XLII Ibero-Latin American Congress on Computational Methods in Engineering

Analysis of cold-formed steel truss and prefabricated concrete slab composite floor system

Odivaldo B. Dias — 2024-06-09

Steel and concrete composite floor systems improve the resistance capacity and flexural stiffness. Stud-
ies on composite floor of buildings available in the literature consider, for the most part, open steel cross sections

and solid or steel deck reinforced concrete slabs. The present work is based on the results obtained in an ex-
perimental campaign carried out by the research group on steel and composite construction at the Laboratory of

Structures and Materials from COPPE /UFRJ, and proposes the validation of a numerical model based on the
Finite Element Method (FEM), in order to improve the knowledge of the structural behavior of the construction
system. This work aims to extend the original investigation of the composite structural system proposed and tested
by Luiz Alberto Leal (doctoral thesis in 2019), associating lattice girder in cold-formed steel members (CFS) and
composite unidirectional prefabricated concrete slab, for which there are few numerical and experimental studies.

In this context, the present work performs the FEM-based numerical modeling, calibrated with the help of exper-
imental results, consisting of CFS trussed girders and unidirectional slabs, combined with innovative thin-walled

perfobond (TWP) shear connectors.

Computational study of concrete-filled steel tube columns produced with aggregates from construction and demolition waste

Athila V. Lima — 2024-06-09

The use of concrete-filled steel tube columns – CFSTC had begun about 70 years ago and, until today,
these elements have been widely used worldwide. The behavior of the steel-concrete system can be seen as an
advantage, since it opens space for the possibility of using alternative materials in the manufacture of concrete for
composite columns, once the stress triaxial state minimizes the strength reductions that can occur with the use of
such alternative materials. For this reason, this work aimed to computationally analyze the behavior of composite
columns of circular section filled with concrete (manufactured with aggregates of the type CDW – Construction
and Demolition Waste) and subjected to centered compression. In this study, the influence of the use of CDW in
short CFSTC subjected to axial compression was analyzed. In the present study, a computational model of short
CFSTC was constructed. Two groups of models were analyzed. Considering the results, it was possible to affirm
that the increase of strength and ductility verified in the CFSTC are very important characteristics to make possible,
from the structural point of view, the use of CDW, in the production of the concretes used in concrete-filled steel
tube short columns.

Dynamic structural behaviour of steel-concrete composite floors subjected to rhythmic human activities

Nathalia de A. C. Branco — 2024-06-09

Over the last few years, a lot of structural problems associated with excessive vibration of building floor
systems when induced by human rhythmic activities have occurred in places such as fitness centres, event halls
and offices. On the other hand, it’s well known that the resonance phenomenon can occur due to equality (or
proximity) between one of the excitation frequencies and the structure natural frequencies. Having this thought in
mind, this paper investigates the dynamic structural behaviour of a steel-concrete composite floor when subjected
to loadings induced by human rhythmic activities. This way, the studied structural system consists of a health club
that presents an area used for aerobics. The composite floor system presents dimensions of 22.5 m by 14 m and a
total area of 315 m2. In this study, the dynamic loadings were obtained through the use of several dynamic load

models (only force models) and also based on the modelling of biodynamic systems, to incorporate the human-
structure interaction dynamic effect to the analysis. The composite floor numerical model was generated based on

usual modelling techniques adopting the mesh refinement present in the Finite Element Method (FEM) and
implemented in the ANSYS program. The investigated floor dynamic structural response was calculated through
the consideration of 20 people practising rhythmic activities on the original area specified in the project and on the
other two possible areas of the structural system aiming to verify the occurrence of excessive vibration and also to
assess the human comfort having in mind the recommended limits proposed in the traditional international design
standards.

The Effect of Rounded Corners in the Moment Resistance of Steel Shuttering of Composite Slabs

Mayane C. Loureiro — 2024-06-09

The objective of this paper is to analyze the influence of modeling rounded corners on the bending
moment resistance of steel formworks used in composite slabs. The Finite Strip Method (FSM), as well as the
constrained Finite Strip Method (cFSM) were implemented via the software CUFSM for trapezoidal cross-sections
to predict the bending moment resistance with the Direct Strength Method. The FSM was used to determine the
critical loads and the cFSM served to identify distinct buckling modes for signature curves without unique minima.
Five different steel sheet geometries were analyzed - four commercially available sections and one extracted from
the literature. Based on these, 4 additional geometries with no intermediate stiffeners and 5 with straight-line
models were designed. In total, this study investigated 5 and 9 cross-sections with straight-line and rounded corner
models, respectively. Results show a slight influence of the corners on the critical moment of local buckling, with
straight-line models reducing this value, as well as increasing the distortional critical moment. Overall, the
difference between the cFSM and the FSM decreases for the local mode when considering rounded corner models
with stiffeners and for the distortional mode when using straight-line models with stiffeners.

Buckling analysis of storage tanks based on the use of geometric imperfections measured by laser scan dimensional inspection techniques

Matheus A. Lopes — 2024-06-09

Storage tanks are thin-walled equipment often subjected to wind loadings, which may lead the
equipment to structural instability. The critical buckling load of storage tanks are too sensitive to structural
imperfections, that can be present at its structure taken into account damage mechanisms which tend to reduce
the structural integrity of this type of equipment along its life cycle. Inspection techniques are employed to
characterize damage mechanisms, which in turn are assessed to evaluate whether or whether not the equipment
may have a safe operation. The laser scan technique has been shown to be accurate in dimensional inspection of
storage tanks. This paper focuses on the structural integrity assessment of an actual damaged surface of a real
storage tank. The tank is 43.428 m in diameter and 14.63 m in height and is used for diesel storage.
Deformations are present at the structure of the tank, which are measured with an industrial laser scan. The point
cloud resulting from the dimensional laser scan inspection is used to build a finite element model taken into
account all geometric imperfection. Geometric and Material with Imperfection Nonlinear Analyses (GMNIA)
are performed considering different load combinations and different wind pressure coefficients to assess plastic
collapse, excessive local plastic strain failure and buckling. Simulations considering structural steel shapes at the
shell of the tank are performed to evaluate failure from wind induced buckling, once the structural integrity of
the equipment is reduced by deformations present at the structure of the tank. The results show that the
equipment

Project and construction of a didactic wind tunnel for the vibration analysis of buildings experimental models

Leonardo F. de Miranda — 2024-06-09

The usual practise in design of structures assumes that wind effects are represented by static loads.
However, the wind presents a dynamic nature, and its effects on buildings can lead to problems associated with
excessive vibrations. Therefore, it is important for Civil Engineering students to be able to investigate and
understand the dynamic phenomena of structures. To facilitate the teaching of these concepts, this research work
presents a practical methodology supported by the construction of a wind tunnel in order to simulate the dynamic
actions of the wind on representative building models. These models are exposed to the wind and the dynamic
response is filmed using a smartphone, and then analysed using appropriate computer programmes for image
processing. Thus, it is possible to evaluate the dynamic structural response of the models (displacements and
accelerations), in the time domain. It is worth noting that, despite the experimental tests showing larger total
displacements in the wind direction, the floating part of the displacement is larger in the transverse direction,
which is due to the occurrence of wind vortices. In conclusion, the authors believe that the development of this
teaching methodology will support both, undergraduate and graduate Civil Engineering students, to better
understand tall buildings dynamic behaviour when subject to wind actions.

Fatigue assessment of steel-concrete composite highway bridges considering a progressive pavement deterioration model

Ana Célia S. da Silva — 2024-06-09

Highway bridges are subjected to random traffic loads with relevant impact dynamic loadings along
all their service life. The road-roughness of asphalt pavements represents a key issue to the significant decrease
of the highway bridge decks service life. Having this context in mind, this article aims to develop an analysis
methodology to assess the fatigue performance of highway bridges, including the dynamic actions due to
vehicles and the effect of the progressive deterioration of the pavement, taking into account the road surface

damages. The developed methodology is based on a linear cumulative damage rule, and the use of the Rainflow-
counting algorithm and S-N curves from main design codes. The investigated structural model corresponds to a

steel-concrete composite highway bridge deck, with straight axis, simple supported and spanning 13.0m by
40.0m. In this work, 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 results of a parametric analysis are presented aiming to
verify the extension of the dynamical effects on the service life of highway bridges due to vehicles crossing on
the irregular pavement surface.

Nondeterministic dynamic analysis and fatigue assessment of wind turbine towers

Rodrigo G. Simões — 2024-06-09

Wind energy has been playing a very important role in whole world energy matrix. In this sense, a
great technological evolution has occurred over several decades, transforming old windmills into extremely tall
and slender towers, with the capacity to generate large amounts of energy. In Brazil, considering this advance,
the conventional conical steel tower is a predominant type of supporting structure. According to this context, this
research works aims to study the dynamic structural response and structural fatigue assessment (service life) of a
steel tower to support a wind turbine model MM92 by Repower. In this way, a numerical model was developed
to represent the investigated tower, using the Finite Element Method (FEM) simulations 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 research work
are evaluated and compared with the limit values recommended by international design codes and
recommendations.

Assessment of the human comfort of floors based on the use of biodynamic models

Jefferson V. Aguiar — 2024-06-09

This research work aims to investigate the structural dynamic 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 related to a steel-concrete composite floor building which is composed of a hot-rolled framing
system, with a total area equal to 1300m2.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 steel-concrete composite floor building dynamic analysis, adopted the usual mesh refinement techniques
present in finite element method (FEM) simulations implemented in the ANSYS computational 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) have an elastic behavior. The complete interaction between the
concrete slab and steel beams was considered in the analysis, i.e., the numerical model coupled all the nodes
between the beams and slab, to prevent the occurrence of any slip. Regarding the structural behavior of the
connections present in the investigated structural model, the beam-to-beam connections and the beam-to-column
connections were considered as rigid joints. 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 and RMS values. A numerical study was made of the number
of people influence on the slab using a biodynamic model. Then, the modal and forced vibration analysis numerical
responses were compared to experimental responses. In addition, all numerical and experimental values were
determined and classified according to several human comfort criteria, considering situations of the current design
practice.

Vibration analysis and human comfort investigation of floors when subjected to rhythmic human activities

Felipe A. de Sousa — 2024-06-09

Nowadays, determined buildings structural problems can be associated, for example, to floors
excessive vibrations subjected to human rhythmic activities. This type of structural project situation can occur
when the rhythmic activities are performed in a group, due to the fact that produces a high degree of
synchronization, especially when there is the proximity between one of the excitation frequencies and the floor
natural frequencies. This way, this research work consists of the assessment of the structural dynamic response
of a real reinforced concrete floor with dimensions of 16 m by 35 m and a total area of 560 m2 located on the
eighth story of the State University of Rio de Janeiro (UERJ). The main focus of the investigation is to study the
human-structure interaction dynamic effect between the occupants and the reinforced concrete floor through the
use of several dynamic load traditional only-force models and also based on the use of biodynamic systems
(mass-spring-damper systems). The numerical modelling of the reinforced concrete floor was performed using
the ANSYS program, based on usual modelling techniques adopting the mesh refinement present in the Finite
Element Method (FEM). The maximum values related to the floor dynamic structural response were investigated
and compared with the human comfort criteria limits. Therefore, it was verified that the floor presents excessive
vibration and human discomfort when the only force models were considered in order to generate the dynamic
loads. On the other hand, when the dynamic response of the structure was evaluated considering the dynamic
load models generated based on the use of biodynamic systems the structural system attends the human comfort
criteria and there are no excessive vibrations. However, it must be emphasized that this dynamic loading
mathematical model (biodynamic systems) was formulated based on experimental tests where the dynamic
characteristics of the people and the human damping were included in the formulation.

Comparative study between structural systems in prestressed concrete

Cristiano Talhas — 2024-06-09

This work presents a theoretical comparison of distinct modeling of a model structure through linear
analysis using the commercial structural analysis and design software, CSiBridge. The selected structure was a
20.0m spar beam. The central idea was to compare its behavior when varying parameters in the models that
characterize the adopted prestressing system. Aspects such as the structural system, the steel class used, which is
a function of the type of reinforcement, the level and type of prestressing system and the geometric design of the
reinforcement, stand out. The response values investigated in all lines of study were displacements, bending
moments and axial and shear stress, aiming to present a complete and critical analysis, pointing out possible
reasons for the perceived differences.

Structural analysis of steel towers used in power transmission lines subjected to wind induced dynamic actions

Mariana S. Rechtman — 2024-06-09

The lattice steel towers have been widely used as supports for power transmission lines becoming
essential elements since their stability contributes to a better functioning and electrical safety of the transmission
systems. Although the main loading applied to this type of structure be produced by the wind acting dynamically
on the elements of the transmissions system (conductors, shield wires, insulators and steel towers), in the current
design practice the dynamic structural behaviour of the structural system (towers-conductors) is not considered.
Therefore, the main objective of this investigation is to develop an analysis regarding the behaviour of power
transmission lines when subjected to wind dynamic loadings, having in mind the assessment of the forces and
displacements of the steel towers of the system. In this research work, a power transmission line, composed by the
main tower, two adjacent towers, conductors, shield wires and insulators was studied based on a finite element
modelling, considering the wind non-deterministic dynamic characteristic, where the wind loads were modelled
by an aleatory process based on their statistical properties. The results obtained along the analysis have shown
relevant quantitative differences associated to the forces and displacements values when the structural response of
the investigated power transmission line was calculated based on a static analysis and a dynamic non-deterministic
analysis.

Nonlinear dynamic analysis of tall buildings considering nondeterministic wind loads

Jean Carlos M. Silva — 2024-06-09

In recent years, the technological advances of the civil construction associated to a favourable economic
scenario have promoted the project and construction of tall buildings in several countries, such as the United States,
and more recently, some of the Asian countries, like China, Malaysia and the United Arab Emirates. However, the
architectural dareness and also the increasing in the structural project’s slenderness have been crucial to reducing
the natural frequencies values of these buildings, and in some situations, these facts could induce excessive
vibration problems and human discomfort. On the other hand, other aspect generally disregarded in the current
design practice is related to influence of the effect of geometric nonlinearity on the building’s structural response.
This way, this research work aims to develop an analysis methodology to evaluate the dynamic structural behaviour
and assess the human comfort of tall buildings, when subjected to the wind nondeterministic actions, including in
the analysis the effect of geometric nonlinearity. This way, the dynamic structural behaviour of a 40-storey
reinforced concrete building, 140 m high and dimensions of 29.05 m by 9.00 m was investigated. Several numerical
models were developed to obtain a more realistic representation of the structural system, based on the Finite
Element Method (FEM), using the ANSYS program. The results obtained throughout this investigation have
indicated important quantitative differences when the dynamic structural response of the studied building was
analysed, having in mind the effect of geometric nonlinearity.

Steel-concrete composite floors subjected to mechanical equipment loads: dynamic analysis and fatigue assessment

Álvaro E. do A. M. Junior — 2024-06-09

This research work aims the study of the dynamic structural behavior and assesses the service life of
steel-concrete composite floors when subjected to the vibrations induced by mechanical equipment. The
development of this research becomes necessary due to the growing issues associated with excessive floors
vibrations arising from dynamic loads, which are likely to cause human discomfort or even reduce the system
service life. This way, the investigated structural design is based on a steel-concrete composite floor with
dimensions of 5m x 5m and a total area of 25 m2. The numerical modelling of the composite floor model was
generated based on usual modelling techniques adopting the mesh refinement present in the Finite Element
Method (FEM) and implemented in the ANSYS program. The applied loads were simulated based on harmonic
forces related to the dynamic loadings imposed by the equipment on the concrete slab (generation unit: motor,
gear unit and coupling). The investigated floor dynamic structural response was calculated by considering
several types of equipment acting on the floor areas specified in the project, aiming to verify the occurrence of
excessive vibrations and assess the steel-concrete composite floor service life, considering the recommended
limits proposed in the traditional international design standards.

Educational tool for analysis of steel frames with semi-rigid connections

Christian L. Dias — 2024-06-09

The article describes the implementation in Ftool of semi-rigid connections with nonlinear behavior of
the moment-rotation relationship. The main objective is to describe the extension of the program's graphical
interface and its use to demonstrate the behavior of steel frames with semi-rigid nonlinear connections. Although
it is possible to couple the physical nonlinearity of the connection with geometric nonlinear analysis, the article
deals only with physical nonlinearity. The semi-rigid connection is modeled using a finite element with two nodes
with a stiffness matrix that relates the relative rotation between the two nodes and the moment in the connection.
Nonlinear behavior is provided by multi-linear curves relating moment to rotation. The monitoring of the
equilibrium trajectory of the structure with nonlinear behavior is performed in an incremental-iterative manner
using several types of classical algorithms in the literature. It is also possible to show structure buckling and
vibration modes considering the linear behavior of the semi-rigid connection.

Basic Fundamental Approach of 2nd Order Geometric Nonlinear Analysis: Concepts and Computational Implementation

Sara de J. Bulhosa — 2024-06-09

One of the main objectives of structural engineering has been to make the structures slenderer and more
economical, reducing their weight and the consumption of materials without, however, compromising their
stability. The increase in the slenderness of the structural elements makes them more susceptible to large lateral
displacements before their rupture occurs. The stability analysis of slender structural systems currently involves
the application of the Finite Element Method (FEM). As a consequence, a system of non-linear algebraic equations
is generated and its solution is obtained, in general, through incremental-iterative procedures. This article initially
presents structural single-degree-of-freedom systems (SDF, scalar variables), subjected to geometric nonlinear
behavior, showing their analytical and numerical solutions, using the Principle of Stationary Total Potential
Energy. Four SDF systems, with different behaviors, are presented: stable or unstable post-critical behavior and
with and without bifurcation. Geometric imperfections are incorporated. The work ends with the presentation of
two-degree-of-freedom systems, where the variables become matrix and vector, expanding the concepts of SDF
systems for the multi-degree-of-freedom (MDF) ones.

Modelagem BIM e otimização com algoritmo genético de coberturas treliçadas

Alexandre L. Bitencourt — 2024-06-09

O advento da tecnologia Building Information Modeling (BIM) introduziu uma mudança de paradigma
no desenvolvimento de projetos estruturais na engenharia civil. Os modelos computacionais em BIM são capazes
de armazenar mais dados sobre elementos e sistemas do que as tecnologias CAD e CAE que a precederam. Em
lugar das usuais simplificações em engenharia, as plataformas BIM integram ferramentas de programação,
modelagem geométrica e simulação de desempenho em projetos de qualquer grau de complexidade, aumentando
a produtividade e reduzindo a perda de informação entre diferentes etapas de trabalho. O maior volume de dados
disponível torna mais difícil, em projetos de geometria incomum, que o projetista alcance soluções de alto
desempenho sem o auxílio de ferramentas de Inteligência Artificial (IA). Dado o elevado custo computacional dos
aplicativos BIM e das tecnologias IA em geral, faz-se necessária averiguar os limites e as potencialidades destas
ferramentas no projeto de estruturas, face à capacidade de processamento dos computadores pessoais disponíveis
atualmente. Este trabalho visa empregar o algoritmo genético NSGA-II (otimização multicritério com fronteira de
Pareto) para determinar parâmetros de geometria e seção transversal dos perfis de uma cobertura de aço composta
por vigas treliçadas planas. A implementação do algoritmo é realizada no ambiente Dynamo disponível no Revit,
um programa BIM, enquanto os esforços solicitantes são determinados através do Robot Structural Analysis. São
estudadas treliças com vão fixo e diferentes parâmetros de geometria, como, alturas, inclinações, número de
diagonais e montantes, para avaliar a configuração que consume menos material. Um dos principais desafios
envolvidos nesta tarefa é a proposição das funções de aptidão, que abarcam os objetivos a serem maximizados e
as restrições de projeto que não podem ser violadas, de modo a informar automaticamente aos algoritmos de
otimização os ajustes a serem efetuados no projeto. Embora as implementações realizadas nesta pesquisa indicam
que a programação nos sistemas BIM pode elevar o custo computacional das tarefas de otimização, este estudo
empregando o algoritmo genético NSGA-II teve um consumo de aço menor quando comparado a um valor de
referência que foi o consumo de aço de uma cobertura treliçada dimensionada conforme procedimento de
escritórios de projeto. É possível diminuir o consumo de material neste valor de referência, mas o processo de
redefinição dos parâmetros da estrutura e modelagem da mesma tomaria tempo do projetista.

Numerical study of CHS-SHS T-joints with chord face failure

Luiza G. V. Alves — 2024-06-09

National and international normative prescriptions do not currently predict the design of joints with
sections containing high slenderness values. In this work, tubular T-joints containing chords with square hollow
sections and braces with circular hollow sections, which offer an easiness to the welding process, were studied
with the intention of enabling the of lighter profiles in tubular structures. A numerical model was developed using
finite elements in a commercial software (ANSYS), in which the stress distributions, the joint resistance, the failure
mode and the load-displacement behaviors were analyzed in joints with different geometric properties. An axial
compression load was applied to the brace, and the joint results were compared with the analytical results using
the equation recommended by ABNT NBR 16239:2013. Chord face failure was the failure mode found in all
profiles analyzed. It was observed that, for higher values of brace diameters and chord thicknesses, higher joint
resistance results were found. In the joints analyzed, it was observed that the current normative design equation
did not predict the joint resistance values from the numerical model with high accuracy, with a general mean ratio
of the normative joint resistance divided by the numerical joint resistance equal to 0.717.

Structural reliability for the design of cold-formed steel I-sections members undergoing web crippling under interior loading conditions

Nathália Barbosa de Melo — 2024-06-09

Cold-formed steel sections (CFS) are subjected to different buckling modes. This work presents the
results of structural reliability analysis of web crippling strength expression currently used in the Brazilian
Standard, with a particular focus on I-sections (Stiffened Flanges) beams subjected to the loading conditions of
Interior-One-Flange (IOF). Previous research studies of web crippling showed that I-sections members fastened
to the bearing plate (support), subjected to IOF load case, presented inadequate reliability indexes (β) when
compared to the target reliability index. Experimental data of I-sections members reported in the literature were
analyzed to obtain the professional factor statistics. The First-Order Reliability Method (FORM) was used for
the standard calibration procedure. The reliability analysis was developed for load combinations found in the
North American and the Brazilian standards, in addition to the nominal live-to-dead load ratio, Ln/Dn, equal to 3
and 5. Target reliability indexes usually used in the calibration of the main international standards for CFS
members were considered. It was found that the resistance factor present in the Brazilian standard should be
increased for the I-sections members. A revision is necessary to standardize the level of safety of the design to
the limit state of the web crippling.

Numerical modeling of cold-formed steel-concrete columns

Lays R. A. da Costa — 2024-06-09

The objective of this study was to perform numerical simulations through the FEM method, using
ABAQUS®, to investigate the structural behavior of Cold – formed steel - concrete columns (CFSC). The
concrete’s influence on the system's efficiency was investigated for systems with different heights between 2.50
and 3.00 meters, since most of the articles with CFSC show results for short columns up to 1 meter. The results
showed that the concrete favors the structural behavior, but this resistance’s gain is reduced as the systems become
higher due to the buckling action: In the columns with 1.5 meters, concrete contributed to a more than 100 %
increase in the strength of the columns, while for columns with 3 meters, this gain was only 28%. In columns with
2.5 meters, this gain represents 70%. Even with the loss in strength of the composite systems due to the increase
in slenderness, the encased columns with 3 meters in height presented strengths of almost 100 kN, which
corresponds to the average values requests in small buildings. In simple steel tubular columns, these values did
not reach 60kN.

Reliability analysis of cold-formed steel beams susceptible to distortional buckling using numerical analysis data incorporated into the professional factor variable

Márcio M. da Silva — 2024-06-10

In cold-formed steel (CFS) beams subjected to simple bending with restriction to lateral-torsional
buckling and without restriction on the compressed flange, distortional buckling can be the predominant failure
mode. This work aims to develop a study on the distortional instability mode in CFS lipped C-section subject to
simple bending by numerical analysis using ABAQUS finite element software and CUFSM, a finite strip method
software. The Matlab software was used to automate the modeling so that a range of numerical simulations with
material and geometric nonlinearity was performed and validated with experimental results from the literature. A
reliability analysis with the FORM method was performed using load combinations according to the calibration
parameters of AISI-LRFD and AISI-LSD to obtain the reliability index (β) and probability of failure (PF). From
these results, it was observed a good achievement between the reliability indexes of the models and the established
target index of βo = 2.50, a reference for the calibration of the AISI-LRFD.

Determination of composite slabs resistance by the partial shear connection method considering friction at the support

Giovanni Morais Mercuri de Figueiredo — 2024-06-10

This paper aims to evaluate the behavior and longitudinal shear strength of the steel-concrete composite
slab using the Steel Deck P75 through the partial shear connection method considering the contribution of the
friction acting in the interface of the steel deck with the concrete at the region of supports. The method proposed
by EN 1994-1-1:2004 for the design of composite slab systems is based in the analytical model similar to that of
composite beams which allows to determine the degree shear connection between the steel sheeting and the
concrete. This method allows analysis the influence of friction at the support, in addition to the contribution of
stud bolts on the mechanical resistance of composite slab. The composite slab was tested in the Federal University
of Minas Gerais structure laboratory which used the semi-empirical "m-k" method to obtain its resistance. The
behavior of the composite slab system was analyses through of the graphics deflections, end slips and strains,
allowing the determination of its failure mode. Finally, the results obtained from the longitudinal shear resistance
considering the friction at the support were applied in one practical examples.

Stress numerical analysis of cold-formed steel angles

Brenda Vieira Costa Fontes — 2024-06-10

This work is a stress numerical study of cold-formed tensile-loaded steel angles with bolt-connections.
Due to the bolted connection, the angle does not deform evenly, resulting in a phenomenon known as shear lag,
which reduces the resistant capacity of the angle under tension. This phenomenon is also investigated in this
work. For the calculation of the piece final capacity, the hypothesis of rupture of the net section is examined and
the phenomenon of shear lag considered through the Ct factor. In order to verify the behavior of cold-formed
angles with bolted connections subjected to traction, several angles were modeled using the ABAQUS
commercial finite element analysis package, considering geometric and material non-linearity. The results
obtained in the numerical analysis were compared with results of experimental tests, reaching a good agreement
between them. However, it was verified the feasibility of numerical modeling in the support and
complementation of experimental research involving thin sheet profiles.

Reliability of perforated cold-formed steel channel-section beams using FORM method

Rogério F. Santos — 2024-06-10

Cold-formed steel (CFS) members can be designed with the AISI Direct Strength Method (DSM) which
utilizes the local, distortional, and global elastic buckling properties of a cross-section to predict ultimate strength.
The Brazilian standard also includes the DSM, but does not consider the presence of holes in the section. This
paper develops the reliability assessment of beams, designed based on available methods in the literature adapted
for sections with perforation. Such methods have their origin in the Direct Strength Method. An experimental
database of cold-formed steel channel-section beams was established. Using this database, a statistical analysis of
test results was conducted to determine the probability distribution function that provides the best fit to the
professional factor data and the distribution parameters. The statistical parameters of professional factor, material
strength, geometrical properties, load type, and load ratio were considered in the reliability evaluation. Then, the
structural reliability indexes of beams subject to the local and distortional buckling modes were evaluated using
the first order reliability method (FORM). The results showed that the target reliability index of 2.5 was not reached
when the load combination of the Brazilian code was applied for profiles susceptible to the distortional buckling
mode.

Application of an incomplete similarity approach in the analysis of impact problems

Mateus C. Redin — 2024-06-10

The assessment of safety to the impact of motor vehicles requires costly experimental tests, such as
crash-tests and advanced methods of structural analysis. The design of bus structures in Brazil, for example, does
not have adequate calculations methods and regulatory standards, and safety is difficult to assess. Therefore, a
methodology is proposed for conducting impact tests on small-scale models that have incomplete similarity, in
order to facilitate access to experimental data about vehicle crashworthiness. The methodology is applied to the
simplified problem of a drop test on a fully clamped tubular steel beam. The test was numerically simulated using
the Abaqus® software, from which it was possible to reproduce results from prototypes and models. Through a
methodology presented in the literature, two models were used to correct the incomplete similarity characterized
by the parameter regarding the beam thickness. This approach demonstrated a good correlation with the numerical
results in the range of the dimensionless group in which the models were made, and started to diverge from the
numerical results as it moved away from that range. A second approach, with a second non-similar parameter, was
used for comparison with experimental data, which demonstrated a good correlation.

Advanced parametric study of three-pinned steel arches

Matheus M. Oliveira — 2024-06-10

The arches are structural elements widely used from antiquity to the present times, since these elements
generally present an increase in rigidity due to their curvature, outstanding in the use of drainage structures and
vaults. Arches are characterized by a strongly nonlinear behavior, being an important target of study to know the
structural behavior and to guarantee reliability and safety of structures that have such an element. Thus, this work
focuses on the parametric study of three-pinned arches with physical and geometric nonlinearities. To investigate

the complete behavior, first-order elastic (FOE), second-order elastic (SOE), first-order inelastic (FOI) and second-
order inelastic (SOI) analyses are performed using the computer software MASTAN2. Therefore, the influence of

the geometric and physical parameters, the arch’s shape, the boundary conditions, and the stiffness of three-pinned
arches are evaluated. The results obtained indicate under which conditions the arches present the better behavior
performance in terms of stability and resistance.

Numerical strategies for complete assessment of the moment-curvature re- lationship of steel, concrete and steel-concrete composite sections

́́Igor J.M. Lemes — 2024-06-10

In the non-linear evaluation of the behavior of steel, concrete and steel-concrete composite cross sec-
tions, increment and iteration strategies are necessary for the complete construction of the moment-curvature re-
lationship. For the correct simulation of sections composed of strain softening materials, a strategy of constant

force increments fails to capture the downward stretch of the moment-curvature relationship. The present study
aims to couple path-following strategies to the Strain Compatibility Method (SCM) to pass load limit points in the
construction of the relations that describe the mechanical behavior of the section. In this context, the generalized

displacement technique, depending on the generalized stiffness parameter, and the minimum residual displace-
ment method, will be adapted to the cross sectional problem. Concomitantly, strain control strategies will be

implemented as a comparison parameter, since when using it, the load limit points do not prevent the complete
construction of the cross section equilibrium paths. The constitutive relationships will be addressed explicitly as
well as the residual stresses present in the steel profiles. To validate the proposed numerical formulation, the results
obtained are compared with numerical and experimental data available in the literature.

Numerical study of steel trusses in fire conditions

Gustavo H.C. Ferreira — 2024-06-10

A structural system under fire is subject to loss of strength and stiffness and may eventually collapse.
In this context, the need for studies to investigate the structural behavior under high temperatures is necessary.
Therefore, the present study proposes to perform numerical analyses of steel trusses in a simplified way,
considering the physical non-linear effects from the deterioration of the material at high temperatures, as described
in NBR 14323. Thus, a methodology was adopted that considers the effects caused by temperature on the stiffness
of the structural element. The calculation of displacements and internal forces is done through the Fool Software.
With the reduction of the stiffness parameter, the results show that the structure displacements increase with the
rise in temperature, and the more accentuated this steel deterioration, the greater the influence of the external load
on the displacement.

INELASTIC-LARGE DISPLACEMENT ANALYSIS OF STRUCTURES WITH CONTACT CONSTRAINTS

Jéssica L. Silva — 2024-06-10

This work presents a numerical methodology based on inelastic-large displacement approach to simulate
the 2D nonlinear behavior of structures under contact constraints imposed by the soil/rock. Non-linearities sources
are addressed, such as: second-order effects, plasticity and contact. It is worth mentioning the adoption of a
nonlinear finite element formulation based on the explicit separation between rigid body movements and those
that cause strain (co-rotational approach). The finite element formulation also considers the nodal concentrated
plasticity in which the material nonlinear behavior is represented by an explicit constitutive relationship by using
the Strain Compatibility Method (SCM). The SCM is also applied here to define any cross-sections typology

strength under axial force and bending moment. Thus, this numerical formulation can be used to obtain the non-
linear response of problems involving structure-support interaction. The contact constraints imposed by the

soil/rock can be considered as bilateral and unilateral. In case of unilateral constraints, a penalty method is applied
in each load increment and during the iterative process. Numerical modeling of a structural circular ring under
contact constraints are presented.

DEVELOPMENT OF A COMPUTATIONAL TOOL FOR FATIGUE ASSESSMENT OF STEEL STRUCTURES ACCORDING TO THE MASTER S-N CURVE METHOD

Guilherme Alencar — 2024-06-10

In a recent publication, Alencar et al [1] demonstrated that the Master S-N curve method is equally
appropriate to assess the fatigue strength of welded bridge details. The Master S-N curve method is an
alternative option included in the context of the American mechanical engineer’s standard (ASME Sec VIII
Div2) in the last decade, which allows the use of coarse finite elements to carry out estimates of the remaining
fatigue life of welded details, despite its advantage in the use of a unique fatigue strength S-N curve. This paper
presents the development of a computational tool for the Master S-N curve method. The tool was built into
ANSYS Mechanical and allow to carry out fatigue life estimations of welded structures and mechanical
components under constant amplitude loading.

A non-linear finite volume method coupled with a higher order MUSCL- type formulation for the numerical simulation of groundwater solute trans- port

Fernando R. L. Contreras — 2024-06-11

A groundwater solute transport model can predict the process of contaminant migration and play an im-
portant role in groundwater contamination control and remediation. In groundwater solute transport simulation, for

example, reliable prediction of fluid dynamics requires a simulator that can rigorously handle highly heterogeneous
and anisotropic permeability tensors on nonorthogonal grids dictated by complex aquifer geology. In this sense,
to solve the equations that constitute the flow model, it is necessary to make simplifying assumptions about the
aquifer and the physical processes governing groundwater flow. In this study, we applied an improved numerical
formulation which deals with highly heterogeneous and anisotropic medium, that can handle distorted meshes. The
governing equations are solved via an implicit pressure and explicit concentration procedure, where the dispersion
term is discretized by a non-linear Two-Point Flux Approximation Method (NL-TPFA), this method is very robust
and capable of reproducing piecewise linear solutions exactly by means of a linear preserving interpolation with
explicit weights that avoids the solution of locally defined systems of equations. A Monotonic Upstream Centered
Scheme for Conservation Laws (MUSCL) type method is adapted for the solution of the advection term. This

method is based on a gradient reconstruction obtained by a least square technique in which monotonicity is rein-
forced by an appropriate slope limiter. The methods can be used with general polygonal meshes, even though we

restrict ourselves to conforming triangular and quadrilateral grids. In order to validate the formulations adopted,

some benchmark problems found in literature are solved. These numerical experiments suggest that our formu-
lations can provide robust solutions for simulating groundwater solute transport processes, especially in aquifer

systems with complex physical and geological properties.

A Computational Tool for the Geometric Modeling of Naturally Fractured Carbonate (Karst) Petroleum Reservoirs

Filipe A. C. S. Alves — 2024-06-11

One of the main reasons why the modeling of carbonate (karst) reservoirs is a challenging task is the
geometric representation required to capture the complex geological structures in these reservoirs, such as fractures,
vugs, cavities and caves. Mesh generation from a geometrical model is thus affected by the choices made for vugs
and fractures representations. An alternative approach is to assign geological features to the volumes in a fine scale
mesh as physical properties. These discrete models are required when, for instance, Stokes-Brinkman’s equations

are adopted to model multiphase flow simulation in carbonate karstic oil reservoirs, found often in Brazilian Pre-
Salt. In this paper, we propose a computational tool for generation of karst reservoir scenarios by creating a

geometrical model of the geological features and then computing the mesh volumes inside vugs, cavities, caves and
fractures. Vugs are represented by randomly distributed and possibly overlapping ellipsoids in a three dimension
space. They might be connected by fractures, modeled as cylinders, ellipsoids or boxes. Face connectivity between
mesh volumes in a fracture is assured. The code was written in Python using the NumPy library and the IMPRESS
(Intuitive Multilevel Pre-processor for Smart Simulation), an “in-house” pre-processor used for mesh management.
Example scenarios were generated to evaluate the correctness and robustness of the developed computational tool.

Single-phase flow simulation in 3-D naturally fractured reservoirs using a locally conservative formulation, an embedded discrete fracture model and unstructured tetrahedral meshes

Túlio de M. Cavalcante — 2024-06-11

Fluid flow in fractured porous media is a truly relevant phenomenon for the oil industry, but also for
water extraction and aquifer remediation. Modeling this type of problem represents a great challenge, due to the
complexity of depositional environments. In such cases, it is particularly complex to construct structured meshes
capable of adequately modeling the reservoir. In this context, in the present paper, we describe a new strategy to
simulate the single-phase fluid flows in three-dimensional heterogeneous, anisotropic and fractured porous
media using tetrahedral unstructured meshes. Aiming to model fractures, we use the Embedded Discrete Fracture
Model (EDFM) in which fractures are represented explicitly, but without the necessity of building a “fracture
fitting mesh”, which could be an overly complex task. To discretize the elliptic pressure equation, we use the

recently developed 3-D version of the MultiPoint Flux Approximation that uses the "Diamond stencil" (MPFA-
D) which is a robust and flexible formulation, capable of handling highly heterogeneous and anisotropic

reservoir rocks, achieving second order accuracy for the scalar variable and first order accuracy for fluxes. Our
strategy has shown to be notably flexible, and our preliminary results are very promising. has achieved good preliminary results.

Numerical Simulation of Oil and Water Displacements in Petroleum Reser- voirs Using a Non-Linear Two-Point Flux Approximation Method Coupled to a Modified Flow Oriented Formulation Using a Sequential Implicit Pro- cedure

Gustavo L. S. S. Pacheco — 2024-06-11

The numerical modeling of the multiphase and multicomponent flow in oil reservoirs is very complex

and demands the development of robust and efficient computational tools. Two important issues whenever de-
signing numerical formulations for the modeling such problems are the so-called Grid Orientation Effect (GOE),

which is the dependence of the numerical solution with the spatial alignment of the computational grid, and the
non-monotonicity of the solution generally obtained when highly anisotropic reservoir rocks or distorted meshes
are addressed. The GOE effect is linked to the anisotropic distribution of the truncation error in the numerical

approximation of the transport term. The uneven amount of anisotropic numerical diffusion introduced in each di-
rection may trigger a nonlinear process in which the error may grow exponentially, particularly when the displaced

fluid (e.g. heavy oil) is much less mobile than the displacing fluid (e.g. water). Due to the GOE, different and, usu-
ally, wrong solutions may occur considering grids with different spatial orientations with respect to the direction of

the fluid flow. Besides, if the mesh is non k-orthogonal, classical Linear Two-Point Flux Approximation (L-TPFA)

methods, may not even converge to the proper solution. Even the use of more robust linear Multipoint Flux Ap-
proximation (MPFA) methods may produce pressure fields with spurious oscillations for highly anisotropic media

or distorted meshes. Therefore, we propose a truly multidimensional cell centered finite-volume method to sim-
ulate oil and water displacements in heterogeneous and anisotropic petroleum reservoirs. The sequential implicit

procedure is used to handle the coupling between the pressure and the saturation equations. The elliptic pressure
equation is discretized by a positivity preserving Non-Linear Two-Point Flux Approximation (NL-TPFA) using
harmonic averaging points located on cell edges. A variation of the first order Modified Flow-Oriented Scheme

(M-FOS) is used to implicitly solve the non-linear hyperbolic saturation equation. Adaptive weights tune the for-
mulation multidimensionality according to the grid in this scheme. This strategy is used to reduce the occurrence of

Grid Orientation Effects (GOE). In order to verify the accuracy and robustness of our formulation, we test it against
classic benchmarks available in literature. In the future, we intend to extend our formulation to higher-order, to
improve front resolution and further reducing GOE.

On the accuracy of finite element approximations of elliptic problems with heterogeneous coefficients

Giovanni Taraschi — 2024-06-11

In this work, we investigate the accuracy of different finite element post-processing strategies in the
approximation of dual fields in elliptic problems such the stress tensor field in the linear elasticity problem, with
special attention to problems with discontinuous coefficients.

Analysis of high order multilayered functionally graded composite beams: a numerical approach

R. S. de Melo — 2024-06-11

Functionally graded materials (FGMs) are multiphase composites whose properties vary continuously
in one or more directions, obeying a function that better suits the purpose of the structure. In the present work, the
study of FGMs is integrated to multilayered composite beams with varying properties per layer. The continuity of
the material properties from the FGM mode mitigates the stress peaks that occur in the interface between layers
with different orientations. A unified high-order theory for beams incorporating FGMs is developed and applied
to the Equivalent Single Layer theory approach to analyze single and multilayered beams using any order finite
element method. Examples of simply supported beams are analyzed and compared to the results presented in the
literature. The proposed formulation presented results in agreement with the literature.

Crack analysis of mesoscale concrete by FEM using an alternative mesh overlay to represent mortar and coarse aggregate

Welington H. Vieira — 2024-06-11

One of the main mechanisms of deterioration of concrete structures is cracking. As the shapes of the cracks
are influenced by the heterogeneity of the concrete, when looking for a mechanical model that allows to determine
them realistically, it is necessary to discretize the structure in mesoscale. Using the positional approach of the Finite
Element Method (FEM), this work presents an alternative representation of mesoscale concrete. In this modeling,
the finite element meshes that represent the coarse aggregates and the mortar are generated independently and
overlapped to form the composite material. This strategy aims to make pre-processing easier, the nodes of each
mesh need not be coincident and the degrees of freedom of the elements of the aggregates do not add any unknowns
to the problem. To verify the efficiency of this model, it is applied to the concurrent multiscale analysis of a concrete
sample, leading to responses close to the experimental ones.

PERFORMANCE OF ACOUSTIC METAMATERIAL BASED ON A DOU- BLE LAYER MICROPERFORATED PANEL

Linconl C. B. Farias — 2024-06-11

In recent years, the development of models of acoustic metamaterials has received considerable promi-
nence due to the several unique properties found in this absorbers. AMM based on a microperforated panel of type

with internal air cavities have been promising and depending on the application provide satisfactory results at low
frequencies. This work investigates the performance of a honeycomb type acoustic metamaterial (AMM) modeled
as double-layered microperforated panels. The effective sound absorption in the frequency range between 100 and
500 Hz is verified analytical, numerical and experimentally. The analytical results are corroborated numerically

using a 3D finite element (FEM) method. A sound absorber sample was manufactured using 3D printing technol-
ogy and evaluated in an impedance tube considering the normal incidence of waves. Sound absorption of 94% at

182 Hz with a bandwidth of 52 Hz was obtained and good agreement with the analytical model was reached. In
addition, it is verified that this result is due to the high dissipation of sound energy in the perforation region of the
first panel. Therefore, this sound absorber shows excellent performance to control the low frequencies.

Numerical Investigation of Transformation Field Analysis for Elastic-Plastic Periodic Materials

Christiano A. F. Varady Filho — 2024-06-11

Present work analyzes the numerical cost-benefit ratio of Dvorak’s Transformation Field Analysis to

evaluate elastoplastic behavior of periodically perforated metal sheets. The accuracy measurement and the process-
ing time are analyzed by implementing a finite element approach integrated with the Transformation Field Analysis

technique for different meshes and finite element orders. Numerical studies are employed to compare with standard
Finite Element Analysis for elastoplastic analysis of periodically perforated metal sheets. The numerical results
show the technique’s capabilities and favorable scenarios, besides the influence of domain discretization and finite
element order.

Study of the parametric excitation phenomenon of a slender riser using finite element method and a reduced order model

Guilherme Rocha Martins — 2024-06-11

In the context of oil and gas (O&G) exploitation, risers are slender structures connecting the floating
unit to the seabed. These structures experience static and dynamic loads with potentially high nonlinearities. It is
relevant for O&G industry to understand the riser’s mechanical behavior to improve the structure life and predict
failures. In this sense, this work focuses on the analysis of the dynamical behavior of a vertical riser (represented
as a vertical beam) under harmonic excitation in the top, standing for the oscillation of a floating unit. Depending
on the structure’s mechanical properties and on the load frequency, the parametric excitation phenomenon can
take place, yielding large-amplitude lateral motion even for small vertical displacements. More specifically, the
focus is on the Mathieu’s instability regions, which occurs when the excitation frequency is an even multiple of
the structure natural frequency. In this work, we establish a simplified analytical approach using a reduced order
model (ROM), which considers an Euler-Bernoulli beam model undergoing small rotation. For this purpose, the
equations of motion are obtained using the extended Hamilton’s principle (EHP). By applying Galerkin’s method
using three sinusoidal shape functions and considering a time-spatial split, ROM’s non-dimensional final equations
can be obtained. Next, an in-house nonlinear FEM-based solver, called Giraffe (an acronym for “Generic Interface
Readily Accessible For Finite Element”) is presented and some comparative examples are performed using the
ROM and the Giraffe, observing their differences and similarities. These case studies were performed considering
the structure immersed in water and air, and the excitation frequency is varied to evaluate the first and the second
Mathieu’s instability region. The results presented good agreement in both models, with, in general, slightly larger
displacements for the ROM models.

Study on Genetic Algorithms and Constraint Handling Techniques Applied to the Optimization of Jacket Structures for Offshore Wind Turbines

Rodrigo O. Cruz — 2024-06-11

Recently, steel jackets have been an attractive alternative as support structures for Offshore Wind
Turbines (OWT), supporting the production of wind energy. Design of offshore jackets require complex analysis
due to the dynamic environmental loads and the frequencies from the turbine operation. So, it is important to
address coupled models where the interactions between the jacket and the turbine are considered. The jacket weight
also represents an important measure since a lighter structure has a lower cost and a potential of higher efficiency.
The main objective of this work is to study optimization techniques based on Evolutionary Algorithms (EA) to
minimize the weight of jackets for OWT, considering a coupled model. The structure model used in this work was
based on that developed in the OC4 (Offshore Code Comparison Collaboration Continuation) project. A Genetic
Algorithm (GA) was applied as the optimization algorithm. Two constraint handling techniques were compared
in the problem. Preliminary results present feasible solutions which decreased the weight and natural frequencies.

Analytical-numerical study of natural frequencies and mode shapes of interconnected acoustic cavities due to the influence of several significant parameters

Montes, R. O. P — 2024-06-11

Nuclear power plants, industrial plants, refineries, and other engineering installations, are made up of
tubular circuits traversed by fluids, and the dynamic response of these systems excited by flows, are characterized

by fluid-structure problems of great interest in engineering projects. This paper presents a comparative analytical-
numerical study on the behavior of interconnected acoustic cavities, considering the influence of several significant

parameters, such as the number of tubes, the boundary conditions and section changes of the circuit. As a response
to the analysis, natural frequencies and mode shapes are obtained by comparing an analytical method and
numerical modeling. The analytical formulation was developed from the classic idea of the Transfer Matrix

Method (TMM), considering different boundary conditions at the ends of the circuit, such as the open-open, closed-
closed and closed-open system. For all cases, the fundamental equation composed by the association of several

interconnected elements is obtained. All analyzes were compared with numerical simulations obtained by the
Finite Element Method (FEM), with the aid of the commercial software ANSYS. The cases treated in this paper
include the evaluation of the effects of these parameters, oriented to applications in tubular circuits, present in
industrial plants, analyzing the behavior of the acoustic pressures and flows in these cavities, through the study of
natural frequencies and mode shapes in each case. There is a good agreement of the results obtained by the Finite
Element Method in comparison with the analytical solutions obtained by the Transfer Matrix Method. Thus, the
study of the behavior of acoustic cavities interconnected by different methods, in addition to enabling the validation
of this simple analytical formulation, allows the preliminary treatment of the problem, for the fluid-structure
approach, which is a more complex issue and dependent on these analyzes.

Structural Analyses of Fixed Offshore Wind Turbine Jacket-Type Support Structure

Érica M. de Mendonça — 2024-06-11

This work aims to study a steel jacket supporting a 10 MW offshore wind turbine (OWT) in a 40 m
water depth on the Northeastern Brazilian Coast. In order to do so, various structural analyses were carried out.
First, the system’s natural frequencies were evaluated, and stresses caused by local environmental loads of wind,
waves, and currents were assessed. GeniE was responsible for calculating the utilization ratio of the jacket’s
elements under extreme loads. The jacket foundations, composed of piles on sandy soil, were also analyzed in

GeniE, highlighting the representation of soil-foundation interaction and the soil load capacity according to API-
RP-2A-WSD. SIMA-RIFLEX performed fatigue analysis through the Rainflow Counting method associated with

an S-N curve to assess fatigue damage, which is pivotal for the project. Different wind turbulence intensities were
investigated as this factor proved to influence the structure’s lifetime greatly. A final adjustment was made to the
jacket cross-section, after the analyses, in order to guarantee its structural integrity.

Design of a Floating Offshore Structure by a Deep Neural Network

Fillipe R. L. Esteves — 2024-06-11

The design process of an offshore system requires a suitable dynamic model of the floating structure, accord-
ing to the geometry and environmental conditions. However, the choice of the hydrodynamic model is directly

associated with the computational cost since dozens of simulations are necessary during the design process. In
this work, the assessment of different parameters allowed to accelerate the design analysis model applying Deep
Neural Networks instead of the hydrodynamic model. A two-phase study assessed the main parameter’s calibration
to the Deep Neural Network (DNN), with a forced 1 DoF Mass-Springer-Damper (MSD) system and a validated
hydrodynamic model for heave motions of a semi-submersible platform. The use of simplified models in this study
allowed a large volume of cases to compose the dataset. Systematically varying the number of layers in the DNN
and the number of neurons in each layer, the authors selected the combination with the minimum mean squared
error. The response surface provided by the best network configuration provides a response surface that is useful
for optimization tasks of future works.

Study of the parametric excitation phenomenon of a slender riser using finite element method and a reduced order model

Guilherme Rocha Martins — 2024-06-12

An IBEM-FEM model of the Rayleigh wave-scattering function of long walls

David A. S. Carneiro — 2024-06-12

This work presents a numerical method to investigate the ground vibration screening capability of

long walls and how their presence affects the wave propagation in the soil. Incident Rayleigh waves imping-
ing on the wall are considered as seismic excitation. The soil is modeled as a two-dimensional, homogeneous,

transversely isotropic, viscoelastic half-space modeled through an indirect formulation of the Boundary Element
Method (IBEM), discretized by constant boundary elements. The method consists of a superposition of Green’s

functions for uniformly distributed surface loads. The wall is discretized by linear-elastic, four-noded, isoparamet-
ric, quadrilateral finite elements. This coupling results in an IBEM-FEM model in which traction and displacement

fields within the half-space containing the wall subjected to Rayleigh waves are related through sets of contact

tractions applied to the boundary elements. Post-processing from these tractions yields quantities such as the dis-
placement and strain fields within the half-space, which are used to study how the presence of the wall affects the

ground vibration generated by Rayleigh waves.

A 3D IBEM-FEM coupling model for time-harmonic soil-structure inter- action analysis

I. Cavalcante — 2024-06-12

This work presents a numerical model for the analysis of arbitrarily-shaped 3D structures, under time-
harmonic loading, supported by the soil surface. The structure is modeled with the finite element method, and the

soil is modeled by the indirect boundary element method. The present formulation uses superposition of Green’s
functions for loads distributed over rectangular areas to obtain stress and displacement fields anywhere in the
soil. The use of a boundary element-based formulation makes this model capable of representing accurately wave
propagation in the soil and of complying with Sommerfeld’s radiation condition, and avoids truncation problems
and computational cost issues that would result from different methods. Coupling between the elements of the
structure and of the soil is established by imposing equilibrium and continuity conditions at their interface. This
results in an equation of motion of the soil-structure system, written in terms of nodal displacements and forces of
the structure, and involving the effect of soil flexibility. A representative example of a tower interacting with the
soil is analyzed.

Numerical integration method for very high frequencies in the evaluation of Green’s functions for layered media: transient wave propagation phenomena

I. Cavalcante — 2024-06-12

This paper is the sequel of a numerical scheme prepared for numerical integration of improper integrals,
containing an infinite number of singularities and a decaying tail that oscillates indefinitely. This kind of integrals
is common in many engineering unbounded media problems that involve computing Green’s functions, which
are usually solved with transformed integrals approaches. This work considers the Green’s function for case of
the time-harmonic response of a multilayered transversely isotropic half-space under external excitations. This
response is obtained with the aid the Hankel transform and presented in terms of an exact stiffness matrix method.
The solution, in the Hankel transformed domain, was integrated numerically to obtain the corresponding physical
domain displacements for very high frequencies. The Fast Fourier Transform (FFT) algorithm was employed in
the previously synthesized frequency domain solutions, which results in the determination of transient responses
for very small time-steps. The results show that three wave fronts are generated. The displacement velocity of
these wave fronts can be associated to compression, shear and Rayleigh waves. This work contributes to our
understanding of the numerical evaluation of time-harmonic and transient responses of soil media and is important
in many fields of geotechnical engineering and other unbounded media problems.

Non-singular Green’s functions for quadratic-order indirect-BEM discretizations: implementation and numerical results

Iago Cavalcante — 2024-06-12

This article presents original Green’s functions that can used to model bounded and unbounded prob-
lems through boundary discretization and meshless methods. Time-harmonic loads are applied within rectangular

patches within isotropic, three-dimensional full-spaces. The coupled differential equations describing the problem
are solved with the aid of double Fourier transforms. A boundary-value problem corresponding to horizontal and
vertical loads with bi-quadratic distribution over the loaded area is considered. The final stress and displacement
fields are expressed in terms of double Fourier integrals to be evaluated numerically. These non-singular Green’s
functions can be thought of as bi-quadratic boundary elements, to be used within direct and indirect boundary
element formulations.

IBEM-FEM model of the vibratory response of a buried, elastic strip footing

Aldemar P. Siqueira — 2024-06-12

This work investigates the dynamic response of an elastic, partially buried strip footing under vertical
and horizontal external time-harmonic loads. The footing is modeled as a two-dimensional embedded rectangle
discretized by a plane-strain isoparametric finite element. The soil is a two-dimensional, isotropic, viscoelastic
half-space modeled through an Indirect-Boundary Element formulation. Solutions for this medium are obtained
by superposition of Green’s functions for buried loads. Direct kinematic compatibility and equilibrium conditions
are used to couple the finite element mesh to the boundary element mesh, assuming perfectly bonded contact at
the foundation-soil interface. The effect of foundation embedment and elastic properties on the dynamic behavior
of the foundation is illustrated with selected numerical examples.

Computation of moments in quadratic discontinuous anisotropic plane elasticity fast multipole formulation

J. S. França — 2024-06-12

The fast multipole formulation is used in order to solve large scale problems in general boundary el-
ement formulation. In this work we will present the computation of moments in the anisotropic plane elasticity

fast multipole formulation with quadratic discontinuous elements. Fundamental solutions of plane elasticity are
represented by complex functions from the classical 2D elasticity theory. The Multipole Expansion for kernels U
(displacement field) and T (traction field) will be computed using series. The convergence of the series expansion
to the fundamental solutions is analyzed considering different numbers of series terms and different distance from
source point to field point. Moments are computed to evaluate integrals of influence matrices where elements are
far away from the source point, whereas the conventional approach will be applied to evaluate the integrals on the
remaining elements that are closer to the source point. All fast multipole operations are demonstrated in this work
and compared to the standard boundary element formulation.

On the MFS for potential problems in non-homogeneous media

Edmundo Guimaraes de Araújo Costa — 2024-06-12

This paper presents a simple formulation based on Method of Fundamental Solutions (MFS) for the
numerical solution of non-homogeneous potential problems. This formulation makes use of Green’s functions for
dealing with the non-homogeneity of the problems. These Green’s functions are here modified by the method of
images, aiming decreasing the number of surfaces discretized by the MFS and thus reducing the computational
cost of the proposed models. The MFS formulation is then evaluated for different Green’s functions by comparing
its results with the ones given by analytical solutions. Finally, an example is presented, illustrating the good
performance of the MFS for such problems with embedded boundary conditions.

Comparison of two open-source codes of the boundary element method for acoustic problems

Fernando Barreto Soares — 2024-06-12

A comparison between two competing free and open-source codes of the boundary element method
(BEM) for internal and external acoustic problems is carried out in this work. The BEM programs used were
Bempp-cl and BB. While Bempp-cl is an well established Python program developed at University College London
and the University of Cambridge, BB is a more recent code, developed at the University of Bras ́ılia, written in Julia
language. For the mesh generation, an also open-source program, Gmsh, was used. Initially, internal problems on
a cubic geometry were solved, both in terms of response analysis in the resonant frequencies as well as frequency
response analysis for the three first modes of the problem. For the same problem, a processing time analysis was
also conducted, in order to assess the efficiency of the mentioned programs. The solutions obtained by the two
programs were compared with each other as well as with analytical solutions, when available. The results for the
cubic geometry shown that both programs were able to successfully predict the behavior for the modes and for
the frequency analysis, with a satisfactory time consuming. Therefore, the use of BEM and, specially, of both
programs studied in this article are very powerful tools, freely available, to solve large and complex engineering
problems, with great efficiency and accuracy.

Performance Comparison between the Multiple Reciprocity and Direct Interpolation Boundary Element Method in Problems Governed by the Helmholtz Equation

Balista, T.G — 2024-06-12

In this work, response problems applied and governed by the Helmholtz equation are analyzed. The
formulation Multiple Reciprocity Boundary Element Method (MRBEM) can be seen as an extension of the
formulation with Dual Reciprocity (DRBEM) because the original problem as a whole is modeled by a sequence
of fundamental solutions of a higher-order, while the formulation of the DRBEM uses a sequence of radial-based
functions to approximate the kernel the domain integrals. Although both techniques apply the reciprocity
theorem, the idea behind each method is essentially different. For the validation of this formulation, problems
governed by the Helmholtz equation are solved, in which the MRBEM results were compared to a new
formulation of the Boundary Element Method (BEM), denoted in this work as DIBEM-2 (Direct Interpolation
Boundary Element Method without Regularization). DIBEM-2 makes use of radial basis functions to
approximate domain integrals. Performance curves are generated by calculating the average percentage error for
each mesh, demonstrating the convergence and precision of each method.

Analysis of centrifugal body force problems in anisotropic materials using the boundary element method

Leonardo B. Silva — 2024-06-12

The main objective of this work is the development of a formulation of boundary elements for the
anisotropic material problem evaluation under centrifugal loads. The fundamental anisotropic solutions are used
and terms of inertia are considered as body forces. The domain integrals that result from the inertial terms are
transformed into boundary integrals using the radial integration method. As a result, no internal points are needed
to improve the accuracy of the solution. Discontinuous quadratic boundary elements are used whose degrees of
freedom are written in a local reference system, where the directions of the coordinate axes coincide with the
normal and tangent directions to the boundary at the collocation point. Problems with known analytical solutions
are used in order to assess the accuracy of the proposed formulation. There is a good agreement between the
numerical and exact solutions.

Secondary torsion moment deformation effect (STMDE) by Boundary Element Method in composite bars with variable cross sections

Maicon José Hillesheim — 2024-06-12

This paper proposes a formulation for solving torsion problems in composite bars with variable cross

sections including secondary torsion moment deformation effect (STMDE). The Boundary Element Subregion-
by-Subregion (BE-SBS) Technique is applied to model cross sections with general shape and constituted of any

number of different materials. Four boundary value problems are solved. The primary and secondary warping
functions are determined by applying the Boundary Element Method, while the primary and secondary twist
angles, θ pand θs, along the element axis are solved by a process based on the weighted residual method. It is
worth mentioning that iterative Krylov’s solvers are used, which results in saving memory and solver time. The
efficiency, robustness and accuracy of the implemented algorithm are demonstrated in several numerical
examples.

A Comparison Between Cell-less Formulations for Domain Integrals Treat- ment in the Poisson type problem by the Boundary Element Method

Lucas de Paulo de Souza — 2024-06-12

By applying the Boundary Element Method (BEM) to solve Poisson problems, besides boundary in-
tegrals, the final equation also contains a domain integral involving the inhomogeneous term. This integral can

be evaluated by discretizing the domain into cells. However, one of the main advantages of the BEM, which is
the reduction of the problem’s dimension by one order, is lost and several methods have been developed aiming
to treat these integrals without the need to do this discretization. This paper makes a comparison among three
formulations to do this: the Dual Reciprocity Method (DRM), the Multiple Reciprocity Method (MRM) and the
Radial Integration Method (RIM). The formulations and features of each method are presented as well as numeric
results obtained by their applications to some examples with known analytical solutions. The aim of this paper is
to make a critical analysis in terms of the numeric efficiency and accuracy of each technique, primarily about the
number of elements and internal points required for obtaining results inside an acceptable margin of error.

An isogeometric Boundary Element formulation for solids containing trimmed surfaces

Matheus Rocha — 2024-06-12

The Isogeometric Boundary Element Method (IGABEM) is an accurate and recent approach for solving
boundary value problems. This approach is especially accurate in the representation of complex geometries and
mechanical responses. Besides, it enables the direct application over Computer Aided Design (CAD) models, once
they utilise same basis functions in the parametrization of geometric entities. In the context of elasticity problems,

the Non-Uniform Rational B-Splines (NURBS) functions approximate both geometry and mechanical fields. Ad-
ditionally, CAD models often represent complex solids with trimmed NURBS surfaces. The generation of these

type of surfaces rely on the trimming operation, in which NURBS curves represent the edges of a cut. Conse-
quently, a robust IGABEM analysis must account for trimmed surfaces, which is a challenging task nowadays.

Hence, the present research deals with the mechanical analysis within IGABEM and trimmed geometries. For this
purpose, an identification task based on the ray-casting algorithm detects regions and control points unaffected by
trimming operation, trimmed or inactivated. Afterwards, the collocation points in surfaces’ corners are moved into
the surface, which follows the modified Greville Abscissae (GA) strategy. Besides, the integration process applies
the transformations proposed by Kim et al (2009). The proposed formulation applies a non-singular strategy, which
avoids additional singularities’ treatment. One application demonstrates the accuracy of the proposed formulation,
in which the responses have been compared against analytical solutions. A new extension of mechanical analysis
within IGABEM has been reached herein, once trimmed surfaces are also incorporated in this numerical method.

Three-dimensional failure analysis by BEM using cells with embedded discontinuity activated during the nonlinear loading process

Alisson P. Chaves — 2024-06-12

Numerical simulation of brittle fracture of three-dimensional solids is addressed in this work by the
boundary element method (BEM) and the strong discontinuity approach (SDA). In this formulation, cracks are
treated using a non-geometric representation through the use of cells with embedded discontinuity. Into these cells,
the inelastic strain field is obtained as a result of the application of kinematic equations with discontinuities in the
displacement field (strong discontinuities) to standard continuum constitutive models, containing a softening law.
A reinterpretation of some parameters of the constitutive model is also performed to guarantee its compatibility to
the discontinuous kinematics. Since in the BEM only the internal regions where dissipative effects happen need
to be discretized into cells, crack propagation is driven by activations of such cells during the loading process,
followed by an expansion of the matrices that define the discrete model.

Application of the Direct Interpolation Boundary Element Technique with Self-Adaptative Integration to Bidimensional Diffusive-Advective Problems

Loeffler, C.F. — 2024-06-12

The application of the Boundary Element Method (BEM) in the formulation of advective-diffusive models
experiences a solid scientific revival and finds its main challenges in the numerical treatment of the transport term.
Despite the classic formulation, which is based on the fundamental solution related to the problem, being able
to adequately describe physical situations dominated by advection, it does not present flexibility when dealing
with variable velocity fields. The recent Direct Interpolation technique (DIBEM), also based on the robustness
of approximations by radial basis, handles in a more balanced way the challenges imposed to BEM, while able
to represent hydrodynamic fields with spatial variation and maintaining numerical stability up to moderate Peclet
numbers. Basically, the technique procedure transforms domain integrals into boundary integrals, approaching
the entire kernel using radial basis functions. The DIBEM’s mathematical structure is very similar to a classic
interpolation, that in turn requires a significant number of interpolating points in the domain. In this context,
the performance of the Direct Integration formulation as well as it is numerical stability depend, among other
factors, on the quality of the approximation of ordinary, quasi-singular and singular integrals that are inherent to
the discrete linear system. The current article proposes a comparison and analysis of the influence of the numerical
integration scheme selection, testing the classic Gaussian quadrature against a self-adaptive scheme, aiming to
evaluate possible accuracy gains of the Direct Interpolation Technique. Quantitative assessment of the impacts of
integration schemes are evaluated using well-known analytical solutions.

Analytical and adaptive numerical evaluation of all terms required in a 3D boundary element implementations for potential problems using linear triangle elements

Ney Augusto Dumont — 2024-06-12

The present contribution introduces a formulation for 3D steady-state potential and elastostatics prob-
lems that ends up with the analytical handling of all integrals necessary in an implementation using linear triangle

(T3) elements – whether regular, improper, quasi-singular, singular or hypersingular integrals are involved. The
boundary element matrices – including the discontinuous term of the double-layer potential matrix – are obtained
in a straightforward way with the use of analytically pre-evaluated integrals. Results at internal points that may
be located arbitrarily close to the boundary are also given analytically. The paper describes the main concepts and
computational features of the proposed formulation and presents an example of 3D potential problem to illustrate
the most challenging topological configurations one might deal with in practical applications. For source points
sufficiently far from a boundary element an adaptive numerical integration scheme is also proposed for the sake of
computational speed – and how far a point should be in order to be considered far is also discussed.

Direct Transient Response of Coupled Structures-Soil Systems Modelled by Matrix Methods and Green’s Functions Approach

Amauri C. Ferraz — 2024-06-12

Even today it is still a big computational challenge to obtain the dynamic transient response of complex
systems constituted of a structure interacting with a foundation supported by the soil. The most common numerical
solution schemes for the two sub-systems, the structure and the soil-foundation support are distinct. Usually, the
foundation dynamics is modelled by the Finite Element Method (FEM) or related matrix methods. On the other
hand, the soil dynamics has been best solved using either the direct or indirect version of the Boundary Element

Method (BEM). A coupling of both numerical schemes is the most versatile scheme to solve Dynamic Soil-
Structure Interaction (DSSI) problems. The coupling of the methods to obtain transient solutions is still

computationally very demanding. I this work we propose an alternative approach. For subsystem 1, the structure,

modal quantities are obtained in coordinate relative to the structure base displacement. For sub-system 2, the soil-
foundation scheme, the BEM is applied to obtain frequency domain solution of foundations resting on soils or on

piles. A coupling of the structure with foundations in the frequency domain delivers modified Frequency Response
Functions (FRFs). New or modified modal quantities are now extracted from the FRFs that already include the
influence of the soil-foundation dynamics on the structure. These extracted modal quantities may be used to
integrate directly the equations of motion in the time domain. All degrees of freedom of the soil-foundation system
are incorporated in the modified modal quantities, which retain the number of degrees of freedom of the original
structure. The numerical examples will address the transient response of structures resting foundation scheme
composed of a homogeneous half-space and a pile embedded in the half-space.

Machine-precision fracture mechanics evaluations with the consistent boundary element method

Ney Augusto Dumont — 2024-06-12

As hitherto proposed in the technical literature, the boundary element modeling of cracks is best carried
out resorting to a hypersingular fundamental solution – in the frame of either the so-called dual formulation or the
displacement discontinuity approach –, since with Kelvin’s fundamental solution it would not be possible to deal
with the ensuing numerical and topological issues. A more natural approach would be the direct representation
of the crack tip singularity in terms of generalized Westergaard stress functions, as already proposed in the frame
of the hybrid boundary element method. Quite recently, we have been able to demonstrate that the conventional
boundary element formulation is in fact able to precisely represent high-stress gradients and deal with extremely
convoluted topologies provided only that the problem’s integrals be properly evaluated, which has turned out
to be the case. The reference literature on the present subject is briefly outlined along with the paper, which
includes the simplest scheme of evaluating stress intensity factors in terms of crack tip opening displacements
as a viable alternative to the J-integral. We propose 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 micrometers or even nanometers, which would still be mathematically feasible – albeit not mechanically. In
fact, machine precision evaluation of all quantities may be always achieved and stress results consistently obtained
at interior points arbitrarily close to crack tips. The present developments apply to two-dimensional problems.
Some numerical illustrations show that highly accurate results are obtained for cracks represented with just a few
quadratic, generally curved, boundary elements – and a few Gauss-Legendre integration points per element. We
also investigate how different simulations of the crack tip shape affect results, which turn out to be more accurate
with the use of higher-order, such as quartic, boundary elements.

Boundary element analysis of 3D linear potential problems combining fast multipole expansion and machine-precision numerical integration

Ney Augusto Dumont — 2024-06-12

This paper is part of a research work to implement, test, and apply a novel numerical tool that can simu-
late on a personal computer and in just a few minutes a problem of potential or elasticity with up to tens of millions

of degrees of freedom. The authors have already developed their own version of the fast multipole method (FMM)
for two-dimensional problems, which relies on a consistent construction of the single-layer potential matrix of the
collocation boundary element method (BEM) so that ultimately only polynomial terms (as for the double-layer
potential matrix) are required to be integrated along generally curved segments related to a given field expansion
pole. The core of the present paper is the mathematical assessment of the double expansions needed in the 3D
FMM. The 3D implementation is combined with a particular formulation for linear triangle elements in which all
integrations for adjacent source point and boundary element are carried out analytically. As a result, numerical
approximations are due exclusively to the FMM series truncations. This allows isolating and testing truncation
errors incurred in the series expansions – and thus for the first time properly assessing the mathematical features
of the FMM, as illustrated by means of an example. The complete solution of a mixed boundary problem using a
GMRES solver, for instance, is just an additional task and, although already implemented, is not reported herein.

An Isogeometric Boundary Element Formulation for fibre-reinforced 3D domains

Antonio R. Neto — 2024-06-12

This study presents an innovative Isogeometric coupling formulation for the mechanical analysis of
3D solids reinforced by fibres. This formulation is based on the coupling of the Isogeometric Boundary Element
Method (IGABEM) and the 1D approach of the Boundary Element Method (1DBEM). The material matrix (solid
3D domain) is modelled by the IGABEM, which uses NURBS and B-Splines functions to represent both geometry
and mechanical fields. These functions allow the exact representation of complex geometries, such as cylinders,
torus and propellers. Besides, a straightforward connection with the geometry design is possible, since most
CAD packages used in engineering projects represent 3D solids through NURBS surfaces at its contours. The
1DBEM is based on the axial fundamental solution for elastic 1D domains. The interaction between the matrix
and fibres is described by an adherence force over the reinforcements’ line, which is interpolated by high-order

polynomial functions. No relative displacements is considered (perfect bonding) and both materials have linear-
elastic behaviour. The proposed coupling formulation is herein named 1DBEM/IGABEM coupling technique. The

mechanical analysis of a numerical application demonstrates the results obtained by the proposed formulation in
comparison with reference results. The proposed formulation requires fewer degrees of freedom than the reference
for the same level of accuracy. Therefore, the Isogeometric coupling presented herein is not only effective for a
large number of complex geometries, but also efficient in the precise representation of mechanical fields.

Consistent boundary element method for crack propagation problems

Guilherme O. Rabelo — 2024-06-12

This paper presents the development of a crack propagation code to be implemented in a computer
program based on the consistent boundary element method. This method has as its main characteristic an exact
resolution of singularity problems inherent to the formulation. Furthermore, with this method, it is possible to
represent the crack geometry of the models with openings in the micrometer range, similar to the cracks presented
in laboratory tests. In this study, two models with different geometries are analyzed, using the same load, in order
to represent pure mode I and mixed mode (modes I and II) loading configurations. The performance of this method
is compared with the results of other papers found in the literature. As a crack propagation criterion, the maximum
stress in the proximity of the crack tip and the stress intensity factor obtained through the crack tip opening
displacement are analyzed. A study was also carried out on the propagation angle and crack stability, aiming at
improving the accuracy of the model results and reducing the computational cost of the simulations. The study
presented in this article is a work in progress.

An improvement to the frequency response in non-homogeneous Helmholtz problem using the Double Fictitious Background Media Formulation

Markcilei Lima Dan — 2024-06-12

This article proposes a new formulation of the Boundary Elements Method to solve the response
problem in non-homogeneous Helmholtz problems, called Double Fictitious Background Media (DFBMF). The
DFBMF is based on a simple algebraic procedure, creating a fictitious medium, which consists of adding and
subtracting the same term in the governing equation, which divides it into two parts: a homogeneous Helmholtz
equation and a fictitious reactive term. This new governing differential equation is mathematically independent of
the properties of the chosen fictional background medium. Still, considering the Weighted Residual Principles, the
associated integral boundary equation is affected by the Green Function argument through the reactive term, which
accounts for the variation in physical properties. To reduce the numerical error, two integral equations with
different arguments are generated where the reactive term is considered a common source to the two equations.
The numerical simulations show a significant increase in the precision of the results with the application of this
strategy.

Recalculation of internal directional derivatives using the integral equation of the Boundary Element Method in Poisson problems previously solved by the Finite Element Method

H. M. Barcelos — 2024-06-12

The strategy of reusing the integral equation of the Boundary Element Method (BEM) to improve the
accuracy of the values of variables previously calculated on the boundary have showed consistency, addressing
scalar problems governed by the Laplace, Poisson, and Navier equations. In this work, the boundary nodal
values obtained with the application of the Finite Element Method (FEM) in Poisson problems are substituted in
the BEM integral equation for the calculation of the internal values of potential and its derivative. For the
example showed, the results obtained were compared with the values found by the FEM and BEM, both in their
classic form, and the performance was evaluated through the analytical results.

Anomalous diffusion equation modeled by the joint use of domain boundary element method and analytical derived solution based on green equation

W. J. Mansur — 2024-06-12

In some situations, the mathematical formulation of the diffusion phenomenon might be described
through a differential equation, which takes into account complementary and different effects with respect to the
physical processes simulated with the support of the Fick ́s equation, which is usually adopted to represent the
diffusion process. In particular, diffusion applied to spatial-temporal retention problems with bimodal mass
transmission is highlighted. To better understand this physical phenomenon, the proper use of the analytical
Green function (GF) was investigated. The formulation employs the steady-state fundamental solution. In
addition to the basic integral equation, another one is required, due to the fourth-order differential operator
introduced in the differential equation of the problem evaluated. The domain discretization employs linear cells.
The first order time derivative is approximated by a backward finite difference scheme. Two examples are
presented. Numerical results are compared with analytical solutions showing good agreement between them;
such framework provides a novel perspective for the use of the combined approach here developed to assess the
behavior of physical phenomena better described by the fourth order analytical equation based on Green
Function. In this work, the Domain Boundary Element Method (D-BEM) is explored to model that anomalous
diffusion process taking into consideration that we were also able to originally develop the Green analytical
solutions for the fourth order diffusion equation. Such combination of approaches proves to establish a new
conceptual reference in this area.

Analysis of the use of carbon fiber reinforced polymer bars to reinforce concrete beams

Rodrigo S. Baptista — 2024-06-12

The aim of the present work is to analyze the use of bars made of composite material to act as
reinforcement for concrete beams subjected to bending. The analyzed bars are constituted by polymer reinforced
with carbon fibers (CFRP), a material that presents linear elastic behavior until rupture. This material has some
advantages in relation to steel, such as considerably higher tensile strength in addition to not being susceptible to
corrosion caused by environmental conditions. During the development of the work, an article was obtained which
demonstrates results of laboratory tests in which the authors used concrete beams subjected to four-point flexure
testing and reinforced with PRFC bars. In this work, the same test was simulated using the Atena software, a
computer program that performs non-linear analysis for concrete structures, considering the structural cracking.
The results obtained by the software were consistent with those obtained in the laboratory. The flexural
reinforcement design was performed for a section of concrete beam reinforced with steel and another with CFRP,
in addition to having also analyzed a uniformly distributed load that breaks a continuous beam when it is reinforced
with steel bars and when it is reinforced with CFRP bars.

Composite shell formulations: comparison of two geometrically nonlinear implementations

Isadora T. Almeida — 2024-06-12

Composite materials are attractive candidates for structural applications that require high specific-
strength and high specific-stiffness. Laminated composite materials are extensively used in aeronautical, aerospace,

and lately wind energy industries, where weight-sensitive structures are abundant. The structural modeling of
laminates commonly employs the Classical Lamination Theory (CLT). It is an extension of the homogeneous plate
theory introducing the elastic coupling effects present in laminates. In the CLT, the laminate stacking sequence
and material properties of each layer generate a homogenized section. Also, these structures are often slender and
may present large displacements and finite rotations, so that the adoption of a geometrically nonlinear shell model
is appropriate. This work presents the extension of a fully geometrically nonlinear triangular shell finite element
to account for laminated composite materials. The constitutive relations are derived from a quadratic potential
based on the CLT, considering small strains. The method was implemented in the Giraffe solver, accounting for
transverse shear and an additional drilling stiffness parameter. Calibration of the drilling stiffness was performed by
comparing static results from ANSYS® software, as a reference. Modal analysis was also addressed, for the same
composite proposals. Numerical results showed good agreement between Giraffe and ANSYS® implementations.

Development and Characterization of Green Composites for Social Housing

Natália Victoria dos Santos — 2024-06-12

Civil construction is one of the sectors of society that cause the most environmental impacts. The high
consumption of natural resources, emission of carbon dioxide in the manufacture of industrialized materials,
changes in soil, worsening of heat islands, waste production and water consumption. Therefore, the search for
sustainable materials is gaining more prominence. Thus, a solution found is the use of composites reinforced with
vegetable fibers and biodegradable matrix, called biocomposites. In addition to their sustainable character,
vegetable fibers are low specific weight, abundance, low cost, and non-toxicity. The present research aims to
develop and characterize 100% vegetable composites, using jute fiber fabric embedded in a liquid castor-based
polyurethane matrix for application as wall and roof elements of social housing. These plates, in turn, are produced
by the compression molding process, where layers of fabric and matrix are interspersed and compressed. The
specimens produced with 40% fiber were tested under bending according to the ASTM D790 standards to check
mechanical properties. The specimens were made in three directions (0°, 45° and 90°) to analyze the differences
in response in each case. As a result, for the main direction the flexural strength reached 37.2 MPa, while the
lowest result occurred in the 45° direction with a resistance of 16.9 MPa.

Flexural behavior of concrete beams reinforced with BFRP bars – experimental and numerical analysis

Gean M. B. Warmling — 2024-06-12

This study focuses on numerical and experimental analysis of reinforced beams with Basalt Fiber
Reinforce Polymer (BFRP) bars used as longitudinal and transversal reinforcements. The main characteristics of
BFRP are a linear stress-strain relationship and the elasticity modulus which is lower than the conventional steel
bars. Numerical analysis is conducted by carrying out nonlinear tridimensional FE models in the software DIANA
TNO to study load-deflection curves of beams with BFRP as longitudinal and transversal reinforcement. In an
initial analysis are established the more suitable mesh size and load step. Then, a parametric analysis considers the
use of different values for compressive fracture energy and crack orientation. All the results are compared with
experiments. From the obtained results, it is possible to conclude that the numerical models were capable of predict
load-displacement curve for beams with BFRP reinforcement.

Mechanical behavior of strain hardening cementitious composites (SHCC) for structural repair

Matheus P. Tinoco — 2024-06-12

This article presents an experimental investigation on the mechanical behavior of Strain Hardening
Cementitious Composites (SHCC) reinforced with PVA, UHMWPE (ultra-high molecular weight polyethylene),
steel and hybrid fibers for structural repair. The total volume of fibers were kept constant at 2.0% in order to
maintain the workability of the composite system. PVA and UHMWPE fibers were partially replaced by steel
fibers in 0.5% and 1.0%. The mechanical response was measured under tension tests while crack formation was
investigated using a high-resolution image capturing procedure. The results have shown that PVA fibers have a
better performance than UHWMPE and steel fibers for normal strength matrices. It was also found that the partial
replacement of PE fibers by steel fibers has the benefit of increasing the strength, but it has the disadvantage of
reducing the strain capacity of the composite. Finally, the composites were used as structural repair in beams
subjected to previous damage, and the results verify the feasibility of SHCC as a repair material.

Theoretical study of short and long-term behavior in hollow core concrete slabs prestressed with FRP tendons

Pablo M. Páez Gus — 2024-06-12

The aim of this work is to assess the suitability of the use of fiber-reinforced polymer (FRP) tendons in

simply supported, prestressed, hollow core slabs without concrete topping, with respect to their short and long-
term behavior under service load conditions. In this research, the use of carbon fiber reinforced polymer (CFRP)

and aramid fiber reinforced polymer (AFRP) tendons are examined. In the first part of this paper, we present a
framework for the short and long-term analysis of prestressed, concrete, hollow core slabs with FRP tendons in
the cracked and uncracked states. Then, based on a theoretical study, we compare the behavior of fully and partially
prestressed, hollow core slabs with either FRP tendons or steel tendons. Our main conclusions are that hollow core

slabs which have been prestressed with either CFRP or ARFP tendons show lower prestress losses and lower long-
term deflections in the uncracked state and for the same initial prestressing stress levels Although insignificant

differences were observed in the cracked state, the main advantage lies in better use of both materials (concrete
and FRP tendons), as these can give better performance than prestressing with steel tendons.

Overall effective elastic properties of composites by computational homogenization

Wanderson F. dos Santos — 2024-06-12

In composite materials the combination of different constituents promotes heterogeneity and specific
properties. Therefore, the constitutive behavior of a composite can be complex. In this context, the present work

explores a computational homogenization procedure to predict the overall or macroscopic effective elastic proper-
ties accounting for characteristics of the constituents at microscale. The microstructure of the material is modeled

using the concept of Representative Volume Element (RVE). Both uniform strain or periodic boundary condition

are applied on the RVE to compare the results. The effective elastic properties are then obtained from homoge-
nization of the microscopic fields computed with three-dimensional numerical simulations by finite elements. The

macroscopic constitutive properties obtained numerically are then compared to available results. The results show
a strong influence of the boundary condition on the effective elastic properties. On the other hand, the inclusion
morphology has no significant influence on the results. Furthermore, the procedure hereby described is an effective
tool to the more realistic modeling of the macroscopic constitutive behavior of composites materials.

MAGNETIC ORIENTATION OF SISAL AND STEEL FIBERS IN CEMENTITIOUS MATRICES: EXPERIENCES OF SÃO JUDAS TADEU UNIVERSITY

RAMBO, Dimas A.S. — 2024-06-12

This work presents results of experimental investigations focused on the magnetic orientation of steel
and sisal fibers embedded in cementitious matrices. The work addresses the development of magnetic alignment
methodologies and their influence on the mechanical and electrical properties of the resulting cementitious
composites. In the first phase, the materials used in the research are presented, as well as two methods for
magnetic alignment of fibers: neodymium magnets coupled to a computer-controlled industrial robot and a
simplified magnetic circuit using a pair of coils wrapped in a ferromagnetic core. The second phase focuses on
the analysis of the electrical and mechanical properties of the composites and assessment of the fiber orientation
and positioning. X-ray computed tomography, electrical resistivity and bending tests were used in this phase.
The results showed that the projected magnetic systems were able to generate a preferential orientation of the
fibers, increasing the overall mechanical performance of the composites and generating anisotropy on their
electrical properties.

Stability Analysis of Carbon/Epoxy Plate with the use of Finite Elements Method

Helio de Assis Pegado — 2024-06-12

The Laminated plates subjected to in-plane compressive loads are studied in this research, taking into

account laminate different configurations and boundary conditions. The critical buckling load for these configura-
tions is calculated using a commercial Finite Elements Program. The mesh convergence is tested, and the 60x60

mesh is chosen because their results are very close to the classical references, and the time of execution is lower
than sixty seconds. The Finite Element Program is performed and the results obtained show a good agreement
with the literature, which demonstrate the validity of the model adopted. The critical buckling load and its mode
are evaluated, and the influence of several boundary conditions and the fiber directions are studied. The results
obtained are discussed, and the influence of the different design parameters of the laminate on static stability is
verified.

STRUCTURAL ANALYSIS OF A MICROSATELLITE LAUNCHER VEHICLE SUBMITTED TO EXTERNAL PRESSURE

Robert R. A. Oliveira — 2024-06-12

The Brazilian Space Program has advanced in the development and production of microsatellite launch
vehicle (MLV) aiming at having self-sufficiency in sending satellites into space. Even though, the scientific
literature is scarce of works that present detailed results on this type of launcher vehicle. Therefore, this work
presents a structural analysis of a microsatellite launcher vehicle fairing manufactured by composite using a finite
element (FE) model. The FE model was submitted to external pressure obtained from two-dimensional fluid
dynamics simulations. A linear buckling simulation was performed to obtain the collapse pressure of the fairing
and to determine the thickness of the composite laminates. Then, a non-linear static simulation was performed to
obtain the progressive failure of the laminates using Hashin’s criterion. Tree different stacking sequence were
analyzed: [± 28 / 0 / 0]s , [90 / ± 554 / 90] and [± 655]. The failure to the structure was obtained by mapping the
pressure curve with the estimated thicknesses. Regarding the results, it was seen that the first buckling mode occurs
before the material failure in all the stacking sequence conditions.

Flexural response of polypropylene fiber reinforced concrete using the fiber composite model

Luís Felipe Ribeiro — 2024-06-12

In the last decades, several laboratory tests have been carried out to investigate the mechanical
behavior of fiber-reinforced concrete (FRC), especially regarding their flexural response for several structural
applications in Engineering. Modern developments concerning these materials have improved the number of
numerical models capable of predicting mechanisms at the material scale and the load-displacement behavior of
the composite. Therefore, the preliminary stages of advanced cement material design can profit from
mathematical models since the numerical experiments can consider different material working conditions before
prototyping. This paper proposes the numerical modeling of polypropylene fiber reinforced concrete beams
using a mesoscale formulation called the fiber composite model. This model consists of the coupling of uniaxial
fiber finite elements with continuum cementitious elements through cinematic constraint equations, where the
fiber degrees of freedom are eliminated at the element level. Additionally, a cohesive zone with a continuum

damage behavior is inserted into the formulation to simulate the post-cracking material flexural response. Three-
point bending experimental tests reported in the literature are modeled. The results show good agreement

between the experimental references and the reinforced cohesive element model to predict fracture patterns for
FRC beams.

Comparison of the response of reinforced concrete structures modeled in mesoscale for different damage models

Welington H. Vieira — 2024-06-12

The continuous damage mechanics allows the construction of constitutive models that represent well the
behavior of concrete structures. In this work, a computational code is developed, using the positional approach of
the Finite Element Method (FEM), which allows to represent the concrete degradation using two different damage
models. In the first, the degradation is distributed in the elements that discretize the concrete. In the second, the
damage model is applied to interface elements and makes it possible to represent discrete cracks in the structure.
The objective is to compare the performance of these models by applying them to the same structure to verify the
proximity of the force-displacement curves and cracking patterns. Where do we seek to define the best for each
type of use. The concrete is represented in mesoscale, where the finite element meshes that represent the coarse
aggregates and the mortar are generated independently and are superimposed to form the composite material. The
damage models were applied to a reinforced concrete beam and it was found that the model applied to interface
elements represents the cracks better, but the computational cost is higher.

Experimental Study of Polyvinyl Alcohol (PVA) Fiber Reinforced Concrete under Cyclic Loading

Felipe Rodrigues de Souza — 2024-06-12

Fiber reinforced concrete (FRC) elements are widely used in applications subjected to cyclic loadings
such as pavements, wind towers and tunnel-linings. The FRC improves the behavior of structures subjected to
these loadings by controlling the crack opening and the damage propagation and thus can withstands thousands or
millions of cycles during their service life. The purpose of this work is to evaluate the mechanical behavior of
concrete reinforced with PVA fibers comparing to polypropylene fibers, quantifying the damage and the
development of cracks under three point bending cyclic and quasi-static tests. The quasi-static tests results indicate
that the addition of PVA fibers increases ductility and toughness, as it is already known for polypropylene macro
fibers. Moreover, for the cyclic tests, the fibers contribute to the stiffness maintenance reducing the damage in the
material and consequently reducing the crack width and propagation. Finally, when comparing the PVA-FRC with
the polypropylene fiber reinforced concrete (PP-FRC), it was found that the PVA sample presented lower damage
during the cycles and therefore resulting in a smaller CMOD variation.

Mechanical behavior of sandwich panels with curauá fiber reinforced composite skins and autoclaved aerated concrete core

Isabela de Paula Salgado — 2024-06-12

A curauá fiber-reinforced aerated concrete sandwich panel was developed as a sustainable, lightweight,
and low-cost alternative construction material. Each composite skin consisted of long unidirectional aligned curauá
fibers, applied by a cast hand layup technique, and a cementitious matrix with 50% of Portland cement replacement
by pozzolanic materials. The mechanical properties of the sandwich panels and their components were
investigated. The skins displayed a strain-hardening response and multiple cracking behavior. Strength,
deformation capacity, and cracking mechanisms of the composite laminates are presented. The sandwich panels'
monotonic and cyclic four-point bending responses were evaluated. The bonding between the composite layers
and the autoclaved aerated concrete (AAC) core was assessed through pull-off tests and microscopic imaging. The
results revealed the efficiency of the cementitious layers in providing a more ductile behavior and a higher flexural
strength to the material. The ductility properties of the AAC core were improved when assisted by the skin layers
in the sandwich structure. A deflection-softening behavior and a satisfactory post-peak ductility were observed in
the cyclic bending tests. Failure mechanisms, strength, and toughness are reported.

Effect of permanent forms of cementitious composites with short sisal fiber on the shear of reinforced concrete beams

ROCHA, M. J. M. A. — 2024-06-12

Traditional form systems for reinforced concrete structures, produced in steel and wood, have some
deficiencies from the point of view of cost, environment and management. The use of permanent form systems
for beams, produced with cementitious composites reinforced with short sisal fibers, can bring improvements to
the production process and influence the mechanical behavior of the beam when they are subjected to shear
efforts. In this work an experimental investigation of the influence of the permanent forms is made when the
reinforced concrete beam is subjected to shear forces. 8 beams were produced, 2 of them for control and 6 beams
with permanent form. Such forms were produced with 3 composites with short sisal fibers in different levels and
different water/binder ratios. The beams were tested by bending at 3 points with asymmetric load and part of the
beam was produced without stirrups in order to more easily verify the influence of the form. It was observed that
the use of the forms brings improvements in the mechanical behavior, with slightly higher maximum loads,
higher energy absorbed and a lower level of opening in the cracks caused by the shear.

Dynamic analysis of a composite material telecommunications tower under wind loads

João Paulo D. de S. Pereira — 2024-06-12

This work aims to analyze a glass fiber reinforced polymer (GFRP) telecommunications tower under
wind dynamic loads. The natural frequencies of the structure’s first lateral bending modes in both planes, obtained
from a numerical model using the Finite Element Method, were less than 1 Hz. According to the Brazilian standard
NBR 6123, with those values, a dynamic analysis of the structure under wind fluctuation is necessary. A Python
language program was developed in order to simulate the fluctuation of the wind and solve the dynamic
equilibrium equations. With the time domain analysis of the tower, large displacements at the top of the tower
were identified. To solve this problem, a nonlinear pendulum control system adjusted to the natural frequency of
the structure for both planes was designed. The coupled equations of motion of the structure and the controller
attached to its top were also implemented in the Python program, obtaining the controlled and uncontrolled
structure responses. For a set of random simulations of wind conditions, the efficiency of the nonlinear pendulum
control system in reducing displacements amplitudes in the two planes of the structure was assessed.

Development of an optimized moment-connection joint for pultruded profiles

Jessé Henrique Nascimento Beserra — 2024-06-12

The present work aims the development of a novel optimized beam-column moment connection for
pultruded profiles that is characterized by an efficient shape able to transfer load between members due to contact
and friction. To accomplish this task, the work will be divided in two major stages: i) stress analysis via finite
element model; and ii) topology optimization. In the former step, a reference joint geometry will be pre-designed
and stress trajectories are obtained for a given load using software Abaqus. Then, the joint shape is optimized
using a topology optimization technique available in the software package. During the study, stresses are evaluated
and the behavior of both optimized and original joints are compared in the elastic range. This work is part of an
ongoing investigation on the development of novel 3D-printed solutions for joints.

A Numerical Parametric Study on the Effectiveness of Fastener Delamination Arrest Mechanism in Composite Laminates Under Mode I Loading

Rodolfo F. V. de Melo — 2024-06-12

By using the Cohesive Zone Model approach and 3D solid elements to model the fastener fixation
and specimen, this study aims to provide high fidelity numerical models for a double-cantilever-beam specimen
configuration to investigate the effectiveness of fasteners as arrest mechanism for interface crack growth under
pure mode I loading. Additionally, a parametric study was also performed to investigate the influence of joint
design parameters on the specimen behavior for this loading case. Numerical results have demonstrated that a
single-fastener is sufficient to completely arrest mode I delamination growth until other failure modes take place,
independent of the joint design parameters. Despite this, fastener diameter, preload and type of fit have shown some
influence in arrest efficiency, while adding friction penalty to the model appears to have had no significant effect
under mode I loading. As a part of a more complete study for different loading cases, these results represent an
incremental contribution focused on the development of design methods and tools for damage tolerant composite
aerostructures.

An algorithm for distribution of short fibers in multiscale numerical analysis

Andre Peres da Silva — 2024-06-12

Nowadays, it is widely known that the behavior of Steel Fiber Reinforced Concrete (SFRC), especially
the failure process is highly influenced by the distribution of the fibers. For this reason, recently, many numerical
models with a discrete and explicit representation of steel fiber have been proposed in order to consider the effect
of the fiber distribution. In this context, this work presents an algorithm for the distribution of short fibers in
multiscale numerical analyses. Some features and capabilities of the algorithm are assessed through the numerical
analyses of some beams under distinct degrees of fiber segregations.

Experimental analysis of asphalt-concrete composite beams subjected to four point bending test

Vianna, N.J. — 2024-06-12

For thin and ultrathin whitetopping, the bond between the uppermost layer and the lower one has been
pointed out crucial for a proper performance. However, the adherence is gradually lost along time due to
mechanical loads and environmental conditions. Fiber reinforced concrete is an effective solution and improves
the general performance of the structure. This work proposed a four-point bending test for composite beams in
order to investigate the initiation and propagation of cracking at the interface between layers, thus evaluating the
mechanical behavior in a mixed mode failure (combination of shear and normal stresses). It was tested, in static
conditions, two types of overlays (plain concrete and steel fiber reinforced concrete) applied over an asphalt
concrete layer. The experimental results obtained for both concrete overlays were compared. An analysis of
variance was performed to find out if there was no variation between both experiments. It was found that the
addition of fibers did not enhanced the resistance of the composite, however it allowed the material to withstand
greater deformations and not failing abruptly during the test. Therefore, the addition of fibers to the cementitious
matrix has proved to be beneficial to the overall performance of the structure.

Wave propagation analyses considering an enhanced fully adaptive explicit time-marching formulation

Lucas Ruffo Pinto — 2024-06-12

This work presents an enhanced explicit time-marching formulation to analyse hyperbolic models,
which is based on locally-defined adaptive time-integrators and time-step values. The discussed technique

considers single-step displacement/velocity recurrence relations, providing an easy to implement, truly self-
starting methodology. The stability limit of the approach is twice that of the central difference method, and it

allows adaptive controllable numerical dissipation to be applied, improving the accuracy and versatility of the
method. As an explicit approach, the technique does not require the solution of any system of equations, standing
as a very efficient methodology. Subdomain decomposition procedures, associated to multiple time-step values
and sub-cycling, are also considered, improving the performance and accuracy of the technique. The entire
formulation is carried out taking into account automated, self-adjustable computations, requiring no effort and/or
expertise from the user. At the end of the paper, numerical results are presented and compared to those of standard
techniques, illustrating the great effectiveness of the discussed approach.

Approximation of the acoustic and elastic wave equations by generalized finite difference stencils applied the unstructured grids.

Juliano D. B. Santos — 2024-06-12

Classical finite difference methodologies, obtained through Taylor series expansions of the functions,
are feasible only when the points are distributed on structured or Cartesian grids defined over rectangular domains

or mapped to rectangles. In this paper we present a technique capable of generating approximations for the two-
dimensional acoustic and elastic wave equations on structured and unstructured meshes over more general domains.

The stencils were calculated at each point of the arbitrary grid by interpolation techniques and the results shown
that the order of accuracy, obtained when the structured grid is used, is maintain to case unstructured and minimum
number of points of the stencils.

Characterization of gold mine tailings variability and its influence in the study of drainage conditions in the CPTu test

Letícia Perini — 2024-06-12

The effect of drainage conditions on piezocone test (CPTu) measurements is a critical factor in the
assessment of mine tailings properties, as the material is in the intermediate permeability range. Studies of drainage
conditions have been carried out by identifying a characteristic drainage curve. However, accurately identifying
the range of drainage variation is a challenge due to high variability of the material. In this sense, this paper
provides tools to assist the understanding of the effects of data dispersion over the definition of a drainage
characteristic curve. A reference analysis is presented herein in where a characteristic profile of a CPTu test in
gold tailings is used to quantify the statistics and its application. A numerical analysis of cavity expansion is used
to obtain theoretical drainage curves. The variability characterized was applied to the numerical simulations, using
the Monte Carlo method, to define in a rational way the range of possible theoretical drainage curves.

Energy exchange between piled structures through the soil

Amanda M. Oliveira — 2024-06-12

This work presents a study on the energy transfer between piled structures. For this analysis, two
structures, supported by buried pile groups, interact with each other through the soil. A stationary external load is
applied to one of the structures, and its effect is felt by the other structure solely through the energy transmitted
through the soil. The soil is modeled as a three-dimensional halfspace, and the piles through the impedance matrix
method. The structure is modeled via classical finite element discretizations, which enables arbitrarily-shaped
structures to be considered. Coupling between the two systems is obtained by imposing continuity and equilibrium
conditions at their interface. Selected results are shown for different geometric parameters of the piled structures.

Vibratory response of a wind tower considering soil-structure interaction

Amanda M. Oliveira — 2024-06-12

This work presents a model of the vibratory response of a wind tower structure supported by an embed-
ded pile group, considering the soil-pile-structure interaction. The model for the pile group is obtained using the

impedance matrix method. The soil is considered as an isotropic, viscoelastic, three-dimensional half-space, the
response of which is obtained through a boundary element discretization of the pile-soil contact tractions. Piles
are modeled as one-dimensional finite beam elements. Coupling between the systems is achieved by establishing
equilibrium and continuity conditions at the soil-pile and pile-structure interfaces. The results consider arbitrary
harmonic loads applied to the structure in terms of nodal equivalents. This analysis show that disregarding the
influence of the pile group in the model of the tower may incur in considerable misrepresentation of the tower’s
dynamic response.

Use of ML techniques for predicting the bearing capacity of piles and its relative errors

Yago F. Gomes — 2024-06-12

This work presents an application of machine learning techniques for estimating the bearing capacity of pile
foundations and the relative error from these techniques. It uses as raw data 165 load tests results associated
with SPT soundings, taken from several Brazilian regions. A dataset based on the inputs from Decourt-Quaresma
and Meyerhof semi-empirical methods was created and applied to several machine learning techniques with a
leave-one-out cross validation approach for training and testing the algorithms. Using the results obtained from
each model, the metrics RMSE and R2 were calculated through a stacking strategy. The Random Forest technique
presented the best performance for both bearing capacity (RMSE = 640,26) and relative error (R2 = 0.77) prediction
problems. The other five ML techniques performance overcame the semi-empirical methods, which obtained an
RMSE close to 900, indicating the potential of these tools. Then, the errors obtained from the predictions were
used to propose a new machine learning problem, aiming to predict the error of new examples. Although the
preliminary results were not accurate, the authors believe that the study justifies further investigations.

NUMERICAL INVESTIGATION OF GEOSYNTHETIC REINFORCED SOIL MASS WITH BLOCK FACING AND CLOSELY-SPACED REINFORCEMENTS

Bianca A. Vieira — 2024-06-12

Bridge abutments using geosynthetic reinforced soil (GRS) for direct supporting of the deck is a solution
with significant advantages over conventional systems. Among the main characteristics of this type of structure,
the small reinforcement spacing, frequently lower than 0.3 m, requires attention. This paper provides an
investigation to assess the effect of closely-spaced reinforcements on the behavior of a GRS mass using block
facing, and subjected to a uniformly distributed loading with typical value of service conditions. The Plaxis 2D
finite element software was used to conduct a parametric study to investigate the influence of vertical spacing (Sv)
and reinforcement stiffness (J). The numerical investigations were developed according to different approaches to
analyze the effect of vertical spacing. Initially, combinations of Sv and J were adopted without considering a
constant J/Sv ratio and then the J/Sv ratio was kept constant. The results indicated a significant effect of vertical
spacing for both approaches. The maximum lateral displacements of the facing and soil settlements near facing
were found to decrease. This behavior was obtained for all the values adopted for the constant J/Sv ratio.

Performance analysis of an embankment over a soft soil deposit through instrumentation and numerical simulation

Rafael F. Cordeiro — 2024-06-12

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 Coulomb 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.

ANALYSIS OF ARAQUARI SAND BEHAVIOR THOUGHT NUMERICAL MODELING OF TRIAXIAL TESTS

Kauê William Pacheco — 2024-06-12

The present paper describes the numerical evaluation of triaxial tests to assess the constitutive model of
better adaptation to a set of laboratory data. The data considered is part of an experimental campaign carried out on
samples of sandy composition, from the Araquari/SC experimental testing site. To model the triaxial data, an
axisymmetric representation of the triaxial specimen was designed in the finite element software Plaxis. Applications
of the Mohr Coulomb (MC) and the Hardening Soil Model (HS) were evaluated by a direct comparison between
laboratory results and numerical predictions. Considering different confining pressures, both models were able to
predict with good accuracy the maximum bearing load. The greatest discrepancy was observed in the prediction of
strain behavior: as expected, the hardening soil model was more adequate to represent the non-linear behavior of the
sand. As the main scope of the research developed at the Araquari Experimental Testing Site is the investigation of
the complex pile-soil interaction mechanisms, after the analysis of the constitutive model that better represents the
triaxial tests, the hardening model was used to predict the behavior of a reference pile.

Analise limite numérica de problemas axissimétricos em geotecnia: aplicação em estabilidade de poços

David Sebastian Calpa — 2024-06-13

This work presents the implementation of numerical limit analysis with mixed-weak formulation, based

on the lower bound limit theorem and its application in axisymmetric stability problems. The finite element formu-
lation was implemented in Matlab, where the optimization problem was established in two parts, the definition of

equilibrium equation and the adaptation of the Drucker-Prager and Mohr-Coulomb rupture criteria into the Second
Order Cone and Semidefined Programming, respectively. The numerical optimization problem was solved using
the MOSEK optimizer, the collapse factor and the velocities field was obtained, identifying the rupture mechanism
of the models. The presented implementation was applied to the stability analysis of a well. The results obtained
in the axissymmetric analysis were verified through analysis in three-dimensional models and compared with the
results obtained in the software Plaxis 2D, and Optum G2.

Numerical modeling of triaxial tests on salt rocks using a creep law with damage-induced flow

Otavio B. A. Rodrigues — 2024-06-13

This work performs a numerical modeling of triaxial tests on salt rocks, using the Multimechanism
Deformation Coupled Fracture (MDCF) creep law and the software ABAQUS. In the design of wellbores drilled
on salt rocks for oil and gas exploration, computational modeling of creep is important for stability. Constitutive
models describe the salt behavior and are calibrated by laboratory triaxial tests. Brazilian salt rocks are usually
modelled using the double mechanism deformation, which is a good fit to several experimental tests. Yet, one of
its limitations is to describe only the steady-state stage. In the literature, some more complex models represent
salt creep, such as MDCF, which reproduces full creep stages and evolution of damage from the confining and
deviatoric stress. The damage mechanism influences the creep strain rate, especially under low confining stresses.
To achieve the proposed aim, the methodology adopted is divided into three main steps: i) numerical simulation
of triaxial tests using ABAQUS; ii) customization of ABAQUS to incorporate the MDCF; iii) validation of the
incorporation by comparisons with results available in the literature. The results show adequate responses for the
modeled triaxial tests under several conditions. The main contribution of this work is its use as a startup step for
the incorporation of the MDCF creep law in the modelling and verification of oil wellbore drilled on salt rocks
stability.

An elastic-viscoplastic load-transfer method for a single pile and pile groups

Victória F. R. da Costa — 2024-06-13

A nonlinear load-transfer method for determining the load-settlement curve for a single pile and pile
groups under axial loads is presented. The model allows slippage, or plastic soil deformation, and introduces a
new exponential model for load-transfer modeling either strain hardening or softening. Long term deformations
of soil layers and pile material are accounted for by a viscoplastic model. Elastic soil deformation and simultaneous
soil hardening induced by neighboring pile shafts are considered. Validation of the model is done by comparing
numerical and field static load tests from literature. This research is mainly motivated by the need of estimate
piles and pile caps loads when periodic vertical settlement measures are done during building construction in sites
where there exist layers of very soft clay. Present work describes basic formulation and initial applications.

A simple particle pack generation method with predefined grain size distribution and porosity using the discrete element method

Kamila R. Cassares Seko — 2024-06-13

In numerical studies of granular materials, it is often important to realize simulations considering the
realistic granulometry of a sample of the material. In case of soils, in particular, grain size distribution could greatly
influence the material ́s behavior. The aim of this work is to present a simple and rapid method for generating
particle packs with predefined grain size distribution and porosity for discrete element simulations. It is a dynamic
algorithm with simple input data. The methodology considers spherical particles only. The particles’ radii are
determined during the generation process based on the percent fraction of total particles passing thru a sieve and
the sieve mesh size, according to a given granulometric curve and sample porosity, mimicking a real granulometric
characterization in laboratory. Differently from existing methodologies, the particles are generated until the desired
retained mass in each sieve is reached. The generated particles are positioned randomly within a pre-defined
domain in a non-contacting way using a random sequence addition (RSA) algorithm, and then are submitted to
“jamming” pseudo forces. The method proved very effective and showed good results (in terms of attained grain
size distribution and porosity) as illustrated in numerical examples.

Numerical modeling of shear bands in rocks using FEM and a viscous regularization technique

Renan S. B. de Lima — 2024-06-13

Shear bands are narrow zones of intense shear strain that develop within a broad range of ductile
materials. As these bands precede material failure, their study is fundamental to understand the mechanical
behavior of those materials. In general, the modelling of shear bands is performed through the finite element
method considering constitutive laws which use a non-associative flow rule. Moreover, models for porous
materials such as rocks and soils usually incorporate strain-softening behavior observed in experimental tests. Both
non-associative flow rules and strain-softening can cause loss of well-posedness of the initial-value problem in
classical continuum approaches, leading to mesh dependency and poor convergence during the non-linear solution
process. To overcome such issues, some techniques such as viscous regularization have been proposed. However,
the removal of mesh dependency depends on how the viscous parameter is incorporated into the model. In this
paper, we present simulations of shear bands considering biaxial conditions and including a viscous regularization
technique. The efficiency of that technique is studied considering the onset, width and orientation of the resultant
shear bands in carbonate rocks. We show that despite the use of non-associative flow rules and strain-softening
behavior, the obtained shear band widths converge to finite values upon increasing mesh discretization.

Numerical Simulation and Parametric Analysis of Laterally Loaded Piles: Foundation of Tracker Systems

Naloan C. Sampa — 2024-06-13

The need to generate more and more renewable energy has motivated the increasing installation of
equipment in onshore and offshore environments in order to take advantage of sunlight, wind and sea waves. The
foundation elements that support this equipment are designed to absorb not only axial loads but also lateral loads.
This paper investigates, through a 3D numerical model in Abaqus, the effects of the loading and unloading cycle
and the Young modulus of soil on load-displacement curves of laterally loaded piles. Two experimental lateral
loading tests were used to validate the numerical model, and the results are satisfactory. The load-displacement
curves were not affected by the loading and unloading cycle, but the elastic modulus of the system (k) decreases
with the eccentricity. Furthermore, eccentricity influences the values of yres and yPlas, while Young’s modulus of
soil affects the load-displacement curves. The importance of these analyses in planning the lateral load tests and
in interpreting the experimental results are presented and discussed

Numerical Analysis of Laterally Loaded Piles: Foundation of Tracker Systems

Naloan C. Sampa — 2024-06-13

This paper presents and discusses a numerical study of the laterally loaded pile. The numerical analysis
considers two setups, with different excentricities and points to measure horizontal displacements. Results
highlight the effects of eccentricity and displacement measurement points on load-displacement curves. For
practical application, some quantities and considerations about lateral load and horizontal displacements in SLS
and ULS are presented and discussed. The conclusions presented in this paper can be of great importance for
planning lateral load tests and interpreting their results in solar photovoltaic parks.

A Seismic Hazard Analysis in the Southeast Region of Brazil

Tania Bustamante — 2024-06-13

This paper presents an overview of the results obtained from a seismic hazard analysis in the Southeast
region of Brazil. The results provide seismic parameters and criteria for the Maximum Credible Earthquake (MCE)
and design earthquakes considering return periods of 100, 475, 2475, 4975 and 9975 years for a class B (rock)
site.

Finite Element Modelling of Setup Effect during Conductor Casing Instal- lation with Coupled Eulerian-Lagrangian Method

Raniel Deivisson de Alcantara Albuquerque — 2024-06-13

The first tubular section installed in drilling operations is the conductor casing. Usually run by hammering
or driving, the casing is responsible for guaranteeing well stability, isolating fluids from formation, and providing

areas for installing equipment such as wellhead and christmas tree assembly. By inspecting soil behaviour dur-
ing the installation process, it is notable that pore pressure disturbance triggers what is called the Setup Effect,

a phenomenon where conductor load capacity increases over time due to pore-water pressure dissipation. This
study applies the Finite Element Method (FEM) to model a Conductor Casing installation employing Coupled

Eulerian-Lagrangian (CEL) technique to evaluate the setup effect. CEL technique is well suited to large deforma-
tions problems; however, pore pressure measurement is not supported in Abaqus/Explicit; thus, a Vectorized User

Material (VUMAT) subroutine was implemented to take into account that effect. Mohr-Coulomb model represents
soil’s constitutive behaviour, and the results are compared with data obtained from Brazilian cases in soft clay
soil. This kind of study helps to increase the safety of drilling operations and the structural well integrity analysis
since pore pressure estimation is necessary to determine the ideal weight of the drilling fluid, preventing fracture,
formation damage, and fluid loss, ensuring the borehole stability during drilling.

Modeling of vertical oil well drilled on salt rocks using equivalent subdomains

Gleide K. M. Lins — 2024-06-13

This work proposes an alternative approach based on equivalent subdomains for the numerical modeling
of vertical oil well drilling in Brazilian pre-salt. These regions are composed of large salt rock layers, which, under

high stress and temperature, present creep behavior when they are drilled. Creep causes progressive and time-
dependent strains in the direction of wellbore closure, which it can generate stuck pipe and/or well drilling delay.

Thus, it is common to use computational simulations to predict the salt rock behavior over its drilling. In the con-
ventional approach, the full salt layer is numerically mapped into a single finite element mesh and one can evaluate

the wellbore closure over time using a full plane axisymmetric analysis (Full2D-model) around the oil well vertical
axis. In this work, the proposed methodology subdivides the salt layer (domain) into equivalent and independent
horizontal stripes (subdomains) to distribute their analysis into several computational threads (multiprocessing),
which drastically reduces the computational cost of the wellbore closure evaluation. For each subdomain, a plane

axisymmetric analysis (2D-model) or an even faster one-dimensional axisymmetric analysis (1D-model) for sev-
eral depth values can be used. The 1D-models are simpler and more efficient since they represent the mechanical

behavior of a single independent lithology on a given depth. However, on lithology interfaces, the associated me-
chanical discontinuity is properly managed only by 2D-models because they aggregate a multi-lithology behavior

along a given depth interval. Since 1D-models are faster, first a full1D-model is used to estimate the error in the
displacement field on the wellbore. The error is measured based on a reference Full2D-model. Then, given a
target admissible error, an adaptive scheme that gradually increases 2D-model subdomains over critical regions
is employed. This scheme ensures that the maximum error at the wellbore displacement field is the considered
target error and defines an optimized subdomain partition. This proposal aims to use different case study scenarios
and observe how optimized subdomain partitions behave, in order to identify partitioning patterns according to the
characteristics of the scenario. It is expected that the proposed strategy produces good approximations, allowing
faster and more practical simulations aiming to assist oil well design and operational demands.

Parametric sensibility study in a stratified soil trough finite elements methods

Pedro da F. Martins — 2024-06-13

When constructing any type of building, sometimes engineers don’t have all the necessary information.
When using an SPT to prospect the soil, correlations formulas and tables are necessary to determine many of this
soil properties. By using these correlations, the engineer must choose between ranges of values to use the Nspt with.
The use of an incorrect correlation can result in the execution of a project that does not correspond to the local
characteristics of the construction, which can lead to damage to the structure. This research used the finite element
method, through the PLAXIS 2D software, to evaluate the parameters of clayey layers at the construction site of
a pier in the city of Rio Grande. According to the alteration of these parameters, varied results of tensions and
displacements were obtained, thus, its influence on these alterations can be verified.

Principal Component Analysis for the Opening of Underground Caves in Saline Rocks under Different Temperatures

Rayra A. Silva — 2024-06-13

This study aims to analyze numerical data obtained during the process of opening of caves in saline
rocks considering the temperature variations. Over the years, saline caves have been widely used for the safe
storage of supercritical CO2, petroleum products and used as final destination of toxic waste such as radioactive
waste. The main motivation lies in the possibility of determining the variables from a statistical point of view that
most influence the opening process of these cavities. In fact, throughout the development of a cave, the variables
involved play a significant role in the success of the operation and also in determining its final behavior, it is
important to understand the way that they interact with each other and also with the fluids inside. In this work,
numerical simulations of the solution mining process for opening the cave under typical conditions of water
injection in a sodium chloride rock (using a finite difference code) are described and performed, after that, the
interpretation of the data obtained with the simulations is also done through a multivariate statistical tool (PCA).
The simulations show that the temperature and the flow directly influence the cave opening rate, in turn, the
statistical analysis of the data shows that the output variables have an almost similar contribution to the opening
of this cavern, moreover, it is possible to interpret the total variation of the data using only one component (PC1).

Dynamic analysis by FEM of blast-induced ground vibrations

Caroline B. Zorzal — 2024-06-13

Peak particle velocities (PPV) are fundamental for understanding and managing blast-induced ground
vibration levels and their impact on neighboring structures. Given that the numerical analysis of seismic vibrations
has been revealed as a method that may substantially contribute to estimating PPV levels, this research employs a
numerical approach using the finite element method (FEM) to evaluate blast-induced ground vibration in rock
masses. A dynamic module of the stress-strain analysis was developed in ANLOG software based on the FEM
displacement formulation to estimate the variations of displacement, strain, and stress induced by blasting. Since
Rayleigh damping coefficients are frequently used in FEM analysis to model the effect of physical damping in
geological mediums, a study was conducted to determine the effect of Rayleigh coefficients on the PPV numerical
attenuation law. After understanding the influence of the Rayleigh coefficients on the results, the PPV numerical
attenuation law is obtained using ANLOG. It shows good agreement with values estimated by empirical methods
and numerical results available in the specialized literature.

Flower Pollination Algorithm Applied to the Reconfiguration Problem of Electric Power Distribution System

Yanick R. Gomes — 2024-06-13

The electricity sector is undergoing a transformation process driven by a set of factors that have affected
electricity distribution systems. The reconfiguration of the distribution system is a procedure performed mainly to
minimize energy losses. A good comparison oriented to results and performance can be made using the Flower
Pollination Algorithm (FPA). the FPA is a metaheuristic inspired by the pollination of plants by means of flowers
and has an optimization feature to solve the problem under analysis. This work presents an application of the FPA
for Reconfiguration of the Electricity Distribution System (RSDEE) aiming at the optimization of the problem
under analysis. The technique was validated in small balanced systems (5 nodes, 33 nodes and 70 nodes), used in
RSDEE works. The initial results were compared with other techniques, proving the efficiency in solving the
problem in competitive computational time. It was concluded that the FPA metaheuristic presents an adequate
performance for the reconfiguration problem in small and medium sized networks.

A Computational Approach to Predict the Bond Strength of Thin Steel Rebars in Concrete by Means of Support Vector Machine

Priscila F. S. Silva — 2024-06-13

The bond strength between steel bars and concrete is one of the essential aspects of reinforced concrete
structures and is generally affected by several factors. As a phenomenon influenced by many variables, it is
challenging to establish how the steel-concrete adhesion can be described in the standards used for reinforced
concrete design. This study used an experimental data set of 89 pull-out specimens to develop a support vector
machine (SVM). The data used in the modeling was arranged as four input parameters: bar surface, bar diameter
(φ), concrete compressive strength (fc) and the anchorage length (Ld). Several scientific studies on this property
have been performed since the 1940s, among many other investigations in this field. Generally, these studies refer
to bars with diameters greater than 12.0 mm. However, few studies have evaluated the performance of reinforcing
bars with diameters smaller than 10.0 mm, which includes 5.0-, 6.3-, 8.0- and 9.5-mm diameters, usually used in
reinforced concrete elements. This work uses SVM to analyze and build a prediction model for the steel-concrete
bond and its potential to deal with experimental data. The root mean squared error (RMSE) found for the maximum
applied load in the pull-out test was 1.305 kN and the R-squared was 0.95. Therefore, this study can conclude that
the current model can satisfactorily predict the bond strength of thin bars.

Comparison of supervised and self supervised approaches for micro-CT lithology classification of carbonate rock samples

Carlos E. M. dos Anjos — 2024-06-13

The characterization of pre-salt reservoirs is a challenging task in the oil industry due to the geological
peculiarities and the heterogeneity of carbonate rocks. These challenges gave rise to new methods in order to better
characterize these rocks such as computed tomography for inner structure image generation and new computational
methods to analyse them. One of such methods is the use of artificial intelligence techniques, such as deep learning
that is considered the state of the art in several tasks and specially on computer vision. This work employs deep
learning techniques for the lithological classification of rock samples in micro-tomography images of cylindrical
rock samples referred usually as plugs. Two training paradigms are tested and compared, namely, supervised
and self-supervised training. The experiments employed densenet161 pretrained on ImageNet as base model,
which is a notorious model for image classification on the Imagenet dataset. The contrastive learning method
called supervised contrastive (supervised adaptation of SimCLR) was chosen for the self-supervised experiments.
This method allows the use of the label information in the SimCLR loss function while also enabling the authors
to incorporate this information in three different ways: the standard SimCLR framework (where each image is
considered unique), label-based (where each sample belonging to the same lithological classification is considered
equal) and sample-based (where all images generated from the same rock sample are equal). The dataset consists of
46,185 images from 623 rock samples which are distributed between seven different classes labeled by specialists.
Experiments with different training sizes were performed and compared for the supervised and self-supervised
cases. The results obtained over 70% accuracy and F1 score on all experiments with standard deviations equal
or lower than 7 % in most cases. The supervised experiments achieved the best results but the self-supervised
approaches also displayed comparable results.

Granulometric Control of Iron Ore Pellets Using a Fuzzy System.

Caio Mario Carletti Vilela Santos — 2024-06-13

Pellets are concentrates of different chemical and mineralogical, with specific properties and great
application on steel manufacture. This work describes the practical application of a fuzzy control to an industrial
iron ore pelletizing. The objective was to develop a model to detect quality pellet size standard on the process, and
with the identification of the standard, execute the control the rotation and feed rate of the pelletizing disc, since a
specific angular rotation speed of the disc is necessary for the formation of the pellet, because if the disc moves
slowly, don't form pellets and also if the disc moves quickly, the centrifugal force generated raises the mass of the
ore to the limit angle and at this point the mass will fall, not allowing the formation of pellets. When the disc moves
at such a speed that the centrifugal force is overcome by the frictional force, the material is raised to a certain angle
and then rolls over itself, forming the pellets by agglomeration. When we reduce the load on the pelletizing disc,
we reduce the particle size dispersion of the disc product. The system developed aimed to improve the pellet
formation yield, making the production better with quality.

Mixed-integer Optimization under Uncertainty in Reservoir Development and Management

Haniel F. A. Belo — 2024-06-13

Reservoir geoengineering is usually faced with large-scale optimization problems under uncertainty
arising as part of development planning of smart wells locations, performing separated, jointly, or simultaneously
optimization of well locations and control rates of water injection and hydrocarbon productions. This paper
performs a simultaneous optimization of well locations and production rates under geological uncertainty using
Monte Carlo samples over geostatistical realizations. Those optimization problems are of mixed-integer type.
Traditionally, they have been solved by performing projections between real and integer variables using different
strategies, Whitney and Hill [7]. This work investigates the performance of DSPSA, a discrete version of SPSA,
recently described in Wang and Spall [13], and proposes a discrete variant to be applied in mixed-integer problems
where all control variables are ceiling round, taking advantage of practical field implementations. One-sided
deterministic constraints are imposed to reduce search space. For more general one-sided stochastic non-linear
constraints, see Fonseca [3] and Fonseca et al. [9]. In the class of reservoir problem solved in this paper, functional
and constraints derivatives a never available, mainly because industry solves the reservoir simulation problem
using commercial software as a black box. Additional metaheuristics are used to construct the discrete version of
DSPSA. This work makes a preliminary comparison between the new discrete version, DSPSA-R, with SPSA-Z,
the mixed-integer version of SPSA in Fonseca [3].

Systematic review of computational methods for oil & gas exploration and production risk indicators

R. Albuquerque — 2024-06-13

The increasing concerns of stakeholders about environment and safety demand Petroleum industry to

continuously reduce operational risks. Regulators and Industry Associations have been using several risk indica-
tors for decades aiming to compare risk levels for facilities. These indicators play an important role to optimize

resources defining priorities for audits and for other efforts to improve safety levels. However, numerous risk
indicators are Lagging (Reactive) Indicators, which means that they only measure past events such as occurrence
of incidents. Since these indicators are related to significant but rare accidents, they provide limited capacity for
taking preventive actions. Furthermore, several indicators rely on subjective considerations of technicians to adjust
importance of variables to determine risk level. The result may vary depending on specialist teams which suggest
that the adjustments might not be the optimal solution to point out risk level. Petroleum industry is going through

digital revolution and many novel emerging solutions based on computational methods are changing Oil & Gas ex-
ploration and production operations. Hence, the aim of this paper is to provide a systematic review of Optimization

and Machine Learning methods to set risk indicators in Oil & Gas facilities. The review identifies 237 publications
in past 10 years related to risk indicators in three major web-based academic libraries. We selected 27 papers using
defined selection and quality criteria. Then, we grouped the studies according to definition methods of indicators
in a map of findings, highlighting benefits, limitations, and strengths. As result, we attempted to envision the future
of Oil & Gas risk indicators by emphasizing gaps, and possible setbacks or improvement opportunities of studied
methods, paving the way for upcoming research on this topic.

Optimization of FPSO spread mooring systems with a surrogate- assisted Differential Evolution algorithm

Vinicius G. do Prado — 2024-06-13

The design of mooring systems is a complex and time-consuming task that must be thoroughly
addressed in every Oil & Gas upstream project. Up to now, the task is performed mostly based on the expertise
and engineering judgment of the analysts, with little to no optimization ever pursued. This article presents a method
that employs the well-known ε-Constrained Differential Evolution algorithm to design the mooring system and
makes use of Artificial Neural Networks to evaluate its performance, thus eliminating the constraints imposed by
the limited capabilities of the human mind and providing feasible systems with reduced costs.

The Use of an Artificial Neural Network in the Prediction the Compressive Strength of Concrete

Vanderci F. Arruda — 2024-06-13

This study proposes the use of an artificial neural network (ANN) in a mechanical characteristic
prediction of a material widely explored in the design of structures, the concrete. The conventional way to obtain
the mechanical characteristics of such a material is by means of expensive and costly laboratory tests and, as an
alternative, the use of an intelligent simulating system can be proposed. ANNs are based on a bio-inspired model
of the biological neuron, which processes data from simple units. In this study, a well-known (and established in
the academic literature) database was used. The artificial neural network tested used the supervised learning
method and the networks were trained based upon the following algorithms: classical backpropagation,
backpropagation with momentum, backpropagation with learning rate, backpropagation with momentum and
learning rate, and Levenberg-Marquardt. This work includes the use of a preprocessing strategy on the input data
and different backpropagation training algorithms. The main objective of this work was to obtain reliable results
to estimate the compressive strength of concrete by using machine learning. Among the training algorithms tested,
the one that presented the best performance was the Levenberg-Marquardt, which proved to be effective in
predicting the compressive strength of concrete at twenty-eight days, obtaining, as performance metrics, the RMSE
of 4.39 MPa and the coefficient of determination of 0.93. From these results it is possible to verify that this method
proved to be reliable for the calculation of the compressive strength of concrete by reducing possible errors and
amplifying the reliability of the application of computational technology in engineering projects.

ARTIFICIAL NEURAL NETWORKS BASED ON COMMITTEE MACHINE TO PREDICT THE AMOUNT OF SULFUR AND PHOSPHORUS IN THE HOT METAL OF A BLAST FURNACE

Wandercleiton Cardoso — 2024-06-13

Steel is an alloy of iron and carbon containing less than 2% carbon and small amounts of elements such
as silicon, manganese, phosphorus, and sulfur, which together do not exceed 1% of the total. Sulfur and phosphorus
are undesirable elements in steel because they cause brittleness. The best way to control sulfur and phosphorus
content is during the production of cast iron in blast furnace. In the field of simulation and modeling, several
models have been proposed for the simulation of blast furnace, which allow progress and detailed information
about the fluid flow and mass and heat balances of the blast furnace. However, there are few mathematical models
for the prediction of sulfur and phosphorus content. In this context, the main objective of this work was to develop
an artificial neural network for predicting the sulfur and phosphorus content in cast iron. A mathematical model
was developed based on a committee machine using 8 different artificial neural networks simultaneously. The
artificial neural networks with a single hidden layer had neurons varying in 10, 20, 25, 30, 40, 50, 75 and 100
neurons per layer. Pearson's correlation coefficients, RMSE and MAE confirmed that the hidden layer with 25
neurons gave the best results. The conclusion is that high values of mathematical correlation demonstrate the good
statistical performance of ANN and show that the mathematical model is an effective predictor of sulfur and
phosphorus.

Identification System based on Fuzzy Logic for epidemiological control of dengue in the metropolitan region of Sao Luís - MA

Hyngrid H. de C. Coelho — 2024-06-13

Dengue, as a highly prevalent disease in Brazil, impairs the population’s well-being, affecting public
health costs, so it is necessary to take measures to help prevent the onset of the disease. Thus, predicting the number
of cases of the disease in a given region helps in planning and decision-making by Public Agencies. For this reason,
it is extremely important that such forecasts are accurate, although this process has errors, since the factors that
serve to obtain the diagnosis of cases have a behavior that depends on numerous parameters, such as precipitation
rate and ambient temperature . Therefore, fuzzy logic presents itself as a good alternative for modeling a dengue

case prediction system, as well as the development of low-cost technologies for this purpose. For that, a Takagi-
Sugeno (TS) type MISO system (multiple inputs and one output) is proposed, capable of providing a forecast of the

number of dengue cases in the city of Sao Lu ̃ ́ıs - MA, based on the collection of epidemiological data from dengue
in the municipality, which were related to the input variables of the system, obtaining linear submodels through a
fuzzy clustering algorithm. The model obtained, with two input variables (rainfall rate and average temperature),
obtained good computational results.

MATHEMATICAL MODELING FOR CRYOGENIC UPGRADING OF BIOGAS AND CARBON CAPTURE

Wandercleiton Cardoso — 2024-06-13

Biogas is used for various energetic purposes: Electricity generation, thermal purposes, replacement of
fossil fuels in vehicles, injection into natural gas distribution networks and injection into blast furnaces to replace
coke and pulverized coal. However, for the various uses, it is necessary to purify the biogas. The purification of
biogas essentially involves the removal of CO2. When the CO2 is removed, the relative density of the gas decreases
and the calorific value increases. Technologies for purifying biogas are commercially available, such as: Amine
scrubbing, water scrubbing, pressure swing adsorption (PSA), membrane separation, and organic solvent washing.
The use of cryogenics for biogas purification is still an emerging technology. In this context, the mathematical
modeling of a cryogenic upgrading plant for the production of biomethane using Aspen Plus was carried out in
this paper. The final results of the mathematical modeling show that it is possible to produce biomethane with a
purity of 99.6% and to store CO2 with a purity of 92.3%, which could be used for the production of microalgae in
photobioreactors and in MAG welding processes.

Error Pattern-based similarity analysis of task performance in a virtual training environment: a meta graph clustering approach

Alexandre Pereira de Faria — 2024-06-13

Intelligent Tutor Systems, Serious Games, and Simulations are user interaction-based instructional
technologies capable of adapting to the needs of learners. Tracking and logging data from user interactions during
the execution of a task allow for learning assessment and visualization of learner performance, which, in turn,
allows for the identification of learner mistakes. Instructional tasks can be mapped as a graph, and paths represent
the ordered sequences of task activities. Mining path patterns seek similar strategies and anomalous behaviors of
learners in performing the task. In this paper, graph similarity methods are applied to clustering tasks performed
in a virtual training system. Feasible paths on the graph represent the expected sequences for task execution, and
errors are deviations from them. Sequences of activities performed by the learners correspond to free walks on the
graph. Through task rules and reliability analysis, errors in learner walks were extracted and represented by vectors
and then clustered in error patterns. A meta clustering analysis of error pattern-based clusterings and similarities
clusterings reveals which of the former are closest to the error patterns. Based on the findings achieved, in future
work, a new similarity method that is sensitive to error patterns will be proposed.

Impact of COVID-19 pandemic in the Brazilian Air Transportation Multiplex Network

Fernanda Silva Toledo — 2024-06-13

The COVID-19 outbreak disrupted the Air Transportation system on a large scale and reduced
connections worldwide, but the impact is different in each country network. Air transportation is a complex
infrastructure system, adding the weight of interactions and a multilayer approach can make their description even
more detailed. In this field, studies on the evaluation of network structure and topology characteristics are
fundamental to predict and understand dynamical processes. This paper aims to assess the COVID-19 outbreak
impact in the Brazilian Air Transportation Multiplex Network, comparing the network topology over time and
evaluating the effect on airports under concession and regional aviation. The network is based on air passenger
traffic of 2019 and 2020 of the ANAC database, in which the airlines were divided into different layers. The
proprieties obtained were used for network characterization. We found that the average degree of airports reduced
11%, connections reduced 47% on average for each layer, increasing the mean path length to reach destinations.
Passaredo expanded its network during this period but the connection drop reduced the network density and
diameter. Results can facilitate decision-making for market strategies for airlines and incite discussion on
government incentives and subsidies to continue operation in remote cities maintaining airline operation.

Parallel execution of an artificial neural network for data assimilation of the shallow-water 2D problem

Haroldo Fraga de Campos Velho — 2024-06-13

There will always be some error with reality in computational modeling of physical phenomena, even
for the most advanced and sophisticated ones. Techniques that incorporate information from the phenomenon’s
observational data can be applied to reduce this error’s uncertainty. These so-called data assimilation techniques
add information from observational data to the modeling result with a reasonable degree of reliability. The Kalman

Filter is one of the most widely used data assimilation methods in the operational weather forecast to better es-
timate the next forecast cycle’s initial conditions (analysis). This work uses data assimilation through artificial

neural networks, applied to the shallow-water model in two dimensions to emulate the Kalman Filter techniques,
using synthetic observations. According to results obtained in previous works, this method presents a significant
reduction in the processing time, maintaining an equivalent quality of the analyzes obtained through the Kalman
Filter. However, even with this reduction in computational cost, when the spatial domain is discretized by a grid

containing many points, the data assimilation by the neural network can still be configured as one of the perfor-
mance bottlenecks. Since the assimilation by neural networks is carried out independently at each grid point, the

parallel strategy employed consists of sub-dividing the domain to execute each in different computational nodes or
cores.

Syncnet network application for identification of electrical charges

Jorge J. F. Filho — 2024-06-13

The search for optimization of energy resources is growing every day, whether for environmental,
financial or economic reasons. In industries and homes, knowing which equipment is turned on, when it is turned
on, how often it occurs and how long it is used is essential information for energy optimization algorithms.
Therefore, recognizing the characteristic signature of the equipment is a big step. This work proposes the use of a
convolutional network using a Sincnet layer initially proposed by Mirco Ravanelli and Yoshua Bengio, used for
human speech recognition, the dataset used is the WHITED which has the signature of several loads of different
devices, this work will Evidencing the tests carried out on isolated loads and their identification, the success of this
work will allow this network to carry out tests of coupled loads in the future and, in the future, integrated to an
energy optimization system, monitoring a single point in the electrical network.

A Particle Swarm Optimizer for the Optimal Allocation and Sizing of Dis- tributed Generators in Distribution Grids

Marcus Vinicius Goes Mansour — 2024-06-13

Recently, there is a strong worldwide trend for renewable energy sources to reach increasingly higher
levels of penetration, mainly connected at the level of distribution grids. In this paper, a Particle swarm optimization
(PSO) have been applied to allocate and size the Distributed Generator (DG) in distribution grids. The proposed
algorithm proved to be an excellent tool to identify the places and size of DG in electric power distribution systems.
Tests are carried out on real large scale 141-bus system of AES- Venezuela. A detailed performance analysis
demonstrate the effectiveness and robustness of the proposed method to find good solutions with reduce power
losses and improvement the voltage profile. For three DG, the proposed algorithm was able to find a solution that
reduces network losses by more than 95%.

Deep learning for mapping rainwater drainage networks using Remote Sensing Data

Julia Potratz — 2024-06-13

Mapping rainwater drainage networks are traditionally lead from image visual interpretation. With the emergence

of automatic extraction algorithms, remote sensing areas began to modernize. To improve the spatial resolution image, sev-
eral works have addressed strategies to generate drainage networks, however, mapping accuracy and computational resources

needed to process this information are still a problem. This work explores the potential of applying different Deep Learning ap-
proaches to the process of extraction information in rainwater drainage networks through digital elevation models obtained by

the Shuttle Radar Topography Mission (SRTM). To perform this, we evaluated three different architectures: U-Net, DeepLab,

and Cycle GANs (Generative Adversarial Networks). The results show that the average intersection over union (IoU) to deter-
mine the drainage networks proved superior in relation to a decision tree used as baseline that proved unsatisfactory to solve the

proposed problem. However, the proposed UNet, DeepLab + FCN and Cycle GAN networks showed averages equal to 93.89%
81.13% and 92.42% respectively. These results indicate that it is possible to perform the geoprocessing of large-scale images
almost in real time, making it an excellent resource to contribute to the mapping of drainage networks.

Application of Deep Convolutional Neural Networks for Analysis of Appar- ent Density and Porosity of Iron Ore Pellets

Rafael M. Campos — 2024-06-13

The porosity and apparent density of iron ore pellets directly interfere with the blast furnace process
and, therefore, need to be known to assist in its control and optimization. These characteristics are generally
calculated using a pycnometer that uses mercury under pressure to fill the pores of the pellet. Considering the
need to preserve the environment and the safety of operators, proposals were made to replace this process, but
there are several complaints about the repeatability of results achieved, in addition to the time spent in preparing
and executing these essays. At the same time, it is possible to observe a remarkable development in Computer
Vision and Artificial Intelligence, mainly through Convolutional Neural Networks, which can extract patterns
from a set of images and detect these same patterns in images subsequently exposed to this network. In addition
to performing classification and detection, the Mask R-CNN network can perform pixel-by-pixel segmentation of
objects in images. In its evaluation, the network presented a significantly high mAP and accuracy, demonstrating a
satisfactory result for the segmentation and obtaining of porosity and apparent density values, with results similar
to the essays currently used.

Pavement Surface Type Classification Based on Deep Learning to the Automatic Pavement Evaluation System

Aline Calheiros Espíndola — 2024-06-13

Computer vision techniques, image processing, and machine learning became incorporated into an
automatic pavement evaluation system with technological advances. However, in most research, the models
developed to identify defects in the pavement assume that all the segments evaluated are paved and with one
specific pavement surface type. Nevertheless, there is a wide variety of road surface types, especially in urban
areas. The present work developed models based on a deep convolutional neural network to identify the pavement
surface types considering five classes: asphalt, concrete, interlocking, cobblestone, and unpaved. Models based on
ResNet50 architectures were developed; also, the Learning Rate (LR) optimization “one-cycle” training technique
was applied. The models were trained using almost 50 thousand images from Brazil’s states highway dataset.
model results are excellent, highlighting the model based on ResNet50, in which it obtained accuracy, precision,
and recall values of almost 100%.

DIC method applied in the calibration of FEA model of rock-mortar cohesive interface detachment

Edivaldo J. S. Junior — 2024-06-13

In civil engineering, the stability of many structures depends on the physical properties of the contact
between the concrete seated on the rocky foundation surface. Usually, they are critical structures of great
importance to society, such as: bridges, tunnels and dams. Thus, the shear behavior of rock-concrete joints is a key
factor of the structural stability. The method of cohesive zones (CZM) allows to simulate the beginning of the
formation of a crack and its propagation, without knowing the crack location or when it will start. Thus, in this
work, a numerical model was developed capable of simulating the failure due to interfacial delamination of the
contact between a structure formed by mortar seated on a rocky granite leaning surface. The calibration of the
numerical model was performed using the results of an experimental test of simple compression on a block of rock
in contact with the mortar by an inclined interface. The test was monitored using a high resolution digital camera.
The data were processed using the digital image correlation method (DIC) to obtain displacement and deformation
data. The DIC results were used to calibrate the nonlinear numerical model of the test using the bilinear method
of cohesive zone in the rock-mortar interfacial contact elements. By a parametric analysis, the parameters of the
bilinear law were determined (Maximum tensile stress and critical displacement and damage rate). Indirectly, the
rate of release of energy of critical deformation from the rupture of the contact was also estimated.

Evaluation of water superficial runoff in micro surfacing treatment pavement by Digital Image Processing in remote sensing software

Gonçalves A. K. L — 2024-06-13

The tire-pavement adherence is a major factor to minimize episodes of hydroplaning. Conventional
texture assessment methodologies prove to be inefficient and unreliable, due to human intervention in the test.
On the other hand, the development of new technologies has provided more agile assessments through
techniques such as Digital Image Processing (DIP). In this sense, the present paper has the objective to analyze
the superficial runoff of the rainwater with evaluation of the macrotexture of airport pavement through DIP. The
field study was carried out at an aerodrome in the state of Ceará, Brazil, and sought correlations between the
Sand Patch Test and the DIP methodology using remote sensing software (QGIS). With success rates of more
than 70% according to the macrotexture classification.

MONITORING OF SOYBEAN RUST THROUGH IMAGES

Aguinaldo Soares de Oliveira — 2024-06-13

The automatic occurrence of quality in agribusiness is becoming essential in order to reduce costs and
improve quality. Using image analysis techniques, it is possible to carry out pest control in various crops, such as
soybean plantations, by obtaining aerial images, for example using drones. An image when scanned has,
depending on its format, that is, its construction method, three layers called RGB (Red - Green - Blue) that
precede the final image to be demonstrated on monitors, displays and printers. Concepts that the construction of
the image depends on the type of sensor used and considering a digital image sensor capable of capturing the
luminosity of the images that are projected on it continuously, we have the beginning of the process of capturing
a moment of time, called photographs, or for a sequence of images over time. For capturing images in cores, it is
common for video cameras to use three types of sensors, known as the 3CCD system, where each sensor has a
tri-conical filter on it, and photographic cameras generally have a single image sensor that groups your photo
sites under a mosaic of luminosity and color filters. The computational tool developed will allow the soy grower
to monitor and identify the appearance of rust in the early stages and will avoid the unnecessary use of
fungicides, reducing costs and reducing environmental impacts.

Pothole and patch detection on asphalt pavement using deep convolutional neural network

Aline Calheiros Espíndola — 2024-06-13

The main obstacles to the widespread use of the PMS are the high financial and time costs for carrying
out on-site assessments and the difficulty of processing and analyzing the data to generate the diagnoses of the
current condition of the pavement. With technological advancement, some techniques such as computer vision,
image processing, and machine learning can automatically extract the information of the pavements' condition.
The present study proposes the exclusive use of images from cameras attached to a vehicle, simple collection and
reduced cost, and extraction of information on pavement defects using a CNN. The research developed object
detection models with YOLO architecture to identify potholes and patches. It was analyzed the metrics impact of
the image size (224x224, 320x320, 416x416 pixels) and number of iterations for Yolo version 3 and 4. As
expected, the increasing image size resulted in improved metrics results and the expansion of the iterations led to
an improvement in the IoU. The CNN that presented the best overall performance, combining all the metrics, was
based on Yolov3, with an image size of 416x416 and 6000 iterations training, in which it obtained an F1-score of
79.00%, an average IoU of 64.59%, and mAP@0.50 of 73.85%.

Detection and Segmentation of Iron Ore Green Pellets Using Computational Vision

Caio Mario Carletti Vilela Santos — 2024-06-13

In the industry, iron ore pellets, agglomerates with a diameter ranging from 6 to 16mm, composed
mainly of fine iron oxide particles, are one of the essential inputs used in the global production of steel, where
sphericity and strength of the pellets are necessary for the process, as well as the correct diameter, called the
particle size range. To provide mechanical resistance to the newly formed pellets, a characteristic that prevents the
pellets from breaking and turning into fines, a firing process is carried out where the thermal efficiency of this
pellet is intrinsically linked to the ideal diameter and humidity of the pellets. In the work, two neural models of
deep learning were presented and compared among themselves in the segmenting, and then measuring the diameter
of each of the iron ore pellets, they are Mask R-CNN and YOLACT. Such work makes possible improvements in
the controllers of the pelletizing discs, improving the quality of the pellets as a whole, as well as, a greater precision
in the desired granulometric range of the pellets. It was seen that the two networks mentioned had excellent results,
however, the Mask R-CNN proved to be more costly in processing compared to YOLACT.

Analysis of Machine Learning Techniques Applied to Coffee Bean Classification

Igor G. Lube — 2024-06-13

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 producer, consumer and exporter 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 a comparison between three algorithms that classify coffee samples, considering shape
and imperfections. The algorithms are classifiers, one based on MLP (Multi-Layer Perceptron), another in
clustering by K-Means and the latter consists of a classifier based on Deep Learning and regional convolutional
networks (R-CNN). The objective of this work is to compare which of the algorithms is more effective in
classifying the grains according to the intrinsic defects present in the sample.

A CNN-based keylogger using acceleration spectrograms

Cassiano S. N. C. Bueno — 2024-06-13

This work presents a model of supervised Convolutional Neural Network to identify keys pressed in a
computer keyboard based solely on their acceleration signal. In this problem, vibration propagated through a desk
from keystrokes were captured by an accelerometer. Individual keys have different acceleration signatures, and the
network was used to tell keys apart by looking at their particular acceleration spectrograms. The proposed network
showed an accuracy of up to 92% in the identification of individual keys.

Two Neural Methods for Astronomical Image Restoration

Vinicius S. Monego — 2024-06-14

Image analysis is a key issue in astronomy. One critical procedure is the photometric analysis of
astronomical images. Therefore, image restoration is a very important operation for the astronomy community,
being a permanent topic under investigation. In this paper, two different methodologies based on artificial neural
networks are explored. A convolutional neural network and the multiscale neural filter approaches are evaluated
on several astronomical images of different objects (stars, constellations, planets) and compared. The structural
similarity index measure is the image comparison metric used to determine the best restoration method.

Development and evaluation of a ROS package to publish stereo vision sensing data as a LiDAR type message.

Samir E. Silva — 2024-06-14

The ability to obtain a representation of the environment is essential in applications that require
knowledge of the arrangement of objects that make up a particular work space. The collection of environmental
data through the use of Light Detection And Ranging (LiDAR), cameras or a combination of the two methods are
widely studied for several purposes. However, sensors of the LiDAR type still present significatively higher
financial costs when compared to alternatives that employ cameras. Currently, these types of sensing have been
widely used in autonomous mobile robots and vehicles due to the ability of these sensors to provide good detailing
of the scene within its angle of view allowing the objects surrounding the autonomous system to be detected, which
permit it to take necessary actions for its safe motion within the environment. The Robot Operating System (ROS)
is an open-source framework that helps researchers and developers to build and reuse code for robotic applications.
This work proposes the development of a ROS package that uses stereo cameras for the publication of messages
characteristic of a LiDAR system and, hence, be able to evaluate the replacement of a LiDAR by stereo cameras
with minimum changes to architecture of the system.

Image edge detection using SVM regression model for UAV autonomous navigation

Gracieth C. Batista — 2024-06-14

Currently, unmanned aerial vehicle (UAV) has been used for many applications. Few applications
include agriculture, engineering, monitoring, rescue, entertainment, and others. One research topic involving UAV
is related to autonomous navigation. A standard procedure for this process to UAV is to combine inertial sensor
information with the Global Navigation Satellite System (GNSS) signal. However, some factors can interfere with
the GNSS signal associated with natural phenomena or malicious attacks (jamming or spoofing). One alternative
to overcome using the GNSS signal is to apply an image processing approach based on matching UAV images
and georeferenced images. There is a great computational effort on this approach for computing the image edge
extraction. A Support Vector Machine (SVM) regression model, also known as Support Vector Regression - SVR,
is employed for edge detection to reduce computational load and processing time. Our proposal consists of three
general steps; first: pre-processing of the images, where frames of 3x3 pixels were obtained for characterizing
edge or non-edge patterns; second, SVR models were trained, where the predictors were normalized; and finally,
an i.i.d. (independently and identically distributed) test set was used to predict SVR respective responses. The
better-performing model was acquired using the Gaussian kernel function compared to two other kernel functions
(linear and polynomial). Its generalization error is that the out-of-sample mean-squared error (MSE) was 18 times
less than the Linear kernel MSE error. The success rate was 99.98% of accuracy.

Comparison of Computer Vision Approaches for Recognition of Scenarios Suspected of Being Mosquito Breeding Sites in Aerial Images Acquired by UAVs

Rafael Oliveira Cotrin — 2024-06-14

The use of unmanned aerial vehicles (UAVs) for acquisition of aerial images to support health
surveillance teams in activities of combatting the mosquito breeding sites has increased a lot in recent years.
However, it is still common the manual analysis of such images, requiring much time of the health workers. In this
work we investigate two state-of-the-art computer vision approaches which can be employed for recognition of
scenarios suspect of being potential mosquito breeding sites from aerial images acquired by UAVs. The first
approach, named as BoVW+SVM, is based on Bag of Visual Words (BoVW) technique combined with the
Support Vector Machine (SVM) classifier, while the second approach is based on a model of convolutional neural
network (CNN) known as YOLO (You Only Look Once). For conducting the experiments, in which the
approaches were compared in terms of the mAP-50 measure, we employed a dataset containing 230 images,
acquired in urban regions of the city of São Paulo, which contemplate real and simulated suspected scenarios
(gutters and roofs with accumulation of objects, open-air inorganic garbage containing old tires, old tires, pet
bottles, plastic and paper packaging and other open containers that can accumulate water). The results obtained
by YOLO were much superior to those obtained by BoVW+SVM, in terms of precision and processing speed,
demonstrating that this CNN model can be employed to compose a computer vision system for automatic
inspections in real time.

Analysis of the soil domain size for simulations of ground-air heat exchangers.

L. H.N. Maia — 2024-06-14

Based on the fact that climatization systems are responsible for a large portion of electricity consumption
worldwide, the present work was dedicated to analyzing the domain soil size required to simulate a Ground-Air
Heat Exchanger (GAHE): a passive air conditioning system that uses the soil as a heat exchanger, heating or
cooling buildings according to climatic conditions. In transient simulations, the computational time used for the
analysis depends directly on the size of the domain imposed on the soil. However, if the dimensions of this domain
are not adequate, large discrepancies can occur in the results obtained. To obtain the optimized dimensions of this
domain, simulations using CFD (Computational Fluid Dynamics) were performed. First, the best time step was
verified. After, the domain of soil and finally the installation depth of the exchanger were obtained, all under the
same external condition. Sinusoidal equations representing the climatic conditions of the city of Ponta Grossa -
PR were used in this study. The optimized values obtained were 8 hours of the time step, 4 m of soil domain width,
and 2.5 m of pipe depth.

NUMERICAL ANALYSIS OF THE FLOW BEHAVIOR PAST AN AHMED BODY WITH VARYING FRONT RADIUS CURVATURE AND ITS IM- PLICATIONS IN THE AERODYNAMIC FORCES.

Raul Victor Teixeira Rosseto — 2024-06-14

The objective of the present study is to evaluate the dynamics of the air flow past the well-known Ahmed
body benchmark where its original geometry has been changed. The modification consists in changing only the
front radius curvature; 4 additional curvatures were evaluated. These 5 different geometries were evaluated for
4 different flow velocities, so that the Reynolds Number ranged from 4.8x103
to 4.8x104
. The simulations were
performed in the transient regime. The initial condition of the transient model is the result of the equivalent steady
state model. Regarding the numerical schemes, the second order upwind was employed for the discretization of
the Navier-Stokes advective terms, PISO algorithm for the pressure-velocity coupling and second order backward
integration for the transient term. The k-omega SST standard OpenFOAM implementation was used as turbulence

model. The local flow behavior at the frontal part of the Ahmed body, like boundary layer detachment and reat-
tachment, as well as the its global physical behavior are exploited and correlated to the changes in the aerodynamic

forces.

Parameter analysis of Earth-air heat exchangers coupled to galvanized bridges

Marcos Rafael Burlon Olivera — 2024-06-14

Due to the thermal inertia of the soil, it can be warmer or colder than the ambient air. Therefore,
Earth-air heat exchangers (EAHE) connect the ventilation system of a building to buried ducts. Such research is
valuable because EAHE use a renewable thermal source, and they consume little electricity. EAHE heating and
cooling capacities depend on many factors, like the local climate, duct design, and soil properties. This study aims
to evaluate the thermal performance of EAHE coupled to galvanized bridges with high thermal conductivity; the
idea is to increase the overall heat exchange with the surrounding ground. This work analyses the settings of a
subtropical climate, specifically, the southern Brazilian town of Viamao ̃ . The simulations use the validated 1D
GAEA model, and they estimate the soil temperatures (without the ducts) by solving 2D heat transfer equations
with finite element methods. The methodology considers the soil, galvanized bridges, and dynamic boundary
conditions that vary throughout the year. As the thermal potential of EAHE improves with galvanized bridges, this
article examines the reduction of the duct length, keeping high annual efficiency rates.

Finite difference schemes comparison on the drying process of a banana

Maria Rosa Amorim Faria Lisboa — 2024-06-14

Drying is an ancient method for preserving fruit and vegetable crops. It has been used effectively to
extend the lifespan of agricultural products and decrease post-harvest losses. Drying, or dehydration, consists in
lowering the vegetable’s moisture content by evaporation. This procedure reduces microorganisms’ reproduction
and other reactions that would result in rapid deterioration of organic matter. Therefore, it conservates food for
longer periods of time. During drying, complex phenomena occurs then mathematical modeling and simulation are
adequate tools to study the product’s behavior. In this instance, this work aims to compare three Finite Difference
schemes (Crank-Nicolson, Dufort-Frankel and Euler explicit) on how suitable they are for describing the behavior
of a banana during drying. The numerical results obtained were compared to experimental data.

Impact of the angle of attack of longitudinal vortex generator on enhancement heat transfer for a wavy-fin compact heat exchanger with circular and elliptical tubes

Laís S. Bandini — 2024-06-14

The growing industrial development over the last decades led to the improvement of several thermal
devices. Among the main types of equipment that have evolved in the last decades, heat exchangers stand out.
The present work investigates the heat transfer augmentation for a wavy-fin compact heat exchanger operating at
low Reynolds numbers, by combining longitudinal vortex generators. The computational modeling considers a
tridimensional model, for an incompressible, steady-state and turbulent flow. The heat exchanger with wavy fins
is evaluated considering circular and elliptical tubes for staggered arrangement combined with vortex generator
of delta-winglet and rectangular-winglet with aspect ratio of 2 and angles of attack of 15o, 30o and 45o. The heat
transfer was evaluated by Colburn Factor and the pressure drop by Friction Factor. In comparison with the
reference heat exchanger (without vortices generators), the results show an increase in the heat exchange of 41%
using the elliptical tubes associated with a rectangular-winglet vortex generator at the angle of attack of 45o. For
the friction factor, the configuration with rectangular-winglet vortex generators is higher than delta-winglet
vortex generator independently of the angle of attack. Moreover, the friction factor for circular tubes is higher
than elliptical tubes. Overall, the results showed that the compound passive technique is an efficient technique to
improve the heat exchange in the compact heat exchanger, allowing, among others things, the reduction of
materials for fabrication process and manufacturing.

Evaluation of single-phase and two-phase propane release via CFD simulation applied to the hazardous area classification

Natalya A. B. de Almeida — 2024-06-14

Different leakage scenarios can occur in industries that handle flammable substances. Fugitive releases

are frequent leakage scenarios that can result in explosive atmosphere formation. These releases can be single-
phase or two-phase, depending on the storage conditions. For two-phase releases, the leakage condition needs to

consider the thermodynamic state in the storage and the orifice. In this context, methods for hazardous area
classification must be used to ensure process safety. One of the methods used for area classification and
recommended by the international standard IEC 60079-10-1(2015) is Computational Fluid Dynamics (CFD), a
numerical tool that accurately assesses many different release scenarios. Therefore, this work aims to contrast
different approaches from CFD simulations for liquefied propane release scenarios in an open and unobstructed
environment. A pseudo-source approach was assumed to simulate the post-expansion region for both conditions
of thermodynamic equilibrium and superheated liquid in the release orifice. The same pseudo source approach
was considered in the case where only gas is released. The Eulerian-Lagrangian approach was applied to the
multiphase simulation, and the Eulerian approach for the gas phase simulations in both single and two-phase
simulations. The liquid and gas temperature results showed the behavior of an expected flash release when dealing
with liquefied gas depressurization. The extent and gas cloud volume results delimited by specific concentrations
were quite similar for both scenarios. The pseudo-source approach considering only the gas required a shorter
simulation time without losing the accuracy of the results compared to the two-phase simulations. It indicated a

significant gain on reducing the simulation effort required for hazardous area classification assessment in two-
phase releases scenarios when there is no pool formation.

Impact of wave inclination on enhancement heat transfer for a wavy- fin compact heat exchanger with circular and elliptical tubes for staggered tube arrangement

Rafael S. Eller — 2024-06-14

With the increasing industrial development, the improvement of several processes and devices
represents a great need, especially for thermal devices. The present work evaluates the enhancement of heat
transfer in a compact heat exchanger with wavy-fins, operating at Reynolds number of 180 to 900, through
modified inclination of wavy-fin in relation to the main flow direction. A 3D numerical modeling considers
incompressible, turbulent and steady-state flow. The compact heat exchanger is evaluated for staggered circular
and elliptical tubes. The wavy inclination investigated are -25 °, -20 °, -15 °, -10 °, 10 °, 15 °, 20 ° and 25 °. The
heat transfer is performed by the Colburn factor (j) and the pressure loss penalty is performed by the friction
factor (f). Compared to the conventional heat exchanger (θ = 0 °), the results showed an increase in the heat
transfer of 13.5% with elliptical tubes and 7.8% with circular tubes at wavy inclination of -25 °. For the friction
factor, all inclinations led to a decrease, with a reduction of 18.8% with circular tubes and 15.1% with elliptical
tubes. Overall, the wavy inclination proposed is an effective alternative to both increase the heat transfer and
reduce the pressure losses.

Verification of WENO-type extrapolation with different WENO schemes

André C. Rialto — 2024-06-14

The usage of WENO-type extrapolation allows achieving high order and high resolution when solving
fluid dynamics numerical problems with the finite difference method and rectangular meshes. Developing new
modifications for this extrapolation implies better handling of boundary conditions. Hence, in this work, we are
interested in the verification of three WENO-type extrapolations together with four WENO schemes in smooth
and discontinuous test problems. Four different test problems modeled by the Euler equations will be solved with

the finite difference method, positivity-preserving Lax-Friedrichs flux, and strong stability preserving Runge-
Kutta. The first two are one-dimensional, and the others are two-dimensional. The one-dimensional discontinuous

problem is a severe test case for the WENO-type extrapolations. The two-dimensional discontinuous problem is
the double Mach reflection, which presents oblique shock and other nonlinear phenomena interacting with a wall.
We show that the design accuracy is being reached for smooth problems, that the discontinuities and nonlinear
phenomena are well captured, and we identify common features and areas of improvement for the WENO-type
extrapolations.

AN ANALYTICAL-NUMERICAL STUDY OF THERMAL STRESS IN STRUCTURES OF MASS CONCRETE

Nailde de A. Coelho — 2024-06-14

The construction of gravity dams was a milestone for the development of studies and technological
control of the concrete of mass, because the internal temperature increases began to appear and this generated
cracks. During the process of hydration of the cement particles, there is release of heat, in a process called heat of
hydration, raising internally the temperature of the concrete. This phenomenon causes the internal temperature of
the concrete to differ from the surface temperature, resulting in a thermal gradient, in addition to a slow cooling in
the core of the structures. These temperature changes give rise to thermal stresses, which if not foreseen and
prevented can cause damage to the constructions, when they exceed the capacity of resistance of the concrete.
Thermal stresses take into account the phenomenon of the intrinsic creep in the concrete: there is variation of the
modulus of elasticity over time with the change of temperature. There are a few techniques to try to minimize this
problem, such as building in layers, launching concrete at lower temperatures, use of cements with low heat of
hydration, and more. An effective way of preventing thermal problems in mass concrete is the numerical
simulation, being possible with the mechanism, predict the most critical regions and analyze the probability of
structural damage. In view of the context, this work shows numerical thermal simulations using the Finite Element
Method - FEM, through the ANSYS program for mass concrete structures built in layers. With the numerical
results, the analitical tensions arising from the temperature changes of the bodies are analyzed. It seeks to expose
some of the most favorable conditions in the construction process, identifying possible cracking sites, through
numerical and analytical analysis, contributing to the dissemination of these studies and showing to the community
in interest, constructive methods and methods of analysis that can induce safer construction.

Fluid flow and thermal analysis of Al2O3-water nanofluid in multi- microchannel heat sinks

Isabelle Guimarães da Silva — 2024-06-14

This work analyzes different working fluids (DI-water and Al2O3-water based nanofluid) flowing in a
copper microchannel heat sink consisting of 20 parallel rectangular channels of 29.23 mm in length, 1.2 mm in
width, and 1.2 mm in height for each microchannel and investigates their influence on the velocity flow field,
pressure drop, and heat transfer. The CFD software ANSYS FLUENT 2020 R2®

was applied. In the case of
Alumina-water nanofluid with an average nanoparticle size of 10 nm, different volume concentrations were used
(0.5% and 1 vol.%). A uniform velocity and temperature (293.15 K) were applied at the inlet of the heat sink.
The inlet velocity varied from 3.41 to 8.54 m/s, and the Reynolds number based on the hydraulic diameter and
inlet velocity varied from 400 to 1000. A heat flux corresponding to 165 W dissipated power for
an Intel®
CoreTM Serie X processor was applied at the bottom surface of the heat sink. It was possible to obtain
different temperature distributions, the pressure drop, and the requested pumping power consumption by
modifying the working fluid. Comparisons were performed on how the velocity and temperature fields changed
according to boundary conditions. The Alumina-water nanofluid provides a more uniform wall-temperature
distribution; the nanofluid with the highest concentration has the highest friction factor and the highest Nusselt
number regardless of the Reynolds number. The nanofluid thermal behavior with the volumetric concentration
increasing is probably due to the fluid thermal conductivity increasing. Even the higher pressure drop observed
for the Al2O3-water nanofluid, its effect on the pumping power consumption is acceptable (for the highest
nanofluid concentration and Reynolds number, the pressure drop is 93.40 kPa corresponding to a pumping
power of 3 W). Therefore, the microchannel heat sink and nanofluids seem a plausible solution for the cooling
challenge in microscale electronics due to the higher cooling performance.

On The Investigation of Flow Rate Measurements Using Tap Noise and Variational Mode Decomposition

Cleber L. Torres — 2024-06-14

Currently, conventional flow measurement methods are intrusive, and flow meters need to be installed
on pipelines conveying fluid. Some investigations have already been conducted to develop non-intrusive flow
measurement techniques, mainly via using vibro-acoustic signals acquired straight on the pipe, where the flow
induced vibration can be used to estimate the flow rate. However, such techniques are very accurate for high flow
rate values which are related to the level of vibration specially when the flow is turbulent. This is not the case
when considering tap noise vibration associated with the water flow, which is much smaller than for industrial
cases. Here, for tap noise, the induced vibration is measured in a valve next to the tap. Variational Mode
Decomposition Method is then used to give an estimation of the frequency bandwidth over which the tap noise
can be found. The signals are filtered out using such band to attenuate background noise to enhance the flow rate
estimation. This is conducted using classical vibration measures such as the RMS value and Power Spectral
Density for the time and frequency domain, respectively. Actual tap vibration signals were collected at different
flow rates by using two different accelerometers with different sensitivities to validate the methodology. It was
found that the methodology is effective in selecting the bandwidth over which induced vibration due to tap noise
is concentrated, and also estimating the flow rate for tap usage. The sensor sensitivity, however, indicates that for
low flow rates the higher the better for tap flow estimation.

Development of an Intelligent Virtual Assistant to Activate the Devices of a Residence by Voice Command

Leonardo Vinicius de Brito Reis — 2024-06-14

Home automation is increasingly present in people's lives and is already a reality in many Brazilian
homes with differentiated solutions aimed at the needs of each user. However, this technology still has a very
high cost, which makes it difficult for most of the Brazilian population to acquire it. Thus, the present work aims
to present the development of a low-cost smart virtual assistant prototype, using the Python programming
language and the open source Arduino platform, which will allow the activation of devices in a home by voice
commands.

Development of a stall sensor for low weight aircrafts

Izaias A. S. Junior — 2024-06-14

The phenomenon of stall or loss of lift is one of the main factors causing Loss of Flight Control (LOC)

in an aircraft. In Brazil, between 2008 and 2017, most accidents that occurred due to loss of flight control oc-
curred with aircraft weighing less than 2,250 kg. Thus, the objective of this work is to research the development

of a low-cost solution about the devices currently available on the market, capable of identifying a possible stall
situation, alerting, and assisting the pilot through auditory commands in the form of procedures during the flight

envelope resumption maneuver. The results in this work come from tests carried out in a moving land motor ve-
hicle, which have the purpose of simulating the functioning of the sensor developed in an operating aircraftwith

longitudinal average acceleration variation of up to a maximum of 0.2 m/s2

. The preliminary results were promis-
ing since in addition to meeting the proposed objectives, enabled the mapping of low-cost improvements that can

be implemented to increase the performance of the device, which can also be adapted for use in unmanned aerial
vehicles.

MISFIRE DETECTION ON INTERNAL COMBUSTION ENGINE THRORUGH DIFFERENT TYPES OF MACHINE LEARNING MODELS

Eduardo V.T. de M. Andrade — 2024-06-14

Misfire is a phenomenon that can jeopardize the good yield of an engines function, this might result in
a lower efficiency than expected and an increase on pollution produced by elevated gas emission. However,
there are certain systems that are capable of detecting this type of flaw. This article presents a model based on
artificial intelligence that is capable to spot the misfire caused by a malfunction of the spark plug in a 2006
Zetec-Rocan ford motor that consists in a 4 stroke engine of internal combustion. As a result of its usage,
identifying the main source of the problem becomes an easier task and therefore reducing the time spent on its
maintenance. The model mentioned above uses vibration signals generated by an accelerometer. This signals
went through a pre-processing proceedure to extract features in which were used a multiscreen analysis and FFT
(Fast Fourier transform). After the extraction, those features were used as an entry on machine learning models
that allow them to be classified according to its signal so we are able to identify if theres a defect and where the
problem is located. The 5 machicne learning techniques used were Random Forest, Forest Tree, SVM(Support
Vector Machine), KNN(K-Nearest Neighbors) and Neural Network. The results showed that they were all
accurate both in train and in tests. External data validation also showed solid performance.

PARONAMA OF ARTIFICIAL INTELLIGENCE IN BRAZILIAN COURTS

Oliveira, Filipe A — 2024-06-14

The number of processes in Brazilian territory is high compared to other countries. In fact, the number
of judges and court servers does not follow the avalanche of existing cases in our country. With this, a new element
has emerged to assist the Brazilian courts, these are computer systems that use AI (Artificial Intelligence). Such
intelligent tools have generated significant changes in the legal ambit. Among the AI systems currently used in the
courts, are Victor (STF), Socrates (STJ) and Radar (TJMG), which aims to benefit the entire process and facilitate
the work of magistrates and lawyers. To obtain greater productivity, the courts seek to adapt to new reality, aiming
to achieve efficiency that society expects from justice. The present work target to conduct a study about the
panorama of systems that use Artificial Intelligence installed in Brazilian courts to assist in their effectiveness and
improve the Brazilian judicial process, generating productivity of the courts. In addition, it intends to answer which
courts of Justice of Brazil artificial intelligence is being used and how it applies in practice.

Oil-price forecasting based on ARIMA, exponential smoothing, and autoregressive neural network models

Felipe B. P. Araújo — 2024-06-14

Financial time series are sensitive to exogenous shocks. From this perspective, this work presents a
comparative analysis of predictive crude oil prices scenarios, obtained from a historical series of average annual
prices. Two approaches were used: first, a combination of classic strategies based on exponential smoothing, and
ARIMA models. Second, an autoregressive neural network model. Both approaches are complementary when used
for long-term forecasting of oil prices and show good response to volatile data. Therefore, we are able to present
an alternative data analysis, in a field where there is a great amount of relevant historical series, using probabilistic
and non-linear models in order to observe predictions and make more effective decisions.

Support system for Apnea diagnosis using statistical analysis of ECG signals

Ludmila B. Meireles — 2024-06-14

The advancement of technology has given researchers and doctors the possibility to detect abnormalities
in the human body, before they become serious and irreversible diseases. The Electrocardiogram (ECG), which is
an exam whose output value reveals the behavior and heart rate of an individual, is of fundamental importance for
the analysis not only of the health of the heart, but of the individual as a whole. This article proposes to do the
classificatory analysis of ECG data, using healthy databases and apnea. The methods used to separate the two
groups into healthy and apnea groups were the mean, variance and kurtosis. The results achieved by the proposed
methods obtained accuracy greater than 90%. These results can be used in clinical practice to support the diagnosis,
that is, the proposed method has the potential use as a screening method and aid to the diagnosis and monitoring
of cardiac pathologies.

A coupling model for fluid-structure interaction applications with free-surface flows and rigid-bodies

Mateus Guimarães Tonin — 2024-06-14

In the present work, a formulation based on the Characteristic Based Split (CBS) method is proposed
for applications in fluid-structure interaction (FSI) and free-surface flow problems. The flow fundamental
equations are discretized here using the CBS method in the context of the Finite Element Method (FEM), where
linear tetrahedral elements are employed. A semi-implicit scheme is used, where the momentum equations are
solved explicitly while the mass equation is solved implicitly through a Poisson equation. FSI is taken into
account considering a partitioned coupling model and the rigid-body approach, considering an Arbitrary
Lagrangian-Eulerian (ALE) kinematic formulation. The resulting dynamic equilibrium equation is solved using
the Generalized- method. Free-surface flows are analyzed using the Level Set Method (LSM), considering a
two-phase medium. Classic free-surface and FSI problems are simulated in order to evaluate the present
formulation, comparing results obtained here with experimental results and predictions obtained with other
numerical formulations available. It is concluded that the proposed numerical tool is able to obtain results
consistent with the phenomena involved.

Numerical analysis of the mitigation of aerodynamic loads in low-rise buildings using spoilers with PID control

Gabriela P. Bianchin — 2024-06-14

A numerical investigation is performed in this work to evaluate the influence of controlled spoilers on
pressure mitigation over low-rise building roofs. Considering that low-rise buildings are susceptible to severe
damages caused by wind action, spoilers are utilized along the roof windward edges to reduce the aerodynamic

load, which are controlled using PID control techniques. Numerical simulations are carried out using a semi-
implicit CBS algorithm, where linear tetrahedral finite elements are employed for spatial discretization in a

standard Galerkin procedure. Turbulence modeling is performed using Large Eddy Simulation and the flow

fundamental equations are written considering isothermal and incompressible conditions in arbitrary Lagrangian-
Eulerian kinematical description to take into account the spoiler angular motion. Two and three-dimensional

simulations are carried out using a typical low-rise building model, where the influence of controlled roof spoilers
and wall openings on the roof loading is evaluated. Wind tunnel predictions are utilized to validate the numerical
formulation proposed here.

Effect of interface viscosity on the breakup of liquid sheets

Vitor H. C. Cunha — 2024-06-14

Free surface flow is of major relevance in many fluid dynamics applications, both at the macroscopic
scale, like in the study of water waves and the design of watercraft, and at the microscopic scale, such as in thin
films and microfluidics. Understanding the physical mechanisms contributing to the stability of thin liquid sheets
is a challenging problem, as they present a fluid-fluid interface which is free to deform. In systems with high
surface area to volume ratios, such as micro bubbles, blood cells and emulsions, the dynamics of the system are
also highly influenced by the dynamics on the interface. In addition, the presence of surface-active agents such as
polymers and surfactants may lead to complex interfacial rheological behavior. In this work, a computational
investigation of the breakup dynamics of a stationary thin liquid sheet bounded by a passive gas with a viscous
interface is presented. An Arbitrary Lagrangian-Eulerian method (ALE) is used to track the interface position. The
rheological behavior of the interface is modeled by the Boussinesq-Scriven law, and the numerical solution is
obtained through finite element approximation. The results show that the stability of free surfaces is influenced by
surface rheology and that the viscous character of the interface delays the sheet breakup, leading to more stable
films.

Perfomance of free surface capturing methods in the wave absorption

Carolina Maria Nunes Bezerra — 2024-06-14

Different numerical methodologies provided in the literature, associated to Computational Fluid Dy-
namics (CFD), are applied to generation and absorption of marine waves into a Numerical Wave Tank (NWT)

model. However, when the user configures this problem in CFD, it is necessary to select the most appropriate
numerical model to represent the physical phenomenon of wave motion. A standard framework for numerical
modeling is the OpenFOAM software and its two-phase solvers as InterFoam and InterIsoFoam, which allow an
adequate simulation for a wide range of marine hydrodynamic problems. A very common issue that appears in
NWTs is the low capacity of absorption of the marine waves at the inlet and outlet into the numerical models.
An efficient absorption of these waves is important to guarantee the open ocean conditions and to minimize the
error associated with the numerical results. In order to mitigate the wave reflections, a numerical study of the
convergence parameters applied to two-phase solvers was carried out and an analyse of the waves generation and
absorption was performed. The present study allowed to evaluate the hydrodynamic interface treating methods
avaiable in OpenFOAM and foster a discussion of the already established methods.

Computation of dynamic loads exerted by regular water waves on a vertical cylinder with application to offshore wind turbine

Gustavo Ríos Rodríguez — 2024-06-14

Wave forces on near-shore structures constitute relevant information to the design and verification of
structural pieces. This wave loads are particularly important to design reliable piles and foundation of marine
platforms or wind turbines. To investigate the dynamic effects of such forces a numerical wave tank is set in a
finite volume Navier-Stokes solver. In the wave tank a vertical cylinder which represents the wind turbines tower
is affected by free surface waves. Specific inlet and outlet boundary conditions available as part of OpenFoam
distributions are included. Inlet boundary conditions are allowed to recreate either regular and focused wave
conditions, while outlet conditions are established in order to avoid non physical reflections of surface waves
on the artificial limits of the domain. The results obtained for regular waves are compared with experimental
measurements, numerical studies and the Morison equation reference. The wave loads are also used to simulate an
offshore wind turbine where wind loads and soil-structure interaction are considered. Further studies are performed
with focused wave groups and breaking waves.

Reflection of Nonlinear Waves in Reid's Hysteretic Material: A Numerical Perspective

Pravinkumar R. Ghodake — 2024-06-14

Nonlinear ultrasonics is effective in characterizing early-stage damages in solids. Interaction of a single
frequency (f) elastic wave with early-stage damages like dislocation substructures, micro-cracks, and micro-voids,
etc., generates higher harmonics (2f, 3f, 4f, 5f,..). In theoretical and computational studies early-stage damages are
modeled as nonlinear material models. Material models such as quadratic, cubic, and hysteretic nonlinearities are
commonly implemented in nonlinear wave propagation studies. To understand the interaction of the ultrasonic
wave with micro-cracks a pinched hysteretic nonlinearity looks the best fit as it can capture the nonlinear contact
mechanisms like opening and closing of micro-cracks which is also known as crack clapping and sliding at the
interfaces. One dimensional spatial domain is discretized as a long chain of spring-mass elements. Reid’s pinched
hysteretic elements are used in a long chain of spring-mass elements for the numerical study of the nonlinear wave
propagation through symmetric hysteretic material. Interaction of a single frequency elastic wave with Reid’s
symmetric hysteretic nonlinearity generates only odd harmonics (3f, 5f, 7f,...). Nonlinear reflected waves from
both the free and fixed end cases contain only odd harmonics. After reflection, nonlinear wave transfers energy
from 5th and 7th harmonics to 3rd harmonics. Pinched hysteretic loops are observed corresponding to both the
incident and reflected wave. The pinching at the origin of the hysteretic loops gets opened due to the reflection of
nonlinear waves. Evolving pinched hysteretic loops are observed due to Gaussian pulse as an input pulse whereas
repetitive pinched hysteretic loops are observed due to sine pulse as an input pulse. In one-way two-wave mixing,
both incident and reflected waves from free and fixed ends contain sum and difference frequency harmonics along
with the corresponding odd harmonics of input frequencies. Reflected waves transfer energy from the frequency
combinations present near 5th harmonics to frequency combinations present near 3rd harmonics. Minor hysteretic
loops due to wave mixing are observed within the major pinched hysteresis loops. As this numerical study is simple
in understanding, formulation, and implementation, it will help to solve inverse problems in nonlinear waves with
less computational resources and within a short time.

Propagation of Guided Waves in Coated Tubes used in Off-Shore Oil In- dustry

Kelly Robert-Svendsen Rassier — 2024-06-14

This work applies acoustic emission methods to monitor pipes’ integrity and mechanical behavior in
the offshore oil industry, which cannot be inspected visually because they are usually covered with a polymeric
layer to mitigate impact loadings. The elastodynamic response of such a pipe is studied through dispersion curve
charts, implemented with commercial finite element packages: one based on the modal analysis of an axisymmetric
model, and the other using periodic boundary conditions over a 3D model. Both curves are compared to analytical
models based on the classical theories of beam-shaft-bar structures, with effective properties obtained by Voigt
theory, leading to an in-depth discussion about the corresponding mechanical behavior of the overall structure.

A New Strategy for Real-Time Structural Health Monitoring Based on Symbolic Data Objects

Daniel de A. C. Soares — 2024-06-14

Many recent researches have been using Symbolic Data Objects (SDO) as the basis for Structural Health
Monitoring (SHM). The advantage of using SDOs is that they have a very strong capacity to compress raw data,
without losing the essence of the original information. This work presents a complete methodology to perform a
real-time SHM, which was implemented in a software developed by the authors called TW-Parallel. A practical
application was tested in a real structure: a historic tower in Mantua, Italy, called the Gabbia tower. The results
showed that, after an adaptation period - when some false alarms occurred - the software was able to accurately
detect a seismic event that occurred during the structure monitoring period.

DEEP LEARNING FOR INTERFACIAL DAMAGE ESTIMATION IN AN INVERSE ULTRASOUND SCATTERING ANALYSIS

Bernardo Junqueira — 2024-06-14

We formulate and solve a time-harmonic inverse scattering problem to estimate the interfacial defect
distribution at an adhesion interface of a composite plate. We use the incident field that mostly interact with such
defects and assume prior knowledge of the material properties of each layer of the laminate. We model the adhesion
interfaces using the Quasi-Static-Approximation, where approximates it by a set of tangential and normal springs,
and allow the interfacial stiffness to depend upon the position along the interface. To solve the direct problem, the
interfacial defect distribution is generated by a prior of smooth stochastic field. In addition, we develop a deep
learning neural network, using the reflected signal as input, to solve the formulated inverse problem. We validate
our implementation and evaluate the presented method’s performance for noisy input data and different defect
distribution scenarios with the aid of numerical simulations. From the obtained numerical results, we may say
that the proposed method is robust to the presence of noise and has the potential to detect and classify interfacial
defects.

A methodology for development of a digital twin ship

Kennedy L.S. Neves — 2024-06-14

Recently, digital twin has emerged as an alternative technology to predict the structural integrity of

ships and offshore structures with good accuracy in real time. An appropriate digital twin for this field of appli-
cation should consider important aspects such as the harsh environmental conditions and load variations that are

induced during the lifetime of the involved components. The behavior of mooring lines, risers and the floating
unit compose a complex coupled system, which has to be modeled by the digital twin. A large amount of data
can be collected by monitoring systems or inspections. This paper presents a methodology for developing a digital
twin ship for a FPSO (Floating Production Storage and Offloading) capable of being coupled with external data
and automatically run multiple numerical analyses. The proposed methodology employs a three-cargo tank length
model in three dimensions via FEM (Finite Element Method) to receive information, solve the structural analyses
and check the results for damage detection on hotspots of the model. This procedure can be applied in different
approaches to help on ship operation by checking generated results for several conditions that can be considered
with numerous variations of parameters and avoid excessive maintenance proceedings that may have a significant
impact on operations.

Using a Plate FRF set to Identify a Damaged Site Without Employing a Reference Dataset

Horacio Valadares Duarte — 2024-06-14

The procedure is based on the Energy Correlation Distance between each FRF (Frequency
Response Function) collected on a grid and the set composed by all FRFs from a measurement mesh. To
enhance the difference between a healthy and a damaged sites the FRF frequency sequence for highest
modes is employed. This Energy Correlation Distance, at each grid point, is then treated using classical
spacial statistical procedure, Krige method and Spatial Autocorrelation. To illustrate the procedure some
initial results are included. Results for experimental data from composite plates and from a aluminium
shell plate are presented. Remarks about the presented method improvements, limitations and restrictions
are also incorporated.

One-Dimensional Wave Equation Simulation Using Recurrent Neural Networks

Maurício D. Silva — 2024-06-14

This paper presents an application of Recurrent Neural Networks to the one-dimensional Wave Equation.
Nowadays, Neural Networks have been widely used due to the advances in computer hardware, since it allows
that a great amount of data could be processed in parallel. Over the years, new and improved neural network
architectures were developed, as for example the Recurrent Neural Network, mainly used in time series analysis.
In this study, the 1-D wave equation solution is implemented using Finite Differences in Time Domain considering
Neumann Boundary Conditions, and two architectures of Recurrent Neural Networks were explored: LSTM and
GRU. The results were organized according to the hyper-parameters used to train and validate the networks, and
they were evaluated quantitatively, using the mean squared error as loss function, and qualitatively, observing the
response plots for dataset validation. It was possible to achieve predictions with mean squared errors of order 10−6
and a training time of 23 seconds per epoch using GPUs.

On the Discretization Methods for Single-Cell RNA-Sequencing Data when Inferring Gene Regulatory Networks via Cartesian Genetic Programming

José Eduardo H. da Silva — 2024-06-14

Gene Regulatory Networks (GRNs) inference from gene expression data (GED) is a hard task and a

widely addressed scientific challenge. The sequencing of single-cell RNA (scRNA-seq) allows for the transcrip-
tome exploration at the cellular level and it is attractive for the GRNs inference. GRNs can be represented as

Boolean values, in which genes activation and inhibition are presented by logic relationships. Cartesian Genetic
Programming (CGP) can be used to evolve GRNs from gene expressions in a binary data form. Therefore, an
appropriate discretization technique is important due to its effects on the quality of models. Here, we analyze the
performance of ten unsupervised methods for GED discretization when applied to CGP for inferring GRNs. We

considered the following discretization methods, based on: statistics, data distribution, ranking, clustering (e.g., k-
means and Bikmeans), time series (Transitional State Discrimination), and a method developed by Gallo et al. for

data discretization. We also perform a sensibility study of the parameter required by ranking-based methods. We
provide a qualitative and quantitative analysis of the discretization approaches in order to obtain a set of methods
and parameters that are good for modeling GRNs from scRNA-seq data using CGP.

A New Multi-objective Optimization Algorithm inspired by Lichtenberg Figures Applied to Constrained Mechanical Engineering Problems

Pereira, J. L. J — 2024-06-15

The optimization problems that must meet more than one objective are called multi-objective
optimization problems and may present several optimal solutions. Classic optimization methods had their
importance in the past, but they lost space for new algorithms that emerged with the advancement of computing,

better able to deal with a greater number of variables, objectives and nonlinearities. Evolutionary and meta-
heuristic algorithms are exponents in the literature as the main tool for solving complex multi-objective

problems. This work presents the first multi-objective meta-heuristic registered as a computer program in Brazil.

The Multi-objective Lichtenberg Algorithm is an optimizer inspired by the physical phenomenon of radial intra-
cloud lightning and Lichtenberg Figures. The algorithm is tested and compared with other renowned algorithms

(MOPSO and NSGA-II) in some Zitzler-Deb-Thiele test functions and is finally applied to constrained and
unconstrained engineering problems: Welded Beam Design, Disc Brake and 4-bar-truss. MOLA proved to be a
promising multi-objective optimization algorithm surpassing today's most renowned algorithms.

problems. This work presents the first multi-objective meta-heuristic registered as a computer program in Brazil.

Optimized design of composite steel and concrete trusses to minimize cost and environmental impact

Diego Klein — 2024-06-15

The use of composite structures has grown significantly in recent decades, in a global scenario
characterized by the need to reformulate the image of the civil construction sector, responsible for an enormous
environmental impact. In this context, composite steel and concrete trusses have applicability in structural design
with large spans. This research consists in presents the optimization problem of steel and concrete composite
trusses focusing on the cost and CO2 emission, via genetic algorithm (GA), using Matlab software. Three trusses
models were considering: Pratt, Howe and Warren associated with solid slab, for the optimized design according
to ABNT NBR 8800:2008. It was verified which type of truss provides the best results for spans of variable lengths.
Witch the graphical interface for efficient user interaction and the agility provided by the GA, the developed
program identified that the best results were obtained with the Pratt-type metallic truss and that the upper flange
was in a critical situation due to the combined bending effect. Optimizing the cost and CO2 emission of composite
steel and concrete trusses has proven to be an excellent tool for automating these tasks.

Modified Improved Harmony Search Applied to Reinforced Concrete Beams

Fernando L. T. Junior — 2024-06-15

During the structural design, engineers can use optimization algorithms as efficient tools to conceive
structures with lower cost and environmental impacts compared to the traditional trial and error process. This paper
presents the cost optimization of reinforced concrete beams, composed by the cost of concrete, steel bars and
formworks. The design variables were the cross-section dimensions, position, and diameter of the reinforcement.
The constraints applied in the problem are those imposed by the Brazilian Standard NBR 6118 (2014), checking
the ultimate and serviceability states. To achieve that, a formulation to analyze reinforced concrete beams was
implemented in the software developed in this research. The optimization method used was a variant of Harmony
Search, a metaheuristic inspired by the jazz musical improvisation process, called Modified Improved Harmony
Search (MIHS). Aiming to verify the efficiency of the developed software, as well as to investigate the
performance of the optimization method, beams with different spans, loads and concrete strengths were optimized.
The obtained results were satisfactory and competitive, although they show the need for improvements in the
program.

Analysis of two variants of the Generalized Differential Evolution algo- rithm with ordered mutation for real world engineering multi-objective optimization problems

Rafael P. Garcia — 2024-06-15

Differential Evolution (DE) is one of the most powerful commonly used metaheuristics for global multi-
objective optimization. New strategies to improve the DE’s performance are an important and attractive research

study. The third Evolution Step of Generalized Differential Evolution (GDE3) is a widely used DE-based multi-
objective evolutionary algorithm in the literature, especially in real-world multi-objective optimization problems

with two or three conflicting objectives in its formulation. GDE3 uses the most popular mutation strategy of the DE,
DE/rand/1, which randomly selects three candidate solutions from the population without considering any order.
The fourth version of the Generalized Differential Evolution (GDE4) was recently proposed, which presents an
ordered mutation operator based on two well-known schemes: Non-dominated Ranking and Crowding Distance.
Previous studies have shown that GDE4 outperforms GDE3 on a set of many-objective optimization problems.
In this paper, the second version of GDE4 is proposed, GDE4-II, considering a local ordering among the three
randomly selected individuals instead of the entire population as GDE4. Besides, experiments are conducted to
evaluate the performance of the two GDE4 variants in benchmark and engineering multi-objective optimization
problems with two and three objective functions. Metrics such as Hypervolume and Inverted Generational Distance
plus (IGD+) combined with performance profiles are used to point out the robustness of the GDE4 and GDE4-II.

Space trusses optimization using metaheuristic methods: a review

Mateus P. Pauletto — 2024-06-15

Space trusses are one of the most widely studied elements in structural optimization. Many
metaheuristics were used for this purpose over the years, ranging from established methods such as Genetic
Algorithms (GA) and Simulated Annealing (SA), through widespread population methods like Ant Colony
Optimization (ACO) and Particle Swarm Optimization (PSO) reaching the new generation of heuristic search
algorithms (Mine Blast Optimization (MBO), Bat-Inspired Algorithm (BA) and the Charged System Algorithm
(CSA), for example). In recent years, in addition to the appearance of numerous brand new search methodologies,
it has become extremely common the use of hybrid search methods - mixing two or more algorithms - for the
optimization of space trusses. With focus on the exponential increase in publications on the subject, the present
work reviews studies about the optimization of space trusses using heuristic methods, searching studies available
in scientific journals and classifying them using an own methodology. At the end of the article, an overview of the
topic is reported.

Single and multi-objective optimization of spatial steel frame considering different bracing systems.

Claudio H. B. Resende — 2024-06-15

In a structural optimization problem, the objective may consist in minimizing its cost and maximizing
its performance according to horizontal displacements, dynamic behavior, structural stability, etc. In addition to
that, finding the best bracing system configuration which presents the best results according to the objectives of
the problem is not a trivial task. This work is based on multi-objective optimization of steel frames considering
different bracing systems, in which distinct configurations of space frames compete in the same evolutionary
process. An integer index variable defines which type of bracing system configuration is adopted for each candidate
solution. The output of a multi-objective problem is a Pareto-front curve, from where the designer must choose the
most suitable solution according to objectives that are taken into account. A Multi-Tournament method based on
the preferences of the decision-maker is used to extract the solutions. The search algorithm adopted is the Third
Step Differential Evolution (GDE3) coupled with an Adaptive Penalty (APM) Method to handle the constraints.

Optimal Design of Composite Cellular Beams with Partial Interaction and its Environmental Impacts

Gabriel Erlacher — 2024-06-15

This work aims to present the formulation of the optimization problem of composite cellular beams of
steel and concrete considering partial interaction between beam and slab, based on the design restrictions
prescribed in specialized literature adapted to the current Brazilian standardization. Genetic algorithms are used to
solve the optimization problem by finding the combination of geometry of the steel profile, characteristic strength
of the concrete and degree of shear connection that minimize financial cost and CO2 emission. Finally, this
methodology is applied to problems mentioned in literature for comparison and validation purposes.

Optimal orientation of cross-sections of columns of 3D steel frames in a single and multi-objective optimization

Julia C. Motta — 2024-06-15

In most structural optimization problems, the minimization of the structure’s weight is a traditional
objective. Furthermore, it is expected to improve other aspects of the optimum design, leading to conflicting
objective functions. This paper analyses single and multi-objective structural optimization problems of a six-story
space steel frame, considering the structure’s weight minimization as the first objective function and the second one
concerning the maximum horizontal displacement at the top of the frame to be minimized. The design variables are
the profiles assigned to the beams and the profiles assigned to the columns in which their orientations, concerning
the principal axes, are also design variables. Pareto fronts with the non-dominated solutions are presented. A
Multi-Tournament Decision method is adopted to extract solutions from the obtained Pareto fronts based on the
decision maker’s preferences. The search algorithm adopted is the Third Step Differential Evolution (GDE3)
coupled with an Adaptive Penalty Method (APM) to handle the constraints.

Environmental Impact and Cost Analysis on the Optimum Design of Composite Frame System

Paulo A. T. Arpini — 2024-06-15

The objective of the present work is present the optimization problem with a focus on the financial and environmental
impacts of a system formed by a column of steel columnsthat support a floor with beams and compositeslabs of steel and concrete,
steel deck formwork welded on beams, reinforcing steel mesh, crack reinforcement and different concrete compression strength
(fck). The genetic algorithm was used to find the solution to the optimization problem and the objective function is composed of
CO2 emissionsfrom the above-mentioned components. An example has been studied to demonstrate the effectiveness of the
proposed formulation.In this example, the concrete fckwas varied to a value of 50MPa for the analysis andcomparison of emission
values. The results indicated a reduction in CO2 emissions and financial cost.

Optimum Positioning of Outriggers in High-Rise Buildings Subjected to Wind Loads

Felipe M. B. Parfitt — 2024-06-15

Regarding the design of tall buildings, there are two main criteria that are extremely relevant as the
structure height increases: maximum lateral drift (MLD) and core base moment (CBM). The position and number
of outriggers (ORs) throughout the height directly affect both aforementioned criteria. Therefore, knowing the
locations where the structural system under study is most efficient is a way to minimize even more the MLD and
CBM. This work aims to perform a structural optimization of the OR location along the structure height using a
heuristic algorithm in order to find its optimal positions/quantities for each criterion separately. In addition, a
multi-objective optimization is performed with the intention of obtaining the Pareto frontier. Therefore, in order
to achieve this objective, a three-dimensional parameterized numerical model of a tall building will be employed
under the action of the lateral wind loads.

Comparison of multi-objective particle swarm algorithms for truss design optimization

Erica C.R. Carvalho — 2024-06-15

Multi-objective structural optimization problems (MOSOPs) with two or more objectives are extensively
considered in the literature. Due to the great interest in solving these types of problems, several Multi-objective
Evolutionary Optimization Algorithms (MOEAs) have been developed. They are applied to problems in several

fields, mainly engineering. This paper compares multi-objective optimization algorithms based on swarm intel-
ligence and applies them to solve structural optimization problems concerning three objectives. The objective

functions are the weight, the natural frequencies of vibration, and the maximum nodal displacement, considering
stress constraints. The design variables, discrete or continuous, are the cross-sectional areas of the bars. Some
traditional benchmark problems in the literature in structural engineering applications were performed. Finally,
Pareto sets are presented where a Multi Tournament Decision (MTD) method is adopted to extract the desired
solutions from these problems.

Multi-objective optimization of ground structures with constraints of over- lapping bars and maximum stresses

José P. G. Carvalho — 2024-06-15

Structural multi-objective optimization problems are common in real-world problems of the Engineering
field where one or more objective functions may be considered and desired to be optimized. In general, these
functions are conflicting, leading to complex optimization problems. This paper analyses the multi-objective
structural optimization of truss ground structures considering the weight minimization (or volume) as the first
objective function and compliance as the second one. The constraints refer to the allowable axial stresses in the
bars and also the bars overlapping. Thus, the structural optimization problems consider sizing and topology design
variables simultaneously, and they can be continuous, discrete, or mixed. After obtaining the Pareto Front, one of
the most important steps is defining which solution or solutions will be considered after obtaining the Pareto curve.
Unfortunately, this task is not trivial, and a Multi-Tournament Decision method is applied to extract the solutions
from the Pareto based on Decision-Maker preferences. The search algorithm adopted here is a modified version of
the Differential Evolution called Third Evolution Step Differential Evolution (GDE3).

A VON MISES STRESS-BASED TOPOLOGY OPTIMIZATION OF CONTINUUM ELASTIC STRUCTURES THROUGH THE PROGRESSIVE DIRECTIONAL SELECTION METHOD

Luiz C. L. Véras — 2024-06-15

This work presents a study applying the von Mises equivalent stress as a performance parameter for
topological optimization of two-dimensional continuous elastic structures employing the Progressive Directional
Selection (PDS) method. A typical objective to achieve the ideal topology of a structure is to define the best
material distribution of the design domain, considering an objective function and mechanical constraints. In
general, most studies deal with minimizing the compliance of structures. Numerical methods for optimizing the
topology of continuous structures have been widely investigated. Most of these methods are based on finite element
analysis, where the design domain is discretized into a fine mesh of elements. Evolutionary Structural Optimization
(ESO) is one of these methods based on the simple concept of gradually removing inefficient finite elements from
a structure. This method was formulated from the engineering point of view that the topology of the structures is
naturally conservative for safety reasons and contains an excess of material. In such a context, the optimization
consists of finding the optimal topology of a structure and determining whether there should be a solid or void
element for each point in the design domain. ESO's algorithms are easy to understand and implement. The stress
level of each element is determined by comparing the von Mises stress of the element and the maximum von Mises
stress of the entire structure. After each finite element analysis, elements that present a stress level below the
defined rejection ratio are excluded from the model. However, the ESO is a heuristic method, and there is no
mathematical proof that an optimal solution can be achieved by eliminating elements. In addition, the original
approach is inefficient because it needs to find the optimal topology comparing several solutions generated
intuitively, adjusting the rejection ratio and evolutionary rate. To avoid this problem, but taking advantage of the
simplicity of applying ESO, a new approach using the PDS method is proposed, inspired by the natural directional
selection observed in biology. In the first work using PDS, the optimization problem was the minimization of the
strain energy of a structure analyzed through the Finite-Volume Theory (FVT). This investigation discusses a
scheme to minimize the von Mises equivalent stress of a discretized domain with a volume constraint. One example
of topological optimization of 2D continuous elastic structure inspired by a classic literature problem is
investigated.

A strategy for the optimal design of steel portal frames

G. S. Brasil — 2024-06-15

This article presents a strategy for the optimal design of single-span steel portal frames used in the
primary framework of single-story buildings. A methodology that integrates a structural analysis program and a
heuristic optimization algorithm for the design process is developed and evaluated. The methodology is applied to
the design of single-span symmetric pitched roof portal frames fabricated from built-up welded I-shaped sections
with rigid connections. Geometric properties of beams and columns cross-sections are optimized for the
minimization of the weight of the portal frame. The flange width and the total section depth are taken as continuous
design variables, while web and flange thicknesses are limited to the discrete standard values. The portal frame is
subjected to self-weight, the secondary elements weight, the service load and wind load. The optimization
constraint functions include checks of serviceability and ultimate limit states given by Brazilian standards.
Numerical experiments indicated that the proposed strategy produce high quality design with reasonable
computational cost. Additional tests showed that increasing the number of iterations of the optimization algorithms
or reducing the range of the design variables based on engineering judgment may improve the efficiency of the
design strategy.

A TIME DOMAIN FATIGUE PROBLEM TAYLORED INTO FREQUENCY DOMAIN THROUGH AN OPTIMIZATION APPROACH

Raphael Paulino Gonçalves — 2024-06-15

Time domain is the most broadly choice in fatigue testing to completely represent random events,
happening in numerous synchronous input channels. The primary disadvantage of this approach is the broad testing
span and equipment cost. Time domain-based equipment tests are made from an intricate equipment, which
requires servo engines be working to instigate an amount of load at a particular time window. These tests spend a
huge time cost, since they require a similar length span of the event that they are repeating, times the necessary
reiterations. The frequency domain strategy for fatigue testing requires less intricate equipment, since there is no
requirement for servomotors. Moreover, the test length is reduced, since there is no compelling reason to run the
full event times the necessary reiterations. The current disadvantage is the limitation to represent random events
with different synchronous information channels. Thus, frequency domain tests are mainly applied for basic binary
tests, unfit to represent random events. This work aims to introduce another approach that utilizes the fatigue result
as input, reversing it to discover the loads that would be required to replicate the result in frequency domain. This
can help future developments reducing costs and time required for fatigue testing. Optimization approaches and
computations simulations are applied to solve this inverse problem.

A discussion on ideal and nonideal systems

Reyolando M.L.R.F. Brasil — 2024-06-15

In this paper we discuss the nature of the so called ideal and non-ideal models for a two-degree-of-
freedom unbalanced motor foundation. In the latter model, the mutual interaction between the machine and the

foundation is taken into account, while in the former only the action of the motor on the foundation is considered.
In the non-ideal system, for limited power conditions, the so-called Sommerfeld Effect may occur, of stagnation
of rotation frequency before resonance peaks. If mode energy is available to overcome this situation, a jump occurs
to considerably higher frequency rotation regimes, no intermediate stable steady states in between.

Acoustic vibration environment prediction for Amazonia 1 satellite using SEA method

Bruno C. Braz — 2024-06-15

The dynamic vibration environment applied to a satellite during its launch is predominantly acoustic.
Therefore, the prediction of acoustic levels and the satellite and its onboard equipment vibroacoustic responses
are mandatory in all project phases. In this sense, one of the most important tests to qualify a satellite for flight is
the acoustic vibration test, whose levels are usually specified by launcher vehicle manufacturer. In the first
phases of a project, several viability studies may be running simultaneously and important changes in structure
design and even in concept can occur. Thus, a method that can produce analyses with low computational cost in
a short period of time and with a reasonable accuracy would simplify the development process and reduce its
costs. Usually, the acoustic analysis is performed by using the finite element method (FEM) for lower
frequencies and statistical energy analysis (SEA) for higher frequencies. The present work describes the use of
SEA method to perform the vibroacoustic analysis of Amazonia 1 satellite, a satellite developed by Instituto
Nacional de Pesquisas Espaciais (INPE). The numerical results are compared to acoustic tests results performed
at INPE on the satellite structural qualification model. Amazonia 1 is a remote sensing satellite designed by
INPE to provide images on green, red, blue and near infrared (NIR) bands with resolution better than 70m with
the goal to monitor forests, vegetation, agriculture, coasts, and others areas.

Modeling and simulation of an aircraft’s hydraulic distribution system based on a LMS Amesim® Model and a Bond Graph support

Marcos P. Caldas — 2024-06-15

This paper presents two different and complementary modeling techniques to analyze the main char-
acteristics of hydraulic systems and identify potential failure scenarios. To assess the behavior of system relevant

variables the LMS Amesim® was used and a dashboard was developed to enhance the post simulation analysis of
the aircraft operation. As a study case, a typical commercial aircraft hydraulic architecture was modeled and some
failure scenarios were studied, such as single engine failure during take-off, complete propulsion system failure
during the flight, and also a normal landing operation. In parallel, a bond graph diagram representing the system
components is developed as a support tool to provide a more detailed understanding of the modeled physics.

Computational aeroelastic analysis of a competition cargo UAV of box wing type

Geraldo M. N. Junor — 2024-06-15

SAE aero design is a competition in which university teams design a radio-controlled cargo aircraft
aiming to obtain its highest structural efficiency. Several unconventional configurations have been developed and
the aeroelastic analyses during the design phase must be well established. Analytical aeroelasticity methods are
difficult to implement in unconventional aircraft, given the difficulty of obtaining the structural interaction of all
components. Besides, the analysis needs to have a well-defined modeling workflow to not obtain erroneous results.
The main objective of this work is to contribute to the aeroelastic analysis of an unconventional box wing type
aircraft and also to assist aero design competitors, through the implementation of an aeroelastic analysis workflow
in a real aero design project. The work starts with the elaboration of a CAD model for the selected aircraft, followed
by the construction of a finite element model for the structural model. To represent the unsteady aerodynamics,
aero panels were used accordingly to the Doublet Lattice Method and then interpolated with the structural mesh,
allowing a complete aeroelastic analysis. Both static and dynamic aeroelasticity analyses were conducted. The
initial results showed that the aircraft would present flutter inside the flight envelope, so it was necessary to apply
flutter suppression techniques by modifying the geometry and structural elements to mitigate the problem. The
work presents aeroelastic information about the box wing aircraft configuration as well as techniques for solving
problems related to this kind of geometry. An aeroelastic workflow for an aero design aircraft is presented aiming
to assist aero design teams to carry out their aeroelastic projects.

Aircraft anti-skid system modeling and simulation during landing runway path using Simcenter Amesim® and Bond Graphs for failure condition performance evaluation

Amorim J. P. F. — 2024-06-15

Anti-skid is an electro-hydraulic control, applied in a brake system, that works to prevent aircraft
wheels to lock and slip, mainly with runways under wet or icy conditions. Velocity sensors at the wheels measure
its braking rates. If the speed decreases too rapidly, this could indicate wheel lock-up. In these situations, anti-skid
control acts to relieve pressure at the brakes, so the wheels could be unlocked to prevent slipping.
A business aircraft was selected as a case study, in which the main landing gear system consists of 4 wheels (2
on each side). Brakes are operated by a hydraulic system, which is composed of two segregated hydraulic pressure
sources, actuating on the internal and external wheels, respectively. This configuration prevents inadvertent yaw
movements in the case of failure in one of the hydraulic sources.

The goal of the present work is to model an anti-skid system using bond graph methods and making sub-
sequent computational modeling in Simcenter Amesim®. The model takes into account several effects such as

the contact between tires and runaway; the contact between braking discs; braking disc thermal inertia; hydraulic
actuator dynamics; hydraulic servo-valve dynamics and electric system PID control.

Modeling and Simulation of Shimmy Behavior in an Aircraft Steering Sys- tem Using Bondgraph-based Software

Bruno A. Regina — 2024-06-15

Most aircraft steering architectures do not actuate the system during landing, allowing the aircraft to

align itself to the runway track. This lack of control results in a condition where the wheels may experience high-
amplitude and high-frequency oscillations, known as the shimmy effect. One of the methods for preventing this

phenomenon from happening is to connect the piston chambers to anti-shimmy valves, acting as a damper for
the steering oscillation. In this paper we present the modeling and simulation of shimmy in an aircraft steering
wheel using a bondgraph-based software. The paper presents a simplified model of a rack-pinion steering wheel
system under landing conditions. Later, anti-shimmy valves are included and their effect in the model dynamics is
evaluated. Tire-pavement interactions are modeled through the Pacejka Formula, informally known as the ”Magic
Formula”, which was adapted for the aeronautical context. Simulations are made using Simcenter Amesim 15.2,
where the model is implemented using components found on the Student Version library. The model fully captures
the shimmy behavior and allows one to visualize the importance of the anti-shimmy valve diameter on steering
dynamics.

Structural and Modal Analysis of the L75 Rocket Engine Turbine Disk at Operating Conditions

Daniel Bourdon — 2024-06-15

The development of a biofuel turbopump was initiated at the Institute of Aeronautics and Space (IAE)
in 2013 under Brazilian Space Agency (AEB) support and in the context of the L75 Rocket Engine project. The
turbopump is composed by an oxidizer pump, a fuel pump and a supersonic-flow single-stage turbine. Due to the
high rotational speed and high temperature it is subjected for, the turbine is considered one of the most critical
components of the rocket engine. In this study, an appropriate structural and modal FEM analysis of the turbine
rotor is performed. Temperature and rotational influence on material properties, the temperature gradient,
rotational speed and gas pressure distribution effects are considered. The main failure modes of the L75 turbine
are elastic deformation, plastic deformation, high-cycle fatigue and low-cycle fatigue. It was not considered creep
as a failure mode due to the short life the turbine is designed for. Therefore, a thermo-elastic and a modal analysis
of the turbine rotor are performed using a FEM commercial software, considering actual operation environment
conditions. The results are presented graphically, a discussion is carried out and a design modification is proposed
in order to reach the turbine requirements.

São Paulo Airplane: Model and Evaluation

De Aguiar, João B. — 2024-06-15

Dimitri Sensaud de Lavaud developed the first airplane designed, constructed and tested in Brazil. The
flight of the São Paulo airplane, as named, took place in 1910 in Osasco, nearby São Paulo. The design was
inspired in a monoplane of Louis Blériot. Dimitri himself was the pilot. The airplane construction, included
structural and mechanical components, the engine for example, used materials and shop machines available in
the country on those days. The plane flew a short, but certified distance, before it crashed with the soil due to an
engine stop. Little is known of the design of that important airplane however. Hence, in this work a model of the
airplane is created in computer to make an analysis. From drawings and a replica of the plane, a structural model
is developed using the finite element method. Based on its characteristics, some airplane parameters are also
estimated. An evaluation of the structure to some forms of failure is then conducted. Aside the simplicity of design,
materials and inherent technological difficulties, the design reveals being fit and robust

Vibration Modes Localization in Aircraft Engines Turbine Blades

Reyolando M.L.R.F. Brasil — 2024-06-15

The present work refers to the identification and analysis of structural issues in aeronautical engine
blades referring to the possible occurrence of the Phenomenon of Vibration Modes Localization. We study the
distribution of vibrational energy in turbine models in which a large number of nominally identical subsystems
(the blades) are coupled by the rotor to which they are attached. Thus, an analysis was adopted considering, first,
an ideal model, where we have characteristics, such as length, stiffness, angle of the blades etc., given as identical
for all subsystems. In this case, the vibration modes extend to the entire set of blades. Next, the model is considered
for a more real consideration, varying certain structural characteristics of the blades (in this work, the focus was
on varying the length of the blades). It is shown that, in this type of more real model, the Phenomenon of Vibration
Modes localization in Aeronautical Turbine appears and must be considered. In this phenomenon, the vibration
energy ends up being located in only part of the system, sometimes in a single blade. For these analyzes, the Matlab
language was used in a program based on the Finite Elements Method to identify the vibration modes of a cyclic
system such as turbine, generating graphs to allow a better visualization of the presence of this phenomenon and
the comparison between the models, real and ideal. This work is carried out using matrix structural analysis and
we consider real geometric characteristics of jet turbine motors for a more accurate modelling. Geometric stiffness
due to traction centrifugal forces are also taken into account, as such turbines rotate at very high frequencies. A
case study of a N2 turbine of the CFM56 engine is presented. Failure to monitor this phenomenon by manufacturers
and maintenance companies can result in serious incidents related to overload or fatigue, of one or more blades in
the system.

Dynamic Analysis of Aircraft Floors

Reyolando M.L.R.F. Brasil — 2024-06-15

In this paper, we present a study of the dynamic analysis of aircraft floors. These are usually constructed
of either composite materials plates or metal plates resting on longitudinal spars. In either case, bending of multiple
materials layers must be considered. As we are studying vibrations, that is, small displacements about a static
equilibrium configuration, small strains are also to be expected, leading to validity of the assumption of linear
behavior of all involved materials. Further, we also consider valid Bernoulli-Euler’s Hypothesis that plane sections
remain plane after bending, that is, strains are linearly proportional to the distance of a particular layer to the
neutral axis of the section, whose position must be determined via equilibrium considerations. Thus, an equivalent
Young’s Modulus can be determined. After this phase of the analysis, usual linear vibration frequencies and modes
computation can be carried out either via the Finite Element Method or closed form solutions available in literature.
We also present forced vibrations due to people motion on the floor using a Fourier approach.

Origami-based metamaterial to attenuate the impact load in a landing gear for the recovery of the Microsatellites Launch Vehicle first stage

Hernani Cordeiro Dionísio — 2024-06-15

The metamaterials have been studied and pointed as the future of many engineering areas, such as
mechanical, aeronautical, civil and electrical. A metamaterial structure differs from another due to the geometry
of the unit cell, which provides unique physical properties. Among those properties, it is found the high capacity
to absorb and mitigate impact loads. It was verified the viability of applying an origami structure in a landing gear
for the Microsatellites Launch Vehicle (VLM-1), the binational project between Brazil and Germany, aiming to
recover its first stage. The dynamic response of that structure is compared to a classical structure and the reaction
force in the connection between the vehicle and the landing gear is mainly analyzed. The verification was carried
out numerically, though impact analysis simulated in the commercial software ANSYS®. The results reveal that the
studied application is feasible, attenuating the force reaction in the extremities of the leg in contact with the vehicle.

ASSESSMENT OF THORACIC INJURY PROBABILITIES IN AIRCRAFT PASSENGERS DURING EMERGENCY LANDINGS

Fabio Matiello — 2024-06-15

Over the years, airliners have been pushing passengers closer to each other in order to increase profit.
One of the measures being taken is the reduction of pitch (distance between seats) in commercial aircrafts. This
work uses dynamic simulations to examine how pitch values affect the passenger safety. By using numerical
methods, a belted dummy is placed seated behind another seat, at different distances and the model is, then,
subjected to longitudinal and lateral accelerations. CTI – Combined Thoracic Index and AIS – Abbreviated Injury
Scale criteria are used to measure the probability and severity of injury in each case. This work complements
previous studies, which have focused on head and neck injuries.

DETERMINATION OF THE FIRST NATURAL FREQUENCY OF VIBRATION OF A STEEL POLE, UNDER THE EFFECT OF GEOMETRIC NONLINEARITY, USING OPTIMIZATION TECHNIQUES

Paulo H. dos S. Matos — 2024-06-15

This work aims to find a procedure to obtain an alternative formulation that represents the first mode of
vibration of slender steel poles considering the effect of geometric non-linearity, using the Reyleigh-Ritz method,
trigonometric formulations with optimization techniques and a finite element mathematical model of an existing
polygonal steel pole. In order to consider the geometric non-linearity in the calculation of the natural frequencies
of the respective structure, the concept of initial stiffness, geometric stiffness and effective stiffness computed by
the Rayleigh method for vibration problems in mechanical systems was used. So, to optimize the time to obtain
the modal response in the dynamic analysis of the described structure, without replacing the precision of the results
of a rigorous analysis with sophisticated methodologies, alternative formulations to those described in NBR 6123
(1988) will be presented in this work.

Integrative backstepping for one link manipulator quadrotor trajectory tracking

Reginaldo Cardoso — 2024-06-15

The Unmanned Aerial Vehicle Manipulator (UAVM), is a robotic system formed by a UAV equipped
with a manipulator and because of their high maneuverability and vertical takeoff and landing is possible to perform
activities in small spaces. To face the dynamical coupling challenges, a mathematical model of the UAVM in
the vertical plane is developed, considering a quadcopter UAV, with three degrees of freedom, equipped with a
planar manipulator with one degree of freedom. The model is based on the classic Euler-Lagrange equation,
considering the aerodynamic effects on the vehicle and the manipulator (drag forces), neglecting the effects of
rotors on the manipulator. A backstepping control approach, divided into two sub controls, position control and
attitude control, is studied. The controller is tested through numerical simulations for cases of passive and active
manipulation, while the vehicle is tracking a trajectory. Movements of the vehicle with the manipulator locked
showed the smallest errors in trajectory tracking. Both vehicle and manipulator moving simultaneously, make
the error increase. Therefore, it is recommended that the vehicle only performs decoupled movements, avoiding
sudden changes in the UAVM center of mass (CoM).

Tuned Mass Damper Passive Control of Aircraft Wings Vibrations

Kaique M. M. Magalhães — 2024-06-15

In this paper we study passive control of aircraft wings vibrations using simple Tuned Mass Damper
(TMD). This kind of structures are prone to large amplitude oscillations excited by time varying lift and drag
forces, especially in turbulent conditions. These are low frequency vibrations, mainly in the first mode of vibration,
as the stiffness is also low due to large cantilever spans and small thickness. We propose to include a thin cantilever
metal bar inside the wing, carrying a point mass at its tip. This subsystem will be tunned so to be approximately
in resonance with the first wing vibration mode. Numerical modeling and simulation of the system, via the Finite
Element Method (FEM), will be performed to check the efficiency of this proposed Tuned Mass Damper.

An EKF formulation for pose estimation of a landing platform fixed to a moving vehicle for an autonomous landing system

Eder A. Moura — 2024-06-15

Automatic landing systems are heavily dependent on sensors to map the environment around the aircraft
in order to support the subsequent control strategy to accomplish the task. This work proposes a discrete-time
Extended Kalman Filter (EKF) formulation, using camera measurements, to estimate the position and orientation
(yaw) states of a landing platform, fixed on top of a Ground Vehicle (GV). GV moves freely at constant speed
The camera is attached to an Unmanned Aerial Vehicle (UAV) and is pointed down. For each image taken by the
camera, a computer vision algorithm returns the relative position and attitude (pose) of each identified marker. Its
is adopted the open-source library Aruco for generating the printable square-based fiducial markers. Its adoption
is justified because it allows quick fixation to the landing platform, being easily detectable and providing a robust
determination of the relative pose. The EKF is formulated as a constant velocity model for the pose estimation.
The simulation consists of the UAV following the GV along a path, where the desired states are estimated from
noise-corrupted measurements. The proposition is validated via Monte Carlo simulation. The results showed that
the proposed formulation for the EKF is able to estimate the desired states when operating at low speeds.

Wave propagation in acoustic ducts with periodic side branch resonators

Flaianny B. Pacheco — 2024-06-16

This paper presents the behavior of an acoustic duct with periodic side branch tube resonators commonly

used as a noise control device, which can be tuned to enlarge the resonance bandwidth and improve the transmis-
sion loss. An interesting approach to obtain a broader attenuation range in a duct consists in to distribute side

branches tubes resonators periodically along the duct. This generates some frequency bands, known as bandgaps,
where harmonic waves do not propagate. Bandgaps are generated based on the special frequency of mismatched
impedance areas which produce Bragg scattering (destructive acoustic interference) and local resonance effects
from the duct-tube system. This work investigates bandgaps created in duct-tube system using acoustic transfer
matrix method and finite element models. Numeric results are presented as dispersion diagrams, sound pressure

level and transmission loss. These results are discussed and compared with each other. Periodic geometry varia-
tions of the side tubes are also investigated.

ANALYSIS OF A FINITE STAGGERED PERIODIC BEAM DYNAMICS UNDER DIFFERENT BOUNDARY CONDITIONS

Vitor P. Giolo — 2024-06-16

Passive solutions for the vibrations control via metamaterials have gained relevance due to the possi-
bility of developing a considerable vibration attenuation on lightweight and compact structures, with competitive

performance in certain frequency bands. In this context, the modelling of these periodic systems has central impor-
tance in the design of such structures, allowing for sensitivity analyses, design refinement, and even, optimisation.

Two families of modelling procedures can be highlighted: those that require the full system to be modelled, in-
cluding the full structural domain, boundary conditions and external loads (if needed), and those that are based on

a single unit-cell model under periodic boundary conditions, more compact than the latter but with some important
limitations, e.g. the representation of global boundary conditions and external loads. Typical solutions for the

modelling of dynamic systems make use of numerical methods, such as the Finite Element Method (FEM); how-
ever, this may become an unlikely alternative in systems that have a very large number of degrees of freedom due

to the high computational costs involved. Regarding the modelling of periodic systems, the Wave Finite Element
(WFE) approach has been presented as an interesting alternative due to the possibility of reducing the computation
effort, as it is based on an FEM model of a single unit cell, with the force/displacement relationships between 2

adjacent unit cells determined through the transfer matrix. The WFE requires the resolution of an eigenvalue prob-
lem, which may present ill-conditioning depending on the properties of the system. In this study, the dynamics of

staggered periodic beams are evaluated using the WFE approach to calculate the forced response in the frequency
domain of such systems subjected to a bending load. The influence of different boundary conditions imposed on

an increasing number of unit cells (the so-called metastructure) is evaluated against vibration attenuation perfor-
mance. In addition, the results obtained via FE and WFE are compared and contrasted both, in terms of accuracy,

and in terms of computational effort.

Dispersion relation of flexural waves in metamaterial plates with periodic shunted piezo-patches

Edson J. P. de Miranda Jr. — 2024-06-16

The wave propagation in a 2-D mechanical metamaterial plate with periodic arrays of shunted piezo-
patches is investigated. This piezoelectric mechanical metamaterial plate is capable of filtering the propagation of

flexural waves over a specified range of frequency, called band gaps. The dispersion relations are obtained by the
improved plane wave expansion (IPWE) and extended plane wave expansion (EPWE) methods. The Bragg-type
and locally resonant band gaps are opened up. The shunt circuits influence significantly the propagating and the
evanescent modes. The results can be used for elastic wave attenuation using 2-D piezoelectric periodic structures.

Band gap and modal interaction analysis of metastructures with high-static- low-dynamic stiffness with multiple scales

Diego P. Vasconcellos — 2024-06-16

In this work, we explore the dynamical response of metastructures with high-static-low-dynamic stiff-
ness (HSLDS) characteristics, with focus on the vibration attenuation performance through band gaps and band

stops. A metastructure consists fundamentally of identical components, the cells, connected in a way that charac-
teristics of mass, stiffness, and or damping are spatially repeated. Metastructures present interesting characteristics

for vibration attenuation that are not found in classical structures. These characteristics have been explored for

automotive and aerospace applications, among others, as structures with low mass are paramount for these indus-
tries, and keeping low vibration levels in a wide frequency range is also desirable. One unit cell with three degrees

of freedom is used, with an axial harmonic force applied at the rightmost element. The dynamical response of the
linear metastructure is found by mechanical impedance and transmissibility methods. The cell dynamical response
of the nonlinear metastructure is found using the method of multiple scales (MMS), and the response is compared
to the fourth-order Runge-Kutta method (RK). The influence of the mass ratio between the elements of the cell and
number of cells in the complete structure are analysed in the frequency response of the metastructure.

A Review of Acoustic Metamaterials applied to noise control in Civil Engineering

Caio Zanin — 2024-06-16

Over the past 10 years, the research of acoustic metamaterials has branched out in many directions,
presenting numerous potentially applicable geometries for the composition of noise control structures, such as
structural resonators, acoustic resonators, and membranes. Therefore, keeping track of these multiple applications
can be considered a rather difficult task. Moreover, the application of this novel concept in civil engineering has a
high potential. In this context, an article review is proposed, identifying the most important acoustic metamaterial
concepts that were applied or could be applied in civil engineering. The study performs a qualitative survey of
articles in this segment, classifying the leading literature proposals, according to physical principles of cells
working and to the facility of application in civil engineering, considering the production factors and construction
implementation. It was found that the number of works with this focus is incipient when compared to the strictly
theoretical works. A great number of articles contain dimensions and geometric propositions that feature
difficulties of precise and large-scale manufacturing in the current civil construction scenario, which is
traditionally less industrialized and technological. Finally, the advantages and disadvantages of the physical
principles and acoustic structures were compared to point out ways that allow the development and popularization
of acoustic metamaterials in civil engineering.

Vibration attenuation in a graded metamaterial rod

Fabio C. M. Oliveira — 2024-06-16

In this work, a broadband vibration attenuation approach using a graded metamaterial rod is proposed.
A set of spring-mass local resonators with different spacing are attached to an elastic rod to obtain a graded
metamaterial rod. Instead of a single local resonator, two or more integrated resonators are used in each unit cell.
The Finite Element (FE) method and the Spectral Element(SE) method are used to model the graded metamaterial
rod. A simulated study is conducted to investigate the effects of the length spacing in the graded metamaterial rod.
Simulated example results in terms of attenuation constant, frequency response function (FRFs), transmittance and
dispersion diagram are presented and discussed.

Periodic structures with exponentially varying cross-section areas

Camila A. X. da Silva — 2024-06-16

Periodic structures have been used for many years in different areas such as aerial and terrestrial
vehicles, civil engineering structures and many other products. The term periodic structures come from the
repetitive arrangements of smaller structural units, also known as cells. Among the different phenomena
concerning wave propagation of such systems, the most important is probably the Bragg scattering effect. The
Bragg scattering occurs when the wavelength becomes of comparable size to the structural cells. This results in
frequency ranges where waves cannot propagate, known as bandgaps. In this context, this paper proposes the study
of the formation of bandgaps on a mono-coupled periodic structure consisting of longitudinal wave propagation
in rods. The paper proposes the modeling and analysis of finite periodic structures with exponentially varying
cross-section area. An investigation is conducted on the effects of using symmetric and asymmetric cell matrices.
The structure is modeled using the receptance and dynamic stiffness matrices. The transfer matrix method is used
to determine the properties of the structure from the transmissibility of a single cell. Results show that asymmetric
cells have a wider frequency range when compared to symmetric cells; however, occurring at higher frequencies
ranges.

Acoustic metamaterial modeling using space-coiling resonators

Luciano S. Oliveira — 2024-06-16

In the last decades the development of metamaterial has motivated new solutions for noise control,
where labyrinthine type absorbers emerged recently. Due to their attracting features, these types of absorbers have
been investigated. The strategy is to bend and coil up quarter-wavelength sound damping tube. The original bulky
volume is decreased into a subwavelength scale, and the absorber with a coiling chamber can produce a high sound
absorption at low frequency. The aim of this paper is to establish reliable analytical and numerical approaches for
the designing and modeling of an effective metamaterial with space-coiling resonators. A duct-resonator acoustic
device is modeled by the Transfer Matrix (TM) and the Finite Element (FE). Simulated examples are performed
and the compared between the methods. The duct-resonator efficiency to attenuate the sound is evaluated.

Attenuation of Vibration and Mass Reduction using a Finite Hollow Periodic Rod

Jean P. Carneiro Jr. — 2024-06-16

Through the decades, periodic structures have been studied using different models and configurations,
and recently, metamaterial design has emerged as a hot topic for research. The effect of creating pass and stop
bands for this type of system considerably expands the possibility of applications. However, there is a knowledge
gap regarding practical analysis, which relates attenuation gains with physical properties, such as structural mass.
This work presents a design improvement to increase vibration attenuation and mass reduction for a periodic rod.
Asymmetric cells are considered using solid and hollow configurations. Using the transfer matrix method,
displacement transmissibility expressions are derived as a function of the internal diameter. Numerical simulations
show that a structure with hollow cells results in a reduction of 24% in the minimum transmissibility and a
reduction in mass of about 40%, compared to a similar structure with solid cells.

Design of tunable shunt rainbow trap smart beam for multi-frequency vibration attenuation

Matheus C. R. Borges — 2024-06-16

This paper analyzes a strategy for tunable, broadband vibration attenuation in electro mechanics alone-
dimension guided wave coupled with shunted piezoelectric. The piezo patches are in periodic arrays over the beam.

They are connected in shunt circuits that resonate at distinct neighbouring frequencies, creating a tunable rainbow
trap capable of attenuating vibration with broadband characteristics. Based on the effect of electrical energy
dissipation, the shunt circuit connection is applied to provide damping in the system vibration. An efficient method
to model and analyze the dynamic of structures is the spectral elements method (SEM). Although, a single spectral
element can model geometrically uniform members. Therefore, it can reduce the total number significantly in the
mesh. Results show the efficiency in attenuating vibrations over a broad frequency range can be obtained by tuning
different shunt circuits to resonate at different frequencies, which create a tunable rainbow trap.

Noise control in ducts using local resonator acoustic metamaterial arrays.

Higor G. Pozza — 2024-06-16

Acoustic local resonators (Helmholtz, side branch, expansion chamber etc.) are usually used to control
noise in acoustic systems. Noise attenuation in local resonators occurs due to impedance mismatch of incident,
transmitted, and reflected waves induced by the addition of resonators. The frequency band and the attenuation
level generated by the resonator depend on its geometry and behave as a narrow-band filter. However, if they are
distributed properly (periodically or not) along the duct length, a much larger frequency band, called bandgap, is
obtained. In this paper, acoustic metamaterial noise attenuation is investigated using the transfer matrix method and
assuming plane wave propagation. Also, a study about the arrangements of the local resonators (serial and parallel)
is conducted to verify the method accuracy and efficiency related to band width enlargement and transmission loss.
Simulated results are obtained for different examples and geometries.

Modeling and analysis of periodic and quasi-periodic sandwich structures with internal resonators

Marcelo A. Trindade — 2024-06-16

The use of internal resonators, acting as vibration absorbers, for low-weight closed periodic structures,
such as honeycomb core sandwich plates is an interesting alternative for vibration control treatments that do not
rely on significant strains on the host structure. One of the main challenges for the study of such solutions is the
computational cost required for their analysis, design and optimization. This work presents a modeling strategy and
procedure applied for periodic and quasi-periodic sandwich structures with internal resonators aiming at reducing
the required computational cost while still allowing parametric analysis, design and optimization.

INFLUENCE OF PARAMETRIC VARIATION IN BANDGAPS FOR ONE- DIMENSIONAL STRUCTURES

Wanderson V. O. Monteiro — 2024-06-16

In engineering projects where the noise reduction or vibrations is desired, some control methodologies
are applied in order to provide safe and comfortable environments. For that, structural dynamic analysis is done to
verify the effects of wave propagation in the structure. Focusing on this analysis, a parametric variation on elastic
rods phononic crystals (PCs) was performed. The rods are made by two types of materials spatially distributed
periodically along its length. Each period will form a cell, in which was made the variation of the proportion of
each material in order to observe its influence on the bandgap formation. Another approach to have the formation
of the bandgap was the variation of the cross section of the cell. Those analyses were made both separately and
assembled. It was used the Spectral Element Method – SEM to obtain the results. FEM was used to validate the
results. Then, it was possible to obtain the rod behavior due the change of the proportion of materials and cross
section. In the case of the two variations there was a coupling of Bragg scattering effect, allowing both an increase
in its frequency band and in the attenuation level.

Using the de Rham sequence for accelerating mixed finite element computations

Jeferson Wilian Dossa Fernandes — 2024-06-16

Mixed finite element computations arise in the simulation of multiple physical phenomena. Due to its

characteristics, such as the strong coupling between the approximated variables, the solution of such class of prob-
lems may suffer from numerical instabilities as well as a computational cost. The de Rham diagram is a standard

tool to provide approximation spaces for the solution of mixed problems as it relates H1

-conforming spaces with
H(curl) and H(div)-conforming elements in a simple way by means of differential operators. This work presents
an alternative for accelerating the computation of mixed problems by exploring the de Rham sequence to derive
divergence-free functions in a robust fashion. The formulation is numerically verified for the 2D case by means of
benchmark cases to confirm the theoretical regards.

A multiscale recursive numerical method for semilinear parabolic problems

Eduardo Abreu — 2024-06-16

We present a multiscale recursive numerical method in the context of time-dependent initial-boundary
value problems for semilinear parabolic equations with discontinuous and high-contrast coefficients. We consider

a backward Euler scheme for the temporal discretization along with an extension of the Recursive Mixed Multi-
scale Method based on domain decomposition technique, recently introduced in the literature by Ferraz [1], for

the spatial discretization of the semilinear parabolic operator. Thus, at each time step, the spatial and temporal
discretizations lead to large linearized systems of equations that involve solving local multiscale boundary value
problems followed by the solution of a family of decomposed interface problems that showed excellent scalability.
We will also briefly discuss some ideas of the proposed recursive multiscale approach for non-linear parabolic
problems, by considering efficient approximation strategies along with the reuse of the multiscale basis functions

and parallelization. Numerical examples with both homogeneous medium and heterogeneous high-contrast coeffi-
cients for semilinear problems are considered to show the behavior of the multiscale approach and our findings.

A posteriori error estimates for primal hybrid finite element methods

Victor B. Oliari — 2024-06-16

We present new fully computable a posteriori error estimates for the primal hybrid finite element methods
based on equilibrated flux and potential reconstructions. The reconstructed potential is obtained from a local L
2
orthogonal projection of the gradient of the numerical solution, with a boundary continuous restriction that comes
from a smoothing process applied to the trace of the numerical solution over the mesh skeleton. The equilibrated
flux is the solution of a local mixed form problem with a Neumann boundary condition given by the Lagrange
multiplier of the hybrid finite element method solution.
To establish the a posteriori estimates we divide the error into conforming and non-conforming parts. For the
former one, a slight modification of the a posteriori error estimate proposed by Vohral ́ık [1] is applied, whilst the
latter is bounded by the difference of the gradient of the numerical solution and the reconstructed potential.
Numerical results performed in the environment PZ Devloo [2], show the efficiency of this strategy when it
is applied for some test model problems.

An assessment of interface spaces for the accurate simulation of two-phase flows in high-contrast formations

Rafael T. Guiraldello — 2024-06-16

The design of accurate multiscale methods for the simulation of multiphase flows in channelized,

high-contrast porous media remains as an important challenge in typical problems posed by the energy and envi-
ronmental sectors. The Multiscale Robin Coupled Method (MRCM) [1] is a recently proposed multiscale domain

decomposition method, that is a generalization of the Multiscale Mixed Method (MuMM) [2]. Such method en-
sures weak continuity of both normal fluxes and pressure for local problems with Robin boundary conditions,

through low-dimensional interface spaces defined over the skeleton of a domain decomposition. The accuracy
of the MRCM depends on the choice of the functions that span these interface spaces as well as on a Robin

condition parameter. In this study we compare the accuracy of the MRCM in two-phase flow simulations with in-
terface spaces spanned by: (i) piecewise polynomial functions; (ii) informed functions [3]; and (iii) physics-based

functions [4]. We investigate the effect of such choices in approximating the saturation fields as well as the oil

production curves for high-contrast channelized permeability fields. Numerical experiments indicate that the spe-
cialized interface spaces (ii) and (iii) have the potential to produce more accurate results by better accommodating

the channelized features in comparison with standard polynomial functions.

Genetic Algorithm applied on the Optimization Problem for the Synthesis of a Walking Mechanism

Kelvin R. F. Santos — 2024-06-16

This paper deals with the synthesis of articulated mechanisms employed to simulate the walking
motion, which can be applied on robots, toys, vehicles and other legged locomotion systems. A six-bar
mechanism comprised of a four-bar linkage with an embedded pantograph is the planar mechanism chosen for
this study. The synthesis is based on the desired curve to be described by the mechanism, which is generated
with the four-bar linkage and enlarged by the pantograph. The mechanism rendered by this synthesis is compact
and presents links with small dimensions in comparison with the motion step. An optimization technique is used
to generate the curve described by the mechanism. A computational procedure based on genetic algorithm and
differential evolution is implemented to optimize the curve generation for the selected planar mechanism.

Spectral Modal Seismic Analysis of a Structure in the Republic of Ecuador

Gallardy Nery Zambrano Intriago — 2024-06-16

Republic of Ecuador is in a high seismic risk region. The country is near to the junction between the
Nazca tectonic plates and the South American one. Therefore, seismic analysis is necessary to ensure that
structures are sufficiently competent in relation to events of this nature. The analyzed building was designed
according to the 1977 Ecuadorian Construction Code, but without seismic criteria. In this context, the aim of the
study was to test the seismic behavior of this structure, making a comparison between a dynamic analysis using
response spectrum and an equivalent static analysis, from the current Ecuadorian Seismic Code. The results
showed the irregularities can affect basal shear force value final.

Effect of the cable system on the static and dynamic stability of Guyed Towers

Ícaro R. Marques — 2024-06-16

This paper aims at understanding the influence of the cable setup on the static and dynamic stability of
the guyed towers. For such, simplified models consisting of mast and cables at different inclinations and guys level
are studied. The effect of these structural characteristics is studied through a nonlinear finite element model. First,
the influence of the configuration of the guys on the linear vibration frequencies and buckling load of the mast is
investigated considering the initial deformations and internal forces due to self-weight and cable pretension.
Coincident buckling loads and vibration frequencies happen for an even cable distribution around the tower. This
symmetry condition may lead to interactive buckling and internal resonance, increasing the effect of the geometric
nonlinearities on the response of the structure. Second, the nonlinear static and dynamic frequencies and buckling
loads are determined for the different guys configurations. The results show that the towers exhibit highly nonlinear
responses, even at low load levels. Thus, the geometric non-linear behavior must be considered in the design stage.
In addition, the results indicate the necessity of further investigation of the nonlinear dynamic response of these
structures for guys setup and mast dimensions used in actual towers.

Numerical and Analytical Study of the Torsional Stiffness of a Flexible Disks Coupling

Leonardo N. Carvalho — 2024-06-16

This work presents a study of torsional stiffness of flexible disk coupling used in synchronous generators
coupled in diesel combustion engines. Stiffness analyzes are important basic systems to identify possible instabilities in
torque transmission as a function of number disks. Torsional stiffness is an important parameter for the control of
torsional vibrations in rotating machines analytically obtained based on simplified models. As it is a simplified method,
the analytical method presents results, where constructive details of the coupling are not considered. This study focused
analyzes the torsional stiffness responses considering different numbers of disks, screws pretension and disk material
through numerical solution based on Finite Elements Method (FEM). The numerical results induced that the torsional
stiffness increases in a non-linear way with the number of disks, being this behavior also identified in the analytical
solution. It was also possible to verify that the screws pretension does not affect the torsional stiffness significantly.

A membrane finite element based on position applied to the contact of fabrics with rigid surfaces

Christian L. Perlin — 2024-06-16

In this paper, a total Lagrangian and position based formulation of membrane finite elements is
employed to solve dynamic problems of contact between a non-tensioned fabric and a rigid surface. The geometric
nonlinearity is naturally considered in this positional strategy, resulting in a simple description of the membrane
elements by mapping gradients for the initial and current configuration. The dynamic solution is obtained by the
classical Newmark-β method using alternative parameters to improve numerical stability in contact analysis. The
Newton-Raphson procedure is used to solve the set of nonlinear equations. To enforce contact conditions, the
penalty technique and the Lagrange multipliers are employed. A representative example for an isotropic fabric
with frictionless contact is presented and results shown that the proposed numerical approach is effective for this
class of problems, properly evaluating large displacements and dynamic draping.

Geometric nonlinear analysis of tensioned membranes using the Positional Finite Element Method

Christian L. Perlin — 2024-06-16

This paper describes a total Lagrangian formulation of the Finite Element Method based on positions
and its application to the analysis of tensioned membranes. In these structures, the geometric nonlinearity is very
pronounced due to large displacements and the lack of flexural stiffness of the elements; therefore, the equilibrium
must be evaluated at the current configuration and the geometric stiffness plays an important role in the analysis.
The use of nodal positions as main variables allows a direct consideration of the geometric nonlinearity. For the
positional description of membrane elements, two mappings are employed: one for the initial configuration and
other for the current configuration, resulting in a simple chain rule to calculate the deformation gradient. These
mappings are defined in such a way that results in square and invertible mapping gradients for the membrane
element in three-dimensional space. In the form finding stage, the dynamic relaxation technique is employed
to find an initial prestressed configuration for further loaded analysis. Numerical examples for isotropic fabrics
are presented to demonstrate the applicability of the positional formulation in the assessment of stiffness and
displacements in this category of problems.

ANALYTICAL STUDY ON HORIZONTAL VIBRATION VELOCITY AND ACCELERATION IN SOILS NEAR RAILWAY LINES

BARROSO C. GABRIEL FILHO — 2024-06-16

Buildings are subject to vibrations caused by the environment, such as those from industry,
constructions, vehicle traffic, among others. These vibrations can damage the building over time or cause
discomfort for its users. The construction of buildings near railway lines is a reality increasingly present in large
and small cities around the world. This work shows an analytical methodology for predicting velocities and
accelerations in the soil caused by rail traffic, which affect nearby buildings, people or nearby improvements.
Using equations validated in the literature, an analysis of the physical vibrations and noise generated by train traffic
will be performed. The objective is to achieve a better understanding of the propagation of vibrations and to make
better use of regions close to the railway lines. They are verified for four soil types in order to evaluate their
influence on the propagation of the velocity and instantaneous acceleration in the horizontal axis of induced
vibration in the medium. Other parameters are also analyzed, such as the distance from the railway, train speed
and load, and the type of track. These analyses are performed using a mathematical program. In this way, it is
expected to contribute to the standardization and understanding of the behavior and propagation of vibrations
caused by the railways.

Static and dynamic nonlinear behavior of a multistable structural system

Carlos H. L. de Castro — 2024-06-16

The persistent search for new structural solutions has generated great interest from the scientific
community in understanding the static instability and nonlinear dynamics of multistable structural systems.
Structural multistability is achieved through structural arrangements that have several stable equilibrium
configurations and have a wide field of applications, such as: vibration control, self-deployable and collapsible
structures, dynamical systems with a periodic pattern and in the development of new materials (metamaterials),
among others. In this work we study the static and dynamic nonlinear behavior of a multistable structural system
formed by a sequence of von Mises trusses. For this, the non-linear equilibrium equations and equations of motion,
in their dimensionless forms, are obtained through the criterion of minimum potential energy and Hamilton’s
principle. Based on dimensionless parameters, equipotential energy surfaces and curves, non-linear equilibrium
paths, time responses, phase portraits and basins of attraction are obtained. Then a parametric analysis is conducted
to identify the influence of the dimensionless parameters on the quantity and stability of equilibrium positions.
From the results, the importance of geometric nonlinearity in the dynamics and stability in this new class of
structural systems is verified.

Análise não linear física e geométrica de placas retangulares

Daniella M. O. Aguiar — 2024-06-16

Estuda-se o comportamento estático de placas retangulares de material hiperelástico, isotrópico,
homogêneo e incompressível. As placas estão simplesmente apoiadas e são avaliadas sob efeito de um
carregamento axial na direção x e, posteriormente, um carregamento de pressão transversal uniformemente
distribuído. Ambas as não linearidades são consideradas, sendo a não linearidade geométrica incorporada com a
teoria não linear de von Kármán e a não linearidade física, por sua vez, inserida com a utilização do modelo
constitutivo hiperelástico Neo-Hookeano. O sistema de equações de equilíbrio é obtido com a aplicação do
Princípio de Hamilton e do método de Rayleigh-Ritz, e resolvido utilizando o método de Newton-Raphson. Para
a solução do problema consideram-se expansões no campo de deslocamentos de três graus de liberdade (GDL)
para ambos os carregamentos e, além disso, para o caso de pressão consideram-se doze GDL e o desenvolvimento
de um método denominado modelo local (MML). Obtêm-se as relações carga-deslocamento e observa-se a
influência da não linearidade física quando obtidos grandes deslocamentos.

Bi-modularity representation proposal of quasi-brittle materials through isotropic degradation constitutive model

Guilherme Ribeiro Caetano — 2024-06-16

Quasi-brittle materials are governed by different stress-strain laws when subjected to tension and com-
pression, so this characteristic is called bi-modularity. The classical Mazars model represents the behavior of

bimodular materials through damage variables that comprises degradation in compression and tension. These vari-
ables are obtained through an exponential type law based on a single parameter to limit the material elastic domain

and a unique equivalent strain. In this scenario, a new approach is presented. The proposed model considers
modifications in the damage calculation, employing independent damage evolution laws and equivalent strain for
tension and compression. This modification aims a better representation of the realistic behavior of quasi-brittle
materials, especially the correlation between the model parameters and the material properties.

Nonlinear vibrations of a FG cylindrical shell on a circumferential discontinuous elastic foundation

Jonathas K. A. Pereira — 2024-06-16

The nonlinear vibrations of a simply supported cylindrical shell made by a functionally graded material
with a circumferentially discontinuous elastic base is analyzed. The equilibrium equations are obtained from
Donnell's nonlinear shallow shell theory. The modal solution to the transversal displacement field, used to
discretize the equilibrium equations, is obtained by perturbation techniques. The discretized equations are
analyzed, considering a harmonic excitation in the form of the combination of the lowest vibration modes of
cylindrical shell. The chosen geometry of the cylindrical shell presents natural frequencies nearly commensurate
to an internal resonance 1:1:1:1, due to the discontinuity of the elastic base in the circumferential direction. The
nonlinear dynamic behavior is analyzed from the resonance curves that they are obtained by the continuation
method and the basins of attraction. Several resonance peak regions are observed, due to the interaction between
the modes of the transversal displacement field, showing the competition of multiple stable, quasi -periodic and
chaotic solutions. Time responses, phase portraits and Poincaré sections are also used to understand the nonlinear
dynamic behavior of the cylindrical shell.

Structural verification of an oil-cutting tank affected by corrosion and differential settlements

Cindy G. Wozniuk — 2024-06-16

Crude oil cutter tanks are essential components in the hydrocarbon production process. In Argentina's
Patagonia region, these metal tanks sit over a concrete platform, which may be affected by differential settlements
caused by uneven compaction of the soil or damage by unexpected water flow. Additional damage can occur due
to corrosion originated by the emulsifying mixture stored in the tank. This work analyzes the structural behavior
of an oil cutter steel tank with evidence of damage due to localized corrosion and differential settlements and its
structural response under wind loads. The analysis is implemented by modeling the tank with a multipurpose finite
element code following three scenarios: tank without damage, tank damaged by corrosion measured by thickness
reduction and unevenness obtained by surveying work, and progress of deterioration. Simulation results are
compared with measurements carried out on a real tank using non-destructive tests. Results show that the
equilibrium paths are non-linear, with clear signs of instability. The presence of imperfections, such as reduced
thicknesses and vertical settlements, diverts the structure from the undamaged configuration and bifurcation
buckling for much lower load levels. Reduced wall thicknesses and differential settlements generate stress
concentrations that increase the deterioration of the structure.

Theoretical analysis of the active human-structure interaction on rectangular plates

Phablo V. I. Dias — 2024-06-16

When analyzing the effect of human actions on structures, it is common to consider only the dynamic
force generated by the crowd (only force models) in the design practice, where the biodynamic properties, such as
mass, stiffness and damping, are neglected. However, several studies have shown that human properties influence
the dynamic response of structures. On that basis, in this work the human induced vibrations on thin rectangular
plates are investigated. For this, a biodynamic model is used to represent the people walk, where the biodynamic
properties are coupled with the properties of the plate. The boundary conditions are considered by linear rotational
springs on all edges in order to characterize a plate almost clamped. The influence of the biodynamic properties,
as walking velocity, mass and damping ratio of a single person in the dynamic response of system is studied. The
biodynamic model is also compared with a force-only model and the results are discussed. Obtained results shown
that the modeling using the force-only model provides an increase of transversal displacement of plate when
compared to the biodynamic model. It was also noted that increased of modal mass and walking velocity cause a
reduction of displacements, while increases in pedestrian damping ratio lead to larger vibration amplitudes and the
position of amplitude peak point is also modified.

Human structure interaction: approaches to consider crowd effects

Igor Braz N. Gonzaga — 2024-06-16

Pedestrians walking in slender footbridges may lead to dynamic behavior that does not satisfy the
serviceability limits proposed in codes. On the other hand, the presence of pedestrians may bring beneficial effects
to the structural behavior by providing damping to the coupled system structure plus pedestrians. In this work,
three approaches are assessed to evaluate the response of a footbridge in a crowd situation: (i) pedestrians
represented by a moving load model (MLM) applied to an equivalent single degree of freedom model (SDoFM)
of the empty structure (ii) pedestrians represented by MLM applied to an equivalent (SDoFM) of the occupied
structure whose modal properties are obtained from free vibration analyses and, (iii) pedestrians represented as
biodynamic models (BM) walking along the footbridge deck. Comparisons between the results in terms of the
maximum midspan acceleration of a composite footbridge using the three formulations evaluated herein are
performed.

Development of a computational tool for immediate assessment of the structural integrity of corroded pipelines

Marco Antonio Figueirôa da Silva Cabral — 2024-06-16

Pipelines are one of the safest ways to transport hydrocarbons however this type of transport is subjected
to severe damage that can be associated, mainly, with corrosion. Therefore, the structural integrity assessment of
corroded pipelines is of great importance for the oil and gas industry. For the prediction of the failure pressure of
pipelines with corrosion, semi-empirical and numerical methods are commonly used. Semi-empirical equations
are computationally inexpensive, but, in general, lead to more conservative results. On the other hand, the finite
element method (FEM) is more accurate and presents less conservative responses, but it is more expensive. In
this work, a system developed with a low computational cost equivalent to semi-empirical methods, but with more
accurate results will be presented. For this, a set of models, previously defined, that have a single idealized defect,
dimensions, and the material curve, were evaluated through the FEM and the results, together with the model data,
were stored in a database, where they can be accessed remotely via an API. These data can be used to estimate the
failure pressure of any new model. The obtained results were validated against experimental test results found in
the literature, finite element analysis, and semi-empirical models.

Nonlinear Analysis of Snapping Hyperelastic Prestressed Arches

Filipe Fonseca — 2024-06-16

Over the past decades, a variety of applications of multistable structures has appeared in different
branches of engineering. Among the structures exhibiting multistability, metamaterials, formed by a sequence of
structures able to undergo large displacements and deformations without presenting damage, thus being able to
assume different equilibrium positions, are investigated in the current literature. Many of these structures display
a nonlinear behavior with limit point instability, allowing the structure to jump between various stable equilibrium
positions and thus present a reversible hysteretic behavior. Among the materials used in this type of structure are

hyperelastic materials. In this work, the behavior of hyperelastic arches obtained from buckled columns in a post-
buckling configuration, under transversal loads, is studied; a bistable structural unit typical of metamaterials. To

understand the nonlinear behavior of these structures, a finite element model is used by means of the Abaqus

software that allows specifying several constitutive laws commonly used for hyperelastic materials. To obtain non-
linear equilibrium paths, the Riks method is applied. A parametric analysis of the nonlinear behavior of the arch

shows the influence of the geometry of the arch (height-to-span ratio and thickness), self-weight and load
imperfections on the nonlinear equilibrium paths, load capacity (critical load) and stored energy of the structure.

The effect of geometry on the dynamic instability of clamped-free cylindrical shells

Zenón José Guzmán Nuñez Del Prado — 2024-06-16

In this work, the influence of geometry on the dynamic instability of clamped-free cylindrical shells
subjected to lateral harmonic loads is studied. For this, to model the shell the Koiter – Sanders is considered, and
the Rayleigh-Ritz method is applied to obtain a set of non-linear dynamic equations which are solved in turn by
the fourth order Runge-Kutta method. A detailed study is performed to evaluate the correct nonlinear coupling of
field displacements. To study the dynamic instability, a model with eighteen degrees of freedom is considered and
the resonance curves are obtained for three different shell geometries. It is possible to observe that, depending on
the geometry ratios, the shell will display softening, hardening, chaotic or quasi-periodic oscillations.

Influence of Guy Rupture and Plasticity on the response of Guyed Telecommunication Towers

Luiz Eduardo Fernandes Sequeira — 2024-06-16

A large number of tall guyed towers consisting of a mast laterally supported by pretensioned cables
have been recently built due to an increasing demand for taller antenna towers. The cables act as a supporting
system, increasing the towers critical load and natural frequencies. Their influence depends on the number of guy
levels and the distribution setup. However, many accidents have been reported involving guyed towers, being
cable rupture one of the frequent causes of structural failure. Here, the sudden rupture of one or two, arbitrarily
selected, cables on the linear and nonlinear response of the guyed tower under static and dynamic loads is
investigated. Also, the elastoplastic behavior of the mast and cables is taken into account. For this, models
consisting of a mast supported by different cable set ups are investigated. The analysis is conducted using the finite
element software ABAQUS. The mast is modelled using three-dimensional beam-column elements and the cables
using tension only truss elements. Thus, the tower-cables interaction leads to a highly non-linear behavior under
static and dynamics loads. First, the critical load and natural frequencies of the structure are determined for the
intact structure and for configurations missing one or two cables. Coincident buckling loads and vibration
frequencies are observed due to the symmetric cable distribution around the tower. This symmetry condition may
lead to interactive buckling and internal resonances, increasing the effect of the nonlinearities on the response of
the structure. Then the nonlinear post-buckling behavior is studied using the Riks method and the influence of
rupture and plasticity on the tower load carrying capacity is evaluated. Finally the influence of cable rupture and
plasticity on the free and forced vibrations of the tower is investigated.

Numerical analysis of soil-pile interaction problems using 8-node hexahedral finite and infinite elements

Michael R. M. Visintainer — 2024-06-16

A numerical analysis to study three-dimensional soil-pile interaction problems is presented in this
paper. The soil mass and the pile are spatially discretized using eight-node hexahedral isoparametric elements
with underintegration techniques and hourglass control to suppress volumetric and shear locking. Load transfer
between the soil and the pile is performed by a three-dimensional contact algorithm based on the penalty
method, where the classical Coulomb’s law is adopted as constitutive relation for friction. A corotational
approach at element level is adopted to deal with physically and geometrically nonlinear analysis. For dynamic
analysis, the Newmark’s method is employed for time integration and infinite elements are used at the domain
boundary to avoid the reflection of energy waves in the region of interest, providing a quiet boundary. Numerical
examples are performed and compared with numerical results obtained by other authors in order to verify the
present algorithm.

An Integrated Formulation to Predict Pre and Post-Critical Behavior of Frames

Marcos A. C. Rodrigues — 2024-06-16

To reduce the discretization influence and allow a minimal beam subdivision in geometric nonlinear
analysis of a framed structure, using the finite element method (FEM), the present work evaluates an integrated

formulation in the pre and post-critical phases. This updated Lagrangian formulation considers the Euler-
Bernoulli beam theory with high-order terms of the strain tensor and a tangent stiffness matrix calculated with

analytical interpolation functions. These functions are obtained from the solution of the equilibrium differential

equation of a deformed infinitesimal element, which includes the influence of axial forces. In pre and post-
critical stages, the nonlinear response of the proposed integrated formulation is evaluated with robust nonlinear

solution schemes, and the results are compared with conventional formulations. Examples clearly show the
efficiency of the integrated formulation to predict the pre-critical phase using a low discretization and consistent
results with conventional formulations in the post-critical behavior.

The effects of parametric uncertainties on the nonlinear vibrations of a pressure-loaded spherical hyperelastic membrane

Kaio. C. B. Benedetti — 2024-06-16

Hyperelastic membranes are found in many engineering fields. A key step in their mathematical
modelling is the choice of an appropriate constitutive law and, subsequently, the determination of the associated
material parameters, usually obtained from experimental results, with the occurrence of multiple sets of optimal
material parameters for the same data sets, depending on the fitting process. The influence of the constitutive law
of a hyperelastic material on its nonlinear behavior is well known and both static and dynamic responses can vary
greatly, depending on the parameter values. Thus, the application of the uncertainty propagation analysis, capturing
the expected outcome in a probabilistic sense, constitutes an interesting tool in the analysis of hyperelastic
structures, particularly in the dynamic case. Here it is applied to the analysis of a pressure-loaded spherical
hyperelastic membrane with constitutive uncertainty. Different hyperelastic constitutive models are addressed,
comparing the static and dynamic nonlinear response under parametric uncertainty. Finally, the global stability is
developed by expanding a previous concept of (Q, Λ)-attractors to the dual space where basins are defined.
Specifically, the inclusion of parametric uncertainty is responsible for the diffusion of attractors and basins
boundaries, drastically changing the phase-space topology. A novel methodology of phase-space discretization is
also considered to represent the phase-space topology under uncertainty. A global dynamical analysis framework
in the context of parametric uncertainty is yet to be addressed, specifically for hyperelastic constitutive models,
constituting the novelty of the present work.

Evaluation of laminated composites strength with different fibers direction subjected to impact load from the implicit and explicit dynamic analysis

Rodrigo E. Aguiar de Souza — 2024-06-16

The composite materials are widely used in mechanical engineering applications. Understand their
behavior and how will load influence on structural elements is extremely important for technological evolution
and innovation. The complexity to evaluate elements of composite materials makes the subject a fertile field for
learning and new proposals. Thus, it is proposed to investigate the performance of implicit and explicit dynamic
methods in the impact analysis of some composite plates. The modelling of problem consists of applying an impact
load in center of the plates, which are represented by bidimensional and linear finite elements with 6 degrees of
freedom per node. The influence of fiber orientation and the number of plies of the plates on their ability to resist
stresses is verified. The results showed good agreement with literature and some behaviors were highlighted.

Estimation of the damping ratio of composite arch footbridges considering human-structure interaction

João M. Ribeiro — 2024-06-16

The footbridge dynamic analysis under the action of human walking involves many variables that
influence the structure. With this in mind, this article analyzes the dynamic responses of composite material
footbridge with different spans submitted to the action of human walking in order to measure the increase of
damping ratio on footbridge caused by the human-structure interaction. Two models used to represent the action
of human walking: the moving biodynamic model (MBM) and the moving force model (MFM). Analyzing the
difference between the results obtained from each of the models it is possible to find the increase of the damping
ratio of the structure in the presence of pedestrians.

Modelling of the P-δ effect using interpolating functions

Rodrigo B. Burgos — 2024-06-16

P-Delta is a second-order effect that arises from the consideration of loads acting on the deflected
configuration of the structure. This effect is especially relevant in slender structures, which present lateral
displacements large enough to significantly increase the bending moment caused by an axial load P acting upon
a displacement Delta (hence P-Delta). There are typically two sources of P-Delta, known as P-Δ (P-"big-delta")
and P-δ (P-"small-delta"). The P-big-delta result is easier to obtain in any geometrically nonlinear analysis, as it
is a global effect associated with displacements of the member ends. On the other hand, the P-small-delta effect
is associated with local displacements relative to the original shape of the element. The usual way to capture this
behavior is to subdivide the elements, thus transforming the problem into a P-Δ effect within each segment.
Since discretization can sometimes be unwanted, especially when dealing with students who still do not grasp
this concept, a solution to overcome it is interesting from a didactic point of view. This work proposes the use of
different sets of shape functions to interpolate the bending moment along the element’s length, to account for the
P-small-delta effect. Shape functions obtained directly from the solution of the differential equation of an axially
loaded deformed infinitesimal element and traditional Hermitian polynomials are used. Comparisons were made
with analytical and numerical solutions. Initial results for Euler Bernoulli beam theory indicate the ability of the
formulation to capture the P-δ effect successfully.

Análise da segurança de vigas pré-moldadas sobre aparelhos de elastômero com relação a falhas por instabilidade lateral

Lethicia O. Costa — 2024-06-16

O concreto pré-moldado apresenta vantagens como rapidez de execução e elevado controle tecnológico

quando comparado ao concreto convencional. Diferentemente de estruturas moldadas no local, os elementos pré-
moldados necessitam usualmente serem transportados, içados e montados. Estas condições devem ser verificadas

pois as vinculações das peças são diferentes da situação final. No entanto, as indicações normativas não
apresentam recomendações adequadas, principalmente para longas vigas pré-moldadas, e por isso, ainda há
muitos incidentes de colapso ou comportamentos não previstos registrados. Portanto, este trabalho apresenta uma
análise de confiabilidade de uma viga longa de concreto pré-moldado com relação a sua estabilidade lateral,
levando em conta um modelo mecânico que considera a flexibilidade dos apoios na carga de flambagem. A fase
transitória de construção estudada é a situação em que a viga está sobre aparelho de apoio, com vinculações
definitivas incompletas, sobre a qual há poucos trabalhos com foco em confiabilidade. O estudo mostra que as
incertezas

Structural Optimization of trusses considering different buckling models

Marcela A. Juliani — 2024-06-16

Constraints related to buckling usually have a significant impact in the structural optimization of trusses,

and may be evaluated by employing different models. In this paper, an approach that considers a single global sta-
bility constraint, related to the so-called inelastic critical load, is presented and compared with other approaches

widely used in the literature. In this approach, each element of the truss is discretized into several frame elements.

After applying geometrical initial imperfections in the structure, inelastic buckling can be taken into account im-
plicitly via second-order inelastic analyses. The optimal structures obtained by employing inelastic critical loads

for the entire structure, as well as those obtained by considering, for each one of the truss elements, Euler buckling
loads or the inelastic buckling loads given in the AISC code, are compared. The optimization problems addressed
herein may demand high computational efforts, especially for the inelastic analyses, thus a previously proposed
optimization framework based on surrogate models is employed. As a result, higher objective function values
occur when the model from the AISC code is used. Furthermore, the inelastic model can lead to structures with
large displacements, so the displacements must be limited to result in more realistic designs.

Simplified analytical and finite element models of the vibration frequencies and buckling loads of a metallic tapered hollow tower.

Dick Anelise — 2024-06-16

Structural analysis of slender structures, goes through the study of the static, dynamic and instability.
This requires the evaluation of natural frequencies and buckling loads. The Rayleigh method was an analytical
formulation used to access these data. To verify the accuracy of the formulation we applied the analytical method
to a cantilever metallic hollow tower, used as a small wind turbine tower, to estimate the first eigenfrequency and
the buckling load, assuming different shape functions, the results are carefully compared with the results obtained
by a finite-element model using the SAP2000 software. The frequency values are also compared with vibrations
measurements in the real structure. Results showed that Rayleigh quotient are reliable to evaluate the frequency,
with the first frequency in good concordance with FEM simulations and experimental results. Nevertheless, the
analytical prediction of buckling loads shows some incongruent results with differences in the range of (3-50)%
and highlights the importance of select the appropriate model to represent the structure.

Thermal buckling of functionally graded plates

Thamires X. Cavalcante — 2024-06-16

Plates and shells are widely used in several areas, such as civil construction, automotive, aerospace,
naval, and defense industries. The application of Functionally Graded Materials (FGM) in plate and shell structures
can provide several benefits. FGMs are composed by two or more materials, in which the microstructure changes
continuously and smoothly from one surface to another, being designed to achieve the desired properties according
to the application of interest. The most common are those composed of ceramic and metallic materials, used for
example in structures subjected to high temperatures used in the aerospace industry. The structures of plates and
shells can be highly slender, becoming sensitive to collapse due to buckling. Thus, this study focuses on the analysis
of FGM plates stability at high temperatures, evaluating the influence of the slenderness and the volume fraction
distribution in the critical temperature and post-critical behavior. The numerical simulations of the FGM structures
are performed using the commercial software Abaqus. To correctly represent the thermomechanical behavior
of functionally graded materials, the Virtual Lamina Method (VLM) for buckling and user material subroutines
(UMATs) for post-buckling are applied.

Multiple scale analysis of energy harvesting in aeroelastic system in flutter condition

Ana Carolina Godoy Amaral — 2024-06-16

The ever increasing need for efficient, environmental-friendly and sustainable energy sources has pro-
pelled the study of energy harvesting and its applications in many fields of engineering in the last decade. Nonlinear

aspects of energy harvesting have been extensively investigated for two main reasons: improve the accuracy of the

mathematical models of systems that inherently present nonlinear behaviour, and to intentionally introduce non-
linear behaviour to the system in order to improve the harvesting performance. Electrical nonlinear aspects can

have large influence on the harvesting device. Investigations of the effect of quadratic nonlinear piezoelectrical
coupling showed that the amount of harvested power can be significantly influenced. In this paper, we show the
contributions of cubic nonlinear stiffness on the dynamic behaviour of an aeroelastic energy harvesting system.
Analytically, each case is analysed using the method of multiple scales. The first case is a linear system with
finite degrees of freedom, the second case evaluates forced oscillations of system having cubic nonlinearity. We
relate natural frequencies present in the system and target energy transfers (TET). TET uses non-linear modes and
internal resonance to transfer vibration energy, passively. Numerically, the response is calculated using a 4th order
Runge-Kutta method. The results for the analysed system indicate that cubic nonlinear stiffness has more influence
in increasing flutter speed than increasing electrical power.

Modeling of a broadband double-beam piezoelectric energy harvesting system

Vinícius C. Smarzaro — 2024-06-16

In this work, a mathematical model, that describes the mechanical and electrical behaviors of an energy
harvesting system composed by a cantilever beam (primary beam) and a bimorph piezoelectric beam (energy
harvester) attached to the primary one, is presented. From a mechanical excitation (acceleration) at the base of the
primary beam, a voltage is generated in the piezoelectric. The primary beam is modeled as a multiple degrees of
freedom system, while the harvester is modeled as an equivalent spring (dynamic stiffness), which has the
mechanical and electrical characteristics of the piezoelectric beam. In order to obtain the equivalent stiffness, the
harvester is modeled as a single degree of freedom system. The equations of motion of the composite system are
obtained from Lagrange Equations. Using the generated voltage and the acceleration at the base of the primary
beam signals, a Frequency Response Function (FRF) was calculated, which can be used to identify a physical
system of this kind and to optimize its physical parameters in order to maximize power in a desired frequency
range. The numerical results showed the ability of the proposed compound system to generate energy over a wide
frequency range.

Remarks on nonlinear dynamics of a suspension bridge model

Felipe Lima de Abreu — 2024-06-16

The following paper aims to analyze the Lazer-McKenna suspension bridge model, a system with a
nonlinear response. The proposed model has as a difference the presence of a rubber band in a mass-spring-damper
system, where the rubber band exerts force only against the extension. The dynamic response is analyzed in time
and frequency domains with time tools like Phase Portrait, Poincare Maps and frequency tools like Fast Fourier
transform, and Continuous Wavelets transform, where the nonlinearity is investigated. Both the time response,
obtained by numerically solving the second order differential equation with Runge-Kutta methods, and the signal
processing were obtained using the python programming language.

Some Comments on Signal Processing Analysis in Nonlinear Dynamics and Chaos

Marcus Varanis — 2024-06-16

Signal processing analysis in nonlinear dynamics applications is the main subject of this article, written
for overview comparing different time-frequency analysis methods applied to nonlinear mechanical systems. The
theory was carefully exposed and complemented with sample applications on mechanical vibrations and nonlinear
dynamics. A particular phenomenon that is also observed in nonlinear systems is the resonant capture and
Sommerfeld effect, which occurs due to the interaction between a non-ideal energy source and a mechanical
system. Another application is to characterize the chaotic dynamics of mechanical systems using signal processing
techniques. In addition, experimental and simulated signals are used that show the methods have high accuracy
for the analysis of nonlinear dynamics.

Switching between impacting and non-impacting co-existing attractors via intermittent control

Dimitri D. A. Costa — 2024-06-16

Multistability manifests itself in several nonlinear systems and structures including origamis, energy
harvesters, oil well drilling and microelectromechanical systems. In some applications, this effect is a desired
aspect that brings adaptability but in others, only a specific configuration is useful. In all cases, the ability to
exchange between undesired and desired responses is crucial for the system proper operation. Usually, this
configuration change occurs in a quasi-static framework where the system operation is required to halt for
reconfiguration, leading to losses of productivity and waste of time. Hence, control techniques that can transfer
between coexistent orbits in a dynamical framework are required. However, there are only a few studies that
tackle the control of multi-stable systems, with most controllers only working in the vicinity of the desired
behaviour. This work aims to study the intermittent control application from numerical and experimental points
of view and analyse its properties in a realistic scenario where noise is present. An experimental impact
oscillator is used as a standard multi-stable system. Results show that the controller presents difficulties to
exchange coexistent orbits when noise is considered, needing high control gains.

Stress distribution analysis of single overlap adhesive bonded joints - An analytical and numerical study

Brandão, Vinícius D. — 2024-06-16

The present work aims to present a comparative study of stress distribution along a single lap bonded
joint between analytical and numerical methods, which will be both 2D and 3D for further comparison. Through
this comparison, it is expected to display the stress concentration behavior predicted in traditional solid mechanics
bibliography, highlighting jap edges as main stress concentration areas as well as critical fracture regions, where
the adhesive layer is likely to peel. For this analysis, a number of hypotheses are raised, such as an isotropic
adherend (composed of steel), a homogenous adhesive lap joint and both adherend and adhesive components
behave as elastic materials. The present study is based on the international standard ASTM D1002 [1] tensile test.
This standard test is considered simple, especially given the low number of elements involved: two steel adherends
and an adhesive lap joint. However, the test provides important information regarding the parameters that directly
influence the stress distribution. The analytical methods used were modeled in the MATLAB® software, whereas
the numerical methods were conceived in ABAQUS® finite elements software.

A strain-rate dependent material model for adipose tissue under blunt impact considering microstructural aspects

Felicitas Lanzl — 2024-06-16

Subcutaneous adipose tissue (SAT) is one of the superficial soft tissue layers covering the human body.
Its mechanical behavior is important for various fields of impact biomechanics as it influences stresses and strains
that are transferred to the underlying tissues. Modeling of SAT is challenging as it exhibits non-linear, strain rate
and load case dependent characteristics. Here, we propose a new model of SAT under impact loading that considers
microstructural aspects. The approach is based on a hyperelastic model whose strain energy function is split into
a part for the incompressible lipid inside the cells and into a term for the collagen network encircling the spherical
cells. Strain rate dependency is realized via a normalized relaxation function represented by a Prony series. The
model is implemented as user defined material model into an FE code and used to simulate drop test experiments
on porcine SAT specimens (n = 12) with varying thickness at an impact velocity of 1 m/s. The model has a stable
and consistent behavior in the simulations. A reasonable match between experimental and simulation results is
achieved for different specimen thicknesses, i.e. varying strain rates.

The influence of time integrator on contact/impact problems using the positional finite element method

Darcy Hannah Falcao Rangel Moreira — 2024-06-16

The dynamic structural problems involving contact/impact are strongly nonlinear, and can lead to spu-
rious numerical oscillations, generating unsatisfactory results or even convergence problems depending on the

applied temporal and spatial discretization techniques. The use of Newmark method with traditional parameters is
proven to be inefficient in this case, making necessary the application of specialized time integration techniques.
Some authors propose alternative values for the Newmark parameters to circumvent this problem, introducing a

numerical damping in the system, and reducing artificially the high frequency oscillations. However, this strat-
egy is highly sensitive to the time discretization, decreasing the accuracy of the results when the time steps are

not sufficiently refined. As an alternative, one can employ the alpha-generalized time integration method, which

allows the control of numerical dissipation by using appropriate parameters. In this work, we apply different com-
binations of said parameters, including the ones which reproduce the Newmark method and its variations, in order

to analyze the numerical stability of two-dimensional impact problems. The applied computational framework
is the positional finite element method, which is characterized by using positions as nodal parameters, instead of
displacements, and naturally considering geometrical nonlinearities in its formulation. The applied constitutive
model is the Neo-Hookean, for large strain. For the numerical implementation of structural contact, we make
use of a node-to-segment model with Lagrange multipliers, employing a contact detection algorithm based on the

intersection of trajectories. Finally, a representative numerical example is proposed with different time integra-
tion techniques. The results indicate that the adequate choice of alpha-generalized parameters can lead to quite

significant improvements to the numerical stability when compared to the traditional Newmark method and its
modifications.

NUMERICAL STUDY FOR LUBRICATION EFFECTS IN METAL FORMING THROUGH THE PROCESS OF BARREL COMPRESSION

Fellipe M. Egito — 2024-06-16

In metal forming process, friction is one of the most important factors, as it has a great influence
on the shear stress behavior. The shear stress pattern determines the material’s properties, structures and energy
requirements. In addition, the importance of friction analysis also arises from the efforts to which the material
is subjected and from the reaction force on the machinery used, with direct implications for the efficiency of
the manufacturing process, the cost and the time employed. Therefore, analyzing ways to reduce the damaging
consequences of friction is extremely important. In this sense, the analysis of lubrication becomes too relevant
since, through the reduction of friction, it is possible to increase the efficiency in the metal forming process.
Thus, the present study aims to relate the effect of lubrication on the shear stress of the specimen with the
analysis using the computational method of Finite Elements in the Barrel Compression process. For this purpose,
the friction coefficients of the main lubricants on the market were used and the effects on the test results were
simulated.
Therefore, numerical analysis was performed in the Ansys Structural Analysis® software environment. Thus,
the CAD models for the specimen and for the test matrix were created. In addition, a mesh evaluation was made,
scoring the effects arising from the precision change. Besides, the boundary conditions were also scored, using the
various tools that the software offers. It should be noted that the program resolution algorithms were verified, as
well as their convergence criteria.
Finally, in possession of the computer simulation results, their validation is sought by comparing them with
the theoretical expected for the same test, but in the absence of lubrication. In this way, gains from surface
lubrication are quantified and the extent to which the change in lubricant causes a relevant consequence in shear
stress is also measured. This article, therefore, seeks to be another source of research in the promising area of
metal forming analysis.

A numerical study of damage evaluation in jointed plain concrete pavements considering alternative materials for dowel bars

Edmir J. Santos Júnior — 2024-06-16

Abstract. It is well-known in the design of jointed plain concrete pavements (JPCP) that the concrete damage due
to stress near the dowel bars is a key factor that affects the service life of such structures. This study aimed to
evaluate numerically the differences in the damage distribution in the concrete near the dowel bars in JPCP
considering alternative materials for the bars. Two materials were considered for the dowels: steel and glass fiber
reinforced polymer (GFRP). The adopted constitutive model for the concrete was the concrete damage plasticity.
Interactions between the concrete and the dowel bars were simulated by surface-to-surface contact type. The finite
element models were validated by comparing available experimental load-displacement curves with the obtained
numerical ones. The results for the damage distributions reveal that the use of GFRP bars has induced smaller
damage values within a smaller damaged zone when compared with the dowel steel bar model. As a consequence,
smaller cracks in such zones will appear which will increase the structural life of the pavement. Also, a higher
ultimate load for JPCP with GFRP bars is observed.

Discrete crack model based on nodal duplication for nonlinear analysis of concrete structures

Natalia de Oliveira Assis — 2024-06-16

Concrete is classified as a quasi-brittle material and exhibit a gradual decline in response of the stress-
strain law in inelastic regime. Upon reaching its strength limit, this material starts to crack. This cracking process

critically influences the material’s response in its state of stress, which makes crack evaluation an important factor
in the analysis of concrete structures. A numerical strategy that can be used to analyze cracks is the Finite Element
Method and the cracks can be classified as smeared and discrete. The smeared approach considers that a set of
small size cracks are distributed along the finite element. In the discrete approach, which will be used in this work,
the crack is considered a geometric discontinuity in the finite element mesh and its analysis involves the following

essential keys: a constitutive model for describing the material; a crack propagation criterion; an adequate proce-
dure for remeshing, and an efficient technique for solving a system of nonlinear equations. This work proposes

the implementation of a discrete cohesive crack model with mesh redefining based on nodal duplication capable of
evaluating the crack behaviour in concrete beams subjected to bending.

Computational Aspects in the Evaluation an Existing Structure by the Global Safety Method

Claudia Interlandi — 2024-06-16

The re-evaluation requirement for existing reinforced concrete structures, considering new regulatory
design requirements is an unquestionable reality. For this, computational analysis tools with an emphasis on
probabilistic input data have been developed and improved over time. In order to be able to consider more realistic
situations, where the structure is collapsed instead of those defined in the original project, following the Ultimate
Limit States, refined and complex computer programs are increasingly needed. In this article, a methodology based
on the concepts of the Global Resistance Format is presented, as defined in the fib Model Code 2010. The proposed
methodology is applied in the re-evaluation of an existing bridge. Bayesian updating of material properties is also
applied in computational analysis. Structural analysis programs and reliability analysis are considered in these
studies. With the proposed method it is possible to evaluate the need for rehabilitation or not, from the point of
view of structural safety, directly depending on the reliability of the structure in view of new regulatory
requirements. The gain in computational terms, is to generate the input data update in a more refined way,
generating more realistic results.

Numerical analysis of a smeared cracking model for concrete structures

Eduarda M. Ferreira — 2024-06-16

Analytical models for concrete often become ineffective or difficult to parameterize due to its highly
complex and heterogeneous microstructure, as well as its physically non-linear behavior. This fact justifies the use
of numerical methods, such as the Finite Element Method, for modeling the mechanical behavior of the material
more realistically. One of the main phenomena responsible for the physical nonlinearity of concrete is cracking,
which occurs even at low loading levels, due to its low tensile strength when compared to the compressive one.
In this context, the present work aims to study cracked concrete structures using a smeared cracking model based
on monitoring the deterioration of the material’s physical properties. The Finite Element model was implemented
using an isoparametric element for plane elasticity. The cracking process is described by the decay of stresses with
increased strains, through different stress-strain relationships extracted from the literature that represents the overall
behavior of concrete in tension or compression. A cracking model based on the inversion of compliance with a
local secant constitutive matrix was used, which takes into account the undamaged secant Young’s modulus of the
material. This nonlinear model has been implemented using the MatLab platform with a generalized displacement
control sover. The results for different combinations of stress-strain curves were compared and the method was
validated through comparison with the ones of other authors.

Computational modeling of steel fiber reinforced concrete

Victor Sloboda — 2024-06-16

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.

Modeling of a pumped hydropower storage wall in 3d printing using the software Diana Fea

Larissa D. Fonseca — 2024-06-17

Pumped Hydropower Storage (PHS) reservoirs are mass concrete structures; therefore, the effects of
cementitious materials in early ages, such as heat generation and autogenous retraction, must be assessed to avoid
thermal cracking. Construction in layers is one of the solution used to reduce the heat generated from the hydration
of the cementitious material and decrease concrete pouring heights and volume of cement. In this paper, 3D
printing that uses the deposition of thin layers is studied for a PHS reservoir wall. A 3D numerical model of a
0.40x2.0x3.0 m structure was developed in DIANA FEA software considering concrete mechanical properties
defined by Wolf [1] and thermic properties of a 400 kg/m3

concrete from the Japan Society of Civil Engineers [2].
The software was evaluated as a good modeling tool to simulate the layered construction technique and hydration
reactions through Finite Element Analysis. The thermal effects on concrete for 3D printing were discussed, and
the impacts of 3D construction on mass concrete were evaluated. It was concluded that the rising temperatures of
mass concrete do not damage the structure during the 3D printing; on the contrary, it accelerates the strength gain
of the cementitious composite for this construction method.

Finite Element Analyses of mesh-objectivity for Smeared, Damage and Discrete models applied to concrete cracking

Gustavo L. X. da Costa — 2024-06-17

This paper will address the issue of mesh objectivity regarding Smeared, Damage and Discrete models
applied to concrete cracking in the framework of the Finite Element Method. It will be shown that assigning the
same stress-strain relationship with softening for all elements regardless their size and shape will lead to spurious
results. This will make the fracture energy decrease as the mesh is refined, sometimes even converging zero which
is completely unacceptable. This problem is related to the negative slope of the tangent stiffness tensor, that is, the
increase in strain with decreasing stress which will make a small portion of the body experience softening while
the rest of it unloads elastically. In order to circumvent this issue, it must be employed a regularization technique,
also known as localization limiter. The first localization limiter that this study will adopt is the Crackband
technique applied to both Smeared and an isotropic scalar Damage models. It is easily implemented in an existing
Finite Element code and its main feature is the assumption of a bandwidth where the crack is supposed to
propagate. It will be presented that the Crackband technique is the simplest but crudest approach. Nevertheless, it
will assure the convergence of the results but its accuracy hinges on choosing the bandwidth properly. The second
localization limiter adopted in this paper is the Nonlocal integral-type technique which recovers the objectivity by
taking the weighted average of a variable that controls cracking. This technique will be used in the isotropic scalar
Damage model. Finally, it will be discussed the Discrete crack approach through interface elements with
vanishingly thickness. This technique won’t need any regularization since the constitutive relationship is already
written in terms of Stress-Displacement. The three approaches will be employed in the simulation of a notched
fiber-reinforced concrete beam and compared with its experimental data. In order to show the feasibility of each
methodology, these analyses will debate their convergence properties which is the main focus of the present study
and features such as computational effort, crackpath and assessment of input parameters.

FINITE ELEMENT MODELLING OF CRACKING IN FIBER- REINFORCED CONCRETE BEAMS

Carlos A. C. Brant — 2024-06-17

In this paper, a fiber-reinforced concrete beam is modelled in the framework of Finite Element Method.
It is adopted three approaches, namely Smeared crack, Discrete crack and Damage models. The analyses are
conducted through commercial software DIANA FEA and an in-house computational routine. To do so, it was
selected an experimental data of concrete notched beam presented in literature to compare with the proposed
models. First, Smeared crack model with Crackband regularization technique was studied and compared with
Discrete crack model. The Discrete cracking approach was used to simulation and sought to reproduce the
experimental Force-CMOD curve considering the experimental cracking pattern of the specimens. To do so, it was
necessary to obtain mode I fracture energy (Gf), the tensile strength of the fiber-reinforced concrete (ft) and the
associated softening behavior. Numerical results show a convergence towards the experimental results. In parallel,
the Damage models with crack band, nonlocal integral and interfaces elements techniques are also used to simulate
the experimental structure. To do so, now it was necessary to obtain the maximum crack opening (wu), ft and the
associated softening behavior. They demonstrate similar results when compared to laboratory tests.

Stress and strain in beam-wall interface in transition floor on support columns of structural masonry buildings

Desir J. Marie — 2024-06-17

This article aims to understand, through numerical modeling, the influencing parameters in the arch
effect, a phenomenon that arises in the interaction of structural masonry walls on reinforced concrete beams in
transition floor on column supports. Among the consequences of the arc effect is the migration of the acting loads
to the region close to the columns, causing stress peaks in the wall and reducing the bending moment acting in the
support beam. The finite element modeling and the properties of the materials adopted are presented. The increase
in stiffness due to the presence of the wall caused deflections in the beam of order up to 8 times smaller than
expected from the elastic line equation. In the wall, even in the most favorable situations, such as beams supported
by columns, we noticed an increase in acting stresses of up to 2.2 times. This points out that, by not considering
the arc effect, the support beam may be oversized, exposing the wall to stresses greater than those calculated.

Mechanical Performance Analysis of Reinforced Concrete Continuous Beams

Edmilson Lira Madureira — 2024-06-17

Concrete is a material cast from Portland cement and aggregates. Since the stress level around 30% of
its compressive strength, a concrete specimen, tested on a single compression, presents nonlinear stress-strain
relationship. Steel bars are used to supply its low tensile strength resulting the reinforced concrete that presents
complex mechanical performance. For the accomplishment of suitable study of mechanical performance of such
a material, it is necessary the adoption of finite element analysis over a nonlinear model, at least, in plane state of
stresses. Several models of analysis, such as, the model from the European community’s standards, the one from
AIC, Torrenfeldt’s model, Hognestad’s model, the Rashid’s Smeared Crack Model, Branson’s model, among
others, have been proposed to the mechanical behavior of concrete description. The Branson’s model is, specially,
attractive due to its simplicity, because in its formulation the beam nonlinear behavior is simulated from an
equation applicable to a beam structural member, resulting, in this way, computational effort economy. The
purpose of this work is to report the nonlinear mechanical performance limit analysis of reinforced concrete
continuous beams. To accomplish such a subject, a computational code was developed, based on the finite element
approach on the Branson’s formulation.

Progressive collapse of a flat slab building

Bernardo Cruz Pereira Galdino — 2024-06-17

The possibility of progressive collapse in a flat slab was analyzed using the reinforced concrete structural
design softwares Eberick and TQS. After the failure of a slab-column connection, the punching capacity of the
slab was verified according to NBR 6118:2014, EUROCODE 2:2004 and ACI 318:2011 and the remaining
capacity of the failed floor was assessed by the Yield Line Theory. Integrity reinforcement was also sized
according to NBR 6118:2014, CEB:2010 and GSA:2013. It is concluded that there is a possibility of propagation
of the failure after an initial failure by punching, and the presence of integrity reinforcement can help preventing
the propagation of a localized failure.

Numerical analysis of a prestressed bridge considering construction processes.

Marcela P. Miranda — 2024-06-17

Significant variations in geometry and supporting conditions can take place during the construction
process of structures. These situations certainly influence the distributions of internal forces, displacements, and
other structural responses during the construction phase and serviceability life of the structure, as customary
occur in multi-span bridges. Thus, it is important to highlight these effects since collapses are recurrent during
the construction period. In this sense, this study aims to contribute to a better understanding of structures during
the construction phase by using numerical analysis. The sequential construction analysis is modeled using a
ghost approach, which is coded into a three-dimensional finite element program, named VIMIS, developed at the
PPGEC/UFRGS. To verify the code implementation in the context of the viscoelastic behavior of materials, a
prestressed concrete bridge is analyzed, including the construction conditions, creep, shrinkage and relaxation
effects. The obtained results expressed in terms of displacements and stresses are then compared with those of an
academic software. As expected, VIMIS can capture the structural effects associated with construction phasing,
reinforcing the necessity of include these analyses in structural designs.

Numerical modeling of 3D-printed concrete dams designed for pumped-storage hydropower

Marina B. de Farias — 2024-06-17

Pumped-storage hydropower (PSH), also called “the world ́s water battery”, represents one of the most

sustainable, economical and efficient solutions for energy storage, being an excellent alternative for non-
intermittent energy generation. This work aims to study new shapes of concrete dams for PSH using the

possibilities opened by 3D printing technology. Solid shapes and hollow shapes were modelled, with different
base and height dimensions. After selecting possible shapes, finite element modeling was performed using
DIANA-FEA, analyzing stability and stresses due to water pressure and dead load. Within the framework of this
analysis, concrete was considered as hardened in complete hydration. To verify the stress levels, a cracking index
was used, allowing the evaluation of the efficiency of the shapes. The results indicated that the use of 3D printing
can open several new possibilities for the design of concrete dams typically used for PSHs.

Study of the relationship between fracture energy and concrete hydration degree through a finite element model

Ítalo Arruda de Carvalho — 2024-06-17

The fracture energy of concrete is an important physical parameter that describes its behavior under
stress, and it is especially important for modeling concrete structures. As a consequence of the concrete stiffening
process, the fracture energy will depend, among other factors, on the degree of hydration of the material. The
development of a model that describes this process is important so that concrete behaviors can be predicted at
different ages. A form of modeling widely used is the Finite Element Method (FEM), which consists of a numerical
model to approximately determinate several physical behaviors. The inverse analysis through FEM starts from the
knowledge of some given parameters, from the constitutive laws of a material and from physical results, to
correlate a numerical model with similar result, in such a way that it is possible to determine the unknown
parameters. The objective of this work is to obtain the relationship between the degree of hydration and the fracture
energy of a concrete using the inverse analysis through its numerical modeling. Starting from the results of concrete
bending tests, its modulus of elasticity and compression strength, fracture energy was obtained with reverse
analysis through the FEM, using the DIANA software. The analysis was repeated for different degrees of
hydration, thus establishing a correction between hydration of the concrete and fracture energy.

Study of constitutive models of DIANA FEA for long-term analysis of pre- stressed beams with bonded tendons

Luana Andreza G. Moura — 2024-06-17

The work presented here was motivated by the existence of several constitutive models capable of
numerically representing the time effect on prestressed beams. The main goal of this study is to analyze different
models, comparing their influence on the long-term behavior in prestressed concrete beams. The study compares
the behavior of prefabricated concrete beams with bonded post-tensioning using different constitutive models for
concrete and steel tendons. The simulation was carried out using DIANA FEA. Some of the models adopted are
from design codes, and others from models and theories available in literature. The study proposes a parametric
study among the different models as well as the effect of the input parameters on the overall behavior of the
structure. The nonlinear behavior of cracked concrete and the steel yield behavior in addition to the creep behavior
of the concrete were considered. The results were compared with experimental results of prestressed beams tested
for creep analysis for a long period of time. The results pointed out to the importance of choosing the appropriate
constitutive model in simulations of prestressed elements.

NUMERICAL ANALYSIS OF DAMAGED CONCRETE MICROSTRUCTURES

D. C. Borges — 2024-06-17

The numerical analysis of the mechanical behaviour of composite materials considering the specificity
of each of its phases requires complex models leading sometimes to unfeasible analyses. Thus, the present work
deals with the modelling of the mechanical behaviour of damaged heterogeneous materials within a multiscale
approach in order to overcome this problem. The modelling is based on the concept of Representative Volume
Element (RVE) representing the microstructure of the concrete, using the Finite Element Method (FEM) to
perform a computational homogenization within the multiscale approach. The matrix is considered as a damaged
material following the Mazars ́ damage model. Linear elastic behaviour is adopted to aggregates. To represent the
transition zone, contact and cohesive finite elements are considered. The main objective is to show that the damage
material can be represented by a formulation based on a computational homogenization technique considering a
multiscale approach. Results of representative microstructures of the concrete submitted to deformation states are
presented and the homogenized responses obtained show the expected behaviour of the concrete.

Computational modeling for simulation of post-cooling systems in mass concrete structures

Igor A. Fraga — 2024-06-17

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
important, 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, this work will present the numerical implementation for simulating a post-cooling model for mass
concrete structures, on a mesoscopic scale, in which the temperature of the material is reduced during hydration
by the circulation of water in tubes embedded in the forms by a post-cooling system. The implementation was
executed using the finite element method (FEM), in a parallel computing environment, coupled to the TENCIM
software, developed in FORTRAN programming language, developed by PEC / COPPE / UFRJ.

Proposed multi-strut macro models for structural analysis of RC infilled frames under lateral loads

Alessandro O. Rigão — 2024-06-17

There is knowledge of contribution to the gain of lateral stiffness and stresses distribution in structural
elements provided by infill walls in RC framed structures. The non-inclusion of masonry infills in structural

model not always leads to structural safety positively. The redistribution of internal forces caused by frame-
masonry interaction may submit the structural elements to high stresses not predicted in design. One of the

factors for not considering the masonry infill walls in the structural model is the complex behavior of the panel-
frame and the dependence of several mechanical and geometric variables of the frame structure and masonry. A

simple macro model to simulate the contribution of the infill walls is by an equivalent single strut. This macro
model is unable to capture properly the local effects caused by the interaction between infills with columns and
beams. In this case, there is the need of macro model with multiple struts. The paper intends to compare the
internal forces in columns (shear forces and bending moments) and lateral stiffness in masonry-infilled RC
frames obtained from proposed multi-strut macro models. These results are compared with ones obtained from a
more accurate model developed by FEM capable to take into account the friction effect and slipping between
masonry and frame members.

Numerical simulations of four-point beam bending test using a macroscopic probabilistic model

Mariane R. Rita — 2024-06-17

This article aims to present the numerical simulations of a four-point bending test of a large plain con-
crete beam, performed by using a three-dimensional macroscopic probabilistic model. The model is developed

in the context of the finite element method and considers that each finite element represents a volume of hetero-
geneous material, with the mechanical properties of tensile strength and local cracking energy being randomly

distributed over the mesh. In this way, that means the cracks are created within the concrete with different energy
dissipation depending on the spatial distribution of material constituents and initial defects. Once the model is
based on a probabilistic approach, a Monte Carlo procedure is used to give coherent statistical results. In order
to verify the efficiency of the developed model related to different levels of refinement, analyzes for two mesh
refinements are presented. The results show agreement with the expected physical behavior for this type of beam
in terms of global response and macrocrack propagation. Regarding the mesh refinements, the results are quite
similar indicating that the model provides a suitable global response in both cases and, therefore, it can be stated
that the utilization of the model with the set of adopted parameters furnishes a consistent outcome for the analyzed
cases.

Numerical analysis of unbonded prestressed concrete beams under long term service loads by Finite Element Method

Leonardo do N. Cunha — 2024-06-17

This work aims to develop a finite element formulation for a numerical analysis for long-term loads of
unbonded prestressed concrete beams. The finite element formulation consists of unidimensional elements of plane
frames with models of 7 degrees of freedom per element, based on the Euller-Bernoulli beam theory for the
reinforced concrete section and a truss element for the simulation of the unbonded tendons. The formulation was
developed for the examples of beam under long term loads with the purpose of evaluating the effects due to creep,
shrinkage, and relaxation of the prestressing steel. The analysis used the Age-Adjusted Effective Modulus and
normative relationships to obtain long-term effects. The numerical results were evaluated through a comparative
study with long-term load-displacement curves from the literature, obtaining excellent approximations.

Computational Modeling of Small-Scale Flow of Thixotropic Yield-stress Materials

Carlos E. Sanchez-Perez — 2024-06-17

Computational modeling of flow of thixotropic yield-stress materials is challenging, because it requires

an accurate model which should be able to describe the break and buildup of the material microstructure. Tradi-
tionally, thixotropic flows have been modeled by using very empirical equations which have a very restricted range

of feasibility. Alternatively, in the present work, it is used a novel fluidity-based constitutive model that involves no
postulated functions or parameters. Instead of using empirical parameters, this model involves measurable material
functions whose parameters are obtained from data of standard experiments. Likewise it is more appropriate to
describe the behavior of thixotropic material flows. In addition, the model assumes a one-to-one correspondence
between the fluidity (i.e., the reciprocal of viscosity) and the microscopic state.
A numerical model of thixotropic yield-stress materials flowing through a capillary with a constriction is
presented here. The complex flow is governed by the continuity and momentum equations coupled with two
additional equations. One is a scalar evolution equation of fluidity while the other is a tensorial equation. The
latter relates stress and strain rate. The system of equations was solved by using the Galerkin and Petrov-Galerkin
/ Finite Element Method.
The results show how fluidity , which represents the internal microstructure level, and velocity of thixotropic
yield-stress liquids change inside the capillary. Both velocity and fluidity are a function of the flow behavior index,
the yield stress and two material properties associated with different thixotropic characteristic-time scales: the
avalanche time and the construction time.

Modeling turbidity currents: the effects of bottom morphology and fluid rheology over the final sediment deposits

Gabriel M. Guerra — 2024-06-17

Turbidity currents are the main means by which sediments are transported across the ocean
floor and one of the principal mechanisms that leads to the formation of basins hosting oil reservoirs.

Detailed modeling of this phenomenon may offer new insights to help geologists to understand the de-
position mechanisms and the final stratigraphic form of the reservoir. As turbidity currents propagate

over the seafloor, they trigger the evolution of a host of topographical features through the processes of
deposition and erosion, such as channels and sediment waves. We aim at enhancing the understanding
of the underlying physics, with particular emphasis on the sediment deposition mechanisms. Numerical
experiments in setups intended to mimic, partially, as the bed morphology is not allowed to change,

close with experimental, have adopted. We present in this work a finite element residual-based varia-
tional multiscale formulation applied to the numerical simulation of particle-laden flows. We employ an

Eulerian–Eulerian framework to describe the flows in which the mathematical model results from the
incompressible Navier–Stokes equation combined with an advection-diffusion transport equation, where

viscosity depends non-linearly from the sediment concentration. Sediment-laden turbidity currents inter-
acting with irregular bottoms are investigated. The impact of bed morphology over turbidity currents

with viscosity varying with concentration is investigated through quantities of interest such as bottom

shear stresses and deposition. The spatial pattern of the deposition and its correlation with flow struc-
tures are the main focus of this analysis. Quantitative and qualitative observations of the currents are

captured in the experiments, we discuss the morphodynamics of the different scenarios for different bot-
tom bathymetry. Further studies may be carried out in order to constructing new concepts of bedforms

generation by density currents.

Influence of the ratio of drill bit size and conductor casing diameter on jetting with Lattice Boltzmann method

Anderson F. C. Gomes — 2024-06-17

Conductor casing is the first stage of the wellbore. It is responsible for supporting the installation of the
following strings by resisting the stresses involved in the entire process. The conductor seals unconsolidated
formation and guarantees the ideal pressure balance between internal and external environments. Installation by
jetting is a widely adopted solution in deep water due to its reduced execution time. Furthermore, the process
requires attention to control the size of the cavity. This work presents a numerical simulation of the jetting in a
clayey offshore soil during conductor casing placement, aiming to quantify the influence of the ratio between the
drill bit and conductor diameters on soil disturbance and operation time and other operational parameters. A Lattice
Boltzmann (LBM) model is adopted to deal with the soil-fluid interaction. A drill bit with three inclined nozzles
rotates while jetting drilling fluid and descends alongside the jetting system toward the soil domain. The soil
domain is governed by a viscoplastic model based on a Herschel–Bulkley fluid. The size of drill bit influences the
soil area reached, allowing better control over the advance. The presented results help to properly understand the
operational jetting parameters and can be employed to set optimal installation procedures.

Approximated method of nonlinear geometric analysis applied to steel frames designed by Eurocode 3 and optimized with Genetic Algorithm

Breno D. Breda — 2024-06-18

Structural optimization is a process that can demands high data processing power depending on the
algorithm adopted. In addition, a rigorous geometric nonlinear analysis is performed with iterative numerical
algorithms increasing computational efforts. In order to reduce the amount of data to be processed, the Two Cycles
Iterative Method (TCIM) is implemented in the Structures3D (S3D), an optimization software under development
in Matlab® using its Genetic Algorithm (GA). The structural analysis, carried out in accordance to Eurocode 3, is
also implemented in S3D to improve it as well. The final product is an optimization module that take in account,
by approximation, the geometric non-linearity and design by Eurocode 3 of steel structures. An example of
application of this module is presented and the result obtained is compared with other author.

Time-dependent analysis of critical buckling load using optimization technique

Kaique M. M. Magalhães — 2024-06-18

A mathematical and numerical analysis was developed to determine the time-dependent critical buckling

load of a slender reinforced concrete column, by applying optimization techniques. In the analysis, the non-
linearity due to the slenderness of the system together with the rheological property of the concrete considered

through the Eurocode 2 was considered in the calculation. The analytical solution was based on the Rayleigh
method and the numerical one was developed using the Finite Element Method (FEM). To compare results, two
trial functions of the Rayleigh method were used, a trigonometric and a quadratic. In this context, the quadratic
equation was used to apply the optimization technique with its coefficients adjusted to produce results as close as
possible to that from FEM, which had been evaluated the found error.

Comparison of Constraint-handling Methods for the Sequential Approxi- mate Optimization of Functionally Graded Plates

Leonardo G. Ribeiro — 2024-06-18

The optimal material design in Functionally Graded (FG) structures can be defined by an optimization
procedure. This is often performed by the use of bio-inspired algorithms, even though they may require thousands
of function evaluations. Alternatively, a surrogate model can be used to provide a faster assessment of the structural
response. In this work, the Sequential Approximate Optimization (SAO) will be employed, where the approximate

surface will be iteratively improved by the addition of new points in regions of interest. When constraint func-
tions need to be approximated by a surrogate model, a feasibility function can be considered to account for the

uncertainty in determining the design’s feasibility. The SAO approach will be employed in the optimization of
Functionally Graded Plates considering expensive constraints, and different feasibility functions will be tried out.
The optimization will also be carried out using a bio-inspired algorithm, and these approaches will be compared in
terms of efficiency and accuracy.

Surrogate-Based Optimization of Functionally Graded Plates under Thermo- Mechanical Loading

Igor L. Passos — 2024-06-18

Efficient designs for a Functionally Graded Plates (FGP) can be defined via structural optimization.
Usually, bio-inspired algorithms are employed in order to carry out the optimization process. However, when
analyses are very time-demanding, the process may be too costly, since hundreds or even thousands of analyses
may be required. In this work, Sequential Approximate Optimization is employed to provide a more efficient
approach. This paper focuses on the maximization of buckling temperature of a ceramic-metal FGP. B-Splines
are used to define a continuous material gradation along the thickness direction. Effective material properties are
evaluated by the rule of mixtures. The Particle Swarm Optimization (PSO) is applied for structural optimization
and Isogeometric Analysis (IGA) is employed to evaluate the structural responses. Then, Sequential Approximate
Optimization (SAO) is carried out to reduce the computational cost using Kriging to fit an approximate response
surface. A comparison between conventional optimization and SAO is performed, and results show that SAO
achieved the optimum design much earlier the conventional approach, requiring fewer high-fidelity evaluations.

Application of Sequential Explicit Coupling of Reservoir, Well, and Surface Facilities for 3D Compositional Simulation Models

Alireza Bigdeli — 2024-06-18

The assessment of hydrocarbon production systems requires the utilization of a simulator with the
capability of handling different scenarios, such as the simulation of fluid flow in porous media and also in
pipelines, at steady-state and unsteady-state conditions. Recently, there have been efforts in the development of
reliable simulators, which are capable of accurately modeling surface and subsurface environments simultaneously
through the usage of flow tables. In this paper, first, we discuss the importance of nodal analysis and different
wellbore boundary conditions. Based on the foregoing, we introduce a new approach for our in-house simulator
UTCOMPRS. The new approach further extends the previously developed flow table algorithms for 3D reservoir
models. We also compare the results of two case studies with a commercial compositional simulator. The
operational parameters, such as bottom hole pressure, injection pressure, oil, gas, and water rates, among others,
are in good agreement with both UTCOMPRS and the commercial simulator. Herein, we also show the importance
of controlling well constraints. The results showed that the developed framework was successfully implemented
and validated for 3D reservoirs. It enables the simulator to handle more realistic conditions, advancing its
flexibility and providing an infrastructure for the coupling of the reservoir, well, and surface facilities.

A MULTI-SCALE MIXED METHOD FOR A TWO-PHASE FLOW IN FRACTURED RESERVOIRS CONSIDERING PASSIVE TRACER

Jose B. Villegas Salabarría — 2024-06-18

In this research, the mathematical model represents a two-phase flow in a fractured porous reservoir
media, where the Darcy law represents the flow in both fractures and matrix. The flux/pressure of the fluid flow is
approximated using a hybridized mixed formulation coupling the fluid in the volume with the fluid flow through the

fractures. The spatial dimension of the rock matrix is three and and is coupled with two-dimensional discrete frac-
tures. The transport equation is approximated using a lower order finite volume system solved through an upwind

scheme. The C++ computational implementation is made using the NeoPZ framework, an object oriented finite
element library. The generation of the geometric meshes is done with the software Gmsh. Numerical simulations
in 3D are presented demonstrating the advantages of the adopted numerical scheme and these approximations are
compared with results of other methods.

A COMPARISON OF OPTIMIZATION ALGORITHMS FOR THE PRE-SIZING OF REINFORCED CONCRETE STRUCTURES

D. M. Santos — 2024-06-18

Structural engineering is an opportune field for numerical optimization as it pursuits economical designs
that comply with safety and usability requirements. The search for the dimensions of the cross-sections of beams
and columns is a major step on the design of reinforced concrete frames, which will implicate greatly on the
stiffness of the structure and its displacements. Then, with the objective of enhancing the structural design process,
this work analyzes three algorithms to optimize the problem of obtaining a minimum concrete volume while
complying with the stability criteria of small displacements, imposed by the Gamma-Z parameter. The algorithms
for the interior point method, active set and sequential quadratic programming are briefly discussed and their
implementations in the pre-sizing of concrete buildings are compared in terms of efficiency and quality of the
solution by several numerical simulations.

Cost analysis on the optimum design of prestressed doubly-symmetric steel beams

Protáze Mageveske — 2024-06-18

In the last few years, the utilization of steel beams has shown great growth in civil construction.
Although steel has a higher cost, its use is justified when wanting to overcome large spans. This aspect motivates
the development of more economical alternatives as well as the implementation of prestressing tendons. The

objective of this paper is to present the optimization problem aimed to reduce the total cost of prestressing doubly-
symmetric I-sections of steel beams. MATLAB’s native Genetic Algorithm technique was implemented in the

mixed integer programming optimization problem, focusing to optimize the cross-section’s geometrical properties
(i.e., depth of cross-section, flange widths and thicknesses, and web thicknesses) and the number of tendons. The
evaluation and validation steps used two examples from the literature. The design method, through constrained
functions, verifies the Ultimate and Serviceability Limit States from the standard NBR 8800:2008. Therefore,
results showed an efficient alternative for the structural engineering practice, giving a reduction in the total cost of
24.43 and 25.62% for the studied cases.

Comparison of different optimization methods applied to steel trusses structures

Luiz E. G. de Mattos — 2024-06-18

The objective of the present paper is the adaptation and development of algorithms to minimize the
weight of trussed steel structures based on different optimization methods (mathematics and heuristics). Compare
the efficiency between the Sequential Quadratic Programming (SQP) and the Genetic Algorithm, taking into account
the quality of the solutions found, the complexity of implementation and the computational cost required. The
results show that, when using the technical standards for compressed bars, it is necessary to adopt bars with more
robust cross sections when compared to solutions whose restrictions derive from the classic formulation of Euler’s
critical load. A similarity between the results obtained by the SQP and the Genetic Algorithm is observed, but due
to the combinatorial nature of the latter, the heuristic method requires longer processing time. In addition, the results
obtained by the Genetic Algorithm are shown to be random during the iterations, and may converge in slightly
heavier solutions than the SQP. Justified by the results presented, it is stated that the developed algorithms are good
tools for structural optimization and can be used in real steel truss designs.

Well rates and location optimization considering genetic algorithms and surrogate models

Eduarda de F. Andrade — 2024-06-18

In this work, we solve an optimization problem of a known reservoir of the literature through an
integrated optimization by a Genetic Algorithm (GA). The location of the wells and their flow rates are the
variables. The main objective of this paper is to maximize the net present value (NPV). The optimization utilized
the GA from Toolbox Optimization MATLAB to define, simultaneously, the best position for the wells and best
flow rates for each well in each of the three defined control cycles. During the optimization process was performed
a series of function evaluations using a Reservoir Simulator. Due to the high cost of this process and aiming to
avoid it, a methodology with adaptive surrogate models was employed here. As the optimization problem is
restricted, using an adaptive penalty method allowed the GA to run smoothly. The Egg Model is the study reservoir
in this work. It was executed 20 optimizations to verify the uniformity of the obtained results. The best solution
improved the NVP by 45.32% as compared with the original case. The methodology suggested here brought
consistent results with significant improvements in the NPV, the main objective of this paper.

Thermo-mechanical analysis of continuous and discrete media with PFEM and DEM

Rafael Rangel — 2024-06-18

This work presents the development of coupled formulations of the Particle Finite Element Method
(PFEM) and the Discrete Element Method (DEM) for the simulation of thermo-mechanical problems involving
materials that can be modeled both as a continuous or a discrete medium. The thermally-coupled PFEM combines
the Lagrangian and remeshing features of the PFEM for solving fluid dynamics problems with the FEM solution
of the diffusion in thermodynamics problems. The result is a numerical tool that provides the possibility to apply
different types of thermal boundary conditions, including to the free-surface contours. In addition, temperature
dependency can be set to the mechanical and thermal properties of the materials. Concerning the constitutive
models, both Newtonian and non-Newtonian constitutive laws can be employed. The thermally-coupled DEM, on
the other hand, is developed by combining the classical soft-sphere approach for the mechanical behavior of
particles with the solution of the energy conservation equation for the thermal behavior of the elements. Several
different models of contact forces and heat transfer between particles can be employed. With these two numerical
tools presented, the continuous and discrete approaches for thermo-mechanical analysis of granular materials will
be explored together in the next steps of this project.

A DEM-FEM exploratory study on the mechanical interaction between lipid particles and the endothelial glycocalyx layer

Ricardo A. Andreotti — 2024-06-18

This work develops an exploratory study aiming at modeling (from a purely mechanistic point of view)
the complex interactions that are observed between the Endothelial Glycocalyx Layer (EGL) and Low-Density
Lipoprotein (LDL) particles, serving as a gateway to more complex studies about the transport of macromolecules

in arterial vessels. Here, the EGL is represented through an advanced finite element formulation for thin, large-
deformation beams, following a continuum description. The LDL particles, in turn, are handled through a discrete

element approach. The two phases (discrete and continuum) interact with each other through multiple contacts and
collisions, the forces and moments of which being thoroughly computed and passed from a discrete element (DEM)
to the finite element (FEM) model (and vice-versa) at run-time in a staggered, iterative solution scheme, following
the framework developed by the authors in Gay Neto and Campello [1] and Andreotti et al. [2]. The fluid (blood)
phase is represented only indirectly, through drag forces applied on both the FEM beams and DEM particles.
Possibilities of the proposed strategy are illustrated through a preliminary numerical example, herein taken in the
form of a model problem.

Slope Stability Analysis using Element-Free Galerkin Method and a visco- plastic approach with the shear strengh reduction technique

Leandro H. S. Yorinori — 2024-06-18

The majority of slope stability analyses are performed using either the computational approach of tradi-
tional Limit Equilibrium Methods (LEM) or the Finite Element Method (FEM). Several applications in geotechni-
cal engineering involve large displacements, thus it becomes attractive to employ meshless methods. In this paper

the meshless method Element-Free Galerkin (EFG) with a visco-plastic approach is applied to the slope stability
analysis. An analysis is performed to demonstrate the capability of the EFG model to evaluate the slope stability,
which is considered as a plane strain state for the stability analysis of homogeneous, isotropic and dry soil slope.
A non-linear EFG approach with the shear strength reduction technique is applied to assess the factor of safety and
potential slip surface. The results show good agreements with values found in the literature of classical methods
(LEM and FEM), and with a meshless method. The failure criterion is assumed to be reached when the iterative

process does not converge after a maximum number of iterations. The location and form of the potential slip sur-
face are naturally obtained from the results of displacements and principal plastic strains.Therefore, the principal

plastic stress or strain analysis becomes a strong alternative to verify the slope stability state.

Unified positional PFEM formulation for fluid-structure interaction prob- lems with free surface flows

G. Avancini — 2024-06-18

This paper aims to present a positional unified PFEM formulation to solve problems of free surface
flows interacting with elastic structures. In contrast with traditional FEM formulations of fluid mechanics that
use velocities, here we use nodal position as the main variables for both solid and fluid. In addition, the same
solution scheme is used to solve the governing equations of both physical problems. In fact, the coupled problem

is treated as an unique spatial domain containing two different materials. For the solid, a hyperelastic Saint-Venant-
Kirchhoff model is adopted, which is suited for large displacement analysis within the small strain regime, while

the fluid is considered to have an incompressible-Newtonian behavior. A mixed position-pressure approximation
is adopted for the fluid domain to ensure incompressibility, together with a Pressure Stabilizing Petrov-Galerkin
(PSPG). The time marching procedure is performed by means of the second order alpha-generalized scheme. The
usage of a Lagrangian description naturally allows the simulation of deformable solids and free surface flows as
the movement of the mesh nodes coincides with the physical particles motion. However, free surface flows tend
to deteriorate the mesh quality as topological changes and several distortions of the fluid domain may occur. To
deal with that, the PFEM plays a key role by constantly regenerating the mesh and automatically detecting the
physical boundaries by combining an efficient Delaunay triangulation-alpha-shape procedure. The applicability of
the developed approach is demonstrated by the simulation of selected problems.

Simulation of a Free Surface Laminar Flow Using The SPH Method

Willian Teles Pinto — 2024-06-18

The Smoothed Particle Hydrodynamics Method (SPH) is a Lagrangian numerical method used to
solve engineering problems, notably on free surface flow. This article deals with numerical simulation using the
SPH method to one-dimensional laminar flow on a free surface in an infinite channel. The numerical code
developed discretizes the fluid domain in particles with constant mass, which do not move during the simulation
and only present variation in their velocity. The boundary conditions at the bottom of the channel were
implemented using ghost particles to reflect the no-slip condition. Ghost particles with corrections are
implemented on the free surface to ensure that the shear stress on the free surface is zero. This correction ensures
that the numerical results obtained in the SPH method are the closest to the analytical ones. The transient
velocity profile was obtained by adopting the Eulerian framework in the SPH method and compared with the
analytical ones, showing agreement between the results.

Strain rate effects on the mechanical behavior of thick-walled pressurized cylinders

Andrey Brezolin — 2024-06-18

This work studies strain rate effects on the mechanical behavior of thick-walled cylinders subjected to
internal pressure. The material is assumed to present an elastic-viscoplastic behavior presenting strain hardening,
strain rate hardening and instantaneous rate sensitivity. In an effort to elucidate the expected strain rate effects, the
thick-walled cylinder is assumed to radially expand due to an imposed displacement on its internal surface. The
influence of the imposed expansion velocity on the mechanical field that develops through the thickness is assessed
by means of an analytical solution and using finite element simulations. The analysis considers constant velocity
expansions and tests in which the expansion velocity is abruptly changed: stopped, decreased or increased. Such
imposed loading conditions allow evidencing instantaneous and strain rate history effects on the stress response
and on the material hardening behavior.

FATIGUE ANALYSIS USING THE FINITE ELEMENT METHOD

José Pereira R. Junior — 2024-06-18

Fatigue failure analysis becomes a constant concern when intending to produce mechanical components
subjected to alternating loads and stress concentration. Therefore, the study that provide the development of safe
structures and with longer fatigue life proves to be of significant importance. This article presents the formulation
of the finite element method applied to the fatigue problem in continuous structures from the modified Goodman,
Gerber, and ASME-elliptic criteria. The stress field is obtained using a linear quadrilateral element, with four

nodes per element and two degrees of freedom per node. It is considered two structures of optimized and non-
optimized shape under boundary conditions of crimping and point loading at the free end. The numerical results

obtained showed the effect of fatigue on the structures and among the various fatigue failure criteria. The modified
Goodman criterion was more conservative, since it presented significantly higher results for the safety conditions
considered, followed by the Gerber and, ASME-elliptic criteria, respectively.

Reinforcement learning for model selection applied to a nonlinear dynamical system

Thiago G. Ritto — 2024-06-18

In the context of digital twins, and the integration of physics-based models with machine learning tools,

this paper proposes a new methodology for model selection and parameter identification, applied to nonlinear dy-
namic problems. Reinforcement learning is used for model selection through Thompson sampling, and parameter

identification is performed using approximate Bayesian computation (ABC). These two methods are applied to-
gether in a one degree-of-freedom nonlinear dynamic model. Experimental data are used in the analysis, and two

different nonlinear models are tested. The initial Beta distribution of each model is updated according to how
successful the model is at representing the reference data (reinforcement learning strategy). At the same time,
the prior Uniform distribution of the model parameters is also updated using a likelihood free strategy (ABC). In
the end, the models’ rewards and the posterior distribution of the parameters of each model are obtained. Several
analyses are made and the potential of the proposed methodology is discussed.

Uncertainty and Global Sensitivity Analysis of Wind Turbines Power Pro- duction in Non-Ideal Conditions

Bruno M. Mazetto — 2024-06-18

Starting from a consolidated open-source software for wind turbine simulation (OpenFAST), the effects

of operation in non-ideal conditions on power production of a theoretical 5 MW wind turbine are evaluated. Ca-
pacity factor (CF) and the levelized cost of energy (LCOE) for a 500-MW wind farm considering two locations,

one in the northeast of Brazil and another on the North Sea, in Europe, are evaluated. Representative parameters of

non-ideal operational situations are identified and probabilistic models are proposed for the associated uncertain-
ties. Afterward, propagation of uncertainties through Monte Carlo simulations is carried out, and finally, supported

by a global sensitivity analysis based on Sobol indexes, situations that should be primarily treated are identified.
The results indicate that the mean CF is up to 9% lower and mean LCOE is up to 12% lower than their reference
values. Finally, the sensitivity analysis indicates that the greatest influence on generation of the wind turbines and
economic feasibility of wind farms are regarded to rotor misalignment with the wind.

Robust Design of Piezoelectric Energy Harvesting Devices using Multiobjective Optimization Techniques

Paulo H. Martins — 2024-06-18

For the robust design of piezoelectric energy harvesting devices, it is necessary to estimate the mean
and variance of the harvesting performance due to uncertainties in device parameters. This is done here using
Polynomial Chaos Expansions (PCE). Aiming at overcoming the total computational cost required for the robust

optimization, a discussion on the selection of the most relevant uncertain parameters and on the degree and con-
vergence of the PCE is performed. Then, with a satisfactory modeling choice, a multi-objective optimization using

Non-dominated Sorting Genetic Algorithm (NSGA-II) is performed to determine Pareto fronts and box-plots that
allow to choose the harvesting devices with better compromise between performance mean and dispersion.

Time dependent reliability: a time series point of view

Henrique M. Kroetz — 2024-06-18

Engineering problems where material properties deteriorate over time or in cases of random loading

modelled as a random process, the evaluation of the probability of structural failure generates a significant compu-
tational cost, mainly because it is a time-variant reliability problem. Stochastic problems, in which the probability

of failure is time-dependent, shows to be interesting to know about the computational cost and accuracy of the

method disponible in the literature to evaluate the reliability. The assessment of time-dependent reliability prob-
lems 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 general 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 represent 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. Thus, this work makes
a comparison of the application between the expansion optimal linear estimation (EOLE) method and time-series
model (e.g. ARMA), used to evaluate the time-dependent failure probability, presenting the computational cost
and the accuracy of the results obtained, and details about the solutions are addressed.

Effect of the load factor on the construction of Kriging surrogate models for structural reliability analysis of redundant systems

Mariana O. Milanez — 2024-06-18

The combination of surrogate models with structural reliability methods has helped to reduce com-
putational demands, allowing to perform reliability analysis of more complex problems, such as those related to

redundant systems. When surrogate models are employed, the actual value of the limit state function is usually
necessary for the construction of the surrogate. Then, for all simulations, the load must be incremented until Plim,

when failure of the system occurs, increasing the computational costs associated to the mechanical model evalu-
ations. If the simulation is stopped before reaching Plim, there is a loss of accuracy in the evaluation of the limit

state function, which may lead to less accurate surrogate models and, consequently, errors in the estimated failure
probabilities. This paper aims to investigate when the simulation may be stopped without significant losses in
the accuracy of the surrogate model. Failure probabilities and computational costs are compared for a number of
structural reliability problems from the literature. For the examples presented herein, results have shown that when
the load factor is larger than 1.1, the metamodel may be capable to estimate the failure probability, although it can
be necessary more limit state function evaluations to achieve the convergence.

Truss topology optimization considering uncertainties in the applied loads and progressive collapse

Lucas Araújo R. da Silva — 2024-06-19

The progressive collapse is a phenomenon that has received increasing attention from engineers and
researchers in recent years. The study of optimal structural design considering load redistribution due to the
progressive failure of elements is recent. In this context, this paper deals with the topology optimization of truss
structures, considering uncertainties in the applied loads and the progressive collapse of elements. The optimal
topologies are determined following the ground structure approach. Uncertainties are included in the optimization
problem through the RBDO (Reliability Based Design Optimization) and RO (Risk Optimization) formulations.
Progressive collapse is incorporated into the analyses by considering load redistribution after member failure. The
PSO algorithm is applied to solve optimization problems. System reliability is evaluated using the Monte Carlo
Simulation method with stratified sampling. In RO problems, the costs of hyperstatic and isostatic failures are
differentiated and solutions are obtained for different costs. The results suggest that the RBDO formulation leads
to isostatic optimal topologies, since there is no incentive for the permanence of hyperstatic elements in the final
solution. On the other hand, in the RO formulation, hyperstatic structures are among the optimal solutions,
indicating that this formulation is the most appropriate for dealing with problems including progressive collapse.

Risk optimization of RC beam under column loss scenario

Lucas da Rosa Ribeiro — 2024-06-19

The sudden column loss of a single supporting element in a RC frame may lead to the disproportionate
partial or total structural collapse if its design fails to confine the initial damage through resisting mechanisms.
Since uncertainties like material properties and geometrical parameters plays a major role in the behavior of the
resisting mechanisms, and consequences are highly significant for such failure events, the risk optimization is a
very convenient tool to optimize the balance between economy and safety. This is shown herein by the
optimization of a RC beam sub assemblage, considering the beam height, longitudinal steel rebar areas, stirrup
cross section area and stirrup spacing as design variables. Failure consequences are included for service limit state,
ultimate limit state of confined concrete at snap-through instability, and ultimate limit state of the steel rebars at
catenary action stage. A physical and geometrical nonlinear static analysis is employed, in which the samples are
submitted to pushdown displacement control over the removed column. Material behavior is represented by an
elastoplastic model with isotropic hardening for the steel rebars, and by combination of Mazars μ model with the
modified Park-Kent model for the confined concrete. Failure probabilities are evaluated by the Weighted Average
Simulation Method, and the Risk optimization is done by the Firefly Algorithm. In order to reduce the
computational cost due to the nonlinearities involved and the high number of sample points required, Kriging is
used to generate a sufficiently accurate metamodel for the limit states and for the system failure probabilities. It is
shown, for the analyzed problem, that the confinement of concrete plays the major role in providing structural
safety, since a design that survives the initial stages but fails in the instability stage is sudden, not allowing the
occurrence of catenary action.

Ultimate strength optimization of stiffened panels based on a meta- model for prediction by Artificial Neural Networks

João P. S. Lima — 2024-06-19

To determine an optimum geometry of stiffened panels applied to hulls of ships about their ultimate
strength (σult), analyses are performed applying nonlinear FEM on stiffened panels subjected to axial load. A
Artificial Neural Networks (ANN) metamodel is presented to predict responses demanding a smaller number of
simulations by the nonlinear FEM to accurately assess the structural capacity. Initially a simply supported thin
plate without stiffeners was adopted, called a reference plate, using its ultimate strength as a reference value for
the study. A panel of volume Vt=91.035x106 mm3 was adopted. After that, part of its volume has been converted
into stiffeners, which were incorporated into the plate, without varying the final volume of the plate. This made it
possible to evaluate the design variables plate thickness (tp), as well as the ratio between the height of the
stiffener and its thickness (hs/ts). In response, the use of Cross-Entropy (CE) optimization algorithm and the
ANN to predict a sampling by Monte Carlo allowed an optimization of the design variables resulting in a
stiffened plate model with approximately 3.5 times resistance of a plate of the same volume, length, and width,
but without stiffeners.

Probabilistic optimization of a quarter car suspension with multiobjective framework and gradient based approximation

Ewerton Grotti — 2024-06-19

In this paper, a multi-objective robust optimization methodology is applied to the suspension
optimization problem of a quarter-car numerical model. In order to increase the driver’s comfort without
compromising the drivability, the chosen objective function was the weighted RMS acceleration according to
ISO 2631 with constrain regarding the suspension working space. The robust optimization is based in a
probabilistic approach, more advanced compared to the interval based approach. Monte Carlo simulations are
made to compare the statistics of the problem, as well as the failure probability. While the deterministic solution
found 3.97% better mean acceleration values when compared to the robust optimization, the chosen solution
generated by the multi-objective robust optimization results in a much lower failure probability: 10.55% for the
Robust against 50% for the deterministic.

Modeling and optimization of multimodal piezoelectric energy harvesters from broadband vibration

Virgilio J. Caetano — 2024-06-19

Piezoelectric energy harvesting technologies from ambient vibration sources have attracted considerable
attention in recent years for powering low-power autonomous electronic devices. In real-world applications,
environmental vibration excitation may feature in a broadband spectrum presenting random characteristics. In this
work, circular-shaped and pizza-shaped configurations are investigated as candidate designs for multimodal
piezoelectric energy harvesting systems to harness energy from wideband vibration sources. A comparison with a
conventional beam-type energy harvesting system is performed. The system dynamics are modeled, designed,
optimized, and investigated using the finite element method implemented in ANSYS Workbench. Numerical
simulations are carried out to investigate the system performances aiming to establish suitable performance
conditions, considering harmonic and random excitations. The modeling approach is interesting to design other
energy harvesting systems, especially with complex geometries. The proposed multimodal harvester has potential
to harvesting energy from broadband vibration excitations showing performance advantages compared with
classical single-mode energy harvesters.

Use of a recurrence based fractional derivative model in the analysis of the influence of geometrical parameters in the transient response of viscoelastic beams

Erivaldo P. Nunes — 2024-06-19

This paper aims to analyze the influence of geometrical parameters on the dynamical behavior of
viscoelastic beams. Viscoelastic materials are widely used in vibration control of dynamic systems. Usually, a
viscoelastic layer is applied on the surface of the structure and a second layer with elastic properties is used to
restrict viscoelastic displacements. This restrictive layer intensifies energy dissipation once it introduces shear
deformation in the viscoelastic material. Naturally, geometrical parameters, mainly the width of the viscoelastic
layer may influence the shear deformation and the efficiency of the vibration control treatment. For this analysis,
a recurrence based fractional derivative model is used, the system is discretized in finite elements and solved
using Newmark's method. This procedure makes it possible to compare the mechanical behavior of several
viscoelastic beams with different geometries, and determine how they affect vibration control treatment.

Chaotic behavior analysis of two-bar trusses under inelastic effects through Lyapunov exponents

Gustavo B. Barbosa — 2024-06-19

The advancement of engineering structures is increasingly leading to slender and light elements that
require more complex analysis. Instability problems are frequently observed in such situations, and their study is
of fundamental importance. Numerical methods are commonly used in those analyses. It is proposed in this work
to use a variation of the Finite Element Method, called for a Positional Formulation (PFEM), with the advantage
that the geometric nonlinearity is naturally incorporated into the method. In terms of physical nonlinearity, a
mixed-hardening model is used in the Formulation. The dynamic analysis is carried out by Newmark‘s method
of integration in the time domain, and the Newton-Raphson Method is used to solve the equations of equilibrium.
Also, Lyapunov exponents are employed to determine the regions where the chaotic behavior occurs. One example
of a two-truss bar is used to verify the effectiveness of the implemented formulation and the influence of inelasticity
in the chaotic behavior. The analysis is done by different values of the initial conditions, since chaos is sensitive to
such variations.

Dynamic of Launch Vehicle with Slosh Effects CILAMCE-PANACM-2021

Domingos Sávio Aguiar — 2024-06-19

The use of liquid propelled rocket engines in launcher vehicles offers many advantages over its solid
counterparts: higher specific impulse; the possibility of re ignition and the control of thrust vector magnitude. The
launch vehicle experiences different dynamics environments during its mission, which can affect the propellant
tanks and drive oscillations of the liquid volume center of mass. Since the mass of liquid propellants in a launcher
can be significant in relation to the whole vehicle mass, oscillations in the fluid volumes can lead to important
dynamic effects. In this work, the dynamics characteristics of a launch vehicle with liquid propellant are analyzed
considering lateral slosh effects. The launch vehicle body is modelled as a beam and the liquid is modelled by a
spring-mass system. The natural frequencies and mode shapes of the vehicle with and without including the liquid
sloshing modes are evaluated for different fill ratios of the propellant tanks.

Influence of First Stage Mass Variation on Satellite-Launch Vehicle Longitudinal Vibrations

Augusto Molica Silva Guimarães — 2024-06-19

During the launch phase, satellites are subjected to intense dynamic loads. Part of these loads is due to
acoustic excitation from the exhaust jet stream and other aerodynamic effects and part is due to different
phenomena that originate in the launch vehicle propulsive system. The later can cause vibrations that propagate
longitudinally along the rocket structure and can reach the satellite. This paper analyzes the influence of the effect
of mass variation of the first stage of a launch vehicle in the longitudinal dynamic response of its payload during
lift-off and the first phase of the flight. A discrete multi degree of freedom model was implemented to evaluate the
longitudinal vibrations of a real launcher-satellite set when subjected to thrust oscillations.

Influence of Geometrical Dimensions of Reservoir on the Fluid- Structure Coupled Dominant Modes in Concrete Gravity Dams

Davidson de O. França Júnior — 2024-06-19

Properly determining the dynamic structural response of a dam is complex as it involves aspects related
to fluid-structure interaction (FSI). The coupled response depends on numerous variables, and among them is the
fluid domain, which has a significant influence on the coupled dominant modes. In the design phase, such a
reservoir is idealized as an acoustic cavity that must have dimensions and boundary conditions appropriate to the
problem. However, depending on these geometric parameters considered for the reservoir, the natural frequency
ranges and the order of the fluid vibration modes are different, directly influencing the coupled fluid-structure
vibrations, this is because the coupled response depends on the decoupled frequency range of the structure and
fluid domain in isolation. Thus, in this paper the uncoupled and coupled fluid-structure free vibrations of the Koyna
gravity dam located in India are studied. The natural frequencies, vibration modes of the structure and
hydrodynamic pressures are investigated and compared under different numerical modeling (reservoir dimensions)
using the finite element method (FEM) by means of ANSYS®. For validation of the numerical approaches
presented here the results obtained are compared with values available in the literature.

Didactic bench for the analysis of cantilever beams submitted to harmonic vibrations from a cam-follower system

Vladimir T. Barbosa — 2024-06-19

Practical classes are essential for learning in engineering courses, but there are many difficulties in
implementing them. Therefore, the development of equipment, which help in carrying out practical activities in
the course, facilitates the absorption of theoretical concepts. This work describes the procedures adopted for the
development of a didactic bench for vibration analysis. The system is consisting of a cantilever beam, where the
shaker is represented by a cam-follower system that apply a harmonic excitation force at the free end of the
beam. The project involved the implementation of a frequency control system and the development of routines
on the software LabVIEW for data collection and signal process from the bench. The LabVIEW application
allows comparisons between the theoretical signal simulated from the mathematical modeling of the beam and
the experimental signal collected by the accelerometer sensors. The construction of the didactic bench was
satisfactory because the cam-follower system was able to generate the harmonic force and control its frequency.
In addition, the application developed in LabView offered a simple interface to help students absorb the concepts
of vibration and machine design.

Bipedal model experimentally adjusted to simulate human walking forces in vertical direction

Vega D. — 2024-06-19

In this study, a damped bipedal model with compliant legs is adopted from the literature to represent
a walking pedestrian. Forty-five volunteers are recruited to participate in an experimental program to walk on a
rigid surface covered by force plates. The walking forces and accelerations at the pedestrians’ center of mass are
recorded in the experimental campaign. The bipedal model parameters are estimated by adjusting the numerical
and experimental vertical ground reaction forces (GRFs). Monte Carlo simulations are performed within wide
ranges of input parameters and initial conditions to obtain the best possible matches between the model predictions

and experimentally measured data. It is found that the bipedal model can reproduce stable gaits and typical M-
shape GRF profiles for step frequencies in the range of 1,42-2,42 Hz. The best correlations are found at slow

and normal walking speeds. Moreover, empirical values for pendulum length, attack angle, leg stiffness and leg
damping are proposed.

Numerical and experimental analysis of the mechanical response of a rota- tory balancing system for industrial in situ calibration

Otavio T. Krey — 2024-06-19

The present work introduces the validation of an unorthodox solution for the balancing of rigid rotors:
SimMov, a piece of customized equipment for the transport of specific machinery to carry out the balancing process
in situ. For such purpose, the FE models used to assess the mechanical response of the structure are exposed. The
numerical results were compared, in terms of acceleration, with experimental measurements obtained with the
SimMov equipment. The acceleration response was also tested through standard balancers with a permanent and
rigid base, which is the usual practice for similar machinery. Moreover, a simple rotor dynamics model was solved
to verify the structure’s critical operating behavior. These solutions were used as input data for the FE models
employed to predict the structure’s response. In the FE models, high-order shell elements were used to solve
modal problems using the Lanczos block algorithm. The experimental results were probed and compared at critical
points, predefined by the numerical models. Data acquisition was performed with six MEMS sensors (designed for
industrial applications). A sampling rate of 10.00 kHz was employed. Data processing was performed using power
spectral density (Welch’s method). The comparison of results demonstrated the correct functioning of SimMov for
the unbalance level considered as allowable by the machine manufacturer.

Influence of soil-structure interaction on the dynamic behavior of a structure subject to seismic action

Patricia Grezelle — 2024-06-19

The soil-structure interaction (SSI) is present in the structural analysis in the coupling between structure,
foundation, and the soil. The consideration of this interaction is important in studies involving seismic events,
considering that the structure interacts with the soil, which alters the structural response. Attentive to the damages
caused by dynamic loads coming from the ground, the study aims to compare a structure receiving excitation
directly at the structure without considering the effects of SSI and another case considering these effects. The
excitation would be represented by an already known seism. The structures of the two situations would, firstly, be

modeled in discrete spring-mass-dampener systems and solved through the state-space method for a linear time-
invariant system. This solution method allows solving problems composed of a set of input, output, and state

variables from first-order differential equations in a matrix form. The two models were implemented in Matlab
Software. The results were expressed in the time domain via state-space and frequency by applying the Fast Fourier
Transform (FFT) in terms of displacement and velocity. The results were compared to verify the influence of SSI
on the dynamic response of the structure, which was shown to be beneficial to the structure.

Structural Optimization and Vibration Control using Magneto- Rheological Dampers in Tall Buildings under Dynamic Wind Load

Alex Koch de Almeida — 2024-06-19

The importance of the wind action in structures, in a context in which the maximum possible and
acceptable slenderness is desired, increases directly and proportionally to the height of the buildings. Those tall
and slender buildings, respecting safety criteria, always aim at the minimum cost. This work is part of that scenario,
which aimed to apply structural optimization methods combined with the use of Magneto-rheological (MR)
dampers in tall buildings under dynamic wind load. The structure, idealized in concrete, was modeled using the
finite element method and, the dynamic wind load, through a stochastic process. The optimization of the structure's

mass was performed using the Particle Swarm Optimization (PSO) algorithm. Finally, a set of MR dampers (RD-
1005-03, Lord Corporation), considering the modified Bouc-Wen rheological model with parameters obtained

experimentally was applied in the structure. The results showed that the structural optimization combined with the
control produced by the MR dampers was able to reduce the response, demonstrating that smart structures, which
combine optimization techniques and semi-active control in their design, are a promising alternative.

Dynamic analysis of a footbridge subjected to human load

Alex Koch de Almeida — 2024-06-19

The structural branch of engineering is constantly evolving, especially with regard to advances in
modeling with the use of improved software, with trends in optimized processes that aim to save time and money.
Constructive trends have led to the development of more resistant materials and the design of structures capable
of overcoming large spans, using structural elements with smaller sections, that is, thinner, lighter and more
flexible. At the same time, the vibration frequencies of these structures tend to become lower, becoming closer to
the dynamic excitations, subjecting themselves to oscillations that generate some human discomfort or cause a
feeling of insecurity. In this context, the main objective of this research is to verify the performance of a metallic
truss footbridge, subject to human loading and to analyze its natural frequencies and mode shapes. According to
the chosen structure, the dynamic action that will be applied and analyzed in this study was determined. For this,
human excitation was chosen. Newmark's Numerical Integration Method was used to find the system's response
to dynamic excitation. Finally, the developed algorithm was validated and the results analyzed, concluding that
the footbridge under study would meet the acceleration criteria, therefore, requiring no intervention.

Influence analysis of suspension parameters on vehicle dynamics through an analytical method

Lucas da S. Gomes — 2024-06-19

This study was based on a prototype developed by the Automotive Technology Group - ULBRA, whose
aim is to evaluate the influence of suspension system parameters on the vehicle's directional behavior. An
analytical method was used to calculate the lateral load transfer between the wheels and thus predict the under- or
over-steering behavior. A model developed in the CARSIM® software served as a comparison and validation of
the method. It was possible to define the stiffness of the springs and stabilizer bars to get a vehicle with neutral
behavior and it is concluded that the method is effective for understanding the vehicle roll dynamics in curves and
the influence of each parameter, such as height and center position gravity, roll center, stiffness, and other design
parameters, although it does not consider aspects such as traction or curvature angle variation.

Coupling Model for Viscoelastic Sandwich Beams Used for Vibration Control

Samuel Cavalli Kluthcovsky — 2024-06-19

Dynamic neutralizers are simple devices used to minimize the levels of vibration and noise radiated
from a mechanical structure in a certain frequency range. They operate by inserting a high mechanical impedance
in the region of interest, applying reaction forces, and dissipating vibratory energy. Composite sandwich beams
with viscoelastic materials are used to control vibration in structures with high modal density, such as plates,
slender buildings and electrical transmission lines due to their dynamic characteristics. In addition to the high
damping factor, the use of these neutralizers with multiple degrees of freedom (MDOF) is favorable for the control
of these structures, especially when working in a wide frequency band. This study presents a novel coupling model
using angular and translational degrees of freedom between the structure to be controlled (primary system) and
the MDOF auxiliary system attachment point. The dynamic behavior of the MDOF sandwich beam under study is
modeled using the commercial finite element software ANSYS®. Then, in the Matlab® software, the compound
system is assembled using the primary system modal parameters coupled to the dynamic behavior of the sandwich
beam using translational and rotation equivalent springs. The finite element method was validated with
experimental data of a single degree of freedom viscoelastic neutralizer. The numerical and experimentally
dynamic behavior showed an excellent approximation. Additionally, the transfer functions of a fixed-free beam
with a sandwich beam attached to the free end are analyzed studying the coupling of translational and rotation
DOF. For MDOF neutralizers, the coupling model accuracy is extremely important to ensure the proper design of
the auxiliary system physical parameters for vibration control.

3D topology optimization of a tall tower considering soil flexibility

Iago Cavalcante — 2024-06-19

This paper investigates the effect of soil flexibility on the solution obtained by topology optimization
of a tall tower in continuous contact with the soil throughout its base. The tower is modeled with classical finite
elements, while the soil is modeled with boundary elements, which is more adequate to deal with unbounded soil
domains. Coupling between the tower and soil is established by imposing equilibrium and continuity conditions
at the soil–tower interface. The paper shows strategies for solving the different orders and types of elements at
that interface. The final equilibrium equation resulting from the coupling scheme contains the linear superposition
of the tower and soil stiffness matrices, and connects nodal forces and displacements as in classical finite element
assembly schemes. The Bi-Directional Evolutionary Structural Optimization method (BESO) is chosen to solve
the compliance minimization problem under prescribed volume constraints. The solutions for the tower resting
on the ground surface and for resting on rigid supports are compared, and the results show that both the optimal
topology of the tower and the compliance that is achievable are significantly affected by the flexibility of the soil.

Efficient compliance-based topology optimization with many load cases scenarios

Lucas do Nascimento Sagrilo — 2024-06-19

In topology optimization setting, we can cast a variety of problems into a weighted-sum of compliances
minimization. Robust design, for example, is commonly addressed in the form of a finite sum of deterministic load
cases scenarios. Another example is the optimization of structures subjected to dynamic loads using the equivalent
static load method, where a finite set of associated loads is defined according to the displacements over time. But
when the number of loads involved is high, the solution of these problems becomes extremely expensive from a
computational point of view, due to the necessity of solving one finite element problem for each of these loading
cases along the steps of the optimization algorithm to evaluate the objective function. In this context, two methods
for dimensionality reduction of the problem are presented. First, an equivalent stochastic problem to the original
one is determined, which reduces to only a few the number of necessary load cases at each step. The second
approach uses the singular-value decomposition of the matrix that gathers the different loading scenarios to reduce
the number of linear systems to be solved. The applicability of both methods to different topology optimization
scenarios is discussed, and numerical examples are proposed to compare the final topologies obtained and quantify
the reduction in the number of necessary finite element solves.

Topology optimization applied an threshing separation rotor component

Aquiles S. Schauenberg — 2024-06-19

Threshing separation rotors are extensive used as extensively in a combine harvester as a flow separator
that includes at least one rotary axis. Among the components of the rotor, the finger is one of the main ones because
it is responsible for separating the grains and the straw. Nonetheless, the optimization is little explored which
makes it a component of low structural performance. This work aims to develop a topology optimization using a
finite element (FE) model in order to reduce the mass of the finger. In the first step, the model is performed
considering the pre-torque of the screw and the bending load that the straw generates on the finger. Besides, the
normal and tangential contacts are considered between the components. Then, the topology optimization is
performed by Solid Isotropic Material with Penalization (SIMP) method. The objective function is defined as
minimizing the volume of the finger subject to von Misses stress and displacement constraints. The topology
optimization results present that the volume reduced achieve 84% in comparation with original model.

Topology Optimization of Binary Structures Subjeted to Self-weight Loads

Lucas O. Siqueira — 2024-06-20

The study of structures subject to self-weight loads is particularly important for the fields of civil,
aeronautical, and aerospace engineering. Topology optimization emerges as a crucial tool in this analysis providing
structures with non-intuitive conceptual designs and greater material savings. Binary methods are among the most
established methods, where the design variables assume discrete values 0 and 1 for the void and for the solid
material, respectively. In previous studies, it has been reported that topology optimization of structures subject to
self-weight loads using binary methods is almost impossible to be employed without the RAMP material model.
This article shows that binary topology optimization for self-weight loads depends on the formulation and not only
on the material interpolation. To illustrate that, the classic SIMP material model is used together with the recently
developed Topology Optimization of Binary Structures (TOBS) method for topology optimization of structures
subject to self-weight loads. The algorithm was tested and verified to analyze two bidimensional benchmarking
problems. The effect of penalty variation on the final topology was discussed for modified SIMP model. From
the results, it was demonstrated that the modified SIMP model combined with TOBS allows to efficiently optimize
structures subject to self-weight loads.

A geometry trimming approach for topology optimization of acoustic problems

T. de Castro — 2024-06-20

One challenging scientific problem in Topology Optimization (TO) is how to set its framework to ac-
count for different physics, such as acoustics. In this case, the dynamic acoustic pressure oscillations and numerical

issues when interpolating acoustic and solid material properties become a burden. In this paper, we first investigate
the use of Topology Optimization of Binary Structures with Geometry Trimming (TOBS-GT) for solving acoustic
problems. The governing equations are solved via the Finite Element Method and sensitivities are computed with
the adjoint method by using automatic differentiation. In order to verify the proposed methodology, a 2D acoustic
problem was investigated. The objective is to minimize the average sound pressure level on a certain part of a
2D rectangular room by trimming out the design domain along the ceiling. The obtained results are similar to the
ones found in the literature solved with different TO methods. The potential advantages here are obtaining designs
without gray scale and with well-defined boundaries. This indicates that the TOBS-GT approach is a promising
tool for solving acoustic problems.

An efficient Python code for modelling strut-and-tie tridimensional models for topological optimization using SESO and ESO methods

Higor E. V. O. Prado — 2024-06-20

This paper presents a methodology for the automatic generation of optimal strut-and-tie models in
reinforced concrete structures using the Evolutionary Structural Optimization (ESO) and Smoothing Evolutionary
Structural Optimization (SESO) methods. The presented methodology is developed to minimize the compliance
and is implemented in Python. The proposed approach deals with the generation of projects with truss-like
elements, addressing a console. The obtained results show a good accuracy compared with those described in the
literature.

Reliability-based topology optimization using evolutionary methods for three-dimensional structures analysis

Aline R. M. Madruga — 2024-06-20

This paper addresses structural topological optimization considering the reliability analysis using the
Evolutionary Structural Optimization (ESO) and Smoothing-ESO (SESO) methods, whose heuristics allow that,
at each iteration, whichever elements of the mesh whose contribution to the structure stiffness is considered
inefficient is removed / added during the optimization procedure. A code in Python was developed based on the
minimization of compliance to determine the optimal three-dimensional topologies of an L-shaped structure. The
reliability analysis is performed using First Order Reliability Method (FORM), which aims to obtain a model with
lesser volume and greater stiffness than the deterministic topological optimization (DTO) analysis.

A parameterized level set topology optimization strategy using FEniCS and radial basis functions with compact support

Giovanna C. Andrade — 2024-06-20

This work addresses level-set based methods for structural topology optimization. Compact support C2-
Wendland radial-based functions are employed to parameterize the level sets. Structures are assumed to be in static
equilibrium, under plane stress state and built with isotropic linear elastic materials, and the classical compliance
minimization problem is considered. Aiming to save the computational effort of the potentially large number of
linear systems to be solved, the computational linear algebra of the resulting sparse interpolation matrix is explored
in contrast with the use of classic multiquadric radial basis functions, with dense matrices in the related systems.
Implementation is made in Python using the FEniCS project for the resolution of the equilibrium system and

the sensitivity analysis, based on a recent work of Laurain, that uses direct numerical resolution of the Hamilton-
Jacobi equation for the level set update. Both strategies are, therefore, compared. Additionally, our approach is

put into perspective with the radial basis function parameterization Matlab code of Wei et al. Numerical results
of experiments with classical benchmark problems are presented.

MULTIOBJECTIVE OPTIMIZATION OF REINFORCED CONCRETE BUILDINGS

Estevão Alencar Bandeira — 2024-06-20

The application of parametric and topological optimization in the conception of buildings is a problem
of high complexity due mainly to the large number of variables of interest to be optimized and to its nature
intrinsically multiobjective. Due to the computational development occurred in the last decades, it has arisen the
opportunity for a broader study and development of numeric models in this field. For the conception of structural
projects, it counts on vary computational programs that automate great part of the structural projects’ conception
process. However, in the stage of definition of the structural elements position, such as columns and beams, there
is still a high level of dependency of the designer because it is long the time spent in the project’s conception and
not always the solution found is the most viable in economic and executive terms. In view of this problem, the
current work aims to initiate the development of a computational model of structural optimization of buildings in
reinforced concrete to decrease the designer dependency with the objective of minimizing the costs – such as
concrete volume and steel weight – through the search of columns positions and its dimensions, restricted to an
imposed architecture. It must be employed the evolutionary computation philosophy through the use of the
heuristic method of genetic algorithms, in the generation of the various feasible solutions, which are obtained by
the results of the model of analysis by spatial framed structures, based on the finite element method. For the
generation of the cost function, it will be considered the determination of the section area of the column and the
steel needed that attends the equilibrium of each reinforced concrete section subjected to biaxial (oblique) bending
with axial force state. Lastly, it will be performed comparative studies, qualitative and quantitative, between
structural conceptions with and without the optimization technique in order to verify the consequences of its use.

Multi-material continuum topology optimization with multiple volume constraints and material nonlinearity

Danilo B. Cavalcanti — 2024-06-20

Most existing studies in multi-material continuum topology optimization consider linear elastic material
models. Since actual materials, in general, display a nonlinear constitutive relation, this paper presents an initial
study to evaluate the influence of the material nonlinearity in the solutions obtained using a multi-material topology
optimization approach with multiple volume constraints. Material nonlinearity is considered by means of an
Ogden-based model or a bilinear model. To achieve this, a Matlab implementation using the educational code for
multi-material topology optimization, PolyMat, was made. We took advantage of the modular structure of the
educational code to make changes mainly in the structural analysis routine and adapt the optimization formulation
for the maximization of the stationarity total potential energy. Numerical examples are presented to demonstrate
the influence of material nonlinearity in the optimized topological solutions.

A MATLAB implementation for topology optimization of compliance minimization problems based on the standard finite-volume theory for continuum elastic structures

Marcelo Vitor Oliveira Araujo — 2024-06-20

Topology optimization is an important technique for the design of optimum structures. Its main
objective is to determine the best material distribution inside of an analysis domain. In the last three decades, a
significant part of the advances in structural topology optimization has been achieved by employing finite-element

strategies for structural analysis. Therefore, the advantages and disadvantages of this numerical technique are well-
known. For instance, the checkerboard pattern is directly associated with the finite-element method numerical

assumptions, which leads to some artificial stiffness. An alternative to the finite-element method is the finite-
volume theory, which has been shown to be an efficient checkerboard-free numerical technique. Many algorithm

implementations have been published for educational purposes over the last decades to promote topology
optimization strategies. However, most of these algorithms are constructed based on the finite-element method.
Therefore, the present paper proposes a MATLAB® implementation of a topology optimization approach for
compliance minimization problems based on the standard finite-volume theory of linear elastic continuum
structures. A sensitivity filter is also implemented to control the mesh dependence and length scale issues.

Stress-based topology optimization with bi-directional evolutionary tools

José M. Cuevas Zárate — 2024-06-20

This work presents a stress-based application of the bi-directional evolutionary structural optimization
(BESO) method for topology optimization of structures where the objective is to minimize the stress while
subjected to a structural volume constraint. The structure is discretized with a finite element mesh and subjected
to a static external load to evaluate the von Mises stress distribution that will be used to obtain an equivalent
global stress measure through a modified P-norm approach. The elemental sensitivity numbers are derived from
the modified P-norm stress and filtered to update the design. The results were compared to cases found in the
literature for problems based on stress and compliance. It was verified that the applied methodology was able to
obtain a maximum stress reduction.

Machine learning models for characterizing macroscopic properties of diesel/ biodiesel surrogate fuels

Rodolfo S. M. Freitas — 2024-06-20

Accurate determination of fuel properties of complex mixtures over a wide range of pressure and tem-
perature conditions is essential to utilizing alternative fuels. Obtaining thermophysical properties of complex fuels

is important for design and analysis but difficult to measure/predict, especially in the range of extreme conditions

operations. Molecular dynamics (MD) simulations have been widely used to characterize physicochemical proper-
ties of fuels, including transport properties at supercritical conditions. Although MD simulations provide molecular

details that can be potentially be used to predict fuel properties accurately, they are generally too expensive in terms
of computational costs. In addition, MD predictions also need to be validated against experimental measurements,

which can be even more costly, especially in extreme conditions. Accordingly, it is not feasible to establish com-
plete and detailed fuel property databases consisting of a wide range of pressure and temperature conditions using

MD simulations or experimental measurements. Machine learning (ML) has great potentials to discover from data
the relation between inputs and outputs of complex systems. ML can be a powerful tool to predict fuel properties
from chemical compositions of the fuel mixture and/or chemical structures of the fuel molecules. Those models
can be trained using the database from MD simulations and/or experimental measurements in a data-fusion-fidelity

approach. The present work aims to construct cheap-to-compute ML models to act as closure equations for pre-
dicting the physical properties of diesel/biodiesel surrogate fuels. Here, Gaussian Process (GP) and probabilistic

generative models are adopted. GP is a popular non-parametric Bayesian approach to build surrogate models
mainly due to its capacity to handle the aleatory and epistemic uncertainties. Generative models have shown the
ability of deep neural networks employed with the same intent. In this work, machine learning analysis is focused
on a particular property, the fuel density, but it can also be extended to other physicochemical properties.

Dynamic analysis of a helical gear pair under uncertain bearings properties

Laís B. Visnadi — 2024-06-20

The complexity of the dynamic response of gear pairs models may vary, depending on the approximation
chosen to time-varying mesh stiffness. When uncertainties are considered in the model, another layer of difficulty
is added and the computational cost increases. To solve the stochastic model, Monte Carlo methods are usually
implemented. However, the large number of samples plus the complex deterministic model may make the problem
unfeasible to solve. The use of stochastic collocation with generalized polynomial chaos expansion can diminish
the number of samples, allowing the study of complex gear pairs. In this work, the stochastic dynamical response
of a pair of helical gears is analyzed. The mesh stiffness is calculated by the accumulated potential energy method
and uncertainties on the translational bearing’s stiffness are considered. The stochastic dynamical response of the
system was approximated through a generalized polynomial chaos expansion and the expansion coefficients were
evaluated by the stochastic collocation.

Condition monitoring of ball bearings using Bayesian neural networks

Matheus de Moraes — 2024-06-20

Rotating machines play a fundamental role in several engineering applications. In most of these ap-
plications, they are subjected to unexpected overloads that can cause the premature failure of their components.

This work aims to present a condition monitoring framework that employs the Bayesian neural networks approach,

which includes uncertainties quantification associated with the damage detection in ball bearings. Images of vi-
bration signals of ball bearings were used to feed a Bayesian neural networks and the algorithm predictions were

given in terms of the probability density function of the possibility of the vibration image belongs to a specific type
and severity of damages. The results demonstrated that Bayesian neural networks (BNN) as a powerful technique
for damage diagnosis, and it can quantify uncertainties in condition monitoring of ball bearings.

On a kinematically exact rod model for thin-walled open section members

Marcos P. Kassab — 2024-06-20

In the context of frame structures, kinematically exact rod models are pivotal to correctly describe
critical loads and post-critical behaviour. For thin-walled open-section members, such formulations need to take
cross-sectional warping into account, since it becomes a relevant load-carrying mechanism due to the very small

torsion stiffness of such members. Most thin-walled rod models available in the literature consider only the so-
called primary warping, which is the warping in the direction of the cross-section ́s walls lengths. The walls ́

thickness warping, or secondary warping, is typically neglected. Although primary warping generally suffices to
properly capture the rod ́s deformation, there are particular cases wherein secondary warping becomes relevant,

and to which existing models often fail to perform. This work develops a kinematically exact rod model for thin-
walled open section members taking into account both primary and secondary cross-sectional warpings. Advanced

elastic constitutive equations are then incorporated in order to enable full bending, compression and torsional strain
couplings in the finite strain regime. The model is implemented in an in-house finite element program and its
outcomes are validated against reference solutions obtained using hierarchically higher order formulations, having
as reference large deformation ANSYS’s shell 181 elements.

A co-rotational model for elastoplastic analysis of planar frames

Rafael I. Tasinaffo — 2024-06-20

A co-rotational model is employed to analyze planar frames considering plasticity effects lumped at
plastic hinges. The element is locally formulated as the traditional linear element based on the Euler-Bernoulli
theory. The hinges effects are introduced into the generalized strain fields as Dirac deltas centered at the element
ends, which naturally results in the formulation of the element with plastic hinges. The plastic constrained
nonlinear system of equation of the local problems is solved with the Newton-Raphson method running through
all plastic possibilities, whereas a classical force-control procedure solves the global nonlinear equilibrium
equations. Two examples are presented to demonstrate the robustness of the formulation to deal with geometrical
nonlinear elastoplastic analysis of frames.

Numerical study of a two-dimensional problem in a constrained minimization theory of elasticity

Adair R. Aguiar — 2024-06-20

We consider the equilibrium of a cylindrically orthotropic disk subject to a prescribed displacement on

its boundary. In the context of classical linear elasticity, this problem has a solution that predicts material inter-
penetration. To prevent this unphysical behavior, we minimize the energy functional of classical linear elasticity

subject to the local injectivity constraint. In previous work, we have obtained computational results showing that

this problem has a rotationally symmetric solution that bifurcates from a radially symmetric solution. This sec-
ondary solution differs from a secondary solution reported in the literature, which was obtained by making no

assumptions about the symmetry of the solution. Here, we extend the investigation of our previous work by mak-
ing no a priori assumption on the symmetry of the displacement field. Using two different formulations, we obtain

sequences of numerical solutions that converge to the rotationally symmetric solution mentioned above as the mesh
is refined. In addition, there is no evidence of the existence of a third solution, which indicates that the rotationally
symmetric solution is the only possible secondary solution. This research is of interest in the investigation of solids
with radial microstructure, such as carbon fibers and certain types of wood.

Fracture mechanics of aircraft structures with riveted and adhesive stiffeners

Vitor Lima Mesquita — 2024-06-20

A structural component is tolerant of damage if it can safely sustain critical length fractures until it is
repaired or its economic life has expired. Reinforcers or stiffeners have the main function of improving the
resistance and stability of these structures and providing a means of decelerating or stopping the propagation of
fractures in nuclear containments, reactors, viaducts, tall buildings, aircraft, ship hulls, bridges and offshore
structures. Analyzing the stress intensity factor and how the behavior of a sheet with and without stiffeners is
different are some of the issues studied in this work. The stress-intensity factor (SIF), a parameter that describes
the intensity of the singular stress field, has been used successfully to estimate fracture strength and fatigue crack
growth rates in situations where the assumptions of linear elasticity are valid.

Boundary Layer Phenomenon in the Limit Analysis of Reissner- Mindlin Plates

Eric L.B. Cavalcante — 2024-06-20

The Kirchhoff and Reissner-Mindlin plate theories are the most frequently used models for describing
the behavior of linearly elastic plates. In what concern the limit analysis of plates based on the static theorem, the
most significant difference between those theories lies in the fact that for a Reissner-Mindlin plate the transverse
shear resistance is included in the yield criterion. It is numerically shown that the Kirchhoff plate theory
increasingly overpredicts the collapse load of plates with decreasing side-to-thickness ratio. For this reason alone,
the Reissner-Mindlin plate theory should be used in the limit analysis of relatively thick plates. On the other hand,
transverse shear locking and boundary layer have been major sources of convergence delay of Reissner-Mindlin
plate models, especially towards thin plate solutions. While the former is a well investigated finite element defect,

the latter is a real physical phenomenon likely to be manifested in more refined theories, such as the Reissner-
Mindlin plate theory, that nearly no attention has been paid in the framework of yield design. In this sense, it is

used in the present work a recently developed shear locking-free finite element for the yield design of Reissner-
Mindlin plates based on the static theorem to illustrate boundary layers along certain types of plate edges, which

may not be of the same type as those in linear elastic solutions. Finally, a brief state-of-the-art review about limit
analysis of Reissner-Mindlin plates is then provided.

A finite strain elastoplastic model based on Flory’s decomposition

Vitor H. Kishino — 2024-06-20

In this study, an alternative formulation is proposed to solve large strain elastoplastic problems. In the
proposed strategy, the Flory decomposition is adopted, enabling the separation of volumetric and deviatory
stresses at the Lagrangian space. In addition to stresses, the energetically conjugated strains, namely, volumetric
and isochoric, are also established, enabling the construction of an elastoplastic model for which the flow law
comes from the stress state, regardless the yielding surface. Representative examples are used to validate and
show the possibilities of the proposed formulation.

A simple formulation applied to finite strain viscoelastic solids and compressive flows

Renato T. Kishino — 2024-06-20

When writing movement equations in stresses for continuous media, it makes no difference if the
media is solid or fluid. The fundamental difference in the solution of these two problems relies on the respective
constitutive laws. For solids shear stresses are related to shear strains and the Navier-Cauchy equation takes
place, while for fluids, shear stresses are related to the time rate of shear strains, resulting in the Navier-Stokes
equation. For solid and fluid isothermal problems, the pressure is related to the volumetric change. Based on
hyperelastic relations, we present an original total Lagrangian numerical approach capable of modeling simple
large strain viscoelastic solids (Kelvin-like) and free-surface compressive viscous isothermal fluid flows. The
proposed model is implemented in an in house positional prismatic finite element formulation and is explored in
numerical examples.

Computational modeling of an adolescent’s reduced functional spine unit: a comparative study between isotropic and anisotropic hyperelastic intervertebral discs

Tainan M. Brandão — 2024-06-20

Computational finite element analysis has been used in investigations of the spine, contributing to the
understanding of its biomechanical behavior. Intervertebral discs (IVD) are structures that make the connection
between the vertebrae, allowing movement between it and, consequently, increasing the mobility of the spine and
been one of the most critical components of the spine. Therefore, the present paper has as main objective to propose
two analyzes of a reduced thoracic functional spine unit: in the first, the IVD is modeled as a hyperelastic rubber
like isotropic structure and, in the second, a hyperelastic anisotropic property is adopted to represent the fibers of
the annulus fibrosus. Finally, these models were compared with each other to assess the contribution of anisotropy
hyperelastic analysis to the biomechanical behavior of the spine. Through the results obtained, it is concluded that
the hyperelastic anisotropic models of the annulus fibrosus can bring more authentic results to the computational
models of the spine, considering the contribution of fibers and the large deformations to which soft tissues are
subjected. Furthermore, the reduced model can predict the spine's biomechanical behavior, being useful in spine
mechanical studies.

CFD Applied to the Simulation of the Vibration Phenomenon Due to the Cadenced Shedding of Vortices in a Circular Cylinder

Alexandre Miguel Silva Araujo — 2024-06-21

The formation of vortex is related to the separation of the boundary layer close to the immersed body,
depending on the pressure distribution. The aeroelastic phenomenon, known as vortex-induced vibration (VIV),
occurs when the shedding frequency of these vortex approaches one of the structures natural frequencies. Its
study is of practical interest in many branches of engineering, such as risers, bridges, and aeronautical profiles.
In this work, the VIV around a circular cylinder was analyzed numerically through CFD (Computational Fluid

Dynamics) simulations. The numerical method is described by solving the incompressible Navier-Stokes equa-
tions in a Lagrangian-Eulerian framework in a two-dimensional geometric model. In this study, the open-source

OpenFOAM® was used. The numerical experiments were carried out in a cylinder with a unit diameter, with
Reynolds number values of 100, 200, and 400, for reduced velocitys Ur from 1 to 13, and a damping rate ranging

from 0 %≤ ξ ≤5%. The movement of the cylinder is described using a mass-spring-damper system. For the cylin-
der movement, the sixDoFRigidDisplacement solver was used and the solution algorithm for pressure-velocity

coupling was the pimpleFoam. The results of the simulations were consistent when compared to the literature. It
is observed that the damping factor affects the responses of the cylinder, depending on the reduced velocity. It
is also observed that the movement of the cylinder significantly affects the flow field, varying parameters such as
Strouhal, drag coefficient, lift coefficient, and pressure on the studied surfaces. Finally, it was concluded that the
results were satisfactory and that the proposed computational model is a useful tool in solving problems involving
the phenomenon of vortex-induced vibration.

A simple fully nonlinear Kirchhoff-Love shell finite element with thickness variation

Matheus L. Sanchez — 2024-06-21

The current paper develops a new multi parameter Kirchhoff-Love shell finite element with thickness
variation able to reliably simulate thin nonlinear shell for static structural boundary value problems. The study is
a continuation of previous elements developed in Sanchez et al [1] and Costa e Silva [2]. The element has 6 nodes
and uses penalty (or optionally Lagrange method) to deal with the C1 continuity, which is a kinematical
requirement of the Kirchhoff-Love shell model. It is also used a nonconform field of an incremental rotation
variable φΔ (this parameter is firstly introduced in Costa e Silva [2]) to assist with the C1 continuity on element
edges. As a novelty in this study, the C1 continuity on the edges between elements is not further guaranteed by the
maintenance of the kinking angle (as done in Viebahn et al [3]) or by the equivalence of φΔ calculated through
the displacements and the DoF shared by elements (as done in Sanchez et al [1] and Costa e Silva [2]). Now the
C1 continuity is achieved by enforcing the transverse shear strain to zero. For the thickness variation, it is
implemented a double linear non conform field similarly to Pimenta et al [4] to represent the quadratic
displacement at transverse normal to midplane of the shell. The quadratic displacement field of the mid plane is
represented as usual by the 6 parameters at the 6 nodes of the element.

Analysis of the calibration of the constants of the Modified Wohler Curve ̈

Simelia D.Santos — 2024-06-21

This analysis is based on the critical plane approach combined with the Modified Wohler Curve, using ̈
uniaxial fatigue results, of ASTM743 CA6NM steel, subjected to loading ratios R = (0, −1,
−1
3
,
−2
3
,
1
3
,
2
3
). In
this scenario, we show the indicated procedures to calibrate as constants of the Wohler Curve. We postulate that, ̈
by incorporating the effects of multi-axiality, the critical plane approach parameters can be used successfully in

estimating fatigue life under different test conditions. Thus, unlike the classical approach, the use of this enhance-
ment has the advantage of allowing the construction of the verses relationship, regardless of the type of test used

for calibration. To define the new relationship, a calibration strategy considering the Susmel and Lazzarin critical
plane model is presented.As a result, it was found that from the constants A and b curve by the SN curve, we can
represent an intermediate curve by means of these constants versus the compressibility ratio. This relationship is
influenced by the loading rate of Rρ. This new parameter can be used as a multiaxial fatigue criterion for life
prediction. Regarding the parameter A, for this material presented, for the conditions of R = (−1,
−2
3
,
1
3
,
2
3
),

converged with the Susmel and Lazzarin hypothesis, the curve evolved according to the variation of the compress-
ibility relation, changing a linear behavior. However, for the conditions of R = (0,

−1
3
), there is inconsistency in
the available data about the theory. The tensions increased proportionally to the increase of rho, diverging from
the assumed hypotheses. The b parameter behaved similarly to the A parameter.

A Collaborative Web Computer-Aided Design Application

R. L. Soares — 2024-06-21

Computer-aided design (CAD) applications have been helping engineers to design and understand better

the structure and the behavior of models. These applications usually have a complex data structure and are stand-
alone. However, the advance in cloud-based systems has made applications scale better and brought the possibility

of real-time collaborative applications. This study presents a proof of concept of a collaborative web CAD
application. The application uses a client-server architecture. The server is responsible for keeping the data
structure and crossing data between clients using the collaborative functionality while the client has a user interface
and a canvas component to display data and the model. The application uses WebSocket to communicate between
client and server.

Development of a Python Application Aiming at the Teaching-learning Process of the Half-Edge Data Structure

Danilo S. Bomfim — 2024-06-21

Solids modeling is an area of research and development with diverse applications spanning several fields
such as mathematics, computer science and engineering. All these applications require the computational
representation of physical objects as well as the storage of information related to the geometry and physical
properties of these objects. In all these cases, solid modeling aims to produce geometric models that can be used
to perform analyzes of physical phenomena. These geometric models store information describing the position,
dimension, and shape of a physical object. In this way, geometric modeling aims to create computational
representations of real objects so that it is possible to address all geometric and topological issues in a simple, fast,
and efficient way. The representation and manipulation of geometric models properly requires the use of a data
structure that allows to manage all the information necessary to describe such models. This data structure must
have characteristics such as efficiency and economy in the use of memory Therefore, understanding how the data
structure works is essential for researchers and students in the field. With this premise in mind, a Python application
called Hetool was developed to help understand the Half-Edge data structure that is commonly used in many

applications. The developed application aims to help teachers, researchers, and students during the teaching-
learning process. Furthermore, the code developed in the application will be open to users.

Steel beam crack propagation simulation and experimental verification

Sebastián Moya Lazo — 2024-06-21

Steel is a structural material par excellence due to the great ductility it offers, and its excellent behavior
under tensile and bending loads. However, steel can also crack after a significant number of static and dynamic
load cycles. These cracks can be the cause of a later structural failure and, being part of important constructions,
they bring with them a considerable economic loss. During the last years, engineering has studied with
determination the concept of damage tolerance. In this work, two types of commercial steel beams were selected,
where with small interventions to their geometry and inducing a crack in their center, it was possible to study the
propagation of said crack. At the same time, the geometric dimensions and constitutive properties of the tested
beams were entered into the Salomé-Meca finite element software, seeking to compare the experimental behaviors
with those of the simulation. Finally, the tests carried out in the laboratory and the computational simulation
indicated a crack propagation and a new location of the crack front that is millimetrically similar. This shows that
the experimental test is verified with respect to the computational simulation, validating this method to study
tolerance to structural damage.

Consistency assessment of plate bending theories for the implementation of efficient hybrid finite elements in linear statics and dynamics

Ney Augusto Dumont — 2024-06-21

The present developments are part of a research work that aims to implement computationally efficient
models of foldable and deployable structures, which are finding increasing application in the industry. In spite of
the availability of powerful commercial codes, numerical models of large foldable and deployable systems would

rather work with a minimum amount of degrees of freedom to allow for straightforward engineering conceptual-
izations while preserving the structure’s basic static and dynamic properties. A thorough survey of the literature on

moderately thick panels points out the existence of too many theoretical contradictions since the papers by Hencky,
Timoshenko, Mindlin and Reissner, to mention just a few early researchers. This very critical literature review is
part of the present contribution, which also presents a proposition that may claim some originality in terms of both
mechanical consistency and ease of computational implementation.

Analysis of the plasticity regions in elastoplastic torsion problem using mixed complementarity algorithm

Tatiana D. Assis — 2024-06-21

The elastoplastic torsion problem (ETP) consists of defining portions of elasticity and plasticity in the
cross section of a bar twisted by terminal couples. This problem can be modelled by using variational principles
and is considered an obstacle type problem by means of the membrane analogy. At points where the membrane

touches the obstacle, permanent deformations ensues. Thus, the problem can be rewritten as a mixed complemen-
tarity problem and solved using the FDA-MNCP algorithm (Feasible Directions Algorithm for Mixed Nonlinear

Complementarity Problem). In this work, the objective is to analyze the influence of the shape of the cross section
in the resulting regions of plasticity. Some numerical simulations were made for different rectangular proportions,
with the fixed area, to observe how the shape of these regions varies and the percentage they represent in relation
to the total area. In addition, the plastic portions were compared for three sections of the same area and material,
in the formats: disk, square and L.

Mechanical response of bilayer graphene under different loading modes

Euclides Mesquita — 2024-06-21

Carbon-based materials remain promising nanostructures for the development of efficient and
innovative nanotechnologies due to their outstanding properties. Among these nanostructures, bilayer nanoporous
graphene has been considered a good candidate for applications involving water desalination, energy storage,
among others. However, the remarkable mechanical properties of the pristine graphene sheets are strongly affected
by the presence of nanoporous. Thus, in this study, molecular dynamics (MD) were conducted to investigate
bilayer nanoporous graphene's mechanical response under several loading and constraints. Our results reveal that
the introduction of porosity in the graphene's layers decrease significantly their fracture strain. The idea of adding
a second, constrained layer or constrained patches of different sizes, to improve the mechanical tensile properties
of the upper layer yielded no significant modification of its mechanical properties. This behavior suggests that to
influence the mechanical properties of a defect or porous graphene layer by adding parallel layers or repair patches,
other kinds of bonds, not van der Waals, must be created among the layers.

Comparison of Analytical and Numerical Solutions to the Stresses Problem in a Cylindrical Shell with a Circular Hole

Stanislava V Kashtanova — 2024-06-21

The cylindrical shell with a circular hole under three types of boundary conditions is considered: axial
tension, internal pressure and torsion. A new mathematical approach that allows reducing an infinite system and finding
unknown coefficients for the deriving stress is offered. This approach lifts classical mathematical restrictions for
curvature parameter. The comparison of analytical and numerical results by collocation method is described.

Applying beam sizing concepts along with topology optimization on the design of continuum structures

Tarcísio L. de Oliveira — 2024-06-21

Using beams as a modeling and design tool in structural design has long been displaced by more recent
numerical methods, such as finite element analysis and structural optimization, while those concepts became more
restricted to the design of trusses and shafts. But is there still room for it to be applied in contemporary design
of continuum structures? This research investigates some possible aplications of beam theory and beam sizing
concepts when used along with contemporary technologies such as topology optimization, additive manufacturing
and numerical methods, and how it could impact the structural design process.

Sound transmission loss for double panels using the Wave Finite Element Method

G. P. Zanoni — 2024-06-21

Double panels are a usual solution for noise control. In this study, the sound transmission loss (STL)
of an infinite double panel with an air cavity and two solid layers was analyzed. The STL was calculated from
a dynamic stiffness matrix of the system, where the air layer was modeled analytically, and the solid layers were
modeled using the Wave Finite Element (WFE) method, where only one small segment of the structure is modeled
using conventional Finite Element Method (FEM), reducing the computational cost. The influence of the thickness
of the cavity and the specific masses per area of the solid layers in the STL were analyzed. Also, an optimization
procedure to maximize STL in different octave bands was performed. The results demonstrated that the WFE
method is suitable for STL calculation; that a higher STL is obtained for a wider air cavity and higher specific mass
(below coincidence frequency), and the optimization procedure led to different optimal parameters depending on
frequency because of various physical phenomena presented at a double panel.

Peridynamic Prognostic Tool Potentiality Measured by the Finite Elements Method

André de Moraes Vinha — 2024-06-21

At different times and in different applications, humanity needed knowledge about flaws in materials,
such as cracks in structures and components, but the influence of such flaws was not clearly known. At the end
of the 20th century, a theory called Peridynamics emerged, first introduced by Stewart Silling[1], as an extension
of the standard theory of solid mechanics, a different way of seeing what happens internally to the material (a
non-localtheory), using Newton's second Law and making use of displacement integrals, to solve problems in
structures with discontinuities, such as cracks. In parallel, there is the Finite Elements Method (FEM) like
mencioned for J. P. Dias [2], which is already well established and widespread both in academia and industry,
which can also be used to investigate the behavior of solid elements that have discontinuities. Thus, the work in
question hás the intuition to compare two different programs, one written using the FEM and the other the
Peridynamic theory, to achieve results of the effectiveness and convenience of Peridynamics, since the FEM
already presents several references proving its results.

A large strain thermodynamically-based viscoelastic-viscoplastic model applied to two-dimensional finite element analysis of solids

Pericles R. P. Carvalho — 2024-06-21

In this work, we propose a large strain viscoelastic-viscoplastic constitutive model applied to two-
dimensional finite element analysis of solids. The model is developed in a thermodynamic framework, based

on the multiplicative decomposition of the deformation gradient into elastic, viscous and plastic components.
The viscoelastic part is represented by Zener’s rheological model, and is formulated with an internal variable
approach, with evolution law in terms of the viscous deformations gradient rates. For the viscoplastic part, we
apply a Perzyna-like model, including a large strain generalization of the classical Armstrong-Frederick kinematic
hardening. In order to characterize the proposed constitutive model, we present results of uniaxial relaxation and
creep tests under different analysis conditions, as well as more complex examples showing the potentialities of the
developed framework.

Equivalent strain measures for micromorphic continuum damage models

Pamela D. N. Reges — 2024-06-21

Various applications of the micromorphic continuum theory have been proposed in the past mainly
due to its regularization properties in strain localization problems as a consequence of its non-local character. The
micromorphic theory is particularly suited for the analysis of quasi-brittle materials as the microstructural behavior
is incorporated in its formulation through the consideration of additional degrees of freedom related to the material
particle. In order to allow the application of the micromorphic theory associated to damage models, extending its

regularization properties to different constitutive models, this work presents a generalization of classical scalar-
isotropic damage models for the micromorphic theory implemented in a constitutive models framework for elastic

degrading media. To guarantee conformity to a classical implementation, a compact tensorial formulation is used,
allowing the application for the micromorphic theory of theoretical and numerical resources already defined for
the classical theory. A homogenization strategy is also employed to obtain the micromorphic constitutive relations
through the consideration of a Cauchy continuum in the micro-scale, what makes possible non-linear analysis of
micromorphic media with only the definition of the material parameters of a classical continuum.

PORO-MECHANICAL COUPLING STRATEGIES FOR LARGE STRAIN COMPRESSION OF SOFT BIOLOGICAL TISSUES

Jose L. M. Thiesen — 2024-06-21

Early studies related to current poroelasticity theories are oriented towards problems in geomechanics.
In addition to their use in soil mechanics, biphasic theories play an important role in the field of biological soft
tissue mechanics. In this context, the elucidation of how mechanical stimuli are able to modify the behavior of

cells within the tissue makes computational mechanics and mechanobiology extremely relevant fields. In gen-
eral, due to the highly nonlinear coupled response coming from the biomechanical nature of the problem, large

time-dependent deformations, damage, and fluid-structure interaction are complex behaviors that usually lead to

difficulties in numerical solutions. Different types of schemes arise as an option to solve the mechanical equilib-
rium and mass conservation equations. Iteratively coupled methods emerge as an alternative to solve the biphasic

problem. Therefore, in this paper, we propose a numerical investigation of the so-called undrained scheme applied
to the finite element method using the updated Lagrangian approach. An unconfined case study is used to compare
the response of the iteratively coupled method with the monolithic scheme, where the governing equations are
solved simultaneously. In addition, the influence of an exponential permeability model on the volumetric strain
and pore pressure fields is assessed.

STUDY CASE OVER AN AGRICULTURE SPRAYER EQUIPMENT USING MULTIAXIAL FATIGUE CRITERIA COMPARED WITH EXPERIMENTAL RESULTS.

Roberto I. Rodrigues — 2024-06-21

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.

Comparative Analysis of the Seismic Behavior in Latin American Countries using Response Spectra

Juliana Ferreira Novaes — 2024-06-21

This research compares the seismic behavior of a construction in five Latin America countries,
considering the design spectrum for seismic excitation corresponding to each region. An 18-storey reinforced
concrete structure was defined, in which a seismic spectral excitation was applied to get a bar graph showing
structural damage data in the building elements for each country under study: Brazil, Colombia, El Salvador, Peru
and Venezuela. Analyses and responses were worked using the SAP2000 v.20 computer program. All the seismic
parameters required in each case were used in the modeling of the various design spectra. Design seismic spectra
considering a rigid soil and an acceleration of 0.10g, 0,20g, 0,30g and 0,40g in all countries was tested. The results
show potential structural damage scenarios for each beam and column element in the structure.

Program for finite element analysis of grillages with circumferential arc-shaped and straight elements

Humberto M. Lima — 2024-06-21

This paper presents the development of a program for structural linear-elastic analysis of grillages with
circumferential arc-shaped elements and regular straight bars under concentrated and distributed loads. It was
based on the Finite Element Method, and the code was written in FORTRAN (FORmula TRANslation). The force
method was used initially to calculate the flexibility matrix and then by inversion the stiffness matrix and load
vectors were determined. Results of deflections, rotations, bending, torsion and shear, from numerous examples
were checked against some of those available in the scientific literature, in order to validate the code. A comparison
was also made with the validation results and those calculated by the virtual work method, or extracted from two
similar softwares where the curved bars needed to be approximated by various small straight elements. The
program developed was shown to give closer values to the exact solution, with a much simpler input data (just
angles and radiuses), than the other softwares.

Static stochastic analysis in cylindrical panels’ geometry

João Pedro Xavier Freitas — 2024-06-21

Cylindrical panels under uncertainties, described by a uniform probability density function, on
parameters such as thickness and radius, are investigated when static loading is submitted. Firstly, an analytical
approach - based on the equilibrium equations governed by Donnell’s nonlinear shallow shell theory, Airy’s stress
function and standard Galerkin method - is taken to evaluate the effects of parameters uncertainties on the buckling
load and post critical nonlinear equilibrium. Then, an approach based on the finite element method is considered
to model the same geometry where the mesh is composed by shell elements and its convergence is conducted in
terms of buckling load. The nonlinear equilibrium path is obtained through the modified Riks method and a
perturbation parameter. In both methodologies, a set of deterministic samples simulates the stochastic system,
which are evaluated from Chi-Squared hypothesis test. The uncertainty in the thickness results in a stochastic
system where the nonlinear equilibrium path can be described as a uniform probability distribution. On the other
hand, the radius shows a stretching along the curve where a two-component Gaussian mixture fits better the
obtained response where the mean of axial load as respect to a certain displacement cannot be represented by the
mean of its lower and upper boundaries.

The static structural analysis of a historical masonry building at Curitiba, PR.

Fornajeiro C. S. Henrique — 2024-06-21

The structural analysis of historical structures is an important requirement to accomplish the conservation
of historical heritage efficiently. Frequently the structural analysis of historical buildings is a hard task. These
difficulties are due to the empirical way in which most of these structures were designed and built, making it
difficult to obtain the structural material mechanic parameters, and to obtain the knowledge of the way they were
built. Although Brazil presents several historical buildings there are few studies concerning the structural analysis
of such structures. In this scenario, this work has as aim to contribute to the structural analysis of Brazilian
historical building in order to be useful to future researchers of the subject. This work consists of a case study
which uses a numerical finite element method using the Abaqus/Cae program to perform the static analysis of a
colonial Building, built in structural brick masonry with a wooden truss system roof dated from the 18TH at
Curitiba, PR. The obtained static analysis consists of the stresses and displacements of the masonry walls under
the action of self-weight and wind loads. The obtained results allow to assess the current structural safety condition
of the building.

Numerical simulation of wind effects on the Church of Saint Francis of Assisi by Oscar Niemeyer

Guilherme S. Teixeira — 2024-06-21

Numerical simulations are viable and reliable alternatives in the study of wind action in buildings.
Using the Ansys Workbench software were estimated the effects of wind action on the Church of Saint Francis of
Assisi, in Belo Horizonte, designed by Oscar Niemeyer, constituted of parabolic and circumferential generatrices.
For validation, were determined the pressure coefficients considering monolithic domes according to Brazilian
Standard ABNT NBR 6123. The wind effects on the Church of Saint Francis of Assisi by Oscar Niemeyer were
simulated and, in a particular case, disregarding the slope. Here, were presented the visualization of the flow
around the geometry from the streamlines and the analysis of external pressure coefficient isobaric lines.

Numerical study of the wind effect on scallop domes

Camila C. Guerra — 2024-06-21

The effects of the action of wind on scallop domes were numerically investigated using the software
Ansys, as well the interference of the neighborhood on the external pressure coefficient and the streamlines
between geometrically identical domes. The influence of the proportion on the neighborhood interference in
scallop domes and the variations in the dimensions of the structures on the pressure coefficients and streamlines
were also investigated. Five simulations were analyzed involving six-grooved domes and geometry height
variations for validation. The numerically obtained coefficients were compared with values in the literature. Other
applications investigated the influence of grooves on the external pressure coefficient and the effect of wind on the
grooved domes. Another application analyzed the interference of the neighborhood on the external pressure
coefficients and streamlines between three geometrically identical domes and, finally, the influence of the
proportion in the study of the interference of the neighborhood. Here, the variations in the dimensions of the
structure affected the pressure coefficients and the streamlines were analyzed. It was possible to verify the
versatility and efficiency of the computational method used in the analysis of the action of wind.

Evaluation of engine-induced vibration levels on a Baja SAE frame: a pilot comfort improvement assessment using the Finite Element Method

João Vítor F. M. Silva — 2024-06-21

The development of reliable virtual models to evaluate vehicle attributes, such as comfort, is crucial for
the automotive industry to reduce time and costs on the product development process. The vibration levels
generated by the engine can potentially cause uncomfortable effects on the passengers and compromise the vehicle
operation when in resonance with other components, thus they should be carefully analyzed. The objective of this
work is to numerically evaluate the vibration levels of a Baja SAE frame on the interface regions with the pilot
and develop countermeasures to decrease these levels. To reach this objective, a finite element model of the frame
was built, using shell elements. Modal and torsional stiffness analyses were performed to validate the model.
Frequency Response Functions were generated to evaluate the vibration transmissibility from the engine to the
seat and steering wheel fixing points, within the operational frequency range of the engine. To decrease the
vibration levels, engine mount bushings and structural countermeasures were tested on the model to define the
best solutions for the pilot comfort, comparing the frequency response functions amplitudes under different frame
designs and bushings properties.

Kinematic analysis of one degree of freedom mechanisms using the SolidWorks and the MATLAB

Tiago S. Miranda — 2024-06-21

The following article intends to present the kinematic analysis of three different mechanisms with one
degree of freedom, being one four-bar mechanism, one quick return mechanism, and one slider-crank mechanism
using different methods, first the Solidworks motion study tool, and afterwards codes developed in the MATLAB.
To determine the dimensions of the elements were utilized a shaping machine for the quick-return mechanism,
and the LS3 engine for the slider-crank mechanism. Graphics and maximum values of displacement, velocity, and
acceleration for specific frequencies of rotation of the crank were shown, and the results were validated by
comparison. Furthermore, some kinematic details of the mechanisms were analyzed, including the ratio between
the time of advance and return of the quick-return mechanism. The same results - extreme values and graphics -
were found by both methods, which demonstrates that they were correct.

Isogeometric Analysis of Functionally Graded Plates using different Mi- cromechanical Models

Renan M. Barros — 2024-06-21

Functionally Graded Materials are a class of composite materials with a gradual and continuously
varying composition. Given the constituents, the volume fraction is evaluated by a mathematical function and the
effective properties by a micromechanical model. This work presents an isogeometric formulation for the analysis
of functionally graded plates based on a Third-order Shear Deformation Theory. Distinct micromechanical models
are adopted for the analysis and the displacements found are compared with the First-order Shear Deformation
Theory.

Algorithm for extracting points from images: irregular contours

Rafael Furlanetto Casamaximo — 2024-06-21

This work proposes the development of a software to implement a contour extraction algorithm for
two-dimensional geometries. The algorithm uses different image processing and data analysis techniques to build
an object mask. From the object mask, a finite set of points that describe the image contour is extracted. Next,
the contour is separated by parts with different enumerations delimited by rectangles. All data processed and
extracted from the image can be downloaded by the user in file form. Then, the information from the contour
data is used to generate two-dimensional meshes for finite difference calculations and numerical simulations.
Our automated algorithm generates meshes for irregularly contoured geometries. For this, the mesh elements
in rectangular coordinates are not equally spaced, so that the vertices of the border coincide with the contour of the
geometry obtained by the algorithm. For the development of the algorithm, techniques are used that select a pixel
range of an object to generate the mask. The software uses the Python programming language, together with the
OpenCV library that performs image and data analysis.

Influence of Dataset Structuring on Condition Monitoring of a Rotating System by Machine Learning

Flavio C. A. Pereira — 2024-06-21

Condition monitoring consists of constant data acquisition from a machine of interest to determine its
operational condition, and also to give reasonable predictions regarding its behavior over time. Considering that
vibration generated by a machine carries information about internal conditions and is sensitive to structural
changes, vibration analysis can be employed to detect faulty components. As some defects have known vibrational
responses (“vibrational signatures”), it is possible to infer the type of defect by analyzing the vibration signal
characteristics. An algorithm capable of automatically doing this type of analysis could potentially prevent
financial or physical harm. In this context, the present study focuses on preprocessing vibrational response data
related to induced defects in a rotating system, extracting features of interest, using a machine learning classifier
to identify common problems, and segregating troublesome conditions from expected normal operation ones. The
processed data was obtained from the Machine Fault Dataset (MaFaulDa/UFRJ). The obtained results show the
influence of dataset structuring on the algorithm generalization capability, revealing that bigger datasets do not
always lead to superior performance and that an increase in the amount of attributes is not always the most
interesting choice.

Graphical User Interface (GUI) Application to Perform Stability Analysis in ANSYS

Rafael V. Oliveira — 2024-06-21

There is few commercial software, based on finite element method, that are able to perform buckling
analysis. One of the most popular commercial software based on FEM that can perform this kind of analysis is the
ANSYS, and is considerably complex. Due to a big range of possibilities and resources that the program offer,
sometimes the interest in some specific analysis, like stability, can be hard to perform because of the difficulty in
the input data. Also, sometimes it is necessary to run a set of analysis with several profile dimension, so this task
can be extremely difficult with a not friendly GUI of drawing. Then, the aim of this work is to give a GUI
application that offer to the users an easy and friendly way to run buckling analysis in profiles using ANSYS. The

application was developed using Python Language and the framework Electron and can perform linear and non-
linear analysis. Moreover, was carefully developed to be easy to use to facilitate access and speed up numerical

analysis of buckling for researchers and interested people. At the end, are presented the application use in a set of
analysis of flexural stability of pultruded glass fiber reinforced polymer I-sections.

Computational analysis of the mechanical behavior of soil-cement mixtures applied to shallow foundation of small building

Everton A. B. Ferreira — 2024-06-21

This paper aims to analyze computationally the mechanical properties of soil-cement mixtures applied
to shallow foundations modeled from the project of a small building of social interest. The paper followed a

methodology divided into three steps: systematic review, computational modeling and the result analysis of soil-
cement mixture application in shallow foundations. Firstly, values for the mechanical properties of soil and soil-
cement mixture were collected and estimated by equations from the literature. The properties were collected

considering the same soil type for both soil and soil-cement mixture. Based on the collected data, it was possible
to create a finite element computational model that allowed to perform the stress analysis. The dimensions and the
loads applied to the model were estimated from the standard project of building of social interest. The feasibility
analysis of the mechanical properties of soil-cement shallow foundation were made on the graphs and figures
generated from the computational modeling. The results allowed to evaluate the stress concentrations of the model
and compare it to the strength of the soil-cement mixture. Finally, this investigation plays a fundamental role in
the production of knowledge about the mechanical behavior of soil-cement mixtures applied to shallow
foundations of small buildings.

Structural reliability for the design of rack columns using the Direct Strength Method

Victor A. M. de Faria — 2024-06-21

Cold-formed steel profiles have been increasingly used in civil engineering applications. A very
common section of cold formed profiles is the rack section, mainly used in industrial storage systems. In a few
situations, rack profiles present repeated perforations along the length of the member to provide greater freedom
of assembly. The structural design standards need to ensure that profiles used in these conditions guarantee the
required safety. This work aimed to evaluate the reliability indexes (β) of perforated rack profiles under axial
compressive load, using the FOSM and FORM reliability methods and the Monte Carlo Simulation (MCS). In
order to obtain the professional factor (P), a database of experimental tests from several authors was elaborated,
to be compared to three proposals for adapting the Direct Strength Method (DSM) to perforated columns. The
reliability indexes were calculated for the load combinations of AISI S100 (2016) and NBR 14762 (2010)
specifications. The β values obtained using two of the methodologies were shown far from the 2.5 and 3.0
calibration targets. The β values obtained by the third methodology were close to the 2.5 target. The last method
proved to be the safest, although it requires the Form Factor (Q), that needs to be obtained experimentally.

Evaluation of the Internal Forces in a Plane Steel Frame under Fire Situation

Maria Eduarda S Piccolo — 2024-06-21

The study of the high temperature effects on the steel structure systems analysis has been usual. The
structural behavior under fire is an important part of fire protection engineering and the high degree of complexity
and cost of experimental analyses under fire is remarkable. Thus, numerical analysis has been a widely used tool
for investigating the structural behavior in fire. In this context, the present study has as objective to evaluate the
behavior of the internal forces of a double steel frame, submitted to the action of fire. The temperature field in the
cross-section of the structural elements that makes up the frame is obtained by the simplified method of NBR
14323 without thermal protection. Once the temperature of the structural elements is established, the behavior of
the internal forces as a function of the temperature increase is evaluated using the Ftool software. Additionally, an
analysis considering five different scenarios of exposure to fire is performed. The results showed that the
magnitude of the internal forces increases with increasing temperature, which contributes to the loss of structural
strength and, depending on how the fire reaches the structural elements, there is a significant difference in these
forces.

Análise Térmica de Perfil I Variando as Condições de Exposição ao Fogo e Comparando Métodos de Análises

Lavínia L. M. Damasceno — 2024-06-21

Quando uma estrutura está sob incêndio, as características físicas e de rigidez são afetadas provocando
perda da capacidade resistente do sistema estrutural. No contexto numérico, informações provenientes da análise
térmica são fundamentais para se alcançar o comportamento termoestrutural. Sabe-se que existe uma série de
variáveis que podem influenciar na análise térmica. Assim, no presente trabalho é realizada a análise térmica de
um perfil I variando as condições de exposição ao fogo bem como a utilização de material de revestimento térmico
comparando métodos de análises: avançado e simplificado. A metodologia da análise pelo método avançado é
realizada em regime transiente, considerando fatores relevantes como os mecanismos de transferência de calor,
além da variação das propriedades térmicas dos materiais em função da temperatura atráves do módulo
computacional CS-ASA/FA. O método simplificado de obtenção da temperatura no elemento estrutural em aço é
definido pela NBR 14323. Os resultados mostraram que a forma como o elemento estrutural é exposto ao fogo
influencia na temperatura que o elemento pode atingir e a importância da utilização de material de proteção térmica
na redução da temperatura dos elementos de aço. Além disso, mostraram a importância de se considerar as
propriedades térmicas dos materiais variando com a temperatura.

PRELIMINARY ANALYSIS OF FLOW OVER A CIRCULAR CYLINDER USING CFD

Luiz F. C. de Oliveira — 2024-06-21

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.

The influence of wind direction and source location in the flow pattern and concentration field over an urban canopy

Gabriel G. Almeida — 2024-06-21

The flow characteristics and pollutant dispersion around a group of obstacles are investigated
numerically using a Reynolds stress turbulence closure model. The mathematical modeling is based on the solution
of the conservation equations (mass, momentum, and chemical species). Numerical simulations were performed
over an idealized urban canopy with twenty-four unequally spaced buildings with rectangular cross sections and
constant height with a commercial software ANSYS-FLUENT 16.0, that uses a finite volume method. The
influence of the source location was evaluated. Two different locations of the point sources were considered. Wind
direction influence was also analyzed and discussed. It was found that the flow pattern is very affected by the wind
direction, with the formation of eddies and low-velocity regions, and the mean concentration distribution was also
determined by the source location and building configuration relative to the wind.

Influence of Non-linear Damping on Non-linear Structures Vibrations

Thiago R. Carvalho — 2024-06-21

The study of linear and non-linear dynamic behavior of structures is an area that has received constant
attention in recent decades, due to the fact that the structures have become increasingly light and slender, causing
vibration problems to be taken into account during the project. Many studies have been developed to try to
understand the nonlinear response of structural systems, especially chaotic vibrations considering different types
of nonlinearities in systems with gain or loss of stiffness. In this sense, many studies have been developed
considering linear damping, but in many applications, it is necessary to consider non-linear damping, such as drag
forces or vibration isolation, which mainly affect the non-linear dynamic response of systems. This work aims to
study the role of non-linear damping in non-linear oscillations of a discrete system with a degree of freedom. It is
considered a discrete system of a degree of freedom and subjected to variable loads over time considering three
types of damping (linear, quadratic and cubic). Resonance curves are obtained for various load and damping values
in order to observe their influence on the dynamic instability of the system.

A SIMP-based algorithm to maximize natural frequencies in two- dimensional structures

Sheyla Maurício Maia — 2024-06-21

This paper aims to study the topology optimization of two-dimensional structures based on their
dynamic response by implementing a computational algorithm that optimally distributes the material in a project
domain based on the SIMP approach (Solid Isotropic Material with Penalization). It allows for a well-defined
result and therefore a layout that can be manufactured since it penalizes intermediate densities thus eliminating
them from the final result. The model uses the Finite Element Method (FEM) for spatial discretization and to
evaluate the objective function, the restraints, and the sensitivities through iterations. Since it does not depend on
the initial representation, the solution of a topology optimization problem can be represented with a high degree
of geometric complexity, requiring a certain level of refinement of the finite element mesh. This refinement can
cause sub-regions of the domain resembling a checkerboard pattern, which is avoided when a sensitivity filter is
used. The optimization objective function is taken as the lowest eigenfrequency of the structure, as to avoid
resonance, a common problem in civil and mechanical structures.

Evaluation of Internal Forces in Cold-Formed Steel Truss exposed to Fire

Fernanda Freitas — 2024-06-21

The use of cold-formed steel structural elements is evident in recent decades and motivated by their
structural efficiency as a function of the relationship between strength and weight. Its application is wide ranging
in buildings or hangars. However, due to the slenderness of the elements, projects involving cold-formed steel
are governed by the instability phenomena. In a fire situation, it is known that the physical and mechanical
characteristics of materials deteriorate during exposure to fire and the resistant capacity decreases with
increasing temperature. Thus, this work aims to analyze a truss subjected to the action of fire. The CS-ASA/FA
program defines the temperature field of the cold-formed steel cross-sections without fire protection and the
simplified method of NBR 14323 is used to obtain the temperature in the truss section with hollow encasement
fire protection material. Additionally, the behavior of normal force on the most requested bar due to temperature
increase is evaluated. The results showed the importance of using fire protection material in reducing the
temperature of steel elements and showed that the magnitude of normal force increases with increasing
temperature, which contributes to the loss of structural strength.

Stationary Evaluation of CPTu Data in Brazilian Marine Clay

Adlehr G. C. Oliveira — 2024-06-21

Structural integrity is an important premise in oil well design. In this context, soil characterization helps the well
design team to assess soil resistance and design conductor and surface casing strings that supports all construction

and operation loads. Piezocone Penetration Test (CPTu) is commonly used as it is simple and provides comprehen-
sible soil data. Using CPTu dataset, it is possible to characterize geomechanical behavior using statistics presented

in the literature. Application of statistics procedures in parameter characterization must be done using samples that
attend stationarity criteria i.e. constant mean and variance of the fluctuating component. Present work applies a

modified Bartlett Statistics in experimental marine soil CPTu data to evaluate sample sizes that satisfy stationar-
ity criteria. Initally, trends in parameters are calculated using linear regression analysis and layer classification is

applied in detrended parameters. Subsequently, autocorrelation samples are evaluated and fit into models. These
autocorrelation models estimate the scale of fluctuation which measures high statistical correlation domain and
Bartlett profiling is then applied. Bartlett’s peak value is compared with critical modified Bartlett Test formula
evaluated by Phoon et al. [1] to assess if stationarity of the sample is within 5% confidence level. Results show
sample intervals that achieve stationarity.

Dynamic instability of cable stayed masts

Antônio Vaz Eduardo Júnior — 2024-06-21

Cable stayed structures are widely used in several engineering areas such as civil, mechanical,
telecommunications and offshore engineering. These structures are light weight and efficient to carry both axial
and lateral loads due to the stayed cables and can be characterized by large displacements and high load bearing
ratios. As these structures can display large displacements which are associated to both nonlinear static and
dynamic behavior, the research of its nonlinear response is of high interest by engineers and scientists. In this
work, the dynamic instability of cable stayed masts is studied. For this, the mast is described as a simplified
nonlinear one degree-of-freedom system subjected to a lateral harmonic load. The Hamilton principle is applied
to obtain the nonlinear dynamic equilibrium equation which is solved using the 4th order Runge-Kutta method. A
parametric detailed analysis is considered to obtain the time response, Poincaré maps and resonance . Obtained
numerical results show the great influence of both cable tensioning and cable positioning on the non-linear
behavior of the system and could be used as a tool for an analysis of the nonlinear dynamics of the structure
previous to design.

A general purpose library for solving multiphysics problems

Gustavo P. Exel — 2024-06-21

This article presents a numerical library specifically developed for solving partial differential equations
(PDEs) using the Element-based Finite Volume Method (EbFVM). The library supports two and three-dimensional
unstructured grids composed of different types of elements. The user is responsible for providing the mesh file,
boundary and initial conditions, the physical properties and typing the model equations in a math-like text format.
The library is responsible for integrating the equations in time and space, obtaining the set of algebraic equations,
assembling the linear system and running the simulation. In this manner, the user is not required to possess
any previous knowledge of the underlying numerical scheme, i.e. the EbFVM. Another appealing feature is that
coupled multiphysics problems can be easily configured through a user-friendly interface.
For demonstration purposes, we present three well known test cases. In the first one we solve a simple heat
conduction problem with the main goal of introducing the basic guidelines of the library. Next, we present the
procedure for solving a linear elasticity problem, in which the three displacement components are the unknowns.

Finally, a coupled consolidation problem modelled by Biot’s [1] equations is presented. In this case, the un-
knowns are pressure and displacements, which is easily handled by the library. We remark that, to the best of our

knowledge, there is no general purpose and open source code available on the internet that uses the EbFVM as a
numerical scheme.

Machine Learning strategy in comparison to Physics-based models to predict the Resilient Modulus response of Soil-polymer composites under triaxial and cyclic loads

Ruan A. Carvalho — 2024-06-21

The objective of the work is to propose a Machine Learning (ML) strategy to predict the Resilient
Modulus (RM) for soil-polymer composite materials. It is developed regression models capable of accurately
predicting the material stiffness under cyclical tests based not only on traditional predictor variables defining the
stress state but also incorporating information such as curing time and polymer dosage in the composite. This
strategy aims to answer the question of whether ML data-based models, considering a larger range of independent
variables, can perform better than various physics-based constitutive models specialized to specific ranges of the
independent variables. Gaussian Process Regression (GPR) models are trained from data from triaxial cyclic load
tests performed on specimens of different polymer dosages and curing times. The predictor variables are confining
stress, deviator stress, curing time, and percentage of polymer incorporated into the composite, whereas the
Resilient Modulus (RM) is the response variable. The optimization of hyperparameters and model performance
measurements were employed using cross-validation methods. The results show that the accuracy of the ML
models is competitive and, in some cases, better than the ones provided by the physics-based constitutive models
traditionally used to model the RM response.

Multi-Objective Structural Design Optimization of a Wind Turbine Blade

Lucas de Landa Couto — 2024-06-21

This paper studies the structural design of a 60m long 5MW wind turbine blade to achieve optimum
results using different optimization techniques. Due to the high aspect ratio of this component, its design involves

many challenges, including large deflections, stability, and aeroelastic phenomena. Therefore, it’s proposed an op-
timization problem with conflicting objectives and design constraints based on international standard IEC-61400-1

and Certification Guidelines. The two objective functions are the minimization of the structural weight of the blade
and the maximization of the first natural frequency of vibration. Using a parametrized Finite Element Model, the
composite layup of the blade, including the material of each ply, number of plies, and fiber orientation, are the
design variables. The results were compared to the reference blade developed by the National Renewable Energy
Laboratory (NREL) to validate the optimization strategy.

Sensitivity analysis of viscous properties of salt rocks during oil well drilling

Luiz E. da Silva Filho — 2024-06-21

This paper presents a sensitivity analysis of viscous properties of salt rocks during well drilling used to

explore and produce oil and gas. The definition of viscous properties of salt rocks is based on triaxial tests per-
formed on samples extracted in-situ. These properties can be difficult to characterize since demand obtaining core

samples and performing laboratory tests. In practical terms, the estimated properties of some pre-salt fields are
commonly extrapolated to others. However, this generalization can generate elevated errors in several cases. An
alternative is to use information about other oil wells already drilled in the same region with similar or equivalent

formations to predict anomalous behavior events. In this context, it is studied in this work the mechanical behav-
ior of oil wells drilled through salt rocks according to the variability of its constitutive parameters. The adopted

methodology includes: a) data collection on viscous properties of Brazilian salt rocks; b) simulations of oil wells

drilled on salt rocks varying the viscous properties of the surrounding formation; and c) calculation of the sensitiv-
ity of the variables related to well borehole radial displacement, aiming the better understanding of the relationship

between the constitutive properties of the salt rocks and the global mechanical behavior. This study can be used
as a startup reference for a retro-analysis to calibrate salt rock constitutive parameters from anomalous behavior
events in correlated oil wells. The main contribution of this work is associated to fitting a regression model to
events in correlated oil wells using a set of simulation results from the range of the constitutive parameters.

Comparative study for evaluating the gradient of the failure function of wells drilled on salt rocks

Luiz E. da Silva Filho — 2024-06-22

This paper presents a comparative study of strategies for obtaining the gradient of the failure function
used in the First Order Reliability Method (FORM) applied to oil wells drilled on salt rocks. The evaluation
of the mechanical behavior of complex structures is commonly performed using the finite element method. In
these cases, several challenges are found when it is desired to carry out a structural reliability analysis, since the
function that defines the structural behavior is numeric and each query requires running a finite element analysis.
This demands a high computational cost, making it practically impossible to perform the reliability analysis from
classical simulation methods. On the other hand, to use transformation methods it is necessary to evaluate the
gradient of the failure function, which is also a numerical expression, requiring the use of alternative techniques
to perform its calculation efficiently. In this context, this work presents the comparison between several numerical
methods to obtain this gradient. Several methodologies such as the response surface method (RSM), the adaptive
response surface method (ARSM) and the finite differences method (FDM) are applied to a model of an oil well
drilled on salt rocks. The main contribution of this paper is to check the efficiency of some procedures for obtaining
the gradient of the failure function in the evaluation of the structural behavior of oil wells drilled on salt zones.

Influence of flow rate and operating time on the temperature profiles of oil wells

Luiz E. da Silva Filho — 2024-06-22

During the production of oil and gas wells fluids at high temperatures flow through the tubing string.
Consequently, the well structure experiences thermal gradients along its depth and in the radial direction. This
affects different components such as casings, cement sheath and rock formation. Among the undesirable effects
caused by the temperature variation there is the Annular Pressure Buildup (APB), associated to expansion of the
fluids trapped between strings, and, the decrease of resistance of steel tubes and connections. The changes in
temperature of fluids and components during the operation of a well depend on many factors, among which are:
operating flow rate, inlet pressure and temperature, operation time, and the produced/injected fluid properties. In
this context, this paper presents a parametric study aimed at understanding how the variation of the operating
flow rate and production time impact the temperature profiles generated. The temperature profiles are evaluated
at realistic operational values of flow rate and production time using an in-house developed thermal simulator,
based on the simultaneous resolution of energy balance, momentum balance and mass balance equations. The
main contribution of this work is to demonstrate the importance of isolated properties in the thermal response of
well components. In addition, the methodology presented can be applied to other parameters and thus improve the
understanding of how each property influences the well temperature.

Optimizing the volume of reinforced concrete floors using grid analogy

João Geraldo Menezes de Oliveira Neto — 2024-06-22

One of structural engineering’s main goals is to model a structure able to withstand the loads to which
it is subjected, but consuming the least amount of material possible, which is the concept of structural
optimization. This article aims to use an algorithm in Python 3.0 capable of optimizing the sizes of beams and
slabs from a conventional building system made of reinforced concrete, so that the Serviceability Limit State of
excessive deflection is satisfied in the most economical way. For this purpose, the floor is modeled by beam
Finite Elements to represent both the structural beams and the slabs, in a Grid Analogy Method. For the
optimization process, it is necessary to use a library able to solve constrained minimization of multivariate scalar
function problems, in order to do this, the SciPy library is used. This framework is applied to typical sizing
examples of reinforced concrete floors and results are compared in terms of displacements and volume of
concrete.

Unsupervised Learning Algorithms Applied to Anomaly Detection in Oil and Gas Wells

Hugo V. F. Azevedo — 2024-06-22

Monitoring through sensors is a powerful tool in the evaluation of vibrations, loads, deformations,
among other problems in which gathering data allows to detect undesirable events that may arise in structures.
Growing opportunities have been observed in companies offering sensing, monitoring, and digital transformation
services, which offer cost reduction, increased operational safety and improved performance. Technologies for
processing the data collected by sensors using machine learning (ML) methodologies have proven to be efficient
tools in engineering processes. In the context of petroleum engineering, the prediction and detection of unexpected
events stands out, by supporting decision-making processes and adding value to products and services. Thus,
this paper aims to study and develop ML-based models for detecting anomalous states in oil wells, by applying
classical techniques such as Support Vector Machines, Isolation Forest and Deep Neural Network. It is expected
to compare the efficiency of these methodologies applied to time series datasets of pressure, temperature and flow
rate, allowing to predict the anomaly occurrence and generate alerts to the production operator. It is observed the
practical application and potential of the proposed methodologies for the intended product, being able to improve
the fault detection process in oil wells, as well as ensure their integrity.

Parametric study of a tubing string buckling model with friction in petroleum wells

Otavio B. A. Rodrigues — 2024-06-22

This work presents a parametric study of a buckling model with friction applied to tubing strings while
production or injection of fluids occurs in a petroleum well. The tubing buckling can lead to structure failure,
and to new regions of contact between the string and the casing. In these regions, frictional forces seem to have
an important impact on the tubing elongation. In addition, ignoring friction might not be a conservative design
strategy. To achieve the proposed objective, the adopted methodology is divided into three main stages: i) study
of buckling models with friction for tubing strings; ii) implementation and validation of the chosen model; iii)
definition of the scenario and variables for the parametric study, such as tubing and casing diameters and well
depths. The main contribution of this work is quantifying how friction’s relevance on buckling varies with tubing
and casing diameters.

Development of a web tool for analysis of fatigue life of free span pipelines

Matheus A. Miranda — 2024-06-22

Throughout the last decades, with the discovery of oil and gas fields in offshore zones, more extensive
pipeline systems are needed and, consequently, more prone to the occurrence of free spans, caused by seabed
irregularities. Pipes in this situation are exposed to the Vortex-Induced Vibrations (VIV) phenomenon, which can
cause damage, mainly related to fatigue. In this way, several recommended practices provide formulations that can
be implemented in electronic spreadsheets to assist in academic and professional projects. The problem with the
approach of spreadsheets is the difficulty in using their implementations for the coupling with other software. In
this sense, the objective of this work is to develop a web tool for the analysis of rigid free-spanning pipelines in
VIV, using modern web programming resources and enabling its reuse in the development of other applications.

Modeling strategies on the geological formation for APB calculus in oil wells

Gilberto L. L. Santos — 2024-06-22

The thermal gradient imposed on oil wells along its life cycle can cause pressure variations in the

annular spaces, a phenomenon called Annular Pressure Build-up (APB). This subject is relevant, given the fre-
quency of occurrences in offshore fields located in deep and ultra-deep areas, such as the Brazilian Pre-salt, whose

exploratory interest has grown, given its potential for oil and gas production. The accurate modeling of the APB
phenomenon can prevent damage to the casing and the cement sheath, which may even lead to loss of well integrity.
Among the several variables involved in the problem, considering the geological formation as rigid or deformable
directly influences the APB estimate. Thus, this work aims to evaluate the effect of the flexibility of the geological
formation in the APB calculation. Numerical simulations of the pressure increase are performed using a multilayer
one-dimensional axisymmetric thermomechanical model. The methodology adopted is based on four macro steps:
reproduction of the reference scenario to verify the implementation of the APB calculation; considering formation
with null stiffness, result analysis considering rigid formation; evaluation of results adopting a linear constitutive
equation for the rocks. For the reference scenario, it was observed that the value of the formation modulus of
elasticity modifies the APB level by up to 35%.

Validation of photovoltaic model for application in a distributed energy source using weather data

Eduardo G Pignaton — 2024-06-22

This work presents a photovoltaic model for a simulation of the electric energy production of a
distributed energy system. The model will be validated through measured weather data and energy produced by
an 88.04 kWp power plant installed on the Federal University of Espírito Santo (UFES) in Vitória. The validation
consists of comparing the real power data acquired by the photovoltaic plant and the power data calculated from
the model using weather data, specifications of the panels and inverters and the constructive characteristics of the
system. The proposed model is based on the paper “Management of an island and grid-connected microgrid using
hybrid economic model predictive control with weather data”, Applied Energy, v. 278, 2020,
https://doi.org/10.1016/j.apenergy.2020.115581. In addition, the model has been improved with the inclusion of
new intrinsic parameters of the material, the calculation of losses and the adjustments for different tilt angles and
azimuth orientations. Results of this method reveal that the model was able to reproduce the behavior of the real
photovoltaic plant, presenting a mean absolute percentage error of 8.8% between real and simulated data.

Study of the maximum wind speeds and meteorological characteristics in Paraguay in order to differentiate synoptic and non-synoptic events, for a future update of the NP-196.

Álvaro J. Martínez — 2024-06-22

The Paraguayan standard NP-196 Acción del Viento en las Construcciones, estimates wind action on
structures taking into consideration only synoptic events and does not account the effects of thunderstorms (TS).
Nonetheless, severe storms usually have higher values of the wind speeds than synoptic events in the region.
Currently, the adoption of a vertical profile of wind speeds for TS events is being studied internationally in order
to be included in several wind standards. Therefore, there is an urgent need to statistically study these events in
order to consider the loads of the TS and EPS winds over structures. The present work aims to classify synoptic
(EPS) and non-synoptic winds (TS) of three Paraguayan meteorological stations, looking forward to a future
update of the basic wind speeds of the NP-196.

A Designing Methodology for Bicycle Frames Using the Topology Optimization Method

Henrique G. Dadda — 2024-06-22

This work aims to present a methodology to design bicycle frames using the topology optimization
method. The goal is to find an optimized layout of a structure within a specified fixed domain, applying known
quantities (loads, support conditions and design restrictions) as boundary conditions. The optimization problem
is written to obtain the minimum structural compliance with a given final mass and it was solved using the
Sequential Convex Programming method (SCP). To simplify the process, the problem was divided into two
steps. The first step consisted of performing a topology optimization analysis on a two-dimensional model. The
result was then adapted into a three-dimensional domain on which the last optimization was performed to
achieve the final geometry. Several combinations of load conditions were applied, and the obtained design was
post-processed through a finite element analysis to check the structure’s response. Results show that the
proposed methodology can produce stiff and lightweight frames with reduced mass and unusual designs.

FATIGUE ANALYSIS FOR A STEERING KNUCKLE OF A BAJA SAE VEHICLE

Gustavo C. Rodrigues — 2024-06-22

Fatigue in automotive components is of great interest for both automakers and consumers. Due to high
costs and time involved in experiments and tests of these vehicles, engineers often resort to analytical and
computational models during the design project phase. This work presents the fatigue analysis and expected
lifetime calculus for a steering knuckle used in an offroad BAJA vehicle. Different models were tested to choose
one which could most accurately represent known vehicle behavior, as experimentally verified by the Tchê Baja
team. Using loads obtained through a ride simulation in MSC Adams/Car, critical fatigue points were
determined for the component analysed. Cycle-counting was done through the rainflow algorithm, and correction
for mean stresses through the FKM directive and Goodman methods. The results show the differences in loads in
both critical points, as well as differences in the mean stress correction methods.

PYTHON ALGORITHM FOR CALCULATION OF INTERNAL FORCES AND DISPLACEMENTS IN BEAMS USING THE FINITE ELEMENT METHOD

Diego R. Figueira — 2024-06-22

A beam finite element under linearly distributed loading is presented. The finite element has two nodes
and two degrees of freedom per node, totaling four degrees of freedom per element. The nodal parameters are
translations and rotations. A cubic polynomial and a linear polynomial are used, respectively, to approximate the
solutions of the problem and describe the loading. The total potential energy functional and the stationarity
principle of energy are used to obtain the finite element equations system. Python 3.9.0 programming language
and PyCharm IDE 2020.2 are used to implement the developed algorithm. After determining the problem

unknowns by solving the system of equations, the internal forces and support reactions are determined in the post-
processing phase. To validate the implemented code, a simply supported beam subjected to a uniformly distributed

load was chosen. The results shown by the algorithm were compared with analytical and FTOOL solutions, and
show that the code was successfully implemented.

2D STRUCTURAL ANALYSIS EDUCATIONAL SOFTWARE: A FORCE PROCESS SIMULATOR USING FREECAD

Mateus Felipe Marques de Oliveira — 2024-06-22

The technological advances and the consequent modernization in various sectors of society evidence
and foster the emerging tendencies to the usage of computational tools in behalf of the analysis of structures, more
specifically with regard to the field of Civil Engineering. Along with it, the training of future engineers with the
use of new methodologies that assist in the teaching-learning process, is frequently debated and encouraged.
Among these educational tools, stand out those that have an appeal in computational mechanics based in the use
of numerical methods with a very well characterized and absorbed theoretical basis. In this context, knowledge of
the behavior of structural systems is essential, especially when using numerical analysis methods and their
computational implementations. In undergraduate courses that deal with hyperstatic structures, two solution
methods are studied: the Displacement Method and the Force Method. The Force Method, despite having a very
consistent physical appeal and being the one that better represents the structural behavior, does not have an
interesting approach for an integral computational implementation. In this circumstance, the present work intends
to present an expert software developed for computer-assisted learning of the Force Process. The idea is to have a
Simulator of the Flexibility Process with the explanation of each of its steps, so that the user, a structural mechanics
student, can interact not only by entering initial data and obtaining the final analysis data. On the contrary, he will
have the definition/explanation of his choice of the fundamental isostatic model and the subsequent steps of its
systems, leading to the obtention of the flexibility matrix of the simulated problem. The computational code was
written in Python, using FreeCAD, an open parametric modeling software, as the user interaction platform, taking
advantage of its graphical directives and its interoperability with the Python language. The simulation is done by
using personalized buttons for data entry, inherent to the pre-processing stage of the application, that is, the stage
of modeling the structure, which is presented visually, in order to facilitate the user ́s understanding. Subsequently,
the program calls for the computational processing of the plane structure and presents each step of the Force
Method. For

Solution based on the DCIM model to assist in the energy efficiency process of small and medium data centers

Alexandre Barbosa de Souza — 2024-06-22

In the current scenario of large data centers, the increase in demand for the provision of digital services
coupled with the increase in the volume of traffic generated by these services has driven the excessive and
increasing consumption of energy needed to supply and maintain the availability and quality of the services
provided. In order to improve and increase Energy Efficiency in Data Centers, several solutions are available
(policies, methods, metrics, tools, etc.) that assist in the process of implementing and maintaining modern and
efficient Energy Management. However, small and medium data centers also have characteristics similar to large
data centers. Only with consumption on a smaller scale but with the same challenges of increasing energy
efficiency. However, small data centers do not have the input and / or infrastructure available to large ones to
implement solutions related to Energy Efficiency, thus becoming a challenge in the area. This work proposes the
implementation of a solution based on the existing model on the DCIM platform (Data Center Infrastructure
Management), performing real-time monitoring of some of the infrastructure characteristics of the Data Center
environment that will assist in Energy Management aiming to achieve the maximum Energy Efficiency without
impacting the quality of its services. For this purpose, a physical layer will be implemented using SBC (Single
Board Computers) equipment that will function as a centralizer of the information collected through sensors
responsible for monitoring the Data Center environment, and an application layer that, in possession of the
information collected, it will carry out the treatment and analysis, resulting in analytical data, alerts and reports
that will serve as a basis to assist in the Energy Management process.

DEVELOPMENT OF A DYE DETECTION SYSTEM CONCENTRATION IN WATER USING DIGITAL IMAGES

Willian M. Oliveira — 2024-06-22

This study aims to detect dyes at different concentrations and diluted in water using RGB digital images
captured with a webcam dispositive. This detection is a low-cost alternative for the spectrophotometer, an
equipment consolidated for this type of application. From the captured images, it was cut areas with 40x100 pixels
and the average value for these pixels were used during the image’s process, creating 4 types of models. It
compared these models results with the obtained ones by the spectrophotometer. The greater result obtained by
the logarithm model referred to the R band normalized with a quadratic approximation, presenting a correlation
coefficient of 0.9912. Therefore, it concluded that the use of this technology has the potential to detect different
dye concentrations with the spectrophotometer backing.

Simulating submarine landslides combining the material point method with a spatially adaptive scheme to improve numerical accuracy

Lucas D. F. Lino — 2024-06-22

Particles, in the material point method (MPM), are the representation of the material domain, which
moves through a background mesh. As deformation occurs, particles positions are updated accordingly and may
generate regions with suboptimal particle density. In cases with excessive tractions, increased deformations can
make distance between particles to be greater than the background mesh element size, causing fractures to occur in

materials where no fracture law was applied. Moreover, this numerical fracture undermines computational accu-
racy and stability of the simulations. Therefore, a spatially adaptive method is a suitable alternative to prevent the

formation of numerical fractures in problems with large deformations. Furthermore, spatial adaptivity, a technique
that tunes the spatial discretization of the problem dynamically, has already been used to simulate engineering
problems with large deformations and complex soil-structure interactions. However, such simulations are unstable
depending on the material constitutive model and the computational cost is quite expensive. This study proposes
a spatially adaptive algorithm based on the accumulated deformation of each particle. The algorithm divides each
particle into four new ones that inherit the quantities of interest from old particles, maintaining the continuity of
state variables. The algorithm showed to be efficient in problems with analytical solutions, such as the vibration
of an elastic bar. In addition, as submarine landslides involve large deformations, numerical fractures are bound to
happen and often imposes constraints to the scale of the mesh discretization. In this regard, our algorithm handled,

successfully, submarine landslides simulations, introducing new particles to regions that presented a poor distribu-
tion of particles during the sliding process, enhancing the visual aspect and allowing a correct computation of state

variables. Lastly, the spatial adaptivity scheme was coupled into the software E-Sub, a numerical analysis software
developed by the Laboratory of Scientific Computing and Visualization (LCCV).

MODELING OF BEAMS WITH WEB OPENINGS USING THE BOUNDARY ELEMENT METHOD

Maylla Guedes Cabral — 2024-06-22

This paper presents an alternative modeling of beams with openings in the web, using the 2D
Boundary Element Method formulation (BEM) to analyze the stress and displacement distributions at internal
points. The material is considered to be elastic linear. A "2D MEC" program was elaborated using Kelvin's
fundamental solution with continuous and discontinuous linear elements for the boundary discretization, including

the openings. The PYTHON programming language was used to develop the computer code, since it’s an open-
source platform. Some examples already evaluated in other scientific works are presented, to test the effectiveness

of the implemented computational code, as well as the formulation used. The results found demonstrate that the
Boundary Element Method, in a simple program, can be inserted in simple practical solutions as usual structural
calculation.

MODELING BOUNDARY ELEMENT METHOD FOR THE ANALYSIS OF BEAMS COMPOSED OF DIFFERENT MATERIALS

Eduarda Abreu Vanderlei de Souza Silva — 2024-06-22

In structural engineering more and more elements characterized as composites are being used. A
previous understanding characterizes materials consisting of layers, in general, even varying the nature of the
materials. The present paper presents an approach for analyzing the structural behavior of a beam formed of
different materials from 2D modeling in numerical method. A computational implementation of the Boundary
Element Method (BEM) was developed using the PYTHON programming language. The code "MEC 2D" was
elaborated using Kelvin's fundamental solution with the use of continuous and discontinuous linear elements for
the discretization of the boundary and interfaces of the subregions characterizing each material. The BEM
formulation allows, therefore, the modeling of subregions for the assembly of the domain, in this case, the complete
beam. The behavior is evaluated from the displacements obtained for the boundary and internal points, as well as
the stresses, evaluating these fields conveniently in graph form. Applications were performed to test the
implemented modeling.

Automated Design of Steel Columns Under Axial Compression Using Genetic Algorithm

Igor M. Lima — 2024-06-22

This paper is concerned with the automated design of steel columns with W or I cross section geometry,
using Genetic Algorithm optimization. Provided with basic design parameters, the algorithm automatically search
for the optimal cross section shape and deliver the most suitable solution, constrained or not by the commercial
shapes available. In order to show the efficiency and reliability of the algorithm, some benchmark examples
were provided. Based on the results and the analysis, the automated design algorithm proved to be a faster and
reliable alternative for designing steel columns with equal load carrying capacity of conventional methods, under
the Brazilian and international standards.

Aerodynamic and structural analysis using computational fluid dynamics and finite element method applied to an arched bamboo greenhouse

Felipe Frizon — 2024-06-22

The protected cultivation system uses greenhouses to partially control soil and climate conditions, such
as temperature, air humidity, radiation, wind, and atmospheric composition, thus exhibiting quantitative and
qualitative advantages compared with field cultivation. Bamboo is considered a sustainable material because it is
renewable, absorbs carbon dioxide, uses solar energy, and is easily incorporated into nature at your life cycle end.
The aim of this paper was to analyze the aerodynamic and structural behavior of a bamboo greenhouse, aiming at
the use of this material as a sustainable and low-cost construction element. For this, computational tools were used
to obtain the loads acting on the structure, such as the computational fluid dynamics method to determine the wind
loads and the structural analysis by finite element method to obtain the natural frequencies, the nominal stresses
and the maximum displacements.

Reliability-Based Plastic Limit Analysis of Plane Frames

Diogo L. F. Pinto — 2024-06-22

In engineering, the possibility to simulate the structural behavior using computers has been extremely
useful to guarantee safety and economic projects, as well as to evaluate the integrity of structures. The growing
demands for evaluation of structural safety have led to the development of new analysis methods, structural design
and verification. With that in mind, it is proposed in this paper a methodology for determining the collapse load
for plane frame structures using plastic limit analysis and reliability analysis. The problem formulation is obtained
using the plasticity limit theorems, which allow the limit analysis to be written in the form of linear programming.
The reliability analysis is performed using the Monte Carlo method. For the implementation of the algorithms
involved in the methodology, the Python programming language was used. A graphical user interface was
developed to allow the structural modeling in a very intuitive and dynamic way. It is expected that the tools
developed in this research can be used in further research involving computational simulations of real engineering
problems.

The use of the Ansys computational tool in the initial study of the fatigue phenomenon

Mila Fernanda Esper — 2024-06-22

The fatigue phenomenon in structural elements is a major concern. Most of the structures, even when
projected in the elastic regime, are subject to failures after a certain time of exposure of the load. These failures
can lead to collapse and affect not only the target element, but also compromise the integrity of everything around
it. Experimental and numerical analysis are tools used to evaluate this phenomenon and its implications,
contributing to offer subsidies to guarantee a long life to the structural element. The purpose of this study is to
validate the use of the fatigue tool in the Ansys Student software. For this purpose, a cantilever beam subjected to
a harmonic force at its free end was studied. The numerical values extracted, such as stress, fatigue life, safety
coefficient and fatigue damage, were compared with those obtained by the analytical procedure. The achieved
values converged, demonstrating in addition to the correct conduction in the use of the computational tool, the
understanding of the basic theoretical concepts of the study of fatigue.

Comparative Analysis of a Sustainable Bamboo Bridge and a Steel Bridge

Fernando F. Oliveira — 2024-06-22

This paper is concerned with a numerical analysis and comparison between a steel bridge and a bamboo
bridge, both designed for pedestrian traffic. First, the finite element (FE) method was used to build a numerical

model of an existing steel bridge. Later, another FE model was considered changing steel elements with Dendro-
calamus giganteus sustainable bamboo elements, in order to verify the bamboo feasibility as a structural material.

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 a Dendrocalamus Sustainable Bamboo Warehouse

Fernando F. Oliveira — 2024-06-22

The concern of the paper is a numerical comparison between a steel warehouse and a bamboo ware-
house using its natural geometry, both designed for industrial storage. This analysis was performed considering an

existing steel warehouse in Brasilia, modeled using the Finite Element Method (FEM). To demonstrate how the
bamboo would fare against a traditional material, another FE model was considered changing steel elements with

sustainable bamboo elements. The results presented in the paper are in perfect agreement with the Brazilian stan-
dards and obtained satisfactory load carrying capacity. Based on the analysis, the sustainable bamboo warehouse

proved to be lighter and cheaper than the real steel warehouse counterpart with equal load carrying capacity.

Models for Representation of Cracks in One-dimensional Finite Element Method

Filipe G. Sanches — 2024-06-22

Structures can develop discontinuities in their material in the form of cracks or generalized damage,
changing their properties and resulting in malfunction or even collapse. Thus, to identify and monitor the existence
of cracks, some numerical models have been proposed in recent decades, where different approaches regarding
the representation of the crack are treated. Considering this scenario, the objective of this work is to study different
ways of representing cracks in numerical models, based on the one-dimensional Finite Element Method (FEM).
For crack representation in numerical models, 3 methods are highlighted in the literature, namely the reduced
section method, the local flexibility method, and the continuous method. Thus, this work contemplates the
numerical implementation of the mentioned methods, focusing on the analysis of free vibration of Euler-Bernoulli
beams. The natural frequencies obtained by these 1D methods are compared to those obtained by other researchers
using different models (Timoshenko, 2D, etc.). Different crack configurations and boundary conditions are tested
numerically and compared to reference values presented in the literature, obtaining good results. In a comparative
analysis, the models presented divergence in the answers for deeper cracks, evidencing a significant difference
between these approaches.

Numerical Modeling of Dencrocalamus Asper Densified Bamboo under Flexure

́Icaro B. M. Carvalho — 2024-06-22

The concern of the paper is the numerical analysis of a densified bamboo plate of the species Den-
crocalamus Asper. Nonlinear finite element (FE) models utilizing ABAQUS software were developed to study

the material behavior when the densification process is performed. Results obtained with experimental tests were
compared with results obtained from the numerical model, in order to validate the model. The numerical analysis

showed the improved performance obtained with the densification process when compared to plain bamboo speci-
mens, where the maximum load carrying capacity was increased depending on the densification ratio. The results

obtained with the numerical model are in good agreement with those obtained on the experimental tests. Over-
all, densified bamboo specimens proved to be reliable substitute for the conventional bamboo and can be safely

introduced for other uses.

Reliability analysis of reinforced concrete sections for ultimate limit states

Daiane D. L. Leite — 2024-06-22

The application of probabilistic methods in the design of reinforced concrete structures has paramount
importance. Several uncertainties in the structural design, which range from variations in material properties and
model hypothesis to the applied loads can affect the final predicted structural behavior. Besides, even if the design
is developed with the highest degree of strictness, deviations in the final executed structure may happen. Factors
such as, the opening of the formwork when concreting, the lack of spacers in the reinforcement and the inadequate
concrete dosage, all can contribute to the uncertainty. These are factors that may result of unsatisfactory structural
performance, because they can compromise safety. In this context, the objective of this paper is to evaluate the
reliability of reinforced concrete sections under bending loads in ultimate limit states. The uncertainties that can
affect the ultimate strength comprise reinforcement cover, concrete strength, external loading, and cross-section
dimensions. This study uses First Order Reliability Method (FORM) and the Monte Carlo Simulation (MCS) with
Importance Sampling (MCIS) to obtain the reliability indexes. Uncertainty propagation is also performed by MCS
to study cross-section strength sensitivity to uncertainties. At the end, the most important parameters are discussed
and probability density plots and reliability index curves presented.

Finite element solution of an elastically connected double Bernoulli-Euler beam system on Winkler-Kerr foundation

Welky Klefson Ferreira de Brito — 2024-06-22

In the last decades, studies on the double-beam system, which consists of two parallel beams connected
by an elastic layer, have been focus of much researches and applied to a wide variety of engineering problems
such as, adhesively bonded joints, rail on geocell-reinforced earth bed and many others. Different models of one,
two and three parameters have been used to represent the inner connecting layer of the beams and the support
base. In this paper, a finite element formulation is derived assuming the Euler-Bernoulli beam hypotheses to
represent the beams, the Winkler foundation model to idealize the inner layer, and the Kerr elastic foundation
assumptions to model the support base. The double beam finite element has ten degrees of freedom and its stiffness
matrix and equivalent load vector are explicitly shown. Numerical bending analysis for many different load cases,
beam properties, and foundation parameters is done and compared with analytical solution or numerical responses,
according to their availabilities.

Simplified analytical-numerical study of the static behavior of the hemispherical dome of the Roman Pantheon

Fillipe M. Faria — 2024-06-22

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 ancient times, has currently sparked 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. In order to understand how
these monuments were built, it is necessary to understand their structural response (displacements, efforts,
tensions, etc.), which is characterized by a complex problem. Current computational tools provide more realistic
approaches, which in turn also provide the opportunity for robust testing of more consistent analytical theories,
which allow in a simplified way to investigate the behavior of these structures, aiming to shed light on the
understanding of this “art of construction”. Thus, in this work, the static structural response of the hemispherical
dome of the Roman Pantheon with simplified geometry is investigated. A progressive analytical methodology
through the membrane and bending theory of spherical shells, as well as the finite element method (FEM) using
the SAP2000 software are used and compared to model the problem. The results obtained have a good correlation
with each other, which corroborates with the methodology used. In addition, with the analysis of the membrane
and bending efforts of the hemispherical dome, it was possible to discuss and relate them to the structural and
architectural conception adopted at the time.

Análise numérica para avaliação de desempenho de Modelo de Bielas e Tirantes via análise linear e não-linear

Philipe Q. Rodrigues — 2024-06-22

O dimensionamento de elementos lineares de concreto frequentemente ocorre admitindo as hipóteses
de bernouli das seções planas facilitando o cálculo. Entretanto, existem regiões de descontinuidade geométrica
ou estática onde tais hipóteses não podem ser aplicadas visto que surgem deformações não-planares. Cita-se
como exemplo vigas-parede, consolos, dentes geber, vigas com abertura na alma e blocos de coroamento sobre
estacas. Dentre os recursos disponíveis para dimensionamento destaca-se o método de bielas e tirantes, método
dos elementos finitos e método corda-painel. A fim de reduzir o tempo de cálculo, algumas ferramentas

computacionais tem sido desenvolvidas empregando o modelo de bielas e tirantes. O CAST (Computer aided-
strut-and-tie) auxilia no cálculo e verificação de regiões de descontinuidades do modelo de bielas e tirantes de

acordo com códigos normativos definidos pelo usuário. Dispõe de recursos para análise linear, para estudo do
comportamento de modelos de bielas e tirantes estaticamente indeterminados e análise não-linear baseado na
relação de tensão-deformação definida pelo usuário. Este trabalho se propõe a aplicar o programa no estudo de
uma viga-parede pelo MBT comparando seu desempenho via analise linear e não-linear. Desenvolveu-se uma
avaliação da região nodal simplificada e refinada como parte da análise numérica. São analisados os resultados
através da analises linear e não-linear expondo a convergência de dados e o tratamento da região de
descontinuidade pelo CAST.

Infinite Numerical Series Convergence Application to Slender Columns Mechanical Analysis

Edmilson Lira Madureira — 2024-06-22

A numerical series represents the sum of terms in a numerical sequence. If the quantity of its terms is
unknown, it constitutes an infinite series, and the sum of its terns must be obtained from the convergence analysis
procedure. The series used to approach the values of given function, must be of the infinite mode because, in such
cases, the quantity of terms that the series needs to attend such demand, is unpredictable. There are cases wherein
the solution of engineering problems that may be aided, directly, by the modeling based on approach for infinite
numerical series, as the slender columns analysis. The slender columns analysis cast by elastic and ductile material
has been based on the concept of critical load. Such modeling version is not suitable to mechanical analysis of
specimens cast by weak rupture pattern material, as the reinforced concrete, but even thus, some concepts involved
in such a formulation are used as a classificatory reference. The Mechanics of the Materials uses the physical
modeling capabilities in deriving the equations object of approach on the featured theme. The aim of this work is
the slender columns mechanical performance modeling through infinite numerical series convergence concept.

Analysis of concrete masonry structures considering soil-structure interaction

Marco A. S. Bessa — 2024-06-22

This paper analyses the behavior of a concrete masonry structure with piled raft foundation, where the
number of floors and piles are changed, in order to respect the capacity of the soil and it also studies the
differences between the rigid and elastic support, when you apply or not wind efforts. During investigation, were
collected the stresses in the walls and the bending moments in the raft. The results showed that neither the wind
or the support changed the behavior of the structure and the stresses in the walls, but it modified the bending
moments in the foundation. Moreover, the experiment presented that the piles had more influence in the
maximum stresses and their location than the raft.

Finite element simulation of cross-laminated timber panels under compression perpendicular to plane

Rodrigo A. Benitez Mendes — 2024-06-22

Cross-Laminated Timber (CLT) is a composite panel made up of structurally glued layers of wood
lamellae stacked crosswise at 90° that has been standing out in the sustainable construction scenario. Among its
main features, it is possible to highlight the excellent weight/strength ratio, when compared to other traditional
construction materials, and great stiffness in both directions, provided by its orthogonal layerwise configuration.
Frequently employed as a slab element in mid-rise and high-rise timber buildings, these engineered wood panels
are often subjected to elevated compression loads perpendicular to plane in different loading conditions. This paper
focus on the column-slab-wall load case of CLT slabs by proposing a numerical finite element model capable of
simulating its elastoplastic nonlinear behavior under compression perpendicular to plane. An orthotropic
constitutive model employing Hill’s yield criterion combined with isotropic bilinear hardening was used, applied
to 20-node solid hexahedral finite elements in Ansys Mechanical APDL software. The numerical results presented
a good correlation with experimental data of non-edge-glued CLT panels, especially when gaps between lamellae
were considered in the model’s geometry. Finally, the anisotropic failure criterion of Tsai-Wu was assessed,
showing potential in estimating the CLT layers’ structural integrity under different load levels along the
elastoplastic regime, even though it requires detailed mechanical characterization of wood as input data.

Random Walk simulation of Nuclear Magnetic Resonance for characterization of reservoir rocks using micro-CT data

Andres Zuniga — 2024-06-22

Random walk algorithms have been used to simulate nuclear magnetic resonance (NMR) transverse
relaxation (T2) decay in porous media since the early 1990’s. Since the time of their first implementation, they
have been primarily based on geometric models of pores and grains such as the grain consolidation model. These
models have been useful for examining mismatches between the actual T2 distributions and the pore size

distributions from mercury injection capillary pressure (MICP) and those from X-ray microtomography (micro-
CT) images. Noticeable success has been achieved, particularly in complex carbonate rock samples where the T2

distributions may represent an average pore size between the macro-pores and the micro-pores due to diffusive
coupling. In typical random walk simulations, the position of the walker is calculated geometrically in terms of
the radius of the macro-pore to determine if it has arrived at the grain surface. This approach is useful for
geometric models with Euclidean geometry pores. Currently, micro-CT images would require an intermediate
step, where the image is converted and approximated to Euclidean geometries such as spheres and prisms to
represent the macro-porosity. An alternative approach would be to construct a binary cube for 3D simulations (or
square for 2D). In this approach, the position of the walkers is linked to the binary cube index where 0 would
represent macro- pores and 1 would represent the micro-porous grains. Comparison between the results of these
two approaches shows similar computational times and the indexed method is more suitable for binary images
from micro-CT.

Comparison of different experimental data inputs in history matching pro- cedure for relative permeability and capillary pressure determination

Tarcísio Fischer — 2024-06-22

In order to determine relative permeability (Kr) and capillary pressure (Pc) curves, several laboratory tests
are performed, for instance, Core Flooding (CF) experiments using one or two fluids, from which experimental
data such as pressure drop (DP), net produced volume (NP), and Computed Tomography (CT) scans of saturation
profiles (SP) may be derived, and input into a history matching software. History matching is a technique used to
approximate unknown numerical properties of a model based on the knowledge of experimental data. It is usually
performed by solving the inverse problem upon the physical modeling of a system. The SCAS module of the
software RFDAP, developed by ESSS, was used to compare the curves obtained using several combinations of
experimental data inputs: (1) Only DP, (2) Only NP, (3) DP and NP, (4) DP and SP, and (5) DP, NP and SP. The
purpose is to compare the quality of the solutions, in relation to a reference. The synthetic data used for the studies
is based on an CF experiment performed by LRAP (UFRJ).

Three-dimensional geological mapping based on cross sections restoration

Vinicius Almada — 2024-06-22

The geological restoration of cross sections is one of the main oil and gas industry resources to assist

in structural interpretation. In general, geological processes occur three-dimensionally. However, 3D restora-
tion is complex and costly. The present work proposes a methodology and the tools development to map the

three-dimensional movement based on the geological cross sections restoration. This methodology addresses the
problem in 2 steps. The first maps the movement of the cross sections to the surfaces of the model. Subsequently,
the movement of the sections together with the movement of the surfaces maps the movement of the volume. The

numerical approach for the first step performs the movement of the surfaces considering control points, restric-
tions from movement of the cross sections, together with the minimization of a functional tri-harmonic in order to

guarantee surfaces of minimum variation. The second step performs the movement of the volume based on control
points given by the movement of the cross sections added to the movements of the surfaces, obtained in step 1.
The basis for the development of these studies is the RECON-MS System, a software developed by PETROBRAS
in partnership with the Tecgraf PUC-Rio Institute, which allows the restoration of geological sections.

Fractal dimension from the box counting method for REV permeability estimation

Tatiana Lipovetsky — 2024-06-22

Thomeer-based methods, widely used for permeability estimation of rock samples, rely on the
determination of pore throat distributions from mercury injection capillary pressure, for both sandstones and
carbonates. These methods comprise three different approaches for permeability calculation, all of them based on
concepts related to the Thomeer hyperbola. In this work, for the sake of permeability evaluation, we review and
adapt the expansion of the tubular bundle model of Purcell to a fractal tubular bundle for permeability calculation.
Our study is motivated by the assumption that fractal theory can be used to improve upscaling procedures, since it
provides the ideal mathematical tool to deal with the commonly observed self-similarity properties of complex
natural media. Furthermore, fractal concepts have been introduced and presented as a well-suited approach for
flow modeling because of their simple description of highly ramified spaces. Adding up to mercury injection data,
the box-counting method is applied to the analysis of thin-sections of thirty limestone samples as a way to obtain
their fractal dimension and hence permeability at the representative elementary volume (REV). It turns out that
the fractal approach proves to be not only of straightforward application but also to improve estimates of
permeability carried along the lines of Thomeer methodological principles.

Numerical modeling of damage zones in rocks at reservoir scale using FEM

Thiago J. de Andrade — 2024-06-22

Damage zones are structural domains present in most geological faults that can act either as a
preferential flow path due to fracture sets or as a barrier due to compaction bands. Therefore, the characterization
of damage zones can be essential for adopting adequate production strategies in oil fields. Unfortunately, the
geophysical methods used to characterize damage zones in geological faults hardly allow their identification due
to low seismic resolution. Alternatively, the characterization of the damage zones can be done through superficial
outcrops. However, there is a wide dispersion of data in this type of study. In this paper, we present a numerical
model based on the finite element method (FEM) to analyze the structural evolution of damage zones at the
reservoir scale. In the proposed model, the fault plane is included through two contact lines within a host rock that
presents elastoplastic behavior. The obtained results allow the identification of different deformation mechanisms
along the damage zone and confirm the capabilities of the proposed model to assess the damage zone width.

Integrating Multiple Log Measurements for Uncertainty Reduction in Reservoir Evaluation

V. Simoes — 2024-06-22

The methodology presented in this work aims at reducing uncertainties in the petrophysical evaluation using
machine learning, statistics, and physics-driven methods to increase the level of confidence in advanced workflows
in complex formations.

The proposed method saves days in repetitive processes when compared to traditional workflows and quanti-
fies the level of confidence associated with the answers considering multiple uncertainty sources.

This methodology enables the petrophysicist to provide an analysis containing one final porosity, water sat-
uration, and permeability estimation with minimized uncertainty considering the multiple measurements available

for the well and the multiple sources of uncertainties in a reproducible and fast manner.

Development of tool for estimating the diagram Residual Stress versus CMOD for the SFRC under 3BPT assay based on experimental results

Felipe Marques Queiroz — 2024-06-22

The three-point bending test, commonly used for the experimental analysis of a steel fiber reinforced
concrete beam (SFRC) involves difficulties, such as its cost of operation and mainly by the values of steel fibers
and test equipment. However, relatively few studies are done, especially in Brazil, and much remains to be done
for more accurate analyses of the results that corroborate each other. This study deals with the developing of a
practical algorithm that is easy to understand the user to provide expected results of a three-point bending test
based on experiments conducted by [1], [2] and [3]. The program was developed with the aid of the Matlab
software and stores the results obtained from the literature in the form of a database and returns to the user a
graph of Characteristic Residual Resistance (MPa) versus CMOD (mm).

Estimation of the Mass, Stiffness and Damping Matrices From Complex Frequency Response and Real Frequency Response Matrices

Ferro, M. A. C. — 2024-06-22

A frequency-domain method for estimating the mass, stiffness and damping matrices of the mass-
spring-damper system is presented. The developed method is based on the extraction of real and imaginary parts

of the Complex Frequency Response Matrix (Complex Transfer Matrix) and the Undamped Frequency Response
Matrix (Normal Matrix or Real Frequency Response Matrix). A relationship among these matrices is used to
obtain the Damping Matrix explicitly. The Mass and the Stiffness Matrices are calculated from the Undamped
Frequency Response Matrix using the Least Squares Method. Three examples were employed in order to illustrate
the applicability of the proposed method and the results were quite accurate.

Inversion of an Effective Seismic Force at a Domain Reduction Method (DRM) Boundary and Reconstruction of Wave Responses inside the DRM Boundary

Bruno P. Guidio — 2024-06-22

A new inverse modeling is presented for reconstructing an SH wave input motion (i.e., its corresponding
effective seismic force vector) in a 2D domain that is truncated by a wave-absorbing boundary condition (WABC).
The domain reduction method (DRM) is utilized to model seismic input motions coming from the outside domain
of the WABC. The partial differential equation (PDE)-constrained optimization method aims at reconstructing
a targeted effective seismic force vector, corresponding to targeted incident wavefields, at the DRM boundary.
The presented method includes the discretize-then-optimize (DTO) approach, the finite element method (FEM),
which is used for solving state and adjoint problems, and the conjugate-gradient scheme, determining the desired
search path throughout a minimization process. The numerical results show that an effective force vector at a
DRM boundary is accurately reconstructed when a regularization, aimed at suppressing wave energy in an exterior

domain outside a DRM boundary, is utilized in conjunction with a typical misfit functional. By using such a regu-
larization term, the presented algorithm can minimize the kinetic energy associated with scattered wave responses

outside the DRM boundary and, eventually, improve the inversion performance. It is also shown that our inverse
modeling can accurately reconstruct the wave responses within a domain inside the DRM boundary.

Estimation of the Mass, Stiffness and Damping Matrices in the Frequency- Domain by Nonlinear Regression Techniques

Ferro, M. A. C. — 2024-06-22

A frequency-domain method for estimating the mass, stiffness and damping matrices of the mass-spring-
dumper model is presented. The developed estimation is based on the Least Squares Method in the Nonlinear

Regression Approach, where the input data are the elements of the Complex Frequency Response Inverse Matrix
and frequencies, which were chosen randomly from the range of frequencies. The amount of frequencies for
an accurate result is described in this work. It is shown that each element of the mass, stiffness and damping
matrices can be estimated independently, using the corresponding element of the Complex Frequency Response
Inverse Matrix, when the nonlinear regression is adopted properly. Although the method is developed for viscous
damping, it can be generalized for other types of damping, material or hysteresis, for example. Three examples are
employed in order to illustrate the applicability of the proposed method and the results are quite accurate.

Reservoir Properties Estimation based on Pressure and Temperature Data using ES-MDA

Vinicius Mattoso — 2024-06-22

Well test comprises a set of planned data acquisition activities and interpretation. The acquired pressure
and temperature data are used to estimate reservoir properties and oil field performance. The pressure data have
several noise sources that may compromise the accuracy of test results. The noise may mask the transient reservoir
behavior. Therefore, estimated reservoir properties, such as permeability, porosity, and skin effects, from those
acquired field data have a high level of uncertainty.

In this work, we use an in-house flow simulator that solves the complete coupled system of equations repre-
senting the wellbore/reservoir system. The thermal energy balance equation considers the Joule-Thomson heating

and cooling, adiabatic fluid expansion/compression, conduction, and convection effects. The synthetic measured
data was obtained by adding gaussian and harmonics noises to simulate equipment and tidal effects, respectively,
to the solution of the problem for different scenarios.
Reservoir properties estimation using pressure and temperature transient data obtained from well tests is a

classical inverse problem. We use Ensemble Smoother with Multiple Data Assimilation (ES-MDA) as a non-
deterministic method to solve this inverse problem. It provides a better data matching and quantification of uncer-
tainty when compared to other methods.

The results show that the properties of a reservoir with skin are better characterized by using combined
pressure and temperature data.

Numerical Simulation of the Flow Around Wind Turbines using the Im- mersed Boundary Method

Joao E. F. Martini — 2024-06-22

The aerodynamics study in wind turbines by computational fluid dynamics (CFD) techniques is funda-
mental since these tools help improve the performance of wind turbines and the choice of design of the rotor blades

more efficient. Thus, we perform a computational simulation to (i) obtain the lift and drag coefficients of the s809
airfoil (ii) obtain the torque and power of the NREL PHASE VI wind turbine. The wind turbine simulations were
performed with a fixed 3-degree blade pitch angle and constant 72 rpm rotational speed. The inlet velocity was
equal to 7 m/s, 10 m/s, 15 m/s, and 20 m/s. The angle of attack of the airfoil was varied from 0 to 20 degrees to

obtain the lift and drag coefficients curves. The closure turbulence models Unsteady Reynolds-Averaged Navier-
Stokes (URANS) were used in both cases. All of the implementations and simulations were developed using the

in-house software MFSIM (Multiphysics Simulator). The cartesian-structured block mesh was used to model the

fluid dynamics, and the immersed boundary methodology was necessary to model the aerodynamics bodies. Fur-
thermore, using an adaptive grid is a powerful way to save mesh refinement and, therefore, save processing time.

Finally, the aerodynamic results showed a good accord with the reference’s data, being the measurements made in

the NASA AMES wind tunnel for the wind turbine. Therefore, the immersed boundary methodology and adapta-
tive mesh refinement employed in this work proved to be promising computational tools to simulate complex and

moving bodies.

TMD’s control effect on the nonlinear dynamic response of a barge FWOT

Elvidio. Gavassoni — 2024-06-22

The use of wind turbine is increasing all over the world. Floating support-platform configurations, such
barge, are used at deep water conditions. The barge configuration achieves basic static stability in pitch and roll
using a large waterplane area and shallow draft. Such structures can exhibit large displacements when vibrating
which demands a nonlinear dynamic analysis. Passive structural control, such a tuned mass damper could be used
in order to keep the structure stability. The main goal of this work is to investigate the effects of a tuned mass
damper (TMD) upon the nonlinear oscillation of a barge-type floating offshore turbine. The analysis uses the
nonlinear normal modes to obtain reduced order models of the system. 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. The analytical obtained method is used to investigate important nonlinear phenomena such jumping and
multiple coexisting solutions. A parametric TMD damping and mass ratio is performed in order to obtain their
optimized values.

HYBRID MASS DAMPER COUPLED TO A WIND TURBINE TOWER: A PARAMETRIC STUDY

Pedro H. Q. Rocha — 2024-06-22

In this work, it is studied the application of structural control in the protection of wind turbines subject
to external loads, such as wind and earthquake, which can compromise the safety and integrity of the structure due
to 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. The aim of this research is to analyze, numerically, the behavior and efficiency
of the HMD using the Instantaneous Optimal Control (IOC) control algorithm to calculate the control force, and
present a parametric study that looks for the most appropriate weighting matrices to ensure the robustness of the
control system by minimizing the permanent response of the main system. In this study, the performance of the
Instantaneous Optimal Control (IOC) to control the dynamic seismic and wind response in the tower of a wind
turbine with a hybrid mass damper will be performed through a parametric study according to the variation of the
coefficients of the weighting matrices. The results of the IOC certify the efficiency of the controller through
numerical simulations carried out using the computational package MAPLESOFT, MATLAB, and its Simulink
control toolbox.

Improving HAWT Blade Design with multiphase BEM application and GA based airfoils for Low Reynolds conditions

Christiano P. Neto — 2024-06-22

Over the years, renewable energy sources are being implemented and improved. One such case is of
wind turbines. Some of the many challenges in this area are wind turbine placement and design. In low Reynolds
conditions coupled with highly turbulent air flow, the airfoil design is particularly complicated. By extension, this
complicates the design of the whole blade. In this paper, a fast method to determine good geometry for the wind
turbine blade is established. After flow conditions are set, by repeatedly applying the BEM method, more accurate
descriptions of the flow on the blade are obtained. Afterwards, finding best NACA airfoils as a base and using
Bezier curves as a geometry creator, a population of airfoils goes through a Genetic Algorithm. For each blade
region, a GA generated airfoil is found. Finally, the BEM method is used to determine the new expected power
coefficient with the new airfoil geometries. For the case used in this study, the final power coefficient obtained
was 0.28% lower than the target.

OPTIMAL DESIGN OF VISCOELASTIC LINKS CONSIDERING TEMPERATURE INFLUENCE IN VIBRATION CONTROL

Fantin. Eduardo Salmoria — 2024-06-22

Viscoelastic links can be characterized by the connection of a structure to the ground by a device with a
layer of viscoelastic material. When the structure vibrates, it provokes a relative displacement between the ground
and itself, leading to a deformation on the viscoelastic material. Due to high damping, viscoelastic materials are
used in devices for vibration control, working through dissipation of vibratory energy, and introducing stiffness.
Mechanical properties of viscoelastic materials vary, mainly, according with temperature and vibration frequency.
Changes in environmental conditions, like temperature, can lead to a non-optimal behavior of devices designed
with viscoelastic materials. The GVIBS group, which the authors are part of, has been developing over decades a
methodology for optimal design of passive vibration control devices, including some that use viscoelastic
materials. The goal of this paper is to expand the group methodology to design viscoelastic links, as well as model,
into a graphical interface, the effects of temperature changes on the behavior of viscoelastic links. A Fortran code
is developed to optimize the physical parameters and location of viscoelastic links, while considering the effects
of temperature changes. Experiments are done on a steel plate, with and without viscoelastic link, to validate the
developed methodology.

Nonlinear Solution of Tuned Liquid Column Dampers Compared to Linearized Analytical Solution

Marcos Wilson Rodrigues de Lima — 2024-06-22

This article compares the nonlinear and equivalent linearized solutions of an isolated Tuned Liquid
Column Dampers (TLCD), a kind vibration control device. A numerical simulation of the nonlinear behavior of
the structure under harmonic excitation was performed to determine the frequency response function (FRF). The
stepped sweep-sine procedure was performed to numerical estimation of nonlinear transmissibility FRF. With
TLCD’s transmissibility FRF due to base acceleration, the equivalent damping coefficient was determined using
the linearized solution proposed by Gao et al. [1]. Both non-linear and linearized FRF was compared to verify the
precision of Gao’s equivalent damping technique. The present implementation were done in Python programming
language and its native scientific libraries Numpy, Scypy and Matplotlib. The solution of nonlinear TLCD ODE
was calculated with the Odeint tool, a general-purpose integrator developed under the LSODA procedure

(Livermore Solver for Ordinary Differential Equations with the automatic switching method for rigid and non-
rigid problems).

Hand vibration analysis due to agricultural machine vibration

Leonardo Pessoa Linhares Oliveira — 2024-06-22

This study aims to present vibration’s effects on the human hand of agricultural machine drivers, often
neglected, which are related to work and cause serious health issues. The chosen equipment does not produce an
extreme vibration, such as cement breakers, in order to show that even minor vibration can generate stress and
strain on the body. In addition, the continuous exposure to this situation can cause fatigue, unpredictable health
issues, performance decrease, nausea, among others. The vibration used in this article was smaller than the ones
found in the literature.

About the performance of nonlinear tuned mass damper on the nonlinear dynamic controlled equation

Zenón J. G. N. del Prado — 2024-06-22

In this work, the performance of a nonlinear tuned mass damper is evaluated when applied to a nonlinear
Duffing equation with both softening and hardening behavior. For this, a damped Duffing nonlinear oscillator is
considered and subjected to a harmonic load, first the optimal linear control parameters are obtained and these
parameters are used to evaluate its performance on the nonlinear vibration regime. The quality of the nonlinear
tuned mass damper is observed on the resonance curves, basin of attraction, time responses, phase planes and
Poincaré sections.

Experimental Validation of a Finite Element Model of a Flexible Parallel Manipulator

Fernanda T. Colombo — 2024-06-22

Parallel manipulators present better dynamic performance than serial robots in terms of positioning
accuracy and operating speeds. However, it is complex to develop control strategies for parallel robots due to the

difficulty of obtaining the end-effector’s pose given the position of the joints. This task can be even more com-
plicated if the robot is lightweight and the links are flexible. A model of the system’s dynamics can be used in

the design of model-based controllers and may be essential to improve the performance of flexible manipulators
subject to undesired vibration. In this paper, we developed in a multibody dynamics environment a finite element
model of the parallel manipulator 3RRR. The current setup has thin and light links connecting the revolute joints

of each one of the three kinematic chains. To validate the multibody model implemented, we performed an exper-
imental modal test with accelerometers placed on the links and a roving impact hammer. Modal parameters such

as the natural frequencies of the numerical model and experimental setup were compared for different poses of the
manipulator.

Seismic performance of buildings equipped with dual isolation systems

Oscar Contreras-Bejarano — 2024-06-22

Nowadays, researchers from the academy and the industry have proposed several novel seismic isolation
schemes to improve the seismic performance of structures such as buildings, bridges, and water tanks, among
others. One of such schemes consists of including two layers of elastomeric isolators between the building and the
foundation to control both floor accelerations and the large displacement at the isolation level. This paper presents
a numerical study on the seismic response of buildings equipped with dual isolation systems. A total of three
buildings (4, 7, and 10 stories) modeled by using the shear-type representation (i.e., one horizontal degree of
freedom per story) are analyzed. Values of the properties of the elastomeric isolators were obtained from typical
values in single–isolation buildings. In contrast, the mass of each isolation layer is assumed to be equal to the story
mass of the superstructure. Simulated earthquake signals were generated from realizations of a non–stationary
stochastic process representing realistic earthquake ground motions recorded on stiff soils. The average seismic
response of the structure (peak displacements, peak inter-story drifts, and peak accelerations) is compared against
that obtained for the fixed–base condition and the single-layer isolation condition. Possible advantages of the dual
isolation system over the traditional single–layer are then discussed.

Dynamic Performance of Controlled Composite Structure of Footbridge

Pedro H. G. Neiva — 2024-06-22

Footbridges are structures subject to dynamic loads caused by a single or a varied number of pedestrians.
The dynamic interaction between pedestrians and the structure may bring discomfort to the users. Based on this,
the design of this type of footbridges require the evaluation of the behavior and the verification of the structure
strength under the combined action of static and dynamic loadings. This article presents a footbridge to be
constructed in composite steel-concrete structure considering only static loadings. Based on this, a dynamic
analysis of the footbridge was carried out to investigate the performance of the structure subjected to the
pedestrians traffic, considering two loading conditions, established by the Sètra guide: (i) a single pedestrian; (ii)
a crowd of pedestrians. Based on the maximum vertical accelerations, it was verified that the footbridge does not
attend the user comfort criteria to vertical vibration established by Sètra guide and ISO 10137 standard. Thus, it
has been made a parametric study to choose the features and design details of the passive attenuator of the TMD
type (Tuned Mass Damper) that is more appropriate. The results for the controlled footbridge show that the
structure meet the required comfort criteria.

Optimization of the constructive parameters of a tuned mass damper for the control of a cantilever beam

Janicely Fatima Stresser — 2024-06-22

Beams are structural elements widely used in engineering. During their useful life, they are subject to
different forms of static and dynamic loading. When dynamic actions are applied, they can assume a state of
vibration, causing large amplitudes that can compromise the structure from the point of view of environmental
comfort and also structural safety. These problems can be solved by inserting into the main structure a device
called a tuned mass damper (TMD). From the dynamic characteristics of the main structure, the TMD is scaled
and modeled as a mass-spring-damper system. In this context, the objective of this work is to present the
effectiveness of the use of TMD for the control of vibrations in a set beam. The TMD used was of the cantilever
beam type with a concentrated mass at the tip. This was modeled and fixed at the end of the main structure. Its
optimization parameters were scaled from the mass ratio and damping. The simulation responses were obtained
using the finite element method (FEM) using the computer program Ansys®. The results were satisfactory, for a
mass ratio equal to 0.05 and damping factor of 0.1273.

Control of vibrations in the frame structure using dynamic vibration absorber

Fabiana da Rosa Sufiatti — 2024-06-22

Structures are physical systems subjected to external actions that cause transmission of efforts. These
actions can be classified as dynamic when they vary with time, in magnitude, direction, position, and/or direction
and generate relevant loads. They are responsible for causing vibrations in the structure that can damage it, cause
fatigue of the materials, and affect the users' comfort. The Dynamic Vibration Absorber (DVA) device aims to
control these unwanted vibrations, increasing the life of the structure and providing comfort to users. This study
aims to develop a dynamic analysis of a frame structure and design an DVA-type device to control the vibration
of the structure. Initially, a numerical dynamic analysis of the primary structure was performed to identify the
frequency response function and the first modes of vibration, using the Finite Element Method (FEM). From this
analysis, the ideal parameters of the device were determined: stiffness, the mass ratio between the mass of the
DVA and the primary structure, and the damping ratio to control the vibrations in the first natural frequency of the
frame. The DVA was modeled as a cantilever beam with concentrated mass at the tip, using the Euler-Bernoulli
equation. This DVA was coupled to the structure and the same previous numerical analysis were performed, where
a reduction in displacement amplitude was observed. This result demonstrates that the device is efficient to control
of vibration in the first mode of vibration of the frame under study.

Parametric optimization of TMD inerter for vibration control of vehicle suspension

Pedro C. Gomes — 2024-06-22

In Tuned Mass Damper (TMDs), the increase of mass increases the effectiveness and frequency band
of vibration control. To get around this difficulty, Smith [1] [2] propose a new device called inerter to automobile
suspension. The present work aims to determine the optimal parameters for a Tuned Mass Damper Inerter (TMDI)
applied in a discrete model of quarter-car suspension for comfort and roadhold criteria. The addition of a parallel
TMDI configuration result in a better performance only to low frequencies (0-5Hz).

Experimental and numerical study of 3D-printed parts for a pulmonary ventilator circuit

Lara E. P. Santos — 2024-06-22

The speed of propagating COVID-19 has culminated in an alert from the World Health Organization,
characterized by a global health problem and an emergency state. In Brazil, the growing demand for obtaining
spare parts for respirators motivated researchers of the University of Brasilia to assist in the task force of providing
studies in this area. The 3D printing could be a solution for the low-cost respirator parts replacement attending
ISO standards. Such verification is the main objective of the current work. The structural integrity tests showed

the agreement of the 3D-printed parts with the ISO 80601-2-80 technical requirements. The numerical simula-
tions were based on the transient Navier-Stokes equations to study the flow patterns in a ventilator circuit with

original and printed components. The geometry discretization method took into account boundary layer and flow
recirculation zones. The following studies have been analyzed: simulation of the flow path built from the original
components and 3D-printed components, doubled flow circuit for two patients, and an evaluation of the usability of
the newly fabricated parts. The simulation results showed reduced pressure losses and improved flow patterns for
the newly designed 3D-printed parts and their complete attendance to the ISO requirements to medical connections.

Numerical simulation of a connected-pipe test ramjet motor

Douglas C. Cerbino — 2024-06-22

This work presents both analytical and numerical simulations of a ramjet engine developed at the Chemical
Propulsion Laboratory (CPL) of the University of Brasilia (UnB) to aid its design and safety for future hot tests.
The test facility comprises a connected-pipe test bench with a heater simulating the diffuser flow. The test bench’s
primary objective is to study the ramjet combustion chamber performance and the cooling wall effect provided by
the presence of the flame holders. Transient time-averaged Navier-Stokes equations in two-dimensional form and
the k− turbulence model describe the flow behavior. The non-premixed model based on GriMech 3.0 mechanism
takes into account chemical transformations. Implementation of the structured mesh and mesh sensitivity analysis
yielded optimal simulation accuracy and time. The numerical simulation studies the motor performance in three
flight regimes. The validation of the simulation results to analytical and numerical ones presented an acceptable
level of data conformity. As a main result, CFD simulations proved the ramjet wall cooling concept with an efficient
flame holder and separator. Consequently, more advanced simulations will be provided in the future resulting in
recommendations for hot tests.

Comparison among numerical approximations in the simulation of the grain mass aeration process

Daniel Rigoni — 2024-06-22

In technological development and in the high scale of agricultural production, in the specific case of

grains, efficient structures and ways are required to store the product. One widespread form is aeration, which con-
sists of the forced passage of air through a mass of stored grains. The high cost of acquisition and maintenance of

this technology is a factor that may inhibit its dissemination and acceptance, especially to a large number of small
grain producers. There are several mathematical and numerical models in order to solve this type of problem. This
work aims to solve numerically the model proposed by Thorpe of the aeration of the grain mass, using the finite

difference technique and employing the spatial approximations UDS, CDS and UDS with deferred correction. Ad-
ditionally, the explicit, implicit and Crank-Nicolson time formulations are used. The results obtained numerically

were compared with experimental data taken from the literature, so the difference between the experimental data
and the numerical solution for each approximation used can be observed. Thus, it was found that using the spatial
approximation UDS with deferred correction and the Crank-Nicolson time approximation obtained the smallest
difference to the experimental data.

Numerical simulation of turbulent flows using the Finite Element Method and GPU-CUDA parallelization

Alminhana, G. W. — 2024-06-22

In the present work, an investigation is carried out on the use of Graphics Processing Units (GPUs) as
a powerful tool to accelerate Computational Fluid Dynamics (CFD) simulations and problems of interest for CWE
(Computational Wind Engineering). With this intent, different code versions (OpenMP and CUDA-Fortran) are

utilized to compare response accuracy and computational performance obtained using an explicit two-step Taylor-
Galerkin scheme, with turbulence modeling via Large Eddy Simulation (LES), where the flow equations are

discretized in the context of the Finite Element Method (FEM) considering eight-node hexahedral elements. From
the 3D simulation investigated here, it is observed that the use of GPUs leads to high levels of computational
processing speed, generating little, if any, loss of accuracy in the numerical results, and still allows increasing the
refinement level of computational meshes and time increment without increasing the simulation time compared to
other approaches.

Heat transfer enhancement using delta-wing streamwise vortex generators

Luciano Garelli — 2024-06-22

In this work, a three-dimensional thermo-fluid dynamics simulation using the multiphysics code Code Saturne
is carried out, in order to analyze the performance of delta-wing vortex generators for enhancing the heat exchange

in panel type radiators. These radiators are widely used in electric power transformers. The study is focused on nat-
ural convection and buoyancy-driven flows, which are common working conditions for this type of heat exchanger.

First, the performance of a single delta wing which is placed between parallel vertical plates is analyzed. The best
combination of characteristic parameters (aspect ratio, angle of attack) to obtain the highest thermal enhancement
factor is established. It is found that separating the vortex generator from the surface of the panel has positive
effects in this sense. Then, with the selected configuration, a set of delta-wing arrays is placed on the surface of
the heat exchanger and the resulting thermo-fluid dynamics is analyzed. The total heat flux and local / global heat
exchange coefficients are reported. Using these passive devices, the overall heat transfer improves by 12%.

Analysis of Inlet Conditions in a CFD Application on Ester Immersed Power Transformers

Agustín Santisteban — 2024-06-23

This work presents a study of the cooling performance of a natural ester in a power transformer winding
by using CFD analysis. Thus, the study is performed under heat-run test conditions and considers two different
dielectric fluids, a mineral oil which is the original cooling fluid and a natural ester as an alternative fluid. The
inlet boundary conditions are calculated by considering the thermal and hydraulic balance of the transformer
cooling system. When considering natural ester, the inlet mass flow rate and temperature obtained are lower than
the mineral oil case. For the CFD analysis, a portion of the low voltage winding in a 3D model is selected, using
the Conjugate Heat Transfer model for the fluid-solid thermal interaction and the Boussinessq approach for the
buoyancy terms. The results from transformer balance and thermal model obtained for mineral oil are compared
to the heat run test results to validate the model. Regarding the CFD results, natural ester leads to higher hot-spot
temperature in the winding and higher oil temperature rise than mineral oil.

Comparison between the global flow stability of isothermal and adiabatic gaps in a boundary layer

Marlon S. Mathias — 2024-06-23

The global stability of a flow provides great insight to its behavior in the real world. Small imperfec-
tions in flat surfaces may accelerate the transition to turbulence, which has a great impact on the flow behavior

downstream as well as the overall lift and drag caused by such flow. The literature contains several simulations of

the flow over open cavities – of which gaps are a subset – however, there is no standard treatment for wall tempera-
ture, which is usually either isothermal or adiabatic, whereas the real-world condition is somewhere between both

scenarios. We wish to compare the global stability of both cases to measure the impact the wall temperature mod-
eling has over the overall flow. To achieve this, we will use and in-house developed open-source Direct Numerical

Simulation (DNS) code, coupled with its global stability routine. The simulation is subsonic yet compressible and
the parameters are chosen so that the flow is close to a critical stability condition, so that any differences between
both temperature treatments are maximized. Different temperature boundary conditions to cause the base flow to
settle at different temperatures, which in turn affects the flow density as well as the local Mach number. Our goal is
to better understand the role of surface temperature on flow stability so that we can better compare our simulations,
as well as those found in the literature, to experimental results as well as to real-world scenarios.

Numerical simulation of tornado flows using anisotropic mesh adaptation

Miguel A. Aguirre — 2024-06-23

A numerical model for tornado flow simulation is proposed in this work, where Adaptive Mesh
Refinement (AMR) techniques are utilized. Owing to the increase observed in the annual occurrence of storms
with tornado formation, investigations on tornado flow characteristics and its effects on buildings and structures
are required. In this sense, a numerical algorithm based on the explicit Characteristic-Based Split (CBS) scheme
is adopted to solve the system of flow equations, where four-node tetrahedral finite elements are employed in the
spatial discretization procedures. An anisotropic mesh adaptation scheme based on Riemannian metric is coupled
to the flow solver in order to capture high flow variable gradients in the tornado vortex region. Tornado flow
fields are simulated here using numerical modeling of tornado experimental simulators and results obtained with
the present model are compared with predictions presented by other authors in order to evaluate the influence of
mesh adaptation on the accuracy of the numerical results.

Improved Well Drilling Simulation With Transient Thermal Model For Predicting Wellbore Temperatures

Mostafa M. Abdelhafiz — 2024-06-23

Drilling simulators have been utilized as a key for drilling optimization and cost reduction for the drilling
process. Supporting the drilling simulator with realistic and accurate models can enhance the simulation processes

leading to a more efficient drilling operation. This paper presents the implementation of a newly developed tem-
perature model in the software simulator at Drilling Simulator Celle (DSC). The model can simulate and predict

the temperature of the wellbore fluids, drill string, casing, cement, and the surrounding formation for depth and
time. The model is also able to simulate both the flowing condition of the drilling fluids and the static condition or

the so-called thermal recovery period. The model is embedded into the drilling simulator through an application-
programming interface (API) which allows the communication between each model and the drilling simulator

itself. The user of the simulator can monitor the wellbore system temperature at each depth in real-time or even in
accelerated mode. This allows the pre-drilling of the well on the simulator in the design and planning phase. For
application and demonstration purposes, a case study has been conducted for a geothermal well in the Hanover
(Germany) area. The historic data has information about the formation, drill string, and bottom hole assembly, as
well as operational parameters. Different simulation runs have been conducted using the drilling simulator, and
the transient behaviour of the wellbore temperature is analyzed during circulation and shut-in periods.

Structural analysis of antiviral N95 filtering facepiece respirator VESTA

Caio Bilio — 2024-06-23

The pandemic caused by the coronavirus (SARS-CoV-2), which causes the disease COVID-19, forced
health authorities and research institutes to propose solutions. An important and accessible tool to fight against the
virus the use of masks. The VESTA respirator's designed product is the new antiviral N95 filtering facepiece
respirator developed by the researcher team from the University of Brasilia. The facepiece mask is composed of
three layers of non-woven that can retain up to 95% of solid, liquid, oily and aerosol particles besides inactivating
the virus. The Vesta differential is the chitosan nanofilm, present in the intermediate layer, that works as a physical

barrier for the virus. The nanofilm has antimicrobial action and greater ability to filter viruses, including the SARS-
CoV-2 that causes COVID-19 and prevent infectious diseases with self-cleaning protection and drug delivery

properties. This paper aims to perform structural simulations like tension, deformation, and vibration analysis on
the respirator VESTA. It demonstrates the mechanical characteristic of the designed mask and certifies its
resistance under the certain application. The numerical simulations were performed in the commercial finite
element software ANSYS.

Analysis and application of a fractional SIR model constructed with Mittag- Leffler distribution

Noemi Zeraick Monteiro — 2024-06-23

We have discussed previously the construction of an arbitrary-order SIR model with physical meaning.
We believe that arbitrary-order derivatives can be obtained through potential laws in the infectivity and removal

functions. This work intends to complete previous discussions, showing new results in a model with Mittag-
Leffler distribution, with an emphasis on equilibrium points and reproduction numbers. We also discuss our prior

application to COVID-19, now from the current perspective.

A Nonlinear Dynamical Map for COVID-19

Eduardo V. M. dos Reis — 2024-06-23

The new coronavirus disease (COVID-19) has rapidly spread around the world, being considered a
pandemic with serious consequences. In this regard, epidemic models became an essential tool to describe and
predict epidemic evolution. A classical approach is the compartmental models where different populations are
employed to describe the system evolution. Typically, four populations are considered: susceptible, exposed,
infected and recovered, giving rise to the SEIR model. This paper proposes a dynamical map to describe Covid-19
epidemic based on the classical SEIR model taking into consideration the effect of vaccination. This novel map
describes the evolution of currently infected, cumulative infected and vaccinated population using three coupled
nonlinear algebraic equations. Due to the simplicity of the novel model description, useful information to evaluate
the epidemic stage can be obtained analytically, allowing the support of decision making. In this regard, the
herd immunization and the estimation of the number of deaths should be pointed out. Real epidemic data from

Germany, Italy and Brazil are employed in order to verify the model capability to describe the evolution of Covid-
19 dynamics.

Parameter calibration and uncertainty quantification in an SEIR-type COVID- 19 model using approximate Bayesian computation

Thiago G. Ritto — 2024-06-23

The present paper applies the approximate Bayesian computation (ABC) for parameter estimation and
uncertainty quantification in an SEIR-type model with data of hospitalisation and deaths from the city of Rio de

Janeiro. The analysed model considers eight compartments: susceptible, exposed, infectious, asymptomatic, hos-
pitalised, recovered and deceased (SEIAHRD). ABC is employed to update the prior probability density function

of the model parameters, where a two objective optimisation problem is formulated (data of healthcare and deaths)
and eleven parameters are identified. The transmission rate is allowed to vary over time (to change its baseline).
The applied model seems to be consistent with the available data.

Multi-agent simulation of Coronavirus contamination on public transport

Victor Geraldo Gomes — 2024-06-23

Since the beginning of 2020, we are experiencing a worldwide pandemic of the coronavirus. Since then, health
authorities around the world have tried to prevent people from infecting themselves with this virus. In Brazil, states and
cities plan and take decisions to restrict movement or release some activities to return to normal operation. As noted, these
are decisions that can, on the one hand, harm the economy and the citizen's interpersonal relationships and, on the other,
lead to overcrowding of hospitals, health chaos and more deaths. For this work, a computer simulator was developed where,
together with a mathematical model and multi-agent systems, it was sought to show contamination situations in real
environments. The simulator has an interface where it is possible to visualize people moving in a pre-established
environment. The objective of this work is to add to the studies already in progress, bringing more data and information
that can help to improve policies and actions to combat the pandemic.

Understanding the R0 of Epidemics

Harisankar Ramaswamy — 2024-06-23

A fundamental parameter in the epidemiology of infections is the so-called basic reproduction number,
R0, loosely defined as the number of new infections an infected individual will subsequently cause. This parameter
is central to traditional SIR models and plays a key role in dictating transmission dynamics. However, R0 is
typically ill-defined since it does not specify the time interval over which such secondary infections will occur.
In SIR models, R0 also has a different interpretation depending on the assumed kinetics of infection. In this
paper, we borrow concepts from a recent publication [1] to provide explicit expressions for R0 in terms of key
physio-chemical, environmental, and operational parameters, including the spatial population density, which is
fundamental to the health policy of spatial distancing. We then explore how R0 varies depending on the kinetics
assumed, motivated by the special case of interactions in enclosed environments for which the SIR model needs to
be reformulated. We consider, as a special case, super-spreader events, where we show that if one were to use the
SIR model, the effective value of R0 will be a significantly large, albeit decreasing, function of the duration of the
event, suggesting a delta-function-like behavior. We comment on a possible extension of the SIR model to capture
different infection kinetics by introducing an additional dimensionless number m, which represents the one-to-m
collision mechanism expected for the spread of infections in enclosed or high-density environments.

An Object-Oriented Solver for Modeling the Multi-regional COVID-19 Outbreak

Yujia Hao — 2024-06-23

This paper presents the result of the work of a group of Undergraduate Students at Emory University, Atlanta (GA),
USA (under the mentorship of A. Veneziani). We present a solver of a classical epidemiological model addressing

the space-dependence of the outbreak by splitting a domain of interest (the “Domain”) into subdomains (the “Ge-
ographical Units”) connected by matrices representing the inter-regional mobility. We address the implementation

of the solver with an Object-Oriented approach to promptly manage an arbitrary number of GU in the domain and
to enable an easy, modular refinement of the local model.

Extension of a Least-Squares Finite Element Method for a Meso-Scale Model of the Spread of COVID-19 for a vaccinated Group

Fleurianne Bertrand — 2024-06-23

In this work, we aim at extending our previous findings on a meso-scale SEIRQD model for the spread
of COVID-19. The model and its extension are based on the division of the total sum of the living population into
different compartments and the virus contraction and recovery dynamics are formulated in a coupled system of
PDEs. This system is to be solved by a Least-Squares Finite Element Method and the results will be compared to

actual real-life data gathered on the spread of the virus in Germany to evaluate the accuracy of predictions com-
puted with our method. We opt to extend the SEIRQD model by incorporating the growing group of vaccinated

individuals. Based on the knowledge on the efficiency of the various vaccines currently in use, we chose to im-
plement this new factor with a certain backflow of vaccinated individuals to the group of exposed individuals to

mimic a failure rate, where the vaccination has not been successful.

COVID-19 FORECAST: COMPARISON AND COMBINATION OF AU- TOREGRESSIVE AND COMPARTMENTAL MODELS

Fabiano A.S. Ferrari — 2024-06-23

The Imperial College was responsible for the firsts forecasts for covid-19 propagation, in the early
stages of the pandemic. Their study had a positive effect in the British Lockdown and it may have saved many
lives. Besides the Imperial College study, many other studies were proposed based on different approaches. Some
models have projected much more deaths than we have observed, while others have projected much less. There
are plenty reasons to explain why the model can fail, it can be caused by bad data, virus mutation, health care
system collapse, and others. One strategy to reduce the error in the propagation forecast is to combine different
approaches. In this work, we are going to present error analysis for the forecast of covid-19 propagation based on
autoregressive models (such as ARIMA and SARIMA models) and compartimental models (such as SIR model
and variations) and how the forecast can be improved by the combination of these two approaches.

A Peridynamic Approach to Calculate the Elastoplastic Stress and Strain Fields

Átila L. Cruz — 2024-06-23

The peridynamic theory is a new approach developed in recent years for the numerical solution of
elastodynamics problems. One of the advantages of the peridynamic theory is the natural capacity to simulate the
initiation and growth of cracks in solid materials, without the aid of numerical procedures commonly employed in
the conventional finite element formulation. This advantage is due to the peridynamic constitutive relations are
based on partial integral equations, rather than differential ones, where these equations keep definite even with a
geometrical discontinuity. This theory relies on the displacement fields of a given simulated problem, where the
stress and strain fields are not obtained natively. Within this context, a numerical approach to calculate the strain
and stress fields for a peridynamic elastoplastic simulation is presented, based on the developments published in
the literature. The accuracy of this approach is verified by comparing the results for the Von Mises stress field
obtained with the peridynamic theory, to those obtained with a commercial finite element code, and conclusions
are drawn.

An SPIM-FEM coupling strategy for damage modelling

Samir S. Saliba — 2024-06-23

This paper proposes a coupling strategy between the finite element method (FEM) and meshfree meth-
ods belonging to the family of Smoothed Point Interpolation Methods (SPIMs), to analyse two-dimensional prob-
lems with scalar damage. Starting from a model that is fully discretised by the FEM, the proposed strategy is

capable to identify the regions where nonlinear phenomena occour, and to convert the FEM mesh to an SPIM
discretisation in such regions, in order to obtain a coupled FEM-SPIM model. When the FEM mesh is replaced,

the SPIM discretisation is built using the original FEM nodes and additional nodes, in order to improve the ap-
proximation in the nonlinear regions. The characteristics of the proposed approach are illustrated with a set of

numerical simulations, comparing the results of the coupled model with the results of full FEM and SPIM models.

A meshfree approach for the Timoshenko beam

Felipe P. dos Santos — 2024-06-23

Besides the finite element method, there are a number of numerical methods for the analysis of shear de-
formable beams available in the literature, developed to improve the convergence properties and the shear-locking

behaviour exhibited by the finite element method. This paper investigates the application of a meshfree method of
the family of Smoothed Point Interpolation Methods (S-PIM) to the analysis of the Timoshenko beam. Numerical
simulations are also presented, in order to illustrate preliminary results in terms of convergence properties obtained
with a peculiar type of shape function, among the ones of the S-PIM approach.

Point Interpolation Methods for phase-field modelling of brittle fracture

Larissa Novelli — 2024-06-23

The present work investigates the application of meshfree Point Interpolation Methods (PIM) to the
phase-field modelling of brittle fracture. The phase-field modelling is an efficient tool for the simulation of complex
cracks. Within this approach, a crack is modelled as a diffuse crack where a length scale parameter controls the
size of diffusive region and the value of phase-field indicates the integrity of the material. Point Interpolation
Methods can be based on polynomial or radial shape functions. These shape functions possess (i) the Kronecker
delta property, that allows a more simple imposition of essential boundary conditions, (ii) the compact support
property and (iii) the partition of unity property. This paper discusses the computational aspects of the application
of the PIM strategy to the phase-field modelling, and presents numerical simulations to illustrate the characteristics
of the proposed approach.

Comparing meshless methods with the finite element method for applica- tion of a bio-inspired remodelling algorithm intended to design bone scaf- fold

A.I.Pais — 2024-06-23

The design of bone scaffold involves the consideration of stress shielding which occurs when the
Young’s modulus of the implant is higher than the Young’s modulus of the bone it is replacing and therefore, bone
decay occurs in the surrounding tissue. It is therefore very important that the material is adequately adapted to the
properties of the surrounding tissue to allow for appropriate load transfer between the bone and the implant. There
are several studies to evaluate the occurrence of proper bone ingrowth in scaffold using bone remodelling models
and most studies assume an already existing scaffold design.
This work aims at combining meshless methods combined with the bone remodelling algorithm as a way to
develop optimized functional gradients of infill density for bone scaffold with the intent of obtaining mechanical
properties in the scaffold that will be compatible with bone tissue.

eXtended Isogeometric Analysis - a numerical investigation of simulation of two-dimensional elastic fracture.

Karla F. Santos — 2024-06-23

When compared with the Finite Element Method (FEM), the Isogeometric Analysis IGA presents as
advantages the exact representation of the problem geometry, the possibility of using the same basis functions to
describe the geometry as well as the solution field and a straightforward and automatic scheme to refine the mesh.
The eXtended Isogometric Analysis (XIGA) enlarges the approximate space of IGA incorporating customized
functions, by the enrichment strategy of Generalized/eXtended Finite Element Method (G/XFEM). The present
work evaluates the performance of the eXtended Isogeometric Analysis (XIGA) in the context of the Linear Elastic
Fracture Mechanics. Several parameters related with the enrichment strategy, such as the region to be enriched,
the number of nodes enriched, the type of enrichment functions are combined with the special features of IGA and
the behavior of the solution is investigated. This work is a first step of the expansion of the INSANE (INteractive
Structural ANalysis Environment) platform, originally developed with FEM functionalities and later expanded to
G/XFEM simulations. It is an open source software developed at the Structural Engineering Department of the
Federal University of Minas Gerais.

NON-STRUCTURED GRID REFINEMENT USING GENETIC ALGORITHMS

Elton F. Doehnert — 2024-06-23

Refinement of non-structured grids is an important topic related to the accuracy of numerical solutions
of the most used methods to solve engineering problems, such as the finite elements method and the finite volumes
method. Considering this fact, the current paper presents a methodology to optimize triangular non-structured
meshes using a floating point genetic algorithm to choose the best position for grid vertices. Such position is
based on a fitness function evaluated to each internal grid vertex; it is based on the average of the quality of
volumes to which the vertex belongs to. The algorithm is executed to a grid firstly generated with the Delaunay’s
triangularization and then disturbed to obtain a non-optimal grid, which needs to be improved. Results show that
the quality parameters were improved, although the method needs high computational efforts.

A projection technique for nonlinear adaptive analyses exploring the Generalized Finite Element Method

Bruno R.S. Souza — 2024-06-23

When solving complex engineering problems of structural and solid mechanics, the adoption of lin-
earity hypotheses may not be accurate and the use of nonlinear models can become necessary. Also, numerical

methods are often used to generate approximations to them since analytical solutions are unknown for most of
these problems. In this context, solving the equilibrium equations requires the use of specific strategies, with the
Newton-Raphson Method being one of the most commonly adopted. In standard nonlinear analyses using the
Finite Element Method, an initial solution is obtained for a first discretization. Then, the quality of this solution
is evaluated to decide if further analyses are needed in order to obtain more accurate results, therefore exploring
an improved discretization. If a more refined mesh is necessary, for example, the solution must be recalculated
once again. In this paper, an alternative to this process is presented using a projection technique. Accordingly, all
the information obtained during the analysis using a less refined discretization is transferred to the more refined
one. Thus, the results provided by a first mesh is used as an initial guess for the iterative scheme in order to solve
a second mesh. This also helps improving the convergence within the Newton-Raphson Method. A discussion
related to the performance and effectiveness of this technique, that can be explored in combination with adaptive
procedures for nonlinear analyses, is also presented. Finally, a two-dimensional geometrically nonlinear numerical
problem, using the Generalized Finite Element Method, is shown to validate the presented technique.

A Finite Difference Energy Method to Arbitrary Grids Applied the Plate Bending Problems

Paulo H. Silva dos Santos — 2024-06-23

The finite difference energy method (FDEM), although already used in several structural problems
so far, including dynamic and nonlinear analysis, has always been applied to regular grids, making it limited to
applications with geometries formed by (or mapped to) rectangles. In order to make it competitive with other
methods, such as finite elements and meshless, it is necessary to generalize the FDEM to arbitrary domains and
boundaries, endowing it with ability to manipulate arbitrary grids. Thus, this paper presents a FDEM formulation
for regular and irregular grids applied to the thin plate bending problem. The coefficients were obtained at each
point of the arbitrary grid by expanding the Taylor series. The results show that using the proper choice of points
for the stencils we can keep the order of approximation of the case regular, but now allowing the generalization of
the use of the method that was only applied to rectangular grids.

Enriched Modified Local Green’s Function Method for singular Poisson problem

Ramon Macedo Correa — 2024-06-23

The Modified Local Green’s Function Method (MLGFM) is a hybrid method that couples the Finite
Element Method (FEM) and the Boundary Element Method (BEM). The method presents high convergence rates
for both potential and flux in the problem boundary and does not require a priori knowledge of the fundamental
solution of the problem or a Green Function. In fact, the method automatically obtains an approximation of Green
tensor by solving an auxiliary problem. On the other hand, some improvements have been made in conventional
FEM to expand its approximation space, mainly by the Generalized Finite Element Method (GFEM) and its stable
version, the Stable Generalized Finite Element Method (SGFEM). The GFEM uses the Partition of Unity Method
idea to bring previous knowledge about the solution of the problem to enrich the traditional FEM approximation
space with appropriate functions. Here the MLGFM will be enriched with GFEM and SGFEM to obtain an
approximated Green tensor projection, using singular functions as enriched functions. This Enriched Modified
Local Green’s Function Method will be applied to singular Poisson problem and the potential and flux will be
compared with reference results.

Computational analysis of crack propagation in structures with imposition of a deformation field

Felipe A. Bacelar — 2024-06-23

Cracks have been present in several types of structures since man started using them. However,
currently, accidents due to loss of structural integrity can be of larger proportions causing great social, financial
and environmental loss since, due to the modern technological advances, the structures are getting bigger and more
complex. Fracture mechanics is the science that studies this type of failure. This work aims to analyze pre-fractured
structures composed of fragile materials subjected to the imposition of deformations, better understanding the
crack behavior in this case and verifying the fracture propagation path. The modeled structures were presented by
Portela et al [1] and the objective of this work is to present a comparison between the paths formed by the crack
propagation with the extended finite element method (XFEM) and the boundary element method (BEM) presented
as a reference.

Solving the Poisson Equation using Virtual Element Method and Artificial Neural Networks

Paulo Akira Figuti Enabe — 2024-06-23

The Virtual Element Method (VEM) is a recent method that proposes a generalization of the classical
Finite Element Method (FEM). VEM formulation is complex and requires a strong mathematical base. VEM
models are able to use any simple polygon (convex or non-convex polygons) as mesh discretization elements,
which leads to the functions associated with each of those elements being not strictly polynomials. Thus, the
core proposal of VEM is to compute those functions implicitly, by projecting then in a polynomial space. The
Virtual Element Method was originally formulated for the Poisson Equation, which is largely explored both in
mathematics and natural sciences due to its versatility.
Approximation methods like VEM are widely applied to solve partial differential equations (PDE). A less
common approach is to use artificial intelligence techniques like Artificial Neural Networks (ANNs). Solve PDEs
with ANNs is not new, but with the increasing popularity of deep learning techniques and new frameworks (e.g

Pytorch and Keras), this approach is becoming more relevant. In the present work, the Poisson Equation is trans-
formed into an optimization problem and them ANNs are used to compose a trial solution, aiming to obtain the

best one (i.e., the one that reduces the error as much as possible). Artificial Neural Networks are widely used in
this kind of approach since they are very popular in classification problems.
Throughout the article, the formulation of VEM and the ANNs approach is presented, highlighting their main
characteristics. The implementation of both approaches is discussed and the results are compared.

POST-PROCESSING OF ANISOTROPIC LAMINATES IN DYNAMIC PROBLEMS MODELED USING GENERALIZED FINITE ELEMENT METHOD

Diego Pavani Guimarães — 2024-06-23

The paper presents a post-processing method to be applied in results obtained from dynamic analysis in
thin laminated structures. The problems are modeled using the Generalized Finite Element Model (GFEM) and
are based on first order shear deformation theory. The main goal of this work is to analyze the effects of the inertial
and body forces on the results obtained from the stress and displacement recovery method. The method relies on
values obtained from GFEM which are next are applied to the general local constitutive, kinematic and motion
equations. GFEM are integrated and the values of the transverse stresses are then corrected using stress-strain
relations. Also, all components of displacements can be recovered. These new corrected displacement and stress
values are then compared with results obtained from analytical and numerical solutions for validation.

Analysis of suspended cables by the Generalized Finite Element Method using trigonometric enrichment functions

Leonardo A. C. Basso — 2024-06-23

Presenting light weight, cost-effective construction and the possibility of pre-tensioning, cables have
been used as structural elements in suspension bridges, mooring lines, transmission lines, guyed towers, marine
and off-shore constructions, cable trusses and roof structures. The analysis of cable structures by the Finite Element
Method (FEM) using straight elements usually requires a high number of degrees of freedom in order to obtain
acceptable results for the cable shape and its properties, such as cable tension and length. In this paper the
Generalized Finite Element Method (GFEM) is studied with the use of trigonometric enrichment functions,
considering a linear and inextensible cable analysis. The results obtained by the GFEM using the proposed
trigonometric enrichment functions are compared to linear solutions provided by the Hierarchical Finite Element
Method (HFEM). The computational cost is analyzed in terms of the total number of degrees of freedom and the
program execution time. The condition number of the stiffness matrix is also discussed.

Mixed Dimensional Coupling in GFEM Global-Local

Lorena L. Gomes — 2024-06-23

The global-local Generalized Finite Element Method (GFEM) is use here to solve mixed dimensional
structure problems. Considered as an instance of the Partition of Unity Method (PUM), the GFEM uses enrichment
functions that, multiplied with the Partition of Unity (PU) functions, augment the space of problem solving. These
enrichment functions are chosen according to the problem analyzed, but they can also be numerically obtained from
the results of the analysis of a local problem, the so-called GFEM global-local. The application of this method,
however, is limited to models, for which both global and local meshes use the same formulation of finite element.
Here, the two scale of the analysis are discretized not only by different meshes, but also with different types of finite
elements. Combining mixed-dimensional elements and a multi-scale analysis can be highly effective to capture
the local structure features without overburden the global analysis of the problem. An iterative procedure, that
balances the forces of the two multi-dimensional models, is combined with the global-local analysis of GFEM. A
numerical example is presented, considering the coupling of a large-scale model with Timoshenko beam elements
and a small-scale model with quadrilateral plane elements.

A positional isogeometric formulation for two-dimensional analysis of elastoplastic solids

Rosicley J. R. Rosa — 2024-06-23

In this work, we propose a numerical formulation based on Isogeometric Analysis (IGA) for solving

two-dimensional problems of elasto-plastic solids at large displacements and small/moderate strains. The Isogeo-
metric Analysis aims to connect CAD (Computer Aided Design) concepts with the structural analysis method. In

this work, we employ basis functions generated from NURBS (Non-Uniform Rational B-Splines) to construct the
initial and also the final domains. The current positions are taken as main variables, so that the problem is naturally

under the isoparametric idea and also naturally considers geometric nonlinearities. The von Mises criteria is em-
ployed to detect plasticity occurrence and an additive elastic-plastic strains decomposition is adopted to represent

the elastic-plastic constitutive models. Finally, two-dimensional numerical examples are simulated considering
plane strain, in order to verify the proposed methodology.

On the imposition of the local boundary conditions in the G/XFEM-gl analysis

Túlio Roberto Eládio Marques — 2024-06-23

The present work investigates the imposition of boundary conditions in the scope of the Generalized
Finite Element Method with Global-Local Enrichment (GFEMgl) in the analysis of a two-dimensional linear
elastic fracture mechanics problem. In the GFEMgl, the “global problem” is firstly solved with a course
discretization, and a “local problem” is defined in the region containing singularities, imposing the previously
obtained solution as boundary conditions. The solution of the local problem provides numerically obtained
enrichment functions capable of representing the singular features. Two aspects are analyzed here: the
application of Cauchy boundary conditions (displacements and stresses), as well as the influence of the local
domain size. As for the Cauchy boundary conditions, the problem is simulated using average stresses and
recovered stresses obtained by the ZZ-BD recovery procedure (based on the stragey of Zienkiewicz-Zhu to
recover a smooth stress field, but using a block-diagonal matrix in its formulation). The results are presented in
terms of the stress intensity factors and the strain energy of the enriched global problem. The numerical
simulations are performed in INSANE (INteractive Structural ANalysis Environment), an open-source software
developed in the Department of Structural Engineering at the Federal University of Minas Gerais.

Application of polynomial and discontinuous SGFEM for analysis of structures in damage process under mixed-mode fracture

Guilherme Oliveira Ferraz de Paiva — 2024-06-23

This work aimed to implement polynomial and discontinuous enrichment functions, according to the
strategy of the Stabilized Generalized Finite Element Method (SGFEM), to simulate mixed-mode failure problems

in structures. The mixed-mode model was formulated and developed based on a bilinear damage model for quasi-
brittle materials. The results were verified by comparison with experimental curves drawn from test results from

the four-point shear test. The computational efficiency and accuracy of the polynomial and discontinuous SGFEM
were then tested to improve the prediction of the failure behavior over a conventional Finite Element analysis,
especially for coarser meshes. The results showed that the proposed models had accuracy equivalent to others
found in the literature but employing a much smaller number of elements and degrees of freedom.

A quadratic GFEM formulation for fracture mechanics problems

Murilo H.C. Bento — 2024-06-23

The Generalized Finite Element Method (GFEM) is a Galerkin approach that generates numerical ap-
proximations belonging to a space obtained by augmenting FEM spaces with enrichment functions capable of

representing well local behaviors of the problem solution. The method has already proved to accurately solve
different classes of problems, including those within the linear elastic fracture mechanics context. For these
problems, GFEM shape functions can represent both the discontinuous and singular behaviors of cracks by a
convenient choice of enrichment functions. Regarding convergence and conditioning aspects, recent works have
proposed well-conditioned and optimally convergent first-order approximations based on GFEM enrichments. In
this work, an initial version of a well-conditioned quadratic GFEM for problems of fracture mechanics is presented.
The methodology consists of using a quadratic Partition of Unity (PoU) to combine local approximation spaces.
A two-dimensional (2-D) numerical experiment with a linear elastic fracture mechanics problem is presented to

demonstrate that the proposed formulation delivers optimal convergence and well-conditioned systems of equa-
tions. Moreover, the robustness of the proposed approach is also demonstrated by showing that the stiffness matrix

conditioning is preserved even for some critical situations regarding the relative position between the mesh and the
crack line.

Hybrid Discontinuous Galerkin methods for elliptic problems based on a Least-Squares variational principle

Diego T. Volpatto — 2024-06-23

We propose new hybrid finite element methods for elliptic problems based on a Least-Squares varia-
tional principle (LS-h). We devised the LS-h formulation considering local minimization problems in each element

of the mesh, with the objective function composed of Least-Squares residual terms in each element and local in-
terface conditions (i.e., transmission conditions on the mesh skeleton). The LS-h formulation can be rewritten in

terms of independent local problems and a coupled global problem. The former consists of Least-Squares formu-
lations and the latter is written in terms of a Lagrange multiplier – identified as the trace of the primal variable –

imposing the transmission condition on the mesh skeleton. Thus, we obtain the global system by static conden-
sation, reducing considerably the number of unknowns to be solved. For the resulting algebraic system, through

Singular Value Decomposition (SVD) numerical calculations, we estimate the condition number of the LS-h using
the l
2
-norm. We compare the LS-h with classical Hybridizable Discontinuous Galerkin (HDG), showing that LS-h
has similar condition number estimates in spite of the different block structure in its resulting system. Furthermore,
we performed numerical experiments using the method of manufactured solutions to show that LS-h has optimal
convergence rates – in terms of l
2
-norm – for both primal and flux variables.

An efficient two-stage form of the Crank- Nicolson scheme with application to an HDG method for poroelasticity

Ismael S. Ledoino — 2024-06-23

We propose an alternative form of the Crank-Nicolson scheme devised for linear space operators,
though its properties, such as convergence and stability, also hold for nonlinear ones. The discretization mimics
the implicit Euler scheme by adding a decoupled weighted average equation as a second stage for each time step.
This creates a two-stage method in contrast to the classical one-stage one, but it also evaluates the space operator
at only the middle point, therefore generating a scheme that is computationally more efficient for highly expensive
space operators. The scheme also simplifies the time update of the solution, and its implementation easily extends
from the implementation of the implicit Euler scheme. In order to verify the scheme’s stability and convergence,
we apply it to a series of time dependent one-dimensional problems, and also to a two-dimensional poroelasticity
problem, also known as Biot‘s Consolidation problem. Our application to the Consolidation problem uses an HDG
method to approximate the space operator, which exemplifies yet another feature of our scheme: it does not rely
on Lagrange multipliers to update the solution at the interior of elements.

Phase-field models for ductile fracture: a comparative study

Lívia Ramos Santos Pereira — 2024-06-23

Fracture is a usual failure mode of engineering structures. Thus, the prediction and prevention of
cracking-induced failure is a crucial point in engineering projects. Many formulations have been proposed for
modeling this phenomenon. The Phase-Field (PF) theory has become popular because it couples Continuum
Damage Mechanics and Fracture Mechanics principles. Initially proposed for brittle fracture, the PF theory has
been extended for ductile materials. A possible strategy is introducing a yield surface degradation function that
depends on the PF variable. Besides this consideration, the stored energy must also be changed, including a plastic
work contribution. A different option is to couple the yield surface degradation function with a fracture toughness
depending on the accumulated plastic strain. In this case, the phase-field driving force remains defined only by
the elastic strain. From this context, this paper presents both PF models’ formulations applied to an elastoplastic
constitutive model and their implementation. These two approaches are compared. The material parameters are
also evaluated to identify how they influence the models’ behavior. Finally, numerical simulations via the Finite
Element Method are presented to highlight the ductile phase-field models’ main characteristics.

Applications of a new computational model of interface and phase-field fracture

Roman Vodicka — 2024-06-23

Computational analysis of fracture in multi-domain structures is considered so that cracks may appear in
material bulks and also along material interfaces. The proposed computational model introduces two independent
damage parameters relying on representation of rupture by mechanical damage theory. One of them being pertinent
to the interface considering it as a negligibly thin adhesive layer of a contact zone between structural components.

The arising interface cracks are supposed to appear so that cohesive zone models with general stress-strain relation-
ships are implemented. The other damage parameter defined for the bulks uses the theory of phase-field fracture

which causes elastic properties degradation only in a narrow material strip that forms a diffused crack. Both of
these damaging schemes are expressed in terms of a quasi-static energy evolution process. Having such an energy

formulation, the proposed computational approach is introduced in a variational form. The solution evolution be-
ing approximated by a semi-implicit time stepping procedure related to a separation of deformation and damage

variables. The deformation and damage solutions at each instant being obtained by non-linear programming algo-
rithms implemented together within a MATLAB finite element code. The numerical simulations with the model

include an analysis of fibre separation arising in a fibre-reinforced composite material.

OOP Implementation of Phase-Field Models

Hugo M. Leão — 2024-06-23

The study of fracture mechanisms to prevent the catastrophic collapse of structures is an important re-
search trend. Among the possible approaches, the phase-field modelling, starting from a variational formulation of

the Griffith’s criterion, allows for a smoothed representation of a sharp crack, without the need for a discrete rep-
resentation of the sharp crack itself. The phase-field modelling of fracture was recently implemented in INSANE

(INteractive Structural ANalysis Environment), an open-source software based on the Object-Oriented Program-
ming paradigm developed by a research group at the Structural Engineering Department of the Federal University

of Minas Gerais (UFMG), and currently used in a number of research projects of the group. The results available in
the literature and the recent advancements of the group, point out that the phase-field approach is effective for the
simulation of cracks nucleation and propagation. In this paper, new results obtained with the phase-field modelling
of fracture through the implementation in INSANE will be presented.

Implementation of a bound-constrained solver in phase-field modelling of fracture

Rafael G. Bayao — 2024-06-23

In phase-field modelling of fracture, the cracking representation is conditioned by the relation between
the displacement field and a phase-field variable that measures the degradation of the material. In this sense, the
cracks are modelled as smooth and diffuse according to a group of functions that best represents the geometry of the
region where the phenomenon takes place and how the strain energy is degraded during crack propagation. Using
a variational formulation of Griffith’s criterion, these functions are combined in such a way to attend to the balance
laws and the crack irreversibility condition, as well as the bounds of the phase-field variable. The Department of
Structural Engineering of the Federal University of Minas Gerais (UFMG) has been currently incorporating, in its
open-source software INSANE (Interactive Structural Analysis Environment system), various phase-field models.
Nonetheless, the software still has some limitations as the use of some functions may extrapolate the phase-field
bounds during solving. The literature has described the use of a bound-constrained solver that can overcome this
issue. Therefore, this work proposes the implementation of this solution strategy without the use of any external
libraries.

Parallel Solution of 3D Ohta-Kawasaki Nonlocal Phase Field Model in FEniCS

Gabriel F. Barros — 2024-06-23

This study presents new results for the parallel solution of the 3D nonlocal Cahn-Hilliard equation
derived from the Ohta-Kawasaki free energy functional with adaptive time step control. The temporal adaptivity
scheme is recast under the linear feedback control theory equipped with an error estimation that extrapolates the
solution obtained from an energy-stable, fully implicit time marching scheme. We use three time-step controllers
with different properties: a simple Integral controller, a complete Proportional-Integral-Derivative controller, and
the PC11 predictive controller. We explore how different controllers affect the convergence of the nonlinear solver
for two values of the nonlocal parameter. The efficiency of the adaptive schemes for the nonlocal Cahn-Hilliard

equation is evaluated in terms of the number of time steps required for the complete simulation and the com-
putational effort measured by the required number of nonlinear and linear solver iterations. We show numerical

evidence of mass conservation and free energy decay for both nonlocal parameters.

A bound-constrained solver for phase-field modelling of diffuse fracture

Matheus M. Fortes — 2024-06-23

In a structural analysis it is important to know the propagation of cracks to prevent a possible failure
of the material or the structure. One way to model a crack is by the phase-field strategy. Within this approach,
the problem is described by the displacements field and by an additional variable, the phase-field, that measures
the degradation of the material, like a damage variable. Using this variable, a crack is represented in a smooth
and diffuse way. In the current version of the INSANE (INteractive Structural ANalysis Environment system),
an open-source software developed at the Department of Structural Engineering (DEES) of the Federal University
of Minas Gerais (UFMG), some phase-field models have been implemented. However such models have certain
limitations, due to how the crack irreversibility condition is handled. The present work proposes to remove these
limitations with the implementation of a bound-constrained solver that, as pointed out in the literature, constitutes
a more general approach to deal with the irreversibility condition. In the implementation, the library PETSc
(Portable, Extensible Toolkit for Scientific Computation) is used. Numerical simulations are presented to illustrate
the characteristics of the implementation.

Simulation of gas bubble dynamics using a phase-field model

Malu Grave — 2024-06-23

The modeling and simulation of gas bubble dynamics is still an active research area, mainly when
surface tension is present. One way to model the gas and fluid phases is with interface capturing methods. Three
well-established interface capturing models are the Volume-of-Fluid (VOF), level-set, and phase-field models. The
main advantage of the VOF method is mass conservation, while the implementation of the surface tension may
be challenging. The level-set is known for its ability to compute the surface tension accurately, and phase-field
models are known for satisfying the second law of thermodynamics. This work uses a conservative Allen-Cahn
equation to model and simulates the effects of the surface tension in gas bubble dynamics. We include concepts of
the level-set and VOF methods and verify the energetic stability of the methodology. We also compare the results
with the convected level-set method. Results are analyzed and discussed.

Capturing Provenance to Improve the Model Training of PINNs: first hand- on experiences with Grid5000

Romulo M. Silva — 2024-06-23

The growing popularity of Neural Networks in computational science and engineering raises several

challenges in configuring training parameters and validating the models. Machine learning has been used to ap-
proximate costly computational problems in computational mechanics, discover equations by coefficient estima-
tion, and build surrogates. Those applications are outside of the common usage of neural networks. They require a

different set of techniques generally encompassed by Physics-Informed Neural Networks (PINNs), which appear

to be a good alternative for solving forward and inverse problems governed by PDEs in a small data regime, espe-
cially when it comes to Uncertainty Quantification. PINNs have been successfully applied for solving problems in

fluid dynamics, inference of hydraulic conductivity, velocity inversion, phase separation, and many others. Never-
theless, we still need to investigate its computational aspects, especially its scalability, when running in large-scale

systems. Several hyperparameter configurations have to be evaluated to reach a trained model, often requiring
fine-tuning hyperparameters, despite the existence of a few setting recommendations. In PINNs, this fine-tuning
requires analyzing configurations and how they relate to the loss function evaluation. We propose provenance data
capture and analysis techniques to improve the model training of PINNs. We also report our first experiences on
running PINNs in Grid5000 using hybrid CPU-GPU computing.

PINNs for Parametric Incompressible Newtonian Flows

Romulo M. Silva — 2024-06-23

In this paper we demonstrate the application of Physics-Informed Neural Networks (PINNs) for learning
the solution of the parametric steady incompressible Navier-Stokes equations for multiple flow regimes for the
well-known channel-driven cavity flow problem, given only the geometry and boundary conditions.

Addressing uncertainty in seismic imaging by using deep learning surrogate model for reverse time migration

Rodolfo S. M. Freitas — 2024-06-23

In seismic exploration, many decisions are based on interpretations of seismic images, which are affected by the
presence of multiple sources of uncertainty. Uncertainties exist in data measurements, source positioning, and subsurface
geophysical properties. Reverse time migration (RTM) is a high-resolution depth migration approach useful for extracting
information such as reservoir localization and boundaries. RTM, however, is time-consuming and data-intensive as it
requires computing twice the wave equation to generate and store an imaging condition. RTM, when embedded in an
uncertainty quantification algorithm (like the Monte Carlo method), shows a many-fold increase in its complexity and
cost due to the high input-output dimensionality with computationally intensive requirements’. Hence, one of the main
challenges facing uncertainty quantification in seismic imaging is reducing the computational cost of the analysis. In this
work, we propose an encoder-decoder deep learning surrogate model for RTM under uncertainty. Inputs are an ensemble
of velocity fields, expressing the uncertainty, and outputs the seismic images. We show by numerical experimentation
that the surrogate model can reproduce the seismic images accurately, and, more importantly, the uncertainty propagation
from the input velocity fields to the image ensemble.

A investigation of data quality in reservoir characterizations using Machine Learning

Alesson M. Torres — 2024-06-23

Inferring the capacity of reservoirs is one of the essential tasks in the oil and gas exploration process.
The characterizations of transport and storage are crucial for reservoir evaluations and, therefore, depend on the

permeability and porosity. Although estimating the permeability in porous media is challenging since experi-
mental data gathering is very costly, estimations are not accurate. Machine Learning (ML) methods have been

applied to predict the permeability in oil-producing areas as cost-effective and quick characterization strategies.

However, the quality predictions of ML algorithms depend on the available data quality and the algorithm param-
eters optimization. In this work, in order to have a comprehensive understanding, we investigate the permeability

inference employing algorithms as Multivariate Linear Regression, Decision Tree Regression, Support Vector Ma-
chines (SVM) and Multilayer Perceptron (MLP). The ML approach was constructed and tested via data samples

experimentally gathered from Australia and Papua New Guinea region. Data pre-processing metrics are optimized.
The most relevant feature was analyzed and optimized parameters improved the inferences as expected. The mean
squared error and root mean squared error for the test set are on the order of 0.0066 and 0.0811, respectively,
indicating that our results are very promising.

Fault detection with Stacked Autoencoders and pattern recognition techniques in gas lift operated oil wells

Rodrigo Scoralick Fontoura do Nascimento — 2024-06-23

The offshore industry is responsible for most of the oil and gas production in Brazil. When the level of
complexity in this industry is high, it has been a precursor to new technologies in recent years. The main objective

of the present work is the development of a system for the detection and classification of failures in oil produc-
tion wells operated with elevation by gas lift. Stacked autoencoders are used and pattern recognition techniques

for fault classification, verifying performance metrics and applying cross-validation to check the generalization of

the models for the available observations. After the development of the classifiers, high recall values were ob-
tained (much higher than 0.88), which shows the great applicability of the proposed system in detecting failures in

offshore production wells.

Method for Treating Anomalies in Multivariate Time Series

Thiago Moeda — 2024-06-23

In recent years, the classification of time series has gained great relevance in significant sectors and

segments of society. Machine Learning Techniques make it possible to interpret the behavior of anomalous phe-
nomena in multivariate datasets. This work proposes a study of three methods from the perspective of their ability

to provide relevant information for the detection, validation and prediction of anomalous events in time series data.
To achieve this goal, a case study was carried out exploring algorithms based on neural networks and inductive
symbolic learning applied to a real problem of detecting anomalies associated with the oil well drilling process.
The main results indicate that this method can be a promising way to treat anomalies.

A Fast Algorithm for Training Dynamical Neural Networks Using Steady- State Prior Information of Offshore Oil Platform

Leandro Freitas — 2024-06-23

In systems identification, the use of auxiliary information configures a grey-box approach. This paper
describes a methodology to estimate model parameters including auxiliary information about the static behavior
of the system in a bi-objective approach and discusses a decision maker based on the auxiliary information. The
procedure can be applied to many model structures, such as polynomial models or multilayer perceptron (MLP)
neural networks, without the need of computing the model fixed points. The grey-box modeling procedure was
applied to design a soft-sensor for the downhole pressure of a real gas-lifted deep-water offshore oil well. To this
end, steady-state values of the downhole pressure were estimated from historical data from (almost) stationary
conditions. The available training and validation (dynamical) data had information over a limited operating range,
while test data had operating ranges not present in the training and validation data. The identified dynamic models
used only platform variables with a fixed MLP structure. The results indicate that the procedure yields suitable
models with good static and dynamic performance. Besides, the use of auxiliary information helped to find models
with better dynamical performance on operating regimes not originally represented in the dynamical data. Whereas
an identified black-box MLP model obtained a root mean squared error (RMSE) of 6.7 kgf/cm2

in a free-run

simulation over test data, the proposed approach achieved an RMSE of 3.7 kgf/cm2

. This is very relevant for many
practical situations where the available dynamical data does not cover all operating regimes of the system. The
procedure described in this work can be applied with different model classes with greatly reduced computing time.

Characterization of Porosity Properties of Carbonate Rocks through a Fast Image Processing Approach

Victor G. Cardoso — 2024-06-23

The characterization of porous media represents a critical issue for recovering oil and gas from reser-
voir rocks. Analyses of digital images generated by X-ray micro-computed tomography (μCT) help build detailed

models of rocks and extract petrophysical parameters. For this purpose, we have developed an efficient 2D mi-
crotomographic image processing method for the extraction of samples’ porous system properties. The proposed

method utilizes a histogram-based analysis to perform the segmentation of the images. Our approach allows the

automatic computation of the total porosity, pore size distribution, and general pore orientation data of seven lime-
stone plugs from the Eocene Tambaba Formation by the usage of image processing techniques. The porosity values

extracted by the new segmentation technique were compared against porosity values obtained through porosime-
try (helium) essays. The average error between experimental values (obtained by porosimetry) and the porosity

values obtained through the proposed segmentation process is 3,42%. A comparison of pore orientation distri-
bution provided automatically by the proposed technique and the orientation obtained through classical methods

showed excellent correlation. Computation time spent for the automatic calculation of pore system properties was

approximately 9 minutes per sample (performed in an Intel Core i7 CPU with 8GB of RAM PC). Further experi-
ments of calculations with smaller quantities of slices provided similar petrophysical properties, with a reduction

of 95.7% on the processing time. The accomplished results showed the new automatic segmentation technique’s
great potential for the extraction of porous system properties of calcareous rocks with accuracy and efficiency in
computational time.

Software Engineering Best Practices for Using Machine Learning in the Oil and Gas Industry

Rodrigo da S. Cunha — 2024-06-23

The widespread adoption of Machine Learning (ML), due to the increased availability of data and the fast
evolution of computing power and software techniques experienced in the last decade, has fundamentally changed
our world. The implementation of ML models has become fast and cheap, allowing state-of-the-art discoveries to
become widely accessible. That context enabled innovation in several industries and businesses, with problems

hitherto untouched by science being addressed, therefore requiring a reduction in the gap between scientific re-
search and its application in real-world issues. However, ML models have proven to be expensive to maintain and

scale. New challenges emerge as ML models are deployed and monitored, driving a rising concern about best
practices for building reliable ML systems. Despite the increasing popularity of this subject and the consolidation
of specialized literature, applying the best practices is not a simple task. Depending on time or team experience
and size, such practices can represent a technical overhead, making the enforcement of such practices an arduous

task in many situations. This paper proposes a strategy for adopting software engineering best practices by com-
mitting to a set of principles from the beginning of an ML project. To illustrate our strategy, we will use mooring

line failure detection in the floating production storage and offloading unit (FPSO) mooring system, providing an
example of our strategy applied in the Oil and Gas industry.

Neural Network Meta-Model for FPSO Roll Motion Prediction from Environmental Data

Lucas P. Cotrim — 2024-06-23

The current design process of mooring systems for Floating Oil Production and Offloading units (FP-
SOs) is highly dependent on the availability of the platform’s mathematical model and accuracy of dynamic sim-
ulations, through which resulting time series motion is evaluated according to design constraints. Out of the six

degrees of freedom, roll motion is among the most complex to accurately simulate. We propose a Neural Simu-
lator, a set of neural network surrogate models designed to predict an FPSO’s roll motion statistics directly from

metocean data when subject to different loads. This approach bypasses the need to perform traditional time series
dynamic simulation, as the trained models take measured metocean conditions and directly output the desired roll
motion statistics. This allows for Artificial Neural Networks (ANNs) to be trained through simulation and later
fine-tuned on real FPSO motion. As a result, our proposal presents higher accuracy and reduced computational
time when compared to traditional methods. The ANN surrogate models are trained by real current, wind and wave
data measured in 3h periods at the Campos Basin from 2003 to 2010 and the associated roll response of a Spread
Moored FPSO subject to different drafts, which is obtained through time-domain simulations using the Dynasim

software. Hyperparameter Optimization techniques are performed in order to obtain optimal ANN models special-
ized in different platform drafts. Finally, the proposed models are shown to correctly capture platform dynamics,

providing good results when compared to the statistical analysis of roll motion time series obtained from Dynasim.

We conclude that an ANN surrogate model can be trained directly on real measured metocean conditions and plat-
form roll motion to provide increased accuracy and reduced computational time over traditional methods based on

dynamic simulation. Moreover, the proposed architecture can be integrated into an automated learning framework:
The data-based surrogate models can be continuously fine-tuned and updated with newly measured data, resulting
in improved accuracy over time.

ALINE: A Computational System Based on Seismic Data and Machine Learning for Gas Reservoir Detection

Luiz Santos — 2024-06-23

Reflection seismic is one of the most used geophysical methods by the O&G industry for subsurface

imaging. Through the processing and interpretation of seismic data, geoscientists infer the positioning and geome-
try of potential hydrocarbon accumulations. However, the reflection seismic method can produce ambiguous data

owing to similar signatures in natural bodies with different physical properties. Moreover, onshore seismic data
have in general less quality when compared to offshore seismic data, making the interpretation process even more

difficult. Artificial intelligence (AI) techniques have been adopted in several applications, particularly for the inter-
pretation of salt bodies and geological faults. However, for identification of hydrocarbon reservoirs, AI techniques

are still under development, particularly owing to the great amount of seismic data to be processed. Recently,
Eneva and Tecgraf/PUC-Rio developed the computational system ALINE (Automated Learning Intelligence for

Exploration) based on Machine Learning techniques and seismic data to generate indicators of potential gas accu-
mulations in on-shore fields. In this study, we focus on the description of ALINE’s system, its current capabilities

and methods, advantage and limitations, and future developments. The current methodology uses modern neural
network architectures through the analysis 1D of seimic traces to identify specific signatures of gas accumulation.
Several onshore seismic sections from Parque dos Gavioes at Parna ̃ ́ıba’s Basin were provided by Eneva during the
first validation tests. The results obtained for that region showed an accuracy of 75 - 80% of the gas class and 90
- 95% of the non-gas class. Although other approaches for similar applications are not available in the literature
for comparisons, the global average of success shows that the system has a significant potential for exploratory
purposes. Moreover, ALINE’s system also can be adopted for predictions considering offshore 3D seismic data, as
performed on the Block F3 in the North Sea that enabled better accuracy rates owing the best quality of data. Those
results highlight the potential of ALINE as a computational tool for the interpretation of 2D or 3D seismic data,
onshore or offshore, boosting the value of seismic data and minimizing uncertainties, representing an effective
technological advance in the sector O&G.

Online event detection for sensor data

Eduardo Ogasawara — 2024-06-23

In streaming time series analysis, it is often possible to observe the occurrence of a significant change in
behavior at a certain point or time interval. Such behavior change generally characterizes the occurrence of an
event. An event can represent a phenomenon with defined meaning in a domain of knowledge. The event detection
problem becomes particularly relevant in this context, especially for applications based on sensor data analysis.

The algorithms for detecting events online or in real-time run simultaneously with the process they are monitor-
ing, processing each data point as they become available. Online event detection for streaming applications is a

challenging problem that creates an increasing demand for high-performance computing and advanced machine

learning techniques. Although there is a wide variety of methods, no silver bullet technique exists for event detec-
tion. In this context, this work contributes by providing a taxonomy for online detection of events in time series,

including incremental and adaptive learning and some of the main methods addressed in the literature.

Seismic Facies Segmentation Using Atrous Convolutional-LSTM Network

Maykol J. Campos Trinidad — 2024-06-23

In this paper, we provided new end-to-end approaches to the task of seismic image segmentation, as
human analysis requires a lot of effort and time due to the large pixel dimensions. Given that seismic dataset
contains temporal information along its axis (inline and cross-line), we also proposed the use of recurrent neural
networks (RNN) together with convolutional layers. After several experiments, we found that the application
of crop and rescale (zoom) as a data augmentation technique, as well as the use of focal loss, shows significant
improvements in performance and training speed. Our best LSTM-based model achieved a very close to the best
one using fewer parameters.

Compositional pore-network modeling of gas flooding in gas-condensate reservoirs

Paula K. P. Reis — 2024-06-23

Gas flooding in gas-condensate reservoirs can delay pressure depletion below the dew-point and re-
vaporize accumulated condensate in the near wellbore region. For condensate bank removal, the method’s success

depends on a series of parameters, such as the injected gas composition, the total injected volume, the reservoir
depletion level and the porous medium heterogeneity. In order to investigate the influence of these parameters at

the pore-scale, we used a compositional pore-network model to reproduce gas injection in porous media after con-
densate accumulation. With the model, the effects of complex phase behavior arisen from the interaction between

injected gas and accumulated fluids in the porous medium could be evaluated. The performances of methane,

ethane, carbon dioxide, nitrogen and produced gas flooding to improve flow following condensate banking at dif-
ferent pressure levels were compared. Condensate re-vaporization rate, recovery of heavy components, relative

permeabilities, and final saturations were quantified so that optimal injection scenarios were identified. Results
indicated that the injected gas composition affects significantly condensate banking removal by gas flooding, with
C2 and CO2 being the most favorable candidates among the tested gases for the method. The injection pressure
also affected greatly the results, curtailing the condensate recovery as it was decreased below the dew point.

Optimizations in an numerical method code for two-phase fluids flow in porous media using the SDumont supercomputer

Stiw Herrera — 2024-06-23

In petroleum reservoir simulations, the level of detail incorporated into the geologic model typi-
cally exceeds the capabilities of traditional flow simulators. In this sense, such simulations demand new

high-performance computing techniques to deal with a large amount of data allocation and the high

computational cost to compute the behavior of the fluids in the porous media. This paper presents opti-
mizations performed on a code that implements an explicit numerical scheme to approximate the solution

of the governing differential equation for water saturation in a two-phase flow problem with heterogeneous
permeability and porosity fields. The experiments were performed on the SDumont Supercomputer using
2nd Generation Intel® Xeon® Scalable Processors (formerly Cascade Lake architecture). We employed
the domain decomposition method to split the 3-D reservoir onto n sub-domains that are solved using each
Message Passing Interface (MPI) process. We analyzed the performance of the domain decomposition
strategies and identified communication bottlenecks as the mesh size and the number of computational
nodes increase. The results show that the optimizations implemented in the numerical code remarkably
reduce the execution time of the simulations.

Validation of a new finite element formulation for unsaturated flow in porous stiff solids.

T. Scussiato — 2024-06-23

This paper presents the validation of a finite element formulation of Richards’ equation for transient
unsaturated flow. The formulation is presented and its results are compared to an exact analytical solution obtained
for the model of Gardner of water retention curve and hydraulic conductivity. The results obtained with a coarse
regular mesh with the element are in excellent correspondence with the analytical solution. Numerical aspects of
application of this formulation for unsaturated flow in concrete slabs are commented.

Numerical study of different forms of synergetic CO2 injection and storage as an Enhanced Oil Recovery method

Vinicius Czarnobay — 2024-06-23

Carbon capture, utilization, and storage (CCUS) is already seen as essential for sustainable development.
In the oil & gas sector, injecting CO2 into the reservoir is also an important Enhanced Oil Recovery (EOR) method,
producing effects on oil properties. Continuous injection, the CO2 use in Alternating Water and Gas (WAG) and
carbonated water injection, for example, can contribute to further oil recovery. This study aims to compare the
recovery factor (RF) and the geologic storage for different CO2-EOR techniques through numerical simulation.
For this, a reservoir model and a compositional fluid model were implemented in a commercial software. Then,
different injection settings were compared. As a benchmark, the injection flows were selected to maintain a similar
average Bottom Hole Pressure (BHP). As results, all CO2-EOR methods were better than water injection, with an
emphasis on continuous CO2 injection, with increases of more than 33% in the RF. The selection between
CO2-WAG cycles showed differences of more than 4.5% in the final RF. The tertiary CO2 injection, after water
injection, had the highest geological carbon storage efficiency, of 23%. With the results, it is expected to contribute
to the analysis of the CCUS potential and in optimizing the use of CO2-EOR.

NUMERICAL MODELING OF HYDRAULIC FRACTURE PROPAGATION USING FEA IN SHALE RESERVOIRS

Pablo A. Medina — 2024-06-23

The aim of fracking procedures is enhancing the permeability of non-conventional reservoirs. This
process is influenced by the in-situ stresses. Throughout history, in Vaca Muerta (Argentina), wells production has

been technically challenging. Vaca Muerta formation is made of shale and limestone layers which induce a dif-
ference in the in-situ stresses. In a strike-slip regime this stress difference in combination with the geomechanical

properties might promote the appearance of horizontal fractures. Given the above, the following research discusses
numerical modeling of the stresses during the fracking procedure.
Several numerical experiments will be presented to identify opportunities to optimize operations in Vaca
Muerta, considering different features, such as: geomechanical properties, weak interfaces (density and properties),
and laminations (shale vs limestone).
This work presents numerical results concerning the growth of a vertical hydraulic fracture in a 3D shale
domain. This fracture growth is limited by a thin layer of limestone, which creates a weak interface between the
limestone and shale. The goal of this analysis is focused on the interaction mechanism between the weak interface
and the growth of the vertical fracture. Arrest, crossing and T-shapes fractures can take place. A cohesive mode
with mixed damage is carried out. Furthermore, this study explores different properties for the limestone layer,
given by a geomechanical model from Vaca Muerta, effect in fracture growth. Results will provide an optimized
operating window for injection and fracture process in order to improve the resultant stimulated reservoir volume.

Numerical simulation of engineered water injection: Effect of Oil Composition and Rock Charge Distribution

Mateus S. Neto — 2024-06-23

Oil production demands Enhanced Oil Recovery (EOR) techniques. Numerical simulation can simulate
recovery techniques such as injecting low salinity water into offshore carbonate reservoirs. However, numerical
modeling of LSWI has not been done mechanistically and needs solid scientific foundations. A numerical model
based on these foundations was created, using the PHREEQC program and the Python programming language as
a tool, to understand the effect of the presence of acidic and basic groups in the oil, positive and negative sites of
calcite (typical carbonate rock in Brazilian pre salt reservoirs), in the change of wettability, due to changes in the
composition of the injection water. For the development of the algorithm, the Complexation Surface Model (SCM)
and the Bond Product Sum (BPS) concepts were applied, aiming to predict the efficiency of the brine injection, to
increase the EOR. For oil, the acidic and basic numbers, when increasing, raise the BPS, when decaying, decrease
the BPS. But the acid influence is greater. For calcite, the influence of positive and negative sites have the same
proportion on BPS, following the same behavior of oil numbers. Because of that, wettability is changed, the higher
the BPS, the lower the EOR.

Buckley-Leverett theory applied in Low-Salinity Water Flooding displacement

Joao Victor Correia Lopes — 2024-06-23

In offshore operations, due the amount of sea water, it is common to inject water in the wellbore as
an EOR (Enhanced Oil Recovery) method to help maintain reservoir pressure and improve the oil production.
However, it is necessary to evaluate the best method where it can improve the recovery factor and avoid spending
a lot of money purchasing chemicals and equipments. The recovery factor is impacted by the interaction between

the oil and the reservoir rock. The effect of the wettability is an example where the rock needs to be more water-
wet than oil-wet to increase the recovery factor. Present studies indicate the injection of water with ion additions,

also known as Low Salinity Water Flooding (LSWF), is efficient in wettability change and is cheaper than usual
methods in the industry. This work aims to estimate the advance of water and LSWF displacement implementing
Buckley-Leverett theory in numerical simulation with Python. Fractional flow, saturation profile, oil recovery
factor and pressure drop are the outcomes that indicate higher oil production and lower decay when comparing
LSWF to waterflooding.

Analysis of solution by traveling waves for an in situ combustion model

Ecos Sanchez Jhonatan — 2024-06-23

In-situ combustion is a medium and high viscosity oil recovery technique. In this work, a mathematical
model was proposed describing the in situ combustion technique. Also, the study of the existence and uniqueness of
the solution using traveling waves is presented. Unlike previous works, we use the Ideal Gas Law and the fractional
flow theory, resulting in a more realistic model. This physical phenomenon is described by a mathematical model
composed of three partial differential balance equations: energy balance, the molar mass balance of gas, and the
molar mass balance of oil.

A comparison among Vanka, Uzawa and Fixed-Stress smoothers for the one-dimensional poroelasticity problem using Multigrid Time-Stepping

Vanessa Terezinha Ales — 2024-06-23

The poroelasticity equations mathematically model the interaction between the deformation of a porous
elastic material and the fluid flow inside it. The mathematical model that describes this theory, in its most simplified
version, considers the variables displacement, pressure and time, related to each other by a system of partial
differential equations. The importance of deepening the knowledge about this problem is related to the difficulty
of obtaining a numerical solution, due to the presence of saddle points that generates instability in the numerical
analysis. In this work, the problem of 1D poroelasticity is solved, whose boundary conditions assume a left
boundary without displacement variation and with free drainage, and a rigid right border without pressure
variation. For the discretization of differential equations, the Finite Volume Method is used for spatial
discretization and the implicit Euler method with Time-Stepping sweep for temporal discretization are used. The
linear systems from discretization are solved using Vanka, Uzawa and Fixed-Stress smoothers. The results
obtained demonstrate that the different smoothers are equivalent with respect to accuracy. However, there are
differences regarding the convergence factor, computational time and complexity.

Modeling and Simulation of an Isothermal CO2 Capture System using a Hollow Fiber Membrane Contactor

Wanderson F. A. dos Passos — 2024-06-23

This manuscript provides an analyzes of a one-dimensional modeling approach for post-combustion
CO2 capture in a Hollow Fiber Membrane Contactor (HFMC), which uses a 30% (w/w) MEA
(monoethanolamine) solution as a solvent. A reactive absorption is considered, with variable gas and liquid
resistances. The influence of the volumetric rate (G°) on the system parameters was evaluated, and then, the system
behavior was studied, fixing the parameters to achieve a capture ratio of 90%. The MATLAB 2021a® software
was used to solve the equations, and a routine was created, allowing to solve the problem as an initial value problem
(IVP), which shown to be efficient.

Alternatives for the simulation of the lysozyme protein structure

João M. Regauer — 2024-06-23

The application of solid mechanics has recently expanded to various new fields, which were unthinkable
a few years ago. Studies focusing on structural characteristics of microscopic entities have helped other areas such
as biochemistry to enhance our understanding of complex phenomena. Special attention has been given to proteins,
where the dynamic, flexibility, and vibration analysis are fundamental to comprehend their biological activities.
This work seeks to evaluate the protein's structure through a frame representation where the links simulate the
chemical bonds, using finite element method and optimization procedures to verify the feasibility of solid
mechanics techniques. The numerical simulation of three conformational states of the lysozyme protein is
performed (PDB code: 1DPX, 1DPW, and 4YM8), where modal analysis is used to investigate the protein
dynamics, obtaining vibrational frequencies, modes shapes, and a local measure of flexibility. Special attention is
given to the influence of the secondary bonds on the protein's behavior. The results are compared using Pearson's
correlation of the temperature factor distribution obtained experimentally for each atom. The application of
optimization tools utilizing the temperature factor to define the links' stiffness increased the correlation with
experimental results. The method brought acceptable outputs with low computational cost, with potential for
improvements, indicating the technique's feasibility.

The analyze of the functional and emotional levels of development of DIR/Floortime model: a fuzzy system approach

Ben-Hur M. M. Montel — 2024-06-23

The human development has a lot of different areas and the most unpredictable is the neurodevelopment,
that starts at the first moments of life, and do not have any physical feature, specific exam or methodology to do
their analyze and diagnostic. They have only a treatment that should start early to get better results. The process
of identification is based on the specific features demonstrated by the patient, who are normally children. In
this context, the DIR methodology, that covers from the approach method to the treatment, shows the stages of
development that every human must pass to accomplish your healthy growth, they were defined as the functional
and emotional levels of development, and through your co-relation may be possible diagnose a particular delay of
development or a neurodevelopment disorder. However, this process has a lot of variable to be analyzed, and very
hidden information due the difficult to obtained information by the kid. In this paper is proposed a fuzzy system
to analyze the functional and emotional levels of development, through variables obtained by the psychologist
professional. The neuro-fuzzy identification was used to construct the Takagi-Sugeno Rules based on a previous set
of data, where your input was randomly generated, and your output were validated by the psychologist professional.
The backpropagation was applied to adjust the antecedent membership function. The results shows that the system
can deal with the hidden and vague information, and have a strong potential to be applied in the diagnostic of
neurodevelopmental disorders.

Numerical simulation of viscoelastic fluid flows with free surfaces

Hugo L. França — 2024-06-23

In this work we will present a numerical study of viscoelastic fluid flows under surface tension effects.
The mathematical model adopted involves the governing equations for incompressible fluids with free surface,
along with the constitutive equations that describe a viscoelastic material. From a computational point of view,

the free surface dynamics will be handled using the Front-Tracking representation with marker particles, com-
bined with the Marker-And-Cell (MAC) method to discretize the equations using a finite differences scheme. Our

current interest is the study of small-scale flows with droplet impact, such as the collision between two droplets.
Viscoelastic models will be adopted in order to represent the non-Newtonian contributions on different post-impact
outcomes, e.g., coalescence, separation and bouncing between droplets. Considering the classical dimensionless
numbers on viscoelastic free surface flows (Reynolds, Weber and Weissenberg), we will present parametric studies
on the simulation of droplet collisions to investigate how these parameters affect the final outcome.

Mesh construction and computational analysis of the biomechanics of an endovascular intervention in cerebral aneurysms using Kirchhoff–Love shells

Nicolas Muzi — 2024-06-23

The mechanism of aneurysm rupture is still not fully understood. The rupture risk of the intervention may
increase during endovascular occlusions of cerebral aneurysms due to a localized load in the parent vessel close

to the neck, a common day-to-day situation. As a first attempt on the road towards developing a plausible anal-
ysis capable of dealing with many cases in a statistical sense, we describe the deformation kinematics using a

geometrically nonlinear thin shell model under Kirchhoff-Love’s assumptions in conjunction with a simplistic
Kirchhoff-St. Venant’s hyperelastic material model. Though it cannot assess the artery’s complexity, this more
straightforward yet not trivial approach enable us to statistically study the application of a concentrated load in

many locations, which mimics the action of an instrument during the endovascular treatment. We performed nu-
merical simulations on 34 cases from the AneuriskWeb Database. We present preliminary results considering a

smoothly varying thickness between the parent vessel and the aneurysm dome, focusing in the mesh construction
process and loading.

Propagation of bone micro fracturing: a numerical approach

Icaro C.A. Almeida — 2024-10-01

Fracture mechanics can be understood as the area of science that studies the propagation of fractures,

cracks, slits, and other flaws from mechanical processes that may negatively affect the strength of the material.

Traditionally, the concepts on which the strength of the materials are based do not consider the toughness to

fracture of the material, which can be defined as the property that quantifies the resistance to crack propagation.

The essence of these studies can be applied to any type of material, such as in the medical field when studying the

behavior of bone fractures. This type of fracture usually arises through high-energy trauma. Bone, under normal

conditions, can support loads and absorb this energy. However, if there is a high level of energy associated with

the trauma, the bone cannot support it and ends up suffering a fracture. This paper aims to develop a numerical

microscale analysis of a bone fracture using the Extended Finite Element Method (XFEM). This paper will study

Two-dimensional simulations of the initiation and propagation mechanisms of an initial fracture in a compact bone unit called the osteon, which is bounded by the cement line, a zone that is low in type 1 collagen. In this way, it will be possible to understand the influence of the cement line on the propagation of the microscale fracture.