XL Ibero-Latin American Congress on Computational Methods in Engineering

CRITICAL BUCKLING LOAD BASED ON MODAL ANALYSIS BY RAYLEIGH METHOD AND FINITE ELEMENT METHOD OF A NONPRISMATIC SLENDER REINFORCED CONCRETE COLUMN

Alexandre de M. Wahrhaftig, Kaique M. M. Magalhães, Reyolando M. L. R. F. Brasil — Mon, 26 Aug 2024 00:00:00 +0000

In this study, an analytical and computational procedure were developed for determining the
critical buckling load. The analytical solution was based on the Rayleigh method and the computational
one on the finite element method (FEM). Rayleigh method preconize that one equation named as shape
(or trial) function should be defined to represent the vibrational movement of the system. Therefore, the
result obtained by this method is entirely conditioned to the correct choice of this equation. Different
equations even respecting the boundary conditions of the problem can lead to different results. Four
mathematical expressions as shape function were used in the present study: a trigonometric, two
polynomials and a potential equation. All these functions obey to the boundary conditions of the problem
and were valid in the whole domain. Therefore, the integrals obtained by the Rayleigh method were
solved considering the structural geometry. With comparative purpose the results obtained on the
analytical procedure were compared with those yielded by computational modelling using a finite
element modal analysis. The structure analyzed was a 46-m-high reinforced concrete pole, including its
foundation, which has geometry and reinforcement arrangement varying along its length. For both
solutions, three important items were considered: the geometric nonlinearity, due to the slenderness of
the system; the material nonlinearity and the creep of the concrete. The last one aspect was introduced
into the analysis by means of Eurocode criteria. Significant differences on the absolute value of the
critical load were found in comparison with the adopted procedures, being possible to observe that the
potential equation led to results too distant from the other equations. Analysis considering an elapsed
time of 4000 days revealed an average decreasing of 22% on the intensity of the critical buckling load.
The FEM presented the biggest percentual difference, 28%.

NONLINEAR ELASTIC TRANSIENT ANALYSIS OF STEEL FRAMES WITH SEMI-RIGID CONNECTIONS

Mon, 26 Aug 2024 00:00:00 +0000

Steel structures are reputed to have high slender ratio and excellent ductility. Due to these
features, the second-order effects and the influence of connection flexibility can play an important role
on the behavior of such structures since they can increase the risk of instability. Additionally, it has been
observed that only the linear static analysis may not describe the real behavior of a structure submitted
to various external requests, especially in the case of atypical situations, such as earthquakes and strong
wind gusts. Thus, the aim of this research is to evaluate the repercussion of the geometrical nonlinearity
and connection flexibility on the transient elastic response of plane steel frames. To this end, it is
employed a geometrically exact nonlinear formulation, based on Euler-Bernoulli model, that considers
the updated Lagrangian formulation and the corotational approach for the consistent deduction of the
element’s tangent stiffness matrix. The theory predicts that nodes will suffer large displacements and
rotations, and the elements of the structure, large stretches and curvatures. The semi-rigid connection is

modelled by a rotational spring element whose behavior is obtained on the basis of a bilinear moment-
rotation diagram that follows the kinematic hardening rule. In order to solve the nonlinear transient

equations, it is adopted the Newmark’s implicit time integration method combined with the Newton-
Raphson technique. The results of the performed analyzes showed a good agreement with the numerical

solutions available in the literature, demonstrating the efficiency of the proposed method in obtaining
the geometrically nonlinear dynamic response of steel structures with semi-rigid connections.

FATORES QUE INFLUENCIAM NO MOMENTO CRÍTICO ELÁSTICO DE FLAMBAGEM LATERAL COM DISTORÇÃO DE VIGAS CASTELADAS MISTAS

Carla Cristiane Silva, Rodrigo Barreto Caldas — Mon, 26 Aug 2024 00:00:00 +0000

Vigas casteladas são projetadas para atender diferentes requisitos estruturais e feitas de perfis
laminados com aberturas hexagonais padronizadas na alma. O processo de expansão da alma
proporciona maior momento de inércia, aumentando a resistência e a rigidez à flexão. Essas vigas podem
ser simplesmente apoiadas, contínuas e semicontínuas e podem ser projetadas como mistas quando há
uma conexão de cisalhamento entre o perfil de aço e a laje de concreto. Em vigas mistas contínuas e
semicontínuas, o deslocamento lateral e a rotação da mesa inferior na região de momentos negativos,
onde uma parte do perfil de aço é comprimida, podem causar uma flambagem global geralmente
conhecida como flambagem lateral com distorção (FLD). A norma europeia EN 1994-1-1:2004 e a
norma brasileira ANBT NBR 8800:2008 fornecem um procedimento para a verificação deste estado
limite último em vigas mistas com seção de alma cheia nas quais o momento fletor resistente à FLD é
calculado considerando o comportamento do mecanismo “U” invertido. Um parâmetro essencial para a
determinação desse momento resistente é o momento crítico elástico. Portanto, este artigo tem como
objetivo investigar o comportamento deste momento analisando os principais fatores que influenciam
no fenômeno, tais como, altura e espessura da alma, largura e espessura das mesas, comprimento do
vão, tamanho e espaçamento das aberturas. Além disso, uma análise comparativa foi realizada com vigas
mistas de alma cheia. Para atingir este objetivo, foram desenvolvidos e calibrados modelos numéricos
no software ANSYS com vigas casteladas mistas de aço-concreto submetidas a um momento fletor
uniforme.

ASSESSMENT OF THE DYNAMIC STRUCTURAL RESPONSE OF BUILDINGS BASED ON EXPERIMENTAL MONITORING AND FEM SIMULATIONS

Mon, 26 Aug 2024 00:00:00 +0000

Numerical analyses based on the Finite Element Method (FEM) simulations are present in
everyday routine of many academic centres and structural design offices around the world. However,
one of the problems to be solved is the FEM reliability, in order to represent the actual response of the
analysed structural model. Currently, it is possible to use the results of dynamic experimental monitoring
to verify and adjust the numerical model and consequently improve accuracy of the results. The dynamic
experimental monitoring allows the extraction of modal parameters (natural frequencies, vibration
modes and damping coefficients). These parameters are relevant for a correct characterization of the
investigated model and are calculated based on the experimental signals of accelerations, velocities and
displacements. This way, in this work, the modal parameters, related to a real 5-story steel building
constructed in laboratory are determined, based on dynamic experimental monitoring. In sequence,
aiming to validate the motion equations of the structural system, both numerical and experimental
dynamic responses of the physical model were correlated. The results are presented in terms of modal
parameters, frequency response functions (FRFs) and time history. These modal parameters were used
to calibrate the steel building FEM. The proposed computational model, developed for the investigated
steel building dynamic analysis, adopted the usual mesh refinement techniques present in FEM
simulations implemented in the ANSYS program. In this numerical model, the steel columns were
represented by three-dimensional beam elements, where flexural and torsional effects are considered.
The slabs were represented by shell elements. After that, a forced vibration analysis was carried out and
the dynamic response of the building, when subjected to impact loads, was compared with the actual
structural response of the steel building model. The conclusions emphasize the relevance of the dynamic
experimental monitoring to characterize and adjust the developed FEM of the investigated building. The
good agreement between the numerical and experimental results can corroborate the adequate use of the
developed numerical model.

ASSESSMENT OF THE DYNAMIC STRUCTURAL RESPONSE OF SOCCER STADIUMS GRANDSTANDS BASED ON THE USE OF BIODYNAMIC MODELS

Danielle Fernandes Campista, José Guilherme Santos da Silva — Mon, 26 Aug 2024 00:00:00 +0000

Over the years, many soccer stadiums in Brazil have been designed to withstand accidental
loads (people loads) to be of static type (4kN/m2). However, based on the changes in the people’s
behaviour, especially in soccer matches, through the action of groups of fans and also with the use of
these structures for music shows, these structural systems have been subjected to dynamic impacts
related to the dynamic nature of the applied loads. Therefore, some of these stadiums have presented
excessive vibration problems and have required an effective consideration of the dynamic loadings in
the structural design. This way, this research aims to study the dynamic behaviour and evaluate the
structural system performance of the Brasilia National Stadium grandstands, when the human comfort
is considered, incorporating the effect of the people-structure dynamic interaction, based on the use of
biodynamic models representative of the people. It should be noted that the stadium was designed and
constructed to be used at the World Cup 2014, held in Brazil. Finally, a human comfort assessment
was performed on the investigated grandstands and the results are compared with those provided by
design standards and international recommendations. The presented results show the relevance of the
dynamic analysis in the structural design of soccer stadiums grandstands and the influence of the
people-structure dynamic effect with respect to obtaining relevant data for human comfort of this type
of structure.

DYNAMIC ANALYSIS OF STEEL-CONCRETE COMPOSITE FLOORS CONSIDERING THE EFFECT OF THE BIODYNAMIC MODELS

Fernanda Fernandes Campista, José Guilherme Santos da Silva — Mon, 26 Aug 2024 00:00:00 +0000

The main objective of this research work is to investigate the dynamic structural behaviour
of steel-concrete composite floors when subjected to human rhythmic activities, considering the effect
of the people-structure dynamic interaction, based on the use of biodynamic models representative of
the people. The investigated structural model was based on a real steel-concrete composite floor
spanning 40m by 40m with a total area of 1600m2. The structure represents a typical interior floor of a
commercial building used for gym purposes, and designed according to the usual ULS and SLS
Eurocode provisions. The composite floor is supported by steel columns and is currently submitted to
human aerobic rhythmic loads. The floor is made from composite beams and a 100mm thick concrete
slab and the columns height is equal to 4m. The human comfort evaluation methods used in the
investigation indicated that the steel-concrete composite floor presented excessive vibrations. This
way, the presented results show the relevance of the dynamic analysis when the structural design of
floors is considered, and also the influence of the people-structure dynamic interaction effect on the
assessment of the human comfort of this type of structure.

EVALUATION OF THE HUMAN COMFORT OF A TALL BUILDING CONSIDERING THE WIND NON-DETERMINISTIC ACTIONS

Mon, 26 Aug 2024 00:00:00 +0000

Based on a favourable economic scenario combined with a significative technological
advance in science materials and also construction processes, it must be emphasized that the Brazilian
cities have shown substantial growth, regarding the construction of tall and slender buildings. This
architectural trend has conducted the design of these buildings to structural solutions composed by
very flexible structural systems, resulting in slender buildings with very low natural frequencies values
and therefore more susceptible to excessive vibration problems. In this context, it is possible to
observe the project and construction of tall buildings and a notorious example is the city of Balneário
Camboriú/SC, which has several buildings exceeding 100 meters of height. Usually, in the verification
and structural calculations of buildings, the loads due to the wind action are considered purely static.
However, as the buildings become slender and taller, problems related to excessive vibrations tend to
be present, since the wind actions have a dynamic nature. This way, the main objective of this research
work is to investigate the static and dynamic structural behaviour of a slender 39-storey reinforced
concrete building, with height of 140 meters and a floor plan with 29 meters wide and 9 meters deep,
inspired by the real and existing building constructed at Balneário Camboriú/SC. The numerical
modelling of the investigated building is carried out based on the use of the Finite Element Method
(FEM) utilising the ANSYS computational program. The investigation considers all the usual loads
used in building projects and also the effect of the wind non-deterministic actions, defined based on
the spectral density of the dynamic excitation. The conclusions reached along this study deal with the
critical evaluation of the non-deterministic dynamic structural response of the investigated building
and the assessment of the human comfort.

NUMERICAL ANALYSIS OF THE FLEXURAL BEHAVIOR OF DELTABEAM® IN THE SLIM FLOOR SYSTEM

Tainá M. Borghi, Ana Lúcia H. C. El Debs — Mon, 26 Aug 2024 00:00:00 +0000

The composite structures take the advantages of steel and concrete, creating a more resistant
system and with an easier assembly. These structures comply the current demands of civil construction,
saving time and consequently reducing costs. Therefore, new composite structures have being studied
and established worldwide, such as the slim floor beam. This system consists in steel beams and concrete
or composite slabs, reducing the total height of the floor by introducing the slab at the height of the
beam. It is a system that provides a range of possibilities, it may vary the type of steel profile employed,
can be the Deltabeam®. Thus, a numerical study of this slim floor typology was carried out, aiming to
compare its flexural behavior with the most usual typology, the Asymmetric Slimflor Beam. The study
is part of an extensive theoretical-numerical research in development at the University of São Paulo
(USP), which aims to elaborate a study of slim floor typologies. The finite element modeling is presented
as an alternative to conducting experimental investigations, due to its lower demand for financial, human
and time resources. The ABAQUS® was the software employed in the simulations, and were used
experimental and numerical studies to calibrate the model, carried out by the National Technical
University of Athens in partnership with Peikko, which holds the patent of Deltabeam®. From the
results of the simulations, it was possible to conclude that the characteristics of Deltabeam® contribute
to a greater rigidity and flexural strength of the system.

OPTIMUM DESIGN OF AN URBAN BUS CHASSIS BASED ON GENETIC ALGORITHM AND FINITE ELEMENT METHOD SIMULATIONS

Mon, 26 Aug 2024 00:00:00 +0000

A very important part of the vehicles design is related to the chassis, on which several
mechanical components are mounted. An important feature to the chassis is to provide the highest
service reliability for as long as possible in a cost effective way. During its service life, the chassis is
subjected to several static and dynamic loadings. This way, this research work aims to obtain an
optimum design of an urban bus chassis manufactured based on current steel rectangular and “C”
section structural elements and subjected to deterministic loads. The optimization problem considers
the dimensions of the structural elements sections of the investigated chassis as its design variables,
which are established based on commercial standard dimensions. The lengths of these structural steel
elements are fixed in 9.75 m and 2.46 m, respectively. Throughout this investigation, the numerical
model of the analysed chassis was developed, based on the use of the Finite Element Method (FEM),
utilising usual discretization techniques implemented in the ANSYS computational program. The
optimization problem was resolved using Genetic Algorithms (GA), utilising the MATLAB software.
A properly interface between this two software ANSYS and MATLAB was developed in this
investigation to work in synergy considering the FEM and the GA. The results of this study show that
it is possible to obtain lower cost designs to the chassis, based on the application of optimization
techniques as the Genetic Algorithms in structural analysis.

ASSESSMENT OF THE DYNAMIC STRUCTURAL RESPONSE OF HIGHWAY BRIDGES BASED ON A PROGRESSIVE PAVEMENT DETERIORATION MODEL

Ana Célia Soares da Silva, Rodrigo Guedes Simões, José Guilherme Santos da Silva — Mon, 26 Aug 2024 00:00:00 +0000

Highway bridges are usually subjected to random dynamic actions of variable magnitude
due to vehicles convoys crossing on the bridge pavement deck along their service life. These dynamic
actions can generate the nucleation of fractures or even their propagation on the bridge deck structure.
The deteriorated road surface condition of the asphalt pavement represents a key issue to the
significant increase of the displacements and stresses values on the highway bridge decks. Therefore,
this investigation aims to develop an analysis methodology, in order to evaluate the displacements and
stresses values of a steel-concrete composite highway bridge, including the dynamic actions due to
vehicles convoy and the effect of the progressive deterioration of the pavement surface, considering
the road surface damages. This way, the investigated steel-concrete highway bridge is constituted by
four longitudinal composite girders and a concrete deck, spanning 40m. In this investigation, the
developed computational model adopted the usual mesh refinement techniques present in finite
element method simulations implemented in the ANSYS computational program. The main
conclusions of this study focused on alerting structural engineers to the possible distortions, associated
to the steel-concrete composite bridge dynamic structural response when subjected to vehicles
dynamic actions.

HUMAN-INDUCED VIBRATIONS OF STEEL-CONCRETE COMPOSITE FLOORS SUBJECTED TO HUMAN RHYTHMIC LOADS

Mon, 26 Aug 2024 00:00:00 +0000

The increasing incidence of building vibration problems due to rhythmic activities led to
need of a specific design criterion for rhythmic excitations. This was the main motivation for the
development of a design methodology centred on the structural system dynamical response submitted
to dynamic loads due to human rhythmic activities. This way, this paper investigated the dynamic
structural behaviour of steel-concrete composite floors subjected to the human rhythmic activities,
when the human comfort is considered, incorporating the effect of the people-structure dynamic
interaction, based on the use of biodynamic models representative of the individuals. The dynamic
loads were obtained through experimental tests with individual carrying out rhythmic activities. The
proposed analysis methodology adopted the usual mesh refinement techniques present in the finite
element method (FEM) simulation implemented in the ANSYS program. The investigated structural
system was used based on a health club facility with an adjacent aerobics area. The floor system
consists of long span joist supported by concrete block walls. The floor effective weight was estimated
including people practicing aerobics and also sitting in the health club internal area. The floor effective
weight was estimated to be equal to 3.6 kPa, including 0.6 kPa for people activities. The effective
composite moment of inertia of the joists was selected based on its required strength, i.e.: 1.1x106
mm4. The peak acceleration values were compared to limits proposed by design codes, based on
human comfort and those values were not satisfied. Such fact has indicated that these rhythmic
activities could generate peak accelerations that surpass design criteria limits developed for ensuring
human comfort.

DETERMINATION OF STRENGTH OF A COMPOSITE SLAB SYSTEM OF STEEL AND CONCRETE BY SEMI-EMPIRICAL M-K METHOD

Mon, 26 Aug 2024 00:00:00 +0000

In this work the results of an experimental study of the behavior and strength of a composite
slab system, after the cure of the concrete, are presented. The steel deck consists of trapezoidal profile
with embossments in V-shape. Tests were carried out on a series of twelve composite slab models,
simply supported, submitted to bending. Different thicknesses of the steel deck, heights of composite
slabs and shear spans, were employed in the manufacturing of the models, according the EN 1994-1-
1:2004 and ANSI/ASCE 3-91:1992. During the tests deflections, end slips and strains of the steel
decks were measured, allowing the analysis of the behavior of the composite slab system and the
determination of its failure mode. The semi empirical “m-k” method, according ABNT NBR
8800:2008, were used for the determination of the longitudinal shear strength of the composite slab
system of steel and concrete. In order to illustrate the use of the longitudinal shear strength obtained by
the m-k method, an example of practical application will be made.

STRESS ANALYSIS IN FOUNDATION ELEMENTS USING SOIL- STRUCTURE INTERACTION

Sabiniano Fernandes Terceiro, Gilvan Bezerra dos Santos Júnior — Mon, 26 Aug 2024 00:00:00 +0000

In the structural building design, it is usually considered the structure supported on a rigid
surface, which does not occur in real situations. It is necessary to analyze the soil deformations to
perform a structural determination closer to actual behavior. This work had as objective to analyze the
vertical and horizontal stresses of footing and pile cap subjected to normal force of compression. It
modeled with software that uses as a basis the Finite Element Method. It was analyzed in the footing
with fixed supports, that the loads imposed migrate to the supports just below the perimeter of the
column, without significant distribution and the strut-and-tie model was not verified. Therefore, the
foundations model on rigid supports does not satisfactorily represent the actual stresses behavior on the
element. In the footing supported on spring elements, more excellent distribution of the vertical
compressive stresses and the formation of tension and compression areas next to the column can be
observed in horizontal stresses analysis, describing the theoretical strut-and-tie model. The soil-structure

interaction analysis in the pile cap did not modify the stress behavior due to being supported as non-
deformable or in soil with high resistance. As usually are the supporting layers of piles, with the soil

spring stiffness coefficient high, considered as rigid. Therefore, the use of flexible supports made it
possible to analyze the stresses in the footing in an approximate way of real behavior, as observed in the
literature.

DEVELOPMENT OF A FINITE ELEMENT MODEL OF STEEL-CONCRETE COMPOSITE ALVEOLAR BEAMS

Matheus E. Benincá, Inácio B. Morsch — Mon, 26 Aug 2024 00:00:00 +0000

The use of steel-concrete composite beams allows the best properties of these materials to be
explored, enabling the design of larger spans and the achievement of more economical structural
solutions. The alveolar steel beams, in turn, provide a greater rationalization in the use of this material,
since, with almost the same amount of steel, expanded profiles are produced with greater moment of
inertia and, consequently, greater flexural strength and better performance under serviceability limit
states. Through the union of these structural systems the composite alveolar beams are obtained, in
which the advantages of the two systems are enhanced, and their disadvantages are mitigated. Thus, it
is possible to reduce materials consumption and, consequently, the generation of environmental impacts.
Considering that the Brazilian and the international standards do not specify criteria for analysis and
design of composite alveolar beams, numerical and experimental studies have been carried out at the
academic level in order to deepen the understanding about the behavior of these structures, whose
complexity involves the occurrence of different modes of collapse. The present work aims to contribute
to the advances in the field of numerical analysis of composite alveolar beams by developing a finite
element model with ANSYS software, version 19.2, in which the steel profile was modeled by shell
elements, the concrete slab by hexahedral solid elements, the connectors by non-linear spring elements,
the steel deck sheet by shell elements and the slab reinforcement bars by embedded elements. In order
to capture the effects of local instabilities, initial geometric imperfections were added to the profile
through the combination of buckling modes. For the simulation of concrete behavior, two models have
been used: the first, denominated DP-Concrete, is a native ANSYS model, available in the more recent
versions of this software; and the second, denominated usermat, is a customizable model based on
Ottosen criterion. The validation of the model was done through the numerical analysis of beams tested
experimentally by other authors. The obtained results presented a good correlation with the experimental
results and with numerical results from previous works.

NUMERICAL ANALYSIS OF PARTIALLY ENCASED STEEL AND CONCRETE COMPOSITE BEAMS IN FIRE USING THE FINITE ELEMENT METHOD

Mon, 26 Aug 2024 00:00:00 +0000

It is known that unprotected steel elements perform poorly when exposed to high
temperatures. However, when the concrete is associated with steel elements, there is a gain in both the
structural and thermal aspects. Thus, in this paper, the numerical results of the thermal elevation -
obtained by the finite element method - are compared with the experimental resu
for partially encased composite beams in a fire. For this, a transient analysis was used to
determine the thermal gradient in the studied sections in order to obtain results closer to those
observed in the reference tests. The numerical results showed good approximation, accurately
representing the experimental model. From that point on, new analysis were carried out in order to
compare the numerical results with those obtained by national normative codes. It was verified that the
normative methods are not able to predict with precision the elevation of temperature in partially
encased steel and concrete composite sections, being necessary to use alternative methods found in the
literature.

NUMERICAL STUDY OF FAILURE MODES ON SLEEVE CONNECTIONS SUBJECTED TO COMPRESSION

Matheus Miranda de Oliveira, Lucas Roquete, Arlene Maria Cunha Sarmanho — Mon, 26 Aug 2024 00:00:00 +0000

This work presents a study of failure modes on a type of connection between circular hollow
sections (CHS), called sleeve connection. It allows a harmony in the continuity of tubular profiles,
becoming a discrete connection in a real structure. The proposed connection is composed of two tubes,
in which an inner tube with a smaller diameter is connected to the outer tubes by bolts. The objective is
to evaluate the behavior of sleeve connections subjected to compression, evaluating the possible failure
modes caused by the variation of the number of bolts and inner tube geometric properties. The studies
were performed through a numerical analysis using the finite element computer program ANSYS. From
this model, the variation of the number of bolts and inner tubes properties was performed, where
alterations in the connection’s rigidity were observed. Thus, with the discovery of the failure modes it
is possible to propose analytical formulations for sleeve connection design subjected to compression.

A SIMPLIFIED NUMERICAL METHOD OF PREDICTING SETTLEMENTS ON AX- IALLY STRESSED PILES

Mon, 26 Aug 2024 00:00:00 +0000

The aim of this article is to simulate soil-structure interaction on multi-story buildings with
deep foundations (building + pile cap) using a simple numerical model via the Winkler model, based on
Mindlin’s equations, considering an empirical load transfer model proposed by Aoki-Velloso to calculate
bearing capacity in order to obtain settlements and coefficients of subgrade reaction between soil and
pile. The advantage of applying this methodology is supported by its simplicity and easy computational
implementation as well as avoiding a significant computational cost and memory. The use of this simple
proposed procedure is due to the future application in the analysis of more complex group, considering
the geometric non-linearity of the building and the coupling with a dynamic model associated with
fluid mechanics in the numerical wind tunnel solution. The formulation proved to be consistent when
comparing the responses obtained with analytical model - Poulos and Davis - and by numerical procedure
via the Boundary Element Method.

METODOLOGIA PRÁTICA PARA DETERMINAÇÃO DE CABLAGEM EM VIGAS DE PONTES ISOSTÁTICAS

Huber R.Tokunaga, Paulo Chaves de R. Martins, Willian Taylor M. Silva — Mon, 26 Aug 2024 00:00:00 +0000

This paper aims to develop a practical methodology for determining the tendons in
prestressed bridge beams. In general, in Brazil, the tendons are defined by methods based on iterative
processes, highly dependent on the experience of the designer. Basically, the process involves the
definition of tendons and section checking. If the expected results are not achieved, the process is
repeated. The proposed methodology will include the determination of the tendons using Magnel
diagrams and the definition of the feasible domain, as well the definition of the limit zone for the
prestressing steel, considering isostatic structures. This article refers only to a methodology for cases
of isostatic bridges. However the final research also aims at the cases of continuous beams an
indeterminate bridge structures (Tokunaga,H.[1]). The developed proposal can be applied in manual
calculations or inserted in automated routines, in the framework of an application for practical design
process as in theoretical studies.

COMPARATIVE STUDY OF CONVERGENCE METHODS FOR NUMERICAL ANALYSIS OF THE BEHAVIOR OF CRESTBOND CONNECTORS APPLIED TO SLENDER CONCRETE FILLED STEEL TUBE COLUMNS

Pereira, A. C., Caldas, R. B., Santos, L. R., Vilela, P. M. L. — Mon, 26 Aug 2024 00:00:00 +0000

Este artigo apresenta um estudo comparativo dos diferentes métodos de convergência em análises
numéricas não lineares do comportamento dos conectores Crestbond quando utilizados como
dispositivos de transferência de carga nos pilares mistos preenchidos com concreto (PMPC). A etapa
experimental foi realizada na Universidade Federal de Minas Gerais e, a partir dos resultados obtidos,
foi proposto um modelo numérico, elaborado no software Abaqus, capaz de representar o ensaio. No
processo de desenvolvimento dos modelos numéricos, testou-se a eficiência de diferentes métodos de
convergência para verificar qual deles apresentaria o melhor custo-benefício em relação ao custo
computacional e ao poder de convergência. Os métodos presentes na biblioteca do Abaqus analisados
no presente estudo foram: Static General, Static Riks e Dynamic Implicit. No entanto, também foram
feitas abordagens sobre o método Dynamic Explicit. O método Dynamic Implicit, bem como o
Dynamic Explicit, é geralmente, utilizado em problemas dinâmico e com maior grau de deformação.
No entanto, esse método pode ser adotado em ensaios mecânicos quando estes apresentam um
acréscimo de carga, ou deslocamento, com aceleração consideravelmente baixa, podendo considerar o
ensaio como quase estático. Realizadas as análises, verificou-se que os métodos estáticos não foram
capazes de obter convergência após ocorrer um decréscimo de força no processo iterativo, apesar de
praticamente coincidir com a curva obtida pelo método Dynamic Implicit. Sendo assim, verificou-se
que o método Dynamic Implicit não apresentou um custo computacional elevado e demonstrou melhor
convergência, se tornando o método de convergência escolhido para todos os modelos numéricos do
presente estudo.

AVALIAÇÃO NUMÉRICA DE VIDA À FADIGA DE LONGARINAS DE PONTES UTILIZANDO MODELOS DE LARGA ESCALA

Mon, 26 Aug 2024 00:00:00 +0000

Fatigue can be characterized as a form of failure of elements subject to cyclic stress/
deformation throughout their lifecycle. The phenomenon occurs mainly in mechanical machines,
bridges, aircrafts, among other kind of structures. In this context, the study of fatigue is of fundamental
importance for the design of civil engineering structures, since most of the reported failures can be
related with fatigue. Particular for bridges, the phenomenon is the main responsible for the decrease of
the bridge’s life, due to the increase of traffic volume and vehicles weights. In this work, the nominal
stress method and the hot-spot stress method were used to assess the fatigue strength S-N curves of three
different large-scale girder bridge specimens. The girders were modelled using shell and solid elements
and the models were calibrated against fatigue experimental tests available in the literature and
performed mainly in the Fritz Engineering Laboratory of the Lehigh University, Pennsylvania, USA.
The fatigue assessment carried out obtained stress results similar to that found in bridges. The
experimental lives were compared with the lives obtained from the numerical models. Therefore, this
work emphasizes the importance of the fatigue limit state, either in the design stage or for evaluation of
existing bridges.

ANALISE NÃO LINEAR DE VIGAS MISTAS AÇO-CONCRETO PROTENDIDAS CONTÍNUAS COM INTERAÇÃO PARCIAL

Bruno M. S. de Oliveira, Joao B. M. Sousa Jr. — Mon, 26 Aug 2024 00:00:00 +0000

Vigas mistas de aço e concreto podem se beneficiar pela protensao, particularmente pós ten-
sionamento, tanto para projeto quanto para reabilitação, avaliação e reparação. A Protens ̃ ao aumenta o ̃
regime elastico e melhora o comportamento ultimo e em servico das vigas. A maioria das pesquisas pub-
licadas, contudo, foram para o caso simplesmente apoiado de vigas mistas reforçadas por cabos externos
e muito poucos trabalhos lidaram com o caso contínuo. Essas vigas tem muitas aplicações, por exemplo,

pontes de grandes vaos. As restrições hiperestáticas de vigas mistas mistas protendidas contínuas resul-
tam em um comportamento mais complexo quando comparado as simplesmente apoiadas. Além disso, a ́

conexao entre o perfil de aço e a laje de concreto permite deslocamentos relativos entre os componentes,
que e chamado conexão parcial de cisalhamento ou interação parcial. O foco deste trabalho e apresentar
o desenvolvimento e implementação de uma formulação numérica, baseado em elemento finito unidi-
mensional de viga e cabo para analise n ́ ao linear de vigas mistas ac ̧o-concreto cont ̃ ́ınuas protendidas por
cabos externos. A interac ̧ao parcial ̃ e levada em conta por meio de elementos finitos especializados que ́
simulam os deslocamentos relativos entre ac ̧o e concreto. A acuracia e precis ́ ao da formulação e avali-
ada em comparac ̧ao com testes experimentais. Aspectos específicos da continuidade entre vaos foram
analisados e discutidos.

A COMPARATIVE STUDY OF COST AND RESISTANCE BETWEEN TUBULAR STEEL COLUMNS AND CONCRETE-FILLED TUBULAR STEEL COLUMNS

Mon, 26 Aug 2024 00:00:00 +0000

The use of steel-concrete composite structures is not a recent trend in construction; however,
it has significantly increased after the 1960s. The quest for streamlining construction processes
encouraged the employment of steel and steel-concrete composite structures. Both structural systems
provide reductions in cost with labor and materials, as well as increased dimensional precision, structural
efficiency and cleaner construction sites. In this context, the use of steel-concrete composite columns is
commonly observed, and these may present themselves as steel tubular sections, filled with concrete.
Such sections provide an increase in compressive strength due to concrete confinement within the steel
tube and eliminate the need for form-work and steel reinforcement during construction. Circular steel
sections are more efficient to bear torsional forces, and present good behavior when subjected to
combined actions. This study analyzes the main criteria and concepts for the design of composite
columns with concrete-filled circular hollow sections and steel circular hollow sections according to the
Brazilian standards ABNT NBR 8800 and ABNT NBR 16239, under compression and combined
bending. A cost comparison between the two aforementioned types of column was obtained by means
of an algorithm developed with Visual Basic for Applications, considering equivalent resistances and
the prices applied in Brazil’s Southeast region. As an additional analysis, the effect of the confined
concrete on the overall mechanical resistance of the columns was also evaluated.

INVESTIGAÇÃO DO COMPORTAMENTO DOS FUROS DE CONECTORES PERFOBOND EM DIFERENTES CONDIÇÕES DE PROFUNDIDADE E CONFINAMENTO DO CONCRETO

Otavio Prates Aguiar, Paulo Estevão Carvalho Silvério, Rodrigo Barreto Caldas — Mon, 26 Aug 2024 00:00:00 +0000

O presente trabalho refere-se a um estudo numérico experimental para desenvolvimento de
um novo modelo de cálculo para o conector Perfobond. Este trabalho está sendo empreendido, pois
observou-se na literatura que as diferentes disposições geométricas em que se insere o conector do tipo
Perfobond têm grande influência sobre seu comportamento mecânico, podendo-se observar variações
significativas na ductilidade, capacidade resistente e modo de falha do conector em função da

profundidade e nível de confinamento do concreto na região da conexão. Portanto, nesse trabalho optou-
se por adotar uma nova geometria de ensaio de cisalhamento, similar a um ensaio de arrancamento, que

permite simular o conector tanto em situação superficial quanto profunda. Observou-se que o furo
confinado com barra passante apresenta um estágio de resistência secundário onde, após a ruptura
localizada do concreto, a barra passante é mobilizada até sua ruptura, o que dá um acréscimo de
capacidade resistente e ductilidade ao conector. Esse acréscimo não é observado no conector superficial,
cuja capacidade resistente é definida pela falha localizada do concreto, que, devido à ausência de
confinamento, imediatamente se espalha para a superfície, causando fissuração e destacamento do
concreto. Visando gerar mais dados para a formulação de um novo modelo de cálculo, construiu-se um
modelo numérico no software ABAQUS que reproduz a configuração dos ensaios de cisalhamento
realizados. O modelo foi capaz de simular com boa precisão ensaios experimentais realizados e será, em
seguida, utilizado para extrapolar as configurações físicas e geométricas dos protótipos experimentais.

GEOMETRICALLY NONLINEAR TRANSIENT ANALYSIS OF PLANE STEEL FRAMES USING A COROTATIONAL UPDATED LAGRANGIAN FORMULATION

Mon, 26 Aug 2024 00:00:00 +0000

The objective of this research is to present a study of the influence of the geometrical
nonlinearities in the dynamic behavior of plane steel frames. The adopted geometrically nonlinear
formulation is based on Euler-Bernoulli model and uses the updated Lagrangian description and the
corotational approach to deduce the tangent stiffness matrix of the element with both fixed ends. The
theory predicts that nodes will suffer large displacements and rotations, and the elements of the
structure, large stretches and curvatures. The solution of the nonlinear equations of motion is achieved
by combining the Newmark's implicit time integration method with the Newton-Raphson technique.
The results of the performed analyzes showed a good agreement with the numerical solutions available
in the literature, demonstrating the efficiency of the proposed method in obtaining the geometrically
nonlinear dynamic behavior of steel structures.

SOLUÇÃO DE VIGA VAGONADA, COMPARADA COM O MODELO DE TRELIÇA PLANA, NO USO DE PASSARELAS COM GRANDES VÃOS.

Eduardo Bicudo de Castro Azambuja, João da Costa Pantoja — Mon, 26 Aug 2024 00:00:00 +0000

Steel structures, due to the characteristics of the material, presents an efficient relation of
the resistance with its own weight, which makes it more suitable in works with needs to overcome
bigger spans. The Pavilhão com Estufa para Parque Botânico, winner of the 11th Architecture
Students Competition of the Centro Brasileiro da Construção em Aço (CBCA), stood out for its good
urban insertion and the choice of the place of implantation, which adapted well to the topography of
the land and valued the local biome, as well as presenting good use and adequate detailing of the steel
structure. According to the judging committee, the group provided good programmatic integration and
an aesthetic quality that stood out from the others. With the aim of promoting lightness and a better
interaction with the environment, a pedestrian walkway was proposed as a solution to access the set of
buildings, designed in a metallic structure with a span of 45m and a width of 10m, formed by
longitudinal wagon beams, structural model composed of a horizontal full-width element, columns and
cables. The trussed beams is another structural model used in large spans, formed by bars that join in
nodes, forming triangles. This ensures that when loads act on the nodes, only axial tensile and
compressive stresses will be developed, presenting a slimmer bar sizing and a lighter set to overcome
large gaps. In this article, we will analyze the structural model of the design of the Pavilhão com
Estufa para Parque Botânico, proposed with the use of steel wagon beams and compare with a
solution in Pratt trussed beams supported by the same actions and the weight aspect of the structure as
a function of the maximum vertical displacement defined in Annex C of ABNT NBR 8800: 2008 [2].

ANÁLISE INELÁSTICA DE SEGUNDA ORDEM DE ARCOS METÁLICOS COM SEÇÃO I

Mon, 26 Aug 2024 00:00:00 +0000

Este trabalho se insere no contexto da Análise Inelástica de Segunda Ordem (AISO) de
estruturas metálicas, em particular de arcos metálicos. São apresentas as AISO de arcos metálicos, tanto
abatidos, quanto não abatidos, com variadas características, como diferentes seções transversais,
condições de contorno e carregamento. Para a realização dessas análises a plataforma computacional
utilizada na simulação dos modelos é o CS-ASA (Silva [1]), um programa baseado no Método dos
Elementos Finitos (MEF) que realiza a análise não linear estática e dinâmica de estruturas. Nesse
trabalho, a formulação do Referencial Corrotacional (RCR) é adotada para introduzir os efeitos da não
linearidade geométrica, e o comportamento inelástico do material é modelado através do acoplamento
do Método da Rótula Plástica Refinado (MRPR) com o Método de Compatibilidade de Deformações
(MCD). A solução estática não linear é baseada numa estratégia incremental iterativa (Método de
Newton-Raphson Modificado aliado a técnicas de continuidade). Nos modelos de arcos metálicos
simulados, atenção especial é dada aos caminhos de equilíbrio, à influência do fator de abatimento,
condições de contorno e carregamento, curvas de capacidade de carga, entre outros. Finalmente, os
resultados obtidos com a metodologia proposta são validados através de resultados encontrados na
literatura e aqueles obtidos via MASTAN2 (Ziemian e McGuire [2]; www.mastan2.com), comprovando
o bom funcionamento das formulações utilizadas na análise de diversos arcos, demonstrando que o fator
de abatimento influencia diretamente na malha de discretização da estrutura, que o posicionamento das
cargas concentradas em um arco é determinante para conseguir seu melhor desempenho estrutural,
dentre outras conclusões.

NUMERICAL STUDY OF STEEL-CONCRETE COMPOSITE STRUCTURES UNDER FIRE SITUATION

Rafael C. Barros, Dalilah Pires, Ígor J.M. Lemes, Ricardo A.M. Silveira — Mon, 26 Aug 2024 00:00:00 +0000

This work aims to study the behavior of steel-concrete composite structures under fire
situation. For this, numerical formulations were developed, implemented and evaluated. It is well
known that high temperature causes changes in physical properties and mechanical strength of
materials. In both steel and concrete, such characteristics deteriorate during the exposure to fire, and
the structure load capacity and stiffness are reduced significantly as a consequence of the temperature
rises. This work shows the efficiency of the CS-ASA/FA and CS-ASA/FSA FE code in the analysis of
steel-concrete composite structural elements. The first provide the temperature distribution at the
cross-section level of the elements; the second module was developed to performs the inelastic
second-order analysis of composite structures under fire using a large displacement FE co-rotational
formulation; the plastic effects are captured through the refined plastic hinge method (RPHM) coupled
to the strain compatibility method (SCM). The proposed numerical methodology success is proved by
comparison with experimental and numerical responses available in the literature, which concludes
that the developed computational tool can be used to study the composite steel-concrete cross-section
strength and advanced progressive collapse analysis of beams, columns, arches and composite frames
under fire.

COMPARISON BETWEEN STANDARDIZED APPROXIMATED AND RIGOROUS STRUCTURAL ANALYSIS FOR ESTIMATING 2ND ORDER EFFECTS APPLIED TO STEEL STRUCTURES

Mon, 26 Aug 2024 00:00:00 +0000

Considering the approximated method of structural analysis estimating 2nd order effects
applied to steel structures, recommended by the ABNT NBR 8800 (2008) standard, also known as
Amplification Coefficients Method, and the constant search for greater structural efficiency and
consequently economy, the aim of this study was to compare the numerical responses of steel
structures subjected to horizontal and vertical loadings, obtained by approximated standardized
analysis and by rigorous geometrically nonlinear analysis. For that, a program was developed to
perform all the constituent steps of the Amplification Coefficients Method and to determine internal
forces and displacements. The resulting considered models are useful for medium lateral
displaceability class in which the 2nd order analysis, as a rule, can be performed by simplified or
approximated method. The results from the approximated approach were compared to the results from
a more rigorous nonlinear approach aided by the software SAP2000. It was observed that the internal
forces obtained by approximation are similar to those with the rigorous one, concerning axial and
shearing forces. Differences can be witnessed regarding bending moment results, being the
standardized method conservative. Analysis of the results from structures classified with small and
large lateral displaceability were also made, grounding standard classification method and following
proceedures recommendations. Concluding, the normative methodology is a proper approach to
nonlinear analysis in steel structures as long as classification permits.

INFLUÊNCIA DA VARIAÇÃO DA SEÇÃO DE CONCRETO NO DIMENSIONAMENTO DE PILARES DE SEÇÃO I MISTOS DE AÇO E CONCRETO VIA COMPUTACIONAL

Mon, 26 Aug 2024 00:00:00 +0000

This paper presents the development of a program in C++ language that intends to design
composite concrete encased steel (CES) columns, which are composed of I-shaped steel that it will be
totally surrounded by concrete. The formulation of the program is based on expressions of Attachment
P of ABNT NBR 8800:2008, so it can be possible to obtain an axial compressive force and moments as
well as to verify the interaction between concrete and steel, steel contribution factor and slenderness. It
was analyzed the influence of the variation of the concrete section in the resistance in terms of moments
of the CES column considering that other parameters remained constant. It is concluded that with the
increase of the concrete section there is an increase of the resistance in terms of bending moments. It is
also possible to perceive that if there is an increase in the height of the concrete section there is a growth
in the percentage variation of the bending moment in relation to the x and y axes. While only increasing
the width of the concrete section there is an increase of the bending moment with relation to the y-axis
and a small increase with relation to the x-axis, it occurs because the moment of inertia of the profile

with relation to the x-axis is much larger than the moment of inertia of the profile with relation to the y-
axis.

ESTUDO NUMÉRICO DE VIGAS MISTAS PROTENDIDAS COMPOSTAS POR PERFIS TUBULARES RETANGULARES DE AÇO PREENCHIDOS COM CONCRETO

Mon, 26 Aug 2024 00:00:00 +0000

Este artigo apresenta um modelo numérico capaz de representar o comportamento de vigas
mistas com protensão externa passiva durante seu processo de fabricação e quando estão submetidas a
solicitações de serviço. Essas vigas mistas são constituídas por perfis tubulares retangulares de aço
preenchidos com concreto auto adensável. Esse método de aplicação da protensão consiste em duas
etapas. Na primeira, o perfil de aço de seção tubular retangular é submetido a duas forças verticais
concentradas, localizadas nos quartos do vão; o perfil tubular retangular é, então, preenchido com
concreto e, à medida que este adquire resistência, as forças usadas para deformar o perfil metálico são
retiradas – segunda etapa. Ao tentar retornar à sua forma inicial, o perfil de aço introduz forças de
compressão no núcleo de concreto por meio das superfícies internas tracionadas do tubo que estão em
contato com o núcleo – protensão “passiva” no concreto. O modelo numérico proposto foi desenvolvido
no programa ABAQUS® com elementos sólidos tridimensionais C3D8R. Uma vez que a modelagem
numérica do processo de fabricação dessas vigas é bastante complexa nessa fase da simulação foram
utilizadas algumas ferramentas avançadas do programa, como “predefined field” e “orphan mesh”.
Finalmente, o modelo numérico de viga mista com protensão externa passiva é submetido a um
carregamento distribuído, e os deslocamentos verticais obtidos são comparados com resultados para
vigas de aço e mistas de mesma seção transversal sem protensão.

CONCENTRATED NUMERICAL APPROACH FOR SIMULATION OF STEEL-CONCRETE COMPOSITE BEAMS WITH PARTIAL SHEAR CONNECTION

Mon, 26 Aug 2024 00:00:00 +0000

The present work aims at the implementation and validation of a two-dimensional displace-
ment-based numerical formulation for nonlinear analysis of steel-concrete composite beams with de-
formable shear connection. A finite element corrotational formulation is adopted in order to allow large

displacements and rotations in the numerical model. The degradation of the axial and flexural stiffness is
determined exclusively at the nodal points of the structural discretization, characterizing the concentrated
plasticity. In the cross sections level, the Strain Compatibility Method is used to capture the axial strains
in the component members of the section as well as the slipping at the steel-concrete interface. Thus,
the constitutive models of materials under normal stresses and shear connection elements are described
by continuous functions. For validation of the proposed numerical formulation, the results obtained
are compared with numerical and experimental data available in the literature. Since the model proposed
here is based on the concentrated simulation of nonlinear effects, a finite element refinement study is also
performed. The numerical responses obtained in this paper are closed to experimental and numerical data
presented in literature.

COMBINANDO AS TÉCNICAS DE BUSCA LINEAR COM CONTINUAÇÃO PARA A SOLUÇÃO DE PROBLEMAS ESTRUTURAIS NÃO LINEARES

Mon, 26 Aug 2024 00:00:00 +0000

The demand for computational tools that simulate the real behavior of structures has been
intensified. Such numerical simulations usually involve highly nonlinear problems. For nonlinear
static problems, in particular, it is fundamental the implementation and use of numerical strategies to
trace the structure equilibrium paths in a complete way, overcoming critical points (limit and
bifurcations points). In the Finite Element Method (FEM) context, where incremental-iterative
strategies are usually adopted, the nonlinear solvers must have a high level of efficiency in the two
phases of the solution process (predictor and corrector), for each load step. In solving the nonlinear
algebraic equations, it is quite common that Newton-Raphson's iterations do not converge or require
an excessive number of iterations near the critical points. Therefore, the linear search optimization
technique appears as an additional sophistication. Basically, this technique aims to stagger the
corrective displacements vector in the iterative phase, seeking to guarantee and accelerate the
convergence of the process. The purpose of this work is to verify the efficiency of linear search
technique coupled with Newton-Raphson iterations and different path-following methods, and verify
its influence on the nonlinear solver efficiency. The effectiveness of the linear search algorithm
implemented is verified in solving slender structures with accentuated nonlinearity. It is previously
perceived that such a resource is triggered near load limit points (with more success when applied to
structures with these critical points), accelerates the iterative process and increases the chances of
convergence.

ATUALIZAÇÃO DE UM MODELO NUMÉRICO EM ELEMENTOS FINITOS DE UMA TORRE EÓLICA PARA AVALIAÇÃO DE PERFORMANCE ESTRUTURAL

Aurelio C. Feliciano, Guilherme S. Alencar, José Guilherme S. da Silva — Mon, 26 Aug 2024 00:00:00 +0000

Wind towers installed around the world have a particular behavior according to their
mechanical properties due to their ability to answer these questions in relation to their structural
performance. Consisting of steel elements and with a unique cross section, each tower has its own design
parameters and state variables that induce other analytical characteristics to be studied. From these we
can find a real model of a wind tower and from this, develop numerical analytical studies, encourage
and monitor the execution conditions and structural behavior. This paper presents a calibration of an
experimental model of a wind tower studied by Christophe Thierry Loraux in 2018 in Switzerland.
Hoping to determine the optimized natural frequencies of the structure, take the numerical-experimental
model as a future research tool for static and dynamic analysis. The numerical optimization performed
was based on the Powell Subproblem Approximation method proposed in 1964, where the limitation of
inaccurate parameters of the tower rotor set mass and the rigidity of the soil-structure interaction is
restricted in the motivation to determine the values. of the unlimited natural frequencies of the
experimental model.

ANÁLISE ESTRUTURAL NUMÉRICA DE PÓRTICOS PLANOS

Caroline Martins Calisto, Cristiane Caroline Campos Lopes, Hisashi Inoue — Mon, 26 Aug 2024 00:00:00 +0000

As estruturas reticuladas podem ser divididas em estruturas planas e espaciais. Nesse trabalho
serão abordadas as estruturas planas, mais especificamente os pórticos planos. Então, esse artigo
apresenta o desenvolvimento de um programa em linguagem C++ que analisa numericamente essas
estruturas. A formulação do programa se baseia no Método da Rigidez e é denominado de PORT2D. A
sua versão possibilita obter os valores de esforços nas barras, as reações de apoios e os deslocamentos
a partir dos seguintes dados de entrada: número de barras, número de nós, número de restrições de apoio,
número de nós restringidos, módulo de elasticidade de material, número de barras carregadas e número
de nós carregados. Para validar a estratégia proposta, os resultados obtidos pelo programa PORT2D são
comparados com a resposta encontrada na literatura e com o software SAP2000. Em ambos os casos, os
resultados obtidos pelo PORT2D mostraram ser numericamente coincidentes. Assim, o programa
PORT2D apresenta resultados satisfatórios para a análise estrutural de pórticos planos.

MODELO NUMÉRICO PARA ANÁLISE DA CAPACIDADE RESISTENTE ÚLTIMA DE VIGAS HÍBRIDAS SUBMETIDAS À FLEXÃO

Mon, 26 Aug 2024 00:00:00 +0000

Este artigo apresenta um estudo do comportamento de vigas híbridas de aço com seção
transversal do tipo I submetidas à flexão. Para isso, foram desenvolvidos modelos numéricos no
software Abaqus. Nos modelos, desconsidera-se a flambagem lateral com torção, uma vez que a viga
será contida lateralmente, de maneira que somente as instabilidades locais sejam avaliadas. As análises
foram divididas em duas etapas, a saber: primeiramente, realizou-se a análise de flambagem elástica

para obter as cargas críticas de flambagem e os modos de flambagem das vigas; posteriormente, efetuou-
se a análise da capacidade resistente última das vigas considerando tensões residuais e imperfeições

iniciais. Os resultados obtidos a partir do modelo numérico desenvolvido foram satisfatórios e, como
esperado, mostraram que as vigas híbridas resistem a um esforço maior de momento fletor quando
comparadas com suas vigas homogêneas correspondentes.

COLAPSO DE VIGAS DE SEÇÃO I AFUNILADAS EM ESTRUTURAS DE AÇO DE GRANDE VÃO: VALIDAÇÃO DO MODELO DE ELEMENTOS FINITOS

Tiago C. Zampaolo, Ernesto Massaroppi Jr., Miguel Abambres, Tiago P. Ribeiro — Mon, 26 Aug 2024 00:00:00 +0000

Tapered steel beams and columns have been increasingly used as primary load carrying
members. The determination of their accurate ultimate capacity can only be achieved by means of
advanced numerical methods such as the finite element method. This paper presents a systematic study

on the influence of the finite element model parameters on the ultimate load of I-section tapered beam-
columns typically used in large-span steel frames. It aims the determination of optimal sub-step

number to be used during the arc-length scheme and the finite element mesh size for the performance
of an accurate, robust and efficient inelastic post-buckling parametric analysis. This is part of an
ongoing investigation aimed to use the parametric analysis results to develop analytical predictive
models of buckling and collapse loads of this type of members, using artificial neural networks. Once
validated the finite element model, using hexahedral 8-node finite elements, 5 sub-steps and finite
element edge sizes of 30 and 40 mm have been selected for use in the future parametric analysis.

NUMERICAL SIMULATION OF THE NONLINEAR SOIL-STRUCTURE INTERACTION PROBLEM

Jéssica Lorrany e Silva, Ricardo Azoubel da Mota Silveira, Ígor J. M. Lemes — Mon, 26 Aug 2024 00:00:00 +0000

Structural elements in contact with the soil (or rock) can work as support for the soil itself or
can be supported by the soil. In both cases it is important to evaluate the system movement to reach a
more efficient and realistic project. In this context, this work aims to perform a numerical study of the
nonlinear soil-structure interaction problem response, always looking for the most realistic engineering
problem modeling. This interaction will be considered initially as bilateral, i.e., when the structure and
the medium do not lose contact during the strain process, and the soil will be represented by discrete or
continuous spring models. The numerical methodology is based on the Euler-Bernoulli's theory to
simulate the nonlinear behavior of the structure and on the adoption of the FE corrotational formulation
to capture the structure’s large displacements. Plasticity is also considered, concentrated at the finite
elements nodes, through the Strain Compatibility Method (DCM), where the constitutive relations of
the materials are used explicitly. The DCM is also applied in determining the bearing capacity of the
sections. The agreement of the results obtained here with those from the literature and Mastan2 validated
the numerical formulations implemented in the CS-ASA.

ANÁLISE DE ESTRUTURAS DE CONCRETO EM SITUAÇÃO DE INCÊNDIO

Mon, 26 Aug 2024 00:00:00 +0000

O comportamento do concreto frente a altas temperaturas vem se tornando uma linha de
pesquisa muito requisitada nos últimos anos. Estes estudos se justificam pela alta procura do
mercado por um elemento estrutural cada vez mais adequado e resistente a situações adversas que
possam ocorrer. Desta forma, o calor ocasionado pelo fogo poderá causar alterações na estrutura
do concreto, provocando efeitos como perda de resistência, fissuração e modificação da
tonalidade da coloração do concreto. Algumas situações podem levar uma estrutura ao colapso
quando exposta a altas temperaturas, como: a máxima temperatura atingida pelo fogo na
edificação, o tempo que a estrutura ficou exposta ao fogo e a velocidade do resfriamento. Este
trabalho pretende apresentar através da leitura e literatura contemporâneas algumas situações de
incêndio existentes e uma forma de minimizar estas situações a fim de proporcionar um devido
conforto e conhecimento sobre os assuntos de estruturas de concreto em situação de incêndio na
construção civil.

BOUNDARY CONDITIONS FOR HIGH-ORDER LATTICE BOLTZMANN MODELS

Mon, 26 Aug 2024 00:00:00 +0000

In this work, lattice Boltzmann (LB) regularization is extended to boundary conditions (BC).
Dealing with boundary conditions was ever considered a puzzling question in the LB method, especially,
when a large set of lattice vectors is required for the description of a given physical problem in high
order models. The most popular BC models are based on Ad-Hoc rules and, although these BC models
were shown to be suitable for low-order LBE, their extension to high-order LBE was shown to be a very
difficult problem and, at authors knowledge, never solved with satisfaction. In fact, the main question
to be solved is how to deal with a problem when the number of unknowns (the particle populations
coming from the outside part of the numerical domain) is greater than the number of equations we have
at each boundary site. A new boundary condition model is here proposed. The main idea is that when
we write both the equilibrium and non-equilibrium parts of the discrete populations in terms of its
equilibrium and non-equilibrium hydrodynamic moments, these moments replace the discrete
populations as unknowns, independently of the number of discrete velocities that are needed for solving
a given problem. This idea is here applied to the 2D lid-driven cavity flow problem and improved
stability properties are demonstrated.

DETERMINATION OF RELATIVE PERMEABILITY CURVES IN DIGITAL ROCKS AS FUNCTION OF INITIAL SATURATION USING LATTICE-BOLTZMANN METHOD

Mon, 26 Aug 2024 00:00:00 +0000

The characterization of fluids in a porous media has attracted interest both academic research
and in engineering. Particularly, the comprehension of fluid displacement in a two-phase system affects
areas as, enhanced oil recovery, geological carbon dioxide sequestration and contaminated groundwater

remediation. To properly characterize multiphase fluid transport in porous media it is necessary to con-
sider a set of properties that exerts influence in the subsurface flow like wettabillity, capillary pressure,

viscosity and initial saturation. In this work, we aim to establish a correlation between initial saturation
and relative permeability. The later is a key to estimate two-phase flow in petroleum reservoirs because
it represents the mobility of one phase in a multiphase saturated porous media. There are many ways to
distribute the initial saturation in a porous media. The most common is to randomly allocate the fluids

in porous space. Although easily computational implementation, it has no relation with initial distribu-
tion expected both from experiments and from natural migration inside reservoirs rocks. To solve this

inconsistency, some approaches can be applied: (i) Using gravitational and oscillatory forces to induce
separation in an initially random saturated media; (ii) performing forced-drainage and forced-imbibition
processes; (iii) allocating the wetting phase next to the solid walls and (iv) filling the smaller pores with
wetting phase. In this work we quantify how relative permeability curves respond to the initial condition
(i) e (iii) using the color gradient Lattice-Boltzmann Model to simulate relative permeability curves in
a two-dimensional porous medium image obtained previously by Sheppard et al. [1]. It was possible to
see that random saturation implied in relative permeability deviations due the lack of control in filling
porous medium. To EDT, it was also observed some deviations because the nature of algorithm that used
random saturation to avoid tendentiousness in filling some porous. The deviations were less apparent in
wetting phase than in non-wetting phase. Also, it was observed increase in relative permeability to lower
contact angles due the lubrication effect, both, to random and EDT cases.

LATTICE BOLTZMANN SIMULATION OF A 2D BACKWARD FACING STEP AT LOW TO MODERATE REYNOLDS NUMBER: A COMPARISON OF THE STABIL- ITY OF BGK AND TRT COLLISION OPERATORS

Mon, 26 Aug 2024 00:00:00 +0000

In this study we present Lattice-Boltzmann simulations of a 2D backward facing step flow in
the low to moderate Reynolds number range. A single relaxation time model for the collision operator
(BGK) is compared to a two-relaxation-time model (TRT) and 3-D experiments of [Tihon, J., Penkakova,
V. and Pantzali, M., 2010. The effect of inlet pulsations on the backward- facing step flow. European
Journal of Mechanics B-Fluid, Vol. 29, pp. 224-235]. Special attention is devoted to detachment and
reattachment locations along the line of center of the computational domain, and to numerical stability
comparison between BGK and TRT as a function of grid resolution for similar accuracy. A traditional
finite volume method is also implemented for comparison. Results show that the BGK implementation

achieves similar accuracy at lower grid resolution, maintaining numerical stability of the method at re-
duced computational cost. BGK and TRT implementations agree with experiments and the finite volume

method at Reynolds number of 590.

PERFORMANCE ANALYSIS OF THE LATTICE BOLTZMANN METHOD IMPLEMENTATION ON GPU

Waine B. de Oliveira Jr., Alan Lugarini, Admilson T. Franco — Mon, 26 Aug 2024 00:00:00 +0000

The computational interest on the lattice Boltzmann method (LBM) has grown over the years.
The simplicity of its implementation and the local nature of most of its operations allows the use of
a parallel computing architecture. In this way, GPUs (Graphics-Processing Units) suits very well for
LBM implementation, offering good performance and scalability for a relatively low price. This work
presents a LBM implementation on GPUs for D2Q9 and D3Q19. It is written in C/C++ programming
language and uses CUDA for the use of its GPU resources. For the code optimization, strategies such as
memory layout and merging all operations are presented. Also, designs principles to facilitate alternating
boundary conditions are described. The code is validated and its performance is evaluated. Because of
the lack of work on the matter, it is analyzed and discussed how some simulation’s parameters affects
the performance of the code. These are: single and double precision; number of threads per block; ECC
(error-correcting code memory) on and off; storing macroscopic variables; domain size; rates of saving
and residual. Tests are made using Nvidia’s GPUs from Kepler, Pascal and Volta micro-architectures.
The results are considered satisfactory, achieving the state-of-the-art performance.

HIGHER ORDER DISCRETIZATION OF PSEUDO-POTENTIAL MODEL

Mon, 26 Aug 2024 00:00:00 +0000

In this paper several discretization schemes that result in a improved multicomponent pseudo-
potential model of the Lattice-Boltzmann method are investigated. The discretization scheme here pro-
posed, when compared to the model original of Shan and Chen [1], considers the explicitness of the

force term, the second order discretization of the stream term, the regularization model and also higher
orders of discretization of derivative terms. To verify the accuracy of the proposed model, the effect of
the viscosity ratio and the spurious currents obtained for the static bubble problem is investigated. The

resulting algorithm maintains the simplicity of the pseudo-potential model while allowing an easy im-
plementation for multicomponent problems. The results show that the current model, besides showing

a higher viscosity ratio range than the literature results, show a significant improvement in the spurious
currents range.

DEVELOPMENT OF A COMPUTATIONAL CODE TO CALCULATE HEAT TRANSFER IN MULTILAYER WALLS

Mon, 26 Aug 2024 00:00:00 +0000

The main objective of this research is to analyze the thermal behavior of walls submitted to
different situations, through a program developed by the author. In the program, it is possible to vary
the amount of layers in the wall with different materials, to change the color of the surface submitted to

the solar radiation, as well as the orientation of the wall in relation to the Sun. The transient and one-
dimensional model of the heat equation for solve the problem. Four examples with different properties

(number of layers, azimuth, surface absorptivity) were analyzed. The influence of these variations was
verified in each case. In one example, the outer wall temperature without insulation was 28.1667 ° C,
internal 27.0295 ° C, while the insulated wall temperatures were 28.1127 ° C and 25.5351 ° C. An
internal wall reduction of 1.4944 ° C, with a decrease of 5.5287% of the temperature with the inclusion
of 2cm (1 cm on each surface) of polystyrene, pearls.

APPLICATION OF INVERSE PROBLEMS ADDING VALUE TO CONTINUOUS MEASUREMENT DATA IN WELLS: THERMAL PROFILE OF REHEATING IN OIL RESERVOIRS

Victor Costa da Silva, Paulo Couto, Franciane Conceição Peters — Mon, 26 Aug 2024 00:00:00 +0000

The authors main objective in this work is to present, from different real conditions of the
Braziliam Pres-Salt wells, under various operating conditions, and through complex numerical models
and optimization tools and problems conversely as the temperature signatures can be considered for the
injectable effect, while the active zone, as well as the saturation of the rest environments as well as the
cooling of the same. This objective will be reached though the solution of an inverse problem, regarding
linear optimization aiming the history matching process. The optimization will gives the pursued
information, critical for the reservoir management.

MODELING AND SIMULATION OF THE CONCENTRATION OF SPECIES FOR A DIRECT ETHANOL FUEL CELL

Marcelo M. De Souza, Ranon S. Gomes, Alvaro L. De Bortoli — Mon, 26 Aug 2024 00:00:00 +0000

The generation of energy is a subject in constant debate, either for its efficiency and renewa-
bility or for the emission of pollutants. In addition, energy consumption has grown over the years, and

fossil fuels, which account for around 80% of the world’s energy generation, run the risk of becoming
scarce. A technology with renewable features that has proven to be promising and more efficient than
traditional power generators is the fuel cell, making the process clean and efficient. The fuel cell is an

electrochemical device that directly converts chemical energy into electricity. In this work, a numeri-
cal model is developed for fuel cells with proton exchange membrane and fed by ethanol. The model

takes into account the flow, the variation of the concentration of chemical species, the rate of passage of
ethanol through the membrane and the overpotential losses in the anode and the cathode. In addition,
the concentration of each species is modeled according to the current density of the fuel cell. The finite
element method is used to calculate the flow and concentration of the species in different layers of the
cell (inlet and outlet channels, diffusion layer and catalyst layer). The Crank-Nicolson method is used

for time discretization. Overpotential losses are calculated using parameters obtained with the numeri-
cal model. These losses can be estimated by calculating the activation, the ohmic polarization and the

concentration overpotentials. The flow results, the variation of the species concentration, passage of the
ethanol through the membrane and the limiting current density are shown. Results of cell voltage are
compared for different catalysts and temperatures with experimental data found in the literature.

HIGH ORDER COMPACT METHOD USING EXPONENTIAL DIFFERENCE SCHEMES IN THE SOLUTION OF THE CONVECTIVE DIFFUSION EQUATION

Henrique Mariano C. do Amaral, Rogerio Gonçalves dos Santos — Mon, 26 Aug 2024 00:00:00 +0000

We will present in this paper scheme for the numerical solution of the convective-diffusive

equations in incompressible, inviscid, stationary and transient flows by the technique known as High-
Order Exponential Finite Difference Schema. Today, it is generally accepted that a realities arise in the

various branches of science, such as physics, biology, chemistry, materials, engineering, ecology, bio-
mechanical economics, combustion, computer science, epidemiology, finance, groundwater pollution,

heat transfer, neurosciences, physiology, infiltration flow, solids mechanics, and turbulence are modeled
by EDP typically similar to the RDC equation - Reaction-Diffusion-Convection Equation. In the last
decades, many known numerical techniques have been applied to solve this problem. RDC equation:
finite differences, finite volumes, finite elements and spectral or meshless, to name a few.
In this respect, a general-purpose numerical methodology still does not seem to be available actually.
In general, the methods cited are successful when convection, reaction or combination of both acting

together are largely dominated by diffusion, tending to purely diffusive process. The situation is drasti-
cally altered when convection, reaction, or a combination of both overload diffusion. In such situations,

numerical instability arises in cases where diffusion becomes less predominant. Thus, the purpose of this
paper is to present the above scheme.

OPTIMIZATION OF THE GEOMETRIC PARAMETERS OF A TWISTED TAPE FOR THE INTENSIFICATION OF HEAT TRANSFER IN SOLAR COLLECTOR

Silva Junior, L. G., Leandro O. Salviano — Mon, 26 Aug 2024 00:00:00 +0000

Large is the amount of thermal energy that needs to be supplied for the heating of water in
domestic or industrial environments, whether by burning gas, biomass or by direct use of electricity.
Today, these traditional methods have been resisted in their expansion in response to the inexorable
increase in demand. In this sense, solar energy has emerged as one of the most attractive renewable
sources for this type of application, requiring, in this way, the continuous technological development
of solar collectors more efficient thermally that meet the application requirements. Thus, the objective
of this paper is to perform the numerical simulation of the process of intensification of heat transfer in
a flat plate solar collector with active system and indirect circulation of single-phase working fluid,
through the device known as Twisted Tape, down Reynolds number 600. The geometric parameters of
the twisted tape subjected to the Direct Optimization approach are: Twisting tape pitch (P), length (L),
Translate (T) and twisted tape radius (R1 and R2). The analysis of the optimization process associated
to the heat transfer intensification performance and the associated pressure loss were analyzed through
computational modeling in ANSYS and ESTECO ModeFrontier software. The main results of this
project indicate that the optimization process using the Genetic Algorithm method led to a geometry
with asymmetric radius for both the Reynolds number evaluated, yielding significant results
corresponding to a global heat transfer increase of approximately 170 %, while the symmetric tape
with twist ratio 4 (R4) increased by 52 %. Evaluating the flow loss, the optimized tapes again showed
better performance as they increased the pressure loss by about 248 %, while the symmetrical (R4)
tapes increased by 268 % for Reynolds 600.

NUMERICAL SIMULATION OF CHOCKED TWO-PHASE FLOW FOR HAZARDOUS AREA CLASSIFICATION

Mon, 26 Aug 2024 00:00:00 +0000

Two-phase flashing jet is the type of flow that results from the release of liquefied gas into
the atmosphere. The study of this multiphase release is of particular interest in industrial risk
assessments, especially when hazardous area classification analysis is applicable. The understanding of
those release phenomena using numerical techniques is relevant since it contributes with reliable data
when experimental setup of several scenarios is not feasible. Both the behavior and the characteristics
of these two-phase flow can significantly affect the hazard zone, it means that as more accurate the
flashing jet model is, the more rigorous is the definition of the hazardous area. Hence, this work aims to
propose a Computational Fluid Dynamic model to predict chocked two-phase flow, thus a more reliable
vapor cloud shape can be obtained. The Leung model was implemented for calculating critical
conditions of a propane leak, along with a Eulerian-Lagrangian approach for particle tracking and Shear
Stress Transport turbulence model in Ansys CFX® software. Simulation results show the plume extent
and volume within a safety factor of the lower explosivity limit, velocity and molar fraction profiles
along the jet axis, and shock wave prediction expressed through the Mach number profile. The present
work demonstrates that the predicted spread angle outcome is crucial to determine the plume volume
and, consequently, to quantify the risk factor.

INVESTIGATION OF SOME PARAMETERS OF A LOW CONCENTRATION EVACUATED TUBE SOLAR COLLECTOR

Mavd R. Teles, Kamal A. R. Ismail — Mon, 26 Aug 2024 00:00:00 +0000

This paper investigates the influence of essential parameters on a low concentration
evacuated tube solar collector in their efficiency. The conventional models of evacuated tube solar
collectors have an absorber tube covered by a glass tube with a vacuum between them. The studied
model collector has an absorbing tube eccentrically positioned inside a glass cover tube which has a
reflective film insert on its inner surface and vacuum in eccentric annular space. The proposed model
is based on the conservation equations of mass, momentum and energy and discretized by using the
finite volumes method. A home-built numerical code is developed to evaluate the desired parameters.
This code is validated against available experimental and numerical results. The influence on the
efficiency of parameters such as absorptivity of the absorber tube, reflectivity of the reflecting surface
and radius of the absorber tube will be evaluated. Effects of the tracking systems in the thermal
efficiency are also evaluated. The results showed that a 20% drop in the absorber’s absorptivity can
generate a 15% reduction in collector efficiency and a 10% drop in reflectivity of the reflecting surface
can lead to a drop of around 4% in the efficiency of the solar collector.

NATURAL CONVECTION IN A VENTILATED DOUBLE GLASS WINDOW

Taynara Geysa Silva do Lago, Kamal Abdel Radi Ismail, Mário Ventura Mondlane — Mon, 26 Aug 2024 00:00:00 +0000

This study presents the numerical results of the flow problem induced by natural convection
in a channel between asymmetrically heated vertical parallel glass sheets of a ventilated double glass
window. The model is based on the equations of conservation of mass, energy and momentum in its
two-dimensional forms. The Finite Volume Method was used in the resolution with discretization
schemes of central differences for diffusive terms and Power Law for the convective terms. For the
coupling of pressure and velocity the SIMPLE algorithm is used, while the TDMA method is used in
the solution of the systems of equations. The numerical code is used to determine the velocity and
temperature fields between the glass sheets under real ambient conditions and asymmetric heating
conditions. The results were validated with available literature results indicating that the model is
adequate to solve this type of problem.

NUMERICAL MODELLING OF AXIAL HYDROCYCLONE – PHASE SEGREGATION OF DISPERSED OIL IN CONTINUOUS WATER PHASE

Rodrigo V. Cabral, Andre D. Rocha — Mon, 26 Aug 2024 00:00:00 +0000

This paper presents a numerical model of the particle trajectory in an axial hydrocyclone
under laminar flow conditions using Discrete Phase Model (DPM). The DPM is an implementation
of Lagrangian particle tracking which is essentially a means of tracking discrete particles through a
continuum of fluid. The primary phase (continuous phase) is water and the second phase (discrete phase)
is oil. The numerical analysis has been carried for laminar axial Reynolds numbers along a 91.2 mm
internal diameter size and 2.7 m long pipe. The swirling flow is generated from static swirler with 7
vanes, deflection angle of 65.5◦

, and a gap width of 5 mm. The particle trajectory was obtained for
two Reynolds numbers (150 and 300) and three different diameters (10, 100 e 1000 μm). From this
conditions it is possible to conclued that the larger particle diameter the closer to the center of thecan
get closer to the center of the tube along the dowstream flow of the swirler. Besides that, the Reynolds
number impact shows that how smaller it was, the closer to the center the particle remais and reaches a
stable radial position.

THREE-DIMENSIONAL NUMERICAL SIMULATION OF A CENTRIFUGAL COMPRESSOR OPERATING WITH SUPERCRITICAL CO2

Mon, 26 Aug 2024 00:00:00 +0000

Centrifugal compressors performance can be benefited by the low viscosity, high density and
small compression work of the supercritical CO2. The design and aerodynamic optimization of such
devices must take into account the flow behaviour under these conditions, that can be ensured by high
fidelity three-dimensional computational fluid dynamic simulations. This work presents a numerical

modeling and simulation of the highly turbulent, compressible flow inside the impeller of the proof-of-
concept supercritical CO2 microcompressor experimentally tested at Sandia National Laboratories. The

steady state solution was obtained by solving the three-dimensional Reynolds Averaged Navier-Stokes
equations using the comercial software ANSYS CFX. The equation system was closed by the Shear

Stress Transport turbulence model. Thermodynamic properties were evaluated through the Aungier ver-
sion of Redlich-Kwong equation of state, providing better accuracy near critical point condition than its

original version. A grid convergence study was conducted to verify possible numerical error induced by
computational domain discretization. Finally the numerical method was validated against experimental
data and the flow characteristics, typical to centrigual compressors, like the suplementary depression and
leakage flow losses was discussed.

STABILITY ANALYSIS OF SOLUTIONS OBTAINED BY THE LTSN METHOD FOR A RADIATIVE TRANSFER PROBLEM IN A HIGHLY NON-HOMOGENEOUS MEDIUM

Roberto P. Souto, Haroldo F. Campos Velho, Stephan Stephany — Mon, 26 Aug 2024 00:00:00 +0000

Heat transfer can be a result of a radiative process. In such case, it is modeled by the ra-
diative transfer equation (RTE), which is an integro-differential mathematical model that simulates the

movement of photons in a medium. However, many other applications are also modeled with the RTE.
Here, the RTE outputs the radiance distribution in the considered medium given the boundary conditions,
source term, and inherent optical properties, such as the absorption and scattering coefficients as well as

the scattering phase function, in the case of a translucid medium. The domain is discretized into the az-
imuthal, polar and vertical dimensions. The azimuthal discretization is obtained by the finite expansion

of the Legendre polynomial of the scattering phase function, and by the radiance expansion using the
Fourier decomposition of cosines. The resulting number of azimuthal modes is equivalent to the order of
anisotropy of the medium. The discretization in polar direction domain is made by an approximation of
the corresponding integral in the RTE, and the number of polar angles denotes the employed quadrature
order. Consequently, the RTE is expressed by a set of linear differential equations, one for each azimuthal
mode. The selected case study tackles an anisotropic and non-homogeneous medium, where the vertical
domain is discretized in 80 regions, with 50 polar angles, and the number of azimuthal modes is 174.
Therefore, each azimuthal mode requires to solve a linear system of differential equations with 80x50,
or 4000 unknowns. The chosen solver is the LTSN method. It emerged in the early 1990s in the neutron
transport research, being further extended to solve radiative transfer problems. The aim of this work is
to optimize the number of azimuthal modes and of the quadrature nodes while obtaining stable solutions
with accurate values of radiance. Another approach that is presented here is to solve only one linear
system for all azimuthal modes, in a single step, with a much larger number of unknowns.

NUMERICAL STUDY OF AN ALUMINOTHERMIC REACTION BY A FOURTH-ORDER FINITE DIFFERENCE SCHEME WITH THE REACTION RATE MODELED AS CONSTANT AND BY THE N-ORDER METHOD

Kesiany Maxima de Souza, Marcelo Jose Santos de Lemos — Mon, 26 Aug 2024 00:00:00 +0000

Aluminothermic reactions have been widely applied in rail welding, pyrotechnics, and mate-
rial synthesis, as they are highly exothermic. However, they are not easily modeled since they involve

condensed phases, hardly result in gas products, and produce heterogeneous combustion waves where

no thermodynamic equilibrium condition is attained. Moreover, the reaction rate of these reactions de-
pends on particle sizes, oxidizer type, mixture ratios, and other physicochemical characteristics. So,

major studies about aluminothermic reactions have been experimental, and just a few authors have tried
to model the front propagation, shock generation and the kinetics of them. In this point of view, the
present study aims to model the aluminothermic reaction between hematite and aluminum by solving the

energy and mass conservation equations with a fourth-order finite difference scheme in space and first-
order forward scheme in time. As there are not enough experimental studies about the activation energy

and pre-exponential factor for this specific reaction, the reaction rate was modeled both as a constant
and by the n-order method, which considers the dependence of reaction rate on temperature and species

concentration and made it possible to observe the sensibility of these parameters. Moreover, the tem-
perature dependence of density, specific heat capacity and thermal conductivity were considered in the

model. The geometry and boundary conditions were based on experimental data from literature, which
successfully enabled validation of the mean temperature and velocity propagation of the reaction.

NUMERICAL STUDY OF CONJUGATE NATURAL CONVECTION OVER VERTICAL FLAT PLATE WITH PROTRUDING HEAT SOURCES

Henrique L. Castro, André D. Rocha, Marcelo M. Ganzarolli — Mon, 26 Aug 2024 00:00:00 +0000

The paper presents a numerical simulation of conjugate natural-convection heat transfer from
protruding heat sources in a flat plat mounted vertically. This problem arises as a typical concern of
designing electronic systems that involves buoyance-driven flows above heat sources modules. The

main objective is to apply a methodology to validate numerical results for vertical position using a bi-
dimensional, steady state, finite-volume method and to obtain dynamic and thermal fields. The plate

contains seven elements uniformly distributed at the upper surface and an insulation layer at the bottom
guaranteeing convection mechanism in only one side of the sources. Fluid physical properties are
assumed uniform except for the buoyancy terms, which are obtained from the Boussinesq approximation
of Navier-Stokes equations. Heat conduction in the plate is accounted in addition to convection and
radiation in order to evaluate heat transfer mechanisms and non-dimensional parameters. Three different
power inputs were simulated and evaluated using temperature distributions and Nu distribution around
the sources

THERMOELECTRIC POWER PLANT PERFORMANCE AND EMISSION CONTROL SIMULATION

Barbara A. P. C. Ferro , Ricardo A. V. Ramos, Augusto S. Bornschlegell — Mon, 26 Aug 2024 00:00:00 +0000

Energy is undoubtedly a subject that concerns the government and society. In addition
to the economic liability, the environmental aspects are equally important. A thermoelectric power
plant is a solution that fulfill both requirements. The present work evaluated the composition of the
combustion products of a thermoelectric power plant through an analytic and numerical models. The
main polluent components found in the methane combustion products are COX , SOX , NOX and
solid particles. Regarding the ozone formation, the NOX is the most harmful combustion product.
Brayton’s thermodynamic cycle, including combustion, was numerically modelled and implemented
through Scilab
c
routines. The input data was based on real power plant operation conditions, which the
compressor isotropic process, the compression rate, the air and fuel mass rates, the combustion chamber
and gas turbine’s efficiency are known. The combustion reaction methodology takes into account the
equilibrium constants, as proposed in the literature. The combustion products concentration were then
evaluated as they flow through the turbine and are released to the atmospheric conditions. The chemFoam
solver of the OpenFOAM software was used in order to compare the combustion product’s concentrations
obtained with the proposed model. In addition, the results from the combustion model were compared
with the equivalent air (ideal gas) model, without combustion. The difference in thermal efficiency
estimation was approximately of 28 %.

NUMERICAL SIMULATION OF THERMO-HYDRAULIC PERFORMANCE OF SOLAR AIR HEATER CHANNEL-TYPE WITH PERFORATED DWLS

Alexia Ysabelli Antunes, Rafael Módolo Dias Duarte, Daniel Jonas Dezan — Mon, 26 Aug 2024 00:00:00 +0000

The present work numerically investigates the effect of perforated area of DWL pairs in
common-flow-down arrangements mounted in a solar air heater channel-type on thermo-hydraulic

performance of the channel. The flow is considered laminar, steady and incompressible. The three-
dimensional numerical simulations are performed by using the Finite Volume Method. The imposed

inlet velocity to run the numerical simulations is 0.15737 m/s, corresponding to Reynolds number of
500 (based on the hydraulic diameter). The angle of attack is kept constant and equal to 30o, and the
aspect ratio of the DWLs is 1.9. Results show that, depending on the perforated areas, the friction
factor decreases about 8% in relation to a standard DWL pair whereas the useful heat gain increases
about 3%. Finally, the flow field and heat transfer characteristics are investigated and the main results
are discussed.

TRANSIENT BEHAVIOUR OF VOLUMETRIC SOLAR RECEIVERS

Roberta R. Ribeiro, Marcelo J.S. deLemos — Mon, 26 Aug 2024 00:00:00 +0000

The transient behaviors of the volumetric solar air receiver are crucial for understanding
and optimizing the receiver characteristics. The present work numerically analyzes the transient
behaviors of the volumetric solar air receiver under various working conditions. Effects of inlet velocity,
and thermal conductivity ratio s f k / k

on equilibrium temperature was investigated. Higher inlet
velocities attain quicker stabilization times and decreases equilibrium temperature, Teq. In addition,
increasing s f k / k

increases stabilization time as well as equilibrium temperatures. The results are useful
in designing of volumetric solar air receivers and the thermal efficiency increases for lower inlet
velocities and higher thermal conductivity ratios, whereas η is reduced for more permeable structures
and higher porosities. Thermal efficiency (η) increases for lower inlet velocities and higher thermal
conductivity ratios.

EFFECTS OF DARCY AND REYNOLDS NUMBERS ON THE THERMAL BEHAVIOR OF A THERMOCLINE THERMAL STORAGE SYSTEM

Fernando A. Rodrigues, Marcelo J.S. de Lemos — Mon, 26 Aug 2024 00:00:00 +0000

This work explores the transient behavior of different flow velocities and porosities on the
charging cycle of a thermocline thermal storage system for a concentrated solar power plant filled with
solid porous material. In order to accomplish this goal, a transient model describing turbulent flow in a
hybrid medium (porous/clear) with mixed convection was used. Macroscopic flow equations are
obtained using the concept of double-decomposition. Discretization of the governing equations was
performed with the SIMPLE method and the SIP procedure was used to relax the algebraic system of
equations. Turbulent flow was modelled using the k-ε turbulence. A two-energy equation model was
employed to assess heat transfer between solid and fluid phases. The analyzed geometry consists of an
axisymmetrical tank with convection in the exterior, hot air flow entering the system from the top and
clear regions at the top and bottom of the tank. Transient temperatures and storage and charge
efficiencies were evaluated for different Da and Re number values. Results indicated that increasing Re
values improve efficiency up to Re= 3.104

and further increases in Re slightly decreases thermal
efficiencies. Finally, it was found that decreasing the permeability of the system by either lowering
porosity or lowering particle diameter was beneficial for the thermal charge efficiency.

COMPUTATIONAL SIMULATION AND ANALYTICAL PREDICTION OF AMMONIA LEAKAGE FOR HAZARDOUS AREA CLASSIFICATION

Mon, 26 Aug 2024 00:00:00 +0000

Ammonia is widely used in several chemical and food industries around the world,
nevertheless it is a toxic and flammable component which may cause accidents due to leakage and
dispersion. The international standard IEC 60079-10-1 regards flammable components leakage, it
accounts criteria and guidelines for explosive atmosphere formation and reducing the risk of explosion.
The standard claims, based on experiences, that a release of ammonia vapor will often dissipate rapidly
in the open air. This scenario will result in a negligible hazardous area extent in most cases. Hence, this
work aims to investigate ammonia leakage in open air under different leakage conditions. For this
purpose, the authors compared the extent of hazardous area, at the Lower Flammable Limit (LFL), using
analytical models with those obtained from a 2D Computational Fluid Dynamics model. The CFD model
was able to predict a characteristic barrel pattern at the exit of the leaking orifice, typical of choked flow.
The results obtained from analytical models show that the extent of hazardous area was overestimated
compared to the CFD model. Among the analytical models used in this study, Souza’s, Tommasini’s,
and Ewan and Moodie’s yielded results were closer to the CFD model. Furthermore, the extent of
hazardous area for ammonia release are small, just as the plume volume, when compared to definitions
presented at the international standard IEC 60079-10-1.

THERMAL-HYDRAULIC OPTIMIZATION OF A SOLAR WATER HEATER THROUGH LONGITUDINAL VORTEX GENERATOR

Felipe A. S. Silva, Luís G. Silva Junior, Leandro O. Salviano — Mon, 26 Aug 2024 00:00:00 +0000

Nowadays, the development of technologies to harness energy from renewable sources as
solar and wind energy has increased a lot, mainly because of concerns about the burning fossil fuel
and the fast growth of the populations. The solar energy is a great alternative to meet the increasing
demand based on cost effectiveness and accessibility compared to other sources. For thermal solar
application, the researchers have been working to enhance the systems to find cheaper process and
higher efficiency. These studies are fundamental in order to promote the use of solar energy for,
among other, communities with financial restrictions, domestic activities and industry that need of
temperature at medium level. The Computational Fluid Dynamic (CFD) and Genetic Algorithm
Methodology have been successfully coupled to optimize an objective function problem related to
enhancement heat transfer of a solar water heater through Longitudinal Vortex Generators (LVG)
which increase the mix between the cold and hot streams near the wall of circular tubes. This passive
technique can improve the heat transfer by changing the flow dynamic and delay the detachment of the
boundary layer. This work aims to find the optimal shape of a stamped vortex generator over a flat
plate inside a circular tube for operating conditions similar those find in Brazil. The parameters of the
longitudinal vortex generator evaluated are the angle of attack, height and length which were
optimized through Genetic Algorithm approach using a commercial software called by ESTECO
ModeFrontier. The heat transfer and the dynamic flow were solved by ANSYS Fluent for Reynolds
number 900. The results show the optimal design of LGV which enhance 62% the heat transfer and
increase 3 times the pressure drop. The velocity and temperature contours show the mix between the
hot and cold streams and the low pressure zones size, besides, the streamlines indicated a corner
vortex presence.

COMPARING AN ANALYTICAL AND A NUMERICAL MODEL FOR EARTH-AIR HEAT EXCHANGERS IN THE BRAZILIAN SOUTH REGION

Nóbrega, E. S. B., Brum, R. S., Ramalho, J. V. A., Quadros, R. S. — Mon, 26 Aug 2024 00:00:00 +0000

The Earth-Air Heat Exchangers (EAHE) represent a promising option to reduce the
heating/cooling load of buildings. Unlike traditional air conditioning systems, the EAHE employ a
renewable source of energy and they can operate using little electric power. Basically, EAHE use
buried ducts, where the air is blown by fans to exchange heat with the soil. Since the first layers of the
ground are warmer than the outside air in the winter, and colder in the summer, the Earth can be used
as heat source or sink. Therefore, the air leaves the ducts at milder temperatures. Recent research has
shown that these devices can work properly in the south region of Brazil, where prevails a subtropical
climate. This work aims to compare an analytical model with a numerical one, analyzing their results
with experimental data from an EAHE installation in the city of Viamão, located in the Brazilian state
of Rio Grande do Sul. As it is shown ahead, the analytical model is not only more simple, but also
more accurate than the numerical model.

EFFECTS OF STEP POSITION ON THE AERODYNAMIC SURFACE QUANTITIES OF A RAREFIED HYPERSONIC FLOW OVER FORWARD-FACING STEPS

Paulo H. M. Leite, Wilson F. N. Santos — Mon, 26 Aug 2024 00:00:00 +0000

This work describes a computational analysis of a non-reacting hypersonic flow in thermal
non-equilibrium over forward-facing steps at zero-degree angle of attack. Effects on the aerodynamic
surface quantities due to changes on the step position have been investigated by employing the Direct
Simulation Monte Carlo (DSMC) method. The work focuses the attention of designers of hypersonic

configurations on the fundamental parameter of surface discontinuity, which can have an important im-
pact on even initial design. Results highlight the sensitivity of the heat transfer, pressure, and skin friction

coefficients due to changes on the step position for forward-facing step with different step height. The
analysis showed that the upstream disturbance in the step configuration decreased with increasing the

step position and increased with increasing the frontal-face height. In addition, it was found that pres-
sure and heating loads decreased with increasing the step position and increased with increasing the step

frontal face height.

SENSITIVITY ANALYSIS BASED ON MORRIS SCREENING METHOD FOR BLADE DESIGN OF A CENTRIFUGAL COMPRESSOR

Mon, 26 Aug 2024 00:00:00 +0000

Sensitivity Analysis is an important tool for works that have a several number of input
variables which can influence the final results when the goal is enhancement of any machine or
system. For centrifugal compressors, the efficiency depends on the behavior of several phenomena
such as shock waves and recirculation, which these effects are dependent of the geometry parameters
as thickness, angle and shape. In order to find the influence of the thickness and distance between
main blade and splitter on total isentropic efficiency, an Elementary Effects analysis associated to a
robust CFD model using ANSYS CFX was performed, considering a 4:1 compressor known by
NASA CC3. The results indicate that the thicknesses at medium spanwise position are more important
than those at border. Furthermore, the leading-edge parameters are also more influent than those in
trailing-edge. Finally, four variables are found as no significant effect and other five can be used for
future analysis as optimizations reducing computational cost. The work also shows that the variation
on efficiency is closely connected with the changes in most influent parameters due to its geometric
changes in specifically regions which are immersed in the source of losses cited previously.

COMBUSTION SIMULATION OF A PARAFFIN BASED SOLID FUEL WITH GASEOUS OXYGEN INSIDE A HYBRID ROCKET MOTOR

Mon, 26 Aug 2024 00:00:00 +0000

During the past two decades, the state of art of hybrid rocket propulsion area has been in
research of blends containing paraffin-based fuels because paraffin itself shows higher regression rate

compared to traditional fuels commonly used, such as hydroxyl-terminated polybutadiene or polyethy-
lene, but it does not have good mechanical properties, which increases the risk of grain cracking and

rupturing. With the objective to benefit the database development of paraffin-based hybrid rocket propul-
sion, this work is devoted to present a numerical study of the combustion process of paraffin and gaseous

oxygen during the propulsion of a 100 newtons hybrid rocket motor. The paraffin solid wax was chosen
for the simulation since it exhibits more data about the regression rate with gaseous oxygen in literature.
The simulations utilize a mesh with around 100000 quadrilaterals elements, with an average orthogonal
quality of 96.5% and an average skewness of 11% . An axis-symmetric volume domain is considered.

Paraffin is studied as hexadecane (C16H34) using a reduced reaction mechanism of diesel from “Creck-
modeling”. Paraffin is evaluated as a gas at 0, 5 and 10 seconds during a test of the hybrid rocket motor

and the results of the simulations are compared. The results analyzed are temperature, pressure and ve-
locity profiles inside the hybrid rocket motor. The nozzle and the plume of the exhaust product gases are

as well evaluated. This work will contribute to a project of a hybrid rocket motor, where it will operate
with paraffin solid wax and other paraffin-based blends on a laboratory test bench.

STUDY OF BIODIESEL INJECTION OF FLUID DYNAMICS IN DIESEL ENGINES USING OPENFOAM

Mon, 26 Aug 2024 00:00:00 +0000

Since the nineteenth century, internal combustion engines their development due to
thermodynamic models that describe their operation. The combustion and performance of a diesel
cycle engine depend on the quality of the air-fuel mixture and the amount of fuel injected. A
homogeneous blend results in reduced particulate emissions and higher engine efficiency. For fuel
injection optimization in compression-ignition engines, the use of computational methods as a tool is a
viable scientific method. Adding to this the implementation of free and open software enhances the
advantages of numerical methods, since it allows the researcher to have access and can modify the
routines and algorithm used in the simulation calculations. This work aims to study the injection of
biodiesel (soy) in diesel engines with direct injection. The simulations were performed with
OPENFOAM v6, using the cavitatingFoam solver, for the treatment of flow with phase change (liquid
- vapour), the simulation is transient, with three-dimensional geometry based on the BOSCH CRIP-1
injector, the turbulence model used and the κ-ω SST. The results of numerical simulations compared
with experimental data available in the literature. Preliminary results show the occurrence of cavitation
in the injection channel as a function of injection pressure.

NUMERICAL INVESTIGATION OF UNIFORM FLOW PAST STATIONARY SPHERE USING IMMERSED BOUNDARY-LATTICE BOLTZMANN METHOD

Rodrigo S. Romanus, Alan Lugarini, Admilson T. Franco — Mon, 26 Aug 2024 00:00:00 +0000

The Lattice-Boltzmann method (LBM) has been attracting lot of interest as a tool to solve
hydrodynamic problems, mostly due its suitability for parallelization. However, the implementation of

boundary conditions in LBM has some hardships, especially for flow domains containing immersed par-
ticles. An alternative to overcome this problem is the immersed boundary method (IBM), a numerical

technique that uses a secondary Lagrangian mesh and imposes a boundary condition through a force field.
This study presents the development of an IB-LBM based algorithm that simulates a free flow around a

stationary sphere, which can also be described as a uniform jet stream that encounters a spherical obsta-
cle. The fluid domain is described using a D3Q19 lattice arrangement and, a geodesic polyhedron based

mesh delineates the spherical boundary. The flow evolution for fluid mesh is simulated using LBGK
equation, whose stability is enhanced through regularization, a process which discards non-physical high
order moments from LBM. In order to verify algorithm consistency, this document presents comparison
with literature benchmark data of flow profiles and drag coefficients for different Reynolds numbers,
showing good agreement between present work and available studies.

A STUDY OF CONTINUUM MECHANICS AND PHASE CHANGE PROBLEMS AND IT’S NUMERICAL MODELLING USING OPENFOAM

Mon, 26 Aug 2024 00:00:00 +0000

Several applications in continuum mechanics involve processes such as solidification and

melting of materials, natural convection, stresses and deformations in solids, among other related pheno-
mena. Given the complexity of the phenomena related to these processes, the numerical and computati-
onal modeling are powerful and of low costs tools suitable to understand and simulate problems which

may envolve one or more of these complex phenomena. In this paper, a set of mathematical models
representing some of these processes is introduced, discretized and solved by the Finite Volume Method,

using open-source package OpenFOAM, a based C++ toolbox for the development of customized nume-
rical solvers, and pre-/post-processing utilities for the solution of continuum mechanics problems from

computational fluid dynamics, including also static solid elastic problems. Application examples are

shown including the gallium melting problem, a process commonly needed in computer chips manufac-
turing; the lid-driven cavity problem, widely used for testing, verification and validation of numerical

procedures and a simple linear elasticity problem. We show some of the basic features of OpenFOAM
as well as explore some of its potential pointing on some possible disadvantages of this code.

ENERGETICAL ANALYSIS OF A REFRIGERATION CYCLE COMBINED WITH CO2, PROPANE AND BRINE

Lívia M. S. de Pontes, Josegil J. P. de Araújo — Mon, 26 Aug 2024 00:00:00 +0000

The destruction of the ozone layer was mainly caused by chlorofluorocarbons (CFCs) used
as refrigerants, which were widely utilized during the twentieth century. Another problem produced by
the use of these substances was, and still is, the Global Warming, since these fluids have high "Global
Warming Potential" (GWP). Due to these consequences, this category of refrigerant was banned and
gradually replaced by natural refrigerants such as carbon dioxide (CO2 – R744) and propane (C3H8 –
R290). In this work a cascade refrigeration system was analyzed according to the First Law of
Thermodynamics (energy analysis). The cascade cycle consists of three subsystems: a vapor
compression cycle using R744 as a working fluid, a system operating with 40% ethylene glycol and a
vapor compression cycle which uses R290 as a refrigerant. The propane cycle receives heat that has
been absorbed in cycles of R744 and 40% ethylene glycol and rejects it into the atmosphere in the
condenser of the R290 cycle. For the cycle analysis, the system was subdivided into 18 control volumes
and 23 state points. Equations of mass and energy balances were applied, along with complementary
equations, which they were used to complete the system of equations. The solution of the system of
equations was obtained by applying Newton-Raphson method. The model was implemented in EES®
and simulated under different operating conditions. Finally, the thermal efficiency of the R744 cycle
was 8.784; for the R290 cycle, it was 4.09 and 3.393 was the result of the combined cycle.

COMPORTAMENTO FLUIDODINÂMICO DA INTERFCE ÁGUA - AR: MODELAGEM E SIMULAÇÃO

Mon, 26 Aug 2024 00:00:00 +0000

Pollution of watery regions such as rivers, lakes, and seas with contaminants that disperse in
water has been a major concern in society in recent times. The dispersion of the various contaminants
present in the aqueous regions is influenced by various parameters such as: water and air velocity.
Therefore, it is of fundamental importance to know the relation of these properties in the propagation
of these pollutants.The use of tools that employ numerical methods are applied to predict the
dispersion behavior of contaminants present in free surface flows. The purpose of this study was to
evaluate the influence of air currents on the water surface. In the proposed mathematical model the
Eulerian-Eulerian approach was adopted for the two - phase (air-water) flow assuming the free surface
model, standard k–ε turbulence model. The constant physicochemical properties were adopted.
Numerical simulations were performed using the Ansy CFXR commercial package, varying the values
of air velocity and height of the water level. The results of the simulations confirm that the behavior of
the water-air interface is affected by the variation of the air velocity quantity and the height of the
water level of the reservoir.

FEM PARALLEL FRAMEWORK USING OPENCL AND MULTIPROCESSING AP- PLIED TO COMPRESSIBLE TURBULENT REACTIVE FLOWS ON ROCKET EN- GINES WITH THE NEW SUBGRID CLOSURE MODEL

Mon, 26 Aug 2024 00:00:00 +0000

The objective of this work is to develop a methodology for the numerical analysis of a turbulent
compressible reactive transient flow of a homogeneous premixed mixture within a convergent-divergent
nozzle, applicable to rocket engines. The equations of continuity, momentum, energy and conservation
of chemical species are discretized by applying the Galerkin finite element method through the CBS
(Characteristic Based-Split) stabilization procedure. The Flamelet/Progress Variable scheme is employed
to simulate the combustion process and capture the flame front behavior. For the modeling of chemical
kinetics Canterar software is employed which uses GRI-3.0, a combustion mechanism that contains
325 reactions and includes 53 chemical species as combustion products. In the context of turbulence, the
LES methodology with the novel subgrid closure model will be applied. For the temporal and transient
resolution, the Euler explicit scheme was applied, while for the spatial behavior the Element by Element
(EbE) method was used, based on the Biconjugated Gradient method for the linear systems resolution,
incurring the low memory space associated to local full matrices. A solver was developed in Python,
deploying Object Oriented Programming (OOP), with the algebraic system resulting from the temporal
and spatial discretization of finite elements combined with homogeneous and heterogeneous parallelism,
with CPUs and GPUs through the control of multiprocessing, multithreads and using the OpenCL library.
to this type of analysis.

NUMERICAL SIMULATION AND EXPERIMENTAL ANALYSIS FOR THE BUBBLE GROWTH RADIUS BY CONSIDERING THE FLUID-SURFACE INTERACTION

Mon, 26 Aug 2024 00:00:00 +0000

The advance of new technologies, associated with the minimization of manufacturing and
installation costs, presents a great challenge for the refrigeration area since the heat generation has
increased in recent years. Several studies have shown the influence of surface topography on the heat
transfer performance, a strategic subject for the development of techniques for cooling of miniaturized
electronic components, thermal control of satellites, cooling of high concentration photovoltaic cells
and others. The objective of this work is to develop a theoretical and numerical study of the heat
transfer phenomenon with phase change involving pool boiling, taking into account the influence of
the heating surface characteristics and the use of different fluids (e.g., water or refrigerants) by the
numerical simulation of a vapor bubble dynamic onto the heating surface. A computational code is
developed in Fortran 90 language to solve the continuity, momentum, energy and interface capture
equations in three-dimensional spherical coordinates. Moreover, it is implemented a method to
capture the interface based on the coupled algorithm of Volume of Fluid Method and Level Set
Method (CVOFLS). The effects of microlayer, contact angle and surface tension on the vapor bubble
dynamic are also considered. The CVOFLS algorithm also allows the simulation in Eulerian fixed
mesh. The finite element method is applied for space discretization and the Characteristic Based Split
scheme (CBS) is applied for time discretization. The comparison with experimental data obtained by
the research group and by other researchers is used to validate the numerical model. Thus, the rate of
bubble growth and the bubble shape could be predicted until its departure time taking into account the
effects of microlayer and surface/fluid interaction.

A COMPUTATIONAL STUDY OF THE HEAT TRANSFER PROCESS IN ANNULAR FINS

Lucas E. F. de Souza, Jonatha W. S. Araújo, Sandi I. S. de Souza — Mon, 26 Aug 2024 00:00:00 +0000

In this work numerical simulation techniques was used as a way to evaluate the effects of
natural convection on a horizontal tube with annular fins. Three configurations were studied by
varying the spacing between the fins, 5 mm, 10 mm and 20 mm. The changes in the process of heat
transfer as a function of the spacing S and the existence of natural driving were investigated. For this,
a geometric model with two domains was developed. A domain contains fluid, Air outside, and a solid
domain composed of a steel tube with fins, where a fixed temperature has been set at the base of the
fins. A geometric model was developed and a CFD commercial code, ANSYS-CFX, was used in the
numerical solution of the transport equations. Results for the fields of temperature in the fins and the
heat transfer rates are presented. The results showed that the spacing between the fins has a thermal
influence until stabilized. The temperature distribution on the face were similar.

DISCRETIZAÇÃO MATEMÁTICA DAS EQUAÇÕES NECESSÁRIAS PARA MODELAGEM DE FLUIDO COMPRESSÍVEL BIDIMENSIONAL COM CVFEM

Bruno de Sousa Barros, Fábio Alfaia da Cunha — Mon, 26 Aug 2024 00:00:00 +0000

The present work provides in details the discretization of a set of mathematical equations
required to model a two‐dimensional compressible fluid flow. The hypothesis of not viscous flow is
considered in this work for effect of simplifying the equations, thus the compressible flow of the fluid
can be described by the Euler equations. The control volume based finite element method – CVFEM
was chosen to describe the differential equations of conservation. The numerical method uses
unstructured mesh (based on triangular elements) to discretize the geometric domain and the polygonal
control volumes for discretization of conservation equations. For that purposed, it was opted for the
segregated solution of the momentum and mass conservation equations, by the use of primitive variables
(velocity, pression and temperature) and co-located (integration of the momentum and mass
conservation equations is done above the same control volume for pressure and velocity). A
computational code programmed in MATLAB software language was developed to realize the
numerical simulations of compressible flows, two-dimensional (planar or axisymmetric) and transients.
The case of a subsonic / supersonic flow through a Channel with a Circular Arc Bump and the case of
the supersonic flow through the convergent-divergent channel were used to verify the developed code.
At the end of the work are presented results obtained by means of a numerical solution and these results
are compared to results available in literature, to ascertain that the computational code developed works
as it was expected.

NUMERICAL STUDY OF CARBON MONOXIDE DISPERSION IN AN URBAN MICRO REGION

Vivian Machado, Thiago Antonini Alves, Yara de Souza Tadano — Mon, 26 Aug 2024 00:00:00 +0000

This paper presents the numerical study of the dispersion of carbon monoxide (CO) in an
urban micro region, located in the city of Ponta Grossa/PR, Brazil. Three main roads are considered
polluting sources: Vicente Machado Avenue, Ermelino de Leão Street, and Benjamin Constant Street.
The mass flow of CO emission in the simulated routes was calculated based on emission factors and
the counting of the vehicles (cars, buses, trucks, and motorcycles) in the place. The simulations were
performed using ANSYS/FluentTM 19.1 software. With the results it was possible to obtain
visualizations of the fluid dynamics conditions in the place, behavior of the pollutants and possible
regions of accumulation due to the recirculation. The pollutant concentration results presented values
of 14.4 ppm, at the monitoring point considering a height of 1.5 m in relation to the soil level. The
values obtained in the simulations presented concentrations higher than the 9 ppm limit established by
the guidelines of the World Health Organization (WHO).

TRANSPORTE SIMULTÂNEO DE CALOR, UMIDADE E SAL EM CONCRETO

Rhayssa M. M. Ribas, Gerson H. Santos — Mon, 26 Aug 2024 00:00:00 +0000

Concrete structures can suffer various types of damage, which can considerably shorten
their life. One of the responsible for this process is the transport of salts into the concrete pores. In
addition to accelerating the corrosion process in the steel frame, these salts can concentrate at some
points (nucleation), causing cracks and fractures in the structure, consequently decreasing its
resistance. Thus, the objective of this work is the analysis of how this transport takes place inside the
porous structures, simultaneously considering the transport of heat, moisture and salt in the porous
medium. The discretization of the governing equations was performed using the finite volume method,
and the algebraic equations system was solved through the MultiTriDiagonal Matrix Algorithm
(MTDMA) algorithm, which allows the simultaneous solution of the governing equations. For the
model verification, several simulations considering different boundary conditions were performed and
compared with a model proposed by other authors, showing good similarity between the results. From
the results it was possible to observe the influence of moisture transport on the salt displacement inside
the concrete, in the drying and imbibition processes.

NONLINEAR MODELING OF TWO LINKS OF A THREE DEGREES OF FREEDOM ROBOT

José Antonio Riul, Paulo Henrique de Miranda Montenegro, Naor Moraes Melo — Mon, 26 Aug 2024 00:00:00 +0000

The objective of this paper is the nonlinear modeling of two links of a manipulator robot
with three degrees of freedom (3 DOF).The manipulator robot consists of two rotational joints and a
prismatic one. A gearmotor with frequency inverter and two electropneumatic valves are used to drive
the robot. There are dynamic systems that can’t be represented by linear models; in these cases, the
use of nonlinear models is indispensable. Robot Models, known as white box models, that are coupled
and presenting nonlinear equations can be obtained using Newton-Euler or Lagrange equations. In this
work a nonlinear model, known as black box model, will be obtained using data collected from links 1
and 3 of the robot and considering the dynamic coupling between the links of the robot. In the models
obtained the nonlinearities will be in the inputs, and the parameters of the obtained models are linear.
A parametric model described by an equation the difference with nonlinearity at the input, is called the
Volterra parametric model. Finally, the results obtained will be presented through the generated
model.

MINERAÇÃO E ANÁLISE EM BASE DE DADOS EDUCACIONAIS: UMA ABORDAGEM UTILIZANDO CLUSTERIZAÇÃO NOS DADOS DA PLATAFORMA LATTES

Mon, 26 Aug 2024 00:00:00 +0000

Recent technological developments have enabled the generation of large volumes of data that
due to their complexity, require computational assistance to generate accurate results in a short period of
time. The Lattes Platform is a set of Web systems containing databases of curricula, research groups and
institutions, focused on the field of Science and Technology and maintained by CNPq. Due to its rich
database it has important information in the field of Science & Technology. In this article, the feasibility
of applying the data mining methods in the Lattes Platform database is demonstrated externalizing its
knowledge. Thus, as main contributions of this article forms of interpretation, development of standards
and generation of knowledge are presented from this data base, where clustering techniques were applied.

MISSING DATA: BRIEF REVIEW AND CASE STUDIES

Giovanni Amormino da Silva Junior , Alisson M. Silva, Paulo E. M. Almeida — Mon, 26 Aug 2024 00:00:00 +0000

A major difficulty faced in developing real applications that use data streams to solve pre-
diction and/or classification problems are the missing data. Although there are techniques to reduce

the impacts caused by this problem, most systems are not preventively modeled to allow the adequate
treatment of this type of occurrence. Unreliable or damaged sensors, partial occlusion, interference in
communication, restrictions in the data transmission band, are some of the reasons that can cause this
problem. Some authors classify this lack of data regarding their randomness and show that in some cases
this absence may also be related to the lack of other attributes. Basically there are two ways of dealing
with missing data: i) exclusion, where all or part of the sample is removed or ignored; and ii) imputation,
where the missing value is replaced by zero, by the average of the variable up to the sample with the
problem or by an estimated value, where the problematic variable has its estimated value by some model
that, in some cases, can lead to variables and/or previous values. In this context, this article presents a
review of the literature addressing the main methodologies used to address the problem of missing data.
In addition, case studies are presented for comparing results and defining situations where each type of
approach is best employed.

ANALISE COMPUTACIONAL DE CONDICIONANTES DE RISCOS AMBIENTAIS

Mon, 26 Aug 2024 00:00:00 +0000

The intense urbanization process since the 1970s, coupled with the lack of adequate housing
and social policies, has led large urban centers to disordered occupations and situations of geotechnical
risk. These occupations were not implemented in a technically correct manner from the point of view of
civil engineering, considering landscaping, drainage and paving, as well as in the edification. Areas at
risk are regions where it is not recommended to build houses or facilities because they are very exposed to
natural disasters, such as landslides and floods. In Brazil, the main institution responsible for monitoring
areas at risk is Civil Defense. There is a large database with history of occurrences of risk areas served
by the Municipal Civil Defense, in Juiz de Fora city, Minas Gerais state - Brazil, from 1996 to 2017.
Some important informations contained in this database are the physical aspects of the soil, such as
slope, altitude, amplitude, curvature and accumulated flow, as well as processed data from the sliding
risk susceptibility methodologies. The objective of this work is to apply Machine Learning techniques to
identify, from the mentioned database, the susceptibility to the risk of environmental disasters in regions
that have not yet participated in events attended by the Municipal Civil Defense. This database is large
and unbalanced, so it is necessary to apply data analysis methodologies so as a machine learning model
can correctly identify the standards with the least human intervention.

BITCOIN OPENING VALUES ANALISYS

Filipe Barreto de Oliveira, Luciana Conceição Dias Campos — Mon, 26 Aug 2024 00:00:00 +0000

A crypto-currency is a decentralized exchange means that uses blockchain technology, which
is a type of distributed log book operated on a point-to-point network of thousands of computers, where
everyone has an equal copy of the entire transaction history, preventing a central entity from promoting
changes to the registry or to the software unilaterally, and from cryptography to ensure the validity of
transactions and the creation of new currency units. Bitcoin, the first decentralized digital currency in
history, was created in 2009. The idea with Bitcoin was to replicate the properties of physical money in
a digital environment, the digitization of money in the fullest sense of the term. Since then, many other
crypto-coins have been created, and the challenge has been raised to discover which crypto-coins are
most promising to invest. Investing in the financial market involves buying and selling financial assets,
and every investor expects to find standards in the market that allow him to buy low value’s assets and sell
high value’s assets. The objective of this work is to propose a deep learning method to learn the behavior
of increasing or decreasing the opening values of each day of the Bitcoin crypto-currency in an interval of
up to 20 days. We used Bitcoin purchase values from April 2013 to February 2018. Different forecasting
strategies were studied. The experimental results showed relevance in the price trend of Bitcoin.

ANALYSIS OF THE ACADEMIC FORMATION PROCESS OF PHD’s IN ENGINEERING IN BRAZIL

Higor A. D. Mascarenhas, Thiago M. R. Dias, Patricia M. Dias — Mon, 26 Aug 2024 00:00:00 +0000

The exodus of individuals for various reasons or circumstances has been growing
significantly in recent years in the Brazilian and worldwide scenario. One of the reasons identified for
this migratory flow is the academic formation of these individuals who seek to qualify in higher quality
educational institutions. Therefore, this work will correspond to the type of qualitative and quantitative
research, whose objective will be to analyze how the scientific exodus of Ph’d engineers occurs in Brazil,
in which individuals from different localities of the country migrate in search of a better academic and
scientific formation. It will be necessary to extract academic data from the curricula of this set of
individuals registered in the Lattes Platform. Thus, the set to be analyzed will be all individuals with
doctorate degree completed in the Engineering Areas. Then, the data will be filtered, selecting the
relevant attributes to the research, and finally the data will be processed in order to find the geographical
location of the institutions in which they trained. As result it will be possible to make a portrait about
how the Brazilian scientific exodus occurs with the set of individuals analyzed.

Prediction Brazilian’s Information Science Future Co-Authorships

Felipe Affonso, Thiago Magela Rodrigues Dias — Mon, 26 Aug 2024 00:00:00 +0000

When publishing a work together with other scientists, a connection is formed by the colla-
boration done. Papers written together represent the edges, and the authors represent the nodes of the

network. By using the concepts of social network analysis, it is possible to better understand the relati-
onship between these nodes. At this point, the following question arises: ”How does the evolution of the

network occur over time?”. In order to answer this question, it is necessary to understand how two nodes

interact with one another, that is, what factors are essential for a new connection to be created. The pur-
pose of this paper is to predict connections in co-authorship networks formed by doctors with resumes

registered in the Lattes Platform in the area of Information Sciences. Currently, the Lattes Platform has
6.1 million resumes from researchers and represents one of the most relevant and recognized scientific

repositories worldwide. With this, it will be possible to understand the behavior of the network and mo-
nitor its evolution over time. Through this study, it will also be possible to identify the researchers who

can collaborate in a future moment of time. To this end, recommendation systems will be used, these
represent a specific approach to the concepts of machine learning. Through the use of this technique it is
possible to understand which attributes of the nodes make them closer to each other, and therefore have
a greater chance of creating a connection between them in the future. This work is extremely relevant
because it uses a data set that has been little used in previous studies. Through the results it will be
possible to establish the evolution of the network of scientific collaborations of researchers at national
level, thus helping the development agencies in the selection of future outstanding researchers.

ANALYSIS OF THE CONTEXT OF WORDS IN PORTUGUESE USING WORD2VEC

Alexandre D’Elia, Myrian C.A. Costa, Nelson F.F. Ebecken, Valéria M. Bastos — Mon, 26 Aug 2024 00:00:00 +0000

Due to the wide availability of textual documents on the Web, there was an intense study on
how the machine should deal with related words and contexts. The usual methods of
representing words as index in a vocabulary have become obsolete for new applications. Faced
with this demand was developed a new way to study words and contexts efficiently. Word2Vec,
presented in [1], is a group of templates used to produce word integrations. These models are
two-layered neural networks trained to reconstruct linguistic contexts of words.Word2Vec takes
as input a large text corpus, producing a vector space, typically containing several hundred
dimensions, with each unique word in the body being assigned to a corresponding vector in
space. The word vectors are positioned in the vector space so that words that share common
corpus contexts are located close to each other in space.This paper aims to make an analysis of
documents in contexts in the Portuguese language. For a general study on the language, a
database of 37.5 million randomly selected Web pages was used. In this way, it became possible
to observe the use of words based on the context in which they are inserted in an empirical way.
Finally, according to tests, the performance was higher than expected.

A CO-AUTHORSHIP NETWORK ANALYSIS OF RESEARCH FROM GRADUATE PROGRAMS OF THE INTERDISCIPLINARY AREA IN BRAZIL

Solon M. Soares, Pedro H. T. Schimit — Mon, 26 Aug 2024 00:00:00 +0000

Scientific collaboration has an increasing acknowledgment as one of the keys to research
quality, which impacts the academic performance of graduate programs (GP). This investigation
assesses the researchers' collaboration in terms of the co-authorship network formed by scientific papers
published by permanent professors in Brazilian GPs from the Interdisciplinary area in 2017. In general,
the co-authorship network is formed by permanent professors as the vertices, and the joint publication
of a paper identifies the edges. We obtained data from the Sucupira and Lattes platform of a sample set
of 1040 permanent professors, in 56 graduate programs, in 48 universities for the 2017 year. For each
GP, a collaborative network was created based on published articles, and topological parameters, like
cluster coefficient, density, diameter, degree, and shortest path were calculated. Other variables have
been taken into consideration to help the analysis, such as the GPs number of permanent professors, the
GPs evaluation grade applied by CAPES in the 2013-2016 period analysis, the university management
type (public or private), and the region from Brazil where it is located. Therefore, the objective is to
verify the variables which may indicate the GP quality, and although the properties of the network are
not statistically related to the GP quality, they help to analyze some characteristics of GPs according to
the management type of the institution.

SOLAR IRRADIATION FORECASTING BY THE APPLICATION OF FIVE MACHINE LEARNING ALGORITHMS

Mon, 26 Aug 2024 00:00:00 +0000

In this work, the forecast of global solar irradiation for a one-day ahead forecast horizon was
carried out using some machine learning models, namely: Minimal Learning Machine, Support Vector
Machine, Random Forests, K- Nearest Neighbors and a regression tree with the application of a Bagging
procedure. The Minimal Learning Machine algorithm is a relatively recent method based on the distance
calculation between vectors and used for supervised learning purposes in both classification and
regression problems. In addition, we used a data set with the presence of attributes (predictors) formed
by exogenous variables (insolation, air temperature, precipitation, etc.), endogenous variables (solar
irradiation historical data) and temporal variables (year, month and day of measurement) totalizing 44
attributes and 3254 observations. The root mean squared error and forecast skill obtained by applying
the Minimal Learning Machine in the validation set were respectively 40.882 W/m2 and 7.637 %, and
the arithmetic mean of the root mean squared error in conjunction with the arithmetic mean of the
forecast skill obtained by the use of the other models for the same validation set were 40.752 W/m2 and
7.93 %. In this way, it can be drawn by the evaluation of the results that the Minimal Learning Machine
presents a performance comparable to the classic machine learning methods. Furthermore, it presents
the advantage in the training stage of using only a single adjustment parameter.

BINARY SHADING CLASSIFICATION BY MEANS OF AN IDENTIFICATION ALGORITHM FOR RADIATION TRANSITIONS USING LOW COST SENSORS

Mon, 26 Aug 2024 00:00:00 +0000

In the current energy scenario, renewable energies such as solar and wind power have
significant relevance. In this context, an algorithm capable of recognizing irradiation transitions was
implemented. This algorithm was used to classify data obtained from light dependent resistance in two
classes: shadow and non-shadow. These results were compared with those obtained by a standard
algorithm that has a input global or beam irradiation values collected by pyranometer and pyreliometer
sensors, respectively. This way, a practical tool was obtained. Such tool uses data collected by low cost
sensors to perform an initial statistical study about days and hours when there is a higher level of
irradiation. Therefore, this information can be used to optimize the solar power capture. The irradiation
transition identification algorithm, generally, had a better compilance at peaks hours, where for the same
days it reached ranging around 100% and 87.10% using the global and beam components as input to the
standard algorithm, respectively. From the results, it is clears that a better performance of the irradiation
transition identification algorithm when using global irradiation values as input to the standard
algorithm, as well as a lower compilance of the irradiation transition algorithm during the dawn and
twilight periods.

GENETIC ALGORITHMS TO DETERMINE THE OPTIMAL PARAMETERS OF AN ENSEMBLE LOCAL MEAN DECOMPOSITION

Willian T. F. D. Silva, Filipe D. D. M. Borges — Mon, 26 Aug 2024 00:00:00 +0000

An optimization method for an ensemble local mean decomposition (ELMD)

parameters selection was proposed by using evolutionary algorithms. ELMD is an adaptive, non-
stationary and non-linear signal processing method based on the addition of different white

noises to the target signal to be decomposed into a local mean decomposition (LMD) in order to
solve its large mode mixing problem. Even though it has satisfactory performance for fault
diagnosis of rotating machinery and reduced maintenance costs, the execution of this technique
depends heavily on the correct choice of the parameters of its model. Although it was proposed
to optimize the selection of these parameters through relative root-mean-square error (RRMSE)
and signal-to-noise ratio (SNR), the optimized ensemble local mean decomposition (OELMD)
based its selection by testing several values for amplitude, noise bandwidth and ensemble trials in
order to obtain the optimum value. However, even with excellent signal processing results, this
technique can raise computational costs and become prohibitive, especially in real-time analysis.
Thus, this work also proposed an optimized ELMD, but in this occasion using the inclusion of
genetic algorithms. The effectiveness of the proposed method was evaluated using synthetic
signals, which was used by several authors for such purposes. Despite presenting inferior results
to OELMD in avoiding mode mixing problem, the suggested algorithm obtained better results
regarding the signal processing time.

ANALYSIS AND COMPARISON BETWEEN REGRESSION MODELS FOR TEMPERATURE ESTIMATION OF SOLAR COLLECTORS OPERATING WITH NANOFUIDS

Mon, 26 Aug 2024 00:00:00 +0000

The objective of this work is to verify the application of polynomial regression methods,
Ridge and Lasso regression in the nowcasting of the fluid temperature and energy gain of a solar
collector operating with nanofluids. The collector has temperature and global/direct solar radiation
sensors for data logging. In addition the R programming language was used for the statistical analysis
of R2, MAE (Mean Absolute Error) and RMSE (Root Mean Squared Error). The models were applied
in three different data sets, which regarded to the data for water temperature prediction and TiO2
nanofluids with a concentration of 25 ppm and 75 ppm, where each method applied seven predictors
for the fluid temperature nowcasting. The best Root Mean Squared error found in the test sets was
2.281°C for a degree 3 polynomial regression, whereas the Ridge presented an RMSE of 3.190°C. The
Ridge and the Lasso usually improve least squares methods but they did not perform well in this data
set, the Ridge regression considered a model with all the predictors and got a high test error, as far as
the Lasso excluded some predictors and got an improved result. A cross-validation was performed to
know the degree of the most effective polynomial for the analysis of these data and the polynomial
regression of degree 3 obtained the best result, confirming that the fluid temperature does not follow a
linear trend mainly during the hours from 5:30 to 21:30.

DATABASE TO SUPPORT ENERGY PLANNING APPLICATIONS

Mon, 26 Aug 2024 00:00:00 +0000

Currently, obtaining updated real data for analyzes related to the generation of hydroelectric
and thermoelectric energy in Brazil is only accessible through the database provided by the National
System Operator (ONS), by means of a file package used in the computational model NEWAVE (Long
and Medium Term Interconnected Hydrothermal Systems Operation Planning Model). NEWAVE was
developed to determine the optimal operation policy for the hydrothermal power system, but working
with this information in a direct way is practically impossible, which makes it difficult to carry out new
studies by industry and academia. Opposing this difficulty, researchers at the Laboratory of Technologies
and Bioinspired Solutions of the Federal University of ABC (LabBITS) implemented an open platform
for general access of the information of the Brazilian electric power generation system, where the main
objective was to concatenate all the information to foment the studies with different operative scenarios
referring to the energetic planning in Brazil. The data is constantly updated with files from the Electric
Energy Trading Chamber (CCEE) database. The data was reorganized through JAVA programming
language and was recorded in a new single database with MySQL as a template, to facilitate the reading
and recording of study’s input data and results. From this organization, a visual query platform is being
developed to support the development of modules for the determination of optimal generation within a
bioinspired computational platform called Energ.IA. 1

CONSTRUÇÃO DE REDE DE INFLUÊNCIAS VIA GRAFO DE VISIBILIDADE HORIZONTAL

Rabelo, A. F. C., Dias, T. M. R., Moita, G. F. — Mon, 26 Aug 2024 00:00:00 +0000

Redes de influências são capazes de identificar relações intrínsecas entre elementos distintos
em um universo. O método chamado de Grafo de Visibilidade Horizontal (Horizontal Visibility Graph
– HVG), tem como função transformar uma série temporal em um grafo. Atualmente, este método pode
ser utilizado para estudar diversos sistemas dinâmicos. Pode ser utilizado também, como ferramenta de
distinção entre sistemas caóticos e estocásticos. Neste artigo, os autores propõem a construção de uma
rede de influência, baseada nas variações diárias das moedas mundiais. Para tanto, analisou-se este
sistema de natureza estocástica, utilizando quantificadores tradicionais de redes, por meio dos quais foi
possível a distinção entre os diferentes graus de estruturas de correlação. Por fim, apresentamos a rede
gerada a partir das séries temporais do Movimento Browniano Fracionário, comparando os resultados
com a distribuição da distância e do grau de elementos da rede.

DETERMINATION OF IDF CURVE: COMPARATIVE STUDY BETWEEN THE BELL METHOD AND RAINFALL EQUATION IN THE CITY OF BREVES, PARÁ

Mon, 26 Aug 2024 00:00:00 +0000

Urban drainage systems are often planned and designed using rainfall intensity equations.
These equations allow to estimate the maximum precipitation of heavy rainfall and may be obtained
through different methods based on the correlation of a few rainfall data, such as its duration, frequency
and distribution. One of those is the Bell’s method, used in this paper. However, the lack of pluviograph
records as well as short duration data in certain areas have pointed out to the use of pluviometry registers
and statistical models as alternatives to assist the design of drainage infrastructure. This paper aims to
investigate and compare the performances of the Bell’s method and the rainfall equation proposed by
Souza et al. (2012) for the city of Breves, in the State of Pará, Brazil. The study was carried out mostly
by the processing of rainfall data repositories of three meteorological stations situated in Breves using
periods of observation of 8, 11 and 26 years and its statistical analysis. The results obtained showed that
the Bell methodology and the intense rainfall equation for the estimation of maximum rainfall with small
return periods is applicable and consistent, considering the use of a large data series.

DYNAMIC ANALYSIS OF PLANE STRESS PROBLEMS BY THE HIERARCHICAL FINITE ELEMENT METHOD WITH THE USE OF ERROR INDICATORS FOR SELECTIVE MESH ENRICHMENTS

Carolina C. Cittadin, Marcos Arndt — Mon, 26 Aug 2024 00:00:00 +0000

The search for optimized projects has led to the design of leaner and lighter structures, which
are more susceptible to dynamic effects. These must be thoroughly analyzed in order to avoid excessive
displacements, structural damage and to guarantee user comfort. However, the analytic solution of
dynamic problems tends to present great difficulties and, in some cases, cannot be obtained. Therefore,
researchers developed approximated methods. The most used approximated method is the Finite
Element Method (FEM). As a well-established method, the main focus of FEM studies has shifted from
the development of the method to the improvement of its results. In this context two lines of research
have proven to greatly influence the accuracy and efficiency of the method, the study of refinements
and the study of error indicators. Even though refinements improve the accuracy of solutions they can
lead to greater computational efforts and complexity. A way to balance these drawbacks is to combine
them with error indicators. These allow the engineer to specify which mesh elements have greater
influence on the results and apply refinements selectively. The present study focuses on precisely these

characteristics and evaluates the use of the Friberg Error Indicator in the dynamic analyses of two-
dimensional structures as a mean to the application of a selective p-refinement. Numerical examples,

considering plane stress state, are computationally modeled with the use of Lobatto’s hierarchical shape
functions and trigonometrical enrichments. The results of eigenvalues for the enrichment of different
elements are compared with those present in past literature.

APPLICATION OF THE GENERALIZED FINITE ELEMENT METHOD TO THE FIRST ORDER SHEAR DEFORMATION THEORY APPLIED TO ISOTROPIC AND SANDWICH PLATES UNDER LARGE DISPLACEMENTS

Wellington Rhoden de Lemos, Paulo de Tarso Rocha de Mendonça — Mon, 26 Aug 2024 00:00:00 +0000

This paper presents a procedure to extract accurate transverse normal and shear stresses, and
the transverse and in-plane displacements, in isotropic plates, symmetric laminated composite plates and
plates with sandwich structure, modeled by the First Order Shear Deformation Theory (FSDT), under
large displacements considered in the von Kármán sense. The Generalized Finite Element Method
(GFEM) is used, in which the enrichment of the Partition of Unity (PoU) functions is done by complete
polynomials functions, improving the obtained results, and making it possible to obtain basis of
approximate functions with degree 4 of polynomial reproducibility. This makes possible to obtain
straightforwardly the third derivatives of transverse displacement w, which is needed in most extraction
procedures based on the integration of the local equilibrium and kinematic equations. The procedure
starts with the integration of the local differential equations static equilibrium, using the results obtained
from the direct calculations of stresses and displacements by the constitutive equations using the results
of the GFEM. Modifications of the stresses at given integration points are performed to enforce the
following conditions: (a) the satisfaction of boundary conditions on both faces of the laminate, (b)
equivalence with the resultant shear forces, and (c) interlaminar continuity of stresses. The transverse

and in-plane displacements are integrated along the thickness using the three-dimensional local stress-
strain relations for anisotropic layers. The stresses and deflections calculated with the proposed post-
processing are compared with the stresses and deflections obtained in the literature or calculated using

a three-dimensional Finite Element (FEM) analysis that serves as a reference. The proposed stress
recovery procedure, when applied to geometrically nonlinear problems, generate estimates that show a
good correlation with the three-dimensional FEM reference solutions and with the solutions present in
the literature, for all test cases of isotropic, laminated plates and sandwich plates. For the displacements
along the thickness the results are satisfactory, considering that the solution comes from a first order
model.

INTEGRAÇÃO NUMÉRICA NO CONTEXTO DO MÉTODO DOS ELEMENTOS FINITOS GENERALIZADOS THE NUMERICAL INTEGRATION IN GFEM ANALYSIS

Bruna C. Campos, Felício B. Barros, Samuel S. Penna — Mon, 26 Aug 2024 00:00:00 +0000

Structural problems involving variables with a quick change in a small scale of a certain do-
main requires a numerical approach which considers discontinuities, singularities and high gradients.

Fracture Mechanics problems are an example of this kind, considering its process of evaluation of crack
nucleation and propagation. Using the conventional Finite Element Method (FEM) for modelling this

type of situation may be time spending and not achieve great precision due to remeshing and inexact nu-
merical integration. An alternative approach is the Generalized Finite Element Method (GFEM), which

associates FEM with enrichment functions in local regions of the problem. In this paper it is evalu-
ated some strategies for GFEM numerical integration, allowing the representation of non-polynomial

enrichment functions – frequently seen in GFEM for crack modelling – to be more precise with less
processing time when compared to those results obtained with conventional Gauss quadrature rule. The

computational analysis is inserted on the open source software INSANE (Interactive Structural Analy-
sis Environment), developed by the Structural Engineering Department of Federal University of Minas

Gerais.

VIRTUAL ELEMENT METHOD VS FINITE ELEMENT METHOD FOR PRANDTL’S SOLUTION OF ST. VENANT TORSION PROBLEM

Tiago Fernandes Moherdaui, Alfredo Gay Neto — Mon, 26 Aug 2024 00:00:00 +0000

This work presents a comparison of the novel virtual element method and the traditional finite
element method for Prandtl’s solution to the St. Venant torsion problem. The solved field is the Prandtl
function for a given cross-section that experiences torsion. This function is approximated using both
methods with a collection of different meshes. These meshes vary in properties such as the element size,
geometry (Delaunay triangulations and Voronoi tessellations are employed), and polynomial order
(linear and quadratic elements). The numerical error measurement is based on the torsion constant, a
global scalar associated with the solution, with physical significance for the problem. Two different
cross-sections with analytical solutions are used as benchmarks. The results are presented in a set of
convergence curves for each cross-section geometry. The virtual element method showed more
versatility regarding element geometry, while retaining the same convergence properties of the finite
element method.

THE TRIGONOMETRIC WAVELET FINITE ELEMENT METHOD APPLIED TO FREE VIBRATION ANALYSIS OF EULER-BERNOULLI BEAMS

Thamara Petroli, Marcos Arndt, Roberto Dalledone Machado — Mon, 26 Aug 2024 00:00:00 +0000

Over the past years several numerical methods have been formulated so as to not only find the
numerical solution of a mathematical model that describes a phenomenon, but also to find this solution
in the fastest way, with low computational cost and especially, in the most accurate way. One of the
characteristics of the enriched methods based on the Finite Element Method (FEM) is the possibility of
including new shape functions, which are not necessarily polynomial, in the approximate solution space.
The Wavelet Finite Element Method (WFEM) is an example of an enriched method that seeks to find
numerical solutions to engineering problems using the adaptability that Wavelet functions present. The
WFEM is the combination of FEM and Wavelets. WFEM uses the so-called scaling functions as shape
functions, whose linear combination, using the FEM techniques, will describe the approximate solution
space. In this sense, the objective of this work is to study the use of trigonometric Wavelets as enrichment
functions in WFEM for dynamic analysis of structures, seeking to combine the high convergence rates
of enriched methods with the trigonometric Wavelet properties. In this work the trigonometric WFEM
method is applied to free vibration analysis of Euler Bernoulli beams in order to verify its efficiency in
dynamic analysis. The natural frequencies obtained by the WFEM are compared with those obtained
from analytical solutions and by other numerical methods such as the traditional FEM.

DYNAMIC ANALYSIS OF THICK CURVED BEAMS WITH THE GENERALIZED FINITE ELEMENT METHOD

Ramon Macedo Correa, Marcos Arndt, Roberto Dalledone Machado — Mon, 26 Aug 2024 00:00:00 +0000

The traditional Finite Element Method (FEM) is widely applied in the dynamic analysis of

structures, but, mostly, for higher frequencies, a great computational effort is required. In order to de-
crease this computational effort, the Generalized Finite Element Method (GFEM) arise as an alternative.

The GFEM is based on the Partition of Unity Method and it has as its main characteristic the ability to

incorporate aspects of the problem solution into the approximation space, which may decrease the com-
putational effort involved. The curved beam element has received much attention from researchers for

two main reasons: firstly, because it is a very efficient structural element that can span large distances;
and secondly because it provides insight into various aspects of shell element behavior. The curved beam
element is very sensitive to membrane and shear locking. In order to avoid these issues, trigonometric
functions are used to expand the traditional FEM approximation space using the GFEM approach. In this
paper the application of the GFEM for modal and transient analysis of thick curved beams is proposed.
The GFEM results are compared to reference solutions found in literature and traditional FEM results.

COMPARATIVE ANALYSIS OF TRIGONOMETRIC ENRICHMENTS USED IN DYNAMIC ANALYSIS OF TIMOSHENKO BEAMS BY THE GENERALIZED FINITE ELEMENT METHOD

Mon, 26 Aug 2024 00:00:00 +0000

The Finite Element Method (FEM) is widely used in the dynamic analysis of structures, how-
ever it has some limitations. In order to improve the numerical response, enriching functions can be

incorporated to FEM approximation space using the Generalized Finite Element Method (GFEM) pro-
cedure. Several studies have already been carried out to prove the efficiency of GFEM in the dynamic

analysis of bars, Euler-Bernoulli beams, trusses, among other structural elements, but few studies have
investigated the application of GFEM in the dynamic analysis of Timoshenko beams. The present work
aims to contribute to this field presenting modal and transient analyses of Timoshenko beams using the
GFEM technique. Three different trigonometric enrichments are used to perform modal and transient
analyses of Timoshenko clamped-free beams without damping and the results are compared with those

obtained by FEM. The normalized spectrum is obtained by the modal analysis and displacements, ve-
locities and accelerations of the beam along the time are also calculated by transient analysis. In that

manner the efficiency of each GFEM enrichment in modal and transient analysis of Timoshenko beams
is discussed.

NUMERICAL ASSESSMENT OF A STRESS RECOVERY PROCEDURE APPLIED TO STABLE GFEM USING FLAT-TOP PARTITION OF UNITY

Murilo H. C. Bento, Caio S. Ramos, Rafael Marques Lins, Sergio P. B. Proença — Mon, 26 Aug 2024 00:00:00 +0000

The Generalized Finite Element Method (GFEM) is a Galerkin method based on augmenting
low-order FE approximation spaces with functions that well represent local behaviors of the solution.
Since its proposition, the method has demonstrated good performance and has provided higher-order
convergence rates. A particular drawback related to it, however, is the possibility of linear dependencies
between its shape functions, which leads to loss of accuracy and convergence rates decrease. In this
context, stable versions for the method, with modifications in the enrichment functions and Partitions of

Unity (PU), were developed aiming to eliminate these dependencies and keep GFEM optimal conver-
gence rates. On the other hand, it is known that for displacement formulations the stress field coming

from numerical approaches is less accurate than the main displacement field. Very recently, a stress
recovery procedure was proposed for Stable GFEM (SGFEM). This process is based on a weighted L
2
inner product, which leads to a block-diagonal matrix, being therefore very efficient. In this work, we
aim to assess this recovery procedure when applied to SGFEM using Flat-Top PU for quadrilateral FE
meshes. In particular, we evaluate the effect of using Lagrangian PU for weighting the L
2
inner product

used to generate the recovered stress field and the conditioning of this system coefficient matrix. Numer-
ical examples show that the combination of this GFEM version and the recovery procedure in addition

to guaranteeing stability for the solution also provides very accurate stress distributions.

SHIFTED BOUNDARY METHOD FOR POISSON PROBLEMS IN LIBMESH

Vinicius da C. Reis, Alvaro L.G.A Coutinho — Mon, 26 Aug 2024 00:00:00 +0000

The embedded finite element method is one approach to diminish the mesh generation burden in
finite element analysis. It consists of dealing with a description of a boundary that does not necessarily
match the problem’s physical boundary. It can potentially shrink the workflow giving the opportunity
of immediately inputting a CAD geometry or tomographic image into a simulation, without necessarily

using isogeometric elements or performing substantial preprocessing. This work presents an imple-
mentation of the recently proposed embedded formulation for Poisson problems in the general purpose

library libMesh. In the formulation, the boundary condition is shifted and enforced weakly by a Nitsche

approach, and then referred as surrogated boundary. This is accomplished provided the surrogate bound-
ary is close enough to the physical boundary so a Taylor expansion can be used to describe the chopped

off region. This approach provides a significant computational relief compared to the alternative selected

point integration, especially when dealing with complex domains where the total point-locating opera-
tions’ cost can be significantly high. Moreover, computational experiments indicates that second order

convergence can achieved.

A STABLE AND IMPROVED VERSION OF THE GFEM FOR THE ANALYSIS OF PROBLEMS IN ELASTIC LINEAR FRACTURE

Caio S. Ramos, Murilo H. C. Bento, Sergio P. B. Proença — Mon, 26 Aug 2024 00:00:00 +0000

Currently the Generalized Finite Element Method (GFEM) has been widely applied in the
modeling of localized solids failures. Its main advantage consists of the expansion of the Finite Element
Method (FEM) approach space by inserting functions (known as enrichment functions) that best locally
represent the behavior of the searched solution. Such functions may have specific characteristics or even
be generated numerically. On the one hand, the GFEM provides optimal convergence, however, it is
prone to introduce linear dependencies into its system of equations, making the matrix ill-conditioned or
even singular. The so-called stable version of the Generalized Finite Element Method (SGFEM) explores
a modification in the enrichment functions to improve the conditioning of the stiffness matrix. However,

such a modification leads to loss of precision in problems such as strong discontinuities. In order to rec-
oncile the incompatibility between the solution precision and the system matrix conditioning, this work

addresses a new modification of the space of GFEM shape functions associated with enrichment: flat-top

functions as Partition of Unit (PU) and a new PU based on trigonometric functions, these are used exclu-
sively in the construction of enriched shape functions. This new version of the GFEM presents a system

matrix conditioning almost insensitive to the mesh / discontinuity configuration, even if the crack path

approaches the element nodes. In addition, for flat-top PU with a small stabilization parameter, this ver-
sion is almost of the same precision as the GFEM. Since only the PU is modified, the presented proposal

can be easily implemented in pre-existing GFEM codes. Several representative numerical simulations of
benchmark tests are presented to validate the proposal, considering both the accuracy of the solution and
the conditioning of the system matrix.

Estrategia Global-Local Automatizada para o Método dos Elementos Finitos Generalizados

Mon, 26 Aug 2024 00:00:00 +0000

This work presents an automation of the global-local strategy under the Generalized Finite
Element Method approach, evaluating its performance in the analysis of two-dimensional problems of
Linear Elastic Fracture Mechanics. An automated strategy for building local problems, defined in order
to follow the crack growth path, is proposed. Solutions of the local problems, obtained with reduced user
interference, enriches a single global problem. The automated creation of local problems significantly
reduces the time spent in the simulation, which can be quite high for problems involving the propagation
of defects. The implementation was carried out as an expansion of the INSANE (Interactive Structural

Analysis Environment) system, a free software project developed in the Department of Structural Engi-
neering of the Federal University of Minas Gerais. The proposed approach is validated by the numerical

simulation of problems with different characteristics, seeking the extraction of stress intensity factors for
opening modes I and II. Influences of the global-local analysis cycles and polynomial enrichments in the
global problem are considered.

Development of a procedure for the solution of non-homogeneous partial differential equa- tions using the Scaled Boundary Finite Element Method

Karolinne O. Coelho, Philippe R. B. Devloo — Mon, 26 Aug 2024 00:00:00 +0000

The Scaled Boundary Finite Element Method (SBFEM) is a finite element approximation
technique in which the shape functions are constructed based on a semi-analytical approach. Due to its
features, this method is particularly efficient to approximate problems with strong internal singularities,

for instance, fracture mechanics simulation. The main focus of this study is to analyze the approxi-
mation properties of SBFEM and use them to develop a procedure to approximate non-homogeneous

partial differential equations (PDEs). It was observed optimal rates of convergence for problems with
square-root singularity. Furthermore, the orthogonality between SBFEM approximation at the boundary

and the internal bubble functions, which represent the non-homogeneous term, is observed. Such a prop-
erty is applied to extend the SBFEM to approximate non-homogeneous PDEs with internal polynomial

functions. Rates of convergence are computed to demonstrate the effectiveness of this technique.

ANALISE DE MEIOS PARCIALMENTE FR ́ AGEIS VIA ABORDAGEM GLOBAL-LOCAL COM METODOS SEM MALHA

Mon, 26 Aug 2024 00:00:00 +0000

Meshfree Methods have been used as alternatives to Finite Element Method, due to the fle-
xibility in building conforming approximations. Another attractive feature is the capacity of obtaining

approximate solutions of high regularity. Such characteristics can be successfully used to describe state
variables based on the derivatives of the problem solution and responsible for representing the nonlinear

behavior of structures of quasi-brittle material. On the other hand, the lack of the Kronecker-delta pro-
perty, a more complex computation of the shape functions and numerical integration problems represent

drawbacks that can overburden the computational analysis. In nonlinear analysis, the time processing be-
comes an important issue to be considered. Aiming to conciliate the efficiency of finite element analysis

with the flexibility of meshfree methods, coupling techniques for both methods have been proposed, es-
pecially in cases where the nonlinear phenomenon is confined in a small part of the structure. Here, a new

coupling strategy is proposed based on the Global-local Generalized Finite Element Method (GFEM-gl)

to simulate damage propagation in quasi-brittle media. The global domain of the structure is represen-
ted by a coarse mesh of finite elements. The region of damage propagation defines the local domain,

represented by a set of nodes of the meshfree approach called Element Free Galerkin Method (EFG).
This local discretization is responsible for providing a numerically obtained function used to enrich the

approximate solution of the global problem. Numerical examples in two-dimensional domain are pre-
sented to discuss how the meshfree method can efficiently describe the damage propagation, while the

global behavior of the structure is represented by the enriched finite element solution.

STATIC ANALYSIS OF INEXTENSIBLE SUSPENDED CABLES BY THE GFEM

Mon, 26 Aug 2024 00:00:00 +0000

Cable structures have high performance when required for traction and therefore provide
lighter and thinner structures. On the other hand, the shape of the cable may vary according to its
loading, which makes its analysis difficult. The Finite Element Method (FEM) has good results in the
analysis of cable structures, but demands a high number of degrees of freedom to achieve a better
accuracy. In order to evaluate the application of the Generalized Finite Element Method (GFEM) in
suspended cable structures, a simplified cable model is presented, considering a static and inextensible
analysis. The formulation considers the weak form of the inextensible cable problem and does the
enrichment of the shape functions space for the conventional Finite Element Method. The model is

implemented in Python language and tested with applications in the literature. In this work, second-
degree Lobatto’s polynomials are used and also hyperbolic enriching functions are proposed. The

efficiency and convergence of the proposed model are verified and the matrix condition number is
calculated to examine the numerical stability. The application of GFEM for inextensible cable
problem, as presented here, is an original approach. Models based on parabolic or catenary
configuration, when compared with others found in literature, have the closest results with the
analytical solutions. GFEM proved to be an excellent method for cable problems. In conclusion, it is
possible to solve several cable problems with a single element, surpassing the results presented by
FEM.

FLAT-TOP PARTITION OF UNIT IN THE GENERALIZED FINITE ELEMENT METHOD APPLIED TO DYNAMIC ANALYSIS

Mon, 26 Aug 2024 00:00:00 +0000

The Generalized Finite Element Method (GFEM) has presented excellent results in the
dynamic analysis, especially in the obtaining of higher frequencies, one advantage compared to the
standard Finite Element Method (FEM). An important feature of GFEM is the possibility of expanding
the approximation space through the inclusion of non-polynomial enrichment functions, which usually
contain a-priori knowledge about the solution of the problem. However, this enrichment process may
lead a problem considerably ill-conditioned, limiting its applicability. This paper proposes the use of
flat-top functions as a Partition of Unit (PU) for the construction of approximation spaces enriched
with non-polynomial functions, aiming to improve the conditioning of the problem by reducing the

condition number of stiffness and mass matrices. Results are presented for one-dimensional and two-
dimensional problems, such as bars and membranes modal analysis, respectively. The condition

number of stiffness and mass matrices are evaluated and compared with results obtained by GFEM
with approximation spaces constructed with PU linear. Results obtained with the PU flat-top shown
improvement in the conditioning of the problems, with the reduction of the condition number of
stiffness and mass matrices, however with influences in the accuracy of responses.

STUDY OF POLYMOMIAL ENRICHMENT FOR ANALYSIS OF STRUCTURES IN DAMAGE PROCESS USING S/GFEM

Guilherme Olivera Ferraz de Paiva, Francisco Evangelista Junior — Mon, 26 Aug 2024 00:00:00 +0000

This work aimed to implement polynomial enrichment functions, according to the strategy of
the Stabilized Generalized Finite Element Method (S/GFEM), for application in simulations of failure
problems in structures using a bilinear damage model for quasi-brittle materials. The results were
verified by comparison with experimental curves drawn from the three-point bending test in central
notched beam. The efficiency and accuracy of the polynomial S/GFEM were then tested to improve the
prediction of the rupture behavior over a conventional Finite Element analysis. This has become more
evident in simulations with coarse meshes, presenting results with precision equivalent to others found
in the literature, but with a much smaller number of elements.

IMPLEMENTATION OF THE CONVECTED LEVEL-SET METHOD WITH ADAPTIVE MESH REFINEMENT USING LIBMESH

Malu Grave, Jose J. Camata, Alvaro L.G.A. Coutinho — Mon, 26 Aug 2024 00:00:00 +0000

In the computation of flow problems, the modeling of moving boundaries and interfaces
is still challenging. There are different techniques to model such problems: interface-tracking and
interface-capturing methods. Here we study an interface-capturing method called convected level-set.
The difference to the standard level-set method is that the reinitialization step is embedded in the transport
equation model, avoiding a separate step during the calculation. We also use a hyperbolic tangent
distance function to get a smooth truncation far from the interface. We couple this interface-capturing
method with the Navier-Stokes equations to simulate free-surface problems. We implement all equations
on libMesh, an open finite element library that provides a framework for multiphysics, considering
adaptive mesh refinement. Numerical results are presented for classical interface-capturing benchmarks
to study the influence of mesh refinement, time-step, and time discretization. Finally, we present the
results of a free-surface problem, simulating a dam-break benchmark.

ESTUDO CONFIABILÍSTICO DE CHAPAS PERFURADAS UTILIZANDO O MÉTODO DOS ELEMENTOS DE CONTORNO

Mon, 26 Aug 2024 00:00:00 +0000

Neste trabalho, é desenvolvido uma análise da redução do custo computacional no cálculo
da probabilidade de falha de conexões metálicas, utilizando-se de fundamentos da computação
paralela. Na análise, dimensionamento e manutenção de estruturas de aço, verificações no que diz
respeito a requisitos mínimos para um bom funcionamento estrutural se traduzem em critérios quase
sempre definidos como eventos estatísticos, ou seja, as variáveis envolvidas nesses eventos traduzem
incertezas inerentes a fatores presentes em todas as etapas do projeto. O método de simulação de
Monte Carlo surge como uma ferramenta a quantificar essas incertezas presentes, considerando os
parâmetros estatísticos presentes no processo. Embora possa obter respostas satisfatórias, a precisão
está relacionada com o número de simulações executadas para obter uniformidade na solução.
Inicialmente foi desenvolvido um estudo referente à computação de alto desempenho, analisando os
conceitos da programação paralela, bem como os seus principais padrões. Dentre eles, destaca-se o
MPI o qual se baseia no conceito de comunicação entre máquinas paralelas com memória distribuída
por meio da troca de mensagens, e foi escolhido como foco para desenvolver o estudo proposto neste
trabalho. Posteriormente, é elaborado a formulação linear do Método dos Elementos de Contorno
(MEC), desenvolvendo suas equações integrais e apresentando a discretização utilizada no contorno
do problema, através de elementos isoparamétricos com aproximação linear. Em seguida, são
formulados os conceitos da confiabilidade estrutural, com foco no método de simulação de Monte
Carlo. Por fim, é realizado a validação da teoria apresentada com uma aplicação referente à ligação
metálica de uma chapa perfurada. Exemplos foram desenvolvidos e uma significativa melhoria em
termos de custo computacional foi observada quando a computação de alto desempenho (MPI) foi
utilizado em associação com o método de simulação de Monte Carlo. A principal contribuição deste
trabalho é fornecer resultados que apontam as contribuições benéficas da utilização da computação de
alto desempenho em problemas de engenharia. Auxiliando engenheiros e estudantes no
desenvolvimento deste tema, contribuindo para a disseminação e avanço da sua análise.

ASSESSMENT OF EDDY VISCOSITY MODELS IN A RESIDUAL-BASED VARIATIONAL MULTISCALE FRAMEWORK

Gabriel V. Badiola, Alvaro L.G.A. Coutinho, Renato N. Elias — Mon, 26 Aug 2024 00:00:00 +0000

Highly turbulent flows are present in several industrial applications and natural phenomena,
such as flows around aircraft airfoils and turbine blades, fluid-structure interaction problems in offshore
platforms and formation of turbidity currents. In this work, a general family of eddy viscosity models
(EVM) for the large-eddy simulation (LES) of turbulence is implemented in an edge-based stabilized
finite element incompressible Navier-Stokes solver within the framework of the residual-based
variational multiscale method (RB-VMS). We evaluate and compare the different fine-scale eddy
viscosity models proposed by Oberai and Hughes. These models are incorporated into EdgeCFD, a
highly optimized fully implicit parallel edge-based code, with inexact Newton solver and adaptive time
step. The performance and accuracy of the proposed models are tested with validation problems for high
Reynolds numbers. Results are then compared to those of highly resolved numerical simulations and
experimental data and discussed.

A CUDA ACCELERATED NUMERICAL INTEGRATION OF ELASTOPLASTIC FINITE ELEMENTS RESIDUALS

Natalia R. Vilas Boas, Philippe R. B. Devloo, Omar Duran — Mon, 26 Aug 2024 00:00:00 +0000

Finite Element Method (FEM) is a numerical technique to approximate partial differential
equations. It has been widely used to approximate solutions of physical problems in different fields
of research. The numerical simulation challenging engineering problems with small error require fine
meshes and leads to high computational cost. To overcome this difficulty parallel computing is becoming

a mainstream tool. Among the techniques available to improve the performance of this type of computa-
tional application is the execution of the algorithm using Graphics Processing Unit (GPU) programming.

Although GPU was originally developed for graphics processing, it has been used in the last years as a
general purpose machine with high parallelism power through the availability of libraries such as CUDA
or OpenGL. The purpose of this research is to develop an efficient algorithm for the evaluation of the

finite element residual and Jacobian matrix. We target the particular variational formulation of an elasto-
plastic problem with associative plasticity but will try to show that the approach can be extended to other

fields and problems. The presented strategy for the calculation of the residual and tangent matrix rely

on several computational ingredients such as gathering and scattering operations, sparse matrix mul-
tiplications, and a parallel coloring procedure for assembly process. The verification of the nonlinear

approximated solution includes comparison with regular CPU implementation in terms of numerical re-
sults and execution efficiency. For residual computations of elasto-plasticity, the GPU outperforms the

CPU by a factor of up to 10 (details of the architecture are given in the paper).

APPROACH OF A FUZZY PID CONTROLLER INVOLVED IN RASPBERRY ARCHITECTURE PI AND PYTHON: A CASE STUDY OF A THERMAL PLANT

Mon, 26 Aug 2024 00:00:00 +0000

Computational intelligence has several techniques that are executed in several fields for learn-
ing, perception, prediction and control. We can use computational methods allied to fuzzy logic to obtain

control meshes with a minimal degree of error. In this work we have developed a PID controller based
on fuzzy logic written in Python programming language that can be applied to microcomputers such
as Raspberry Pi for control with robustness, reliability and connectivity. The PID, or also known as
proportional integral derivative controller is a method of control of processes that groups computational

executions, generating minimum degree of error. This control was modeled in Python from object ori-
ented programming and with mathematical and fuzzy libraries, executed in a microcomputer, that has

GPIO‘s (General Purpose Input / Output) which are an interface of data input and output directly on
the board and can be connected to sensors / actuators and M2M (Machine to Machine) communication,
which facilitates the final application in industrial or residential plants, crossing concepts of IoT and
Industry 4.0. The PID controller coupled with fuzzy logic produces a fuzzy-PID controller, robust and
dynamic based on IF-THEN rules and pertinence functions, capable of working with linguistic variables
that model physical media based on human cognition. The set of rules used in the code can be extended
to various models and plants, such as in temperature control. The data obtained can be exported and
analyzed in software such as MATLAB, SCILAB, thus obtaining graphs and analyzes in real time, being

able to perform the parallelism with analysis and simultaneous control. We can apply the control algo-
rithm in an electric thermal plant where the desired temperature and the current temperature are input

data of the plant, these values are fuzzified and are processed mathematically based on the system rules,
inference machine and the fuzzy-PID operation, the values where they are transformed into a PWM
(Pulse-Width Modulation) control signal applied to an electric resistance. As one of the goals of control
and automation is to try to minimize human interference in a machine or procedure, making the system
more optimized, safe and efficient. The computational control establishes relations with the automation
area in order to transform processes control as more ”intelligent” and implement decision making so that
their choices are progressively more reliable.

A COMPARATIVE STUDY ON THE USE OF STABILIZED AND FLUX-CORRECTED TRANSPORT FINITE ELEMENT METHODS TO SOLVE THE SHALLOW WATER EQUATIONS

Tulio L. Santos, Alvaro L. G. A. Coutinho — Mon, 26 Aug 2024 00:00:00 +0000

A study is carried out to assess the use of stabilized and flux-corrected transport (FCT) finite
element approaches to solve the shallow water equations. The adopted stabilized formulation employs a
Streamline Upwind Petrov-Galerkin term supplemented by a shock-capturing operator. In the examined
FCT technique, the low-order equation considers an artificial viscosity term based on a Rusanov-like
scalar dissipation. Anti-diffusive fluxes are linearized around the low-order solution and limited with

the Zalesak’s algorithm. Both approaches use semi-discrete finite elements with implicit time integra-
tion over time steps constrained by a CFL condition. Numerical results are presented for standard test

problems available in the literature, and the accuracy and stability of the solutions are discussed.

A COMPARATIVE STUDY OF GLOBAL AND LOCAL PRECONDITIONERS FOR PARALLEL FINITE ELEMENT COMPUTATIONS

Leonardo Muniz de Lima, Andrea M. P. Valli, Lucia Catabriga — Mon, 26 Aug 2024 00:00:00 +0000

Numerous engineering problems require an enormous computational effort to solve large
sparse linear systems with matrices resulting of finite element discretizations. Parallel computing of
GMRES or other Krylov subspace-based method combined with a good preconditioner is an excellent
option to fulfill this role. Mostelly, the two main operations of Krylov subspace methods, the inner
and the matrix-vector products, demand less memory consumption and present better parallelism when
compared with the main operations of the traditional direct solvers. Global storage allows the use of
block Jacobi preconditioners based on incomplete LU factorization. In contrast, local storage schemes

provide preconditioners performed at the element level factorizations (e.g., the local LU, the local Gauss-
Seidel and the diagonal or the block-diagonal schemes). In this work, we present a trade-off analysis

between global and local preconditioners for parallel finite element implementations. In the context of a
specific domain decomposition approach, we evaluate the preconditioners according to memory usage,
load balancing and MPI communication. Robustness and scalability of these parallel preconditioning
strategies are demonstrated for two benchmark cases: the rotating cone modeled by the transient transport
equation, and the explosion problem modeled by the Euler equations. All experiments point out the
supremacy of the global preconditioners, and the local preconditioners dependence on the number of
degrees of freedom per node.

IMPLMENTAÇÃO DE CONEXÃO SEMIRRÍGIDA EM MODELOS RETICULADOS NO CONTEXTO DA PROGRAMAÇÃO ORIENTADA A OBJETOS

Ícaro R. Marques, Pedro C. Lopes, Rafael L. Rangel, Luiz Fernando C. R. Martha — Mon, 26 Aug 2024 00:00:00 +0000

This work presents the implementation of a methodology to simulate semi-rigid joints in two

and three-dimensional framed models using the Direct Stiffness Method. The idea is to add a linear-
elastic rotational spring to the structure by inserting new degrees of freedom to the system of equilibrium

equations to account for the spring rotations. This implementation was incorporated to the LESM
(Linear Elements Structure Model) program, which is an educational open-source program. This
program is based on the Object Oriented Programming (OOP), which was used in order to handle the
problem in a generic fashion. A new class in the context of the OOP was created to simulate the behavior
of semi-rigid joints.

ACCELERATION OF FEM MECHANICAL SIMULATIONS WITH A PARALLEL IMPLEMENTATION IN GPU

Cicero Vitor Chaves Junior, Paulo Marcelo Vieira Ribeiro — Mon, 26 Aug 2024 00:00:00 +0000

Finite element simulations with the use of large scale models are becoming more frequent.
Modern strategies applied to transient problems seize efficient assembly of global matrices as well as the
fast solution of system of equations in models with hundreds of millions of degrees of freedom. The use
of General-Purpose computing on Graphics Processing Units (GPGPU) enables extreme parallelization
and acceleration of these processes. In this direction, the present work presents several applications of

computational mechanics problems using the C ++ programming language coupled to the NVCC (NVI-
DIA CUDA Compiler) for the CUDA platform. These simulations require only native C ++ functions,

without external dependencies. The code was developed in a modular structure, with the hybrid imple-
mentation of subroutines in CPU and Graphical Processing Units (GPU). An iterative solver with the

conjugate gradient method is presented and can be coupled to codes developed in other programming
languages for dedicated GPU solution. CPU solutions using the Eigen linear algebra library are also
developed, and several benchmarks are discussed, including the use of OpenMP for parallel computing
and computations on the GPU using double and single precision accuracy, as well as different GPU
kernels for sparse matrix-vector multiplication (SpMV). Results obtained using the proposed strategies
reveal that computations using the described routines are effective and provide significant speedups over
single-threaded computations.

AN ALGORITHM FOR AUTOMATIC DISCRETIZATION OF ISOGEOMETRIC PLANE MODELS

Mon, 26 Aug 2024 00:00:00 +0000

Mesh generation is an important component of Computer Aided Engineering (CAE) systems.

To generate a high quality mesh, suitable discretization must be assigned to a model’s boundaries. Un-
fortunately, many CAE software packages require considerable user interaction to define appropriate

discretization when models have complex features, such as high curvatures and narrow regions. This
work presents an algorithm for the automatic discretization of boundary curves of plane models capable
of handling complex features. Moreover, the algorithm is capable of producing curvilinear boundary

discretization by taking into account the parameterization of the boundary curves, and these curvilin-
ear boundary discretizations may be used to generate high quality isogeometric meshes consisting of

Bezier triangles. The algorithm has three input parameters, the maximum and minimum edge length ́
and the maximum curvature angle. The proposed algorithm is applied in complex geometric models,
demonstrating its ability to balance mesh size and quality.

ALGORITHM TO PERFORM GENERALIZED ASSEMBLY OF FINITE ELEMENT MATRICES

Natalie von Paraski, Ítalo Rangel P. Mendes, Alexandre da Silva Galvão — Mon, 26 Aug 2024 00:00:00 +0000

Each type of computational system, with its dimension and degrees of freedom, makes the
implementation of the finite element (FE) matrices assembly developments very specific, sometimes
generating unnecessary redundancy in codes, which make them more difficult to understand,
implement, read and update. A generalization of the assembly numerical methodologies for any kind
of FE matrices can give us a unique algorithm that can be implemented once for all FEM
computational problems, without the necessity to create a new code for each different case. This work
presents an algorithm based on the general assembly strategy for finite-elements matrices for plane
frames, implemented in Paraski [2]. This one algorithm tries to extrapolate the previous idea, being
capable to perform the assembly of FE matrices for simple and multi connected systems, not only for
plane frames, with one-dimensional FE bar, having three degrees of freedom, but for other kinds of
finite element types, like FE triangular and quadrilateral in two dimensions, and FE hexahedron and
tetrahedron in three dimensions, all of them having their own variations on their quantity of degrees of
freedom. Some validation tests using MatLab codes for static analysis for plane frames with one
dimensional FE bar, and Helmholtz equations problems with two-dimensional FE quadrilateral, was
successfully made, showing the efficiency of this algorithm being used in different cases, for different
elements working in different dimensions, with specific degrees of freedom.

FINITE ELEMENT MODELLING OF PLANE FRAME SUBJECTED TO RANDOM WIND EXCITATION WITH DYNAMIC ELASTOPLASTIC BEHAVIOR

Hsu Yang Shang, Igor Alexandre Deitos — Mon, 26 Aug 2024 00:00:00 +0000

This work presents a finite element approach of dynamic elastoplastic analysis in plane
frame subjected to random excitation caused by wind action. The wind random velocity is modelled
mathematically by using Power Spectra Density Method in combination with Shinozuka’s model, with
commonly employed wind spectra, such as von Kármán, Davenport, Kaimal and Harris. From these
spectra, the dynamic wind loading is determined from the sum of the mean and floating wind
velocities. Thus, it is possible to obtain the wind loading vector that is applied in the structure dynamic
governing equation. The governing equation is formulated by Euler-Bernoulli beam theory, and it is
discretized by using a conventional Lagrange – Hermite element. The time stepping process is carry
out by HHT algorithm, and the material nonlinearity is modelled by von Mises isotropic hardening
model. Finally, several applications are presented, where different wind spectra are employed to
determine mechanical parameters of structure responses, such as stress, strain, displacement, among
the other. The error norm L2 of displacement is determined for different finite element discretization
refine, which aims to analyze the effects of space discretization in this type of analysis. Also, the
relative differences are determined with the purpose to compare the different mechanical behavior of
structure when subjected to different wind spectra.

SEISMIC INTERFEROMETRY TECHNIQUE FOR BUILDING MONITORING: A COMPUTATIONAL METHOD TO DETERMINE DYNAMIC PARAMETERS

Mon, 26 Aug 2024 00:00:00 +0000

Seismic interferometry applied to environmental vibration data is an advantageous strategy
used to verify structures responses, especially regarding to continuous data logging and in situations
where it is not practical or even unsafe, to allocate dynamic sources. Its application yields important
information about mechanical properties and discontinuities of the medium, since the produced waves
establishes an elastic response regarding the medium in which it propagates. The analysis, after the
monitoring procedure, consisted in an application of a computational technique known as
“deconvolution” of environmental-vibration records to obtain traveling waves and extract the natural
frequency due to the linear response of the building, from peaks of the average power spectrum of
these deconvolved waves. As application, the environmental noise propagated in a five-story building
located at Federal University of Rio Grande do Norte was studied to obtain responses of frequencies.
Accelerometers localized on the floors of the building registered the environmental noise along some
days and, consequently, made it possible to observe the relation between human and environmental
activities and the oscillation amplitude of the signal. To confirm these values, a computational
mathematical model of the building was built, using a commercial software, in order to obtain the
numerical natural frequencies. At last, a critical analysis of the results is performed.

DIFFERENT STRUCTURAL MONITORING TECHNIQUES IN LARGE RC BUILDING: A CASE STUDY

Mon, 26 Aug 2024 00:00:00 +0000

Civil construction area is in continuous technological evolution, either related to new material and
execution techniques or development of analytical and design methods. In Brazil, particularly, standard
codes have been created and updated in the last 10 years due to new studies related to a better behavior
of concrete structures, i.e., ABNT NBR 15961 (2011), NBR 16055 (2012), NBR 15575 (2013), NBR
6118 (2014), etc. These standard codes are fundamental to ensure the safety of structures, qualifying
them for their use. Nowadays, however, it is still able to find recent buildings with obvious pathologies
which are consequence of error and mistakes in different stages of the construction and might cause
the building interdiction or even collapse. Excessive displacements and crack openings in reinforced
concrete constructions represents examples of pathology and require structural intervention to eliminate
or mitigate these effects. After the pathologies correction, it is important to verify the structural behavior
regarding to acting forces, in order to ensure safety and the correct structural performance. In this paper,
a retrofit study was conducted in a large RC building after the structural intervention to correct some
pathologies found. Vertical displacement of slabs and supporting beams was measured in specific points
with auxiliary of dial gauges and precision geometric levelling as the load was applied in increments. In
addition, numerical models were created using the computational programme TQS, which allowed for
grid analogy method, in order to compare its results with experimental values. The results showed good
agreement in terms of vertical displacement and structure behavior. It was possible to validate numerical
results obtained by grid analogy and also certify both the safety and the performance of these structural
elements.

NUMERICAL AND EXPERIMENTAL CORRELATION OF A RECTANGULAR BEAM USING A GUYAN-SEREP MIXED METHOD

Mon, 26 Aug 2024 00:00:00 +0000

Structures and equipment under dynamic loading are susceptible to a vibration response,
which can reduce its reliability and life span. Continuous monitoring can be a complicated and expensive
task, its complexity makes it impossible to always measure vibration in the locations with higher risk of
failure, especially in regions with poor accessibility. One way of estimating vibration levels of the
structure in areas of interest is using numerical Finite Element method models, however, these models
have the disadvantage of not always representing the real structure adequately, as they do not take into
account manufacturing errors and other uncertainties. The differences between model and real structure
may be minimized through calibration using experimental data, nevertheless, another difficulty arises,
as the number of degrees of freedom in the finite element model are a lot bigger than the number of
measured degrees of freedom, therefore, calibration cannot be performed directly. The use of reduction
techniques makes the calibration, regarding the modal parameters, feasible as it allows the compatibility
between model and experimental degrees of freedom, therefore allowing prediction of vibration levels
at any point in the structure. In the present work we have used a mixed GUYAN-SEREP methodology
for the model reduction of complex structures. This process is based on two steps: first, using GUYAN
method to reduce, on the physical domain, the complete model up to a manageable number of degrees
of freedom; then, secondly, using SEREP method to end the reduction, on the modal domain, ensuring
the compatibilization of the degrees of freedom with the available experimental data. This methodology
was applied to a rectangular beam, free-free condition, the results were compared with data obtained by
an experimental modal analysis, by means of MAC, relative difference (RD) and coordinate modal
assurance criteria (COMAC), obtaining high accuracy. Finally, a correlation of numerical modes was
undertaken in relation to the experimental modes yielding improvements on the results for the criteria
used.

MODAL PARAMETER IDENTIFICATION OF A RECTANGULAR BEAM USING EXPERIMENTAL AND OUTPUT-ONLY MODAL ANALYSES

Mon, 26 Aug 2024 00:00:00 +0000

In order to obtain the modal parameters of a structure, different approaches can be used: (i)
Experimental Modal Analysis (EMA), which uses excitation (input) and response (output) data; (ii)
Output-Only Modal Analysis (O-OMA), which uses only the output. Both techniques are widely used
and their advantages and disadvantages are known. The EMA allows performing a full numerical
validation, because the estimated modal matrix is already mass normalized. In the O-OMA case, since
the excitation force is unmeasured, the estimated modal matrix can only be normalized to unity. This
paper aims to identify the modal parameters of a rectangular beam, simulating “free-free” boundary
condition in the excitation’s direction. The beam was instrumented with 9 accelerometers equidistantly
arranged along the length and the excitation was through a multiple reference impact testing. The
modal parameters were identified using the Polyreference Least Square Complex Frequency Domain
method, considering two approaches: (i) EMA and (ii) O-OMA methods. Results from the EMA and
O-OMA showed that the discrepancies between the natural frequencies were at most 0.5%, and all the
vibration modes presented MAC values higher than 0.9. Experimental results were also compared with
those obtained through a finite element model of the rectangular beam, showing small differences both
in the natural frequencies and vibration modes. It is therefore concluded that the two approaches lead
to good estimates of natural frequencies. As for the vibration modes, the modal matrices obtained by
the two methods present a small difference, since the mass of the beam is small.

OUTPUT-ONLY MODAL PARAMETER IDENTIFICATION OF A RECTANGULAR BEAM USING MIMO AND SIMO TESTS

Mon, 26 Aug 2024 00:00:00 +0000

The dynamic behavior of structures can be evaluated through modal parameters, which can
be obtained experimentally, and used to solve vibration problems, in sensitivity analyses, in structural
modification, for numerical and experimental model correlation, for updating numerical model, for
structural health monitoring, etc. The present work aims to identify the modal parameters (natural
frequencies, damping ratios and vibration modes) of a rectangular aluminum beam suspended in the air,
simulating the “free-free” boundary condition. The rectangular beam was instrumented with 09
accelerometers arranged equidistantly along the length. Two types of tests were performed: (i) the
multiple reference impact testing (MRIT), which simulates MIMO (multiple input/multiple output) test;
(ii) the SIMO (single input/multiple output) test, which generates responses in the 09 accelerometers
due to the impacts in 01 degree of freedom. Modal parameters were identified using only the vibration
responses, through two frequency domain techniques: Enhanced Frequency Domain Decomposition
(EFDD) and Frequency-Spatial Domain Decomposition (FSDD). Results showed that the average
difference in natural frequencies estimation with the EFDD technique, using MIMO and SIMO tests,
was 0.25%, a low and acceptable percentage. When comparing EFDD (MIMO test), FSDD (SIMO test)
and FEM model results, the average differences in natural frequencies estimation are 0.33% and 1.63%,
respectively. According to the results, both EFDD and FSDD methods can be used to identify the modal
parameters, with similar results, using either the MIMO or SIMO tests. As the SIMO test demands less
time, it becomes a fast alternative for modal identification of structures.

APPLICATION OF SMOOTH ORTHOGONAL DECOMPOSITION ON DAMAGE IDENTIFICATION

Vinícius Vaguetti da Costa, Guilherme Rosa Franzini — Mon, 26 Aug 2024 00:00:00 +0000

This is an ongoing research in which a Structural Health Monitoring (SHM) methodology,
namely, the Smooth Orthogonal Decomposition (SOD), is employed on damage identification on beams.
In a first step, displacement data from the structure is subjected to a Spectrum Analysis Amplitude and the

most energetic vibration frequencies are acquired. Subsequently, SOD is applied to the same displace-
ment data in order to obtain the linear mode shapes and natural frequencies of the structure. Finally, most

energetic mode shapes are selected by correlation of frequencies obtained on the two previous steps. The
procedure is applied to both a damaged structure and a similar healthy one. Damage spot identification
is achieved by mode shapes comparison of healthy and damaged models. The technique is tested using
Finite Elements models for beams under two boundary conditions, namely, simply supported beams and
cantilevered beams. For each of the two case studies above, numerical models concerning damage in
different spots are generated for comparison. The results show that the method is successful aiming at
identifying structural damage. Robustness and limitations of this procedure are discussed.

NUMERICAL ANALYSIS AND APPLICATION ON COVARIANCE-DRIVEN STOCHASTIC SUBSPACE METHOD IN MODAL PARAMETERS IDENTIFICATION

Yeny V. Ardila, Ivan D. Gomez, Jesús D. Villalba, Luis A. Aracayo — Mon, 26 Aug 2024 00:00:00 +0000

The SSI-COV method (Covariance-driven Stochastic Subspace Identification) is a technique
within time domain modal identification methods that uses ambient vibrations as the input forces for the
identification of modal parameters (natural frequencies, damping ratios and vibration modes). In this
method two alternatives are available for the identification of the state space transition matrix: a)
applying the decomposition property of a shifted block Toeplitz correlation matrix or b) by applying the
shift property of the observability matrix. In this research, the SSI-COV was applied for the
determination of dynamic characteristics (natural frequencies and damping ratios) of a concrete block
of the Itaipú Hydroelectric Dam. This dam is equipped with a monitoring system, currently in operation,
which collects acceleration data. For the implementation, the method was programmed in the Python
language and validated through two types of simulations in which the sensitivity of the method was
evaluated. Then, for the identification of modal parameters of the concrete block, it was applied to the
acceleration records from a sensor installed in it the two alternatives for identification. Finally, the
obtained results from the two variants to compute the state transition matrix allowed us to define that
applying the shift property of the observability matrix is more advantageous in terms of data accuracy
and computational cost.

Damage analysis in metal beams by changes in their natural frequencies.

Rodrigo Vieira Fonseca, Maira Rolla Campos, Claudio José Martins — Mon, 26 Aug 2024 00:00:00 +0000

Nowadays, the concern with structural damages in the civil construction is in growth,
slender structures, of great dimensions, and old or more economic generate constant concern for the
engineers responsible for its maintenance and stability. In this scenario, considering the growing
demand for structural damage monitoring, this paper presents the results of laboratory tests performed
to indicate the feasibility of a simple signal processing method to identify structural damages. This
method consists of experimental tests using a set of accelerometers that were coupled in two metal
beams to obtain acceleration responses at various levels of structural integrity (cuts in the cross section
of the profile corresponding to 80%, 60% and 40% of the original). The recorded accelerations went
through a simple processing of data for identification of natural frequencies. The numerical modeling
of the beams was also performed in the ANSYS software based on the finite element method, from
which the natural numerical frequencies were extracted. Finally, the experimental natural frequencies
were compared with the numerical ones for the validation of the results. It was possible to identify
damages in the two beams since changes in the natural frequency values were identified at all levels of
section integrity. A good approximation between the experimental and theoretical values was
observed, and in this way, it was concluded that the tests were able to detect structural damage
correctly.

A METHOD FOR INFERENCE OF THE UNCERTAINTIES OF THE MODAL PARAMETERS THROUGH THE BOOTSTRAP AND CLUSTERING TECHNIQUES ASSOCIATION

Mon, 26 Aug 2024 00:00:00 +0000

The evaluation of structural integrity is a complex task that has increased the development of
techniques for monitoring the physical responses of structural systems. Monitoring can be accomplished
by acquiring different types of response from the structure to the loads that act on it through continuous
signals in time. These signals can be studied through modal analysis, obtaining estimates of the modal
parameters and, after them, global information of the structural integrity. In this context, it is of
paramount importance to quantify the uncertainties of the estimated modal parameters. An inaccurate
estimate can compromise the entire monitoring of a structure, and thus avoid a possible interruption of
its operation, or even its collapse. This work aims to develop a modal analysis methodology capable of
obtaining more robust estimates and with lower levels of uncertainty of the modal parameters of a
structure through the association of bootstrap, clustering and Data-driven Stochastic Subspace
Identification (SSI-DATA) techniques. To achieve this goal, simulated data of a structural system
subjected to uncorrelated random loading introducing noise are used. Finally, we discuss the results
found for the uncertainties of the estimated parameters.

AVALIAÇÃO DO ACRÉSCIMO DE MASSA EM UM PÓRTICO METÁLICO, ATRAVÉS DO ESPECTRO DE FREQUENCIAS

Mon, 26 Aug 2024 00:00:00 +0000

A investigação estrutural não-destrutiva baseada na Análise Modal Operacional consiste em
uma técnica de determinação dos parâmetros modais (frequências naturais, modos de vibração e taxas
de amortecimento) a partir do registro das acelerações em pontos localizados sobre uma estrutura. Essa
técnica considera apenas as ações de operação como fonte de excitação, evitando, dessa forma, a
interrupção ou paralisação da estrutura. Essa peculiaridade torna a técnica bastante atrativa na análise
de estruturas civis. Este estudo tem por finalidade a obtenção dos parâmetros modais de um pórtico
metálico localizado no laboratório de estruturas do Programa de Pós-Graduação em Engenharia Civil
(PPGEC) do Centro Federal de Educação Tecnológica de Minas Gerais (CEFET-MG), e, a partir desses,
verificar alterações nas matrizes de densidade espectrais devido ao acréscimo de massa. Para atingir tal
objetivo, foram realizados ensaios de campo no pórtico para obtenção dos dados dinâmicos com o
auxílio de acelerômetros e uma modelagem computacional da estrutura, utilizando o método dos
elementos finitos. Os dados obtidos em ambas atividades foram processados, utilizando a técnica de
processamento de sinais e, posteriormente, analisados. Os resultados obtidos no experimento
apresentaram diminuição da frequência natural, à medida que o acréscimo de massa aumentou, o que
respeita integralmente a equação da frequência natural e, consequentemente, permite inferir que o
resultado do estudo foi satisfatório. Além disso, os erros médios das frequências naturais medidos nos
ensaios de campo, quando comparados ao modelo numérico, foram inferiores a 4,0%, o que indica que
o modelo foi calibrado corretamente.

A SPRING-MASS-DAMPER MODEL OF BIPEDAL WALKING TO SIMULATE GROUND REACTION FORCES PRODUCED BY HUMANS

Dianelys Vega, Carlos Magluta, Ney Roitman — Mon, 26 Aug 2024 00:00:00 +0000

The pedestrian-bridge dynamic interaction problem has been the focus of significant research
worldwide due to the increase in vibration problems of footbridges caused by walking pedestrians. On
this topic, several authors have proposed biomechanical models to represent the pedestrian. However,
turning these models practical for use in engineering is still a challenge as numerous experimental results
are needed to validate them and identify their parameters. In this research, a numerical model of bipedal

walking with stiffness and damping was implemented in MATLAB. In parallel, experimental tests in-
volving different volunteers were carried out at the Structures Laboratory of COPPE/UFRJ (LabEst).

The volunteers were asked to walk at three different speeds on a test structure. The step forces were
measured by instrumented force plates and the acceleration nearest to the pedestrian’s center of mass
by using an accelerometer placed on a belt attached at the waist of each subject. In order to validate

this model, the simulated ground reaction forces (GRFs) were correlated with the experimental measure-
ments obtained from force plates, and thus the model parameters were identified. A large number of

Monte Carlo simulations were performed to find the best numerical-experimental correlation for each
case. This work intends to provide a database of parameters for a bipedal walking model aiming the
future use of this model in practice.

MODEL UPDATING ANALYSIS BASED ON BAYESIAN INFERENCE

Michael L. M. de Souza, Ney Roitman, Daniel A. Castello, Thiago G. Ritto — Mon, 26 Aug 2024 00:00:00 +0000

The aim of this work is to estimate unknown system parameters based on observed dynamic
data, e.g. natural frequencies and damping rates. These dynamical inputs are extracted from experimental
modal analyses on a simply supported aluminum beam. Measurements come from three accelerometers
and the input excitation is provided by an impact hammer. The experimental setup is submitted into a
process of assembling and disassembling the beam for the purpose of increase the variability of modal
data. The Young’s modulus and the coefficients of the proportional damping model are considered the
updating variables in this study. The exploration of the posterior density function (pdf) of these unknown
model parameters is performed by a novel Markov Chain Monte Carlo method (MCMC) named Delayed
Rejection Adaptive Metropolis (DRAM). In other words the Bayesian paradigm for inverse problems
is adopted to tackles the structural identification. The impact of two likelihood functions at posterior
parameter distributions is analyzed.

STRUCTURAL MONITORING SYSTEM The use of Accelerometers for Structural Analysis

Eng. Ricardo Luiz Coutinho, MSc. Eng Renato Raposo, Eng. Claudemar Moura — Mon, 26 Aug 2024 00:00:00 +0000

due to the high investment for construction, the major disorders and risks that involve the
maintenance of Special Artworks (OAE - Obra de Arte Especial in Portuguese), increases the
importance of monitoring the performance of these works to ensure the project has been adequacy of
the project to the actual conditions of service. Monitoring the performance of these structures ensures
planning to aim to prolong the average times between maintenance and decreasing repairs downtime.
This study seeks to analyze the movements of arrows at a viaduct stringer, verifying its behavior
compared to that specified in structural previous design. The applied methodology consists in the
implantation of sensors in part of the structure, aiming to capture the displacement caused by the bending
moment. The results are aimed at the creation of computational modeling with the aid of a specific
computer program to compare the behavior of the viaduct loaded with data from the calculation
memorial with the data presented in the readings performed by the sensors of monitoring in a given
charging period.

INVESTIGAÇÃO DE DANOS EM PLACA USANDO OTIMIZAÇÃO DE SEGUNDA ORDEM

Mon, 26 Aug 2024 00:00:00 +0000

The need to monitor the condition of the structures is of fundamental importance for safety
and perfect use. With this, the numerical analysis allows significant cost reduction in a possible real
analysis of the structure. Methods of identifying structural damage are increasingly developed and
applied more easily in Structural Engineering. This paper applies the discretization of a structural
element of plate in finite elements and through comparisons of the static and dynamic responses of this
structure reaches an optimal solution for the inverse problem of damage identification. In order to
achieve the optimal solution, the second order optimization of Broyden-Fletcher-Goldfarb-Shanno
(BFGS) and Davidon-Flecher-Powell (DFP) methods coupled to an objective function is used in this
paper, which deals with the solution in identification of internal damage to the structure, which will be
compared to each other, highlighting the one with the best efficiency in plate structure. The minimization
of the residuals between the static (displacement) and dynamic responses (natural frequencies of
vibration) between the predicted damages and the actual damage allows the observation of the structural
mechanical behavior and with it the identification of the damage in the structure.

HIERARCHICAL MODELING OF SHEAR-WALLS STRUCTURES

Mon, 26 Aug 2024 00:00:00 +0000

The consideration of the horizontal displacements and forces produced by lateral actions
such as wind or earthquake is mandatory for tall buildings. In order to reduce the effects generated by
bending and twisting of the building, structural systems known as "bracing" are used. As examples of
these systems, there are frames and shear-wall elements; this last one, usually located inside the
buildings, with a small thickness when compared to the other dimension of the cross section. The
Brazilian design of concrete structures standard code (NBR 6118:2014) has some procedures related
to the shear-walls analysis. Although the NBR 6118 considers it as a surface structure, this code
permits its representation by a linear element. This structural model simplification has advantages, but
nowadays, considering the wide access to computational softwares for structural analysis, it is
important to evaluate the shear-wall behavior and internal forces with more complex models. This
paper analyses several mathematical models with increasing degree of complexity (hierarchical
modeling) to simulate usual geometries of shear-walls such as rectangular, U, lipped-U and E sections,
evaluating their behavior by a Finite Elements code. The results were compared to those obtained from
the evaluation of a model considered more complex called the “comprehensive mathematical model”.
In addition, the main theoretical concepts of the hierarchical modelling are discussed.

METODOLOGIA ESTATÍSTICA PARA REMOÇÃO DOS EFEITOS OPERACIONAIS DAS RESPOSTAS DINÂMICAS DE UMA TORRE DE TELECOMUNICAÇÕES

D. Ribeiro, J. Leite, A. Meixedo, N. Pinto, R. Calçada — Mon, 26 Aug 2024 00:00:00 +0000

This paper describes a statistical methodology for removing the influence of operational
factors from the dynamic responses of a telecommunications tower. The characterization of the
dynamic responses of the structure, over a period of 3 months, was based on a continuous monitoring
system that included accelerometers and anemometers. The analysis of the results allowed to identify a
significant number of critical events, for which the dynamic response under wind action is amplified,
as well as sporadic events, associated with high peak acceleration values, due to the influence of
operational factors related to the lift movements, technical staff and equipment. Automatic
identification of critical events based on extreme acceleration values requires the prior removal of
operational effects from the records, which was performed using a methodology based on the crest
factor (CF) and autoregressive models (AR). The methodology demonstrated efficiency and
robustness in eliminating acceleration peaks due to operational factors, as well as being
computationally efficient, minimizing the possibility of false positives in the identification of critical
events. The developed methodology has potential be integrated in a Structural Health Monitoring
(SHM) system in order to evaluate the safety and operational conditions of the tower.

FINITE ELEMENT NUMERICAL IMPLEMENTATION OF A MICROMECHANICS-BASED VISCOELASTIC MODEL FOR FRACTURED GEOMATERIALS

Mon, 26 Aug 2024 00:00:00 +0000

The constitutive behavior of geomaterials is generally affected by the presence at different
scales of discontinuity surfaces with different sizes and orientations. According to their mechanical
behavior, such discontinuities can be distinguished as cracks or fractures. Fractures are interfaces that
can transmit normal and tangential stresses, whereas cracks are discontinuities without stress transfer.
As far as the formulation of the behavior of materials with isotropic distribution of micro-cracks or
fractures is concerned, previous works had essentially focused on their instantaneous response induced
by structural loading. Few research works have addressed time-dependent (delayed) behavior of such
materials. The present contribution describes the formulation and computational implementation of a
micromechanics-based modeling for viscoelastic micro-fractured media. The effective viscoelastic

properties are assessed by implementing a reasoning based on linear homogenization schemes (Mori-
Tanaka) together with the correspondence principle for non-aging viscoelastic materials. It is shown

that the homogenized viscoelastic behavior can be described by means of a generalized Maxwell
rheological model. The computational implementation is developed within the finite element
framework to analyze the delayed behavior of geomaterials with presence of isotropically distributed
micro-fractures under plane strain conditions. Several examples of applications are presented with the
aim to illustrate the performances of the finite element modeling. The accuracy of the approach is also
assessed by comparing the numerical predictions with analytical solutions.

MICROMECHANICS-BASED CRITERION FOR MICRO-FRACTURE PROPAGATION IN VISCOELASTIC MATERIALS

Cássio B. Aguiar, Samir Maghous — Mon, 26 Aug 2024 00:00:00 +0000

Most of engineering materials exhibit natural or load-induced fractures, which strongly
affect both the instantaneous and delayed mechanical behaviors at macroscopic level. Unlike cracks,
fractures are mechanically regarded as interfaces able to transfer normal and tangential efforts. The
aim of this paper is to formulate the conditions for fracture propagation in randomly-micro-fractured
viscoelastic materials. The homogenized viscoelastic relaxation tensor was formulated by applying the
correspondence principle upon the already-known homogenized elastic stiffness tensor. Extending the
Griffith-like thermodynamic framework to the macroscopic viscoelastic context, the propagation
criterion is first formulated, once again comparing the energy release rate to the critical energy.
Mathematical evidences shows the energy release rate is written as the derivative of the macroscopic
elastic energy, written to the viscoelasticity, with respect to the parameter which represents the
damage in the macroscopic scale. Under certain conditions, the elastic energy derivative can be
simplified, being reduced only to an instantaneous term, leading to a simplified propagation criterion.
It was notably found that for constant strain loadings, the fracture propagation is exactly driven by
elastic components. Analyses performed for constant strain rates on specimen made of Burger solid
matrix show that the energy release rate increases from zero to a constant asymptotic value. This
asymptotic energy release rate is used in a time-independent propagation criterion, evidencing an
interval to initial damage parameter where the propagation is possible. The main contribution of
asymptotic energy release rate, however, refers to the estimative of final damage parameter after the
end of propagation.

EVALUATION OF EFFECTIVE THERMOELASTIC PROPERTIES OF PERIODIC COMPOSITES USING A THREE-DIMENSIONAL FINITE-VOLUME MODEL

Camila S. Vieira, Severino P. C. Marques — Mon, 26 Aug 2024 00:00:00 +0000

The prediction of the effective thermomechanical behavior of composite materials has been
a matter of great interest over the last decades. This is justified because in many important industrial
applications such materials are subjected simultaneously to high thermal gradients and mechanical
loading. The level and distribution of the stress and strain produced by these actions are strongly
dependent on the microstructural details of the composite. This work presents a theoretical study on
the evaluation of the effective thermoelastic properties of composites with periodic microstructures.
The focused effective properties are the elastic moduli and thermal expansion coefficients. For this
end, it is applied a three-dimensional micromechanical model based on the parametric finite-volume
formulation. In the employed three-dimensional model, the repeating unit cell of the composite is
discretized into hexahedral subvolumes to capture the in situ microstructural details. The effective
thermal expansion coefficients are evaluated using the well-known Levin’s formula. To demonstrate
the efficiency of the homogenization model, numerical examples of periodic composites reinforced by

short and long aligned fibers are presented and their results are compared with analytical and finite-
element solutions.

ANALISE TERMOMECÂNICA DE MATERIAIS COM GRADAÇÃO FUNCIONAL

Diogo R. Ramos e Silva, Marcelo S. Medeiros Junior, Evandro Parente Jr. — Mon, 26 Aug 2024 00:00:00 +0000

Materiais com gradac ̧ao funcional (MGF) foram primeiramente estudados no Japão no inicio
da decada de 1980. Esses materiais foram desenvolvidos para atuar como barreiras térmicas em reato-
res de fusao e na indústria aeroespacial, devido aos elevados gradientes de temperatura as quais estas
estruturas sao submetidas. Esse tipo de composito geralmente é formado por dois materiais, usualmente
ceramica e metal. O uso da ceramica proporciona melhor comportamento frente a cargas térmicas,
enquanto que melhores propriedades mecanicas são obtidas graças a matriz metálica. As fraçõees de
volume variam ao longo de uma direção predefinida para se obter o comportamento termomecanico desejado. Devido a variação das propriedades mecanicas, a obtenção de soluções analíticas para estru-
turas com MGFs se torna mais difícil, sendo necessaria a utilização de métodos numéricos para análise

de estruturas com MGFs. Portanto, neste trabalho realiza-se um estudo sobre a aplicac ̧ao de MGFs a
placas submetidas a diferentes cargas mecanicas e térmicas. Para isso, são implementadas sub-rotinas
de usuario (UMAT e UMATHT) no programa de elementos finitos ABAQUS de forma a representar a
variação espacial das propriedades termomecanicas. Diferentes métodos de homogeneização são utiliza-
dos para avaliar as propriedades efetivas desses compositos como função das frações de volume. Neste
trabalho, as cargas mecanicas e térmicas são aplicadas e os resultados são comparados com soluções
anal ́ıticas encontradas na literatura, as quais consideram o desacoplamento entre os campos termico e ́
mecanico. Após a validação, realiza-se um estudo parametrico que considera diferentes métodos de
homogeneização e frações de volume.

A STUDY ON EFFECTIVE THERMAL CONDUCTIVITIES OF PERIODIC COMPOSITES REINFORCED BY UNIDIRECTIONAL LONG FIBERS

Eduardo N. Lages, Severino P. C. Marques — Mon, 26 Aug 2024 00:00:00 +0000

Due to their excellent physical properties, the composite materials have achieved an
increasing field of industrial applications over the last decades. In many of these applications such
materials are subjected to high thermal gradients which can generate critical stresses and strains. The
magnitude and distribution of the thermal fields induced inside a device or structural element have
strong dependency on the composite microstructure. For the analysis and design of these composite
systems under thermomechanical loading, the effective thermal conductivity of the material is a
property of paramount importance. This effective property depends on many microstructural details,
such as, volume fractions and thermal conductivities of the constituent phases, geometrical shapes and
distribution of the fibers, among others. The present work consists in a theoretical investigation on the
influences of the cross section geometry and volume fraction of the fibers and the contrast between
thermal conductivities of the phases of unidirectional periodic fiber reinforced composites. To develop
the study, a semi-analytical model expressed in terms of Fourier series and based on the thermal
equivalent inclusion strategy is employed. Those mentioned influences are illustrated and discussed
for several numerical examples. Results obtained by other homogenization procedures available in the
literature are also presented to demonstrate the efficiency of the model used in the study.

EXPERIMENTAL AND MICROMECHANICAL APPROACH TO ELASTIC PROPERTIES OF PERVIOUS CONCRETE

Vanessa F. Pasa Dutra, Samir Maghous, Angelo S. Pessutto, Bruna Gonçalves — Mon, 26 Aug 2024 00:00:00 +0000

Pervious concrete refers to a material composed by Portland cement, coarse aggregate, little
or none fine aggregate, water and, at times, additives and additions. The pervious concrete porosity
affects its elastic properties, as pointed by available studies. In the perspective of a wide use, a
comprehensive formulation of the corresponding behavior is necessary. In this context, the present
study describes a micromechanical model for the macroscopic elastic properties of the pervious
concrete. Reasoning on the representative elementary volume (REV) of such a composite, the overall
elastic characteristics are determined from the knowledge of the elastic properties of its constituents
(aggregate + cement paste + pores). Moreover, aiming the comprehension of the elastic and strength
behaviors of pervious concrete produced with local supplies (Porto Alegre, RS), this work evaluates
experimentally the following parameters: elastic modulus and uniaxial compressive strength. The
results show how the elastic properties are related to the porosity of pervious concrete produced with
local materials and confirm the possibility of estimating the elastic properties through the
micromechanical approach.

EDUCATIONAL CODE TO COMPUTE PERMEABILITY OF POROUS MATERIALS USING HOMOGENIZATION, MICRO-CT AND FEM

Mon, 26 Aug 2024 00:00:00 +0000

In this work, we present a description of the method and an educational program to
determine permeability of a porous media considering the microstructure of pores provided by micro
computed tomography (micro-CT) images using numerical homogenization based on finite element
(FE) implementation. Permeability is a very important parameter for transport analysis that is
commonly determined in laboratorial tests using the Darcy’s law. However, laboratorial tests can be
expensive, time-consuming and do not offer a deep understanding of the internal structure of the
material. An alternative and efficient strategy to determine permeability of porous materials
considering their microstructures is by means of numerical homogenization technique. In this strategy,
determining permeability requires dealing with a multiscale problem, where the determination of the
macro parameter relies on the simulation of a fluid flowing through canals created by connected pores
presented in the material’s internal microstructure. This paper aims to explain how to model a Stokes
flow through the porous media using FE code implemented in MatLab/Octave to compute materials’
permeability. The boundary value problem is modeled with periodic boundary conditions and a unit
gradient pressure applied in the desired direction to obtain the macro parameter. The velocity field
caused by the prescribed pressure gradient is determined solving the Stokes equation. Lastly, the micro
and macro scales are linked together with the average volume flow rate and the unit pressure gradient
using Darcy’s law. The accuracy of the method depends on reliable computational models, therefore
micro-CT has an important role in numerical homogenization generating representative virtual models
for numerical simulations.

THE MODE LOCALIZATION PHENOMENON IN TURBINES BLADES

Gabriel M. Cavalheiro, Reyolando M. L. R. F. Brasil, Henrique C. Margon — Mon, 26 Aug 2024 00:00:00 +0000

We present a numerical study of vibration modes localization phenomenon in blades of
aeronautical turbines. This kind of equipment is an example of a class of structures called periodic, that
are composed of a sequence of a large number of nominally identical substructures, the blades
themselves, lightly coupled by their hub. In the case they are really equal, the vibration modes will
extend to the whole set of substructures. If, as is to be expected of real machinery, there are very small
differences between the dynamic characteristics of the blades (stiffness, mass etc.), the mode localization
phenomenon may occur.
For localized modes, energy may get to be restricted to very few or even a single one of the substructures,
the turbine blades. This unexpected behavior may lead to catastrophic failure of the affected part due to
excessive vibration amplitude or accelerated fatigue considerations.
Our 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.

FINITE DIFFERENCES FOR PLATES MODAL ANALYSIS

Adson Batista, Reyolando M.L.R.F. Brasil — Mon, 26 Aug 2024 00:00:00 +0000

Plates are flat structural members with a thickness much less than the other two dimensions,
loaded in the direction perpendicular to the plane containing these two larger lengths. In case the
thickness does not exceed 1/10 of the other dimensions, these structures are called thin plates. In this
case, it is possible to adopt the so-called classical thin plate theory of plate dynamics, developed by
Lagrange / Sophie-Germain, in which Kirchhoff's hypotheses are given as valid. Due to the difficulty of
obtaining analytical solutions for the differential equations that govern this structural model, and to the
advancement of software and computational hardware, numerical methods have been used in the
modeling of this type of structural system. Our objective in this paper is to present modal analysis of
aircraft plates using a computer implementation of the Central Finite Differences Method. The
numerical results will be compared to solutions available in the literature. The numerical method of
finite differences is an approach to obtain the approximation of the solution of differential equations.
The basic idea of this method is to transform the resolution of a differential equation into a system of
algebraic equations, replacing the derivatives by differences.

NUMERICAL SIMULATION OF DYNAMIC LARGE DISPLACEMENTS OF HALE AIRCRAFT WINGS

Reyolando M.L.R.F. Brasil, Lucas F. Picchi, Amanda P. Perroni — Mon, 26 Aug 2024 00:00:00 +0000

We revisit a classical structural engineering problem, fist solved by Euler and Bernoulli, that
of large transversal displacements of cantilever beams. Their pioneering work, in the 16th century,
stablished that curvature is proportional to the applied bending moment. In this context, many posterior
authors simplified the resulting differential equation by assuming that, for small displacements, this
curvature could be taken as the second partial derivative of the beam’s axis transversal displacement
with respect to the its longitudinal coordinate. This assumption may be adequate for Civil, Naval and
Mechanical Engineering usual purposes, as in these fields of application such displacements are usually
small. In recent aerospace applications this assumption is no long acceptable. HALE (High-Altitude
Long-Endurance) aircraft wings are known to undergo large flexural displacements, due to their
relatively small stiffness. Further, they are usually built of new high technology flexible materials. Thus,
it is a design necessity to evaluate its deformed shape along time as it interferes with aeroelastic and
aerodynamic concerns. In this paper, we present a simple, low cost, numerical solutions of the exact
Euler-Bernoulli differential equation of the “elastica”, to be compared to contemporaneous nonlinear
large-scale Finite Element models via available either academic or commercial codes. The proposed
algorithms basically numerically integrates the exact Euler-Bernolli differential equation using the
MATLAB ode 45 code. The goal is always simulation of the dynamic behavior of such aircraft wings
under turbulent aerodynamic excitation.

INFLUENCE OF AXIAL FORCE ON THE DYNAMIC CHARACTERISTICS OF A BEAM SUPPORTING A ROTATING MACHINE

Flávio José Garzeri, Reyolando M.L.R.F. Brasil — Mon, 26 Aug 2024 00:00:00 +0000

We present an experimental study of the effects of geometric nonlinearities on
vibrations of rotating machines support structures. Dynamic characteristics of structures depend on
their stiffness, damping and mass. The initial stiffness of a structure, computed in its unloaded state, is
affected by the applied forces, the so-called geometric stiffness. Compressive forces reduce the
stiffness and the frequencies and may lead to buckling, for zero frequencies.
In bases of machines excited by the supported equipment, vibrations may affect the structures but,
in general, they may generate damage to the suspended equipment and the quality of the production.
Although machine support structures are, as a rule, very bulky, little affected by geometric
stiffness considerations, the tendency of modern structural engineering, especially in aerospace
applications, is towards slender members, due to more efficient materials and powerful analysis tools.
Here we study these effects via experimental methods designed to evaluate previous
mathematical models. Our model is a metal beam under compression supporting a DC motor. We
suppose the original design provided natural frequencies away from the excitation frequency.
Nevertheless, the presence of large axial compressive force will reduce the beam stiffness and natural
frequencies leading to unexpected, potentially dangerous resonance states.
Experimental imperfections led to observation of interesting phenomena not predicted in our
previous theoretical and numerical studies. We also observe, as expected, occurrence of the so called
Sommerfeld Effect, when underpowered excitation sources get their rotation regime stuck at
resonances.

ANALYSIS OF THRUST EFFECTS ON DIRECTIONAL STABILITY OF A SIMPLIFIED 2-DOF MODEL OF AN ELASTIC ROCKET STRUCTURE

Leandro Petrini-Jr., Reyolando M. L. R. F. Brasil — Mon, 26 Aug 2024 00:00:00 +0000

A simplified model of a rocket structure by means of a 2-DOF, lumped parameter Beck
column analogue was studied through stability analysis by Lyapunov’s first method linearization of the
equations of motion around equilibrium under different thrust intensities and spring constants. The
equations of motion were generated from the analytical differentiation of the Lagrange’s equations
with dissipative effects lumped into a Rayleigh function and external forces represented by the action
of a single follower force, which is tangent to the nozzle.

SPACECRAFT ATTITUDE CONTROL SYSTEM DESIGN CONSIDERING FUEL SLOSH DYNAMICS AND PARAMETERS ESTIMATION

Alain G Souza, Luiz C Gadelha de Souza — Mon, 26 Aug 2024 00:00:00 +0000

The design of the satellite Attitude Control System (ACS) becomes more complex when the
satellite structure has great number of components like, flexible solar panels and antennas, mechanical
manipulators and tanks with fuel. Besides, the ACS performance and robustness depend on the effects
of dynamics interaction between these components being considered in the satellite controller design.
When the satellite is performing a translational and/or rotational maneuver the fuel slosh motion can
change the center of mass position damaging the ACS accuracy. Therefore, controller performance and
robustness depend not only on a good control technique but also on the knowledge of the system
interactions characteristics. In this paper one apply the Linear Quadratic Regulator (LQR) technique to
designs the ACS for a rigid satellite with a partially filled fuel tank taking into account the slosh
dynamics using mechanical analogies type pendulum. During the LQR controller design some physical
parameters of the system are estimated using the Kalman filter technique. The focus of the estimation is
the length of the pendulum which represents the sloshing dynamics. The investigation is performed
considering planar maneuver of the satellite caused by fixed thruster.

NONLINEAR DYNAMIC STUDY OF A SIMPLIFIED SOLAR SAIL STRUCTURE

Lucas Sardinha de Arruda, Reyolando M.L.R.F Brasil — Mon, 26 Aug 2024 00:00:00 +0000

We propose a nonlinear dynamic study of a solar sail model, to understand the structural
response of large lightweight appendages in space environment and to set an adequate procedure to
simulate one. Initially, a static linear/nonlinear analysis is carried out using the commercial software
ABAQUS® and an implemented nonlinear algorithm to determine the limit conditions of this structure.
After that, we perform a dynamic simulation in order to determine the real impact of the nonlinear
assumption in the final response of this lightweight model. The numerical algorithm is written in
MATLAB® language and based on a ‘composite scheme’, where the first sub-step solution is obtained
via the trapezoidal rule, and for the second sub-step solution, a 3-point Euler backward formula is
employed. The dynamic equilibrium at each load step is achieved via a path following methodology,
seeking to solve the nonlinear systems of equations derived from the time integration procedure. The
proposed 450m2

solar sail is modelled as a kite-shape structure, consisting of four-swallow lattice
members kept in the cross configuration by guyed cables, each one modeled with nonlinear space truss
elements. To represent working conditions, solar wind pressure is applied at the upmost elements of
the lattice members in conjunction with a set of concentrated forces at the corners of the cross
configuration to represent the cables linking the appendage to a supposed mother spacecraft/satellite.

A DYNAMIC ANALYSIS STUDY OF AIRCRAFT SEAT CONFIGURATION FOR CRASHWORTHINESS

Lucas T. Farias, Fábio Matiello, Rogério J. Marczak — Mon, 26 Aug 2024 00:00:00 +0000

Every day, around 180,000 commercial flights transport people to all parts of the globe.
Although the airplane is one of the safest means of transportation, it is well known that when accidents
occur many lives are at risk. Through dynamic simulation, these situations can be computationally
modeled to understand the forces, velocities, displacements, and accelerations acting at the plane
components/ passenger model and more suitable materials, convenient geometries and seat structures
can be tested/ improved to increase passenger’s safety. In the present work, a specific guideline is
developed in the software LS-DYNA for those who are interested in this type of research. From
import/create the aircraft CAD seat geometry, meshing the model, dummy positioning, belt fitting,
contact definitions, setting the boundary conditions and model parametrization, to post-processing, a
simple example is given showing the step by step procedure to model an aircraft seat with a dummy in
emergency landing conditions. The result is to obtain the head injury criterion (HIC) for this example
and compare with the ones found in literature, showing the importance of studying passenger's safety
and keep improving their survival conditions in emergency landing situations.

MATHEMATICAL MODELING AND DYNAMICS OF TWO TETHERED SATELLITES: RIGID BODY APPROACH

André Fenili, Leonardo Monteiro Mazzariol — Mon, 26 Aug 2024 00:00:00 +0000

A two-dimensional nonlinear mathematical model for two tethered satellites is developed.
This complex system comprises of a long cable (also known as tether or, in this case, space tether)
connecting two masses (satellites). Tethered satellites can be used in a variety of space applications
such as electrodynamic propulsion, energy harvesting, momentum exchange, artificial gravity, etc. As
a first rough mathematical model, the cable connecting the satellites is approximated by two
connecting rod-like rigid bodies. If these rods are not aligned, it is assumed that the cable is not
stretched (i.e. the cable is not under tension). This is an undesirable situation for this type of system.
The whole system is allowed to rotate and translate only on a two-dimensional space. The set of
ordinary differential governing equations of motion are obtained using the Lagrange ́s equations
approach. These nonlinear equations are numerically integrated and the dynamics of the system is
investigated under several practical circumstances.

SEARCHING FOR "DISTANCE-STABLE" ORBITS FOR A SPACECRAFT TO OBSERVE THE TRIPLE ASTEROID 2001SN263

Antonio F. B. A. Prado — Mon, 26 Aug 2024 00:00:00 +0000

Missions to asteroids are very popular in current space research, for many reasons. In the
scientific side, it is believed that some asteroids have information about the original cloud of particles
that formed the Solar System in the past. There are also commercial reasons, with a large interest in
exploring minerals from asteroids, and even planetary defense related studies, searching for
alternatives to avoid a collision of an asteroid with the Earth. The objective of the present paper is to
search for stable orbits to locate a spacecraft that has the goal of observing the triple system of
asteroids 2001SN263. This is a very interesting system and a very good candidate to receive a
spacecraft. Trajectories near the primary body, in the middle of the orbits of both smaller bodies of the
system and outside the orbit of the external satellite body are investigated. A new definition of
stability for the orbit is made, with a very practical goal, which is to keep the spacecraft-primary body
distance inside a given interval. We called this type of stability "Distance-Stability". Preferred orbits
are found in the three regions studied, and a physical explanation is made, based in the integral of the
accelerations received by the spacecraft.

EVALUATION OF THE APPROACHING TRAJECTORIES FOR LANDING ON THE ASTEROID 216 KLEOPATRA

Evandro Marconi Rocco — Mon, 26 Aug 2024 00:00:00 +0000

The goal of this work is to evaluate some orbital trajectories seeking the approaching for
landing on surface of the asteroid 216 Kleopatra. This asteroid, discovered by Johann Palisa in 1880,
has a very irregular shape with approximate dimensions of 217 x 94 x 81 km. Due to its shape, the
gravitational field around the asteroid cannot be considered central. Thus, a spacecraft approaching the
asteroid is subject to orbital perturbations, which can hinder the vehicle to describe the nominal
trajectory. In maneuvers for approach and landing, the trajectory deviations may result in very high
approach velocities, making impossible the soft landing on the surface of the asteroid. In addition, the
rotation of the asteroid is another difficulty for missions aimed at the soft landing. Due to the irregular
shape of the asteroid the relative distance between the surface and the spacecraft varies significantly
depending on the orbital plane adopted for the trajectory. In this work, the intention is to evaluate,
through numerical simulations, orbits of a spacecraft around the asteroid Kleopatra more appropriate
to get closer to the asteroid in order to minimize the relative velocity between the surface and the
spacecraft. For this, was used a polyhedral model of the asteroid's volume, based on radar
measurements from the Arecibo Observatory, to model the non-central gravitational field generated by
the heterogeneous mass distribution of the asteroid. Using the model of the gravitational field and the
simulation environment Spacecraft Trajectory Simulator (STRS), several approach paths were
simulated and compared in order to assist the choice of trajectories, considering the minimum value
for the velocity with respect to the surface at the point of the trajectory with minimum altitude.

ASSESSMENT OF SUB-OPTIMAL SDRE CONTROL SYSTEMS PERFORMANCE BY DEFINING A SET OF RANDOM WEIGHTING MATRICES

Leonardo M. Mazzariol, Andre Fenili — Mon, 26 Aug 2024 00:00:00 +0000

It is well known that the design of a huge class of non-linear control systems depends heavily
on the state-space representation of the to-be-controlled system. So, the task of choosing appropriate
control parameters for the nonlinear system’s stability and performance requirements tends to be time
consuming, tedious and relies mostly on the designer’s experience. The work presented here evaluates the
system performance using sets of random weighting matrices as input for the feedback control technique
based on the State-Dependent-Riccati-Equation (SDRE). These randomly generated sets are obtained by
using Monte Carlo sampling and UQLab, then evaluated using numerical simulations of two one degree
of freedom strongly non-linear systems and a slewing flexible structure. The results showed that these
sets serve as an interesting tool to map controllable regions of interest while allowing the designer to
visualize the effects of these weights on the system’s constraints and the performance requirements of
the systems response.

MATHEMATICAL MODELING, LINEAR CONTROL AND CONTACT DYNAMICS OF A UN- DERWATER VEHICLE WITH 2 DEGREES OF FREEDOM

Eduardo dos Santos Sousa, Andre Fenili — Mon, 26 Aug 2024 00:00:00 +0000

This paper investigates the contact dynamics of a hybrid underwater vehicle operated remotely.
In this first model, the vehicle has two degrees of freedom, executing the movement of submersion and
rotation around it‘s center of mass. The main activity of such vehicle is to perform inspections on
underwater and naval structures. For this, it is equipped with a set of motorized tracks. In this model,
two points of contact will be considered along the length of the motorized tracks. Each of these points,
when in contact, caracterizes a solution to the problem. The contact occurs on horizontal surface with
complicity. To analyze this phenomenon will be using the Lagrange multipliers method to compute the
contact force at each point of contact of the motorized tracks. In order to control the angular position
of the vehicle, a control law will be proposed based on the LQR (Linear Quadratic Regulator) control
methodology, the purpose of this control law is to provide that the two contact points established on the
vehicle‘s motorized tracks will simultaneously contact or ensure that vehicle contacts the surface through
one of these points.

ATTITUDE CONTROLLER DESIGN OF THE BRAZILIAN SATELLITE LAUNCHER VIA HYBRID NEURAL-GENETIC APPROACH

Paulo R. Silva, Ivanildo S. Abreu, Henrique M. C. do Amaral — Mon, 26 Aug 2024 00:00:00 +0000

This work proposes the design of an attitude controller for the Brazilian launching vehicle via
mode-selection using a hybrid neural-genetic method. Given the high complexity of the rocket dynamic
equations, the model was linearised and minimized with a model order reduction technique, in particular
mode-selection. The hybrid approach performs the weighting matrices search of the linear quadratic
(LQ) method and the solution of the Algebraic Riccati Equation (ARE) that leads to the attitude controller
gains. The performance analysis of the reduced order model and the designed controller was performed
in the frequency and time domain, while the hybrid neural-genetic approach was evaluated through fitness
function and energy and infinity norms, respectively. The proposed controller reached the time domain
specifications, i.e. rise time, settling time and overshoot for the maximum dynamic pressure instant. The
results suggest that the hybrid approach could speed up the attitude controller design process of Brazilian
launchers, reducing costs and re-design possibility.

EXPERIMENTAL AND NUMERICAL ANALYSIS OF WING PLATE MODEL.

Barreto F., Fenili A. — Mon, 26 Aug 2024 00:00:00 +0000

The development of thin plate theory was due to the evolution of engineering that
continually needed to improve the mode of analysis of elements in a plate. In 1888 Augustus Edward

Hough Love (Weston-Super-Mare, 1863 - 1940) used Kirchhoff's hypothesis to determine a two-
dimensional mathematical model for the determination of stresses and deformations in thin plates

subjected to forces and moments, assuming a surface plane. Average can be used to represent a three-
dimensional plate in two-dimensional form (LOVE, 1897). As the flat plate theory has been refined by

adding new methods of analysis and theories, the approximation of equations by a discrete point
system in spacetime has become a fundamental necessity, the most common methods being: 1.
Volume Method Finite; 2. Finite Element Method and 3. Finite Difference Method. Equations can be
written in different forms depending on the coordinate system, such as Cartesian, cylindrical,
spherical, curvilinear, orthogonal, and non-orthogonal curvilinear. The present work had as main
motivation the comparison between two (2) different methods of analysis of flat plates of thickness t /
a << 1, where “t” is the thickness and “a” the largest dimension of the plate, with the configuration
Free-Free-Embossed Edges (LLLE). Thus, the objectives of this work are the assembly of an analysis
system using accelerometers (Model MPU 6050) in meshes (5x8 points) to verify the displacement of
x, y and z coordinates, spread over forty (40) points forming a mesh, and two (2) points with Geokon
@ 4150 vibrating string sensors horizontally and vertically.With these sensors it was possible to verify
the plate displacement dimension for both methods, as well as the difference between the experimental
analysis methods and their applicability in other projects.

ATTITUDE CONTROL OF SATELLITE WITH PROPELLANT SLOSHING DYNAMICS

Victoria de Souza Rodrigues, Andre Fenili — Mon, 26 Aug 2024 00:00:00 +0000

Space vehicles can carry large amounts of liquid propellant in their tanks, especially

when performing interplanetary missions. When these tanks are not completely filled, the move-
ment of the vehicle excites the propellant such that the free surface of the liquid describes an

oscillatory movement. This movement confined inside the tank is known as sloshing. Depend-
ing on the type of excitation and the geometry of the tank, the liquid sloshing may have an

infinite number of natural frequencies; these frequencies tend, in turn, to excite the movement
of the vehicle and, consequently, affect attitude control. This paper investigates the attitude
control of a satellite, modeled as a rigid body, whose motion is coupled with the slosh effect
of the liquid propellant in its interior, represented by an equivalent mechanical model, in this
case a simple pendulum. The equations of motion are obtained through Lagrangian formalism.
The excitation frequency is assumed to be remote from resonance. Only small amplitudes of

oscillation are allowed for the pendulum, so that the free surface remains planar without rota-
tion of its nodal diameter. Attitude control is investigated for different volumes of liquid in the

tank. The control technique used is the Linear Quadratic Regulator (LQR) and the results are
obtained numerically.

Topology Optimization for Elastic Analysis of 3D Structures using Evolutionary Methods

Mon, 26 Aug 2024 00:00:00 +0000

This work aims at the study and application of Topology Optimization (TO) in problems of
elasticity for the determination of the final configuration in 3D structures using the criterion of minimum
compliance, seeking the minimization of volume and maintaining its rigidity. The methods of
evolutionary structural optimization employed are: a) Solid Isotropic Material with Penalization (SIMP);
b) Evolutionary Structural Optimization (ESO); c) Smoothing Evolutionary Structural Optimization
(SESO) and d) Sequential Element Rejection and Admission (SERA) which are based on the systematic
and gradual removal of the elements following a set of sensitivity criteria. For this, all the methods are
implemented in Matlab software and numerical examples are presented to demonstrate the ability of the
proposed methods to solve 3D topology problems, presenting the difference in computational time
among them.

FOUNDATION OPTIMIZATION OF PREFABRICATED PILES

Lucas Estrela Portigo, Marcelo Araujo da Silva — Mon, 26 Aug 2024 00:00:00 +0000

The prefabricated foundations of concrete are deep piles driven in situ with a high-quality
concrete, due to its regularized and controlled production at factories. This concrete can be reinforced
or prestressed so it can resist flexure, traction and shear force within the soil, and even during the
transport and handling. The prefabricated pile to be treated in this current study is the centrifuged pile,
which has a circular hollow section. This type of piles has a high-quality concrete, less self-weight,
cheap cost of machinery (pile driver) and dispensable digging. Under the eyes of sustainability,
nowadays people concern a lot about the reduction of construction supplies, avoiding the excessive
waste of those. The objective of this research is to optimize the calculus of prefabricated concrete piles
sizing with circular hollow section to minimize the involved components, consequently reducing the
final cost of the item. In the optimization problem, the project variables are the diameter, the thickness
and the length of the piles, the objection function is the volume, and the project constraints are defined
by the ABNT norms. Therefore, in order to optimize, it’s needed to evaluate the bearing loads, and the
soil and pile structure resistance, searching for an optimal cost, ensuring the safety of the construction
with less consumption of steel and concrete, attending to the project constraints. Thus, will be used the
Excel’s function SOLVER, allied with the semiempirical methods described by Aoki-Velloso (1975)
and Décourt-Quaresma (1978) to obtain optimal project values.

OTIMIZAÇÃO TOPOLÓGICA DE UMA LONGARINA UTILIZANDO-SE O PROGRAMA MATLAB E COMPARAÇÃO DOS RESULTADOS COM O SOFTWARE ANSYS.

Júlia da Silva Maschietto, Marcelo Araujo da Silva — Mon, 26 Aug 2024 00:00:00 +0000

O presente trabalho visa estudar e determinar computacionalmente a otimização de
estruturas aeronáuticas, determinando o máximo de material a ser retirado da estrutura com
confiabilidade e segurança. Para isso, o elemento estrutural de alumínio pertencente a longarina de
uma asa, formato I será otimizado através de um algoritmo de elementos finitos implementado em
Matlab e os resultados comparados aos do software Ansys. Primeiramente, a estrutura será
discretizada através dos elementos finitos, logo após serão determinados os carregamentos e
parâmetros como tensão, deformação e deslocamento, para que a análise estrutural seja realizada,
respeitando os parâmetros desejados.

OTIMIZAÇÃO TOPOLÓGICA DE UMA AERONAVE UTILIZANDO O SOFTWARE AUTODESK INVENTOR

Paulo Henrique Matavelli Junior, Marcelo Araujo da Silva — Mon, 26 Aug 2024 00:00:00 +0000

This work intends to perform the topological optimization of the Cessna 172 Skyhawk
aircraft, with the objective of reduce its mass, using the software Autodesk Inventor. Given a choice
among several options, the optimization is related to the choice that is the best possible, considering
criteria and limitations, such as available resources and design requirements, which directly impact
the analysis, manufacturing, sales research and development of the design of an aeronautical product
(Silva and Brazil, 2017) [1.] After structural and performance studies, each part of the chosen aircraft
will be modelled in the Autodesk Inventor software. Boundary conditions and loading applications will
be carried out, simulating different flight assumptions, in order to make optimization consistent with
the reality; afterwards, the topological optimization will be carried out in this software, followed by
analysis.

IMPACT ABSORBERS FOR APPLICATION TO THE CASING OF EXPERIMENTAL ROCKETS

Willian Kenji Takaracy, Marcelo Araujo da Silva — Mon, 26 Aug 2024 00:00:00 +0000

This project had an intent to research and determine materials with good damping
characteristics that serve as impact absorber.The materials determined here can serve as the inner
casing of experimental rockets, minimizing the damage caused by impacts to the ground to the ejected
capsules, aiming the reuse of internal components. A mathematical model with a degree of freedom
was used, which shows the spring, the damping and the mass of the capsule. The dynamic loading was
due to the impact on the ground. The elastic, damping and inertial forces were considered. The goal
was to minimize the acceleration of the part through the use of materials that could serve as the inner
lining of these rockets. Several materials were researched, with the objective of determining its
modulus of elasticity, coefficient of internal damping and density. A material with a high density, or a
low damping factor, is not desirable. Once these properties were determined, they were introduced in
the mathematical model to verify the ones that produce the most acceleration reduction after impact.

ANÁLISE DE FORMULAÇÕES DE PROBLEMAS DE CONFIABILIDADE ESTRUTURAL

Marcelo Araujo da Silva — Mon, 26 Aug 2024 00:00:00 +0000

A formulação clássica dos problemas de confiabilidade estrutural, como aquela utilizada nos
métodos GRG (Generalized Reduced Gradient) e FORM (First Order Reliability Method), é definida
através de um problema de otimização, onde se tem as variáveis aleatórias como variáveis de projeto,
o índice de confiabilidade como a função objetivo e a restrição de igualdade dada pela função de
performance, calculada como a margem de segurança. O índice de confiabilidade pode ser definido
como a menor distância, no espaço das variáveis reduzidas, entre a função de performance e a origem
do sistema. Então o problema de confiabilidade é usualmente formulado como: determinar as variáveis
de projeto (variáveis aleatórias) que minimizem a função objetivo (índice de confiabilidade) sujeito à
restrição de igualdade (margem de segurança). Como a função objetivo é a distância do projeto até a
origem, no espaço das variáveis reduzidas, não importa na equação se estas variáveis apresentam
valores positivos ou negativos. Este fato pode trazer problemas para a solução, pois o sinal destas
variáveis interfere significativamente no cômputo da probabilidade de falha do modelo analisado.
Serão mostrados exemplos onde esta formulação não é válida. Conclui-se no trabalho que as
formulações mais adequadas são aquelas baseadas na definição do índice de confiabilidade como
sendo a razão entre a média e o desvio padrão da função de desempenho. Formulações como o
Processo de Monte Carlo (MC) usam esta definição e, portanto, não causam prejuízos aos resultados
obtidos, sendo mais confiáveis, principalmente em problemas mais complexos, com um número
significativo de variáveis aleatórias. Serão apresentados exemplos com a utilização do método GRG e
do Processo de Monte Carlo e mostradas as discrepâncias daquele e dos resultados coerentes dados
por este em alguns problemas clássicos. Sugestões para estudos futuros também serão apresentadas.

AUXETIC MATERIAL DESIGN THROUGH STRUCTURAL OPTIMIZATION APPROACH

Cícero Ribeiro de Lima, Paula Fregnani — Mon, 26 Aug 2024 00:00:00 +0000

Unlike conventional materials, an auxetic material has negative Poisson’s ratio, that is, it
increases the size of its cross-section when is under traction and decrease when is compressed. The
auxetic structural behavior can provide many benefits, since the structural material may acquire
notable mechanical properties, such as increased resistance to impact. Due to this improved impact
absorption capacity, the auxetic materials have great potential for use in the aerospace structures. In
this work, parametric optimization has been applied to develop a re-entrant structure (periodic cell)
that simulates the behavior of the auxetic material microstructure. Thus, the auxetic behavior arises
from the mechanism deformation of geometric configuration of the re-entrant structure. The main
motivation of this work is to contributes with a more systematic methodology to design of the auxetic
structures, make it independent of the designer expertise. Some 3D re-entrant auxetic structures of the
literature are adopted as initial design domain and a parametric optimization is carried out to obtain
optimized dimensional configurations for the geometry of the auxetic structure. Dimensional
parameters of the domain, such as angles, wall thickness, height, and width, are considered as design
variables in the optimization problem, in which the objective function is formulated to maximize de
behavior of the auxetic structure (negative Poisson’s ratio). Computational simulations of finite
element models are carried out to evaluate the optimized auxetic structures.

DEVELOPMENT OF A NOVEL FRAMEWORK FOR SEQUENTIAL COUPLING OF RESERVOIR, WELLS, AND SURFACE FACILITIES

Mon, 26 Aug 2024 00:00:00 +0000

Petroleum production systems consist of three individual elements that are operating together:
reservoir, wells, and surface facilities. Design, construction, and maintenance of surface facilities for
hydrocarbon production require realistic simulation studies. These studies become much more realistic
when well and surface facilities are simulated together with the reservoir. In this work, a literature survey
was performed and different coupling approaches were discussed. Then, the new framework was
introduced as a tool for coupling the reservoir, well and surface facility using the in-house UTCOMP
simulator. UTCOMP is a compositional simulator, which has been developed at The University of Texas
at Austin. This formulation is designed to use flow tables in order to compute wells and surface facility
interactions. The presented framework enabled UTCOMP to read surface facilities data, which were
generated by a commercial simulator. Some new software was developed to read and compare the flow
table’s data and enable surface facility option within UTCOMP. In this study, the new features added to
UTCOMP were: (a) inserting a new flow table option, (b) including surface pipelines length and
diameter, (c) calculation of operational condition like gas-oil ratio and water-oil ratio at the surface
condition and (d) an output file for surface facilities information. Also, we show results of two case
studies. Using the developed tool, we are able to understand the behavior of petroleum production
systems and identify the main factors that affect production operations.

METHODOLOGY TO ACCELERATE EXPLICIT INTEGRATION BETWEEN RESERVOIR AND PRODUCTION SYSTEM SIMULATORS

João Carlos von Hohendorff Filho, Denis José Schiozer — Mon, 26 Aug 2024 00:00:00 +0000

Integrated models are needed in some situations to analyze the interaction between
reservoirs and production system models. However, the dynamics of the two systems is different and
there are situations in which the production system response is very similar over time. The aim of this
work is to propose a more efficient interaction between the simulators, avoiding repetitions, reducing
the total time of the numerical coupling and accelerating the decision making process for the field. The
methodology of this work proposes a proxy model for the production system, similarly to that done in
decoupled approach with VLP (Vertical Lift Performance) tables previously generated, but with the
proxy model being generated during the integrated simulation using explicit coupling. Integration with
proxy model obtained total time values close to those obtained with the use of VLP tables previously
generated, showing an efficient way of efficient interaction between the reservoir and production
system simulators for the explicit coupling approach, without the need to run unnecessary values, as
done in the generation of VLP tables.

OTIMIZAÇÃO DA LOCAÇÃO DE POÇOS EM RESERVATÓRIOS DE PETRÓLEO UTILIZANDO MODELOS SUBSTITUTOS E ALGORITMOS GENETICOS

Matheus Alves Garrido, Silvana M. B. Afonso, Leonardo Correia de Oliveira — Mon, 26 Aug 2024 00:00:00 +0000

O desenvolvimento de um reservatorio de petr ́ oleo envolve diversas vari ́ aveis, sendo o seu ́
desempenho altamente dependente de escolhas otimas por parte de seus operadores. Dentre aquelas, se ́
destaca a localizac ̧ao de poc ̧os, visando um maior varrido do fluido de interesse e menor produc ̧ ̃ ao de ̃
agua durante a vida produtiva do campo. O objetivo deste trabalho ́ e maximizar o valor presente l ́ ́ıquido
(VPL) de um modelo sintetico de reservat ́ orio, atrav ́ es da locac ̧ ́ ao de seus poc ̧os produtores e injetores. ̃
Para tanto, utilizou-se o algoritmo genetico (GA) na otimizac ̧ ́ ao da func ̧ ̃ ao objetivo (VPL) acoplado a ̃
um simulador comercial, que fornece as curvas de produc ̧ao de ̃ oleo e ́ agua do modelo. Foi verificado ́
um aumento de 60% no valor presente l ́ıquido em comparac ̧ao ao caso base, devido, principalmente, a ̃
reduc ̧ao da produc ̧ ̃ ao de ̃ agua. O cen ́ ario otimizado apresentou diferentes posic ̧ ́ oes para todos os poc ̧os, ̃
daquelas propostas incialmente pelo operador, ressaltando a robustez do GA no aux ́ılio de tomada de
decisoes.

OPTIMIZATION OF THE NATURAL FREQUENCIES OF EULER-BERNOULLI BEAMS

Juan G. Q. Blanche, Simone S. Hoefel — Mon, 26 Aug 2024 00:00:00 +0000

Various types of engineering structures are subject to periodic loading such as offshore plat-
form parts and wind turbine blades. One of the main causes of failure in these structures is due to the

resonance effect, when the frequency of external loading coincides with some natural frequency of the
structure. Therefore, the maximization of natural frequencies is an increasingly sought-after topic in the

design of these components. In this paper a genetic algorithm is developed to maximize natural frequen-
cies of Euler-Bernoulli beams. Genetic algorithms are stochastic search methods, which are based on

biological concepts of adaptation, natural selection, fitness and evolution, to solve optimization prob-
lems. A beam population is created, each of them discretized in a mesh of cylindrical elements with

different diameters, initially random. The natural frequencies of the beam are found by the Finite Ele-
ment Method, and the one with the highest natural frequency creates a new generation of offsprings. In

each offspring is applied a mutation scheme that changes the diameter of any random element, making

the entire population change. So over the generations the algorithm finds out the best diameter combina-
tion that maximizes the natural frequency of the beam. Results present different shapes are obtained for

several boundary conditions and different natural frequencies maximized.

SEQUENTIAL APPROXIMATE OPTIMIZATION USING KRIGING AND RADIAL BASIS FUNCTIONS

Marina A. Maia, Leonardo G. Ribeiro, Evandro Parente Jr., Antonio M. C. Melo — Mon, 26 Aug 2024 00:00:00 +0000

Despite steady advance in computing power, the number of function evaluations in global opti-
mization problems is often limited due to time-consuming analyses. In structural optimization problems,

for instance, these analyses are typically carried out using the Finite Elements Method (FEM). This issue
is especially critical when dealing with bio-inspired algorithms, where a high number of trial designs are
usually required. Therefore, surrogate models are a valuable alternative to help reduce computational

cost. With that in mind, present work proposes three Sequential Approximate Optimization (SAO) tech-
niques. For that purpose, two surrogate models were chosen: the Radial Basis Functions (RBF) and

Kriging. As for the infill criteria, three methodologies were investigated: the Expected Improvement,
the Density Function and the addition of the global best. Two bio-inspired meta-heuristics were used
in different stages of the optimization, namely Particle Swarm Optimization and Genetic Algorithm. To
validate the proposed methodologies, a set of benchmarks functions were selected from the literature.
Results showed a significant reduction in the number of high-fidelity evaluations. In terms of accuracy,
efficiency, and robustness, Kriging excelled in most categories for all problems. Finally, these techniques
were applied to the solution of a laminated composite plate, which demands a more complex analysis
using FEM.

COMPARATIVE STUDY ON MULTIPLE WIDTH-DEFINING METHODS FOR RADIAL BASIS FUNCTIONS

Mon, 26 Aug 2024 00:00:00 +0000

In structural problems, numerical methods such as the Finite Element Method are often used
due to the scarce and limited applicability of analytical methods. In these cases, the design optimization
may become computationally costly and the time consumed starts to be a hindrance. To overcome this
problem, a significant effort has been made by researchers to understand and improve the so-called
surrogate models. Surrogate models provide computational efficiency by using a few samples from
the true function to build an approximated response surface to predict points in the design space not
yet evaluated during the optimization process. This approximated surface may also be improved at each
generation with the addition of new samples in regions of interest on a methodology known as Sequential
Approximate Optimization (SAO). In this context, the Radial Basis Functions (RBF) are a powerful and
robust surrogate model while keeping implementation simple. The Gaussian function is often chosen as
the basis function despite uncertainty on the definition of one of its main parameters: the kernel width
(σ). This paper performed a comparative study on different methods to estimate the width parameter
using two types of solutions: closed-form expressions proposed by different researchers in the last few
years and direct search methods. The efficiency of each of these approaches is assessed using metrics
such as the number of high fidelity model evaluations and the error at the end of each optimization.

OPTIMIZATION OF GEOMETRICALLY NONLINEAR LATTICE STRUCTURES UNDER DYNAMIC LOADING

Larissa B. Martinelli, Élcio C. Alves — Mon, 26 Aug 2024 00:00:00 +0000

This study addresses the optimization of lattice structures with geometrically nonlinear

behavior under dynamic loading. The formulated optimization problem aims to determine the cross-
sectional area of the bars which minimizes the total mass of the structure, imposing constraints on

nodal displacements and stresses. In order to solve this optimization problem, it was developed a
computational program on MATLAB®, using the Interior Point method and the Sequential Quadratic
Programming method, the algorithms of which are available on Optimization ToolboxTM. The
nonlinear finite space truss element is described by an updated Lagrangian formulation. The
geometric nonlinear dynamic analysis performed combines the Newmark method with
Newton-Raphson iterations, being validated by comparison with solutions available in the literature
and with solutions generated by the ANSYS® software. Examples of trusses under different dynamic
loading are solved using the developed computational program. The results show that the Sequential
Quadratic Programming method is the most efficient to solve the studied optimization problem and
that the consideration of structural damping can lead to a significant reduction in the total mass.

DIMENSIONAMENTO ÓTIMO DE PILARES MISTOS PREENCHIDOS DE AÇO E CONCRETO ATRAVÉS DO EN1994-1-1:2004

Jéssica Salomão Lourenção, Élcio Cassimiro Alves — Mon, 26 Aug 2024 00:00:00 +0000

The objective of this work is to present the formulation of the optimization problem and
applications of filled composite columns of steel and concrete with and without reinforcement according
to EN 1994-1-1:2004. The solution of the optimization problem was obtained through the Genetic
Algorithm Method. A software was developed on the Matlab platform using the tool guide. Numerical
examples are presented, and the results found by the elaborated software demonstrated that the Genetic
Algorithm Method obtained relatively lower costs due to the use of hollow section catalogs.

Analyze of colapse modes in the optimum design of alveolar steel beams through the Genetic Algorithm method

Tiago Cetto Pietralonga, Élcio Cassimiro Alves — Mon, 26 Aug 2024 00:00:00 +0000

The application of steel structures in Brazil has grown considerably in recent years, not only
in industrial sectors, such as large warehouses, but also in buildings with a high number of floors.
With this, new solutions in the field have become more studied, such as beams of sequential apertures
in the web (alveolar) that are formed by "I" or "H" laminated profiles previously cut in the web to the
established standard and later displaced in the longitudinal to weld them, thus increasing the capacity
resistant to bending stress without adding weight to the profile. Moreover, these profiles have a great
advantage to the installations, such as electrical and plumbing systems, because the journey by web is
not restricted. The objective of this work is realizing an analysis and comparison of the optimized
sizing of castellated and cellular steel beams by means of genetic algorithm (AG) in a system
implemented in the MATLAB. The optimization process is of greater relevance in the elaboration of
less expensive projects, whereas is found a solution with smaller steel consumption to comply with all
requirements established in standards and resit to the active efforts. To validate and show the
applicability of the proposed problem, we will analyze the sizing of 12 alveolar beams (roof and floor)
for each type of cut, cellular and castellated (Peiner, Litzka, Anglo-Saxão), observing the linear weight
of optimized profiles and the collapse modes that govern the sizing of the same.

STRUCTURAL OPTIMIZATION OF TRUSSES UNDER ELASTIC AND INELASTIC BUCKLING CONSTRAINTS

Marcela A. Juliani, Mariana O. Milanez, Wellison J. S. Gomes — Mon, 26 Aug 2024 00:00:00 +0000

It is well known in the literature and practice of structural optimization that optimal struc-
tural configurations are highly dependent on the constraints applied to the problem or, in other words,

on the definition of what is feasible or not. Results obtained under a certain type of constraints may
be not optimal, or even not acceptable, if other types of constraints are considered. Discussions related
to constraints and their effects on structural optimization are found in many papers, but only a few of
them directly address this subject. In the specific case of optimization of trusses, it is common to find
applications involving two different scenarios, where stress-based constraints are combined with elastic
buckling or with inelastic buckling constraints, respectively. The first scenario is much more common,
and the differences between results related to each of these combinations are hardly ever discussed or

emphasized. The present paper focus on the comparison of structural optimization of trusses, consid-
ering these two scenarios, in an attempt to identify in which cases similar results are obtained and how

different the results can be. The paper also proposes a simple multistart optimization scheme combined

with sequential quadratic programming, so that the optimization problems are solved in a global and ef-
ficient manner, and the comparisons are not significantly compromised by local minima. Two trusses are

evaluated, for some different cases of boundary conditions, and the results indicate that the optimal con-
figurations may be significantly different in the cases where a sufficient number of compressed slender

bars is present.

Optimization of unbonded post-tensioned concrete ribberd floors

Mon, 26 Aug 2024 00:00:00 +0000

Floors represent a great portion of the total cost of multistory reinforced concrete structures.
The ribbed slabs, benefited by the reduction of concrete in the tension region, become a good alternative
when it is necessary to overcome large spans. Solutions more efficient with respect to structural behavior
and economy can be obtained combining the ribbed slabs with post-tensioning unbonded tendons. This

way, it is important to find the optimum section and vertical tendons profile which improve its capabili-
ties. The traditional design process can be aided by the use of optimization techniques. Hence, several

works with cost optimization of isolated ribbed slabs of reinforced and prestressed concrete have indica-
ted new design trends of formwork. In this research, it is performed the optimization of a typical one-way

multiple spans ribbed floor. Formulations to minimize the cost of the slab are studied, considering the
cost of material, formwork and labor. The design variables are the dimensions of formwork, the vertical

profile of unbonded post-tensioned tendons and the number of tendons, considering all variables as dis-
crete ones. The analysis is performed by grid analogy considering the entire floor, considering the beams

as non-deformable elements. A Finite Element Model is used to stress analyses. The load balancing
method is used to simulate the effect of prestressed unbonded tendons. Constraints on Serviceability and
Ultimate Limit States are verified. A Genetic Algorithm of an open-source program, that has presented
robustness for structural optimization, is used to solve the discrete optimization problem. In order to
investigate the effects of optimization process against the traditional modeling, literature examples have
been chosen trying to represent the widest range of cases faced in practice.

TRAJECTORY PIECEWISE LINEARIZATION (TPWL) USING THE MATLAB RESERVOIR SIMULATION TOOLBOX (MRST) FOR RESERVOIR SIMULATION

Andresa Dornelas de Castro, Alexandre de Sousa Júnior, Bernardo Horowitz — Mon, 26 Aug 2024 00:00:00 +0000

The goal of the present work is to show the Trajectory Piecewise Linearization (TPWL)
procedure for modeling of two-phase flow in subsurface formations, using the Matlab Reservoir
Simulation Toolbox - MRST for reservoir simulation, developed by SINTEF Digital. In this work we
will show how MRST can be used to simulate black-oil models using automatic differentiation to
compute the Jacobian matrices required for the nonlinear Newton-type solver. In automatic
differentiation (AD) the key idea is to keep track of quantities and their derivatives simultaneously:
every time an operation is applied to a quantity, the corresponding differential operation is applied to
its derivative. Thus, MRST-AD allows the fully-implicit nonlinear pressure equation, using a discrete
operators and equations simulator, to compute automatically the correct Jacobian for black-oil system.
In general, the simulator code presented in automatic differentiation black-oil module (ad – blackoil)
is modified to export the necessary data to build the TPWL procedure. This is known as semi-intrusive
methodology, since it requires knowledge of the simulator code, but the changes do not affect the
equations solutions. The Trajectory Piecewise Linearization (TPWL) procedure reduces the numerical
complexity of the problem by performing the linearization of governing equations around converged
states stored during a training simulation. Therefore, we will show implementation of TPWL after
getting the system states (pressure and saturation) and the derivatives of residual equation from the
MRST. The method is shown to be accurate in the neighborhood of the training trajectory.

INFLUENCE OF STIFFENING IN COLD-FORMED CHANNEL SECTIONS IN THE NATURAL FREQUENCY OF VIBRATION

Mon, 26 Aug 2024 00:00:00 +0000

The modernization in structural engineering in the last years led to the search for economic

and modern solutions, using quickly built systems, elements with lower self-weight as well as column-
free structural systems, which allows for more architectural flexibility. This practice, however, gave

rise to elements with thinner cross-section and, consequently, lower natural frequencies, which are
closer to the dynamic excitation frequency of loads due to human activities such as running, jumping
and walking. This fact can be specially noticed in cold-formed steel (CFS) structures on account of its
lightness and lower stiffness when compared to rolled and welded steel sections. Hence, this article
aims to evaluate the influence of stiffening in cold-formed isolated elements with lipped channel
sections. Finite element analyses were carried out in order to assess its influence in the range of first
natural frequency of vibration. For the most results obtained, the increment in the edge stiffener’s
width has increased the natural frequency of vibration while the presence or absence of web stiffener
did not affect the outcomes.

AN OVERVIEW OF LOCAL AND DISTORTIONAL BUCKLING IN COLD- FORMED U LIPPED SECTIONS IN FLEXURE

Mon, 26 Aug 2024 00:00:00 +0000

The design of cold-formed steel elements in flexure can be easily performed by the Direct
Strength Method – a simplified alternative based on experimental data, in which the critical buckling
bending moments are needed to assess the ultimate resistance of steel elements. Whereas numerous
theoretical models are found in the literature to appraise local and distortional buckling loads, they’re
usually based on simplifications and don’t provide their exact values so that different formulations
conduct to different results. In this sense, through analyses based on the Finite Element and the Finite

Strip Methods, this work seeks to numerically obtain local and distortional buckling loads of a cold-
formed U stiffened section bent about both principal axes and compare the results with those provided

by the theoretical models. While numerical results have shown good agreement between them, with
deviations less than 5% on mean, the analytical ones seemed to be conservative but not accurate when
compared to the firsts, with deviations varying from 7% up-to 60%.

CAPACIDADE RESISTENTE DE COLUNAS CONTRAVENTADAS EM PERFIS FORMADOS A FRIO COM PERFURAÇÕES

Mon, 26 Aug 2024 00:00:00 +0000

The use of cold-formed profiles, due to its versatility, economy and lightness, has been
increasingly incorporated into the civil construction. The workability found in the thin-walled sections
allows a great variety of cross sections, allowing its use in several segments. One of these uses is in
the Industrial Storage Systems, usually called racks, in which the cold-formed steel profiles are used in
most elements, including the uprights. These uprights have perforations along the length, in order to
facilitate the assembly of the system as a whole. The objective of this work is to evaluate the influence
of the perforations and the arrangement of bracings in the ultimate load of pinned uprights under axial
compression, with lengths in which the distortional buckling mode is dominant. The analyzed cross
sections are of the rack type, commonly used in these systems. Numerical studies were carried out
using ANSYS commercial program, calibrated with results of experimental program. An elastic
stability analysis was performed in the ANSYS and in conjunction with a modification of the Direct
Strength Method proposed by the authors, were obtained the ultimate loads that were compared to the
experimental results.

COMPRESSION TESTS AND ANALYSIS OF BUILT-UP COLD-FORMED STEEL COLUMNS

Cristiane C.D.O. Bastos, Eduardo M. Batista — Mon, 26 Aug 2024 00:00:00 +0000

The present article includes the results of the structural stability of laced built-up cold-formed steel
(CFS) columns, subjected to axial compression. The objective is to analyze the behavior of these
spatial laced columns through full scale experimental tests, in which the collapse is caused by the
interaction between local and global buckling in the compressed chord members. The spatial columns,
composed of four plane-trussed members designed with lipped channel CFS and fully connected with
self-drilling screws, were tested with 12200 and 16200mm length, 0.8 or 1.25mm plate thickness. In
addition to these tests, it was also carried out experimental tests of columns ́ chord members to obtain
the collapse loads and comparison with the analytical DSM equations (direct strength method). The

tested chord members were of 480mm length, double 88x86x40x42x12mm lipped channel cross-
section and 0.8mm thickness. The results showed that the DSM can be applied to obtain the collapse

loads of the chord built-up members, composed of two lipped channels connected with self-drilling
screws. Two analytical methods were applied to obtain global buckling load of the special laced
column and compared with numerical results. The obtained results indicated that critical buckling load
may be accessed with the help of available analytical equations. The final results of the investigation
indicate the adopted methodology, including the column global buckling nonlinear behavior combined
with the collapse mode of the double lipped channel CFS chord members connected by self-drilling
screws, is able to be applied for regular structural design of the CFS spatial trussed arrangement.

EFFECTIVE SECTION METHOD APPLICATION TO COLD-FORMED STEEL LIPPED ANGLE COLUMNS

Mon, 26 Aug 2024 00:00:00 +0000

In the structural design of the cold formed sections, the procedures described in NBR
14762:2010 are adopted. The Brazilian standard establishes three bar design methods: Direct Strength
Method (DSM), Effective Section Method (ESM), and Effective Width Method (EWM). The DSM is
developed by calculating the geometric properties of the gross section. In the ESM, the local buckling
is considered through the effective section obtained directly, and not by the calculation of the effective
widths of its elements, as in the case of the traditional Effective Width Method (EWM). The
dispensation of numerical methods for elastic stability analysis constitutes a certain advantage of the
ESM in relation to the DSM. For cold formed steel section on compression, an important step is to
obtain the elastic buckling axial force, which in the case of ESM is obtained by means of an equation
that is a function of the local buckling coefficient for the complete section. The NBR 14762:2010
presents expressions of this coefficient for open sections of the type U, Z and rack, besides hollow
section. The objective of this work is to present a procedure to obtain the axial force of elastic
buckling, for lipped angles on compression, in order to complement the Effective Section Method. In
this context, an equation is present for the local buckling coefficient for lipped angle, as a function of
the geometric properties of the cross section.

STABILITY AND STRENGTH OF COLD-FORMED STEEL COLUMNS WITH INTERMEDIATE STIFFENERS

Amanda Isabela de Campos, Eduardo de Miranda Batista, Juarez Moara Santos Franco — Mon, 26 Aug 2024 00:00:00 +0000

Cold-formed steel (CFS) profiles have the advantage of combining low weight with high
strength capacity, which can be improved with the inclusion of intermediate stiffeners. This paper
analyzes the influence of stiffeners on CFS columns and proposes a search for geometry with highest
critical buckling load and highest compressive strength. For this purpose, (i) the lipped channel-type
parametric model was developed with flange and web stiffeners and (ii) performed the sensitivity
analysis that relates these variables to the mechanical performance of the columns. The elastic buckling
analysis was performed using the Finite Strip Method (FSM), which allowed identifying the local (L)
and distortional (D) buckling modes and the relationship between their critical loads (Rdl). The resistance
was obtained by nonlinear analysis with arc control technique, in an implementation of the Finite
Element Method (FEM). The parametric model also incorporated manufacturing constraints, such as
coil width, sheet thickness and usual bending angles. All studies adopt, as restriction, a constant area in
the cross section of the profile. This study is particularly interested in (i) verifying whether the signature
curves of the optimal profiles present common properties, such as the Rdl ≈ 1, and in cases where this is
verified (ii) measure resistance erosion due to LD interaction. The ultimate objective of this work is to
determine the value for Rdl that maximizes the strength of stiffened columns. Future applications of these
results include the development of resistance optimization routines based on FSM.

COLUNAS METÁLICAS EM PERFIL FORMADO À FRIO SOB COLAPSO FLEXO-TORCIONAL E TEMPERATURAS ELEVADAS

Antonio Renato Albuquerque Bicelli, Alexandre Landesmann, Dinar Camotim — Mon, 26 Aug 2024 00:00:00 +0000

Este artigo apresenta e discute os resultados numéricos relativos a colunas de aço em perfis
formado a frio, com seção-transversal U enrijecido (Ue) submetidos a temperaturas elevadas devido a
condições acidentais de incêndio, com colapso por flambagem flexo-torcional. Tais resultados
consistem na trajetória de equilíbrio da pós-flambagem elasto-plástica e cargas últimas, que foram
determinadas por meio de análises não-lineares em elementos finitos de casca utilizando o código
comercial ANSYS. De modo a cobrir uma ampla faixa do índice de esbeltez flexo-torcional, várias

tensões de escoamento em temperatura ambiente, comprimentos de colunas e dimensões de seção-
transversal foram considerados. A dependência da temperatura nas propriedades mecânicas do material

é simulada usando o modelo prescrito no Eurocode 3 – parte 1.2. Aborda-se a influência da temperatura
no comportamento de pós-flambagem elasto-plástica e na carga última, fornecendo um primeiro passo

na busca por uma diretriz de dimensionamento eficiente e confiável para colunas sob colapso por flexo-
torção em temperaturas elevadas

CROSS-SECTIONAL OPTIMAL DESIGN OF COLD-FORMED STEEL LIPPED CHANNELS USING ACCELERATED PARTICLE SWARM OPTIMIZATION

Mon, 26 Aug 2024 00:00:00 +0000

This study aims to present a practical method for optimizing cold-formed steel (CFS) lipped
channel beam-columns using an Accelerated Particle Swarm Optimization method (APSO). To
eliminate impracticable cross-section shapes from the optimization results, several manufacturing and
construction constraints are applied into the optimization process. Targeting this goal, 128 different
lipped channel sections prototypes were selected and then optimized with respect to their buckling load,
determined according to the finite strip method (FSM), then assessing the strength according to the
provisions based on direct strength method (DSM). Comparing the structural resistance of the optimized
sections with the sections of the original channel CFS with the same steel consumption, significant
improvements were obtained. The results indicate that the optimized sections provide a compressive
strength which is up to 50% higher than the initial shapes, and for flexural strength 30% higher than the
reference profiles, while they meting predefined design and manufacturing constraints. The results of
this study demonstrate the useful of APSO in CFS practical design problems.

ANALYSIS OF COLD-FORMED OPEN STEEL SECTIONS UNDER SIMPLE BENDING

Nadia S. N. Ota, Eduardo M. Batista, Juarez M. S. Franco — Mon, 26 Aug 2024 00:00:00 +0000

Cold-formed open steel sections under flexural loading are subjected to the combined
phenomena of bending, local (L), distortional (D), global (G) buckling and flange curling. Some of the
main challenges in evaluating the results obtained by numerical and experimental analysis are (i)
defining the displacement portion due to each one of these phenomena, as some of them occur in the
same plane of loading; (ii) the presence of intermediate stiffeners in these members makes the
buckling modes classification imprecise. Additionally, it is known that small changes in the section
geometry may imply large variations in the structural performance. This paper analyzes stiffened CFS
beams through Finite Strip Method (elastic stability analysis) and Finite Element Method (non-linear
analysis with arc-length control for strength prediction). The careful records of the displacements by
numerical analysis, combined with linear regression techniques, allowed evaluating the evolution of
the different mechanical phenomena during loading. The contribution of the stiffener height variation
on the critical bending moments was investigated. Particular interest is addressed to the strength
erosion due to the modal LD interaction, since the tendency of McrL/McrD = 1 ratio is obtained by
optimization methods where the objective function is directed towards the maximization of critical
moments. In this work, the geometric parameters were defined in order to generate variations of the
commercial self-supporting roofing tile RT-260/620 (Regional Telhas), with steel plate thickness of
0.95 mm.

COLD-FORMED STEEL LIPPED CHANNEL COLUMNS UNDER LOCAL- DISTORTIONAL-GLOBAL BUCKLING MODE INTERACTION

Gustavo Yoshio Matsubara, Eduardo de Miranda Batista — Mon, 26 Aug 2024 00:00:00 +0000

Thin-walled steel cold-formed lipped channel members in axial compression are susceptible
to buckling phenomena in the following modes: Local buckling (L), Distortional buckling (D) and
Global buckling (G). In these cases, the Direct Strength Method (DSM) predicts the ultimate strength.
However, some geometries are affected by the occurrence of coupling phenomena involving two or
three buckling modes interaction. The buckling modes interaction produces additional column strength
reduction if compared to isolated buckling modes occurrence. Furthermore, the design specifications
and codes for cold-formed steel members do not handle properly the ultimate strength for the cases of
L-D, D-G and L-D-G interactions. In this context, the present article is aimed at developing a Direct
Strength Method (DSM) approach to estimate the ultimate strength of lipped channel columns affected
by Local-Distortional-Global buckling mode interaction. To achieve this goal, the investigation is based
on: (i) literature review of experimental columns affected by buckling mode interaction (ii) calibration
of the FEM model based on experimental results; (iii) nonlinear FEM analysis of post-buckling behavior
affected by mode interaction performed with the help of the ANSYS computational program; (iv)
propose a Direct Strength Method (DSM) approach to estimate the ultimate strength of lipped channel
columns affected by Local-Distortional-Global buckling mode interaction.

BEHAVIOR AND STRENGTH OF DISTORTIONAL-GLOBAL INTERACTION IN COLD FORMED STEEL LIPPED CHANNEL COLUMNS

João Alfredo de Lazzari, Eduardo de Miranda Batista — Mon, 26 Aug 2024 00:00:00 +0000

The cold formed steel members (CFS) are light steel options widely applied in the civil
construction. Furthermore, the CFS is a very slender option that allows the buckling behavior to develop
on local, distortional and global modes. In this away, it is expected that a greater attention over this
structural solution is necessary to guarantee the reliability and safety of the structure. On recent studies,
it has been shown that when the local, distortional and global modes occur with similar critical loads,
the strength capacity of the structural member is reduced due to a coupled phenomenon. The proposed
paper will discuss the distortional-global (D-G) buckling interaction of CFS lipped channels columns
under axial load. Additionally, it is developed a computer program (FStr) for elastic buckling analysis,
based on Finite Strip Method (FSM), in order to find CFS columns experiencing D-G interaction. The
program is developed on MATLAB with an easy graphical user interface. After settled the profiles under
strong interaction, a non-linear analysis using Finite Element Method (FEM) is used to find the strength
of the columns. Additional analysis and comments are discussed in order to understand the behavior and
the strength capacity of the CFS lipped channel columns under the proposed buckling interaction.

INTERAÇÃO ENTRE OS MODOS DE FLAMBAGEM LOCAL E DISTORCIONAL EM COLUNAS DE SEÇÃO RACK FORMADAS A FRIO

Mon, 26 Aug 2024 00:00:00 +0000

Na última década, diversas pesquisas foram desenvolvidas para investigar a interação local-
distorcional de colunas com seções U enrijecido. Entretanto, estender as descobertas para colunas

exibindo outras formas de seção transversal é essencial para avaliar a generalidade, abrindo assim o
caminho para o desenvolvimento de uma abordagem de projeto baseada no Método da Resistência
Direta (MRD) para colunas afetadas pela interação local-distorcional. Deste modo, este trabalho de
pesquisa tem como objetivo investigar o comportamento de interação entre os modos de flambagem
local e distorcional em perfis de aço formados a frio com paredes finas de seção rack sem furos. O estudo
será baseado (i) em resultados experimentais divulgados por pesquisadores anteriores, (ii) no
desenvolvimento de um modelo numérico computacional tridimensional apropriado, com a utilização
do programa de elementos finitos ANSYS e, (iii) na adoção dos princípios do Método da Resistência
Direta (MRD). Espera-se que a combinação dos recursos de análise estrutural citados permita melhorar
os procedimentos de projeto de perfis de aço formados a frio com paredes finas de seção rack.

DETERMINATION OF THE CRITICAL LENGTH EQUATION OF DISTORTIONAL BUCKLING

Mon, 26 Aug 2024 00:00:00 +0000

The use of cold-formed steel members has grown significantly and for this reason a number
of design codes have been used such as NBR 14762 [1], AISI S100 [2] and AS/NZS 4600 [3]. The
susceptibility of these types of profiles to the phenomena of local, global and distortional instability
mainly has made the design codes to approach this topic in more detail. Nevertheless, the present
methodologies are little simplified or result in high conservatism. Thus, several studies have been carried
out aiming at the presentation of more simplified equations that result in a less conservative way to
represent the real behavior of these profiles. It was observed that the buckling length has relevant
participation in determining buckling mode, however there are many difficulties in determination of the
distortional buckling stress and its associated length. Thus, this paper aims to express a more simplified
equation for the length associated with distortional buckling. So, a selection of profiles with a C-section
with stiffener that complied with the geometric and mechanical specifications of the design codes was
performed. Using software based in Generalized Beam Theory, presented by Silvestre and Camotim [4],
several simulations were made with these profiles. The profiles were analyzed with end support
condition pinned-pinned under centered compression. The results were used to create artificial neural
networks from which were generated equations for the critical length of distortional buckling. The
equations were validated with the results available in the literature, whether experimental or numerical,
and showed good correlations.

PORTAL FRAMES WITH I-BEAM TO RHS-COLUMN JOINTS

Mon, 26 Aug 2024 00:00:00 +0000

This paper analyses welded joints in portal frames with I-beams and rectangular hollow
section columns. The study of joints is essential to the understanding of the structural behavior of portal
frames, and the analysis of its stiffness enables a better understanding of moment transmission between
tubular columns and I-beams, besides enabling the joint classification. Through numerical analysis using
a commercial software, the representation of the models was implemented in finite elements, with
subsequent displacement simulation. The slenderness of the tubular columns and the beam-to-column
width ratio were varied. The moment-rotation curves for each joint in a portal frame were presented,
and the influence of the parameters involved was presented graphically, where it was possible to
visualize yielding in some regions. Plastification of the column face occurred in the cases, while all
connections were classified as semi-rigid. Arrangements with different beam lengths were made, where
it was possible to observe its influence on the joint classification.

STRUCTURAL BEHAVIOR OF NEW THIN-WALLED COMPOSITE TRUSSED BEAMS AND PARTIALLY PREFABRICATED CONCRETE SLABS

Luiz Alberto Araújo de Seixas Leal, Eduardo de Miranda Batista — Mon, 26 Aug 2024 00:00:00 +0000

The composite trussed beams consist of a very traditional solution for building floors and
are associated to several benefits, such as reduced consumption of materials, excellent structural
response in terms of bending capacity, as well as flexural stiffness, ease of fabrication and erection.
Furthermore, the adoption of open-web composite beam enables larger free-spanning, compared to
traditional T-sections (composed by the association of hot-rolled I-shaped steel member and concrete

slabs), and allows the detailing of electric, hydraulic and HVAC (Heat, Ventilation and Air-
Conditioning) lines through the web of the trusses. One of the first researches regarding the structural

behavior of this type of composite floor system was conducted in 1960’s, from the experimental full-
scale tests in the United States. In the last 40 years, a lot of work has been published to provide

reliable information in terms of shear connection solutions, degree of interaction between the steel
trusses and concrete slabs, mechanisms of collapse and analytical models for the prediction of the
bending capacity. In almost all cases, the steel members are composed with hot-rolled sections (double
angle, for example) and the shear connectors are welded to the top chord of the truss. In this context,
the objective of the present work consists of presenting (a) alternative types of shear connectors, (b)
innovative structural floor system, composed by thin-walled trusses and prefabricated concrete slabs.

Three types of steel shear connectors were developed, manufactured with 0.95 mm thick plates: Thin-
Walled Perfobond, Thin-Walled Channel and Thin-Walled Vertical Post. The connection between the

connectors and the top chord of the trusses were provided with the help of 4.8 mm self-drilling screws.
Cold-formed lipped channel members (0.95 or 1.25 mm thick), partial prefabricated one-way concrete
slabs and styrofoam blocks compose the floor systems. Based on the results of an extensive
experimental program, important preliminary conclusions can be assessed. The obtained data revealed
higher bending capacity compared to traditional analytical predictions and excellent structural
response in terms of flexural stiffness and ductility.

ANÁLISE DAS CURVAS DE FLAMBAGEM DISTORCIOANAL DE VIGAS DE AÇO EM PERFIL FORMADO À FRIO VIA MRD E GBTUL

Emerson Rodrigues da Silva, Gregório Sandro Vieira — Mon, 26 Aug 2024 00:00:00 +0000

Due to the wide variety of transverse shapes as well as their good mass / strength ratio, cold
formed steel (CFS) components are gaining prominence among metal structures. However, this material
is more susceptible to local, distorted and global buckling. The Direct Strength Method (DSM) requires
obtaining the full limb buckling critical loads and applying these data in conjunction with a series of
resistance curves to determine the final cross section strength. This study aims to investigate the behavior
of different buckling modes for a supported single beam CFS, and to compare the results obtained
through DSM and GBTUL (program responsible for numerical computational analysis). To obtain the
data, the Finite Element Method (FEM) was used, which, in turn, uses the geometries and flow stresses
to be studied in this work, as well as the understanding of the influence that the bending moment diagram

has on the behavior. buckling and post buckling. For this analysis, a cold-formed, non-drilled, multi-
dimension steel member design was chosen. From the analyzes presented in this paper it was noticed

that the distortive curves available in the Brazilian standard underestimate the final strength of the bars
simply supported by cold formed steel members when subjected to uniform bending.

MECHANICAL CHARACTERIZATION OF THIN-WALLED GFRP MEMBERS BASED ON EXPERIMENTAL DYNAMIC TESTING

Jessé Beserra, Cássio Gaspar, Daniel Cardoso — Mon, 26 Aug 2024 00:00:00 +0000

The use of composite materials such as pultruded members of glass-fiber reinforced polymer
(GFRP) has increased in recent years, with important applications for footbridges, bridge decks, cooling
towers, stair towers, industrial structures, and rapid-assembly kits for temporary accommodation. The
mechanical characterization of GFRP in terms of elastic properties is often carried out by means of
destructive tests as specified by international standards. On the other hand, recent studies have proposed
the use of non-destructive techniques based on dynamic testing also known as experimental modal
analysis (EMA). In this sense, this work aims to identify the dynamic properties of thin-walled GFRP
members regarding their natural frequencies, mode shapes and damping ratios. These experimental
dynamic characteristics obtained for a C-channel beam are, then, used to determine specific material
elastic properties back-calculated from numerical optimization process. Finally, the properties
determined from proposed approach are compared to those obtained from classical destructive tests.
Therefore, the non-destructive procedure presented in this paper gives an alternative approach for the
mechanical characterization of GFRP members, which is especially important for low cost in situ quality
control.

SOBRE O COMPORTAMENTO ESTRUTURAL E O DIMENSIONAMENTO DE CANTONEIRAS PULTRUDADAS PRFV SUBMETIDAS À COMPRESSÃO

Anne C. L. Monteiro, Maria A. Branquinho, Maximiliano Malite — Mon, 26 Aug 2024 00:00:00 +0000

With high values of strength-weight ratio, non-corrosivity and low levels of electrical
conductivity, glass fiber reinforced polymer (GFRP) pultruded profiles have been attracting interest in
the civil construction market. Although promising as structural elements, further research is needed,
especially on the design approach. Given the singularities of the angle profiles – widely discussed in the
context of steel structures – this paper presents a brief review of the mechanical behavior of GFRP
pultruded angles columns and a theorical analysis of predicted strengths from design standards. Almost
90 experimental results of angles subjected to compression were summarized and compared to the
predicted strengths from pre-standard for pultruded GFRP structures, design standard for steel members,
variations of normative approaches and proposed procedures in literature. A total of 14 procedures were
compared using the model error parameter. The results allowed to conclude that, among the available
procedures for pultruded profiles, the consideration of the shear effect and the use of the classical
flexural-torsional equation guarantee greater accuracy of the theoretical prediction. Although steel
procedures do not present clear advantages, the similarity observed between the mechanical behavior of
steel and pultruded angles leads to believe that, from adjustments to the resistance curves due to the
material characteristics, more sophisticated procedures than the current ones for pultruded columns can
be proposed.

ESTUDO NUMÉRICO SOBRE O COEFICIENTE DE FLAMBAGEM LOCAL DE SEÇÃO COMPLETA DE PERFIS S ENRIJECIDOS: PROPOSTA DE FORMULAÇÃO

Mon, 26 Aug 2024 00:00:00 +0000

Os perfis de aço formados a frio têm sido amplamente empregados na construção civil em
função da facilidade de fabricação e montagem, variedade de formas de seção transversal, além da
leveza e eficiência estrutural. Entretanto, tais perfis apresentam elevada esbeltez, tornando-os
suscetíveis a fenômenos de instabilidade, como, por exemplo, a flambagem local de seus elementos. No
dimensionamento de barras com esse tipo de perfil, um dos métodos empregados consiste no Método
da Seção Efetiva (MSE), definido pela ABNT NBR 14762:2010. Nesse método, a flambagem local é
considerada por meio de propriedades geométricas efetivas da seção transversal completa das barras,
sendo essa definida pelo coeficiente de flambagem da seção completa. A norma brasileira preconiza
formulações para obtenção desse coeficiente apenas para algumas seções transversais específicas, sendo
que seções S enrijecidas não constam no escopo de fórmulas da prescrição normativa. Em casos de
perfis distintos dos apresentados na norma, é necessária consulta à literatura ou aplicação de métodos
numéricos. Neste contexto, o trabalho em questão tem como objetivo a obtenção de uma formulação
para o coeficiente de flambagem local para seção completa de uma barra de seção S enrijecida submetida
à compressão uniforme, com elemento central inclinado. Para tanto, uma análise numérica consistente
foi desenvolvida utilizando o software de elementos finitos ABAQUS, a fim de determinar a tensão
crítica de flambagem local e, a partir de um estudo paramétrico do perfil S enrijecido, definir uma
formulação válida para o coeficiente de flambagem. Uma formulação com boa correlação de valores
para o coeficiente da seção em questão foi obtida, sendo apresentadas informações relevantes para o
dimensionamento de barras com perfil S enrijecido com elemento central da alma inclinado.

A NUMERICAL INVESTIGATION ON THE INTERACTION BETWEEN GLOBAL AND LOCAL BUCKLING MODES IN CASTELLATED BEAMS

Felipe da C. T. T. Souza, Daniel C. T. Cardoso, Elisa D. Sotelino — Mon, 26 Aug 2024 00:00:00 +0000

The present work aims to investigate the interaction between lateral torsional buckling and
compression ‘tee’ local buckling in castellated beams. Finite element method (FEM) is used to perform
a parametric analysis for Litzka-beams subject to pure bending moment and considering combinations
of flange-to-web width and thickness ratios and unbraced lengths. To account for the possibility of
different yield strengths, non-dimensional local and global slenderness are used to assess the behavior
in a comprehensive manner. The responses for beams having different combinations of slendernesses
are compared and the relative strengths are discussed. The FEM ultimate bending moments are
compared to those calculated according to the current design recommendations for castellated beams,
showing that these may either over or underpredict actual capacities. Finally, a direct strength method
approach is tested for the prediction of the nominal bending strength.

EXPERIMENTAL INVESTIGATION ON THE MOMENT-ROTATION PERFORMANCE OF PULTRUDED GFRP WEB-FLANGE JUNCTIONS

Gisele Góes Cintra, Daniel C. T. Cardoso, Janine D. Vieira — Mon, 26 Aug 2024 00:00:00 +0000

This paper aims to present an experimental investigation on the rotational stiffness of
pultruded glass-fiber reinforced polymer (pGFRP) cross-section junctions. Channels and I-sections with
different types of resins were studied and a novel set-up was developed to experimentally characterize
the junctions in a direct manner. The digital image correlation (DIC) technique was used to monitor
deflections and angles of rotation, as well as the cracks formation. In addition, fiber architecture was
analyzed through an optical microscope and correlated with the moment-rotation response.

NUMERICAL AND EXPERIMENTAL ANALYSIS OF FIBER REINFORCED COMPOSITE BEAM

Mon, 26 Aug 2024 00:00:00 +0000

Composite materials have advantages like their lightness and strength that make them
attractive for purposes in engineering. This paper describes a thin-walled square composite beam
subjected to three-point bending test. Computational and experimental models are studied for this beam
using carbon fiber as composite material. It is also explored ways to make it as light as possible,
supporting a minimum pre-established load. Using ANSYS® Composite PrepPost it is possible to
defined layers, thicknesses and orientations for the studied layered composite structures. Then, structural
analysis of the geometric model defined is performed with the aid of ANSYS® Mechanical. Numerical
results obtained are compared with experimental models produced in laboratory. The beam is made of
carbon fiber and epoxy resin by the application of vacuum bagging process after the hand lay-up
lamination and post-curing at high temperature. This work is part of the researches of an undergraduate
engineering program that aims to study composites, specially for civil and mechanical engineering, in
order to analyze their main features using computational tools and experiments.

BAMBOO STRUT AND SISAL CABLE TENSEGRITY STRUCTURE FOOTBRIDGE

Nathalia B. de Albuquerque, Daniel C. T. Cardoso, Mario Seixas — Mon, 26 Aug 2024 00:00:00 +0000

This paper presents a study on the behavior of a pedestrian bridge tensegrity structure built
with natural materials. Initially, a prototype module of the structure is developed in a 1:25 scale. A
constructive method is proposed applying foldable techniques for assembly and disassembly procedures.
The methodology for the construction of the structure applied scaled models, from small to full-scale
models. Bamboo culms of Phyllostachys aurea species were employed for the struts (compressive
elements) and sisal ropes were selected for the cables (tensile elements). The modeling of the structure
is carried out using the software Galileo, a program for structural analysis of tensegrity structures
developed at PUC-Rio. Bar and cable elements were adopted to model the tensegrity footbridge. The
effect of the prestress of the cables on the structure is studied. A comparison between the computational
models considering a steel tensegrity structure and a bamboo strut and sisal cable net tensegrity structure
with regard to the stresses acting on the cables and the displacement of the mid-span. Finally, the use of
natural materials in civil engineering is evaluated regarding the mechanical performance of the structure.

AEROACOUSTICS ANALYSIS OF TRAILING EDGE INCLUDING POROSITY EFFECTS

William D. P. Fonseca, Adriano M. Goto, Lourival M. S. Filho — Mon, 26 Aug 2024 00:00:00 +0000

Trailing edge noise on rigid surfaces is a significant source of sound in aircraft. In order to minimize

the sound radiated by a process involving acoustic waves, the present article investigates the effects of trail-
ing edge noise generation on rigid semi - infinite and porous plates. For this purpose, the Boundary Element

Method is employed to solve the Helmholtz equation, subject to boundary conditions that seek to model the
vibration and porosity effects of the plates. The study is developed for a two-dimensional problem, in which
the incident source of noise generation was a lateral quadrupole, positioned at the trailing edge. In this paper
the lateral quadrupole represents a turbulent vortex in the boundary layer of the plate, according considerations
presented in the literature. Initially, the study verified the acoustical directivity for the rigid plate with the wave
numbers k = 0.1, 1, 5 and 10. In a second moment, the directives for the porous plate with k = 0.1 and 10 were
analyzed. From the results it was found that because the sides of the porous plate have opposite phases, the
pressure variation on the surface of the plate opposes pressure in the region above it causing noise reduction. It
was also found that the porosity effect causes noise reduction more effectively at low wave numbers.

AVALIAÇÃO DA INFLUÊNCIA DO POSICIONAMENTO DO NÚCLEO RÍGIDO EM ESTRUTURAS DE AÇO: ESTUDO DE CASO

Erasmo A. B. Silva, Aline S. R. Barboza, Ayslan D. A. Santos — Mon, 26 Aug 2024 00:00:00 +0000

One of the main ways of stiffening tall buildings or formed by slender profiles, case of multi-
storey steel buildings, are based on the introduction of the concrete core, capable of resisting both

vertical and horizontal efforts. Generally, this bracing subsystem is positioned around the service core
in the central regions of the building. However, architectural proposals accasionally lead to asymmetry
of the plant core, a factor that influences the capability of the structure to withstand lateral efforts, and
to the appearance of torsion. This work proposes the analysis of displacements, distribution of efforts
and overall stability of models of a twelve-story steel structure, with the indicated variations: 1) center
of gravity of the coincident concrete core and structure; 2) shear center of the concrete core coinciding
with the center of gravity of the structure; 3) asymmetric concrete core in relation to the two axes. The
models were analyzed in the SAP2000 finite element software, where the efforts were obtained in the
metallic profiles in linear and geometrically non-linear analysis by the process P-delta process and
displacements used to calculate second order efforts through the Effort Amplification Method
Applicants. For verification of the core and calculation of the coefficient γz was used the TQS software.
It was concluded that the core positioning influences the torsion efforts, which become more accentuated
by the increasing distance from the shear center to the action resulting from the lateral loads. For the
building under analysis, the greatest variation of second-order efforts occurred in the Amplification
Method of the Requester Efforts, but did not show considerable variations through the P-delta analysis
process and the enhancement method γz coefficient. The difference of efforts between the models was
basically die to the geometric distribution generated by the positioning of the concrete core.

DYNAMIC INSTABILITY OF WIND TOWERS

Matheus Moreno Fortes, Zenón José Gúzman Núnez Del Prado — Mon, 26 Aug 2024 00:00:00 +0000

In this work the dynamic instability of a coupled tower-blade wind turbine system is
investigated numerically. For this, the linear Euler-Bernoulli theory is used to describe the coupled
tower-blade system and considering the lateral acceleration of the nacelle at the top of the tower,
which is the base of the flexible blade. The Galerkin method is applied to obtain a set of linear
ordinary differential equations of dynamic equilibrium which are, in turn, solved using the runge-kutta
method. First, the coupled eigenvalues are obtained considering several blade rotational speeds and
both the veering and instability phenomena are studied. Second, an external harmonic load is applied
to the system and the linear dynamic behavior is analyzed. A parametric analysis is performed to

observe their influence on the linear oscillations of the system. Obtained results show that the tower-
blade system can show instability or veering regions mainly due to blade rotation and, it is possible to

observe jumps or large amplitude oscillations due to external loads

MODELLING AND SIMULATION OF TUBULAR REACTORS PACKED WITH A BED OF INERT PARTICLES AT SUPERCRITICAL CONDITIONS

Mon, 26 Aug 2024 00:00:00 +0000

The usage of tubular reactors for triglycerides transesterification process at supercritical
condition has gained contrast as a promising technology to large-scale continuous production of
biodiesel. Among the features which make this technique feasible, it is possible to highlight the use of
low quality oils, absence of catalyst and smaller reaction time when compared to conventional
processes.The intensification of continuous processes is possible applying mixing promoters, which
purpose is reducing the mass transfer resistances as a consequence of increasing the contact between the
components. A bed of inert particles inserted in a pipeline might work as a mixing promoter. Thus, this
study aims to examine the triglycerides alcoholysis process at supercritical conditions in a tubular reactor
fulfilled with inert particles. Two types of fillings were considered in this study: glass and stainless steel
316.The Method of Lines was selected to solve the proposed mathematical model. The use of stainless
steel spheres had better simulation results and this behavior occur mainly due to the thermal properties
of this material.

EVALUATION OF A MODEL BASED CONTROL STRATEGY FOR A NON- ISOTHERMAL SYSTEM WITH MULTIPLE INLETS AND OUTLETS

Mon, 26 Aug 2024 00:00:00 +0000

With the rising development of embedded technologies, the use of a controller with a
traditional control strategy, such as a PID, can be replaced by advanced control methods. Advanced
control methods guarantee greater efficiency in complex situations which enhances process security
and final product quality. The present work investigated how model-based control methods performed
in a laboratorial tank system scenario. For this purpose, a theoretical and stochastic model was
developed which was based on mass, energy, momentum, and analysis of the data collected. After

validation, a model-based control strategy with a generic and then optimal approach was applied off-
line, with ISE tuning. To solve the model, an explicit Runge-Kutta’s method and parameter

optimization with PSO method was used. Finally, the influence of data reconciliation processing on
control development was investigated. It was concluded that both model-base strategies were more
efficient regarding the stability and proximity of the controlled variable to the setpoint, especially
when the data reconciliation was present.

ANÁLISE DE PLACAS DE VIDRO LAMINADO UTILIZANDO O MÉTODO DOS ELEMENTOS FINITOS

Lara de Andrade Kunhen dos Santos, Carlos David Rodrigues Melo — Mon, 26 Aug 2024 00:00:00 +0000

A utilização do vidro laminado na construção civil tem crescido muito nos últimos anos,
principalmente devido ao avanço das pesquisas e ao aumento da compreensão sobre seu comportamento
mecânico, apesar do seu uso em estruturas ainda ser considerado recente. O vidro laminado é composto
de lâminas de vidro intercaladas com camadas intermediárias (interlayers) poliméricas. Esta estrutura
faz com o que o compósito adquira maior resistência quando comparado ao vidro monolítico. A
interlayer geralmente é composta por um material viscoelástico não-linear. Este trabalho tem como
objetivo analisar a influência do tipo de interlayer na rigidez de placas de vidro laminado à flexão. Os
modelos desenvolvidos são baseados na norma EN 1288-3:2000, que determina a resistência à flexão
do vidro por meio de um ensaio de quatro pontos. São estudadas as três camadas intermediárias mais
comuns comercialmente, PVB (Polivinil Butiral), EVA (Etileno Vinil Acetato) e DuPont’s SentryGlas
(SG). As placas são modeladas no programa comercial de elementos finitos ABAQUS e os modelos
validados a partir de ensaios disponíveis na literatura científica. São utilizados modelos constitutivos
lineares elásticos para os elementos de vidro e as interlayers. Uma análise paramétrica é realizada
considerando a variação da espessura e o material das camadas intermediárias. Os resultados mostram
que o modelo numérico desenvolvido apresenta uma boa aproximação ao resultado experimental. A
partir dos modelos estudados, mostra-se que o PVB e o EVA diminuem a rigidez do conjunto conforme
o aumento de suas espessuras. Entretanto, o SG segue o comportamento contrário, aumentando a rigidez
do conjunto.

DETERMINAÇÃO DA CAPACIDADE RESISTENTE DE SEÇÕES GENÉRICAS DE CONCRETO ARMADO USANDO O MÉTODO DA COMPATIBILIDADE DE DEFORMAÇÕES

Mon, 26 Aug 2024 00:00:00 +0000

The development of computational routines for structural analysis allows great engineering
evolutions. With its use, more accurate results are obtained and the study of more complex
architecturally cases become possible. The present work aims at the dvelopment of an algorithm for
calculate the bearing capacity of an arbitrary reinforced concrete cross section. The Strain
Compatibility Method (SCM) was used as numerical formulation to obtain the normal effort-bending
moment interaction curves. This method is based on Euler-Bernoulli's theory for the evaluation of
cross sections deformations admitting them linear and continuous. The constitutive models used for
steel rebars and concrete were based on the requirements of NBR 6118 (2014). The solution of the
non-linear problem and obtaining the moment-curvature relationship were approached through an
incremental-iterative strategy coupled to the Newton-Raphson method. In addition, the scanning of the
strain domains was carried out in a comparative manner. It is hoped that the results obtained will be
compatible with the pre-existing literatures and even more accurate.

MODAL ANALYSIS IN A 2U CUBESAT STRUCTURE

Mon, 26 Aug 2024 00:00:00 +0000

The miniaturization of satellites has helped students practice their knowledge and build a
real satellite. Many universities have turned to this study, as other private and important institutions.
The CubeSat standard gives a set of specifications to developers and defines a cubic picosatellite with
less than 1.33kg. The vibration tests are some set of important tests to improve a satellite structure
safety. Also, before doing vibration tests, FEM analysis is largely used to analysis the CAD model,
before built the satellite. In this work is aimed make some modal analysis in an ordinary structure
developed. The results can be applied in a real CubeSat that is going to be developed and later
withstand the vibration tests in the Mechanical Vibration and Acoustics Laboratory of Federal
University of Ceará. It was made modal analysis varying the load conditions and putting a circuit
plate. In addition, it was also made harmonic analysis evaluating slack in the CubeSat’s feet. Some
changes in the mode shape were found in the presence of the circuit plate, and principally with
slacking in the feet. There are mode shapes that all the deformation concentrates in the circuit plate,
this natural frequency may damage the circuit. The results and observations will help in future analysis
and tests.

MODELING FOR SIMULATION AND NUMERIC ANALYSIS OF CREEP GROAN IN DISC BRAKES

Mon, 26 Aug 2024 00:00:00 +0000

According to Brecht, Hoffrichter & Dohle [1], Creep Groan is a low frequency noise, from
20 to 200 Hz, that appearing in automotive brakes, mainly in automatic transmission cars, occurring in
disc brake systems at low pressure and velocity conditions, i. e., in the beginning of movement and
instants previous a complete stop. The Creep Groan noise may be easily identified by drivers and
passengers which impacts directly the impression about the vehicle quality and reliability. Thus a
better understanding of the parameters that cause the phenomenon is necessary to mitigate it and
provide greater comfort to the passengers. Considering the existing means to study the phenomenon, a
computational model was developed to numerical analysis focusing in the friction coefficient
variation, so it may be compared to experimental test results. The model was developed aided by the
MATLAB software. The model consists in a disc brake system simplification, a spring-mass model
with one degree of freedom, so the movement and forces patterns may be easily described and
understood.

A COMPARISON BETWEEN THE CLASSICAL BEAM THEORIES BASED ON EQUIVALENT SINGLE LAYER AND MURAKAMI’S ZIGZAG THEORY.

Herbert C. L. Melo, Gabriel D. de Menezes, Fabio C. da Rocha — Mon, 26 Aug 2024 00:00:00 +0000

The necessity for better properties materials has made advances in the composition of
structural elements such as composite beams introduced in the fields of civil, marine, aerospace
and mechanical engineering, which requires better material properties. However, the rapid
increase in using composite materials required improvements in the kinematics of classical
beam theories made to describe the mechanical properties of composited laminated beams. This
paper presents a comparison between the Euler-Bernoulli Theory (EBT) and Timoshenko Beam
Theory (TBT), applying in laminated composited beams associated with multilayer composite
analysis theories: Equivalent Single Layer (ESL) and Murakami’s ZigZag Theory (MZZ). The
work reported here shows examples of different beam configuration and loading, subject to
both theories. It was possible to compare the results with the exact solution derived by Pagano
[1]. Defining the length/thickness relation in which these theories are valid. EBT presents
precise results for low thickness beams; however, it presents low precision in the interlaminar
stress analysis. To contour this limitation and get better results in the stress field this paper used
the equilibrium equations of the elasticity theory. Meanwhile, TBT presents more accurate
results for thicker laminate beams, and the effects of transverse shear deformation are more
relevant in these cases. This article recognizes that TBT is more precise than EBT in all
comparisons presented and can represent the mechanical properties with certain precision and
simplicity.

EVALUATION OF NORMATIVE MODELS INTEGRATED TO NONLINEAR COM- PUTATIONAL MODELS FOR SIMULATION OF STEEL-CONCRETE COMPOSITE BEAMS WITH PARTIAL INTERACTION

Tawany A. Carvalho, Samuel S. Louzada, ́Igor J. M. Lemes, Ricardo A. M. Silveira — Mon, 26 Aug 2024 00:00:00 +0000

The present study refers to the composite steel-concrete beams analysis considering the vari-
ous nonlinear effects inherent to the structural typology. These effects generate complexity to the design

requiring computational methodologies for the accurate measurement of structural behavior. With good

numerical efficiency, the Refined Plastic Hinge Method also stands out for its simplicity. This method-
ology will be used considering rotational pseudo-springs at the finite elements ends for the simulation

of plasticity. However, this approach was developed for isotropic materials with elastic-perfectly-plastic

behavior, implying loss of precision in the analysis of structures containing concrete in their compo-
sition. Furthermore, the effects of partial interaction can not be simulated by the inherently rotational

behavior of the pseudo-springs. Thus, the introduction of the cracking and partial interaction effects will
be approached through effective moment of inertia defined by normative criteria. The validation of the
implementations will be done based on the comparison with numerical and experimental data present in
the literature through several parameters extracted from the program.

OBJECT-ORIENTED GRAPHICAL INTERFACE FOR COMPUTATIONAL TOOL OF TWO-DIMENSIONAL ELASTIC-LINEAR ANALYSIS OF BARS WITH STRAIGHT AND CURVED AXIS

Fernanda G.B.S. Oliveira, André S. Müller, Luís F.S. Soares — Mon, 26 Aug 2024 00:00:00 +0000

This paper describes the details of a graphical interface for a linear-elastic analysis program
based on the finite element method with two-dimensional straight and curved bars elements, without
considering the shear deformations (Navier beams theory). The software adds curved-axis elements,
such as circular arcs, to the linear analysis of bars based structures (beams, frames) as a way to assist

the teaching and learning in the structural environment. The interface was developed in Java, object-
oriented paradigm and associated with the program already developed in FORTRAN. The system

generates the preprocessing of the analysis. Preprocessing includes data entry with constitutive and
geometric properties, graphical arrangement of nodes and elements, boundary conditions and loads.
This graphical interface is part of a research project aiming to develop a software for analysis of
frames with both straight and curved bars, as well as bars with variable inertia.

FERRAMENTA DE MODELAGEM GEOMÉTRICA PARA ANÁLISE ISOGEOMÉTRICA DE COMPÓSITOS LAMINADOS

Jonas Aguiar Junior, Evandro Parente Junior — Mon, 26 Aug 2024 00:00:00 +0000

The finite elements method (FEM) is the most commonly used numerical approach for
structural analysis. Recently, the Isogeometric Analysis (IGA) was proposed as an alternative method
to FEM. IGA uses the same functions used in CAD systems in geometric modeling as B-Splines and
Non-Uniform Rational B-Splines (NURBS). Thus, IGA has gained attention by being able to exactly
represent complex geometries due to the use of B-Splines and NURBS in the numerical solution,
eliminating errors caused by geometry approximation present in FEM. NURBS are described by a set
of control points, weights and knot vectors, allowing the representation of both analytical shapes (e.g.
circles, cylinders, and quadrics) and free form models using the same database. However, as the IGA is
more recent than the FEM, there are not many tools to perform isogeometric modeling and analysis.
Therefore, in this paper presents a simple approach for preprocessing isogeometric models based on the
use of a well-known geometric modeler. This program is used for geometry creation and model
refinement using NURBS. These data and the associated attributes (e.g. material, loads and boundary
conditions) are saved in an input file for the analysis program. This preprocessing tool was validated
using of a set benchmarks and very good results were obtained.

NUMERICAL ANALYSIS OF THE FLOW OF A 2-D JETS UNDER VARIABLE NOISE

Thiago F. S. Freitas, Andreia A. Nascimento, Leonardo Q. Moreira — Mon, 26 Aug 2024 00:00:00 +0000

The present paper shows an physical analysis for bidimensional fluid flow evolutions of a
submerged rectangular free jet at low Reynolds Number. The flows were simulated using a code based
on the Fourier Pseudospectral Method coupled with immersed boundary method (IBM) IMERSPEC2D
(Mariano [1]), which uses the Fast Fourier Transform (FFT) to solve the bi dimensional Navier-Stokes
equations; the jet profile was implemented using the multidirect-forcing method, and the Runge-Kutta
4th order method with 6 steps (RK46) was used temporal method. The aims of this paper is validate
of noise required (0%, 1% and 3% of noise) to simulate the jet flows to Re = 100, at five different
mesh: 64x16, 128x32, 256x64, 512x128 and 1024x256. The results presented in this paper are based in
the velocity profile at five positions: vertical profile at position 12D, 16D, 32D and 64D, where D is the
diameter of the jet. A preferential mesh of 256 x 64 is chosen according to its accuracy and computational
cost, however when the noise was being analyzed, the mesh was considered inadequate due to its low
precision and the already existing numerical noise in its structure.

IN-SITU OFFSHORE PIPELINE MONITORING: A SYSTEMATIC REVIEW

Mon, 26 Aug 2024 00:00:00 +0000

In-situ monitoring of submerged pipelines is an extremely important procedure since the
continuous monitoring of this system helps to avoid possible errors and allows better visualization of
a necessary solution. In this sense, the retro-analysis also shows a very fundamental method, which
consists in the observation and analysis of a real situation, already occurred. In this way, mistakes or
poorly adjusted parameters that prevent the success of the work, are more easily adjusted. This work
consists of a systematic review of free spanning pipelines in-situ monitoring. A systematic review of the
literature consists of investigating the state of the art of a subject or area, however against a common
literature review, systematic reviews have the purpose of being replicable, accurate and methodical.
Therefore, they are accomplished through the definition of a research question, a search strategy, the
establishment of inclusion and exclusion criteria and the careful analysis of the material. In this sense, a
whole study on the chosen theme, as well as the definition of a search string is being elaborated to reach a
final amount of Works that represent the subject of this article. Thus, the careful analysis of the keywords,
abstracts, and introductions has been of great relevance in this phase of the research. Finally, through
the application of systematic review techniques, the most relevant works of the area were identified and
the construction of a bibliographic review was made possible. Hence, as a final result of this project,
it is intended to build a systematic review article that serves both to exercise this tool and to base other
studies that need a precise and in-depth knowledge regarding the subject in question.

APPLICATION OF SYSTEMATIC REVIEW TECHNIQUES IN THE STUDY OF STRUC- TURAL MODELING OF FREE-SPAN RIGID DUCTS SUBJECTED TO VORTEX-INDUCED VIBRATION

Mon, 26 Aug 2024 00:00:00 +0000

The project focuses on the analysis of rigid duct structures on the phenomenon of vortex
induced vibration (VIV) in free-space areas in the underwater bed from the perspective of the Systematic
Review (RS). the SR methodology was utilized for its systematic and explicit ways of identification,
selection and critic evaluation in a large quantity of other researches and studies. In this project, the
systematic review techniques were applied to analyze the state of the art for Computational Modeling
and Analysis of Structural Behavior of Hard Ducts in Free Spans Undergoing Vortex Induced Vibration.
Computational analysis, via finite element simulation, is one of the best tools to study this complex
phenomenon. The simulation replicates the situation of the subsea pipeline when in vain free. It was
necessary to define the string that would be used for the beginning of the search, by testing with the
keywords. Already structured string, it was possible to gather a material cluster, starting the filtering,
choosing the inclusion and exclusion criteria that fit the process as a filter, separating the most relevant
material. Thus, with the previous steps already performed, it was possible to draw a script to be followed
during the research, therefore, StArtwas used as support the steps of the SR process, helping from the
creation of the script to the result. A systematic review was applied to the subject of research, providing
reproducible results and pointing out what is current in the area, proving its potential in the survey phase
in scientific research.

INFLUÊNCIA DA CURVATURA E DAS CONDIÇÕES DE APOIO NOS ESFORÇOS DE UMA CASCA CONOIDAL

ALVES, Rafael Henrique Claudino Peres, SOARES, Renata Machado — Mon, 26 Aug 2024 00:00:00 +0000

The structural elements of the shell type are a good technical and aesthetic solution for
application in different types of construction works. In general, the shells can be used as cover, they
have a structural function and, in this situation, the knowledge of the influence of their contour
conditions and their curvature on the behavior of the structure assists in the execution of structural
projects. Thus, this paper studies the influence of curvature and boundary conditions on the behavior of
a conoidal shell of parabolic curvature when subjected to a uniformly distributed transverse load on its
surface. The solution of the problem is done by means of the finite element method (MEF), using the
commercial software Abaqus ® and one obtains the relation of the displacements, moment bending and
normal stress with the variation of the magnitude of the applied load. It is observed that the increase of
the height of the curvature and change of the conditions of support in the bark influence in the magnitude
and the distribution of the efforts of flexion and of membrane. In addition, a greater non-linearity of
responses is observed for certain combinations of curvature height and support conditions.

COMPUTATIONAL FLUID DYNAMICS FOR THE ANALYSIS OF THE FLOW AROUND A SQUARE PRISM IN TURBULENT REGIME

Mariana Reis Pereira, Patricia Habib Hallak — Mon, 26 Aug 2024 00:00:00 +0000

The use of models in Computational Fluid Dynamics (CFD) has been increasing
considerably, since the description of the phenomena in an analytical way is sometimes very complex
and wind tunnel tests can not always be used. In this research, the characteristics of the turbulent flow
around an obstacle of square section, for different Reynolds numbers, were studied, using the
computer code in CFD, OpenFoam, which is an open source program in C ++ programming language.
The choice of the OpenFoam code was due to the fact that is a free open source program and has a
great study potential. The square obstacle was chosen because it has similarities with several structures
studied by the engineering, that is to say, it is a blunt body with sharp corners and has many already
consolidated data. The beginning of the study was done by performing a mesh analysis. For this, a
value of the Reynolds number was set and analyzes were carried out with meshes of different
refinements in order to evaluate the sensitivity of the mesh. The turbulence model used was the RANS
category (Reynolds Averaged Navier-Stokes Equation) and the values of the aerodynamic coefficients
found were compared with those obtained in the literature. The most efficient mesh was defined
relating the aerodynamic coefficients with the execution time of the analysis and the level of the
refinement of the meshes. In a second instance, the Reynolds number were varied and thus the values
of the aerodynamic coefficients and their fluctuations were obtained.

AN APPLICATION FOR THE CALCULATION OF WARPING CONSTANT AND OTHER GEOMETRIC PROPERTIES FOR THIN-WALLED ARBITRARY SECTIONS

Ítalo Samuel da Silva Araújo, Selma Hissae Shimura da Nóbrega — Mon, 26 Aug 2024 00:00:00 +0000

In the design of structures, when loadings that cause torsion and / or buckling are
considered, it is essential to calculate the warping constant. This parameter can be easily obtained by
expressions available in many technical publications, and they are applicable to mono-symmetric or
double-symmetric profiles (standard sections). The problem, however, is to obtain the warping
constant for thin-walled arbitrary sections, without symmetry axes, that can eventually be found in
structural designs. This paper does not focus on the explanation of torsion theories (that was in fact
used) nor the presentation of all expressions that allow the calculation of the warping constant, but
summarizes and organizes them in a computer application. The idea is to offer an easy and friendly
code to the technical community so that undergraduate students and even structural engineers can use
it in their projects. In order to make it comprehensive and employed in the various levels of the
Engineering courses, several other geometric properties were considered, such as centroid and shear
center positions, moments of inertia, radii of gyration, principal moments of inertia, section moduli,
among others. The obtained results are compared with those presented in expressions available in
technical literature and international publications.

ON THE DEVELOPMENT OF DOMAIN PARTITIONING TECHNIQUES APPLIED TO THE MATERIAL POINT METHOD

Mon, 26 Aug 2024 00:00:00 +0000

This paper aims the development of domain partitioning techniques applied to numerical sim-
ulations using the Material Point Method (MPM). The MPM can be used to simulate various engineering

problems, including those involving submarine landslides, installation of torpedo anchors and dynamical
analysis of structures. The parallel solution of MPM involves the use of parallel computing libraries
and domain partitioning techniques. This procedure potentially increases the processing speed of the

problem and, consequently, reduces computational time. In this work, two geometric domain partition-
ing techniques were adopted: 1) division by horizontal or vertical bands; 2) the Recursive Coordinate

Bisection (RCB) method. Both partitioning algorithms were developed using the C/C++ language and
the Message Passing Interface (MPI) library. The MPI library allows the exchange of data among the
several processors used in the simulations considering the use of distributed memory systems. In order to

measure the partitioning quality for the obtained results in several simulations, the load balance param-
eter was adopted. The obtained values were compared to the optimal value calculated analytically. The

results show that the RCB implementation drastically reduces the communication regions between the
processors, which represents a computational gain in simulation time. Therefore, the RCB partitioning
technique has a better performance, compared to the technique of division by bands, since the method
optimizes the partitioning, due to its recursive and iterative characteristics.

GEOMETRIC MODELING OF PROPELLERS AND VALIDATION OF AERODYNAMIC COEFFICIENTS VIA BEMT

Mon, 26 Aug 2024 00:00:00 +0000

Advances on aeronautical sector demand research in all areas involved in the project. This
includes the aerodynamic analysis of propellers, since these are used to generate the necessary thrust to
move the airplane, absorbing to the best possible way the supplied power. Among the analytical theories,
those of Theodorsen [1] and Adkins and Liebeck [2] are notable. These theories are denominated blade

element momentum theory (BEMT). The interest in these study in the UFJF was encouraged by the Aero-
design Team (Microraptor), which participates annually in the SAE BRASIL AeroDesign competitions.

In these competitions, the team develop an aircraft, from initial design to construction and testing. In this
context, the present work proposes the study of a propeller chosen by the team for the 2019 season. The
study consists of the geometric modeling of this propeller and subsequent calculation of the aerodynamic
parameters through BEMT model. The necessary data was provided by the manufacturer, and also via
a 3D scanner. The aerodynamic coefficients of the profiles were obtained using the XFOIL program,
developed by Drela [3]. Subsequently, for the calculations of thrust, power and efficiency coefficients,
the QPROP Program, also developed by Drela [4], was used and applies the BEMT methodology. It is

possible to obtain satisfactory values of the traction generated by the propeller, validating both the geo-
metric and the analysis methodology with wind tunnel results. After validation, the power and propeller

efficiency curves were generated, certifying their use for the flight envelope.

USE OF DIGITAL IMAGE CORRELATION AND FINITE ELEMENT METHOD TO SOLVE INVERSE PROBLEM USING DISPLACEMENT FIELDS.

Mon, 26 Aug 2024 00:00:00 +0000

One of the most common problems in solids mechanics is the determination of displacement,
strain and/or stress fields of a sample, given the geometry, constitutive parameters and boundary
conditions. This problem is known as Direct Problems, being solved numerically by techniques such as
the Finite Element Method (FEM). In this work, however, it is explored how to solve the inverse
problem. To calculate the constituent parameters of the sample, we use the displacement fields obtained
with a Digital Image Correlation (DIC) algorithm. Then, FEM simulations are performed using the same
geometry, loading, boundary conditions and an arbitrary set of elastic parameters (Young's Modulus and
Poisson's Coefficient). Displacement data measured via DIC serves as a reference in an optimization
algorithm that minimizes the difference between the FEM and DIC offset data set using the initial FEM
simulation as kickstart and updating the set of constituent material parameters for subsequent iterations.
Material parameters are obtained when the optimization is completed, and the two displacement fields
are close enough. At the end of the work, numerical examples are presented and compared with those
obtained by the Finite Element Method Updating (FEMU), which works with deformations states.

CONSIDERATIONS ABOUT APPROXIMATE AND RIGOROUS METHODS FOR ANALYSIS OF REINFORCED CONCRETE BRIDGE DECK

Mon, 26 Aug 2024 00:00:00 +0000

This paper presents an evaluation of the approximated methods for the calculation of
reinforced concrete bridge deck, considering the available numerical resources. In the past, it was
common to use simplifications in the calculation of the constituent elements of the bridge: the
superstructure and substructure, on the definition of the internal forces on the ultimate limit state
(ULS) and the displacements on the serviceability limit state (SLS). From this trivial analysis, usually
analytical, the verification of the parameters of the structure was made. It is known, however, that the
simplified structural analysis causes eventual inaccuracy on the internal forces and deflection values of
the bridges and viaducts, since it is not considered the real interaction, three-dimensional, between the
main constituent elements of the structure: bridge deck, girders, columns, abutments, wing walls and
foundation elements. Thus, an oversizing of the inputs is done, for example, consumption of steel and
concrete, thus, burdening the project in question. Considering the above, it was intended in this
research to make a comparison of the results obtained analytically in a reinforced concrete slab bridge
with the results using the tables of Rusch [1] taking into account the moving loads based on Brazilian
Technical Standards NBR 7188 [2] and NBR 7187 [3]. The analyzed bridge has two spans and total
lenght of 23.10 m, with central reinforced concrete pier. The abutments are closed and have, each one,
two wing walls, simultaneously acting as containment element and columns. For the analysis of the
bridge moving load, was considered the standard Brazilian vehicle class TB-450. Finally, after a
systematical analysis of results obtained from the analytical and numerical models of the bridge, some
considerations are made, especially regarding the use of simplified methods of structural analysis and
design.

BEAMS: APPLIED COMPUTATION TO SOLVE PROBLEMS OF SOLID MECHANICS

Juscelina R. Ferreira, Lukerman D. Almeida, Sofia M. C. Diniz — Mon, 26 Aug 2024 00:00:00 +0000

This paper aims to present the program BEAMS, initials in Portuguese for Exercise Bank
Applied to Solid Mechanics. It is an open source software-in-progress that intends to available a bank
of editable examples about different issues of Solid Mechanics. It has been developed in State University
of Minas Gerais, using Scilab and LaTeX. Scilab language has some advantages: It is open software, in
continuous improvement and evolution; Obtaining high-resolution graphics is simple; working with
vectors and matrices is easy; Good Graphical User Interface with icons, selection buttons, editable input
fields, checkboxes and others. Regarding to the LaTeX, it is a high quality typesetting system that
produces technical and scientific documentation, allowing to write equations in a mathematical format,
by using symbols and specific characters. In this way, the output file obtained via BEAMS displays the
results in a pdf format file, with all detailed calculations, adding formatted texts to the explanations,
math equations, figures and tables. It is possible because Scilab uses the LaTeX syntax, through of
JLaTeXMath library. The implementation developed until here of BEAMS lets the calculation of
unsymmetrical bending of the cross-section. Since the whole process is automated, it is enough to
modify the input data so the calculations are updated according to each type of cross section. In this way
the solution of different examples can be done quickly, allowing teachers and students to conference the
calculations and visualizing how to the dimensions and each cross section induce the value of the
calculated stresses.

NUMERICAL STUDY OF NEIGHBORHOOD EFFECTS ON WIND ACTION IN A BUILDING

Camila C. Torreão , Thaís L. V. Saldanha, Ricardo S. Romão Filho — Mon, 26 Aug 2024 00:00:00 +0000

The modernization of civil construction led to the appearance of taller and more slender
buildings. As a result of this new trend, the buildings became more susceptible to the impacts of natural
actions, one of the main being the wind action. ABNT NBR 6123:1988 predicts the efforts generated by
the wind action in the structures according to the location in which it is located. Another way to analyze
the wind action is through the wind tunnel test, which can be replaced by computational simulations.
The present work intends to analyze the wind behavior on the influence of neighborhoods through a
comparison of the results found by ABNT NBR 6123:1988 and by the finite element method. The
analysis aims to study a hypothetical concrete building in isolation and with the insertion of five distinct
neighborhood models on the influence of high turbulence winds. The incidence of wind will be
considered every 30 degree. With the results, the influence of neighborhood in all the directions of wind
incidence was observed, being possible to realize that the values obtained by norm are not appropriate
for all the cases of proposed neighborhoods. In this way, it is necessary to produce more individualized
analyzes for each type of building as well as for each type of environment in which the building may be
inserted.

AUTONOMOUS NAVIGATION FUZZY SYSTEM FOR UNMANNED AERIAL VEHICLES

Diego Dutra Sampaio, Washington Luis Santos Silva, Marcos Reis Conceição Rocha — Mon, 26 Aug 2024 00:00:00 +0000

This Academic research aims to develop an autonomous navigation system for unmanned aerial
vehicles (UAV) of quadrotor type, based on fuzzy logic and the vehicle sensing, in order to automate the pilot
function, to allow the maximum degree of autonomy. To develop the project, the radio hardware control of the
drone Syma X8HC and the common ultrasound sensors used on the market were changed to allow the vehicle
to identify the presence and distance of several obstacles during the course. The fuzzy controller of structures
was tested by computer simulations and laboratory tests. The experiments results conducted on a test platform
and computer simulations have demonstrated the effectiveness and performance of the both used methods and
the main system in this work.

AN AUTOMATED STRATEGY FOR SIMULATION OF WELLBORE DRILLING IN SALT ROCKS

Mon, 26 Aug 2024 00:00:00 +0000

This work proposes an automated strategy for simulation of wellbore drilling in salt rocks.
Drilling operations in salt rocks are often complex due to the creep behavior of such materials inducing
borehole closure. In many cases, this behavior may lead to stuck pipe problems and, once the drilling
equipments get stuck, they cannot be freed without damaging the well, not to mention that it can delay
the well execution for several days. To avoid such undesirable event, numerical simulations are used to
predict the closure of the borehole, providing support in backreaming operations. Also, the information
of salt response in some zones may lead to a better decision-making process of drilling or not in an area
of interest, once the technical and economical feasibility of the operation can be better evaluated. In this
context, this work presents an automated strategy for simulation of wellbore drilling in salt rocks. The
model is based on finite element analysis using Abaqus software. Python routines are developed using

the abaqus scripting API to automate the modeling and simulation procedures for different scenarios con-
sidering user-defined variations on geometric and material properties and allowing a proper visualization

of obtained results. Case studies are presented in order to verify the reliability of the proposed strategy.

SIMULATIONS OF NON-PREMIXED LAMINAR COMBUSTION CONSIDERING DIFFERENT CHEMICAL MECHANISMS

Pedro F. P. Ferreira, Fábio A. da Cunha, Lucas G. Vivacqua — Mon, 26 Aug 2024 00:00:00 +0000

Our understanding of combustion has developed greatly over the past century and the most
recent improvement is associated to modeling and simulation of combustion. To contribute to such
advancement this work presents a mathematical modeling of non-premixed gaseous combustion and
verifies the effects of chemical kinetic mechanisms over the velocity, temperature and chemical species
concentration fields. This paper presents simulations with two different reaction mechanisms: global
mechanism and skeletal mechanism. On the utilized mathematical model, the flow field is obtained by
the solution of the Navier-Stokes equations, the temperature field is obtained by the solution of the
energy conservation equations and the species concentration fields are obtained by the solution of the
conservation equations for individual chemical species. A computational code was written on MATLAB
for the simulations, considering bidimensional domain and axial symmetry. The simulation model is
validated by comparing with experimental data.

MODELING OF EMBEDDED FUZZY SYSTEM TO CONTROL HYDROPONIC CROPS

Kayon V. L. Lopes, Danubia S. Pires, Orlando D. R. Filho — Mon, 26 Aug 2024 00:00:00 +0000

The hydroponics consists of a technique for cultivation that dispenses the use of soil, cul-
tivating the plants in water medium, from a solution enriched with nutritious substances necessary for

the development of the plant. Although still incipient, there is a significant increase in the use of this
technique in several locations where the unstable climate harms agricultural production. In this sense,
automation is extremely necessary to minimize the losses, through the control of several variables in
crop shelters. In addition to minimizing the risk of crop failure, automation enables a higher quality

of products by providing optimal conditions for production, allowing autonomy in cultivation and, con-
sequently, that the human workforce is directed to activities that require greater dedication. This paper

presents a system of multiple inputs and multiple outputs (MIMO) that allowing to control the production

and the monitoring of vegetables in greenhouses for cultivation, collecting and controlling essential vari-
ables such as temperature, humidity, luminosity, among others, using fuzzy logic. This system optimizes

production by automating data collection and hydroponic crop management in order to minimize errors

resulting from these activities. First, the study of the variables and the survey of the components neces-
sary for the assembly of the system were realized, defining the following input variables: temperature,

humidity, time and luminosity as input variables, and LEDs irradiation and ventilation, as output vari-
ables. Then, a study of how these variables are related in the fuzzy system decision-making process was

carried out. The Mamdani model was chosen as an inference method, since it is better suited to use in
systems to support decision making. Thus, the fuzzy sets and rules of the Mamdani model were defined.
The fuzzy controller was implemented in C language using an Arduino Mega 2560 board. In order to
verify the operation of the system, tests were performed in the data collection stage, inference procedure
and output activation. The test results converged, and the system outputs responded appropriately.

COMPARATIVE STUDY OF METAHEURISTICS BASED ON SWARM INTELLIGENCE: WHALE OPTIMIZATION ALGORITHM AND PARTICLE SWARM OPTIMIZATION

Mon, 26 Aug 2024 00:00:00 +0000

Optimization is the field of studies that seeks to develop techniques to improve processes,

leading them to the best operating scenario. Within the field of optimization studies, the idea of con-
structing new techniques influenced by the adaptation mechanisms of living beings has been developed.

In the context of computation, the construction of bio-inspired algorithms gains notoriety because it al-
lows agents that perform computationally simple tasks to contribute to solve complex problems when

grouped together. This paper presents a comparative study between the metaheuristic techniques based
on swarm intelligence: WOA (Whale Optimization Algorithm) and PSO (Particle Swarm Optimization),
in order to identify among the techniques the algorithm that obtains the best performance, investigating

the influence of the number of individuals of the population, the influence of parameters on computa-
tional cost and execution time, as well as enriching the literature regarding the choice of methods and

parameters according to the determined domains. The algorithms were implemented and benchmark
functions widely known in the literature were used to evaluate the efficiency of the proposed methods
and compare the results obtained. The results demonstrated the optimum performance for the search of
minimums and maximums, and the best parameters for each algorithm.

IMPLMENTAÇÃO DE CONEXÃO SEMIRRÍGIDA EM MODELOS RETICULADOS NO CONTEXTO DA PROGRAMAÇÃO ORIENTADA A OBJETOS

Ícaro R. Marques, Pedro C. Lopes, Rafael L. Rangel, Luiz Fernando C. R. Martha — Mon, 26 Aug 2024 00:00:00 +0000

This work presents the implementation of a methodology to simulate semi-rigid joints in two

A COUPLED VISCOELASTIC DAMAGE MODEL APPLIED TO SALT ROCK MECHANICS

Mon, 26 Aug 2024 00:00:00 +0000

This work describes the application of a viscoelastic damage formulation to the
preliminary study of one-dimensional finite element (FE) modeling of salt caverns structural
behavior. The evaluation of damage in salt rocks is important due the stress relief caused by the
cavern dissolution that generates a large strain energy. If this energy is not reduced, it can lead to
instabilities, and the collapse of the cavern walls. The proposed methodology is divided in two main
steps: a) incorporation of a damage model to one-dimensional analysis of elastic and viscoelastic
materials considering analytical and numerical FE approach, aiming to acquire sensitivity on the
studied problem; b) application of the referred model to the simplified evaluation of salt caverns,
addressing strain levels, damage accumulation due to cyclic load induced by temperature and
pressure variation, and the closure of such caverns. It is expected that this preliminary study allows
the evaluation of the damage modeling influence on the behavior of caverns open in salt domes
under cyclic loading, addressing the rupture mechanisms of these rocks.

RBDO AS A DECISION-MAKING TOOL IN THE TUBULAR DESIGN AGAINST COLLAPSE

Gabriel T. da Silveira, Eduardo T. Lima Junior — Mon, 26 Aug 2024 00:00:00 +0000

During drilling and lifetime production of an oil well, the casing system is responsible for its
hydraulic isolation and structural integrity, having a high associated cost in relation to the total amount
of the well. The occurrence of failure events in casing tubes can result in large environmental damage
and human losses. Its structural design must comprise the different load scenarios acting on the tubular,
including internal and external pressures, besides axial, bending and torque efforts. Among the possible
failure modes, the collapse of the tubulars, due to the action of external pressure, stands out. The casing
design methodology currently adopted in the oil and gas industry is the Serviceability Limit State (SLS)
verification proposed by API/TR 5C3 (2008), based on a model of four collapse regimes, depending on
the slenderness of the tube. Its formulation does not deal with the uncertainties inherent to projects of
this magnitude, which could improve the structural safety analysis of the tubular, without compromising
its economicity. In this way, it is proposed to apply reliability-based design optimization (RBDO)
techniques in confluence with an Ultimate Limit State (ULS) model in order to find optimal
configurations for the design variables, taking into account the variability of some geometrical and
mechanical parameters, due to the manufacturing process, considering required target safety levels.

ANÁLISE DE VIGA DE TIMOSHENKO PELO MÉTODO DOS ELEMENTOS FINITOS

Amadeo K. P. de Souza, Fernanda R. Mittelbach — Mon, 26 Aug 2024 00:00:00 +0000

This work aims to analyze the structural behavior of beams in linear elastic regime by the
Finite Element Method (MEF) based on the Timoshenko Beam Theory. A numerical study of the
problem was developed and used as a base to a computational code that was developed in Fortran
language to be capable of simulating the structural behavior of beams through the aforementioned
theory. In order to validate the computational code, the results obtained through the analytical solutions
of the Timoshenko Beam Theory were compared with the numerical results, which were also compared
with the results of the analytical solutions obtained through the Euler-Bernoulli Beam Theory,
highlighting the differences between the two theories.

STUDY OF VISCOELASTIC LAWS APPLIED TO SALT ROCK MODELS

Gleide K. M. Lins, Ricardo A. Fernandes, William W. M. Lira, Eduardo N. Lages — Mon, 26 Aug 2024 00:00:00 +0000

This work proposes a preliminary analysis of discrete mechanical models considering viscoe-
lastic laws as an introduction to the study of salt geomechanics. For the oil industry, the presence of salt

rocks during exploration significantly increases the probability of finding oil due to its sealing capacity.
However, its viscoelastic rheological properties promote a faster closure of the well over time, causing,
e.g., pipe stuck issues during drilling procedure. In this context, a discrete numerical model is used as a
standard numerical framework to the proposed constitutive investigations. A time-dependent approach is
incorporated and a double deformation mechanism is applied to consider the viscous effects on problem.

Based on this methodology, creep tests using applied forces as user-defined time functions are simula-
ted. Finally, in the way to model the wellbore closure problem, a simplified axisymmetric analysis is

proposed. Case studies are presented in order to verify the obtained numerical results.

NONLINEAR NUMERICAL MODELING OF TRUSSES

Gabriel de Carvalho Freitas, Eduardo Toledo de Lima Junior — Mon, 26 Aug 2024 00:00:00 +0000

Trusses are a type of structural system widely applied in Engineering, performing, in many
cases, as an agile and economically advantageous solution. In Structural Engineering, computational
modeling consists of a powerful tool for representing the behavior of structural elements and systems,
especially if a non-linear approach is utilized, allowing the evaluation of its mechanical performance
both in the design phase and throughout its lifetime. Metal alloys, specially the steel, are currently

employed on the construction of trusses. This kind of ductile material presents a pronounced non-
linear mechanical behavior, more specifically an elastoplastic one. Therefore, it is of importance the

consideration of the hardening effect in the structural analysis of structural systems constituted by
ductile materials, for allowing a better understanding of the structural behavior of these systems and
the study of their resistance in the post-yield regime. This work aims to develop numerical models of
trusses, considering different elastoplastic models – e.g., perfectly elastoplastic, isotropic hardening
and Ramberg-Osgood – in order to verify its influence on the response of the trusses, regarding
serviceability limit state (SLS) failure modes, in terms of allowable displacements and stresses. The
models are implemented in Python language and validated according to examples presented in the
literature.

NUMERICAL AND EXPERIMENTAL ANALYSIS OF THE CHEVRON NOTCHED BRAZILIAN DISC

Mon, 26 Aug 2024 00:00:00 +0000

The Linear Elastic Fracture Mechanics (LEFM) tries to describe the fracture and damage
phenomena in materials that obey Hooke ́s law. However some small scale plasticity can be bypassed.
The main studies in the fracture mechanics area come from the energy balance of Griffith, in 1920 and
some improvement with the energy release rate added by Irwin, in 1956. Rocks often features structural
defects, including flaws, cracks, cleavages and natural fractures. Fracture toughness represents the
capability of fragile materials, such as rocks and concretes, containing initial cracks to resist further
fracturing. A widely used test that provide this information to model fracture propagation is the Cracked
Chevron Notched Brazilian Disc (CCNBD). Nevertheless, there is some discussion about the precision
of this test. In this study, mortar specimens had their fracture toughness experimentally assessed by the
CCBND method. Numerical fracture analyses were carried out using the Extended Finite Element
Method (XFEM) trying to reproduce the CCNBD test comparing with the experimental results aiming
to better understand this test.Results indicate that the CCNBD test underestimatesthe fracture toughness
in about 13%.

RELIABILITY-BASED ANALYSIS OF BURST STRENGTH OF CASING TUBES: THE INFLUENCE OF CORRELATION BETWEEN DESIGN VARIABLES

Mon, 26 Aug 2024 00:00:00 +0000

In structural design normative codes, safety factors are used to reduce the value of the
resistance and the probability of failure of the structure due to project uncertainties. Regarding oil
exploration, there is a concern about the risk of oil well failure, considering the new challenges of this
sector, especially in offshore exploration. Even applying safety factors, these uncertainties leads to a
non-zero probability that the structural system does not meet the requirements for which it was
designed. In order to improve the decision-making process in structural safety analysis, the structural
reliability methods arise with the possibility of calculating the probability of failure of the structure,
taking into account the inherent uncertainties of the design variables. However, in order to assure the
success of the reliability analysis, it is necessary to have the statistical description of the design
variables and a mathematical model to determine the failure functions of interest. In the context of oil
well design, the API 5C3 [1] recommends the use of data with independent random variables (r.v.) in
the reliability analysis of well casing tubes, because this consideration simplifies the problem and is
beneficial for safety. However, the present work aims to analyze the influence of the use of correlation
between the r.v. in the results obtained through structural reliability methods. The limit state of ductile
rupture under internal pressure is defined, in which the tube strength is defined by the Klever-Stewart
[2] model, as determined by API 5C3 [1]. The First Order Reliability Method (FORM) and the Monte
Carlo simulation are applied for extreme correlation values of a real sample of casing tubes
manufactured in industry. Finally, the results obtained are discussed, in order to evaluate the
importance of the use of correlation between r.v. on the casing integrity analysis.

DEVELOPMENT OF COMPUTATIONAL TOOL FOR STATISTICAL ANALYSIS OF CONCRETE’S HOMOGENEITY BY DETERMINATION OF REBOUND HAMMER TEST’S RESULTS

Christian Carneiro de Oliveira, Flávio Barboza de Lima — Mon, 26 Aug 2024 00:00:00 +0000

This paper presents the development of a computational tool that provides support to in-site
structural concrete integrity analysis through the determination of its homogeneity, parameter that is
directly related to fundamental aspects of the quoted material, such as resistance and durability. The
related homogeneity determination is made by statistical analysis of the results of rebound hammer tests,
which are non-destructive tests (that is, tests that does not compromise the integrity and functionality of
the measured structural element) that determinates the superficial toughness of concrete. The statistical
analysis is consisted in the computational implementation of comparative hypothesis tests associated to
a program logic that prioritizes the effectuation of the most statistically trustable, according to the sample
characteristics of the rebound hammer test’s indexes obtained during the tests. From the comparison
between the measured indexes in different regions of the same structural element, it is determined if
those are, or not, homogeneous. In addition to this, regions of different elements are also compared to
statistically determinate if those are (or not) of equal characteristics concretes. Regarding to the
programming language, the tool was written in Visual Basic for Applications (VBA) language linked to
Microsoft Excel applications, which provides the automatization of several processes inside Excel’s
spreadsheets and tables through the creation of personalized routines; Therefore, through the integration
with Microsoft Excel, an widely used software, it was possible to create an useful, trustable and easy to
access tool of health concrete evaluation and monitorization.

AN OPEN SOURCE FINITE ELEMENT CODE FOR STRUCTURAL DYNAMIC RESPONSE OF OFFSHORE WIND TURBINES

Alan Lins Alves, Paulo Marcelo Vieira Ribeiro — Mon, 26 Aug 2024 00:00:00 +0000

The wind energy potential of the Brazilian Exclusive Economic Zone (EEZ) is significant,
with a shallow continental shelf and extremely favorable wind speed in the northeast region. The
exploration of offshore wind energy emerges as an alternative for the growing energy demand of the
country, as well as for renewable energy requirements. Offshore wind turbines are slender structures,
subjected continuously to dynamic actions mainly from wind and sea. Therefore, these structures
demand an accurate prediction of eigenvalues to avoid mechanical resonance concerning loading
spectra. This paper presents a study of natural modes in NREL Phase 2 offshore wind turbine, as well
as the steps required for the development of an open-source finite element solution in Python. The
computational solution developed in this paper considers both fluid-structure (FSI) and soil-structure
(SSI) interactions in tridimensional models. This code is embedded in SALOME preprocessor as a
plugin. This plugin extends the preprocessing capabilities of SALOME to a complete code for modal
analysis of offshore wind turbines. The blades, hub, tower, and monopile are discretized using DKT
shell elements. The nacelle is modeled using tetrahedral elements. FSI is evaluated using additional
masses, and Winkler springs define SSI. Comparisons between the proposed plugin and ANSYS
simulations present errors inferior to 1%. Case studies were made, similar to those found in literature,
considering elastic or rigid supports, and additional fluid masses, or neglecting FSI. The results confirm
that both SSI and FSI are required for accurate modeling and ignoring these effects might lead to
divergences that compromise the prediction of offshore wind turbine behavior.

ANÁLISE AUTOMÁTICA DE ESTRUTURAS RETICULADAS PLANAS E ESPACIAIS

Mon, 26 Aug 2024 00:00:00 +0000

The structural analysis allows the determination of fundamental quantities to evaluate the
behavior of the structures due of the requesting actions, as well as to carry out their correct design. In
the case of framed structures, the objective of the structural analysis is the determination of nodal
displacements, support reactions and nodal internal forces. To achieve this goal it is necessary to create
an analytical structural model by which the real structure is represented mathematically, thus making an
idealization of its behavior. Most commercial programs are limited to the analysis of plane structures,
restricting the number of elements of structures, as well as not allowing multiple support configurations.
Therefore, this work has proposed the development of a computational code, using Fortran, to solve
plane frames and space frames structures, with formulation based on the Direct Stiffness Method.
Subroutines were developed to solve plane trusses, space trusses, plane frames, space frames and grids,
with the objective of determining their support reactions, nodal displacements and nodal internal forces.
In plane frame, sub-routines were developed to consider the insertion of hinges (rotation liberation). In
order to validate the obtained results, they were compared with those obtained in commercial programs
already validated (Ftool and Salt), considering acceptable divergences of up to 2.0% between the values
provided by the code and those provided by the cited programs. Considering the results, it was possible
to verify that the parameters evaluated were congruent with those obtained in commercial programs and
their values did not exceed the divergence criterion.

OPTIMIZATION STRATEGY BASED ON GENETIC FUZZY LOGIC APPLIED IN PUBLIC TRANSPORTATION MANAGEMENT

Hadriel R. Santos, Danubia S. Pires, Orlando D. R. Filho, Kayon V. L. Lopes — Mon, 26 Aug 2024 00:00:00 +0000

The search for the implementation of intelligent systems that provide greater effectiveness
in urban planning, especially urban mobility, in order to facilitate the development of metropolises,
has grown in recent years. The real world is too complicated to get accurate descriptions, therefore
the approximation or inaccuracy must be introduced to get a reasonable model. In view of this, fuzzy
logic presents itself as a powerful tool, since it is able to deal with systems that present problems for
conventional techniques, mainly the nonlinearity and the lack of precise knowledge about these systems.
Initially it was only approached the quantitative population of a given region and o timetable as input
variables. The objective of cluster analysis is to classify objects according to the similarities between
them and the organization of data in groups. Therefore, the Fuzzy C-Means (FCM) fuzzy clustering
algorithm can be used to work with the initial collected data. The centers of the clusters provided by FCM
correspond to the parameters of the rules of the proposed Takagi-Sugeno model. In order to guarantee
the characteristics of performance, robustness and stability, the use of hybrid systems, it is necessary,
specifically, to include the genetic algorithm to aid and optimize the fuzzy system, having as a function
of suitability the output of the Takagi- Sugeno system. Consequently, the current routes are evaluated
according to their cost of implementation, since they include as many people as possible, in order to
validate or even reformulate existing routes.

MOBILE APPLICATION DEVELOPMENT FOR LEARNING MECHANICS OF MATERIALS

Pedro P. Sarkis Rosa, Ramon Pereira da Silva — Mon, 26 Aug 2024 00:00:00 +0000

This work presents Mechanics of Materials 3D, a mobile application initially targeting the
Android platform. This app is the result of a beginner's research program at the Federal University of
Minas Gerais, whose objective is to design a tool to help students to learn elementary concepts of
Mechanics of Materials, especially in the study of stress states. The fundamental idea of the project was
to make knowledge more accessible to students by allowing abstract concepts to be better understood
and absorbed through playful interaction and graphic representation. It is an attempt to reconcile
traditional teaching with new learning possibilities provided by technology, with a special focus on the
new generations of students enrolling at universities every year. The application uses the matrix library
JAMA to perform the diagonalization of the stress tensor provided, thereby obtaining the principal
stresses and corresponding directions. In sequence, it gives access to graphical interfaces that present in
an intuitive and interactive way these results, as well as other results such as the Mohr’s circle and the
infinitesimal cube in different configurations (state supplied by the user, principal stresses and maximum
shear stress). These interfaces were elaborated through the synthesis of Java programming, layout design
in the XML markup language, the Android Canvas class along with the OpenGL ES graphic API.

INFLUÊNCIA DA VARIAÇÃO DA SEÇÃO DE CONCRETO NO DIMENSIONAMENTO DE PILARES DE SEÇÃO I MISTOS DE AÇO E CONCRETO VIA COMPUTACIONAL

Mon, 26 Aug 2024 00:00:00 +0000

with relation to the x-axis is much larger than the moment of inertia of the profile with relation to the y-
axis.

Optimization of Police Contingent Management Based on a Genetic Fuzzy System

Lucas N. Mendonça, Danubia S. Pires, Orlando D. R. Filho, Kayon V. L. Lopes — Mon, 26 Aug 2024 00:00:00 +0000

In a worldwide trend for technologies development that assist in the efficient management
of people and resources, there is a great effort by the scientific community to provide viable ways to
atach this goal. In this way, to insert in these approaches the analyses of variables that influence the
public safety administration assists in the decision making of an intelligent system. This paper proposes

a software development based on Genetic Fuzzy system to help authorities in police contingent manage-
ment in order to reduce crime in urban centers. Were selected indicators that have a greater impact on

the planning and management of public security and, from this perspective, was searched for data that
best represent the real situations and correlate with the study object. The data used in the modeling and
training of the algorithm were extracted from a database that shows the occurrence of Intentional Lethal
Crimes in Sao Lu ̃ ́ıs, Brazil. The Fuzzy C-Means (FCM) algorithm was used as a fuzzy grouping and
unsupervised learning tool to estimate the performance regions (antecedent parameters) and the rules

number of the Takagi-Sugeno (TS) inference model. The genetic algorithm is a search and optimiza-
tion technique based on the principles of genetics and natural selection. A fitness function is used in

each generation of the algorithm to gradually improve the solutions. Since the output of Takagi-Sugeno

model is the weighted sum of functions of the consequent rule, the local models parameters are opti-
mized from a fitness function. With the algorithm convergence, the answer given is a family of solutions

wich representing the best police force distribution scenarios within the optimized areas. This feature is
important for the proposed system operation, because it allows this software to function as a tool to aid
decision-making, contributing to the responsible authorities. The use of the structure of a Genetic Fuzzy
system has been shown to be efficient to the proposed problem. It can be noted as advantages of using

this method in solving problems of resource management and people the possibility of acting on contin-
uous or discrete variables, efficiency in the treatment of multiple variables, possibility of working with

numerical data, experimental and analytical functions. Computational results demonstrate the efficiency
of the methodology developed.

AN ALGEBRAIC DYNAMIC MULTILEVEL (ADM) METHOD FOR THE SIMULA- TION OF TWO-PHASE FLOWS THROUGH HIGHLY HETEROGENEOUS PETROLEUM RESERVOIRS

Joao Paulo Rodrigues de Andrade , Darlan Karlo Elisiario de Carvalho — Mon, 26 Aug 2024 00:00:00 +0000

Nowadays, large reservoir geocellular static models may size up to 106
- 109
cells. In practice,

this might turn impossible the dynamic multiphase flow simulation, even using the most powerful High-
Performance Computing techniques. To overcome this problem, industry standards to apply some kind of

homogenization (upscaling) technique, in order to reduce the original fine scale problem into a coarser

one, containing less degrees of freedom. Despite the gains in CPU performance, these homogeniza-
tion methods imply in scale information losses. An alternative approach is to use multiscale/multilevel

methods, such as the Multiscale Finite Volume Method (MsFVM). In the MsFVM, nested solutions are
calculated in coarser scales then projected back to the fine scale, by using restriction and prolongation

operators. These operators are constructed using auxiliary primal and dual coarser grids. Recent de-
velopments in multiscale techniques led to the Algebraic Dynamic Multilevel (ADM) method. This

methodology allows for the use of more than one auxiliary grid levels in a fully automatic adaptive scale
approach. In this paper, we use the classical IMPES (Implicit Pressure Explicit Saturation) strategy for
the modeling of oil-water flows on highly heterogeneous porous media using the ADM methodology.
The ADM solver is used for the implicit solution of the elliptic pressure equation and is constructed

using the Two-Point Flux Approximation scheme (TPFA). The explicit solution of the hyperbolic satu-
ration equation is calculated using a First Order Upwind Method (FOUM). As a preprocessing stage, a

pressure error estimator is performed to define regions to keep the mesh more refined, such as wells and
geological features (channels, barriers, etc.), to define a Static Multilevel Grid (SMG). For the simulation
of multiphase flows an algorithm that detects high gradients in the saturation solution (e.g., the saturation
front) is used, in order to define the Dynamic Multilevel Grid (DMG), nested to the SMG. In order to
evaluate our methodology, we have solved some benchmark problems found in literature. Our results,
are very promising, as we are able to obtain solutions almost as accurate as using the fine grid solution,
with a significant reduction in computational efforts.

DISCRETE TOPOLOGY OPTIMIZATION APPLIED TO DESIGN A CONCEPTUAL MODEL FOR LOWER LIMB PROSTHESIS

Mon, 26 Aug 2024 00:00:00 +0000

The objective of this work is to develop a methodology for a conceptual model for lower
limb prostheses using the discrete Topology Optimization (TO) techniques as a design tool. The TO
of structures is currently presented as a very promising tool for the conceptual design of structures,
structural components, and even the materials microstructure. The TO techniques allow the conception
of the structural model to be part of the optimization process, giving great freedom for the designer.
The bridging of the TO technics and the addictive manufacturing is very promising to associate the
personalized design with its manufacture. The prostheses are elements that replace partially or totally
the members and that bring an increase of the independence and functionality of the people or animals
that have incapacity or reduced mobility. In this context, the application of TO techniques allows the
creation of personalized and low cost prostheses, that, in Brasilian context, is very impor tant. The
discrete TO is based on the ground structures method that consists of the generation of truss members
connecting a mesh of nodes. The level of connectivity between the nodes can be defined by the designer.
In this work, the initial mesh is based on the 3D parameterization of ellipses defined by the geometry
of the personalized lower limb of the patient. We use the elastic topology optimization formulation
with multiple load cases and the cross-sectional areas of the members as design variables. Illustrative
examples are presented to show the potentialities the formulation.

CONTRIBUIÇÃO DE LAJES E PAREDES DE VEDAÇÃO NA RESISTÊNCIA DE UM PÓRTICO ESPACIAL DE CONCRETO ARMADO FRENTE A SISMOS NA CIDADE DE FORTALEZA

Wandson L.Mota, Carlos David Rodrigues Melo — Mon, 26 Aug 2024 00:00:00 +0000

No projeto de estruturas em geral, é importante uma análise dos possíveis carregamentos
estáticos e dinâmicos que venham a ocorrer. Casos comuns são cargas estáticas relativas à utilização
da estrutura, a ação de ondas nos pilares de uma ponte, ação do vento, sismos etc. Um bom projeto
estrutural deve ter rigidez suficiente para resistir aos possíveis carregamentos atuantes, ao passo que
busca manter a configuração mais eficiente possível. Vários fatores influenciam na rigidez das
estruturas, como a resistência dos materiais constituintes, área de seção transversal dos elementos,
tamanho dos vãos, condições de apoio etc. No entanto, a literatura mostra que lajes e paredes também
podem tem um papel importante na rigidez global dos edifícios. Considerando que a norma técnica
brasileira NBR 15421 – Projeto de Estruturas Resistentes a Sismos, em vigor desde 2006, considera
que parte do nordeste, incluindo o Ceará, possui risco sísmico não desprezível, é importante conhecer
o quanto esses elementos (lajes e paredes) influenciam na rigidez e até que ponto vale a pena
considerá-los no modelo de cálculo. Dessa forma, o objetivo deste trabalho é estudar a influência das
paredes de vedação e das lajes na rigidez e desempenho de um pórtico espacial de concreto armado
submetido a um sismo. Para isso, foi projetado a estrutura de um edifício de utilização residencial com
cinco pavimentos segundo a NBR 6118:2014 e através do software TQS. Em seguida, o efeito do
sismo foi aplicado e sua resposta estudada através do programa Autodesk Robot Structural Analysis,
baseado no Método dos Elementos Finitos. Para o estudo proposto, foram criados três modelos, a
saber: pórtico espacial sem lajes e paredes, pórtico espacial apenas com lajes e pórtico espacial com
lajes e paredes. Cada um foi analisado e as respostas comparadas. Os resultados apontam que modelos
que consideram lajes e paredes de vedação tendem a ter deslocamentos, rotações e frequências
naturais até 40% menores dos que não consideram. Além disso, não só a laje apresenta importante
participação na rigidez e resposta a sismos, as paredes podem ter significativa importância e atuar
como um amortecedor.

EFICIÊNCIA DE MODELOS MICROMECÂNICOS NA OBTENÇÃO DAS PROPRIEDADES MECÂNICAS DO CONCRETO DE ULTRA ALTO DESEMPENHO REFORÇADO POR FIBRAS

Daniel Nascimento Campos Dos Anjos, Carlos David Rodrigues Melo — Mon, 26 Aug 2024 00:00:00 +0000

Devido as características excepcionais de resistência a compressão, durabilidade e ductilidade,
o concreto de ultra alto desempenho reforçado com fibras (CUADRF) apresenta-se como uma
alternativa a elaboração de projetos estruturais que possuam condições específicas de elevadas
solicitações, seja por ação de agentes deletérios ambientais, proeminentes cargas estruturais ou variações
térmicas extremas. Neste cenário, o CUADRF tem sido utilizado preponderantemente em recuperação
ou reforço de estruturas. Para que as propriedades do CUADRF sejam integralmente desenvolvidas,
demanda-se que sua microestrutura se apresente densa, resultando em um material de baixa porosidade.
Em vista disso, a caracterização do comportamento mecânico depende primordialmente da interação
entre as diversas fases que compõe a mistura, muitas vezes tornando-se necessária uma análise da
microestrutura para definir o desempenho global do material. Dessa forma, o presente artigo visa estudar
a obtenção das principais propriedades mecânicas do CUADRF por meio de simulação numérica
utilizando uma abordagem micromecânica. Os resultados obtidos são comparados com resultados
experimentais e analíticos obtidos na literatura. Os modelos de homogeneização adotados no presente
artigo são: Mori-Tanaka, Auto Consistente, Voigt e Reuss. Ao final, os resultados aprontam que os
modelos de Mori-Tanaka e Auto Consistente apresentam relativa precisão, subestimando os resultados
experimentais do módulo de elasticidade. Enquanto que os modelos de Voigt e Reuss se mostram
imprecisos para elevadas frações volumétricas de fibras.

OPTIMIZATION OF PRESTRESSED WAFFLE SLABS VIA GENETIC ALGORITHM

Levy Ivel Sousa Ribeiro, Antonio Macario Cartaxo de Melo — Mon, 26 Aug 2024 00:00:00 +0000

In the majority of current buildings, the use of prestressing has enabled the design of projects
with larger spans than the conventional ones. Besides, the technique has favoured greater durability of
the structures, since it avoids problems of cracking and excessive deformation in service. However, most
projects are still heavily guided by the expertise of the structural designer, which does not guarantee
optimal projects from an economic point of view. This work aims to present an optimization formulation
for waffle slabs executed with current plastic moulds, using the heuristic of genetic algorithms in the
program ‘BIOS‘ (Biologically Inspired Optimization System). The analysis of the efforts was integrated
into the model using the ‘FAST‘ program (Finite Element Analysis Tool). To evaluate optimum changes
in the geometric characteristics of plastic moulds, currently provided in commercial catalogues, design

variables related to the cross-section geometry of the slab, the number of tendons per rib and their ec-
centricity in the middle of the span were selected. Thus, the application of the evolutionary algorithm

seeks to minimize the objective function of the model, composed of the costs with the materials and
labour used, while attending to the constraints of ultimate and service states in the design, arranged in
standards. In all cases, the slabs are simply supported and the prestressing was considered as equivalent
load. A comparison is made between the costs of the formulated optimization model and another one that
incorporates the geometry of the plastic moulds currently available in the market. The outcomes indicate
that reasonable reductions can be achieved in the total execution costs of the waffle slabs by varying the
input parameters of the algorithm, such as the spans adopted. Also, is evaluated the effect of adopting
slabs with higher spans ratio over the optimization results.

COMPARATIVE STUDY OF PHYSICAL MODELS FOR STRINGED INSTRUMENT SOUND SYNTHESIS

Mon, 26 Aug 2024 00:00:00 +0000

Despite the growing accessibility to computational power, sound synthesis via physical mod-
elling still demands fast algorithms to allow its popularization. This work is concerned with a time-based

comparison of two hybrid modal models for sound synthesis implemented in Python. One of them ap-
proaches the modal based synthesis problem coupling the string and body in the frequency domain. The

other works in the modal domain, that is, it uses a finite difference scheme to integrate directly the modal
differential equations governing the string motion coupled to the body. Both models are called “hybrid
modal” because the string modal parameters, i.e., natural frequencies, modal shapes and damping factors,
are obtained from analytical expressions, and the body modal parameters are extracted from numerical

modal analysis. In this paper, a set of time-domain simulations including the planar and nonplanar mo-
tions of a monochord string is presented. The measurements of their execution time are obtained for

the same computational setup, programming language and simulation parameters, delivering a quantita-
tive comparison about the execution cost of these models. Furthermore, an asymptotic analysis for the

proposed algorithms is also presented for the understanding of their scalability.

A STUDY ON THE INFLUENCE OF STEEL REINFORCEMENT IN FORCE PATHS IN RC STRUCTURES USING TOPOLOGY OPTIMIZATION

Danilo B. Cavalcanti, Sylvia R. M. Almeida — Mon, 26 Aug 2024 00:00:00 +0000

Strut-and tie models are mechanism-based models used to describe the complex behavior of
reinforced concrete structures that do not satisfy the Bernoulli hypothesis. The continuum structure is
replaced by truss representing the force paths inside the cracked continuum. This paper uses topology
optimization techniques to generate the force paths automatically in reinforced concrete structures. The
traditional density approach is adopted to represent the behavior of the concrete continuum and, in
addition, truss elements are used to represent the steel reinforcement. Bi-linear models are associated to
each material in order to separate the tensile and compressive paths. A numerical example shows the
influence of the reinforcement in the final force path.

OBTAINING STRUT-AND-TIE MODELS USING TRUSS STRUCTURAL OPTIMIZATION

Camilla Pereira, Sylvia R. M. Almeida. — Mon, 26 Aug 2024 00:00:00 +0000

Strut-and-tie models are mechanism-based truss models applied in the design of reinforced
concrete structures. This paper applies the plastic formulation of the ground structure method to obtain
the force paths used in such models. The educational code GRAND is adapted to include the reactions
in the constraint nodes in the design variables in addition to que cross-sectional areas and the axial forces
of the bars. The optimization problem is written as a linear programing by introducing slack variables
related to the areas, axial forces and reactions. The maximum filter is applied to extract a topology in
equilibrium at the end of the optimization process. The original filter is adapted in order to apply the
filter to the maximum areas of the tensile and compression bars. This procedure prevents inadvertent
cut of thin bars of the resistant material. Numerical examples are presented to demonstrate the
applicability of the proposal.

APPLICATION OF OPTIMIZATION TECHNIQUES TO MINIMIZE THE EFFECTS OF VORTEX-INDUCED VIBRATION (VIV) IN FREE SPANNING PIPELINES

Mon, 26 Aug 2024 00:00:00 +0000

The use of submarine pipelines to transport oil and gas is a common practice. However, one of
the main problems associated with the use of this technology is related to the irregularities of the seabed,
which creates regions with free spans, propitiating the occurrence of the phenomenon of vortex-induced
vibration (VIV). The design of pipelines in regions with free spans involves a thorough evaluation, which
allows identifying the VIV and the probable damage due to fatigue, to find out the need to increase the
operational life of pipelines. A widely used method for VIV mitigation is the reduction of the effective
length of the span installing supports at strategic points of the pipeline, minimizing the fatigue damage.
The search for these points can be seen as an optimization problem to identify the position and the
adequate amount of supports to minimize the occurrence of VIV. Thus, this work consists of a study on
the use of optimization techniques to identify the most suitable configuration for the installation of the
supports, assisting in the development of pipelines projects. For that, different situations were analyzed,
involving the change of bathymetry and the variation of the effective span length.

BEMGUI: Graphical Interface for Modeling via Boundary Element Method

Tito A. Grossi, Gilberto Gomes — Mon, 26 Aug 2024 00:00:00 +0000

Developing and adapting computation methods for engineering problems, especially the
Boundary Element Method (BEM), has been an important area of research. In this context, BEMGUI

emerges with the goal of being a graphical user interface (GUI) for the generation of drawings, physical-
geometric modeling and contour element meshes, in order to interact with programs that use the BEM to

analyze elastostatic problems. It also aims to give a form of visual representation of the results, being a pre
and post processing tool. For this, the program is implemented in the Python language and follows the
object-oriented programming (OOP) paradigm, as Python adapts well to the application programming
interface (IPA) of a GUI. In addition, the flexibility and powerful ideas of this paradigm offers great
advantages to the scripting of a program. The result is a fast, interactive GUI that talks to the user through
mouse click and mouse movement events, in addition to keyboard keys. User-supplied information is, at
the end of a modeling process, provided to programs such as BEMCRACKER2D, which uses BEM to
generate results in crack problems, for example.

STATISTICAL INFERENCE TECHNIQUES APPLIED TO LARGE SAMPLES

Hugo Vinícius Ferreira Azevedo, Eduardo Toledo de Lima Junior — Mon, 26 Aug 2024 00:00:00 +0000

The growing evolution of structural materials and analysis models demands a proper un-
derstanding of the safety levels adopted in the design practice. The uncertainties inherent to structural

engineering problems can be evaluated from the statistical description of their design variables – dimen-
sional, mechanical and loading ones – and incorporated into the analysis by using structural reliability

models. The statistical characterization is a crucial part of the whole process, being carried out by
inference techniques, as the goodness-of-fit (GoF) tests, which verify if sample data fits a theoretical
distribution model, given a specified significance level. The GoF tests can be very sensitive to large
samples - from the order of thousands of data, becoming unsuitable for this kind of analysis. Alternative
techniques can be applied to handle large datasets. This is the case of the subsampling principle, which
involves the random, non-biased withdrawal of subsamples from the original dataset, so that a part of the
sample is used in the parameterization of the model and another part is used for the GoF test, in varying
proportions, to be studied. In addition, the AIC and BIC (Akaike and Bayesian Information Criteria)
values can be used as a preliminary indicative of the congruence between data sample and a theoretical

distribution. It is proposed the analysis of two different samples, in order to apply some inference tech-
niques, implemented in Python language. It is expected to contribute with the characterization of large

samples for studies in data science and reliability analysis applied to engineering.

UNCERTAINTY QUANTIFICATION OF FRACTURE POTENTIAL AT CONCRETE-ROCK INTERFACE FOR GRAVITY DAMS

Mariana de Alvarenga Silva, Francisco Evangelista Junior — Mon, 26 Aug 2024 00:00:00 +0000

The uncertainties are present in engineering projects, in which can be due to materials,
models or constructive inaccuracies. This is very important in dams, because the failure of this
structure can lead to enormous social, economic and environmental impacts. In addition, dams must
resist overtopping occurrence, in which it has intensity, period and duration variabilities. Thus, this
paper aims to analyze the behavior of a concrete gravity dam in the presence of a crack along interface
dam/foundation, where it is, normally, the weakest zone of the structure. The study of this
discontinuity was based in linear elastic fracture mechanics, considering mixed-mode propagation, due
to the particulars of the problem. Furthermore, a reliability analysis was made to take account the
uncertainty of main design properties and loadings. The results showed the tendency of energy release
rate to follow a lognormal distribution. The importance of flood control was evidenced, because the
analyzed dam presented high failure probability with overtopping. Moreover, consider triangular uplift
or constant uplift acting on the crack generated great differences in reliability analysis.

REVISION AND VALIDATION OF FILTERING TECHNIQUES FOR CASING WEAR PROFILES IN OIL WELLS

Mon, 26 Aug 2024 00:00:00 +0000

Aimed to achieve a better petroleum well planning, engineers have to correlate several data
about drilling parameters, geological formations and reservoir properties, as well as many other details
collected from drilled wells databases. This information helps to generate well’s trajectory and improve
casing design. In the actual scenario of reaching deeper reservoirs and running complex well paths, a
common problem is casing wear. This phenomenon mainly results in material removal from casing inner
wall during well drilling process. Since this problem impacts well’s integrity and safety, the
improvement of casing design to consider accurate material loss is crucial. A regular procedure for
casing wear inspection is to use a logging device, like the ultrasonic logging tool, to collect several
discrete measures of inner radius and thickness variations. This data is used to determinate wear rate
along well depth. Therefore, wear profiles obtained from drilled wells, could be used to express
important information about wear intensity to future projects on planning phase. A problem that usually
appears in attempt to analyze this profiles, is the spurious spikes constant presence that corresponds to
unrealistic wear values, which are known as noise. The source of this meaningless data is mostly
attached to the presence of numerous connections between pipes, due to the great casing string
extension, and it is called casing collars. This study aims to use ultrasonic logging data to determine
more representatives wear profiles ignoring positions of unrealistic wear measurements. A revision and
validation of filtering methods is used to accomplish the wear profile improvement study. A Fast-Fourier
Transform low-pass filtering is implemented. The filter’s input is a raw profile with wear rate estimated
for several measure depth and with intrinsic noise that could be misinterpreted as casing wear. It is
discussed the effectiveness of the filtered profile when correlated to casing collars positions input
obtained from logging. Therefore, a study is performed using a regular industry’s procedure to
demonstrate the potential of the methodology to improve a casing wear representation.

OPTIMIZED STRUCTURAL DESIGN OF STEEL TUBULAR TOWERS OF WIND TURBINES

Raphael de Oliveira Guedes de Melo, Márcio André Araújo Cavalcante — Mon, 26 Aug 2024 00:00:00 +0000

The wind energy is an important renewable energy resource, and it has been recently
explored in Brazil, with a strong tendency to increase in the next decades, considering the Brazil's
potential. The most common way to explore the wind energy is through the wind turbines, usually
designed to have a maximum efficiency. The tower is an important part of the wind turbine design,
once it defines the wind turbine efficiency and must be designed to resist to different loadings,
responding for 30% of the wind turbine cost, approximately. This work presents a structural
optimization study of steel tubular towers of wind turbines, within a framework based on the strength
of materials and the principle virtual work for the structural analysis of the tower, besides optimization
techniques, with the goal to minimize the tower’s weight. Some comparisons are made with optimized
aluminum tower. The minimization of the tower’s weight through the employment of optimization
techniques allows a reduction of the costs with inputs, transportation, assembling and maintenance of
the tower, especially those ones that will be installed in remote areas with difficult access, besides
contributing with the study of this technology.

ANÁLISE COMPARATIVA DOS ESFORÇOS INTERNOS EM VIGAS LONGARINAS UTILIZANDO O MÉTODO DA LINHA DE INFLUÊNCIA E O MÉTODO DOS ELEMENTOS FINITOS

Lara de Andrade Kunhen dos Santos, Bergson da Silva Matias — Mon, 26 Aug 2024 00:00:00 +0000

A determinação do trem-tipo de vigas longarinas em pontes de duas vigas retas utiliza, de
forma simplificada, a hipótese de que a rigidez destas vigas é suficiente para que possam ser
consideradas como apoios rígidos. Apesar de ser considerada uma metodologia eficiente em muitos
casos, não é capaz de abranger todas as possibilidades. Isto porque, em situações onde a rigidez das
vigas é baixa, a obtenção do trem-tipo para a viga longarina pode não ser uma metodologia apropriada.
Desta maneira, o presente trabalho apresenta um estudo comparativo entre o método de obtenção de
esforços nas vigas longarinas através da linha de influência da seção transversal com o Método dos
Elementos Finitos (MEF), buscando demonstrar a influência da rigidez nos resultados de esforços
internos das vigas e da laje. Neste trabalho, foram analisadas as envoltórias de esforços internos de vigas
longarinas em três modelos, utilizando duas metodologias: obtenção do trem-tipo da viga longarina por
linha de influência e MEF. Os três modelos foram feitos variando-se a altura das vigas longarinas. Os
resultados mostraram que há uma influência direta da rigidez das vigas na distribuição de esforços
internos. Além disto, a flexibilidade das vigas acarreta em distribuições distintas de momentos fletores
na laje do tabuleiro.

DESIGN OF REINFORCED CONCRETE UNDER ECCENTRIC LOADS WITH NEWTON-RAPHSON’S METHOD

Jéssica Yasmin Vieira Lima, Danilo Menezes Santos, Jorge Carvalho Costa — Mon, 26 Aug 2024 00:00:00 +0000

This article aims to use a numerical algorithm in Matlab for the design of rectangular
reinforced concrete columns under eccentric loads. Usually, both in academic and professional practice,
the design of such columns makes use of dimensionless charts or tables. These charts are subject to
specific restrictions as section shape, reinforcement positioning, covering dimensions, among others, so
that the design is limited to their availability. The alternative described employs Newton-Raphson’s
method to solve the nonlinear system of equations that arises from section equilibrium, keeping the
neutral axis position and reinforcement diameters as variables. The nonlinear constitutive behavior of
both materials involved is considered so that the equilibrium is expressed as a system of two nonlinear
equations for bending normal to a symmetry axis. The concrete stress distribution proposed by Brazilian
standard NBR 6118:2014 was used and a perfect elasto-plastic model was adopted for steel. The
algorithm was validated by comparing the steel area and modes of failures obtained with traditional
design methods, for several columns on different limit states.

ESTUDO SOBRE EFICIENCIA DE RESOLUÇÃO NUMÉRICA DO FENÔMENO MASSA-MOLA

Joao Marcos Alves de Oliveira, Rodrigo Toledo Teixeira Camara — Mon, 26 Aug 2024 00:00:00 +0000

The study of numerical methods is essential for the sciences, being that we often can’t solve
analytically the mathematical problems. However, these generate errors, in which they can often cause
catastrophic disasters if proper precautions are not taken. In this article, we will make a case study for the
mass-spring phenomenon. For purposes of comparison and demonstration of efficiency, we will solve
the problem by the numerical methods based on Taylor series, Euler First Order, Runge-Kutta Second
and Fourth Order, and by the classic analytic form. The theory about Taylor series allows us to only
estimate the order of magnitude of the error. In this case study, the error generated by each method
will be analyzed directly and compared by means of the relative error criterion, absolute and relative
amplitude. As a measure of quality, we will propose an adapted variation of the six-sigma quality control
system. We conclude that the method of Runge-Kutta Fourth Order is of excellent quality (“four sigma”)
under some conditions (step h of lengths 0.025).

RAFT TELEMETRIC SYSTEM: A PROTOTYPICAL IMPLEMENTATION

Mon, 26 Aug 2024 00:00:00 +0000

This paper has as the main objective to help rafts to be stable and safe by doing a printed circuit
board (PCB) based on the Arduino platform - with sensors as MPU6050 and NEO-6M GPS - which
have the goal of sending data to a receptor base in an external computer, where this data is processed
and analyzed, and shows the current rotation and location of the rafts. In this project, a phenolic sheet,
Heat Exchangers and Photographic methods were used to manufacture a printed circuit board, the main
object of the work. Also, a specific software was developed to process, analyze and show all the data
collected by the sensors on the PCB. This software uses the C/C++ language with Arduino libraries
and the Karman complementary filter, it is executed at the Arduino IDE and saved at the ATMega328p
microcontroller and for the communication of the PCB with an external computer, the XBee module with
ZigBee and SPI protocol using a 2.4GH frequency transmitted by a prototype was used.

TRANSIENT CFD ANALYSIS OF FLOW OVER A CIRCULAR CYLINDER

Luiz F. C. de Oliveira, Mario R. Freitas, Lineu j. Pedroso — Mon, 26 Aug 2024 00:00:00 +0000

The flow of air over a circular cylinder can be observed in many civil engineering problems.
Tall buildings, towers and silos can be subject to strong winds that can impact the structure local or
global stability. The flow over a cylindrical structure is a dynamic problem with transient response
characterized by vortex shedding. If the Reynolds number is sufficiently high, an alternate vortex
shedding pattern is formed, known as von Karman vortex street. In this scenario, the flow applies
dynamic drag and lift forces on the structure. This paper presents a methodology to simulate the fluid
flow over a circular cylinder and compute the drag and lift coefficients using Computational Fluid
Dynamics (CFD). A two-dimensional cross-section of a structure is modelled in ANSYS Fluent
applying the proper boundary conditions. The pressure fields are computed from the simulations and
numerical integration is used to obtain the drag and lift coefficients. From the simulations, the
streamlines, and pressure fields can also be obtained and plotted. Geometry, mesh and time step size
independence studies are conducted to ensure convergence. The results are compared to numerical data
found in the literature.

DEVELOP0MENT OF 3D WEB PLATAFORM TO SUPPORT THE TEACHING-LEARNING PROCESS IN ENGINEERING

Joao Arthur da Cruz Nunes , Prof. Carlos Magno de Lima — Mon, 26 Aug 2024 00:00:00 +0000

The University of the future, the theme of the Second Academic Congress of UNIFESP, had

as its most defended ideals the need for innovation in higher education and the promotion of social inclu-
sion and integration.The ”Knowledge Society” requires new skills and knowledge from its professionals,

such as technical skills like: application of knowledge and learning continuous updating through re-
search, openness to criticism, search for creative and innovation solutions and team management. Such

demands directly affect universities, which automatically directs us to think of innovation in higher edu-
cation. Studies have shown that the students’ greatest difficulty relates to the ability to visualize and un-
derstand the analyzed problem as well as interpret the results. The exact interpretation of a phenomenon

is the result of training and perfecting these skills. Virtual Reality is an advanced user interface technique
with a computer, which allows simulating a real environment and allows the users to immerse, interact
and navigate in a three-dimensional synthetic environment generated by a computer using multisensory
channels. The potential of using Virtual Reality technology in education is widely recognized. Christine
Youngblut in her work ”Educational Uses of Virtual Reality Technology” lists several experiences with
the development, evaluation, and use of Virtual Reality in Teaching. Recently new technologies aimed
at WEB development have caused a revolution in the construction of content of educational character.
In particular, the JavaScript language and new paradigms of programming have become the basis for the
proliferation of frameworks that make it possible to transform the WEB into a development platform for

Virtual Reality, generating an effective environment for the simulation of the sensorial channels respon-
sible for capturing the content and retention learning. This work aims to present a Platform developed

for WEB 3D content in Virtual reality focused on the exploration of contents that require the under-
standing and interpretation of a phenomena and complex concepts in Mathematics, Physics, Biology and

Chemistry disciplines seeking to help teachers and students in a journey in search of knowledge.

A RESERVOIR SIMULATOR BASED ON FORMULATIONS OF ISOGEOMETRIC BOUNDARY ELEMENTS

Mon, 26 Aug 2024 00:00:00 +0000

The development of the reservoir simulator for the study of water and gas cone phenomena
in the producer well (represented by a sink) is obtained by combining the Boundary Element Method
(BEM) and the Isogeometric Formulation using the NURBS (Non Uniform Rational B-Spline) as
shape functions. Through the Isogeometric Formulation, the discretization of the geometric model
(mesh generation), which is the step of the numerical analysis that requires more time for the engineer,
is no longer necessary, since the same functions that describe the geometry can also approximate the
field variables in the BEM, making it a great advantage in its use. The same discretization used in the
geometric model, generated in CAD (Computer Aided Design) modeling programs, can also be used
by the BEM. From the modeling of the potential flow, i.e. the study of multiphase flow in porous
media from the Laplace Equation, the isogeometric formulation can be coupled to the problem and,
therefore, to obtain the reservoir simulator for the single phase case. The determination of the
boundary conditions for the model, including the analysis of fluids interface movement, is also
presented. The final code is able to present itself as an efficient tool for the analysis of oil extraction in
reservoirs in the presence of undesirable fluid production. Validation of the results is carried out by
comparing to the conventional Boundary Element Method.

AN EXTENDED BOUNDARY ELEMENT FORMULATION FOR PUNCTUAL BOUNDARY CONDITIONS MODELLING

Matheus Rocha, Edson D. Leonel — Mon, 26 Aug 2024 00:00:00 +0000

The Boundary Element Method (BEM) is a numerical approach accurate in the solution of
several elastostatic problems. Because the method formulation involves integrals written at the
boundary, solely the bodies’ boundaries are discretised. Then, in three-dimensional problems, the BEM
mesh is composed of plane elements. However, the standard BEM formulation is limited in the solution
of problems where punctual boundary conditions are present. Then, concentrated loads and punctual
support conditions are not properly represented by the standard BEM. Such boundary conditions may

be approximately represented through small BEM elements. However, this strategy may lead to the ill-
positioned algebraic system of equations because of the small distance among the source points in such

elements. In this regard, this study presents an enriched BEM formulation (XBEM) capable to represent
properly punctual boundary conditions in three-dimensional problems. The Dirac’s function is utilized
in this enrichment process. Three numerical applications illustrate the accuracy of the proposed XBEM
scheme. The results achieved by the proposed XBEM formulation are compared with responses
provided by equivalent models constructed on Finite Element Method.

THREE-DIMENSIONAL COHESIVE CRACK GROWTH MODELLING USING THE BEM

Matheus Rocha, Edson D. Leonel — Mon, 26 Aug 2024 00:00:00 +0000

The mechanical collapse of several materials is consistently modelled through the fracture
mechanics theories. The Linear Elastic Fracture Mechanics (LEFM) is properly utilized when the
fracture process zone ahead the crack tip is small in comparison with other structural dimensions.
Nevertheless, such zone is not small enough in various material types. Among them, it is worth citing
the composites, concrete and ceramics, which are generally classified as quasi-brittle materials. In this
case, the fracture process zone may be mechanically represented by the cohesive fracture approach,
which leads to the Nonlinear Fracture Mechanics. In the present study, the three-dimensional Boundary
Element Formulation (BEM) is coupled to the cohesive crack approach for modelling the nonlinear
fracture process of quasi-brittle materials. Moreover, three cohesive crack laws are utilized to represent
the residual material resistance at the fracture process zone. The nonlinear problem is solved by either
constant or tangent operators. The accuracy of the proposed BEM approach is demonstrated through
two applications. The results of the proposed numerical scheme are compared with numerical and
experimental responses available in the literature.

DAMAGE MODELLING WITH SMOOTHED POINT INTERPOLATION METHODS

Lapo Gori, Samuel Silva Penna, Roque Luiz da Silva Pitangueira — Mon, 26 Aug 2024 00:00:00 +0000

Due to the non-local character embedded in their formulation, meshfree methods belonging to
the class of Smoothed Point Interpolation Methods (S-PIMs) have been recently shown to possess certain
regularization properties when applied to localization problems. Since meshfree methods usually provide
only a weak regularization effect, the combination with other regularization strategies is often necessary.
The present work aims to exploit the regularization properties of S-PIMs strategies in the analysis of
quasi-brittle media with scalar damage models; a stronger regularization effect is obtained combining the
meshfree approach with the micropolar continuum theory, another well-known regularization strategy.

The basic theoretical and computational aspects of the application of two S-PIM strategies, the Edge-
Based Smoothed Point Interpolation Method (ES-PIM) and Node-Based Smoothed Point Interpolation

Method (NS-PIM), to micropolar damage models are discussed, and numerical simulations of two plain
concrete experimental tests are presented.

AN EFFECTIVE BEM/FEM FORMULATION FOR THE STATIC INTERACTION ANALYSIS OF PILE GROUPS EMBEDDED IN A SEMI- INFINITE CONTINUUM

Endi S. Luamba, Ray C.S. Silva, Ana P.F. Ramos, João B. de Paiva — Mon, 26 Aug 2024 00:00:00 +0000

In the literature, numerical analysis of pilesoil interaction is performed by a variety of
formulations based on Finite Element Method (FEM), Finite Difference Method (FDM), Boundary
Element Method (BEM) or a combination of two numerical methods. In those formulations, very
complex and computationally expensive meshes are generally used. In this paper, pilesoil interaction
problems are solved with relatively simple and yet efficient meshes as a result of coupling the BEM
with the FEM, and using Mindlin’s fundamental solution for the soil modeling. To adequately

consider the flexibility of the pile, the same is discretized into a parametric number of three-
dimensional finite beam elements. Therefore, the pile can be of any size and subjected to any type of

loading including axial, lateral and moment loads. Moreover, the formulation can be easily extended
so that a foundation plate can be coupled to piles to form a capped pile group or a piled raft. The
efficiency of the developed and implemented formulations is properly demonstrated through
numerical examples including single piles and pile groups.

PREDICTION OF INSERTION LOSS OF THIN ACOUSTIC BARRIERS USING THE METHOD OF FUNDAMENTAL SOLUTIONS

Mon, 26 Aug 2024 00:00:00 +0000

In this paper, the Method of Fundamental Solutions (MFS) is applied to predict the
insertion loss of thin acoustic barriers on a rigid ground in the vicinity of a tall building. The MFS
formulation makes use of suitable Green’s functions defined by the image-source technique, allowing
decreasing the number of discretized surfaces and consequently reducing the computational cost of
the numerical model. Both the ground and the building are modeled as infinite rigid plane surfaces.
To validate the implementation of the proposed formulation, the MFS results are compared with those
provided by the Dual-BEM formulation. Numerical simulations are carried out in order to illustrate
the acoustic performance of thin barriers of different shapes for typical cases of traffic noise.

A 2D BOUNDARY ELEMENT FORMULATION FOR POLLUTANT DISPERSION ON THE ATMOSPHERIC BOUNDARY LAYER

Luiz F. Bez, Rogerio J. Marczak, Marco T. M. B. de Vilhena — Mon, 26 Aug 2024 00:00:00 +0000

This paper presents a boundary element formulation for 2D, steady-state advection-diffusion
problems with a variable velocity field and punctual source terms. The boundary and the variables are
discretized with continuous linear elements. The domain effects are computed with discontinuous linear
cells. The model shows good agreement with analytical results for variable velocity fields. Four cases
are presented with wind configuration typical of the atmospheric boundary layer - a combination of wind
power classes 1 and 4 for mean velocity, and open flat terrain and suburban areas for roughness. The
response of a unitary point source is analyzed and compared for each case.

ISOGEOMETRIC BOUNDARY ELEMENT ANALYSIS APPLIED TO ELASTIC PROBLEMS

Fernando Morais de Loyola, Eder Lima de Albuquerque , Lucas Silveira Campos — Mon, 26 Aug 2024 00:00:00 +0000

The main idea of this work is to solve elastic problems using Isogeometric Boundary Element
Formulation. A standard BEM with quadratic elements is also used in order to compare the efficiency of
both methods. In isogeometric method, instead of using polynomial shape functions, both geometry and
analysis use non-uniform rational B-splines (NURBS). NURBS are widely used for geometric modelling
in CAD software and, due to this, makes the discretization of the geometry unnecessary. One obvious
advantage of using this type of B-splines is that it can perfectly describe complex shapes, making results
more accurate. The most important feature, however, is the decrease in the amount of user’s work,
because the most time-consuming step – mesh generation – is reduced or even eliminated. In order to
easy implementation in existing boundary element codes, NURBS are transformed into Bezier curves ́
(Bezier decomposition). So, each B ́ ezier curve can be viewed as a boundary element in a conventional ́
boundary element implementation.
It is worth mentioning that displacement and tractions have their values solved at the control points

and NURBS curves do not necessarily touch them. For the definition of collocation points, Gauss-
Legendre collocation points are used in this study. Therefore, a transformation matrix, which uses basis

functions for relating values at control and at collocation points, is needed. The equation for isogeometric
BEM is defined in terms of the control points and, after applying the transformation, can be solved as the
standard BEM. Lastly, numerical and analytical solutions are compared in order to validate the method.

NON-UNIFORM DISPLACEMENT JUMPS IN CELLS WITH EMBEDDED DISCON- TINUITY FOR MATERIAL FAILURE ANALYSIS THROUGH THE BOUNDARY ELEMENT METHOD

Tiago S. Mendonça, Rodrigo G. Peixoto, Gabriel O. Ribeiro — Mon, 26 Aug 2024 00:00:00 +0000

The numerical material failures analysis is extremely important, since it allows predicting
the collapse and the structures post-critical behavior. Thus, in this work the implicit formulation of
the boundary element method is adopted to analyze material failures in models commonly studied in
literature. For this purpose, the continuum strong discontinuity approach together with an automatic
cell generation algorithm that accompanies the crack trajectory during the non-linear analysis are used.
Therefore, the main objective is the insertion of non-uniform jumps discontinuities in the displacement
field inside cells aiming at reducing the stress locking phenomenon presented by cells with constant
embedded jumps. This phenomenon is responsible for the stiffening in structural response due to the
constant cells inability to represent rotation movement. In this way, the results presented by linear cells
were more satisfactory than those presented by constant cells, since the stress locking phenomenon was
considerably reduced, demonstrating that the first class is more adequate in the representation of the
crack opening that occurs during the loading process.

O MÉTODO DOS ELEMENTOS DE CONTORNO COM INTERPOLAÇÃO DIRETA APLICADO A MEIOS SUAVEMENTE HETEROGÊNEOS UTILIZANDO A TÉCNICA DE SUPERPOSIÇÃO DE DOMÍNIOS

Mon, 26 Aug 2024 00:00:00 +0000

This work presents a formulation of the Boundary Element Method (BEM) applied to
problems governed by the piecewise inhomogeneous Laplace's Equation. Thus, the constitutive
property is isotropic but varies according to a known function along with the complete domain or then
within of distinct sectors inside it. For solving accurately this complex case, the domain integral
generated by the non-homogeneity of the medium is transformed into a boundary integral using the
Direct Interpolation Boundary Element Method (DIBEM). Another important operational advantage
of the proposed model is given by the application of the Domain Superposition Technique (DST) to
compute the sectorial heterogeneities. Reference results for evaluation of the accuracy are given
through simulations using the Finite Element Method with finer meshes.

STATIONARY AND TRANSIENT DYNAMIC VERTICAL RESPONSES OF STRUCTURES INTERACTING WITH DISTINCT SOIL-FOUNDATION ARRENGEMENTS USING CORRECTED STRUCTURAL MODAL DATA

Tamara Silva Louzada, Luis Filipe do Vale Lima, Euclides Mesquita, Josue Labaki — Mon, 26 Aug 2024 00:00:00 +0000

This work investigates stationary and transient vertical response of multidegree of freedom
structures interacting with different soil profiles through an extended modal analysis procedure. The
methodology was originally proposed by Wu and Smith [1] to analyze the dynamic behavior of
structures subjected to an incident wave fields. The present article revisits the previously mentioned
article and expand it to consider external force excitations acting upon the structure. The original
formulation considered the soil as a homogeneous half-space. In the present article, the response of
structures supported by the half-space, layered soil profiles and also by piled structures is addressed.
The stationary soil and pile response were synthetized through Boundary Element Method. The main
characteristic of the method stated in this work is to modify the modal original parameters of the
structure in other to incorporate in these parameters the dynamic response of the soil-foundation
arrangements. Numerical studies will address the quantity of modified structural modes necessary to
describe, with certain precision, the transient response of structure as a function of the soil-foundation

supporting scheme. The numerical examples presented will also investigate the role of the soil-
foundation system properties, like foundation mass, pile mass, density and length and the soil profile

(half-space, layered) on the structural response. The methodology used in this work will allow to
determine the transient response of multidegree of freedom structures interacting with several soil
profiles with a low computational cost compared to concurrent methodologies.

MLPG-MOM HYBRID MESHLESS METHOD APPLIED TO 2D UNBOUNDED SCATTERING PROBLEMS USING RPIM SHAPE FUNCTIONS

Amorim, Tiago V. L., Moreira, Fernando J. S., Resende, Ursula C. — Mon, 26 Aug 2024 00:00:00 +0000

Meshless methods have increasingly gained attention in recent years. Nonetheless, similar
to the Finite Element Method (FEM), they cannot properly handle unbounded domains. For scattering

problems, however, the Method of Moments (MoM) is fairly well consolidated, efficient, and easily ap-
plied to unbounded homogeneous mediums. This work couples the MoM used to model the unbounded

free space, with the traditional Meshless Local Petrov-Galerkin modeling of a dielectric bounded object.
In the inner region, the meshless method uses shape functions generated by radial point interpolation
with polynomial reproduction, whereas in the outer region, the MoM uses triangular shape functions to
describe the surface currents. As both shape functions possess the delta Kronecker property, the coupling

is straightforwardly imposed by forcing the continuity of the tangential components of the electromag-
netic field. In order to evaluate the convergence of the method, the TEz and TMz plane wave scattering

from a homogeneous dielectric circular cylinder was analyzed since it has a modal analytical solution,

providing means to study the precision of the numerical results. Nevertheless, the formulation is appli-
cable to any arbitrary cylindrical contour shape. Also knowing that meshless methods are quite flexible

to handle material inhomogeneity, a 2-dimensional Luneburg lens, which has a continuous permittivity ̈

profile, was analyzed, and its results were compared to FEM solutions. For both TMz and TEz polar-
izations, it was observed that the convergence rate remains nearly the same for the electromagnetic field

and equivalent current densities. This technique also provided a good agreement for the near and far
electromagnetic field calculation.

A 1DBEM/BEM COUPLING FORMULATION FOR REINFORCED DOMAINS

Antonio Rodrigues Neto, Edson Denner Leonel — Mon, 26 Aug 2024 00:00:00 +0000

This work presents a coupled numerical formulation based on the Boundary Element
Method (BEM) for the mechanical analysis of two-dimensional non-homogeneous reinforced
domains. In this technique, the material matrix (two-dimensional domain) is represented by the usual
two-dimensional singular BEM formulation, considering either isotropic or anisotropic behaviors.
Whereas a one-dimensional approach of the BEM, called 1DBEM, is used to represent the
reinforcements, which can be understood as trusses or fibers. The 1DBEM is based on an axial
fundamental solution for elastic 1D domains, which can be easily found in the literature. The
interaction between the matrix and reinforcements is described by an adherence force over the
reinforcements’ line, considering no relative displacements (perfect adherence). These aspects
characterize the 1DBEM/BEM coupling as an alternative to the usual FEM/BEM technique, which has
been widely applied in the literature for modelling this type of problem. Nonhomogeneous reinforced
domains can be correctly represented in this formulation by the sub-region technique in the 2D BEM,
already presented in the literature. In addition, the use of connection fiber-elements enable the crossing
between reinforcements and sub-regions’ interfaces. A one-dimensional approach of elastoplasticity is
supported over to the 1DMEC elements, which can represent the mechanical degradation of the
reinforcement’s material. Numerical applications exhibits equally accurate displacements results and
better stress/force results obtained by the proposed formulation, when compared to the usual
FEM/BEM approach. The 1DBEM/BEM results exhibit minor perturbations in the force results near
discontinuity points, which are usually observed in this type of coupled formulation. Finally, the
numerical applications show accurate and stable results in the modelling of nonhomogeneous
reinforced structures, when compared to the reference results available in the literature, which
demonstrates the robustness of the formulation proposed in this work.

A 1DBEM/BEM COUPLING FORMULATION APPLIED TO REINFORCED VISCOELASTIC DOMAINS

Antonio Rodrigues Neto, Edson Denner Leonel — Mon, 26 Aug 2024 00:00:00 +0000

This work presents a numerical formulation based on the Boundary Element Method (BEM)
for the mechanical analysis of reinforced viscoelastic materials. The reinforced domain is represented
by a numerical methods coupling technique, in which the material matrix is modelled by the usual
two-dimensional singular BEM formulation and a one-dimensional approach of the BEM, called
1DBEM, is used for the reinforcements. The 1DBEM is based on an axial fundamental solution for
elastic 1D domains, easily found in the literature. No relative displacements between matrix and
reinforcements are considered to formulate the coupling and the contact force is a one-dimensional
load distributed along the reinforcement’s line, which define this 1DBEM/BEM coupling as an
alternative to the usual FEM/BEM coupling. The viscoelastic response is added to the matrix behavior,
using the Kelvin-Voigt rheological model in the two-dimensional BEM formulation. This approach
enables introducing the time-dependent material properties without the need for cells within the
domain or convolution integrals. A time discretization is needed to solve the resulting time-dependent
equation. However, as previously mentioned in the literature, this approach shows a good convergence
behavior regarding the time step size. Finally, the proposed formulation is able to represent reinforced
domains with a viscoelastic matrix, such as reinforced structures or fiber-reinforced materials.
Numerical applications exhibit the convergence of the model and compare the answer obtained with
both 1DBEM/BEM coupling and FEM/BEM coupling techniques with reference results, available in
the literature. The results obtained are stable and accurate, which demonstrates the robustness of the
formulation proposed in this work.

NUMERICAL INTEGRATION OF GREEN’S FUNCTIONS FOR LAYERED MEDIA: A CASE STUDY

Cavalcante I., Labaki J. — Mon, 26 Aug 2024 00:00:00 +0000

Classical Green’s functions for transversely isotropic media are typically expressed in terms
of improper integrals containing a number of singularities and a decaying tail that oscillates indefinitely.
Currently, there are no known numerical methods capable of dealing precisely with both characteristics
of these integrands simultaneously. In this work, Green’s functions for layered media are presented in
terms of an exact stiffness matrix scheme, in which a stiffness matrix for the medium is assembled from
the stiffness matrices of each layer. The integrand in such cases is characterized by an infinite number

of singularities, corresponding to the propagation and reflection waves in the medium. The oscillatory-
decaying tail presents more than one frequency of oscillation, which makes them difficult to integrate

by classical extrapolation methods. This work presents strategies with which to evaluate such integrals
numerically. We have shown that the singularities can be located within the integration interval at points
that correspond to physical wavenumbers of each layer, which are then integrated through a appropriate
contour deformation paths. For the oscillatory-decaying part, we use a combination of strategies. The
first is to use Fast Fourier Transforms to break down the oscillation into its component frequencies.
The fundamental frequency is used to yield a sequence of partial sums, from which the integral can be
obtained by extrapolation though the -algorithm. As a case study, the scheme is used to evaluate the
displacement of layered, transversely isotropic soil medium under time-harmonic external excitations.
The results are compared with classical adaptive quadrature integration schemes.

BOUNDARY ELEMENT FORMULATION TO ANALYZE TORSION PROBLEMS IN GENERIC COMPOSITE BARS

Maicon José Hillesheim, Gabriel Viecelli Renostro, Francisco Célio de Araújo — Mon, 26 Aug 2024 00:00:00 +0000

This paper applies the boundary-element subregion-by-subregion (BE SBS) technique to
solve torsion problems in general composite bars. One presents details of the BE formulation for primary
torsion in coupled domains, including the discussion on the Krylov solvers embedded in the coupling
algorithm. The general principles involved in the derivation of the preconditioned Krylov solvers are
presented, although particular emphasis will be given in the applications to the short-recurrence methods
as the BiCG (biconjugate gradient) and BiCGSTAB(l) (l-dimensional biconjugate gradient stabilized)
solvers. Discontinuous boundary elements, essential to alleviate the modeling process of coupled
domains, are also developed. In this respect, efficient (low-order) quadratures for integrating singular
and nearly-singular fundamental kernels over the boundary elements are proposed. In addition, in order
to accelerate the iterative solution process, the BE SBS matrix structure is used to form an efficient
sparse incomplete LU factorization (SILU) preconditioner. Bars with complex composite patterns (e.g.
with many different materials) are analyzed to attest the efficiency and robustness of the whole
boundary-element technique.

NUMERICAL SIMULATION OF CATHODIC PROTECTION SYSTEMS

Mon, 26 Aug 2024 00:00:00 +0000

In this paper, the Method of Fundamental Solutions (MFS) and the Meshless Local Petrov-
Galerkin (MLPG) method are applied to the numerical simulation of Cathodic Protection (CP)

systems. The problem of CP systems is governed by the Laplace equation. In this problem, the
boundary conditions are characterized by a nonlinear relationship between the electrochemical
potential and the current density, called cathodic polarization curve. Thus, the Levenberg-Marquardt
algorithm is here used to solve the nonlinear problem. The performance of both methods is evaluated
by comparing its results with these provided by the Boundary Element Method (BEM). Furthermore,
the BEM coupled with the Genetic Algorithms (GAs) is applied for the simulation of inverse problems
in CP systems. The van Genuchten-Mualem model is here used to predict the parameters of the
nonlinear polarization curve. A numerical simulation is presented in order to illustrate the good
performance of the coupled BEM-GAs approach.

AN ISOGEOMETRIC BOUNDARY ELEMENT METHOD WITH FAST MULTIPOLE EXPANSION APPLIED TO PROBLEMS OF HEAT CONDUCTION

Emerson Bastos, Eder L. de Albuquerque, Lucas S. Campos — Mon, 26 Aug 2024 00:00:00 +0000

This work presents an isogeometric formulation of the fast multipole boundary element
method and its application in heat conduction problems. The formulation is developed using complex
variables, expansion of fundamental solutions in Taylor series and using NURBS as shape functions. To
reduce the computational cost and facilitate implementation, NURBS are decomposed into Bezier curves, ́
making the isogeometric formulation more similar to the traditional boundary element method. Since
influence matrices are not explicitly assembled, it is necessary to use an iterative method for solving
the linear system. The generalized minimum residue method (GMRES) was chosen, based on previous
work. A description of the hierarchical data structure and of the implemented algorithm is presented.
Validation is performed by comparing results of the proposed formulation with those of the conventional
boundary element formulation. The computational cost of both formulations are analyzed showing the
advantages of the proposed formulation for large scale problems (problems with more than 100 thousand
degrees for freedom).

ANÁLISE DE DESEMPENHO DE ALGUMAS FUNÇÕES DE BASE RADIAL COM A TÉCNICA DE INTERPOLAÇÃO DIRETA PARA CALCULAR FREQUÊNCIAS NATURAIS EM PROBLEMAS ACÚSTICOS TRIDIMENSIONAIS

João Paulo Barbosa, Carlos Friedrich Loeffler, Luciano de Oliveira Castro Lara — Mon, 26 Aug 2024 00:00:00 +0000

Direct Interpolation Boundary Element Method (DIBEM) has been an effective alternative to
other techniques aimed at transforms domain integrals in boundary integrals since it solves problems
modeled by non-adjoint differential operators. The DIBEM was successfully applied to two-dimensional
problems involving the solution of Poisson, Helmholtz, and Diffusion-advection equations. The reason
for its better performance is based, above all, on the fact that the approximation is given by on the use
of radial functions whose mathematical model is more similar to an interpolation procedure, compared
to other techniques. Intended to further improve the knowledge about the particularities of DIBEM, in
this work, an extension of the technique to the three-dimensional eigenvalue problems was done,

focusing on the performance analysis of the various classic radial basis functions, widely used in two-
dimensional problems. Some radial functions have already been used satisfactorily in the solution of

three-dimensional problems, but in this work, the tests are performed with a broader spectrum of radial
functions. To evaluate the accuracy of the results, the natural frequencies are calculated numerically and
comparison with the available analytical solutions.

APPLYING THE BOUNDARY ELEMENT METHOD TO ANALYZE STEADY- STATE HEAT CONDUCTION IN GENERIC MULTIMATERIAL HEAT EXCHANGER TUBES

Maicon J. Hillesheim, Lidianne P. Pinto Mapa, Francisco C. de Araújo — Mon, 26 Aug 2024 00:00:00 +0000

The determination of the temperature distribution in exchanger tubes of arbitrary geometric
shapes, under different boundary conditions of temperature and normal fluxes, allows for their optimized
design. In this paper, we apply the Boundary Element Method (BEM) to carry out two-dimensional
analysis of steady-state heat transfer in exchanger tubes with cross sections of any shapes, and having
walls that may present any type of prescribed boundary values (temperature, normal flux or convective
condition). For simulating heat exchangers constituted of multimaterials, the generic boundary-element
subregion-by-subregion (BE SBS) technique is applied. In this technique, the global matrix resulting
from coupling the many domains available is not explicitly assembled. Instead of that, Krylov solvers
are applied to the iterative solution of the global system of equations by taking into account the separate
contributions of the systems stated for each independent subdomain. A very important step in this
strategy is the inclusion of discontinuous boundary elements, which are fundamental for the simulation
of sharp corners inside interface boundaries or at outer boundaries with prescribed temperature values.
To cope with the quasi-singular and singular integrals involved in the BE models, the Telles cubic
coordinate transformation is applied to derive efficient (low-order) quadratures. They are particularly
relevant for dealing with the quasi-singular integrals resulting from the use of discontinuous boundary
elements. Comparisons with the ANSYS software are considered in the validation/efficiency discussion
of the strategy proposed.

ANALYSIS OF PLANE STRESS PROBLEMS USING THE SUBDOMAIN MESHLESS METHOD

André L. A. Silveira, Edmundo G. de A. Costa, José A. F. Santiago — Mon, 26 Aug 2024 00:00:00 +0000

In this paper, the Subdomain Meshless Method (SMM) is applied to the numerical solution
of plane stress problems. An efficient integration scheme is proposed by using only a support of
approximation centered at the base point for all Gauss points. At the end of the paper, an example is
presented in order to assess the efficiency of the proposed method by comparing its results with those
provided by analytical solutions reported in the literature.

NUMERICAL MODELING OF VISCOELASTIC BIDIMENSIONAL PROBLEMS USING MESHLESS LOCAL PETROV-GALERKIN METHOD

Mon, 26 Aug 2024 00:00:00 +0000

In engineering studies, most of the existing phenomena are modeled by differential and in-
tegral equations. The analysis of the behavior of these systems can be performed through analytical or

numerical methods, the latter which presents an approximate approach to the results. Due to the com-
plexity of the real-life structure models, the use of approximate solutions is increasing.Among these

solutions, the Meshless methods are the most recent and have as advantage over those without of mesh,

making easy the refinement where existing more complexity of the behaviors variables. However, be-
cause they are relatively recent methods, the use of these solutions is not still enough to research and

to apply in real structures. Viscoelastic materials are defined as presenting a combination of elastic and
viscous elements. A viscoelastic structure is represented by physical models that increase the number of
elements as the complexity of the problem grows. Therefore, for more complex models,it is necessary to
use numerical solutions. In this context, the purpose of this paper is the application of the Meshless Local
Petrov-Galerkin 01 (MLPG-01) and MLPG-02 or Local Collocation Method to study two-dimensional
viscoelastic structures, subjected to in-plane state, in order to perform an analysis of the effectiveness
and convergence of each method evaluated, thus verifying its efficiency for these structures.

EVALUATION OF A HOMOGENIZATION-BASED APPROACH FOR ANALYSIS OF METAL MATRIX COMPOSITES BY THE BOUNDARY ELEMENT METHOD CONSIDERING PHASE DEBONDING

Gabriela R. Fernandes, José J. C. Pituba — Mon, 26 Aug 2024 00:00:00 +0000

A formulation of the Boundary Element Method (BEM) to perform analysis of ductile
heterogeneous microstructures considering phase debonding is presented in the context of multi-scale
analysis. The microstructure is modelled by a zoned plate, where different mechanical behaviour can
be adopted for each sub-region. To solve the domain integrals written in terms of in-plane
displacements or plastic forces, the matrix and inclusions domains have to be discretized into cells
where the displacements and forces are approximated. In multi-scale analysis, a point of the
macrocontinuum is represented by a Representative Volume Element (RVE) which in this work, to
model metal matrix composites, is assumed to contain a ductile matrix, rigid inclusions and interface
zone. The rigid inclusions are considered as elastic medium whereas the matrix behaviour is governed
by the Von Mises elastoplastic model with linear strain hardening. The phase debonding is modelled
by a cohesive fracture model using embedded cohesive contact finite elements in the boundary
element mesh. The homogenized results are compared with the ones obtained from a model based on
Finite Element Method (FEM). The accuracy of the results show the capability of the new formulation
based on BEM to deal with complex microstructures.

DYNAMIC DISPLACEMENT AND STRAIN FIELDS WITHIN TRENCHED SOILS: POST-PROCESSING QUANTITIES FROM INDIRECT-BEM’S FICTITIOUS LOADS

David A. S. Carneiro, Josue Labaki, Simone S. Hoefel, Persio L. A. Barros — Mon, 26 Aug 2024 00:00:00 +0000

This work investigates time-harmonic strain and displacement fields within trenched soils
through an Indirect-BEM (IBEM) approach. The method consists of a superposition of Green’s functions
for surface and buried loads. Solutions for surface loads are used to discretize a rigid plate at the surface
of the soil, on top of which time-harmonic vertical loads are applied. Solutions for buried load are used
together with zero-stress boundary conditions to model the presence of trenches in the soil. The soil
is modeled as homogeneous isotropic or transversely isotropic half-spaces, for which classical Green’s
functions are available in the literature. Stress and displacement fields within the trenched half-space
containing a surface plate are related through sets of fictitious loads. Post-processing from these loads

yield quantities such as the displacement field anywhere in the half-space. This work uses these post-
processed quantities to study how the ground vibration propagating from the loaded plate is affected by

the presence of trenches.

STUDIES ON THE STATIONARY DYNAMIC RESPONSE OF A FOUNDATION SUPPORTED BY FLEXIBLE PILE AND SOIL TO A VERTICAL INCIDENT WAVE FIELD OR EXTERNAL FORCE

Luis Filipe do Vale Lima, Josue Labaki, Euclides Mesquita — Mon, 26 Aug 2024 00:00:00 +0000

This paper investigates the vertical response of rigid circular foundation resting on the surface
of a three-dimensional, transversely isotropic soil. In a previous study, the dynamic response of a surface
foundation laying on a homogeneous transversely isotropic half-space was compared to the response of
the same foundation supported by a pile embedded in the soil profile. External forces and vertical
incident waves were considered as exciting energy sources in those studies. But the modelling presented
in the previous analysis was subjected to many simplifying assumptions. The incident vertical wave
field was assumed to impinge solely at the head of the pile. The response of the pile to an incident wave
field impinging the whole length of the embedded pile was not considered. The present article intends
to show a numerical methodology and results to overcome these mentioned simplifying assumptions. In
the present case the surface foundation is rigid and the incident vertical wave field will be interacting
with the pile throughout its entire length. The soil response was previously obtained through the
synthesis of a series of Green’s functions. The pile was modelled as a one dimensional, elastic finite
element body. This pile-soil coupling was obtained by establishing direct kinematic compatibility and
equilibrium at discrete points of the pile-soil contact. The numerical studies reported in this article
investigate the role of the pile inertia ratio as well as the relative stiffness of the soil and the pile. The
results show the influence of the pile presence on the vibration amplitude on the foundation.

ANALYSIS OF PLATES ACCORDING TO THE REISSNER’S THEORY USING THE LOCAL RADIAL POINT INTERPOLATION METHOD

Mon, 26 Aug 2024 00:00:00 +0000

In this paper, the Local Radial Point Interpolation Method (LRPIM) is applied to analyse
the problem of plates according to the Reissner’s theory. An efficient interpolation scheme is
employed to improve the computational performance of the proposed method. To validate the
numerical implementation of the LRPIM, the results are compared with those provided by the Finite
Element Method (FEM) and the Meshless Local Petrov-Galerkin (MLPG) method. A detailed
discussion of the proposed interpolation scheme is carried out in order to demonstrate the performance
of the LRPIM applied to the problem of plate bending.

RELIABILITY MODELS FOR CRACK PROPAGATION ANALYSIS BY USING THE BOUNDARY ELEMENT METHOD

Mon, 26 Aug 2024 00:00:00 +0000

This work presents a crack propagation analysis using an alternative boundary element
method (BEM), in both deterministic and probabilistic approach. The fracture effects are captured
using an initial stress field, this procedure leads to the appearance of a variable called dipole and
responsible for representing the cohesive zone. Both geometry and fracture boundary are discretized
using linear elements, the fracture elements are discontinuous. Regarding the structural reliability
analysis, the boundary element formulation was coupled with the reliability algorithms for
probabilistic analysis of crack problems. The fracture parameters are treated as random variables. First
Order Reliability Method (FORM) is used in order to evaluate the reliability index and the failure
probability for fractured problems. A comparative study between the Monte Carlo simulation
technique are performed. Numerical examples are presented in order to show the accuracy of the BEM
formulation in crack propagation analysis, as well in the assessment of structural reliability in two
dimensional problems.

INTERACTIVE GRAPHICS TOOL FOR STRUCTURAL ANALYSIS AND DESIGN OF CONTINUOUS PRESTRESSED BEAMS ACCORDING TO NBR 6118/2014

Matheus P. Tinoco, Christian L. Dias, Ronald J. L. Assunção — Mon, 26 Aug 2024 00:00:00 +0000

Nowadays, prestressed concrete structures have been increasingly used for covering long
spans due to several advantages over conventional reinforced concrete structures. In the design of such
structures, a fundamental step consists on the structural analysis to obtain the loads generated by the
prestressing. There are few commercial software, however, that allow the analysis of statically
indeterminate prestressed structures, such as continuous beams, widely used in bridges. In this sense,
the current work presents an interactive graphics software developed in MATLAB, which allows the
analysis of continuous beams for any cable layout. The analysis step is based on an association of the
force method, used to obtain the equivalent loads generated by prestressing, with the direct stiffness
method, used to obtain displacements, support reactions and diagrams, generated by the prestressing and
other user defined loads. The software also allows to obtain the stresses generated by different load
combinations over sections throughout the length of the beam, which can be used for performing
structural checks according to NBR 6118/2014. In order to verify its correct functioning, results of tests
carried out with several beams models are presented, varying the number of spans and the cable layout,
which were compared with values obtained with a commercial finite element software. The results were
satisfactory and show that the developed software is a useful and easy-to-use tool that can be used by
engineers, teachers and students of the area.

SIMULACIÓN NUMÉRICA DE COLUMNAS DE CONCRETO ARMADO REFORZADAS MEDIANTE RECRECIDO DE SU SECCIÓN TRANSVERSAL NUMERICAL SIMULATION OF REINFORCED CONCRETE COLUMNS STRENGTHENED WITH INCREASED THEIR CROSS SECTION

Jose R. Yépez, Rosangel Rojas, Americo Campos — Mon, 26 Aug 2024 00:00:00 +0000

Jacketing in reinforced concrete (enlarging the existing cross section of a column with a
new layer of concrete that is reinforced with both longitudinal and transversal bars) is one of the most
used techniques in the rehabilitation, repair and/or strengthening of columns of this material. This
technique is carried out in most cases without totally discharging the columns during the
reinforcement construction process, due to the difficulty that this represent. There is a small amount of
test where the reinforcement is built under the action of a load on the column, this is a reason why we
still need to delve into the influence of the load on the column during the reinforcement process on the
behavior of the strengthening column. A numerical simulation is carried out by the finite element
method of a series of reinforced concrete columns strengthening by increasing its cross section, the
results are compared with those obtained in the experimental tests.

INFLUENCES OF INTERFACE BETWEEN CONCRETE AND STRAND IN THE WEB SHEAR FAILURE OF HOLLOW CORE SLABS

Mon, 26 Aug 2024 00:00:00 +0000

Many researches have been carried out in the world about hollow core slabs. One area that
has the most of those researches is about web shear failure to represent more accurately the shear
strength. One of those uncertainties is related with the behavior the interface between concrete and slab.
Therefore, in this research a hollow core slab that already were carried out for other researcher was
modelled, wherein the main variable is the interface law with aim to verify what the influence in shear
strength, variating tensile strength and slip. Firstly, one curve, which is present in the software and was
created for Doer in 1980, was used. The results showed that tensile strength of interface influences the
shear strength and the how the hardness of interface law affects the slab strength. Beside, a analyze
strain is realized to verify a concrete behavior. Lastly, is processed a model without stands and prestress
to understand show influences of prestress in the slab and it was compared with Brazilian code.

ANÁLISE COMPARATIVA DE MÉTODOS ANALÍTICOS CLÁSSICOS E NUMÉRICO VIA MÉTODO DOS ELEMENTOS FINITOS PARA A OBTENÇÃO DE ESFORÇOS EM RESERVATÓRIO PARALELEPIPÉDICO ELEVADO EM CONCRETO ARMADO

Mon, 26 Aug 2024 00:00:00 +0000

The objective of this research is to present a comparative analysis of the bending effects and
tension forces of three tanks in reinforced concrete with different storage capacities. To obtain these
efforts two methodologies were considered: (a) one by classical analytical methods and (b) another by
numerical method using the Finite Element Method (FEM). In the analytical methodology, the tanks
were treated as structures composed of isolated slabs where the internal tensions were obtained
through the Plate Theory. In the numerical methodology (FEM), the three tanks were modeled in the
SAP2000® using shell elements. The structures were modeled considering discrete finite elements
meshes with dimensions varying from 20 cm to 40 cm, sufficient to obtain satisfactory bending and
tensile efforts with little computational cost. The results showed that the two methodologies presented
similar results for the slabs of the tank cap while for the tanks bottom slabs, the numerical analysis
presented slightly lower than the values found with the analytical study. The bending moments
between the wall-wall and the wall-bottom were very similar in the two methodologies, while the
positive bending moments presented some divergences.

MODELAGEM DE UMA LAJE DE FUNDAÇÃO UTILIZANDO O SOFTWARE DIANA FEA

Mon, 26 Aug 2024 00:00:00 +0000

There are several types of structures that can be considered as massive structures. They are
structures for which the effects of the cementitious materials at the early ages, such as heat generation
and autogenous shrinkage, can lead to cracking. There are some ways to avoid thermal cracking in
those structures, such as changing the concrete mix, using a pre or post cooling system, adopting
expansion joints, or increasing reinforcement with iron bars or fibers. The use of fibers increases the
ductility from the earliest ages and thus decreases the cracking potential. The numerical modeling of
concrete in the early ages, including the phenomenon of hydration, naturally implies the consideration
of the exothermic and thermally activated nature of the chemical reactions involved. Therefore, a
numerical model that is capable of anticipate the thermal field in the concrete during the hydration and
subsequent cooling process should be used to analysis massive structures.
In order to study the thermal fields in a ground slab, it was used a FEM software known as DIANA
FEA. A simplified 2D numerical model was developed based on the example presented by Rita [1].
With the optimization through genetic algorithms, the best way to build this slab was studied. This
means the way to build it, with the least probability of cracking. In the model developed in DIANA
FEA, the symmetry was used and the construction was simulated without any pre-cooling or
reinforcement method, using cooling pipes and adopting fibrous concrete. The cracking index (ICR)
corresponding to the first days after the casting of the first and second layers were higher than 1,
indicating that the structure does not tend to crack, as in Rita [1]. However, in the model developed in
DIANA FEA, it was observed that at 26 days, there is already a probability of cracking. For the model
using fibrous concrete, this tendency is observed at 28 days, which corresponds to an improvement
compared to the one without the fibers. In the modeling using cooling pipes, it could be observed a
decrease in the maximum temperature in the core of the structure.

FORMULATION OF ORTHOTROPIC DEGRADATION MODELS FROM DAMAGE- EFFECT TENSORS FOR PHYSICALLY NONLINEAR ANALYSIS

Lívia Ramos Santos Pereira, Samuel Silva Penna — Mon, 26 Aug 2024 00:00:00 +0000

In constitutive models based on the continuum damage mechanics, the process of material
degradation is described from damage variables that evaluate the nucleation and growth of micro voids

and microcracks in the medium. These variables can be expressed from tensorial entities called damage-
effect tensors, which is able to describe the material behavior considering, in the most general form,

anisotropic degradation. These entities are defined by a fourth-order tensor. This degradation approach
leads to a generalization of the deterioration process, since the secant tensor is obtained from a product
between the damage-effect tensor and the elastic tensor. This work presents a formulation of a continuum
damage model to deal with orthotropic material degradation, assuming different damage evolutions laws.
The degradation process is considered from damage-effect tensors for the physically nonlinear analysis
of concrete structures subjected to monotonic loadings. Different approaches of damage-effect tensors
presented on literature are discussed and implemented to validate this theory. The formulation was
implemented in the INSANE platform (INteractive Structural ANalysis Environment), a free computing
system developed in the Structural Engineering Department of Federal University of Minas Gerais.

EXPERIMENTAL AND NUMERICAL STUDY OF THE STEEL-CONCRETE BOND PHENOMENON - PULL-OUT TEST ANALYSIS WITH AN ELASTOPLASTIC MODEL

Mon, 26 Aug 2024 00:00:00 +0000

Experimental and numerical analysis were performed to evaluate the bond behavior
between steel and reinforced concrete with thin bars. The pull-out test is the most used mechanical test
to study the bond phenomenon and the results of this test may adequately represent the interaction of
the materials in reinforced concrete structures. Numerical analysis based in the finite element method
may be used to better understand the bond behavior, but the numerical models need some specific
parameters that can influence the stresses and the slip, which are important to understand the interface
zone. However, the correct determination of these values is not an easy job, so in many cases the
experimental data is necessary to develop a satisfactory model. In this study a modified pull-out test
was applied with cylindrical specimens of 150x150 cm, composed by ribbed bars (CA-50) with 6.3,

8.0 and 10.0 mm, conventional concrete and bond length of 10 times the bar diameter. An elastic-
plastic model was developed to study stress bond and the failures mechanisms, using parameters

related to bar properties and the interact mechanisms between steel and concrete. The numerical model
was adequately to represent the bond in pull-out test, with results able to represent the specimen
behavior, especially for the 10.0 mm diameter bar.

THERMAL DIFFUSION OVER A MASSIVE PORTLAND CEMENT CONCRETE STRUCTURE

Mon, 26 Aug 2024 00:00:00 +0000

The thermal diffusion in continuous solid media is of relevant once temperature and its
oscillations influence over a wide diversity of natural phenomena, namely, the alkali-aggregate reaction,
concrete Creep and Shrinkage, that affect the concrete structures mechanical performance. The physical
model referring to phenomenon approached in this paper culminates in the Heat Diffusion Differential
Equation. Despite its modest formulation, the Finite Difference Technique may be used to support the
computational tools applied to the numerical analysis expeditiously, suitable to the endorsement of
studies and designs. The subject of this work is the numerical simulation of te thermal diffusion across
concrete massive structures focusing specially over the temperature fields evolution by time of its
continuous soli mass. With a view to the full development of the proposed subject one-dimensional and
two-dimensional models are implemented using an automatic language translated algorithm through the
Finite Difference Approach on the Heat Diffusion Differential Equation. The obtained results confirm
the proposed model suitability to simulate the studied phenomenon behavior, so that represents
strategically promising tools to perform similar tasks.

THERMODYNAMIC FORMULATION OF CORROSION-CRACKING COUPLING IN REINFORCED CONCRETE FRAMES

C. A. C. Brant, J. Flórez-López — Mon, 26 Aug 2024 00:00:00 +0000

The objective of this work is to propose a mathematical model for the coupling of corrosion,
cracking and plasticity in the analysis of reinforced concrete structures. The corrosion phenomenon is
considered due to chloride ions in the concrete that causes the reduction of the cross section of the steel
bars and the penalization of the yield stress. The modeling of structural behavior is based on lumped
damage mechanics and the laws of the thermodynamics of solids. The model proposed in this work is
called elastoplastic with linear kinematic hardening, damage and corrosion; its internal variables are
plastic rotation, damage level and corrosion level. The proposed model was used for the simulation of a
reinforced concrete slab. In the simulation, the model represents the increase of the corrosion resulting
from increments of cracking. Accelerating the corrosive process, damage evolution causes the reduction
of the corrosion time for the appearance of the first plastic hinge.

MECHANICAL PERFORMANCE ANALYSIS OF PLATES FROM APPROXIMATED METHOD

Mon, 26 Aug 2024 00:00:00 +0000

Due to the lack of consensus among the several models applied to its internal forces

assessment, the design of slabs represents a task of reasonable complexity. The availability of high-
performance software allows its mechanical performance simulation from the continuous plate

concept. Despite its great acceptability the results obtained from such procedure are far from the
reality since the knowledge domain of the mechanical behavior of concrete yet did not reached
fullness. The validation of software’s can be performed by using simplified procedures adopting in
hand calculation or small algorithms. Such kinds of approaches are useful, including, as design
resources for more modest constructive units, namely, residential buildings or small commercial and
industrial structures. The Thin Plates Theory is applied to solid bodies composed by linear, elastic and
homogeneous material, whose thickness is inferior to its remaining dimensions. Some solutions of the
Differential Equation, derived from the referring Model, were proposed by Navier and by Levi. The
aim of this work is the analysis of mechanical performance of reinforced concrete slabs, layered upon
a group of high stiffness beams, from the Thin Plates Theory considering the solutions proposed by
Navier and by Levi. The obtained results have revealed that, even for that cases involving symmetrical
loading and edge conditions, the maximum bend moment in the “y” direction occur at a point deviated
from the center of the plate, and its magnitude is greater than that one recorded at the plate center.

NUMERICAL SIMULATION OF SHALLOW TUNNELS LINED IN STEEL REINFORCED CONCRETE CONSIDERING THE EFFECTS OF CRACKING

Betina M. Jensen, Denise Bernaud, Américo Campos Filho — Mon, 26 Aug 2024 00:00:00 +0000

Tunnel design requires the correct evaluation of both soil strains and lining stresses levels
through an analysis that must contemplate the soil-structure interaction and the excavation process.
When tunnels are installed close to the ground surface, the complexity of the problem increases in
comparison to deep tunnels, since shallow tunnels show an ovalized shape of the deformed cross-section
and a heterogeneous stress field around the excavation, inducing tension stresses to appear and possibly
resulting in the cracking of the concrete lining. In this context, this paper presents a numerical simulation
in finite elements, with the software Ansys, focused on the study of the structural behavior of shallow
tunnels lined in steel reinforced concrete. To perform such analysis, the soil mass was represented by a
plastic model using the Mohr-Coulomb criterion and, regarding the concrete, three different models of
behavior were admitted: an elastic, a viscoelastic and a viscoelastic with cracking consideration.
Moreover, the embedded reinforcement model was adopted to represent the steel reinforcement of the
concrete. The results obtained in the investigation indicate the influence of the cracking consideration
in the tunnel model, which modifies the stresses field of the lining and causes higher values of final
convergence.

OBTENÇÃO DA CURVA TENSÃO-DEFORMAÇÃO DO CONCRETO REFORÇADO COM FIBRAS DE AÇO POR MEIO DE ANÁLISE INVERSA

Danilo B. Cavalcanti, Sylvia R.M. de Almeida, Daniel L. de Araújo — Mon, 26 Aug 2024 00:00:00 +0000

One way to measure the increase of ductility, from the addition of steel fibers in concrete, is
from the uniaxial tension tests. However, this test is difficult to carry out and the equipment is highly

rigid and is not present in most concrete laboratories. Thus, the solution could be obtaining the stress-
strain diagram for uniaxial tension of steel fiber reinforced concrete (SFRC) from inverse analysis of a

bending tests. The inverse analysis proposed in this paper consists of an automatic search of the
softening behavior of the SFRC. To achieve this, the objective function is defined to minimize the
difference between load-deflection curve obtained by the finite element software DIANA®
10.1 and
experimental curves obtained by test a simply supported beam under third-point loading, as proposed
by ASTM C1609/C1609M-12. The optimization process is performed in two steps, that is, first it is

determined the flexural modulus of the SFRC, which defines the initial linear elastic part of the load-
deflection curve. Then, points of the softening diagram of SFRC are determined. Since the design

variables are not explicit in optimization process of the objective function, it was necessary to use a
heuristic method, among which a genetic algorithm (GA) available on MATLAB (2007) was chosen.
The GA algorithmic has been showed efficient to obtain the softening diagram of SRFC with two
volume of steel fibers, 0.5% and 1.5%, with index of agreement over 90%.

VANTAGENS COMPUTACIONAIS DA UTILIZAÇÃO DA MATRIZ DE RIGIDEZ DE ̃ELEMENTOS SEGMENTADOS NA ANÁLISE NÃO LINEAR DE ELEMENTOS DE CONCRETO ARMADO TIPO PÓRTICO

Juan MartÍnez, Luiz C. de Almeida, Leandro M. Trautwein — Mon, 26 Aug 2024 00:00:00 +0000

A segmented element can be defined as a structural member that is composed of segments
whose properties cannot be expressed as a continuous function and vary randomly throughout the element
(e.g. modulus of elasticity, cross section, length). The present work aimed to develop the stiffness matrix
of a segmented element to compare the computational performance of this in relation to the conventional
stiffness matrix. A simply supported reinforced concrete beam was analyzed linearly and not linearly.
The non-linear analysis with stiffness degradation was based on the moment-curvature relationship of
the cross section of the beam, where the stiffness of a segment depends on the bending moment acting at
the midpoint of it. The results confirmed that it is possible to significantly reduce the time of analysis of
a reinforced concrete structure using the stiffness matrix of a segmented element. The numerical models
were able to represent the behavior of the tested beam to values above 95% of the ultimate load

COMPARATIVE ANALYSIS BETWEEN THE CLASSICAL ANALYTICAL METHODS AND THE FINITE ELEMENTS METHOD (FEM) IN OBTAINING EFFORTS ON SUPPORTED AND FREE STANDING STAIRS IN REINFORCED CONCRETE

Mon, 26 Aug 2024 00:00:00 +0000

Free standing stairs in reinforced concrete are important structural elements that make up
the buildings. They are designed and executed to join, through successive steps, without intermediate
support, in a comfortable way the different levels of a building. In this context, the objective of this
research is to realize a comparative study of internal forces of the bending moment, shearing and
torsion in free standing stairs considering two methodologies: (a) one using classical analytical
methods for obtaining efforts in stairs and (b) other using Finite Element Method (FEM). In the
analytical modeling, the free standing stairs were treated as structures composed of: (1) isolated slabs
through the Plate Theory with resolution of Lagrange‘s non-homogeneous fourth-order differential
equation, (2) simplified method proposed by Araújo [1] and (3) Knijnik & Tavares’ simplified method
[2]. In order to obtain FEM efforts, the free standing stair were modeled using the SAP2000® [3]
program, using frame elements, both individual and in grid structures, and shell elements. The
structures were made considering discretized finite element meshes with dimensions varying from 20
cm to 25 cm, sufficient to obtain the satisfactory efforts and with low computational cost. The results
showed that on average the analytical models overestimated the values of internal forces (bending
moments in the transversal direction in the landing and in the longitudinal direction of the stair),
mainly by the fact of not considering the three-dimensionality of the stairs, redistribution of efforts and
the consequent interaction among the bending and torsion efforts. It was also observed that shell
element modeling, when compared to the frame elements, presented results closer to the analytical
models considering the supported stairs. Finally, the conclusions of the research indicated that
although free standing stairs present much greater efforts and require higher thicknesses of bids and
levels than ladders supported in beams, however, the lack of intermediate and adjacent structural
elements results in a much more accelerated constructive process.

STRATEGIES FOR MODELLING BY FINITE ELEMENT METHOD THE DEFORMED STEEL BARS EMBEDDED IN PLAIN CONCRETE

ALVES, Lorena da Silva, ARAÚJO, Daniel de lima — Mon, 26 Aug 2024 00:00:00 +0000

In the study of connections between structural elements of concrete must be guaranteed the
transfer of efforts through connection and sufficient strength to avoid the failure on connections. The
connection strength depends of the bond characteristics of deformed reinforcing steel bars embedded
in concrete. This paper aims to study the bond behaviour of deformed steel bars embedded in plain
concretes from computational modelling of pull out test of high strength ribbed steel bars available in
the literature. Three strategies for modelling the ribs of the steel bar using the finite element method
and two models for characterization the bond between steel and concrete were analysed. The strategies
for modelling ribs of the bars were circular ribs or two longitudinal ribs interspersed by oblique ribs.
In these cases, it was used the real geometry of the ribs. The last strategy modify the geometry of the
ribs from the angle of sliding plane between steel and concrete after crushing. For bond characteristics
of the interface between steel and concrete, the elastic-linear model and the non-linear Coulomb
Friction model were used. The computational results were also compared to the analytical models
available in the literature for deformed bars embedded in plain concrete. The results showed that the
bond characteristics of the interface and the shape of the ribs influence the bond strength. The strategy
modelling with modified ribs to incorporate the crushed concrete in front of the ribs and the Coulomb
Friction model for the interface is the one that shows best approximation of the computational and
experimental tests.

NUMERICAL SIMULATION OF CONCRETE STRUCTURE PILE CAP (“D REGION”) USING CONCRETE DAMAGED PLASTICITY AND NON-LINEAR ANALYSIS

Guilherme Niclewicz Saddock de Sá, Roberto Dalledone Machado — Mon, 26 Aug 2024 00:00:00 +0000

The design of reinforced concrete structures aims to define the amount and distribution of
steel rebars (reinforcement) required in the elements. In complex situations, the Strut and Tie Method is
used for design parts that are subject to complex stress distributions (known in the literature as "D
Regions"). One of the difficulties in the application of the method is the determination of the most
probable distribution of tensions that the part will suffer, since it depends on its own geometry and the
amount of reinforcement used. For this reason, on an initial step, elastic analyzes can be used to suggest
a probable field of stresses to be used in the definition of the Strut and Tie Model. However, in the
ultimate strength, the stress distribution can be affected by non-linear effects like non regular
constitutive relations of the materials (concrete and steel), by damage processes that the part will suffer
and also by the distribution of reinforcements. The objective of this work is to present nonlinear
computational analysis of several elements of reinforced concrete, considering the distribution of
reinforcement, in order to evaluate its real behavior in the ultimate state, and to compare with the results
predicted by the usual methods of design, mainly the Strut and Tie method. In order reach this objective,
the models of reinforced concrete are developed through the software of finite elements ABAQUS,
considering Concrete Damage Plasticity. The models constructed on this paper consider the
reinforcement distribution, including the constructive ones, trying to evaluate its influence in the field
of tensions and its resistant capacity. Several situations are examined and the results are compared with
the conventional design methods or with the Strut and Tie Model. The developed examples confirm that
the stress field and the resistance capacity are affected by the reinforcement distribution. In this way,
the present work intends to discuss how the Strut and Tie models are affected by non-linear behavior
and by the designed reinforcements.

HIGH TEMPERATURES INFLUENCE ON THE REINFORCED CONCRETE PANELS STRENGTH THROUGH THE LIMIT ANALYSIS THEORY

Luisa R. Machado, Vanessa F. P. Dutra, Samir Maghous — Mon, 26 Aug 2024 00:00:00 +0000

The constitutive behavior of reinforced concrete (RC) structures is significantly altered when
exposed to high temperatures. The high thermal gradients cause deterioration of the thermo-mechanical
properties of the materials together with thermal-induced deformations, which in turn modify the
geometry of the structure. The aim of the present work is to evaluate the influence of fire occurrence on
the stability of the RC panel structures, through the limit analysis theory. By modelling the panel as a
beam, determining the interaction diagrams for each time of fire exposure is the first step. The
temperature profiles along the sections of the panels are obtained numerically and the interaction
diagrams by integrating the concrete and steel strengths along the section with explicit account for the
different parameters controlling the problem, such as the section thickness, reinforcement area and
concrete compressive strength. The second step consists in determining the deformed configuration of
panel and associated distribution of axial and bending moment efforts, considering the second order
effects caused by the eccentricity of the self-weight load induced by the thermal deformations. This is
achieved by analyzing the thermo-elastic equilibrium of the panel under the combined action of thermal
gradient induced by fire and self-weight loading. The analysis is done by overlapping the interaction
diagrams of the sections and the distribution of internal efforts along the structure. Several numerical
examples are presented to assess the effect of relevant parameters on the overall fire safety of the
structure, emphasizing the effectiveness of the approach for design purposes.

ESTUDO DA FISSURAÇÃO TÉRMICA DOS BLOCOS DE CONTRAFORTE DA UHE ITAIPU: ANÁLISE NUMÉRICA TERMO-QUÍMICO-MECÂNICA

Gabriella P. Valentim, Mariane R. Rita, Eduardo M. R. Fairbairn, Étore F. Faria — Mon, 26 Aug 2024 00:00:00 +0000

Itaipu Dam’s hydroelectric power plant is the largest producer of electric power in the
world. It is composed by structures made of concrete, rock and earthfill that serve to harness the water
and obtain the difference in levels of 120 m, which allows the operation of the turbines. The first
buttresses blocks, which were located in the right bank dam, began to be built in November 1978. The
first cracks were noticed by visual inspection in August 1980. A 2-D simplified FEM analysis has
shown a high adiabatic raise of temperature in the core of the blocks due to the cement hydration,
causing thermal stresses. The location of the cracks in the modelling is very similar to the pattern of
cracking that is presented in the construction reports. Therefore, it is possible to assure that the cause
of cracking in the buttresses blocks of Itaipu Dam is thermal cracking.

NONLINEAR FINITE ELEMENT ANALYSIS OF UNBONDED PRESTRESSED CON- CRETE BEAMS SUBJECTED TO SHORT-TERM LOADING

Juliana C. Alves, Evandro Parente Jr., Joao Batista M. Sousa Jr. — Mon, 26 Aug 2024 00:00:00 +0000

Prestressed concrete with unbonded tendons is an excellent structural solution for beams and

slabs, allowing the design of slender elements with long spans. However, the consideration of the un-
bonded tendon in the structural analysis is complex, requiring the development and implementation of

adequate methods. This work presents a finite element model formulation for material and geometric
nonlinear analysis of unbonded prestressed beams. The Euler-Bernoulli nonlinear plane frame element
formulation for large displacements and moderate rotations is used to model the reinforced concrete
beam. The tendon is modeled as a single polygonal element with a variable number of straight segments.

The tendon element allows the consideration of material and geometric nonlinearities. The formula-
tion was successfully implemented and the obtained results were in good agreement with experimental

data for beams with external and internal unbonded tendons. The presented formulation was applied
to assess the influence of the geometric nonlinearity on the structural behavior of presstressed beams
with unbonded tendons. The results showed that the geometric linear analysis overestimates the beam
capacity.

ALGORITHM FOR THE CALCULATION OF IMMEDIATE AND TIMEDEPENDENT LOSSES, ON SIMPLY SUPPORTED PRESTRESSED CONCRETE GIRDERS

Mon, 26 Aug 2024 00:00:00 +0000

The prestressing losses are related to physical and geometric factors, from which, through
empirical equations, it is possible to estimate this value for any given time. Temperature will be
considered constant over time and all prestressing procedure will be done for adherent post-tensile. This
paper is based on the development of a tool in programming language Visual Basic for Applications
(VBA) to calculate the immediate and time-dependent losses, on simply supported prestressed concrete
girders of beams in a manner that presents intuitive interface between the user and the system. Starting
from the necessity of automation of the prestressed concrete projects, this tool uses ordinary pre-defined
cross sections (rectangular, “T” and “I”) with user-defined dimensions for the application of prestressing
forces and for an unlimited number of cables, being possible both the visualization of the each cable
layouts in girder, as well as the immediate and time-dependent losses, following the formulation
proposed by Brazilian Technical Standard NBR 6118 [1].

THREE-DIMENSIONAL NONLINEAR ANALYSIS OF RC BEAMS STRENGTHENED WITH EXTERNALLY BONDED CFRP SYSTEMS

Mon, 26 Aug 2024 00:00:00 +0000

The strengthening and rehabilitation of concrete structures using carbon fiber reinforced
polymers (CFRP) has consolidated itself as an attractive alternative in civil construction. Some factors
that led to a greater use of this material are its excellent mechanical properties, low specific weight and
high durability. The development of this type of strengthening, and the concrete technology as a whole,
require refined analysis methods. Therefore, it is proposed to perform a computational modeling of
flexural beams with CFRP externally bonded (EB) strengthening systems, through the finite element
method (FEM) in the commercial software ANSYS. The physical nonlinearities of the materials are
included. A special focus is given to the behavior of the bond between the structure and reinforcement,
through contact elements and bilinear cohesive zone models provided by the program. In this way, it is
possible to detect in the computational simulations, premature failure modes that occur by detachment
of the reinforcement and that often limit full employment of CFRP’s resistance properties. The
developed numerical model was able to predict the instantaneous behavior from systems involving
reinforced concrete beams strengthened with CFRP, analyzed through load-displacement curves, as well
as the failure mode and ultimate load.

CONSIDERATIONS ABOUT APPROXIMATE AND RIGOROUS METHODS FOR SECOND-ORDER GLOBAL ANALYSIS IN BUILDINGS WITH REINFORCED CONCRETE STRUCTURES

Mon, 26 Aug 2024 00:00:00 +0000

This paper presents an evaluation of the approximate methods for the calculation of plane
frames subjected to horizontal actions from wind force, considering the current numerical resources
available. In the past, it was common to use equivalent plane frame in the calculation of tall reinforced
concrete buildings, in the definition of ultimate limit states (ULS) and for the evaluation of the lateral
displacements of the building in service limit states (SLS). From these trivial analyzes, usually theorical,
verifications of the structure's instability parameters were made. It is known, however, that simplified
structural analysis, such as obtaining the parameters α and γz, causes eventual inaccuracy in the internal
forces and the deflection values of the building, since it is not considering the real three-dimensional
interaction among the main constituent elements of the structure: slabs, beams and pillars. In view of
the above, the purpose of this research was to make a comparison of the results obtained analytically in
a usual 9th floor reinforced concrete building, with the results of a 3D structural design and analysis
software in accordance with NBR 6118/2014. Finally, after a systematic analysis of the results obtained
from the analytical and numerical models of the pilot building, some considerations are made, especially
regarding the use of simplified structural analysis methods.

TEMPERATURE FORECAST IN CONCRETE DAM BY HOLT-WINTERS MODELS AND THE FINITE ELEMENT METHOD

Mon, 26 Aug 2024 00:00:00 +0000

The article describes a method of forecasting the temperature fields of a buttress-type concrete
block from the Itaipu Hydroelectric Dam located in a region with high thermal gradients, approximately
7 to 40°C. The method involves the application of Holt-Winters exponential smoothing models and a
heat conduction model that follows Fourier's Law. Initially, the temperature series from 2000 to 2016
of two surface-to-block thermometers, whose read periodicity is not well defined, were adjusted by cubic splines and the now monthly series were used as input for Holt- Winters to produce temperature
forecasts as outputs for 2017. Monthly (interpolated) and 2017 (predicted) monthly temperatures were
used as boundary conditions for the transient thermal block model and it was solved by the Finite
Element Method (FEM) in Python language. The predicted temperature fields of the block for 2017 are
thus obtained. The numerical results at a specific point and interior of the structure were compared with
the observed data of an internal thermometer installed in the block by means of the MAPE error, and
this was around 7%. The proposed method has an innovative approach to the thermal analysis of
structures, particularly in concrete dams, regarding thermal field prediction and a first application of the
Python language to this problem.

AVALIAÇÃO NÚMERICA DA EFICIÊNCIA DO USO DE FIBRAS DE AÇO NO PROJETO DE SEÇÕES TRANVERSAIS DE CONCRETO ARMADO NO ESTADO LIMITE ÚLTIMO

Mon, 26 Aug 2024 00:00:00 +0000

This paper presents a numerical evaluation of the efficiency of the use of steel fibers in
reinforced concrete elements under bending with axial force in the Ultimate Limit State (ULS). The
calculation of the strength of each cross section, is an iterative method that requires the integration of
the stress in the area. This process is performed in a rigorous way using the algorithm implemented by
Ribeiro [6][7] in Java programming language. In order to present the mechanical behavior of the fiber
reinforced concrete (FRC) under tension, it is necessary to assume a constitutive law, since the use of
steel fibers provides an increase of residual strength (Model Code 2010, RILEM TC 162-TDF). The
parameters for the characterization of the compressive strength were obtained from the Brazilian
Technical Standard NBR 6118 (ABNT [8]), and the tensile constitutive law was given by
experimental results of Barros et. al. [9]. In this study, two cross sections of beams with usual
dimensions of buildings and one cross section of bridge column were used. The sections strength are
presented in the form of interaction diagrams for bending with axial forces, for fiber rates of 0 kg/m3
(without fiber), 15 kg/m3 and 30 kg/m3. The analysis of the results demonstrates an increase of the
strength as a function of the fiber content in cases that there are regions under tension.

A LUMPED DAMAGE MODEL FOR THE ANALYSIS OF DUAL SYSTEMS OF REINFORCED CONCRETE

Julio Neumann, Ricardo Picón, Julio Flórez López — Mon, 26 Aug 2024 00:00:00 +0000

The search for mathematical models capable of estimating the level of degradation of
reinforced concrete structures is increasing. However, due to the complexity, the number of variables
involved and the physical non-linearity of the problem, the determination of these models becomes
somewhat complicated. Due to this need, there are behavioral models for elements with bending failure
and behavioral models for elements with shear failure that have been proposed independently. However,
there are still few models that include the evaluation of the inelastic response considering the interaction
between the two types of forces (shear force and bending moment). In addition, the models proposed in
the literature have as main limitation the uncertainty in the selection of parameters that adequately
represent the inelastic behavior of the elements. To overcome these difficulties, in this paper, it is
proposed a constitutive model based on lumped damage mechanics (LDM). A finite element is used that
includes two auxiliary subroutines capable of representing the inelastic behavior of the structure
considering the two types of forces. The model was validated through comparisons of results of
numerical simulations with experimental results. Later, the model is used for the dynamic analysis of
dual systems. The results show that the proposed model is interesting because besides being able to use
to verify the structural integrity of already completed buildings, it can contribute to the realization of
more advanced projects, in such a way that the cracking during a loading can be controlled and prevent
structural collapse.

MODELAGEM NUMÉRICA DA FASE DE PROPAGAÇÃO DA CORROSÃO INDUZIDA POR CLORETOS EM ESTRUTURAS DE CONCRETO ARMADO

Éverton Souza Ramos, Matheus de Godoy Tavares, Rogério Carrazedo — Mon, 26 Aug 2024 00:00:00 +0000

Com o crescimento da indústria da construção civil, o surgimento de patologias relacionadas
à corrosão em estruturas de concreto armado se intensificou globalmente, motivando o desenvolvimento
de ferramentas capazes de prever seu comportamento frente à durabilidade. A corrosão devido ao
ingresso dos íons cloretos promove o cenário mais devastador à integridade dos elementos estruturais.
Este fenômeno é caracterizado pela formação de pites nas barras de aço, promovendo uma corrosão
localizada e não uniforme da seção transversal das armaduras. Neste contexto, o principal objetivo deste
estudo é o desenvolvimento de uma ferramenta computacional para a análise do comportamento de
estruturas de concreto armado sujeitas ao ataque de íons cloretos. A fim de modelar o fenômeno, é
empregado o Método dos Elementos Finitos Posicional (MEFP) com formulação Lagrangiana total,
considerando os efeitos advindos da não linearidade geométrica. A matriz de concreto e as armaduras
são modeladas com elementos finitos triangulares bidimensionais. O acoplamento reforço/matriz é
realizado por meio de técnica de embutimento. A não linearidade física do concreto é considerada com
o emprego do modelo de dano de Mazars. Uma abordagem determinística é adotada para avaliar os
efeitos deletérios do período de propagação. Assim, modelos presentes na literatura são selecionados
para implementar as tensões expansivas provindas da formação dos produtos de corrosão e a redução da
seção transversal das armaduras. Por fim, exemplos numéricos são expostos objetivando evidenciar a
robustez do código desenvolvido e sua aplicabilidade na avaliação da vida útil das estruturas.

A FINITE ELEMENT APPROACH TO UPPER BOUND SOLUTIONS FOR ULTIMATE LOADS OF PLATES AND SLABS

Michael Parisotto, Vanessa F. Pasa Dutra, Samir Maghous — Mon, 26 Aug 2024 00:00:00 +0000

Structural engineering projects involves the elements design considering the ultimate limit
state (ULS) conditions and the service limit state (SLS) check. The ULS is characterized by the
exhaustion of the strength capacity of the entire structure or some specific regions. SLS conditions
should be checked to ensure durability of the structure, maintenance of non-structural elements
appearance and integrity, which influence users comfort as well as the buildings functionality. No
additional loading can be sustained by the structure beyond the ultimate state conditions. The present
work aims at analyzing the ULS of plates and slabs under predominating flexion through numerical
evaluation of their load capacities. The combination of the kinematic approach of limit analysis theory
(LAT) with the finite element method (FEM) enabled the development of a computational tool that
allows for assessing the failure load of plates and slabs with arbitrarily geometry and associated
support conditions when subjected to different loading modes (surface, linear and concentrated).
Adopting the normal deflection rate as main variable that controls the failure mechanism, six-node
triangular finite elements were used for geometry and kinematics discretization. The numerical
determination of ultimate load of the structure relies upon a minimization procedure. The latter is
achieved by Sequential Quadratic Programming (SQP) method, which is an iterative method for
constrained nonlinear optimization. The developed finite element tool also allows the analysis of the

failure mechanism of plates and slabs and visualization through the software of pre-and post-
processing GiD®. For the validation of the proposed analysis methodology (LAT + FEM) and

associated computational implementation, analytical results of various slab and plate configurations
and their respective rupture mechanisms were favorably compared with the numerical predictions.
Comparison with available approaches are also presented, thus indicating the ability of the developed
numerical tool to accurately assess the ultimate loads and failure mechanisms of bending plates or
slabs.

TRANSIENT BOUNDARY ELEMENT FORMULATION APPLIED FOR CORROSION TIME INITIATION ASSESSMENT IN REINFORCED CONCRETE STRUCTURES SUBJECTED TO CHLORIDE INGRESS

Mon, 26 Aug 2024 00:00:00 +0000

The reinforcements’ depassivation in reinforced concrete structures caused by chloride
ingress occurs when the chloride concentration at the reinforcements’ interface reaches the threshold
content. The main transport mechanism of chlorides ions into concrete pores is the diffusion. Then, the
realistic chloride diffusion modelling into concrete pores enables the accurate determination of the
corrosion time initiation. This study presents a transient formulation based on the Boundary Element
Method (BEM) applied for diffusion problems, which provides the accurate assessment of the
corrosion time initiation. The diffusion fields evaluated by the BEM are utilized into a probabilistic
framework, which determines probabilistic values for corrosion time initiation. Therefore, the
uncertainties are properly quantified in this model by an approach based on simulation. Two
applications are presented, which illustrate the accuracy and robustness of the proposed formulation
when compared with classical analytical approaches.

VALIDATION OF A PORTLAND CEMENT HYDRATION MODEL USING CALORIMETRY METHODS

Mon, 26 Aug 2024 00:00:00 +0000

The exothermic characteristic of cement particles hydration is a widely studied phenomenon
by academy, which uses calorimetric methods as a tool to describe the reactions of cementitious
matrixes. The development of models that describe and predict the results of calorimetric tests from few
experiments is essential, given the technical difficulties and time required to perform the tests. This work
aimed to predict the adiabatic temperature rise of a concrete mass starting from the paste isothermal
calorimetry results and thermal properties of its components, using a homogenization model developed
by the authors. The experimental validation was done in comparison with results obtained by the
elevation temperature of concrete of the same cementitious matrix in a full adiabatic calorimeter.

SLENDER COLUMNS MODELING THROUGH INFINITE NUMERICAL SERIES CONVERGENCE

Edmilson Lira Madureira, Gabriel de Bessa Spinola — Mon, 26 Aug 2024 00:00:00 +0000

A numerical series is defined as the sum of terms in a numerical sequence. If the
quantity of terms of the series is known, it is denominated as a finite series, and, the referring sum can
be obtained from the elementary algebra. In the unlike case the series is classified as an infinite series,
and, the employment of elementary algebra is no longer enough, requiring the use of a convergence
analysis procedure. The series used to approach, as a satisfactory numerical quality, a set of values of
given function in a certain work domain, 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 performance analysis. The slender
columns analysis cast by elastic and ductile material has been based on the concept of critical load, or
Euler’s load. Such modeling version is not enough at all, for specimens cast of weak rupture pattern
material, as the reinforced concrete, but even thus, there are concepts involved in such a formulation
that can be 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.

STRUCTURAL MONITORING OF FOZ DO CHAPECÓ POWER PLANT

Mon, 26 Aug 2024 00:00:00 +0000

Hydroelectric power plants represent the most important source of electricity in Brazil.
Hydroelectric plants are a clean source of energy that produce no residua or pollution during its
operational lifetime. However, the storage of great amounts of water may represent a risk to cities
downstream. Although the chances of accidents are small, their impact may be catastrophic. Therefore,
monitoring the structures is paramount to have a safe operation. This work focuses on monitoring the
structural safety of Foz do Chapecó Power Plant. The plant is installed on Uruguai River in the border
of states of Santa Catarina and Rio Grande do Sul, Brazil. The structure consists of a rock fill dam with
asphaltic core and concrete spillways. The spillway structure is 350 meters long and 60 meters high with
15 gates. At the current stage of the research, the numerical simulation of the spillway is developed. The
structure is modelled with the Finite Element Method in 3D, with the entire structure in the same mesh.
Emphasis is given to mesh generation, where details such as galleries, contact with rock foundation and
expansion joints are modelled. Loads are given in terms of reservoir upstream level, openings of gates
and foundation sub-pressures caused by water percolation. The solver is developed using the finite
element program PZ, which provides a whole family of elements morphology, different approximation
spaces and mesh adaption technologies. The displacements obtained by the simulations are compared
to the displacement history of the spillway measured by various sensors. This comparison is used to
adjust simulation data such as the assumed material parameters. In next steps of this work, the numerical
simulation will be integrated to physical monitoring of robotic total stations and other sensors yet to be
installed in the structure.

MODELAGEM NUMÉRICA DO ENSAIO DE VIGA EM DUPLO BALANÇO UTILIZANDO UM MODELO PROBABILÍSTICO

Mon, 26 Aug 2024 00:00:00 +0000

In most published studies with the objective of characterizing the concrete fracture under
tensile loads, the Double Cantilever Beam (DCB) test has been used. This test provides information
that allows to determine the critical stress intensity factor (KIC) and the critical energy release rate
(GIC) of concrete which are values that qualify the toughness of material. Therefore, in this work is
presented a numerical model of the DCB test, performed by means of the finite element method (FEM)
considering a probabilistic approach. The stochastic process is introduced in the model at the local scale
of the material by considering a random distribution of the tensile strength and the local cracking energy,
assuming that cracks are created within the concrete with different energy dissipation depending on the
spatial distribution of constituents and initial defects. The Monte Carlo method whose main idea is to
compute the results based on repeated random sampling and statistical analysis is used to statistically
validate the probabilistic numerical model.

THE EFFECTS OF MODELLING TOWER-FOUNDATION CONNECTION STIFFNESS IN A FINITE ELEMENT WIND TURBINE CONCRETE FOUNDATION MODEL

Robson Ribeiro, José Neres da Silva Filho — Mon, 26 Aug 2024 00:00:00 +0000

Nowadays, one of the main challenges regarding the design of concrete wind turbine
foundations is the search of reliable structural numerical models, which allows concrete and steel
volume reduction, providing more cost benefit solutions. Due to the necessity of modelling the physical
situation in a trustworthy manner, it’s imperative to consider not only the soil-structure interaction, but
also the stiffness of support structure (wind turbine tower). Therefore, the present paper aims to analyse
the effects of tower-foundation connection stiffness in the internal stresses of foundation element (pile
group foundation with a pile cap), as well the global rotational stiffness provided to the system, that
being an essential parameter to guarantee dynamic stability to the wind turbine. The foundations were
model using the SAP 2000, a finite element software. Shell (thin and thick) and solid elements were use
in the foundation model, whilst thin shell elements were designate to represent the tower behaviour. The
results show that the anchor bolt cage provide a high stiffness to the foundation core modifying the stress
distribution along all the pile cap.

ANÁLISE DA FISSURAÇÃO TÉRMICA EM ESTRUTURAS DE CONCRETO MASSA ASSOCIADA ÀS PROPRIEDADES FÍSICO-QUÍMICA DO MATERIAL

Mon, 26 Aug 2024 00:00:00 +0000

Massive concrete structures are those for which the hydration effects of the cementitious ma-
terials at the early ages, such as heat generation and autogenous shrinkage, can lead to cracking, since the

properties of the material are changing rapidly under the influence of hydration. The thermal cracking
in these structures is an important phenomenon, originated and induced mainly by matterss related to
the hydration reaction of the cementitious binder, becoming an important issue to the durability of the

structure. In this way, knowing the influence of the parameters that govern this problem is of remar-
kable importance for engineering, considering that the determination of the values of these parameters

sometimes involves complex and not exact procedures, generally obtained by inverse analysis, or simply

neglected by professionals for lack of knowledge of its impact on the project. I this work, the term mas-
sive concrete is used in a broad sense, comprising all types of concrete elements for which the effects of

cement hydration can lead to thermal cracking risks. With regard to the researches using computational
simulations, programs have been developed to map the temperature in the concrete, besides its transient
fields of tensions and deformations, enabling the prevention of cracking, through the establishment of
strategies to prevent it. In order to establish the influence of some parameters intrinsic to the material,
in this work will be simulated the construction of a concrete slab, previously builded and tested in the

laboratory of FURNAS (Goiania ˆ / GO), using the finite element program DAMTHE implemented in lan-
guage FORTRAN, developed by PEC / COPPE / UFRJ, using experimental data as the starting point for

adjustment of the thermochemical-mechanical model, aiming at obtaining a simulation of reference that
represents the most accurate tests performed and then do an factor analysis, changing intrinsic properties

of the material, such as: specific heat, activation energy, thermal conductivity and convective heat trans-
fer in order to know the influence of the correlations between the uncertainties of the input parameters of

the model in the structure cracking.

SIMULATION OF THE INTERFACIAL TRANSITION ZONE AND AIR VOIDS EFFECTS ON CONCRETE CRACKING USING A MULTISCALE FE APPROACH

Mon, 26 Aug 2024 00:00:00 +0000

Many models successfully consider concrete as a continuous and homogeneous material.
However, mechanical and cracking behavior of concrete can be significantly dictated by its constituents
and interactions between them on a finer scale. This means that considering the different phases of the
mesostructure results in a more accurate modeling of concrete fracturing. Two of the concrete
components that play an essential role in the mechanical response are: air voids and interfacial transition
zone (ITZ), which are acknowledged as the two weakest phases of the material. Therefore, this work
proposes a four-phase mesoscale representation of concrete, which consists of coarse aggregate, cement
matrix, aggregate-matrix interface (ITZ) and air voids. Coarse aggregates and macro air voids are
randomly embedded in the matrix. As a part of the mesh fragmentation technique (MFT) [6], high aspect
ratio elements are placed between regular elements, meaning that the ITZ is explicitly represented and
has its particular properties. An appropriate tension damage model is employed to describe the material
nonlinear behavior. Such approach can also be extended to a multiscale approach, in which a higher
refinement is given only to certain critical regions and the other regions are considered to be elastic with
homogenized properties, resulting in an improved computational performance. The non-matching
meshes are bonded with coupling finite elements (CFE) [8] in their shared boundaries, ensuring
displacement continuity. The analysis of the ITZ and air voids effects on concrete cracking is performed
by comparing the numerical responses for varied ITZ fracture properties and void ratio and size using
the multiscale approach proposed. The study demonstrated that the mechanical response is extremely
sensitive to the air void content, and its increase results in the formation of a very tortuous fracture and
drastic drop of peak load.

USE OF MODAL ANALYSIS AS A METHOD TO ESTIMATE SECOND ORDER GLOBAL EFFECTS IN REINFORCED CONCRETE STRUCTURES

Mon, 26 Aug 2024 00:00:00 +0000

Recent work shows that there is a relationship between the natural vibration period and the
second-order global effects in the reinforced concrete frames, this link occurs because both depend
essentially on the rigidity and mass matrix of the structure. Formulations are developed to demonstrate
and validate that an amplification factor is able to approximate second-order global effects satisfactorily.
Previous studies just consider the additional mass as a load increment. However, the second-order effects
of external loads on the structure not beem take into account to calculate the internal forces in structural
elements and their influence on the dynamic characteristics. Therefore, the second-order effects are
included to analyze the influence of the dynamic characteristics (natural frequencies and vibration
modes) and the amplification of the structure moment. Analyzes will be carried in a regular element of
reinforced concrete. The amplification will be evaluated by means of natural frequencies and modes of
vibration. Thus, this work generally aims at obtaining an alternative parameter of calculation, based on
the natural frequency and mode of vibration of the structure, to be used as an indicator of the necessity
or not of the consideration of the second-order global effects in reinforced concrete structures.

A NUMERICAL 3D MODEL OF SFRC PIPES: PARAMETRIC STUDY OF THE STRENGTH CAPACITY.

Facundo L. Ferrado, Mario R. Escalante, Viviana C. Rougier — Mon, 26 Aug 2024 00:00:00 +0000

The incorporation of steel fibers to concrete is beneficial from the structural point of view,
giving place to the use of the composite material called Steel Fiber Reinforced Concrete (SFRC) in
several applications, among which concrete pipes are found. The main contribution of the fibers is
their ability to improve the tensile strength and tenacity of plain concrete. This contribution depends
mainly on the geometric characteristics and mechanical properties of the fibers, the amount incorporated
and the properties of the cement matrix itself. All these factors together will determine the mechanical
performance of the structural piece under consideration. This work contributes to a better understanding
of the mechanical behavior of this composite material applied to pipes through a parametric study of the
strength capacity of pipes considering variations in the dosage and type of fibers as well as variations in
the concrete class used. The fibers are represented as discrete elements and randomly distributed in the
concrete mass whose characteristics are adopted from fibers available in the local market. The proposed
model is simulated in combination with the Monte Carlo method in order to obtain average probabilistic
values of strength capacity of pipes, considering the variability of the orientation and distribution of steel
fibers within the concrete mass. The maximum load values are obtained by simulating the three edge
bearing test (TEBT) according to the IRAM 11503 standard, which is implemented in a finite element
analysis tool (ABAQUS

R ). A constitutive model of damage-plasticity was used for plain concrete and
a model of steel for the fibers which takes into account the pull-out phenomenon. Finally, results of the
simulations are shown through tables of maximum loads, load-displacement curves and histograms.

STRUCTURAL ANALYSIS OF PILE CAP AS WIND TURBINE FOUNDATION

Mon, 26 Aug 2024 00:00:00 +0000

This paper analyzes the structural behavior of reinforced concrete pile caps, as onshore wind
turbine foundations, using tridimensional numerical models. In order to do, four finite elements models
were constructed, with the aid of the ANSYS software. It was adopted as variables: i) consideration or
not of the soil under the pile cap base; and, ii) soil (under the pile cap base) stiffness. All the materials
constitutive models were considered as with linear elastic behavior. The interest results were: pile ́s
reaction; division of loading between soil and piles; pile cap ́s displacement; radial normal stress and
bending moments in the pile cap.

Vigas de gran altura de hormigon reforzado con fibras: estudio numerico y experimental

Miqueas C. Denardi, Viviana C. Rougier, Mario R. Escalante — Mon, 26 Aug 2024 00:00:00 +0000

The study of new materials for structural uses with better properties than traditional ones has
always been the object of study of scientific researches. Thus, traditional materials have been replaced

by others such as the composites, intelligent and biodegradable materials. In this context, this work con-
tributes to a better understanding of the behavior of steel and hybrid fiber reinforced concrete applied to

deep beams. The latter are structural elements loaded as beams but with small shear span/depth ratios.
They have useful applications in many structures, such as tall buildings, foundations, offshore structures,
tanks, etc. Some studies carried out in the last decades have proved that the use of steel fiber concrete
(SFRC) and hybrid fiber reinforced concrete (HFRC) in those structural elements helps to a better control
of cracking, improves the toughness and the tensile behavior. Although there are numerous publications
dedicated to the study of the behavior of this structural element, a few ones evaluate the behavior of
SFRC and HFRC deep beams. In relation to the latter, the existing information in the literature is limited
and in general it is based on experimental works. Even if the experimental data are valuable, numerical
and analytical solutions are also needed to obtain a better understanding and prediction of the behavior
and failure of mechanisms of SFRC and HRF deep beams. Conventional analytical techniques for the
study of concrete are not suitable for the analysis of elements constructed with FRC. In this work, a

numerical-experimental study of the ultimate shear capacity of SFRC and HFRC deep beams is presen-
ted. In the experimental campaign the contribution of the fibers to the shear capacity and ductility was

evaluated. To do this, reinforced concrete deep beams with traditional bars and stirrups, and SFRC and
HFRC beams without stirrups were built. In addition, a numerical model was implemented in a finite
element analysis software in which the fiber reinforced concrete (FRC) was modeled as a homogeneous
composite material. Finally, the experimental and numerical results are discussed in terms of ultimate
loads and they are illustrated by means of tables, graphs and axial load-displacement curves.

GEOMETRICALLY NONLINEAR LIMIT POINT ANALYSIS OF CONCRETE STRUCTURES WITH DAMAGE AND TEMPERATURE EFFECTS

Mon, 26 Aug 2024 00:00:00 +0000

This work seeks to analyse a buckling and limit point problems of concrete structures based
on a geometrically nonlinear formulation with the consideration of thermal effects and material damage.
The thermal expansion effects due to heating processes in confined structures have an important role in
the stress-strain evolution. Damage is treated in a simple way through the Mazar’s continuum damage
model. The resulting equations are approached by means of a finite element discretization, the solution
of which is pursued through an incremental, iterative standard Newton-Raphson numerical scheme
implemented by the authors in an in-house nonlinear FEM code. We then present two examples of
numerical simulations to validate our formulation and illustrate its applicability to the nonlinear stability
analysis of slender concrete structures under thermal loads.

EXPERIMENTAL AND NUMERICAL EVALUATION OF PRESTRESSED CONCRETE BEAMS WITH WEB OPENNING

Ivan D. Semeniuk, José L. Gutierrez, Antonio Aquino — Mon, 26 Aug 2024 00:00:00 +0000

In the construction of either small or large buildings, we often find problematic openings in
beams of the structure, due to the need of passing of different kinds of pipes.
The present study aims to investigate the influence of lateral openings in beams of prestressed concrete
that were not design to resist this disturbance. Four combinations of openings where selected with height
equal to the half of the total deep of the beam. The height/long rates studied are 1:1, 1:2, 1:3 y 1:4. Three
beams where tested for every configuration of opening, as well as three beams without openings, by
flexural test until the beams reach total collapse.
Once the failure loading was obtained, a numerical model was built that represents the observed and
measure phenomenon in the load test. With the experimental and numerical results, the failure
mechanism for every single configuration of beams was found.
Similar results were identified regarding the ultimate bearing capacity, however, the beams with
openings tend to form cracks in an earlier station.

ANÁLISE DE VIGAS DE CONCRETO ARMADO BASEADA NA ABORDAGEM MOMENTO-ROTAÇÃO

Gilcyvania Castro Corvelo Costa, Daniel Carlos Taissum Cardoso — Mon, 26 Aug 2024 00:00:00 +0000

Neste trabalho, um modelo numérico para análise de vigas de concreto armado estaticamente
determinadas é desenvolvido com base na abordagem momento-rotação para avaliar a rigidez e a
flexibilidade do elemento pós fissuração. Essa abordagem é baseada no deslocamento de corpo rígido
de um comprimento de prisma entre fissuras e nos mecanismos de interação parcial. Esses
mecanismos retratam efeitos importantes que tem como base a fissuração do concreto e o
deslizamento entre interfaces, sendo fundamentados em expressões que utilizam propriedades
adicionais dos materiais. A propriedade bond-slip da interface é base para o mecanismo de
enrijecimento à tração, enquanto que o mecanismo de amolecimento do concreto é tratado por meio de
expressões embasadas na teoria do atrito-cisalhamento. O modelo numérico apresentado permite obter
a capacidade resistente da seção crítica do elemento considerando os efeitos supracitados, além de
apresentar uma resposta carga-deslocamento para vigas. Por fim, os resultados numéricos são
comparados com resultados de ensaios experimentais disponíveis na literatura, além de serem
confrontados com resultados oriundos de uma análise baseada na premissa de interação completa entre
materiais.

MODELAGEM DAS ETAPAS DE PROTENSÃO PARA VIGAS DE CONCRETO PROTENDIDAS PÓS-TRACIONADAS COM CABOS NÃO ADERENTES

Leonardo do Nascimento Cunha, João Batista Marques Sousa Junior — Mon, 26 Aug 2024 00:00:00 +0000

As estruturas de concreto protendido com cabos não-aderentes, especialmente vigas e lajes,
tem sido amplamente difundidas e utilizadas em construções pelo mundo. A solução numérica destes
elementos pelo método dos elementos finitos estabelece alguns problemas desafiadores devido a
ausência de compatibilidade de deformação e deslocamento entre o cabo e o concreto envolto. Este
trabalho apresenta a aplicação de uma formulação de MEF para uma análise numérica não linear de
viga de concreto pós-tracionada com cabos não aderentes, focada na fase de aplicação da protensão.
Foram empregados elementos não-lineares unidimensionais de pórticos planos baseados na teoria de
vigas de Euler-Bernoulli para a seção de concreto armado e um elemento de treliça para a simulação
dos cabos. A simulação da protensão é realizada através de analogia com as vigas pré-tracionadas,
onde uma posição de equilíbrio é alcançada sem aplicação de carregamento externo. Neste estudo, a
formulação é extendida para avaliação sequencial de diversos cabos. Assim, analisou-se três modelos
de diferentes vigas protendidas de diferentes trajetórias de cabos não aderentes, baseados em modelos
reconhecidos na literatura. Os resultados demonstraram a influência da protensão sequencial e os
efeitos nos cabos pós-tracionados anteriormente estirados, principalmente para vigas com valores
elevados de forças de protensão.

ONE-DIMENSIONAL CONSTITUTIVE MODELS FOR NONLINEAR STATIC ANALYSIS OF REINFORCED CONCRETE STRUCTURES

Bergson S. Matias, Evandro Parente Jr, Tereza D. P. Araujo — Mon, 26 Aug 2024 00:00:00 +0000

This work aims at the nonlinear static analysis of reinforced concrete structures using con-
stitutive models based on the Plasticity Theory and the Continuum Damage Mechanics. The elastic

damage model proposed by Mazars and the elastic-plastic damage model proposed by Lee and Fenves
are studied and one-dimensional versions of these models are implemented in a finite element program.
The plane frame elements used in this work are formulated with a co-rotacional Lagrangean kinematic
description. The integration of stress resultants and tangent constitutive matrix is carried out by the Fiber

Method. The formulation and computational implementation at the material and element level are vali-
dated using numerical and experimental results available in the literature. A reinforced concrete column

under the action of a monotonic load is analyzed and the results show that the use of the implemented
one-dimensional models for concrete structures is an effective methodology to capture some important
effects.

NUMERICAL MODELING OF REINFORCED CONCRETE BEAMS USING THE COMPOSITION OF TWO PLASTIFICATION SURFACES

Matheus E. Benincá, Inácio B. Morsch — Mon, 26 Aug 2024 00:00:00 +0000

In order to consider the multiaxial behavior of concrete, several plastification and rupture
surfaces have already been proposed, such as the Ottosen surface or the Willam-Warnke surface.
However, the use of these surfaces in numerical finite element models can often lead to convergence
difficulties, due to the complexity of their formulations. In this context, the present work simulated
numerically the behavior of two reinforced concrete beams tested experimentally in a previous work,
using ANSYS software, version 19.2, with a new elastoplastic model available in the recent versions of
this software, denominated DP-Concrete. This model uses the composition of two simpler plastification
surfaces, one for tensile behavior, which can be a Rankine or a Drucker-Prager surface, and another
Drucker-Prager surface for compressive behavior. This surface composition allows simulating the large
differences in the concrete behavior under tension and compression, which would not be possible with
a single Drucker-Prager surface. In addition, because it is a newly available material model, it can be
applied to the SOLID186 element, which is classified as a current-technology element by this software,
and therefore is compatible with several current ANSYS features, such as the generation of embedded
elements by the mesh-independent method, through the MESH200 guide elements, which were also
used in this work. In order to consider the cracking and crushing phenomena, different softening and
hardening laws available in the software were used. The obtained results were compared with each other
and with the results of the experimental tests. In addition, numerical analyses were performed with a
customized material model based on the Ottosen criterion, whose results were also used for comparison
purposes. It was concluded that the DP-Concrete model is an adequate modeling strategy for the concrete
behavior, and its main advantages are its simplicity, flexibility and compatibility with other current
ANSYS functionalities.

Estudo da Aplicação do Método das Camadas no Método dos Elementos Finitos 1d Para Análise de Vigas de Concreto Armado

Luis Felipe dos Santos Ribeiro, Agno Alves Vieira — Mon, 26 Aug 2024 00:00:00 +0000

Este trabalho apresenta a implementação de uma rotina computacional que realiza análises
nao lineares de vigas de concreto armado por meio do Método dos Elementos Finitos 1d (MEF 1d),
onde o concreto e o aço sao discretizados pelo Método das Camadas. Este, consiste em discretizar a
seção transversal em n camadas, que por sua vez, considera as nao linearidades físicas dos materiais
em cada uma, sendo ele, aplicado nos pontos de integração dos elementos finitos. Os fenômenos como ˆfissuração e seus efeitos de redistribuição de tensões ao longo da seção transversal do elemento são inse-
ridos implicitamente por meio das relações constitutivas dos materiais. A formulação do elemento adota
a hipotese da viga de Euler-Bernoulli, assim como, aderência perfeita entre o aço e o concreto. Para
resolução do problema não-linear utiliza-se o Método da Rigidez Secante. Deste modo, para validação
da implementação proposta, os resultados obtidos são comparados com resultados experimentais propos-
tos por Bresler e Scordelis. Alem disso, são avaliadas a influência dos modelos constitutivos adotados e
da malha de elementos finitos. Por fim, sao observados excelentes resultados numéricos quando compa-
rados com os dados experimentais, apesar de se empregar uma formulação elementar e de baixo custo
computacional em relação ao MEF 2d e 3d.

FINITE ELEMENT ANALYSIS USING THE MODIFIED COMPRESSION FIELD AND THE CRACKED MEMBRANE MODEL FOR STRUCTURAL CONCRETE SUBJECT TO IN-PLANE STRESS

Lucas Marques Teles da Silva, Ezio da Rocha Araújo, Ramiro Brito Willmersdorf — Mon, 26 Aug 2024 00:00:00 +0000

In this paper, the Modified Compression Field Theory (MCFT, Vecchio and Collins, 1986) and
the Cracked Membrane Model (CMM, Kaufmann and Marti, 1998) are developed into a finite element
formulation for the analysis of orthogonally reinforced and prestressed structural elements in plane stress
condition.
MCFT considers orthotropic concrete, distributed and rotating cracks that are normal to the principal
tension stresses. Tension stiffening, aggregate interlock, and interactions between concrete and steel at
surface of cracks use average strains and stress. Use of average constitutive equations relating average
stress and strains are complicated and debatable.
CMM falls into the category of compression field models, combining components from MCFT and
Tension Chord Model (TCM, Kaufmann, 1998) extended to cracked plane stress. In this way, the link
to limit analysis is maintained and there is no need to introduce constitutive equations relating average
stress and average strains in tension: the equilibrium is formulated in terms of stresses at cracks rather
than average stress between cracks. This make easy to evaluated results from practical strut and tie
models (STM).
Two above FE models are verified and compared against experimental results of beams, shear panels
and deep beams.

STUDY OF THE INTERACTION BETWEEN WALLS GROUPS ON VERTICAL LOADS DISTRIBUTION OF STRUCTURAL MANSORY BUILDINGS

Matheus P. Barbosa, Joel A. N. Neto, Adryano J. M. Souza — Mon, 26 Aug 2024 00:00:00 +0000

The walls behavior intersections has been studied by many researchers, the structural
engineers usually incorporate this aspect in the design procedures defining the model of walls group
action. In this specific cases, many researchers have been studied the walls intersections in order to
verify the connections strength. In most cases, the group action of interconnected walls is delimited by
doors and window openings. Despite of that, masonry lintels under openings can affect this behavior
spreading the vertical loads through the openings and inducing a group interaction. This aspect isn ́t
enough explored by researchers. Therefore, the study presented herein developed a systematic analysis
to take into account the lintels masonry in the panels modeling, in order to evaluate it’s influence on
vertical loads distribution. Numerical simulations were performed using the equivalent frame model
developed by Nascimento Neto et al [1] and also using models based on shell finite elements. The
analyses conducted to evaluate the vertical stress redistribution on wall groups and to verify the
internal forces induced on lintels. The results showed that the reduction of stresses intensities must be
take into account carefully because it ́s influenced by many factors and not just by incorporating the
lintel in the modeling.

VIBRAÇÕES E ESTABILIDADE DE CASCAS CILÍNDRICAS SANDUÍCHE COM NÚCLEO DE ESPUMA METÁLICA COM GRADAÇÃO FUNCIONAL

Ewerton Alves Bezerra, Paulo Batista Gonçalves — Mon, 26 Aug 2024 00:00:00 +0000

Cylindrical shells have applications in several areas of engineering. The last decades have
seen the emergence of several new materials and production techniques to be used in these structural
elements. Functionally graded materials, metal foams and sandwich structures are part of this
development. The sandwich shells, with solid metal faces and metal foam core, are used to improve
structural performance in line with a reduction in weight. The objective of this work is to study the
natural frequencies and the critical loads of sandwich shells with a metal foam core (CSCN) and
compare the results with those of a homogeneous isotropic shell (CH) and with functionally graded
(CGF) shells. For this, the Donnell shell theory is used. First, the equations of motion are derived and
using the analytical solution for a simply supported shell, the mass, stiffness and geometric matrices
are obtained, allowing the calculation of natural frequencies and critical loads under axial compression
and lateral pressure. In order to evaluate the importance of the foam core, shells of the same mass and
shells with the same natural frequencies and critical loads are analyze.

MODELAGEM DINÂMICA DE ESTRUTURAS E MECANISMOS 3D COM LIGAÇÕES DESLIZANTES POR UMA FORMULAÇÃO NÃO LINEAR GEOMÉTRICA DE ELEMENTOS FINITOS

Tiago Morkis Siqueira, Humberto Breves Coda — Mon, 26 Aug 2024 00:00:00 +0000

Este trabalho trata do desenvolvimento de uma formulação matemática para ligações
deslizantes aplicadas na análise dinâmica não linear geométrica de estruturas e mecanismos
tridimensionais junto à sua implementação computacional. Esse tipo de conexão permite a modelagem
de diversas aplicações nas indústrias civil, mecânica e aeroespacial como, por exemplo: antenas de

satélites, braços robóticos e guindastes, estruturas aporticadas como as formadas por elementos pré-
moldados, o acoplamento entre veículos e pontes, dentre outras. Emprega-se uma formulação

Lagrangeana total para descrição dos elementos finitos de pórtico espacial e casca utilizados. Nessa
abordagem são utilizadas posições e vetores generalizados como parâmetros nodais, evitando o

emprego de fórmulas para o tratamento de giros finitos. A relação constitutiva de Saint-Venant-
Kirchhoff, que relaciona a deformação de Green-Lagrange com a tensão de Piola-Kirchhoff de

segunda espécie, é adotada para descrever os materiais. As equações do movimento são obtidas pelo
Princípio da Energia Total Estacionária no qual são introduzidos multiplicadores de Lagrange para
impor as equações de restrição cinemática que descrevem as ligações deslizantes. Dada a presença das
restrições, adota-se o método α-generalizado para desenvolver a marcha no tempo. O sistema não
linear resultante é resolvido pelo método de Newton-Raphson e se discute um exemplo de aplicação
da formulação desenvolvida.

PROBABILISTIC MODEL OF HUMAN WALKING ACTION FOR DYNAMIC ANALYSIS OF PEDESTRIAN BRIDGES

Mon, 26 Aug 2024 00:00:00 +0000

The recent use of new materials and innovative structural designs in pedestrian bridges has
been resulting in structures with low natural frequencies susceptible to excessive vibration problems,
requiring a dynamic analysis in the design phase. In the present work, dynamic analyzes were
performed considering initially deterministic models with two distinct formulations of the human
loading simulation, Fourier series and biodynamic model, the latter to evaluate the relevance of the
person-structure interaction in the structural response. To simulate the typical random characteristics
of human walking loading, a probabilistic model was also implemented for the simulation of loading
parameters. The theoretical results, considering the deterministic and probabilistic models for the two
human loading formulations, were correlated with the experimental results of controlled human
walking vibration tests (one and four persons walking on the fundamental frequency of the pedestrian
bridge) and in normal operation. The best correlation between the theoretical and experimental results
was obtained for the probabilistic model of the loading parameters considering the biodynamic
formulation.

AN EFFICIENT LOCKING-FREE COROTATIONAL BEAM FINITE ELEMENT

Mon, 26 Aug 2024 00:00:00 +0000

An efficient and accurate locking-free corotational beam finite element is developed in this
work. The element is locally linear, with the displacement varying according to the Timoshenko
assumption and the difference of electric potential varying linearly through each piezoelectric layer
thickness. The shape functions are appropriately derived from the exact solution of the homogeneous
form of the linear equilibrium equations written in terms of displacements, rotations and differences of
electric potential. Since the resulting 2-node element has the same degrees of freedom as the
associated purely mechanical beam element (two displacements and one rotation per node), it can be
directly plugged into an element-independent corotational algorithm to suitably analyze piezoelectric
plane frames under small strains but large rotations. A consistent incremental-iterative technique based
on the Newton-Raphson method is employed for the solution of the nonlinear equilibrium equations.
Numerical examples that demonstrate the efficiency and large rotation capability of the corotational
formulation are presented. The element results are validated by exact solutions available in the
literature. Very good agreement is found in all cases.

NONLINEAR ANALYSIS OF VISCOELASTIC RECTANGULAR PLATES

Phablo V. I. Dias, Zenón J. G. N. del Prado, Renata M. Soares — Mon, 26 Aug 2024 00:00:00 +0000

In this work, the non linear vibrations of thin, viscoelastic and isotropic clamped
rectangular plates, subjected to concentrated harmonic load are studied. The Von Karman
non linear strains relations are used and to describe the clamped boundary conditions,
rotational springs are considered. The viscoelastic material is described as the Kelvin-Voigt
model and the Raylrigh Ritz method is used to obtain a system of non linear dynamic
equilibrium equations with 39 degrees of freedom which is solved, in turn, by the Runge-Kutta
tnethod. A parametric detailed analysis is performed to study the influence of axial load,

viscosity parameter and geometry on the non linear response of the plate. The frequency-
amplitude relation and resonance curves were plotted. The frequency-amplitude curves

showed that as the viscosity parameter is increased, the maximum amplitudes and the degree
of nonlinearity are reduced, it was also observed that when both the dimentions of the plate
and external load are increased, the frequency-amplitude relations are quasi linear, The
resonance curves showed that the plate has a typical hardening behavior with two coexisting
atractors with high sensitivity to initial conditions.

INSTABILIDADE E VIBRAÇÃO NÃO LINEARES DE UMA TRELIÇA PIRAMIDAL DE MATERIAL HIPERELÁSTICO

Renata M. Soares — Mon, 26 Aug 2024 00:00:00 +0000

In pyramidal space trusses the geometric nonlinearity is particularly significant and
in recent years, intensive research has been conducted on the development of new materials,
including shape memory polymers and elastomers. This work presents an analyzed for a
shallow pyramidal truss composed of 6 equally spaced bars using the finite element method
through the Abaqus®

program. The truss is composed of an isotropic, homogeneous and
hyperelastic material, which is modeled with neo-Hookean and Mooney–Rivlin models. The
loss of stability and nonlinear vibrations of these structures under static and dynamic loads is
analyzed. A parametric analysis of the geometric relation height and base is made and its
nonlinear behavior, time responses, phase portraits are obtained. The results highlight the
complex nonlinear dynamics of this class of structures.

DISTORTIONAL STRENGTH OF COLD-FORMED STEEL PINNED-FIXED LIPPED CHANEL COLUMNS

Warlley S. Santos, Alexandre Landesmann, Dinar Camotim — Mon, 26 Aug 2024 00:00:00 +0000

This work addresses the buckling behaviour, ultimate strength and Direct Strength Method (DSM) design
of pinned-fixed (bolted-fixed) cold-formed steel lipped channel columns, selected to fail in distortional
modes. The end-connections consist of a pair of cylindrical high-strength bolts with hexagonal head and
nut, which are inserted in two standard-size holes located at the intersections of the flanges with the
principal centroidal axis parallel to the web – on the other hand, the fixed end support consist a welded
end-plate. After selecting the columns with various combinations of geometry (length and cross-section
dimensions) and yield stresses, Ansys Shell Finite Element (SFE) analyses are used to investigate the
failure modes of selected columns and assemble ultimate strength data. Together with experimental failure
data previously reported by authors out at the Federal University of Rio de Janeiro, these values are then
employed (i) to assess the merits of the current DSM design curves and, in view of their inadequacy, (ii)
to propose new strength curves that provide efficient failure load predictions for the whole set of columns
considered.

SELF-SUPPORTING LATTICE TOWER UNDER DYNAMIC WIND LOADS

Claudia Slongo, Marcos Arndt — Mon, 26 Aug 2024 00:00:00 +0000

The difficulty to determine time-variant loadings, such as wind loading, stands out among

the structural engineering challenges. For example, the wind is the preponderant action in a self-
supporting lattice tower, and its wrong estimation can lead to unwanted vibration and displacements in

the structure. Those structures are usually designed with a simplified dynamic effect, in which the
wind is considered as a static load, increasing its value by dynamic coefficients proposed in standard
codes. However, this simplification can easily lead an improper design. Although there are various
non-standard methods for the determination of the time variant loading of the wind in order to achieve

a more accurate and reliable analysis, this work focuses on the Synthetic Wind Method, that is a non-
deterministic process using the Monte Carlo simulation in order to obtain wind loadings by

superposition of harmonic functions with random phase angles. This work provides a dynamic
analysis of a self-supporting lattice tower using the Synthetic Wind Method with different wind
spectra (Davenport, slightly modified Davenport, Harris and Kaimal). A comparison between the
dynamic and the static response obtained by the Brazilian code NBR 6123/1988 – Forces due to wind
on buildings is also made. The structure calculated with the original and the slightly modified
Davenport spectra have given similar and the largest displacement responses. Whereas the Harris
power spectral density proved to be the least conservative for this study.

EXPERIMENTAL ANALYSIS OF A BEAM-COLUMN SUBJECTED TO NONCON- SERVATIVE FORCES

Thiago Jose Duprat Fortes, Raul Rosas e Silva, Daniel Carlos Taissum Cardoso — Mon, 26 Aug 2024 00:00:00 +0000

The structure known as Beck’s Column consists of a beam-column, subject to a tangential fol-
lower force applied at its free end. Beck presented in 1952 the critical load, which induces the vibration

of the structure (flutter). This paper uses a simple and general numerical model that allows the solu-
tion of the problem of columns with different properties and different boundary conditions associated to

follower forces. In this work, emphasis was given to the experimental simulation of the phenomenon,
in a qualitative way. A metal ruler was adopted to represent a slender fixed-free beam-column and, to
simulate the following force, a brushless motor was attached to the free end. A thrust force is generated

when air is moved by the propeller and the motor follows the rotation of the free end, changing the direc-
tion of the thrust force. Tests were performed with different setups in order to observe the effect caused

in the presence of gravitational force (motor weight) in concomitance with the tensile and compression

follower effect. The results were remarkably different, showing that the follower force can induce stabi-
lization, flutter and divergence. As the analysis was qualitative, videos and photos were made to record

the results. The values of critical loads and frequencies were within the range expected by numerical
analysis. Attempts to instrument the tests with accelerometers and LVDTs (Linear Variable Differential
Transformer) were made and a discussion is presented on the differences and influence of these devices
on the structure behavior.

ON THE SOLUTION OF GENERALIZED EIGENVALUE PROBLEMS USING PROJECTED ARNOLDI AND DUAL DOMAIN DECOMPOSITION METHODS

Guilherme Jenovencio, Daniel J. Rixen — Mon, 26 Aug 2024 00:00:00 +0000

Modal Analysis plays an important role in understanding the dynamics of structures. The

mode shapes and natural frequencies are crucial structural properties that must the known to avoid catas-
trophic failures due to resonances. Moreover, eigenmodes can be used to reduce the number of degrees

of freedom of a Dynamic System by using Reduced Order Models (ROM) such as Craig-Bampton, Dual-
Craig-Bampton, Rubin, among others. Despite its importance, full eigenanalysis is rarely required, and

in general, only the smallest eigenvalues are computed due to their relevance for practical problems.
Therefore, Lanczos and implicit restarted Arnoldi algorithms are often used as eigensolvers due to their
efficiency. The major cost of those algorithms lies in the multiple solutions of static-like problems, which
can produce prohibitive computational cost when the discretized dynamic model has more than millions

of unknowns. In this work, a nonoverlapping dual domain decomposition method, namely Finite El-
ement Tearing and Interconnection, is combined with a modified version of the Arnoldi Algorithm to

efficiently compute the eigenpairs of large scale structural problems.

VIBRATION ANALYSIS OF A STEEL FLOOR SYSTEM WITH DRY FLOORS: A NUMERICAL – EXPERIMENTAL STUDY

André V. S. Gomes, Priscilla Izabel S. Ribeiro, Adenilcia Fernanda G. Calenzani — Mon, 26 Aug 2024 00:00:00 +0000

One of the trends of contemporary architecture is the design of buildings with long spans and
increasingly slender structural elements. In addition, the use of dry floors has been common in
residential and commercial constructions. Thus, the structural design adopted for current buildings is
usually more susceptible to vibrations from human activities, since these structures have lower natural
frequencies. However, researches dealing with the study of vibrations in dry slab floors supported by
rolled or welded steel beams are scarce. For this reason, this project aimed to study the dynamic behavior
of a steel floor system with dry floors. A finite element (FE) numerical model was developed using
ANSYS 19.0 software to simulate this as-built floor system. This numerical model was adjusted and
validated by the first two natural frequencies of the structure obtained by an experimental modal
analysis. In this practical analysis, two accelerometers, an A/D converter and a portable computer were
used to acquire the signals in the time domain. With features and routines developed in MATLAB, these
signals are processed and transformed into the frequency domain by the FFT algorithm (Fast Fourier
Transform). It was observed that the deviation between the numerical and experimental results were
close enough to prove the reliability of the models developed.

NONLOCAL FINITE ELEMENT ANALYSIS FOR FREE VIBRATION OF ELASTICALLY SUPPORTED NANOBEAMS

Aldemar P. Siqueira Neto, Simone S. Hoefel — Mon, 26 Aug 2024 00:00:00 +0000

Nanobeams are nanoscale structures extensively used in nanotechnology applications. Due
to the small scale effect, this nanostructures cannot be accurately modelled by traditional elastic theory.
To overcome this difficulty, several continuous models including the material length scale effect were
developed, like nonlocal elasticity theory. In this paper, a nonlocal finite element model for elastically
supported Euler-Bernoulli (EBT) and Timoshenko (TBT) nanobeams is developed. Nonlocal differential
constitutive equations of Eringen are considered to account for the small scale effect. The stiffness and
mass matrices for a two-node nonlocal beam element with two degrees of freedom per node are obtained
based upon Hamilton’s principle. The influence of nonlocal parameter, slenderness ratio and support
stiffness on the free vibration characteristics is investigated. Numerical results obtained are discussed
and compared with results obtained by other researchers.

ASSESSMENT OF A ROLLER SEISMIC ISOLATION BEARING FOR BUILDINGS UNDER BIDIRECTIONAL EXCITATIONS

Mon, 26 Aug 2024 00:00:00 +0000

This work presents the assessment of a base isolation bearing system for seismic protection of
buildings under bidirectional excitations. The isolation system consists of roller supports that move on
inclined V-shaped surfaces plus an energy dissipation system. The orthogonal arrangement of the roller
supports seeks to isolate seismically the building in its main directions, while the dissipation system
controls the horizontal displacements of the isolator. Experimental tests of free vibration allowed to
identify damping of the isolation system. Besides, accelerations record was found through bidirectional
and unidirectional test. By the other hand, numerical responses were obtained with the motion equation
solution and these responses were correlated with the experimental accelerations of the system in both
directions. According to the experimental and numerical results, it was possible to conclude that the
isolation system is viable for analysis in the seismic protection of buildings subjected to real records of
earthquakes.

DYNAMIC ANALYSIS OF A BUILDING UNDER SEISMIC EXCITATION

Mon, 26 Aug 2024 00:00:00 +0000

This paper implemented a numerical routine in MATLAB software to analyze the dynamic
response of a building with several degrees of freedom excited by seismic motion. The loading was
modeled as a one-dimensional stochastic process, which was simulated by passing a Gaussian white noise
process through a Kanai-Tajimi filter. Parameters of ground motion such as frequency, damping and peak
acceleration were considered taking into account a region located in Chile where the seismic problem is
of great importance, and another one taken from a region of Brazil that has the largest seismic activity for
this country. The ground acceleration, in the frequency domain, was generated by Kanai-Tajimi spectrum
and it was transformed into the time domain by the Shinozuka & Jan Method. The structure analyzed
is a 12-story building modeled as a two-dimensional finite element discretized into frame elements.
The structural damping model considered was the Rayleigh model and the mass consistent matrix was
adopted. The structural dynamic motion equation was solved by the Newmark Method and the maximum
values, in absolute values, of the displacements, accelerations and the inter-story drift of the building
were calculated. A maximum value established by national codes for the inter-story drift was considered
as a limiting parameter for structural damage. The results indicate that major damages are obtained when
the frequencies of the site condition were closed to the natural frequencies of the first three vibration
modes of the structure.

DYNAMICS ANALYSES OF COMPOSITE MATERIAL FOOTBRIDGE UNDER ACTION OF PEDESTRIAN WALKING

João Pedro de Castro Torres, Eliane Maria Lopes Carvalho, Janine Domingos Vieira — Mon, 26 Aug 2024 00:00:00 +0000

This work aims the optimization of a design of footbridges made of pultruded glass fiber
reinforced polymer (GFRP) profiles, under the dynamic effect of pedestrian walking. First, a footbridge
with a structural arch associated to trusses was designed, respecting the ultimate and serviceability states
for static analysis. The accelerations found in the dynamic analysis, was considerate intolerable for
human comfort according with the design guides. Therefore, it was necessary to design a synchronized
passive dynamic attenuator (SDA) to mitigate the excessive vibrations. Besides this first one, others
structural conceptions using truss beams and inverted queen post truss were analyzed aiming the most
efficient structural behavior. A computation program considering a two-dimensional model was
developed to integrate the equation of the movement taking into account the pedestrian crowd load. The
dynamics properties used in the two-dimensional model were obtained from one three-dimensional
model using a finite element method. Since the pultruded profiles are lightweight, it was considerate the
interaction between pedestrians and the structure by increasing the mass and the damping ratio. It was
noticed that without considering the pedestrian versus structure interaction the accelerations were found
to be excessive high showing that for very light structures, this consideration is extremely important.
Also, it was seen that modifying the structural design increasing the stiffness and mass resulted in
comfortable structures without the necessity of use SDA.

USE OF THE ADAMS-BASHFORTH FOURTH-ORDER SCHEME IN THE NUMERICAL SIMULATION OF DYNAMIC SYSTEMS

Davi H. S. P. dos Santos, Nelson M. Barbosa — Mon, 26 Aug 2024 00:00:00 +0000

Generally, the real physical systems are chaotic and /or dynamics, modeling problems in

conditions similar to this one will be discussed in this work, testing a method that numerically and ap-
propriately models the problems of this class. Ordinary differential equations are used to model these

physical systems, since they present non-linear, deterministic and three-dimensional characteristics. The

numerical method of type predictor-corrector of fourth-order Adams-Bashforth was tested for conduct-
ing simulations. The use of this method proved to be efficient for these types of systems. The method

appropriately simulates the Lorenz Attractor, other models familiar to Lorenz are analyzed, such as the
attractor of Lorenz with source term, attractor of Rossler, attractor of Pan-Xu-Zhou, attractor of Chen and ̈
the modified Chen attractor which are fundamental systems for the processing and estimation of climatic

phenomena, whether natural or controlled forms. The fourth-order Adams-Brashforth method appro-
priately simulated the dynamic systems mentioned, which has proved to be efficient when compared to

other scientific works.

COMPUTATIONAL TOOL FOR BUCKLING ANALYSIS VIA POSITIONAL FINITE ELEMENT METHOD

Henrique B. Soares, Rodrigo R. Paccola, Humberto B. Coda — Mon, 26 Aug 2024 00:00:00 +0000

In this work, a computational program is developed to perform stability analysis of thin-
walled profiles employing the positional formulation of the Finite Element Method (FEM). The profiles

are discretized in shell finite elements, which, unlike the traditional formulation, have position and un-
constrained vector as nodal parameters. Besides, the formulation considers a parameter corresponding to

the rate of thickness variation, which makes the kinematics of the element more general than Reissner-
Mindlin. Due to the use of unconstrained vector instead of rotation, it was necessary to use a strategy

to perform the coupling between non-coplanar elements. This coupling was accomplished by means
of a one-dimensional element connecting the end of the non-coincident vectors of a node. A nonlinear
geometric formulation of FEM is adopted, using the total Lagrangian description of the equilibrium. The
material is assumed to be elastic linear, represented by the Saint-Venant-Kirchhoff constitutive law. To
incorporate the stability analysis, a technique based on the decomposition of the stiffness matrix in the
elastic and geometric parts is used. This technique consists of determining eigenvalues and eigenvectors,

which corresponds, respectively, to buckling loads and instability modes of the resulting generalized ei-
genvalue problem. A graphical interface for the program is developed, making it easier to use. For this,

an algorithm for triangular and quadrilateral finite element mesh generation was also developed, as well
as a post-processing viewer, avoiding possible dependencies with external programs. Finally, numerical
examples are presented to validate the developed code and demonstrate the program functionalities.

EXTENSÃO DE PROGRAMA GRÁFICO PARA ANÁLISE DE VIBRAÇÕES DE MODELOS ESTRUTURAIS RETICULADOS

Pedro Cortez Lopes, Rafael Lopez Rangel, Luiz Fernando Martha — Mon, 26 Aug 2024 00:00:00 +0000

This paper aims to present a user-friendly graphical tool for the dynamic analysis of
reticulated structural models, such as trusses, frames and grillages, implemented entirely on Matlab®.
The code was written as an addition to the LESM (Linear Elements Structure Model) program, an
open source structural analysis software developed in Tecgraf/PUC-Rio, based on the object-oriented
programing paradigm (OOP), with an interactive graphical interface for modeling and an educational
approach. Four numerical solvers for obtaining the dynamic structural response were implemented.
The system of differential equations of motion may be analyzed on its coupled form, where free and
forced vibration are computed numerically, or on an uncoupled fashion, on the modal domain. On the
second case, it is possible to obtain analytical solutions for free vibration. The vibration modes are
found with the solution of the eigenvalue problem of an undamped oscillation system, achieved with a
Matlab built-in function. Viscous damping is treated as proportional to mass and to stiffness.
Consistent mass matrices were formulated for Euler-Bernoulli and Timoshenko beam bending
behavior theories, using parameters that unify both approaches. Alternatively, lumped mass matrices
were implemented as well. An effort in computer graphics was made to obtain multiple result
visualization options. A new interactive dialog of the graphical user interface was created in order to
display results on time and frequency domain, for each degree-of-freedom, being also possible to
visualize phase portraits of the solution. In addition, animations to depict the dynamic behavior of the
model were achieved.

PROGRAMA PARA ANÁLISE GEOMETRICAMENTE NÃO LINEAR DE PÓRTICOS POR MEIO DE UM CONTROLE EXTENSIVO DO USUÁRIO

Rafael L. Rangel, Luiz Fernando C. R. Martha — Mon, 26 Aug 2024 00:00:00 +0000

This work presents the development and use of a graphical tool to analyze two-dimensional
framed models considering geometric nonlinearity. The goal is to provide an application that allows
users to have full control of the numerical procedures for solving the nonlinear problem and, therefore,
to improve their understanding about the nonlinear behavior of structures. This application was
implemented as a new feature of the Ftool (Two-dimensional Frame Analysis Tool) program, which
has demonstrated to be a valuable program for teaching structural engineering over the last years. A
user-friendly interface was designed so that several analysis options, including the most well-known
solution algorithms, and the numerical parameters used in these algorithms, are available to be set. All
of these options and parameters can be changed as the analysis progresses, and it is also possible to go
back and forward in the analysis steps. Since no algorithm is able to solve all the nonlinear problems,
as shown in an example of this work, this extensive analysis control allows a greater possibility to
obtain the convergence along the full path of any geometrically nonlinear analysis. The equilibrium
path of the structures can be plotted in an exclusive environment that provides several distinct data to
be shown in each axis.

ANÁLISE DINÂMICA DE PLACAS CONSIDERANDO O EFEITO DE MEMBRANA SUBMETIDAS A CARREGAMENTOS EXPLOSIVOS

Mon, 26 Aug 2024 00:00:00 +0000

The behavior of civil engineering structures under blast loads has been studied quite
frequently in the last years and much effort has been made to create idealized blast wave curves and
predict the corresponding response of structural and protective elements. The blast phenomenon results
in an abrupt overpressure wave followed by an underpressure wave, the last being usually disregarded
in most structural analyses. However, recent studies show that this suction phase is of paramount
importance since it may lead to substantially higher stresses. In the case of high-intensity pressure
waves, structural elements may experience large displacements, thus requiring second-order effects to
be included in the analysis. This work investigates the nonlinear dynamic behavior of thin rectangular
plates subjected to explosive charges. The problem was modeled as a nonlinear single degree of freedom
system by applying von Karman’s theory for large deflections to simply supported and clamped plate
configurations. A uniform pressure load simulates the overpressure and underpressure waves by
employing the Friedlander equation and a cubic approximation, respectively. Runge-Kutta method was
used to solve the equation of motion for displacement amplitude. Numerical solutions for displacements
and stresses were derived for several plate geometry configurations and blast loads, making it possible
to measure the influence of the suction pressure and the membrane effect on the plate response.

IMPROVED NUMERICAL SIMULATION OF 2D FRAME STRUCTURES USING A GENERALIZED MODAL ANALYSIS

Ney A. Dumont, Rodrigo N. Barros, Carlos A. Aguilar — Mon, 26 Aug 2024 00:00:00 +0000

The hybrid finite element method, proposed by Pian on the basis of the Hellinger-Reissner
potential, has proved itself a conceptual breakthrough among the discretization formulations. A
proposition made by Przemieniecki – for the generalized free vibration analysis of truss and beam
elements – was incorporated into the hybrid finite/boundary element method developed by the third
author and extended to the analysis of time-dependent problems by making use of an advanced mode
superposition procedure that adequately takes into account general initial conditions as well as general
body actions. It is shown that such a consistent approach leads to frequency-dependent stiffness and
mass matrices that enter a generalized modal analysis based on a nonlinear eigenvalue problem for
complex-symmetric systems. This paper presents the basic features of the formulation as applied to
plane frame structures and assesses some examples available in the technical literature to show that
remarkable improvements may be achieved with the proposed formulation when compared to the
classical structural dynamics. Although the formulation is generally valid for three-dimensional
analysis, owing to space restrictions only two-dimensional plane frames and trusses are dealt with. The
analytical frequency-domain expressions of beams with and without hinges on the extremities is
displayed to make evident how axial and transversal modes interact and should be properly taken into
account.

NONLINEAR POSITIONAL FORMULATION APPLIED FOR DYNAMIC 2D SOLIDS ANALYSIS CONSIDERING DIFFERENT TEMPORAL INTEGRATION METHODS

Marcos D. F. S. Saraiva, Daniel N. Maciel, Rodrigo Barros — Mon, 26 Aug 2024 00:00:00 +0000

The analytical resolution for dynamic problems employs partial derivarives regarding time
and space. However, sereral methods of temporal integration replace the resolution of it. Thus, this paper
aims to analyze the dynamic response of two dimensional structural solids through different methods of
temporal integration for both implicit and explicit cases. In this sense, methods of Newmark, Houbolt
and Wilson-θ are used as the implicit one. In addition, methods of Central Differences, Souza and Moura
and Chung and Lee correspond to the explicit case. The analysis of 2D solids under dynamic response
considers both geometric and material nonlinearities. In order to regard nonlinear geometric effect, the
positional Finite Element Method (FEM) formulation wich uses node coordinates as variables instead
of displacements is taken into account. Therefore, the development of each computational routines for
the proposed formulation induces numerical results that are discussed and compared with examples from
the specialized literature.

USE OF MODAL ANALYSIS AS A METHOD TO ESTIMATE SECOND- ORDER GLOBAL EFFECTS IN REINFORCED CONCRETE STRUCTURES

Mon, 26 Aug 2024 00:00:00 +0000

DYNAMIC COMPARATIVE ANALYSIS OF THE RESPONSE OF A BUILDING SUBJECTED TO WIND ACTION IN THE FREQUENCY DOMAIN FOR FUTURE PROPOSAL TO THE NP-196

Mon, 26 Aug 2024 00:00:00 +0000

The accelerated growth of urban centers and the exponential development of real estate
industry have led to an increase of the construction of tall buildings. In addition, thanks to
technological advances, new construction methodologies have emerged that make structures slenderer.
In this sense, wind action is of fundamental importance in the structures design, especially on a
national level, due to the high wind speeds perceived in recent years and that have cause structural
collapses.
The national wind code NP-196 does not consider the dynamic action of high winds in slender
structures. Some international wind codes consider such action through an amplification factor (gust
response factor). Others, such as NBR-6123, present a simplified methodology of a probabilistic
analysis. Both methodologies arise from the spectral density response of a typical building by applying
a theoretical spectrum of wind gusts. In this context, the present work aims to analyze such
methodologies through the application of the mentioned theoretical spectrum on a building, in order to
suggest pertinent recommendations for a future proposal of the dynamic action of wind in structures.
For this purpose, a dynamic comparative analysis is made of the structure response through vibration
theory in the frequency domain. The spectrum of the fluctuating component of the wind force and
response spectra were obtained for different theoretical power spectral density of wind velocity,
suggested by several authors. The gust response factor for each case analyzed is then obtained as well
as the static equivalent fluctuating force, both of which are related to wind codes. Finally, a
comparative analysis is presented in which the variation of the wind force over the structure remains
under 10%, between different velocity spectrums.

ANÁLISE NÃO LINEAR DE PÓRTICO POR ELEMENTOS FINITOS E COMPARAÇÃO COM AS CONSIDERAÇÕES DA NBR 8800:2008 PARA OS EFEITOS DE 2a ORDEM

Mon, 26 Aug 2024 00:00:00 +0000

O presente trabalho procura realizar uma análise estrutural de vários tipos de pórticos planos
com diferentes níveis de pavimentos e com isso diferentes características de deslocabilidade, para
observar o comportamento do mesmo em relação aos esforços gerados e aos deslocamentos quando o
mesmo é sujeito a um determinado carregamento de vento e obviamente ao restante dos carregamentos
normalmente considerados, além da importância do uso de elementos de contraventamento na redução
dos deslocamentos horizontais que a estrutura poderá sofrer global ente. As análises serão feitas
utilizando o software de elementos finitos ABAQUS e também o software para análise d e estruturas
FTOOL. Com isso será feita uma comparação entre os valores obtidos diretamente por uma análise
pura não linear em pórticos planos por meio de elementos finitos utilizando o ABAQUS, com os
valores que serão fornecidos pelo FTOOL e ajustados com as considerações pela norma brasileira de
estruturas metálicas NBR 8800:2008 para amplificação dos esforços solicitantes para a consideração
dos efeitos de segunda ordem nas estruturas PΔ e Pδ, para os comportamento s globais e locais da
estrutura gerando assim uma análise próxima aceitável para uma análise de segunda ordem a partir da
obtenção dos coeficientes B1 e B2. Ao final poderá ser observado as aproximações entre os resultados
obtidos por meio das análises numéricas com os obtidos pelas equações um pouco mais conservadoras
da referida norma. Buscando mostrar principalmente o poder das ferramentas de elementos finitos em
representar de forma bastante aproximada o comportamento real de estruturas porticadas planas.

NON-LINEAR GEOMETRIC ANALYSIS OF DEFLECTIONS IN METALLIC TRUSSES

Mon, 26 Aug 2024 00:00:00 +0000

Geometric non-linearity consists of determining the stresses and displacements of a structure
considering the deformed state of the structure after load application, and therefore the equilibrium
equations must be reformulated for each of these changes. The present paper, in this sense, has proposed
to elaborate a software capable of analyzing the deflections of a structure of the trellis type,
implementing the changes of geometry with each applied load step. In order to perform the calculations,
the Finite Element Method was used, and the algorithm was written in the Python programming
language. With the results obtained in the software developed, and through comparisons with SAP2000
V15, it was verified that the simplified approach of geometric non-linearity, which was implemented in
the computational program elaborated, is very close to the results of SAP2000 as the load increase
decreases. The results show that the lattice node analyzed with the greatest divergence between the
software had a decrease in the difference between the deflections of the two software from 5.61% to
1.89% when changing the number of load steps, from two to one hundred steps.

GEOMETRICALLY NONLINEAR ANALYSIS OF PLANE TRUSSES AND FRAMES USING AN AUTOMATIC DERIVATION ALGORITHM

Danilo Menezes Santos, Jorge Carvalho Costa — Mon, 26 Aug 2024 00:00:00 +0000

Structural analysis requires the derivation of complex functions usually of many variables,
especially when nonlinearities are considered. From a computational standpoint, to derivate can be a
great challenge due to a series of limitations inbuilt in the usual derivation techniques. Surmising both
these factors, this work presents the development of an automatic differentiation (AD) algorithm in
Python 3.x and its application to structural analysis, aiming at preventing possible compatibility and
truncation errors inherent to other derivation processes. The software implemented both the forward and
reverse modes of differentiation and is able to work with algorithms written as string or def Python
classes. Later, the package was used to obtain the local stiffness (tangent) matrices for plane trusses and
frames in linear and geometrically nonlinear analysis, derived through energy methods. The results were
compared with benchmarks found in the literature. Excellent results were found for the stiffness
matrices, nodal displacements and internal forces, supporting that this technique can be used for solid
mechanics problem with ease.

MODELAÇÃO NUMÉRICA DE VIGAS EM PERFIS DE AÇO FORMADOS A FRIO COM SEÇÃO TRANSVERSAL SIGMA EM SITUAÇÃO DE INCÊNDIO

Mon, 26 Aug 2024 00:00:00 +0000

This paper presents the development of a finite element model suitable for predicting the
flexural behaviour of cold-formed steel beams under fire conditions. The numerical simulations were
performed with the finite element program Abaqus in order to understand the potential that this
program provides in modelling cold-formed steel under fire conditions. This paper provides details of
the simulation methodology for achieving numerical stability and faithful representation of detailed
structural behaviour under fire condition. The assessment of the accuracy of the developed numerical
model was conducted by comparing the axial restraining forces, vertical displacements, critical
temperatures and failure modes obtained from finite element simulations with some experimental
results, in order to validate the developed finite element model and to consequently obtain reliable
numerical results.

SIMULATION OF GENERATION AND PROPAGATION OF TENSILE FRACTURES IN LAMINATED CARBONATES OF THE CRATO FORMATION CONSIDERING STRATIGRAPHIC HETEROGENEITY

Mon, 26 Aug 2024 00:00:00 +0000

The Crato-PE Fm is part of the Araripe Basin, being one of the largest areas in relation to
the interior basins of north e astern Brazil. This led to the reactivation of old paddles for inversions,
and converting an old graven into a horst. This work seeks to simulate numerically a generation and
propagation of natural fractures for the effect of vertical lithological variation on fractures. In the
present work, it is proposed the use of the technique of fragmentation of high aspect ratio mesh
elements to model, together with the constitutive model of Damage to traction, a generation and
propagation of fractures. This type of model is able to divert the effect of the materials when submitted
to progressive processes of mechanical degradation by reducing the rigidity of the material. The
problem analysed is the simulation of the generation and propagation of extension fractures in a
profile considering interleaving of laminate layers with other types of lithology’s, representing a
faciological variation with impact on the mechanical competence of the layers on the genesis and
propagation of the extension fractures. In order to perform the study of fracture generation and
propagation, we used the fragmentation technique with special interface finite elements. This
technique was chosen because it numerically represents the behaviour of intensively fractured media,
in which the special interface elements are located between the regular finite elements. Was
considered submitted to a vertical tension representing a vertical burial state, and a horizontal tension
variation the extension direction. The base and one of the lateral borders of the domain are restricted
as to the displacement in the normal direction. The analysis is in flat deformation considering a
Lagrangean approach for the deformations. It has been found that as the prescribed tensile stress on
the left side of the section increases, horizontal tensile stresses develop in the layers, but with a higher
concentration in the laminate layer of greater stiffness and tensile strength.

BEMCRACKER2D: A SOFTWARE PACKAGE FOR TWO-DIMENSIONAL FATIGUE CRACK GROWTH ANALYSIS

Gilberto Gomes, Álvaro M Delgado Neto, Thiago A A Oliveira, Danilo C de Moura — Mon, 26 Aug 2024 00:00:00 +0000

The stress analysis in structures with complex geometry, such as in aircraft
fuselages, where geometry is continuously altered by crack growth, usually requires the use of
numerical methods, since the presence of cracks in the structure raises difficulties related to
the modeling and, consequently, to the calculation of the stress intensity factors (SIF). In this
aspect, the dual boundary element method (DBEM) has been applied in this type of analysis,
taking advantage over the FEM considered, since there is no need for continuous remeshing at
each crack increment. In this context, this work proposes the development of software written

in C ++ and based on Object Oriented Programming, called BemCracker2D, for two-
dimensional analysis by DBEM of fatigue crack propagation problems in the field of linear

elastic fracture mechanics. Parameters such as SIF, crack propagation path, number of load
cycles and others, will be computed and compared with examples from the open literature in
order to attest to the program's efficiency and robustness.

COMPUTATIONAL ANALYSIS OF CRACK GROWTH IN DUCTILE MATERIALS

Machado, G. A., Bittencourt, E. — Mon, 26 Aug 2024 00:00:00 +0000

Rupture in metals can occur by cleavage, where all process is controlled by stresses, or by a
combination of critical stresses and strains in a process known as ductile fracture. The Linear Elastic
Fracture Mechanics, widely used in engineering practice, is in general based on the assumption that
the first process prevails, which occurs only under certain conditions. Consideration of the second
fracture process is not so well disseminated. In this work, two methodologies are considered to take
into account the transition cleavage/ductile. One is based on the Tvergaard-Hutchinson's trapezoidal
cohesive model and the other is based on the Gurson's ductile damage model. The two models are
considerably different and in this work, initially, the relationships between the two models are
established. Then, the conditions for a transition from cleavage to ductile fracture are determined and
discussed. Results are presented based on crack growth resistance curves obtained for different
material parameters. A simple numerical model in mode I rupture is considered.

ANALYSIS OF LOCAL TENSILE RUPTURE INFLUENCING SHEAR STRENGTH ON UNIAXIAL TEST MODELLING

Mon, 26 Aug 2024 00:00:00 +0000

Constitutive models are mathematical formulations capable of describing the macroscopic
behaviour of an ideal medium. These models result from the application of simplifying hypotheses
about the behaviour of the real environment. Therefore, the selection of the constitutive model to be
used must be related to the problem to be solved, since it would not be trivial to obtain a single
formulation that would allow reaching the general solution for the material behaviour. In this sense,
modelling is a feature that describes the behaviour of materials subjected to real stress states, such as
uniaxial tests performed in the laboratory. Modelling of this type of test is generally performed

through models that describe the shear behaviour of the sample, such as Mohr Coulomb and Drucker-
Prager models. However, when observing some experiments in the laboratory, it was verified that

there are local tensile zones in the samples, which allows a reduction of the material resistance. In this
sense, this article presents a study of a rock sample that was submitted to the Uniaxial laboratory test
and its resistance was reduced by the tensile zones. Furthermore, in this work the numerical modelling
of this test will be presented and the impact of considering these zones of damage in the sample, the
constitutive model adopted in these simulations was the tensile damage.

AN AIRCRAFT FUSELAGE FRACTURE ANALYSIS

Thiago A. A. Oliveira, Gilberto Gomes — Mon, 26 Aug 2024 00:00:00 +0000

The continuum mechanics deals with the interaction between two bodies in order to analyze the
stresses in the domain due to the contact load. In this way, to compute the stresses, it is considered
each body as a semi-infinite in extent and having a plane surface. The Boundary Element Method
(BEM) appears as a numerical technique for evaluating this type of problem. Using this technique, the
boundary is discretized and the stresses are computed in the body domain. This paper consists of the
multiscale analysis via Dual Boundary Element Method (DBEM) of fatigue life of aircraft fuselage
plate. The macro analysis is evaluated through the stress field in the plate due to continuum
mechanics. With this stress field, a micro element, composed by different distribution of cracks, is
subjected to fatigue and analyzed by Dual Boundary Element Method (DBEM). This is accomplished
using the software BemCracker2D obtaining fatigue life data in each crack increment. For this,
advanced computational techniques were developed to evaluate the fracture mechanics behavior with
the purpose of ensuring the integrity and the good functioning of the fuselage during its design
lifespan.

2D HYDROMECHANICAL MODELING OF WATERFLOODING IN FRACTURING CONDITIONS USING FINITE ELEMENTS WITH HIGH ASPECT RATIO

Mon, 26 Aug 2024 00:00:00 +0000

Waterflooding is a widely used methodology in the oil & gas industry and its main objective
is to guarantee the pore pressure maintenance in reservoirs during production as well as to sweep the oil
towards the producing wells. Injection of water in pressure conditions that exceed the reservoir fracture
pressure in operations known as IAFP (Injection Above Fracture Pressure) it's often necessary to ensure
the high injection rates required in secondary recovery processes. In order to model the hydromechanical
behavior of the fracking in the presence of producing wells, which particularly occurs in IAFP
operations, this work used the finite element method in two dimensions with high aspect ratio elements
and a constitutive law based on the tensile damage mechanics to model the opening and propagation of
hydraulic fractures. The fluid flow was described by Darcy's law and the fully coupled method was used
to solve the hydromechanical equations. Numerical examples with different injection rates and
production pressures were performed in order to verify the ability of the method to reproduce the
opening and propagation of fractures in the presence of producing wells. The results showed the method
was able to reproduce the opening and propagation of fractures in IAFP conditions and they also suggest
that in some cases the producing wells can play an important role in the propagation length of the
fractures.

CONTINUOUS AND DISCONTINUOUS MODELING OF FAILURE FOR QUASI-BRITTLE MATERIALS

José Fabiano Araújo Moreira, Francisco Evangelista Junior — Mon, 26 Aug 2024 00:00:00 +0000

This research aims to formulate and implement a continuous-discontinuous approach for
failure of quasi-brittle materials. This approach is based on a damage evolution law using only
physical parameters, which can be obtained through fracture and resistance tests without the need of
further calibration. Comparison with experimental results were performed to assess the accuracy and
efficiency. The tests simulated with the model were the three-point bending in a single edge notch
beam. The results obtained herein confirmed the efficiency and accuracy of the model in predicting
rupture behavior. Moreover, the model can provide results with equivalent accuracy to others in the
literature using fewer elements in the mesh.

BOUNDARY ELEMENT TOPOLOGY OPTIMIZATION OF ANISOTROPIC MEDIA

Felipe L. Lorenzi, Rogério J. Marczak — Mon, 26 Aug 2024 00:00:00 +0000

The objective of this work is to present the implementation of a topological sensitivity based
material removal procedure in a standard Boundary Element Method formulation. The approach used
selects the areas showing the lowest sensitivities, where material is removed by opening a small cavity.
As the iterative process evolves, the original domain has volume progressively removed, until a desired
material volume is achieved. Because the Boundary Element Method does not employ domain meshes
in linear cases, the resulting topologies are completely devoid of intermediary material densities.
Additionally, with Bézier Curves, a method of smoothing lines was implemented during the topological
optimization scheme, aiming to reduce some usual problems in the optimization process, such as the
irregularity of the boundaries, eliminating the need for post-processing and reducing the computational
cost of the process. Anisotropic elastic cases are presented and compared with their isotropic counterpart
optimums.

DEVELOPMENT OF A TOPOLOGY OPTIMIZATION ALGORITHM WITH ADDITIVE MANUFACTURING CONSTRAINTS

Lucas S. da Silva, Cícero R. de Lima — Mon, 26 Aug 2024 00:00:00 +0000

Topology Optimization (TO) is a systematic method with wide application to structural
optimization. TO combines optimization algorithms with finite element method, in order to provide an
optimal material distribution inside a design domain, aiming to attend a specified objective function and
to satisfy the constraints on the optimization problem. Additive Manufacturing (AM) is a generalized
term utilized to designate the manufacturing techniques, that employ the principle of fabrication by
adding material layer by layer to obtain the final geometry of a product. This principle is powerful for
manufacturing geometries of higher complexity when compared to traditional manufacturing
techniques, such as machining, forging and others. Although AM techniques have a high capacity of
producing TO geometries, without compromising to much its optimality, these techniques still have
manufacturing restrictions. Feasible AM geometries have associated requirements such as minimum
member size, minimum overhang angle and minimum hole size, for instance. The aim of this work is to
develop a structural optimization algorithm, including in the formulation of the TO problem a
projection-based filter which implicitly applies a manufacturing constraint imposed by the AM
manufacturing process known as FDM (Fused Deposition Modelling), whose technique possess a
critical overhang angle at which the structure does not self-supports. In this case, a projection function
and variable mappings are defined to impose the maximum overhang constraint. Specifically, it aims to
avoid or eliminate the support material utilized in the FDM process and, consequently, reduce the
fabrication costs of the process. Some results are presented to demonstrate the potential of the proposed
TO algorithm.

METAMATERIAL MECHANISM DESIGN BY TOPOLOGY OPTIMIZATION IN TRUSS GROUND STRUCTURE DOMAINS WITH LARGE DISPLACEMENTS

José H. C. Teles, Sandro L. Vatanabe, Cícero R. de Lima — Mon, 26 Aug 2024 00:00:00 +0000

Metamaterials are artificial structures engineered to have extremal properties that are not
found in naturally occurring materials, such as negative Poisson’s ratio (auxetic behavior). These
structures are obtained by repetitive cell patterns. Each cell of the metamaterial can be designed to
have a controlled directional movement. This allows the creation of devices with a desired mechanical
function. Compliant mechanisms perform certain functions from the elastic deformation of its body.
The topology optimization (TO) technique has been shown to be the most generic and systematic for
the design of compliant mechanisms. It consists of a method that distributes material within a domain
in order to achieve the specified objective function, satisfying the imposed constraints. In this work,
compliant mechanism is designed by using the Topology Optimization method to generate
microstructure unit cells that simulate the effect of metamaterials that have negative Poisson’s ratio
(auxetic materials). The unit cell (microstructure) of metamaterial is driven to have the same
characteristics of a compliant mechanism, that is, a monolithic body that delivers a desired motion
when is loaded in a certain way. TO is performed in domains discretized by truss elements (ground
structure), where the cross-sectional areas of the elements are the design variables. Large
displacements are considered, which establishes a nonlinear relation between deformation and
displacement and requires the use of nonlinear FEM. Computational simulations are presented to
verify the results of the metamaterial design.

Simultaneous Optimization of Fiber and Material Distribution for Composite Materials Based on Topology Optimization

Andre Luis Ferreira da Silva, Ruben Andres Salas, Emílio Carlos Nelli Silva — Mon, 26 Aug 2024 00:00:00 +0000

New additive manufacturing technologies are been developed to obtain particular composite
structures. In the case of fiber-reinforced composite structures, fiber angle influences material properties.
This work presents a method based on topology optimization, which combines two models to design
structures made of fiber-reinforced composite, considering simultaneously the distribution of material
and the fiber orientation.

A TOPOLOGY OPTIMIZATION APPROACH FOR THE 2D ACOUSTIC INVERSE PROBLEM IN TIME DOMAIN

Mohammad M. Ghorbani, Ruben A. Salas, Juliano F. Gonçalves, Emílio C. N. Silva — Mon, 26 Aug 2024 00:00:00 +0000

Acoustic Tomography (AT) is a method widely used in the oil and gas industry for the purpose
of finding and/or monitoring sub-sea bed hydrocarbon reservoirs. This approach is based on propagation
and measurement of acoustic waves in order to acquire information about unknown media. As a result,
physical properties of the medium can be identified by solving an inverse problem, which is usually
formulated as the minimization of the difference between the response measured by the receivers, and
a simulated response obtained by a numerical model. An efficient method to solve inverse problems
and to find the distribution of material parameters is the Topology Optimization Method (TOM). This
work proposes a topology optimization approach for the acoustic inverse problem in the time-domain
using finite element method. A material interpolation scheme based on the Solid Isotropic Material
with Penalization (SIMP) is employed to represent the velocity model for the acoustic problem. The
sensitivity analysis is carry out using an automated differentiation tool and the optimization problem is
solved by a Limited-Memory BFGS algorithm. Two examples considering different velocity models are
analyzed and a perturbation is imposed on the measured responses in order to avoid inverse crime.

TOPOLOGY OPTIMIZATION OF SURFACE STRUCTURES SUPPORTED BY PILE GROUPS

Emanuel S. Tavares, Josue Labaki — Mon, 26 Aug 2024 00:00:00 +0000

This work investigates an aspect of topology optimization strategies in dynamic soil-structure
interaction problems. The aim is to understand the influence of the presence of embedded pile groups in

the optimal shape of a piled structure. The surface structure is modeled by classical three-dimensional fi-
nite elements. The embedded pile group that supports the structure is modeled via the impedance matrix

method. The soil is an isotropic, viscoelastic, layered medium, and the piles are elastic isotropic bodies
with fully bonded contact with the soil throughout their interfaces. Coupling between the structure and
the pile foundation is obtained by establishing direct kinematic compatibility and equilibrium criteria at

discrete nodes of the structure that connect to pile heads. The system is considered to be under arbi-
trary static external loads. Shape optimization of the surface structure is obtained with the bidirectional

evolutionary structural optimization method (BESO), in which elements of the mesh of the structure are
included or removed in order to achieve a certain optimal topology. Objective functions in this work is
the stiffness of the structure. The results compare the difference between the optimized shapes in the
case in which the structure rests on rigid supports, and the case in which energy dissipation to the soil
through the piles is considered.

STANDARD FINITE VOLUME THEORY APPLIED TO TOPOLOGY OPTIMIZATION FOR COMPLIANCE MINIMIZATION OF CONTINUUM ELASTIC STRUCTURES

Mon, 26 Aug 2024 00:00:00 +0000

In topology optimization of structures, the objective is to establish the best material
distribution inside of an analysis domain given an objective function, as compliance minimization, and
mechanical restriction to the problem. Normally, in the gradient-based topology optimization
algorithms, there are some problems related to numerical instabilities, such as checkerboard pattern,
mesh dependence and local minima. The checkerboard effect is directly related to the assumptions of
the finite element method, as the satisfaction of equilibrium equations and continuity conditions
through the nodes. On the other hand, the finite volume theory satisfies the equilibrium equations at
the subvolume level, and the static and kinematic continuities are established through adjacent
subvolumes interfaces, as expected from the continuum mechanics point of view. To solve the
problems related to the checkerboard and mesh dependence in the finite element method, it is often
recommended the use of sensitivity or perimeter control filters. For the finite volume theory, the
sensitivity filter is employed with the purpose to control better the mesh dependence and length scale
numerical issues. Comparisons of the optimum topologies and computational performances of the
analyzed approaches are presented, demonstrating the influence of the adopted numerical method on
the obtaining optimal solution when a filtering technique is employed.

Topological Optimization Software Tools: Literature Review and Real Application

Mon, 26 Aug 2024 00:00:00 +0000

The sake for the optimal condition or shape is inherent in us. Some optimization examples are
visible even in nature. In metals, for example, atoms tend to take positions of minimum energy in order
to form unit cells, which define the crystalline structure of these materials. In a zero gravity condition,
a liquid droplet forms a perfect sphere, which has the least surface area for a given volume. The first
historical example of structural optimization is present in Galileo’s work, in which he sought the optimal
structural shape of a cantilever beam. Since then, the optimization field has growth exponentially. In this
context, not only significant evolution in the theoretical field is necessary, but also, computational tools
capable to follow this growth are compulsory. New numerical methods have also been developed, such as
the Finite Element Method (FEM), distinguished for its accuracy and high adaptability for a broad type of
physical problems. Several software tools for topology optimization based on the FEM are available on
the market, however, few or none information about the optimization method or optimization parameters
are explicitly presented. This work aims to fulfill this conceptual lack, as well as, to show an extensive
review of topology optimization tools available for common users, such as commercial softwares or apps.
Thus, a realistic example of topology optimization is presented to show the feasibility of constructing an
optimized mechanical component using the computational tools described on this work.

A HYBRID TOPOLOGY OPTIMIZATION APPROACH TO FORCE VISUALIZATION IN REINFORCED CONCRETE STRUCTURES

Kênia A. T. F. Gouveia, Daniel L. Araújo, Sylvia R. M. Almeida — Mon, 26 Aug 2024 00:00:00 +0000

The Strut-and-Tie Method is a rational approach used to circumvent complexities in the
analysis and design of reinforced concrete structures, especially those that do not meet the Bernoulli’s
hypothesis. This work applies topology optimization techniques to automatically obtain power paths in
reinforced concrete structures to be applied in strut-and-tie models. A hybrid formulation of the
minimum compliance problem is adopted in which the concrete struts are represented by continuous
elements associated with material density and steel reinforcing bars. Bilinear isotropic elastic models
are applied to both materials to separate compressive and tensile load paths. In order to eliminate
resultant thin bars and provide a force layout applicable in the design practice, a maximum filter is
applied at the end of the optimization process. Tikhonov regularization is applied to the potential energy
of the structure to solve singular equilibrium equations and check the equilibrium of the extracted
solutions in the filtering procedure. Numerical examples are provided to demonstrate the applicability
of the proposed formulation.

A STUDY ON THE INFLUENCE OF STEEL REINFORCEMENT IN FORCE PATHS IN RC STRUCTURES USING TOPOLOGY OPTIMIZATION

Danilo B. Cavalcanti, Sylvia R. M. Almeida — Mon, 26 Aug 2024 00:00:00 +0000

TOPOLOGY OPTIMIZATION OF CONTINUUM TWO-DIMENSIONAL STRUCTURE UNDER VOLUME CONSTRAINT

Higo L. S. Nascimento, Rafael B. S. Araújo — Mon, 26 Aug 2024 00:00:00 +0000

This work presents the Topology Optimization Method where the objective is to minimize
compliance with lateral and volume constraints of a rib from aircraft wings profile leading edge. The
problem is solved by a Topology Optimization Method technique, formulated as finding the best
material distribution into the domain. The static problem is solved with the Finite Element Method were

the structural response is given as nodal displacements. The Optimality criteria are based in the power-
law approach, also known as Solid Isotropic Material with Penalization that uses a “fictitious” density

to represent the material distribution into each finite element that defines the elastic properties of
isotropic porous material. The solution is implemented with a didactic algorithm. No linear
programming is used and a heuristic updating scheme is used as standard optimality criteria. Besides,
sensitivity and densities filters are used to minimize the occurrence of numerical instabilities:
checkerboards, mesh-dependencies, and local minima. The results are evaluated in three criteria: first,
the occurrence of these instabilities and filter performance, second the convergence and implementation
time and the last one a brief comparison with the literature and a general analysis of the results.

ANALYSIS OF SLOSHING SUPPRESSORS IN LIQUEFIED NATURAL GAS CARRIERS TANKS

Mon, 26 Aug 2024 00:00:00 +0000

The problem of sloshing has been studied in the last decades, seeking to reduce the
deleterious effects promoted by this phenomenon in liquefied natural gas carriers tanks. Since there is
a need to develop tank designs capable of reducing the damaging effects of sloshing, a study on the
hydrodynamic loads involving the fluid-structure relationship becomes necessary. In this work,
attenuation devices were installed to reduce the effect of sloshing on containers, such as deflector
blades positioned on tank walls. Regarding this topic, our work was devoted to testing two types of
sloshing suppressor bulkheads, where two different heights were assigned and tested for the first
vertical deflector located in the center of the tank. Secondly we change the morphology of the baffle,
leaving it in the shape of an arrow pointing upwards. The results show that the baffles can be efficient
mechanisms for the suppression of slonging and that there is a strongly relationship between the
height of the baffles and the level of fluid filling in relation to the tank.

NUMERICAL ANALYSIS OF THE HOLDING CAPACITY OF TORPEDO ANCHORS CONSIDERING SETUP EFFECTS

Guilherme K. Lopes, José R. M. de Sousa, Gilberto B. Ellwanger — Mon, 26 Aug 2024 00:00:00 +0000

Torpedo anchors have proven to be an outstanding alternative of fixed anchor point for taut
leg mooring systems on Brazilian offshore fields. This type of anchor has low construction and
fabrication costs, which are not dependent on water depth and withstands high vertical loads. Torpedo
anchor has a “rocket” shape and its installation is given by free fall using heavy weights as the driving
kinetic energy. Its driving process induces an excess pore water pressure generation and causes
significant shearing and disturbance, which affects the stress, strain and strength characteristics of the
soil surrounding the anchor. Immediately after installation, the holding capacity of the torpedo anchor
is significantly reduced. Although, after the anchor is driven, holding capacity is observed to increase
with time. This phenomenon is referred as setup. This paper presents a numerical based study of a finless
torpedo anchor embedded in a purely cohesive isotropic soil using an axisymmetric nonlinear finite
element model. The plasticity Cap model was chosen to describe the mechanical behavior of the soil.
Anchor-soil interaction is simulated using surface-to-surface contact pairs with a penalty type contact
property to represent friction behavior between the surfaces in contact. A number of analyses are
conducted using Abaqus/CAE® in order to understand the response of this structure when considering
setup effects. Additionally, a parametric study is also performed. The results indicated that soil
permeability plays an important role into setup process. Furthermore, plasticity parameters are also
investigated and the results followed a pattern of behavior on structure response.

FATIGUE ANALYSIS OF THE GROUTED CONNECTION OF AN OFFSHORE WIND TURBINE

Fellipe A. Gomes, Gilberto B. Ellwanger, José R. M. de Sousa — Mon, 26 Aug 2024 00:00:00 +0000

Due to technological advances, Offshore Wind Turbines (OWT) have proven to be a viable
investment alternative in Brazil. However, unlike offshore structures originally developed for the oil
and gas industry, OWT support structures are subject to large bending moments due to the wind and
wave loads on the structure. One of the critical regions of an OWT is the structural connection between
the superstructure and its foundation. This is commonly performed through a cylindrical joint filled with
high-performance grout, made by a metal transition piece that transfers the stresses to foundation
through the grout. The present article aims to evaluate the structural fatigue, under operational and
parked condition, of the grouted connection of a monopile foundation in water depth of 20 meters in
cohesive soil, using SIMA-RIFLEX and TurbSim software. The soil-structure interaction is simulated
applying p-y curves proposed by ANSI / API-RP-2GEO (2011) and DNVGL-ST-0126 (2016). Fatigue
damage is analyzed by applying the Rainflow Counting and S-N curve proposed by DNVGL-ST-C502
(2018) for the grout. It was identified that more severe environmental conditions generate greater
damages, and this behavior is strongly influenced by the rated speed of the turbine and natural frequency
of the structure.

ANÁLISE DE GARANTIA DE ESCOAMENTO EM SISTEMAS SUBMARINOS

Mon, 26 Aug 2024 00:00:00 +0000

The discovery of offshore fields at great distances from the coast and high water depths made
oil and gas production a challenge to the industry. Some of these challenges are due to the possibility of
solids depositions along the subsea pipes, the high cost of exploration and difficult accessibility.
Therefore, flow assurance studies become important to find mitigation strategies and early identification
of possible complications on the production subsea system. However, this analysis demands knowledge
of the pressure and temperature variation along the pipelines (thermo hydraulic profile of the lines). In
order to predict the possible occurrence of flow assurance problems, more specifically the formation of
hydrates and wax, this paper suggests defining and evaluating the thermo hydraulic profile from the
wellhead to the primary processing plant on the surface and associate it to the possible appearance of
flow problems. Taking as input the physical properties of the fluids and the system’s geometry and
applying heat transfer equations in subsea pipelines. Afterwards, integrating the pressure and
temperature gradient equations in short increments of the pipe to calculate the thermo hydraulic profile.
Finally, pipeline insulation designs will be studied in order to prevent the flow assurance problems,
evaluating from the available methods (pipe-in-pipe system, buried pipelines and insulation layers)
which is the most suitable for the studied scenario.

STUDY OF FLOW AROUND A CIRCULAR CYLINDER - INFLUENCE OF REYNOLDS NUMBER AND TURBULENCE INTENSITY

Leonardo L. V. Rodrigues, Patrícia H. Hallak — Mon, 26 Aug 2024 00:00:00 +0000

Flexible risers, widely used in offshore engineering, are long multilayer tubes designed to
carry fluid — such as oil and natural gas — from the seabed to the sea platforms. In this scenario, the
risers have to be able to withstand efforts ranging from their weight, water column pressure, to dynamic
loads resulting from sea currents. This study aims to evaluate the influence of sea currents on flexible
risers. For this interaction, the fluid passage was evaluated in a uniform flow around the cross-section of
the tube in a two-dimensional analysis. The seasonality and variation of sea currents over time make it
necessary to study different flow regimes. This phenomenon generates pressure variation on the surface
structure, causing dynamic efforts that can induce oscillations, increase drag force and cause structural
failure if the frequency of vortex shedding approaching one of the natural frequencies in a structure.

Therefore, the drag and lift coefficients and Strouhal for Reynolds numbers in the laminar and turbu-
lent regime are so important. They are obtained through modeling using computational fluid dynamics

software, ANSYS

R Fluent, and then compared with the results of other models in the literature. In the
case of the k − ω SST turbulence model simulations, it is used fixed turbulence intensity values for all
Reynolds numbers. This work intends to vary this parameter in order to verify its influence in some
aerodynamics coefficients, taking into account the Reynolds number.

EVALUATION OF THE BEHAVIOR OF MONOPILE FIXED OFFSHORE WIND TURBINES

Gabriel Nogueira, Gilberto B. Ellwanger, José R. M. de Sousa — Mon, 26 Aug 2024 00:00:00 +0000

This work follows a worldwide trend of developing new wind farm projects on sea. Standard
models used by the academy of 5 and 10 MW wind turbines are introduced to the Brazilian environment
being supported by fixed foundations of the monopile type. The aim is to develop a sensitivity analysis
of the fatigue damage in a critical point of the foundation under the effect of important offshore cyclic
loads. The models employed in this paper were firstly validated through analyses of their natural
frequencies. The next step was to subject them to extreme loads caused by wind, wave and current to
determine the critical point in each turbine’s foundation. With these points in hand, the sensitivity
analysis was conducted assuming the wind with and without a dynamic component, while the sea waves
were represented by the Jonswap or Pierson-Moskowitz spectrum. Finally, fatigue was assessed through
the damage calculated by the Palmgren-Miner rule in association with the largely employed S-N curves
and the rainflow method for counting stress cycles in the time series generated by SIMA-RIFLEX. This
study showed the importance of the dynamic component of the wind in the structure’s lifespan, which
was reduced by at least one order of magnitude when considered. No significant change in fatigue
damage was observed with different wave spectra. Lastly, life results obtained for the 10 MW turbine
were better than the 5 MW due to its more robust geometric characteristics.

ARTIFICIAL NEURAL NETWORKS FOR OPTIMIZATION PROCEDURES OF LAZY WAVE FLEXIBLE RISER CONFIGURATION

Mon, 26 Aug 2024 00:00:00 +0000

Risers are among the most expensive and complex components of an offshore production
system, because they suffer the action of a series of dynamic and environmental loads when connecting
the seabed to the floating unit. An optimal design of such structures can bring more security and cost
savings, which can be achieved by optimization techniques. In this context, this work presents the
development and implementation of Artificial Neural Network (ANN) in optimization procedures of
Lazy Wave flexible riser configuration as an alternative to Finite Element simulations, which has a high
computational cost. For the network selection, a parametric analysis has been done considering the mean
square error, accuracy of two different types of training algorithms and different amounts of neurons
layers. A case study is presented comparing the results of the ANN optimization process with a
simulation by the Finite Element Method (FEM). The results indicate a significant reduction of the
computational cost of all optimization process was achieved using ANN, which was able to predict with
accuracy the magnitudes involved in this type of problem.

UNVEILING PATTERNS IN THE INTERACTION BETWEEN RISERS AND SEABED

Edgar Stonyo B. Micolo, Anderson Barata Custódio — Mon, 26 Aug 2024 00:00:00 +0000

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

AN ACCURATE AND EFFICIENT METHOD FOR STATIC ANALYSIS OF MARINE RISERS

Luana A. G. Moura, Juliana C. Alves, Evandro Parente Jr., Ligia Tornisiello — Mon, 26 Aug 2024 00:00:00 +0000

Risers are essential components of offshore oil and gas production systems since they are
responsible for transport these fluids to/from the wells from/to the floating facilities. Thus, structural
analysis of marine risers has been an active research field in the last decades. Currently, there are
many reliable analysis programs for riser analysis based on the Finite Element Method (FEM).
However, this approach incurs in high computational costs due to its complexity and alternatives that
are more efficient have been sought. Risers are subjected to static and dynamic loads, but it is known
that in the earlier steps of riser design it is very important to evaluate the riser behavior under static
loads, as self-weight, buoyancy, hydrostatic pressure, currents and floater movements (static offset).
This paper presents an efficient and accurate approach for riser static analysis based on the numerical
integration of the differential equilibrium equations of a cable subjected to vertical and horizontal
static loads. The riser is modeled as an inextensible cable without bending stiffness, subjected to
effective weight, drag force and offset. The riser behavior is governed by a nonlinear system of
ordinary differential equations. The resulting nonlinear Boundary Value Problem (BVP) is solved
using the Newton-Raphson Method with line searches to guarantee global convergence and increase
efficiency. Initial values are estimated in order to transform the BVP in an initial value problem. The
fourth-order Runge-Kutta method is used in the numerical integration of the resulting initial value
problem. A post-processing procedure is used to evaluate the bending moment along the riser. This
approach is suitable for analyzing analyze different riser configurations, such as steel catenary risers
and lazy-wave risers. The accuracy and efficiency of the proposed approach are assessed and the
results are compared with the FEM for different riser configurations. The results show that the
presented approach is not only much more efficient than FEM but also can be more accurate.

ESTUDO DE UMA NOVA CONFIGURAÇÃO DE LINHAS DE ANCORAGEM PARA PLATAFORMAS DE PETRÓLEO EM ÁGUAS PROFUNDAS

Rodrigo Moretti Kochem, Fabrício Nogueira Correa, Breno Pinheiro Jacob — Mon, 26 Aug 2024 00:00:00 +0000

O petróleo é o principal recurso natural utilizado para suprir a demanda da matriz energética
mundial. Com o aumento progressivo para lâminas d’água cada vez maiores, obstáculos são revelados,
solicitando a engenharia offshore tecnologias cada vez mais sofisticadas para lidar com essa nova
realidade. Dentro desse contexto encontra-se novos desenvolvimentos relacionados ao posicionamento
da unidade flutuante. O sistema de ancoragem é responsável pelo posicionamento da plataforma dentro
dos limites operacionais, proporcionando segurança na exploração de petróleo. Para grandes
profundidades é utilizada uma configuração da linha de ancoragem denominada configuração Taut-Leg,
na qual as linhas se encontram retesadas e apresentam em sua composição materiais mais leves, esta
configuração é composta nas extremidades por cabos de aço ou amarras e no seu trecho intermediário
por cabos de poliéster. A configuração Taut Leg das linhas de ancoragem tem o intuito de diminuir o
raio da ancoragem, garantindo maiores possibilidades de arranjos submarinos, e fornecer maior rigidez
vertical a plataforma garantindo menores passeios. Este trabalho tem por objetivo estudar os efeitos de
um sistema de ancoragem spread mooring com uma variação da configuração Taut Leg, que consiste
em inserir um peso, propondo uma nova configuração da linha de ancoragem. Esta nova configuração,
tem por objetivo diminuir o raio de ancoragem, além de aplicar uma pré-tração inicial menor do que a
prevista em projeto, sendo esta diferença suplantada pela inserção de peso em determinado ponto da
linha, possibilitando o emprego de guinchos menos potentes. Para expor as vantagens e desvantagens
da configuração proposta, foram realizadas análises acopladas no domínio do tempo com o intuito de
comparar a configuração proposta com uma configuração Taut Leg. Para tal, foi utilizado o programa
SITUA-PROSIM.

INFLUÊNCIA DO ROMPIMENTO DE LINHAS DE ANCORAGEM NA RIGIDEZ HORIZONTAL DE UMA PLATAFORMA DE PETRÓLEO

Mon, 26 Aug 2024 00:00:00 +0000

Dada a importância dos sistemas de ancoragem na manutenção do posicionamento projetado
para plataformas de petróleo e da sua influência no comportamento da estrutura (particularmente em
águas profundas e ultraprofundas), faz-se pertinente a investigação da variação dos seus níveis de
rigidez conforme diferentes configurações do sistema. Assim, este trabalho investiga a influência do
offset e da condição de avaria na rigidez no plano horizontal de uma plataforma flutuante com sistema
de ancoragem spread-mooring. Os resultados obtidos em termos de mapas polares de rigidez
confirmam a influência do offset da plataforma, bem como da perda de linhas de ancoragem, na
rigidez horizontal obtida. Observou-se também um comportamento não-linear da rigidez horizontal
global da unidade flutuante. Além disso, sob determinadas condições, há registro de aumento de
rigidez mesmo com a avaria de uma linha de ancoragem. A ferramenta utilizada para as análises foi o
software Situa-Prosim desenvolvido pelo LAMCSO – COPPE/UFRJ para a Petrobras e que simula o
comportamento de sistemas de produção de petróleo utilizado análises estáticas e não-lineares.

A TOPOLOGY OPTIMIZATION METHOD APPLIED TO SUBSEA STRUCTURES UNDER SIMULTANEOUS THERMAL EXPANSION AND HYDROSTATIC PRESSURE LOADS

Renato Picelli, Raghavendra Sivapuram — Mon, 26 Aug 2024 00:00:00 +0000

The effect of severe environmental conditions, i.e., high pressure and high temperature
(HPHT), is known to cause various difficulties for the design of deepwater structures for oil and gas

production [1]. Subsea structures can be difficult to be repaired and/or replaced in response to the oc-
currence of unexpected problems due to severe HPHT conditions. Therefore, several methods have been

developed to design structures to withstand simultaneous pressure and thermal expansion [2]. This paper
aims to propose a topology optimization method to handle the challenges that simultaneous hydrostatic
pressure and thermal expansion impose on structural design. Topology optimization methods aim to find

optimal material distribution layouts (topologies) on specified design domains minimizing or maximiz-
ing an objective function subject to a set of constraints. The structural topologies are usually organic and

non-intuitive designs and they represent a powerful computational tool in the early stage of the struc-
tural design. Herein, the proposed Topology Optimization of Binary Structures (TOBS) method [3] uses

discrete 0,1 design variables within a finite element mesh to indicate the existence of solid 1 and void 0
material inside the design domain. A fluid pressure field is solved with a separate domain and constant
thermal expansion is applied on the structural volume. Sequential integer linear programming is used

to solve the optimization problem iteratively. The discrete nature of the method presents attractive fea-
tures when dealing with design dependent body and surface loads. In this paper, we use the structural

mean compliance and volume as functions for optimization. The methods of topology optimization have
achieved industrial maturity to be applied in stiffness maximization problems, but they are still quite
limited when it comes to Multiphysics design. A numerical example of a subsea structural design is
explored in this paper.

ANALYSIS OF THE MONOPILE FOUNDATION USING THE FINITE ELEMENT METHOD AND THE P-Y CURVES METHOD

Flávia E. S. Cabral, José R. M. de Sousa, Gilberto B. Ellwanger — Mon, 26 Aug 2024 00:00:00 +0000

The Monopile type foundation has been widely used by the offshore industry as an
economically and technically optimal choice for water depths from 20 to 40m. However, with the
current trend towards the installation of wind turbines with higher capacities and deeper waters, the
need for large diameters arises, which directly affects pile-soil interaction and dynamic structure
response. Common design procedures for laterally loaded piles are based on the p-y curves method
present in the API regulation. Such procedures were developed considering small diameter piles
subjected to low loading cycles. However, recent studies have questioned the applicability of the
traditional method for the design of the most modern monopiles, which have diameters between 6 and
8m, whose behavior tends to be rigid body and not a flexible foundation, as expected when using the
curves p-y. This work aims to analyze the behavior of the foundation of a wind turbine of 5MW under
horizontal load induced by wind, waves and currents taking into account the load x displacement curve
obtained from three dimensional models in finite elements. In the construction of the models, the
elastoplastic and non-linear behavior of the soil are considered. The obtained results are later
compared with those obtained by the traditional method of the p-y curves. It is expected to show that
for the monopiles analysis of wind towers, the p-y curves can be imprecise when representing the
behavior of the soil, presenting values of displacements and rotations at the top of the monopile
significantly different from the real displacements, making necessary a method that best represents the
behavior of these structures.

STATIC NONLINEAR ANALYSIS OF VESSELS BERTHED AT DOLPHINS

Arina van L. B. de Carvalho, Eduardo M. B. Campello, Kalil J. Skaf — Mon, 26 Aug 2024 00:00:00 +0000

Vessel mooring systems consist of mooring lines, fenders and a fixed (harborage) structure.
Their role is to ensure the operational safety of port terminals by restraining the vessel movements at
berth during loading and unloading operations. This work presents partial results of an on-going research
on the dynamic behavior of a vessel berthed at dolphins subjected to environmental oscillatory loadings.
It is a case study of a VLCC (Very Large Crude Carrier) berthed at the Porto Central/ES, Brazil,
subjected to wind and current forces. At first, a simplified static analysis, used in structural design’s
current practice, is made to estimate the maximum loads in the mooring lines. Then, a nonlinear static
analysis with geometrical nonlinearities, caused by the slacking of the mooring lines and loss of contact
between the vessel and the fenders, as well as physical nonlinearity due to the fenders ́ stiffness and
buckling-column-type behavior, is performed. The analysis consists of balancing the resultant forces
and moments applied to vessel by the environment against the reaction forces exerted by the mooring
lines’ stretching and the fenders’ compression. As a result, we arrive at a system of nonlinear equations
as a function of the vessel ́s displacements, which are then solved by a fully consistent Newton's
numerical method. At last, the behavior of the mooring system with respect to the vessel’s displacements
is investigated in order to better understand the effects of the considered nonlinearities.

A COMPARATIVE STUDY OF JACKET FOUNDATIONS FOR OFFSHORE WIND TURBINES

Erica M. de Mendonca, Gilberto B. Ellwanger, Jose R. M. de Sousa — Mon, 26 Aug 2024 00:00:00 +0000

The increasing use of wind energy comes from the need to ensure diversity and energy supply,
as well as the search for renewable energy sources, reducing the environmental impacts accentuated by
the use of fossil fuels. In this context, the worldwide trend in the development of technologies associated
with the production of wind energy has become more present in several countries. In Brazil, the first
wind turbines were installed in the northeast region, that suffers most from the critical levels of water
reservoirs and is well known for its great wind potential, which contributes to the success obtained in
the production of onshore wind farms. Aiming at the constant increase of the production of this type of
energy, the studies for offshore turbine installations have started. This work aims to study the installation
of wind turbines in a water depth of 40m using jackets as foundations. The natural frequencies and
stresses in a jacket structure used to support 5MW and 10MW wind turbines are evaluated. The analyses
were performed considering static and environmental loads of wind, wave and current. It was possible
to verify that the structural set related to the 10MW turbine has greater periods of vibration, besides
greater efforts, becoming necessary to adapt the jacket, as base enlargement. In addition, an adjustment
of structures geometries was also necessary in order to obtain greater cost-benefit.

NUMERICAL SIMULATION OF BEAMS MANUFACTURED WITH ULTRA- HIGH PERFORMANCE FIBER REINFORCED CONCRETE (UHPFRC)

Rosangel Rojas, Jose R. Yepez, Américo C. Filho — Mon, 26 Aug 2024 00:00:00 +0000

The ultra-high performance fiber reinforced concrete (UHPFRC) is a new material that
exhibits strength values higher than 150 MPa and 18 MPa in compression and tension, respectively. Its
dense matrix minimizes pores and increases durability. The presence of fibers, increases the energy
absorption capacity, induces deformation hardening behavior in the post-cracking phase and prevents
fragile failure, when subjected to stress tensions. These properties place the UHPFRC among the most
advanced concrete technologies, enhancing their use in the construction or repair of bridges, high-rise
buildings and special structures such as nuclear facilities. The objective of this work is to numerically
model the behavior of beams subjected to bending stress, through a finite element analysis using
ANSYS. A total of thirteen beams were tested experimentally; these results are compared with the
numerical simulation. Steel fibers with an aspect ratio of 65 were used, in percentages of 1% and 2%.
In the simulation, 150.89 MPa is considered as the average value for the compressive strength,
obtained from experimental tests carried out on twenty specimens. The elastic modulus considered is
obtained from the behavior curve, by linear approximation between 5% and 80% of the peak
resistance, whose average value was 48 GPa. Additionally, fracture energy is measured, which
reached values of 16,26 kJ / m2 and 22,60 kJ / m2 for fiber percentages of 1% and 2% respectively.

FINITE ELEMENT ANALYSIS OF KNEE IMPLANTS MANUFACTURED BY FDM TECHNOLOGY

Jayann Ismar Lira Almeida, Ryanne Soares da Silva, Thiago Dantas Gomes — Mon, 26 Aug 2024 00:00:00 +0000

Knee prostheses are used in knee replacement surgery in patients who have or develop some
type of disease in this joint. The prostheses currently on the market have the femoral component in a
metal body and have been used for many years. Problems of metallic implants such as patient sensitivity,
adaptation to existing models of prosthesis and cost of prosthesis are some of the factors that influenced
the study of non-metallic prosthesis materials. The finite element method will be applied in the study of
prostheses made in 3D by Fused Modeling Deposition (FDM) in ABS and PLA materials, and its
orthotropic nature will be evaluated. In order to achieve this objective, the prosthesis was modeled
graphically, in which the load and boundary conditions to simulate the activity of an individual walking
with the prosthesis were applied and the Tsai-Hill’ and Tsai-Wu’ failure theories for composite materials
were used to evaluate the functionality of this prosthesis. Thus, several results are obtained, such as
failure index and strain rate for these materials.

FINITE ELEMENT METHOD APPLIED TO HIGHER-ORDER ZIG-ZAG THEORY FOR LAMINATED BEAMS

Hilton M. S. Santana, Fabio C. da Rocha, Maria S. M. Sampaio — Mon, 26 Aug 2024 00:00:00 +0000

Due to the continuing importance of laminated materials in civil, naval, mechanical
and aerospace engineering, the development of structural analysis theories of laminated beams
has been an active area of research. The well-known classical theories of Euler-Bernoulli and
Timoshenko have limitations because they do not present a field of shear deformation or by the
incorrect consideration of such deformations, without respecting the nullity of the shear stress
in the edges of the beam. Thus, high-order theories have emerged to remedy the limitations of
classical theories, especially the Equivalent Single Layer (ESL) theories. In ESL theory, the
displacement function in the thickness coordinate are assumed to Class C1

. This feature
provides a discontinuous shear stress field at the interfaces of adjacent layers with different
materials. In the 1980s, DiSciuva introduced a new class of laminated theories, where a zig-zag
function is added to the ESL theories to describe the displacement in the thickness coordinate.
This new theory allows the continuity of interlaminar tensions and a number of variables
independent of the number of layers of the beam. In this way, the present work seeks to present
the complete development of a finite element model of several ESL-Zig-Zag theories. Thus, a
unified displacement field will be used that allows the simultaneous development and
comparison of several refined theories found in the literature. After obtaining the governing
equations, the finite element model is constructed using the Lagrange and Hermite polynomial
functions. Finally, to show the good efficiency of the finite element model, numerical results
are shown and compared with the exact solution of the elasticity of Pagano (1970).

NUMERICAL SOLUTION OF THERMAL STRESSES IN A COMPOSITE HOLLOW DISK UNDER STEEP TEMPERATURE

Santiago H. de P. Maciel, Marcelo J. S. de Lemos — Mon, 26 Aug 2024 00:00:00 +0000

This work studies the effects of thermal stresses in composite disk during heating by imposing
high heat fluxes at the inner face. The medium is formed by layers of steel, cement and rock. Thermal
stresses are caused by distinct displacements in different layers. It is important to analyze the movements
of contraction and expansion of these layers in addiction to verify the tensions caused by temperature
difference. This configuration, or say, composite layers, is found in completed oil wells. These stresses
can induce fissures and failures that can let a movement of fluids from oil reservoir through them and
cause environmental problems in oceans and seas where oil is extracted. The numerical solution is based
on finite element method (FEM) applied by the commercial code ANSYS

R which was employed in the
simulations. Materials of layers were assumed isotropic and no thermal resistance between them was
considered. Transient heat transfer was analyzed. The idea of this work is to investigate the interaction
between steel and cement because it configures a point of concern due to the fact that coefficients of
thermal expansion from these materials are different and there is a large probability of unwanted fissures.
Another point is to establish an optimal heat flux that does not allow a formation of fissures and empty
spaces between the layers that allow a flow of fluids from the oil field through them, especially at the
steel-cement interface.

A STUDY ON THE BEST CONVENTIONAL SHAPES FOR COMPOSITE REPAIR PATCHES

Leonel Echer, Carlos E. de Souza, Rogerio J. Marczak — Mon, 26 Aug 2024 00:00:00 +0000

Adhesively bonded repair patches are an excellent approach for repairing locally damaged

composite components. If correctly applied, fiber reinforced patches may restore/increment the me-
chanical response of damaged laminates without significantly increasing the structure’s mass or altering

its geometry. However, in order to take full advantage of this repairing technique, one must employ

patches with a minimal surface area and maximum efficiency in incrementing the strength of the compo-
nent. The present work aims to study optimum-based patch shapes for conventional repair geometries,

namely rectangular and elliptical. Shell Finite Elements models simulated a parent plate, a rectangular
flat laminate, with a central trespassing damage region. Unbalanced single-ply patches were modeled
on the upper surface of the damaged laminate. The patches efficiency was computed as its capability
in restoring the modal response of the repaired component to its undamaged configuration. Sequential
linear programming was employed alongside shell finite element models to obtain optimal geometrical
parameters for the patches shape. The study cases comported two different boundary conditions and two
stacking sequences. The optimum-based repair patches were defined regarding size and fiber orientation
angle.

Finite Element Method applied to the single-layer equivalent theory for laminated beams

Santana H. M, Da Rocha F. C, Kzam A. K. L. — Mon, 26 Aug 2024 00:00:00 +0000

Over the last decades, laminated beams have been widely used as a structural element in
several areas of knowledge, such as in civil, naval, mechanical and aeronautical engineering. Having
advanced the knowledge and development of composite materials, theoretical modeling to describe the
mechanical behavior of laminated beams has become of great importance. Among the various theories,
we have the refined (or high order) theories that have emerged to heal the limitations present in classical
theories. This limitation is represented by the failure to consider the shear strain field or by incorrect
consideration of such deformations, without respecting the nullity of the shear stress at the edges of the
beam. Thus, the present work seeks to present the development of a finite element model applied to the
Equivalent Layer (ESL) theories for laminated beams. Therefore, a unified displacement field will be
used that allows the simultaneous development and comparison of several refined theories found in the
literature. After obtaining the governing equations, the finite element model is constructed using the
Hermite and Lagrange polynomial functions. Finally, to show the good efficiency of the theories and
the finite element model, numerical results for static and dynamics analysis are shown and compared
with the exact solution of the elasticity.

METHOD OF APPLICATION OF FINITE ELEMENT SEMI-EMBEDDED IN CONCRETE BEAMS SIMULATION PRESTRESSED

Jordana F. Vieira, Raul D. Durand Farfán — Mon, 26 Aug 2024 00:00:00 +0000

Computer modeling has become an increasingly integral part of the activities of
researchers and civil engineering professionals. To characterize a model that best represents a
material, one must consider the knowledge of their mechanical behavior. In this context, this
article aims to review the constitutive models that are being used to model prestressed concrete
structures and present a representation proposal for this type of structure based on the model
defined by Durand (2008). This method stems from an adaptation of two already consolidated
methods for this type of structure, the embedded method, and the discrete method and was
adopted as a semi-embedded method. It differs from the other methods, the reinforcing steel
shall be discretized in front of elements and, such as the conditions of contact cannot be
corrected in each node of elements. The final element of the bar is obtained after the
reinforcement and finite element discretization of the concrete, being necessary to obtain stress
and strain fields in the bars and together with the interface. Thus, from the model, it can be said
that the semi-supplied method proposed is more advantageous than other methods of literature,
since, from it, an example of analysis for concrete and reinforcement. Moreover, by simulating
the element with its reinforcement, it is understood that the simulated concrete structures are
approximated in a context closer to the real one.

ROBUST MULTIOBJECTIVE OPTIMIZATION OF REINFORCED CONCRETE FRAMES USING RELIABILITY CONSTRAINTS

Jacqueline C. M. do Nascimento, Renato S. Motta, Silvana M. B. Afonso — Mon, 26 Aug 2024 00:00:00 +0000

In most structural engineering designs deterministic models are used with requirements
defined by standards, specifically, designs of reinforced concrete structures in Brazil are based on the
NBR 6118:2014. This standard recommends the use of safety coefficients, without the consideration
of the uncertainties associated to concrete structures designs. On the other hand, the Reliability-Based
Robust Design Optimization (RBRDO), that will be studied in this paper, is characterized by
optimization problems where the design uncertainties are treated statistically, allowing to measure the
level of structural reliability and performance variability. In this type of problem, some constraint
associated with the probability of failure is present in its formulation. The method to obtain the failure
probability in this work will be FORM (First Order Reliability Method). Robust optimization
problems aim to obtain a robust design, which in addition to a good performance, a low sensitivity to
uncertainties of the problem are intended. The robustness measures employed in this work are mean
and the standard deviation of functions of interest. This leads to a Robust Multiobjective Optimization
(RMO) problem, due to multiple objectives, which has several optimum solutions called Pareto points.
The main aim of the present research is to develop a computational tool to efficiently obtain robust
optimum pareto designs of reinforced concrete framed structures under uncertainties. Such optimum
pareto points will be found through Weighted Sums (WS), Min-Max e Normal Boundary Intersection
(NBI) methods that were implement in the Python language. In addition, it will be used pre-existing
in-house finite element libraries, which will be the method used for structural analysis. The reliability
and optimization public libraries, also in the same language, will be considered. The applications in
this work, is two 2D frames of reinforced concrete with one and three floors, with respectively 3 and
30 bars.

STRUCTURAL RELIABILITY ANALYSIS OF A REINFORCED CONCRETE BEAM STRENGTHENED WITH CARBON FIBER

Vinícius D'Agostini Pittarello, Flávia Gelatti, Alverlando Silva Ricardo — Mon, 26 Aug 2024 00:00:00 +0000

Concrete beams and strengthening design procedures are commonly specified in normative
codes, using simplified deterministic procedures. This prescriptive methodology has as a consequence
in practice in which structural safety is indeterminate, since the innumerable sources of uncertainty when
designing the project can result in significant deviations from reality. As an alternative, the safety of
these beams can be quantified through the application of structural reliability theory. The present work
analyzes safety of a reinforced concrete beam strengthened with carbon fiber. For this, the Monte Carlo
method is applied to determine the reliability index and probability of failure of the structural element.
The steel reinforcement design of the beam was performed according to NBR 6118 [1], and in sequence
a load increase analysis was conducted to justify the strengthening. The fiber strengthening was designed
according to two methods, the available in ACI 440.2R-17 [11] and in Machado [3]. In the specific ACI
method two set of material parameters were tested, the recommended on ACI 318-14 [2] and the
designated on NBR 6118 [1]. As a result of the analysis with both methods it was observed that in some
cases the reliability indexes were unanimously superior to the coefficients targeted. In the case of the
use of parameters of the Brazilian standard in the ACI 440.2R-17 [11] design methodology, there were
cases in which the same indexes were not satisfactory. Because the central verification in the ACI
440.2R-17 [11] design procedure is the steel tension, a different assumption in its yield limit changes
considerably the results and the probabilistic response.

RC BRIDGE FATIGUE RELIABILITY AND BRAZILIAN STRUCTURAL DESIGN ADEQUACY ASSESSMENT

Daniel Higor Leite Braz, Francisco Evangelista Junior, Ph.D. — Mon, 26 Aug 2024 00:00:00 +0000

The fatigue ultimate limit state is one of the most important considerations in the bridges’
design. Sections’ geometric characteristics, material properties and traffic are influential factors
subjected to different levels of uncertainty. Hence, it is interesting to investigate the impact of their
variabilities in the fatigue reliability of the reinforcements, here defined for four isostatic reinforced
concrete (RC) bridges with two girders, through Monte Carlo simulations (MCS). It is also analyzed
how adequate is the typical design approach. The results show that the extrapolated traffic has greater
potential to penalize the reinforcements’ fatigue performance than the Brazilian standard design vehicle
TB-450. The importance of a more accurate technical control in the execution of bridges is highlighted,
since the geometrical and material variabilities also contribute to the penalizations.

RELIABILITY BASED PREVENTIVE MAINTENANCE FOR CORRODED PIPELINES

Mon, 26 Aug 2024 00:00:00 +0000

Pipeline’s infrastructure grows every year, worldwide. Although pipelines are one of the
safest ways of transporting oil and gas, corrosion is a major concern in the petroleum industry. Due to
corrosive environment (underground or undersea), defects can be generated and increased through
time, reducing pipe’s resistance. In order to evaluate effectively pipeline’s integrity during its service
life, understanding uncertainties involved in corrosion is necessary; therefore, reliability assessment is
necessary. With reliability predictions, maintenances plans can be developed. Maintenance means that
a segment of pipe is excavated and the corrosion defects are “fixed”, which restores the pipeline
segment to its pristine condition, without defects. Whenever reliability coefficient falls to a predefined
threshold, maintenance takes place, this approach is called Reliability Based Preventive Maintenance
(RBPM), and it is used in this paper, according to industry’s practice. There are two main
contributions in this paper: first, a parametric study is conducted, using RBPM strategy, and the
parameters are 3 design variables: wall thickness of the pipe, type of steel used (tensile strength) and
also operation (internal) pressure, which is the load considered in all examples. In addition to that, the
second contribution is to evaluate how different ways of modeling growth of defects influence
maintenance planning; preliminary results indicate that the way of modeling growth can cause
significant changes in the reliability coefficient against time. The parameters will be considered as
random variables, with distributions, means and standard deviations considered as indicated in
literature. The internal pressure will be considered as a stochastic process.

STRUCTURAL OPTIMIZATION OF HYPERSTATIC REINFORCED CONCRETE BEAMS CONSIDERING THE SYSTEM RELIABILITY

Lucas da Rosa Ribeiro, André Teófilo Beck — Mon, 26 Aug 2024 00:00:00 +0000

Civil engineering structures are inevitably under uncertainties, constituted by multiple
components, and also subjected to several failure modes. Thus, the design could be made considering
the global system reliability, the correlation between failure modes, and also the correlation between the
failure of its components, defining where it is worth spending more or less material. Thereby, a system
component with little influence over the system reliability could be designed with less reliability, for
instance. However, regarding reinforced concrete structures, the current Brazilian normative that guides
its design presents very few techniques intending to avoid the progressive collapse. Moreover, it
stablishes that the structural system is obtained after the individual design of each of its structural
elements, without any consideration of the system reliability. Aiming to analyze the optimal designs of
usual structural systems, the Reliability Based Design Optimization (RBDO) is performed on a
hyperstatic beam of reinforced concrete while considering the system reliability as a constraint. Optimal
parameters are usual design variables, such as the height of the beam and the concrete compressive
strength. In order to better represent the physical and geometrical nonlinearities involved, a finite
element approach based on positions is used herein. The obtained optimal designs are compared to those
acquired by the semi probabilistic approach proposed by the current Brazilian normative. Results of a
preliminary example shows that the RBDO leads to a more economical results while maintaining the
desired target reliability.

FATIGUE LIFE ESTIMATION USING FREQUENCY DOMAIN TECHNIQUE AND PROBABILISTIC LINEAR CUMULATIVE DAMAGE MODEL

Vagner Pascualinotto Junior, Diego Felipe Sarzosa Burgos — Mon, 26 Aug 2024 00:00:00 +0000

Engineering structures are designed to withstand a variety of in service loading specific to
their intended application. Random vibration excitation is observed in most of the structural
component applications in the naval, aerospace and automotive industry. Likewise, fatigue life
estimation for such components is fundamental to verify the design robustness assuring structural
integrity throughout service. The linear damage accumulation model (Palmgren-Miner rule) is still

largely used for damage assessment on fatigue estimations, even though, its limitations are well-
known. The fact that fatigue behavior of materials exposed to cyclic loading is a random phenomenon

at any scale of description, at a specimen scale, for example, fatigue initiation sites, inclusions, defects
and trans-granular crack propagation are hardly predicted, indicates that a probabilistic
characterization of the material behavior is needed. In this work, the inherent uncertainties of the
fatigue life and fatigue strength of the material are characterized using the random fatigue limit (RFL)
statistic method, which incorporates the maximum likelihood estimation to produce probabilistic S-N
curves. Furthermore, a frequency domain technique is used to determine the response power spectrum
density (PSD) function of a structural component subjected to a random vibration profile excitation.
The fatigue life of the component is then estimated through a probabilistic linear damage cumulative
model, where not only the time to failure is predicted but also its variability. The methodology was
applied to a Titanium alloy structural component, exposed to a specific random excitation, where the
predicted life using the material percentile curves 5% and 95% has shown a significant variability
when compared to the common used percentile 50%. Thus, this characterization might be relevant for
the definition of material design curves.

ASSESSMENT OF THE RELIABILITY OF COLD-FORMED STEEL MEMBERS SUBJECTED TO BENDING AND COMPRESSION USING THE FORM METHOD

Mon, 26 Aug 2024 00:00:00 +0000

The structural reliability consists to the analysis of the probability of limit state violation for
a structural system during the useful life. This paper presents an analysis of reliability indexes for cold
formed members subjected to bending and to the axial compression force, designed according to the
Brazilian standard ABNT NBR 14762:2010 [1] and the North American standard AISI S100:2016 [2].
For this purpose, a database of experimental results of several authors was elaborated for the limit
states in question and the strengths were obtained for each model tested, using ABNT NBR
14762:2010 [1]. The model errors, relation between the theoretical and the experimental values, were
also evaluated, providing a statistical result, also called the professional coefficient. Then, it was
obtained the reliability index (β) as a function of the resistance factor (γ) based on the First Order
Reliability Method - FORM. The resistance factors were obtained to combinations of gravitational
loads of the North American and Brazilian standards, beyond the relations between the live and dead
loads, Ln/Dn, equals to 3 and 5. The results were compared to the target reliability index (β0) usually
employed in calibration of the main international standards and to the recommended values by
Brazilian and North American standards, considering the similarity between both specifications for the
limit states studied.

INTERPRETATION OF THE STRUCTURAL RELIABILITY INDEX BY STUDY OF HOT ROLLED STEEL BEAMS

Mon, 26 Aug 2024 00:00:00 +0000

Reliability analysis is a used tool to measure a structure’s ability of perform safety and
serviceability requirements. Methods for reliability assessment have been developed based on using the
probability distribution functions of input random variables accounting for the uncertainties coming both
structural properties and external actions. In the present structural codes the safety verification is based
on a linear analysis of the structure and the satisfaction of ultimate and serviceability limit states, using
a semi-probabilistic security format through the consideration of resistance factor and load factors,
which affect the action values and the characteristic values of the material properties. This work presents
an investigation of the safety level of hot rolled steel I-beams dimensioned according to Brazilian
building code NBR 8800:2008. The study allows an interpretation of the reliability indexes calculated
for steel beams by the First-Order Reliability Method (FORM), when this reliability analysis is
compared with structural design results. In the analyzed beams, it is assumed that local buckling and
lateral-torsional buckling are not controlling limit states, i.e., the beam section is compact and laterally
supported along the length. The results of this study show the correspondence of the structural reliability
indices with the beams calculated by the standard.

Solution of Time-Variant Risk Optimization Problems using Two-Level Active Learning Kriging Approach

H. M. Kroetz, M. Moustapha, A.T. Beck, B. Sudret — Mon, 26 Aug 2024 00:00:00 +0000

Risk optimization is a general approach for structural optimization regarding uncertainties.
Different life-cycle costs are considered, including expected failure costs, whose calculation requires
the computation of failure probabilities. Although more comprehensive than concurrent approaches,
the literature about this topic is scarce. Time-dependency can be considered, broadening the scope of
the analysis, but further complicating the solution. In this work, a numerical framework for solving
time-dependent risk optimization problems is proposed. It consists in a Monte Carlo simulation based
approach, where two adaptive coupled metamodels are employed. In the first level, objective functions
are approximated, and in the second, the limit state functions related to the computation of the failure
probabilities. An iterative procedure is developed for selecting candidate points to each surrogate model’s
design of experiment. The accuracy and generality of the method is shown in an example including
system-reliability and load-path dependent failures.

RELIABILITY ANALYSIS OF COMPOSITE STEEL-CONCRETE SLABS DESIGNED IN ACCORDANCE WITH ABNT NBR 8800:2008

Gabriela R. Moura, Eunice S. Santos — Mon, 26 Aug 2024 00:00:00 +0000

This paper presents a study on the reliability of composite steel-concrete slabs designed
according to ABNT NBR 8800:2008 (Design of steel and composite structures for buildings) for
longitudinal shear failure mode. For the calculation of the shear resistance, according to m-k method,
results of bending tests were used. The probabilistic models of the random variables considered in the
analysis were found in the literature, except for the model error variable for longitudinal shear
resistance, which was determined from a base of experimental studies. The reliability indexes were
obtained through the Monte Carlo Simulation (MCS) and the First Order Reliability Method (FORM),
implemented in MATLAB®, for several composite slabs configurations and combinations of actions.
In addition, the influence of geometric parameter variation on reliability was evaluated. Regarding the
partial safety factor for longitudinal shear, the ABNT NBR 8800:2008 recommends that it to be equal
to that determined by the specification used in the bending tests, so a comparison was made between
the safety levels recommended by EUROCODE 4 Part 1-1:2004 (Design of composite steel and
concrete structures) and CSSBI S2:2008 (Criteria for the testing of composite slabs).

MAXIMIZATION OF THE RELIABILITY OF FRICTION TUNED MASS DAMPERS USING STOCHASTIC GRADIENT METHODS

Mon, 26 Aug 2024 00:00:00 +0000

We use an efficient stochastic optimization framework to optimize the design of friction tuned
mass dampers (FTMD). To deal with the uncertainties in the model, we use a reliability analysis based
on the out-crossing rate approach. We formulate the unbiased gradient estimator of the reliability index
with respect to the design parameters, a condition for the use of stochastic gradient descent (SGD) and
its variations. We couple SGD with Nesterov’s acceleration, Polyak–Ruppert averaging, and a restart

technique to evaluate their improvement on SGD efficiency for design optimization. To assess the per-
formance of the proposed stochastic optimization framework, we optimize the parameters of an FTMD

in a steel frame building. Comparing the obtained results with the state-of-the-art in the literature, we
observe a reduction of up to an order of magnitude in cost to achieve a given accuracy. Given that an
unbiased estimator for the true gradient can be evaluated, stochastic gradient methods can efficiently
perform local search in design problems on the presence of uncertainties.

PHYSICAL CONSISTENCY IN UNCERTAINTY BASED DESIGN OPTIMIZATION

Andre J. Torii — Mon, 26 Aug 2024 00:00:00 +0000

A previous work demonstrated that standard probabilistic robust optimization (that takes into
account a weighted sum of the expected value and the standard deviation) may become non-consistent
from the physical point of view, when too much weight is given to the standard deviation. If this occurs,
the optimum designs may have no meaning from the physical/engineering point of view. An alternative

probabilistic robust optimization approach was then proposed, that is able to ensure physical consis-
tency of the problem a priori (i.e. before the optimization procedure is started). In this work, physical

consistency of reliability-based design optimization (RBDO) and worst-case robust optimization is in-
vestigated. We show that the RBDO and the worst-case problems are consistent under milder conditions

than standard probabilistic robust optimization. This indicates that RBDO and worst-case optimization
are inherently more consistent than probabilistic robust optimization, at least from the physical point of
view.

RELIABILITY-BASED STUDY OF CIRCULAR TUNNELS IN ELASTIC MEDIA BY USING THE BOUNDARY ELEMENT METHOD

Mon, 26 Aug 2024 00:00:00 +0000

Problems involving cavities or excavations are widely addressed in geomechanics, in both
analytical and numerical approaches. The Boundary Element Method (BEM) is well-known as an
interesting choice for the analysis of problems involving semi-infinite domains, providing accurate
results at a low computational cost. The study of circular tunnels is traditionally performed through a
deterministic approach, not considering the uncertainties inherent to the design variables. Since the
properties of geomaterials vary in a considerable range, the use of mean or characteristic values in the
deterministic methodology does not comprise the several combinations of critical random values (r.v.)
of the variables, for the different failure modes considered. This work deals with the probabilistic
analysis of circular tunnels embedded in elastic media, by coupling a BEM formulation to a structural
reliability model. Some of the loads applied and material parameters are treated as random variables,
whose statistical description is found in the literature. The loadings considered include the vertical
overburden stress and the lateral earth pressure. Regarding the reliability evaluation, First Order
Reliability Method (FORM) and Monte Carlo simulation technique are employed, being compared in
terms of accuracy. Regarding the BEM model, the Multiple Reciprocity Method (MRM) is used in the
evaluation of domain integrals, and the sub-region technique is employed for the analysis of the tunnel
lining. Some examples are presented, in order to validate the coupled BEM-FORM model and apply it
to the estimation of failure probability, evaluating the influence of the r.v. taken into account in the
probabilistic response.

STRUCTURAL RELIABILITY OF A STEEL COLUMN UNDER FIRE CONDITIONS

Lucas Araújo R. da Silva, Alverlando S. Ricardo, Flávia Gelatti — Mon, 26 Aug 2024 00:00:00 +0000

The structural projects are usually made in a deterministic way through normative codes that
do not consider directly the uncertainties associated to the problem. However, for exceptional cases such
as fire and earthquake conditions, the use of prescriptive methodologies may lead to projects with high
costs and indeterminate or unacceptable levels of safety. In this context, the application of the reliability
theory to structures under fire conditions arises as a better option than the deterministic methods
contained in the normative codes. The structural reliability analysis enables that the uncertainties
associated to each variable are considered, quantifying the safety level of the structure and giving the
engineer a better comprehension of the structural behavior under fire situation. The present study aims
to apply the structural reliability theory to a steel column under fire condition, analyzed by the ABNT
NBR 14323:2013. First, the basis of the application of this kind of analysis is stated. Then, the
methodology is applied through computer modules developed in Excel and MATLAB and the
probabilities of failure are determined as a function of time, temperature, and other variables involved
in the problem. Eventually, the results indicate that the deterministic design made according to the
Brazilian code does not lead to an acceptable safety level proving the importance of the reliability
analysis in the structural projects.

SIMULAÇÃO ESTOCÁSTICA DA PROPAGAÇÃO DE TRINCAS EM TUBOS DO GERADOR DE VAPOR

Alexandre S. Francisco, Heber R. Sebastiao — Mon, 26 Aug 2024 00:00:00 +0000

In pressurized water reactor nuclear power plants, the deterioration of steam generator tubes
has been both an economical and safety problems. The steam generator tubes are subjected to
deterioration mechanisms, such as stress corrosion cracking, which lead to structural failure by the
unstable crack growth. The crack growth rate can be estimated from inspection data. As the crack
growth rate by stress corrosion cracking is a phenomenom of highly random nature, a structural integrity
assessment in the steam generator tubes must be performed based on the failure probability along some
operational cycle. In this work, a stochastic model is applied for probabilistic assessment of the structural
integrity of the steam generator tubes. The proposed model is able to provide efficiently results of failure
probability more realistics. The results from this model are compared with others from Monte-Carlo
simulation and a non-evolutionary model.

VIBRATION CONTROL FOR STEEL TUBULAR TOWERS OF HORIZONTAL AXIS WIND TURBINES

Matheus Alves Pereira, Douglas Mateus de Lima, Pablo Aníbal López-Yánez — Mon, 26 Aug 2024 00:00:00 +0000

This paper analyzes the effectiveness of three types of vibration control, namely, Tuned
Mass Damper (TMD), Active Mass Damper (AMD) and a Hybrid Mass Damper (HMD), applied to a
steel tubular tower, 120 m high, for an onshore Horizontal Axis Wind Turbine (HAWT). For this, the
tower was modeled using beam (own code) and shell and solid finite elements (via ANSYS). In all
cases, the insertion of the control device was idealized at the top of the tower. The theory proposed by
Den Hartog was used to determine the coefficients of the absorber and the Linear Quadratic Regulator
(LQR) was applied to obtain the optimal control variables introduced by the hydraulic actuators. It was
observed a reduction of the root mean square (r.m.s) of displacements of the top of the tower with
control in relation to the without control displacements, when subjected to a harmonic and resonant
action to the first mode of vibration of the uncontrolled structure: 67.78% for the TMD and 71.64%
for the AMD in a transient excitation; 93.87% for the TMD and 95.26% for the AMD in a permanent
excitation. In addition, the effective displacements (r.m.s) with the use of HMD were smaller
compared to the TMD results, presenting a reduction of 26.68% in the transient excitation and 39.46%
in the permanent excitation.

PROJETO OTIMIZADO DOS PARÂMETROS DO AMORTECEDOR DE MASSA SINTONIZADO EM VIGAS METÁLICAS

Lucas M. R. Menezes, Fábio M. G. Ferreira, Eduardo N. Lages — Mon, 26 Aug 2024 00:00:00 +0000

Problemas de vibrações em vigas não são incomuns; vigas metálicas que são utilizadas como
suporte de máquinas, por exemplo, estão sujeitas a vários tipos de ações dinâmicas simultâneas
provenientes das diversas máquinas em operação. Outro caso são as vigas que suportam os pisos de
academias, salões de festas e outros ambientes com grande movimento de pessoas que geram
acelerações no piso. As abordagens mais comumente empregadas para controle dessas vibrações
excessivas é o enrijecimento da estrutura, porém em muitos casos este tipo de abordagem é
inviabilizada por restrições arquitetônicas, estéticas ou relativa à própria capacidade da estrutura ao
sofrer o acréscimo de elementos estruturais pesados para o enrijecimento. Este trabalho é motivado em
desenvolver um amparo teórico para controlar vibrações com a utilização de sistemas mecânicos
acoplados às estruturas, especificamente em vigas metálicas, como uma solução alternativa à
resolução do problema de engenharia. Técnicas de otimização são utilizadas com o objetivo de obter
projetos com a melhor relação custo-benefício do atenuador. Dessa forma é realizada uma modelagem
numérica via implementações computacionais do problema de vibração e seu controle em vigas
metálicas. Os estudos realizados neste trabalho apontam a eficiência do atenuador com a inclusão de
uma pequena massa adicional, juntamente com especificação de molas e amortecedores. Um pequeno
acréscimo de massa (em torno de 4%) do atenuador leva a reduções consideráveis (acima de 55%) na
resposta dinâmica da estrutura. Com o emprego de técnicas de otimização é possível automatizar o
dimensionamento dos parâmetros do atenuador, podendo incluir critérios de eficiência quanto à faixa
de operação do mesmo.

OPTIMIZATION OF PARAMETERS OF TUNED MASS DAMPERS FOR USE IN TALL BUILDINGS SUBJECTED TO THE WIND ACTION

Bibiana B. Rossato, Letícia F. F. Miguel — Mon, 26 Aug 2024 00:00:00 +0000

This paper proposes a methodology to optimize the parameters of tuned mass dampers
(TMD’s) installed in a high-rise building subject to wind-induced vibration. The cost function is the
minimization of the maximum displacement at the top-floor of the building, while the design variables
are the spring stiffness and damping coefficients. The total mass of the TMD’s are assumed to be
between 2% to 10% of the total mass of the building. To carry out the proposed optimization, the
Search Group Algorithm (SGA) is employed. Several different scenarios are taken into account, such

as: (i) a single TMD (STMD) installed at the top, (ii) multiple TMD’s (MTMD) positioned at the top-
floor and also (iii) MTMD installed on different stories of the building. The effectiveness of the

proposed method to optimize the parameters of TMD’s in order to minimize the dynamic response of
the building is shown in each case. At the end of this paper, a comparison among the results is carried
out.

COMFORT IN VIBRATIONS FOR THE STEEL-CONCRETE COMPOSITE FLOORS: AN APPRAISAL FOR REVIEW OF ABNT NBR 8800:2008

Mon, 26 Aug 2024 00:00:00 +0000

Steel-concrete composite floors often have human comfort for excessive vibrations as the
most critical Service Limit State, in which vibration-sensitive floor systems must be designed so as to
avoid the unacceptable transient oscillations due to the walking of people or due to other sources.
According to ABNT NBR 8800:2008 [1], this limit state is designed by controlling the natural
frequency of the floor under service loads, keeping it above a certain threshold, generally from 3.0Hz
to 4.0Hz for the most common cases according to its Annex "L". The main objective of this article is
to propose a bibliographic review on the evaluation of comfort for floors, based on their dynamic
characteristics, such as natural frequency (f), modal mass (Mmod) and damping (D) to obtain speed
values (OS-RMS90) and acceleration (peak), when applying dynamic loads as predicted by Sedlacek
[2]. The object of study is a steel-concrete composite slab of a steel construction at the Federal
University of Espírito Santo (UFES, Brazil). After analytical calculations and numerical modeling
with dynamic loads, the floor is instrumented and kinematic results (velocity and acceleration) are
compared between model and experiment. By means of spectral analyzes of vibration energy, stiffness
gains by concrete ageing are observed for calibration of the model, accordingly to Ji Young Kim [3].
Finally, the answers of a questionnaire about comfort answered by the occupants are discussed and
compared with international publications to integrate new comfort thresholds and analysis
methodology in the new related chapter of ABNT NBR 8800:2008, currently under review.

VIBRATION CONTROL USING THE STRUCTURAL COUPLING TECHNIQUE BETWEEN ADJACENT BUILDINGS WITH DIFFERENT CONTROL DEVICES

Augusto S. Pippi, Suzana M. Avila, André M. de Almeida, Graciela Doz — Mon, 26 Aug 2024 00:00:00 +0000

The use of structural control in vibration mitigation is becoming increasingly common in
buildings. Forces of nature such as wind and earthquakes show how buildings are vulnerable to their
actions. A control technique that is gaining space is the structural coupling. This technique consists of
connecting two adjacent structures using different control devices, so that control forces are exerted
from one structure on the other to reduce the dynamic response of each structure individually and the
coupled system. To study the efficiency of this technique, a system containing two adjacent structures
was used. The system was modeled as having two degrees of freedom and subjected to seismic action
of three earthquakes with different frequencies. In the first step of the analysis, a passive control device
was used. The device parameters were optimized through a particle swarm optimization algorithm. In
the second step, an actuator was used, an active control device, in which it was optimized by the Linear
Quadratic Regulator. Finally, in the last step, the two devices, passive and active, were used together,
composing an hybrid control. The results indicated the importance of the structure response in the
performance of each control device. The coupling technique proved effective in mitigating vibration
amplitude, with reductions of up to 80% in displacements and 85% in velocities and accelerations.

SHUNT CONTROL ON CANTILEVER BEAM BY NEURAL NETWORK : OBJECTIVE FUNCTION

Venicio Silva Araujo, Cayo Cespedes da Silva, Heinsten Frederich Leal dos Santos — Mon, 26 Aug 2024 00:00:00 +0000

Piezoelectric materials have been extensively studied in recent years for the development of
electromechanical harvesting devices. Usually connected to a structure, these kinds of materials convert
kinetic energy into electric energy, and your electronic parameters interact directly to the vibrations of
the system they are coupled on. Therefore, this work aims at comparing the use of genetic algorithms and
artificial neural network techniques in the implement of shunt control in a structural set of a cantilever
beam coupled to a piezoelectric layer in the piezo-beam configuration. For the architecture of the genetic
algorithm and the neural network, was used a software with finite element model implemented and
the comparisons were made analyzing the computational demand of the algorithms and their respective
responses when both of them were defined on the task of finding the best combination between the
parameters of resistance and inductance of the piezoelectric patch that result in the best damping to the
structure. The comparison between the techniques had a focus on the use of the objective function of
the system by them, parameter used as a metric to gauge the aggregate computational demand, and the
damping provided with the respective configurations suggested by the two techniques. The results show
that the neural network after training completes your execution in order of 102 seconds, much faster
than the genetic algorithm, presenting a response with an average gain in damping of 23,24dB, but, even
though faster, this technique demands much more iterations than the genetic algorithm, due to its nature
of parallel computations, and additional care for the input data, that need a pre-processing not seen in the
genetic algorithm technique.

STUDY OF VIBRATION CONTROL USING TLCDS AND PERFORMED BY THE SOFTWARE DYNAPY IN A VISUAL WAY

Lucas B. Ghedini, Mario R. Freitas, Lineu J. Pedroso — Mon, 26 Aug 2024 00:00:00 +0000

The problem of scarce construction area in highly populated cities of the world has led to
the use of tall buildings in the modern era. They provide a way to allocate more space for homes and
the commerce, increasing density in major cities. However, this type of structure is more susceptible to
vibration problems caused by winds and earthquakes. Tall building designers need to address this
liability carefully, since even small vibrations can cause extreme nuisance and discomfort to the
inhabitants of the building. One way to reduce the vibrations in a building is to use damper
mechanisms, such as a Tuned Liquid Column Damper (TLCD). This damper is a passive device that
works by absorbing a portion of the building’s oscillation energy, thanks to the relative movement
between them. The energy is mainly dissipated due to local pressure losses, such as the ones that occur
when a fluid is forced to pass through orifices. The effectiveness of a damper in a dynamically excited
structure can be computed by comparing its undamped response to the dampened response. In order to
obtain these responses, a numerical study of shear buildings equipped with TLCDs is done using
DynaPy, an open source software developed in the Python programming language. New features have
been incorporated into DynaPy, allowing the user to visualize and better understand the steps
performed by the program to obtain the dynamic response of the system.

DEVELOPMENT OF A LOW-COST PROTOTYPE FOR PREDICTIVE MAINTENANCE APPLICATIONS BY VIBRATION ANALYSIS

Gabriel S. Vieira, Richard Senko, Antônio A. Silva — Mon, 26 Aug 2024 00:00:00 +0000

Rotary machines typically have vibrations which, due to deterioration and lack of proper
maintenance, cause equipment failure. Predictive maintenance by vibration analysis has the task of
evaluating the operating conditions from global root mean square (RMS) velocity measurements,
comparing them with standards established by technical norms. It is possible to define the causes of
vibrations from the frequencies. Characteristics observed in the frequency spectrum. Nowadays the
conventional equipment used for these analyzes has a high cost and often have a very complex user
interface. In this context, this work proposes the development of a low-cost instrument for vibration
analysis, as this is the main barrier to the application of this technique. The prototype should be able to
acquire system acceleration from this data, calculate instantaneous speeds and RMS speed within a fixed
time frame, the latter being sent to an online server allowing the evolution of vibration severity to be
monitored remotely. By the user. The data obtained will be recorded on a micro SD card so that you can
perform more detailed analyzes with a computer, such as frequency domain spectrum analyzes. To assist
in the analysis, a software with an interactive interface capable of importing the data from the generated
text files, performing the fast Fourier transform (FFT) and plotting the graph for analysis was developed.
For validation of vibration analysis, an Agilent® benchtop analyzer was used. In the calibration tests
with the commercial model, the low-cost prototype was able to identify the defects, unbalances and
misalignments, provided in a rotary system, compared to the Agilent® analyzer. RMS acceleration and
25% for speed. Even with the errors obtained in the measurements, the developed prototype proved to
be effective for the application of low-cost predictive maintenance, since besides being able to identify
the defects in the rotating systems, it can remotely follow the evolution of the vibration severity.

PARAMETRIC OPTIMIZATION OF TLCD-MAIN STRUCTURE COUPLED SYSTEM SUBJECT TO ARBITRARY STOCHASTIC EXCITATION

Juliano F. Martins, Marcus V. G. de Morais, Suzana M. Avila — Mon, 26 Aug 2024 00:00:00 +0000

The vibration levels in slender structures, such as walkways, bridges, high towers, and wind
turbines, are receiving more importance with free span increase. To preserve the structure lifespan, it is
necessary to study additional mechanical devices capable of reducing the vibrational level of the main
structure. Tuned Liquid Column Damper (TLCD) is a kind of passive absorber composed by a U-shaped
tube filled with liquid, commonly, water. This study performs a parametric optimization using response
maps to obtain TLCD optimum parameters to several arbitrary stochastic excitation. First of all, the
optimum parameters of TLCD coupled to the main structure using response maps were compared to
the analytical solution. Finally, the same procedure was reproduced to obtain an optimal parameter for
other arbitrary stochastic excitation. The result obtained show a reasonable accuracy compared to the
analytical solution. With this validation performed, we obtain the optimum values for Kaimal wind
spectrum.

INFLUENCES OF THE CHARACTERISTICS OF A SEMI-ACTIVE FRICTION-TYPE SEISMIC PROTECTION SYSTEMS IN THE SEISMIC RESPONSE OF PALANAR REINFORCED CONCRETE FRAME

Gomez-Martínez A. D., Villalba-Morales J. D., Cundumi O. — Mon, 26 Aug 2024 00:00:00 +0000

The use of semi-active control devices to protect building from the occurrence of earthquakes have
received focused attention in the last decades as these systems combine characteristics from passive and
active control devices. The determination of the optimal parameters of a semi-active system, including
the number and position of the devices, depends on the characteristics of the protection system, the main
structural configuration and the seismic hazard. This research deals with the assessment of the influence
in the seismic response of planar reinforced concrete (PRC) frames of equipping it with proposed
friction-type semi-active dampers. The device is of variable damping, which has a passive reaction while
the ranges of displacements do not exceed the imposed limit to generate the operation of the active part
of the device. The active part has a function is used that allows to generate different frictional forces in
the device that depend on the displacements of the structure due to the earthquake. The function has a
minimum and maximum force that is exclusive of the capacity of the friction device. The assessment
criteria correspond to the number, position and properties of the devices. The state space formulation
for a shear-building configuration including semi-active dampers is reported and implemented in
Matlab. Six PRC frames are subjected to the ten earthquake signals corresponding to the seismic hazard
of Bucaramanga (Colombia).

COMPARAÇÃO TEÓRICO EXPERIMENTAL DA RESPOSTA DINÂMICA DE UM SISTEMA DE UM GRAU DE LIBERDADE COM E SEM ABSORVEDOR DINÂMICO DE VIBRAÇÃO

Fabiana da Rosa Sufiatti, Janicely Fatima Stresser, Paulo Rogerio Novak — Mon, 26 Aug 2024 00:00:00 +0000

The constant progress of the civil construction provided by the increase of the resistance of
materials and control of executive methods, has been designed and built increasingly slender structures
and winning greater spans. However, these structures are more subject to vibrations and have a smaller
capacity to dissipate energy. Therefore, it is necessary for a study to characterize mathematically
external dynamic actions, analyzing the consequences of the fluctuations, for an assertive sizing of the
components and connections of the structure. A technique developed to control unwanted vibrations is
the use of Tuned Mass Dampers (TMD’s), which can be of type mass spring or pendulum type. In this
study, comparison between experimental data and theorical calculations will be made for one degree of
freedom system formed by a rod pivoted at one end and supported by a spring at another end. From the
dynamic characteristics of the system, a TMD will be fixed to the structure for vibration control. The
results demonstrated that the TMD controlled the vibration of the resonance system.

A SIMPLIFIED NUMERICAL APPROACH TO EVALUATION OF RESIDUAL SHAFT FRICTION IN DRILLED SHAFTS

Augusto Bopsin Borges, Renato Vaz Linn, Fernando Schnaid, Samir Maghous — Mon, 26 Aug 2024 00:00:00 +0000

Interpretation procedures of load-tests on instrumented piles rely conventionally upon mea-
surements of strains assuming the instant immediately before starting the test as reference configuration

for strains measures. Some experimental evidence shows that concrete in drilled shafts undergoes strains
induced by the curing process comparable in magnitude to the strains measured during the load-tests. It
is therefore expected that mobilization of shaft friction takes place before the load-test. Several authors

have performed experimental and numerical analyses aiming to quantify the influence of those pre-load-
test concrete volumetric strains on the measured bearing capacity using different approaches. The present

work aimed to establish a reference framework for the existing and future works on this topic. In order to
assess the influence of concrete strains induced by curing process on the shaft friction before the start of
the load-tests in drilled shafts, several finite element numerical simulations are performed, considering
the thermal, autogenous and drying strains. The analyses consider concrete as an isotropic linear-elastic
material and the soil as an elastic-plastic material using the Mohr-Coulomb constitutive model natively

implemented in the software ABAQUS. The results are interpreted focusing on the relevancy on the bear-
ing capacity and load distribution along drilled shafts considering or not the strains induced by concrete

curing.

ON THE POROMECHANICAL MODELLING AND INTERPRETATION OF FIELD VANE TEST

Mon, 26 Aug 2024 00:00:00 +0000

The field vane test is probably the most used apparatus for evaluation of undrained shear
strength of clay deposits. Although being designed for low permeability soils, its application in
intermediate permeability materials can also be found in geotechnical investigation practice. Since the
standard rate of shearing may not ensure undrained conditions in those cases, attention must be paid to
partial drainage effects in the soil surrounding the vane, leading to an increase in the soil resistance
and an erroneous estimation of the undrained strength. This paper aims to investigate the drainage
effects by means of a nonlinear poroelastic model, conceived to capture the transient flow effects in
the medium surrounding a rotating cylinder, which can be viewed as a simplified conceptual model for
the vane geometry. The model relies on a nonlinear poroelastic stress-strain analysis addressed by the
Biot’s poroelasticity framework, where closed-form expressions for pore pressure distribution were
derived while stress and displacements are computed numerically through a finite difference scheme.
The nonlinear poroelastic model is briefly presented and validated through experimental results in low
permeability soils. A parametrical analysis is then conducted to evaluate the response of theoretical
materials varying strength, stiffness and influence radius size. Finally, the numerical model is applied
to the interpretation of experimental data in zinc mining tailings, viewed as intermediate permeability
materials. It has been shown that the proposed poroelastic model is a good tool in evaluating the
drainage effects in vane tests, allowing for the identification of test patterns that ensures the desired
drainage behavior.

FINITE ELEMENT SIMULATION OF THE EXCAVATION-INDUCED DEFORMATION IN TUNNELS DRIVEN IN POROELASTIC MEDIA

Evandro Pandia Cayro, Samir Maghous, Denise Bernaud Maghous — Mon, 26 Aug 2024 00:00:00 +0000

The present paper deals with the formulation of a constitutive and computational model for
the analysis of the deformations induced by the excavation of a tunnel in a saturated poroelastic medium.
The finite element implementation relies upon the discretization of weak forms of local momentum and
fluid mass balance equations in the context of infinitesimal skeleton strains. The simulations of the steps
of excavation as well as placement of the concrete lining are modeled by the method of
activating/deactivating elements. The accuracy of the finite element approach is assessed by comparison
with available analytical and semi-analytical solutions developed for a circular tunnel driven in a
poroelastic medium. The numerical simulations notably show that the strain and stress fields developed
around the tunnel will depend on the depth, cross-section geometry, surface load distribution, soil
poroelastic properties, permeability coefficient and soil porosity. They also allow for the calculation of
seepage forces due to pressure gradient induced by excavation and acting on the tunnel wall and tunnel
face.

FINITE ELEMENT IMPLEMENTATION OF AN ELASTOPLASTIC- VISCOPLASTIC CONSTITUTIVE LAW FOR TUNNELS

Felipe Pinto da Motta Quevedo, Denise Bernaud, Samir Maghous — Mon, 26 Aug 2024 00:00:00 +0000

The paper presents an efficient numerical integration scheme for coupled elastoplasticity-
viscoplasticity constitutive behavior with internal-state variables standing for irreversible processes. In

most quasi-static structural analyses, the solution to boundary value problems involving materials that
exhibit time-dependent constitutive behavior proceeds from the equations integration handled at two
distinct levels. On the one hand, the first or local level refers to the numerical integration at each
Gaussian point of the rate constitutive stress/strain relationships. For a given strain increment, the
procedure of local integration is iterated for stresses and associated internal variables until convergence
of the algorithm. On the other hand, the second or global level is related to structure equilibrium between
internal and external forces achieved by the Newton-Raphson iterative scheme. A review of the
elastoplastic and viscoplastic model will be shown, following the coupling between these models.
Particular emphasis is given in this contribution to address the first level integration procedure, also

referred to as algorithm for stress and internal variable update, considering a general elastoplastic-
viscoplastic constitutive behavior. The formulation is described for semi-implicit Euler schemes. The

efficacy of the numerical formulation is assessed by comparison with analytical solution derived for
deep tunnel in coupled elastoplasticity-viscoplasticity.

COUPLED ELASTOPLASTIC-VISCOPLASTIC SOLUTIONS FOR COMPACTION PROCESS IN SEDIMENTARY BASINS

Paulo Sérgio Baumbach Lemos, André Brüch, Samir Maghous — Mon, 26 Aug 2024 00:00:00 +0000

Simulation of sedimentary basins is a complex multidisciplinary problem that involves
geological, chemical and mechanical aspects. The potential applications are important in geoscience
and petroleum engineering, including exploration, reserves assessment and production activities. In
this context, basin simulators that implement numerical models are used to reconstruct its mechanical

state over geological time in order to optimize exploration processes. This work presents semi-
analytical reference solutions in elastoplasticity-viscoplasticity to describe the compaction history of

sedimentary basins in the context of finite irreversible transformations, which are useful for the
verification of numerical simulators. A finite element based modelling specifically devised for dealing
with basin simulation has been used for comparison purposes. The numerical responses were
favorably compared to the developed solutions, thus providing preliminary verification for the finite
element tool.

STUDY OF THE INTERACTION OF CONCRETE WALLS WITH THE FOUNDATION STRUCTURE

Mon, 26 Aug 2024 00:00:00 +0000

This paper presents a study of the factors that influence the mechanism of soil-structure
interaction in a pilot building in concrete walls and their impact on their performance. Initially, a
research was made on the concrete walls structural system, following a brief bibliographical review on
the fundamental concepts for the study of the soil-structure interaction (SSI), such as: constitutive soil
models, discrete models for soil representation, soil properties, stress analysis and allowable stress,
among others. To illustrate the studies carried out, a numerical modeling of a four-floor concrete wall
pilot building was performed, subjected to vertical actions, supported by slab foundation, using the
Finite Element Method (FEM), using specific 3D software for analysis and structural dimensioning in
reinforced concrete. For the consideration of the geotechnical and structural system (foundation
structure), the discrete spring model (Winkler model) coupled to the superstructure was used and the
slab foundation thickness was varied by 16 cm (model 1), 25 cm (model 2) and 40 cm (model 3). The
local geotechnical formation was represented by a soft clay (SPT = 5) from the Belo Horizonte
Metropolitan Region, Brazil. The influential factors of the SSI analyzed in this research were: relative
rigidity ground structure, uniformity of the requesting stresses, repression in the building and
reinforcement rates found. For a better visualization of the influence of these various factors, an analysis
was made of the distribution of normal stresses and stresses at the base of the walls of this building, in
the form of graphs. Finally, it was concluded that the change in Slab Foundation, stiffness influences
the distribution of stresses and stresses in the foundation, with a tendency to uniformity as the slab
foundation thickness increases. However, this relationship is not linear.

ANÁLISE DO COMPORTAMENTO DE FUNDAÇÕES RASAS FRENTE À GÊNESE DE UM SINKHOLE

Rayane C. R. S Mattos, Nayara T. Belfort, Igor F. Gomes — Mon, 26 Aug 2024 00:00:00 +0000

Sinkholes are depressions on Earth's surface due to underground cavities collapse, and they
are commonly found in karstic fields in which soil is susceptible to erosion and leaching, because, both
erosion and leaching can create tunnels and galleries in carbonatic soil due to dissolution process. By
this sense, unstable caves can be formed below structures or infrastructures, and it can cause economic
losses and generate dangerous situations for human beings, as these caves can collapse, plus lead field
deformations of about 5 cm/year. Following this motivation, the present work aims to present the
influence of a construction with vertical stress equivalent to 15 MPa over a shallow foundation on a
karstic field through numerical modeling. In the first scenario, the structure is represented by a
distributed equivalent load, simulating a raft foundation, and in the second scenario, the structure is
represented by equivalent load distributed by strip footings. By analyzing the numerical modeling, it
was possible to evaluate the influence of both hallow foundations on the behavior of the field, which
allowed to verify that on the surface the footing scenario presented subsidence higher than 1.21 meter,
approximately 3 times the subsidence of the raft scenario, 0.37 m. It was also observed that shear zones
near karst and construction were more intense in the second scenario. In this way, this work alerts to
careful evaluation of cave stability and buildings safety in karstic environments.

COMPUTATIONAL STUDY USING DISCRETE ELEMENT METHOD FOR STRESS-STRAIN RESPONSE OF GEOMATERIALS

Luiz Carlos Facundo Sanches, Ronaldo Carrion — Mon, 26 Aug 2024 00:00:00 +0000

Relevant geomaterials, like soils, concretes or rocks, exhibit similar constitutive response
when considering their yield strength dependencies or dilatancy processes. The continuous description
of these geomaterials encounters limitations when large-scale slip and opening of a large amount of
fractures. Discrete-based methods represent the material as an assemblage of independent elements
interacting with one another and can be reproduce the discrete nature of the discontinuities, which are
represented as the boundary of each element. In this case, for each particle, the interaction law is used
in conjunction with the momentum balance principle so as to specify a set of governing equations to
describe its interactions and motion. By solving these equations, we obtain the final state of rest of
these particles. The constitutive stress-strain response is obtained in an uniaxial compression
experiment were a sample of geomaterial is slowly compressed by a piston until failure occurs. The
peak stress at which failure of the sample occurs is known as Unconfined Compressive Strength
(UCS). This work studies these responses in geomaterials samples using Discrete Element Method
(DEM). In our numeric simulation, a set of particles is placed between two piston walls which are
compressed at constant speed. Then, we monitor the position and forces for construct a curve by each
sample. Interactions incorporate translational and rotational degrees of freedom to rotate relative to
each other when in frictional contact. Analytical relationship between the microphysical parameters
and the macroscopic properties can be obtained by conducting a series of computational simulations to
tune the microphysical parameters until desired macroscopic properties. To simulate elastic-brittle
failure of material, a Mohr-Coulomb criterion is employed. These data are used to measure some
elastic properties of the particle model such as Young’s modulus, wall forces, broken bond and the
UCS himself. Results shows that possible obtain significant values for different geomaterials such as
some specific concretes and rocks.

LATERAL THRUSTS AND SETTLEMENTS ON A GRANULAR SOIL RETAINED BY A SEMI-INTEGRAL ABUTMENT UNDERGOING CYCLIC LATERAL DISPLACEMENTS WITH DIFFERENT AMPLITUDES

Pedro H. dos S. Silva, Yuri D. J. Costa, Jorge G. Zornberg, Carina M. L. Costa — Mon, 26 Aug 2024 00:00:00 +0000

Semi-integral abutment bridges are constructed without thermal expansion joints and the
superstructure-abutment system is not integrally connected to the substructure. In view of this peculiar
characteristics, the abutment undergoes combined movements of translation and rotation due to
expansion and contraction of the superstructure caused by temperature variations. Such behavior can
increase of lateral thrusts and vertical displacements in the soil close to the abutment. Therefore, this
work analyzed lateral thrusts and settlements on a granular soil retained by a semi-integral abutment
undergoing cyclic lateral displacements with different amplitudes. A finite element model was

developed and calibrated based on field data collected from an instrumented and monitored semi-
integral abutment. The soil stress-strain behavior was represented by a hyperbolic constitutive model

and the abutment lateral displacements were given by prescribed horizontal displacements. Predictions
with the elaborated numerical model were found to produce a good match with the field data. After
validation, numerical simulations with displacement amplitudes of ± 5 mm and ± 10 mm were carried
out. The passive lateral thrust increased with the lateral displacement amplitude, while the active
lateral thrust remained virtually the same in both amplitudes. The settlements, heaves and the
disturbance zone within the backfill soil behind the abutment increased with the lateral displacement
amplitude.

TIME-HARMONIC RESPONSE OF LARGE-SCALE PILE GROUPS UNDER SEISMIC EXCITATION

Ana C. A. Vasconcelos, Josue Labaki — Mon, 26 Aug 2024 00:00:00 +0000

Models of the dynamic response of embedded pile groups are fundamental for our under-
standing of their interaction with the surface structure. This understanding is especially important when

the surface structure has particularly strict vibration requirements, such as particle accelerators, nuclear
powerplants, and concert halls. This work presents an implementation of the impedance matrix method
for the vibration of pile groups. Especial attention is given to the case of large-scale pile groups, due
to our goal of modeling and understanding the response of the foundations of a large synchrotron-light
source. The impedance matrix method comprises deriving the flexibility matrix of each layer of soil and
of discretized segments along the body of the pile, and obtaining the impedance matrix of the pile-soil
system by establishing direct kinematic compatibility and equilibrium conditions at their interface. The
soil part is modeled as a isotropic, three dimensional half-space, the solution of which is obtained by the
superposition of classical Green’s functions for such medium. The piles are modeled as one-dimensional
finite beam elements. Vertically-propagating time-harmonic shear seismic waves are incorporated as

excitation sources. The paper presents strategies to deal with the high computational cost of such large-
scale models involving the integration of Green’s functions for soil media. The response of different

constitutive and geometric parameters of the embedded pile group and layered soils are highlighted in
the response of the system to such excitations.

DESENVOLVIMENTO DE UMA FERRAMENTA EM AMBIENTE EXCEL PARA DIMENSIONAMENTO E OTIMIZAÇÃO DE FUNDAÇÕES SUPERFICIAIS E PROFUNDAS

Mon, 26 Aug 2024 00:00:00 +0000

In the engineering, the realization of various activities count with the support of
computational tools due to the demanded time and complexity. Considering the ease of access to
Microsoft Excel Software, your disponible resources and simplified interface, it is shown as an
efficient alternative for the development of those tools. Given the great alterability of the soil where is
situated the foundation, the great challenge in the execution of projects is to ally safety and economy,
optimizing costs and procedures. Thus, the present article has as objective the development of a tool in
the Excel ambience to size and optimize deep and superficial foundations. The sizing is based on the
Terzaghi method (1943) for the superficial foundations and in the Aoki-Velloso method (1975) for the
deep foundations. Utilizing the VBA UserForms resource, for development in a practice way the
graphic interface. The validation of the tool is verified from the results obtained by this one, for
questions presents in base bibliography and in conformity with the vigent standards, showing as a free
efficient alternative both profissional as well pedagogically.

COMPARATIVE STUDY OF SOIL-STRUCTURE INTERACTION METHODS FOR THE ANALYSIS OF LATERALLY LOADED PILE FOUNDATIONS

Mon, 26 Aug 2024 00:00:00 +0000

When foundations are subjected to significant horizontal loads, as in bridges or offshore
structures, a more in-depth research of the soil-structure interaction is of utmost importance. Different
methods are given to carry out such study, among which the Winkler spring models and continuum
models stand out. This work addresses these methods for the analysis of laterally loaded piles inserted
in clayey and sandy soil. For the discrete spring models, both linear springs with a plasticity criterion
and nonlinear springs defined by given p-y curves are adopted. For the continuum model, the soil
plasticity is described by a Mohr-Coulomb criterion within a finite element method (FEM) approach.
As results, the horizontal displacements of the pile-soil sets are taken and a constant of horizontal
subgrade reaction is estimated, which are compared to results from load tests performed in Brazilian
soils of Campinas-SP and Ilha Solteira-SP. In general, displacements obtained by the analysis methods
were higher than the load tests in the initial elastic part and became smaller at a final yielding phase.
The analysis points to the importance of considering concrete as an elastoplastic material and of
precisely defining the Young’s modulus of concrete and the initial stiffness of the superficial soil.
Among the analysis methods, the linear spring model stands out for its satisfactory results and
simplicity, in terms of appliance and input data. On the other hand, the nonlinear spring and
continuum methods require specific geotechnical tools, but already contemplate iterative load
application, which facilitates the account of concrete’s nonlinearity.

THE EFFECT OF FRACTURE TREATMENT PARAMETERS ON DIAGNOSTIC FRACTURE INJECTION TESTS (DFIT)

Renan Marks de Oliveira Pereira, Eleazar Cristian Mejia Sanchez, Deane Roehl — Mon, 26 Aug 2024 00:00:00 +0000

In-situ stresses and permeability of the rock media has a significant role in predicting the
production rate of oil and gas reservoirs. Hydraulic fracturing is a widely used technique to increase the
rock formation permeability in oil and gas reservoirs. The diagnostic fracture injection test (DFIT) is a
commonly used and reliable technique executed prior to a hydraulic fracture stimulation process. Its
main objective is to break a small fracture in the rock formation around the wellbore, in order to evaluate
the closure of the fracture system. This test provides the parameters necessary for hydraulic fracturing
planning, such as minimum horizontal stress, fracture closure pressure, fracture gradient, fluid leak-off
coefficient, fluid efficiency, and formation permeability. These parameters play an important role in
determining the operation window for stability and planning of secondary recovery operations. This
work presents the numerical simulation of a DFIT in a carbonate reservoir of a Brazilian oil field.
Coupled hydro-mechanical continuum elements and coupled cohesive interface elements represent the
porous media and the hydraulic fracture in the numerical model, respectively. This paper aims at
investigating the effect of fracture treatment parameters on the hydraulic fracture geometry before- and
after-closure response of the DFIT. The methodology reproduces numerically all stages of a DFIT.
Therefore, the comparison of the measured bottom-hole pressure and those obtained numerically show
good agreement. The right combination of minimum in-situ stress and permeability estimation was
essential to obtain a good closure response after shut-in.

SOIL BEHAVIOR MODELLING USING CPTU DATA AND NEURAL NETWORKS FOR OFFSHORE OIL WELL DESIGN

Mon, 26 Aug 2024 00:00:00 +0000

Piezocone Penetration Test (CPTu) is widely used in Petroleum Engineering for soil profiling
and estimation of soil parameters (undrained shear strength, submerged weight), which are essential
geotechnical parameters used in the design of oil wells. The in situ test results are used in several
techniques for soil characterization, aiming the design of the conductor casing, which is the tubular that
provide structural support to the well, serving as its foundation element. Despite its efficiency, this test
bears some logistic limitations regarding depth of analysis since CPTu data is usually obtained within a
range of 40% to 50% of the conductor casing drilling depth. Data of undrained shear strength of the soil
beyond the depths covered by CPTu tests are beneficial to the safety of the drilling operation. Due to
the natural variability of the materials, the evaluation technique of this soil property must consider soil
heterogeneity as a premise. The present work uses artificial neural networks (ANNs) to predict undrained
shear strength behavior in offshore soil for depths not reached by CPTu equipment. The MLP (Multilayer
Perceptron) networks are trained with test data of different types of soil from two Brazilian offshore
basins, using classification techniques to define soil strata and segment the soil response estimation.
The error is evaluated using cross-validation procedures for different proportions of training/prediction
data. The expected results include the definition of the network architecture and prediction accuracy in

different types of soil strata. This kind of study on the soil characterization aims to support the decision-
making process on well casing design, allowing a robust structural well integrity analysis.

NUMERICAL AND PHYSICAL MODELING OF REVERSE FAULT PROPAGATION

Mon, 26 Aug 2024 00:00:00 +0000

Regions subjected to greater geological activity can induce faults, through sedimentary
deposits, to the surface of the seabed, affecting structures sensitive to loss of support, especially direct
foundations, piles and pipelines. In the case of a pipeline design crossing an area with geological and
geotechnical threats, there are two options: (1) change the route, which can represent a significant
increase in costs; or (2) allowing the pipeline to cross through the fault with proper design and
understanding of the expected fault movement. Surface fault rupture case histories provide valuable
insights regarding the response of soils to underlying bedrock fault movements. The current studies for
understanding the phenomena of faults propagation are mostly concentrated in dry non-cohesive
granular soils. Therefore, the present work aims to investigate the mechanisms of reverse fault
propagation in loose sand through numerical analyses using the finite element method (FEM). The
elastoplastic Mohr-Coulomb constitutive model has been adopted. The numerical results obtained from
ABAQUS and Plaxis 2D were qualitative compared with those from the literature. This work is part of
a research project to carry out centrifuge and numerical modeling of fault propagation in offshore
seabed. The results obtained through ABAQUS were quite helpful in the design and planning of the
centrifuge tests. The analyses undertaken varied the vertical bedrock displacement (U) at the base up to
20% of the soil layer thickness in order to understand their effect on the fault propagation and ground
deformation using the geotechnical drum centrifuge at COPPE-UFRJ. Results were compared and
conclusions were drawn on the most suitable software to be used for the present studies.

AVALIAÇÃO DE TÉCNICAS DE ACOPLAMENTO HIDROMECÂNICO

Mon, 26 Aug 2024 00:00:00 +0000

Conventional flow simulators simplify important aspects of the mechanical behavior of
rocks that can significantly impact the productivity and integrity of the oil fields. It is important to
consider the influence of the variation of effective stresses on the properties of the reservoir, such as
porosity and permeability, especially for fractured and stress-sensitive reservoirs. Numerical models
that consider the deformation of the porous medium due to the production or injection of fluids can
solve the flow problem (pressure and saturation) and the mechanical problem (displacement field) in a
single system of equations or in separate systems. This work aims to compare coupling schemes (fully
coupled, fixed stress split and the two-way partial coupling) for cases available in literature. For the
fully coupled and fixed stress split methods, the flow and mechanical problems were solved through
the in-house simulator CodeBright, while for the two-way partial coupling, the flow problem was
solved through the commercial flow simulator Imex, while the mechanical problem was solved
through a finite element program in Matlab, and simulators were integrated in an automated way by a
manager code in Matlab. The two-way partial coupling and fixed stress split methods proved to be a
good approximation for the fully coupled method. One of the advantages offered by the two-way
partial coupling method is that the mechanical calculations were performed in only a few steps of
coupling time, reducing the computational effort and making this method very competitive for the
solution of hydromechanical problems of practical interest.

COUNTERINTUITIVE PHYSICAL BEHAVIORS IN COUPLED CONSOLIDATION PROBLEMS

Mon, 26 Aug 2024 00:00:00 +0000

The coupled nature of the equations composing Biot’s consolidation model often produces
quite unexpected behaviors. The most common one is the Mandel-Cryer effect, which refers to a pressure
increase in certain regions of the domain for a short period of time with no apparent reason. Although this
effect is well known and widely reported in the literature, a clear and comprehensive explanation on the
physical mechanism that causes of the Mandel-Cryer effect is not easily found. Another counterintuitive
behavior is observed in a fully saturated poroelastic column under the influence of a gravitational field.
In this case, the poroelastic properties can produce displacement profiles that defies the common sense.
In this paper, we provide a deep discussion on these phenomena and a few hypotheses for explaining
them are proposed. For instance, we argue that there must be a mechanism responsible for transferring
volumetric strain to different regions of the domain in order to occur the Mandel-Cryer effect. For the
poroelastic column, we propose a spring-mass system to explain the displacement profiles obtained in
different situations. All of these hypotheses are carefully tested through numerical experiments.

NUMERICAL MODELING OF BRANCHING FOUNDATIONS

Illa Beghine Soncin, Lucas Teotônio de Souza, Marcelo Miranda Barros — Mon, 26 Aug 2024 00:00:00 +0000

Piles are foundation elements whose mechanism for transferring loads occurs, in many
cases, by lateral friction. It is a fact that branched systems have large surface areas and tree roots use
this fact to increase their ability to withstand requests on the trees, such as lateral wind loads. In this
paper we present a branched structure model based on fractal geometry, used as an alternative solution
for foundations, instead of a standard pile model. With three parameters it is possible to generate an
infinity of classes of branched systems composed of elements in different quantities, lengths and
thicknesses. The aim of this paper is to compare the performance of the branched against standard
models from the point of view of support capacity, stresses and displacements. The model was
simulated using the software PLAXIS 2D, which is based on the finite element method and it was
considered elastoplastic constitutive model with Mohr-Coulomb failure criterion for the soil. The
results evidence that a branched structure compared to a standard pile with same volume presents
higher carrying capacity and lower maximum displacements. For example, for a single branching with
a form of an inverted Y, the load capacity amounts to about three times the carrying capacity of a
single pile, and can reach up to about four times in the case of two and three branching orders.
Moreover, with only one branch it was verified a reduction of the maximum vertical displacement of
the foundation, for a same load, in about 85% of the displacement of the conventional foundation,
being able to reach about 90% for two and three order branches, showing a significant reduction of the
displacement below the foundation. On the other hand, the displacements around the foundation
increase since a branched structure distributes better (because of the higher surface area) the external
solicitation to the ground, which may influence possible neighboring structures. Another characteristic
of a branched foundation is that the highest stress occurs within the structure whereas in a pile
foundation the immediately below soil deals with the highest stress. In addition, we show that the
higher the branching angles the higher the load capacity.

EQUIVALENT MODELS OF VERTICAL WELLS CLOSURE IN SALINE ROCKS

Mon, 26 Aug 2024 00:00:00 +0000

This work proposes the development of a strategy to use equivalent models to estimate the
closure of a salt mass drilled by a vertical well. Drilling in areas with salt formations is a great challenge,
since these rocks develop high creep strain rates – continuous deformation even under constant tension.
Due to this phenomenon, the well diameter tends to reduce over time, what can delay the drilling process
for days or even lead to the well abandonment. To avoid these problems, computational models using
the Finite Element Method are used to predict the behavior of these rocks during drilling. To design
the drilling process, several simulations are needed and they may take many hours or days. Thus, it is
interesting to develop approaches that reduce the simulation time, allowing to evaluate the same scenario
considering different values for the project variables. The methodology adopted in this work is divided
into seven stages: a) definition of the base study scenario; b) simulation of the reference scenario; c)
elaboration of rules for the division of the massif into one and two-dimensional models; d) modeling and
simulation of pre-defined portions; e) verification of the errors; f) possible adjustments in the rules of the
massif division; g) application of the strategy in other scenarios for its validation. With the validation
of this strategy, it is possible to reduce the computational cost and the time of elaboration of the well
project. To validate the strategy, the result of the simulation of a synthetic scenario is presented, where
approximate answers were obtained with reduction in the computational cost, wich leads to a reduction
in the well design time.

FINITE ELEMENT MODELLING OF THE DIRECT SHEAR TEST

Vicente Mafra, Gracieli Dienstmann — Mon, 26 Aug 2024 00:00:00 +0000

The direct shear test was developed to obtain the failure envelope through a simple and
direct analysis. It is one of the oldest and simplest tests for this purpose applied to soil analysis.
However, during the direct shear test, the stress distribution in the sample is complex and not uniform.
In order to improve the interpretation of the direct shear test results, the present work aims to study the
stresses and strains in the sample during the execution of the direct shear test using a model based on
finite elements (FEM). The Finite Element model was implemented in the software ABAQUS®
,
student version. The model is a two-dimensional representation of a section in the direction of the
shear force. The shear is considered by applying displacements in a steady state analysis. For the
material properties a Mohr-Coulomb elastoplastic model was considered. An evaluation of the chosen
model was realised by a direct comparison of model results and laboratory tests, showing in general a
good agreement. To evaluate the adherence between upper and lower plates to the soil specimens two
geometric models were conceived: one considering toothed plates and another with smooth plates. It
was found that the models were able to describe the typical stress and strain curves of the laboratory
direct shear test when the results of shear are obtained from the fixed box reaction, although, with
some discrepancies between the toothed plates and smooth plates models. The differences observed
can be explained observing the failure zone which is distinct in the models: for the toothed plates
model, the failure zone as expected, occurs in the central part of the model; as for the smooth plates
model the failure zone falls out the central region. Differences can also be highlighted when the failure
envelope is reinterpreted from the fixed box reaction, smooth plate models feature slightly smaller
parameters, reinforcing the need for good plate crimping.

SIMULAÇÃO NUMÉRICA NÃO LINEAR DE PROVA DE CARGA BIDIRECIONAL EM ESTACAS ESCAVADAS

Hemilly C. L. Fernandes, Rose C. R. Elias, Leandro N. Duarte, Rafael C. Barros — Mon, 26 Aug 2024 00:00:00 +0000

For the foundation design development it is essential to determine the allowable load capacity
and the prediction of the foundation elements displacements. Thus, it is known that the load test is a
suitable way to establish the load-displacement characteristics. In this context, the bidirectional test is
used for performance evaluation of in-situ molded piles by applying load to an expansive cell located
within the pile. However, these geotechnical tests can present high cost and long execution process,
which sometimes make their application unfeasible. Thus, these procedures can be represented by
mathematical models, provided that the initial and boundary conditions of the problem are known.
PLAXIS 3D, a software that uses the Finite Element Method, is intended for three-dimensional
deformation analysis and stability in Geotechnical Engineering and can be used to simulate pile
behaviour under bidirectional load tests. Therefore, this work proposes to perform a nonlinear numerical
analysis of bidirectional load tests on drilled piles using the PLAXIS 3D software and the results are

compared with those obtained through on-site tests, where a good approximation in the load-
displacement curve can be observed.

ANÁLISE DE ESTABILIDADE DE BARRAGEM ALTEADA PARA MONTANTE POR DOIS MÉTODOS DE EQUILÍBRIO LIMITE

Mon, 26 Aug 2024 00:00:00 +0000

The serious consequences of human life losses and environmental disasters make stability
analysis of dams slopes play a key role in geotechnical engineering. Recently, we have witnessed events
related to the ruptures that make the safety of dams gain more and more relevance and prominence.
Already established methodologies such as Simplified Bishop are used for algebraic calculations of
slope stabilities. However, they require a lot of calculation and effort when applied to very robust
structures. The increasing availability of microcomputers brings important facilities in the systematic
application of these slope stability methods, so that more general and comprehensive analyzes can now
be performed. The commercial software Slope/W, from the GeoStudio package, and Slide, from

Rocsience, are intended for slope stability analysis, simulating the parameters of drained and non-
drained soil resistance of the structure along with water and piezometric lines, using the equilibrium

limit, which has been widely employed for these stability analyzes due to the mathematical simplicity
with which they are formulated and the accuracy obtained. Thus, reflecting on the importance of stability
analysis of dams, this study aimed to evaluate the stability of a tailings dam, located in the iron
quadrilateral (Minas Gerais), using both commercial software. The geotechnical parameters of the
materials were determined through field tests. For the sections analyzed, the variation between the
limiting equilibrium methods used and between the programs that evaluated them.

ARTIFICIAL NEURAL NETWORKS IN SOIL SHEAR STRENGTH PREDICTION

D. Mota, S. Dantas Neto — Mon, 26 Aug 2024 00:00:00 +0000

The estimation of soil shear strength parameters has been of much relevance in Geotechnical
Engineering since the early stages, leading to the creation of many correlations based on in situ tests.
However, Das and Basudhar (2008), Goktepe (2008) and Shooshpasha, Amiri and MolaAbasi (2014)
stated that these existing correlations have limited use and low generalization capacity when compared
to the neural models they proposed from index properties of soils. On behalf of that, this work was
carried on prediction of cohesion and friction angle of soils in the natural state by the use of
backpropagation multi-layer perceptrons built from easy-to-collected in situ input, NSPT, V0’ and soil
type. The architecture chosen, A:3-5-3-2, used hyperbolic tangent activation function, being trained and
tested by 38 soil samples, having reached correlations up to 0,94 for training, attesting its efficiency.

YIELD DESIGN SOLUTIONS TO BEARING CAPACITY OF SHALLOW FOUNDATIONS RESTING ON THE SURFACE OF A GRANULAR SOIL REINFORCED BY A SOIL-CEMENT LAYER.

Mon, 26 Aug 2024 00:00:00 +0000

Shallow foundations are recommended for suitable soils, in terms of bearing capacity and
small settlements. For sites underlain loose soils, conventional practice is either to implement
expensive deep foundations, or remove and replace the soft soils. In this context, soil improvement
with admixtures (such as cement, lime, fly ash, slag, and combinations) turns to be a viable solution.
However, designs procedures conceived to estimate bearing capacity improvement of such soils are
based on empirical methodologies. The present work aims to study the ultimate bearing capacity
problem of shallow foundations resting on the surface of a granular soil reinforced by a soil-cement
layer. Such task is accomplished by means of the kinematic approach of the yield design theory
through the implementation of several admissible virtual velocity fields, under plane strain conditions,
for purely vertical loads. A parametric study is presented as a function of dimensionless parameters,
which are defined from geometrical and strength properties. A comparison is then made, with
available results obtained in the context of reduced models tests, under plane strain conditions. The
maximum gap between the ultimate bearing capacity of the yield design theory and the reduced model
tests was of about 18%.

COMPUTATIONAL MODELING OF FINE SOILS FOR EPB TUNNEL BORING MACHINES

Mon, 26 Aug 2024 00:00:00 +0000

In tunnels excavated using EPB (Earth Pressure Balance) machines, the excavated soil must
have some specific engineering properties for the correct functioning of the excavation system.
Therefore, understanding the many characteristics of the excavated material, along with its rheological
behavior, is essential for a successful mechanized excavation. These conditions present obstacles that,
if not foreseen in design, can result in several problems such as soil loss, instabilities, low excavation
performance and damage to TBM components. Aiming at the main goal of creating a procedure of
investigation for fine soils excavated with an EPB tunnel boring machine, this paper presents a
preliminary step, the calibration of a model using Computational Fluid Dynamics approach making
use of a standard soil (bentonite), with a view at investigating tropical soils’ behavior once the
methodology is established. The experimental procedure was carried out using two rheological
methods, Squeeze Flow and an extrusion technique proposed by Benbow and Bridgewater. These
results illustrated that those rheological tests allow to obtain relevant parameters such as yield stress,
viscosity, rheological behavior, useful for planning EPB excavation. The numerical simulation is
important to predict the behavior of different types of mixtures while changing the variables analyzed
in this research. This paper, therefore, shows the experimental and numerical procedures that will be
used to different soils and may be used to other types of materials, to better understand the flow
through the screw conveyor and give parameters to a better soil conditioning system.

MECHANICAL INVESTIGATION OF AN ANOMALOUS CLAYEY SAND SOIL USED AS LANDFILL COVER LAYER

Fellipe J. R. Brandão, Nayara T. Belfort, Raísa P. L. Bezerra, José F. T. Jucá — Mon, 26 Aug 2024 00:00:00 +0000

Given the increase in the purchasing power of population, there is an increment in waste
generation. Considering it and the scarcity of adequate areas for final disposal of municipal solid
waste, it is recurrent that landfills’ managers invest in increasing the load capacity of landfills. Then,
landfills are work of high geotechnical risk in terms of slope stability. Thus, it is important to
investigate the mechanical behavior and stability of landfill’s slopes. It should also be noted that the
deposits of soil, when mined for raw material supply to compose landfill cover layers, become less
stable representing risks to local workers. Therefore, it is important to verify the stability of soil
deposits too. In this sense, this paper proposes a geomechanical investigation on the landfill slope
stability, as well as on the soil deposits’ slope. Experimental and numerical analyzes were performed.
Experimental ones consist of soil’s grain size characterization, soil compaction, and direct shear tests
in natural condition, from which the needed parameters to proceed with numerical analyzes were
obtained. Numerical analyzes integrate two modeling developed by a software applying the limit
equilibrium method improved by Morgenstern & Price. The soil was classified as a clayey sand; it
presented an expected friction angle (34.8o) for a sandy soil, but cohesion (56.6 kPa) was above the
expected for a soil with 69% of sand. From numerical modeling, it was observed that the soil deposit
is stable with FS = 3.1, as well as the landfill cell, which presented FS = 2.2.

SIMULATION OF TORPEDO ANCHOR INSTALLATION USING THE MATERIAL POINT METHOD

Mon, 26 Aug 2024 00:00:00 +0000

Exploration of deep-sea reservoirs is an important industrial activity due to the amount of oil
and gas the modern society demands. Thus, one needs to find a safe way to moor ships and platforms and

ensure continued and uninterrupted distribution of oil and gas. Torpedo anchors are often used as foun-
dation for offshore facilities as they are cost effective and their usage is independent of water depth. As

it is not easy to predict the behavior of installing such structures, usage of a numerical tool is necessary
and this theme has been the focus of many studies, aided by numerical methods such as Computational
Fluid Dynamics (CFD), Discrete Element Method (DEM) and Material Point Method (MPM). The last

of these, the MPM uses an interesting strategy that benefits from both Lagrangian and Eulerian formula-
tions. For instance, the convective term in momentum conservation is eliminated as a consequence of the

Lagrangian formulation and mesh distortion is avoided by a fixed background grid. On the MPM, ma-
terial information is placed inside material points, which are used to interpolate data to the background

grid, where the equations of motion are solved. Since the grid is fixed, large strains and displacements are
not a problem. Many authors used an axisymmetric formulation to simulate the installation of torpedo
anchors with the MPM. In real-life situations, however, the soil might display asymmetries. Therefore,
this work adopts the usual non-symmetric formulation to simulate the installation of two different anchor
designs on a non-symmetric soil using the MPM.

STATISTICAL EVALUATION OF EMPIRICAL CORRELATIONS FOR THE COMPRESSION INDEX (CC) IN BRAZILIAN SOFT SOILS

Jaqueline S. Santos, Gerson J. M. dos Anjos — Mon, 26 Aug 2024 00:00:00 +0000

One-dimensional laboratory consolidation test is used to discover one of the most important
parameters of consolidation of cohesive soils, the compression index (Cc). However, it is a long test
and requires the utmost care to obtain reliable samples. Geotechnical correlations are largely used
because it can give fast means of parameter prediction using simple tests. These correlations are
constructed from local data and need to be evaluated before used in other regions. This paper reports
on laboratory tests conducted in soft soils of Brazil and shows a more complete form of statistical
evaluation for the correlation of the Cc. The database is formed by 430 results of Cc and moisture
content (wn) collected in the national literature. The correlations analyzed are exclusively in function
of wn. The equations were evaluated using 17 statistical tools for each of the 11 compression index
correlations. Comparison between the results showed the best correlations and the less suitable
correlations for the database in this study. In this paper an attempt has been made to present the
empirical correlations proposed by various researchers for compression index in function of moisture
content. The results will be useful in identifying empirical equations to estimate the compression index
of Brazilian soft soils.

MODELO DE REDE NEURAL ARTIFICIAL PARA PREVISÃO DO COMPORTAMENTO CISALHANTE DE DESCONTINUIDADES ROCHOSAS

Ana R. S. Leite, Silvrano A. Dantas Neto, Matheus C. Albino — Mon, 26 Aug 2024 00:00:00 +0000

The artificial intelligence (AI) has been widely used in engineering due to its capacity to
interpret and process complex information. One of these AI technologies is the
artificial neural network (ANN) which is based on the functioning of the human central
nervous system and its ability to learn and recognize patterns. This work aims to present
an ANN model capable of predicting the shear strength of rock discontinuities. The shear
strength of rock discontinuity is one of the most important factors governing the mechanical
behavior of rock mass whose definition sometimes requires expensive laboratory
procedures not always available. Moreover, the existing analytical models have several
limitations regarding not consider all the variables which influence the shear strength
of rock joints or needing shear testes. Therefore, nine ANN architectures were tested considering the
following inputs: the normal boundary stiffness, the ratio between infill thickness and asperity
amplitude, the initial normal stress, the joint roughness coefficient, uniaxial rock compressive strength,
infill friction angle, and the horizontal displacement. As outputs the shear strength and dilation of rock
discontinuities. The architecture with the best performance is the 7-20-10-2 and with 500,000 iterations
with a correlation of 99% for training data and 96% in the validation data. The results show a nice fitting
for the ANN model output data with experimental data. As the analytical models made so far for infilled
joints are only capable of predicting the peak shear strength, the ANN comes with a handful tool for
predicting shear strength with velocity and low cost.

THE USE OF BIM (BUILDING INFORMATION MODELING) IN PAVING AS A PROCESS FACILITATOR.

Santos J. S., Barbosa V. M., Pereira M. M. — Mon, 26 Aug 2024 00:00:00 +0000

Industry and construction engineering professionals have increasingly sought innovation so
that they become competitive in today's marketplace. We have as an example the use of technologies
of Augmented Reality and virtual reality for construction as attractive for clients. This work aimed to
evaluate the use of the BIM (Building Information Modeling) methodology in road works as a
facilitator of the construction and maintenance process. Initially research was carried out on BIM in
paving works. With the use of software, such as AutoCad Civil 3D, the benefits generated in the
design phases, the optimization in the work of quantitative survey and for the optimization in
earthmoving calculation work. The obtained results indicated a greater control of the materials used
during the execution of the work, reduction of the time of execution of repetitive tasks and a better
general vision of the project of the work in its real conception geography and in 3D which favors both
its study and its execution.

BEARING CAPACITY ANALYSIS OF PILES THROUGH FINITE ELEMENT: CASE STUDY HERCÍLIO LUZ BRIDGE, SANTA CATARINA, BRAZIL

Gabriel D. Andrade, Gracieli Dienstmann — Mon, 26 Aug 2024 00:00:00 +0000

Soil engineering has progressed through the gathering of building experiences and the
development of theoretical knowledge, allowing the creation of estimating techniques for the ultimate
resistance of a foundation element. This ultimate resistance is known as bearing capacity and represents
the maximum load acting on the foundation element. On what concerns pile foundations, it is noted a
significant difficulty to establish the theory that completely describes the bearing capacity of piles. Thus,
different methods aiming to estimate the bearing capacity are currently used, for instance, the
semiempirical methods (Aoki-Velloso, Décourt-Quaresma, and others) and the finite element method.
In the present paper the bearing capacity of the foundation massif of Hercílio Luz Bridge, located in
Santa Catarina, Brazil, will be evaluated through a finite element model of an isolated pile. The pile was
modeled using the software Abaqus v. 6.13, considering an axisymmetric model and linear elastic
behavior. The latter was submitted to an axial compression load until failure. The soil surrounding the
pile was modeled considering the Mohr-Coulomb elastoplastic model. To determine parameters as
cohesion, friction angle, and Young Modulus for the soil, literature correlations with Standard
Penetration Test (SPT) were used. Numerical results were compared to semiempirical values and a
loading test. It was noted that the outcome of the finite element method provided lower bearing capacity
than the semiempirical methods and the results of the loading test.

NUMERICAL ANALYSIS AIMING TO IDENTIFY THE EQUILIBRIUM AND RATIONALIZATION IN THE STRUCTURAL DESIGN OF THE RESIDENTIAL BLOCKS OF THE COLINA - UNB

Marcelo Aquino C. R. da Silva, Marcio A. R. Buzar, Leonardo S. P. Inosoja — Mon, 26 Aug 2024 00:00:00 +0000

The University of Brasília was part of a daring and experimental plan that reached several
areas of knowledge, its conception was marked by the architectural and constructive experimentation.
Rapid execution and cost-effectiveness were key guidelines in the early years of the Darcy Ribeiro
Campus, making room for precast technology. Inserted in this context, the Colina Residential Buildings
designed by the architect João Filgueiras Lima (Lelé) were built within a year and appear in the
expectation of filling the housing deficit of the university in the mid 1960`s. This work covers the
rationalization process of the construction in the initial context of the physical implantation of the
university. Comparative numerical analyzes are performed using available computational tools such as
Ftool and Sap 2000. Through these analyzes it is possible to justify the choice of the precast structures
by means of the balance of forces and to observe the technical solutions of the structural system adopted.
In addition, the studies reinforce the economic issue of precast structures by quantifying the volume of
the situations tested.

ANÁLISE COMPARATIVA ANALÍTICA E NUMÉRICA DO ESTUDO DE PONTES

Mon, 26 Aug 2024 00:00:00 +0000

As 6.612 pontes e viadutos no Brasil, avaliados em 13 bilhões de reais de acordo com o Tribunal
de Contas da União (TCU), apresentam grande importância na nossa economia, pois com uma geografia
bastante acidentada, estas chamadas Obras de Arte Especiais (OEAs) são extremamente necessárias por
proporcionar uma melhor funcionalidade das rodovias e ferrovias existentes no País, sem deixar de lado a
segurança dos seus usuários. No Brasil, as pesquisas com relação às Pontes podem se referir a qualquer
situação desde a sua superestrutura até a infraestrutura proporcionando estudos de casos ou abordagens
numéricas. Esses estudos relacionados às pontes tornam-se fundamental devido a pouca referência
normativa. Diante disso, este trabalho busca observar atenciosamente o estudo perante as normas de
pontes, destacando, porém certas circunstancias através do desenvolvimento em um meio numérico,
podendo apresentar uma forma mais realista da situação, a fim de compreender o estudo e a essência de
alterações mais frequentes nas normas para realizar comparações com intuito de observar a precisão
perante os riscos de construção deste tipo de estrutura. Os resultados numéricos encontrados mostraram
convergência com os obtidos analiticamente.

DESENVOLVIMENTO DE UM APLICATIVO MULTIPLATAFORMA PARA DETERMINAÇÃO DE RESISTÊNCIA DE LIGAÇÕES METÁLICAS FLEXÍVEIS COM CANTONEIRAS

Rafael V. Miranda, Artur M. Reis, William L. Fernandes — Mon, 26 Aug 2024 00:00:00 +0000

Este estudo retrata o desenvolvimento de um aplicativo multiplataforma em linguagem
JAVA® utilizado para a verificação da resistência de ligações flexíveis em estruturas de aço com
cantoneiras duplas de abas iguais. O aplicativo pode ser utilizado para verificação da resistência de
uma ligação com cantoneiras entre uma viga e um pilar ou entre duas vigas de aço. Essas conexões
podem ser aparafusadas ou soldadas. Para verificar a resistência de tais conexões, várias situações de
colapso são verificadas, de modo que a menor resistência encontrada entre todas as possibilidades de
falha é considerada como a resistência da conexão. O usuário precisa especificar o tipo de aço usado
no componente estrutural, selecionando uma das duas opções (ASTM A36 ou ASTM A572); o tipo de
aço utilizado nos parafusos (ASTM A325 ou ASTM A490); os perfis de aço usados no elemento
estrutural e o tipo de ligação com base em um banco de dados salvo. Além disso, o usuário precisa
digitar o diâmetro e o número de parafusos localizados em cada aba da ligação. No caso de ligações
soldadas, é necessário considerar também a resistência à ruptura da solda e do aço base próximo à
solda. Depois de fornecer esses dados de entrada para o programa, calcula-se a resistência limite da
conexão.

ANÁLISE DOS EFEITOS DA EXCENTRICIDADE DA REAÇÃO DA LAJE SOBRE AS PAREDES DE ALVENARIA ESTRUTURAL

Manoel Ignácio Xavier Filho, Jean Marie Désir, Samir Maghous — Mon, 26 Aug 2024 00:00:00 +0000

In the context of the structural masonry system, design of most current building works involve

empirical-based procedures acquired from the engineering practice and transmission from constructor-
to-constructor. This kind of approach has revealed suitable as far as small or medium buildings are

concerned, and no structural pathologies have been associated with such design methods. The current
standards recommend the use of global safety coefficients to cover all the uncertainties that are not dealt
with in detail. It is the case of the reaction efforts exerted by the slabs on the walls in structural masonry,
which are generally treated as linear load applied along the average plane of the wall. This simplification
may lead to uncontrolled approximations in the design the structural elements since it does not account
for the wall out-plane bending moment, nor the twisting moment that can possibly arise along the wall
supporting beam. This contribution aims at investigating the relevance of considering or not such efforts
by analyzing the connection between slabs, walls and beams in a structural masonry building. Emphasis
is given to the way the loads are transferred and verifying the limits arising from application of the
recommendations of the Brazilian standard regarding the effect of the eccentricity. At that respect, a
study case is studied by means of simplified normative approaches as well as by finite element
simulations to support the analysis conclusions.

DIMENSIONAMENTO DE BARRAS COMPRIMIDAS DE MADEIRA TROPICAL UTILIZANDO A DESIDADE BÁSICA

Mon, 26 Aug 2024 00:00:00 +0000

Este trabalho apresenta uma formulação matemática para o dimensionamento de barras
comprimidas de madeira tropical utilizando a densidade básica. A concepção teórica proposta tem a
densidade básica da madeira como variável independente para o dimensionamento de elementos
estruturais solicitados a compressão axial. A formulação toma como referência as prescrições da norma
brasileira NBR-7190/82. O dimensionamento utilizando a densidade básica pode ser adaptado para
qualquer norma de projeto de estruturas de madeira, independentemente se o modelo de segurança é
determinístico, ou probabilístico. A formulação matemática utiliza funções de resistência estimadas por
um modelo de regressão linear simples amostral, construído a partir de banco de dados obtido de ensaios
experimentais para caracterização de espécies de madeiras tropicais. O modelo de regressão linear
estima propriedades físicas e mecânicas dessa amostra utilizando a densidade básica da madeira. O
Banco de Dados é o resultado de um programa experimental consistente conduzido pelo Laboratório de
Produtos Florestais do Ministério do Meio Ambiente, que nos últimos trinta anos estudou e caracterizou

259 espécies de madeira da Amazônia, tendo como referência as normas Pan-Americanas COPANT-
Comisión Panamericana de Normas Técnicas. Foi elaborada análise da significância estatística das

correlações entre propriedades físicas e mecânicas de espécies de madeira e a densidade básica. É
possível concluir, a partir das análises de significância estatística e da discussão dos resultados, que a
formulação proposta para dimensionamento de elementos tracionados de madeira tropical utilizando a
densidade básica, é matematicamente consistente.

DIMENSIONAMENTO DE BARRAS DE MADEIRA TROPICAL SOLICITADAS A FLEXÃO COMPOSTA RETA UTILIZANDO A DESIDADE BÁSICA

Mon, 26 Aug 2024 00:00:00 +0000

Este trabalho apresenta uma formulação matemática para o dimensionamento de barras de
madeira tropical solicitadas a flexão composta utilizando a densidade básica. A concepção teórica
proposta tem a densidade básica da madeira como variável independente para o dimensionamento de
elementos estruturais solicitados a flexão composta reta. A formulação toma como referência as
prescrições da norma brasileira NBR-7190/82. O dimensionamento utilizando a densidade básica pode
ser adaptado para qualquer norma de projeto de estruturas de madeira, independentemente se o modelo
de segurança é determinístico, ou probabilístico. A formulação matemática utiliza funções de resistência
estimadas por um modelo de regressão linear simples amostral, construído a partir de banco de dados
obtido de ensaios experimentais para caracterização de espécies de madeiras tropicais. O modelo de
regressão linear estima propriedades físicas e mecânicas dessa amostra utilizando a densidade básica da
madeira. O Banco de Dados é o resultado de um programa experimental consistente conduzido pelo
Laboratório de Produtos Florestais do Ministério do Meio Ambiente, que nos últimos trinta anos estudou
e caracterizou 259 espécies de madeira da Amazônia, tendo como referência as normas Pan-Americanas
COPANT-Comisión Panamericana de Normas Técnicas. Foi elaborada análise da significância
estatística das correlações entre propriedades físicas e mecânicas de espécies de madeira e a densidade
básica. É possível concluir, a partir das análises de significância estatística e da discussão dos resultados,
que a formulação proposta para dimensionamento de elementos de madeira tropical solicitados a flexão
composta reta, utilizando a densidade básica, é matematicamente consistente.

DIMENSIONAMENTO DE BARRAS TRACIONADAS DE MADEIRA TROPICAL UTILIZANDO A DENSIDADE BÁSICA

Mon, 26 Aug 2024 00:00:00 +0000

Este trabalho apresenta uma formulação matemática para o dimensionamento de barras
tracionadas de madeira tropical utilizando a densidade básica. O modelo de resistência proposto tem
densidade básica da madeira como variável. A formulação matemática aplica-se tanto para modelo de
segurança determinístico, quanto para modelo probabilístico. As funções de resistência para o material
foram estimadas por um modelo de regressão linear simples, obtido a partir de um espaço amostral
formado por 259 espécies de madeiras tropicais. O espaço amostral é o Banco de Dados resultado de
um programa experimental conduzido pelo Laboratório de Produtos Florestais do Ministério do Meio
Ambiente, que nos últimos trinta anos caracterizou espécies de madeira da Amazônia, tendo como
referência as normas Pan-Americanas COPANT-Comisión Panamericana de Normas Técnicas. Na
validação dos modelos de regressão linear foi elaborado minucioso estudo de inferência estatística, com
comentários neste artigo. É possível concluir a partir das análises de inferência estatística, que o modelo
de resistência para tração axial proposto neste artigo, atende aos níveis consagrados de confiabilidade
estrutural, normalmente utilizados para engenharia de estruturas, além de ser de aplicação mais simples
que os modelos tradicionais. Os critérios de dimensionamento de barras tracionadas, conforme
apresentado neste artigo, faz parte de ampla pesquisa conduzida no Departamento de Engenharia Civil
e Ambiental da Universidade de Brasília, para desenvolvimento de modelos de resistência para
elementos de madeira tropical utilizando a densidade básica, para estados limites últimos de compressão
axial, flexão, flexão composta e ligações, além da influência de outras propriedades.

DIMENSIONAMENTO DE BARRAS FLETIDAS DE MADEIRA TROPICAL UTILIZANDO A DESIDADE BÁSICA

Mon, 26 Aug 2024 00:00:00 +0000

Este trabalho apresenta uma formulação matemática para o dimensionamento de barras
fletidas de madeira tropical utilizando a densidade básica. A concepção teórica proposta tem a densidade
básica da madeira como variável independente para o dimensionamento de elementos estruturais

solicitados a flexão. A formulação toma como referência as prescrições da norma brasileira NBR-
7190/82. O dimensionamento utilizando a densidade básica pode ser adaptado para qualquer norma de

projeto de estruturas de madeira, independentemente se o modelo de segurança é determinístico, ou
probabilístico. A formulação matemática utiliza funções de resistência estimadas por um modelo de
regressão linear simples amostral, construído a partir de banco de dados obtido de ensaios experimentais
para caracterização de espécies de madeiras tropicais. O modelo de regressão linear estima propriedades
físicas e mecânicas dessa amostra utilizando a densidade básica da madeira. O Banco de Dados é o
resultado de um programa experimental consistente conduzido pelo Laboratório de Produtos Florestais
do Ministério do Meio Ambiente, que nos últimos trinta anos estudou e caracterizou 259 espécies de
madeira da Amazônia, tendo como referência as normas Pan-Americanas COPANT-Comisión
Panamericana de Normas Técnicas. Foi elaborada análise da significância estatística das correlações
entre propriedades físicas e mecânicas de espécies de madeira e a densidade básica. É possível concluir,
a partir das análises de significância estatística e da discussão dos resultados, que a formulação proposta
para dimensionamento de elementos tracionados de madeira tropical utilizando a densidade básica, é
matematicamente consistente.

NUMERICAL ANALYSIS OF THE STRUCTURAL DESIGN AND THE CONSTRUCTIVE AESTHETICS OF THE VILANOVA ARTIGAS BUILDING – FAU-USP

Mon, 26 Aug 2024 00:00:00 +0000

The University of São Paulo Faculty of Architecture and Urbanism (FAU / USP) building
project is authored by and named after the architect Vilanovas Artigas and stands out for the constructive
rationality, the spatial richness and the didactic aspect with which the building elements are shown for
the users of the building, predominantly architecture students. The project dates from 1961, while the
execution took place in the period from 1966 to 1969. The constructed area is 18.600m2 and the total
high is of 16 meters. The building follows a structural modulation of 11x11 meters, having a total of
110x66 meters. Externally the building is characterized by a rectangular volume, suspended from the
floor, supported by sculptural pillars. Internally it is as if it were two volumes of four decks separated
by a central void. A single concrete roof with 960 domes unifies both volumes. In contrast to the sobriety
and uniqueness of the external form, the internal spatiality is very dynamic, as a result of the game of
advances and retreats of the slabs on the central void, the alternation of openings and closures and the
generosity of the spaces of circulation. Reinforced concrete was the building technique adopted in
almost all of the building, not only in the foundations, beams and pillars, but also in the roof and in most
of the walls. Among the elements of greater prominence in the work are the external pillars that,
positioned outside the structural modulation, have a sculptural form, distinguishing themselves from the
other internal pillars. The objective of the present study is to understand the efforts to which the structure
is subject by means of computational tools such as the SAP 2000 software, verifying the constructive,
aesthetic and didactic justifications of the structural solution and highlighting the importance of the
structural system adopted for the result architectural.

NUMERICAL AND HISTORICAL ANALYSIS OF THE BUILDING OF THE RURAL SCHOOL ALBERTO TORRES IN RECIFE-PE

Mon, 26 Aug 2024 00:00:00 +0000

The project of the Alberto Torres Rural School building in Recife dates from 1935 and was
the fruit of a pioneering initiative for Brazilian modernism. The creation of the Architecture and
Urbanism Board - Diretoria de Arquitetura e Urbanismo (DAU), founded in 1934 by Luiz Nunes, an
architect graduated from the Escola de Belas Artes do Rio de Janeiro, from where it took influences of
Lúcio Costa and Le Corbusier. The project analyzed in this work is authored by Luiz Nunes himself and
has the structural calculation signed by Joaquim Cardozo. Known as the "Engineer of Poetry," Cardozo
is considered a pioneer of the Modern Movement and later would excel as the calculator of the main
works of Oscar Niemeyer, in Pampulha and Brasília. Joaquim Cardozo is responsible for a real technical
revolution in Brazilian engineering, stimulated and inspired by the projects of great architects with
whom he worked throughout his career. In this work an analysis of the structural project of the Rural
School Alberto Torres is sought to show elements of creativity of the designer to balance the structure.
A qualitative numerical analysis of the structural solution is performed using the computational tools
available as the SAP 2000 software. The analyzes seek to understand the efforts to which the structure
is subject and to verify the protagonism of the structural solution, innovative for the time, in the aesthetic
architectural style that is aligned with the precepts of modernism.

ANÁLISE DO COMPORTAMENTO ESTRUTURAL DAS VIGAS DE COBERTURA DO EDIFÍCIO SG 12 DA UNIVERSIDADE DE BRASÍLIA

Mon, 26 Aug 2024 00:00:00 +0000

Projetado em 1962 pelo arquiteto João da Gama Filgueiras Lima, o Lelé, e executado pela
construtora Rabello S.A, o edifício SG 12 tinha como objetivo abrigar funções temporárias e de apoio
da Universidade de Brasília, sendo parte do conjunto de Galpões de Serviços Gerais com mesma
concepção estrutural da Universidade de Brasília, formado pelos edifícios SG 9, SG 11 e SG 12. O

edifício SG 12 abrigou até a década de 1972 a Biblioteca Central, e hoje abriga os programas de Pós-
graduação de Geotecnia, Transporte, Estruturas e Construção Civil e Recursos Hídricos. O edifício SG

12 foi construído com estrutura pré-moldada de concreto armado, conta com subsolo, térreo, mezanino
e cobertura, possuindo uma área construída de 5.437 m2. Uma característica marcante da estrutura é que
o pavimento mezanino é atirantado às vigas da cobertura, o que permite flexibilidade de uso ao edifício.
O presente trabalho tem como objetivo realizar uma análise do comportamento estrutural das vigas da
cobertura do edifício, a partir da modelagem estrutural em elementos finitos, utilizando o programa
SAP2000. São apresentados os esforços atuantes nas vigas, bem como verificações de estado-limite de
deformações excessivas (ELS-DEF) e de vibrações excessivas (ELS-VE), conforme a ABNT NBR
6118: 2014.

CÁLCULO DE CONTRA FLECHAS INCLUINDO DEFORMAÇÕES POR FLUÊNCIA DURANTE A FASE CONSTRUTIVA DE ESTRUTURAS EM BALANÇOS SUCESSIVOS

Mon, 26 Aug 2024 00:00:00 +0000

A análise de estruturas requer a avalição das deformações e, em alguns casos, é necessário
acompanhar essas deformadas durante a construção, como ocorre nas estruturas executadas em etapas
construtivas. Na execução de pontes e marquises pelo Método dos Balanços Sucessivos, os segmentos
são construídos a partir do anterior e uma nova geometria é definida a cada estágio, assim o
comportamento da estrutura anteriormente executada precisa ser analisado devido à nova configuração
deformada. O uso de contra flechas introduz deslocamentos corretivos de modo a compensar essas
deformações. O cálculo dessas contra flechas consideram o ganho de resistência do concreto ao longo
do tempo, mas negligenciam as deformações devido aos efeitos de fluência que são diferentes para
cada segmento, pois o material possui diferentes idades durante a concretagem e aplicação de carga. É
importante que esse tipo de análise seja incorporado a essas estruturas, pois as deformações modificam
a cada estágio e o deslocamento acumulado total é diferente quando comparado a uma análise da
estrutura com estágios construtivos, mas sem os efeitos da fluência. O presente trabalho consiste na
determinação dos valores de contra flecha a serem aplicados em uma estrutura, em balanço sucessivo,
incluindo as tensões provenientes da fluência. Um código em elementos finitos foi desenvolvido para
o cálculo das deformações em vigas que passam por modificação no seu sistema estrutural ou
carregamento ao longo da construção, considerando os efeitos da fluência. Com isso, a análise
incremental em estruturas especiais é aplicada e seus efeitos em cada estágio são compreendidos.
Exemplos em programas comerciais são apresentados para validação das rotinas propostas, de maneira
a mostrar a importância das deformações por fluência no cálculo do projeto.

COMPUTATIONAL TOOL FOR ANALYSIS IN SOUND TRANSMISSION LOSS ON SIMPLE, DOUBLE AND MULTILAYER CLOSING PANELS

Reinaldo C. Fortes, Rovadávia A. J. Ribas, Gustavo P. Guimarães — Mon, 26 Aug 2024 00:00:00 +0000

As edificações construídas sob o sistema estruturado em aço podem apresentar problemas
devido ao mau desempenho acústico quando são aplicados sistemas de fechamento industrializados. A
flexibilidade e vibração excessiva da estrutura, aliadas à reduzida capacidade de isolação sonora dos
materiais dos fechamentos, que, em geral, são mais leves do que as tradicionais alvenarias, podem
transmitir para os painéis, que compõem os sistemas de fechamento industrializados, vibrações que
tendem a diminuir a perda na transmissão sonora da parede. Os transtornos são em geral complexos e
levam a correções onerosas. No entanto, o desempenho acústico de um sistema de fechamento pode
ser previsto e otimizado se aplicados, durante a fase de projeto, conceitos e tecnologias adequadas para
a análise de sua resposta acústica. A perda na transmissão sonora é um parâmetro que permite a
análise do desempenho acústico de sistemas de fechamento, mas sua estimativa envolve vários fatores,
principalmente se sua aplicação envolver múltiplas camadas. Nesse contexto, o objetivo desta pesquisa
é elaborar um modelo computacional para a determinação da perda na transmissão sonora em função
da frequência em sistemas de fechamento constituídos por painéis de fechamento industrializados
simples e em multicamadas, com e sem absorvedores sonoros entre as placas que compõem os painéis
em multicamadas. O modelo é desenvolvido em linguagem JAVA, utilizando a plataforma NetBeans e
o banco de dados sqLite, e possui uma interface gráfica para a interação com o usuário de forma
facilitada. A modelagem é baseada em um método gráfico, aplicado a painéis industrializados simples,
duplos e em multicamadas, com e sem absorvedores sonoros entre as placas que compõem o sistema.
Considera-se ainda a forma de fixação dos painéis, que é determinante na eficiência de sua
transmissão sonora. A validação quantitativa do modelo computacional é realizada, comparando-se os
resultados obtidos com trabalhos publicados, tendo o software apresentado resultados com diferença
máxima de 1,5%, o que viabiliza sua utilização para uma rápida análise acústica de sistemas de
fechamento industrializados.

Structural Optimization of 3D Trusses considering the Dynamic Effect of the Wind

Mon, 26 Aug 2024 00:00:00 +0000

In the civil engineering and construction industry there exists a consistent search for projects
that are more functional, safe and efficient. Based on those exigencies, new technologies and analysis
methods are being developed, where the common objective is to find the optimal structure in terms of
lightweight and efficiency. The use of trusses-kind structures has increased over recent years, this fact is
mainly due to its practicity in terms of structural assembly, lightness and high resistance; allowing, for
example, its use in large roof structures or stadiums. Nonetheless, an accurate analysis of its behavior
is necessary for correctly design these kind of structures. In many cases, a static analysis is sufficient.

However, in structures such as roofs or bridges, the dynamic effects could be relevant, as they can gen-
erate vibration. Resulting in discomfort for the users, or even, leading to structural failure. Thus, the

dynamic effect of the wind should be considered in order to have a more realistic behavior of the struc-
tural response. The main objective of the present work is the parametric optimization of 3D trusses,

considering the dynamic effect of the wind. The brazilian standard NBR 6123 is herewith used in order
to account for this dynamic wind effect. Restrictions are also in accordance with the brazilian standard
NBR8800, which features project restrictions for steel structures. The computational implementation
was made using Matlab programming language. The structural dynamic response was implemented
using the Finite Element Method (FEM), while the optimization procedure was accounted using the
Teaching-Learning-Based Optimization (TLBO) method. The objective function for the optimization
method is the reduction of the total weight of the structure and project restrictions were considered in
accordance with brazilian standards. Some numerical examples are presented to show the applicability
of the proposed methodology.

VERIFICATION OF EXCESSIVE VIBRATIONS ON UNIDIRECTIONAL PRECAST RIBBED SLAB FLOORS

Mon, 26 Aug 2024 00:00:00 +0000

The ribbed slabs (RS) are one of several types of precast slabs. This type of slab is suitable
for any work, but is very much used in small housing and commercial buildings. The construction
system, composed of reinforced concrete ribs, stands out economically when compared to structures
cast in loco, whether they are solid or ribbed, since they require a smaller amount of framework and
shoring, and reduce the consumption of concrete. From the design point of view, these slabs are often
only verified in relation to the ULS and the SLS of deflection, however when the verification of this
SLS of vibration is neglected, it results in vibration comfort problems and, in some cases, may cause
malfunction of machines and equipment. In this context, this work aims to study the static and dynamic
behavior of the RS’s by means of a parametric analysis that evaluates the influence of the useful height,
topping slab thickness and characteristic strength of the concrete (fck) in the natural frequency variation,
through an analytical and numerical approach (via SAP2000®

). The results were discussed comparing
the analytical prediction of the limit values proposed by ABNT NBR 6118:2014 and PCI Design
Handbook (2010). The results show that with the adoption of additional reinforcement, RS's present
worse results for vibration SLS in relation to deflection SLS, fortifying the need to verify the dynamic
behavior.

EXPERIMENTAL AND NUMERICAL STUDY OF MASONRY WITH EMPHASIS ON THE ANALYSIS OF STRUCTURAL EFFICIENCY

Mon, 26 Aug 2024 00:00:00 +0000

In view of the speed and ease of execution, structures such as structural masonry are widely
adopted in civil construction. Although this construction method is considered simple, for the
elaboration of structural projects with satisfactory levels of security and economy, a comprehensive
analysis of the structural behavior is essential. In this regard, numerical modeling is an efficient
approach. In this work, it is carried out the numerical and experimental analysis of the mechanical
performance of small walls of structural masonry, subjected to axial compression. To study the
transmission mechanisms of the stresses and modes of failure, a linear analysis was performed from a
homogenized model, developed in SAP2000® software. As a secondary aim, the strength of the masonry
is compared to that of Light Steel Frame (LSF) panels constructed and modeled with geometric
characteristics similar to those of the small masonry wall and their structural efficiencies was evaluated
comparatively. From the obtained results, it was verified that the macromodeling is an efficient tool in
the prediction of the strength transmission mechanisms in the masonry. About the investigation of the
structural efficiency of the analyzed construction methods, a ratio of 2:1 was verified between the
specific strength of the LSF and the structural masonry.

INFLUÊNCIA DA ELASTICIDADE DA FUNDAÇÃO NA ANÁLISE DE TENSÕES EM UMA BARRAGEM GRAVIDADE DE CONCRETO

Iarly Vanderlei da Silveira, Lineu José Pedroso — Mon, 26 Aug 2024 00:00:00 +0000

A fundação nas barragens gravidade de concreto é um local de destaque nas análises de
estabilidade dessas estruturas, uma vez que os defeitos na fundação ou a sua influência são considerados
como um dos principais mecanismos de deterioração e danos ao longo da estrutura. Este estudo consistiu
em avaliar a influência da elasticidade da fundação em um perfil de barragem gravidade de concreto
com dimensões típicas de uma barragem brasileira, na qual essa estrutura é submetida aos carregamentos
gravitacional (peso próprio), pressão hidrostática e sub-pressão. Dessa forma, avaliou-se as tensões
principais e deslocamentos em alguns pontos na estrutura variando as condições da elasticidade da
fundação. A modelização desse sistema barragem-fundação foi analisada por meio do software ANSYS
APDL cuja idealização do solo da fundação e do concreto da barragem foram considerados como
materiais de propriedades elásticas, homogêneas e lineares. Os resultados mostram que a modificação
da elasticidade da fundação provoca mudanças no comportamento das tensões e deslocamentos na
estrutura.

UM ESTUDO ANALÍTICO-NUMÉRICO DA INFLUÊNCIA DAS CONDIÇÕES DE CONTORNO E DO PROCESSO DE CÁLCULO NA RESPOSTA DE UMA PLACA RETANGULAR NA ZONA DE CONEXÃO COM OS APOIOS

Luan Felipe, Adriana C. Silva, Iarly Vanderlei da Silveira — Mon, 26 Aug 2024 00:00:00 +0000

In civil construction the slab-beam or slab-pillar connections present some uncertainties in
the analysis of their efforts, which has led to discrepancies between the calculation and the actual
behavior of these structural elements. In addition to inaccuracy during its execution, variations from the
conditions adopted in numerical modeling and the accuracy of the calculation procedures also increase
the divergence between the results of these analyzes and those observed in loco. These elemental
connection zones are critical regions that require this questioning, and thus the results of deflection of a
uniformly loaded plate subjected to six different supporting conditions were analyzed comparatively by:
(a) Finite Differences Method; (b) Finite Element Method using ANSYS software; and (c) analytical
formulation available in the literature. The combinations of support conditions ranged from brimmed to
crimped edges. We also conducted a convergence study of the results for each of the imposed conditions,
noting that some of the analyzed conditions require greater caution from the designer, given the nature
of the analysis methods used and the conditions of the problem addressed.

ESTUDO DO COMPORTAMENTO ESTRUTURAL ESTÁTICO EM ELEMENTOS DE PLACA

Mon, 26 Aug 2024 00:00:00 +0000

Um problema prático na engenharia surge com a análise estrutural estática de placas. Soluções
analíticas apresentadas na literatura são complexas e extensas, necessitando o uso de métodos de tabelas
simplificadas para obtenção desta resposta estrutural estática. No Brasil, as placas têm diversas
aplicações práticas e são empregadas principalmente para simular as lajes em concreto armado em
edifícios de múltiplos pavimentos. Nesse sentido, neste trabalho é apresentado um procedimento
analítico utilizado através de implementação computacional para a análise estática elástica-linear de
placas finas retangulares com as bordas simplesmente apoiadas. A solução analítica é obtida tendo por
base o cálculo variacional através de uma formulação energética implementada no software MAPLE.
Os valores obtidos são comparados com o método dos elementos finitos (MEF) através de uma
discretização numérica por meio do software ANSYS. Com base nestes estudos, ficou evidenciado que
a metodologia analítica implementada representa adequadamente os deslocamentos, esforços e tensões
na laje.

ESTUDO NUMÉRICO DE VIGAS DE AÇO SUBMETIDAS À FLEXÃO

Mon, 26 Aug 2024 00:00:00 +0000

Structural analysis consists of identifying and predicting the behavior of the structure in the
analytical, experimental and numerical fields. For this, physical and mathematical theories resulting
from the formalization of structural engineering are used. Numerical modeling is the study of
mathematical problem approximation algorithms that converge to the real solution of the problem
through computational aid. Beams are generally structures used to resist transverse stresses along the
longitudinal axis and to transmit these loads to other structures. This type of element has internal
forces such as bending and shear. Bending bending causes a deformation of the pieces, which is
determined by the elastic line, resulting in displacement along the axis, the deflection. Thus, this work
will have as main objective to perform analytical and numerical study of an isostatic steel beam. After
the analytical study, the elaboration of the numerical model through the Finite Element Method (FEM)
through the SAP2000 modeling software will be made. Then we will compare the values obtained
with the methods used. According to the analytical and numerical results one can infer the
effectiveness of the numerical analysis performed, highlighting the efficiency of the nonlinear
analysis, in view of the approximation of the results obtained through SAP2000, as well as the
refinement of the results. The paper also presents results on the influence of beam variation on
deflection analysis, showing that the greater the stiffness of the profile, the smaller the displacement in
the vertical axis.

DYNAMIC ANALYSIS OF THE BRASÍLIA ROAD PLATFORM THROUGH NUMERICAL SIMULATION AND MONITORING

Mon, 26 Aug 2024 00:00:00 +0000

Brasilia, the first urban ensemble of the 20th century to be recognized as a World Heritage
by UNESCO, turns 60 years since your inauguration in 2020. Given this and considering that the
buildings in Brazil usually have a minimum design life of 50 years (standard reference time), routine
monitoring these structures is required to carry out preventive and corrective maintenance actions, as
required by the Model Code fib 2010. The Plano Piloto Bus Terminal of Brasília is composed of
Ground and Upper Platforms, two squares and an extensive slab-overhang, which holds stairs,
elevators, snack bars, magazine stands, taxi stand, etc. The slab-overhang, target of the test, is formed
by precast beams, placed next to each other, supported on frames of beams in prestressed concrete on
28 metallic pillars. From the monitoring of vibrations, through the use of four accelerometers, two
inclinometers, and one temperature gauge, it was possible to obtain the natural response frequencies of
the structure. With these results, the structural behavior was evaluated by the development of the
numerical model based on the finite element method, using elements in frames and shells. From this
assessment, it was concluded that, despite the need to repair the slab, so that its excessive deformation
is corrected - and thus providing greater visual comfort to the users - the structural performance of the
slab-overhang was satisfactory as for the natural vibration, allowing the normal use defined in design,
with the guarantee of user safety.

EVALUATION OF THE STRAIN ENERGY CAPACITY OF ARTIFICIAL TREES

Paula de Oliveira Ribeiro, Gabriel Vilela, Marcelo Miranda Barros — Mon, 26 Aug 2024 00:00:00 +0000

Nowadays much effort in science and technology is related to renewable energy, once the
actual society is based on available energy and the demand is increasing. One of the actual research
areas in harvesting energy is based on vibration using piezoelectric materials. Natural trees are known
to be very flexible and resilient. Trees are able to absorb relatively high quantities of energy from the
wind due to their flexibilities as well as the high drag force induced by the leafs. Piezoelectric energy
harvesters must contain flexible elements in order to induce vibration within its elements, since the strain
rate is necessary to induce electrical current within these devices. Artificial trees with a given number
of generations may be built by fractal geometry, or iterated function systems. In this paper we propose
a 2D model for the trees extended to 3D by unitary depth. Thus, the geometrical properties of each
branch are the length and the width. The trees are self-similar, i.e. the quantity of children for each father
branch is constant for all branching, as well as the length and width ratios, given by the parameters b, λ
and w respectively. Let n be the number of generations, or iterations, and λ0 and w0 the length and
width of the trunk. Therefore an infinity of trees may be generated through this set of six parameters. In
this paper we present analytical expressions for the strain energy in tree structures generated by fractal
geometry. Some numerical experiments are performed in order to both confirm the analytical
propositions and evaluate the strain energy for some particular structures.

VERTICAL AXIS WIND TURBINE WAKE FLOW ASSESSMENT USING OPENFOAM

Hugo G. Castro, Javier L. Mroginski, Juan M. Podesta ́ — Mon, 26 Aug 2024 00:00:00 +0000

Wind power is one of the means of producing renewable energy that has grown in popularity due
to the horizontal axis wind turbine great efficiency. However, vertical axis wind turbines (VAWTs) are
becoming an interesting option in urban environments. As it is well known, the wake flow generated
by the kinetic energy extraction of the wind turbine blades has a direct influence on the wind turbine
performance, whether isolated or grouped in a wind farm. This work presents a computational fluid
dynamics (CFD) study of a Darrieus VAWT wake flow. The wind turbine is assumed to be located inside
a boundary-layer wind tunnel with different inflow conditions. The complete coupling between the
rotating rigid solid and the fuid flow is implemented by open source CFD OpenFOAM software. Three
dimensional unsteady flow simulations are carried out by means of the Unsteady Reynolds Averaged
Navier-Stokes (URANS) method and using the sliding mesh technique in order to explicity resolved the
turbine rotation. The obtained results are compared with previous experimental work, showing a good
agreement.

COMPARATIVE STUDY OF CFD AND THE DMST APPLIED TO DARRIEUS H-ROTOR PERFORMANCE CALCULATIONS

Willian Minoru Okita, Kamal Abdel Radi Ismail — Mon, 26 Aug 2024 00:00:00 +0000

CFD and other vortex methods are used to predict the performance of horizontal and vertical
axis wind turbines and investigate the wake effects with good precision. The main drawback of these
methods that they usually consume a lot of computational time and consequently expensive for quick
evaluation studies. There are other numerical methods that can be useful for this type of application
needing less computational time and reasonably accurate. One of such numerical methods is the blade
element momentum (BEM) for horizontal axis wind turbine and double multiple stream tube (DMST)
for vertical axis wind turbine. This work reports the results of a comparative study between CFD,
experimental measurements and the DMST to predict the performance of Darrieus H-rotor type vertical
axis wind turbines (VAWTs). The DMST combines the multiple stream tube model with the double
actuator disk theory. The results from the present study compared the CFD results with the present
Matlab DMST code incorporating Xfoil. The DMST overestimated the power coefficient but presented
similar behavior when compared with other numerical and experimental results. The overestimated
values are mainly due to the fact that the wake is not accounted for in a simultaneous way as is the case
in the experiments and CFD simulations.

AERODYNAMIC ANALYSIS OF PROPELLERS BY COMPUTATIONAL FLUID DYNAMICS

Eric Vargas Loureiro, Nicolas Lima Oliveira, Patricia Habib Hallak — Mon, 26 Aug 2024 00:00:00 +0000

Propellers are widely used in our day-to-day for various purposes. Aerodynamic analyzes
are necessary to evaluate the thrust generated and the power that the propeller is capable of absorbing or
delivering. Among the available tools for this purpose, we highlight the computational fluid dynamics
(CFD). In general, the main concerns for the use of CFD lie in the complexity of its geometry, which is
often not provided by the manufacturer, the generation of the mesh, and the use of appropriate numerical
techniques to solve the problem. Regarding this last observation, the computational tools must be able
to accommodate the movement of the rotating domain of the propeller to the computational domain.
Besides, due to the flow characteristics, turbulence models must be incorporated to represent the entire

behavior of the system adequately. This study proposes computational modeling and aerodynamic anal-
ysis of a fan by CFD using the Ansys commercial program (academic version) and OpenFOAM open

source. The computational domain is divided into a rotating and stationary. At interfaces between both,
there is no agreement between the nodes and the elements from one mesh to the other, but the numerical
technique ensures the correct transfer of information. Also incorporated into the codes are the turbulence
models widely reported in the literature. The proposed methodology consists of comparing the responses
in terms of thrust and torque for some operating conditions between both programs, adopting the same
boundary conditions and similar numerical techniques, and verifying the quality of the results.

CONTRIBUTION OF TOWER WIND FORCES TO THE BASE MOMENT OF ONSHORE WIND TURBINES

Mon, 26 Aug 2024 00:00:00 +0000

Wind turbines are analyzed and designed according to specific standards such as IEC
61400-1 which provides design requirements for all subsystems. Internal forces in the structural
elements are obtained through dynamic analyses of the rotor-tower-foundation coupled system under
the action of turbulent wind. This work presents and discusses dynamic analyses of a horizontal axis
onshore wind turbine model, representative of large wind turbines: the 5MW NREL Base Wind
Turbine, designed by the National Renewable Energy Laboratory (NREL). The simulations are
performed using the FAST and TurbSim computational tools, developed and made available by
NREL. The design situations cover normal operating and stationary rotor conditions, with wind
velocity fields given by the normal turbulence profile, extreme turbulence model and extreme wind
velocity model. The results are discussed in terms of the contributions to the base internal forces of the
wind forces applied to the tower, showing that these are predominant in analyses with extreme wind
speed.

HTYPE WIND TURBINE PERFORMANCE PREDICTIONS BY A LOW COMPUTATIONAL EFFORT ALGORITHM

Pedro A. A. Baracat, Kamal A. R. Ismail — Mon, 26 Aug 2024 00:00:00 +0000

The use of vertical axis wind turbines (VAWTs) has been increasing in recent years. H-type
wind turbines may be a good alternative to horizontal axis wind turbines (HAWTs) at places with low
space availability, as occurs in cities, low wind velocity and disturbed wind streams, as occurs in areas
of mountainous reliefs. Hence, methods of wind turbine performance prediction have become even more
important, in wind energy potential studies. They may reduce the number of experimental trials or field
tests needed. However, the wind stream behavior on a vertical axis wind turbine is usually complex and
hard to predict. A low computational effort algorithm for H-type wind turbine performance prediction
was conceived and tested in a regular home computer. At H-type wind turbine simulation, some inputs
are the airfoil, air density and dynamic viscosity, chord length or solidity, rotor height and radius, free
stream velocity, tip speed ratio range for a constant number of blades (also an input), initial guess and
stop criteria of axial induction factor and maximum number of iterations within the stop criteria. For
non-Joukowski airfoils, the lift and drag coefficients are given in input tables, changing with the angle
of attack and azimuthal angle, from π/180 (1o) to 2π rad (360o) and step value of π/180 rad (1o). Each
table refers to a specific Reynolds number. The tables are previously analyzed, and missing or
non-integer angle values of angles of attack with their coefficients are filled-in by linear interpolation.
For Joukowski airfoils, the circle parameters are inputs. The resultant profile and lift coefficients are
analytically calculated. The variation of power coefficient with tip speed ratio curves are similar to the
literature findings. The predicted power coefficient is 2% higher than the maximum value of
experimental results (same tip speed ratio), in a simulation that lasted 34 seconds to run.

ANÁLISE DINÂMICA DE AEROGERADORES OFFSHORE COM FUNDAÇÃO DO TIPO MONOPILAR

Mon, 26 Aug 2024 00:00:00 +0000

The offshore wind power generation has shown a considerable growth over the last few ye-
ars. The wind power potential of the Brazilian Exclusive Economic Zone (ZEE) is significant, with a

continental shelf of low depth and extremely favourable wind speed in the Northeast region. Offshore

wind power exploration appears as an alternative for the expansion of the national primary energy sour-
ces. The monopile type represents approximately 80% of the global foundation solutions for Offshore

Wind Turbines (OWT). In general, OWTs exhibit high flexibility and similar behaviour to an inverted
pendulum. They are constantly subjected to the dynamic actions of wind forces, which are combined

with other loads, such as waves, sea currents, earthquakes. This work presents procedures for the one-
way dynamic analysis of monopile OWTs, where aerodynamic loads are obtained by the Blade Element

Momentum (BEM) theory and the structural dynamic simulation is performed in a one-dimensional mo-
del according to the Finite Element Method (FEM). An integration between aerodynamic loading and

the structural module is performed with the aid of MATLAB. The soil-structure interaction is idealized
by means of four simplified models: fully fixed, distributed springs, apparent fixity length and coupled

springs. Several results are presented for the NREL 5MW reference turbine and validated by robust mo-
del solutions available in literature. The results indicate the efficiency of the developed routines on the

characterization of the transient wind action on the rotor and its possible use for the dynamic analysis of
wind turbines on sea for different environmental conditions.

DYNAMIC ANALYSIS OF ONSHORE WIND TURBINES FROM A LAGRAGEAN APPROACH

Henrique A. N. Castro Filho, Suzana M. Ávila, José L. V. de Brito — Mon, 26 Aug 2024 00:00:00 +0000

Special structures, such as wind turbines, have characteristics and exhibit significantly
different behavior than conventional civil engineering structures. Wind turbines are generally flexible
structures and susceptible to considerable displacement due to external vibrations. Thus, it is of
significant importance to analyze the dynamic behavior of these structures. Considering this, the
present study aims to evaluate the dynamic performance of wind turbines through two approximate
models, investigating three different conditions and how each one will affect the results. The three
studied aspects are the influence of the operational condition (parked and rotating), the influence of
SSI and the influence of rotor speed. The NREL 5MW wind turbine will be the source of tower,
nacelle and rotor properties. The models use multi-degrees of freedom to represent an onshore wind
turbine of horizontal axes; in addition, the Euler-Lagrangian approach is used to process dynamic
analysis. The first model was developed using rotary blades modeled as continuous beams. The whole
model has 8 degrees of freedom. The blades are analyzed as a system of two degrees of freedom, that
is, it is possible to vibrate in the directions in the plane and out of the plane. They are connected in the
center of the tower-nacelle represented by a spring of mass corresponding to a system of two degrees
of freedom, that is to say, also can have vibrations in the directions in the plane and outside the plane.
The second model has the same characteristics as the first; however, a foundation shaped like a spring
with bi-directional rotational stiffness is included therein. In this way, it is possible, from this model,
to study the soil-structure interaction (SSI). Soil stiffness and damping properties were acquired from
the DNV/Risø standards and are used as a comparison. A wind load and an earthquake are used as a
source of vibration for the models. The main objective, then, is to evaluate the impact of three
different conditions through the dynamic response obtained from the two models. From the results, it
can be seen that the responses of the wind turbine in the operating condition are much larger than
those in the parked condition; SSI can greatly affect tower responses; however, does not have a
significant effect on the vibrations occurring in the plane of rotation of the blades. Finally, it is
realized that the amplitude of the response increases with the velocity of the rotor, in general.

OPTIMIZED STRUCTURAL DESIGN OF TUBULAR TOWERS OF WIND TURBINES IN COMPOSITE MATERIAL

Mon, 26 Aug 2024 00:00:00 +0000

The wind energy is an important renewable energy resource, and it has been recently explored
in Brazil, with a strong tendency to increase in the next decades, considering the Brazil's potential. The
most common way to explore the wind energy is through the wind turbines, usually designed to have
the maximum efficiency. The tower is an important part of the wind turbine design, once it defines the
wind turbine efficiency and must be designed to resist to different loadings, responding for 30% of the
wind turbine cost, approximately. The composite materials are an interesting choice to manufacture
tubular towers of small wind turbines, because they present great relations between strength and weight,
and also between stiffness and weight, and they offer more flexibility in the structural design, in
comparison with the conventional materials. This work presents a structural optimization study of
tubular towers of wind turbines in composite materials, within a framework based on the strength of
materials and the principle virtual work for the structural analysis of the tower, besides optimization
techniques, with the goal to minimize the tower’s weight. Some comparisons are made with optimized
steel and aluminum towers. The minimization of the tower’s weight through the employment of
optimization techniques allows a reduction of the costs with inputs, transportation, assembling and
maintenance of the tower, with the intention to make feasible the manufacturing of composite material
towers for small wind turbines, especially those ones that will be installed in remote areas with difficult
access, besides contributing with the study of this technology not much explored in Brazil.

PARAMETER SENSITIVITY ANALYSIS IN STEEL FIBER REINFORCED CONCRETE

Marcello Congro, Fernanda L. G. Pereira, Lourdes M. S. Souza, Deane Roehl — Mon, 26 Aug 2024 00:00:00 +0000

In steel fiber reinforced concrete, the random dispersion of discrete fibers in the cementitious
matrix and the distinct lengths, cross sections and volumetric contents cause deviations in the global
behavior of a given structure. Traditionally, the association of probabilistic and numerical approaches
reproduces the variability effects in the material mechanical behavior. However, the accomplishment
of these simulations is strongly dependent on statistical study of experimental tests. In recent years,
computational intelligence techniques emerge as powerful tools for parameter identification and
calibration in engineering. However, parameter sensitivity analysis is a predecessor stage required for
applying these new concepts into an Artificial Neural Network (ANN). In this sense, this paper presents
a sensitivity study of macroscale parameters in steel fiber reinforced concrete by using the Design of
Experiments (DOE) methodology. This technique is an important method to analyze the influence of one
or more parameters on the given output of the ANN. An experimental database available in literature
provides the input data for the ANN: water-cement ratio, volumetric content, diameter and length of
steel fibers. The parameter outputs are the Young modulus (E), tensile strength (ft) and fracture energy
(G) of the material. Response surface plots are provided in order to identify the relevant experimental
parameters for the description of the mechanical behavior of the composite predicted by the ANN.
Thereby, sensitivity analysis in Artificial Intelligence methods becomes an attractive approach to verify
the mechanical behavior of concrete, establishing the most suitable parameters that will generate a
reliable neural network.

ESTRATÉGIA MULTIESCALA PARA DESCRIÇÃO MICROMÓRFICA DO CONTÍNUO A PARTIR DO CONTÍNUO CLÁSSICO

Leandro Lopes da Silva, Roque Luiz da Silva Pitangueira, Samuel Silva Penna — Mon, 26 Aug 2024 00:00:00 +0000

O comportamento macroscopico dos materiais e função da estrutura que exibem em
nível microscopico. A abordagem fenomenológica adotada na teoria do contínuo classico não
considera o comportamento individual dos constituintes da microestrutura, mas propriedades
macroscopicas efetivas. Por falta de parâmetros microestruturais, esta teoria não descreve
adequadamente materiais com microestrutura complexa ou quando as dimensoes estruturais são
comparativamente pequenas em relação a sua microestrutura. Neste sentido, diversas teorias de contínuos denominados generalizados foram desenvolvidas, incorporando-se o comportamento
microestrutural do meio material. Estas teorias se dividem em dois grupos: (a) as que consideram
gradientes de deslocamento de ordem superior e (b) as que adicionam graus de liberdade
cinematicos as partículas materiais. A teoria do contínuo micromorfico, na qual cada partícula
material possui nove graus de liberdade cinematicos adicionais, representa o caso mais geral
deste segundo grupo. Esta teoria e adequada a análise de materiais cuja microestrutura se deforma
arbitrariamente. A construção heuristica do contínuo micromorfico com base em considerações
termodinamicas (ou no princípio dos trabalhos virtuais) esta bem estabelecida. No entanto, a
identificação das correspondentes leis constitutivas e a determinação do elevado número de
parametros constitutivos limitam a aplicação prática desta teoria. Neste sentido, este artigo
apresenta uma formulação multiescala para obtenção das relações constitutivas micromorficas
macroscopicas a partir da solução de problemas de valor de contorno na microescala segundo

a teoria do contínuo classico. O sistema INSANE ( ́ INteractive Structural ANalysis Environ-
ment), software livre desenvolvido no Departamento de Engenharia de Estruturas da Escola de

Engenharia da Universidade Federal de Minas Gerais, e utilizado na implementação.

NUMERICAL EVALUATION OF MICROPOLAR ELASTIC PARAMETERS FOR A HETEROGENEOUS MICROSTRUCTURE

Raphael A. R. Medeiros, Roque L. S. Pitangueira, Lapo Gori — Mon, 26 Aug 2024 00:00:00 +0000

Materials that, like concrete, possess a heterogeneous microstructure, are characterized by
behaviours at the macroscale that are difficult to be represented with standard continuum descriptions.

Generalized continua models, due to their enriched kinematical description, are well-suited for the repre-
sentation of microstructural effects. The main limitation to the use of generalized models is the presence

of additional material parameters, difficult to be obtained through experiments. The present work deals

with the definition of the two additional parameters of the micropolar continuum theory, using a numer-
ical homogenization strategy. The main aim is, then, to obtain an equivalent micropolar macromedium

starting from a random heterogeneous microstructure. This paper focuses on a homogenization strategy

originally conceived for periodic microstructures, and presents a preliminary investigation on its exten-
sion to randon heterogeneous microstructures. The theoretical aspects are discussed, and some initial

numerical results are presented.

HOMOGENEIZAÇÃO ELÁSTICA DE ALVENARIA UTILIZANDO MECANICA DAS ESTRUTURAS GENE

Francisco P. A. Almeida, Paulo B. Lourenço — Mon, 26 Aug 2024 00:00:00 +0000

A alvenaria e um material compósito formado por unidades e juntas, altamente anisotrópico e de caracterização muito difícil. O presente artigo apresenta de forma inedita a aplicação de mecanica ˆdas estruturas gene (MEG) a homogeneização de alvenarias. Uma vez que se trata de uma técnica semi-
analítica, MEG reduz consideravelmente o custo computacional e mantem a mesma precisão de análises

tridimensionais (3D), por exemplo, pelo metodo dos elementos finitos (MEF). Outras características in-
teressantes sao a possibilidade de obtenção de propriedades 3D a partir da solução de problemas 1D

ou 2D e a nao necessidade de aplicação de condições de contorno. Nos exemplos analisados, são cal-
culadas as constantes elasticas 3D da alvenaria, considerada como material anisotrópico, a partir do
modulo de elasticidade longitudinal e coeficiente de Poisson dos blocos (ou unidades) e das juntas de ar-
gamassa, considerados como isotropicos. Os resultados obtidos s ́ ao comparados com diversos métodos,
numericos ou teóricos, de diferentes autores, inclusive com uma análise 3D do MEF, e apresentam per-
feita concordancia, mesmo para relações entre os modulos de elasticidade dos blocos e da argamassa
grandes. Assim, os resultados apresentados no artigo mostram que o metodo MEG pode ser utilizado
com sucesso na homogeneização de alvenarias e apresenta vantagens com relação a outros métodos para
o mesmo fim.

INFLUENCE OF VOID DISTRIBUTION ON YIELD SURFACES OF POROUS DUCTILE MATERIALS

Wanderson Ferreira dos Santos, José Julio de Cerqueira Pituba — Mon, 26 Aug 2024 00:00:00 +0000

This work deals with numerical simulation of the mechanical behavior of materials composed
of heterogeneous ductile microstructures in presence of voids using a multi-scale approach considering
plasticity processes. This kind of material has been used in several applications as structural solutions.
Therefore, studies about yield surfaces of porous ductile materials are essentials to understanding its
mechanical behavior for safety reasons. The numerical modeling is performed in microstructures using
the concept of RVE (Representative Volume Element) considering the matrix as considered an ideally
plastic material governed by von Mises model with isotropic hardening. Different distributions of voids
are analyzed in order to investigate its influence on the proposed yield surfaces. In general way, the
RVEs containing concentrated void present yield surfaces with lower values when compared to the other
cases therefore the concentration of voids in the RVE decreases its mechanical strength. On the other
hand, the RVEs containing random distributions of voids present yield surfaces with high values and
RVEs containing symmetric distributions of voids present yield surfaces with intermediate values.

CALIBRAÇÃO AUTOMÁTICA DE MODELO NUMÉRICO: ABORDAGEM DE PROBLEMA INVERSO

Mon, 26 Aug 2024 00:00:00 +0000

O modelo Concrete Damaged Plasticity (CDP), implementado no software de elementos
finitos Abaqus, é tipicamente usado para descrever o fissuramento do concreto sob carga mecânica. As
leis de endurecimento e amolecimento são descritas pelo comportamento uniaxial de compressão/tração
do material e pelas leis de evolução de danos. Os parâmetros de plasticidade utilizados no modelo são o
ângulo de dilatação, a excentricidade, a relação entre as tensões de escoamento biaxial e uniaxial, o fator
de forma e a viscosidade. Para que o modelo seja representativo, esses parâmetros devem ser calibrados
com base em resposta experimental. Neste contexto, o objetivo do presente trabalho é realizar uma
análise inversa para calibrar os parâmetros do CDP, bem como as propriedades mecânicas do material
e a condição de contorno a partir de um resultado experimental. A metodologia consiste na atualização
do modelo em elementos finitos por algoritmo genético, implementado em linguagem Python. Os
resultados mostram a influência da escolha dos parâmetros nos resultados e confirmam o potencial da
metodologia aplicada na calibração do modelo em elementos finitos.

DESIGN OF A HIGH-POWER STEEPED PLATE ULTRASSONIC TRANSDUCER

Guilherme Victor Selicani, Flávio Buiochi — Mon, 26 Aug 2024 00:00:00 +0000

High-intensity airborne ultrasonic waves have been used to accomplish several phenomena,
such as defoaming, food drying and agglomeration of aerosol fine particles. In those applications,
circular stepped-plates are often chosen to generate continuous waves due to their high efficiency and
directive radiation patterns. In this study, a high-power stepped-plate transducer is designed for future
investigation of the effects of airborne ultrasonic waves on iron ore flotation froth. The acoustic
energy is generated by a piezoelectric Langevin transducer with a mechanical amplifier coupled to the
stepped circular plate. The finite element method is used to simulate the dynamic behavior of the
device through modal and harmonic analysis. Axisymmetric models are used on a parametric

optimization problem formulated to design the transducer. This problem is solved with a meta-
heuristic (genetic algorithm) employed to determine the set of lengths that define the geometry of the

plate. In this approach, the objective function presented assures the proper vibrational behavior of the
device, given a series of practical considerations. To validate the obtained design, a harmonic analysis
of a three-dimensional model for the stepped plate is used to assess the occurrence of undesirable
modal interactions. The Rayleigh Integral is solved to calculate the acoustic pressure field considering
the vibrational displacements of the plate, obtained by the finite element model. The performance of a
similar transducer with a smaller vibrating surface is presented to establish a general comparison.

DIMENSIONAMENTO OTIMIZADO DE VIGAS DE AÇO E DE CONCRETO ARMADO: ESTUDO COMPARATIVO

Joel Marcos Ozimboski, Zacarias M.C. Pravia, Moacir Kripka — Mon, 26 Aug 2024 00:00:00 +0000

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

DETERMINATION OF ELASTIC PROPERTIES BY MEANS OF FINITE ELEMENT MODEL UPDATING

Mon, 26 Aug 2024 00:00:00 +0000

The range of available 3D printable materials is constantly expanding and unlocking
advanced applications. Thus, the using of 3D printers to manufacture industrial parts is increasing due
to its adaptable manufacturing of complex geometries and reduction in material waste. Especially the
correct adoption of material elastic properties is central to secure and consistent design. However, the
methodologies that allow the researchers characterize the mechanical properties of the parts after the
impression without damage them are scarce. In this way, this paper presents the calibration of elastic
properties by means of a hybrid numerical-experimental methodology that objective the automatic
updating of a finite element model regarding the experimental natural frequency. Here, natural
frequencies were obtained through acoustic tests of a sample of 30x30x30 mm3 with a square periodic
distribution of circular cylindrical holes manufactured by a Fused Deposition Modeling (FDM) 3D
printer. The sample was positioned on a device which simulates the free-boundary condition and excited
by impact using a standard hammer. 10,000 numerical models were processed in ABAQUS and the
calibration was carried out employing a genetic algorithm implemented in Python. Based on
experimental measurements the elastic constants were determined. This proposed methodology presents
high accuracy, the natural frequencies obtained by the calibrated numerical model differed in less than
3% of the obtained ones by the experimental model and could be applied in a wide range of materials.

MULTI-OBJECTIVE TRUSS STRUCTURAL OPTIMIZATION CONSIDERING SIZE, SHAPE AND TOPOLOGY DESIGN VARIABLES SIMULTANEOUSLY

Mon, 26 Aug 2024 00:00:00 +0000

Structural multi-objective optimization problems are common in real-world problems of En-
gineering 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 problems considering the weight minimization (or volume)

with the compliance or the maximum nodal displacement. The constraints refer to the allowable ax-
ial stresses in the bars. Several experiments are analyzed in this paper, presenting their Pareto-fronts

showing the non-dominated solutions. The structural optimization problems consider sizing, shape, and
topology design variables simultaneously, and they can be continuous, discrete, or mixed. One of the
most important steps, after obtaining the Pareto curve, is the definition of which solution or solutions will
be considered after obtaining the Pareto curve. 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).

STRUCTURAL OPTIMIZATION OF DOMES STRUCTURES CONSIDERING AESTHETICAL ASPECTS

Mon, 26 Aug 2024 00:00:00 +0000

Large-scale domes are commonly used in cultural buildings like stadiums, sports gymnasiums,
hangars, and so on. Given a large number of people that interact with the environment, architectural
aspects are desired in the conception of the structure. This paper deals with sizing structural optimization
problems concerning the minimization of the masses of domes considering axial forces, displacements,
and frequencies as the constraints of the problems. It is very common to use tubular cross-sectional areas
of the members in the structural configuration. In this sense, it may be desirable that the bars should have
the same outer diameters for visual comfort as well as aesthetical aspects. For instance, the designer
may set just one outer diameter as the design variable. Thus limiting the maximum number of different
thicknesses, also as design variables, to be used in the optimized structural configuration. The analyzes
of the domes involve bending and torsion moments. Also, it can be attractive to use a reduced number of
distinct cross-sectional areas minimizing costs of fabrication, transportation, storing, checking, welding,
and so on. As a result, it is expected a labor-saving when the structure is welded, checked, and so on.

REGULARIZED SOLUTION FOR STRUCTURE HEALTH MONITORING

Mon, 26 Aug 2024 00:00:00 +0000

Structural damage is a key concern for several areas in civil engineering sector (buildings,
bridges), mechanical engineering, aerospace sector (aircrafts, rockets, satellites), automotive sector, and
many other Therefore, the structure health monitoring is an important topic research and operation. The
structural damage identification can be addressed as an inverse vibration problem. This inverse problem
can be formulated as a generalized least square problem, where the stiffness matrix must be identified in

order to have a best matching between measurements and the mathematical model added to a regulariza-
tion operator. We solve the forward problem using finite element method, and an entropic regularization

is also applied to the cost function. The optimization problem is solved by using a hybrid method, com-
bining a stochastic metaheuristic with a local searching method. The Multi-Particle Collision Algorithm

(MPCA) is the metaheuristic technique and the Hooke-Jeeves (HJ) direct search method complete the
hybrid optimizer. The proposed methodology is applied to different study cases showing good results. A
cantilever beam is the testing structure for the developed approach.

MULTIOBJECTIVE OPTIMIZATION OF REINFORCED CONCRETE BUILDINGS

Estevão A. Bandeira, Yuri Farias da Silva, Valério Silva Almeida — Mon, 26 Aug 2024 00:00:00 +0000

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 tall 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.

INVERSE PROBLEM IN DAMAGE IDENTIFICATION OF A HELICOPTER’S ROTOR BLADE USING BAT ALGORITHM

João Artur Souza Chaves, Dr. Guilherme Ferreira Gomes — Mon, 26 Aug 2024 00:00:00 +0000

In this study, a damage detection method is proposed using the bat optimization algorithm
and vibration data simulated in CAE software. The method was applied in a helicopter rotor blade
based in the AS350’s rotor blades. The rotor blade was modeled and simulated in ANSYS APDL®, the
modal solution was exported to MATLAB® and then the algorithm was applied to optimize the
objective function defined by the authors. Three objective functions of displacement in the three axis
were used and theirs results were compared. The numerical results show that the method is reliable
and adequate for practical application in the industry.

OTIMIZAÇÃO SIMULTÂNEA DO CUSTO E DA CONSTRUTIBILIDADE DE PILARES EM CONCRETO ARMADO

Moacir Kripka, Victor Yepes, Tatiana Garcia-Segura — Mon, 26 Aug 2024 00:00:00 +0000

Structural design, in general, consists of an iterative process developed with base on the
intuition and previous experience of the designer. This strategy makes the design exhaustive and
makes difficult to obtain the best solution. In addition, usually only one design criterion is adopted,
being usually cost or weight. If other issues are considered, such as the environmental impact or
construction facility, a more complex problem need to be solved. In such context, the aim of this work
is to present the development and implementation of a formulation for obtaining optimal sections of
reinforced concrete columns subjected to uniaxial flexural compression, taking as objectives the
minimization of the cost and the maximization of the constructability. The constraints of the problem
are based on the verification of strength proposed by the Brazilian code ABNT NBR 6118/2014. To
the optimization of the column section, Simulated Annealing optimization method was adopted, in
which the amount and diameters of the reinforcement bars and the dimensions of the columns cross
sections were considered as discrete variables. The total cost is composed of the cost of steel bars,
concrete, and formworks, and the maximization of constructability is obtained by minimizing the total
number of steel bars. The optimized sections were compared to those obtained considering only the
cost as the objective function. To the example considered, it was observed that a significant reduction
of the number of steel bars can be achieved with a small increase on the section cost.

DEVELOPMENT OF AN AIDING TOOL FOR THE OPTIMAL DETAIL OF ACTIVE REINFORCEMENT USING GENETIC ALGORITHM

Victoria Carino Neves, Guilherme Coelho Gomes Barros — Mon, 26 Aug 2024 00:00:00 +0000

The aim of this paper is to present the development of an auxiliary tool for the optimal de-
tail of active reinforcement on a prestressed concrete section. To achieve it, the methodology considers

normative requisites and the tension required at the most critical section of the beam. The problem of
optimization seeks to minimize the volume of steel while satisfying the conditions of minimum cover and

spacing between reinforcement cables. Design variables are the number of strands per cable and the po-
sition of each cable within cross section. Due to the nature of the variables and the constraints involved,

genetic algorithm seems to be the most suitable optimization procedure. Hence, the proposed methodol-
ogy is implemented using the native implementation of genetic algorithm of MATLAB, a broadly used

computer program in academy. The developed tool allows to detail different sections, since it treats the
cross section as a general polygon. Thereby, it allows exploitation of new sections for future projects,
as well as assisting in the time of design. It is worth mentioning that a complete automated prestressed
concrete executive project is still far down the road. Numerical examples are analyzed to demonstrate
the efficiency of the presented tool and to illustrate it’s usage in a actual life design process.

GENETIC ALGORITHMS FOR MULTI-THRESHOLDING OPTIMIZATION FOR MRI SEGMENTATION

Mon, 26 Aug 2024 00:00:00 +0000

Image segmentation is an essential task in image processing that aims to simplify and/or
change its representation for easier analysis. Medical images of the brain are extremely important in
the detection and diagnosis of diseases, as well as relevance in research in the biological area. In this
article, an approach for the segmentation of brain images is proposed, using the method based on
genetic algorithms with multiple thresholds, in order to find thresholds that optimally separate gray
matter, white matter and cerebrospinal fluid in cranial images. The most appropriate threshold
parameters were identified in order to obtain the best possible solution for image segmentation.
Magnetic resonance imaging of 10 patients was obtained from the National Center for Image Guided
Therapy database. Next, a preprocessing was established to improve the input images in the
segmentation algorithm. It was based on the application of multi-threshold image segmentation, which
aims to maximize intra-class variation between object(s) and background, as well as the minimization
of inter-class variation, i.e. between background pixels among pixels of objects, then obtaining the
tissues of interest. The genetic algorithm proved to be an efficient method to obtain optimal values for
the thresholds, so it is possible to perform segmentation of the image showing the brain tissues of
interest.

PREDICT STAGE OF DIABETIC RETINOPATHY USING DEEP LEARNING

Mon, 26 Aug 2024 00:00:00 +0000

The diabetic retinopathy (DR) is one of main complications of diabetes mellitus (DM),
presenting in about 40% of diabetics and being the leading cause of blindness in 16 to 64 years old
people.The DR is caused by damage to the blood vessels. The diagnosis is given through analysis of
images generated by retinoscopy, that is an easy operating electronic device. Despite this, in the
Brazilian National Unified Health System (SUS), the access to this type of medical assessment
specialized is still poor, resulting in long queues until an ophthalmological consultation. The latest
Brazilian Diabetic Society Guideline recommends annual evaluations for DR in diabetic patients, a
non-realistic scenario for SUS patients. In view of this, a screening tool that could predict the RD and
that could be used by primary care practitioners could be an awesome public health solution. Then, we
presenting a deep learning framework (DLF) to classify DR stages. In this paper, we will perform the
entire DLF cycle: data collection, data preparation, model creation and validation. The main novelty is
the use of siamese convolutional neural network (SCNN), which will receive input pairs of eye fundus
images.The purpose of using this set of tools is to use the layers to extract the main characteristics of
the inputs of each neural network, so the weights of layers are shared and the similarity degree
between neural networks outputs are measure. We train this network using a high-end graphics
processor unit (GPU) on the publicly available Messidor dataset and, with this approach, we expect
better results in predicting the DR stage when compared to others works.

A COMPARISON OF DIFFERENT CLASSIFICATION STRATEGIES IN MEDICAL IMAGES OF SPECULAR MICROSCOPY TO DETECT GUTTAE IN EARLY STAGES OF FUCHS’ DYSTROPHY

Mon, 26 Aug 2024 00:00:00 +0000

Fuchs’ endothelial dystrophy, or Fuchs‘ dystrophy, is a slowly progressive corneal disease
that usually affects both eyes. Although in many cases early signs of the disease can be seen in people
aged 20-30, the disease rarely affects vision until the person reaches the age 50-60. The tests to diagnose
the disease are: Biomicroscopy, and Specular Microscopy. In both cases, it is possible to find the
morphological changes characteristics of the disease. In this context, this paper compares the use of
three distinct machine learning techniques to perform the Fuchs‘ dystrophy diagnosis on Specular
Microscopy images in order to reduce the time spent in a manual analysis of the specialist. The
approaches used in this work were: Convolutional Neural Networks (CNN); Support Vector Machines
(SVM) with features extracted from Histogram of Oriented Gradients (HOG) and by Speeded Up Robust
Features (SURF). The dataset consists of 123,200 images of both eyes of different people, obtained over
9 years at Hospital Evangélico de Vila Velha, Espírito Santo, Brazil. Due to the absence of labels in the
original dataset, only 2400 images were analyzed and labeled with the help of a specialist. In this subset,
only in 1165 exams the Fuchs’ dystrophy is present. A cross-validation approach using 10-folds was
performed and the results were evaluated through the accuracy, area under the Receiver Operating
Characteristic (ROC) curve, precision, recall and F1 score metrics with the CNNs outperforming the
other methods.

MASK R-CNN APPROACH TO DETECT HEALTHY VEGETATION AREAS IN NIR IMAGES

Rhynner Hugo Richelly Silva Santos, Flavio Garcia Pereira, Daniel Cruz Cavalieri — Mon, 26 Aug 2024 00:00:00 +0000

With the development of new technologies in the field of deep learning, sectors such as agri-
culture have been benefited from the application of intelligent systems allied to the use of UAVs (Un-
manned Aerial Vehicles) in crop monitoring to quickly and accurately detect specific areas of vegetation

and optimize decision making to ensure the quality of planting. Some researchers inspired from the
deep learning advance and its success in many areas have been studied solutions in detection of healthy
vegetation areas, but, how better are the performances of advanced techniques compared to traditional
techniques? In this context, this paper presents a comparison between a traditional technique (K-Means
Clustering) and advanced technique (Mask R-CNN) applied to detect different vegetation areas in NIR

images. The database of this work consists of NIR images provided by a modified RGB camera in-
stalled in a UAV. Basically, as an input were used NDVI (Normalized Difference Vegetation Index), an

important index of vegetation healthy, obtained from the NIR images. Finally, a comparison between the
proposed algorithms for detection of healthy vegetation areas is presented, showing the improvements of
the proposed Mask R-CNN algorithm.

REV ANALYSIS FOR CARBONATE ROCKS USING PNM FROM MICRO-CT IMAGES AND NMR T2 DISTRIBUTION

Mon, 26 Aug 2024 00:00:00 +0000

Reservoir studies have reached a great advance in the last years with the introduction of
microtomography (micro-CT) images of rocks. This technology is a non-destructive method that allows
the investigation of internal structure of rock in pore scale, and to build representative 3D models of the
rock. With the purpose to retrieve representative petrophysical properties from these digital models, the
objective of this work is to apply a Representative Elementary Volume (REV) analysis for the
heterogeneous carbonates, considering threshold values, image resolution and NMR pore-size
distributions, to estimate porosity and permeability REVs. In this study, carbonate rock samples,
Coquina and Edwards Brown, were submitted to three main laboratory measurements: routine core
analysis, NMR experiments, and microtomography scans. The micro-CT images were processed using
a commercial image processing software. The threshold selection analyzed by applying three methods,
but the NMR pore-size distribution oriented threshold was used to proceed with the entire workflow.
Skeletons were extracted from pore space binarized in the micro-CT image and exported to PoreFlow
for the generation of Pore Network Models (PNM) and permeability estimation. The permeability of the
PNMs were estimated considering Hagen-Poiseuille Law to simulate single-phase flow and Darcy’s
Law. This methodology was applied to three samples of different sizes, their volume was further divided
into smaller sub volumes and their relation with REV were analyzed. The rock samples studied could
be considered, with a high confidence, as REV for porosity, but only the larger samples could be
considered as REV for permeability.

OBTAINING PORE-SIZE DISTRIBUTION BY IMAGE ANALYSIS OF STACKS WITH LARGE IMAGE SPACING WITHOUT RESIZING

Mon, 26 Aug 2024 00:00:00 +0000

The characterization of porous media is a crucial process to study the flow in porous
structures and the pore-size distribution (PSD) is a fundamental parameter to perform this
characterization. The PSD describes the porous volume fraction of each different pore-size. The PSD
is usually estimated by laboratorial tests, which have long durations and may be sample destructive.
Yang and collaborators developed an alternative capable to estimate the PSD of porous media by
image analysis, which has a fast result and preserves the sample. The method requires the digital
reconstruction of the porous medium by creating a stack of images that should be spaced by a length
equal to the pixel size used on these images. To overcome this problem, Yang suggests to resize the
image stack to match the image spacing to the pixel size, which reduces the image stack resolutions
and increase the errors. To avoid the resizing procedure and its consequences, this paper tested three
different approaches: the first one consisted in using the method proposed by Yang and collaborators
without resizing the images; the second approach consisted in approximating the pores to spheres and
analytically calculate their volumes; and the last approach was to approximate the pores to prolate
spheroids and analytically calculate their volumes. The results showed that the first and second
approaches were more efficient than the resizing alternative and that the third approach could be used
to improve the results from the other two approaches.

IMAGE DENOISER ENHANCEMENT VIA GENETIC ALGORITHMS

Mon, 26 Aug 2024 00:00:00 +0000

Image processing is becoming a more open and extended field, with endless possibilities
and meaningful applications, specially for medical images. There, a point that brings much interest is
the X-ray imaging, which are generated by sending high-frequency electromagnetic radiowaves, and
then retrieving them in a metal plates that they will collide with. But those metal plates might receive
electromagnetic interference or uncontinuous radiowaves, causing image noise, which are inevitable.
That noise can be decreased by image filters. Although those filters have become standard and work
well, their parameters values are static, even though there are many possible parameters values and
each image will have different denoise results with different values. This articles descibres the use of
Genetic Algorithms to find the best parameters with fewer processes. GA are heuristic search
procedures based on natural selection. Only the algorithms that give the best results will generate other
algs, decreasing the number of processes needed. The method uses Genetic Algorithms to find best
parameters according to each image for the “Non-Local Means” denoise filter from the OpenCV
Python library. The X-ray images used in were Optical Coherence Tomography of people with
Pneumonia, published on the online database Mendeley by the University of San Diego California,
and tested on the Python scripts implementations. By the results obtained, it was noticeable the
positive correlation between the filter parameters chosen by the GA for each given image and the
improvement of image denoise from the classical methods, proving that Genetic Algorithms are great
for such applications, decreasing the number of processes needed to find the the best parameters for
any input.

USE OF GENETIC ALGORITHMS TO AUXILIATE VEHICLE PLATE DETECTION IN IMAGE SEGMENTATION USING OPENCV

Mon, 26 Aug 2024 00:00:00 +0000

One of the fundamental steps of image processing is the segmentation of images, which
aims to partition the image in a way that makes data analysis and extraction simple. In this article, a
method is proposed that performs the segmentation of images, using multiple thresholds, through
genetic algorithms to find the contours of a car's plate. For this, the algorithm should validate a set of
characteristics that define a region as being a car plate. Identify optimal threshold parameters in order
to obtain the best possible solution for image segmentation and detection of vehicular plaques. The
methodology used consists of the bibliographic review of an image segmentation article on Genetic
Algorithm Application for the Evolution of Parameters for Image Segmentation and an article on the
detection of vehicular plaques using Python and OpenCV. The employee image bank was obtained
from a public repository of images. The parameters that will be estimated to validate whether or not a
given object is detected on a board are: the board's outline and the presence of alphanumeric
characters. In this way, it will be possible to optimize detection efficiency by eliminating false positive
results, such as image contours that do not correspond to the plates. The segmentation of the image through multi-thresholds occurred and it was possible to identify vehicle plates in the image with
greater precision.

A CONVOLUTIONAL NEURAL NETWORK-BASED APPROACH FOR VISUAL QUALITY INSPECTION OF READY-TO-EAT CRISP LETTUCE LEAVES

Wilson David Marques, Sidnei Alves de Araújo — Mon, 26 Aug 2024 00:00:00 +0000

Among the leafy vegetables, lettuce is considered a product of great importance, especially
in the context of healthy eating. The species Lactuca sativa var. crispa, or crisp lettuce, is one of the
most produced and consumed vegetables in Brazil. Packaged lettuces have represented a new marketing
model and have been gaining space in the final consumer's table. As they are minimally processed to be
ready for consumption, there may still exist points of dirt or rot in the leaves due to failures in the visual
inspection process that is conducted manually, and consequently the possibility of contamination of the
product. This work presents an approach for automatic visual inspection of the quality of ready-to-eat
crisp leaf lettuce. To this end, we employed computer vision methods and a convolutional neural
network (CNN) that was trained with two databases, one composed by 12400 sub-images (windows) of
30×30 pixels and another composed by 2560 sub-images of 50×50 pixels. These sub-images were
extracted from healthy parts of lettuce leaves and parts containing the major defects (burnt edges,
putridity, and dirt and pest infestation). In the experiments conducted, the databases were enlarged
during the training phase of the CNN employing the data augmentation technique, which increases the
training set in about 1000 times. To evaluate the proposed approach two other databases containing 4211
and 1551 of sub-images were employed. For the 30×30 and 50×50 sub-images, the average hit rates
were 96.1% and 91.6%. These results demonstrate the feasibility of the proposed approach and indicate
that smaller windows provide better CNN performance.

COMPUTER VISION BASED APPROACHES FOR BEAN DEFECTS DETECTION

Peterson Adriano Belan, Robson Aparecido Gomes de Macedo, Sidnei Alves de Araújo — Mon, 26 Aug 2024 00:00:00 +0000

In this work are proposed computer vision approaches to detect three of the main defects
found in beans: broken, bored by insect (Acanthoscelides obtectus) and moldy. In addition, we describe
a fast and robust segmentation step that is combined with the proposed approaches to compose a
computer vision system (CVS) applicable to the Brazilian beans quality inspection process, to determine
the type of the product. The proposed approaches constitute an important practical contribution since,
although there are some papers in the literature addressing visual inspection of beans, none of them deals
with defects. In the conducted experiments a low-cost equipment, composed by a table made in
structural aluminum, a conveyor belt and an image acquisition chamber, was used to simulate the
characteristics of an industrial environment. The CVS evaluation was performed in two modes: offline
and online. In the offline mode, a database composed by 120 images of bean samples containing grains
of different classes and with different defects was employed, while in the online mode the grains
contained in a batch were spilled continuously in the conveyor belt of the equipment for the proposed
CVS to perform the tasks of segmentation and detection of defects. In the experiments the CVS was
able to process an image of 1280×720 pixels in approximately 2 s, with average hit rates of 99.61%
(offline) and 97.78% (online) in segmentation, and 90.00% (offline) and 85.00% (online) in detecting
defects.

A CONVOLUTIONAL NEURAL NETWORK-BASED APPROACH FOR DETECTION OF OBJECTS AND SCENARIOS SUSPECTED OF BEING POSSIBLE BREEDING SITES OF AEDES AEGYPTI MOSQUITO

Daniel Trevisan Bravo, Wonder Alexandre Luz Alves, Sidnei Alves de Araújo — Mon, 26 Aug 2024 00:00:00 +0000

In remote sensing field, the use of satellite images to detect small objects becomes impractical
due to the low spatial resolution of such images. With the use of unmanned aerial vehicles (UAVs),
popularly known as drones, it is possible to acquire aerial images with high spatial and temporal
resolutions that allow the detection of small objects on the earth's surface and the perception of changes
in a certain region in a short period of time. However, the detection of certain objects in the images
acquired by UAVs has been a great challenge due to the amount of details present in these images,
especially those acquired in urban areas. This work investigates the automatic detection of objects and
scenarios in aerial images acquired by UAVs. The proposed approach aims to detect target objects
(typical containers for water storage) and scenarios suspected to be possible breeding sites of the Aedes
aegypti mosquito. For the detection of the objects and scenarios, two convolutional neural network
(CNN) architectures from the YOLOv3 framework were employed. In the experiments conducted, we
considered 142 images acquired in peripheral regions of the city of São Paulo/Brazil containing water
tanks; 25 images of real scenarios, obtained by Google image search, containing garbage and old tires
and 35 images containing scenarios simulating the main mosquito breeding sites (old tires, gutters,
among others). In the experiments performed, in which the proposed approach was evaluated using the
mean average precision (mAP), the rates of 0.95 and 0.97, respectively, were obtained for the detection
of objects and scenarios, indicating that the proposed approach is a good alternative to solve the
investigated problem.

MODELAGEM DE PROTÓTIPOS PARA SISTEMAS REAIS

Mon, 26 Aug 2024 00:00:00 +0000

Models represent physical phenomena mathematically. Through it, it’s possible to obtain

mathematical expressions that describe the behaviour of the real system, allowing, for example, to simu-
late its evolution in time as a response to some input stimulus without actually operating the real system.

They also allow the creation of control laws that are mathematically correct and adequate to the system,

allowing the development of formally correct and performant controllers. In this study, a system of cou-
pled tanks, present in CEFET Campus V’s Signals and System Analysis laboratory, was modelled in 6

different configurations. The system is composed of 4 water tanks, two on the top shelf and two on the
bottom, with valves that allow the water to flow to its sibling or the one directly below it. The valves

allow the user to chose how the water will flow through them. We developed a model for each configura-
tion using physical laws of water flow in cylindrical recipients and estimated the values of the constants

through tests. The models are represented using state-space, as it allows to identify the dynamics of
the system internal energy, as well as the use of modern control techniques. Each model was validated
against the real system to measure its correctness. The models obtained are available for students of the
laboratory, both undergraduate and postgraduate, to streamline the study of system analysis and control
theory.

ESTUDO COMPARATIVO SOBRE CLASSIFICAÇÃO DE LESÕES DE PELE COM RNA-MLP E SVM

Gilson Saturnino dos Santos, Alex F. de Araujo — Mon, 26 Aug 2024 00:00:00 +0000

Technological evolution, evidenced in recent years, has contributed significantly to both
Artificial Intelligence (AI) and Digital Image Processing and Analysis (DIP) areas. Several
computational methodologies can be found in the specialized literature, with different applications, such
as the classification of skin lesions from dermatoscopic images. Although the initial analysis of skin
lesions is based on a set of visual rules known as the ABCD rule (Asymmetry, Borders, Color and
Diameter), the performance of this visual analysis is influenced by factors such as variation of
illumination during capture of the image, the presence of artifacts that cause noise, and the visual
fatigue of the specialist during image analysis. A mistaken initial analysis may lead to delays in the
elaboration of an adequate treatment plan, affecting the effectiveness of this treatment. The
interdisciplinarity between AI and DIP has produced good results when the algorithms are intended for
specific applications and use a priori knowledge based on the problem addressed. In this context, this
work presents a comparative study between the classification methodologies based on Artificial Neural
Networks (ANN) and Support Vector Machine (SVM), using the existing knowledge about the visual
evaluation of skin lesions as knowledge base a priori to train these classifiers. In general terms, it is
expected to better understand the performance of these two AI techniques when applied to classify
skin lesions in malignant and non-malignant, evaluating the performance of each methodology. To
perform this work we used the Weka tool, with the implementation of Artificial Neural Network
(Multilayer Perceptron) and Support Vector Machine (Sequential Minimal Optimization). The dataset
used has 200 examples and 14 attributes. The methodology used was Stratified Cross-Validation in 10
parts. The parameters of each algorithm were defined as standard in the tool. The results obtained
were promising, showing the relevance of the AI algorithms to skin lesion classification and the
relevant features of the Weka to improve the quality of the classification modeling solutions.

PHYSICAL REFLECTIVE BOUNDARY CONDITIONS APPLIED TO SMOOTHED PARTICLE HYDRODYNAMICS METHOD FOR SOLVING THREE-DIMENSIONAL FLUID DYNAMICS PROBLEMS

Mon, 26 Aug 2024 00:00:00 +0000

The mixing of continuum and microscopic laws is a contradiction often existing in the
boundary conditions utilised in meshfree particle methods. Boundary techniques employing fictitious
(or ghost) particles and artificial forces (defined in the molecular microscopic scale) are still used in
SPH simulations and should be avoided. Currently, there is an effort in replacing boundary techniques
that mix concepts of different scales by others that respect the continuum laws. This paper aims to
present the implementation of the physical reflective boundary conditions (RBC) in Smoothed Particle
Hydrodynamics (SPH) method for solving three dimensional (3-D) fluid dynamics problems. In this
work, SPH was applied to solve the physical conservation equations for a Newtonian, incompressible,
uniform and isothermal fluid. Applications in hydrostatics and hydrodynamics are presented as well as
the validation of the results in 3-D domains. Two problems were studied: a still fluid inside an
immobile reservoir and dam breaking flow. The results achieved presented a good agreement with the
analytical solution and literature data.

A COMPARISON BETWEEN SMOOTHED PARTICLE HYDRODYNAMICS (SPH) AND MOVING PARTICLE SEMI-IMPLICIT (MPS) METHODS FOR DAM-BREAKING EVENT

Rubens A. Amaro Jr, Liang-Yee Cheng, Sergei K. Buruchenko — Mon, 26 Aug 2024 00:00:00 +0000

Lagrangian particle-based methods have opened new perspectives for the investigation of
complex problems with large free-surface deformation. Some well-known particle-based methods
adopted to solve non-linear hydrodynamics problems are the smoothed particle hydrodynamics (SPH)
and moving particle semi-implicit (MPS). Both methods modeled the continuum by a system of
Lagrangian particles (points) but adopting distinct approaches for the numerical operators, pressure
calculation, and boundary conditions. Despite the ability of the particle-based methods in modeling
highly nonlinear hydrodynamics, some shortcomings, such as unstable pressure computation and high

computational cost still remains. In order to assess the performance of these two methods, the weakly-
compressible SPH parallel solver, DualSPHysics, and an in-house incompressible MPS solver are

adopted in this work. Two test cases consisting of 3D dam-breaking problems are simulated and wave
heights, pressures and forces are compared with available experimental data. The influence of the
artificial viscosity on the accuracy of SPH is investigated. Computational times of both solvers are
also compared. Finally, the relative benefits of the methods for solving free-surface problems are
discussed, therefore providing directions of their applicability.

SIMULAÇÃO NUMÉRICA DE TRATAMENTO PARA CÂNCER COM ˆHIPERTERMIA E ESTIMATIVA DO DANO UTILIZANDO MALHA OCTREE

Andre Valente , Felipe Loureiro, Franciane Conceição Peters, Webe Joao Mansur — Mon, 26 Aug 2024 00:00:00 +0000

Tratamentos com hipertermia para cancer estão se tornando cada vez mais objeto de pesquisas.
Nestes tratamentos o aumento correto da temperatura no tecido vivo deve ser eficiente para causar um
dano irreversível apenas ao tecido doente, mantendo íntegro o saudavel. Este trabalho apresenta o desen-
volvimento de uma formulação baseada no MVF usando malhas OcTree que visa simular o tratamento

com hipertermia por injec ̧ao de nanopartículas diretamente no tumor e estimar o dano causado. Um mod-
elo 3D com o uso da equaçã não linear de Pennes e empregado para simular a transferência de calor

em tecidos vivos com a presença de um tumor. A malha OcTree e utilizada devido a sua simplicidade
e capacidade de refinamento local. Um exemplo numerico simples e analisado, validando o algoritmo
proposto e mostrando a eficiencia do esquema.

A parallel implementation of a thermoregulation model using the finite element method

Mon, 26 Aug 2024 00:00:00 +0000

This paper presents a parallel implementation of a thermoregulation model using the finite ele-
ment method to perform numerical analyses of brain cooling procedures in neonates and adults. The par-
allel method was designed for hybrid parallel machines, which is the case of PC clusters with multicore

processors connected via a local network. Compressed data structures are used to store the coefficient
matrices and obtain iterative solutions in a subdomain-by-subdomain approach. The MPI standard is

used for distributed memory interprocess communication and for shared-memory, with intranode com-
munication being performed simulating a virtual distributed-memory system in a multicore hardware.

The method is used in a FEM package applied to the solution of the continuum bioheat Pennes equation

with a blood pool approach for arterial temperature changes. The efficiency of the parallel implemen-
tation is tested in two different platforms using a complex three-dimensional geometry obtained from

computed tomography medical images.

UM ESTUDO SOBRE O COMPORTAMENTO MECÂNICO DE TECIDOS TENDINO- SOS VIA ABORDAGEM DE HOMOGENEIZAÇÃO COMPUTACIONAL

Bruno Klahr, Mauricio Lazzari, Thiago A. Carniel, Eduardo A. Fancello — Mon, 26 Aug 2024 00:00:00 +0000

The present manuscript provides a numerical investigation on the multiscale behavior of ten-
don tissues employing a computational homogenization approach. The numerical approach used is for-
mulated considering a variational framework, finite kinematics and based on the concept of representative

volume element (RVE) of the material. Since tensile tests are broadly applied to assess the mechanical
responses of tendons, a proper multiscale boundary condition is used aiming to recover the mechanical
states obtained by such experimental tests. The macroscopic results (homogenized quantities) and the
microscopic ones (stress and strain fields of the RVE) are retrieved from a three-dimensional RVE of
a tendon fascicle designed based on experimental observation. The following aspects are investigated:
evolution of the macroscopic volume of the tissue under physiological strains; microscopic kinematic
fields; strain localization in the cells.

COMPARATIVE STUDY OF EXTRAMEDULLARY OSTEOSYNTHESIS FOR TIBIAL PLATEAU FRACTURES: A FINITE ELEMENT ANALYSIS

Mon, 26 Aug 2024 00:00:00 +0000

This study presents a comparative structural finite element analysis of two different fixa-
tion methods for high energy tibial plateau fractures: through conventional plates and screws and using

blocked plates with locking head screws. The project consists on the modelling of the assemblies in a
CAD environment based on the images from a computed tomography (CT). Autodesk Fusion 360
c was
used to perform the CAD step. Afterwards, finite element analysis was performed in both assemblies.
This type of analysis allows a great modelling versatility and also a great level of correlation between its
results and the expected physical behaviour of the structure evaluated. Altair HyperWorks

c was chosen

to pre-process and post-process the analysis and Abaqus CAE

c for solving. The comparison parameter
chosen to drive the results is the displacement of the bone fragments over the fracture border. Smaller
relative displacements between the bone fragments are desirable for a shorter recovery time, since this
condition provides the required stability for the bone to regenerate and consolidate without defects. The
model was built considering the boundary conditions foreseen in specific bibliography and submitted to
a vertical compressive load of 3224,5 N. The osteosynthesis of blocked plates with locking head screws
showed the best results since it presented inferior relative displacements over the fracture border.

MODAL ANALYSIS OF A HUMAN LUMBAR SPINE BY EULER-BERNOULLI BEAM THEORY

David Santos de Castro, Jose Pereira Ramos Junior, Simone dos Santos Hoefel — Mon, 26 Aug 2024 00:00:00 +0000

Human lumbar spine supports most of loads arising daily activities. Those loads are mainly
dynamic or periodic, therefore, an accurate study of free vibration of this structure can lead to a better
understanding the behavior of the system. In anatomical point of view, there are five lumbar vertebrae
in a human lumbar spine, two adjacent vertebral body are separated from each other by upper end plate,
intervertebral disc and lower end plate. Each part of the column has a unique structure. In this paper, an
analytical approach to study free transverse vibration of a human lumbar spine as a segmental multi-layer
beam by the classical beam Euler-Bernoulli theory is developed. A uniform transverse section of lumbar
spine is considered and the material properties are composed of different mechanic parameters. Free
vibration is analyzed considering different material properties, in order to simulate the aging process.
Continuity and equilibrium conditions are imposed as boundary conditions throughout the junctions of
the segments. Those conditions are in terms of displacement, slope, shear force, and bending moments.

INVESTIGATION OF THE EFFECT OF NOZZLE DESIGN ON RHEOLOGICAL BIOPRINTING PROPERTIES USING COMPUTATIONAL FLUID DYNAMICS

Mon, 26 Aug 2024 00:00:00 +0000

Bioprinting is the utilization of techniques derived from three-dimensional printing to
generate complex bio-logical structures which may replace natural tissues or organs. It employs high
spatial resolution deposition of different cell types, growth factors and biomaterials. Those together
form bioinks, which are the bioprinting inputs, analogously to conventional inks with regard to inkjet
printing. In extrusion bioprinting, continuous bioink filaments are deposited layer by layer on a surface
by means of an extruder nozzle, employing the displacement of a piston or pneumatic pressure. If
mechanical stresses applied on a cell membrane exceed a critical value, which depends on the cell
type, the cell membrane may disrupt. Computational fluid dynamics (CFD) simulations of the bioink
extrusion were done to evaluate shear stresses caused by the internal pressure of extruder nozzles
during bioprinting. Different three-dimensional conical nozzle designs were tested by varying angles
of convergence, lengths, input diameters and output diameters of the nozzles. The power-law model,
with constants k = 109.73 Pa·s0.154 and n = 0.154, was used to describe the expected non-Newtonian
behavior of the bioink. Shear stresses and shear rates were evaluated for each nozzle design
considering different pressures or velocities as boundary conditions at the nozzle entrance. The
maximum wall shear stress value on each different nozzle varied between 1,038 Pa and 4,915 Pa. The
results indicated which details of nozzle geometry are most relevant in order to optimize bioprinting.
The best conditions for bioink rheology were also evaluated to ensure good printability and high cell
viability.

MODELO COMPUTACIONAL DA ARTICULAÇÃO GLENOUMERAL

Mon, 26 Aug 2024 00:00:00 +0000

The development of the shoulder model was based on the information acquired from clinical
exams of a subject and from the literature data. The forces acting on the joint are the arm weight, the
muscle forces, the reaction forces due to the muscle wrapping and the joint reaction force. The amplitude
of these forces were obtained from a mathematical approach in which the objective is the determination
of the lowest forces that the muscles should exert to stabilize the glenohumeral joint. These forces were
then applied on the FE model on Abaqus. The analysis was performed in static positions of 0°, 30°, 60°,
90° and 120° of abduction with the arm in 90° of external rotation. The joint reaction force magnitude
increases up to 690 N at 90o of abduction and decreases at 120o, showing the same trend observed in
other studies. The muscle forces are consistent with the information found in the literature, where there
is a high activation of the subscapularis, possibly due to the absence of the passive stabilizers, and the
deltoid. The articular contact center is initially located in the central region of the glenoid cartilage and
moves in the superior-anterior direction up to 60o of abduction, moving then to the central-anterior
region. The maximum contact pressure is observed at the 60o of abduction and the translation of the
humeral head remains within a sphere with a diameter equal to 3.1 mm, whose center coincides with the
center of the articular surface of the glenoid cartilage.

Um modelo constitutivo variacional com anisotropia induzida para tecidos biológicos moles

Francisco Luiz Bresolin, Jakson Manfredini Vassoler — Mon, 26 Aug 2024 00:00:00 +0000

Viscoelasticity, strongly nonlinear behavior, and damage are commonly observed mechanical
behavior exhibited by most soft biological tissues. Also, tendons, arteries and skin can progressively
show lower extensibility during increasing stretches, which may be referred to strain orientation effects.
In addition, due to its internal organization, experimental observations have shown that finite strains
induce a directional history-dependent organization of the fibers. In order to account these mechanical
behaviors, in this work, a variational micromechanics-inspired constitutive model is presented. This
model is based on the full-network approach with a viscous and a damage internal variable. Some
numerical tests are presented to evaluate the constitutive model capabilities in order to represent soft

biological tissues. The results have shown that the model is capable of representing the anisotropic-
induced behavior observed in soft biological tissues.

UM ESTUDO DE MODELOS MATEMATICOS BIFÁSICOS PARA TECIDOS BIOLÓGICOS MOLES SOB GRANDES DEFORMAÇÕES

Jonatas Stefanello Fagundes, Jakson Manfredini Vassoler — Mon, 26 Aug 2024 00:00:00 +0000

Several biological tissues present a considerable percentage of their weight constituted by
fluid, which directly impacts on its mechanical behavior, mainly due to viscous effects. An appropriate
approach for the description of this material is the biphasic theory, in which the intrinsic mechanical
properties of each phase, as well as their interactions, are taken into account. Therefore, this work has
the objective of evaluating if biphasic models found in the literature are capable of representing the
mechanical behavior of soft biological tissues in large deformations. The biphasic theory was used to
describe the tissue as a continuous mixture of two incompressible phases: a hyperelastic solid phase,
and an inviscid fluid. Finite element formulations, based on mixed elements and penalty technique, were
implemented. The computational cost and accuracy of results were evaluated for an isotropic tissue in
the case of a confined compression. An anisotropic constitutive relation for the solid phase was also
studied under traction for fiber-reinforced biological tissues. The results for the confined compression
shown good agreement with the literature. The traction case allowed to evaluate the ability of the model
to represent the dissipative and anisotropic behavior expected for hydrated fiber-reinforced biological
tissues, which would allow its use for the characterization of tissues under physiological conditions.

PARAMETERS ESTIMATION USING ABC TECHNIQUE OF MHD PULSATILE FLOW OF A NON-NEWTONIAN FLUID IN POROUS BLOOD VESSELS

Mon, 26 Aug 2024 00:00:00 +0000

In this work, parameter estimates of a magnetohydrodynamic model (MDH) representing the

transient pulsatile blood flow were performed, considering blood rheology as a third-degree non-
Newtonian fluid, through a porous blood vessel, under the action of a magnetic field, pressure gradient

and subjected to an externally imposed periodic acceleration field. The direct model (MHD) is solved
by applying the Method of Lines (MOL). For the application of the inverse problem via Approximate
Bayesian Computation (ABC), the sensitivity coefficient was first analyzed to define which parameters
should be estimated simultaneously. The algorithm used was an adaptation of ABC SMC proposed by
Toni et. al., (2009), where verification was performed by simulated measurement generation at different
levels of uncertainty (1%, 5%, and 10%) and considering different particle quantities (200 and 500).
The results show the efficiency of this algorithm to estimate the parameters of mathematical models of
this nature.

DESENVOLVIMENTO DE UM GUIA CIRÚRGICO DE PERFURAÇÃO PRECISA PARA INSERÇÃO DE IMPLANTE EM CORPO VERTEBRAL DE CÃES

Mon, 26 Aug 2024 00:00:00 +0000

A maioria das cirurgias de estabilização de coluna em cães requer perfuração do corpo
vertebral para inserção de implantes. No entanto, tais técnicas de perfuração óssea não são totalmente
precisas, predispondo a complicações graves durante o ato, como invasão do canal medular e danos
neurológicos e vasculares. Propõe-se o uso de ferramentas computacionais e de engenharia para o
desenvolvimento de um guia personalizado de perfuração precisa em corpo vertebral. visando atenuar
estas complicações. Devido à complexidade e à variedade anatômica entre as vértebras de pacientes
caninos, o modelo deve ser confeccionado de forma individual com base em imagens de tomografia
computadorizada obtidas do próprio paciente. O segmento anatômico da coluna proposto para este
estudo é o toracolombar, por ser descrito como a região com maior incidência de lesão que requer
estabilização. O guia cirúrgico será projetado com base em tomografia computadorizada e utilizando
programas como InVesalius, MeshMixer e SolidWorks, testes de eficácia serão posteriormente
realizados comparando as tomografias pré e pós inserção de fios guias, utilizando o modelo do guia de
perfuração obtidos por prototipagem rápida, na coluna vertebral de cadáveres caninos.

MODELING CRACK PROPAGATION PROCESS IN CORTICAL BONE MICROSTRUCTURE

Mon, 26 Aug 2024 00:00:00 +0000

This work aims to simulate the crack initiation and propagation processes in cortical
bone using a two-dimensional mesh fragmentation technique. High aspect ratio elements (triangle
elements with height much smaller than its length) are inserted between the regular constant strain
triangle finite elements, and their behavior is described by a tensile-damage model (stress-strain
relation). The constitutive model is integrated using an implicit-explicit (Impl-Ex) scheme in order to
avoid convergence problems. The proposed approach is applied to simulate cortical bone
microstructures, described as a 4-phased material: interstitial matrix, cement line, osteon and
Haversian canal. The methodology is validated through the simulation of conceptual problems
available in literature, in which the influence of the cortical bone microstructure in crack propagation
process is assessed in three-point bending tests, by considering the presence of one and two osteons.