújo — Mon, 08 Jul 2024 00:00:00 +0000

In addition to the programs of the Brazilian Ministry of Health to prevent and combat the Aedes aegypt
mosquito, the use of unmanned aerial vehicles − UAVs (known as drones) has proved to be an important alternative
to assist the work of health surveillance teams. However, the analysis of aerial images acquired by such equipment
are usually manual, which can be time-consuming for health workers. Thus, it becomes important the proposition
of computational approaches able to recognize and interpret patterns in such images. This work proposes a
computer vision approach to identify scenarios that represent potential breeding sites of the Aedes aegypti
mosquito from aerial images acquired by UAVs. The proposed approach employs the Bag of Visual Words −
BoVW technique combined with the Support Vector Machine − SVM classifier (BoVW + SVM), taking into
account two descriptors based on the SIFT − Scale Invariant Feature Transform algorithm (Transformed color
SIFT and RGB-SIFT), and the descriptors Color Level Co-occurrence Matrices − CLCM and Color Histograms.
For conducting the experiments we compose a database of images, acquired in urban regions of the city of São
Paulo, which contemplate real and simulated scenarios suspected of being breeding sites of the mosquito (gutters
and roofs with accumulation of objects, open-air garbage containing old tires, old tires, pet bottles, plastic and
paper packaging and other open containers that can accumulate water). The results obtained in the experiments
with BoVW+SVM, in terms of hit rate, were: RGB-SIFT (91,37%), Transformed color SIFT (85,34%), CLCM
(64,65%) and Color Histograms (86,20%).

Artificial Intelligence usage for identifying automotive products

Leandro M. Gonzaga, Gustavo M. de Almeida — Mon, 08 Jul 2024 00:00:00 +0000

The Computational Vision process has been presenting a huge development in the recent years. This is
occurring thanks to the development in the field of Artificial Neural Networks, specially the Convolutional Neural
Networks. These networks are capable of training to identify patterns in a large set of images, for latter identifying
these same patterns in other images. A very common architecture used nowadays, due to its high accuracy, is the
Mask R-CNN. This architecture not only classifies and identifies objects, but also realizes its segmentation pixel
by pixel. In this present work, Mask R-CNN was used for segmentation of automotive products (windshields,
headlights, tail lights, bumpers and rearview mirrors) in an aftermarket organization. In its evaluation, the
algorithm presented a significantly high mAP and accuracy – checked through a confusion matrix, even reaching
a val_loss of 2.413, demonstrating a satisfactory result for its proposed applications: a system filter for preventing
human error and a premise for future works of identifying defects in the mentioned products.

Error estimations for multiscale hybrid-mixed finite element methods for Darcy’s problems on polyhedral meshes

Mon, 08 Jul 2024 00:00:00 +0000

A posteriori error estimation for multiscale hybrid-mixed formulations for Darcy’s problems is dis-
cussed. The method adopts two-scale finite element spaces: refined discretizations are adopted inside polygonal

subregions, but flux approximations are constrained over the mesh interfaces by a given coarse normal trace space.

For stability, pressure and flux approximations are divergence compatible. The error estimation is based on po-
tential reconstruction, which is a popular technique for this kind of analysis in the context of mixed methods.

Numerical experiments are presented in order to illustrate the efficiency of the proposals.

Simulation of a drop impact on a moving wall with a liquid film using the convected level-set method

Malu Grave, Jose J. Camata, Alvaro L. G. A. Coutinho — Mon, 08 Jul 2024 00:00:00 +0000

A liquid drop impact on a moving wall with a pre-existing thin film of the same liquid is simulated using
the convected level-set method. We couple this interface-capturing method with the Navier-Stokes equations, and
we apply a global mass conservation procedure to enforce the mass balance between phases. The analysis takes
into account viscous, inertial, and surface tension forces, neglecting gravity. The Continuum Surface Force (CSF)
approach models surface tension forces. We solve the Navier-Stokes equations with the residual-based variational

multiscale finite element formulation and the convected level-set with a SUPG formulation with discontinuity-
capturing. We implement the whole model in libMesh, an open finite element library that provides a framework

for multiphysics, considering adaptive mesh refinement. The values of the Reynolds and Weber numbers determine
different drop splash regimes. Numerical results are presented for 2D and 3D liquid drop impacts, and they are in
good agreement with other simulations.

ON THE DEVELOPMENT OF A REDUCED APPROACH TO THE RE- CURSIVE COORDINATE BISECTION IN THE CONTEXT OF PARAL- LEL SIMULATIONS OF THE MATERIAL POINT METHOD

Joao G. C. S. Duarte, Adeildo S. R. Junior, Diogo T. Cintra, Ricardo G. Borges — Mon, 08 Jul 2024 00:00:00 +0000

This paper aims to develop a reduced approach to the Recursive Coordinate Bisection (RCB) in the
context of parallel simulations of the Material Point Method (MPM). The simulation environment considers the
usage of parallel computing, a powerful tool that allows us to increase computational performance and to reduce

the simulation time. In this environment, a set of computers provides processors, allocates processes and commu-
nicates data among them. MPM can be used to simulate various engineering problems, including those involving

submarine landslides, installation of torpedo anchors and dynamical analysis of structures. Numerical simulations
of MPM can be computationally intensive, especially for those containing a large number of particles. In this work,
the geometrical information of particles inside each solution sub-domain is reduced into statistical information of

centroid and standard deviation in order to avoid excessive data communication during simulations. The root pro-
cess simulates the entire domain geometry from the collected data for each sub-domain. The partitioning algorithm

and statistical strategy were developed using the C++ language and the Message Passing Interface (MPI) library.
The MPI library allows the exchange of data among the several processors in a distributed memory system. The
partitioning quality obtained in this method depending on input parameters such as the number of processes, the
mesh discretization for each sub-domain and the number of points generated in the statistical domain. Numerical
experiments were conducted in order to measure a load balance metric and the processing time (speed up). The
obtained values for the parametric study were compared to an analytical reference of balance. The results show that
the partitioning method generates better load balance values depending on the combination of the input parameters.

Time domain filter application in wave propagation problems.

A. Frasson, F. Queiroz, J. Chacaltana, C. Loeffler — Mon, 08 Jul 2024 00:00:00 +0000

Often in wave propagation problems with explicit methods, instabilities at high frequencies appears.
In methods with structured meshes, spatial filters can be used, but with unstructured meshes the construction of
such filters is more complex. In this work, the high frequencies resulting from instability due to numerical errors
are smoothed with the use of filters in the time domain, making a convolution at each time step. Butterworth IIR
(infinite impulse response) digital filters of maximum flatness are used.

Dynamic mode decomposition for density-driven gravity current simulations

Gabriel F. Barros, Adriano M. A. Cortes, Alvaro L. G. A. Coutinho — Mon, 08 Jul 2024 00:00:00 +0000

In the present work, we evaluate the capability of the Dynamic Mode Decomposition method to extract
spatio-temporal coherent structures of density-driven gravity current simulations. The coupled problem is solved
using the finite element method, and DMD is applied in the concentration dataset instead of all the simulation data.
We generate reduced order models from the DMD with a different number of computed basis vectors and evaluate
their accuracy and performance to capture the dynamics from the original system. We also extend our analysis to
two relevant quantities of interest, the front position and mass conservation, testing the accuracy of the surrogate
models. We also evaluate three different implementations of the Singular Value Decomposition, the core procedure
in the DMD, in terms of performance and accuracy. Furthermore, we investigate the extrapolation ability of the
Dynamic Mode Decomposition and evaluate its accuracy when considering different initial conditions.

PREPROCESSED CONSTRAINT GUIDED QUADRILATERAL MESH GENERATION

Daniel Masarin, Ernesto Massaroppi Junior — Mon, 08 Jul 2024 00:00:00 +0000

Numerical methods, such as the finite element method, have been recognized as a great tool for product
design in the present market, helping engineers to increase product quality in less development time. However,

the quality of the element mesh affects the numerical results, so it is necessary to seek a method that gener-
ates good elements. Quadrilateral (two-dimensional) and hexahedral (three-dimensional) mesh is recognized to

produce good numerical results, although the automatic generation techniques are still complex and face some
restrictions in complex geometries to inhibit distorted elements. In general, methods that generate meshes with
fewer singularities require a more restricted geometric shape to generate elements, which demands a greater time
in its construction. The algorithm proposed aims to produce good quality quadrilateral meshes automatically over

arbitrary geometry, for that it preprocesses the current geometry correcting common features that difficult quadri-
lateral mesh generation. In sequence, it generates a quadrilateral mesh, first adjusting in a topological coordinate

system a mesh that considers constraints coming from geometry, like element density and boundary line angles.
Thus, the singularities are arranged in a way that reduces distorted elements. Hence, it maps the resulting mesh
to the Euclidean coordinate system using the transfinite mapping method for all regions. As a result, it is possible
to generate good quality quadrilateral mesh even on distorted geometries in comparison with methods available in
actual commercial software.

Evaluation on IMU and odometry sensor fusion simulation results for a 4-Wheeled-Drive robot using AMCL on ROS framework.

Mon, 08 Jul 2024 00:00:00 +0000

Mobile robot localization algorithms establish correspondence between the robot’s coordinate system
and the environment map. However, usually, it is not possible to get an accurate direct measurement of the robot
pose. Therefore, it must be inferred from local sensors, which are, in general, susceptible to noise. Some robot
models, such as the 4-Wheeled-Drive, can rapidly increase odometry error, especially due to drift during angular
movements. Hence, correction techniques are recommended to compensate these errors. This paper evaluates the
impact of the Extended Kalman Filter (EKF) to fuse data from an Inertial Measurement Unit (IMU) sensor and
odometry and how it impacts in the Adaptive Monte Carlo Localization (AMCL) algorithm. The use of data fusion
brings better results than using data from only encoders. The experiments were simulated using ROS framework
and Gazebo as simulation environment. A series of goals were given to test the localization algorithms performance
using the move base control algorithm in a map with obstacles. This experimental setup allowed to verify how
each localization method behaves comparing (a) only odometry; (b) odometry and the AMCL; (c) the fusion
between odometry and IMU, and (d) the fusion of odometry with AMCL and IMU.

Numerical modeling of venting of particle-driven gravity currents in reservoirs

Malu Grave, Jose J. Camata, Alvaro L. G. A. Coutinho — Mon, 08 Jul 2024 00:00:00 +0000

Sedimentation in reservoirs results in loss of their storage capacity and impacts the fauna where it is
located. Therefore, effective sediment management is an important task to increase reservoir lifetime and mitigate
the damage that sedimentation may cause. Turbidity currents are the primary source of sediments in reservoirs.
Venting them reduces sedimentation. Numerical models are an efficient tool for studying venting. In this work, we
have introduced a model to predict the flow of particle-driven gravity currents, and we apply it to study the venting
process in reservoirs. The mathematical models result from the incompressible Navier-Stokes equations combined
with an advection-diffusion transport equation for suspended sediments. We implement the mathematical model
in libMesh, an open finite element library that provides a framework for multiphysics numerical simulations.
The model is successfully verified and validated using literature data of lock exchange experiments. We test the
capability of the model to optimize the venting of turbidity currents as an efficient sediment management strategy
for reservoirs. The results show that the concentration field during venting agrees well with observations from
laboratory experiments.

Physics–Informed Neural Networks for the Factored Eikonal Equation

Romulo M. Silva, Alvaro L. G. A. Coutinho — Mon, 08 Jul 2024 00:00:00 +0000

The Eikonal equation often appears in problems including, but not limited to, geometric optics, shortest
path problems, image segmentation, seismic and medical imaging. While there are efficient and stable techniques
for solving the Eikonal equation for regular or arbitrary geometries in several dimensions, it remains a big challenge
to solve inverse problems governed by this equation, especially when it comes to uncertainty quantification. As an
alternative to classical methods for solving forward and inverse problems governed by PDEs, the Physics-Informed
Neural Networks (PINNs) have shown accuracy and versatility for solving problems in fluid dynamics, inference of
hydraulic conductivity, velocity inversion, phase separation, and others, being also able to quantify uncertainty in
these problems. Here we study PINNs for solving the forward and inverse probabilistic Factored Eikonal Equation.
We solve the probabilistic inverse problem using variational inference and the Flipout technique. Our results for a
benchmark problem show excellent accuracy.

Approximate solution of the wave equation using the Multigrid Method

Maicon F. Malacarne, Marcio A. V. Pinto, Sebastiao R. Franco — Mon, 08 Jul 2024 00:00:00 +0000

CONTACT PROBLEMS IN ORTHOTROPIC MATERIALS USING THE BOUNDARY ELEMENT METHOD

Leonardo B. Silva, Fernando M. Loyola, Eder L. de Albuquerque, Jon Trevelyan — Mon, 08 Jul 2024 00:00:00 +0000

The main objective of this work is the development of a boundary element formulation for the evalu-
ation of frictional contact problems in bodies of anisotropic materials under centrifugal loads. The fundamental

solution is obtained using the Lekhnitskii formulation. Centrifugal loads are treated as body forces and are not

included in the computation of the fundamental solution. Because of this, domain integrals arises in the formu-
lation. In order to avoid domain discretization, these integrals are transformed into boundary integrals using an

exact transformation. As a result, an elegant formulation is obtained where only boundaries need to be discretized.

Quadratic continuous boundary elements are used in order to discretize boundaries of contact bodies. As the con-
tact area is unknown, there is a non-linear problem in which the Newton’s method is used in order to compute

tractions and displacements. Problems with known analytical solutions are used in order to assess the accuracy of
the proposed formulation. A numerical analysis of a contact problem in a high pressure compressor of the turbojet
engine is carried out. This problem comprises of anisotropic monocristal blades in contact with an isotropic rotor.
Due to centrifugal and random loads, blades are subjected to stresses of fretting. They are attached at the rotor
by dovetail joints where occur severe contact. Fatigue due to fretting is the main cause of mechanical failure in
turbojet engines, what shows the relevance of this work. If compared to other traditional numerical methods, as
the finite element method, there are many advantages in the boundary element formulation, considering accuracy
in the computation of stress field and an easier mesh manipulation.

Contact study between fiber and matrix in composite materials

Julio A. S. Neto, Luiz C. Wrobel — Mon, 08 Jul 2024 00:00:00 +0000

Composite materials are widely used in engineering, and can be exemplified with reinforced concrete,
one of the main inputs of civil construction. Given its importance in the area, the contact behavior between the
components of these materials was studied, that is, between the matrix and the inclusions. Thus, this paper presents
a study of how different parameters influence the distribution of internal stresses in composites due to external
loads. Several computational models were analyzed using the finite element method, in models with only one
inclusion (fiber or particle), which were evaluated considering how different values of the modulus of elasticity,
Poisson’s ratio and friction coefficient influence the stress concentrations present in the contact between inclusion
and matrix. Furthermore, the models were analyzed under two premises, one where there is a possible detachment
between the matrix and the inclusions and another where the contact is fully-Bonded. The graphics elaborated
from the results of these models clearly show the influence of the various parameters studied, whose the performed
analysis can be used for the production of increasingly efficient composite materials

Assessment of flexible pipes with damaged tensile armor wires using finite element models and symbolic regression

Anderson C. dos Santos, José Renato M. de Sousa — Mon, 08 Jul 2024 00:00:00 +0000

Flexible pipes are key components in several offshore oil and gas applications as production, gas lift, or
gas and water injection lines. However, these structures may be damaged during their service lives, which may
reduce their structural capacity and lead to costs associated with replacement, production loss, and oil spill. Among
the possible damages in flexible pipes, the rupture of their tensile armors is critical, as these armors sustain the
axial loads imposed on these pipes. Therefore, this paper deals with the structural analysis of flexible pipes with
broken tensile armors subjected to tension loads. A previously proposed finite element model is employed to model
the damaged pipes. Forty-seven flexible pipes are analyzed and the Stress Concentration Factors (SCF’s) of the
tensile armor wires are collected to form a database, which is then employed by a symbolic regression package to
fit analytical expressions for the obtained SCF’s. The goal of this work is therefore to find a closed formed
analytical expression for the SCF’s, which is accurate and thus able to replace a time-consuming assessment with
a finite element model.

A finite strain non-isothermal phase-field model for damage and fracture in elasto-plastic impact problem

G.A. Haveroth, A.P.C. Dias, M.L. Bittencourt, J.L. Boldrini — Mon, 08 Jul 2024 00:00:00 +0000

This paper presents a thermodynamically consistent non-isothermal phase-field framework to model
the damage and fracture effects in elasto-plastic materials under finite strain. Following Boldrini et al. [1], the
adopted methodology is based on the use of the principle of virtual power, energy balance, and the second law
of thermodynamics in the form of a Clausius-Duhem inequality for entropy. Contact constraints are introduced
conveniently in the weak form of the resulting motion equation. A frictionless impact fracture problem simulation,
disregarding thermal effects, shows that the proposed model can reproduce qualitatively the crack initialization and
subsequent propagation.

The influence of modeling techniques on the numerical analysis of composite beams

L.M. Santos, T. Doca — Mon, 08 Jul 2024 00:00:00 +0000

This work aims to quantify the effects of implementation choices, such as type and number of
finite elements, on the modeling composite beams. The study is carried-out on a full-size finite element
model of the structure, which provides a more comprehensive description of the mechanical behavior
of the system when compared to the traditional push-out test. We focus on the influence of contact
conditions, physical and mechanical properties, discretization aspects and boundary conditions on the

correct representation of the force-displacement, local stresses and strains in the section-stud and concrete-
stud interfaces. Based on the observations, the importance of nonlinear relationships is discussed and a

criteria for an adequate numerical implementation of models is proposed.

Multiscale approach for fatigue simulation in thermoplastic polymers

SILVA, J. V. A, FARIAS, J. M. C., FANCELLO, E. A. — Mon, 08 Jul 2024 00:00:00 +0000

In mechanical engineering projects, mechanical fatigue is one of the most frequent sources of failure of
devices submitted to cyclic loads.This is the case of orthopedic implants and prostheses, many of which are made
of, or incorporate, polymeric materials. In large semi-crystalline polymers, mechanical fatigue is dominated by the
nucleation process as a consequence of localized inelastic strain accumulation and craze formation. To simulate the
local nucleation phenomenon in polymers, a multiscale model available in the literature was chosen, reproduced

and his features analyzed and compared with experimental evidences. In this model it is considered an Represen-
tative Volume Element (RVE) composed by a matrix with a small volume fraction of ductile damaging inclusions.

A homogenization scheme is formulated according to the Mean Field Homogenization (MFH) approach and the
Mori-Tanaka solution. The mechanical behavior is limited to small deformations and disregards heat generation.
The predictive fatigue life curves for High Density Polyethylene (HDPE) were reproduced and the contribution of
this paper focuses on the sensitivity analysis of the model to load effects and inclusion material parameters.

Numerical modeling of fracture propagation using continuum damage and cohesive crack models

Ilames J. G. Moraes, Rafael O. A. Abreu, Cristian Mejia, Deane Roehl — Mon, 08 Jul 2024 00:00:00 +0000

Damage mechanics is a branch of the inelastic theory, which is concerned with the impact of the growth
of microvoids or microcracks in solids. From a structural point of view, a solid body loses stiffness as a
consequence of damage evolution. This work aims at understanding fracture propagation in quasi-brittle materials,
considering continuum damage and cohesive crack models. The cohesive zone model and isotropic damage model
are implemented into the in-house framework GeMA. In the finite element context, modeling of the material
degradation process is a challenging task due to the occurrence of critical points and convergence problems in the
global solution. Therefore, robust continuation methods are required to overcome this obstacle. Regularization
techniques are applied in the isotropic damage models to reduce the pathological sensitivity of the solution to the
finite element size. Numerical simulations illustrate the ability and limitations of the proposed models to simulate
fracture propagation. Additionally, various damage criteria and evolution laws proposed by several authors are
adopted to evaluate the impact of the model on the global behavior. The results indicate that continuum damage
and cohesive zone modeling are crucial tools to provide realistic responses related to fracture processes.

Finite element modeling of the elastic-viscoplastic behavior of PC/ABS 60:40 blend under uniaxial compression

P.G. Marques Flavio, T. Doca, F.M. Andrade Pires, F. Macedo — Mon, 08 Jul 2024 00:00:00 +0000

Nowadays the use of polymers presents itself as a viable alternative to replace parts and components
that once were composed only of metallic and/or ceramic materials. The advancement of material engineering
has enabled the creation of polymeric compounds with high resistance, but with a low density, which can be an
advantage when compared to a wide range of various other materials. Along with the advances in obtaining new

polymers, there was also an evolution of numerical models that describe the mechanical behavior of these mate-
rials. The numerical formulations previously used for metallic materials have failed to represent them effectively.

Polymeric materials are highly dependent on several factors, among them the strain rate, working temperature and
manufacturing process are configured as those of greatest relevance in the influence of the mechanical properties.

Therefore, it is extremely important to use constitutive equations that consider the aforementioned nonlinear ef-
fects. The main objective of the present work is to model the mechanical behavior of the uniaxial compression test

of PC/ABS 60:40 blends. For this purpose, the numerical models used to describe the elastic-viscoplastic behavior
of the material are based on the works presented by Arruda, Mulliken and Boyce and were implemented as finite
element explicit formulation within VUMAT subroutines using the commercial software Abaqus.

Nonlinear finite element modeling of the impact of spherical and sharp brittle particles against a flat surface

S.G.A Araújo, T. Doca — Mon, 08 Jul 2024 00:00:00 +0000

An impact is defined as a sudden transfer of energy between solids, which often leads to forces of high
magnitude and subsequent damage. Moreover, the repetitive impact of brittle particles on protective surfaces,
enables a failure mechanism known as erosive wear. In this work, a finite element model of the impact of brittle
particles is presented. Two geometries are studied: a sphere and a polygon with sharp edges. Firstly, the proposed
model is validated, in a linear setting, using the classical Hertz’s theory. In a second setting, the particles are
regarded as sedimentary rocks while the flat counterpart is defined as a thick layer of steel coated with protective
materials. Further analysis, including nonlinear phenomena such as frictional contact, finite inelastic strains,
damage and fracture and provided alongside with a discussion on the failure mechanisms observed. Result show
the influence of the particle’s shape weight and speed on the failure of the counterpart.

Experimental and numerical assessment of impact wear resistant coatings: mechanical characterization and surface optimization

O.A.G. PEREIRA., T. DOCA. — Mon, 08 Jul 2024 00:00:00 +0000

The failure process of the protective structures, such as the frame of a flail mower, is mainly caused
by the impact of particles with varied geometries and weights. Moreover, the continuous and cyclic nature of
the loading conditions affecting protective systems often responsible for the development of erosive wear. This
work presents impact wear resistance assessment of the SAE 1045 steel in two surface conditions: uncoated and
with an electrode surface treatment. The goal is to evaluate the influence of coating’s mechanical properties, such
as resilience, elastic modulus, hardness and roughness, on the failure mechanics of the substrate. Sphere-to-flat
compression tests are performed on samples of each surface configuration. Both monotonic and cyclic tests are
carried-out. Results are used for the calibration of a finite element model of the problem. Simulation of various
surface configurations and loading conditions are presented and a solution for the life enhancement of a specific
protective system is proposed.

Formulation and validation of an efficient numerical model for energy conductor cables based on finite beam elements

Mon, 08 Jul 2024 00:00:00 +0000

Brazil is a country with continental dimensions and the availability of energy throughout the national
territory becomes a challenge, since hydroelectric power plants are responsible for 75% of the generation of energy
in the country, which requires large extensions of transmission lines according to the Ministry of Mines and Energy
(1). These transmission lines are formed by cables that need clamps for their fixation. Most cases of conductor
cable failures occur in the contact region within the clamp where visual inspection or the application of sensors
for measuring voltages and controlling the failure process becomes an activity of high level of difficulty according
to CARDOU (2).
This work develops a methodology through computer simulation using finite element analysis to analyze
the contact stresses in 7 layers and 120 wire helical cables. According BAUMANN (3) beam elements were used,
this strategy aims to obtain a lower computational cost compared to modeling with solid elements. The validation
of the results is made by comparing the results for the tensile test present in the literature in the models developed
by LALONDE (4) and JUDGE (13) and also with analytical results. The models showed convergence of results,
showing a difference of about 1%. The commercial software Ansys APDL version 2020 R1 is used to develop this
work.

A Elasto-Plastic Constitutive Model Based on Chaboche Kinematic Hardening of Aluminum Alloy 7050-T7451

Renzo Fernandes Bastos, Ernesto Massaroppi Junior — Mon, 08 Jul 2024 00:00:00 +0000

The elasto-plastic behavior of the aluminum alloy 7050-T7451 subjected to cyclic loading was
investigated and modeled. The objective of this work is to improve the constitutive model of Chaboche with a
special emphasis in the compression. In the proposed model, the part under tension of the stress-strain curve in
the stable hysteresis cycle is modeled separately from the compressed one, where it is considered that they have
different Modulus of Elasticity. The work includes both simulation and experimental data, and they are

compared to each other. The values were collected experimentally by the application of symmetric cyclic strain-
driven loading in the strain range between 0.75% and 2.25%. The experimental results were used to calculate the

parameters of the constitutive model in a MATLAB® software. The responses obtained with the proposed model
have greater adherence to the experimental results than those obtained with the Chaboche model.

Mechanical behavior of 6101 Aluminum alloy

Vinícius A. M. Rodrigues, Leonel L. D. Morales, Lucival Malcher — Mon, 08 Jul 2024 00:00:00 +0000

The paper aims to study the elastoplastic behavior of the aluminum alloy 6101 in different stress
states. In order to obtain different levels of stress triaxiality and normalized third invariant, six types of test
specimens were carried out: cylindrical, cylindrical with 6 mm and 10 mm notch radius, machined for
tensile test, rectangular specimen for pure shear testing, and two rectangular models for combined loading
test (tension and shear). The experimental data are evaluated and used for the calibration procedure of the
numerical simulations, which are performed in a context where it is assumed that the model based on the
von Mises yield criterion with nonlinear isotropic hardening describes the mechanical behavior of the
material. The experimentally obtained reaction curves are compared for the observed and calculated data,
and it is possible to evaluate the influence of the stress triaxiality, the normalized third invariant and the
calibration point, in the level of plastic strain in the fracture and in the proximity of the experimental result
with the numerical one. For the cylindrical specimens, the increase of the stress triaxiality results in the
discordance between the experimentally observed result and the numerical simulation performed, so that
model does not represent satisfactorily the experimentally observed, for these conditions, must being
request another calibration for model suitability. For the rectangular specimens, the observed result was
that both the stress triaxiality and the third invariant contribute to a distance between the results obtained
experimentally with the experimental results. At the end of the work, the equivalent plastic strain in the
fracture is analyzed as an indicator so that the correct beginning of the fracture can be observed.

Ductile-to-brittle transition behavior using peridynamics simulations

Mon, 08 Jul 2024 00:00:00 +0000

The problem of the Size effect on the material's tensile strength becomes a particularly important point
when a transition is made between the size of the structure tested in the laboratory and its actual size. Thus, the
question of the validity of laboratory tests and the prediction of their behavior in engineering structures continue
to be a topic in constant research. It is known that as the size of the tested sample increases, there is a change in
the global behavior from ductile to brittle. Capturing this change is the key to knowing the real behavior of the
sample and offering better predictions for the design of this type of structure. In this work, the application of the
peridynamic (PD) theory is evaluated to predict the behavior of quasi-brittle material specimens of different sizes
submitted the uniaxial tensile load. The potential of the numerical method shown that PD is a powerful tool capable
of successfully representing the transition between global behaviors.

Computational modeling of deformation bands in a plug scale

Renan S. B. de Lima, Roberto Quevedo, Deane Roehl — Mon, 08 Jul 2024 00:00:00 +0000

The strain localization phenomenon consists in the occurrence of narrow regions due to inelastic
deformations and irreversible phenomena. By porous materials such as soils and rocks, localized deformation can
affect the integrity and contribute to the initiation of structural failure. Typical examples of strain localization in
porous materials are the shear bands, which can be observed experimentally in laboratory tests. The formation of
shear bands can be represented through numerical models such as the finite element method (FEM). Thus, in this
study, we model the occurrence of shear bands at plug scale and perform a sensitivity analysis of the main
parameters involved. The Mohr-Coulomb model with strain softening was used to represent the elastoplastic
behavior of the materials. Strain softening was implemented through a progressive reduction of the friction angle
as a function of the plastic strain. In the results, structural features of the shear bands are analyzed, such as
orientation and band width. From the results, it was observed that the dilation angle is directly related to the
orientation of the shear band. Also, the Young's modulus exerts significant influence on the width of the band.
These analyses also allowed to identify convergence problems and dependence of the results on mesh
discretization level. In this work, we also discuss the source of these problems and mention some alternative
techniques that have been proposed to overcome such difficulties using FEM.

Computational modeling of formation and evolution of damage zones in reservoir scale

Thiago J. de Andrade, Roberto Quevedo, Bruno R.B.M. Carvalho, Deane Roehl — Mon, 08 Jul 2024 00:00:00 +0000

Geological fault zones can act as barriers or conducts for oil and gas flow in petroleum reservoirs. Fault
zones are divided into two regions, the fault core and the adjacent damage zone. The core is the region that
concentrates the greatest displacement and in general acts as a barrier for fluid-flow. On the other hand, damage
zones are characterized by relatively less intense deformation and can exhibit geological structures such as
fractures and deformation bands. Such zones can impact not only the fluid-flow within the reservoir but also the
mechanical behavior. Thus, the characterization of the damage zones is crucial for better management of oil fields
during the production phase. In this study, we present numerical models based on the finite element method (FEM)
to study the structural evolution of the damage zones in reservoir scale. Sensitivity analyzes were performed
varying the mechanical properties of intact rocks in order to check their impact on the structural evolution of the
damage zone. The obtained results allowed the identification of key parameters for damage zone evolution and
highlighted some advantages of FEM for the analysis of this kind of process.

Reducing the Discretization Error for Global and Local Variables in Poroelasticity Problems

Mon, 08 Jul 2024 00:00:00 +0000

This work analyzes the efficiency of the Repeated Richardson Extrapolation (RRE) to reduce the
discretization error (Eh) that results from the numerical resolution of one-dimensional poroelasticity problem. The
Finite Difference Method (FDM) was employed with second-order CDS approximation for spatial variables and
Crank-Nicolson approximation for temporal variables. The three-point Vanka smoother was used in the iterative
process. The multigrid method with W-cycles was used to accelerate the convergence of the iterative process,
which involved highly refined grids. The analyze of the results considered as local variables, the displacement and
pressure in the central point of the domain, based on localized fixed coordinate coinciding with a node point in all
grids considered; and as global variable, the average value of the variable of interest from all node values. It was
verified that employing RRE in the problems analyzed results in a significant reduction in Eh.

L-scheme and modified Picard with multigrid method for a 1D two-phase problem in rigid porous media with analytical solution

M. L. Oliveira, M. A. V. Pinto, C. Rodrigo, F. J. Gaspar, S. R. Franco — Mon, 08 Jul 2024 00:00:00 +0000

Applications of two-phase problems in porous media are common in Geomechanics, Hydrogeology,
Engineering and Biomedicine. There are different formulations when working on two-phase problems, in this

work we have chosen to use the pressure-pressure formulation. The equations system generated is a strongly non-
linear system of coupled partial differential equations. Thus, the modified Picard and L-scheme to perform its

linearization, the Finite Volume Method for the discretization of the equation in space and implicit Euler scheme
for the discretization of the equation in time were used. The systems of linear equations generated were solved
by the lexicographic Gauss-Seidel solver in a coupled way. In this work, we proposed to use multigrid method
with the Correction Scheme and W-cycle, in order to accelerate the convergence of this solver. Based on the tests
performed using an example with a known analytical solution, it was possible to notice the convergence to the
solution with a few iterations and little computational time.

Numerical and Experimental Study of Phase Change Around Cold Flat Plate Submersed in PCM

Michel P. Machado, Kamal A. R. Ismail — Mon, 08 Jul 2024 00:00:00 +0000

The global demand of energy is ever increasing due to the continuous increase of the world population,
industrial growth, transport, cooling and heating and similar activities which are strongly energy or electricity
dependents. During the last decades electricity was mainly generated by combustion of fossil fuels such as coal,
petroleum products and similar energy sources. On a global scale this resulted in huge amounts of greenhouse
gases which led to global warming of the planet with the disastrous consequences that humanity is facing in recent
years including melting of snow in the Poles, increasing water level in oceans, uncontrollable heating and cooling
seasons occurrence and duration and many other uncommon changes. In addition to this, fossil fuels fields are
deemed to be exhausted in the near future which leaves mankind without adequate alternatives for survival. This
possible scenario urged the nations to look for other energy alternatives resources to substitute fossil fuels and at
the same time do not degrade the environment. Solar and wind energy appear at the top of the list of possible
alternatives that are well developed and reasonably easy to implement but suffers from intermittency. To solve
this problem, many energy storage systems and technologies are investigated and developed to improve the
efficiency and widen the acceptability of these systems. One of these energy storage systems is energy storage in
latent heat. In the present study it is proposed to investigate latent heat storage with flat plate geometries using
water as a Phase Change Material (PCM). A model based on pure conduction is developed for the solidification
of PCM between flat cold plates. Experiments were done to validate the model. The wall temperature, spacing
between plates and the material of the plate are found to strongly affect the solidified mass, the interface velocity
and the time for complete phase change.

Augmentation of the heat transfer in a compact heat exchanger with asymmetric herringbone wavy-fin

Bruno H. C. Moreno, Leandro O. Salviano — Mon, 08 Jul 2024 00:00:00 +0000

The passive heat transfer intensification technique is a successful approach in thermal

engineering applied to the heat exchanger. Present work evaluates through numerical modeling a compact fin-
and-tube heat exchanger with asymmetric herringbone fins and aligned/ staggered circular tubes arrangement.

Numerical modeling is performed considering a steady-state and turbulent flow. Heat transfer and pressure loss
are evaluated by Colburn (j) and Friction (f) factors. A wave amplitude growth ratio of 0.8 and 1.2 were
evaluated for a range of Reynolds number between 800 and 5000. The density mesh analysis is ensured by Grid
Convergence Index methodology (GCI) and the numerical robustness is verified through experimental
comparison. Colburn factor is increased of 36% and 13% for the configuration with amplitude growth ratio of
1.2, for aligned and staggered cases, respectively, in relation to their reference cases. Friction factor is increased
of 35.3% and 12.7% for the aligned and staggered cases, respectively, for amplitude ratio of 1.2. The main flow
phenomenology found is related to the generation of downstream secondary flow, boundary layer separation at
the waves tip and reduction of the wake behind of the tubes. For higher wave amplitude, mixtures between cold
and hot streams decrease the recirculation zones and increase the local heat transfer coefficient.

Experimental validation and numerical simulation of a direct-expansion solar-assisted heat pump for heating water

Mon, 08 Jul 2024 00:00:00 +0000

In this work, a simulation model was developed to predict the thermal performance and discharge
temperature of a heat pump and compare with the experimental data. In this analysis a lumped model will be used
for each component of the system. The effect of various parameters, including collector area, storage volume,
solar radiation, windy speed, and atmospheric pressure was considered in the simulation. In this case will be
carried out considering the climatic conditions in the city of Belo Horizonte. This model was experimentally
validated using a direct expansion heat pump assisted by solar energy (DX-SAHP) equipped with a thermostatic
expansion valve. The performance of the heat pump simulation was compared with experimental results. The
mean absolute deviation mean deviation between the experimental COP and theoretical COP was 4.2±4.8% and
2.9±5.2%, respectively. The mean absolute deviation mean deviation between the experimental and theoretical
compressor outlet temperature was 3.3±2.0% and -2.0±2.0%, respectively.

Analysis of heat transfer mechanisms on hollow concrete masonry units under standardized fire conditions

Ellon Bernardes de Assis, Jorge Munaiar Neto — Mon, 08 Jul 2024 00:00:00 +0000

Concrete structural masonry is widely used on high-rise buildings in Brazil. Through the past decades
some effort on research in the topic have been made but there is still a need for research on masonry fire safety.
This is reflected in the lack of a Brazilian National Standard regarding masonry under fire conditions. In this
context, it is of interest to assess the influence of the cavities present in concrete masonry units (CMU) on thermal
behavior. This paper uses ABAQUS software to perform numerical simulations and assess the relative importance

of radiation and convection inside cavities in concrete masonry units under standard ISO 834-1:1999 fire condi-
tion. Radiation between cavity surfaces and fluid convection are considered using coupled fluid-solid transient heat

transfer analysis. The simulation procedure is validated using available experimental data on literature. After vali-
dated, parametric analysis is performed through simulations using different concrete emissivity values on cavities.

Results show that when concrete cavity surface has high emissivity value the radiation dominates the solution and
air flow has negligible effect in the heat transfer inside the cavities.

Aerodynamic analysis of a vehicle’s body for the competition Shell Eco-marathon

Carlos E. Maia — Mon, 08 Jul 2024 00:00:00 +0000

The Shell Eco-marathon is a competition that challenges students around the world to make a High
Efficiency vehicle. One of the characteristics that influences the energy consumption is the body’s aerodynamics.
The main objective of this work is to choose, for the UTECO team of The Federal University of Technology –
Paraná, Guarapuava Campus, the vehicle body for the 2020 edition of Shell Eco-marathon Brazil. First, there is a
need to project three possible designs, using Autodesk Inventor software, and after approval of the design by the
team, they will undergo a simulation using computational fluid dynamics, with the software ANSYS Fluent. With
this, there is going to be an evaluation of the drag coefficient values obtained for the three different models. To
simulate the conditions, the results were based on the Reynolds-Averaged Navier-Stokes equations and the
turbulent model k-ε, after a statistical analysis, the model with the lowest drag coefficient was chosen. The
variables used on ANSYS, such as Temperature and Pressure were based on the City of Rio de Janeiro – RJ and
the meshing

Effects of temperature gradients on moisture and salt transport in concrete structures.

R. M.M. Ribas, G. Santos, V. Okita — Mon, 08 Jul 2024 00:00:00 +0000

In maritime zones, with high salt íons incidence, the concrete structures corrosion frequently occurs.
The salt mist is full of salt ions and can be transported by de wind until the civil constructions, penetrating in its
pores. These ions can accelerate the deterioration of steel reinforcement and concentrate in some points,
crystallizing, and increasing the intern pressure until the concrete breaks creating fissures and cracks, becoming
more susceptible to others deterioration factors. Thereby, in this study, the heat, moisture and salt transport were
modelled to a concrete block reached by ions chloride (Cl-) salt mist. The conservation equations were discretized
in finite volumes, being solved in attached form, using the MTDMA (MultiTriDiagonal-Matrix Algorithm).
Comparations using the isothermal and non-isothermal conditions were made, and the results showed the big
influence of the temperature gradients in determination of the concentration of moisture and salt through the
sample.

Implementation of a code to obtain globe and wet-bulb temperatures for application of the WBGT index in the evaluation of the thermal performance of industrial sheds via computational simulations

Mon, 08 Jul 2024 00:00:00 +0000

For the analysis of the occurrence of overload or thermal discomfort in an industrial environment subject
to extreme temperatures, it is necessary to know the environmental conditions of the site. Extreme temperatures
are understood as those that cause serious health risks to workers. In this paper, an algorithm is implemented for
obtaining the hourly globe and internal wet bulb temperatures necessary to determine the WBGT index. The
WBGT index consists of a thermal overload index, defined by a mathematical equation that correlates the globe

temperature and wet-bulb temperature measured in the workplace. An industrial building equipped with a high-
intensity internal heat source and with longitudinal and/or transversal ridge vents is used as the object of study.

The internal environmental conditions of the shed are obtained through computer simulation using the EnergyPlus®
software (version 8.7.0), in three configurations of the devices that provide natural ventilation. The globe
temperature and wet-bulb temperature are not possible outputs to be obtained directly from the EnergyPlus
software and, for this reason, they are found through the algorithms formulated from iterative techniques.
Basically, three variables related to the environment are of interest: temperature, air speed, and relative humidity.
The proposed algorithms converge properly and, when comparing the final annual results of the WBGT index with
the limits provided for in the Brazilian regulatory standard NR-15, it is observed that the shed equipped with
longitudinal and transversal ridge vents has better thermal performance, thus providing less time of discomfort due
to the heat.

Solving one-dimensional two-phase flow problems in rigid porous media using L-scheme

Mon, 08 Jul 2024 00:00:00 +0000

This work aims to obtain the numerical solution for one-dimensional two-phase flow in rigid porous
media. The mathematical model for the problem consists of a system of partial differential equations with a set
of algebraic relations using the pressure-pressure formulation based on L-scheme linearization. The finite volume
method (FVM) is used to discretize the system of partial differential equations in a uniform grid. The spatial
approximation is obtained by the second-order scheme (CDS) and the temporal approximation by the implicit
Euler method. Dirichlet boundary conditions are applied. Iterative methods are used to solve the resulting system
of algebraic equations. A study on L-scheme was carried out to establish a rule and value of L that guarantees the
convergence of this linearization method. The results obtained for the numerical problem are compared with those
of a problem with the same characteristics in the literature that uses the pressure-saturation formulation.

Comparing analytical and numerical simulation models for Earth-air heat exchangers

Mon, 08 Jul 2024 00:00:00 +0000

In subtropical regions, like the South of Brazil, the air and soil temperatures follow phase shifted
periodical patterns with large amplitude variations along the year. This means that the Earth has great potential

to be used as a renewable heat source or sink for buildings, in the winter or summer, respectively. The Earth-
Air Heat Exchangers (EAHE) are devices that take advantage of this phenomenon. They employ buried ducts,

where the air is blown by low power fans (or by a passive method of natural convection) to exchange heat with the
soil, and leave their outlets at milder temperatures. The present study presents a comparison among four different
simulation models for EAHE. It takes into account experimental data available from an experimental installation in
the South Brazilian city of Viamao. Two of the models are one dimensional and analytical, the other two are three ̃
dimensional and numerical. We evaluate their overall accuracy, complexity, computational performances, among
other advantages/disadvantages.

Influence of frost formation in tube-fin evaporators using a distributed model

Caio Cezar Neves Pimenta, André Luiz Seixlack — Tue, 09 Jul 2024 00:00:00 +0000

Evaporators are heat exchangers of the refrigeration systems used to transfer heat from the
refrigerated environment. Their low operating temperatures favor the frost formation on their surfaces that,
depending on its thickness, can reduce the evaporator cooling capacity. This work presents a distributed model
for analyzing the influence of formation and frost densification on the performance of tube-fin evaporators. The
fundamental equations of mass conservation, momentum, and energy conservation are used to model the
refrigerant flow. The energy conservation equation of the evaporator tube wall is also solved. On the airside, the
equations of mass conservation, momentum, and conservation of energy are employed to simulate the formation
and frost growth on the evaporator surface. The system of equations is integrated numerically and solved
iteratively by successive substitutions. The numerical results obtained in this work are compared with
experimental data available in the open literature. Considering the range of inlet refrigerant temperature, -25.9 to
-20.2 °C, the means absolutes deviations, regarding the cooling capacity and the frost mass are 8,1% e 6,0%,
respectively. Among all tests carried out, during the four-hour interval there was an average reduction of 8% in
the cooling capacity due to the concentration of frost on the surface of the tubes and fins.

Modeling of conduction heat transfer between rice grains stored in a grain silo prototype

M.V. Henriques, G.J. Weymar, D. Buske — Tue, 09 Jul 2024 00:00:00 +0000

Grain storage is a vital operation to maintain the quality of the grains, for this you need to have control
over the stored temperature and humidity. Therefore, the objective of this work is through mathematical modeling
to simulate the internal temperature of the rice grains inside the silo. For the resolution of the model, the transfer

of heat by conduction between grains was taken into account, taking into account the type of grain and the dimen-
sions of the silo (height and radius), using classic methods of resolution, such as separation of variables, Laplace

transform and GILTT. To validate the models, experimental data generated are used for the case study. A solution
using only the dimension of the height of the silo T(z,t) showed a good correlation with the experimental data.
While the model, with the temperature depending on the radius of the silo, T (r, t), had results that were more
distant from the experimental data and the model T(r,z,t) had an accuracy higher than the one-dimensional ones in
the first moments of time. Therefore, the results presented show that the proposed methods are great alternative
tools to predict the temperature inside the silos.

Effect of Thermal Radiation on Natural Convection Cooling in a Protruding Heater Channel

Victor H. Sarmento, Andre D. Rocha — Tue, 09 Jul 2024 00:00:00 +0000

Electronic devices are becoming smaller every time and also more powerful, which leads to greater
amount of heat that needs to be dissipated. Cooling systems by natural convection do not need power and do
not involve movable parts to work, therefore they are simpler and cheaper to build and maintain. This paper
investigates numerically the effects of radiation on a cooling system by natural convection. The problem is assumed
as bidimensional and the geometry is formed by two parallel plates and there is a protruding heater in one of them,
while the other one is insulated. The heat flux from the module is responsible by driving the flow inside the
channel. For laminar natural convection, effects of radiation on the cooling were investigated. At first, neglecting
thermal radiation, the numerical results, were validated with the literature. After validation, thermal radiation was
taking account and the effects of emissivity and width channel on Nusselt number were computed and compared
with those without radiation.

Three-dimensional numerical solution of heat transfer in a built-in domestic oven

Gabriel C. de Souza, Francisco A. A. Gomes, Thiago T. Freitas — Tue, 09 Jul 2024 00:00:00 +0000

It is widely observable nowadays the trend of the population, especially in more developed countries,
towards the search for more efficient, safe, and with less environmental impact products and services. This trend
is often reinforced by impositions from regulatory agencies that offer incentives to manufacturers to make their
products better in these aspects. Domestic ovens are a type of durable consumer good and somewhat controversial
in terms of efficiency and safety. Despite the current legislation that aims to guarantee a minimum of safety in
the operation of domestic ovens, especially the most basic models, are still causing accidents, in particular, burns
due to their geometry whose external surfaces can reach high temperatures due to the high dissipation of excess

heat from the cooking process, resulting from fuel-burning or electrical resistors. The present study brings a three-
dimensional and transient analysis of the heat transfer through the numerical solution of the finite volume method

of a standard domestic oven. The analyzed model is based on a small built-in domestic oven, a liquefied petroleum
gas burner, modeled as an insufflation of hot gas, a cavity partially covered by thermal insulation, and a door
composed of a double glass window. From the temperature fields in the model, as well as flow speeds over the
oven’s operating time, a result is obtained that is indicative of the regions with the greatest energy loss, guiding
possible improvements of the model for greater safety during its operation.

Nonlinear Thermal Analysis of Steel Sections with Boundary Element Method

Mon, 08 Jul 2024 00:00:00 +0000

The fire safety is a topic that has been under discussion lately, mainly due to the last fires that have
befallen humanity and to which countless losses are linked. In this context, the role of fire resistance of structural
elements is essential for the security of buildings. Therefore, a non-linear thermal analysis of steel sections is
proposed with the Boundary Element Method. The partial differential equation of non-linear heat conduction is
linearized using the Kirchhof Transformation; the non-homogeneous term of the mentioned equation is
approximated by a series of radial basis functions variable, in order to control the conditioning of the interpolation
matrix and using the Dual Reciprocity Method. In addition, boundary conditions for heat exchange by convection
and radiation are introduced in the model, in order to simulate heat exchange when the section is subjected to
standard fire. Finally, in order to validate and compare, the temperature field obtained for two different steel
sections is compared with the results of the simplified method presented in NBR 14323; obtaining a good identity
of the solutions. The results reveal the validation of the constructed numerical model and the precision of the
simplified method for thermal analysis of sections of steel.

Heat transfer intensification of a compact heat exchanger through- composed passive techniques with wavy-fin and longitudinal vortices generators

Laís S. Bandini, Leandro O. Salviano — Tue, 09 Jul 2024 00:00:00 +0000

Considering the current need for continuous research to develop heat exchangers with high efficiency
with low-pressure drop penalty, aiming to cost reduction in materials and manufacturing process, the present
work evaluates a compact heat exchanger with wavy-fin and longitudinal vortex generator. The numerical
approach considers a heat exchanger with circular and elliptical tubes and delta-winglet and rectangular-winglet
vortex generator with an aspect ratio of 2 and angle of attack angle of 45°, for low Reynolds number. The heat
transfer is evaluated by Colburn’s factor (j) and the pressure drop is analyzed by Friction factor (f). The flow is
considered tridimensional, steady-state and turbulent. In comparison to the reference heat exchanger, the results
showed a heat transfer improvement of 41% by using elliptical tubes associated with a rectangular-winglet
vortex generator. For the friction factor, the configuration with rectangular-winglet vortex generators presented a
higher pressure drop than the delta-winglet type and the arrangements of circular tubes showed a higher friction
factor than elliptical tubes. Overall, the results showed that the composed passive technique is effective to
enhance the heat exchange in compact heat exchangers.

Determination of the heat treatment curve for machine components of power generation plants using finite element analysis

Esteban Foronda, Miguel Villa, Sebastián Cure, Wilfredo Montealegre Rubio — Tue, 09 Jul 2024 00:00:00 +0000

Heat treatment cycles allow stress relieving of machine components of hydroelectric and thermoelectric
plants. Differences between the heating/cooling rate of surface and core of these components during the three heat
treatment stages (heating, holding and cooling) lead to thermal deformation and stresses that need to be controlled
to avoid failure. Finite element analysis is used in this work to determine the optimal heating/cooling rate to
guarantee that the components subjected to heat treatment in a radiant tubes furnace do not suffer damage at any
stage of the process. The results of this work are focused on a Francis turbine runner, which is a critical component
in this industry due to its size, geometrical complexity and maintenance costs. Transient thermo-structural analysis
is implemented in commercial software with non-linear properties. In addition, the proposed numerical approach
allows evaluating the maximum power requirement of the furnace to follow the heat treatment curve. The results
indicate that the lower the heating/cooling rate, the greater the thermal uniformity obtained within the turbine
runner; therefore, there is less risk of mechanical damage. However, the final decision on the heat treatment rate
depends on the duration constraints of the process.

Analysis of Shear Locking Effect on Reissner Plates Using Meshless Local Petrov-Galerkin Method

Daniel D. Monnerat, José Antônio F. Santiago, Edmundo G. de A. Costa — Tue, 09 Jul 2024 00:00:00 +0000

The shear locking is an interesting numerical phenomenon which can be found in several formulations,
such as those based on Finite Element Method (FEM) and Meshless Local Petrov-Galerkin (MLPG) Method, when
they are directly applied to thin plates analyzed through Reissner's theory. It is known that the shear locking effect
is caused by using the same interpolation functions for all generalized displacement fields, producing inconsistent
results in case of thin plates. In order to avoid this phenomenon, the rotations must be built from the first derivative
of the transversal displacement field. In the FEM formulation, this problem is overcome by using reduced-selective

integration schemes. However, this alternative can hardly be extended to Meshless Methods due to the non-
polynomial characteristic of the approximations. More complex numerical formulations can be considered,

however in this paper the variable changing technique is applied, by solving the shear locking effect in a simple
and efficient way, without increasing the number of degrees of freedom in plate’s problems.

Boundary Mesh-Free Model for potential problems

Amanda Araujo, Fernando Martins, Artur Portela — Tue, 09 Jul 2024 00:00:00 +0000

Within the engineering field, many problems are described by the Laplace Equation, which does not
have an analytical solution for complex geometries and boundary conditions. Therefore, numerical methods are
highly important for obtaining approximate solutions for problems of this nature. The most utilized numerical
methods nowadays involve a mesh for the discretization step, which lead to a high computational cost. This work
proposes a Boundary Mesh-Free Model (BMFM) that combines the Boundary Integral Equations and the shape
functions generated by the Moving Least Square (MLS) method. This way, the presented method minimizes
the need of discretization and eliminates the need of a mesh. The proposed formulation was then applied to a
benchmark potential problem governed by the Laplace equation. The results obtained using the BMFM had a
small error when compared to the analytical ones, showing how promising the method is.

A three-dimensional Boundary Element formulation for boundary conditions on small areas

Matheus Rocha, Edson D. Leonel — Tue, 09 Jul 2024 00:00:00 +0000

The accurate prediction of the mechanical behaviour of solids and structural systems has fundamen-
tal importance in structural engineering. This task has been handled by numerical methods, such as the Boundary

Element Method (BEM). In this method, integral equations written over the body’s boundaries represent the mecha-
nical behaviour. Then, in three-dimensional analyses, the BEM mesh is composed of two-dimensional elements.

Nevertheless, the mesh construction depends on the position of the distributed loads and displacements over the
boundary. This is a disadvantage when the geometric modelling is performed on Computer Aided Design software,
once the boundary conditions representation leads to additional and inconvenient modifications. To overcome such
drawback, this study presents a BEM formulation which handles distributed boundary conditions non-coincident to
the boundary element mesh. The overlapping element is required, which overlaps the BEM mesh. Both distributed
loads and supports are accounted by the proposed scheme. A numerical application demonstrates the accuracy of
the proposed scheme, in which its responses are compared against numerical data of an equivalent finite element
model. The results demonstrate remarkable accuracy and robustness.

The three-dimensional isogeometric Boundary Element Method for concentrated boundary conditions

Matheus Rocha, Edson D. Leonel — Tue, 09 Jul 2024 00:00:00 +0000

The Isogeometric Boundary Element Method (IGABEM) is a recent and robust strategy for the me-
chanical modelling of solids. One remarkable advantage of the isogeometric approach is the direct mechanical

analysis from geometries modelled by Computer-Aided Design (CAD) software, in which complex geometries
can be accurately represented. In this context, the non-uniform rational B-splines (NURBS) surfaces approximate

both geometry and mechanical fields. Besides, the non-requirement of the domain mesh contributes to the cou-
pling IGA and BEM, once CAD surfaces are the mesh itself. However, the application of concentrated boundary

conditions in IGABEM is quite challenging, because of two main aspects: the extension of the NURBS curves and
the singular nature of the fundamental solutions. Commonly, few NURBS surfaces are necessary to represent the
entire boundary and trimming these curves is not an easy task. Besides, boundary conditions over small areas may
require small NURBS, which is non-sense in this domain. Additionally, the use of small elements may lead to the
ill-positioned algebraic system of equations, due to the small distance between the source points. Therefore, this
study presents an IGABEM formulation (IGABEM) to account such boundary conditions in three-dimensional
solids. Concentrated loads and supports are introduced by the addition of the Dirac Delta function over the traction
mechanical field. One application demonstrates the accuracy of the proposed formulation, in which its results are
compared against the responses of Finite Element equivalent model. The proposed IGABEM approach predicts
the mechanical behaviour accurately, which proves the accuracy and robustness of the proposed improvements.

PARTICULARITIES IN THE APPLICATION OF THE BOUNDARY EL- EMENT METHOD WITH HIGHER ORDER ELEMENTS IN TWO DIMENSIONAL POTENTIAL PROBLEMS

SANTOS A.J, LOEFFLER C.F, LARA L.C — Tue, 09 Jul 2024 00:00:00 +0000

In this work, the Boundary Elements Method (BEM) applied to two-dimensional potential problems
with quadratic and cubic isoparametric elements are analyzed. Unlike the constant and linear elements, the modus
operandi of the coordinate transformations, the numerical integration procedures and the treatment of singular
integrals are not simple, since the Jacobian of the transformation is no longer constant throughout the element and
are treated numerically. The objective of this work is to analyses the effect of the self-adaptive integration scheme
for solving the Boundary Element Method integrals.

A Boundary Element Coupling formulation for three-dimensional reinforced domains

Antonio R. Neto, Edson D. Leonel — Tue, 09 Jul 2024 00:00:00 +0000

This study presents a numerical coupling formulation for the mechanical modelling of reinforced three-
dimensional (3D) structural systems. This formulation is based on the Boundary Element Method (BEM) for the

mechanical analysis of 3D domains with Lagrangian approximation. In this coupling, the material matrix (solid
3D domain) is represented by the usual 3D BEM formulation with Kelvin’s fundamental solutions for isotropic
linear-elastic materials. Numerical integration and singularity subtraction are applied herein. A one-dimensional
approach of the BEM (1DBEM) represents the embedded fibre-reinforcements, which enforce axial mechanical
solicitation. The 1DBEM is based on the axial fundamental solution for elastic 1D domains, which can be easily
found in the literature. The interaction between the matrix and reinforcements is described by an adherence force
over the reinforcements’ line, which is interpolated by high-order Lagrangian functions. One considers no relative

displacements (perfect bonding). The adherence force is accounted as a body force into the 3D BEM formula-
tion. These aspects characterise the proposed 1DBEM/BEM coupling as an alternative to the usual FEM/BEM

technique, which has been widely applied in the literature. The authors have previously demonstrated in Ro-
drigues Neto and Leonel [1] that the 1DBEM/BEM coupling exhibits superior results when compared against

the usual FEM/BEM approach in 2D applications. This work presents the extension of this formulation for 3D
analyses. The proposed modelling is applied herein in the mechanical analysis of complex 3D applications. The
achieved results are compared against experimental responses available in the literature. The proposed formulation
led to accurate and stable results.

A Nonlinear Boundary Element Coupling formulation for three-dimensional bond-slip analysis

Antonio R. Neto, Edson D. Leonel — Tue, 09 Jul 2024 00:00:00 +0000

This study presents a numerical coupling formulation for the bond-slip modelling of 3D reinforced do-
mains. This formulation is based on the Lagrangian 3D Boundary Element Method (BEM) and the 1DBEM/BEM

coupling. In this technique, the material matrix (solid 3D domain) is represented by the 3D BEM displacements

integral equation. Numerical integration and singularity subtraction are implemented for plane elements. A one-
dimensional approach of the BEM (1DBEM) represents the embedded reinforcing bars. The 1DBEM is based

on the axial fundamental solution for elastic 1D domains, which can be easily found in the literature. The inter-
action between the matrix and reinforcements is described by an adherence force over the reinforcements’ line,

which is interpolated by high-order polynomial functions. The adherence force is accounted as a body force into
the 3D BEM formulation. The bond-slip effects are accounted by considering relative displacements between
reinforcement and matrix. An adherence law represents the relation between slip and adherence force. Thus,
Newton-Raphson solution technique can be utilised to solve the nonlinear problem. The boundary formulation is
applied herein to represent the pullout test, which is essentially 3D. In this regard, a connection element is used
to properly enforce the prescribed displacement directly at the reinforcing bar in a region outside the 3D solid.
The numerical results of the pullout test model show excellent agreement with experimental data. Therefore, the
proposed formulation can be considered stable, accurate and robust.

O Método dos Elementos de Contorno com Interpolação Direta e Técnica de Superposição de Domínio aplicado a problemas de Helmholtz em meios suavemente heterogêneos

H. M. Barcelos, C. F. Loeffler, L. O. C. Lara — Tue, 09 Jul 2024 00:00:00 +0000

This paper presents the coupling between the Direct Interpolation Boundary Element Method
(DIBEM) and the Domain Superposition Technique (DST) addressing problems governed by the
inhomogeneous Helmholtz’s Equation. Specifically, here are approached cases in which the constitutive medium
property varies smoothly according to a known function. As the constitutive properties can be located in
piecewise sectors, the Domain Superposition Technique (DST) is used as a way to compute the different
properties, preserving the particularities of the Boundary Elements Method (BEM). Inhomogeneous problems
are usually solved by domain numerical techniques, but using the DIBEM formulation the domain integral
generated by the non-homogeneity of the medium can be accurately transformed into a boundary integral.
Numerical tests are implemented in two-dimensional problems, with regular and irregular domains, imposing, in
the latter case, numerical difficulties on the proposed method. Simulations using the Finite Element Method are
used to generate the reference solutions.

BE analysis of composite bars having generic cross sections and variable rigidity subjected a nonuniform torsion

Maicon José Hillesheim, Gabriel ViecelliRenostro, Francisco Célio de Araújo — Tue, 09 Jul 2024 00:00:00 +0000

In this paper, a robust and efficient algorithm is presented to solve composite bars with variable cross-
section and subjected to nonuniform torsion. The bar may be subjected to concentrated or distributed twist loads

and is under general boundary (end) conditions. Torsion problems are often encountered in engineering practice
as in members of spatial frames, in curved bridges, in rigid building cores, etc.. In this class of problem, the
warping of a given cross section is described by the known Laplace/Poisson equation, while the angle of twist
along the beam is described by a fourth-order differential equation with variable coefficients. In the present
strategy, the boundary-element subregion-by-subregion (BE SBS) technique, developed in previous works, is
employed to solve the coupled boundary-value problems (BVPs) related to the cross section. An important detail
of the BE SBS technique is the use of Krylov iterative solvers, which allows the elimination of operations with
the large blocks of zeroes existing in the coupled system of equations. For the solution of the global differential
equation of equilibrium in the beam, which describes the angle of twist along the beam, a strategy based on the
weighted residual method is developed. Complex composite cross sections under torsion are analyzed to show
the performance of the whole solution process.

Dynamic analysis of Euler-Bernoulli beams over elastic foundation by the Boundary Element Method

Julia N. Appi, Ramon M. Correa, Luiz A. de Lacerda, Jose A. M. Carrer — Tue, 09 Jul 2024 00:00:00 +0000

Continuous beams are engineering structural elements that can be modeled using the Euler-Bernoulli

beam theory. This work is concerned with the development of a time-domain Boundary Element Method formu-
lation to solve the problem of continuous beams over elastic foundation. The formulation was developed with the

use of the static fundamental solution, generating a formulation of the type Domain-Boundary Element Method
(D-BEM). In all the examples included in this work, geometric and material properties of the beams are assumed
to be the same. Boundary Element numerical results for displacements, rotations, bending moments and shear
forces obtained for uniformly loaded beams, are compared graphically to the results obtained using the Finite

Element Method, since the problem of the vibration of a Euler-Bernoulli beam over elastic foundation has no ana-
lytical solution. The main purpose of this paper is to prove the viability of the Boundary Element Method for the

time-domain analysis of continuous Euler-Bernoulli beams over elastic foundation.

Aplicação do esquema recursivo do Método dos Elementos de Contorno para o cálculo de derivadas direcionais em problemas de potencial resolvidos pelo Método dos Elementos Finitos

H. M. Barcelos, C. F. Loeffler, L. O. C. Lara — Tue, 09 Jul 2024 00:00:00 +0000

The recursive boundary element technique has been used successfully in scalar problems for
recalculation of potential and directional derivatives solutions. It was used for solving problems governed by
Laplace, Navier, and Poisson Equations. In the present work, nodal values on the boundary calculated using the
Finite Element Method are reused by applying them in the boundary element integral equation, aiming to calculate
internal directional derivatives of the basic variable of the problem. It is well known that these internal directional
derivatives calculated by the Finite Element Method (FEM) present low accuracy. Here, to confirm the robustness
of the proposed model, computational tests are performed, in which the FEM results in the classic form are
compared with those obtained by the recursive procedure described former. The solution of problems through the
Boundary Element Method is also presented and benchmark problems that have a known analytical solution are
chosen for analysis, to better assess the quality of the results.

Topology optimization with boundary element method using topological derivative and its gradient

Lucas A. Pacheco, Lucas S. Campos — Tue, 09 Jul 2024 00:00:00 +0000

A new methodology of topology optimization of thermal conducting solids using the Boundary Element
Method (BEM) and Topological Derivatives (TD) is presented. The TD is evaluated on the boundary and the
domain and its gradient is evaluated on the problem’s boundary only. Boundary nodes where TD values are low are
then moved using the TD’s gradient as indicator of direction and the TD’s value as indicator of intensity of change.
The creation of holes inside the domain is made possible by taking isolines of the TD on the domain. Isolines with
low values of the TD are used as the boundary of the new holes. The methodology creates smoother boundaries
with reduced number of elements when compared to previously proposed techniques, while maintaining a simple
mathematical formulation.

Uma Comparação Preliminar entre os Métodos de Interpolação Direta e da Dupla Reciprocidade na solução da Equação de Onda Acústica em duas dimensões

Loeffler, C.F., Serafim, L.D.B., Pinheiro, V.P. — Tue, 09 Jul 2024 00:00:00 +0000

This work presents an initial performance test of the Direct Interpolation Element Method applied to
scalar wave propagation problems, dealing particularly with the response of a bar subjected to an impact load. This
benchmark problem, due to its numerical difficulties, is appropriate to analyze the formulation consistency. The
proposed research aims to compare, in a preliminary manner, the accuracy of the Direct Interpolation technique
versus the well-known Dual Reciprocity formulation, in terms of response and frequencies. Houlboult integration
scheme has been selected as step-time procedure, due to its greater numerical stability.

A LOCAL MESHLESS ANALYSIS OF DYNAMICS PROBLEMS

Flávio Mendonça, Wilber Vélez, Fernando Martins, Amanda Araújo, Artur Portela — Tue, 09 Jul 2024 00:00:00 +0000

This paper is concerned with new formulations of local meshfree numerical method, for the solution of
dynamic problems in linear elasticity, Integrated Local Mesh Free (ILMF) method. The key attribute of local
numerical methods is the use of a modeling paradigm based on a node-by-node calculation, to generate the rows
of the global system of equations of the body discretization. In the local domain, assigned to each node of a
discretization, the work theorem is kinematically formulated, leading thus to an equation of mechanical
equilibrium of the local node, that is used by local meshfree method as the starting point of the formulation. The
main feature of this paper is the use of a linearly integrated local form of the work theorem. The linear reduced
integration plays a key role in the behavior of local numerical methods, since it implies a reduction of the nodal
stiffness which, in turn, leads to an increase of the solution accuracy. As a consequence, the derived meshfree and
finite element numerical methods become fast and accurate, which is a feature of paramount importance, as far as
computational efficiency of numerical methods is concerned. The cantilever beam was analyzed with this
technique, in order to assess the accuracy and efficiency of the new local numerical method for dynamic problems
with regular and irregular nodal configuration. The results obtained in this work are in perfect agreement with
Mesh-Free Local Petrov-Galerkin (MLPG) and the Finite Element Method (FEM) solutions.

COMPARING DIFFERENT ADAPTIVE MESH REFINEMENT STRATEGIES APPLIED TO TWO-DIMENSIONAL POTENTIAL PROBLEMS USING BOUNDARY ELEMENT METHOD

Macedo, L. C., Campos, L. S. — Tue, 09 Jul 2024 00:00:00 +0000

The work consists of comparing the performance of different adaptive mesh refinement strategies adap-
tive refining using the Boundary Elements Method (MEC) based on error estimates made by three error estimators.

The three error estimators adopted in this work are: discontinuous estimator, integral estimator and recursive es-
timator. The parameter adopted in the comparison will be the reduction of the average error calculated in points

internal to the geometry so that the calculation of the average error is for the same points in all cases because
different discretized geometries are generated from each estimator. The results obtained from the error estimators
are compared to the application of uniform refinement to study the efficiency of the refining based on the different
error estimators.

Numerical Modelling of Skin Tumor Diagnostics through Dynamic Thermography

Luiz C. Wrobel, M. Hriberšek, J. Marn, J. Iljaž — Tue, 09 Jul 2024 00:00:00 +0000

Dynamic thermography has been clinically proven to be a valuable diagnostic technique for skin tumor
detection as well as for other medical applications such as breast cancer diagnostics, diagnostics of vascular
diseases, fever screening, dermatological and other applications. Thermography for medical screening can be done
in two different ways, observing the temperature response under steady-state conditions (passive or static
thermography), and by inducing thermal stresses by cooling or heating the observed tissue and measuring the
thermal response during the recovery phase (active or dynamic thermography). Both methods have been used for
medical applications; however, recent research on dynamic thermography has shown many advantages over static
thermography. The numerical modelling of heat transfer phenomena in biological tissue during dynamic
thermography can aid the technique by improving process parameters or by estimating unknown tissue parameters
based on measured data. This paper presents a nonlinear numerical model of multilayer skin tissue containing a
skin tumor, together with the thermoregulation response of the tissue during the cooling-rewarming processes of
dynamic thermography. The model is based on the Pennes bioheat equation and solved numerically by using a
subdomain boundary element method which treats the problem as axisymmetric. The paper includes computational

tests and numerical results for Clark II and Clark IV tumors, comparing the models using constant and temperature-
dependent thermophysical properties, which showed noticeable differences and highlighted the importance of

using a local thermoregulation model.

Performance portability in meshless methods using a parallel implementation procedure based on meta-programming

Tue, 09 Jul 2024 00:00:00 +0000

The present paper focuses upon the development of a parallel implementation procedure to the nu-
merical simulation of boundary value problems by using the principles of functional programming and memory

polymorphism. The proposed procedure aims to evaluate the portability of computational performance in dif-
ferent execution spaces using meta-programming and simplified representation of physical-mathematical models

through simple usage of declarative programming. For this purpose, an execution model for meshless methods is

presented, under the premise that specializations for the execution and memory spaces must occur during the com-
pilation time. This means that the declared model can be simulated in distinct architectures without any changes

in the implementation, allowing ensuring the portability of the computational performance and reducing the com-
plexity of the meshless numerical models. At the end of the paper, an example is carried out aiming to evaluate the

computational performance and the efficiency of the parallel implementation procedure applied to the Helmholtz
problem.

A meshfree cell-based smoothed radial point interpolation method for damage problems

Samir S. Saliba, Lapo Gori, Roque L. S. Pitangueira — Tue, 09 Jul 2024 00:00:00 +0000

Meshfree methods belonging to the class of Smoothed Point Interpolation Methods (S-PIM) have been
shown to provide certain advantages with respect to the standard finite element method (FEM), when dealing with
physically nonlinear problems. The present work extends the Cell-Based Smoothed Radial Point Interpolation
Method with polynomial reproduction (CS-RPIMp), originally proposed for linear problems, to the case of damage
models. The weakened-weak (W2

) formulation and peculiar integration scheme which this method is based on have
been extended to nonlinear damage models. Some numerical examples of nonlinear problems with different kinds
of boundary conditions, performed using different strategies for support nodes selection based on the T-schemes
(T4-, T6/3- and T2L-schemes), are presented, aiming to point out the accuracy, convergence and efficiency of the
Cell-Based Smoothed Radial Point Interpolation Method with polynomial reproduction in comparison with the
standard finite element method.

Comparison of smoothed point interpolation methods in linear static problems

Samir S. Saliba, Lapo Gori, Roque L. S. Pitangueira — Tue, 09 Jul 2024 00:00:00 +0000

Smoothed point interpolation methods (S-PIM), when compared with the standard finite element method

(FEM) in the study of static linear problems, present interesting results due certain characteristics of their formu-
lation. In general, meshfree methods have been shown to be more accurate and efficient. The proposed study

aims to present a comparison between the Node-Based Smoothed Radial Point Interpolation Method with polyno-
mial reproduction (NS-RPIMp), Edge-Based Smoothed Radial Point Interpolation Method with polynomial repro-
duction (ES-RPIMp) and Cell-Based Smoothed Radial Point Interpolation Method with polynomial reproduction

(CS-RPIMp), applied to static linear-elastic problems. Several numerical simulations, performed using differents
strategies for support nodes selection based on the T-schemes (T3-, T4-, T6/3- and T2L-schemes), are presented,
providing a relevant amount of results that allow to understand the behaviour of each one of these methods and
schemes with respect to the accuracy and convergence rate.

Formulação do MEC 2D para Análise de Propriedades de Materiais Compósitos

Tue, 09 Jul 2024 00:00:00 +0000

Os materiais compósitos são amplamente conhecidos, com advento desde meados do século XX, sendo
uma classe de materiais capaz de combinar propriedades específicas em virtude da variedade de materiais
combinados em compósitos multifásicos engenheirados. Na atualidade, cada vez mais pesquisas são amplamente
desenvolvidas nas áreas experimental e computacional. Assim, havendo a união de dois ou mais constituintes que
apresentam características mecânicas distintas em cada uma das fases, os materiais compósitos podem promover
melhores propriedades para o produto final, seja resistência, flexibilidade ou durabilidade. Dentre esses
materiais, destacam-se os concretos autoadensáveis e os reforçados por fibras, ambos, basicamente, constituído
por duas fases: a matriz (contínua) e a fase dispersa (características geométricas das partículas ou fibras). Neste
contexto, o presente trabalho apresenta uma formulação usando o Método dos Elementos de Contorno 2D (MEC)
com as adequações pertinentes à análise de propriedades efetivas de materiais com inclusões em diferentes fases.
O domínio é subdividido em regiões com propriedades físicas diferentes, compartilhando, em suas interfaces,
deslocamentos e tensões. A formulação permite a definição de inclusões em um elemento representativo de
volume, de maneira a observar o comportamento da peça estrutural. A utilização destes procedimentos
proporciona a análise de materiais compósitos a fim de estabelecer propriedades físicas efetivas. O código
computacional foi elaborado na plataforma OCTAVE de código aberto, com discretizações feitas por elemento
linear descontínuo. Exemplos são apresentados para demostrar a adequação da formulação e do código
propostos.

Boundary Mesh-Free Model for elasticity problems

Fernando Martins, Amanda Araujo, Artur Portela — Tue, 09 Jul 2024 00:00:00 +0000

The present work proposes implementing the shape forms obtained through the Moving Least Square
(MLS) method in the Boundary Integral Equations, thus presenting a Boundary Mesh-Free Model (BMFM), based
on the Boundary Node Method. Although based on the Boundary Integral Equations, BMFM does not require a
boundary mesh to approximate the variables. In the proposed BMFM, the boundary is described by linear segments
of integration. Within each segment, the MLS is applied independently, which allows for better representation of
discontinuities on the displacement and force fields. At the end of the paper, BMFM was applied to a benchmark
problem. It was possible to verify that the proposed method led to results with very low errors, proving it to be a
valid alternative to the more classical, robust methods.

Avaliação de integrais no sentido do Valor Principal de Cauchy em elementos lineares contínuos e descontínuos

Dalton Riva de Paula, Luiz Alkimin de Lacerda — Tue, 09 Jul 2024 00:00:00 +0000

This article aims to present expressions for the calculation of strongly singular integrals existing in the
Cauchy Principal Value sense. The expressions are directly applicable to two-dimensional elasticity problems with
the Boundary Element Method and can be easily adapted to other problems. In particular, general expressions
are presented for the calculation in continuous and discontinuous linear boundary elements that can be easily
adapted for direct calculation in classic Boundary Element Method computer codes. The discontinuous element
is considered in a parametric form. With this direct approach, the rigid body movement artifice or equivalent
technique for axisymmetric problems can be avoided. The validation of the presented expressions are done through
a simple example. Basically, integration results from the derived expressions are compared with those obtained
with the classic indirect evaluation of singular integrals with the rigid body movement. The expected correlation
is demonstrated in the results.

A Brief Performance Analysis of Direct Interpolation Technique applied on Bidimensional Advective-Diffusive Problems with Variable Velocity Fields

Loeffler, C.F., Pinheiro, V.P., Almeida, L.M. — Tue, 09 Jul 2024 00:00:00 +0000

Research efforts directed to advective-diffusive equation have resurfaced, strongly motivated by the
recent use of these mathematical models in pollutant dispersion applications, within the scope of environmental
engineering. In the context of the Boundary Element Method (BEM), the treatment of the advective transport term
characterizes a technical challenge. The BEM classic formulation, which uses the problem’s inherent fundamental
solution, is capable of handling high Peclet numbers phenomena, however it is limited to uniform velocity fields.
In parallel, the Dual Reciprocity technique, which is more robust and versatile, offers flexibility in describing
variable flow velocity fields, nevertheless it remains restricted to representing creeping flows. The recent Direct
Interpolation technique provides a balanced alternative to the two previous approaches, as it is able to deal with
variable velocity fields, such as Dual Reciprocity, despite that, it maintains stability up to moderate Peclet number.
This article aims to expose a preliminary performance of the of Direct Interpolation technique comparing it to
the well-established Dual Reciprocity approach, in physical situations with spatial variation of the velocity field,
while the effects of advection are gradually increased. Focusing on determining the relative performance of the
formulations, in terms of precision and stability, the numerical results are evaluated using benchmark problems
with widely known analytical solutions.

Comparison and correlation of computer simulations using the finite element method and the SimSolid software with meshfree method for automotive durability analyses

Tue, 09 Jul 2024 00:00:00 +0000

This paper presents an investigation comparing the finite element method to a meshfree method in the
simulation of structural tests of different nature used in the automotive industry. In this study, the commercial
softwares Altair OptiStruct and Altair SimSolid have been used, in order to know the ability of each one to
reproduce the behaviour of the structure according to the imposed loading. For this, the numerical results were
compared to experimental tests and briefly discussed.

A BEM formulation with Tangent Operator for cohesive crack propagation modeling

Tue, 09 Jul 2024 00:00:00 +0000

This work presents a Boundary Element Method (BEM) formulation for cohesive crack propagation
analysis, in a 2D approach. The fracture effects are captured by using dipoles of stresses, with the introduction of
an initial stress field to represent the cohesive zone. This formulation represents the presence of the Fracture
Process Zone (FPZ) with only three algebraic equations (equations related to stress correction) per source point
located in the crack line. For comparison, dual formulation requires four algebraic equations (displacements and
forces) per source point, and the multi-domain technique requires eight algebraic equations. The consistent
Tangent Operator (TO) is derived for the linear, bilinear and exponential cohesive laws, in order to speed up the
nonlinear solution. Some examples are presented to illustrate the robustness of the Dipole BEM/TO formulation,
including multiple crack analysis in mixed fracture mode. The responses obtained using this new formulation are
compared with experimental and numerical data available in the literature, and in all applications, the numerical
efficiency of the TO operator is presented.

PRELIMINARY RESULTS ON 3D CONTACT SHAPE OPTIMIZATION WITH THE BOUNDARY ELEMENT METHOD

Cristiano J. B. Ubessi, Filipe P. Geiger, Rogerio J. Marczak — Tue, 09 Jul 2024 00:00:00 +0000

This work presents preliminary results applying the Boundary Element Method (BEM) as a structural
sensitivity kernel under a contact shape optimization procedure for 3D problems involving anisotropic materials
under contact, using the Complex-Step Method (CSM) to obtain sensitivities of objective function and restrictions
to the variation of design parameters. In this preliminary work, we present the results for the isotropic case. An
important aspect regarding the fatigue life of ductile materials subject to contact conditions is the occurrence of
the maximum shear stress below the surface. The examples analyzed with the present methodology explore the

optimization of shape aiming towards a smooth stress distribution along the blade root surface. The optimiza-
tion procedure follows the SLP paradigm. This BEM based methodology can avoid the need for extreme mesh

refinements reducing computational cost while obtaining useable results.

Machine-precision fracture mechanics evaluations with the consistent boundary element method

Osmar Alexandre do Amaral Neto, Ney Augusto Dumont — Tue, 09 Jul 2024 00:00:00 +0000

As hitherto proposed in the technical literature, the boundary element modelling of cracks is best carried

out resorting to a hypersingular fundamental solution. A more natural approach might rely on the direct representa-
tion of the crack tip singularity, as already proposed in the frame of the hybrid boundary element method. However,

recent mathematical assessments indicate that the conventional boundary element formulation – based on Kelvin’s

fundamental solution – is in fact able to precisely represent high stress gradients and deal with extremely convo-
luted topologies. We propose in this paper that independently of configuration a cracked structure be geometrically

represented as it would appear in real-world laboratory experiments, with crack openings in the range of microm-
eters or less. Owing to a newly developed integration scheme for two-dimensional problems, machine precision

evaluation of all quantities may be achieved and stress results consistently evaluated at interior points arbitrarily
close to crack tips. Importantly, no artificial topological issues are introduced and linear algebra conditioning is

kept under control. Some numerical illustrations show that highly accurate results are obtained for cracks rep-
resented with just a few quadratic, generally curved, boundary elements and a few Gauss-Legendre integration

points per element. The numerical evaluation of the J-integral turns out to be straightforward and actually the most
reliable means of obtaining stress intensity factors.

Direct numerical simulation of a sphere settling in a thixo-viscoplastic fluid using lattice Boltzmann method

Marco A. Ferrari, Alan Lugarini, Admilson T. Franco — Tue, 09 Jul 2024 00:00:00 +0000

During a drilling operation of oil and gas wellbores it is sometimes necessary to stop fluid pumping,
and this causes the cuttings to settle towards the bottom. To avoid cuttings from accumulating downhole, drilling
fluids are designed for gelification, which in rheologic terms means the build-up of yield stress in a thixotropic
material. To study this phenomenon, the lattice Boltzmann method (LBM) is utilized to solve fluid flow while the
immersed boundary method (IBM) is employed to solve the motion of a spherical particle. Thixotropy is modeled
with a structural parameter model, whose scalar is associated with the fluid’s yield stress. The structural parameter
is transported by the convection-diffusion equation in the mesoscopic scale. The focus of the present work is on
the effects of model parameters on the trajectory and terminal velocity of a spherical particle released from the rest
in a thixotropic fluid initially fully unstructured. Considering that the fluid starts to age as soon as the sphere is
released, the particle velocity decreases because of the increased yield stress and after a while reaches its terminal
velocity. If the maximum yield stress is increased above a threshold, the particle is not capable to break through
the new structured fluid and ceases to move after some time, staying suspended in the gelified fluid.

Computational analisys of slurry drying through filtration using CFD- DEM coupled methods

Matheus D. B. Oliveira, Matheus F. R. Moreira, Cristiana B. Maia — Tue, 09 Jul 2024 00:00:00 +0000

Computational analysis is performed with the objective to virtually represent objects and equipment’s
real physical behavior. With simulation is possible to make geometrical and numerical modifications reaching the
most efficient operational parameters of the equipment before its fabrication. A CFD-DEM coupled in one-way
analysis join two distinct methods of calculation in a single solver, evaluating the iterations between fluid and
particles. This article uses the CFD-DEM coupled analysis studying a filtration equipment that transport slurry
(fluid + particles) to different exits. A rotational valve restraining the main exit, creates a raising pressure location
forcing the slurry to go through a porosity region, with the objective to reduce the number of particles in the
exiting water. It was possible to notice the behavior expected, as the influence of fluid in particles motion and the
possibility to visualize the slurry flow to the exits, showing the regions where the slurry flow has preference to go
through. Good visual results are demonstrated, indicating where the porosity media needs to be cleaned with more
frequency avoiding clog.

On the accuracy of time-stepping methods for flow stability analysis

Marlon Sproesser Mathias, Marcello A. F. Medeiros — Tue, 09 Jul 2024 00:00:00 +0000

Computing the linear stability modes of a flow requires obtaining the eigenmodes of the Jacobian matrix
of its governing equations. For bi-global and tri-global stability analysis, this matrix is very large, which poses a
challenge for solving its eigenproblem. Time-stepping methods are one of the possible solutions for this problem,
as they do not require explicitly building this matrix. One advantage of this class of methods is their relative ease
of implementation, as it can treat the flow solver as a black box, which is integrated into the rest of the algorithm.
The routine calls the flow solver multiple times with different initial conditions to observe the flow behavior. We
study the trade-off between two of the parameters that must be chosen when setting up a case: The length of time
each call to the flow solver will last and the total number of iterations. Longer call times allow the algorithm
to converge in fewer iterations but each one is more costly. The available literature indicates that for a constant
product of call time by number of calls, the accuracy should be roughly the same. We seek both upper and lower
boundaries for the call time length as well as an optimum value that will generate the most accurate results for a
given computational cost.

DNS of a small roughness immersed in a boundary layer: body-fitted and approximated methods comparison

Fernando H. T. Himeno, Marlon S. Mathias, Marcello A. F. de Medeiros — Tue, 09 Jul 2024 00:00:00 +0000

The laminar to turbulent flow transition often initiates from small and irregular disturbances which inter-
act with boundary layers. At some specific amplitude and frequency band, these disturbances generate Tollmien-
Schlichting (T-S) waves which may evolve leading to turbulence in such a process that is very sensitive to the

surface smoothness. Account the effect of tiny roughnesses commonly represent a great difficulty to experimen-
tal and numerical studies. Here we present some of these limitations observed on simulating a rectangular and

localized small roughness placed on zero-gradient flat plate. This study is conducted using a compressible DNS
code at a low Mach regime. We also compare the numerical results obtained by two approaches used for modeling
such a small roughness: a) meshing the element and applying immersed walls conditions and b) approximating
the roughness effect by a non-homogeneous condition on the plate surface at roughness location. Preliminary
results from bidimensional simulations shows that the second approach, b), might present a small phase shift and
low amplitude mismatch when compared to the meshed element. In contrast, we also observe the higher cost on
simulating tiny roughnesses with immersed walls.

Uma formulação baseada em posições para análise 2D de interção fluído estrutura com contato estrutural

Darcy H. F. R. Moreira, Rodolfo A. K. Sanches — Tue, 09 Jul 2024 00:00:00 +0000

Entre os problemas de escoamentos de fluido com contornos moveis, os casos em que há mudanças
topologicas no domínio do fluido sao bastante desafiadores. Essas mudanças podem acontecer devido a efeitos de
superfície livre, como problemas de quebras de ondas, ou devido ao contato estrutural em alguns problemas de
interação fluido-estrutura. Na literatura, com relação ao método dos elementos finitos aplicado a esses problemas,
varios trabalhos tem sido realizados empregando mêtodos de captura de interface. Tais métodos consideram a
interface movel como um contorno imerso que se move dentro de uma malha de fluido fixa. Mais recentemente,
surge um paradigma combinando elementos finitos e metodos de partículas (PFEM), onde fluido e estrutura são
descritos na formulação Lagrangiana. Neste trabalho, tendo como base o PFEM, emprega-se uma formulação
baseada em posições nodais para o meio sólido e posições de partículas para o meio fluido. Assim, gera-se uma
malha de elementos finitos tendo como vertices as partículas, resolvendo-se as equac ̧oes do movimento em descrição
Lagrangiana. As altas distorções da malha do fluido são superadas pela combinação do remalhamento com o
conceito de partícula a cada passo de tempo, atualizando a configuração de referência (descrição Lagrangiana
atualizada). O contato estrutural e considerado por uma abordagem de nó-a-segmento, e a integração no tempo para
ambos, solido e fluido, e realizada pelo método alpha-generalizado. O acoplamento fluido-estrutura e facilmente
implementado de forma monolitica, uma vez que os parametros nodais do fluido e da estrutura são as posições
atuais. Neste artigo, consideram-se problemas em estado plano de deformação, sendo utilizados elementos finitos
triangulares isoparametricos de aproximação cúbica para modelar a estrutura e elementos finitos triangulares de
aproximação linear para o fluido. Conforme demonstrado pelo exemplo numérico apresentado, a formulação
proposta se mostra qualitativamente robusta e com potencial de ser aplicada a diversos problemas, incluindo
problemas de interação sangue-válvulas vasculares.

Application of double Helmholtz resonators in an ICE intake manifold to increase the air mass flow rate

Wender P. de Oliveira, Sérgio de M. Hanriot, Jaqueline M. Queiroz — Tue, 09 Jul 2024 00:00:00 +0000

Wave phenomena that occur in the intake manifold can either increase or decrease the volumetric
efficiency of internal combustion engines (ICEs). In this work, a numerical and experimental investigation is
carried out to evaluate the influence of the intake manifold components on the intake flow rate. In order to calculate
its natural frequency, analytical expressions were developed using the acoustic theory by means of the Transfer
Matrix Method (TMM). The numerical results were obtained using a one-dimensional computational code based
on the Characteristics Method. The experimental tests in unsteady condition were conducted using a flow test
bench equipped with a four-cylinder engine in two conditions: with only two intake valves operating and with all
four operating. The numerical and experimental results were compared and a good agreement between the data
was observed, thus confirming the numerical code's capacity to reproduce this type of phenomenon. The insertion

of the double-chamber Helmholtz resonator increased the air mass flow rate more significantly in the four-
cylinders configurations, compared to the two-cylinders manifolds. The two-cylinders configurations had an

increase in flow rate up to 38.6% in the speed of 1200 rpm, while the higher increase in the four-cylinders with
the insertion of the resonator was only 3.4% in the speed of 1600 rpm.

A Parametric Study of Breaking and Coalescence Mechanisms: Qualita- tive Analysis of Surface Tension Influence via Computational Simulation of Two-Phase Flow in an Upward Bubble Column.

Tue, 09 Jul 2024 00:00:00 +0000

The vast applicability of the gas-liquid multiphase flow in bubble columns within the engineering fields
related to the biochemical, oil and gas, as well as the steel industry, it makes for a compelling research subject. This
paper focuses on analyzing the quantitative influence of the surface tension over bubble breaking and coalescence
mechanisms using VOF multiphase flow and RANS SST κ − ω to treat the turbulence related features. The
simulations were performed by ANSYS Fluent fluid dynamics tool and they exhibit good agreement when properly
validated using the axial velocity profile in comparison to other numerical simulations and experimental data
available in the literature. Moreover, the results reveal an interesting behavior of the diperse phase as the surface
tension was gradually descreased: the disperse phase’s inertia is reduced while the bubble breaking mechanism
gets more intense. In view of the results regarding the topology, it allows for a broader investigation of the impact
of different parameters on the interaction of the phase dynamics, in particular breaking and coalescence processes.

Iteration error estimation in Computacional Fluid Dynamics using a new Empirical Estimator

Caroline Dall’Agnol, Carlos H. Marchi, Diego F. Moro — Tue, 09 Jul 2024 00:00:00 +0000

This study aims to improve the techniques for estimates of iteration errors, through the use of a
new estimator. The new estimator provides estimates of iteration errors based on variables convergence rate.
Its performance was tested in two one-dimensional steady-state mathematical models: Poisson’s equation and
advection-diffusion equation, discretized through the Finite Difference Method (FDM). The numerical schemes
used were CDS and CDS-2 (Central Difference Scheme), for first and second order derivatives, respectively. The
systems of equations resulting from the discretizations were solved by the TriDiagonal Matrix Algorithm (TDMA)
and Gauss-Seidel (GS). The solver TDMA was used to obtain the exact solution and the solver GS to estimate the
errors at each iteration. Two variables were chosen to evaluate the results: function value at the central grid point
(local) and the average value of the function (global). The codes were implemented in Fortran 95, with quadruple
precision, in the Microsoft Visual Studio Community 2013. The results showed that the proposed estimator has a
performance similar to the ones already existing in the literature and that it is necessary to improve the estimates in
the initial ranges of the iterative process and in the final ranges, where the rounding error becomes more significant.

CFD APPLIED TO THE SIMULATIONS OF THE ANGLE OF ATTACK AND FLUTTER DERIVATIVES OF AN AIRFOIL NACA0012

Lucas Lucinda de Sa ́, Patrícia Habib Hallak — Tue, 09 Jul 2024 00:00:00 +0000

This paper presents a study of the aerodynamic behavior of a NACA0012 airfoil modeled in two dimensions
using computational fluid dynamics. In the first analysis, the aerodynamic lift and drag coefficients were obtained
for a range of angles of attack for Reynolds number equal to 700000. The kωSST turbulence model was employed,
and the model has no displacement. The second analysis lies in the identification of the flutter derivatives in
motion-related fluid forces exerted on an airfoil, with Reynolds number equal to 800. The methodology is based
on the idea proposed by Le Maıtre et al. [1], which assumes a linear relationship between force functions and the
laws of motion of the airfoil so that superposition in both frequency and freedom spaces is allowed. To obtain
the flutter derivatives a known sinusoidal vibrations were applied in the airfoil mid-chord. With the response
of these coefficients and using Fourier transforms for the treatment of their signals, the flutter derivatives are
subsequently calculated. A numerical model to solve the incompressible Navier-Stokes equations is proposed
using the OpenFOAM CFD free code. The results from both sets of the simulation were compared with those from
the literature, validating the numerical models.

Investigation of SST and LES turbulence models in the analysis of the wind action on a suspension bridge via CFD simulations

Montiel, Jose Emanuel da Silva, Correa, Laís, Kurokawa, Fernando Akira — Tue, 09 Jul 2024 00:00:00 +0000

In recent years, the use of computational techniques for fluid dynamics for the quantitative prediction of
flow characteristics has grown exponentially. With the advance of computational technology, CFD (Computational
Fluid Dynamics) simulation of numerous complex problems in various engineering areas, such as fluid-structure
interaction, became possible. However, some difficulties appear when working with these problems using the
CFD approach. In general, flows are turbulent with high Reynolds numbers, which makes it necessary to use a
turbulence model. Thus, it is very important to use an adequate turbulence model, especially when it is intended to
analyze the dynamic response of the bridge deck, where it is essential to find out the effect of the vortex shedding.
In this sense, the main objective of this work will be to investigate the turbulence models SST and LES via CFD
simulation in fluid-structure problems one way, in order to analyze the behavior of the wind action on a cross
section of suspension bridge. For this, the Strouhal number and the aerodynamic coefficients will be obtained:
drag, lift and moment of the sectional model submitted to a wind flow with a determined velocity and different
angles of attack.

A STABILIZED PRIMAL HYBRID FINITE ELEMENT FORMULATION FOR THE ELASTIC WAVE EQUATION

Juliano D. B. Santos, Abimael F. D. Loula — Tue, 09 Jul 2024 00:00:00 +0000

We present a stabilized hybrid finite element formulation for the elastic wave equation in two space
dimensions. The proposed hybrid formulation is characterized by the introduction of auxiliary variables on the
edges of the elements, which are identified as Lagrange multipliers associated with the trace of displacement field.
A second order explicit finite difference method is adopted in the time domain. It is well known that when this
second order ”explicit” finite difference approximation in time is combined with classical Continuous Galerkin
finite element approximations in space it does not lead to a really explicit method, given that the consistent mass
matrix in this case is non diagonal. With the proposed formulation it is possible to obtain really explicit methods
with block-diagonal mass matrices. Even diagonal mass matrices can also be obtained, as long as the Lagrangian

interpolation functions are centered in the Gauss integration points. Convergence studies are conducted on uni-
form and on randomly generated non-uniform quadrilateral meshes. Meshes with straight or curved quadrilateral

elements are considered, associated with Lagrangian bases and with Qk and Pk monomial bases.

Computational evaluation of wind loads on structures

Matheus B. Seidel, Geraldo J. B. dos Santos, Jose M. F. Lima — Tue, 09 Jul 2024 00:00:00 +0000

The verticalization of buildings in large cities has been a growing trend in recent decades due to the
advancement in technology and construction materials, which have allowed the construction of taller and more
slender buildings and, therefore, more sensitive to aerodynamic loads. These loads are usually determined by
aerodynamic coefficients that are traditionally obtained through standards or experiments in wind tunnels. Despite
the validity of these methods, standards are invariably limited in architectural complexity and wind tunnels are not
easily accessible, due to their scarcity and high cost. In this perspective, the use of numerical modeling presents
itself as a viable alternative in the aerodynamic study of structures in Computational Wind Engineering. Thus,
this work aims to perform the aerodynamic analysis of structures using numerical modeling and to compare the

aerodynamic coefficients calculated with the Brazilian standard and numerical and experimental data from litera-
ture. Numerical experiments are presented at an increasing level of complexity, from two-dimensional structures

with laminar flow to three-dimensional structures with turbulent flow and two way fluid-structure interaction. The
results obtained are validated with papers published in the scientific literature and demonstrate that the use of
computational modeling in Wind Engineering guarantees an acceptable level of accuracy.

Acoustic performance of double panels in closure systems with point connections

Tue, 09 Jul 2024 00:00:00 +0000

The transmission loss (TL) that occurs though closure system panels used in construction buildings is
a parameter used to evaluate it acoustic performance. TL depends on the frequency of the incident sound, the
type of fixation of the panels to the structure as well as other factors and its curve can be obtained through tests
or graphic methods based on empirical formulation, which can be converted into computational models. In this

work, TL is evaluated in compositions of double closing systems and the highest TL correlated with the Line-
Line (LL) connection is verified, which is when the panel is directly fixed to the metal profile of the closing

system on both sides. Double panels composed of expanded polystyrene (EPS), plasterboard (GEA) and
cementitious board (PLC), with glass wool (LVI) in the air cavity between the panels, are analyzed. Simulations
are performed in a computational model, based on a graphic method, developed to estimate TL in single and
double panels. The frequencies of 500, 1000 and 2000 Hz are considered. It is verified that the EPS panel
provides higher TL values of 68dB, 74 dB and 80 dB for the respective frequencies. The GEA panel presented
values of PT of 47 dB, 52 dB and 43 dB, respectively. Furthermore, the PLC panels presented TLs of 57 dB, 63
dB and 69 dB. Therefore, the EPS double panel is the one that provides the best acoustic performance in terms of
sound transmission losses at the frequencies considered. The computational model could help in the
determination of this parameter in double panels, interspersed with glass wool and Line-Line connection,
allowing a quick analysis of the acoustic performance of the panels.

Numerical simulation of labyrinth seals for pulsed compression reactors (PCR)

Tue, 09 Jul 2024 00:00:00 +0000

A sealing system is proposed using labyrinth seals to minimize gas leaks, for which triangular,
rectangular, and trapezoidal geometric parameters are evaluated. For each one of the geometries a group of
parameters were optimized minimizing the gas leakage, using the multi-objective genetic algorithm (MOGA),
updating in each step the geometry employing a user defined Ansys SpaceClaim Python algorithm. For a new set
of parameters (height, width, and angle of the shape, space between cavities, and piston length) the script creates
the boundary geometry and meshing. The CFD analysis evaluates the gas leakage for the given geometry and
constant boundary conditions (10 MPa inlet pressure, 25 m/s piston speed, 40 m piston/cylinder gap, and ideal
methane gas), and uses this data as input to MOGA. The input set values were reduced to manufacturable
quantities, so finite or discrete values can be used across the iterations. The analysis of distributed properties such
as velocity, temperature, and pression, inside the cavity, showed a steady laminar regime with an energy loss due
to entropy increment. The most sensitive parameters are the piston length and height cavity for all shapes. The
trapezoidal shape presented the best performance in minimizing the mass flow leakage.

A stabilized Arlequin formulation for fluid-structure interaction analysis

Tue, 09 Jul 2024 00:00:00 +0000

Fluid-structure interactions are multi-physical problems which may present complex coupled and local-
ized phenomena. In the literature, most of the methods for these rely in two main approaches: interface tracking

and interface capturing families of methods. In the interface tracking methods, fluid and solid discretizations are
conform to the fluid-structure interface and its location is a part of the solution, requiring an additional step (mesh
moving or re-mesh) when it changes. On the other hand, interface capturing methods employ immersed boundary
techniques to describe the fluid-structure interface position in an Eulerian domain. In this work, an alternative

approach is presented. Frame structures with Timoshenko-Reissner kinematics are modeled in the positional ver-
sion of the finite element method, a simple alternative for the simulation of nonlinear dynamic problems. The

fluid, described by the incompressible Navier-Stokes equations, is modeled in the Arlequin framework, a domain
decomposition method based on the superposition of a local model (located in a particular region of interest) to
a global one, unsuitable to capture the localized effects. The communication between models is provided by a
Lagrange multiplier field, defined in a subset of the overlapping zone. This strategy has been applied successfully

for the simulation of incompressible flow problems with fixed overlapped models, i.e., in an Eulerian descrip-
tion. In this work, the methodology is extended to an Eulerian-ALE version, covering the case of a moving local

model, applicable to the simulation of fluid-structure interactions involving large structural displacements. The
resulting model is coupled by a strong Dirichlet-Neumann partitioned scheme with Aitken’s relaxation. Finally,
flexibility and accuracy of our technique are evaluated by numerical tests. As main advantages, one can point the
flexibility on the treatment of problems with large rigid body motion, such as turbines and rotors (a drawback of
interface tracking methods, that sometimes requires re-meshing steps), while keeps a suitable discretization close
to the fluid-structure interface throughout the analysis (not always possible when interface capturing methods are
employed).

Nonlinear Acoustic Wave Propagation in Stratified Media

F. P. Piccoli, L. C. de Jesus, J. T. A. Chacaltana — Tue, 09 Jul 2024 00:00:00 +0000

The acoustic waves propagation is a subject of great application in several areas of engineering, for
example in marine seismic for the detection of underwater objects, in hydrography and navigation for the detection
of the seabed, among others. In this work, a nonlinear model for the propagation of P-waves in a stratified
environment is developed. Starting from the nonlinear equations that governs the fluid motion of a compressible
fluid with mass source we obtain the nonlinear equations for the acoustic P-wave propagation. The set of equations
in the conservative form are solved numerically using the finite difference method applying the explicit strong
stability-preserving (SSP) multistep method. In order to achieve higher order accuracy in time, the fourth-order
SSP Runge–Kutta time discretization was implemented and the Courant-Friedrichs-Levy (CFL) criterion must be
satisfied for an adaptative time step along the simulation. The second order spatial derivatives are solved using the
minmod based MUSCL spatial discretization. A numerical code is written in Fortran language and simulations
with a Ricker-type pressure source were performed. Numerical results are in good agreement with those reported
in the literature.

Analysis of the fluid-structure interaction of a semi-rigid frame

Tue, 09 Jul 2024 00:00:00 +0000

Fluid-Structure Interaction (FSI) is characterized as a non-linear multi-physical problem and is present
in the most diverse areas of engineering, such as civil, mechanical, naval, aeronautical engineering works, among
others. In steel structures, the forces arising from the wind are actions of relevant importance and due to their
dynamic characteristics, many uncertainties exist, hindering the work of the structural engineer. Among the types
of connections used in practice, the bolt connections stand out for their simplicity and speed in the process of
assembling steel structures, both small and large. The large number of variables existing in this type of connection
- thickness of the plates involved in the connection, diameter and positioning of the bolts, etc. - however, they
make it difficult to analyze their behavior. In this work, a fluid-structure coupling problem is studied considering
low velocity flows. Due to the interdisciplinary of the theme, it is necessary to study three different subjects: the
Computational Structural Dynamics (CSD), the Computational Fluid Dynamics (CFD), and the coupling problem.
The objective of the work is to analyze the physical phenomenon of the fluid-structure interaction in a frame of
a floor with semi-rigid connections, adopting a model compatible with this situation. This model includes all the
necessary considerations for a bolt connection, specifically: contacts between plate and nut; bolt head and body;
contact between plates, as well as friction between them; restressing on the bolt. The coupled problem is solved
using Arbitrary Lagrangian-Eulerian (ALE) approach for the fluid domain, while for the solid domain a Lagrangian
approach is used. ANSYS

R software was used to model and solve the mathematical equations of the coupling
problem. This problem consists of analyzing the dynamic behavior of the structure when it is subjected to the
action of the load from random winds.

Interpolation methods using radial function kernels in non-orthogonal grids

F. Queiroz, A. Frasson, C. Loeffler, J.T.A. Chacaltana — Tue, 09 Jul 2024 00:00:00 +0000

In fluid dynamics, the numerical solution of time-dependent partial differential equations the values for
the dependent variables are calculated at discrete points. When the grid used is structured and orthogonal, there
are well-established methodology to perform the interpolation of the variable for any point of interest that does

not coincide with the points of the grid. This is not simple when it comes to a grid that is unstructured and non-
orthogonal. Non-orthogonality introduces a greater number of unknowns than equations, in this case it is necessary

to balance the number of unknowns with the number of equations and interpolate the information for the remainder
points that will be grouped as source terms. In this work, several bases of radial functions of global and compact
support interpolation were tested in orthogonal and non-orthogonal grids. The numerical results were compared
with those obtained by analytical solution and good agreement was found. Results are organized in terms of
precision and the computational effort required.

Acoustic wave propagation in non-homogeneous media

Luana Maria Kiefer de Araujo, Felix Luis Galeano Queiro, J. T. A. Chacaltana — Tue, 09 Jul 2024 00:00:00 +0000

The propagation of acoustic waves is a subject of great interest in seismic prospecting for oil, where
the medium of wave propagation is not homogeneous. In this work, a linear model for the acoustic P-wave
propagation in a non-homogeneous media is developed. Starting from the nonlinear equations that governs the

fluid motion of a compressible fluid with a point mass source we obtain the linear equation for the acoustic P-
wave propagation in heterogeneous medium. This second order partial differential equation is solved

numerically by the explicit finite difference method. Two types of boundary conditions were implemented in the
numerical model. One of this is pure reflection and the other is of the type "free radiation". The numerical
method is second order in the time and space. The time step satisfies the Courant-Friedrichs-Levy (CFL)
restriction. A numerical code is written in Fortran language and simulations with a source term of the type
"Mexican hat" were performed. The numerical results are compared with those found in the literature and a good
agreement was obtained.

Técnica de Movimentação e Suavização de Malha Baseada na Teoria da Elasticidade Linear Aplicada ao Acoplamento Fluido-Estrutura

Nicolas H. S. de Carvalho, Alessandro R. E. Antunes, Mariana F. S. Villela — Tue, 09 Jul 2024 00:00:00 +0000

Fluid-Structure coupled problems are of great interest in industry, such as aeronautics, naval, oil, etc. In
this kind of phenomena, interaction between different physics occur, therefore they cannot be analyzed separately.
The great challenges in analysis of problems involving FSI is the fact that the computational mesh that discretizes
the fluid domain, undergoes major deformations caused by displacements and/or structural deformations. An
Arbitrarian Lagrangian-Eulerian discretization is used, considering the computational mesh as a physical field.
Additionally, it is necessary to have an adequate treatment so that the computational mesh absorbs these
movements, avoiding excessive deformations. In this work, a mesh movement and smoothing technique is
analyzed, where each element of the mesh can be considered as a deformable structure, with the local Young
module defined in terms of the characteristic length of the element. Furthermore, an edge swap technique was
implemented, which associated with a mesh movement technique allows great structural displacements. Here the
fluid is incompressible, and structure is a rigid body. The study of parameters was performed, considering the
stiffness of the elements, so that there can be large displacements of the structure without excessive mesh
deformation and quality decrease of the elements. Validation results were obtained.

A study of time integration methods for 3D FEM solution of incompressible fluids governed by the Navier-Stokes equations

André S. Müller, Henrique C. Gomes, Eduardo M. B. Campello — Tue, 09 Jul 2024 00:00:00 +0000

This work investigates the influence of using different time integration methods for the mixed finite

element formulation of tridimensional unsteady incompressible fluid flow problems governed by the Navier-
Stokes equations. A classical Eulerian approach is followed to describe the fluid. A Newton-Raphson scheme is

devised to solve the resulting non-linear equations within every time step of the time integration. In order to
ascertain the accuracy and efficiency of the adopted methods, numerical simulations of tridimensional unsteady
flow of an incompressible fluid around a cylinder are analyzed and compared against benchmark solutions.

Modeling and numerical simulation of crack propagation using peridynamics

Adair R. Aguiar, Tu ́lio V. B. Patriota — Tue, 09 Jul 2024 00:00:00 +0000

Different damage models in peridynamics have been proposed to predict dynamic fracture of brittle

materials. The prototype micro-brittle (PMB) material and its modified version, the DTT model, concern a bond-
based constitutive model together with bond-breakage damage criteria. These models consider only the elongation

of peridynamic bonds with fixed Poisson’s ratio. To circumvent this limitation, the state-based model LSJ was

recently proposed, which incorporates a dilatation term in its constitutive relations. It concerns an interaction-
breakage damage criterion that has two distinct damage factors, one associated with elongation and the other one

with dilatation. We modify the LSJ model to obtain bond-breakage damage criteria, called the LSJ-T model. In
addition, we also introduce bond-breakage criteria in a two-dimensional ordinary, state-based peridynamic model,
which we call the LPS-T model. To compare the crack propagation paths obtained numerically from these damage
models, we consider a thin glass plate with an initial semi-crack under mode I loading. Overall, the models were
able to grasp the main characteristics of crack propagation, such as crack propagation speed, branching, and crack
pattern. The modified version LSJ-T and DTT were the only ones presenting symmetry and no arrested branches
in the crack paths, indicating a numerically stable crack propagation.

A discrete element and finite element coupled scheme for particle- structure interaction

Ricardo A. Andreotti, Eduardo M. B. Campello, Alfredo G. Neto — Tue, 09 Jul 2024 00:00:00 +0000

This work presents a computational framework for the simulation of problems wherein discrete solid
particles may interact with thin flexible structures, such as beams, shells and membranes. The particles are assumed
to be spherical, following a DEM (discrete element method) approach, whereas the flexible structures are described
by large displacements/finite rotations kinematics, leading ultimately to large deformations finite element (FEM)
formulations. The DEM model is implemented within a Fortran program called PSY (Particle System Analysis
Program), and the FEM model within a C++ program called GIRAFFE (Generic Interface Readily Accessible for
Finite Elements). Both are in-house codes that have been extensively developed by two of the authors in the past
years. The models are coupled in a staggered, implicit way embedded within a time-marching integration scheme
wherein the two codes communicate with each other in an efficient, run-time, memory-sharing way that truly
boosts up computational performance. The aim of this work is to present the computational scheme devised to
couple both models, which ultimately led to a unified project called GIPSY. A few possibilities of such robust
DEM-FEM scheme are illustrated by means of numerical examples.

CHABOCHE SINGLE MODEL CALIBRATION FOR BAUSCHINGER EFFECT

Daniel de O. Fernandes, Carla T. M. Anflor, Beatriz F. Souza, Besim Baranoglu — Tue, 09 Jul 2024 00:00:00 +0000

In this work a study of Chaboche single model for Bauschinger effect characterization was performed
by using the Ramberg-Osgood relation to determine the Chaboche constants ( and

). A series of adjustment
were made to obtain specific values, and from these values a curve fitting was performed to determine Chaboche
constants. The analysis of Bauschinger effect was executed by finite element method and compared with
experimental data available in the literature. The results showed good agreement in comparison to experimental
analysis.

Unifying the Basic Phenomenology of Monotonic Unidimensional Plasticity

Luiz Claudio Oliveira, Raquel Santini Leandro Rade — Tue, 09 Jul 2024 00:00:00 +0000

Stress and strain quantities and related characteristic subdomains of a common monotonic stress-strain
diagram are studied. “Component quantities” are explicitly defined, encompassing many components which,
although found throughout the literature —e, p, –Y, –Y—, are not usually comprehensively explored together
from one single source. Those quantities are used to form planes (component, component) defining characteristic
subdomains, which contain an exclusive type of curve to be linearized. An environment is thus constructed,
offering a broad context of subdomains where linearized relations can be worked out. As a specific application,
using such components and a logarithmic linearization it is possible to unify the unidimensional monotonic
solicitation in tension/compression from one single source of equations, comprising classical formulations —
Ramberg-Osgood, Hollomon, Swift, Ludwik— and other ones not widely knwon nor used. Numerically (or
algebraically), there are two independent sets of elastic plus plastic equations relating the quantities , ep=–Y,
, ep=–Y, p=–e=–(/E), plus accumulated quantities acc and acc from a previous plastic deformation.
Diverse formulations —e.g. logarithmic and/or polynomial ones— can be specified for each subdomain or model.
Such final models will comprise series of computer implementable, adjoined numerical expressions. Notice that
with this comprehensive context of variables and equations some small inconsistencies in the basic formulation of
unidimensional plasticity are revealed, which are qualitatively important for the due description of the
phenomenon of plasticity, specially when developping into a more complex equationing.

Phase-field modelling of diffuse fracture with FEM

Hugo M. Leão, Roque L. S. Pitangueira, Lapo Gori — Tue, 09 Jul 2024 00:00:00 +0000

In damage models, cracks are considered in a smeared way, without any geometric representation
of the region where the crack takes place, and the energy released is used in crack growth that is controlled by
the energy fracture parameter. Phase-field models consider a diffuse and smooth crack that belongs to a certain
volume region, where a function describes the crack density. In that region each point has a field variable that
quantifies the material degradation. The phase-field techniques allows to detect crack paths and its bifurcation
without having a pre-existent crack. The purpose of this work is to present some phase-field models implemented
in the INSANE (Interactive Structural ANalysis Environment system) software, an structural analysis open-source
software developed by at the Structural Engineering department (DEES) of the Federal University of Minas Gerais
(UFMG). This work opens a new research line inside the INSANE Project. Some preliminary results will be
presented.

H-FEM AND FSDT TO APPROACH THE FREE AND FORCED VIBRATION OF A GRAPHENE SHEET USING A NON-LOCAL CONTINUUM MECHANICS THEORY

Oscar A. Garcia, Rodrigo Rossi — Tue, 09 Jul 2024 00:00:00 +0000

The allotropic forms of carbon as nano tubes and more recently graphene sheet has gained significant
notoriety in the last two decades where its use has been spread in the most diverse areas such as composite
materials, electronics, medicine, fine chemistry, among others. Within this context, the mechanical behavior of
wave propagation at the nanoscale level has received special attention for its relevance in the application of
transport problems of molecules, sensors for detecting gas atoms, resonators for high frequencies, among
others. Recently, classical approaches to nanoscale problems with atomic and hybrid models, more accurate but
with high computational cost, have left some room for approaches that use the principles of continuum mechanics
with the classic (local) and non-local versions. The results observed in the literature on free vibration problems,
obtained with non-local continuous mechanics, have been closer to the results of molecular dynamics than those
obtained with classical or local continuous mechanics. In this work, the authors propose an approach using the
non-local continuum mechanics for the free and forced vibrations problems in graphene sheets using the
approximation spaces obtained with Hermite finite elements (H-FEM) with regularity

Ω, 1,2 together
with the first order plate model “First Shear Deformation Theory” (FSDT). This approach intends to investigate
some aspects of the analyzed problem to improve the proximity of the response to that obtained using molecular
dynamics: provide the regularity requirements of the non-local model equilibrium equations; improve accuracy in
natural modes and frequencies using highly regular approximation spaces; improve the accuracy of the response
of natural modes and frequencies by incorporating the rotational inertia introduced by the kinematic FSDT model.

A numerical comparison between the additive and multiplicative decomposition applied to large strain thermo-elastic models

Pericles R. P. Carvalho, Humberto B. Coda, Rodolfo A. K. Sanches — Tue, 09 Jul 2024 00:00:00 +0000

In this work, we develop a numerical framework, using the finite element method, to perform two-
dimensional analysis of solids with thermo-elastic constitutive model, subject to large displacements and large

strains. Both the thermo-elastic model and the heat conduction equation are derived from the first and second
laws of thermodynamics, where the latter is expressed by the Clausius-Duhem inequality. The formulation uses
the concept of Helmholtz free energy, from which the stress and the entropy are derived. The elastic and thermal
parts of deformations are distinguished by two main strategies: the additive decomposition of the Green-Lagrange
strain tensor, and the multiplicative decomposition of the deformation gradient. For each, both the linear and
exponential thermal expansion laws are considered, and a neo-Hookean model is applied for the elastic part.
Numerical examples are proposed to show the differences and limitations of the applied models on moderate and
large strain levels.

h-adaptative strategy proposal for Finite Element Method applied in structures imposed to multiple load cases

João Pedro Furrier Rosa Pacheco, Jéderson da Silva, João Luiz do Vale — Tue, 09 Jul 2024 00:00:00 +0000

This paper proposes an h-adaptive strategy for structures subjected to multiple load cases to evaluate
and control intrinsic discretization errors of the Finite Element Method. The proposed strategy consists of an
iterative process (i) initially, for each loading case, the ideal size of each finite element is determined by an
estimation of its error; (ii) then, an intersection of the size results is conducted, and a new mesh is generated by
using the Bidimensional Anisotropic Mesh Generator. These two steps are repeated until the relative global error,
based on energy, is less than a previously arbitrated value, considering all load cases separately. The computational
routine implementation is carried out in Matlab®. A posteriori error estimator based on stress recovery,
considering superconverged points, is used for evaluating the discretization errors. Besides that, the definition of
the new finite element mesh is achieved by applying two classical h-adaptive techniques (named in this work as
ZZ and LB) whose results are compared via an evaluation of local and global quality parameters. Both techniques
are underpinned on the equidistribution criterion of the error based on energy norm and depend on a relationship
of these discretization errors comparing two subsequent meshes. A Michell’s structure is considered and the results
obtained show that the proposed h-adaptive strategy results in a mesh with a relative global error below the
allowable value for all loads. Finally, comparing both h-adaptive techniques, LB presents a smaller variation of
the number of elements between iterations, leading to a more stable process with meshes that have better local and
global quality parameters.

Numerical strategies for obtaining strut-and-tie models via topological optimization

Tue, 09 Jul 2024 00:00:00 +0000

The strut-and-tie model is widely used for analysis and design of reinforced concrete structures under
plane stresses state. To apply this model, it is necessary to define strut-and-tie systems that represent the flow of
stresses generated in the analysed structure. In order to make the concept of the model less dependent on the
designer’s experience, in many situations, like regions or structures with geometric or static discontinuity, this
strut-and-tie model is defined through an evolutionary structural optimization (ESO) considering linear isotropic
material, which provides the automatic generation of strut-and-tie models. The evolution criterion adopted by the
topological optimization method considers the elimination of less requested elements in terms of tension, based
on the elastic-linear analysis. The focus of this work is on the development and implementation of different
strategies to control the way these elements are removed, which lead to different final configurations. In this
context, it is possible to obtain optimized solutions to complex problems involving reinforced concrete structures.
Two practical applications are presented and two of them had their results compared with the results provided in
the literature to validate the efficiency of the algorithm proposed.

Numerical investigation of bifurcation instability in constrained minimization problem of elasticity

Adair R. Aguiar, Lucas A. Rocha — Tue, 09 Jul 2024 00:00:00 +0000

There are problems in classical linear elasticity whose closed form solutions, while satisfying the
governing equations of equilibrium and well-posed boundary conditions, predict material overlapping, which is
not physically realistic. One possible way to prevent this anomalous behavior is to consider the minimization of the
total potential energy of classical linear elasticity subjected to the local injectivity constraint. In two dimensions,
the corresponding constrained minimization problem has a solution, which may not be unique. To investigate this
class of problems, we consider the equilibrium problem of a cylindrically anisotropic disk subjected to a prescribed
displacement along its boundary. We search numerically for either radially or rotationally symmetric solutions
defined in a one-dimensional domain. Our discretization strategy uses linear finite elements and yields convergent
sequences of solutions at a very low computational cost when compared to results reported in the literature. It
is clear from our investigation that a small perturbation must be introduced to obtain the rotationally symmetric
solution, for otherwise the solution obtained is radially symmetric. The total potential energy from the rotationally
symmetric solution is lower than the corresponding energy evaluated from the radially symmetric solution.

A simple fully nonlinear Kirchhoff-Love shell finite element

Matheus L. Sanchez, Catia C. Silva, Paulo M. Pimenta — Tue, 09 Jul 2024 00:00:00 +0000

The current work develops a new simple Kirchhoff-Love shell finite element model for reliable and
efficient simulation of thin nonlinear structures. This new shell triangular element has 6 nodes and uses penalty
methods to approximate displacement C1 continuity. The DOF’s are the displacements u at the six nodes and an
incremental scalar rotation parameter φΔ at mid-side nodes. The incremental rotation vector αΔ (incremental
Rodrigues parameters) and incremental rotation tensor Q at the mid-side nodes are computed at element level by
solving simple equations. The displacements “u” are interpolated by quadratic polynomials from the nodal values
as usual. Simulations are done comparing its results to other numerical models in order to verify model reliability.

Computation of mooring systems’ forces of vessels berthed at dolphins

Arina L. B. Carvalho, Kalil J. Skaf, Eduardo M. B. Campello — Tue, 09 Jul 2024 00:00:00 +0000

The operational safety of a port terminal is assured by the adequate restriction of the ship's movements
by the mooring system, composed of lines and fenders. In the current practice of structural design, the mooring
system's forces are determined by simplified linear analyzes enhanced by dynamic amplification coefficients.
However, the system's stiffness has physical and geometric nonlinearities. Besides, the main forces acting on a
ship at berth come from environmental sources and have random and oscillatory behavior in nature, which may
induce dynamic responses that exceed the static estimated. This work presents partial results of an on-going
research on the dynamic behavior of a vessel berthed at dolphins and the current design practice simplification's
consequences. Different hierarchical models will be analyzed (linear static, non-linear static and linear dynamic)
at a case study of a Floating Storage and Regasification Unit (FSRU) permanently berthed at dolphins at
Barcarena's Liquefied Natural Gas (LNG) terminal, in Pará, Brazil. The results in terms of the mooring system's
forces will be discussed and dynamic amplification coefficients will be estimated.

A Machine Learning-based Constitutive Model for Nonlinear Analysis via Finite Element Method

Alefe F. Figueiredo, Saulo S. Castro, Roque L. S. Pitangueira, Samir S. Saliba — Tue, 09 Jul 2024 00:00:00 +0000

This paper addresses a machine learning technique in the context of constitutive modelling. Since it
has been proven that multilayer perceptrons with the backprogapation algorithm are capable of approximating any
class of functions, studies have been developed with the objective of using it as approximation functions for the
nonlinear behaviour of complex material media. This is only possible because neural networks have a powerful
adaptability, capability of learning and generalizability. In this context, a multilayer perceptron is trained with
stress-strain results from a nonlinear analysis via finite element method with Mazars material in order to develop a
neural network-based constitutive model. This implementation is carried out with the help of a recognized machine
learning package in order to obtain more accurate results. To validate the proposed constitutive model, the results
obtained through the multilayer perceptron are compared with the ones of the finite element numerical analysis.

A method to evaluate contact pressure distribution of elastic surfaces using LCP and optimization techniques

Milagros Noemi Quintana Castillo, Marco Antônio Luersen, Francisco José Profito — Tue, 09 Jul 2024 00:00:00 +0000

Contact occurs in various mechanical components such as gears, bearing, wheel and rail of trains, for
which contact fatigue is considered the major cause of failure. For this reason, analyze the stresses in the materials
in contact are of great importance at the study of solid mechanics, in particular tribology, because this allows a
prediction of fails related to the corresponding surfaces. Yet, the elastic contact of bodies is a problem of particular
interest in solid mechanic. The contact between deformable elastic bodies is present in the industry and everyday
life, and it is a challenge to identify and estimate the contact area, as well as the pressure and stress distributions
at the interface and develop efficient numerical methods for solving the problem. Within this context, this work
aims to propose and evaluate a method to calculate the stresses and the contact area between elastic bodies
accurately. The adopted method uses a linear complementarity problem (LCP) approach, obtaining its solution
through optimization techniques.

A superconvergent piezoelectric beam finite element

Tue, 09 Jul 2024 00:00:00 +0000

A piezoelectric beam finite element is proposed, where the displacement is assumed to vary in
accordance with the Timoshenko assumption and the electric potential has linear variation through each
piezoelectric layer thickness. The solution of the homogeneous form of the linear differential equations which
describe the behavior of the piezoelectric Timoshenko beam is used as interpolation functions to develop a 2-
node finite element for planar frames. According to the adopted procedure the element has the following
properties: (a) it has the same degrees of freedom as its purely mechanical counterpart; (b) it is free of shear
locking; (c) it is superconvergent, i.e. the computed nodal values are exact with respect to the element
formulation regardless the applied loading pattern. In the solution of the numerical examples, the efficiency of
the developed finite element is illustrated showing that few elements are adequate to precisely capture the static
response for both mechanical and electrical variables.

Estudo do Comportamento de Painéis de Alvenaria Submetidos a Carregamento Lateral utilizando Elementos de Pórtico com Seção Transversal Variável

Tue, 09 Jul 2024 00:00:00 +0000

The lateral load behavior of masonry panels is one of the main concerns when designing masonry
structures and may depend on several parameters, such as panel aspect ratio, properties of the composite material,
and intensity of the compressive axial load. This behavior may be addressed by means of experimental and
numerical tests, and it is generally represented by plotting the lateral load versus lateral deflection curve. A simple
way for obtaining numerically this curve is to consider the masonry wall as a one-dimensional element and perform
a finite element analysis. Based on some assumptions concerning the normal stress distribution, the panel can be
discretized into frame elements whose geometrical properties are evaluated from the portion of the cross-section
subjected to compression. In the case of employing finite elements of constant cross-sections, good results are
obtained only if the mesh is dense enough as to accurately represent the change in the geometrical properties of
the resisting portion of the panel cross-section. In this work, a finite element with variable cross-section is
employed, so the number of elements required for a reliable solution could be reduced. The proposed model is
tested against some experimental results available in the literature for various dimensions, material properties.

Uniform FEM B-Splines in the analysis of free vibration problem in the axisymmetric nano shells in elastic medium using a non-local elasticity theory

Oscar A. Garcia, Rodrigo Rossi — Tue, 09 Jul 2024 00:00:00 +0000

The search for mathematical and numerical models to address problems of nanostructures has gained
centrality in the last two decades. This importance stems from the increasing applications of allotropic forms of
carbon as nanotubes and more recently graphene in high-performance composite materials, resonators for high
frequency, biosensors, gas sensors, among others. In fullerene nanotubes and graphene sheets, the natural
frequencies are of the order of THz, a fact that enabled the application of these materials in ultra-frequency
resonators and sensors based on the dispersion of mechanical waves in solid media. In the simulation of the
dynamic behavior of nanostructures, the molecular dynamics (MD) method is frequently used, however, with a
high computational cost. Recently, low-cost computational approaches based on the principles of non-local
continuum mechanics have been used to include neighborhood effects of fundamental importance in the treatment
of nanoscale problems. In this work, the authors propose the use of non-local continuous mechanics in the approach
of free vibrations of axisymmetric nano-shells on Winkler's foundation modeled by first-order kinematic theories
considering shear deformation (FSDT) and by cubic kinematic theories (TSDT). To increase the accuracy of the
relatively high frequencies (above ten percent of the eigenvalues approximated by the numerical model) the
approximation space will be built according to Uniform FEM B-Spline (U- FEM B-Spline) technique, with high
order and high regularity. The results will be analyzed under three aspects: the sensitivity of the first natural
frequency to variations in dimensions and the nanoscale coefficient; the relative error with respect to a target
frequency; the relative error for a pre-stipulated frequency range.

Mechanical Behavior comparison of aircraft joints modeling

Marco Tulio dos Santos, Rodrigo de Sa Martins, Marcelo Greco — Tue, 09 Jul 2024 00:00:00 +0000

The procedure of structural design for aircraft parts is widely known and discussed in the academy and
in the industry, although it has been improved along the time. It is based on a detailed process of aerodynamics
loads study coupled or not with specifications required by regulatory agencies. Further, several interactions of

analysis are done to define the critical stress state of the structure submitted to load conditions, because it is a com-
plex structure that needs to be often improved and updated (considering the requirement of assembly/disassembly

simplicity). There are several components in an aircraft attached to each other by the use of fasteners, rivets or nuts
made of different materials (aluminum, steel, Inconel among others). In fact, it is not to easy to obtain stress state
of the aeronautical structure for real loading conditions. Further, it is also difficult to calculate the load acting on
each one of the joints. Several studies were already performed in order to obtain the correct understanding of how
actual loads is distributed through the joints. The present work aims to compare results in aircraft joints (focusing
in spar and skin regions), considering three levels of fidelity to understand the differences in the structural response
using different type of modeling approach. Finite Element Analysis modelings made using Nastran software were
performed. Preliminary results show good response agreement even for high and intermediate detail levels. Low
detail level present promisor response as a tool for predesign.

A viscoelastoplastic approach to model nonlinear polymeric materials

André Kühl, Maria A. Polak — Tue, 09 Jul 2024 00:00:00 +0000

This work presents a new viscoelastoplastic model to describe the nonlinear behavior of polymers. In
this paper, an extension of the results published by Kühl et al. [1] and Kühl and Muñoz-Rojas [2] is developed,
considering viscoelastic and viscoplastic strains simultaneously. To model the viscoelastic strain, a master curve
approach is employed, as proposed by Kühl and Muñoz-Rojas. To account for the viscoplastic deformation, a
power law is used, as detailed by Kühl [3]. Therefore, a final viscoelastoplastic model is defined to predict the
behavior of polymeric materials. The procedure proposed in this work is compared to the traditional
interpolation of properties, and a discussion of the results is provided.

Thermomechanical analysis of spherical domes using Geckeler and Finite Element approximations

Tue, 09 Jul 2024 00:00:00 +0000

Structural analysis consists of obtaining the structure’s response to the various actions to which it will
be subjected throughout its useful life. In this work, it is proposed to develop the analytical calculation for the
resolution of a concrete spherical dome, supported on its base, subjected to own and accidental loads. At the
end, the effort diagrams, the stresses and displacements from these approximate analytical methods are obtained,
where these results are compared with the Finite Element Method (FEM). The chosen example is the semi-spherical
dome, where the influence of the different types of loading on these structures is studied, and the variability of their
importance at the expense of changing the element’s geometry. To validate the analytically determined results, a
refined shell-type mesh (S4R8) was initially used in the ABAQUS program. For the convergence of results, the
type of the element was varied in triangular and quadrilateral using the options of elements S4R8, S3, STRI65 and
S4R. In the end, it was concluded that the adherence of the element type is important for approximations with the
least number of elements possible, however, for this type of element, the triangular types with reduced integration
yielded better adherence.

Visual-Inertial Navigation Applied to a Motorboat

Lucas Braga Proença, Davi Antonio dos Santos, Stiven Schwanz Dias — Tue, 09 Jul 2024 00:00:00 +0000

This work is concerned with the problem of state estimation for a small, nine-meter-long motorboat

navigating in a GPS-denied environment. It proposes a visual-inertial navigation method based on a continuous-
discrete formulation of the extended Kalman filter (EKF) for estimating the state vector of the motorboat, which

includes its position, velocity and attitude, as well as the sensors’ biases. The filter relies on inertial measurements,
provided by an accelerometer and a rate gyro, and on position measurements obtained by a panoramic camera
system. By employing Monte Carlo simulation, this work concludes that the proposed method has an estimation
performance comparable to GPS/INS approaches.

ADAPTIVE CONTROL USED IN TWO LINKS OF A ELECTROMECHANICAL ROBOT OF FOUR DEGREE FREEDOM

José Antonio Riul, Paulo Henrique de Miranda Montenegro, Naor Moraes Melo — Tue, 09 Jul 2024 00:00:00 +0000

This work aims to design adaptive controllers to control the position of two links of an
electromechanical robot with four degrees of freedom (4 GDL). The control is performed through simulation,
using models of the links obtained with real system data, through parameter estimation using the recursive least
squares algorithm (MQR). The link identification is carried out in an open loop, using real data collected from
the robot. Adaptive controllers are designed and implemented via the imposition of poles to control the position
of the two links. The controllers are designed in closed loop based on the models obtained for the links. The
control strategy to be used is based on an explicit model of the system. The controllers are implemented through
a computer program. The excitation and output curves of the two links are shown, and as a result the output
curves of the models of the two links, in open loop and the output curves of the links under the action of the
adaptive controllers, in closed loop, are shown too.

Control Of An Oven With SpaceDistributed Sensors

Tue, 09 Jul 2024 00:00:00 +0000

PID controllers are robust and easily synthesized. The are many techniques that allow its tuning with
simple steps, with or without a system model. The direct synthesis method allows us to find gain expressions
in terms of the model parameters, using its canonical representation. We used a thermal system, available at the
Signals and Systems Laboratory of CEFETMG’s campus V, which is composed of 9 sensors placed in series along
an acrylic path with forced ventilation. Three resistances and a damper act as actuators for the system, heating the
air and regulating its flow. We identified 1280 firstorder models for this system, using different combinations of
damper opening, resistance power and selected output sensor by using the complementary output method and used
a subsample of those to create controllers using direct synthesis. We use a set of equations developed by ourselves
and another set found in an article. We tested them in the real system with satisfactory results.

An efficient bond model for particle adhesion simulation in advanced manufacturing

Osvaldo D. Quintana-Ruiz, Eduardo M.B. Campello — Tue, 09 Jul 2024 00:00:00 +0000

The aim of the present work is to investigate the underlying structure of most common bond models
used in particle dynamics, with an aim to enable their use in additive manufacturing simulation. In this context, in
advanced manufacturing processes proper adhesion between particles requires certain stability requirements to be
satisfied. Conversely, erroneous agglomeration resulting from particle adhesion may affect the particle-size spatial
distribution and thereby compromise the mechanical properties of the manufactured piece. These constitute some
of the reasons why particle adhesion continues to be a particularly important phenomenon in a wide range of
engineering applications. In this work, we propose a simple bond model taking into account such considerations,
with which we are able to capture inter-particle bonding very straightforwardly once a given bonding criterion is
met. The derived stability conditions establish recommendations that can help the selection of proper parameter
values (such as, but not only, the strength of the bond) for most common bond models, thereby guiding (or even
avoiding) burdensome problem-dependent calibration. Numerical examples are provided to validate our scheme
and explore its outcomes.

Numerical simulation of the effect of zinc chloride flux on ATIG welding of aluminum

Tue, 09 Jul 2024 00:00:00 +0000

In this work, a study based on numerical simulation methods was applied to Activated Tungsten Inert
Gas welding (ATIG welding), a simple variant of TIG welding that consists only of applying a thin layer of flux
immediately before welding. A Finite Element Analysis (FEA) method was used to compare the aluminum TIG
and ATIG weld pool to evaluate the effect of zinc chloride flux on the geometric parameters of the ATIG weld
bead. Previous tests have shown that this flux allows an improvement in the final appearance of the weld surface,
possibly due to the removal of the alumina layer, in addition to a small gain in the penetration of the weld bead
using negative direct current instead of positive direct current and alternating currents, commonly used for welding
aluminum. The results have shown that a possible removal of the alumina layer by the zinc chloride flux on the
aluminum ATIG welding does not influence the weld bead geometry. This result is similar to the outcomes of
other experimental works in the literature.

A Share-a-Ride Problem and Occasional Drivers

Hellen C. Spengler, Gustavo V. Loch, Cassius T. Scarpin — Tue, 09 Jul 2024 00:00:00 +0000

In recent decades technological advances have allowed the implementation of solutions designed for
transportation problems. One of these proposals is the Share-a-Ride Problem (SARP), which creates shared travel
environments among passengers and packages, served by a fleet of vehicles. The concept of occasional drivers has
extended transportation problems, approaching the real last-mile transport scenarios. This work proposes a new
formulation called SARP with occasional drivers (SARPOD). We defined as the occasional drivers to the entire
vehicle fleet, with the addition of delay indicators in the drivers’ service time. Tests and analyzes are carried out
for small instances.

Identificação e Modelagem Matemática da Variação de Temperatura da Água do Reservatório do Resfriador Evaporativo e Projeto dos Controladores Clássicos, tipo PID.

Andrei Hudson Guedes Braga, Robson Pacífico Guimaraes Lima — Tue, 09 Jul 2024 00:00:00 +0000

The population growth imposes high rates of production and consumption of electric energy, as well
as the increase of the degradation of the Environment. These conditions drive research into the development of
more efficient machines and equipment. Further research is carried out with the aim of creating systems that are
alternative to existing ones, presenting lower energy consumption and that can produce a positive impact on the
Environment. The air conditioning equipment represents systems characterized by high consumption, as well as
by influencing the degradation of the ozone layer and greenhouse effect. Coolant fluids of the CFC type directly
influence the ozone layer, while the alternative HFC fluids, especially the R 407 C and the R 410 A, influence
the greenhouse effect and, consequently, global warming. An alternative system to the vapor compression cycle
conditioners, when used in hot and dry regions, may be the evaporative cooler. This system performs sensible
and latent heat exchange, which can present good results in the regions mentioned, as in the interior of the
Brazilian Northeast. In addition to providing a milder climate, the evaporative cooler features low power
consumption and may have a low acquisition cost. This work presents the mathematical model of reservoir water
in a new evaporative cooler model, differing from the commercial model because it does not have fins. The new
model also has an atomizer, consisting of a toothed disk coupled to a motor, whose function is to break the
molecule of water and spray it, allowing a greater and faster absorption of water by the air stream. The idea is to
use thermal waste, that is, to use water, whose temperature decreases as the system goes into operation, to cool
products and / or processes. For this, a prototype was created, in laboratory scale, having been instrumented and
prepared to monitor the temperatures and humidity of the air in the entrance and the exit of the prototype, as well
as a temperature sensor for the water to monitor and to collect the necessary data for modeling mathematics.

SIMULATION OF A LONG-TERM OPTIMIZED OPERATION PLAN FOR A HYDROELETRIC PLANT

Tue, 09 Jul 2024 00:00:00 +0000

The main goal of the hydrothermal operation plan is the computation of optimal use of water and thermal
resources in order to attend a predicted demand in a defined time horizon. In order to reduce the computational cost,
it is necessary to consider relaxation in hydrothermal operation plan modeling in terms of detailing the physical
and operational characteristics of the system. Although the optimized system is very useful, certain characteristics
are difficult to model mathematically and these will be treated in the simulation, which is the main purpose of
this work. In this paper, we implemented a simulation tool for the Brazilian hydrothermal system focusing on the
long-term planning, which includes constraints that are not considered in the optimization model. A case study
with Foz do Areia hydro plant using real data indicates that the simulation tool refine and validate the results from
the adopted optimization model, turning the optimized policy more adequate in operational terms.

Automação do Teste de Compressão de Pelotas de Minério de Ferro Verdes usando Visão Computacional

Tue, 09 Jul 2024 00:00:00 +0000

Pelotas de minério são um insumo essencial na produção de aço, matéria-prima de extrema importância
na produção de diversos produtos em nossa sociedade
Pelotas de minério são fabricadas a partir do processo de pelotização de minério e sínter, produto de grande
importância na cadeia mundial da produção de aço atualmente. Durante o processo de fabricação, ainda em seu
estágio inicial, as denominadas pelotas cruas passam por um controle de resistência mecânica e dimensional para
determinar se são aprovados ou não para uso, assim prosseguindo para próxima etapa da produção, onde são
aquecidas em um formo com atmosfera oxidante para adquirir suas propriedades finais, quando passam a ser
denominadas pelotas queimadas. Este artigo discute o desenvolvimento de um teste automatizado de compressão
de pelotas cruas usando sistema de visão computacional para localizar as pelotas e o deslocamento necessário para
a zona de compressão. Este artigo apresenta os resultados preliminares sobre o algoritmo em desenvolvimento,
focados principalmente ao algoritmo de localização das pelotas usando visão computacional.

HYDRODYNAMIC ANALYSIS OF GRAVITY NET CAGE IN OPEN SEA

Pedro V. H. V. Garcia, Artur F. Lagemann, Paulo F. Lamarao, Walter J. P. Casas — Tue, 09 Jul 2024 00:00:00 +0000

This work is orientated towards modeling the hydrodinamic response of a circular net cage for fish-
farming, submitted to the wave conditions of the city of Rio Grande - Rio Grande do Sul (RS). For this purpose,

several routines were created using the MATLAB program, in order to determine the hydrostatic equilibrium of the
structure, the drag force acting on the cage’s net and the mooring systems using different materials. In possession
of given data and taking into account the wave regimes of the study site, simulations were performed using the
ANSYS AQWA software in order to obtain the cable tensions and the net cage behavior. Thereby, it can be noted
that the break strength of the mooring system cables was not exceeded and the mooring systems were effective
to keep the structure stable. At last, the modeling of the drag force acting on the net with the software used,
by applying the drag coefficient formula, proved to be an acceptable solution for questions involving net cage.
However, it is important to emphasize that the model used does not consider the non-linearity of the net. Also, the
study suggests the installation of a smaller diameter net cage for pisciculture at the study site.

A approach of dispersion modeling to determine the impact of odor on the beef food industry.

Santos R. Dominiki, Gonçalves A. Glênio — Tue, 09 Jul 2024 00:00:00 +0000

The consequences due to the increase in the level of pollutants in the air occur in the most diverse
areas, for example, environment and health. Among pollutants, the odor stands out for its greater perception
capacity than the others. The evaluation of pollution by odor is still considered a difficult task, as bad smells are
often caused by different chemical compounds. According to reports from the population that lives near a cattle
confinement area, in the municipality of Capão do Leão, Rio Grande do Sul, Brazil, the animals, quarantined
there for a certain period, give off a smell considered very strong, causing discomfort among the residents. This
work aims to simulate odor dispersion using the advection-diffusion equation as a methodology, with a
stochastic wind component. This stochastic formulation is necessary to consider the light wind scenario, in
which wind disturbances play an important role.

Location of charging stations for electric vehicles

Rodrigo de Almeida Nascimento, Ricardo Poley Martins Ferreira — Tue, 09 Jul 2024 00:00:00 +0000

The establishment of alternative mobility technologies, such as electric vehicles (EVs), is an effective
step forward in reducing restrictions on the use of carbon oxides and nitrogen oxides. However, EVs have other
concerns related to the charging station infrastructure, such as insufficient quantity to meet demand, prolonged
recharge time and the problem of defining the facilities of these facilities. This article studies the location of

charging stations for electric vehicles by applying the median problem, in order to minimize the distance-customer-
station according to the geographic service capacity. The methodology takes into account socioeconomic and

demographic data, obtained and made available by research and statistical institutes in order to delimit, through
these indicators, the set of demand centers and the candidate sites for the installation of charging stations. A case
study is presented to investigate the problem of location and model choices.

Development and implementation of software using the Direct Stiffness Method and Symbolic MATLAB proposing the improvement of teaching and learning processes of matrix methods in civil engineering graduation classes

Guilherme O. Berbert-Born, Gilberto Gomes — Tue, 09 Jul 2024 00:00:00 +0000

The emergence of new programming languages and philosophies allowed the possibility of more
efficient calculation techniques in various engineering fields. Such techniques most often displays the result of
processing without making possible for the user to visualize the process itself. This can bring difficulties to fully
understand the method, impairing didactic purposes that might involve its use. The AESYM is a new structural
analysis program written in MatLab language which uses the Direct Stiffness Method. This method consists in
analyzing reticulated structures, statically determinate or indeterminate, based on the superposition principle,
considering linearity between actions and displacements. The method assumes that the effects of rotation and
translation of the bar elements in given structure due to multiple stimuli can be obtained by the combination of the
effects caused by each stimulus individually. With the AESYM, the user can follow the calculation process both
symbolically and numerically, allowing the understanding of the linear elastic analysis in a didactic and visual
way. This makes possible for the user to observe the global stiffness matrix formation process along with its
properties, displacements and forces in the elements through the resolution of the equation which governs the
structure’s internal behavior. The AESYM has, therefore, practical use in matrix methods teaching-learning
process within graduation level engineering courses.

Isogeometric Analysis of Functionally Graded Beams using different Micromechanical Models

Renan Melo Barros, Evandro Parente Junior — Tue, 09 Jul 2024 00:00:00 +0000

Functionally Graded Materials are a class of advanced composites with a gradual and continuously
varying composition. Its design involves choosing the constituents and a function to describe the volume fraction
variation. This work presents an isogeometric formulation for the static analysis of functionally graded beams.
The governing equations are based on the Timoshenko Beam Theory for membrane, bending and shear strains.
B-spline curves are used as basis functions for the isogeometric formulation. Two micromechanical models are
utilized to evaluate the effective material properties.

SIZING OF THE TRANSMISSION SYSTEM OF A COMPETITION FORMULA SAE PROTOTYPE

Tue, 09 Jul 2024 00:00:00 +0000

The automotive industry is always seeking to improve its processes and technologies in order to obtain
better performance and efficiency in its vehicles, accompanying this growing optimization arises the demand for
professionals increasingly specialized and prepared to assume such responsibilities. One of the main subsystems
in a competition prototype is the transmission system. The transmission system is responsible for converting the
mechanical energy coming from the engines into kinetic energy. This work aims at an approach on the design of
the transmission system of a Formula SAE racing prototype. For the sizing of the proposed system, the first step
was to identify the loads that will act on the components. And from them it was possible to define the geometries
of the projected components and the selection of components not projected. The design of the components not
only involves the values of the loads, but also aspects such as weight, ease of assembly and maintenance,
interactions with other subsystems such as structure and suspension, spatial dimension available for the
transmission system, adaptation to the rules of competition, ease of manufacture and cost of material used. The
use of CAD and CAE software in the dimensioning of the components was of paramount importance in terms of
the need to know the behavior of complex components by means of loads, as well as to validate and verify the
compatibility of the results found.

DESIGN AND ANALYSIS OF THE TORSIONAL STIFFNESS OF THE CHASSIS OF A COMPETITION PROPOTYPE FORMULA SAE USING THE FINITE ELEMENT METHOD

Tue, 09 Jul 2024 00:00:00 +0000

The torsional stiffness of the chassis of a competition prototype is one of the main factors to be analyzed
in structural design. Regarding the vehicle dynamics, the chassis design must have enough torsional stiffness so
that the suspension work does not influence the structure behavior. On the other hand, the chassis should not have
excessive weight, since it is a high performance prototype. In this context, the structural design of the chassis
should take into consideration the balance of the functional aspect (torsional stiffness) and its performance (weight
factor). The purpose of the present work is to design and analyze the torsional stiffness of the chassis of a Formula
SAE Prototype of competition, when subject to the efforts arising from the suspension as a function of vehicle
dynamics during a competition. The finite element study aims to replace the bench test, which in most cases
demands excessive time and high cost. Simulations performed with SolidWorks software will serve to validate
and verify the compatibility of the results found. The results obtained will be presented through the main torsional
stiffness indicator and the other indicators related to the stress and strain variables.

Mesh generation algorithm involving irregularly contoured regions for numerical simulations of partial differential equations by finite differences

Tue, 09 Jul 2024 00:00:00 +0000

This work proposes a mesh generation algorithm, involving irregular contours. In this algorithm, the
contour of the physical domain is approximated by mesh segments, allowing numerical simulations of partial
differential equations using the finite difference method. Hence, the first code analyzed each node in the mesh,
using two loops. However, this algorithm was impracticable for a mesh with many nodes, as a consequence of
the high number of operations, which let the algorithm slow. As a possibility to reduce the computational cost,
the algorithm was adapted to use only one repetition structure. In order to reduce numerical calculations, the new
algorithm calculates the slope of the line defined by a known point of the irregular contours and the neighboring
vertices. Then the algorithm calculates the line points and the shortest distance from these points to a mesh
node, thus generating a point of the approximate contour. This process is repeated until the approximate contour
is obtained. Algorithm results are presented using four geometries. In these figures, the approximated contour
properly describes the irregular given contour.

A computational optimization procedure aiding the design of vehicular suspension systems

André Vivian Farias, Thiago André Carniel — Tue, 09 Jul 2024 00:00:00 +0000

Aiming at the design of formula-style vehicles, this manuscript presents a computational procedure
based on optimization principles for the concept of vehicular suspension systems. The design criteria seek to find
the three-dimensional location of both upper and lower ball joints of a double wishbone suspension in view of
particular relationship between the camber gain and the steering angle. The studied case investigated concerns in
optimize the performance of the vehicle in view of the well-known skidpad test. Geometric constraints imposed
by components of the suspension system are also considered within the formulation, which in turns define the
search space. Due to the small amount of design variables, the Particle Swarm Optimization (PSO) is the heuristic
algorithm chosen to solve the optimization problem. The achieved results show that the proposed design criterium
was reached and the constraints were fulfilled within less than one second in an ordinary laptop computer, showing
the effectiveness of the numerical procedure.

BRAKE SYSTEM DESIGN AND DELEVOPMENT FOR FORMULA SAE COMPETITION VEHICLES

Eduardo V. T. de M. Andrade, Koje D.V. Mishina, Pedro J. M. B. Sobreira — Tue, 09 Jul 2024 00:00:00 +0000

SAE is a Society of Mobility Engineers that, in partnership with several companies in the automobile
industry, promotes the Formula SAE competition. That is the biggest competition among engineering students,
and started in the USA in 1981, expanding to several countries, such as Australia, Germany, Japan and Brazil. In
this context, several students from various universities propose to develop formula like prototypes, to use the
knowledge acquired in the academic scenario and good engineering practices. For security and control issues, SAE
defines rules that must be followed by the teams. One of the main subsystems is the brake system, which must be
hydraulic and composed of two independent series. The brake system is evaluated both in technical tests (technical
inspection) and dynamics tests (braking). This paper shows the design and construction of a robust, effective and
low-cost brake system, with well-defined criteria, from its initial conception to its manufacturing. Therefore, it is
necessary to study the dimensioning and the forces that make up the entire system. The acquired data allows us to
perform an experimental validation and make a comparison between the theoretical and experimental models, to
understand the system and identify possible problems and evaluate its performance.

A statistical investigation of ultrasonic logging data for a petroleum well casing integrity analysis

Tue, 09 Jul 2024 00:00:00 +0000

The structure responsible to maintain well stability against borehole collapse as well as to prevent fluid
flow between formation and the borehole in an uncontrolled way is the casing string. It consists of several high
resistance steel tubulars segments connected along well trajectory. Due to severe conditions in-situ, casing integrity
may be compromised, impacting the capability to withstand loads. The scenario may be more critical concerning
to resistance reduction when casing wear is caused by drilling operation of deeper sections of the well. Casing
integrity is usually assessed by means of logging devices, such as the ultrasonic logging tool, to acquire casing
geometry data, like internal radius and wall thickness along well depth. This work proposes to apply a statistical
investigation on well logging datasets in order to characterize geometric data distribution of in-situ tubulars. It is
discussed ultrasonic logging data treatment to obtain reliable results as well as the comparison between statistical
variables from manufactured tubes presented in API TR 5C3:2008 code and those inferred by logging data. Python
codes are developed using statistic features to assist the data analysis. The statistical study is justified by its
contribution to improve the identification of imperfections and damage in logging data.

Implementation of simplified second order estimation method from NBR 8800/2008 as support of structural analysis learning

Tue, 09 Jul 2024 00:00:00 +0000

Structure analysis aims to obtain appropriate responses like displacements and internal forces in
structures. The results are used in limit state design method in order to maintain levels of reliability and safety in
structural engineering design. A global structure analysis may be conducted in a geometrically linear approach,
also known as a first order analysis, where the structure responses are obtained through equilibrium in an
undeformed configuration, or also in a geometrically nonlinear approach, in which additional effects (so-called
second-order effects) are determined in a deformed configuration equilibrium. NBR 8800/2008 addresses the
recommendations for second-order analysis in steel structures, presenting the possibility of both simplified and
rigorous geometric nonlinear analysis. In this context, the standard recommends the simplified method known as

amplification coefficient method to determinate, through an initial first order analysis, the approximated second-
order effects. In this context, this work introduces an application developed using Python language to assist steel

structure analysis learning. The program presents a first-order and a simplified second-order analysis using direct
stiffness method and the amplification coefficient method respectively. An interface is implemented in order to
become a useful and easy-to-use tool. It is also presented a comparison between the results from a rigorous
geometric nonlinear analysis, using the software AcadFrame, and the simplified method aided by the developed
software both applied to the same steel structure example.

Development of a remote and low-cost bridge monitoring system

Tue, 09 Jul 2024 00:00:00 +0000

Structures made from concrete, metal or any other material, are designed to have a long service life.
However, to ensure a durable structure, it must have constant and efficient maintenance. Structural Health
Monitoring (SHM) can be described as the method of monitoring and evaluating the structural health through the
collection and analysis of data extracted from sensors, which are connected or not to the structure in matter. In this
way, the difficulties are in how to collect that data, analyze it and have information about it to give a final response
about the structure status. This research focus at the development of a low-cost bridge management system, which
will allow remote monitoring of special structures and shows its real time status. Subjects as Finite Element (FE)
modelling, dynamic test and Internet of Things (IoT) are studied to create a viable system. The first step is
modelling a case-study bridge on SAP2000 to analyze the theoretical behavior of the bridge. The second step is
using low-cost devices to extract data with low noise, process it and send a response about the structure status,
involving Wireless Sensor Networks. Then, experimental results are analyzed.

Numerical evaluation of clayey soil under jetting procedure using Lattice Boltzmann Method

Eduardo M. A. Pacheco, João P. L. Santos — Tue, 09 Jul 2024 00:00:00 +0000

Offshore operations in deep and ultra-deepwater increasingly demand usage of different well
construction methods. Regarding a well casing system, the conductor installation by jetting is one of the adopted
techniques in top hole operations in these scenarios. In a deepwater environment, marine soil is cohesive,
presenting mud characteristics and low shear strength. Consequently, from a mechanical perspective, those soils
behave as a combination of an elastic solid and viscous fluid. Thus, the use of fluid rheology by Herschel Bulkley’s
constitutive equations to analyze it is a valid approach. Numerical modeling stands out as an interesting choice for
analysis of jetting problems due to its accuracy and affordable cost of development in the design phase. The Present
work investigates soil response under high shear rates from a vertical jet. The numerical simulations are performed
based on the Lattice Boltzmann Method (LBM). We perform parametric analysis of rheological parameters of the
soil as yielding viscosity and yield stress. Results show that soil behaves in an increasingly structured way by
increasing the values for the yield stress and the yielding viscosity, demanding higher jet speeds or longer jetting
time in order to drill larger depths.

Study of the enriched mixed finite element method using comparisons of computational cost and errors with formulations in continuous and discon- tinuous functions and mixed scheme on quadrilateral finite elements.

Aldo G. Sarmiento, Jose Ayñayanque, Romulo Condori, Jorge L. Diaz Calle — Tue, 09 Jul 2024 00:00:00 +0000

Mixed finite element formulations are used to approximate stress and displacement variables simultane-
ously for Poisson problems. The purpose of this article is to analyze new discrete mixed approximation based on

the application of enriched version of classic Poisson-compatible spaces. With that purpose we decided to measure
the computational cost of applying four formulations for two Poisson problems with known exact solution. The

first model considers a smooth sinusoidal solution and the second model has a high gradient solution. The objec-
tive is not to compare which formulation is better, but rather to highlight characteristics of computational cost and

the errors obtained for both the primal and dual variables. Weak formulations correspond to the use of the FEM
using continuous and discontinuous functions, using the mixed method and the enrichment mixed method. In the
algorithms developed, we computed the error in L
2
and H1 norms and we measured the computational cost of the
assembly and solving processes. When analyzing these costs together with the errors obtained, we visualized that
the cost of enriched version is less expensive computationally than non-enriched version, however they getting the
same approximation errors.

Simulation-based structural reliability applied to fracture mechanics

Hugo V. F. Azevedo, Eduardo T. de Lima Junior — Tue, 09 Jul 2024 00:00:00 +0000

Monte Carlo simulation techniques, applied to structural reliability analysis, have always al-
lowed the solution of complex, large and non-linear problems. However, these techniques demands a

high computational cost in problems presenting small probability of failure. In this context, intelligent

sampling techniques are used to reduce the number of simulations needed to solve structural prob-
lems, reducing the processing time. This paper addresses a study on different combinations of sampling

strategies, such as the Latin Hypercube Sampling, Antithetic Variates Sampling, Asymptotic Sampling
and Enhanced Sampling, all applied within the Monte Carlo technique. The models are applied to

benchmark problems in Linear Elastic Fracture Mechanics, more specifically those ones presenting ana-
lytical solution. The advantages and limitations of each method are discussed based on the accuracy of

the probabilistic response and the associated computational cost.

Topology optimization of 2D truss structures using the BESO method

Gabriel V. O. Padovani, Hugo S. Idagawa — Tue, 09 Jul 2024 00:00:00 +0000

Topology optimization is the process of determining the optimal material layout within a given design
domain, for a set of loads and boundary conditions. It is an important engineering tool that allows the design of
lighter structures with improved strength. Among the many optimization techniques, the Bidirectional
Evolutionary Structural Optimization (BESO) method is a robust and computational efficient algorithm that can
be applied in designing optimized structures. In this work, the BESO method was applied to the design of
optimized 2D truss structures. From a group of reference numerical examples (Michell Structures), the method
capability to achieve optimal solutions was researched. These case studies were also evaluated on the
manufacturability of the final topologies to assess if the BESO method can be used in structural designs of steel
framework structures.

COMPUTATION OF FLOW ABOUT AIRFOILS – COMPARISON OF DIFFERENT METHODOLOGIES

Samuel Vıctor S. Maia, Luís Morao Cabral Ferro — Tue, 09 Jul 2024 00:00:00 +0000

The aerodynamic study of an airfoils is fundamental to analyse the behavior and geometrical characte-
ristics of a wing for prescribed flight conditions. Based on analyzes and simulations we are able to define the

variables for aerodynamic design of an aircraft. The unmanned aerial vehicle (UAV) designed for SAE Aerodesign
competition use high lift profiles for low Reynolds number flow. The viscous or inviscid flow about airfoils can
be computed using different methodologies, such as panel method or finite volume method. The main objective of
this work is to compute and compare the lift and drag coefficients as well as pressure distributions in the contour
of airfoils by calculating the inviscid and viscous flow, using a panel method and a finite volume method. For the
analysis, high lift profiles of the families NACA 4, EPPLER, GOE, CH and SELIG were selected. These classes of
airfoils have very good aerodynamic efficiency with high ratio between the lift and drag coefficients. These profiles
are highlighted by its high mean-line curvature and are used at low speeds, being indicated for the SAE Aerodesign
competition aircrafts. The criterion used to choose the airfoil was the highest lift coefficient generated in relation
to its maximum stall angle, at a number of Reynolds of cruising flight speed, that is close to the transition from
laminar boundary layer to turbulent boundary layer. The panel method analysis was performed using the XFRL5
software that uses XFOIL as source code. In the finite volume method, the Fluent code of ANSYS

R was used.
Different types of meshes, structured and unstructured, are compared and the quality parameters of the elements
generated are analyzed and presented. The pressure distributions and the lift and drag coefficient curves for the
selected aerodynamic profile are presented and compared, calculated using the panel method and the finite volume
method.

Fracture Properties Analysis of Steel Fiber Reinforced Concrete Using Digital Image Correlation

K. de Souza, C. Varady Filho, R. Escarpini Filho, W. Lira — Tue, 09 Jul 2024 00:00:00 +0000

This paper proposes a strategy to obtain fracture properties of steel fiber reinforced concrete (SFRC)
based on the application of the digital image correlation method (DIC), where the data is taken from a three-point
bending test (3PBT). The great demand for mechanical tests in engineering induces the usage and development of
several alternative measurement methods. In this context, DIC is a practical, accurate and inexpensive technique
for measuring surface displacement in a non-intrusive way. DIC consists in correlating pairs of images taken from
the surface of the specimen under stress in distinct stages of load, resulting in the displacement fields. By using
the concepts from linear elastic fracture mechanics (LEFM), the displacement fields can be applied to evaluate
some fracture properties of the material. The strategy explored in this work uses images taken from a 3PBT of a
SFRC specimen as input data and measures the displacement field by DIC using the open-source software NCorr.
This displacement field is used to create virtual extensometers in order to study the crack opening. The fracture
properties are then computed from LEFM equations with the displacement previously calculated. The results show
a clear effect of the fibers on improving the support on Mode I cracks. It also indicates a smaller gap in the
material’s response between the transition phases of the double-K parameter analysis. The proposed strategy is
a simple and inexpensive alternative, and it can be a powerful mechanism to analyze and validate the materials
properties used in several engineering problems.

UNILAstic: Equipment and software to evaluate mechanical properties of materials by acoustic test

Pablo A. Ramirez Nuñez, Iván Dario Gómez Araújo — Tue, 09 Jul 2024 00:00:00 +0000

The complete system consists of a support unit, a measurement unit and software. The equipment was
designed to perform non-destructive tests on small and medium cylindrical samples of different materials. The
support consists of a light but strong aluminum structure for the location of the sample to be tested. The measuring
unit consists of a microphone and a ball hammer. To perform the test, the sample is located in the support unit
where wires serve as support. With the ball hammer, the sample is hit several times and the sound is recorded with
the microphone. The UNILAstic software performs a vibration analysis based on samples of sound records to
establish mechanical properties of the materials (modulus of elasticity, poison ratio and shear modulus) based on
natural frequencies of the specimen (flexural, torsional and longitudinal frequencies). The UNILAstic software
was coded in MATLAB®. This article shows details of the construction of the support unit in order that it can be
replicated by anyone, in addition, the software features are presented showing its simplicity to obtain material
properties through some tests performed on concrete specimens. As a conclusion, the work presents an equipment
that can be replicated in a simple way and at very low cost in the universities of Brazil.

Comparative Study of Different Numerical Alternatives for Modeling Two-Phase Flows in Naturally Fractured Reservoirs

Twany Mirele Correia, Paulo Roberto Maciel Lyra — Tue, 09 Jul 2024 00:00:00 +0000

Two-phase flows of water and oil in heterogeneous and anisotropic porous media can be described by
a system of nonlinear partial differential equations that comprises an elliptic pressure equation and a hyperbolic
saturation equation coupled through the total velocity field. These problems are difficult to model, due to
physical and geometric complex features of oil reservoirs, which can include fractures, inclined layers and
directional wells. In such cases, it is important to use formulations that can deal with full permeability tensors on
unstructured grids. Here, we present a comparative study of different numerical formulations in the context of

modeling two-phase flows in naturally fractured reservoirs. Our simulation tool incorporates different Finite-
Volume Methods with Multi-Point Flux Approximation (MPFA) schemes to obtain implicitly the solution of the

pressure equation. Among the different MPFA approaches we used some non-conventional alternatives proposed
by our research group, namely: MPFA with a diamond stencil (MPFA-D); MPFA with a quasi-local stencil
(MPFA-QL); MPFA with harmonic points (MPFA-H) and the Nonlinear Finite Volume Method that Preserves
Positivity (NLFV-PP). A Hybrid-Grid Method (HyG) was employed to model the fractures and the classical
First Order Upwind Method (FOUM) was adopted to solve the saturation equation applied in its implicit version.

Comparison of second order effects in a plane frame through rigorous analysis and simplified methods from NBR 6118/2014 and NBR 8800/2008

Tue, 09 Jul 2024 00:00:00 +0000

The analysis of second order effects in structures can be performed in a rigorous, simplified or approxi-
mated approach. The rigorous analysis consists in incremental procedures that modifies structure’s stiffness matrix,

according to changes in its geometry. The simplified analysis divides a nonlinear problem in successive linear pro-
blems. In this context, NBR 6118/2014 and NBR 8800/2008 presents simplified methods like the coefficient γZ

and the amplification coefficient method (MAES) for reinforced concrete and steel structures, respectively. This
work aims to investigate coefficient γZ and MAES performance in determining second order effects by magnifying
the first order efforts. To achieve that, a comparison is performed, following normative recommendations, using a

reinforced concrete plane frame from literature. Python codes are developed to calculate both simplified approa-
ches, using direct stiffness method for first order efforts determination and all considerations present on normative

codes for a simplified second order analysis. Therefore, in this work, the results of two simplified methods for
second order analysis are obtained for the same frame designed structure, and these results are also compared to
those obtained from a geometric nonlinear rigorous data, comparing regular procedures in structure designing.

Reliability-based analysis of borehole closure on salt rock

Tue, 09 Jul 2024 00:00:00 +0000

This work proposes an analysis of structural reliability in salt rocks when drilled by vertical wells, in
order to assist the evaluation of their mechanical behavior. In general, the computational modeling of geotechnical
projects in underground structures has two focuses: a) predict the behavior of soil-structure interaction with good
accuracy; and b) evaluate the stability of these structures. The quality of this prediction is strongly associated
with the accuracy with which the parameters of the problem are defined, such as the mechanical properties of
the materials, the layer dimensions, among others. Considering the complexity of obtaining in situ data for this
type of underground problem, there is always a level of uncertainty associated with them. Structural reliability
addresses the randomness of the design variables to estimate the safety level associated to a structural problem,
regarding pre-established failure criteria. The methodology adopted in this work is based on three main steps: i)
Characterization of the salt rock drilled by vertical wells problem; ii) Statistical characterization of the variables of
interest; and iii) Use of reliability analysis methods to assess the probability of failure of salt rocks drilled by wells.
As the main contribution, it is expected to evaluate the influence of the randomness of the variables involved in the
mechanical response of drilled salt formations, providing important statistical information related to the designed
structures and indicating probability of failure in these structures.

Simplified numerical model for analysis of steel-concrete composite beams with partial interaction

Samuel L. Simoes, Tawany A. Carvalho, ́Igor J. M. Lemes, Ricardo A. M. Silveira — Tue, 09 Jul 2024 00:00:00 +0000

The present study refers to the composite steel-concrete beams analysis considering the various non-
linear effects. These effects generate complexity to the design requiring computational methodologies for the

accurate measurement of structural behavior. With good numerical efficiency, the Refined Plastic Hinge Method

also stands out for its simplicity. This methodology will be used considering rotational pseudo-springs at the fi-
nite elements ends for the simulation of plasticity. However, this approach was developed for isotropic materials

with elastic-perfectly-plastic behavior, implying loss of precision in the analysis of structures containing concrete

in their composition. Furthermore, the effects of partial interaction can not be simulated by the inherently rota-
tional behavior of the pseudo-springs. Thus, the introduction of the cracking and partial interaction effects will

be approached through effective moment of inertia defined by normative criteria for partial shear connection and

using the Patel model for cracking simulation in concrete slab. In addition, geometric non-linearity will be in-
troduced to the model considering a corrotational formulation, dismembering from the rigid body displacements

those that actually cause deformation to the element. The validation of the implementations will be done based on
the comparison with numerical and experimental data present in the literature.

Analysis of free-spanning pipelines using design of experiments techniques

Tue, 09 Jul 2024 00:00:00 +0000

The discovery of new oil and gas fields in offshore regions, increasingly distant from the coast, required
the use of pipeline systems increasingly extensive and exposed to more hostile environments. Due to irregularities
in the seabed and the length of the pipes, the occurrence of free spans, when the pipe loses contact with the ground
and is suspended, and the phenomenon of Vortex-Induced Vibrations (VIV) are greater, which can decrease the
system life. Thus, the analysis of free spanning pipelines is necessary for the design of the systems, which normally
requires numerical simulations. However, to reproduce the behavior of the pipe, a set of parameters, that are not
easily or precisely determined, is requested often demanding parametric studies that require countless numerical
simulations. In this way, this work has the objective of using techniques of design of experiments (DOE) in order
to improve the structural analysis of pipelines in free spans. The application of design of experiments techniques
allows to verify which parameters are most significant for the problem. Therefore, it is expected that the design
variables determined from the design of experiments will present accurate responses and the numerical simulation
process will be optimized.

Automação da análise de tensão em vigas através de planilhas no software Excel ®

Tue, 09 Jul 2024 00:00:00 +0000

Os assuntos relativos às tensões e suas transformações em elementos estruturais são amplamente
discutidos pelos autores da área da Mecânica dos Sólidos. Estas tensões são geradas devido aos esforços internos,
os quais predominam o momento fletor e o esforço cortante em elementos submetidos a carregamentos transversais
e mais especificamente as vigas. É importante ressaltar que devido as tensões atuarem nas seções transversais
desses elementos estruturais torna-se necessária a análise das propriedades geométricas dessas seções e a utilização
destes valores para os cálculos das tensões. Desse modo, em função da grande quantidade de etapas necessárias
para a obtenção das tensões em vigas, esse trabalho teve como objetivo principal a elaboração de modelos analíticos
no software Excel® capazes de obter de forma automatizada as propriedades geométricas de seções transversais,
os esforços internos, as tensões cisalhantes e normais e as suas transformações. Para isto foi realizado um estudo
analítico das equações disponíveis na literatura para a determinação destas tensões, aliado com a adequação dessas
equações de acordo com as seções transversais analisadas, que foram as seções transversais em I, T (normal e
invertido) e retangular, considerando vigas submetidas às condições de apoios engastada ou biapoiada, com
carregamento pontual ou distribuído. Ao final do trabalho percebeu-se que a planilha é capaz de auxiliar o estudo
das tensões desenvolvidas em vigas e transformação de tensões.

Implementação computacional do MEC 2D com dipolos de tensão para análise de fraturamento

Tue, 09 Jul 2024 00:00:00 +0000

O presente trabalho apresenta uma implementação computacional da formulação 2D do Método dos
Elementos de Contorno (MEC) para análise de fratura coesiva em materiais elásticos, com inclusão de dipolos de
tensão para simular a não linearidade no domínio. A parcela no domínio da equação integral do método foi
trabalhada para a inserção da linha de fratura, cuja abertura vai sendo verificada pelos acréscimos de tensão
captados pelos dipolos posicionados nos nós funcionais dos elementos da fratura. Assim, um código “MEC dipolo
2D” foi elaborado utilizando a solução fundamental de Kelvin com elementos lineares contínuos e descontínuos,
para a discretização do contorno e da fratura. Foi utilizada a linguagem de programação PYTHON na elaboração
do código computacional, por conta de ser plataforma de código aberto e adequada velocidade de processamento.
Exemplo já avaliado em trabalhos acadêmicos foi adaptado para demostrar a eficácia do código computacional
implementado, bem como a formulação utilizada. Os resultados numéricos finais foram planilhados, para plotagem
das figuras do comportamento do corpo nas situações inicial e final.

Multi-Objective Sizing Design Optimization of an Airfoil via Genetic Algorithms

Tue, 09 Jul 2024 00:00:00 +0000

One of the problems with optimization in aeronautical engineering, with various formulations, refers
to searching for the best airfoil geometric shapes to reach countless objectives for several finalities. Between

the formulations of these optimization problems, there are single and multiple objective problems. The multi-
objective optimization generally contains conflicting objectives. The final solutions generate a Pareto curve that

will enable the decision-maker to choose the one that best suits their expectations. In this work, the formulation
and solution to the problem of multi-objective optimization of a beam with an airfoil as a cross-section with two
conflicting objectives are presented. The maximization of the first mode of natural frequency of vibration and the
minimization of the airfoil structural weight are the conflicting objective functions. The maximization of the first
mode of natural frequency aims to avoid resonance problems with possible loads and minimize the weight, for
an efficient airfoil. The airfoil is modeled in 2 dimensions, and the variable in the project is the thickness of the
cross-section. To solve the optimization problem, it is used the MOGA - Multi-objective Optimization Genetic
Algorithm, available in the software ANSYSr. The model developed and its complexity is presented, obtaining
interesting results, and the desired expectations.

BINARY SEARCH TREE ALGORITHM APPLIED TO CASING DESIGN OF OIL WELL BASED ON MINIMUM COST

Tue, 09 Jul 2024 00:00:00 +0000

This work aims to present a strategy to reach a minimum cost of oil well casing design through a tube’s
selector algorithm using as support the Binary Search Tree algorithm. The oil well casing system consists of tubes
and connections available that are installed on the well phases, having functions as: to prevent rock formation
collapse, to avoid fluid contamination to the well, to block fluid migration to the rock formation, to withstand
many equipment along the well, among others. It is worth pointing out that, on petroleum industry projects, a
significant part of the costs is associated to these casing systems. Therefore, the appropriate choice becomes crucial
in order to resist the solicitations, considering minimum safety factors, without economically compromising the
oil well’s viability. In fact, different weight tubes and grades steel available allows to the designer a wide spectrum
of combinations that, if well chosen, provides to the well a higher structural lifetime and, moreover, a lower cost,
associated to its building. Thus, the selection problem consists in a discrete optimization, considering the catalog
of tubes available by one or more suppliers. To illustrate it and its usability, the algorithm is applied to a
hypothetical oil well. To check these results, it is used the linear search method on the discrete optimization
problem, that allows the resolution of these problems in an intuitive and classical way.

Influence of well drilling modelling strategies on the mechanical behavior of salt rock

Tue, 09 Jul 2024 00:00:00 +0000

This work compares two strategies of computational modelling based on finite element method applied

to vertical wells drilling, evaluating their influence on the mechanical behavior of salt rocks, using Abaqus com-
mercial software. Salt rocks properties favor the entrapment of gas and oil on underlying layers. On the other

hand, these rocks are subjected to the creep effect, which provoke the hole closure. In this context, predictions are
essential to reduce operational risks related to entrapment of drilling column and casing collapses. Currently, as a
simplified approach, it is common to consider the drilling process to be performed instantaneously, at the beginning
of a numerical analysis, disregarding the rate of penetration (ROP). In this way, there may be an overestimation
of the well closure depending on the studied scenario. In this context, this work proposes a strategy considering

the ROP in order to perform the salt rock excavation along time and compares the obtained results with the sim-
plified strategy behavior. In this regard, the main contribution of this work is to evaluate the effect of two classical

strategies on the mechanical behavior of salt rocks during well drilling.

Comparison between simplified and refined models for calculating deflection in rc beams

Lucas S. Cruz, Lucas C. Pellanda, Elisabeth Junges — Tue, 09 Jul 2024 00:00:00 +0000

In this work, a comparative study of different simplified methods and refined models used for
calculating deflections in reinforced concrete (RC) beams, under service loads, is performed. Simplified methods
employed are the one recommended by Brazilian Code (ABNT NBR 6118), and the method recommended by the
European Code FIB. Two refined FE models are presented, one based on the NBR 6118 model and one based on
FIB model. These models use FE beam elements, and the material nonlinearities are considered by means of
moment-curvature diagrams. The models are implemented on the computational program named AVSer, limited
to analysis of beams up to yielding of reinforcing steel. Numerical results obtained by the different models are
compared with an experimentally tested beam. Some examples of simply supported RC beams under service loads,
by varying the beam geometry, the loading type, and the reinforcing ratio are analyzed. The results obtained by
the different models are compared. In the end of this work, differences between the models are pointed and
recommendations regarding the use of then are drawn.

Proposal for consideration of inertial and drag parcels to deformable anchor lines in catenary configurations

Milton M. G. dos Santos, Eduardo N. Lages — Tue, 09 Jul 2024 00:00:00 +0000

This work proposes the construction of an alternative method for dynamics analysis of deformable
anchor lines, in free catenary configuration, linked to the floating units of oil exploration systems. Among the
various methods used for numerical simulation of offshore lines, the catenary and finite element methods are the
most widely used. The catenary method generates a quick analysis and not so faithful to the dynamics exercised
by the line, while the finite element method proves greater fidelity in exchange for high computational cost.
Observing the problems of mechanical representativeness and computational cost present in the catenary and finite
element methods, respectively, the aim is to develop a methodology to which the computational cost is reduced
and that provides results more consistent with the physical problem, respecting the mechanics of deformable solids.
For that, this work proposes, after reviewing formulations of structures in deformable cables and finite element
method, to combine the positive aspects of each modeling mode and incorporate the environmental actions,
providing data related to the line, such as its geometry and traction in the fairlead. Thus, a study about the
representativeness of the model was executed through dynamics analysis, which showed promising results through
the developed methodology.

Finite element code for modal analysis on navigation locks considering fluid structure interaction

Joao V. S. T. Araújo, P. M. V. Ribeiro — Tue, 09 Jul 2024 00:00:00 +0000

Navigation locks are classified as hydraulic structures inside the engineering domain and represent huge
importance for the waterways system, once they turn the waterbodies navigable by enabling the ships to overcome
unevenness. Through a mechanical point of view, this type of structure reunites two distinct types of materials: one
solid, the other fluid. From the contact between those two fields, the fluid-structure interaction arises, characterized
by pressure and deformation compatibility, due to dynamic coupling. Whether before the variety of the studied cases
were limited by extensive analytical solutions and simplified geometry, at the last fifty years, due to the evolution
of numerical methods, there was an advancement on the diversity of possible cases to be assessed over conditions
closer to the reality concerning the geometry. Therefore, the present paper proposes the study of bidimensional
cases of reinforced concrete navigation locks based on a unique MATLAB finite element method code. The cases
will be submitted to modal analysis and their results will be validated on the ANSYS software. Those analyses
will allow the identification of intervenient parameters on the structure behavior. From the outcomes interpretation,
solutions will be formulated towards a design of those structures more consistent and less vulnerable to this type of
solicitation.

Numerical Simulation of Multiphase and Multicomponent Fluid Flow in Petroleum Reservoirs Using an IMPEC Compositional Formulation and a Second Order MUSCL Type Finite Volume Method

Maria E. S. Galindo, Darlan K. E. Carvalho — Tue, 09 Jul 2024 00:00:00 +0000

The numerical modeling of multiphase and multicomponent fluid flow in petroleum reservoirs is ex-
tremely complex and computationally demanding. Frequently, simpler black-oil models are not suitable for cases

in which the reservoir fluid is volatile and composed by several pseudo-components with distinct characteristics.
For those cases, the use of a compositional simulation based in Equations of State (EOS) is of utmost importance.
In this work, we present an Implicit Pressure Explicit Composition (IMPEC) formulation using cartesian grids for
the compositional reservoir simulation based on an EOS approach. Diffusive terms in flux and transport equations

are discretized by the Two-Point Flux Approximation (TPFA) finite volume method. Besides, to improve front res-
olution and accuracy, we discretize the advective terms of the transport equations by the second-order Monotonic

Upstream-centered Scheme for Conservation Laws (MUSCL) method. So far, the implemented model considers
isothermal flow, up to three-phase flow and that there is no mass transfer between water and hydrocarbon phases.
Physical dispersion is neglected. Our IMPEC formulation is evaluated by solving a benchmark problem found in
literature. The accuracy of our approach is evaluated comparing our results with those obtained by a commercial
reservoir simulator (CMG-GEM).

PRELIMINARY ANALYSIS OF FLOW OVER A CIRCULAR CYLINDER USING CFD

Luiz F. C. de Oliveira, Lineu J. Pedroso — Tue, 09 Jul 2024 00:00:00 +0000

The flow of air over a circular cylinder can be observed in many civil engineering problems. Tall
buildings, towers and silos can be subject to strong winds that can impact the structure local or global stability.
The flow over a cylindrical structure is a dynamic problem with transient response characterized by vortex
shedding. If the Reynolds number is sufficiently high, an alternate vortex shedding pattern is formed, known as
von Karman vortex street. In this scenario, the flow applies dynamic drag and lift forces on the structure. This
paper presents a methodology to simulate the fluid flow over a circular cylinder and compute the drag and lift
coefficients using Computational Fluid Dynamics (CFD). A two-dimensional cross-section of a structure is
modelled in ANSYS Fluent applying the proper boundary conditions. The pressure fields are computed from the
simulations and numerical integration is used to obtain the drag and lift coefficients. From the simulations, the
streamlines, and pressure fields can also be obtained and plotted. Geometry, mesh and time step size independence
studies are conducted to ensure convergence. The results are compared to numerical data found in the literature.

Strong Stability Preserving Runge-Kutta Methods Applied to Advection- Diffusion Problem

Marlon Mesquita Lopes Cabreira, Renan de S. Teixeira — Tue, 09 Jul 2024 00:00:00 +0000

Heat transfer phenomena are related to several applications in different scientific branches. Advection-
diffusion problems with spatial properties variation describe the wave development associated with a physical

change in heterogeneous media or multi-layered materials, such as laminated media or conjugated problems. Fur-
thermore, an incompressible thermally developing laminar flow with hydrodynamically developed fluid, known as

the Graetz problem, is a typical example of this phenomenon . However, the fluid property variation imposes some
mathematical challenges to predict accurate solutions. The Strong Stability Preserving (SSP) methods are capable
of numerical schemes to increase their accuracy order while maintaining the original stability properties from their

generator Euler method. This methodology is developed basically by rewriting the multistage scheme as a combi-
nation of steps in the Euler method and introducing a time step barrier. On the other hand, the Generalized Integral

Transformation Technique (GITT) is a hybrid numerical-analytical approach that provides an infinite system of
coupled ordinary differential equations (ODE) that needs to be solved numerically by truncating the expansion.
Indeed, GITT consists of this solution procedure characterized by a hybrid analytical-numerical nature. Therefore,
the present work studies the SSP Runge-Kutta schemes compared to the GITT to solve the Graetz problem in the
absence of the axial diffusion.

PATIENT-SPECIFIC SIMULATIONS FOR THE TRANSCRANIAL DIRECT CURRENT STIMULATION THERAPY

Tue, 09 Jul 2024 00:00:00 +0000

Transcranial direct current stimulation consists of applying small electric currents through electrodes at
certain points in the scalp, to deliberately alter the brain activity. This technique has been applied in the treatment
of some patients to reduce seizures as in cases of stroke and microcephaly. The experimental results are promising,
but there are open questions such as the best position for the electrodes and the best current magnitude that should
be applied. Therefore, the creation of a computational platform for preliminary tests can bring more efficacy in the

treatment and, consequently, more comfort for the patient. This work aims to build a computer simulation environ-
ment able to evaluate the distribution of electric potential in the patient’s brain due to the transcranial stimulation.

A geometric head model of the patient’s head will be reconstructed from medical images, such as magnetic res-
onance and computed tomography, which will be segmented according to the head region. The electric potential

distribution will be described by the partial differential equation known as the Laplace equation, considering differ-
ent conductivities for each part of the head. The finite element method was chosen to solve the governing equation

due to the ease of adaptation to complex geometries such as the human brain. Then, numerical experiments will
be carried out to assess the electric potential distribution over the patient’s brain, considering different settings of

electrodes position and current magnitude. This work expects to build a computational platform capable of pre-
dicting the electric potential behavior in the brain during electrical stimulation, which can be used to improve the

transcranial stimulation treatment.

Rotina Computacional Para Projeto de Mola Helicoidal de Compressão Aplicado a um Protótipo Veicular Baja SAE

Joao P. R. Deodato, Ramon R. B. Medeiros, Zoroastro T. Vilar, Vinícius M. Melo — Tue, 09 Jul 2024 00:00:00 +0000

O sistema de suspensao automotivo é responsável por garantir mais segurança à veículos de passeio
ou para oferecer um melhor desempenho para veíulos de competição. Sabendo que a mola é um dos principais
componentes do sistema de suspensao automotivo, este trabalho visa a elaboração de uma rotina computacional
em ambiente Scilab com uma interface grafica para o dimensionamento de uma mola helicoidal de compressão
sujeita a fadiga que possa ser aplicada a uma suspensao de um veículo off-road baja SAE. A rotina fornece dados
suficientes a fabricação de uma mola helicoidal de compressão e resistente a fadiga, a partir de dados relacionados
a carga, a dimensao e a vida útil, fornecidos pelo usuário. Esse conjunto de rotinas é desenvolvido com base em
teorias de elementos de maquina, de maneira a possibilitar uma maior compreensão e celeridade no projeto do
referido sistema, fornecendo as informac ̧oes necessárias para uma melhor análise de custo benefício na escolha do
material utilizado e para o início da viabilização física da mola.

DAMAGE EVOLUTION INVESTIGATION IN STEEL AND POLYPROPYLENE FIBER REINFORCED CONCRETE

Lara Zanotto, Marcello Congro, Deane Roehl — Tue, 09 Jul 2024 00:00:00 +0000

In fiber-reinforced concrete cement-based materials, the random dispersion of discrete fibers in the
cementitious matrix causes deviations in the global structural behavior. Bending tests are crucial to analyze the
mechanical performance of the composite for project and design at a structural level. Different numerical
approaches have been employed in the literature in order to analyze fracture propagation and damage evolution
in fiber reinforced concrete beams under bending. Traditionally, the association of probabilistic and numerical
approaches reproduces the variability regarding the fiber dispersion in the cement matrix and its influence in
the material mechanical behavior with less computational effort. In this sense, this paper proposes a damage
evolution investigation to perform a numerical fracture analysis using the Extended Finite Element Method
(XFEM). Mixed-mode fracture behavior is considered. Probability density functions are used to generate
random values of tensile strength, which are assigned to each finite element in the model. These numerical
methodologies are based on a constitutive damage model, adjusted to experimental results of failure
mechanisms in fiber-reinforced concrete. The numerical analyses reproduce experimental tests reported in the
literature by Monteiro et al. (2018), as the three-point bending tests, for steel and polypropylene fibers. The
results show that the probabilistic techniques can efficiently predict the load-displacement behavior at the
macroscale since the load capacity ranges present a good agreement with the experimental reference. Moreover,
it is possible to study and predict the fracture behavior of the beam in mixed mode based on numerical models
and Computational Damage Mechanics.

Mesh sensitivity analysis in the fatigue life simulation based on the experimental load history

Alan Tibola, Ariane D’Avila, Leonardo R. Colpo, Rene Q. Rodríguez — Tue, 09 Jul 2024 00:00:00 +0000

Generally, in motorsport, loads are highly dependent on road conditions, with the wheels being sensitive
to oscillations on the road surface. In the case of off-road vehicles, these loads can be considerably unpredictable,
as they depend on the ground unevenness, dimensions of each ground element, speed, angle of attack, among other
several variables. In these cases, to predict the components behavior, experimental forms of analysis can take
place through techniques like extensometry in already existing vehicles, allowing the acquisition of real dynamic
loads and the creation of a database. The durability of many vehicles componets is affected by cyclical nature’s
failure, where there are dynamic stresses and variables as a function of time, in most cases with stresses below
the yield point and material rupture. For an analysis of fatigue life in vehicle structural components with variable
load in computational analysis, the experimental load history can be applied, considering the cumulative damage
effect. The analysis of resistance and durability is a crucial task in the dimensioning of automotive components
and, in complex geometries, the use of finite element software becomes advantageous. In these analysis, the mesh
parameters are directly related to the quality of the analysis, as it refers to a discretization of the model. In this
perspective, the present work presents an approach on the influence of the mesh parameters for the model in finite
elements, applied to the mechanical component most requested by the suspension of the prototype within the scope
of fatigue. Therefore, the load history acquired experimentally was considered for the excitation of the component,
while the interference of the main mesh parameters in the final results was verified. The fatigue tool from the
Ansys software was used to insert a variable gain in the load parameters. The load history was also incorporated
through files obtained experimentally. This history makes the nominal load applied to the component have variable
amplitude.

UM ESTUDO SIMPLIFICADO ANALÍTICO-NUMÉRICO DA CÚPULA DO PANTEÃO ROMANO.

Fillipe Marinho Faria, Lineu José Pedroso — Tue, 09 Jul 2024 00:00:00 +0000

The interest in the recovery and maintenance of historical heritage requires mastery of the structural
behavior of old buildings. The historical curiosity of contemporary scholars in the builders of the past, and in the
construction methods adopted in Antiquity, has led to the development of knowledge, tools and innovative
theoretical approaches, which allow the understanding of monumental works of architectural and historical
interest, which has resisted time, as is the case with the Roman Pantheon. To understand how these monuments
were built, how they behave and how the creative genius of their engineers and architects were used, comparative
studies of methods from the past with more recent methods, aim to shed light on the understanding of this "art of
construction".
Thus, in this work, mathematical models based on modern engineering theories, supported by advanced
computational apparatus, are used to analyze in a simplified way the dome of the Roman Pantheon. A progressive
analytical methodology through the Membrane Theory of spherical shells, and the Finite Element Method via SAP
software are used to model the problem and compare the results, as well as its confrontation with previous studies
of the literature also carried out with similar purposes.

An Embedded Discrete Fracture Model (EDFM) Approach Using a Multipoint Flux Approximation (MPFA) Formulation in Naturally Fractured Reservoirs

André Demski de Oliveira, Darlan Karlo Elisiário de Carvalho — Tue, 09 Jul 2024 00:00:00 +0000

Naturally Fractured Reservoirs (NFR) form part of major water and energy sources around the world.
However, due to their geological complexity and high-contrast permeability, it is difficult to obtain accurate
forecasts and estimates of their production behavior. The numerical modeling and simulation of such reservoirs,
involving fractures of different scales is a great challenge from a mathematical and numerical point of views. In
this context, a very interesting way of representing fractures is through the Embedded Discrete Fracture Model
(EDFM). The strategy was initially developed as a technique that directly incorporates fractures in a conventional
structured mesh, bypassing the additional computational cost of using unstructured meshes, and remaining
compatible with the complex fracture geometries, such as non-planar fractures and fractures with variable aperture.
In this context, our simulation tool incorporates a Multi-Point Flux Approximation method via a diamond stencil
(MPFA-D), which is a very flexible and robust formulation capable of handling highly heterogeneous and
anisotropic domains using general polygonal meshes to solve the pressure equation. To verify our formulation, we
solve some representative problems found in the literature.

Numerical Simulation of Batch Settling in Non-Newtonian Fluids

Tue, 09 Jul 2024 00:00:00 +0000

The study of particle sedimentation in viscous fluids plays a fundamental role in several applications

of different scientific and industrial branches. Furthermore, it is crucial to emphasize the relevance of this pro-
cedure in the control of pressures inside oil well. For instance, the transportation and suspension of sediments

during the disable operation and diminishing the hydrostatic pressure on the annular to avoid the oil well collapse.

Although the extensive applicability of the sedimentation phenomenon, the problem complexity is related to pro-
vide reliable predictions. Hence, mathematical models accomplish a considerable approach in experimental and

theoretical researches. The highly nonlinear characteristics of the model and the development of rarefaction and

shock waves in concentration profiles require appropriate numerical schemes for prediction solutions. Nonethe-
less, the employment of implicit methods is infeasible due to high computational effort. Moreover, there is an

absence of numerical-theoretical studies of the sedimentation phenomenon in non-Newtonian fluids. The present
research employs the non-oscillatory corrector-predictor explicit method developed by Nessyahu and Tadmor for
the numerical simulation of batch settling in viscoelastic fluids.

Application of Mechanics of Structure Genome in the homogenization of masonry reinforced by CFRP

Tue, 09 Jul 2024 00:00:00 +0000

Masonry is one of the most widely used construction methods worldwide, however, as it is a hetero-
geneous material, its modeling is presented as a time-consuming process. As one of the main difficulties about

working with a composite material is due to its anisotropy, caused by the different physical properties of each
present component, mathematical or computational techniques for structural analysis have become essential tools
in this study. In this article, the used technique is Mechanics of Structure Genome (MSG), because it allows the
obtainment of three-dimensional models from simpler systems and smaller dimensions. The tests were performed

in the computational tool SwiftComp, available for computers and also in its mobile version minimizing compu-
tational costs and enabling the homogenization of the studied composite, which is masonry reinforced by mesh

of carbon fiber reinforced polymer (CFRP). After possessing the Young’s modulus and the Poisson’s ratio of the
components, both of the CFRP and of the masonry, it is possible to perform the homogenization of each one,
separately. Thus, the elastic constants of each of them are obtained to finally present the three-dimensional elastic
properties of the masonry reinforced by CFRP, assuming a small variation for the Poisson’s ratio of the matrix, in
order to obtain the constitutive relation of the element.

Comparative analysis in the homogenization process of heterogeneous materials using mechanics of structure genome

Joao F.L. Nunes, Francisco P.A. Almeida — Tue, 09 Jul 2024 00:00:00 +0000

Concerning the mechanical properties studies of heterogeneous materials, its behaviours are obtained by
ideal models. With the aim of simplify this modelling process, in other words, formulate an homogeneous model
which represents the heterogeneous material (process called homogenization), as the microscopic analyses of stress
and strain (process called dehomogenization), the so called Mechanics of Structure Genome method (MSG) was
developed. The MSG method proposes to model a representation of a smallest particle possible that could describe
the behaviour and geometry of the heterogeneous material, showing its microscopic behaviour. The method is
named as so from its similarity with the gene concept in biology, standing for organic microparticles that contains
all the information of a live cell. To observe the capacity and reliability of MSG compared to methods already in
use among researchers and industry, this work models a stiffness matrix of an heterogeneous material, composed
by a matrix of titanium and silicon carbide (SiC) fibres using SwiftComp software, available on cloud, Android and
iOS, exposing the substantial reduction in computer effort and time compared to existing methods, and compares
the results to the respective matrix for the same material obtained by the Zheng and Fish method, Self-Consistent
Method (SCM) and Mori-Tanaka Method (MTM), discussing in the end the reliability and usage in the industry
and academy of the exposed method.

Numerical study of non-saturated porous media flow

Mario J. dos R. Moura, Renan de S. Teixeira, Wilian J. dos Santos — Tue, 09 Jul 2024 00:00:00 +0000

Water is an essential natural resource in maintenance of life, considering physiological/biochemical
aspects related to living beings. In addition, water is livelihood for plants and animal species. Water resources

play an important role in countries’ economic development, as industries demand large volumes of water to man-
ufacture products. In agriculture, water is widely used for crop production, guaranteeing the supply of food to

the population. Due to the large use of such natural resource, it is necessary the optimization of its use. Irrigation
systems are required to supply the necessary amount of water to the soil, providing ideal humidity for plant growth.
Prediction of retention curve is an essential tool to describe water flow in soils, providing an estimative of water
availability used in plant growth, at different depths. The present work aims to study the water retention curve of

the non-saturated flow problem in soils by performing a numerical simulation of the soil moisture profile with re-
ported data in the literature, using Picard iterative scheme. To prove the effectiveness of the method, a comparison

with an implicit scheme is made, both based on finite differences.

Optimized Structural Design of Lattice Towers for Wind Turbines

Tenorio C. Mayara, Cavalcante A. A. Marcio — Tue, 09 Jul 2024 00:00:00 +0000

Wind energy is a valuable renewable energy resource, and it has been recently explored in Brazil, with
a strong tendency to increase in the next decades, considering the Brazil's potential. The most common way to
explore wind energy is through wind turbines, usually designed to have maximum efficiency. The tower is an
essential part of the wind turbine design, once it defines the wind turbine efficiency and must be designed to resist
to different loadings, responding for 30% of the wind turbine cost, approximately. This work presents a structural
optimization study of steel lattice towers of wind turbines within a framework based on the strength of materials
and the finite element method for the tower's structural analysis, besides optimization techniques, to minimize the
tower's weight. Some comparisons are made with an optimized aluminum lattice tower. The minimization of the
tower's weight through the employment of optimization techniques allows a reduction of the costs with inputs,
transportation, assembling, and maintenance of the tower, especially those installed in remote areas with difficult
access, besides contributing to the study of this technology.

The Analysis of a SAE Formula Prototype Chassis Via Finite Element Method

Matheus C. Paulino, Koje D. V. Mishina, Monã G. G. V. Souza — Tue, 09 Jul 2024 00:00:00 +0000

Engineering has always promoted efficiency linked with a safe and profitable design. In light of this, a
tool has been growing, which is the CAE (Computer Aided Engineering). That tool models a design and tests it
on a software via virtual prototypes. To put it simply, the CAE simplifies the development of a project, since
having a computer-based study of the problem allows the developer to visualize the design without having neither
cost with material nor with manufacturing the prototype. The engineer therefore saves time and money, besides
not having accidental risk of a prototype’s real failure, as it is all virtual. That is why the CAE perfectly fits in
naval and aerospace engineering, because in those areas any minimal error can generate a fatality. Within the CAE
technology, there are some subdivisions, the most famous are: CFD (Computational Fluid Dynamics), which
studies transfer of heat and mass; and FEM (Finite Element Method), in which structural mechanics is studied. In
the present work we will present the FEM in a chassis of a FORMULA SAE vehicle model, which will be modeled,
made as discretization, simulated and by finalization an experimental table will be made, where the real results
(experimental table) and the results obtained via software will be analyzed. Either the experimented and the
simulated tables will demonstrate a very important factor in a vehicle chassis, that is the torsional stiffness. Thus,
by analysing the torsional stiffness of the table, the engineer knows how a car will behave in a torsion, and such
knowledge is crucial for the vehicle dynamics and pilot’s safety.

Predictive modeling based on Deep Machine Learning models coupled to Discrete Wavelet Transform applied to short-term solar radiation forecasting

Tue, 09 Jul 2024 00:00:00 +0000

Forecasting solar radiation is important for analyzing the feasibility of power generation and optimizing
the operation. In this context, approaches using simple Machine Learning models, such as Artificial Neural
Network (ANN) and Support Vector Machine (SVM) were made, but could not satisfy the performance
requirements in complex scenarios. Therefore, it was necessary to use hybrid models with the Discrete Wavelet

Transform (DWT). This paper intended to implement solar radiation forecasting using ANN, SVM, Long-Short-
Term-Memory Network (LSTM) and their hybrids coupled with DWT as a preprocessing technique using Python.

The results obtained were compared to the Autoregressive Integrated Moving Average model (ARIMA). The data
of solar radiation was collected by the automatic weather Salinas station of Nova Friburgo (RJ), the Holdout
validation was used to evaluate the prognosis performances using Root-Mean-Square error (RMSE) and
Coefficient of Determination (R2). The results revealed that the simple models had worse results than ARIMA,
and that hybrid models had superior performance, especially the DWT-LSTM which had an R2 of 0.994 and an
RMSE of 0.516. In addition, Python showed to be powerful as an Open Source tool for implementation of robust
models that are useful for applications in science and engineering.

Structural optimization of trusses considering geometric stability

Omar M. I. Matar, Andre J. Torii — Tue, 09 Jul 2024 00:00:00 +0000

Structural optimization is a required area where the aim is to reduce project costs, reducing the amount
of material used and meeting the requirements for the safety and use of the structure. The objective of the study
is develop computerized routines for the structural optimization of trusses submitted to nodal loads considering
geometric stability. The optimization problem seeks for an answer that minimizes the volume of trusses subjected
to stress, displacement and geometric stability constraints. The design variables are those commonly used, given
by the bars cross-section area and nodal coordinates. To solve this problem, computerized routines were developed
using MASTAN2

R program for the structural analysis and MATLAB

R program, for numerical optimization.

Different sample structures were created to analyze the resourcefulness of the routines. The program found diffi-
culties in optimizes some structures that have bars that are not necessary in the final design, a classical difficulty in

this area.

Development of a computational tool in Python language based on Principal Component Analysis, Self-Organizing Map and Support Vector Machines applied to process monitoring

Tue, 09 Jul 2024 00:00:00 +0000

Industry is going through a new transformation, called Industry 4.0, in order to absorb recent advances
in technology as a way of meeting the constant need for efficient and automated processes. In the chemical industry
specifically, these techniques enable to understand the behavior of process guarantee his safety and good
performance. There are many methods for implementation of process monitoring system, between techniques of
unsupervised and supervised machine learning, such as the Principal Component Analysis (PCA), Self-Organizing
Map (SOM) and Support Vector Machines (SVM). In this context, in this paper was studied the development of a
computational tool for monitoring the process variables based on cited techniques in order to detect conditions that
can affect process performance and, consequently, product quality. The implementation was developed in Python
environment and it was applied in a generated fault data from data available in the literature for drying process in
an evaporator bed. The statistical metrics F1, accuracy and precision were used to evaluate the techniques and the
results indicated that the computational tool showed to be effective on application that was studied. Finally, the
tool presented advantages for being free, having an intuitive interface and can be easily used for process
monitoring.

OPTIMIZED STRUCTURAL DESIGN OF TRANSMISSION LINE CONDUCTOR

Joelington Tadeu da Silva Filho, Márcio André Araújo Cavalcante — Tue, 09 Jul 2024 00:00:00 +0000

The transmission line conductor is an essential element of an electrical transmission system, once it
defines the system efficiency, in terms of electrical conductance. However, the choice for the best material for a
transmission line conductor does not consider just electrical properties, but also mechanical properties, as
strength and stiffness. In terms of design, material cost is also an essential factor. Taking in account only electrical
and mechanical properties, copper would be the best choice. However, it presents a high price, which makes the
aluminum conductor steel reinforced the most common solution for a transmission line. The combination of these
two materials overcomes the limited mechanical properties of the aluminum. In this study, optimization techniques
are employed at the design of aluminum conductor steel reinforced to minimize the conductor’s weight, based on
a strength material approach, considering only its self-weight. In the optimization procedure, the aluminum and
steel cross-sectional areas and the wire sag are the design variables, the conductor’s weight is the objective
function, and some electrical and mechanical considerations are adopted as restrictions. Thus, this study proposes
a framework for an optimized design of transmission line conductors.

Evaluation of Annular Pressure Buildup in Oil Wells

Pedro R. Magalhaes, Thiago B. Silva — Tue, 09 Jul 2024 00:00:00 +0000

In the search for new sources, the oil wells become increasingly deep and, consequently, new challenges

arise in their construction and operation. Annular Pressure Build-up (APB) is a phenomenon caused by the resis-
tance imposed by the casing strings, that limit the annulus, against the free thermal expansion of the trapped fluid.

This balance between the pressure increase and the volume changes due to deformations in the well structure,
which cannot be treated as a totally rigid system, is fundamental to the correct scaling of the problem according to
the multistring casing design philosophy. APB usually occurs in the production phase, when the hot fluid from the
reservoir flows through the tubing, radially transferring heat to the outermost layers. In this paper, a computational
APB model was developed, considering the effect of the interaction between casing strings (multistring), and it is
applied in a case study in order to validate the formulation and illustrate its efficacy. This model can be broken
down into selecting a thermal simulator, a Pressure-Volume-Temperature (PVT) model suitable for annular fluids,
a casing displacement model, and a numerical method to solve the APB equations.

Gompertz model in the study of confirmed cases of COVID-19 in the city of Porto Alegre

Eduarda de C. Castro, Eliete B. Hauser — Tue, 09 Jul 2024 00:00:00 +0000

In the present study, the behavior of the cumulative number of confirmed cases by COVID-19 in the
city of Porto Alegre (RS) was analyzed based on official data from March 8th to July 31st

, 2020, contained in the
COVID-19 Bulletin and published daily by the City Hall. The analytical solution of the Gompertz differential
equation was deduced and its exact solution was expressed by the Gompertz sigmoidal model, P(t). Nonlinear
regression techniques were used to determine the parameters of the P(t) function. Simulations were performed,
ranging the maximum number of contaminants from 100% to 20% of the total population of Porto Alegre. The
results obtained were adequate with a Pearson correlation coefficient of at least 0.99. The models were used to
predict the data for August 7th, 2020 and the largest relative percentage deviation was approximately 13% and 21%
for August 19th, 2020. The inflection point of P(t) was calculated, which shows a change in the growth rates of the
number of accumulated cases (large at the beginning of the process and changing to a slower growth).

Modelling P-SV seismic wave in homogeneous media for the Brazilian territory

Andina, A. Lerma., Paulo L. Natti, Eliandro R. Cirilo,, Neyva M. L. Romeiro — Tue, 09 Jul 2024 00:00:00 +0000

In the literature, there are few works of seismic modeling in Brazil. We know that Brazil is on the
South American plate making the country have very few seismic events, but it is not a guarantee for some faults
can collapse at any time, and earthquakes of magnitude greater than normal are possible. Earthquakes are violent
vibratory phenomena of short duration and, at times, of great intensity generated around a point source called
procedente, in which large displacements of masses are produced, generating longitudinal and transverse waves.
The longitudinal waves vibrate in the direction of the wave propagation and they are the first to be perceived. The
tranverse waves vibrate perpendicular to the propagation direction and they delay in relation to longitudinal waves.
In this context, the mathematical modeling of seismic waves allows the elaboration of theorical seismograms that
allow predicting the characteristics of earthquakes, depending on the geogical conditions. This work describes
the propagation of P (longitudinal waves) and SV (transverse waves) seismic waves modeled by equations of
motion in elastical media, since the Earth behaves as a deformable material. So, our partial differential equations
(PDE) describe the propagation of seismic waves in a vertical two-dimensional system (x and z coordinates), in
homogeneous media, given by a source, assuming Neumann boundary conditions. For simplicity, the vertical
two-dimensional domain is considered rectangular. The point source is modeled using a Gaussian-type function,
located at a point inside the domain. To solve this PDE system, the finite difference method (FDM) is used. The
boundary conditions are also discretized by FDM. The simulations will be carried out for different media, described
by different densities in the terrestrial layers, and for different vertical positions for the point source (hypocenter),
generating different seismological maps.

Numerical modeling of pullout tests in an extremely soft, sensitive, and thixotropic clay

Tue, 09 Jul 2024 00:00:00 +0000

Three usual challenges related to numerical modeling of geotechnical problems are addressed in this
paper - large distortions of finite element meshes, the soil-structure interface, and calibration of soft clay
parameters. The objective of this paper is to obtain a reliable numerical model to reproduce experimental results
and perform parametric analysis. The paper presents the approaches and techniques adopted to numerically
simulate pullout tests of mini piles submitted to large displacements in extremely soft, sensitive, and thixotropic
clay. A two-dimensional finite element model was assumed, considering the axisymmetric condition, to simulate
the fluid coupled analysis in Abaqus/CAE software, taking into account two conditions: saturated clay and
pullout undrained loading. Considerations and conclusions on the mobilization mechanisms of the total pullout
force, base resistance and shaft resistance, and the influence of the parameters were presented and discussed. The
validity of the approaches and techniques used was highlighted by the good agreement between the numerical
and experimental results. The quality of the parametric results corroborates the conclusion that the numerical
model is reliable and the software is a powerful tool to analyze complex interface problems related to piles
embedded in very soft clay.

Yield design upper bound approach to uplift bearing capacity of offshore strip anchors

Mateus Forcelini, Samir Maghous — Tue, 09 Jul 2024 00:00:00 +0000

The offshore oil and gas exploration activities require several subsea infrastructures to be installed
over the ocean floor, this equipment being commonly supported by shallow foundations namely anchor plates or
mudmats. By the environmental conditions, live loads imposed during the structure lifetime, and the requirement
for extraction processes, the design practice for anchor plates strongly relies on the evaluation of the vertical
uplift capacity of the foundation system under undrained settings, being subjected to suction forces acting below
the anchor interface which compose a rather complex subject in geomechanics, usually not addressed by the
classical foundation theories. In this context, this paper aims to evaluate the uplift bearing capacity of a shallow
foundation embedded in a purely cohesive material based on the theoretical framework of limit analysis theory
and related kinematic approach. The latter allows for the formulation of rigorous upper bound estimates of the
uplift bearing capacity by implementation and analysis of appropriate failure mechanisms that involve the anchor,
the surrounding soil, and their mechanical interaction along with the interface. It is shown that the optimal uplift
estimate bearing capacity amounts to minimizing a non-convex functional with respect to the parameters defining
the geometry of considered class of failure mechanisms. The considered minimization procedure is handled by
analyzing the stationary condition of the associated variational form, thus leading to the analytical determination
of the optimal failure mechanism. For application purposes, the strength capacity of the soil is modeled through a
Tresca-like yield condition with a tension cut-off, whereas the soil/anchor interface is modeled by a tensile stress
threshold. The predictions obtained from the approach are compared to available finite element solutions derived
in a particular situation with a perfectly smooth soil/anchor interface. An extensive parametric study is then carried
out to assess the effects of relevant problem parameters on the uplift bearing capacity, such as the threshold stress
controlling the breakaway condition at the interface and the strength parameters of the soil.

Numerical modeling of shallow tunnels: analysis of the surface settlements

W. C. Ferrão, B. M. Jensen, D. Bernaud — Tue, 09 Jul 2024 00:00:00 +0000

The analysis of shallow tunnels is necessarily related to the study of the excavation influence on the

ground surface. As the excavation proceeds, surface settlements are expected to be generated, forming the so-
called settlement basin. Thereby, its correct evaluation is important since these movements could create

disturbances in surrounding structures. Estimation of tunneling-induced ground movements can be done by
analytical, empirical, and numerical methods and, currently, the best assessment of tunneling process consists of
finite element modeling. The current paper presents a numerical model elaborated in the software ANSYS with
the aim to evaluate the surface settlements induced by tunneling. The 3D finite element model concerns soil and
lining elements, using the activation and deactivation tool to simulate the excavation and lining placement. To
perform the analysis, the soil mass was represented by a plastic model using the Drucker Prager criterion and the
concrete lining is considered elastic. Five reported cases of real tunnels (Heathrow Express, Green Park, Barcelona
Subway, Brasília Subway, and São Paulo Paraíso tunnels) are simulated to validate the model with analytical and
experimental solutions.

Variation of Measured CPTu Data of Brazilian Marine Soil

Tue, 09 Jul 2024 00:00:00 +0000

Soil profiling and estimation of soil parameters (e.g. undrained shear strength) are essential to the
design of oil wells. Piezocone Penetration Test (CPTu) is one of the most used tests to characterize geomechanical
behavior. Uncertanties regarding CPTu data reflects in transformation models for undrained strength evaluation.
Present work assess variability of cone tip resistance and total vertical stress data obtained from CPTu tests in
brazillian geological basins and its effect in undrained shear strength transformation model. DNV’s recommended
practice C207 assess undrained strength characteristc values that are used in conductor casing design, which plays
an important role in structural integrity and safety of well operations serving as foundation element, supporting
all construction and operation phases. Results shows low levels of uncertanties and good overall repeatability, an
indicator of good quality of data.

DEVELOPMENT OF A GUI FOR THE PARAMETRIC STUDY OF MASS FLOW RATES USING THE MATERIAL POINT METHOD

Tue, 09 Jul 2024 00:00:00 +0000

Measuring flow rates in engineering applications, whether it’s fluid or solid, it’s an important

task as it often leads to good phenomenon characterization. Particularly, in marine environments, it pro-
vides a metric that can be used to safeguard facilities susceptible to landslides. Solving flow rate related

problems is a difficult task due to fluid-structure interactions, nonlinearities and phase transitions. There-
fore, analytical solutions can be very complex, even impossible to achieve, which usually are the cases

approached by geotechnical engineering. Hence, it’s preferable to use numerical techniques to solve such
problems. In this regard, the material point method is a Lagrangian numerical method where particles
move through a background mesh, avoiding distortion problems. This work develops a parametric study
of the mass flow rate of a submarine landslide using the software E-Sub, a numerical analysis software
developed by the Laboratory of Scientific Computing and Visualization (LCCV). Modelling a submarine
landslide often involves many parameters which can dramatically alter the results of the simulation. For
this reason, a graphical user interface was developed in which the model is visualized. Furthermore, the
interface also allows marking out section planes in which the flow rate is going to be analysed. Lastly,
our results showed that the ocean floor plays a major role on all other variables involved in the problem,
in which minor changes on its angle lead to bigger changes into flow rates.

Poroelastic Modeling of Piezocone Tests Using Poroelastic Cavity Expansion Analysis

Vicente Mafra, Gracieli Dienstmann — Tue, 09 Jul 2024 00:00:00 +0000

The CPTu (Cone Penetration Test with pore pressure measurements) is a field test widely used to
obtain stratigraphic characterization and geotechnical properties of a subsoil profile. In general, the speed used
for driving the cone is standardized at 20 mm/s. In this way, predominantly sandy soils tend to show drained
behavior, in such manner the analysis is based on effective tensions; and predominantly clayey soils tend to
show undrained behavior, thus the analyze is based on total stresses. In this sense, classical methods of
interpretation are set to define with an accepted reliability behavior of typical sands or clays. However, for
mixtures or silty soils, drainage may be partial. In this condition, the pore pressure around the cone is altered
introducing errors in the interpretation. The present work aims to present a model capable to identify the
drainage behavior of soils submitted to CPTu with intermediate permeability characteristics (silty soils). To
evaluate the drainage behavior during the execution of the test, simplified semi-analytical models of cylindrical
cavity expansion were developed, based on the theories of poroelasticity presented by Biot [1]. Preliminary
results indicate that the model has the capacity to evaluate the typical drainage behavior of the soil submitted to
CPT.

An alternative approach for fast oil well drilling simulations in pre-salt

Wed, 10 Jul 2024 00:00:00 +0000

This work proposes an alternative approach for fast oil well drilling in pre-salt. Under high stress and
temperature conditions, salt rocks develop a progressive time-dependent deformation, called creep. This behavior
promotes the borehole closure over time, leading to stuck pipe and well drilling delay. Thus, numerical simulations
of the salt rock behavior can be used to assist in oil well design and also along drilling operation. Currently, these
simulations are based on the finite element method. The classical approach performs a full plane axisymmetric
analysis considering the whole domain, but, in general, these simulations demand a high computational cost. As
observed, large zones of well-behaved salt rocks can be represented by a faster one-dimensional axisymmetric
formulation without loss of accuracy of results. Moreover, the division of the original domain into sub-sections
of independent analysis, considerably reduces the total computational cost. Therefore, aiming to speedup the
solution, case study scenarios are defined for elaboration of spatial subdivision rules, combining the two mentioned
formulations. Finally, the results obtained are compared to the classic reference approach. It’s expected that
the proposed strategy can lead to good approximations of reference results, making possible to carry out faster
simulations to assist in oil well drilling.

Numerical and Experimental Study for Determining Hydraulic Parameters in Unsaturated Soils

Wed, 10 Jul 2024 00:00:00 +0000

Studies to determine the hydraulic properties of unsaturated soils, named soil water characteristic curve
and hydraulic conductivity function, are generally carried out using laboratory measurements. Even though such
experiments are capable of producing accurate results they are time consuming, labor intensive and may not
represent large scales. In this context, this work sought to obtain the hydraulic parameters through inverse
modeling from the Monitored Infiltration field tests. Such approach provides a simple way to merge observed
data and models. The measurements for inversion procedures were carried out on a road embankment located in
Ouro Branco, Minas Gerais. To solve the generated problem the Finite Element based Hydrus 2D software package

was used to obtain the van Genuchten empirical parameters. In this process, the standard first order Levenberg-
Marquardt optimization algorithm was used, which is a local search method that generates a set of candidate

parameters around the initial values given by the user, which has the advantage of a high convergence rate. Thus,
the empirical parameters α e n, and the saturated permeability (Ksat) were estimated, while the, residual volumetric
moisture (θr) and saturated volumetric moisture (θs), were considered as known. Our results indicates that this type
of test is an accessible and accurate choice to calibrate soil hydraulic parameters.

Incorporation of a damage model to salt rocks viscoelastic modelling

Wed, 10 Jul 2024 00:00:00 +0000

This work describes a numerical study using finite elements about the structural behavior of vertical
wells through salt rocks, using a coupled viscoelastic damage model. The salt rocks have porosity and permeability
close to zero, performing as a sealing structure, so that is common to find oil reservoirs under these formations.
However, to reach such reservoirs it is necessary to pass through thick layers of these rocks, that develop high
creep strain rates in the direction of the borehole closure. In some situations, this closure can cause problems
like equipment entrapment and poor cementing in casing installation. Depending on the strain rate and on rock
exposure time, the accumulated strain can be too large, leading to material breakdown, which generates washout
regions. Thus, for an accurate prediction of well profile over time it is necessary to consider the damage caused on
rock due to the accumulated strain, searching to map washout regions. Due to the complexity of the problem, the
studies are performed through numerical simulations. The proposed methodology is divided in four main steps:
a) choice of a constitutive model with damage to salt rocks; b) verification of numerical modelling of vertical
well through salt rocks; c) implementation of viscoelastic model with coupled damage for salt rocks; d) numerical
modelling of the well considering the implemented constitutive model. This study identified a damage model for
salt rocks proper to the vertical well scenarios under study. The incorporation of this model to the computational
methodology should contribute to a better understanding of the rupture mechanisms of these rocks and should help
to forecast the washout regions.

Soil-Structure Interaction Analysis in a Port Wharf Through Finite Element Methods Using the PLAXIS 2D Software

Pedro F. Martins — Wed, 10 Jul 2024 00:00:00 +0000

During the project lifespan, berthing structures are exposed to several types of stress. Mooring strains,
weight of the structure and external loads from machinery and soil may generate stresses and displacements on the
foundations. As they are structures that normally present a high level of complexity, the analysis of their behavior
through numerical methods becomes an interesting tool. The use of these methods also allows to model the soil in
a satisfactory way, since, as it is a heterogeneous medium, its properties are of difficult determination. The
objective of this work is to use numerical methods as a way of analyzing the displacements and tensions imposed
on the foundations of a port wharf. Standard penetration tests performed at the site were used to estimate the
geotechnical parameters through correlations found in the literature. The numerical modeling was generated in the
PLAXIS 2D AE. software, through a two dimensional plane-deformation analysis of the problem. Preliminary
analysis identified the presence of these effects on the foundations of the wharf, thus showing the importance of
their verification at the project stage. Through this work, it is expected to better understand the behavior of the
soil-structure interaction present in this wharf, so that in future projects these effects can be taken into account.

Prediction of settlements generated by a static load test through numerical modeling using PLAXIS 2D

Pedro F. Martins — Wed, 10 Jul 2024 00:00:00 +0000

When it comes to geotechnical engineering, one of the greatest concern when building any type of
structure is the settlements that occurred on its foundations. As a way of predicting these settlements, static load
tests can be performed. This test consists in the application of successive loading stages at the top of the pile and
in the respective measurement of the settlements occurred. This article uses numerical modeling as a way to
estimate the settlement of piles caused by this test. The analysis was performed through an axisymmetric two
dimensional model in PLAXIS 2D AE. software, using the finite element method as a way to obtain the results.
This method allows to model satisfactorily the behavior of the local stratified soil and its interaction with the pile.
PLAXIS software allows the use of different constitutive models in the simulation of the soil, thus obtaining greater
precision in the results. The objective of this work is to improve the numerical modeling of static load tests using
the PLAXIS 2D software. Results obtained through an initial model were consistent with a static load test report
carried out at the site, thus evidencing the tool's potential in predicting settlements.

Thermo coupled elastoplastic-viscoplastic solutions for compaction process in sedimentary basins

Paulo Sergio Baumbach Lemos, Andre Bruch, Samir Maghous — Wed, 10 Jul 2024 00:00:00 +0000

This work presents semianalytical solutions for the deformation induced by gravitational compaction in
sedimentary basins. Formulated within the framework of thermo coupled plasticity–viscoplasticity at large strains,
the modeling dedicates special emphasis to the effects of material densification associated with large irreversible
porosity changes on the stiffness and hardening of the sediment material. The analysis is restricted to the fully

drained setting in which excess pore-pressures are disregarded. In addition, the thermal problem is posed, for-
mulating the thermal field with constant parameters. These solutions can be viewed as reference solutions for

verification and benchmarks of basin simulators.

On the Equivalence of Forchheimer and Inertial Terms in Fluid Dynamics in Porous Media

Karl Igor Martins Guerra, Celso Romanel — Wed, 10 Jul 2024 00:00:00 +0000

With the advance of numerical methods and the capacity of computers to solve problems of high
computational cost, the dynamics of fluids in porous media started to give up with the simplifying hypotheses and
started to not only solve the complete equations, but also allowed to incorporate coupled phenomena such as
deformation of porous media, temperature, chemical reaction and electromagnetism. The first steps towards a more
rigorous study from the mathematical point of view, necessarily involve the progressive incorporation of more
rigorous equations as a state of the art in flow problems. The transition from Darcy’s law to Brinkman’s equations
and even the direct numerical simulations (DNS) of the Navier-Stokes equations on a pore scale, started to take
place in the current methods of predicting the hydrogeological behavior of materials. This work seeks, in a succinct
and humble way, to highlight and propose an analysis of the possible equivalence between the Forchheimer term
to simulate the nonlinear effects on the flow in porous media and the natural convective term of the Eulerian
formulation of the conservation of the of momentum in fluids. Despite the equivalence being affirmed in some
works, there seems to be a lack in literature concerning rigorous demonstrations of this affirmation. This paper
uses tools such as the topology of metric spaces and the weak formulation in finite dimensional spaces in the
analysis of the differential equations that govern the problem and seeks to be as clear as possible so that a reader
not used to the mathematics involved can understand, at least, the central idea.

Contributions to the study of soil-structure interaction in bridge abutments

Vinícius M. Spricigo, Eduardo M. B. Campello, Pedro Wellington G. N. Teixeira — Wed, 10 Jul 2024 00:00:00 +0000

Bridge abutments are structures of varied characteristics that enable the transition between bridges and
highways, with the function of supporting decks at the ends, in addition to retaining access embankments. A poor
assessment of the soil-structure interaction (SSI) in these structures might compromise the bridge’s in-service
performance and structural safety. However, this topic has not yet been properly consolidated in international
standards, and it is a common practice to design abutments through isolated and simplified models. This paper
aims to investigate aspects that are not considered in the usual analysis, such as the three-dimensionality of the
problem and a more realistic assessment of SSI. For that purpose, a parametric study is conducted through the
numerical computational modeling of a conventional stub type concrete abutment, with deep foundations, the
adjacent embankment and the foundation soil. Two- and three-dimensional finite element models are generated,
considering variations in geometry, constructive phasing of the abutment and different constitutive models for soil
representation: Winkler or continuum models. The comparative analysis of the results, in terms of stresses/strains
of the soil and structural elements, should provide a broader understanding of the theme and contribute to the
establishment of a modelling framework of SSI for bridge abutments.

Numerical modelling of geothermal piles in tropical environment: group effect on heat dissipation

Luísa P. Barakat, Caique R. Almeida, Cyro A. Neto — Wed, 10 Jul 2024 00:00:00 +0000

In tropical countries, geothermal piles are foundation elements that, besides providing structural support,
dissipate heat from the internal environment of buildings to the foundation soil. Since foundations are usually
composed of pile groups, the interactions among piles should be investigated also from the thermal efficiency
standpoint. This paper presents a numerical model of a 5-pile group to study the influence of number and position
of thermo-active piles on the heat transfer of the geothermal system. The numerical model was developed with
ANSYS FLUENT and was validated with results obtained by Almeida [1] in his numerical model for a single pile.
Results indicated that the thermal influence radius does not increase linearly with the number of thermo-active
piles and that, in the limit, a group of piles may thermally behave as single pile. This study showed the importance
of simulating heat transfer on pile groups for the improvement of geothermal foundations design, since the
activation of all piles may lessen the thermal performance of the group.

Numerical analysis of twin tunnels including long-term effects considering the creep and shrinkage of concrete

Felipe Pinto da Motta Quevedo, Denise Bernaud, Américo Campos Filho — Wed, 10 Jul 2024 00:00:00 +0000

This paper aims to show, through three-dimensional numerical analysis on finite element method, the
effect that the twin tunnel causes on the convergence profile considering several constitutive models of rockmass:
elastic, elastoplastic and viscoplastic. The elastic and viscoelastic constitutive models for the lining are considered.
For the viscoelastic constitutive model of the lining, the concrete creep and shrinkage are considered. For the case
studied in this paper a difference in the magnitude of the convergence profile of up to 9% for the twin tunnel was
observed, considering the rockmass and the lining with elastic behavior. For the other models, plastic rockmass
with elastic lining, viscoplastic rockmass with elastic lining and viscoplastic rockmass with viscoelastic lining,
minor differences were observed. Considering the viscoplastic rockmass, the presence of the viscoelastic lining
increased the deformations by about 20% (at the end of tunnel construction) and by about 40% in the long-term
behavior, in relation to the elastic lining.

Performance analysis of an embankment over a soft soil deposit through instrumentation and numerical simulation

Rafael F. Cordeiro, Miryan Y. Sakamoto, Gracieli Dienstmann — Wed, 10 Jul 2024 00:00:00 +0000

The present paper describes the performance analysis of an embankment over a soft soil deposit. The
embankment is part of the duplication of the Brazilian Federal highway, BR 470, a major infrastructure project
that crosses several soft clay deposits in the State of Santa Catarina, Brazil. To increase stability the reference
section was reinforcement with geogrids, equilibrium berms, and stage constructions of the landfill (slow
construction) was specified combined with preloading and pre-fabricated vertical drains (PVDs) to accelerate
consolidation. The performance during field construction was mainly evaluated through instrumentation
considering the evolution of horizontal displacements and the stabilization of settlements. Given the limitations of
the methods used for control during the construction process, and a discrepancy between field settlements and
original project predictions, soil profile and geotechnical parameters were revaluated during construction, and used
in a revised performance analysis. The revised performance analysis was done in finite element software PLAXIS,
using Mohr Coulumb and Soft Soil Models. Some important considerations were observed when proceeding this
back analysis that could have been used to modify the construction process during execution. Additionally, to
analyze the effects of the inherit variability, a sensibility analysis to determine levels of possible settlements and
time of consolidation was performed.

Effect of lateral movement type on earth pressures developed behind the abutment of a semi-integral bridge

Pedro H. dos S. Silva, Yuri D. J. Costa, Jorge G. Zornberg, Carina M. L. Costa — Wed, 10 Jul 2024 00:00:00 +0000

Semi-integral abutment bridges are constructed without thermal expansion joints, and the
superstructure-abutment system is not integrally connected to the substructure. In view of this peculiar
characteristic, the abutment undergoes combined movements of translation and rotation due to the expansion and
contraction of the superstructure. This work proposes to analyze the effect of different lateral movements on the
earth pressures developed behind the abutment of a semi-integral bridge. Numerical simulations were carried out
by using a finite element model. Lateral movements of the abutment were simulated in three different conditions:
combined rotation and translation (Case 1), rotation only (Case 2), and translation only (Case 3). Predicted lateral
earth pressures were compared with experimental field data obtained from a semi-integral bridge abutment.
Predicted values were obtained at the same position where the field measurements were performed on the
abutment. The best match between field and numerical pressures were obtained with Case 1. During expansion
phases of the bridge superstructure, Case 2 slightly underestimated the lateral earth pressures, while Case 3
overestimated them. The opposite occurred during contraction phases. The combined movement of rotation and
translation proved to be more suitable to represent the lateral movements of the bridge abutment in field conditions.

Aplicação da Técnica de Redução de Ordem em Elementos Finitos para Simulações de Fluxo Transiente em Aquíferos.

Wed, 10 Jul 2024 00:00:00 +0000

Aquifers are geological formations whose water extraction has guaranteed the supply of populations
worldwide. The management of this type of system composed of porous rocks aims at both longevity of the natural
resource and security of the extraction. Management is carried out through the solution of flow equation that
represents the balance between water extraction (represented mainly by production wells) and aquifer recharge.
The flow equation is a partial differential equation whose unknown is the hydraulic head and can be solved through
numerical methods such as the finite difference method and the finite element method. In this modeling, a high
level of discretization is required in order to have a reliable description of the permeability and porosity fields,
fundamental properties that respectively control the flow and storage of water in the pores of the rock. At the same
time, the aquifer is a very extensive domain (on the kilometer scale), thereby generating numerical models with
high degrees of freedom.
In this type of problem, techniques that promote the reduction of the number of degrees of freedom, without
considerable loss of the quality of the solution, can be extremely useful, especially when combined with
uncertainty or optimization analysis, which require a large number of water flow simulations at aquifer scale. In
this context, this paper discusses and proposes methodologies for reducing the model order of the water flow
problem in aquifers solved by the finite element method.

Technical feasibility of using energy piles in tropical soils in the State of Rio de Janeiro: A numerical study

Nathália Gil Nunes, Júlio César da Silva, Karl Igor Martins Guerra — Wed, 10 Jul 2024 00:00:00 +0000

Over time, human development requires monitoring of the renewal of resources that is difficult to
achieve, so the search for sustainable alternatives that cause less impact on nature is necessary across the planet.
Although Brazil claims to have its energy matrix based on hydroelectric generation, the State of Rio de Janeiro
differs from the Brazilian and, being one of the pillars of the Brazilian economy, any proposal to revise the
production methods of energy is necessary. It is known that 96% of the energy consumed in Rio de Janeiro comes
from non-renewable sources. Energy foundations, more precisely geothermal piles, are solutions widely studied
in northern European countries. It is known to date that its use can reduce electricity consumption by up to 30%
in cold countries like Sweden and Canada. It consists of a cooling and / or space heating system through the heat
transfer from the soil depth to the construction structure made by a pump system, besides being promising, it is an
ecological and sustainable alternative. The main motivation of this study is to verify whether, in tropical soils and
tropical climates, such a reduction can also be achieved. To achieve the proposed objective, this work will consist
of numerical analysis via Finite Element Method (FEM) implemented by the authors in the MatLab 2020 program
so that there is greater mathematical rigor. Thus, according to the thermal performance of each soil with the
interaction of the pile element, it is possible to predict an application checking its viability in each location.

Particle shape and its importance to Discrete Element Modeling in the context of railway ballast simulation

Sílvio Tumelero de Moraes, Alfredo Gay Neto, Liedi Legi Bariani Bernucci — Wed, 10 Jul 2024 00:00:00 +0000

Computational tools may be helpful to understand the railway ballast mechanical behavior. In the
context of the Discrete Element Method (DEM), a numerical simulation may be performed considering different
grain shapes and parameters to represent the actual ballast. It is well-known that modeling faceted aggregates
(polyhedral) provides interlocking between particles. This may avoid rolling movements. On the other hand,
employing spherical particles to represent non-spherical grains may neglect the physical expected rolling
resistance. In this paper a shear box test simulation using DEM was investigated, considering distinct shapes of
ballast aggregate. The macroscopic mechanical behavior will be addressed for each case. It will be considered
realist railway ballast retained at sieves of 25 mm, 38 mm and 50 mm. An inexpensive laser scanning technique is
also employed with realistic grains, in order to incorporate their shape into the DEM. An extensive parametric
study was conducted exploring the influence of the particle shape (spheres, basic polyhedral and scanned particles),
in order to find the best compromise way to simulate a desirable scenario, from the engineering point of view.

Analysing a statistic index in identify change in data behaviour : Apply case in Itaipu Dam

Guilherme L. Campos, Sheila R. Oro, Claudio I. Osako — Wed, 10 Jul 2024 00:00:00 +0000

The safety of dam is a set of techniques whom to obtain maximum information and data to forecast
possible structures damage. The statistical indexes are multivariable approach that to account information from:
deformation, uplift, shift. The present paper, apply the factorial analysis to modelling a statistical index, in the
purposes of describe jointly the structural status and assess sensibility of index, on the way to complement and
describe the better control chart and quantify the relation between new data and extrapolations of control limits.
The control chart in this paper, it was used as feedback of type : exponentially weighted with moving average. The
analysis through plot, relate amount of occurs and standard deviation manipulated in the exponential regression
between variables. The sensibility brings better interpretation for occurs and in decision- making.

Modelagem matemática e computacional do comportamento térmico da barragem de contrafortes de Itaipu via Método dos Elementos Finitos

Wed, 10 Jul 2024 00:00:00 +0000

Dentre as diversas grandezas mensuradas para análise da saúde e segurança da barragem de concreto de
Itaipu, destaca-se a temperatura, uma vez que as barragens, em particular as de contrafortes, são fortemente
influenciadas pelas oscilações de temperatura [1]. Isto se deve às cargas térmicas oriundas da radiação solar e das
variações de temperatura do ar, fundação e reservatório, que podem ocasionar deformações e desenvolver fissuras
no concreto [2]. Neste contexto, é proposta uma modelagem numérico-computacional para o comportamento
térmico de um bloco de contrafortes da barragem da Usina Hidrelétrica de Itaipu, em fase de operação, via Método
dos Elementos Finitos com auxílio do software Ansys®. Para alcançar este propósito, foi desenvolvida a
formulação matemática do modelo térmico em elementos finitos utilizado computacionalmente, bem como a
definição das condições de contorno do sistema com dados reais de instrumentação. A partir da resolução
computacional do modelo térmico em elementos finitos para o período de 2010 a 2016, foram obtidos erros médios
percentuais absolutos (MAPE) abaixo de 10% em todos os pontos internos analisados, o que valida o modelo
térmico e possibilita a utilização dos resultados em trabalhos futuros para a determinação dos deslocamentos
estruturais causados pelo campo de temperaturas ao qual a barragem está submetida.

TEMPERATURE FORECAST IN CONCRETE DAM BY HOLTWINTERS MODELS AND THE FINITE ELEMENT METHOD

Wed, 10 Jul 2024 00:00:00 +0000

The article describes a method of forecasting the temperature fields of a concrete block from the Itaipu
Hydroelectric Dam located in a region with high thermal gradients, approximately 7 to 40°C. The method involves
the application of Holt-Winters exponential smoothing models and a heat conduction model that follows Fourier's
Law. Initially, the temperature series, from 2000 to 2016, of two surface-to-block thermometers were adjusted by
cubic splines, and, the monthly series, were used as input for Holt-Winters to produce temperature forecasts as
outputs for 2017. Monthly (interpolated) and 2017 (predicted) monthly temperatures were used as boundary
conditions for the transient thermal block model and it was solved by the Finite Element Method (FEM) in Python
language. The predicted temperature fields of the block for 2017 are thus obtained. The numerical results at a
specific point and interior of the structure were compared with the observed data of an internal thermometer
installed in the block through the MAPE error, and this was around 7%. The proposed method has an innovative
approach to the thermal analysis of structures, particularly in concrete dams, regarding thermal field prediction
and the first application of the Python language to this problem.

Modal and Structural Analysis of Section E, composed by Buttress blocks, including the Hollow Gravity block of Itaipu Dam

Wed, 10 Jul 2024 00:00:00 +0000

This work presents a numerical computational analysis methodology of dams using
experimental dynamic tests and instrumental monitoring data to calibrate and validate the numerical
models. A case study was carried out on part of the Itaipu dam, composed by buttress and hollow gravity
blocks. The model allows to analyze the influence between blocks, the dynamic properties and the
displacements due to the hydrostatic pressure of the reservoir and uplift. Dynamic field tests were
performed using accelerometers on each block of the dam to determine the experimental natural
frequency and the mode of vibration. These data were used to determine the boundary conditions and to
perform the calibration of the numerical model through the dynamic properties. Reservoir level and
piezometer data were used to determine loading conditions. Finally, the displacements of the model were
compared with the data from the direct pendulum and the joints measure instrument. The results are
satisfactory and show the complexity of a model composed of several independent blocks.

Thermal-Transient Analysis of Dams Using the Finite Element Method: Case Study Block A-7 (Spillway) of the ITAIPU Hydroelectric Plant

Wed, 10 Jul 2024 00:00:00 +0000

The structural behavior of a concrete dam due to thermal variation is an important topic studied in the
literature because high thermal gradients influence the performance, strength and structural stability of the dam.
Currently, there are several methods to estimate the behavior of concrete structures in the early ages and also
during their useful life. Due to the complexity of structural analysis, it is necessary to implement a methodology
using programs based on the Finite Element Methods (FEM). A case study was developed in a block of the ITAIPU
Hydroelectric Power Plant. A thermal-transient analysis was performed in block A-7 of the Spillway during the
years 1982 to 1985. The surface thermometers data were used to determine the boundary conditions in thermal
simulations. Solar incidence was also considered on each side of the block. In order to calibrate, the temperatures
recorded by the internal thermometers were used and compared with the results simulations performed in the
ANSYS program. The results were validated through the percentage difference, which is less than 10%, justifying
the use of the thermal model presented.

Transient Thermal Analysis of the Hollow Gravity Dam of the ITAIPÚ Hydroelectric Power Plant

Wed, 10 Jul 2024 00:00:00 +0000

Large critical structures, such as dams perform a lot of functions as water supply and power generation.
Since this kind of structures must be constantly studied to guarantee safety behavior during their useful life and
after that. Thus, Numerical computational tools are used in this type of structure to reevaluate limit values of
several parameters related to thermal and structural performance. Therefore, in this work, was used the computer

simulation program Ansys, based on the Finite Element Method (FEA) to perform a thermical analysis of the F-
5/6 block of hollow gravity dam from the Itaipu Hydroelectric Power Plant. In order to know the temperature

distribution resulting from the thermal variation. A thermal-transient analysis was performed during the first four
years when the reservoir was filled in 1982. To perform this analysis, the data from the external thermometers
were interpolated and used as initial conditions. Subsequently, at the location of the internal thermometers, test
points were implemented in the model in order to compare the temperatures obtained in the numerical simulation
with the data recorded by the thermometers. The results was satisfactory.

Redes Neurais Artificiais Aplicadas à Modelagem de Instrumentos de Deformação em Barragem de Concreto

Wed, 10 Jul 2024 00:00:00 +0000

As usinas hidrelétricas são o principal meio de geração de energia no Brasil. Para garantir a viabilidade
deste método de geração, por questões econômicas, sociais e ambientais, este meio precisa ser seguro e monitorado
durante todo seu período de operação, garantindo a integridade da estrutura e a segurança para a região em torno
da usina. Diversos instrumentos instalados na barragem fornecem, continuamente, dados sobre variáveis como
temperatura e deformação. Possíveis anomalias que possam acontecer na barragem podem ser previstas, desde que
se use ferramentas numérico-computacionais adequadas. Neste contexto, o artigo apresenta uma metodologia por
meio do uso de inteligência artificial para modelar séries temporais, advindas da leitura de um instrumento que
mede deformação do concreto, denominado roseta de deformímetro. Esta se localiza no bloco D-38 da barragem
da Usina Hidrelétrica Itaipu. As previsões obtidas podem contribuir com a equipe técnica da usina nas tomadas de
decisão quanto a uma intervenção preventiva na estrutura da barragem. Utilizou-se duas arquiteturas de redes
neurais simuladas na linguagem de programação Python, a MultiLayer Perceptron (MLP) e a Long Short Term
Memory (LSTM). Obtiveram-se valores de predições de dois anos à frente, com menor erro MAPE da amostra
teste de 1,07% com a arquitetura MLP.

Numerical analysis of a beam with and without viscoelastic treatment subject to cyclic loading in the time domain

G.F. Garcia, E.P. Nunes, J.P. Sena, A.M.G. de Lima — Wed, 10 Jul 2024 00:00:00 +0000

Its well-known that, the use of viscoelastic materials has been one efficient strategy to minimize fatigue
in structures. They have the characteristic of absorbing part of the vibratory energy of mechanical systems and
dissipating it in the heat form. Thus, the lower the vibrations produced, the lower the cyclic stresses and
consequently, the longer the beam supports the loading, increasing its fatigue life. Thus, in the context of fatigue
analysis, this work aims to analyze two scenarios: (1) the estimation of the fatigue life of an untreated beam made
of 1020 steel subjected to cyclic loadings; (2) the analysis of a beam treatment with passive constraining
viscoelastic layers. For this, the analysis of the results is performed in the time domain using the finite element

method. For the viscoelastic structure, a new fractional derivative model (FDM) is used to describe the time-
domain behavior of the viscoelastic part. For the fatigue analysis, the Rainflow method is used herein, based on

the stress-strain behavior of the material. Using this method, it was possible to determine the accumulated damage
by the Palmgren-Miner technique and, consequently, the fatigue life of the beam with and without viscoelastic
damping.

Nucleação e propagação de fraturas em placas de Kirchhoff utilizando o método da derivada topológica

Daniel M. Vaneli, Marcel D. Xavier, Sebastian M. Giusti, Antonio A. Novotny — Wed, 10 Jul 2024 00:00:00 +0000

O modelo de dano de Griffith-Francfort-Marigo descreve o comportamento de materiais frageis em
regime quasi-estatico, com foco na evolução das regiões de dano. Baseia-se na minimização de um funcional de
forma dado pela soma da energia potencial total do sistema com o termo de dissipação energética de Griffith, com
relação a distribuição das fases saudáveis e danificadas, sob uma condição de irreversibilidade. A energia potencial
total do sistema, se da, neste trabalho, pelo modelo mecánico para flexão pura baseado nas hipóteses de Kirchhoff ́
e e conhecido como teoria das placas de primeira ordem. Uma abordagem natural para lidar com esse problema
de minimização consiste em utilizar o conceito de derivada topológica. Portanto, inicialmente é apresentada a
derivada topologica para o funcional de forma em questão, com respeito a nucleação de uma inclusão circular.
Em seguida, a sensibilidade associada e utilizada para propor um esquema numérico simples a fim de determinar
a nucleação e a propagação de fraturas em placas. Em outras palavras, a derivada topológica e utilizada como
direção de descida para minimizar o funcional de Francfort-Marigo, indicando, em cada iteração, as regiões que
serão danificadas. Por fim, alguns exemplos numéricos são apresentados a fim de validar a metodologia proposta.

Uncertainty quantification of the Collipriest random model by the Fast Crack Bounds and Monte Carlo methodology

Valdinei A. Pedroso, Claudio Roberto Avila S. Junior — Wed, 10 Jul 2024 00:00:00 +0000

Mechanical structures are subjected to cyclical stresses and collapse under fatigue conditions. There
are several mathematical models that describe the crack propagation. In general, crack propagation models are
classified by the type of loading, which can have constant stress amplitude or variable stress amplitude. In this
work, the constant stress amplitude model proposed by Collipriest will be explored. For many engineering
applications a reliable estimate of crack behavior is required. Therefore, this work presents theoretical results,
which consist of the quantification of uncertainty in the definition parameters in the model used, based on lower
and upper bounds, which envelop the estimators of the first and second order statistical moments of the function
size of crack, based on the Fast Crack Bounds method. These dimensions are polynomials, defined in the
variable number of cycles, which take into account the uncertainties in the parameters that describe the crack
propagation models. The Monte Carlo simulation method will be used to obtain the realizations of the crack size
function from a set of random samples of the characteristic parameters of the Collipriest model. These
achievements will be used to obtain the estimators of statistical moments of crack size. The efficiency of the
bounds for the estimators of the statistical moments of the crack size is evaluated through relative deviation
functions between the bounds and the approximate numerical solutions of the initial value problem that describes
the Collipriest model. In general, the solution of the initial value problem that the crack propagation models
describe is obtained through the use of numerical methods, such as the explicit fourth order Runge-Kutta
method. In this work, a mathematical software will be used for numerical analysis of the solutions of the crack
propagation model of the Collipriest model, therefore an analysis of the computational performance between the
Fast Crack Bounds and Runge-Kutta methods and presented by the computational time, graphs and tables.

AVALIAÇÃO DO FATOR DE INTENSIDADE DE TENSÕES EM CORPOS FRATURADOS

Nayara D. S. Barbosa, Luiz C. Wrobel — Wed, 10 Jul 2024 00:00:00 +0000

Este artigo compara os Fatores de Intensidade de Tensões (FIT) obtidos a partir de análises numéricas
de um caso de fratura sob os conceitos da Mecânica da Fratura Linear Elástica (MFLE). Para tal, aplicaram-se
duas técnicas de modelagem em Elementos Finitos: Elementos Quarter-Point 2D e 3D e o Método Estendido dos
Elementos Finitos (XFEM) 3D. As análises foram feitas no programa ABAQUS versão 6.14-1, que utiliza a
integral de interação para o cálculo do FIT em ambas as técnicas. Por fim, os resultados numéricos são comparados
com os resultados publicados na literatura. Apesar das vantagens associadas ao uso do XFEM para modelagem da
propagação de fraturas, o cálculo pela integral de domínio para esta técnica apresenta oscilações nos valores
fornecidos para as diferentes solicitações de contornos. Os melhores resultados são obtidos com o uso dos
Elementos Quarter-Points 2D e 3D.

Bidimensional numerical study of crack propagation on austempered ductile iron

Gustavo von Zeska de França, Marco Antônio Luersen, Carlos Henrique da Siva — Wed, 10 Jul 2024 00:00:00 +0000

The austempered ductile iron (ADI) has a wide range of applications, due to its high mechanical
strength, fatigue resistance and wear resistance. ADI is composed by an ausferritic matrix with graphite nodules.
The nodule size and amount can be controlled by chemical composition and austenitizing temperature. The
nodules have strength lower than the matrix and can act as stress concentrators and influence on crack
propagation through changing its trajectory that may generate a protective effect. However, according to the
literature, the crack propagation mechanism in ADI is not yet fully understood. In this context, this work
presents a bidimensional numerical model that simulates crack propagation based on Paris law for ADI material
subjected to cyclic load. The model was implemented in Python language and uses the commercial finite element
code ABAQUS. The simulations showed that the presence of a nodule generates a shear load on the crack tip
which is the main parameter responsible for changing the crack direction to the nodule itself. Modifications such
as increasing nodule size and decreasing nodule distance to crack tip intensify this action. In simulations with
two different ADI materials with the same graphite area fraction, increasing the number of nodules causes the
crack to have a shorter lifetime until it intercepts a new nodule. Therefore, this suggests that the protective effect
of nodules in ADI material may be correlated with the number of intercepted nodules.

Controle de crescimento de trincas em corpos elásticos submetidos a esforços cisalhantes baseado no método da derivada topológica

G. C. R. de Barros, M. D. da S. Xavier — Wed, 10 Jul 2024 00:00:00 +0000

Uma questao fundamental no estudo da mecânica da fratura diz respeito ao controle do crescimento de ˆtrincas em componentes mecanicos previamente danificados. Neste trabalho, a metodologia baseada na derivada
topologica, recentemente proposta para tratar esta questão, é aplicada no contexto de corpos elásticos danificados
submetidos a esforços cisalhantes. A ideia central consiste em nuclear inclusoes rígidas e/ou complacentes longe
da ponta da trinca visando maximizar a vida util do componente fraturado. O método fundamenta-se em minimizar
um funcional de forma baseado na famosa integral de Rice com respeito a nucleação de inclusões utilizando as
informac ̧oes extraídas da derivada topologica. Mais precisamente, a sensibilidade associada e utilizada para indicar
as regioes onde as inclusões, também chamadas de controles, devem ser posicionadas. De acordo com o critério de
energia de Griffith, este procedimento permite aumentar a vida util do componente mecánico fraturado. Algumas
simulações numéricas são apresentadas evidenciando a aplicabilidade da referida metodologia no caso de esforços
cisalhantes.

Calibration of a ductile damage model dependent on triaxiality and Lode angle parameter

Iago S. Santos, Diego. F. B. Sarzosa — Wed, 10 Jul 2024 00:00:00 +0000

This paper presents a numerical study using the Finite Element Method (FEM) to model the ductile
fracture in ASTM A285 Gr. C steel through calibration of a phenomenological damage model. The calibrated
damage model is composed of a damage initiation criterion dependent on the stress triaxiality and the Lode angle
parameter coupled with a post-initiation damage evolution law. A series of experimental tests on round bars
having smooth and notched cross-section, flat notched specimens under axial tensile loads, and fracture
toughness tests in deeply cracked bending specimens SE(B) were carried out to calibrate the elastoplastic
response and the damage parameters. Verification of the calibrated parameters is performed using a SE(B)
sample having a shallow crack size ratio. The agreement between the experimental tests and the numerical model
results is quite good. The adopted numerical procedure can be used to predict the response of a more complex
structure.

STUDY CASE OVER AN AGRICULTURE SPRAYER EQUIPMENT USING MULTIAXIAL FATIGUE CRITERIA COMPARED WITH EXPERIMENTAL RESULTS.

Wed, 10 Jul 2024 00:00:00 +0000

In many situations in engineering, the fatigue phenomenon determine the catastrophic collapse of the
structure generating a significant loss in material resources and human life. The analysis of the real problem is in
general complex. On the other hand, the classic fatigue criteria approach is reasonably well established.
However, the methodologies based on these criteria are not applied directly when some complexities are part of
the problem. Examples such as the excitation generated by multiaxial stress or strain states, ; the proximity to the
weld region; among other situations that could happen in real problems. In the present case, a component of an
agricultural sprayer is analyzed. Over the cited structure, an experimental verification was carried out. Also, a
finite element method was applied to determine the level of stresses/strains in the critical region. In the present
work, different fatigue multiaxial criteria, Findley; McDiarmid; Brown and Miller, Fatemi and Socie and
Carpinteri Spagnoli were analyzed. The Wang Brown method was applied to count the equivalent cycles,
considering the multiaxial nature of the load history. Therefore, a comparison with real field observations could
be performed, leading to the evaluation of the proposed methodologies and their associated advantages and
disadvantages. Additionally, the implementation based on a nonproportional nature, considering the multiaxial
stress history, was developed.

Peridynamics as Predictive Maintenance Tool for Crack Monitoring

Heitor Nunes Rosa, Davi Moraes Monelli, Márcio Antonio Bazani — Wed, 10 Jul 2024 00:00:00 +0000

The purpose of this work is to demonstrate the initiation and propagation of a crack in a plate of an
A-36 Structural Steel with a pre-existing notch through simulation using a peridynamic model. In the analise it
was used a mesh established through the discretization of 250,000 material points distributed between
coordinates x and y of dimensions: 0.05 meters of length and width and 3x10−4 meters of thickness. A notch of
0.012 meters was added to the left side of the plate breaking the peridynamic interactions between material
points of the site. A force of 10,000 Newtons was applied over the entire lower. In the explicit integration,
pairwise forces were calculated for all points using peridynamic interactions of the neighboring points in
addition to the influence of loading. Determining the acceleration of a point, velocity and displacement were
calculated. Time step used was approximately ∆t = 13,37ns to stability and convergence criterion. The software
used to resolve was FORTRAN and demonstrated results VisIt. It was concluded that for the specific component
of a pre-notched plate of A-36 Structural Steel, common material for mechanical constructions, the results
demonstrated that the nucleation phenomena were well represented by the models and peridynamic simulations.
The discovery of the crack propagation direction and its velocity are also extremely important to know the
degree of plate commitment, since in the final state of integration the crack length reached almost 37% of the
plate length.

Parametric study of random fields of the mechanical properties of the material in a peridynamic model

Wed, 10 Jul 2024 00:00:00 +0000

Simulations based on the peridynamic theory are a promising approach to understand the processes
involved in the fracture of different materials. Failure mechanisms of materials are intrinsically related with
nonhomogeneity and randomness on small scales. This fact is an important aspect, because it can change the
mechanical behavior and the fracture location. This work presents a parametric study of the implementation of the
material’s specific fracture energy (Gf) correlated random fields. The specific fracture energy, which is directly
related to the critical stretching of peridynamic bonds, is defined as a 3D scalar random field with Weibull
probability distribution and a defined correlation length. A plate subjected to a traction load illustrates the proposed
approach. The results shows an independence of the fracture pattern with the level of discretization used. This
parametric study contribute to provide flexibility in the calibration of the peridynamic model response allowing
that the fracture patterns and the global material behavior to change and mainly disconnected from discretization.

Fatigue life estimation in a beam subject to random loads using probabilistic methods in the frequency domain

Joao P. Sena, Gabriella F. Garcia, Antonio M. G. de Lima, Erivaldo P. Nunes — Wed, 10 Jul 2024 00:00:00 +0000

Mechanical structures subjected to alternating cyclic loads are subject to failure due to fatigue, a result-
ing from the accumulation of damage caused by alternating cycles. The aim of this work is the use of theoretical

random excitations of the stationary and Gaussian type in the computational study of probabilistic criteria in the
frequency domain for fatigue analysis in beams. Using the Finite Element Method to perform a dynamic analysis
of the system, a theoretical random load is applied to the structure and the Frequency Response Function, PSD
(Power Spectrum Density) and spectral parameters are calculated. With these structural characteristics, the fatigue
life of the requested structure is estimated using several probabilistic criteria, comparing the values obtained and
analyzing the difference of each methodology. From these results, it is possible to verify the importance of fatigue
life calculation of dynamic systems, the efficiency of modeling procedures as a tool for fatigue analysis of random
dynamic systems and also the influence of the variation of the results obtained in this type of structure.