XLIII Ibero-Latin American Congress on Computational Methods in Engineering

Investigating Satellite Attitude and Orbit Control System Performance of the SDRE Technique regarding Parametric Uncertainty

2024-05-13T12:19:46+00:00

The satellite attitude and orbit control subsystem (AOCS) can be designed with success by linear con-
trol theory if the satellite has slow angular motions. However, for fast maneuvers, the linearized models are not

able to represent all the perturbations due to the effects of the nonlinear terms present in the dynamics which
compromises the system’s performance. Therefore, in such cases, it is expected that nonlinear control techniques

yield better performance than the linear control techniques, improving the AOCS pointing accuracy without re-
quiring a new set of sensors and actuators. Nonetheless, these nonlinear control techniques can be more sensitive

to parametric uncertainties. One candidate technique for the design of AOCS control law under a fast maneuver

is the State-Dependent Riccati Equation (SDRE). SDRE provides an effective algorithm for synthesizing nonlin-
ear feedback control by allowing nonlinearities in the system states while offering great design flexibility through

state-dependent weighting matrices. The Brazilian National Institute for Space Research (INPE, in Portuguese)
was demanded by the Brazilian government to build remote-sensing satellites, such as the Amazonia-1 mission.
In such missions, the AOCS must stabilize the satellite in three-axes so that the optical payload can point to the
desired target. Currently, the control laws of AOCS are designed and analyzed using linear control techniques
in commercial software. Although elsewhere the application of the SDRE technique with opensource software
has shown to yield better performance for the missions developed by INPE, a subsequent important question is
whether such better performance is robust to parametric uncertainties. In this paper, we investigate whether the
application of the SDRE technique in the AOCS is robust to parametric uncertainties in the missions developed by
INPE. The initial results showed that SDRE controller is robust to ±20%, at least, variations in the inertia tensor
of the satellite.

On the implementation of SGFEM simulation of cohesive crack propagation problems

2024-05-13T12:27:06+00:00

The present work aims to discuss some details regarding the implementation of a cohesive crack prop-
agation system using the Stable Generalized Finite Element Method (SGFEM), a relatively new approach that

derives from a simple modification of enrichment functions used in Generalized/eXtended Finite Element Method
(G/XFEM). For this, a combination between Heaviside functions that employ a stabilization parameter, presented
in Wu and Li [1], and a trigonometric function [2] is used as enrichment. A cohesive crack model is considered.
Though nonlinear material models, e. g., damage or plasticity, could be used, the bulk is considered as a linear
elastic material for the discussions carried out in this work. Results involving crack direction criteria, as proposed
by Wells and Sluys [3] and Moes and Belytschko [2], are also compared. To the best of the authors knowledge, ̈

SGFEM has never been applied to simulate cohesive crack propagation problems with the presence of trigonomet-
ric enrichment functions. This work is related to a proposal of expansion of the INSANE (INteractive Structural

ANalysis Environment) system, an open-source project developed at the Structural Engineering Department of
the Federal University of Minas Gerais. This platform has enabled the resources that allowed the implementation
discussed in this work.

Human comfort assessment of floors subjected to dynamic loading induced by people groups

2024-05-13T12:36:19+00:00

This research work aims to investigate the dynamic structural behaviour and evaluate the human comfort
of steel-concrete composite floors when subjected to loads induced by rhythmic human activities in places such as
fitness centres, event halls and offices. The investigated structural model is characterised by a steel-concrete
composite floor of a commercial building used for aerobics, which presents dimensions of 40m x 40m and a total
area of 1,600m2. The dynamic loads were obtained through the use of traditional mathematical models associated
to “only force” and also based on the use of biodynamic systems, aiming to incorporate the human-structure
interaction dynamic effect to assess the human comfort. The floor numerical model was developed based on usual
modelling techniques, adopting the mesh refinement present in the Finite Element Method (FEM), and
implemented in the computer program ANSYS. The dynamic structural response (displacements and
accelerations) was determined through the investigation of several dynamic loading models related to people
groups practising rhythmic activities on the floor concrete slab. Finally, based on the dynamic structural response
(peak acceleration), the results were compared with the floor project serviceability limits, indicating that the
maximum peak acceleration values surpass the design criteria, causing excessive vibration and human discomfort.

Methodology based on Genetic Algorithms and Finite Elements to obtain the 3D Surgical Planning for the Periacetabular Osteotomy procedure in treatment of hip dysplasia

2024-05-13T13:12:53+00:00

Developmental dysplasia of the hip is characterized by a condition of joint instability in which the
head femoral artery presents an abnormal relationship with the acetabulum, which may be accompanied or not a
partial (subluxation) or complete dislocation (dislocation) of the femoral head. The treatment of hip dysplasia in
adults aims to prolong the longevity of the joint by performing the periacetabular osteotomy. In patients without
early diagnosis and treatment and in treated young adults inappropriately or incorrectly, surgical interventions
such as osteotomies are performed to prevent coxarthrosis and other pathologies that can develop secondary to
dysplasia. Periacetabular osteotomy aims to change the biomechanics pathological condition of the hip, causing a
reorientation of the acetabulum and consequent improvement of joint stability. In view of the complexity presented,
both by the curve of learning and the performance of the surgical procedure, it is interesting to use of tools and
computational models in order to assist the surgeon in his achievement and, consequently, in the improvement of
results. The present work seeks study the application of a genetic algorithm in conjunction with simulations via the
method of finite elements using the ABAQUS®software, in a geometric model obtained through of a computed
tomography in a real patient, aiming to optimize the surgical planning based on maximizing the resulting force
obtained as a function of contact pressures and contact area in the acetabular cartilage. A comparison is made with
the results obtained from the surgical planning developed according to radiographic parameters, from which it is
verified that the proposed methodology results in an optimal configuration for the fragment, which translates into
improved joint stability. The values of rotation angles in the x, y and z directions are shown.

Nondeterministic dynamic analysis and structural optimization of the steel towers design for wind turbines support

2024-05-13T13:19:49+00:00

Considering the growing demand for electricity and the need to reduce the greenhouse gases emission,
the adoption of renewable energy has presented considerable growth in recent years. Having in mind its
technological development and competitive prices, the use of wind energy has shown an increasing growth on its
installed capacity around the world. In Brazil, a wind potential of 1.78 TW is estimated. This way, this research
work aims to perform a dynamic structural analysis of a steel tower used to support a Repower model MM92 wind
turbine, with a production capacity of 2 MW. The dynamic analysis is performed based on a three-dimensional
finite element model through the utilization of the ANSYS software, considering the soil-structure interaction
effect, the wind loadings on the rotor and non-deterministic wind loadings applied on the steel tower. To do this,
a wind velocity in the range of survival mode of the turbine is considered, aiming to investigate the tower structural
behavior under this condition. After the steel tower nondeterministic dynamic structural assessment, the
displacements and stresses values calculated in the steady-state response will be considered for the system
optimization, based on the Genetic Algorithms, and using the MATLAB software.

Investigation on the nondeterministic dynamic structural response of tall buildings

2024-05-13T13:26:43+00:00

Based on the last few decades, the Brazilian cities have presented a relevant increasing when the design
and construction of tall and slender buildings is considered. It must be emphasized that this architectural trend
produced very flexible structures, with low natural frequency values and more susceptible to excessive vibrations
problems, especially when subjected to wind dynamic loads. Having these ideas in mind, this investigation aims
the study of tall buildings non deterministic dynamic structural response, considering the soil-structure interaction
effect. This way, the developed analysis methodology considers the wind pressure coefficients on the building’s
facade determined based on the use of CFD (Computational Fluid Dynamics) techniques that nowadays represents
an increasingly important role in high-rise buildings projects, utilised as a sophisticated analysis method to predict
the airflow on the building’s structural system. This way, the nondeterministic dynamic structural behaviour of a
40-storey reinforced concrete building, 140 m high and floor dimensions of 9 m by 29.05 m was investigated. The
building numerical model was developed to obtain a realistic representation of the structure, based on the Finite
Element Method (MEF), using the ANSYS program. It must be emphasized that the results obtained throughout
this research work, considering the wind pressure coefficients calculated based on CFD techniques and those
determined by the Brazilian design standard NBR 6123 have indicated important quantitative differences, when
the dynamic structural response (displacements and peak accelerations) and the building human comfort were
investigated.

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

2024-05-13T13:32:50+00:00

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

Verification of the order of accuracy of the discretization error in the simulation of tumor growth

2024-05-13T13:36:05+00:00

In Engineering there are several problems to be studied, such as applications in biomedicine, which
are typical problems in Computational Fluid Dynamics (CFD). To solve these problems, numerical methods are
used regardless of complexity, geometry, physical parameters, boundary and initial conditions. Linear or nonlinear
models can be considered to assess both temporal and spatial evolution. However, one of the main disadvantages
of numerical methods is the determination of computational errors associated with their use, in which numerical
solutions can be affected by truncation, iteration, rounding, and programming errors. Although numerical errors

cannot be eliminated, they must be controlled or minimized. The discretization error is considered the most signif-
icant among the sources of numerical error, requiring its analysis. Therefore, this work aims to verify the accuracy

of the discretization error of a one-dimensional model of tumour growth, using a priori and a posteriori estimates
of numerical solutions. We predict the asymptotic behaviour of the discretization error in the a priori estimation.
We estimate the magnitude of the error based on multiple meshes using the Richardson estimator in the a posteriori
estimation. The model used in this work is described by a system of partial differential equations in a transient

regime, with four variables involved in the process of tumour cell invasion, resulting in the description and evolu-
tion of cancer cell density, extracellular matrix (ECM) density, the concentration of matrix degradative enzymes

(MDE) and tissue inhibitors of metalloproteinases (TIMP). To discretize the mathematical model, we used the
finite difference method with Central Difference Scheme (CDS) for spatial discretization and the Crank-Nicolson
method for temporal discretization. The nonlinear terms involved in the model were linearized by applying the

Taylor series expansion. To advance in time, this discretization procedure results in the resolution of a set of alge-
braic equations to be solved with the aid of the iterative Gauss-Seidel method. The simulations are performed with

Dirichlet boundary conditions. We use the manufactured solutions method for code verification and error analysis.

Experimental and numerical dynamic analysis of buildings floors when subjected to human-induced loads

2024-05-13T22:20:00+00:00

Numerous cases involving excessive vibrations on buildings floors due to human dynamic actions have
been reported over the years. However, it is worth to mention that the human rhythmic activities, especially when
performed by people groups tend to increase the degree of synchronization that may result in discomfort for the
building users. Therefore, this research work aims to investigate the dynamic structural behaviour of a reinforced
concrete floor when subjected to rhythmic human activities. The investigated floor corresponds to a gym with
dimensions of 16 m x 35 m, and total area of 560 m2. Initially, the floor dynamic properties (natural frequencies
and structural damping) were determined based on the structure experimental monitoring. Afterwards, a floor
numeric model was developed, based on the use of usual mesh refinement techniques present in Finite Element
Method (FEM) simulations and implemented in software ANSYS. This way, several dynamic loadings
mathematical formulations (only-force models and biodynamic systems) were implemented in order to assess the
floor dynamic structural response. The obtained results (displacements and accelerations) and the human comfort
assessment presented in this study indicate the relevance of the dynamic analysis to investigate the structural
behaviour of the reinforced concrete floor and also the influence of the people-structure dynamic interaction.

Influence of the progressive pavement deterioration on the steel- concrete composite highway bridges service life

2024-05-13T22:23:00+00:00

Nowadays, the significant increase associated to the vehicle’s weight and traffic volume on the highway
bridge decks has made these structures subjected to several degradation phenomena. In this context, structural
fatigue is one of these progressive degradation events induced by vehicles dynamic impacts that can produce
significant increasing of the stress values. Having these ideas in mind, this research work aims is to develop an
analysis methodology to assess the fatigue performance of steel-concrete composite highway bridges, including
the dynamic actions due to vehicles convoys and the pavement progressive deterioration effect. The developed
analysis methodology is based on the use of Miner-Palmgren linear cumulative damage rule, Rainflow algorithm
and S-N curves associated to the traditional design codes. This way, the investigated structural model corresponds
to a steel-concrete composite highway bridge spanning 40 m subjected to vehicles traffic. The developed numerical
model adopted the usual mesh refinement techniques present in Finite Element Method (FEM) simulations
implemented in the ANSYS program. The main conclusions of this investigation focused on verify the extension
of the dynamical effects on the service life of steel-concrete composite highway bridges due to vehicles crossing
on the deteriorated pavement surface.

Nonlinear analysis and parametric study on steel beams with circular web openings

2024-05-13T22:26:22+00:00

Steel beam with circular web opening have been gaining more space in the Brazilian industry. They
bring countless benefits to the construction, in addition to reducing the cost, there is also a reduction in weight,
allowing the passage of service ducts, which integrate the installations with the floor system. The variability of
this system can make it difficult to carry out experimental tests that evaluate all possibilities, as they demand more
financial, human, and time resources. Thus, numerical analysis presents as an alternative for this evaluation,
seeking the best option for applying this system. Therefore, this paper aims to simulate numerically steel beams
with circular web opening, using the finite element method. The analysis includes material and geometric
nonlinearities, as well as the study of instability. Through experimental results performed by Morkhade and Gupta
(2015), the numerical model was calibrated to carry out a parametric study that evaluates the spacing of openings
(s), diameter of openings (d), height of beam web (h) and beam thickness (t). Calibration was performed by
comparing the load x mid-span deflection experimental curve with the numerical one, obtaining satisfactory
results. The parametric study concluded that, in general, the parameters significantly influenced in the structural
behavior of the beam, except the spacing of openings.

Fluid-Structure Interaction between Broad Crested and Hydrodynamics Effects under Sand bed sediments

2024-05-13T22:32:43+00:00

The present study intends to report the initial findings results in the hydrodynamic and sediment
transport modeling with a study case of a broad crested weir considering a sediment bed made of sands. The
adopted numerical model is the REEF3D, a Computational Fluid Dynamics tool, which is able to do sediment
transport simulations, according to Bihs and Olsen [1]. The main objective is to examine the hydrodynamics effects
of the flow around the structure in a movable sediment bed.

Unsupervised feature selection-based technique for locating structural deterioration: a multi-domain approach

2024-05-13T22:35:12+00:00

Structural monitoring methods have been extensively researched in recent years due to developments

in Artificial Intelligence (AI) technology. In this regard, the purpose of this work is to offer an automated data-
driven approach for deterioration localization based on the extraction of features from raw vibration data utilizing

domain knowledge and a filtering procedure. To diversify information retrieval, feature extraction is conducted
concurrently in temporal, frequency, and quefrency domains. This filtering process is known as feature selection
(FS) and is used to reduce redundancies and raise the relevance of the feature set by removing a subset based on a
predefined criterion. The key idea is that the proposed approach may be tuned to the structure while offering
generality for whatever shape, material, or excitation it comes across. The deterioration index is calculated via

outlier analysis referenced by the structure's healthy condition. The technique was successfully tested in a full-
scale bridge, demonstrating a performance that is encouraging for real-world monitoring scenarios.

Comparison among four techniques to predict the compressive strength of concrete: Extreme Gradient Boosting, Support Vector Regression, Artificial Neural Networks, and Gaussian Process Regression

2024-05-13T22:38:23+00:00

The compressive strength (Rc) of concrete is an important feature that influences the safety, durability,
and cost of a structure. To achieve the desired Rc, professionals generally use mix design methods based on empirical
tables. Then, the Rc must be confirmed in laboratory with tests that cost time and resources. To mitigate this issue,
this study proposes and compares the use of four Machine Learning (ML) techniques to predict the Rc of concretes
from their components. The techniques are: Extreme Gradient Boosting, Support Vector Regression, Artificial Neural
Networks, and Gaussian Process Regression. Initially, a dataset vastly used in the literature for this purpose was used
as input. Secondly, a dataset built by the authors was used to validate the models’ generalization ability. All models
were cross-validated (10-fold) and their accuracies were measured by R2, MAE, and RMSE. XGBoost and GPR
presented the best performance, while SVR presented the worst. Despite the positive performances measured in all
models with the first dataset, the metrics dropped sharply in the validation step involving the second dataset. Thus,
the ML techniques are promising tools for the mix design of concretes, but attention must be taken to guarantee that
models are not overfitted because of the homogeneity of the input data.

A continuous-discontinuous strategy to represent the crack process in concrete structures

2024-05-13T22:42:00+00:00

The study of fracture in quasi-brittle materials such as concrete has significant importance since it is
one of the main causes of material failure. There are two numerical approaches to representing fracture: smeared
and discrete models, and both techniques have pros and cons. Among the smeared approaches, damage models
are used to reproduce the degradation of a continuum media. These models are appropriate for describing the first
stages of degradation, identifying damaged regions, and replacing original mechanical properties with damaged

ones. This strategy assumes that the cracks are spread over an area known as the fracture process zone. How-
ever, this phenomenological approach cannot represent the crack path properly since the discontinuities are not

geometrically described. In contrast, the discrete methods are the most indicated to characterize the fracture ex-
plicitly. Such methods frequently deal with remeshing, an alternative that has been avoided because of the high

computational cost. Although, based on the efficiency of modern computers, it is now possible to evaluate the
viability of coupling continuous and discontinuous models to reproduce fracture in its entirety, from nucleation to
collapse. In this context, it is proposed a combined strategy that associates nonlocal damage models to represent
the smeared aspects of crack propagation with a discrete crack description based on nodal duplication to capture
the crack discontinuity. Finally, numerical simulations were performed to analyze the efficiency of this strategy in
representing the degradation processes from smeared cracks to geometric discontinuities.

Uncertainty Quantification in 1d Pore Pressure Prediction of Exploratory Wells

2024-05-14T21:15:40+00:00

The pore pressure model serves as a subsidy for the well project, predicting potential risk events. Events
such as stuck pipe and inflow of fluids into the well result in a high cost in exploratory oil projects, either due to
the time spent fighting them, or the complete loss of the well. Unfortunately, in exploratory projects we do not
have enough data, nor the indirect data have good reliability, therefore, these models have high uncertainties. The
present work proposes the application and evaluation of the uncertainty and sensitivity analysis methodology in
the 1D pore pressure models used in the drilling of exploratory oil wells, to quantify and measure their impact. For
this purpose, data from wells drilled in the Santos Basin, southeastern Brazilian margin, were used.

Neighborhood and wind direction effects on wind pressure distribution on the low-rise building roof

2024-05-14T21:19:31+00:00

Low-rise buildings are the majority of the houses that are constructed all over the world. Experiments
of the wind loads acting on these buildings provide vital information to design secure structures and adverse
weather conditions resistants, considering the basic parameters in the analysis of gable buildings as roof slopes
and the wind direction. This study estimated the distribution of wind pressures around the contour of buildings
with gable roofs, considering diverse neighborhood conditions such as the number and geometric configuration of
buildings on the ground, in conjunction with the different angles of wind incidence. The simulations took place
with Ansys Workbench software, and the RNG K-Epsilon turbulence model and tetrahedral mesh were employed.
The application validation of the CFD technique occurred in the double sloped pitched roof structure. The results
showed good concordance with the literature. The pressure coefficients were analyzed, and in the flow
visualization, highlighted the attachment points and the recirculation zones.

Effects of epistemic uncertainties on truss topology optimization considering progressive collapse

2024-05-14T21:21:52+00:00

The history of engineering contains many examples of structural failures. Despite being related to
diverse causes, these collapses can be attributed to the existence of uncertainties, which are usually classified as
aleatory and epistemic. In this context, optimization techniques can be employed in order to obtain optimal
structural solutions that are robust to the effects of uncertainty. Additionally, the progressive collapse phenomenon
has raised engineers' and researchers' awareness in recent years. However, there are still very few papers addressing
the optimal structural design under uncertainty considering progressive collapse. Hence, this paper aims to
investigate the effect of aleatory and epistemic uncertainties on truss topology optimization considering

progressive collapse. Uncertainties are considered in the optimization problems through the RBDO (Reliability-
Based Design Optimization) and RO (Risk Optimization) formulations. Non-structural factors, which are

epistemic in nature and can lead to progressive collapse, are considered using a formulation based on the latent
failure probability concept. Through a simple six-bar truss problem, the huge impact of epistemic uncertainties on
optimal topologies is shown. The variation of the latent failure probability indicates the existence of two transition
points in the optimal solutions, named Hyperstatic and Redundancy Thresholds. We conclude that these bounds
are mainly controlled by the magnitude of epistemic uncertainties, having a strong effect on the reliability and
costs of the optimal solutions. These results reveal something that has already been recognized in practice:
engineering structures need to be redundant in order to cope with the effect of epistemic uncertainties. Therefore,
despite being an idealized concept, the latent failure probability proves to be a simple tool to impose minimal
redundancy in optimal structural solutions.

Assessment of the distortion-induced fatigue strength in steel-concrete composite bridges welded joints

2024-05-14T21:24:50+00:00

Highway bridges are known as structural systems permanently affected by random loads that can cause
significant damage to the structural elements. Nowadays, a challenging problem for structural engineers is
associated to the high-stress amplitudes related to the fatigue induced by distortion on the steel elements.
Therefore, in this research work, the hot-spot stress method was validated aiming to assess the distortion-induced
fatigue strength in welded joints of steel-concrete composite bridges. It is important to emphasize that for the
validation of the hot-spot stress method, a full-scale fatigue tests database was taken into account, designed
precisely to serve as a basis for the evaluation of the fatigue resistance induced by distortion. This way, the
investigated highway bridge finite element model, developed based on the use of the ANSYS program, was utilized
as a global model with a local sub model, aiming to perform the compatibility and interpolation of the
displacement’s fields of both models (global and local). The numerically obtained results based on the hot-spot
approach were compared with those calculated with the conventional methods, resulting, therefore, in a
considerable difference, showing that the hot-spot method is more realistic, in view of its effectiveness in terms of
capture of stress concentrations due to the geometry of welded details, over for evaluation of fatigue damage.

Plastic Stress Concentration Factor KF in Fatigue

2024-05-14T21:28:08+00:00

This study uses the stress gradient factors (SGFs) ahead of notch tips to determine the notch effects in

fatigue, which are generally smaller than notch stress concentration factor due to the material tolerance to non-
propagating short cracks. Even under elastic nominal stress levels, the notch vicinity may accumulate plastic

strains when the maximum local stress exceeds the material yield strength. Considering the significant role of local
plasticity in the propagation behavior of short cracks within the notch plastic zone and therefore in the notch
sensitivity, a methodology is proposed to take into account the elastic-plastic stress and strain fields modeled by
Neuber’s rule and cyclic Ramberg-Osgood equation. 2D finite element analyses are conducted to compute the
stress intensity factors (SIFs) of smooth and notched specimens, which in turn are used to calculate the SGFs and
finally to obtain plastic fatigue notch factor predictions. To validate the methodology, experimental S-N data of
centre-notched, U-notched and V-notched plate specimens made of different materials and tested at uniaxial load
ratio R=-1, 0 and 0.1 are collected from the literature and compared with simulation results.

Dynamic analysis of Baja-type vehicle subjected to excitation by irregular road profile

2024-05-14T22:18:52+00:00

Automotive vehicles are complex dynamic systems that travel over uneven roads of different qualities.
This interaction induces vibrations whose characteristics depend on the suspension system, speed, and pavement

type, among other factors. Extended exposure to vibrations can be annoying and harmful to human health, de-
pending on the acceleration levels. At Baja SAE competitions, small off-road vehicles are designed and built to

withstand rough terrains. Therefore, knowing the vehicle’s response to irregularities is relevant to ensuring compli-
ance with safety requirements. In this paper, a computational routine is designed to evaluate the dynamic response

of a BAJA-type vehicle to excitations induced by an irregular surface. A three-dimensional full-car model with
eight degrees of freedom simulates the vehicle’s vertical dynamics. The road surface roughness is modeled in
the frequency domain using Power Spectral Density functions, which are converted to time-domain signals. The
numerical integration of the equations of motion is made through Newmark’s method. The code is validated using

commercial software and data from the literature. The outputs are the displacement, velocity, and acceleration sig-
nals for each vehicle’s degree of freedom. Results evidenced the suspension system’s effect on damping vibration

levels experienced by the driver in relation to the base motion of the wheels.

Experimental nonlinear dynamic analysis of a machine supporting structure

2024-05-14T22:24:43+00:00

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.

A three degrees of freedom model of the support structure of a non- ideal motor

2024-05-14T22:28:41+00:00

n rotating-unbalance-machine/structure systems, stable regime is when angular velocity is constant, all
energy supplied by the motor consumed by internal friction and energy dissipated by damping of structure. Energy
beyond this accelerates the system. Each energy level provided by the motor corresponds to stable constant angular
speed. H is the torque consumed by the motor internal friction. Summed to the R torque to overcome damping
forces of the support structure gives the S torque. L is the active motor torque provided. In an ideal system, the

motor provides power to go over the resonance peaks of the structure and achieve the rated motor speed. In a non-
ideal system, with limited power supply, an available motor torque level L can intercept the torque curve S

consumed by friction and the structure at a constant rotation point before or after the resonance peak. If before, is
a stable point of capture at resonance. Angular velocity no longer increases, stagnating before the peak, not
reaching higher rotation speed. Jumps happens when more energy is supplied to overcome this stagnation. There
comes a point the torque curve goes over the peak and intercepts the consumed torque curve further ahead in steady

higher angular velocity, no intermediate stable steady states. There is really no difference between ideal and non-
ideal systems. Only the available power level. A model considering mutual interaction support-structure/machine,

should always be used. In that sense, all systems are non-ideal. In practice, if the motor has enough power this
effect is negligible and we only consider interaction between the motor and the structure but not the reverse
interaction, simplifying the model. Literature is available on 1-DOF support structure models, with 2 coupled
autonomous equations of motion, 1 for the structure, 1 for the motor. In this paper we present a better representation
of a machine foundation moving in horizontal and vertical directions, with mass, stiffness and damping for each
one. Thus, we study 2 possible occurrences of the Sommerfeld Effect in the same model

Numerical Modeling of Reinforced Concrete and EPS Core Sandwich Panels under Bending

2024-05-14T22:31:04+00:00

The use of construction systems based on the use of Sandwich Panels has grown significantly in the
Brazilian civil construction market in recent years, with greater application in residential buildings. However, due
to the absence of normative regulation and reliable calculation standards, this system is often used without a
fundamental understanding of its structural behavior. Thus, in order to evaluate the resistant capacity of these
panels when subjected to bending forces, this work consisted of the elaboration of a three-dimensional numerical
model of a Sandwich Panel of reinforced concrete with EPS core and metallic connectors, being used the ABAQUS
for its conception, which is a software based on the Finite Element Method (FEM). In addition, the model considers
the non-linear behavior of materials, through the use of the Concrete Damage Plasticity model (CDP) and the
Plasticity model for steel, which is calibrated and validated by experimental studies present in the literature,
presenting results in agreement with those obtained by the experiments.

Evaluating Different Neural Networks Architectures for the Solution of Heat Conduction Problems in NVIDIA Modulus

2024-05-14T22:44:45+00:00

The use of neural networks to address engineering problems is increasing considerably. A limitation
of using neural networks is the need for large amounts of data to fit nonlinear problems with acceptable accuracy.
An alternative to the purely data-driven approach is the physics-informed neural networks, which add physical
constraints that significantly reduce the amount of data needed to achieve acceptable accuracy. In this work, we
solve two simple heat conduction problems using PINNs, evaluating the complexity of different neural network
architectures. A direct comparison to the analytical solution proved the PINNs to be good solvers for the evaluated

partial differential equations. A fully connected neural network (FCN) handles the problem well for the steady-
state case. However, a gated recursive unit (GRU) architecture is needed to solve a transient problem. For both

problems, an architecture of 6 layers with 64 units each is sufficient to achieve good results.

Numerical observation of traveling wave solution in a non-Newtonian foam model

2024-05-14T22:50:26+00:00

Foam injection is an oil recovery technique with great potential to be applied in the Brazillian Pre-salt
reservoirs. It consists of injecting gas and surfactant solution into the reservoir to control the gas mobility, avoid the
fingering formation, and improve sweep efficiency. Investigating the foam flow in porous media is challenging due
to foams’ non-Newtonian behavior. That is why most mathematical studies on this subject consider Newtonian
models. In the literature, there is a non-Newtonian model describing the foam displacement validated through
laboratory experiments. In the present work, we numerically verified that this model possesses a traveling wave
solution i.e., a stable-shape profile displacing in space with constant velocity. Such a solution is similar to ones
appearing in Newtonian models. We validate our results by comparing them to the experimental data found in the
literature. The numerical method is based on a finite difference Crank-Nicolson scheme with the Newton-Raphson
method for time step evolution.

Wavefront velocity for foam flow in three-layer porous media

2024-05-14T23:13:00+00:00

The foam became interesting for many applications, including the oil industry, due to its capacity to
control gas mobility, which is specifically relevant in fractured reservoirs. In the present work, we use a simplified
bubble population balance model to describe foam displacement in porous media. We approach the fractured
structure of the porous medium in a three-layer configuration, where the middle layer possesses a small width and
high permeability. Numerical investigation using Foam Displacement Simulator (FOSSIL) points out the existence
of a stable traveling wave water saturation profile evidencing the applicability of the foam injection to control gas
mobility in fractured reservoirs.

Nonlinear resonance curves of a cylindrical panel with unilateral contact of a discontinuous elastic base

2024-05-14T23:32:27+00:00

The aim of this work is to analyze the influence of a discontinuous unilateral elastic base and an initial
geometrical imperfection on the nonlinear vibrations of a simply supported cylindrical panel. The cylindrical panel
is described by the nonlinear shallow shell theory of Donnell and discretized by the Galerkin method, using a
reduced order model which is obtained by a perturbation method. The discontinuous elastic base model is described
by a Heaviside function and the unilateral contact is defined by the Signum function. The results show the dynamic
analysis of the cylindrical panel through the backbone curves, bifurcation diagrams, phase portraits and resonance
curves to understanding the influence of the discontinuous unilateral elastic base and the initial geometrical
imperfection of the cylindrical panel. An efficient modal solution with two degree-of-freedom is sufficient to
describe the nonlinear softening behavior of the cylindrical panel with a discontinuous unilateral elastic base. The
influence of the unilateral elastic base and the initial geometrical imperfection on the dynamic stability of the
cylindrical panel is demonstrated in the resonance curves, phase planes, Poincaré mappings and bifurcation
diagrams, where it is possible to identify important changes in the stable and unstable regions of the resonance
curves when compared with a cylindrical panel with a discontinuous bilateral elastic base.

Comparative analysis between different integration methods for frames subjected to earthquakes

2024-05-14T23:36:19+00:00

The choice of the type of structure model, the duration time of the dynamic loading, the size of the time
step, as well as the inclusion or not of nonlinearity are factors that should be taken into consideration when deciding
on different solution methods for the dynamic analysis, as they are able to influence the stability and accuracy in
the response of the structure. This paper presents a comparison of dynamic analysis results for different integration
methods in the time domain. This comparison is evaluated using a steel plane frame subjected to a Tohoku
earthquake that occurred in 2011 in Japan. The structure is modeled in two-dimensional finite elements and
discretized into bar elements. The entire analysis is developed by implementing a numerical routine in Python 3
language. It is expected to find distinct results regarding the accuracy in displacements, velocities and accelerations
due to the spurious oscillations inserted due to the characteristic of the finite element method.

Mode Localization in Quasi Periodic Cyclic Structures

2024-05-14T23:39:32+00:00

In this work, we study the phenomenon of localization of vibration modes in quasi-periodic cyclic
structures with linear behavior. They are composed of nominally identical substructures loosely coupled together,
taking into account possible small imperfections. Such linear systems in the face of the disorder caused by small
imperfections, can lead to the confinement of vibrational energy in certain regions of the structure, a phenomenon
known as Mode Localization. This phenomenon can cause catastrophic failure due to high vibration amplitude and
fatigue. The identification and study of the location effect from a modal perspective, as well as the response of the
structure and its components to dynamic requests is of fundamental importance, as it is a diagnostic tool for
possible preventive mitigation actions or even use of this phenomenon in damping of the system. Through the
implementation of computer simulation via MATLAB® software, based on the Finite Element Method, the
distribution, interference and consequence of vibrational energy on the adopted model are analyzed with reference
to the periodic and ordered or aperiodic and disordered dynamic characteristics. The so-called “real case” considers
the small variations in characteristics (length, stiffness, attack angle), resulting from manufacturing tolerances or
FOD (Foreign Object Debris) impact. This work presents graphically the amplitude of normalized vibration
amplitude resulting from the appearance of the phenomenon of localization of vibration modes in the substructures,
which can be restricted to one or a few of them.

A mathematical and rheological study of the pastes that make up obturator endodontic cement from MTA base

2024-05-15T15:36:08+00:00

The MTA-Fillapex endodontic cement is constituted from base and catalyst pastes. In the present
work we investigated, from several rheological models, the model that described the best relationship between the
shear stress and shear rate for the pastes. To the investigation, five paste lots were selected, and the Brookfield
RST-CPS rheometer was used to the measurements. The rheological laws were deduced according to the models:
Bingham, Ostwald-de Waele, Herschel-Bulkley, and Casson. The models parameters were calculated by means of
our code. We used the Levenberg-Marquardt Method, from the computational platform OCTAVE on the version

5.2.0. Additionally, we analyzed the parameters’ existence domain, the fitted determination coefficient, the maxi-
mum deviation, and the correlation matrix. From this, the preliminary results showed that the Ostwald-de-Waele

was most representative rheological model to characterize the base paste, and to the catalyst paste we had the
Herschel-Bulkley model as the better representation.

Modelo reduzido para análise estática de uma placa retangular hiperelástica

2024-05-15T15:42:14+00:00

Realiza-se a análise estática de uma placa fina retangular, composta de material hiperelástico sujeita a
carregamento de pressão uniformemente distribuído. Ambas as não linearidades são consideradas e, para isso,
aplica-se o modelo Neo-Hookeano, que descreve a não linearidade física do material, e a teoria não linear de vón

Kármán, que incorpora a não linearidade geométrica. Compara-se as respostas obtidas para os diagramas pressão-
deslocamento de um sistema de equações com doze graus de liberdade, obtido com aplicação das ferramentas do

cálculo variacional no funcional de energia da placa, com um modelo reduzido pelo Método de Karhunen-Loève.
Para a geometria analisada, o modelo reduzido, de custo computacional menor que o sistema original, representa
de forma satisfatória o comportamento estático da placa.

Application of the G/XFEM, quasi-3D theory, and the nonlocal elasticity in the vibration analysis of thick functionally graded nano-plates

2024-05-15T15:54:24+00:00

In this study, the problem of free vibrations in functionally graded moderately thick nanoplates is
addressed. The numerical models are obtained employing the quasi-3D plate theory and the approximation spaces
are obtained according to the G/XFEM with PU's with regularity

, = 1,2. The choice to use the cited
approximation spaces is related to their regularity, which is extremely relevant in non-local dynamic elastic
problems. In this sense, the use of approximation spaces obtained with

FEM-Lagrange produces significant
differences in the nanoscale result which does not occur in classical or local elasticity. In the case studies, the
following effects on the first resonance frequency are analyzed: increase in the nanoplate size, distribution of the
biphasic material, and increment of the nanoscale parameter. As a complementary result, the effect of the regularity
of the approximation spaces in the verification of the stiffness softening phenomenon is analyzed. The normalized
frequencies resulting from those obtained with high order FEM-Lagrange, a semi-analytic solution, and the
Hermitian elements (H-FEM)

, = 1,2.

Fission and Deformations in the Colon Epithelium using Finite Element Methods

2024-05-15T15:56:41+00:00

The goal of this work is to model and simulate a crypt deformation and fission in the colon epithelium
originated by an abnormal cell proliferation located in the crypt walls.

Nonlinear transient vibrations of an orthotropic silo longitudinally stiffened considering the charging/discharging of the grains

2024-05-15T15:59:40+00:00

The type of structure most used for the storage of grains are the cylindrical metallic silos, being slender
structures in shell, which have great capacity to withstand the axial loads and the lateral pressures that are
submitted. This paper aims to develop a low-dimensional model, with a reduced number of degrees of freedom,
capable of analyzing the behavior of orthotropic and longitudinally stiffened silos subjected to static and dynamic
axisymmetric actions. The nonlinear Sanders-Koiter theory is used to model the silo and Chebyshev polynomials
are used to simulate the cantilever at the base and the free end in which these types of structures are commonly
built. Grain pressures are determined according to the Janssen model, including the Heaviside function to simulate
charging, and discharging inside the silo. In addition, the Heaviside function is also applied to the kinetic energy
and the natural frequency of the system, to compose the variation of mass and damping generated by the grains
over time. The motion equations are obtained by applying Hamilton's Principle and the Rayleigh-Ritz method and
using the 4th order Runge-Kutta method, the maximum axial and transverse displacements during charging, and
discharging are found, noting that an increase occurs when compared to the static values of grain storage, which
generates greater efforts being applied to the silo structure.

Artificial Intelligence methods applied to the damage detection in beams

2024-05-15T20:26:19+00:00

Structural health monitoring (SHM) has become increasingly important in the field of civil engineer-
ing. The objective of this paper is on the application of Artificial Intelligence Methods in the SHM field. The

formulation uses modal parameters of a structure to detect damage related to the reduction of stiffness of a section.
The databases for training and validating the AI methods were generated in a structured and automatic way by
an algorithm developed in Python programming language within the finite element software Abaqus. The modal

parameters analyzed were the first five natural frequencies of a beam. An exploratory analysis was performed us-
ing other characteristics such as: length of the beam, failure severity, material, boundary conditions, cross section

and others. It was possible to evaluate the performance of the AI methods on the proposed problem. Finally, a
parametric comparison was made between the different Artificial Intelligence methods.

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

2024-05-15T20:31:48+00:00

A groundwater solute transport model that predicts the process of contaminant migration plays an impor-
tant role in the control and remediation of groundwater contamination. For example, in simulating solute transport

in groundwater, reliable prediction of fluid dynamics requires a simulator capable of correctly handling highly het-
erogeneous and anisotropic permeability tensors on nonorthogonal grids due to the complex geology of the aquifer.

To solve the equations that constitute the flow model, simplifying assumptions must be made about the aquifer and
the physical processes that govern groundwater flow. In this study, we applied an improved numerical formulation

that deals with highly heterogeneous and anisotropic media and can handle distorted grids. The governing equa-
tions are solved via an implicit pressure and explicit concentration procedure, where the advective term is solved

using a Monotonic Upstream Centered Scheme for Conservation Laws (MUSCL) type method. This method is
based on a gradient reconstruction obtained by a least square technique in which the monotonicity is enhanced by a
multidimensional limiting process (MLP). The essence of the present limiting strategy is to control the distribution
of both cell-centered and cell-vertex concentration in a multidimensional way to flow physics. Is showed in the
literature that this strategy satisfies the local extremum diminishing condition in a truly multidimensional manner.
The dispersion term is discretized by a nonlinear two-point flux approximation method (NL-TPFA). This method
is very robust and able to exactly reproduce piecewise linear solutions through a linear-preserving interpolation
with explicit weights. The methods can be used with general polygonal meshes, although we restrict ourselves
to conformal triangular and quadrilateral grids. To validate the adopted formulations, some benchmark problems

found in literature are solved. These numerical experiments indicate that our formulations can provide robust so-
lutions for simulating groundwater solution processes, especially in aquifer systems with complex physical and

geological properties.

Analysis of the nonlinear vibration of a clamped cylindrical shell considering the influence of the internal fluid and oceanic waves

2024-05-15T21:10:58+00:00

Cylindrical shells are used in various engineering installations, such as nuclear power plants, tanks,
cooling towers and oil platforms, which can fluid-filled. In addition, offshore structures are subject to the incidence
of ocean waves, which can change their dynamic response. Due to the slenderness of the cylindrical shells, the
interaction between these structures and the fluid presents a complex dynamic behavior, and understanding these
phenomena is of great interest for the development of these designs. This article presents an analytical-numerical
comparative study to analyze the nonlinear vibrations of a clamped cylindrical shell, considering the effects of the
presence of an internal fluid, that is incompressible, non-viscous and irrotational, and its free surface. It is also
applied to the outer side walls of the cylindrical shell, a load from the action of ocean waves, which are derived
from the Airy theory and are time dependent. To describe the deformation field and curvature changes of the
middle surface of the cylindrical shell, the nonlinear Sanders-Koiter theory was used. Chebyshev polynomials are

applied to define the modal expansions that describe the displacement field of the structure. Finally, the Rayleigh-
Ritz method is used to obtain the nonlinear equations of motion of the system. The free vibrations were compared

with a numerical model obtained by the Finite Element Method (FEM), with the aid of the commercial software
ANSYS. As a response of the nonlinear analysis, the response in time and phase-plane is obtained for the
cylindrical shell with the presence of the internal fluid and the action of ocean waves, in addition to evaluating the
influence of two types of waves, for shallow and intermediate waters.

Local Homogenization of Composite Materials

2024-05-15T21:14:24+00:00

The homogenization process has as its basic premise to change multiphase materials into a single
material with a representative phase, regardless of which model is being used, whether based on the theory of
elasticity, solid mechanics, or the mean-fields micromechanics models. These models, however sophisticated they
may be, takes into account the interaction between the inclusions, the geometry of the inclusion up to the physical
nonlinearity of the problem, which is always associated with the geometric limitation of the global model. To
circumvent the geometric problem, it is proposed the development of a homogenization process that takes into
account the geometry of the problem, in addition to the volumetric fractions and properties of each phase. This
consideration is given by the generation of a quadtree recursive spatial subdivision, where the mesh nodes represent
the inclusions and the elements connected to the nodes represent the matrix. With this, it can be shown the
reduction of the global problem to a local problem of the Eshelby equivalent inclusion and homogenize of the
mesh node by node. The obtained results are a map of properties homogenized locally since each node has different
volumetric fractions for each problem of equivalent inclusion. This procedure opens a range of different
possibilities of materials, including the application in multiphase cementitious composite materials.

Wind load effects on photovoltaic modules

2024-05-15T21:16:48+00:00

Wind loads are a major concern regarding steel structures, which is the case of the photovoltaic modules.
These devices have been studied using different approaches in order to determine their aerodynamic characteristics.
Nevertheless, the argentine regulation in this aspect (CIRSOC 102 Ed. 2005) does not contribute with detailed
specifications for unconventional structures. In order to provide more data about the influence of the photovoltaic
module aerodynamics on its constitutive structural elements, an interdisciplinary approach is presented to define
the aerodynamic properties and the mechanical states of a specific model of the photovoltaic module. In the first
place, the pressure coefficients obtained experimentally in the Wind Tunnel by other authors were used to determine
the most hostile wind loads applied to the studied panel. Secondly, numerical modeling of the type structure in
the physical and geometric nonlinear field was carried out, thus obtaining the natural modes of vibration and the
structural components with critical solicitation.

Solution of ill-posed problem in plane wave decomposition for sound field reconstruction

2024-05-15T21:45:03+00:00

Plane-wave decomposition is a recently developed technique in the field of acoustics that stems from
an approximation in the inverse spatial tri-dimensional Fourier transform so that it considers that the sound field
is represented by the superposition of plane waves traveling in well-defined directions. The calculations for the
technique involve the solution of an ill-posed matrix equation, requiring a regularized solution for the least squares
problem. This paper will show the implementation of the plane wave decomposition using Tikhonov regularization
in the context of a simulated and a measured impedance tube. The classical L-curve algorithm and a fixed-point
algorithm for the calculation of the regularization parameter were investigated and compared with the goal of
defining which technique produces the least error in this scenario. The reconstructions of the transfer functions
in both the simulated case and the measured case were realised, with the fixed-point algorithm displaying an
advantage over the L-curve with respect to reconstruction errors in both scenarios.

Pisciculture 4.0: Technology and innovation in the fish production

2024-05-18T21:19:07+00:00

The aquaponics system is a sustainable model of food cultivation that involves the creation of fish and
plants in controlled environments (Aquaculture and Hydroponics) that require a high level of quality,
maintenance, and production. This work's main objective is to present the development of a monitoring system
based on the Internet of Things (IoT) technology. It proposes the supervision of a substrate cultivation method
(Media-filled bed) in which several parameters are monitored through sensors connected by the ESP32
microcontroller, and actuators such as pumps and others. The system collects sensor data and stores it in a
database. They are treated by optimization algorithms and presented in a graphical visualization WEB interface.
Information is delivered in real-time, facilitating safe decision-making at the production and maintenance levels
of the aquaponics system. The framework also allows the safe presentation of time series for analysis and
production planning. This system was developed and is being installed in a Research Base of the Aquaculture
Engineering and Mechanical Engineering courses with the participation of students from the Science and
Technology and Mechatronics Engineering courses at UFRN, using the PBL (Problem Based Learning)
methodology.

Multi-agent simulation of Coronavirus contamination on public transport

2024-05-18T21:22:40+00:00

Since the beginning of 2020, we are experiencing a worldwide pandemic of the coronavirus. Since then, health
authorities around the world have tried to prevent people from infecting themselves with this virus. In Brazil, states and
cities plan and take decisions to restrict movement or release some activities to return to normal operation. As noted, these
are decisions that can, on the one hand, harm the economy and the citizen's interpersonal relationships and, on the other,
lead to overcrowding of hospitals, health chaos and more deaths. For this work, a computer simulator was developed where,
together with a mathematical model and multi-agent systems, it was sought to show contamination situations in real
environments. The simulator has an interface where it is possible to visualize people moving in a pre-established
environment. The objective of this work is to add to the studies already in progress, bringing more data and information
that can help to improve policies and actions to combat the pandemic.

Yield design approach to uplift bearing capacity of shallow rectangular plate anchors

2024-05-18T21:24:54+00:00

Plate anchors are a widely used class of foundation systems for structures subject to uplift forces. Its
bearing capacity evaluation has been object of constant revisions in literature, notably as a result of the recent
decommission operations of large offshore structures. In this context, the present paper aims to evaluate the uplift
resistance of shallow rectangular plate anchors based on the theoretical framework of limit analysis and its related
kinematic approach. Upper bound estimates of the collapse load are obtained from a class of failure mechanisms
considering generic discontinuity surfaces defined from the functional minimization of the uplift bearing capacity.
The rock is modeled as a Tresca material with a tension cut-off criterion, whereas the lower interface of the anchor
exhibits a tensile stress threshold. A parametric study is conducted to evaluate the effect of the problem main
parameters, allowing for an estimate of the ultimate pullout force for several cases. Finally, the semi-analytical
predictions obtained are compared with available results in the literature, thus validating its application. Results
show that model predictions are in good agreement with available results for plates with low embedment ratios.
The dependence on the tensile stress limit of the Tresca material and the interface resistance are also highlighted.

On a High-Order Generalized Finite Element Method

2024-05-18T21:27:26+00:00

In recent years, technological development has grown exponentially. In this context, numerical methods
consist of an attractive tool that guarantees flexibility and ease of access in modeling Science and Engineering
problems. In particular, the High-Order version of the Finite Element Method (FEM), based upon orthogonal
polynomials as a means for constructing hierarchic approximation spaces, is of special interest, due to its high
convergence rate and adequate matrix conditioning. However, albeit FEM achieves good results in a large class

of problems, it is not as adequate when non-smooth solutions are expected. Aiming to circumvent such a limita-
tion, the Generalized Finite Element Method (GFEM) introduces enrichment functions, selected on the basis of a

previous knowledge about the solution of the problem, in order to enlarge FEM’s approximation space. Despite
providing scope and generality expansion to the FEM, such technique may lead, nevertheless, to ill-conditioned
systems of equations, therefore penalizing numerical precision. Taking this into account, this paper proposes a
methodology for integrating positive features of the two aforementioned versions of the FEM, resulting in a stable,
precise and high performing numerical tool. The methodology herein presented allows for the possibility of being
easily implemented in previously existing codes, already designed to handle GFEM. Planar elasticity applications
are considered – including Linear Elastic Fracture Mechanics problems, for which GFEM is more suitable – in

order to demonstrate the previously mentioned convergence and conditioning properties of the proposed formula-
tion.

Numerical analysis on pollutant dispersion in naturally ventilated buildings: nonisothermal conditions

2024-05-18T21:29:45+00:00

Pollutants dispersion and human exposure in urban areas are closely linked to urban and building
ventilation. In this sense, the main target of the present work is to study the pollutant dispersion phenomenon in
naturally ventilated buildings using a numerical model considering incompressible flows with heat and mass
transport. For the flow simulation, a semi-implicit Characteristic-Based Split (CBS) model is used in the context

of the Finite Element Method, where linear tetrahedral elements are used in spatial discretization. The Navier-
Stokes equations and the conservation equations for mass, energy and chemical species form the system of

fundamental equations for the flow field. Flow turbulence is treated through Large Eddy Simulation (LES),
where the Smagorinsky’s approach is adopted for subgrid scale modeling. Thermal effects on the flow field are
considered in the momentum balance equation through buoyancy forces, which are calculated taking into
account the Boussinesq’s approximation. Classic examples of Fluid Dynamics and Transport Phenomena are
analyzed to verify the numerical model proposed here and a numerical investigation is performed considering a
building model subject to natural ventilation, where pollutant dispersion and thermal effects are evaluated
simultaneously.

Numerical Verification for the Asian Rust Dispersion in Paraná

2024-05-18T21:31:56+00:00

This work aims to study the discretization error of a numerical model describing the atmospheric
transport of the Asian Rust spores in Parana. The model was obtained from the discretization of a two-dimensional ́
Partial Differential Equation with diffusive, convective, and reactive terms by the finite difference method. To study
the behavior of the discretization error, a priori and a posteriori analyzes were performed. From the verification
process, it was found that the apparent order converged to the asymptotic order. Thus, the process of estimating
numerical errors through the Richardson Estimate presented promising results.

Analysis of Convergence Diagnostics for MCMC methods

2024-05-18T21:34:33+00:00

The most used method in Bayesian inference is the Markov Chain Monte Carlo (MCMC). But they
are expensive, not only because they require a lot of simulations of the model to explore the posterior distribution
but also because there are no clear criteria to determine if the method has converged to ensure the quality of the
obtained parameters and error estimates. This work objective is to explore a set of convergence diagnostics or
MCMC methods and their strategies for a convection-diffusion model and an epidemiological model, a SIR-type
model.

A new dual boundary element formulation for cohesive crack propagation

2024-05-18T21:36:39+00:00

A cohesive dual boundary element formulation is presented for crack propagation analysis and a path-
following method is proposed to solve the nonlinear system of equations by the direct control of one of the known

degrees of freedom. The simple linear cohesive model is introduced into the algebraic boundary element equations
by local stiffness matrices. According to the cohesive law, the stiffness coefficients decays as crack displacement
discontinuities increases. The acting loads are divided into two groups: one in which the load is perfectly known
and another in which only the direction is known. The magnitude (or load factor) of the latter is determined with
respect to the equilibrium of the boundary fields (indirectly controlled) and an additional path-following constraint
equation. The resulting non-linear system is solved using an incremental iterative scheme. For each iteration, the
corrections to the boundary fields are obtained in a partitioned manner, in which the load factor is calculated
independently using the direct control of the degree of freedom as the path-equation. The results show that the
proposed approach can efficiently capture the equilibrium curves.

Structural Damage Identification based on the Curvature Matrix of the Accelerance

2024-05-18T21:40:04+00:00

In this work, a damage identification method based on the curvature-matrix of the Frequency Response
Function-FRF is proposed. This is used in the formulation of two indices to predict the damage location and to
estimate the severity of the damage in a structure. To evaluate the effectiveness of the method, numerical

simulations are performed in different damage scenarios simulated in a one-storey, one-bay frame using Euler-
Bernoulli beam elements. The structural damage is simulated by reducing the flexural stiffness of selected

elements. The FRF-Accelerance for the undamaged and damaged frame is numerically obtained with the
frequencies and mode shapes of the lower modes. The curvature of the FRF is calculated numerically using finite
differences, based on an expansion of the Taylor series. The results of the simulations indicate that the proposed
method can localize and estimate the damage severity in a one-storey, one-bay frame. The proposed damage
indices could be an alternative to the traditional modal analysis methods.

A numerical study of damage evaluation in jointed plain SHCC pavements using new damage evolution laws

2024-05-18T21:41:55+00:00

It is well-known in the design of jointed plain cementitious pavements (JPCP) that the damage in the
cementitious matrix due to stress near the dowel bars is a key factor that affects the service life of such
structures. This study aimed to evaluate numerically the differences in the damage distribution in the near dowel
bar region in JPCP considering alternative materials: strain-hardening cementitious composites (SHCC) in
substitution to concrete and glass fiber reinforced polymer (GFRP) in substitution to the steel bar. The adopted
constitutive model for the cementitious materials was the concrete damage plasticity. A new damage evolution
law proposed by the authors in [13] was adopted. Such a law can be very effective in reproducing the SHCC
behavior because both damage and plastic strain variables are involved with. Interactions between the
cementitious matrix and the dowel bars were simulated by surface-to-surface contact type. The finite element
models were validated by comparing available experimental load-displacement curves with the obtained
numerical ones. The results for the damage distributions reveal that the use of such alternative materials has
induced smaller damage values within a smaller damaged zone when compared with the model with
conventional materials: standard concrete and steel bars. Consequently, smaller cracks in such zones will appear
which will increase the structural life of the pavement.

Nonlinear dynamic structural analysis of tall buildings considering the nondeterministic wind-induced actions

2024-05-18T21:45:34+00:00

In recent decades, technological advances in civil construction have driven the project and construction
of tall buildings in several countries around the world. However, the structural design slenderness increasing has
been crucial for reducing the natural frequencies values and the damping structural levels generating, in some
situations, excessive vibrations and human discomfort. Aspects generally disregarded in current day-to-day design
practice are related to the geometric nonlinearity effect and the soil-structure interaction on the tall buildings
structural response. Thus, this investigation aims to evaluate the dynamic structural behaviour of a steel-concrete
composite building with 48 floors and 172.8 m height, when subjected to wind nondeterministic actions, including
in the dynamic analysis the geometric nonlinearity effects and the soil-structure interaction. The investigated
building numerical model was developed to obtain a more realistic representation of the structural system, based
on the Finite Element Method (FEM), using the ANSYS program. In this investigation, the found results, based
on the calculated displacements and accelerations values, have indicated relevant differences, when the geometric
nonlinearity effects and the soil-structure interaction were included in the building dynamic response assessment.

Nonlinear dynamic analysis of storage tanks when subjected to nondeterministic wind loadings

2024-05-18T21:47:49+00:00

Storage tanks are associated to thin-walled equipment subjected to wind-induced loads, which can
lead the system to structural instability. The storage tanks behavior is too sensitive to imperfections that can be
present on the structural system, taken into account damage mechanisms which tend to reduce the integrity of
this type of equipment along its service life. In fact, inspection techniques are employed to characterize the
damage mechanisms. This way, the laser scan technique has been shown to be accurate in dimensional
inspection of storage tanks. Therefore, this research work focuses on the nonlinear dynamic analysis of an actual
damaged surface related to a storage tank. The investigated tank presents a diameter of 43.428 m and height of
14.63 m, and is used for diesel storage. The deformations present on the tank structure were measured based on
the use of a laser scan. The point cloud resulting from the dimensional laser scan inspection was used to build a
finite element model taken into account all geometric imperfections. After that, the nondeterministic wind
loadings were used to perform the nonlinear dynamic analysis considering the actual deformed structural system
of the studied tank. In this investigation, the results have indicated relevant differences, when the geometric
nonlinearity effects were included in the structure dynamic response assessment, when compared to those
calculated based on the traditional static analysis.

Steel-concrete composite floors dynamic assessment when subjected to human walking loads

2024-05-18T21:55:00+00:00

This work aims to evaluate the people-structure dynamic interaction effect on the floor’s structural
behaviour, considering the development of experimental tests and also numerical modelling. This way, the

investigated structural model is related to a steel-concrete composite floor building which is composed of a hot-
rolled framing system, with a total area equal to 1300 m2. The floor system is used for normal school occupancy

and is supported by steel-concrete composite columns with a ceiling height of 3.40 m. In this investigation, the
biodynamic models associated with “spring-mass-damper” systems with one degree of freedom (SDOF) were
adopted aiming to represent the people’s walking on the investigated floor. The proposed numerical model,
developed for the steel-concrete composite floor building dynamic analysis, adopted the usual mesh refinement
techniques present in finite element method (FEM) simulations implemented in the ANSYS computational
program. Considering the experimental results calibration, the investigated floor dynamic response was
evaluated based on a parametric study, to study the influence of the people’s step frequencies, number of people
walking and stationary on the floor, structural damping, and also different trajectories of people walking on the
structure. The composite floor dynamic response was determined based on the displacement and acceleration
values, and the results were compared with those calculated utilising the traditional dynamic loading
mathematical models (“only-force models”); and with recommended limits for excessive vibrations related to the
design codes, aiming to assess the floor human comfort.

Micromechanical Approach to the Effective Poroelastic Behavior of Jointed Rock Masses under One-Dimensional Consolidation and Finite Element Implementation

2024-05-18T21:58:13+00:00

A micromechanics-based formulation of the macroscopic behavior of saturated jointed rocks regarded
as homogenized anisotropic poroelastic media is presented. At the material level, the rock matrix forming the
skeleton phase of the porous medium is assumed to be linear elastic, whereas the crosscutting joints stand for
the porous space and are viewed as planar interfaces endowed with a specific generalized poroelastic behavior.
The effective anisotropic poroelastic properties, including the homogenized drained elastic stiffness tensor C, Biot
tensor B, Biot modulusM, as well as the permeability tensor K of the jointed medium are derived. At the structure
level, the consolidation problem of a jointed rock layer is addressed in a one-dimensional setting with anisotropic
flow conditions introduced by joints orientations. For verification purpose, the analytical predictions derived from
the analysis are compared with finite element solutions implementing the effective constitutive state equations,
thus emphasizing that the analytical predictions can be viewed as reference solutions.

Evaluation of Structural Dynamic Modification by Viscoelastic Neutralizers based on Response Reanalysis Methods

2024-05-18T22:36:22+00:00

Structural modifications can occur for several reasons, such as unsatisfactory product for the customer,
structural defects, updating of obsolete parts, generation of intense noise from the equipment to the operator, and

unwanted vibrations. When there is some prior knowledge of the dynamic characteristics of the mechanical sys-
tem of interest, particularly in association with the region where the changes will occur, a practical and convenient

approach is to analyze the effects of these changes using reanalysis techniques. These techniques aim to predict
the dynamic behavior of the system after implementing modifications, from a compact and specific set of data

related to the system and the modifications. The present work aims to investigate the use of two response reanal-
ysis techniques - in matrix formulation - to evaluate the effects of inserting viscoelastic dynamic neutralizers as

localized structural modifications. Viscoelastic neutralizers are considered in the context of future implementation
of vibration control on a cantilever steel beam. In modeling the neutralizers, concepts of generalized equivalent
parameters are used to maintain the same dimension in the system matrices before and after inserting the devices.

To validate the use of the employed techniques, their predictions are compared to the results obtained by an es-
tablished computational program dedicated to the optimal design of dynamic neutralizers in mechanical systems,

named LAVIBS-ND®. It is shown that the investigated techniques do not differ, as far as their predictions are con-
cerned, from the technique currently used in the above mentioned program, which is employed as a benchmark to

assess the accuracy of the evaluated methods. It is then concluded that the focused techniques are actually capable
of accurately predicting the effects of structural modifications by viscoelastic dynamic neutralizers for vibration
control purposes.

A new approach for the Modified Local Green’s Function Method applied to Poisson equation

2024-05-19T15:34:59+00:00

Originally proposed at the end of the 80 ’s, the Modified Local Green’s Function Method (MLGFM) is
an integral method that was described as a hybrid of the Finite Element Method (FEM) and the Boundary Element
Method (BEM). The method was proposed to apply the BEM methodology to problems with no knowledge of
the fundamental solution. Essentially, the MLGFM creates discrete projections of the Green’s function solving
an auxiliary domain problem, and this problem can be solved, for example, by the FEM formulation. Despite the
good convergence of the secondary variable in the boundary, the method has a major disadvantage over FEM, the
obtainment of the Green’s function projections implies in to solve the system of equations in the domain, resulting
in a great computational effort. However, this paper aims to show a new approach to the MLGFM where it is
not necessary to obtain the Green’s projections and the final equations system has the same number of degrees
of freedom as FEM and still presents high convergence for the secondary variable in the boundary. The new
formulation can be obtained directly by the weighted residual sentence and variables using the same approximation
of the original MLGFM. The processing time of the two approaches are compared and the method is applied to
Poisson Equation.

Evaluation of Numerical Parameters of a global-local GFEM approach simulating damage propagation in a L-shaped concrete panel

2024-05-19T15:39:39+00:00

The nonlinear modeling of concrete structures requires strain-softening models that properly represent
the nucleation and propagation of damage. The description of those phenomena, by Finite Element Method (FEM),
is highly dependent on the quality of the mesh and the type of the approximation function adopted. The Generalized
Finite Element Method (GFEM) has been developed in order to overcome some limitations inherent to the FEM
aiming to use some knowledgment about the expected solution behavior to improve the analysis. The GFEM
enriches the space of the polynomial FEM solution with a priori known information based on the concept of
Partition of Unit. In this context, the global-local approach to the GFEM (GFEM global-local) is investigated here
as an alternative to the standard GFEM to describe the deterioration process of concrete media in the context of
Continuous Damage Mechanics. Succinctly, the global-local function used to enrich the global problem is obtained
through physically nonlinear analysis performed only in the local domain, represented by constitutive models and
discretized by a refined mesh, where in fact damage propagation occurs. In the global domain discretized by a

coarse mesh, it is performed a linear analysis considering the incorporation of local damage through the global-
local enrichment functions and damage state mapped from local problem. In this paper, the Smeared Crack Model

is the constitutive model used in the local domain to simulate the damage propagation experimentally obtained in
an L-shaped concrete panel. The numerical simulations aim to evaluate the influence of the following numerical
parameters of the GFEM global-local approach on the equilibrium paths: number of local steps added to each block
of global-local analysis and the size of the global step. The obtained results are compared with the experimental
ones, the most suitable sets of parameters can be found and then applied in other simulations that involve the
expansion of the local domain and the variation of the nodes enriched with the global-local function.

Two-dimensional nonlinear analysis of elastic columns stability using the convected particle domain interpolation material point method

2024-05-19T15:42:32+00:00

This paper presents an elastic two-dimensional analysis of columns stability, using an extension of the
material point method (MPM), called convected particle domain interpolation (CPDI). As instability phenomena

require a large-deformation study, MPM is chosen by its ability to deal with this situation, using a simple and reg-
ular cartesian background grid to calculate the spatial gradients and divergences, besides automatically considers

explicit dynamics. The CPDI extension is applied in order to facilitate natural boundary conditions treatment and

to avoid the cell-crossing error, since the subdomains are explicitly tracked through the analysis and the shape func-
tions have continuous derivatives into these subdomains. A computational routine is implemented using Python

3 language, employing Euler-Gauss explicit time integration and update-stress-last (USL) scheme. A rectangular-
section slender column is submitted to 4 different load cases. The results obtained are the load-displacement

behavior of the columns and its total mechanical energy time variation, which are validated by comparison with
the results produced by classic analytical Euler’s theory. It can be verified, after the analyses, that CPDI MPM is
able to predict the columns buckling loads and to reproduce the post-critical instability phenomena with a good
accuracy. The conservation of energy is achieved in all tests.

Tri-objective optimization of steel frames with the bracing system configuration as a design variable

2024-05-19T15:46:56+00:00

In steel structural design, especially concerning tall buildings, it may be desired to minimize its cost and
improve its performance concerning horizontal displacements, dynamic behavior, and structural stability. Also, the
predefinition of which bracing system geometric configuration is more suitable for each objective is not evident,
and usually, it is made according to the designer’s experience. Thus, solving this problem considering different

cases of three simultaneous objectives is not a trivial task. Therefore, this paper deals with the tri-objective op-
timization of spatial steel frames, considering the bracing system configuration as a design variable. The third

evolution step of generalized differential evolution (GDE3), the success history-based adaptive multi-objective
differential evolution (SHAMODE), and the multi-objective meta-heuristic with iterative parameter distribution
estimation (MM-IPDE) are the differential evolution algorithms adopted in this paper. In addition, a multi-criteria
tournament method is used to extract desired solutions from the Pareto front according to the decision-maker
preferences.

Truss chords buckling

2024-05-19T15:51:29+00:00

The present work proposes reducing coefficients on the buckling length of trusses chords when the
normal acting on these chords is not constant throughout the chord. The normal maximum is considered acting
on the entire compressed part of the chord, but with a reduced buckling length. In this text, it is obtained an
equivalent normal, which, constant in the chord, generates the same deformation energy as the acting variable
normal. This equivalent normal has a value lower than the maximum acting normal. It is made, then, the

proportion to obtain the reduced buckling length to consider. It is solved, step by step, the case of the double-
supported truss under point load in the middle of the span and shown the results for the double-supported truss

under uniformly distributed load and the two-span continuous truss, also under uniformly distributed load. The
solution of the differential equation with the variable normal in the chord, exact, of difficult solution, is also
showed to notice the validity of doing the procedure via energy, approximate. An illustrative numerical example
of the application of these buckling length reduction coefficients is shown to easy the practice.

An Efficiency Study of the Radial Polynomial Expansion Method for Solv- ing Singular Integrals in the Dual-BEM

2024-05-19T15:53:13+00:00

In the Boundary Element Method (BEM), when the element which is being integrated contains the
source point, singularities arise in the integrals that govern the problem. Although several classical methods
have already been proposed and successfully used, their numerical implementation is laborious and often requires
particular codes for each type integral kernel. Recently, a method that allows the solution of integrals with different
singularity orders in a single numerical procedure has been proposed. It is based on the polynomial expansion
of the radial distance between the source and field points and it is called here as Radial Polynomial Expansion
Method (RPEM). The RPEM has its efficiency studied for application to the Dual-BEM. Elements with quadratic
interpolation functions are analyzed. The efficiency is verified in terms of the element distortion and the number
of terms needed in the expansion. For this, the method is implemented in a computational code in Fortran 95 and
the results are compared with other formulations, such as the singularity subtraction method. Once the reliability
and applicability of the method have been proven, it is intended to apply the solutions found in a Dual-BEM code,
for the analysis of fatigue crack propagation.

Recent Advances in a Multiscale Flux-Based Method for Simulating Flow in Fractured Porous Media

2024-05-19T15:55:28+00:00

Computational simulation of reservoir flow is an important tool that provides valuable insight into the
decision process in oil extraction. Several types of commercial software have been developed over the years for this
application, the majority using low-order schemes, which can become prohibitive for very large models. This issue
becomes more apparent since, nowadays, the accuracy of a simulator is dominated by the accurate simulation of the
multiscale characteristics of a reservoir such as permeability heterogeneity. To capture these multiscale features in
low-order schemes, very refined models are required. Therefore, developing a high-order scheme able to simulate
fractured reservoir flow that is accurate and can efficiently capture the multiscale features of the reservoir is of great
value for the field. With this motivation, this presentation reports on recent advances in a methodology to simulate
flow in highly heterogeneous fractured porous media using the Multiscale Hybrid-Mixed (MHM) method with
H(div)-confirming flux approximations. This method is particularly appealing because of its inherent properties
such as local mass conservation, multiscale features, and strong divergence-free enforcement for incompressible
flows. Flow in the porous media is modeled with traditional Darcy’s equations and the coupling between flow
in the porous media and fractures is based on the conceptual Discrete-Fracture-Matrix representation, where the
fractures are idealized as lower-dimensional elements at the interface of matrix elements. The methodology is
compared with benchmark examples to demonstrate its robustness, accuracy, and efficiency.

A reducer order model approach for fuzzy field seepage analysis

2024-05-19T16:03:49+00:00

This contribution proposes a strategy for performing seepage analysis where uncertainty associated
with permeability is characterized by means of fuzzy fields. In order to decrease numerical costs associated with
uncertainty propagation, full system analysis is replaced by a reduced order model. This reduced order model
projects the equilibrium equations to a small-dimensional space, which is constructed using a single analysis of
the system plus a sensitivity analysis. The associated basis is enriched to ensure the quality of the approximate
response. A simple numerical example shows that with the presented strategy, it is possible to accurately estimate
the fuzzy seepage flow with reduced numerical efforts.

Study on the modeling of the actuation system of a quadrotor

2024-05-20T15:16:01+00:00

This work compares the actuator model based on constants, the non-linear model of the actuator’s
components, and the experimental data. The actuation model is composed of the following components: electronic
speed controller (ESC), motor and propeller. The non-linear modeling of the ESC will be done using the pulse
width modulation signal (PWM) as input and the current as output. These current will be the input of the motor
which will have as output the angular velocity which will be the input of the propeller model which will have
as output thrust and torque. A helical trajectory was defined as a desired in the simulation. In both models, the
integral backstepping control was applied. A comparison criterion was used the power consumption, which is one
of the major barriers of these types of vehicles.

Bimoment loads on space frame elements

2024-05-20T15:18:22+00:00

This paper presents an algorithm based on the Direct Stiffness Method to solve bars with composite
variable cross sections under nonuniform torsion. In this formulation, the primary and secondary torsion modes
are described by 2D Neumann's boundary-value problems, which are solved at the cross-section level by
employing the BEM. The torsional rotation angle along the element length is described by a set of ordinary
differential equations, which are solved by using weighted residual techniques. Herein, a nth-order polynomial is
adopted to approximate the torsion angle function. In this paper, we will especially assess the effects of external
bimoment loads on the calculation of stresses along the beam. Accuracy of the formulation is observed by
comparing results obtained with the present beam formulation and 3D solid ANSYS models.

Modeling and Numerical Simulation of Drug Transport and Absorption in a Tumor

2024-05-20T15:20:38+00:00

This work describes the diffusion-convection process of transport of the drug (doxorubicin) administered
by bolus injection through the tumor and interstitium. We numerically solve a coupled system of partial differential
equations that models the drug transport, its uptake, and effect in the tumor.
It is used a high order finite difference method that allows to accurately describe the drug effect in the tumor.
In fact, we can determine the time needed by the drug to reduce the tumor cell density and approximate the drug
spatial distribution in the tumor and interstitium. In addition, the simulations shows how the doxorubicin effect in
the tumor increases as its dose level increases.

On a kinematically exact rod model for thin-walled open section members: incorporating polyconvex constitutive equation

2024-05-20T15:25:04+00:00

In the current work, advances on kinematically exact rod models for thin-walled open section members,

taking into account both primary and secondary cross-sectional warpings, are proposed. Advanced elastic consti-
tutive equations are incorporated in order to enable full bending, compression and torsional strain couplings in the

finite strain regime. The paper extends a previous contribution by the authors (Kassab and Campello [1] ”On a

kinematically exact rod model for thin-walled open section members”, CILAMCE-PANACM-2021) by incorpo-
rating a more advanced constitutive equation, now based on the polyconvex neo-Hookean Simo-Ciarlet’s material.

The older version contemplated only linear elastic and Saint-Venant ́s constitutive equations, which are known for
being unsuited for truly finite strains. Differently from what was performed in a past attempt, all the terms of the
constitutive equation were retained. The model was implemented in PEFSYS, which is an in-house FEM program.
Validation is performed using existing results from the literature as well as solutions obtained with the Ansys’s
shell 281 element.

Comparative experimental and numerical analysis of pile under lateral load in granular soil in Chilca, Perú

2024-05-20T15:30:23+00:00

Piles are frequently used in low resistance soils and often are subjected to lateral loads from different
phenomenon as wind, waves, earthquakes events, ground lateral pressure, etc. Lateral resistance of piles should be
analyzed to guarantee the stability by theoretical methods or in situ tests for correct design. These investigation
compares the deflection results of a lateral load test with the responses in ultimate limit state, p-y and finite element
method to serve as an example that the different procedures, some more than others, provide a real approximation
to the behavior of the pile under lateral load, therefore carry out an optimal design. The test to analyze experimental
behavior was carried out in Chilca, to the down south of Lima in Peru, where full-scale load test provides a solid
basis for understanding the problem. The geotechnical characterization was carried out with SPT field tests and
seismic refraction results. The properties of the tubular A572 grade 50 steel pile are known for being standardized.
Pile under lateral load test followed the guidelines of the ASTM D3966 standard. The analytical and numerical
calculations were compared with the experimental measurements through graphs of displacements along the pile,
these by performing 3D numerical analysis with the commercial program Abaqus® using elastoplastic constitutive
model with Mohr Coulomb failure criterion for the FEM, using GEO5® to solve the subgrade reaction approach
(p-y) problem using Matlock and Reese approximation as soil modulus, at last for the ultimate limit state, Broms
and Meyerhof formulations for flexible piles were used.

APPLICATION OF THE NEWMARK INTEGRATION METHOD TO DETERMINE THE DYNAMIC RESPONSE OF A COMPLETE VEHICLE MODEL SUBJECTED TO THE EXCITATION OF A RANDOM ROAD PROFILE ACCORDING TO ISO 8608

2024-05-20T16:12:16+00:00

When analyzing a vehicle traveling on a lane, irregularities in this lane can expose the driver to
vibrations that can result in health damage. This implies the need for a suitable suspension system. This study is
justified by the fact that the determination of the dynamic response of vehicles traveling on irregular lanes allows
us to understand the behavior of the vehicle in terms of displacement, velocity and acceleration as a function of
time. The general objective of this study is to determine the dynamic response of a complete vehicle model
subjected to the excitation of a random road profile, according to the ISO 8608. The specific objectives are: (I) To
reproduce a vehicle model; (II) Determine a random road profile; (III) Apply the Newmark method. The
methodology of this study consists of simulating the vehicle in Matlab software and validating this model. Apply
the random road profile as road excitation. Determine the dynamic response using the Newmark Method. As a
result, the dynamic response of the vehicle subjected to the excitation of a random road profile was obtained. It is
concluded that it was possible to complete the specific objectives, reaching the general objective.

Numerical analysis of optimum designed models of viscoelastic supports for rotating machines

2024-05-20T16:14:23+00:00

Viscoelastic supports (VES) are a simple solution for vibrations in rotating machinery with a low
associated cost. The objective of this work is to complement an optimal design methodology for VES, developed
by the GVIBS/UFPR group for rotating systems subject to unbalanced excitations, inserting a static stiffness in
parallel, whose purpose is to increase the load capacity of the device. The dynamic behavior of the rotating system
is represented through the finite element method. For the viscoelastic material, the fractional derivatives model of
four parameters is used, which allows considering the effect of temperature and excitation frequency. For the
optimal design, the concept of generalized equivalent parameters (GEP) is used, allowing to describe the equation
of motion of the composed system with VES, being able to obtain the response of the composed system in a space
or subspace of the primary system, efficiently from a computational time perspective. The primary system is
modeled considering a simple rotor and the support is introduced via GEP. Nonlinear techniques allow for optimal
design of the VES. Numerical simulations on rotors with known dynamic behavior allow showing the results of
the proposed methodology and the effectiveness of viscoelastic supports.

Some modeling features for two-dimensional isoparametric and isogeometric finite element analysis

2024-05-20T21:37:26+00:00

This work describes some modeling features of an interactive graphics system for finite element
simulations in two dimensions. The specific objective of this article is to describe the strategy for domain
decomposition into patches ready for isoparametric and isogeometric analysis. The main objective of this system
in the future is to provide students and researchers of computational mechanics with an open educational tool for
understanding the integration of geometric modeling, mesh generation, finite element analysis, and visualization
of results. The presented geometric modeling resources are based on the Half-Edge topological data structure. The
system is developed in Python, based on the object-oriented programming paradigm, and uses the Qt user interface
system. Modeling is performed through the interactive creation of parametric curves of various types: polygonal
lines, quadratic and cubic Bezier curves, composite cubic Bezier curves, circles, circle arcs, ellipses, ellipse arcs,
and NURBS (Non-Uniform Rational B-splines). The system automatically recognizes the creation of closed
regions.

A Comparison between Dual Reciprocity and Direct Interpolation Techniques for Solving the Helmholtz Problem by Frequency Scanning

2024-05-20T21:44:40+00:00

The identification of the modal content of a dynamical system through the excitation frequency
scanning procedure is a very common procedure, especially with regard to experimental models. In terms of
numerical simulation, this technique is also very accessible and computationally inexpensive. In the case of the
Boundary Element Method (BEM), this procedure is much simpler than the direct solution of the associated
eigenvalue problem, if the fundamental solution is frequency-dependent since the problem becomes nonlinear. In
order to simplify the solution of these problems with the BEM, which are stationary acoustics problems
governed by the Helmholtz equation, techniques were developed that use simpler fundamental solutions. Among
these are the well-known dual reciprocity technique (DRBEM) and the more recent direct interpolation
technique (DIBEM). Both are characterized by employing radial basis functions and thus avoiding domain
integrations generated by the reactive term of the governing equation; however, Dual Reciprocity interpolates
only the primal variable of the problem, while the Direct Interpolation technique approximates the entire kernel
of the domain integral. Although they allow the direct solution of the eigenvalue problem, this article compares
the two techniques mentioned to solve the problem of stationary acoustics, through scanning of imposed
frequencies. The stationary data was obtained in a chosen frequency range. Error curves are obtained by
comparing numerical solutions and available analytical solutions for a more accurate assessment.

A numerical scheme for solving a mathematical model derived from larvae- algae-mussel interactions

2024-05-20T21:47:12+00:00

In this work we present a numerical formulation for solving a mathematical model, derived from larvae-
algae-mussel interactions in aquatic environments, proposed in [1]. The model is composed of three unsteady and

nonlinear advective-diffusive-reactive equations for species densities coupled with the Navier-Stokes equations to
simulate the velocity field of the water. We employ the operator splitting technique in the finite element method

context for solving the transport problem in two stages: first, given the velocity field, we solve the advective-
diffusive problem to obtain the densities of larvae, algae and mussels; then, we use this first step approximation as

initial condition for solving the system of ordinary differential equations for the reactions terms. In the first stage,
the nonlinear stabilized finite element method CAU and the two-step Backward Differentiation Formula of second
order are employed in the spatial and time discretizations. The nonlinear process is solved by a Picard fixed point
iteration. In the second stage, the system of ordinary differential equations for reactions is approximated by the
fourth-order Runge-Kutta scheme. The numerical formulation proposed is used to simulate the 3D dynamics of
species proliferation and quantify the golden mussel population in a stretch of the Pereira Barreto channel, located
in Brazil, with a focus on population control actions. The preliminary results as well as other considerations related
to the problem and the numerical model are discussed.

Use of Random Forest to predict the accumulation of plastic strain at grain boundaries of a polycrystalline material

2024-05-20T21:55:09+00:00

The main motivation is the study of the accumulation of plastic strain in the grain scale, through
the use of machine learning. This alternative can be a significant contribution towards creating models capable
of predicting the accumulation of strains. In this way, machine learning becomes a tool capable of helping to
understand which physical parameters control damage accumulation. The objective of this study is to predict the
accumulation of plastic strains at grain boundaries using the Random Forest model. For all machine learning
models, it is necessary to perform effectiveness tests and in this study cross-validation was used. It is a numerical
work, based on machine learning, which uses the Random Forest algorithm and cross-validation to authenticate
the model. The metric used to measure the performance of the model was the coefficient of determination (R2).
Results for the predictions of the accumulation of plastic strains, when considering the same microstructure, are
coherent and of good quality. When comparing the results obtained in this work with the predictions found in the
literature, the results obtained are satisfactory. Concluded that the Random Forest model is reliable for predicting
the accumulation of plastic strains in grain boundaries of a polycrystalline material.

Analysis of global stability of guyed towers considering unilateral constraints

2024-05-20T21:57:37+00:00

Guyed structural systems are present in several engineering applications, and as a large portion of these
structures have a high level of slenderness, their designs are based on stability criteria. The set of cables present in
these elements are characterized by high efficiency when they are tensioned. The main objective of this study is
to analyze the static and dynamic nonlinear behavior of a discrete guyed tower model with two degrees of freedom.
Furthermore, the present work devotes special attention to the consideration of the unilateral contact (boundary
condition) in the nonlinear oscillations of this structure. The unilateral contact is manifested in this type of
application from the consideration of the capacity of the stays to resist only the traction efforts, as an effect, this
approach strongly modifies the analysis of the proposed structural system. For this model, there is a significant
influence of the consideration of unilateral contact on the post-critical behavior, with a marked decrease in the
critical load of the structure. Thus, the results show that this type of structure is highly sensitive to geometric
nonlinearities and to the restriction of certain stays, indicating that these effects must be considered in the tower
design phase.

Evaluation of the Nonlinear Behavior of Concrete Structures Using a Flat Shell Finite Element

2024-05-20T21:59:51+00:00

This work presents a study of the coupling of the geometric and material nonlinearities applied in

plain and reinforced concrete structures, using flat shell finite elements. For geometric nonlinearities, the prin-
ciple of virtual works and a generalized finite element method (GFEM) approximation are explored to directly

formulate the nonlinear governing equations in a total Lagrangian approach. The material’s behavior will be
described by a smeared cracking constitutive model, capable of representing the concrete degradation process,
from the phenomenological approach of crack propagation. In order to evaluate variations in stresses, strains,

and, consequently, degradation due to cracking along the thickness, the shell element is subdivided into N dis-
crete layers, allowing the measurement of the inelastic behavior of the material. In this proposal, each layer can

be represented by different materials, allowing the representation of reinforced concrete structures with the steel
described by a classic elastoplastic model. Finally, numerical simulations of shell structures will be presented,
considering the coupling of the referred nonlinearities.

Nonlinear analysis of inelastic frames considering a corotational approach and plasticity by layers: a discussion about computational implementation

2024-05-20T22:02:19+00:00

This work presents the development of a numerical solver for nonlinear analyses of plane frame

structures using the corotational formulation to take into account geometric nonlinearity and considering an elasto-
plastic constitutive model. A one-dimensional rate-independent plastic model with isotropic hardening was

implemented, and the cross-sections of beam-column elements were subdivided into layers to simulate
plastification. The goal is to discuss the computational implementation aspects of the inelastic material behavior
in an object-oriented framework for nonlinear finite element analysis of frame structural models. A numerical
example is presented to highlight the influence of the inelastic behavior in the equilibrium path of structures.

Numerical experiments to assess the performance of different formulations and solution algorithms for geometrically nonlinear analysis of two-dimensional frames

2024-05-22T09:30:13+00:00

This work presents an investigation, through numerical experiments, of different geometrically
nonlinear formulations and solution algorithms for the structural analysis of two-dimensional frame models. The
goal is to determine the most suitable formulation and algorithm to be adopted for structural analyses of this type.
The formulations investigated for the tangent stiffness matrix of beam-column elements are based on different
kinematic descriptions of motion, namely the Updated Lagrangian and Corotational approaches. The algorithms
to solve the nonlinear system of equations are continuation methods based on the standard Newton-Raphson
iteration strategy commonly used to suppress limit points of load and displacement. The numerical experiments
cover a wide variety of simple benchmark models, each one with a distinct nonlinear behavior, to evaluate the
performance of the formulations and algorithms selected for this study.

FTOOL: Three decades of success as an educational program for structural analysis

2024-05-22T09:34:39+00:00

This article describes the history of the development of the educational program FTOOL, which is a
user-friendly software used all over the world for teaching structural analysis of two-dimensional frames as well
as for engineering projects. The paper highlights the main milestones in the evolution of the program since its
creation in 1992. It reports how the main features of the program were progressively incorporated, through the
contribution of several academic works, until reaching the current state. The focus is given to the experience of
using FTOOL as a powerful educational tool in many structures’ disciplines of a Civil Engineering undergraduate
course. It also presents the program's latest improvements and the new features that are coming in the next versions.
These new implementations include buckling modes for stability analysis, vibration modes, geometrically
nonlinear analysis, semi-rigid connections with linear and non-linear behavior, and reinforced concrete design.
With these developments, the program will remain up-to-date with the engineering demands of nowadays.

GES: INTELLIGENT SYSTEM FOR DETECTION AND CLASSIFICATION OF DEFECTS IN GRANITE PLATES

2024-05-22T09:36:56+00:00

According to information from BANDES (Development Bank of Espírito Santo) in 2021,
Espírito Santo was responsible for 82% of brazil's marble and granite exports. This is one of the most
relevant industries of the Economy of Espírito Santo, representing about 7% of its GDP (Gross Domestic
Product). As a comparison, in November 2021 alone, Brazil exported 221,800 tons of ornamental rocks for
$138.1 million, accumulating 2.21 million tons of exported rocks in the year, totaling $1.2 billion in the
period. Using the process of processing granite sheets, there are many manual activities, such as inspection,
cataloging, photography, and registration. Such volume of interactions makes the process slow, and prone
to errors that can influence the last price of the product. The applicability of artificial intelligence techniques
in these processes is observable, and it is possible to present results from the use of high-resolution digital
images, initially fitting the classification and organization of images in a dataset applicable to machine
learning techniques. The present work aims to build a classification system of these granite plates, called
"GES System", trained from the dataset with images provided by the companies participating in the project
and that will be able to identify the rock class, and its defects. The classification process will be done using
YoloV5 artificial intelligence tools. The uses of other languages for the complete completion of the project
and release for the use of the system in a production environment are planned for other stages. Among the
benefits of process automation are cost reduction, agility in the process of identifying defects and
standardization of classification.

A MULTI-FIDELITY REDUCED-ORDER MODEL APPLIED TO RESER- VOIR ENGINEERING

2024-05-22T09:39:58+00:00

Although the rapid evolution of computational power, some applications (e.g., optimization, uncertainty
propagation), combined with the increase of simulation complexity, may still require computational times that are
unsuitable for practical purposes. Therefore, in the present work, a multi-fidelity surrogate strategy for expensive
reservoir engineering numerical models is presented. The main idea of the approach is to combine information
from few high-fidelity samples (of long computational duration) and accurate simulations with faster evaluations
from a low-fidelity model with lower accuracy. This strategy provides enough information for creating a surrogate

model, however with a lower computational cost than what would be obtained by evaluating just high-fidelity sam-
ples (for the same level of quality). Furthermore, conversely to the majority of multi-fidelity models, the present

strategy includes a dimensionality reduction technique to deal with multi-dimensional outputs. The presented ap-
proach is employed in an example of a reservoir engineering problem for predicting both the net present value and

the saturation of oil in the reservoir. The results obtained are suitable when evaluating both time and accuracy,
indicating that the presented approach is promising for practical applications. Moreover, it also suggests that the
same framework may be used in other computationally demanding applications.

Modelising the grain mass aeration process using the Thorpe Model with the Finite Volume Method

2024-05-22T09:42:35+00:00

By the technological advancements in agriculture, rural production is searching for ways to improve
grain storage. Rigorous control of temperature and moisture is essential as they are the main factors contributing
to product deterioration and plague proliferation. One of the most effective ways of achieving this is by aeration, a
process widely applied to maintaining grain quality in silos and warehouses. This work aimed to develop a control
system for the aeration of stored grains based on experimental data from literature and process simulations. The
control strategy employed in the aeration aims to maintain temperatures uniform inside the silo and cool down the
grain mass whenever possible. During this process, the grain mass is split into multiple thin layers according to
the flow of air (upwards). The mathematical model used was proposed by Thorpe and associates psychometric
properties of the air with mass and energy balance equations. In this sense, the system of equations resulting
from the mass and energy balances was solved iteratively for each time increment and each layer. Additionally,
the model equations were discretized using the Finite Volume Method combined with the Upwind Differencing
Scheme for the spatial approximations as well as explicit, implicit, and Crank-Nicolson temporal formulations.
Moreover, a posteriori analysis of the discretization error orders was carried out. The proposed model in this study
has proved satisfactory, with some variations depending on the combination between the method and the spatial
and temporal approximations employed.

Numerical simulation of bulging and their effects on ultimate bearing capacity in bored piles

2024-05-22T09:46:59+00:00

Piles are deep foundations that are used to overcoming difficulties of founding on soft soils to ensure
structural safety to carry the loads imposed by a structure through a weak soil to a resistant stratum. It is becoming
more important to design piles and avoid their shortcomings. Bulging in bored piles is a common event that can
occur due to multiple factors. This type of imperfection increases the ultimate bearing capacity of the pile, due to
the increase in its geometry, which increases its ultimate shaft resistance. This can be beneficial for the
superstructure that said pile supports. However, said increase in the ultimate bearing capacity of the pile must be
analyzed cautiously, to avoid overestimations when conducting the structural design of the superstructure. For this
reason, a simulation of the ultimate bearing capacity in a concrete pile without a bulging was conducted, in order
to compare the results with different cases of piles with bulging, and to calibrate the model.

BEAM TRANSVERSAL AREA DIMENSIONS OPTIMIZATION USING ARTIFICIAL NEURAL NETWORKS

2024-05-22T09:50:47+00:00

The present work shows the analysis of a numerical experimental test that was performed using
randomized and combined data to study the bending behavior of beams, through the deflection equation
considering plane stresses in two different examples. The first is a cantilever beam with force concentrated at the
free end and the second is a pinned-pinned beam with loading uniformly distributed along the span. The variables
width, height, length, longitudinal modulus of elasticity, deflection, and loading were used as estimated parameters
to calculate the ideal width and height dimensions for each beam and obtain a structural optimization considering
the limits of deformation according to ABNT NBR 6118/2014. The data generation was generated in Excel
spreadsheet format and worked in an Artificial Neural Networks in TensorFlow Python language, with six hidden
layers. In addition, the functions 'mae', 'sgd' and 'loss' were used as optimizers or activation function in TensorFlow.

Experimental and numerical study of heat generation by energy dissipation in a rotating drum filled with particulate material

2024-05-22T21:28:25+00:00

This work aims to investigate the generation of heat by dissipation of mechanical energy in particulate
flows. The behavior of material in a rotating drum is considered in experimental and numerical analyses. In the
physical experiments, the temperature of the particles inside the drum was monitored by means of infrared
thermography and the influence of rotation speed and filling ratio was explored. The experimental data were later
used to calibrate numerical simulations using the Discrete Element Method (DEM). The numerical results were
then analyzed to gain more insights into the mechanisms of heat generation.

Deep learning algorithm based on YOLOV5 Neural Network for dermatoscospic classification and detection of epithelial cancer (MELANOMA)

2024-05-22T21:33:01+00:00

Technical concepts are introduced about epithelial cancer or melanoma, one of the most common and
aggressive types of existing cancers, and about the use of applications or tools based on Artificial Intelligence
techniques and the influence of the application of machine learning to perform pre-diagnoses in medicine in
general, which accelerate the time of discovery of the disease and exponentially increase the chances of cure of
the affected patient. The technical details of the algorithm based on Deep Learning Yolov5 are developed. The
possibility of applying this tool for various purposes is discussed. The dataset used in this research is analyzed and
the possibilities of characterizing tumors between benign and malignant are verified, as well as the types of
epithelial formations found are classified. The possibility of using these classifications as input for algorithms
based on deep learning by scanning images is discussed. It is concluded that it is possible to create logical filters
that use the readings of the output data provided by the execution of the Yolov5 algorithm on a photographic basis
of dermoscopic exams, obtaining relevantly high levels of accuracy that would point out with great precision the
possible existence of cancerous formations, thus facilitating the pre-diagnosis and early combat of skin cancer,
considerably increasing the survival of patients.

Detection and classification of firearms applied to entertainment media

2024-05-22T21:36:29+00:00

Entertainment media have evolved considerably over the years. With this, the immersion and reality in
the production of films, series and electronic games has increased. By improving this virtual reality, there are side
effects in the production of content aimed exclusively at the younger audience, which, depending on the content,
usually has an excessive load of violence, especially content related to firearms. Although the state of the art
already has a significant advance in object detection through deep learning algorithms, real-time weapons detection
is still a challenge. The detection of two classes of firearms was introduced to this work: handgun and heavygun.
A dataset containing 2,000 images was used and another 2,000 were collected from various entertainment media
and later annotated. The YoloV5 algorithm was used in this research, since it is already a consolidated model
among researchers in the area. The analysis of the result is based on the exposure time in which firearms were
exposed in entertainment content.

ANALYSIS OF AEROELASTIC STABILITY OF VISCOELASTIC SANDWICH PANELS IN SUBSONIC REGIME USING THE NONPLANAR DOUBLET-LATTICE METHOD

2024-05-22T21:38:56+00:00

The engineers of aeronautical industries are frequently facing with subsonic panel flutter phenomena,
where the design and analyses of aerospace vehicles requires the knowledge of their critical flutter speeds for
safety requirements and to avoid catastrophes. Thus, whenever possible it is important to evaluate efficient and
low-cost aeroelastic control strategies to deal with the problem of panel flutter phenomenon. In this context, the
use of passive constraining viscoelastic layers seems to be an interesting alternative to be used in such situations.
However, the structural and aerodynamic modeling procedures of an aeroviscoelastic system subjected to a
subsonic airflow are not easy. In most of the cases, the difficult is related to the fact that, the viscoelastic behavior
depends strongly on the excitation frequency and temperature, resulting in some difficulties during the coupling
between the structural and aerodynamic models to account for the unsteady aerodynamics and complex behavior
of the viscoelastic part, simultaneously. In this study, it is proposed an efficient numerical strategy to model
aeroviscoelastic systems under subsonic airflows for panel flutter suppression. Here, the curved plate model of a
thin three-layer sandwich panel and aerodynamic loadings using the nonplanar doublet lattice method are
constructed both in MATLAB® environment code. Also, to solve the resulting equations of motion of the complex
aeroviscoelastic system, an improved version of the p-k method is proposed herein to estimate the critical flutter
speeds and to verify the possibility of increasing the critical flutter speeds of the base panel by using viscoelastic
materials. The influence of design parameters characterizing the performance of the viscoelastic treatment and its
operation temperature on the flutter boundary has been also addressed herein.

Theoretical and finite element analysis of a laminated composite pipe under combined axisymmetric loading

2024-05-22T21:43:23+00:00

An essential aspect of hydrocarbon exploitation in offshore fields is ensuring the integrity of the
employed flexible pipes. In deep and ultradeep waters, new materials, structural configurations, and numerical
and experimental methodologies are required to obtain viable solutions depending on the operational and
environmental conditions. For instance, flexible pipes typically employ steel armors to resist the imposed
mechanical loads. However, the dimensions of these armors significantly increase with increasing water depths,
frequently causing the overload of the top supporting structures in floating production systems. Moreover, these
armors are particularly sensitive to stress corrosion cracking (SCC) when transporting fluids rich in
contaminants. Aiming to overcome these difficulties, a viable alternative to the typical flexible pipes is the
thermoplastic composite pipe (TCP), which is lighter and insensitive to SCC. Hence, this work investigates the
response of a composite pipe to combined axisymmetric loadings with two models: an analytical model based on
equilibrium and compatibility equations; and a finite element (FE) model. The responses obtained with both
models are compared in a parametric study, where the lay-up of the pipes and the operating temperatures are
varied. Finally, the burst pressures of these pipes are predicted following different failure criteria.

Sensitivity analysis of dry friction damper position in stay cables

2024-05-22T21:47:09+00:00

The aim of this study is to perform a comparative analysis regarding position influence of a damper
with the dry friction mechanism to control the cable vibrations in cable-stayed bridges. The finite element method
is used to implement the cable model and its validation by analytical theory. Lumped mass matrix and stiffness
matrix considering the applied stress were generated considering the cable discretization in one hundred elements.
The proportional damping matrix is obtained by the Rayleigh method with a damping rate of 0.13%. Damping rate
evaluation take into account the damper position varying unitarily in the first 10% of the cable total length. The
excitation force simulates the cable shape in its first mode of the vibration. To numerically solve the second-order
nonlinear ordinary differential equation, Newmark’s method with average acceleration is used. The damping
factors obtained made it possible to compare with other studies for viscous dampers. Time domain was used to
analysis the amplitude variation in the middle of the cable and at damper position, where it was possible to assess
mobility limitations and the feasibility of choosing the position. It can be concluded that changing the damper
position towards the cable center caused a total damping increase.

Panel Flutter Investigation including Thermal Effects through the FEM

2024-05-22T21:49:59+00:00

Thermal effects in aeroelastic stability are of the main concern of super and hypersonic vehicles, since
the aerodynamic heating causes, with the rise of temperature, the degradation of elastic properties of the material
and, in addition, compressive stresses due to thermal expansion, which can make flutter more critical. In recent
decades authors have developed non-linear methods in order to verify this behaviour. This paper aims to verify if
the use of the FEM in a two steps analysis employing the Nastran software with a non-linear heat transfer analysis
and subsequent eigenvalue flutter analysis can produce results agreeable with the literature. It is used in the linear
third-order Piston Theory with Van Dyke’s correction for aerodynamic modelling and the Mindlin-Reissner plate
theory for structural modelling. The PK method is used to solve the aeroelastic eigenvalue problem in a range of

flow conditions in order to determine the instability boundary. The results are obtained from a metallic simple-
supported square panel.

TWO-DIMENSIONAL ELASTIC LINEAR PROBLEMS USING THE VIR- TUAL ELEMENT METHOD

2024-05-22T21:52:38+00:00

Virtual Element Method (VEM) is a relatively new method for solving partial differential equations,
which proposes to generalize the classical Finite Element Method (FEM) with respect to the mesh discretization.
In the two-dimensional case, any simple polygon can be used as discretization element and, as a result, the shape
function are not strictly polynomials. The method main characteristic is to compute those functions implicitly,
without the necessity of knowing their explicit form, giving it great versatility when treating complex geometries.
The VEM presents a dense mathematical formulation, and it was originally developed for the Poisson equation. In
recent years, a considerable number of works has applied the method for different engineering problems usually
treated using finite element models. For example, VEM formulations were adapted to different rheology problems,
contact problems and topological optimization. However, the usage of the Virtual Element Method is not so popular
when compared to the Finite Element Method or the Extended Finite Element Method. The main goal of this paper
is to present the Virtual Element Method applied to linear elasticity problems in two-dimensions by focusing on
its implementation, aiming to contribute for the popularization of the method. The results obtained with VEM are
compared with the results from a Finite Element Method commercial software, showing good agreement and the
great potential of the method in engineering problems.

Measurement of classified points using stereo vision and techniques of segmentation in disparity map for detection of obstacles.

2024-05-22T21:54:47+00:00

This work presents an obstacle detection system using a stereo camera as a sensor and segmentation
techniques in occupancy maps identifying navigable and non-navigable regions. The disparity images are used to
build a 3D point cloud whose distances are calculated from the ground plane. Then, points that are in a range of
distances are classified as potential obstacles and recorded on an occupancy map. Clustering techniques are then
applied to identify obstacles to identify the position, size and speed of obstacles. To validate the algorithm
developed in this work, some real tests were carried out with a full-scale autonomous vehicle.

COMPARATIVE ANALYSIS BETWEEN TURBULENCE MODELS FOR THE RECTANGULAR 2:1 CROSS SECTION

2024-05-22T21:57:44+00:00

Flow around rectangular structures is a classic topic in computer simulation due to its incidence and
characteristic similar to structures in engineering such as tall buildings, bridge decks, water treatment plants,
etc. Therefore, this work discusses the results of two-dimensional computational fluid dynamics simulations of
turbulent flow, performed for a rectangular cylinder with Re=105

. The Navier-Stokes equations were solved with
Reynolds mean turbulence models, specifically, k-ω SST, k-ω SST LM, k-ε. The simulations performed are
used as a parameter for a comparative analysis of the performance of these turbulence models. The objective of
the research is to carry out a discussion about the presented turbulence models, making a correlation with the
coefficients of drag, lift, Strouhal number and the pressure coefficient around the studied section. The analysis
showed that for the case studies considered, the k ω SST and k ω SST LM models were able to provide results
closer to the literature when compared to the others. All developments were performed with non-commercial
OpenFoam code.

COMPARISON OF DIVERGENCE SCHEMES APPLIED TO THE STATIC CASE OF THE GREAT BELT EAST BRIDGE

2024-05-22T22:01:00+00:00

The behavior of slender structures to the action of the wind is the object of study in numerous works.
With the constant evolution of Computational Fluid Dynamics (CFD), obtaining and analyzing results through
numerical methods has been increasingly used by researchers in order to provide reliable parameters for new
engineering projects. In this study, simulations are presented with a 2D approach of the static case of the Great
Belt East Bridge in turbulent flow with Re 105

, applying the k-ω SST turbulence model to the simulation with
the Reynolds Averaged Navier-Stokes methodology (RANS), which deals with an averaging operation applied
to the Navier-Stokes equations to obtain the average fluid flow equations. The simulations were performed via
OpenFOAM®, using four divergence schemes: Gauss QUICK, Gauss upwind, Gauss linearUpwind, and Gauss
limitedLinear. Then, a comparison was made of the average values of the dimensionless aerodynamic coefficients
of drag (Cd), lift (Cl) and moment (Cm), in addition to the Strouhal number (St). There was also an evaluation
of the computational performance of the schemes applied in the simulations. In conclusion, the QUICK scheme
presented promising results in all analyses, and the others were within an acceptable range, with some values close
to those found in the literature. Finally, the results obtained via CFD were validated and considered satisfactory,
proving the effectiveness of this methodology.

Aerodynamic and aeroelastic analysis of the NACA0012 airfoil using CFD

2024-05-22T22:04:56+00:00

The aerodynamic analysis represents the beginning of the conceptual planning of an aeronautical project.
These analysis result in the establishment of important parameters, such as the maximum weight that the aircraft
is allowed to have, as well as the aerodynamic coefficients, which define geometric and flight aspects. There are
several ways of evaluating the aerodynamic coefficients of a wing, such as, for example, the use of wind tunnels
(database in the laboratory), traditional analytical methods, or even computer modeling, which can be based on
the method of panels, or finite volume method (FVM). In order to develop this work, FVM and the open source
code called OpenFOAM (in C++ programming language) are used. The aim of this experiment is to analyze the
activity of the aerodynamic coefficients with the increase of the angle of attack (AoA) of the airfoil NACA 0012,
through a two-dimensional model, and apply these data to evaluate the aeroelastic phenomenon of divergence of a
conceptual wing. The aerodynamic coefficients of lift and drag were evaluated for a Reynolds number 700000, by
the consideration of a turbulence model of the RANS class of the Reynolds averages called k-omegaSST. For the
computational solution, the implementation of pressure-velocity coupling was used, through the SIMPLE method.
The angle of attack started from 0 degrees to the limit region for the start of the stall. The results were consistent
with those established as a reference, which was obtained for data validation of the NACA 0012 airfoil. The
rate of variation of the lift coefficient, as a function of the angle of attack of the airfoil, allows the evolution of
the aerodynamic loading in the structure, an essential factor for the aeroelastic study of a project. The example
discussed in this work does not fail structurally, and presents a divergence velocity value above the limit for the
flight envelope.

Acoustic cavity theoretical and numerical analyses for noise attenuation by applying Helmholtz resonators

2024-05-22T22:09:10+00:00

From the passive methods of acoustic cavity sound control, the use of reactive silencers is widely ap-
plied in many engineering sectors. These devices consist of segments of interconnected cavities that do not use

materials with dissipative properties. There is a variety of reactive silencers and the present work has highlighted
the Helmholtz resonator. Methodologies for the evaluation of acoustic cavities using these resonators for sound
control purposes are not extensive, so a theoretical method for the analysis of noise attenuation performance in this
acoustic system is presented. In addition, in order to evaluate and discuss the theoretical results obtained, analysis
was performed using the finite element method with the aid of ANSYS® software with acoustic extension. In

this methodology, the pressure-formulated element has been used. The theoretical and numerical results demon-
strated good agreement and evidenced the sensitivity of the acoustic parameters and sound control efficiency to

the resonator neck geometry which exerted a strong influence on the modal parameters and on the transmission

loss in theoretical results. Lastly, an experimental study of acoustic cavity sound control using Helmholtz res-
onators developed at the University of Brasilia is evaluated by the methodology presented, in order to obtain a

numerical-experimental comparison of the results obtain.

Multi-level optimization of maintenance planning for corroded pipelines considering different corrosion growth models

2024-05-23T09:42:01+00:00

Pipelines are safe and efficient elements used to transport oil & gas products, but over time their
structural integrity can be compromised due to corrosion defects. In order to ensure the safety and efficiency of a
pipeline, risk management through periodic inspections (and repairs when needed) is essential. In this work, the
influence of different corrosion growth models - namely linear and power-law - on the estimated total costs (the
sum of cost of inspections, failures and repairs) of inspection schedules is assessed; these schedules are, then,
optimized for a given number of inspections, constrained to a predefined reliability threshold. Our findings

reaffirm those of previous studies that show the linear model as being more conservative than the non-linear power-
law one providing larger optimized total estimated costs.

Optimal maintenance planning in pipelines with corrosion defects considering different types of steel.

2024-05-23T09:45:26+00:00

Recent studies indicate that most of the world's fuel is composed of oil and gas, being transported by
pipelines. In this scenario, corrosion is considered one of the main problems that affect the integrity of these
elements, in which the risks associated with failures can have human, environmental and financial repercussions.
Thus, planning its maintenance is essential to control the risk of failures and prevent accidents. In this context, the
present work aims to evaluate the influence of the types of steel, considering different expressions for the
calculation of the pressure of failure, in the cost and probability of failure of the optimal timeline for different
numbers of inspections, not being restricted to the approach of fixed intervals. More than one failure mode is
considered, the 'interior-point' algorithm is used in the optimization and the reliability analysis is performed with
Monte Carlo simulations, commonly used in the literature. To determine the starting point of the optimization, the
objective function is calculated on a sample constructed using the Latin Hypercube - LHS technique. Preliminary
results shows that different types of steel have a significant effect on optimal costs and probability of failure for
different numbers of inspections.

Shear Strength Prediction of SFRC Beams Using Machine Learning

2024-05-23T09:48:51+00:00

Concrete is one of the most used structural materials in the world, but it has some limitations such as
brittle behavior and low deformation capacity when being tensioned, which makes it susceptible to the appearance
of cracks that occur in its interior. The steel fiber reinforced concrete (SFRC) improves the mechanical behavior
of concrete structures allowing, for example, the partial or total replacement of the stirrup reinforcement in
structural elements. However, due to the complex shear behavior, it is necessary to understand the contribution of
each composite parameter to the behavior of the structural member in order to better design new structures with
this material. Therefore, the present work uses Machine Learning algorithms to predict the shear strength of SFRC
beams from a survey of experimental data found in the literature. Different input parameters are considered for
this study, such as the fiber volume fraction, fiber aspect ratio, among others. The results demonstrated a high
accuracy of the ML algorithm, reaching a R2 = 0.96. Moreover, a comparison of the shear prediction capacity
between ML approach and the analytical models available in literature is performed. This research aims to
contribute to a better understanding of the shear phenomenon of SFRC beams, taking into account different aspects
that can assist and aid design engineers in the conception and execution of structural projects.

Numerical Resolution of the One-dimensional Shallow Water Equations by the Discontinuous Galerkin Method

2024-05-23T19:58:48+00:00

The 1D shallow water equations model the unstable flow of an incompressible newtonian fluid in a
channel. These equations are given by the conservation of mass and linear momentum, and can be viewed as an
average of the Navier-Stokes equations under the assumption that the vertical length scale is much smaller than the
horizontal length scale. These equations, also known as Saint-Venant equations, compose a system of conservation
laws of hyperbolic nature, allowing for discontinuous solutions. In order to provide a numerical methodology for
the approximation of the Saint-Venant equations capable of accurately representing such discontinuous solutions,
in this work we adopt the Discontinuous Galerkin method. This class of finite element methods is based on
the weak formulation of the differential equation to be studied, and uses discontinuous piecewise polynomial
approximations. We present some numerical experiments for different flow regimes and non-horizontal beds for
the 1D shallow water problem, such as idealized dam breaking, hydraulic jumps and transcritical flows in channels
with non-constant bathymetry.

Full-interaction design of composite ribbed lattice girder slabs with cold-formed lipped channel shuttering

2024-05-23T20:01:52+00:00

The development of design methods for steel-concrete composite slabs grew in importance due to an
ever-increasing demand for architectural flexibility, which allows for the reduction of total construction cost and
simplifies construction procedures. An alternative to traditional pre-cast lattice joist slabs was recently developed,
which implements a cold formed steel (CFS) profile fastened to trussed rebar by uniformly distributed plastic
spacers. Previous theoretical studies resulted in methods for predicting the ultimate allowable live load of this slab
system. However, steel-concrete composite behavior was neglected due to the absence of experimental data. As
such, this paper relies on standardized design codes to propose a design method that accounts for composite
behavior, considering full interaction between CFS profile and reinforced concrete (RC). Altogether, the results
obtained have evidenced a better performance of the system regarding the previous design methods, expressed by
the increase of unpropped span in more than 80%.

THE INFLUENCE OF GEOMETRIC STIFFNESS IN THE SIMULATION OF A WIND TURBINE TOWER

2024-05-23T20:08:34+00:00

Taking into account that technological advances have enabled increasingly slender projects, it is increasingly
necessary to study the influence of second order effects on the behavior of structural elements. When a flexural element
is subjected to a significant axial load its elastic stiffness is altered. Wind towers are an example of this, in addition to
being subject to bending by the incidence of wind action, they support a large compression load. Item 15.1 of NBR
6118:2014 states that the assessment of the second-order effects occurs when the balance analysis is conducted
considering the configuration of the deformed. Thus, the present work aims to study the dynamic response of a wind
tower considering the influence of geometric nonlinearity resulting from the weight that the tower supports. The
modeling of the structure performed in ANSYS adopts the geometric simplification of the blades of Murtagh et al [1].
To experiment with the computational procedure used in the analysis of the tower, a beam cantilever submitted to a
normal static compression load and a transverse dynamic load at the free end was evaluated. The results obtained by
the analytical procedure and numerical simulation were compared and, besides to presenting a good agreement with
what is expected, shows the influence of pre-tensioning on the bending resistance of a piece.

Recurrent Neural Networks for air-quality forecast models in the city of Rio de Janeiro

2024-05-23T20:11:12+00:00

The tropical climate of the metropolitan region of Rio de Janeiro is especially susceptible to air
pollutants such as Ozone and Particulate Matter, which are directly connected to serious cardiopulmonary
illnesses. The goals of the present work were: to explore the local meteorological data to find useful patterns
among the information and to exam the performance of an ensemble model of Recurrent Neural Networks on the
prediction of daily maximum pollutant levels. The analyzed dataset is provided by the Rio de Janeiro local
government and it is composed by hourly-levels for pollutants and meteorological features from eight different
locations. The Spearman correlation test among the variables of different stations showed that adjacent locations
have similar data, with values up to 95% of correlation depending on the examined variable. The experiments
showed that the ensemble model has superior performance to simpler models in 3 out of 4 studied scenarios.

APPLICATION OF NEURAL NETWORKS IN A PARALLEL MANIPU- LATOR WITH FLEXIBLE LINKS FOR MODEL EXTRACTION

2024-05-23T20:13:20+00:00

Parallel manipulators (PMs) are a viable design alternative for industrial applications. Due to their
closed kinematic architecture, they present some advantages compared to their serial counterparts: lightness, high
speed/acceleration ratios, high rigidity, load capacity, and high compactness. However, this design option could
yield undesired vibrations due to its components‘ flexibility requiring the implementation of novel joint and task
space control strategies. Two main challenges arise when designing a control strategy for a PM: the lack of a
direct measurement of the end-effector‘s pose and their coupling dynamics. This work proposes an estimator for
assessing the end-effector‘s pose of a PM using Artificial Neural Networks using measurements from encoders,
strain gauges and camera. The encoders measure the angular displacement of the active joints of the manipulator,
the strain gauges the deformation of the links and the camera the position of the end effector. The proposal is
validated using experimental data from a 3RRR PM with flexible links. The estimator can be used in control
schemes to enhance the performance of flexible PMs.

AN INVERSE PROBLEM APPROACH FOR THE IDENTIFICATION OF THE REFRACTIVE INDEX IN THE HELMHOLTZ EQUATION

2024-05-23T20:17:27+00:00

The Identification of parameters for differential equations is one of the most common types of discrete
inverse problems. Formulations like these can be used to calculate the thermal conductivity of a material, the drag
coefficient in a body during freefall and the diffusion of matter through a certain media. Following this trend, this
paper shows how the refraction index of a pre-established domain can be calculated applying inverse problem
techniques to the Helmholtz equation. As the main endeavor in inverse problems arise from the necessity of solving
matrices with large condition number, this work contains an overall review and a numerical comparison between
classical and more recent regularization schemes to solve these ill-posed matrices. In order to validate the results,
the problem was also solved in a direct manner using the Finite Elements Method. Results include numerical
examples for uniform and non-uniform mesh grids.

Identification and location of steel coils using the GNSS system with RTK correction

2024-05-23T20:19:50+00:00

The precision, repeatability, and accuracy of the system were measured in order to verify if it is possible to

identify a coil stored in the yard through its geospatial position. To obtain the desired result, it was necessary to de-
velop a hardware that allows tracking the forklift using real-time kinematic correction, also known as GNSS-RTK.

The proposed system had a base station communicating directly with one or more rovers, sending data through the
RTCM protocol to perform correction calculations based on the received information. After the development of
the hardware and validation tests in the laboratory, the hardware was installed on forklifts with load capacity of 40
tons that operate in a real coil production and storage environment. The average weight of the coils operated by
forklift machinery was 20 tons. This manuscript communicate the real results of the identification and location of
steel coils procedures by using GNSS-RTK. The tests were carried out in a large-company producer of steel coils.
Our data analysis and results confirm the efficiency of the proposed system in an open-sky yards environment.

Application of a neural architecture to estimate the wear of down and up throats in RH degassers

2024-05-23T20:21:32+00:00

During the metallurgical process of steelmaking, conformity is achieved in the processes of primary and
secondary refining. One of the types of secondary refining takes place in the RH degasser, where the molten steel
from primary refining is fed into a ladle below RH. RH and the ladle are connected by two tubes called "up leg"
and "down leg". The steel is encouraged to circulate in the up leg, while the molten bath flows back into the ladle
through the down leg. The edges of the refractory bricks of both legs, also called "throats," are subject to wear.
This observation is made by an operator who goes to the top of the degassing ladle and uses a cell phone to take a
picture of the condition of the throats on the lower vessel of RH. The image is evaluated to check for throat wear
and to ensure the integrity of the process to avoid perforations and unavailability of RH. To provide a more
meaningful measurement, YOLACT, a neural architecture designed for real-time image segmentation, is used to
extract the coordinates describing the segmentation of the throats in the images, which are later processed to
estimate the actual wear.

Virtual Element Method for 3D Poisson Equation

2024-05-24T11:46:33+00:00

This work reports some of the challenges met with when implementing the Virtual Element Method
(VEM) for Poisson’s problem in a three-dimensional setting. The method’s generalization of the Finite Element
Method (FEM) for polytopal shapes and arbitrary order introduces many challenges, such as integration over the
element, mesh generation, etc. There is a significant increase in complexity when going from a two-dimensional
to a three-dimensional implementation of the method, thus the main topic of this work. The Poisson problem is
chosen because of its simplicity, allowing the focus to remain on the method itself. The main comparisons are
between the two and three-dimensional versions of the method, as well as between the latter and the equivalent
Finite Element Method.

A Survey Of Machine Learning Based Techniques For Hate Speech Detection On Twitter.

2024-05-24T11:48:22+00:00

The use of the internet and social networks, in particular for communication, has significantly
increased in recent years. Twitter is the third most popular worldwide Online Social Network (OSN) only after
Facebook and Instagram. Compared to others OSN’s, Twitter presents a simpler data model and more
straightforward data access API, which makes it a useful tool to study and analyze online behavior, including
abusive patterns. This survey is an attempt to create a machine learning based guide for hate speech automatic
classification including a description of twitter’s technology and terminology, social graphs, sentiment analysis
concepts and hate speech identification. This study also adopted a systematic literature review on the most
advanced computing techniques involved with the subject, focusing on the machine learning state-of-art and
research directions.

Post-cracking behavior in tensile for UHPFRC using inverse analysis, fracture energy and finite element method

2024-05-24T11:50:55+00:00

Ultra-high performance fiber reinforced concrete (UHPFRC) is an advanced composite material
characterized by compressive and tensile strengths above 150MPa and 7MPa, respectively. Initially, an
experimental procedure was used to characterize the tensile performance through bending tests, using beams with
1% and 2% content by volume of steel fibers. Three-point bending load arrangement notched prisms were used to
determine the contribution of the fibers to reinforcing a cracked section. With that, the (F vs. ω) experimental
curves were graphed, and from there, the analytic tensile curves (σ vs. ω) was obtained point by point by
application of the inverse analysis procedure proposed by the AFGC. With the analytic curves, the fracture energy
was calculated, following a procedure proposed by RILEM. Subsequently, the crack width was transformed into
strain using a relationship that involves the characteristic length. The resulting analytical behavior law was used
to carry out computational modeling applying the finite element method. Both the finite element method and the
fracture energy were used to validate the procedures, comparing experimental and numerical results. Models and
experiments showed good agreement and finally was determined the constitutive law for the UHPFRC in tension.
It can be concluded from this study, therefore, that the post-cracking tensile behaviour of UHPFRC can be
appropriately evaluated and validated through the applied analysis procedure in this research.

A thermo-mechanical DEM framework for the simulation of selective laser sintering

2024-05-24T11:53:25+00:00

This work presents a simple thermo-mechanical model based on the Discrete Element Method (DEM)
for the rapid simulation of SLS processes. Our approach combines the DEM with lumped heat transfer equations
to describe the various thermal phenomena that may take place when the particles are excited by external heat

sources such as laser beams. We consider the essential ingredients that are relevant to the problem, such as inter-
particle contact and bonding, heat transfer (through conduction, convection and radiation) as well as phase

transformation due to high temperature changes (which may be critical in certain applications). The model is
relatively simple and straightforward to be implemented by engineers and analysts interested in the field, and may
be a useful tool for practical, rapid process simulation, design, and analysis. Numerical examples are provided to
illustrate the practical use of the proposed framework for the simulation of SLS advanced manufacturing processes.

A methodology to predict the effective thermal conductivity of a granular assembly using deep learning

2024-05-24T11:55:26+00:00

In this work, an Artificial Neural Network (ANN) is employed to predict the effective (i.e., bulk) thermal
conductivity of a granular assembly. The ANN is trained with the help of computed thermal conductivities of
various different assemblies, obtained through several simulations with our in-house DEM (Discrete Element
Method) code. Convection and radiation are not considered as to isolate the conduction problem and allow for a
better estimate of the assembly’s effective response. The methodology enables the effective thermal conductivity
of a granular assembly over a wide range of parameter values, including particles’ size and their material’s
conductivities.

Solution construction for a drainage process for a system modeling the foam flow with linear surfactant adsorption

2024-05-24T11:58:17+00:00

In this work, we present an analytical solution for a drainage process of a system of non-strictly hyperbolic
Conservation Laws describing the foam flow in porous media under effect of linear adsorption of surfactant. We
adopt a system composed of two differential equations, one modeling the conservation of saturation of the wetting
phase and the other the conservation of chemical in the wetting phase with linear surfactant adsorption.
The foam flow dynamic is assumed to follow the implicit texture STARS model. In this model, the foam
texture assumes local equilibrium, meaning that the foam formation rapidly attains a state where the bubbles
generation rate matches the coalescence rate. We present a geometrical construction of the analytical solution and
compare our results with a direct numerical simulation.

Implementation of an elastoplastic finite element code in Python

2024-05-24T12:00:56+00:00

The use of the finite element method is one of the most efficient approaches to dealing with a problem
with non-linearity. It is common that such problems are taken to commercial engineering programs, whose main
purpose is to obtain the stresses for the user's decision-making, without a deep focus on the methodology that
governs such analyses. In this paper, a finite element code with non-linearity of the material was implemented in
Python, which is a language highlighted for being an Open-Source technology. The work aims to facilitate the
understanding of a practical application of finite elements with perfect elastoplastic behavior and, thus, to serve as
a guide for undergraduate and graduate students interested in the subject. As a practical application, a rectangular
steel plate was modeled and evaluated against a vertical load on one of its edges. To this end, the Von Mises yield
criterion was used to determine the stresses and, after reaching the yield of the material, the Newton-Raphson
iterative method was used to determine the displacements. At the end of the work, there was a good agreement
between stresses obtained with the finite element code and the chosen commercial finite element program.

Buckling of piles in soft clay: comparison between analytical and numerical forecasting

2024-05-24T12:03:16+00:00

Steel piles are deep foundation elements that are mostly used in multi-storey buildings,
transmission towers and industrial constructions. It is a structural element that is industrially produced, with
laminated or welded steel profiles, single or multiple layer, pipe bending or calendered sheet metal tubes, weld
seam or seamless tubes and railway tracks. By the use of reduced cross-sectional area of piles in Brazil, especially
thinner steel piles (profile I or simple rails) that cross thick soft clay layers, it is considered the risk of pile buckling,
even with fully embedded piles. This work evaluates the critical buckling load of a steel pile in a soft clayed soil
using analytical and numerical methods. A comparison between the critical load test result obtained using these
methods and the allowable load provided by the pile manufacturer is made. There are differences between the
methods mostly due to the limitation on top of the pile. Therefore to verify the critical buckling load on a
foundation project, the suitable method should be the one most resembling the real situation acting on the structure.

Offshore wind farm layout optimization via metaheuristic algorithms using a three-dimensional analytical wake model

2024-05-24T13:13:53+00:00

Due to the increasing demand for renewable energies, the wind energy industry has been in continuous

progress through studies that aim to contribute to its technological advancement. This work proposes the minimiza-
tion of the cost of energy (COE) of an offshore wind farm, given by the ratio between the cost of the farm and its

annual energy production (AEP). For this purpose, the layout (continuous variables) and the different commercial
types of each wind turbine (discrete variables) were considered as decision variables. Furthermore, econometric

models were used to estimate the costs due to wind farm rated power, length of interconnection electricity ca-
bles between wind turbines, and different water depths to account for the supporting structures as a function of

the installation layout for each wind turbine. To account for the mutual interference of the flow among the wind
turbines and its impact on the AEP, and for comparison purposes, this study was conducted under two analytical
wake models in the optimization process, namely, Gaussian wake model and the well-known Jensen wake model.
The performance of the wind farm, subjected to different wind conditions, was then evaluated as a function of the
probability of occurrence of wind direction and speed throughout the year to account for the AEP. To solve this
optimization problem, the metaheuristics (Genetic Algorithm and Differential Evolution) were employed, resulting
in a comparative study of their performance.

Structural damage detection with autoencoding neural networks

2024-05-24T13:16:51+00:00

Structural Health Monitoring (SHM) is a growing field in civil engineering, having relevance for the de-
tection of changes in the state of structures, including the identification of possible damage conditions. Commonly

used SHM strategies involve employing Artificial Intelligence (AI) techniques on raw dynamic data measured
from structures to perform classifications or extract features from the original data. Among the AI algorithms for
SHM, autoencoding neural networks, or simply autoencoders, have been identified as promising solutions, being

the focus of this article. An autoencoder is designed to reproduce its inputs as closely as possible after unsuper-
vised training. This characteristic is a useful tool to extract features that represent the original data with lower

dimensionality, which facilitates classifications through statistical methods. A sparse autoencoder (SAE) is a type

of autoencoder that includes a sparsity penalty at its training process. In that way, this paper presents a method-
ology to detect structural damage by using sparse autoencoders as parameter extractors applied to signals in the

frequency domain, combined with the Mahalanobis distance to perform an unsupervised classification. Tests per-
formed with data extracted from the Z24 bridge have shown promising results in detecting changes in the structural

states, demonstrating the potential of SAE for SHM systems.

DYNAMIC ANALYSIS AND OPTIMIZATION OF A 6X6 VEHICLE’S ACTIVE SUSPENSION SYSTEM

2024-05-24T13:19:48+00:00

In a big dimensions vehicle, the suspension system performs an essential role in stability, driveability
and comfort, being responsible to reduce vibrations induced by ground irregularities, which provides the
increasement of suspension and vehicle components life cycle. In this context, the objective of this work is to
analyze the dynamic time response of an active front suspension model in a space-state formulation, obtaining
through multibody modeling the optimized response for the system, taking into consideration the variables of
interest: control force and reduction of the speed of the suspended mass. The closed loop control systems are
designed and compared using different strategies: Linear Quadratic Regulator (LQR) and Genetic Algorithm (GA)
associated with LQR in order to check the optimal model. The plant parameters are, at first, equivalent to a 1⁄4 car
model of a 6X6 Military Vehicle, and the results obtained are simulated through MATLAB/Simulink® for a 1⁄2 car
model to understand the vertical dynamics phenomenon including variables as pitch and center of gravity speed.

PARAMETRIC GEOMETRY GENERATION OF WIND TURBINES

2024-05-24T15:48:13+00:00

Wind energy is an alternative of interest to other energy forms, since it is renewable and can reduce the
environment damage as compared to other more pollute forms of generation. Thus, understanding wind turbines
and how they operate is a key to increase efficiency and production. For numerical analysis of wind turbines, the
geometry must be adequately defined, which is a complicated task due to the shape of their blade profiles. Thus,
this article proposes a way to create parametric wind turbines geometries using the software Grasshopper, a plugin
from Rhinoceros 3D. Grasshopper is a visual programming language, allowing to produce parametric geometries
as function of different input parameters. In this work, National Renewable Energy Laboratory (NREL) geometries
are modelled, which are the horizontal axis wind turbine (HAWT) references proposed in the project known as
Wind Partnership for Advanced component Technologies (WindPACT). As wind turbines have generally the same
shape and their dimensions are proportional to each other, the intention of parametrizing the process is to facilitate
the geometry creation when some parameters change, avoiding remodeling the entire turbine if it were produced
in a usual CAD software. This paper shows how to model and obtain the final geometry, which is readily readable
by any simulation software, such as Ansys. All the benefits and problems encountered are commented and the
results are shown.

On the non-linear vibrations of clamped-free cylindrical shells subjected to combined loads

2024-05-24T15:50:22+00:00

In this work, the nonlinear vibrations of clamped-free cylindrical shells subjected to combined loads is
studied. Combined loads such as axial, lateral and base acceleration can generate complex vibrations in shells and
its combination is important to consider in project of these kind of structures. For this, to model the shell the Koiter

– Sanders nonlinear shell theory is considered, and the Rayleigh-Ritz method is applied to obtain a set of non-
linear dynamic equations which are solved in turn by the fourth order Runge-Kutta method. To study the nonlinear

dynamic response, an expansion with fifteen degrees of freedom in the axial, radial and lateral directions, which
represents the correct modal coupling, is considered. The nonlinear static paths, the parametric instability
boundaries, resonance curves and Poincaré maps are obtained. It is possible to observe that, depending on the
geometry ratios, the intensity of the loads, the shell will display complex nonlinear response showing softening,
chaotic or quasi-periodic oscillations.

Development Of A Real-Time Monitoring System For Detect The Use Of Personal Protective Equipment (PPE) From Machine Learning

2024-05-24T15:52:24+00:00

PPE is the equipment for individual use used by the worker where its main purpose is to protect against
risks capable of jeopardizing their health and safety, in addition also reducing costs to the employer with personnel
replacements, dismissals and indemnity processes. However, many times, either through negligence or discomfort,
there is resistance to its use and/or the removal of the equipment during the performance of activities. In view
of this problem, the HSE department must therefore inspect and monitor the proper use of workers‘ personal
protective equipment mostly of the time. As an alternative to assist the security department in verifying, demand
and quantifying the use of protective equipment in the workplace, this project presents a machine learning model
based on the You-Only-Look-Once (YOLO) architecture to verify the workers‘ compliance regarding their safety
behavior in real time, using images / video of a security system installed in a busy place within an industry. The
algorithm uses the approach of detecting workers and basic PPE as helmet, gloves, goggles simultaneously by deep
learning previously trained by a image dataset of workers in differents types of labour ambient, and next verifies
that each bounding box generated is in the correct position, thus confirming if the worker is carrying PPE or not.
Later, a program developed in python using the opencv library will quantify the use or not of the use of PPEs,
from the bounding boxes generated by more specifically YOLOv4, providing in this way a statistical report as an
output. This statistical report will be useful for the HSE (Health, Safety and Environment) department to use its
statistics as indicators of reliability that will assist in decision-making and in the management of security within
the company.

A Continuum Damage Micromechanical-Based Model for Fracture Propagation in Viscoelastic Material

2024-05-24T15:54:56+00:00

The paper aims to model via micromechanics and macroscopic thermodynamic concepts a
propagation law for high densely fractured materials, formulated through a continuous damage variable that
account for incorporates the delayed viscoelastic material behavior. The first step of the approach is intended to
present the effective behavior of the viscoelastic fractured material and the damage activation criterion. The
Mori-Tanaka elastic homogenization scheme and the Laplace-Carson elastic/viscoelastic correspondence
principle are combined with an appropriate thermodynamic approach for formulating the damage propagation
criterion. This approach allows for analytical description of the macroscopic damage law, which can be handled
numerically in the time domain. Due to the damage variable evolution, it is necessary to formulate a non-linear
viscoelastic behavior law. The damage evolution rate is assessed by means of a reasoning inspired from
plasticity theory. The damage evolution algorithm relies upon the time integration of the damage evolution
through an incremental implicit scheme. The numerical implementation and application of the model emphasize
the time-dependent effects on damage propagation.

Numerical evaluation of modal indices for damage identification in steel footbridges

2024-05-24T15:57:22+00:00

Among several damage detection methodologies, the vibration-based damage identification methods
(VBDI) are remarkable since the deterioration in structural elements reflects directly on both global and local
dynamic response of the structure leading to changes in modal parameters. Different approaches focus mainly on
one-dimensional structures, which, in turn, may not represent the actual dynamic behavior of bold structures such
as bridges and footbridges. Some modal indices, namely mode shape curvature, modal flexibility, and modal strain
energy were evaluated considering a finite element model of a real curved steel footbridge and three-dimensional

vibration modes. Moreover, a recently proposed modal index called resultant vector which incorporate three-
dimensional modal coordinates is also compared to the aforementioned indices. Results show that the accuracy of

the indices is correlated with the region of the structure where damage is found. The influence of damage presence
on adjacent girders and how it is reflected in these indices is also discussed.

Mesh generation and manipulation for finite difference method usage

2024-05-24T15:59:59+00:00

This work proposes a rectangular mesh generator software which discretize complex geometries, al-
lowing computational fluids dynamics (CFD) simulations. To this porpuse, the software uses different image pro-
cessing and data analysis techniques to extract a finite set of points that describe the image contour. The resulting

coordinates represents the maximum refinement, describing each pixel from the image contour. Hence, procedures
with meshs would require high cost of memory. For this reason, the software approximate the coordinates to mesh
nodes, compliant with the mesh size selected by the user, allowing a efficient contour description with low memory
cost. Then, the approximate contour mesh is obtained, which can be used as parameters to numerical simulations
of partial differential equations using the finite difference method. Also, the software allows selection of regions

from the geometry to contain more nodes than the rest of the mesh, creating sparse meshs, resulting in better re-
finement using less memory. Finally, the obtained meshs are compared with the original coordinates by their area,

ensuring the mesh generation efficiency.

NUMERICAL MODELING OF CONVENTIONAL STEEL, STAINLESS STEEL AND INCONEL ALLOY SOLID ELEMENTS THROUGH THE FINITE ELEMENT METHOD

2024-05-24T16:09:37+00:00

The work will present the development and implementation of linear numerical models, with the
objective of performing mechanical analyzes on solid elements of conventional steel (MS250 and HS350),
stainless steel (SS304) and inconel alloy (IA718). For this, we intend to implement computationally, with the aid
of the FORTRAN programming language, a mathematical formulation based on the Finite Element Method
(FEM), whose purpose will be to obtain the values of deformations and nodal displacements at different points of
the parts, in addition to the von Mises stresses in each finite element that compose the structures. For the
discretization of solid elements, 4-node tetrahedral (T4) and 8-node hexahedral (H8) finite elements were used.
For a greater scope of validation of the implemented module and to prove its efficiency, solids with different
geometric and physical characteristics will be analyzed. In order to verify the responses obtained from the
implemented computational program, comparisons will be made with results found in the literature.

A Timoshenko Beam Formulation with 3D Response for Linear and Nonlinear Materials

2024-05-24T16:12:02+00:00

Beam finite elements are computationally efficient, widely used, and sufficiently accurate for many
applications. The intrinsic a-priori assumptions and simplifications of classical beam theories do not always
represent the actual three-dimensional stress-strain distributions. The cross-section of the Euler-Bernoulli beam
remains both plane and orthogonal to the beam axis. This theory does not account for shear deformation, which is
considered by Saint-Venant’s solution. Timoshenko beam theory includes the rotation of the cross-section, which

remains plane. This assumption yields an average shear strain, which does not correspond with the actual three-
dimensional distribution of shear strains. Shear coefficients can be adopted as a correction for beams made of

linear materials. However, the analysis of beams of nonlinear materials must consider the three-dimensional stress-
strain relationships at each point. An integrated formulation of a beam element with three-dimensional response is

discussed. The arbitrary cross-section of the corresponding Timoshenko beam element remains neither plane nor

orthogonal to the beam axis. The element kinematics is defined by two fields: the displacement shapes of the cross-
sections and the axial functions of their corresponding averaged movements. The deformed displacement shapes

are obtained by minimizing the potential energy of a beam slice submitted to the compatibility constraints of the
kinematics framework. Higher order models reproduce the three-dimensional distribution of stresses and strains
of Saint-Venant’s solution for concentrated loads and Michell’s solution for uniformly loaded beams. The solution
also agrees with three-dimensional finite element models with idealized boundary conditions. This paper presents
improvements that simplify the theory, focuses on first-order linear and nonlinear analyses, and discusses some
examples.

Impacts of the halt of ITA flight operations on the Brazilian Multiplex Air Transportation Network

2024-05-24T16:24:30+00:00

The bankruptcy of Avianca Brasil, the COVI-19 outbreak and the sudden halt of operations of
Itapemirim Airlines in 2021 changed the topology of the Brazilian Air Transportation Network in past years. The
effect was the reduction in the number of network layers and the network concentration. The aim of this paper was
to characterize structural properties and evaluate changes in the Brazilian air network after the halt of operations
of Itapemirim airline using a multilayer complex network. The multilayer approach considering the weight of
interactions makes the network description more detailed than the usual monolayer analysis. We used data related
to passenger traffic from November 2021 and January 2022 and each network layer represents an airline. The
proprieties and centrality measures were used for Brazilian network characterization, which concentrated into four
layers. Gol and Passaredo increased their market share and operating airports while Gol became the biggest market
share. The number of routes increased for all airlines, especially Gol which increased by 24%. Gol became the
densest layer with the minimum mean path length probably because ITA’s layer had the highest correlation with
Gol and edges overlapping. Results suggest Gol may have had the best strategy to incorporate the ITA’s pent-up
demand.

Computational Implementation for Seismic Assessment of Existing Structures

2024-05-24T16:27:28+00:00

Increasing of seismic record in Brazil resulted in first Brazilian code of seismic NBR 15421:2006. Once
publication succeed Brazilian sample building assessment must be developed in order to prevent or mitigate effects
of horizontal accelerations from seismic. For preliminary screening of existent reinforced concrete structures
qualitative Hirosawa method seems to be suitable to Brazilian reality. This paper aims to implement
computationally seismic vulnerability assessment method in order to optimize assessments through opensource
SMath Solver and programming language is C#. Adapted Hirosawa method compares resistance of building
through seismic index of structure IS and Seismic demand index IS0
. Index IS
is a product of indexes (Basic seismic

index of structure, Irregularity index, Time index) and index IS0

is formed by zone index, ground index and usage
index. Model structure proposed by literature are analyzed in different levels of seismic acceleration as well as
types of soil defined by Brazilian seismic code in order to demonstrate usability of tool. Graphical interface and
results obtained from the application are showed aiding in decision-taking about new refined assessments or
feasible interventions.

Fatigue life analysis of a wind turbine blade subjected to Davenport loading using the computational Tool ANSYS

2024-05-24T16:31:43+00:00

Most mechanical elements are subjected to periodic loadings so that throughout their lives some fibers
are damaged due to bending cyclic. Even if the stress does not exceed the yield limit, the dynamic characteristic of
loads can cause catastrophic failures. Finite Element programs are excellent tools to obtain important parameters
of fatigue analysis. In this way, ANSYS uses its structural analysis potential to also analyze the phenomenon of
fatigue through the ANSYS Workbench Fatigue Tool module. Firstly, in order to experiment the computational
procedure of fadigue analysis a retangular cantilever beam was investigated. It was submitted to harmonic loading
and modeled with a solid element of 20 nodes, each one with 3 degrees of freedom, Results obtained in numerical

analysis at ANSYS were compared with those obtained in the analytical methodology. The good agreement be-
tween them is an important step to encourage the understanding of the quantification of fatigue life of the verne555

wind turbine blade submitted to a davenport wind load. The blade modelling was done using shell elements of
4-nodes and 6 degrees of freedom per node. The results obtained are presented as expected, which demonstrates
the correct use of the chosen computational tool.

Validation of the numerical procedure to calculate the fatigue life of welded joints using the Ansys computational package

2024-05-24T16:34:44+00:00

The phenomenon of fatigue is highly complex and is present in most mechanical component appli-
cations. In this sense, according to Ruchert (2007), fatigue shows itself as the predominant cause in structural

failures. Recognizing the importance of fatigue in engineering studies, the goal of this research is to gather infor-
mation and data that may become relevant for the computational modeling and analysis of welded joints, as well as

the calculation of fatigue life. Thus, was reproduced the modeling of a beam-column assembly, which is subjected
to a transverse loading to the free section of the beam, performed previously by Moreira et al (2017). The ANSYS
Finite Element software was used, specifically the Fatigue Tool module of the Ansys Workbench environment.
The weld element on which fatigue life is evaluated is of the fillet type. The results obtained are compared with
those presented by Moreira et al (2017) and showed agreement with each other. Thus, since the adopted procedure
proved to be effective in the study of fatigue life, it is details are presented here as a contribution to the development
of future works.

Micromodeling of a dual-phase steel using an idealized micrograph generated by Voronoi diagrams

2024-05-24T16:36:49+00:00

Dual phase (DP) steels are high strength steels used mainly in the production of vehicle bodywork,
currently about 74% of the structural components are manufactured in this type of material. These DP steels are
composed of a soft ferrite matrix with a hard, martensite phase. In this research, mechanical properties
characteristic of these materials are linked, establishing dependence between volume fractions of each phase and
simulations of the mechanical behavior in different situations are developed. Implementing a 2D bilinear plasticity
model from the synergy of three design programs, regions of the martensitic phase of the material were generated
in a 3D space. In the same way, these inclusions were parameterized and modeled together with a ferritic matrix.
Then, using FEM to simulate 3D micromodeling (RVE), stress-strain diagrams are obtained. Finally, the results
show deviations of 10% on average from the experimental values.

Micromodeling of a dual-phase steel using an idealized micrograph generated by Voronoi diagrams

2024-05-24T16:39:09+00:00

Influence of fire resistant steel bars on the fire design of simply supported reinforced concrete beams

2024-05-24T16:41:44+00:00

The exposure to fire conditions can cause damage to reinforced concrete structures by reducing their
strength. As a result, even today these accidents cause irreparable material and immaterial losses. Therefore, it is
understood that the technological improvement of structural elements is essential for the advancement of fire safety
engineering. A form of improvement that has been studied in recent years are the steels with enhanced fire
behavior, or “fire resistant steels”, as they are usually known. These special metallic alloys are able to maintain
their mechanical properties for longer when exposed to high temperatures and are already applied to metallic
structures, although their contribution to the performance of reinforced concrete structures is still poorly
understood. The present research seeks to evaluate the influence of this type of material on the fire design of simply
supported reinforced concrete beams using a methodology that adapts the tabular method to verify these structures.
The developed methodology is similar to those presented in NBR 15200 (ABNT, 2012) and Eurocode 2 (CEN,
2004) and considers the use of the improved steel in replacement to the conventional tensile reinforcement. The
study is essentially theoretical and numerical, through the use of the finite element software Super TempCalc, and
the results achieved have shown that there can be a reduction in the minimum dimensions required for beams’
cross-sections by the aforementioned codes if the fire resistant steels are used.

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

2024-05-24T16:43:52+00:00

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

TOPOLOGY OPTIMIZATION OF CONTINUUM ELASTIC STRUCTURES EMPLOYING THE FINITE-VOLUME THEORY AND THE EVOLUTIONARY STRUCTURAL OPTIMIZATION METHOD

2024-05-24T16:48:07+00:00

In this paper, an original approach that combines Finite-Volume Theory (FVT) and Evolutionary
Structural Optimization (ESO) is presented. ESO is based on the simple idea that the optimal structure can be
delivered by gradually removing the ineffectively used material from the design domain. Through this procedure,
the resulting structure will evolve towards its optimal shape and topology. In theory, one cannot guarantee that
such an evolutionary procedure would always generate the best solution. However, the ESO technique provides a
useful way for designers to explore forms and shapes of structures during the conceptual design stage. In literature,
it is frequent that the design domain is constructed aiming at a Finite Element Analysis (FEA). However, some
problems are related to numerical issues, such as the checkerboard pattern and mesh dependence. The checkboard
effect is related to the assumptions of the finite element method, as the satisfaction of equilibrium and continuity
conditions in the element nodes. FVT overcomes this problem because it satisfies the equilibrium equations at the
subvolume level and the compatibility conditions are established through the adjacent subvolume interfaces, as
expected from the continuum mechanics point of view. Some ESO’s classical problems are investigated to
compare FVT and FEA results.

Two-dimensional thermomechanical creep analysis of solution-mined cavern convergence – Regina cavern n°5 – Phase 2.

2024-05-24T16:56:57+00:00

This study aims to evaluate the convergence of the second phase of a cave, obtained by dissolution in a
bedded salt, under the effect of different temperatures applied in its cavity. The shape of the cave was obtained
from sonar surveys at Regina Cave No.5 in 1983 by TransGas Ltd. The creep model used is based on an empirical
formulation that considers the stationary phase of creep, this model is known as the double mechanism creep law
or also called the Norton simplified model, presenting good results when the analysis involve long periods.
Numerical geomechanical simulations, with a maximum time of 30 years, were performed with CODE-BRIGHT
(Coupled DEformation BRIne Gas and Heat Transport) finite element code to the evaluation of rock stability and
deformation, showing excellent results in this type of numerical simulation scenario.

Phase-Field Modelling of a Multiphase Material

2024-05-24T17:00:31+00:00

The Phase-Field Modelling has been widely used to model crack propagation. In that model, the discrete
crack of Griffith’s theory is transformed into a diffuse crack that spreads on a certain region, according to the length
scale parameter. The Phase-Field variable is calculated as a new nodal degree of freedom. It represents, at each
point, the amount of damage suffered by the material, in such way that when it’s zero the material is intact, and
when it’s equal to one the material is completely damaged. In this work the Phase-Field analysis has been used to
study the fracture process in a multiphase material, composed by a mortar with aggregates randomly distributed
across the domain. The influence of the material properties on the structural behaviour was also investigated. All
the implementation was done in INSANE, an open-source software, developed in Java at the Structural Engineering
Department of the Federal University of Minas Gerais. Numerical simulations will be presented considering the
variation of the sample size and the parameters of the materials.

Modeling complex mechanical computer codes with functional input via Gaussian processes

2024-05-24T17:03:56+00:00

Surrogate models based on Gaussian processes (GPs) have been successfully used as a complement
of costly-to-evaluate complex computer codes. They are capable to provide accurate predictions with confident
intervals but require fewer costs (in both time and resources). Here, we focus on a class of mechanical codes
with functional inputs and output force-displacement curves. We further investigate a GP framework where inputs
are handled in a continuous setting, which results in more tractable and scalable models. Both input and output
information are correlated using a composite kernel function that can be efficiently computed (and inverted) when
tensor-structured data are considered. We demonstrate the reliability and scalability of the GP in a synthetic
example with highly variable input and output curves, as well as on a real-world mechanical application modeling
the self-piercing riveting (SPR) in a single hat component. Our experiments show that the methodology is able to
correctly detect the maximum forces and the displacements at peak force where the failure of SPR appears.

Contact interaction law based on the Hertz theory for multibody applications

2024-05-24T17:08:18+00:00

The normal component of the contact interaction between two bodies arises from the fact that their
material boundaries cannot go through each other. One way to deal with this non-penetration geometric constraint
is to allow its violation on a controlled manner by adding an increasing magnitude force pair to the system, as long
as the constraint violation increases. Methods that use this approach are usually referred as penalty-based methods.
The simplest penalty method imposes a force proportional to the normal indentation. The proportionality constant
acts as a stiffness parameter. An alternative interface law originates from Hertz’s theory of nonconformal contact
between elastic bodies. According to this classic theory, the contact force is proportional to the normal indentation
raised to the power 3/2. The proportionality coefficient is not a constant, it has a dependency on the local curvatures
of the contacting surfaces. Ultimately, the proportionality constant depends on the configuration of the system at
a given time. In this work, we implement a penalty method based on Hertz force law for imposing contact between
rigid bodies. The nonlinear dynamical equations for multibody dynamics are solved numerically. In the required
linearization process, the dependency of the stiffness parameter on the degrees of freedom of the system is
neglected. The results of the present method for a set of simple examples are presented. We verified that the

considered simplification has a negative effect on the solution process if the stiffness varies throughout a time-
step. The effect may be diminished using a large quantity of time-steps.

A limit analysis approach for plane stress problem

2024-05-24T17:10:28+00:00

A finite element is developed for plane stress problems based on the static theorem of limit analysis.
This four-node quadrilateral element satisfies the equilibrium equations and the mechanical boundary conditions
on average, and, as such, it is not expected lower bounds on the collapse load from the computed results.
Numerical tests are carried out using the von Mises criterion, which is exactly satisfied throughout the element.
The nonlinear convex optimization problem posed here is treated as second-order cone programming and solved
with a primal-dual interior-point algorithm implemented in the MOSEK optimization package.

Machine Learning Applied to Predict Pile Bearing Capacity

2024-05-24T17:46:19+00:00

The present work presents the application of machine learning algorithms to the problem of predicting
load capacity of piles. A dataset was compiled from the literature, composed by 165 load tests associated with

SPT results performed in different regions of Brazil. From this raw base, 5 datasets were generated based on well-
known semi-empirical methods. Such sets were then applied to six ML algorithms and a linear regression. The

performances, measured by R2

and RMSE, were compared to those achieved by semi-empirical methods. The
RF technique stood out from the others, with a maximum R2 of 0.77. A case study was then carried out and its
results reinforced the good performance of ML algorithms against semi-empirical methods. Despite the limitations
of the work regarding the dataset, the conclusions point to the use of ML tools as a good alternative to the classical
methods of calculating load capacity.

BIM Methodology applied to Structural Analysis of the Built Heritage

2024-05-24T17:48:13+00:00

Built heritage is one of the key elements through which the identity and culture of a society manifests
itself. The so-called Building Information Model (BIM) is a methodology that has gained wide notoriety in
fulfilling the role of portraying the physical characteristics and storing information of historic monuments. One of
the most useful applications of the BIM methodology is structural analysis, which can be performed based on the
graphic representation of the building itself. Structural analysis makes it possible to obtain parameters that are of
great value for the study, maintenance, monitoring, and eventual repair of structures. The present work had the
objective of comparing two parallel models of the “Nossa Senhora de Fátima” church, known as “Igrejinha”, in
Brasília, and the results of their respective structural analyses. The first model was developed based on the
structural documents of the building, and the second one, based on accurate survey methods usually employed in
historic BIM modeling - terrestrial laser scanning and aerophotogrammetry. The methodology adopted was based
on automatically obtaining the analysis results from the architectural representation of the building and its
corresponding analytical abstraction. The physical comparison of the models showed a high dimensional
similarity. The resulting values of the structural analysis showed, however, significant variations for certain
internal forces, demonstrating the influence of the modeling process and the discretization of the structure on the
calculation results.

Fully Implicit Algebraic Dynamic Multilevel and Multiscale Method with Non-Uniform Resolution for the Simulation of Two-Phase Flow in Highly Heterogeneous Porous

2024-05-24T17:56:29+00:00

Large reservoir flow models today can contain more than a billion unknowns. Simulation of these
models is not feasible even with the most powerful parallel computers. Generally, upscaling techniques are used
to define coarser, i.e., smaller, models that can be processed with reasonable computer resources and in a
reasonable amount of time. These techniques consist in a kind of homogenization of the models to obtain
representative properties. Such procedures, of course, lead to loss of information. In the last decades, Multiscale
Finite Volume (MsFV) methods have been developed to solve these problems. These techniques, in which
operators are responsible for transferring information between the fine and coarse scales, provide more accurate
solutions than upscaled models at an acceptable CPU cost. Several authors have developed different strategies to
obtain accurate solutions using multilevel or multiscale strategies, such as: the i-MsFV, an iterative procedure to
smooth the multiscale solution with an efficiency comparable to the original MsFV; the Algebraic Multiscale
Solver (AMS), as a preconditioner; the Two-stage AMS (TAMS), which applies an algebraic variant of the MsFV;
the monotone Multiscale Finite Volume, with a selective coarse-scale stencil fixing, where either the RBC is
replaced by linear boundary conditions (LBC) or "large" non-physical terms are recalculated with upscaling; the
zonal MsFV (zMsFV), which splits the domain of interest into a classical MsFV or with additional zonal functions;
and the Adaptive Algebraic Dynamic Multilevel (A-ADM), which solves flow problems in highly heterogeneous
petroleum reservoirs using non-uniform levels. In this work, we have implemented the Algebraic Dynamic
Multilevel with Non-Uniform Resolution (NU-ADM) using a finite volume formulation of the Two Point Flux
Approximation (TPFA) for fully implicit simulation of two-phase flows in highly heterogeneous porous media.
The NU-ADM operators are based on the Algebraic Multi Scale (AMS) operators. This method provides adaptive
multiscale resolution based on the contributions of each volume to the non-physical terms on the coarse scale
matrix. We use mesh adaptivity to control these terms. Our parameters are based on the pressure-pressure terms
of the Jacobian matrix and the saturation field and takes place during the Newton-Raphson procedure that is used
to solve the nonlinear system.

Nonlinear numerical analysis of a concrete frame under corrosion due to carbonatation

2024-05-25T14:05:49+00:00

Reinforced concrete structures are used worldwide due to their durability, resistance and flexibility to
conform to different geometries. However, exposure to weather causes degradation, and pathological
manifestations may appear. One of the most common is corrosion, their be generated by chloride ingress and
carbonation. In the initiation stage, the corrosion agents cause depassivation of the rebar. Afterwards, the
propagation stage begins, where the structures suffer loss of rebar area, cracks, strength loss and, in the end,
collapse. In this paper, the displacements evaluation of a structure under carbonation was accomplished by
implementing the loss of rebar area. Through the coupling of the reduction of the stiffness of the structure in the
propagation stage with the Finite Element Method based on Positions code dedicated to the analysis of laminated
frames, developed in FORTRAN programming language, that naturally considers geometric nonlinearities,
allowing high displacements and rotations, and using Saint-Venant-Kirchhoff’s constitutive law. FEM based on
Positions uses total Lagrangian formulation and its degrees of freedom for frame elements are given by nodal
positions and generalized vectors which may express the variation of section heigh and rotations. The physical
nonlinearity of concrete was considered by implementing Mazars damage model. The results have shown that the
numerical model is efficient to simulate the degradation of structures under uniform corrosion.

Comparison between Newton and Picard methods for the nonlinear heat transfer modeling

2024-05-25T14:08:36+00:00

A equac ̧ao do calor n ̃ ao linear possui grandes aplicações em diversas áreas, como nas Engenharias, na
Biologia e na Medicina. Neste trabalho comparamos os metodos de Newton e de Picard para resolver numeri-
camente a equacão do calor unidimensional não linear, onde a condutividade térmica depende da temperatura do
meio. Primeiramente, discretizamos a equação no tempo usando o método de Euler implícito, obtendo-se uma
sequencia de problemas de valor de contorno não lineares e a varredura no tempo será realizada com o método
padrão, Time-Stepping. Para a derivada espacial que também e dependente do gradiente da temperatura, usamos
o Método das Diferenças Finitas. Os sistemas não lineares obtidos são linearizados usando o método de Newton
e o metodo de Picard. Com base nos testes numéricos comparamos a quantidade de iterações e os tempos computacionais para resolver os sistemas com o uso de cada um dos metodos de solução e elencamos suas vantagens
e desvantagens para este tipo de problema.

On the application of a global post-processing strategy for stress recovery in nearly-incompressible elasticity problems

2024-05-25T14:14:34+00:00

In the context of linear elasticity problems, the two major variables to be determined are the displace-
ment and the stress tensor fields, which are often required in real-world applications. However, some classical and

widely used finite element methods for these problems only provide approximations for the displacement, and the
stress tensor needs to be post-processed. In this work, we study a post-processing strategy for the stress recovery
obtained by combining the weak form of the constitutive equation with a least-square residual of the equilibrium
equation. We will focus our studies on the application of this post-processing strategy in elasticity problems with

nearly-incompressible materials, which are known in the literature to offer additional challenges. Providing an ac-
curate approximation for the displacement field, our main goal is to evaluate whether the post-processing strategy

is able to obtain satisfactory approximations for the stress tensor field on nearly-incompressible problems.

ROS 2 in the development of an autonomous navigation application for a 4WD mobile robot with GPS, odometry and inertial systems

2024-05-25T14:17:50+00:00

Developing software for robots is a complex task as it involves many fields of knowledge, from sensor
drivers for data acquisition, data processing, control loops, artificial intelligence, task management, etc. In
addition, the hardware is often built distributed across different devices with different computing capabilities.
Based on this, the Robot Operating System (ROS) was developed, which is a framework for developing distributed
robot applications. ROS provides a communication layer that abstracts the way communication is performed and
allows transparent and distributed access to data. In addition, ROS provides tools for viewing information,

compiling, managing packages, etc. A new version called ROS 2 has been launched, and it includes industry-
standard features, best practices in software development to better support commercial and research robotic

applications. To demonstrate the use of ROS in the development of robotic applications, this paper presents an
outdoor autonomous navigation application of a 4WD robot. This application explored the use of microcontrollers
to control wheel speed, embedded minicomputer running algorithms for sensor fusion of odometry, inertial sensors
and GNSS for localization and navigation algorithms. Navigation tests were conducted in a parking lot.

Multi-objective structural optimization of a planar truss considering dy- namic and global stability aspects

2024-05-25T14:22:24+00:00

The literature has broadly discussed the development of multi-objective structural optimization prob-
lems (MOSOPs) with two objectives: minimizing the structure’s weight and the maximum nodal displacement.

This paper proposes the formulation of MOSOPs with three objective functions. New objectives are considered,
such as the maximization of the first natural frequency of vibration and the maximization of the difference between
the second and the first ones, to avoid the superposition of their modes. MOSOPs are also proposed to maximize
the first critical load factor related to the structure’s global stability and the difference between the second and the
first ones. The analyzed structure is a 10-bar truss. The design variables are the cross-sectional areas of the bars.

The evolutionary algorithm is the third step of generalized differential evolution (GDE3). The Pareto fronts ob-
tained for the problems are presented. It is possible to observe how the growth of the truss’ weight causes increases

in the first natural frequency of vibration and the first critical load factor, as well as its influence on the differences
between the frequencies of vibration and the critical load factors of the structure. Finally, optimized solutions are
extracted from the obtained Pareto fronts.

Odometry and speed control of a 4WD mobile robot integrated with ROS 2

2024-05-25T14:30:48+00:00

With the advancement of technology and artificial intelligence, robots are increasingly used in various
applications. There are various types of mobile robots, such as air, land and sea. Among the various types of
wheeled mobile land robots, the differential drive 4WD mobile robot stands out for its better performance in
navigating outdoor environments, mainly due to the presence of four-wheel drive. However, the differential drive
4WD robot exhibits greater wheel slippage especially in the moments of rotation. This type of behavior
complicates the accuracy of classical localization methods, such as odometry. In this paper, a real case of odometry
implementation is presented, as well as wheel speed modeling and speed controller implementation in a 4WD
robot. To enable the use of more advanced libraries and later the development of various applications, the odometry
and linear and angular speed control of the robot were integrated into the ROS (Robot Operating System). Practical
results in internal and external environments are presented at the end of the paper using graphs and a video with
an access link.

Effective elastic properties of fractured materials by means of a homogenization approach

2024-05-25T16:19:20+00:00

A main characteristic of many engineering materials is the presence of natural fractures at different
scales. The effective mechanical behavior of these materials is strongly affected by that of the fractures, which can

be viewed as discontinuities able to transfer stresses. The contribution of the present work relies upon microme-
chanics for assessing the effective stiffness through homogenization upscaling of elastic materials with embedded

microfractures. In the context of Eshelby equivalent inclusion theory, the approach makes use of the Mori-Tanaka

scheme to formulate estimates for the homogenized elastic moduli. For this purpose, the fractures are geometri-
cally modeled as oblate spheroids endowed with appropriate elastic properties. Particular emphasis is dedicated to

addressing the configurations of a single family or two families of parallel fractures, as well as the configuration
of randomly oriented fractures.

Time domain aeroelastic analysis of clamped wings and determination of V-g-f plots using modal parameter identification

2024-05-25T16:22:37+00:00

Aeroelastic analyses are performed either in time or frequency domains. Frequency domain
analyses have the advantage of providing a fast computation of the flutter speed and are more widespread.
Their results are presented in the so-called velocity-damping-frequency (V-g-f) plots, which shows the
evolution of the natural frequency and damping ratio of each vibration mode as a function of airspeed.
This way, the flutter speed (where zero damping occurs) can be determined with precision. On the other
hand, time domain analyses allow the inclusion of different types of nonlinearities in the simulations,
with the price of being more time consuming. Their results consist of time histories whose vibration
amplitudes should be visually inspected to find a constant amplitude situation (zero damping condition).
This paper presents time domain aeroelastic analysis of a set of rectangular cantilever plates with different
aspect ratios that represent aircraft wings in a simplified way. Time domain results are then used to
generate V-g-f plots through modal parameter identification. For the structural dynamics modeling,
both the classical beam theory (Euler-Bernoulli) and the classical plate theory have been applied, and
the natural frequencies and mode shapes were obtained via the Finite Element Method (FEM). For the
aerodynamic modeling of the plates, the Unsteady Vortex Lattice Method (UVLM) was used, which
is a three-dimensional aerodynamic model based on a potential flow formulation. The structural and
aerodynamic models are coupled using a surface splines interpolation method, and the movement equation
is solved iteratively on a time-domain basis, applying a predictor-corrector method. The frequency
spectrum of each time response serves as input to the modal parameter identification method, which uses
the Least Squares Complex Frequency estimator (LSCF). A stabilization chart is obtained based on the
frequency and damping convergence criteria, thereby allowing the identification of the modal parameters.
The structural and aeroelastic results of the plate, considering both beam theory and plate theory, are
evaluated. It was possible to obtain very clear V-g-f plots, with a precise identification of flutter speeds,
for all tested cases. The influence of the structural model on the flutter speed results was assessed.

Numerical Modelling of the Internal Erosion Process in Granular Soils using the Material Point Method

2024-05-25T16:25:46+00:00

Accidents caused by landslides, landslides, or large soil pits in cities are often seen in the media. These
events are usually related to erosion, and there are several causes related to this phenomenon, but without a doubt,
the main cause is the runoff of water in direct contact with the soil mass. A specific type of internal erosion
called piping is the most common cause of failure in dikes and / or earth dams, such as the Aznacollar-Spain dam
failure in 1998. Internal erosion can be a natural process, but sometimes they are due to poor decisions or lack of
foresight in structural design. The main challenge, then, is to predict with a certain degree of reliability the danger
of undermining in this type of structure, subject to large deformations and important changes in its edge conditions.
As is well known, one of the great limitations of classical numerical methods, such as the Finite Element Method
(FEM), in the simulation of large deformations is the mesh distortion, thus a better alternative should be used. The
objective of this work is to present a theoretical/numerical approach to the scour problem using the Material Point
Method (MPM), which was developed in order to correct mesh dependence problems with extreme deformations.

Influence of Soil-Structure Interaction (SSI) on the performance of the Connected Control Method (CCM)

2024-05-25T16:28:47+00:00

The Connected Control Method (CCM) has proved to be an effective strategy to mitigate the building
vibrational response and prevent inter-building pounding effects. In this technique, adjacent buildings are linked
together by means of coupling devices to provide appropriate reaction control forces. The application of the
CCM using different kinds of passive, active, and semiactive linking devices has been investigated with positive
results. It should be noted that most of such research considered the adjacent buildings supported on a fixed base.
Nonetheless, every structure generally interacts with the surrounding soil. This process is known as soil-structure
interaction (SSI) and there are still few studies in literature about its influence on the CCM and the mathematical
formulation regarding the problem is merely incipient. Thus, this work aims to evaluate SSI influence on the
performance of this control technique, besides presenting a simple analysis methodology to this type of problem.
For this purpose, two buildings connected models supported on a fixed and flexible base are compared. The
buildings are modeled as shear buildings and the soil is simulated by a discrete model representing a viscoelastic
homogeneous half-space. The results are compared in a way to evaluate SSI influence on coupled buildings
dynamic behavior. The numerical analysis was performed in GNU Octave software.

ASSESSMENT OF HUMAN COMFORT IN A FOOTBRIDGE SUBJECT TO DYNAMIC LOADS

2024-05-25T16:31:35+00:00

Footbridges are structures susceptible to excessive vibrations. To avoid this type of problem, it is
necessary to study these, especially the modal characteristics. Thus, the present study aims to perform a numerical
dynamic analysis in finite elements and experimental of a pedestrian footbridge, located in the city of Natal. For
this, a computational model of the structure was developed using the ANSYS 2019 – R3 software, from which a
modal analysis was performed to numerically determine the natural modes and frequencies of footbridge vibration.
Finally, an experimental modal analysis was performed, using the smartphone application iDynamics, in order to
compare the results of the two analyses. The horizontal and vertical numerical frequencies are similar to the
experimental ones and are in the range of 2 Hz for the frequency that characterizes the first lateral vibration mode
and 4 Hz for that corresponding to the first vertical mode. The results achieved are analyzed in light of current
national and international standards and indicate that the structure is in the critical range, which may lead to
resonance problems. They also indicate that a smartphone can be used to perform early and fast measurements of
the natural frequencies of mixed footbridges.

A Modified Drucker-Prager Cap Plasticity Model for Triaxial Simulation of Residual Soils

2024-05-25T16:33:39+00:00

A large area of Brazil, even as the world, is covered by residual soils. These soils arise as the result of
the weathering process of the intact rock and are characterized by the permanence of fragmented elements at the
site of formation. The accuracy of a numerical simulation depends on the adequacy of the model and its parameters
to the soil behavior. In this context, this research aims to numerically evaluate triaxial tests of residual soils to
assess the influence of the model parameters on the stress-strain-volumetric response. The analysis was performed
using ABAQUS software, in which an elastic-plastic model with Drucker-Prager failure criteria and CAP plasticity
was used. The numerical response was compared with a laboratory test in which confining stresses of 20 kPa, 35
kPa, and 50 kPa were employed. A sensitivity analysis of the parameters of the model was performed. The results
indicated that the studied model showed a satisfactory prediction of stress-strain-volumetric behavior of the
residual soil. In the sensitivity analysis, the cohesion, friction angle, cap eccentricity, and hydrostatic yield stress
parameters presented more impact in the numerical response.

Influence evaluation of high-order terms in the strain tensor for a complete geometric nonlinear analysis with Timoshenko element

2024-05-25T16:36:57+00:00

This work evaluates the influence of high-order terms in the strain tensor associated to Timoshenko
beam theory for a geometric nonlinear analysis. The tangent stiffness matrix of the studied element considers an
updated Lagrangian formulation, shear deformation and the high-order terms in the strain tensor. A complete
geometric nonlinear analysis with robust nonlinear solution schemes are performed for structures with a
moderate slenderness ratio. The response is compared with a conventional updated Lagrangian formulation
disregarding the high-order terms in the strain tensor, and with a corotational formulation. Examples evidence
the importance of the high-order terms in strain tensor to perform geometric nonlinear analyses when
considering an updated Lagrangian formulation. Moreover, the analysis with reduced element discretization,
using the proposed formulation, provides equilibrium paths that are closer to highly discretized models
compared to the others formulations.

A low-order preconditioner for high-order element-wise divergence con- stant finite element spaces

2024-05-25T16:40:38+00:00

Mixed finite element problems are a class of problems that arises when modeling several physical
phenomena, such as in computational fluid dynamics, structural analysis, optimization, etc. Designing efficient
iterative schemes for such a family of approximations has been the subject of several works in the past decades.
However, its success is intimately related to the proper definition of a preconditioner, i. e., the projection of the
original algebraic system to an equivalent one with better spectral properties. In recent work, we have proposed
a new class of H(div)-conforming finite element spaces with element-wise constant divergent. This family of
elements was designed to improve reservoir simulation computational cost and are obtained by choosing the lower
order space with piece-wise constant normal fluxes incremented with divergence-free higher-order functions. In

this work, we propose an iterative scheme to solve problems arising in the context of the above mentioned element-
wise constant divergence approximation spaces. The strategy consists on using the matrix of linear fluxes as a

preconditioner to solve the higher-order flux problem. The latter is solved iteratively by means of a conjugate
gradient scheme. In the presented numerical tests, this strategy has shown to be convergent in a few iterations for
different problems in 2D and 3D. In addition, as internal fluxes are condensed, only boundary variables need to
be computed. This strategy relates to the MHM technique and can be efficiently used to access fast multi-scale
approximations in future work.

Comparison between Monte Carlo Dropout and Variational Inference Techniques for Bayesian Neural Network Models applied to Rotating Machinery Diagnostics

2024-05-25T16:43:00+00:00

Rotating components play a crucial role in mechanical systems and are present in several industrial
areas. These systems suffer from the adverse actions of loads and environmental condition. Thus, condition-based
maintenance of these components is a fundamental technique to synchronize and support maintenance schedules,
and machine learning algorithms are nowadays supporting these tasks. This paper aims to present a comparison
between Monte Carlo Dropout and Variational Inference techniques applied to Bayesian neural network models in
damage dignostics of ball bearings. The Bayesian Convolutional Neural Networks were tested, evaluated, validated
against the physical data, and their prediction performances were compared. Results showed that both models had
high performance in diagnosis. The comparison between the methods applied to Bayesian neural network models
showed similar results but each method present their own characteristics that could provides advantages in certain
specific situations.

Nonlinear static and dynamic behavior of a multistable structure formed by elastically connected trusses

2024-05-25T16:47:26+00:00

Multistable systems have proved to be important in several engineering areas, from nano to
macrostructures. Important applications can be found in vibration control, deployable and collapsible structures,
dynamic systems with a periodic pattern and in the development of new materials (metamaterials), among others.
However, there is a need to investigate the static and dynamic behavior of these eminently non-linear systems.
The most basic example of multistable structures is the classic Von Mises truss, which presents two
configurations of stable equilibrium, that is, a bistable behavior. In this work, the multistable behavior of a
sequence of Von Mises trusses connected through the insertion of a flexible element represented by a linear
elastic spring is studied. This system has multiple equilibrium configurations, both stable and unstable, which
significantly influences its non-linear static and dynamic behavior. For analysis, the nonlinear equilibrium and
motion equations, in their dimensionless forms, are obtained through the criterion of minimum potential energy
and Hamilton's principle. Their behavior is then investigated through the use of equipotential energy surfaces
and curves, nonlinear equilibrium paths, phase planes and basins of attraction. The parametric analysis
investigates the effect of the connection stiffness and the physical and geometric parameters of the trusses on the
behavior of the system. Through the results, it is possible to observe the importance of geometric nonlinearity
and connection stiffness in the dynamics and stability of this new class of structures.

MODELING AND ANALYSIS OF SOLAR CONCENTRATORS FOR DRYING SUGARCANE BAGASSE USING FEM

2024-05-25T16:51:08+00:00

To reduce the impacts of Brazilian agro-industry residues, sugarcane bagasse can be widely used as
biomass, however, due to its high moisture content, this biomass has low efficiency for energy production. The
conversion of sunlight into thermal energy through Concentrated Solar Energy (ESC), would bring the possibility
of achieving good results in terms of sugarcane bagasse efficiency through drying, roasting and charcoal, this work
was divided into two parts, initially Solar concentrators were built in different areas, 1 m2 and 2.5 m2, where
temperature measurements were carried out and the effect of high temperatures analyzed in batch and rotating
reactors. Subsequently, the modeling and reliability analysis of the reactors in the solar concentrators will be
carried out through the finite element methods (FEM), using the ABAQUS software, determining the stresses and
thermal fatigue resulting from the heat transfer, identifying the failure criteria, determining the more effective
parameters to be assigned as random variables such as temperature gradients. Making it possible to identify
solutions that can reduce thermal stresses and, if necessary, change the reactor materials.

A coupled finite element-meshfree smoothed point interpolation method for phase-field modelling

2024-05-25T17:42:08+00:00

The present work investigates the coupling between the finite element method (FEM) and smoothed
point interpolation methods (SPIM) for the solution of crack propagation problems. The region of the model
where the crack propagates is previously discretised by the SPIM method and the rest of the domain is represented

by the FEM. The phase-field model is adopted as a constitutive model to simulate the degradation of the mate-
rial during the analysis. In this model, the crack is considered as a diffuse crack where a length scale parameter

controls the size of the diffusive region and the phase field value indicates the integrity of the material. The compu-
tational implementations were performed in the INSANE (INteractive Structural ANalysis Environment) system,

developed at the Department of Structural Engineering of the Federal University of Minas Gerais. Numerical sim-
ulations are performed using different smoothing domains and support nodes selection strategies. The results of

simulations are compared with the standard finite element method in the complete domain.

A Computational Approach to Predict the Bond Strength of Thin Steel Rebars in Concrete by Means of Artificial Neural Networks

2024-05-25T17:45:40+00:00

The bonding between steel rebars and concrete is one of the critical aspects of reinforced concrete
structures. As a phenomenon influenced by many variables, it is challenging to establish how the steel-concrete
adhesion can be described in the standards used for reinforced concrete design. This study used an experimental
data set of 190 pull-out specimens to develop an artificial neural network (ANN). The data used in the modeling
were collected from 8 different studies and were arranged as four input parameters: bar surface, bar diameter (φ),
concrete compressive strength (fc) and the anchorage length (Ld). The output result was the pull-out load.
Several scientific studies on this property have been performed since the 1940s, among many other
investigations in this field. Generally, these studies refer to bars with diameters greater than 12.0 mm. However,
few studies have evaluated the performance of reinforcing bars with diameters smaller than 10.0 mm, which
includes 6.0-, 6.3-, 8.0- and 9.5-mm diameters, usually used in reinforced concrete elements. This work uses
ANN to analyze and build a prediction model for the steel-concrete bond and its potential to deal with
experimental data. The root mean squared error (RMSE) found for the maximum pull-out load in the pull-out
test was 2.35 kN and the obtained R-squared was 0.94. Therefore, the pull-out load results found were compared
with the results obtained through the equation available in CEB 2010. Finally, it is possible to conclude that the
current model can satisfactorily predict the bond strength of thin bars.

A comparison of the effects of nonlinear damping on the free vibration of laminated circular cylindrical shells

2024-05-25T17:49:54+00:00

Knowing the damping level is important for the analysis, experimentation, and use of the systems. Most
of laminated shells studies are concerned with viscous damping, however in several engineering applications the
nonlinear damping is introduced by dissipative forces. For this reason, in this study the influence of the nonlinear
damping term proportional to the power of velocity on the free vibration of laminated circular cylindrical shells is
considered. To model the shell, the Donnell nonlinear shallow shell theory is used, and from energy approaches
the set of nonlinear ordinary differential equations of motion is obtained, and then solved by Runge-Kutta method.
For these analyzes is considered expansions to describe the axial, circumferential and radial displacements
totalizing fourteen degrees-of-freedom. The obtained results show that nonlinear damping have a great influence
on the attenuation of free vibration of the laminated circular cylindrical shells.

Numerical analysis of the cold start of a distribution transformer filled with biodegradable oil

2024-05-25T17:52:12+00:00

This work presents a numerical analysis of the cold start of a distribution transformer filled with
biodegradable oil in order to obtain a detailed description of temperatures and velocities distributions inside the
transformer. When the transformer is placed in very extreme conditions, like in a wind farm with very low ambient
temperature, and is filled with biodegradable oil the pour point of the oil can be reached. This type of analysis
has not been necessary since mineral oils have very low pour point temperatures, below −40 °C, but in the case
of conventional sunflower oil can be −18 °C. When the transformer is started from a temperature near the pour

point the fluidity and hence the natural convection phenomena, which is the principal mechanism of the heat trans-
portation inside the transformer, can be dramatically reduced. This reduction can lead to a local increase in the oil

temperature, principally in the windings oil channels. In this work, several working temperatures are analyzed for
a transformer with a rated power of 315 kVA and a voltage ratio of 13.2kV/0.4kV filled with biodegradable oil,
through three-dimensional thermo-fluid dynamics simulations using the multiphysics scientific code Code Saturne.
This work is carried out as part of the EU Horizon 2020 BIOTRAFO project.

Study of a roller seismic isolation bearing coupled with an eddy current damping system.

2024-05-25T17:56:11+00:00

In seismic protection of structures, seismic isolation systems have been implemented successfully. By
this year, Japan is probable to exceed 4500 buildings built with this technology. Seismic isolators, in addition to
decoupling the seismic excitation of the structure, provide energy dissipation capacity through different
mechanisms such as friction and yield of materials. A disadvantage of these dissipation methods is the contact
between the damping system components with seismic isolation system. This work studies an efficient energy
dissipation alternative, with the application of eddy currents in a roller seismic isolation system; it should be noted
that this alternative does not require direct contact with the isolation system components. The characterization of
the dissipation system was carried out with the use of magnets and non-ferromagnetic material, coupled to a
seismic isolator with rolling supports. Seeking to reduce the horizontal displacement of the seismic isolation
without affecting its dynamic behavior, several aspects were considered in this study, such as: rolling friction
coefficient, eddy current damping forces and the gap between the conductor and the magnetic system. According
to the study’s results, the proposed damping system is viable for use in seismic isolation.

Risk optimization of a RC frame under column loss scenario

2024-05-25T17:59:10+00:00

The sudden loss of a single supporting element in a RC frame may lead to the disproportionate partial
or total structural collapse if its design fails to confine the initial damage through resisting mechanisms, like
compressive arch action, Vierendeel action, and catenary action. Since uncertainties related to material properties
and geometrical parameters plays a major role in the behavior of these resisting mechanisms, and consequences
are highly significant for such failure events, the risk optimization is a very convenient approach to optimize the
balance between economy and safety. This is shown herein by the optimization of a RC frame, considering the
cross sections and the steel rebar areas of the beam and columns as design variables. Failure consequences are
considered for serviceability, beam bending, shear failure, flexo-axial compression of the columns, and steel
rupture at and before catenary action. A physical and geometrical nonlinear static analysis is employed, in which
the sample points are submitted to pushdown analysis. Material behavior is represented by an elastoplastic model
with isotropic hardening for the steel rebars, and by combination of Mazars μ model with the modified Park-Kent
model for the confined concrete. Failure probabilities are evaluated by the Weighted Average Simulation Method,
and the Risk optimization is done by the Firefly Algorithm. In order to reduce the computational cost due to the
nonlinearities involved and the high number of sample points required, Kriging is used to generate a sufficiently
accurate metamodel for the limit states and reliability indexes. It is shown that the adopted formulation leads to
more allocation of material when a column loss scenario starts to be significant in terms of safety x economy.

Three-dimensional Dipole BEM formulation for Cohesive Crack Propagation Modelling

2024-05-25T18:01:53+00:00

This work presents a boundary element method (BEM) formulation for cohesive crack propagation
analysis in a 3D approach. BEM is a well-known and remarkable approach in fracture mechanics, providing
effective stress concentration modelling in addition to less complex remeshing procedures during crack growth.

The fracture effects are captured by using an alternative BEM formulation based on introducing a set of self-
equilibrated forces, called a dipole, which describes the cohesive zone. This BEM formulation demonstrates some

advantages in comparison to the classical DBEM approach. The DBEM solves the fracture problem with the
discretization of both crack surfaces, which leads to six integral equations (three displacements and three tractions)
per a couple of points at the crack surface. Alternatively, the dipole approach requires the discretisation of solely
one crack surface. Besides, the nonlinear solution scheme corrects the stress components solely at the FPZ, which
in the present case are three. Thus, the dipole approach requires solely three integral equations at the FPZ, which
is half compared to the DBEM. It leads to faster and more effective performance in terms of computational effort.
Some classic examples from the literature are presented in order to validate the 3D Dipole BEM formulation in
the light of cohesive crack propagation analysis. Finally, this proposal contributes toward advancing BEM in
engineering analyses, especially in nonlinear fracture mechanics.

THERMAL REGULATION OF A PHOTOVOLTAIC PANEL BY PIN FINS: A NUMERICAL AND EXPERIMENTAL ANALYSIS

2024-05-25T18:04:15+00:00

Due to the growing interest in solar radiation to generate electricity, the use of photovoltaic panels
(PV) has been increasingly explored in recent years. Most photovoltaic modules have low efficiency in
converting solar energy to electricity, even under ideal operating conditions. Due to this low efficiency, the
remaining energy is converted into heat, increasing panel temperature and decreasing efficiency. In addition, the
effect of operating at high temperatures reduces the module's lifespan. Therefore, it is crucial to apply a cooling
system to regulate its temperature; this system can be passive or active, which the latter is often unsuitable due to
the power required to operate the compressor or pump used in the cooling process. Thus, in the current work, an
experimental and numerical investigation is performed considering a passive cooling system consisting of 4
segmented L-shaped aluminum fins arranged in the central region on the rear surface of a PV panel. A serial
experiment was conducted on different days with clear sky conditions for December 2021. The fins decrease the
panel temperature (up to 4.7 °C) and the efficiency and the output power increase by 2.4% and 2.1%,
respectively, compared to the reference panel. Moreover, the ANSYS program was used to predict the PV
surface temperature; the numerical results were validated with the experimental results for a conventional PV
panel without a cooling system. By the numerical analysis considering the fins on the rear surface of the PV
panel, satisfactory results were obtained compared to the experimental values, with an average deviation of about
2.7%. The proposed cooling method improved the convective heat exchange and cooled the PV system for all
days considered in the current analysis; reducing the PV surface temperature can avoid electrical conversion
efficiency losses and increase the PV system lifespan.

Position Guidance and Control for Fully Actuated Multirotor Aerial Vehicles in Dynamic Environments

2024-05-25T18:08:42+00:00

This paper is concerned with the robust position guidance and control of fully actuated multirotor
aerial vehicles subject to velocity constraint in dynamic environments involving external disturbances. The overall

method consists of an outer-loop guidance based on an acceleration-velocity-obstacles strategy and an inner stabi-
lizing control loop based on an integral sliding mode policy. The guidance strategy generates velocity commands

to reach a target position while avoiding collision with moving obstacles and respecting velocity bounds. On the
other hand, the integral sliding mode ensures that the velocity commands are, in theory, exactly tracked all the
time. The proposed method is numerically evaluated using a fully actuated octacopter and shows to be effective.

Numerical simulation methodology for active-adaptive vibration control using a state-space formulation and IIR filters

2024-05-25T18:10:52+00:00

Undesired vibrations can affect performance, reduce life cycle, and generate excessive noise. Therefore,
they should be controlled. The present work focuses on an active-adaptive vibration control approach which is
implemented and investigated through simulation and experimental trials. The adaptive feature of the control
system allows a satisfactorily low level of vibration to be sustained even if some eventual changes affect the
structure of concern. The current control system is composed of sensors, actuators and a control unit with digital
filters, in a feedforward architecture that uses the FxNLMS or CVA-FxNLMS adaptive algorithms. Such a system
is applied to a clamped-clamped metallic beam subjected to harmonic excitation. The main contribution of this
work is the development of a time-domain numerical simulation methodology for the aforementioned system using
state-space formulation and IIR filters. The model parameters resulting from such a methodology are adjusted
via numerical optimization. The proposed simulation methodology is validated by experimental trials, showing
reliable performance.

On crack simulation by mixed dimensional coupling in GFEM Global- Local

2024-05-25T18:14:28+00:00

The Generalized Finite Element Method (GFEM) is a numerical method established as an alternative to
Finite Element Method (FEM). Considered as an instance of the Partition of Unity Method (PUM), the GFEM uses
enrichment functions that, multiplied by the Partition of Unity (PU) functions, expand the space of the solution
problem. These enrichment functions could be chosen according to the problem analyzed or numerically obtained
from the results of the analysis of a local problem, in the GFEM global-local strategy. Extending the field of
application of this method, the global-local Generalized Finite Element Method (GFEM) is used here to solve
mixed dimensional structural problems. Combining mixed-dimensional elements and a multi-scale analysis can be
highly effective to capture the local structure features without overburdening the global analysis of the problem.
An iterative procedure, which balances the forces between the two multi-dimensional models, was automated and
combined with the global-local analysis of GFEM. This new procedure incorporated into a computational system
made possible the simulation of quasi-static crack propagation. In the numerical example a small scale plane
stress problem, where the crack propagates, is coupled with a large-scale model described by Timoshenko beam
elements.

The use of intelligent algorithms in the prediction of bonding strength in steel-concrete interfaces

2024-05-25T18:16:39+00:00

The current study proposes the use of intelligent systems and a statistical technique to predict the
strength of steel-concrete bond using a database of academic literature. The work used as the reference deals with
the pull-out test that evaluated the steel-concrete bond behavior in thin bars. The experimental program employed
concretes of class C25, C35 and C40, and CA-50 ribbed bars (with diameters of 6.3, 8.0, and 10 mm) and CA-60
notched bars (with diameters of 5.0, 6.0, 8.0, and 9.5 mm). The database was subjected to data mining strategies
for statistical treatment. Conventionally, bond strength is obtained by pull-out and beam tests, as proposed by BS
EN:10080, involving expensive and lengthy experimental tests. Alternative ways are the application of machine
learning-based methods and the use of statistical techniques. Using these methods it is possible to assess their
efficiency in predicting the maximum pull-out force. In the present research two particular methods are used to
solve the problem. One technique is Multiple Linear Regression which is a generalization of Least Squares, where
the minimization of the sums of the n-th powers of the residuals is considered. Multiple regression analysis is also
very useful in experimental situations, where the experimenter can control the predictor variables. The other model
is based on statistical learning theory and is called Support Vector Machines (SVM). It is a machine learning and
computational intelligence technique, where it is possible to obtain a classification of data from the same domain
in which the learning is performed. The method uses a principle called induction, where it is possible to draw
generic conclusions from a training set. The main objective of this work is to propose an alternative way to predict
the bond strength of thin bars using computational methods and a statistical technique. The methods used is
compared via performance metrics to verify which one proves to be more reliable to predict steel-concrete interface
bond, considering the safety coefficients used in engineering.

DYNAMIC ANALYSIS OF A VEHICLE PLATFORM MADE OF COMPOSITE MATERIALS, USING THE FINITE ELEMENT METHOD IN THE DEVELOPMENT OF MATHEMATICAL MODELING

2024-05-25T18:19:42+00:00

The present work consisted in the discretization of a vehicle platform in finite elements in a simplified
way, responsible for representing a generic vehicle, using 12 elements of Kirchhoff Plates (whose thickness is
negligible in relation to the other dimensions), with 3 degrees of freedom per node (one vertical displacement
and two rotations), aiming at obtaining an adequate mathematical model, determining the natural frequencies and
the time responses of the structure. The simulations were performed with three different materials, two
composites and 1040 steel. The results obtained show that the structure made with carbon fiber has the highest
natural frequencies when compared to the others, a fact that is linked, above all, to the high modulus of elasticity
that the material has. Regarding the responses over time, the structure made with e-glass fiber presented the
highest amplitudes of oscillation, indicating that the parameters used may not be very suitable to simulate the
structure made from this material. In addition, the structure made from carbon fiber proved to be more stable in
the simulations, as it returns to the equilibrium situation in a relatively shorter time when compared to the other
materials studied.

Member grouping optimization in a multi-objective structural problem of a steel spatial frame

2024-05-25T18:22:01+00:00

Structural optimization problems arise from a demand for a low-cost and high-performance structure.
Thus, the structures are optimized to minimize the weight, volume, or cost concerning their mechanical aspects of
strength and displacements. In theory, these optimization problems are searching to find structures with various
elements such as columns and beams. On the order hand, in practice, the wide variety of distinct elements can be
an inconvenience in the case of real constructions. This paper analyzes the optimum design of steel spatial frames
in which these frames are submitted to a multi-objective optimization considering the weight as the first objective
function and the number of distinct members in the frame as the second objective function, both to be minimized.
Thus, the paper aims to evaluate the behavior of these two conflicting objective functions to provide to the designer
the benefits and disadvantages of increasing the number of distinct profiles in a frame. As a result, a Pareto front
that summarizes the conflict between the number of distinct members and the structure’s weight will be placed. In
addition, the paper compares this curve of conflicting objective functions with other existing alternatives, such as
those obtained by using cardinality constraints.

Efficacy of an Adaptive Integration Scheme on the Numerical Performance of DIBEM applied to the Solution of Compressible Diffusive-Advective Problems

2024-05-25T19:23:15+00:00

Advection-diffusion models can adequately describe several industrial applications in relevant areas such
as heat and mass transfer, fluid flow, metallurgy, pollutant dispersion among a wide spectrum of engineering
problems. This class of problems presents challenging numerical aspects to the boundary element method (BEM),
in special for formulations that employ radial basis functions to approximate the advective domain integral as
occurs in the Direct Interpolation technique (DIBEM). Furthermore, the representation of variable velocity fields
and the reproduction of compressibility effects in low to moderate Peclet flows also require a more robustness
numerical model. For definition, BEM formulations generates singular and quasi-singular integrals that demand
an adequate treatment. Specifically, the application of DIBEM requires a greater number of interpolation poles in
the domain for a better accuracy. As the internal points are also source points, more refined meshes require the
use of adaptive schemes to handle the quasi-singular integrals that arise from locating the source points closer to
the boundary. In the present article, the performance of the Telles’s self-adaptive integration scheme is compared
to the classical Gaussian quadrature, in a two-dimensional diffusive-advective application with variable velocity.
DIBEM results are compared with Dual Reciprocity technique (DRBEM) and the available analytical solution.
These preliminar results indicate that the use of the adaptive scheme provides more significant improvements in
accuracy for DRBEM when compared to DIBEM.

Kriging-based optimization algorithms for noisy data

2024-05-25T19:27:40+00:00

Responses to many real-world problems can only be evaluated perturbed by noise. Intelligent opti-
mization strategies, successfully coping with noisy evaluations, are required in order to enable making efficient

optimization of these problems. The surrogate model has been popularly used in the area of design optimization
with high computational cost, especially in Kriging-based optimization algorithms. The performance of those
algorithms depends on a sequential search of so-called infill points, used to update the Kriging meta-model at

each iteration. This article explores the most relevant single and multi-objective infill algorithms used for Kriging-
based optimization with noise-handling strategies. Those algorithms explore information about the variance of the

predictor and the noise from stochastic simulation.

Comparison of Kriging-based algorithms for optimization with heterogeneous noise

2024-05-25T19:30:20+00:00

Problem modeling through response surfaces, or meta-models, has been a great solution adopted for opti-
mizing problems with high computational cost, especially Kriging-based optimization algorithms. In recent years,

algorithms have been proposed which extend the traditional Kriging-based simulation optimization algorithms
(assuming deterministic outputs) to problems in the presence of noise or uncertainty. This paper approaching
stochastic kriging meta-model in a comparative study of the performance of three Kriging-based algorithms for
unconstrained minimization a noisy function. The Minimum Quantile criterion (MQ), stochastic Efficient Global
Optimization (sEGO) and Expected Improvement with Reinterpolation (EIR) will be the algorithms compared

using an analytical test function. The conclusions and insights obtained may serve as a useful guideline for re-
searchers aiming to deal with optimization problems, especially to apply Kriging-based algorithms to solve engi-
neering problems, and may be useful in the development of future algorithms.

On the initial investigation of the use of temperature gradient measurements to estimate the presence of leaks

2024-05-25T19:34:28+00:00

Leakage in water pipes is of great concern, so that techniques for its detection have been widely studied
over the years. In this scenario, vibro-acoustics techniques are the most used ones because they can be no intrusive,

can provide information on the amplitude (severity) and location (time delay) of leaks in buried pipes with reason-
able precision, however, requiring the use of equipment and instrumentation of high cost in addition to the training

of specialized labor workers. The latter may restrict the application of this kind of solution to a few specialized
companies. Hence, the initial investigation of detecting leaks via using temperature gradient measurements is
proposed in this work as an attempt to develop a technique that is less costly but still effective in indicating the
existence of leaks. This initial investigation is carried out using a straight-horizontal water plastic pipe generally
found in ordinary houses, so that the heat transfer mechanism of such situation can be modeled via finite volume
method (FVM) considering steady-state condition and the developed code (situations) validated using the software
OpenFoam. The simulations were carried out considering a range over which the Reynolds number relies within
according to the average leak flow rates commonly found in ordinary residential buildings in Brazil. Moreover, the
Nusselt and temperature gradient were then evaluated regarding their variability in the fully developed flow region,
as a function of the variation of the external environment condition.

Numerical Analysis on Distortional Failure of Cold-Formed Steel Hat- Section Beams under Non-Uniform Bending

2024-05-25T19:37:24+00:00

Cold-formed steel (CFS) members stand out among steel structures notably due to their lightness,
structural efficiency (high strength-to-weight ratio) and versatility. However, given their high width-to-thickness
ratio, CFS are highly susceptible to instability phenomena (buckling). The objective of this research is to analyze
the structural behavior of cold-formed steel hat-section beams under non-uniform bending about the major and
minor-axis, regarding the risks of distortional failure. Through the Generalized Beam Theory (GBT), using the
computational program GBTUL, the geometries where the distortional failure is predominant were selected,
presenting: distortional modal participation (Pdist) greater than 85% and distortional critical buckling moments
(McrD) significantly below their local (McrL) and global (McrG) counterparts. The beams were analyzed for two
end support conditions that differ only by the restriction to warping (free or prevented), and were subjected to
moments at the end sections, constituting different loading hypotheses. Through the computational program
ABAQUS, a shell finite element model was developed to perform the buckling analysis on the selected elements.
The results obtained with the model present appropriate values and the expected behavior, indicating that it
adequately simulates the elements. In addition, they demonstrate how support conditions and loading affect the
distortional critical buckling moments.

Sensitivity and Aerodynamic Analysis of a Darrieus Wind Turbine Using Different Geometric Parameters

2024-05-25T19:41:03+00:00

Considering the demand for renewable energy, this work has the objective of contributing to the
development of Small-Scale Darrieus Vertical Axis Wind Turbine that can be employed in decentralized electrical
generation through computational fluid dynamics, operating at a low tip speed ratio (TSR). A 2D numerical
modeling is performed with unsteady-state and turbulent flow. Geometric parameters analyzed are profile camber

(m), camber position (p), profile thickness (t), chord (c) and pitch angle (β), the first three being based on NACA-
4 digit parameterization. A sensitivity analysis using the Smoothing Spline ANOVA algorithm is conducted to

predict the influence of each parameter on the power coefficient ( Cp

̅̅̅) of the turbine. Two Designs of Experiments
(DoE) were created with 100 and 192 possible configurations of the Darrieus turbine, so it was possible to evaluate
which parameters and interaction of them have the most influence on Cp

̅̅̅. The main finds showed that the pitch

angle (β) contribution on Cp

̅̅̅ is the highest among others (69%). An analysis considering only the geometry of the
blades profile showed its influence on the flow through the turbine. Finally, an increase in aerodynamic efficiency
of Darrieus VAWT is the main responsible for increasing Cp
̅̅̅.

A modified super-twisting algorithm with specified settling time: numerical investigation

2024-05-25T19:43:13+00:00

The super-twisting algorithm (STA) is a finite-time stable algorithm that can be employed in control
and observation of dynamical systems to ensure a good transient performance of tracking and estimation errors.
However, only a conservative estimation of the convergence period can be obtained when using a classical STA.
To address this limitation, the present work proposes two novel specified-time stable algorithms, in which the
convergence instant can be directly specified as a system parameter. For the first one, we modify the right-hand
side of an STA by replacing its non-smooth continuous term with a time-varying specified-time stabilizing function.
For the second one, we alter the previously obtained system to recover the conventional STA performance after
the specified period. We extensively analyze the algorithms’ sensitivity to variations in each of their parameters
through numerical simulations. With proper tuning, the last proposed dynamic system is shown to provide robust
convergence to the origin at a specified instant of time.

Numerical-experimental analysis of frost formation on copper flat plates

2024-05-25T19:45:48+00:00

In the present work, a numerical-experimental analysis of frost formation on copper flat plates was
performed. The process of formation of frost is a physical phenomenon that occurs through the change of phase
by resublimation, in which a flow of moist air solidifies when it comes into contact with surfaces with temperatures
below 0°C, which occurs in various equipment present in refrigeration processes. Such accumulation gives rise to
a porous structure, acting as a thermal insulator, decreasing the heat transfer rate from the surface and the efficiency
of the cooling systems. A low-cost experimental apparatus was developed, enabling an experimental analysis of
the phenomenon under study. Through numerical simulations, based on a mathematical model of this phenomenon,
it was possible to determine the frost thickness. The numerical-experimental analysis demonstrates measurements
and simulations of the frost thickness as a function of the elapsed time. The numerical results were in good
agreement with the experimental results.

The influence of non-isothermal flows in the Taylor-Couette instability through numerical analysis

2024-05-25T19:49:01+00:00

The Taylor-Couette flow is a classic rotational flow studied since the beginning of the 20th century. The
phenomenon occurs in the gap between two cylinders with different rotational velocities. It happens when one of
the cylinders, usually the inner one, has a rotation that causes centrifugal forces higher than the viscous forces.
The most recognizable characteristic of the flow is the Taylor vortex, an eddy-like pattern that appears across
the cylinders length. The present simulation of Taylor-Couette in the gap inside an electric machine considers
an aspect ratio air gap - cylinder length of 1:20 and the radius rate of 0.9859. The present work evaluates the
necessary rotation, under the geometric conditions presented, to form the Taylor vortices in isothermal flow and
when the flow is submitted to temperature gradients. The GCI method is used to validate the grid dependency. We
have observed and discussed the sensibility of temperature gradients to the identification of the critical flow, to the
velocity field and to the torque at the outer cylinder.

Preference-Based Whale Optimization Algorithm for Multi-Objective Struc- tural Optimization Problems Using Reference Points

2024-05-25T19:56:03+00:00

Several structural optimization problems can be formulated as multi-objective optimization problems
(MOOPs) due to the existence of multiple conflicting objectives, which must be minimized simultaneously. Most
MOOP solvers find the Pareto front formed by the best trade-off solutions, and then the decision-maker (DM)
chooses the one that best meets his/her personal preferences. However, many Pareto front solutions have no
chance of being chosen once they are outside DM’s region of interest (ROI). On the other hand, some solvers use
information from the DM’s preferences and can focus only on DM’s ROI rather than all Pareto front, consequently
obtaining better solutions from the DM’s perspective. This work proposes an algorithm named R-WOA to solve
the multi-objective structural optimization problems (MOSOPs) using the Whale Optimization Algorithm (WOA)
guided by reference points formed by DM’s desired values for the objective functions. MOSOPs having 10-,
25-, 60-, 72-, and 942-bar trusses are carried out to test the R-WOA’s performance. The numerical experiments
compare the R-WOA with algorithms R-NSGA-II, R-GDE3, and R-GDE3+APM regarding Hypervolume and
IGD+ performance measures. Using a non-parametric statistical test and the Performance Profile, the R-WOA
proves to be competitive in most of test scenarios.

Numerical analysis of the bifurcation point sensibility to the temperature field in the Taylor-Couette flow

2024-05-25T21:12:16+00:00

The flow between concentric cylinders, called Taylor-Couette flow, has been extensively studied during

last century in works describing its governing parameters and presenting the various flow regimes for each con-
figuration. This kind of flow is present in the air gap of electrical machines and its characteristics affect the heat

transfer and the torque generated on the outer cylinder due viscous forces. The intensity of these effects depends
on the flow state, which is governed by geometric characteristics and Reynolds number. Our objective is to analyze
the effect of heat transfer on the surging wavy vortex and on the torque generated at outer cylinder. The numerical
simulations are done using the software OpenFOAM v9 with K-Omega SST as the main turbulence model. All
the simulations were in the transient regime. The pisoFoam solver was employed for the isothermal problem and
for the buoyantPimpleFoam solver for the thermal problem. A mesh independence study was done based on Grid
Convergence Index (GCI) method, where we found satisfactory values. For the thermal cases, we analyzed the
behavior of the flow as we increase the Reynolds number and the temperature at the walls, comparing its results
with the isothermal. It is notable the delay in the formation of the wavy vortices comparing with the rotational
speed and the decrease of the torque on the external wall.

Beams non Linear Analysis from Envelope Concept

2024-05-25T21:19:23+00:00

The heterogeneous nature of the Portland cement concrete promotes its irregular mechanical
behavior. Due to the shrinkage deformations, the mass of concrete presents cracks, even before loading. Such
material exhibit non linear performance since the stress level around 30% of its compressive strength, and, in this
way, some researchers developed mathematical models designed to describe that kind of mechanical
phenomenon. A model proposed by Branson, is especially useful to analyze reinforced concrete beams from
beam finite elements resulting, consequently, computational effort economy. It is known that, in some cases, it
may be suitable to carry out continuous beam analysis considering several loading arrangement, culminating
over a bend moments envelope. Preliminary comparative studies made over continuous beam, considering the
bend moments due to full load and bend moments envelope drafted from different load arrangement alternatives
show remarkable differences between these two kinds of analyses versions. The purpose of this work is to report
the nonlinear mechanical performance limit analysis of reinforced concrete continuous beams considering,
include, the bend moments envelope. To accomplish such a subject, a computational code was developed, based
on the finite element approach, applied upon the Branson’s formulation.

COMPARISON OF THE IMPACT FORCE ON THE BOTTOMHOLE SURFACE BETWEEN PDC AND ROLLER CONE BITS

2024-05-25T21:22:02+00:00

In the process of drilling the well, the mud is pumped through the drill string, passing through the drill
bit until it reaches the ground, and finally the drilling mud with the particulate material is taken to the surface
through the annulus region. The impact of the fluid that leaves the nozzles of the drill bit to the ground, will allow
the degradation of the soil and removal of the particulate material. The influence of the rotating drill string on the
impact force will be studied through a numerical platform under development based on the Navier-Stokes
equations, discretized using the finite volume method using staggered arrangement, with a second order of
approximation in space and time. The immersed boundary method is employed, where the fluid is represented by
the Eulerian mesh and the geometry by the Lagrangian mesh, which in our case will use two different types of
drill bits (Polycrystalline Diamond Cut-PDC and Roller cone) to compare them. The Large Eddy Simulation
method was also employed with the dynamic sub-grid scale model, which is associated with describing the
turbulence phenomenon. The Reynolds number based on the fluid inlet diameter was 3500.

Non-linear numerical modeling of reinforced concrete structures considering bond slip

2024-05-25T21:27:40+00:00

Depending on the stress magnitude in the interface of rebar and concrete, relative displacements may
develop. Thus, to develop a reliable numerical model, interaction between rebar and concrete must be included by
a bond slip constitutive relationship. Therefore, in this work we propose a numerical model to evaluate the bond
loss between reinforcement and concrete, based on the Positional Finite Element Method. In this method,
geometric nonlinearities are considered and static equilibrium are obtained though the Principle of Stationary
Potential Energy, considering total Lagrangian description. An incremental-iterative Newton-Raphson procedure
was used to solve the non-linear system. Fibers (rebars) are immersed in the matrix (concrete) though nodal
kinematic relationships, allowing mesh independency. Physical nonlinearity for concrete is considered by Mazars
damage model, and for reinforcement it is considered an elastoplastic constitutive relationship. Bond rupture is
simulated by Lagrange multipliers and relative displacement of matrix and fiber (slipping) is made up by a
dimensionless bonding element after rupture. Results are compared to experimental and analytical examples,
showing that the proposed method is reliable and accurate.

Study of simplified elements for static and dynamic analysis of origami structures

2024-05-25T21:31:01+00:00

Research works involving structural origami have grown in recent years, especially applied to science
and engineering problems. Early applications took advantage of the idea that a system can be folded compactly
and subsequently deployed, and that self-assembly can be used to construct a three dimensional structure by
starting from a thin sheet. The present work, as part of an M.Sc. thesis carried out by the first author, compares bar
and hinge models with the simplest hybrid finite element models for plate and shell in order to represent origami

structure panels. The bar and hinge model approach, as given in the literature, is based on folded patterns as pin-
jointed truss frameworks: each vertex in the folded sheet is represented by a pin-joint, and every fold line by a bar

element. The hybrid finite element formulation is based on the Hellinger-Reissner potential for an approximation
of the stress field, thus satisfying the equilibrium equation of the elasticity problem in the domain and leading to
a consistent structural model obtained at almost no additional cost when compared with the latter, too simplified,
formulation. We assess the mechanical behavior of these structures and the folding energy measured in terms of
the eigenvalues associated to the relevant eigenmodes of a cell for both the traditional bar and hinge scheme and
the proposed equilibrium-based finite elements. The displacement response in time for a four-cell assemblage is
also investigated for the implemented models.

Optimization of a 2D reinforced concrete frame considering a seismic load via cross-entropy method

2024-05-25T21:34:47+00:00

Finding an optimal design for reinforced concrete structures to attend a specific goal is a desirable
step for engineers. This paper aims to optimize the dimensions of columns and beams of a 2D reinforced concrete
frame subjected to a dynamic load. The structure considered has the specific goal to attend for a seismic action, and
this is an important search, since structures in Brazil, for many years, were built with no consideration regarding
seismic events. Even after ABNT NBR 15421 (2006) [1] was released, seismic actions were still not considered by
most engineers during the design phase, according to Miranda et al. [2], which can lead to catastrophic structural
damages if events like these happens in urban regions. The problem is formulated in terms of the dynamical
seismic response of 2D reinforced concrete frame, and the optimization algorithm used considers a stochastic
solution strategy combining penalization and the cross-entropy method, proposed by Cunha [3]. The consideration
of the probability of failure and cost of failure on the objective function makes it a Risk Optimization problem.

Numerical Serie Convergence Applied to Columns Buckling Analysis

2024-05-25T21:41:03+00:00

A numerical series represents the sum of terms in a numerical sequence. If the quantity of its terms is
unknown, it constitutes an infinite series, and the sum of its terns must be obtained from the convergence analysis
procedure. The series used to approach the values of given function, must be of the infinite mode because, in such
cases, the quantity of terms that the series needs to attend such demand, is unpredictable. There are engineering
problems which may be solved, directly, by the modeling based on approach for infinite numerical series, as the
slender columns analysis case. The slender columns analysis cast by elastic and ductile material has been based
on the concept of critical load. Such modeling version is not suitable to mechanical analysis of specimens cast by
weak rupture pattern material, as the reinforced concrete, but even thus, some concepts involved in such a
formulation are used as a classificatory reference. The Mechanics of the Materials uses the physical modeling
capabilities in deriving the equations object of approach on the featured theme. The aim of this work is the slender
columns mechanical performance modeling through infinite numerical series convergence concept.

Numerical solution of non-isothermal flow in heavy oil reservoirs using parallel computing

2024-05-25T21:44:33+00:00

In this work, we have used the OpenACC to parallelize a reservoir simulator aiming to simulate two-
dimensional non-isothermal flows in a heavy oil reservoir. We have considered the production scenario with

a vertical well and two static heaters. We have also applied the Control Volume Finite Difference Method to
discretize flow and energy governing equations. We have chosen the Conjugate Gradient Method to solve the
systems of algebraic equations to obtain pressure and temperature fields along with an operator splitting method. In
the study of computational performance, we have employed different computational meshes and achieved speedup
values greater than eight.

Nonlinear Kirchhoff-Love Shell Finite Element: Two Simple Triangular Shell Element

2024-05-25T21:47:18+00:00

Shells are one of the most important models in solid mechanics since many structures in engineering
may be associated with it: metal sheets-based products, slabs, thin-walled pressure vessels, and other objects with
one of its dimensions considerably smaller than others. Shell models may be adaptable to finite element usage, but
some particularities must be watched it, such as locking behaviours.

This work aims to study and develop a nonlinear formulation for shells models using a special simple trian-
gular shell element, which is a new displacement-based triangular shell element with 6 nodes. Moreover, the shear

locking and membrane locking behaviour are not observed at the performance of this new element.
In formulation of shell models, we consider finite strains, large displacements, and rotations. Rotation field
is re-parameterized in terms of the Rodrigues rotation vector, resulting in a simpler update of rotational variables.
The Kirchhoff-Love kinematical assumption and an initial plane reference configuration for the shell is considered
here.
A computational implementation is done with several numerical examples using the new element developed
here. Furthermore, a comparison with numerical examples using the well-known element T6-3i (Campello et al.
[1]), a six parameter (3 displacements and 3 rotations) element, is done with the aim to also illustrate the robustness
of our formulation.

The Morley plate element in the frame of a generalized, frequency-dependent hybrid finite element formulation

2024-05-25T21:50:56+00:00

The Morley plate element is the simplest triangular finite element for homogeneous, isotropic material,
and represents constant bending curvature/moment exactly, as the flexural counterpart of the membrane, constant
strain/stress finite element. It has six degrees of freedom: three corner-node transversal displacements and three
edge rotations. We propose a slightly modified, improved Morley element based on a frequency-dependent hybrid
finite element formulation to be used in the frame of a generalized modal analysis for stiffness and mass matrices
given as frequency power series. The domain stress solution satisfies the homogeneous elastodynamic equilibrium
equations for moderately thick plates, as we resort to the concept of mean transversal shear distortion proposed
in a previous conference contribution (PANACM/CILAMCE 2021). We show that the formulation for just one
mass matrix corresponds to a plain displacement formulation, as proposed in the literature for the thin-plate, static
problem (although introducing some due corrections). Some numerical tests with one and two mass matrices show
that the model can be seamlessly applied to both moderately-thick and thin plate problems – thus without the
shear-locking inconvenience – and in spite of its shape-function simplicity ensures good, asymptotic convergence
for natural frequencies. As we have a similar generalized modal development for the membrane triangle, this leads
to the simplest – and consistently – conceivable shell element.

Structural analysis with nonlinear behavior: The importance of going beyond the line

2024-05-25T21:52:59+00:00

This work discusses the importance of numerical methods in structural analysis. It deals specifically
with the analysis of frame structures where geometric and material nonlinearity is taken into account. The
importance of considering these effects is highlighted with examples of catastrophic events related to instability
phenomena. A computational program developed by the authors with educational purposes is presented and used
to perform the analysis of a simple frame.

Thermoelastic stationary analysis of non-oriented grain steels using BEM

2024-05-25T21:56:09+00:00

This work deals with a thermoelastic analysis of anisotropic cold-rolled non-oriented grain steels (FeSi)

where the material is subjected to severe thermal and inertial loads. Following the stationary thermoelasticity for-
mulation of the boundary element method (BEM), this model focuses on the 2D study of these materials when

the elastic properties are temperature-dependent. The cold rolling process promotes a deformed microstructure on
steels with 3%Si. After the cold rolling process, this material is subjected to an annealing process to recrystallize
the microstructure. This process promotes crystallographic texture in the material, with a strong Goss fiber and
weak (hkl)[110] and (111)[uvw] fibers. That is, although classified as non-oriented grain steel after the annealing

process, steels with 3%Si produced by the cold-rolled process have crystallographic texture in all stages of man-
ufacturing, resulting in an anisotropic material. An industrial application is shown to illustrate the feasibility of

using the presented formulation, and the stationary thermomechanical response of the material. Taking advantage
of the BEM capabilities to solve high gradients and secondary mechanical fields within the domain.

Approach to connecting non-matching meshes applied to concrete beams of different sizes in multiscale modeling

2024-05-25T22:00:01+00:00

This work contributes by presenting an alternative way for connecting non-matching meshes. It uses

coupling elements that do not add degrees of freedom to the problem. These coupling elements are used for con-
necting the mesoscale with the macroscale in concrete beams subjected to three-point bending tests in multiscale

modeling. The beams are of different sizes, so it is possible to analyze the quality of the coupling between meshes
with different ratios between the dimensions of their elements. The problem is solved using a geometrically exact

version of the Finite Element Method (FEM). At the mesoscale, a damage model allows representing the degra-
dation of concrete, including the formation of discrete cracks. The studies carried out showed that the coupling

elements used allow connecting meshes with different ratios between the sizes of the elements.

Computational tool for information management and integrity assessment of subsea rigid pipelines

2024-05-26T12:58:37+00:00

Subsea rigid pipelines, widely used to transport fluids in oil and gas production activities, require an
Integrity Management System to ensure that there are no economic, environmental, material nor human losses
throughout their design life. In this work, an overview of methodologies for data management and generation of
results for integrity assessment will be presented. Then, such methodologies are implemented into an integrated
specialist software that is currently under development. The aim is to obtain a robust and efficient computational
tool whose application in real scenarios will provide the following benefits: a) Productivity gains during the
processes of evaluating the integrity of submarine rigid pipelines, including the centralization of relevant
information from the history of inspections and pipeline operating conditions; b) Generation of standardized
technical reports containing results of integrity assessments under operational conditions; c) User-friendly
interface to access information on the operational history of the pipelines during its design life; d) Assistance in
the integrity management of subsea rigid pipeline systems, according to the normative and regulatory
requirements; e) Ease in analysis sensitivity of relevant parameters, since it integrates, within the same
computational system, resources for data acquisition, information processing and integrated assessments of
different engineering analyses.

GFEM modeling bending of Functionally Graded Material (FGM) plates

2024-05-26T13:02:17+00:00

This paper presents a Generalized Finite Element Method (GFEM) formulation for mechani-
cal analysis of Functionally Graded Material (FGM) plates acting both under mechanical loads and under

the effect of high gradient thermal fields. It describes the development, implementation and validation of
said formulation, based on a composite plate model ruled by Reissner-Mindlin’s first-order shear theory.
The calculation of temperature field along the structure’s thickness is made by solving the stead-state
heat conduction problem through Finite Difference Method, considering given the boundary conditions
on both faces of the plate and thermal conductivities of the base materials. Elasticity moduli and thermal
conductivities’ temperature-dependence is considered. Thickness-wise numerical integration procedures
are used to compute both the stiffness matrices of the plate and the thermal portions of nodal force
vectors. A C
k
continuous GFEM model with three-noded triangular shaped elements is considered and

a linear strain-displacement relationship is adopted. Shepard Partitions of unit with smooth approxima-
tion functions are used and enriched by linearly independent polynomials. Solutions are obtained through

Newton-Raphson method.

On the manufacturing condition estimation of spray nozzles via image processing and epicycle representation

2024-05-26T13:09:12+00:00

Defects on irrigation spray nozzles, occurred during the manufacturing process, can affect such distribu-
tion pattern leading to an uneven product application and increasing wastage. With a specific test bench, side-view

images of hollow-cone nozzle sprays were collected as an attempt to assess the manufacturing condition of very

brand-new nozzles. Classical image processing tools was applied on this side-view images, using a filter to re-
duce any spurious noise and the combined use of power-law transformation together with the contrast stretching

technique to enhance image contrast, highlighting the presence of grooves in sprays, which is an indication of
uneven distribution. An algorithm was develop to represent the spray as a contour with a few representative points,
reduced from the large number of pixels and so compressing heavily the image size. These points were then used
as input to estimate the spray format via epicycle representation carried out using a computation algorithm based
on the discrete Fourier transform (DFT) leading to coefficients that are sensitive to the spray jet format. Samples
of nozzles presenting no manufacturing defects was used to define threshold values for these coefficients, so that,
any change in this regard can be an indication of manufacturing problems.

Analysis of Isolated Battered Pile and Soil Interaction via BEM/FEM Coupling

2024-05-26T13:12:58+00:00

The use of battered piles is more and more recurrent in view of their efficiency in certain problems,
these are deep-foundation elements widely used in civil engineering due to their ability to reach more resistant soil
layers and to support large loads. Bearing in mind that the numerical analyzes appear as an alternative in relation
to the empirical analyzes, the present work aims to perform the numerical analysis of isolated battered piles and
in groups through the BEM/FEM coupling. The pile is modeled by several finite elements of three-dimensional
frame with two nodes, five nodal parameters and any inclination. The soil is modeled by the boundary element
method, being considered a semi-infinite, elastic-linear, homogeneous and isotropic medium. Having been the
fundamental solution of Mindlin used, the soil discretization is done only on the contact surface with the pile, it is
not necessary to discretize the soil surface. The coupling of the BEM / FEM formulation is done considering the
transformation of the matrix of soil coefficients (BEM) into a matrix equivalent to the FEM, which added to the
stiffness matrix of the three-dimensional frame provides the final system. The interaction forces at the stake-ground
interface have a linear distribution. The results obtained were validated by comparison with those available in the
literature, showing effectiveness and robustness of the formulation. Finally, the results of which showed little
influence of the angle of inclination on the displacements of isolated battered piles.

EFFECT OF MICRO PIN-FIN GEOMETRY ON HEAT TRANSFER PERFORMANCE AND FLUID FLOW IN A SINGLE-PHASE HEAT SINK: NUMERICAL AND EXPERIMENTAL ANALYSIS

2024-05-26T13:15:23+00:00

The growing demand for electronic devices with high processing capacity with increasingly smaller
dimensions has been requesting solutions from the scientific community to dissipate the high rates of heat
generated in such devices, ensuring their integrity and functioning. Thus, research on applications in compact
heat sinks, such as micro pin-fins, has gained visibility, mainly associated with using environmentally friendly
working fluids. In this context, the current work analyzes the thermal and hydrodynamic behavior of HFE-7100
in a heat sink based on different shape pin-fins. Moreover, different micro pin-fins (with 350 μm height) arrays,
in-line and staggered configurations, are tested at different mass velocities. Thus, a numerical and experimental
study is carried out on the single-phase heat transfer and pressure drop characteristics. The numerical results
showed a good agreement with the experimental data for both geometries and operational conditions analyzed,
with a mean absolute error lower than 3.1% for heat transfer coefficient and 12.8% for pressure drop. The results
showed that the surfaces with staggered arrays present slightly better thermal performance than the in-line
arrays, probably due to the highest number of pin-fins. The staggering array yielded a higher Nusselt number at
the same mass velocity, which can be explained by the higher flow velocity and enhanced flow mixing.
Regarding the hydrodynamic aspects, the numerical data sets for in-line and staggered pin-fin configurations
have the same tendency, increasing with the mass flux. However, the in-line pin-fin values are higher, probably
due to the diamond pin-fin shape for the staggered configuration, which, compared to the in-line square shape
pin-fins, causes a reduced disturbance to the flow, giving smaller pressure drops. To conclude, both the in-line
and staggered configurations of the heat sink are reasonable solutions for the current cooling challenge, with an
advantage for the staggered configuration compared to the in-line configuration.

Numerical Modeling of the Elastoplastic Flexural Response of Ultrahigh Performance of Fiber Reinforced Concrete (UHPFRC) using the XFEM Fracture Model

2024-05-26T13:18:29+00:00

Recently, several experimental and numerical models have been carried out to investigate the
mechanical behavior of fiber-reinforced concrete (FRC), especially concerning their flexural response to
structural applications. Modern developments regarding these materials involve using ultrahigh performance
fiber-reinforced concrete (UHPFRC) in strengthening layers or jackets. This particular type of FRC is a
relatively new construction material with excellent mechanical properties and a crack propagation control.
However, for the structural applications and design, it is necessary to carry out direct tensile and bending tests to
obtain the tensile stress-strain behavior and the flexural response of the composite. In this sense, this paper
proposes the elastoplastic numerical modeling of the mechanical behavior of UHPFRC, including the fracture
evolution analysis using the Extended Finite Element Method (XFEM). Mixed-mode fracture behavior is
considered. The finite element models reproduce a four-point bending test reported in the literature by
Lampropoulos et al. (2021). The results show that the concrete damage plasticity constitutive model can
efficiently predict the load-displacement behavior since the load capacity ranges present a good agreement with
the experimental reference. Moreover, it is possible to predict the fracture path of the beam in a mixed mode
based on the application of the XFEM model.

Application of Artificial Intelligence in Jurisprudence Search Engine

2024-05-26T13:21:16+00:00

Search for jurisprudence is an arduous task that requires hours of commitment on the part of the legal
professional. Currently, there are several software that help in the search for the ideal document that the lawyer
needs to corroborate his processes. However, such systems use search for key words, that is, from a phrase or set
of words typed by the user, the software performs research in each document of the databases of jurisprudence.
This is a slow process and, by using keywords, the documents resulting from the search are mostly irrelevant with
the intention of the lawyer. Thus, this project aims to implement a web software to perform search in databases of
jurisprudence using artificial intelligence in its search engine. The methodology applied consists of obtaining the
database with all published jurisprudence and training an artificial intelligence algorithm with all the content of
the documents. After training the model, it will be inserted into a web software that will receive the lawyer's
research. Currently, an artificial intelligence model was generated with 420 documents and the results were
satisfactory. In the tests, the model reached 95% accuracy.

A novel Newmark-based method applied to an anisotropic damage phase field model

2024-05-26T13:31:13+00:00

We present an anisotropic phase field model for fracture that uses a fourth-order tensor field to describe
the damage that degrades the material’s elasticity. The governing equations were obtained based on the use of the
principle of virtual power (PVP), the balance of energy and the Clausius-Duhem inequality for the entropy. Small
deformation isothermal case was considered. A failure criteria is also presented to define fracture and to establish a
numerical criterion for damage irreversibility. The model was implemented using the finite element method (FEM)
for the case of plane stress. Results are presented using two time integration methods for the motion equation: the
standard and a modified Newmark method. The backward Euler method was used for the damage equation. Time
efficiency and accuracy of results were compared for both Newmark methods.

Numerical model of high-strength reinforced concrete columns subjected to the ultimate limit state of instability

2024-05-26T17:52:07+00:00

High-strength reinforced concrete columns have greater tendency to slenderness and to higher
compressive axial loads. Both aspects contribute to a significant magnified moment, and to a potential context to
lead those columns to instability failure. Although the second order effects can be determined by simplified
methods in some circumstances, the general method allows to identify the Ultimate Limit State of Instability
clearly and to evaluate the second order effects precisely. Thus, it is proposed the employment of general method
in two distinct two-dimensional models on finite element Abaqus software to obtain a load-deflection diagram.
The first model is a plane stress element with embedded reinforcement, with the Concrete Damaged Plasticity
representing the constitutive behavior of the concrete, and the second model adopts a beam element with the rebar
embedded into concrete section using Abaqus/Standard, with the Cast Iron Plasticity as a simplified representation
of the concrete. The adequacy of the models is validated by experimental data from literature. The results have
shown that two-dimensional model is effective to simulate the uniaxial bending High-strength concrete column
subjected to the Ultimate Limit State of Instability. In addition, the most simplified model, which adopts beam
element with rebar and neglects tensile strength, provides suitable load-deflection diagram. Therefore, this model
is recommended to represent such analysis.

Design of a Two Degree-of-freedom Tuned Mass Damper for a Suspension Bridge Model

2024-05-26T17:54:11+00:00

Tuned Mass Dampers (TMDs) are very useful when one aims to mitigate vibration-related problems.

This device, once attached to a structure, considerably attenuates the effects of dynamic loads (e.g, wind and seis-
mic activities). Although TMDs exhibit a favorable performance over one specific frequency range, structures have

multiple natural frequencies, and sometimes this raises the necessity of attaching a different TMD for each one of
them. However, this kind of solution often overloads the primary structure and limits TMDs’ damping performance

(weight penalty). The purpose of this work is to design a TMD capable of damping two vibration modes of a sus-
pension bridge’s deck. For this, the primary structure is modeled by the Finite Element Method, using ANSYS®

combined with a MATLAB® routine, then it is conceived its modal and harmonic analysis, identified the targeting
modes, and applied the “Equal Peak Design” technique to estimate the TMD’s optimum damping and frequency
ratio. Based on those factors, it is determined the final TMD dimensions. The results shows the developed TMD
has the potential to significantly reduce deck’s vibration levels, for its parameters can be effectively tuned to realize
the target modes control.

TOWARDS AN EFFECTIVE DRONE-BASED TECHNOLOGY TO COMBAT MOSQUITO BREEDING SITES

2024-05-26T17:57:20+00:00

Drones have become an important technological tool to support health surveillance teams in locating
and eliminating mosquito breeding sites in urban areas, since they allow the acquisition of aerial images with high
spatial and temporal resolutions. However, such images are often analyzed through manual processes, consuming
a lot of time in the inspections. Thus, researchers from different parts of the world have proposed computer vision
technologies to enable automatic identification of mosquito breeding sites with the use of drones. However, despite
the advances achieved, many of these technologies have some limitations that difficult their use in practical
situations. This study is focused on such technologies aiming to investigate their potential, limitations and
scalability. The literature review carried out shows that some proposed computer vision approaches could easily
compose low-cost softwares to be used in tasks aimed at combating mosquito breeding sites with the use of drones,
optimizing time and human resources. Despite that, works addressing software development from the proposed
computational approaches are very rare. Other limitations found in the present study are the non-identification of
water in the detected targets (suspicious objects and scenarios) and the non-provision of accurate geolocation of
them. In addition, in the case of Brazil, the lack of public policies to adequately support the use of the investigated
technologies can also be seen as a limitation.

Study of the high temperature effects on steel structural elements via Finite Element Method

2024-05-26T18:02:30+00:00

This article addresses the analysis of the steel behavior, as a structural material, subjected to high
temperature and then cooled. This study began with the influence of the cooling method on steel elements
at high temperatures questioning, considering the impact this research can bring to day-to-day fire
situations. Thus, to have a better understanding of the consequences of thermal actions on steel, tests were
carried out on the structural parts, under conditions like those of material characterization, at room
temperature and after cooling, using immersion in water and cooling without interference. To validate the
proposed constitutive model, the results obtained are compared by the numerical analysis of finite elements.
Such simulation was performed using the Abaqus software and considering the refinement of the mesh of
the elements for better data accuracy. Thus, the results achieved in the modeling were in accordance with
the results obtained experimentally, so that the numerical model was validated.

Structural Health Monitoring of prestressed concrete beams using different CNNs architectures

2024-05-26T18:04:14+00:00

There are several damage detection techniques that use signal data and can evaluate and ensure the safety
of a structure. Recently, machine-learning algorithms have been used to help classify and detect damages as well as
extract structural features from signal data. Learning algorithms have the advantage of using raw data or data with
minimum pre-processing as input. Convolution neural networks (CNN) is a supervised learning technique that
uses a combination of filters and pooling layer to extract features and classify these types of data simultaneously.
The performance of CNNS can vary drastically due to the architecture and the input shape of the input selected. In
this study it is compared different CNNs proposed by the literature in order to identify damage presented in a set
of eight identical prestressed concrete beams. Tests with sixteen 1D and 2D different CNNS were conducted with
results of accuracy, recall and f1-score varying from 50% to 99%.

An analytical model for stresses induced by pore-water pressures in porous rock slabs

2024-05-26T19:28:32+00:00

A well-known issue of marble slabs casted in building fac ̧ades is the phenomenon of bowing, which
may cause damage to constructions all over the world. Laboratory studies have shown that some kinds of marble
subjected to temperature oscillations suffer from non-uniform and permanent expansion, and that this problem is

exacerbated in saturated environment. The understanding of this pathology is still incomplete, despite its impor-
tance for civil construction, in order to prevent or even avoid this issue. In the formulation developed herein, heat

transfer problem is modeled by sol-air formulation, in order to linearize irradiation transfer and convective transfer.
The fully linearized problem is then solved by trigonometric series specially developed for time-periodic problems
in order to represent the daily cycles of heating and cooling. The analytical solution developed is compared to a
formulation previously developed by one of the authors of this work (Ito), extended to saturated environment under
undrained conditions. The result of this study is a contribution to the understanding of bowing and demonstrates
that the development of pore pressures in undrained conditions can accelerate the degradation of marble.

Comparison of EGO and sEGO optimization algorithm based on Kriging for noisy function

2024-05-26T19:32:44+00:00

In many engineering optimization problems the number of function evaluations is severely limited by time
or computational cost. In addition, the representation of randomness due to noise and uncertainties in the model
is essential. One strategy adopted for these cases is solve the problem through response surfaces, or meta-models,
especially Kriging model. A traditional Kriging-based algortihm optimization is the Global Efficient Optimization
(EGO) method. An most recent algorithm for stochastic problems was sEGO in which it introduces a parcel that
reflects the intrinsic noise of the stochastic function in your framework. In this paper these optimization algorithms
will be approached through some examples for demonstrate the importance of the variance quantifying approach
in the optimization process through Kriging meta-model, highlighting the influence of the noise amplitude in the
choice of the optimization strategy. The conclusions obtained may serve as a guideline for choose the best approach
for each type of optimization problem.

Stochastic live load model for buildings and its application in reliability based code calibration

2024-05-26T19:35:59+00:00

While the exact loading to which a structure will be subjected cannot be precisely assessed during the
design phase due to its stochastic nature, probabilistic models are useful for the rational determination of nominal
values, partial safety factors and load combination factors employed in limit state design that accurately reflects the
variability of these loads. In this paper, a simple probabilistic model describing the spatial and temporal variabilities
of live loads in buildings is presented. This model consists of a sum of a sustained load and an intermittent load
stochastic processes. Due to the lack of national data to back up the model, parameters are taken from the Joint
Committee on Structural Safety (JCSS), based on international surveys. Using this stochastic model, sample values
for live loads are generated for buildings with different occupancy types, and statistics for the fifty-year extreme and
arbitrary point-in-time distributions of live loads are derived using Monte Carlo simulations. These values are then
compared with those of Brazilian design codes ABNT NBR 6120:2019 (Design Load for Structures), and other
major international standards. The resulting statistics are also employed in a reliability-based calibration of the
partial safety factors presented in Brazilian design codes for steel (ABNT NBR 8800:2008) and concrete (ABNT
NBR 6118:2014) structures. It is shown that, with the resulting set of optimized partial safety factors, reliability
is made more uniform over different load ratios, with a smaller variation around a chosen target reliability value,
while attaining no significant economic impact when compared with the currently employed factors.

Analytical model for dissipation of thermally induced pore pressure in marble slabs

2024-05-26T19:38:40+00:00

This paper presents a thermomechanical model of a saturated porous slab, which is suitable to the study of
rocks subjected to thermal exchanges with the surrounding environment of a building. This model involves linear
differential equations of stress equilibrium and transient pore pressure dissipation and its main purpose is to help
to the understanting of the bowing, which is an important phenomenon that occur when some porous rocks are
subject to temperature cycles. Moreover, an analytical solution for a steady state condition for pore pressure is
developed, which describes the situation where the generation of pressure due to cooling of a slab is compensated
by pressure dissipation caused by water loss (consolidation). This analytical solution should be useful to test future
numerical implementations of the thermoelasticity model presented herein.

Numerical analysis of the effect of penetration rate in piezocone tests on silty soils

2024-05-27T19:43:18+00:00

Partial drainage is a relevant effect in piezocone tests (CPTu) performed on geomaterials with
intermediate permeability, such as silts and mine tailings. However, the penetration rates that cause partial drainage
vary for each material. Thus, to investigate the effects of the cone penetration rate on different geotechnical
properties, numerical simulations of cavity expansion were performed. The Cam-Clay model was used, and the
parameters of strength (M), stiffness (κ and λ), and permeability (k) were varied for different cone penetration
rates. The material studied was silt from the Yellow River Delta (China) through the tests performed in centrifuges
by several authors. With the results of the numerical simulations, it was possible to obtain the theoretical drainage
curves of the material, which indicate the penetration velocities that trigger partial drainage. Sensitivity analysis
demonstrated the large effect of the friction coefficient on the drainage curve, the increase in soil stiffness leads to
a decrease in penetration rates and the alteration in the material permeability does not change the magnitude of the
resistance and excess pore pressure generated. The comparison with experimental centrifuge results indicated good
agreement of the numerical analysis.

Robust design of piezoelectric energy harvesters using polynomial chaos expansions and multi-objective optimization

2024-05-27T19:45:54+00:00

The generation of electrical energy from mechanical vibrations and using piezoelectric materials is an
attractive alternative due to the high density of electrical charge present in these materials. Although energy can be

harvested, the design of devices for this purpose must satisfy specific criteria, because the energy available for con-
version into electricity is low. This work suggests the robust design of beam type piezoelectric energy harvesters,

considering the presence of uncertainties in certain parameters. Thus, the study presents a finite element can-
tilever beam model and, through multiobjective optimization, designs the energy harvesting devices to maximize

the mean power and minimize the relative dispersion simultaneously. The mean and variance for the frequency

response function of the power output are estimated using polynomial chaos expansion. Results show that harvest-
ing devices with smaller length and larger masses generally lead to best nominal performance but also to higher

dispersions. Also, the dispersions can be reduced by using effective circuit resistances smaller than the nominal
values. With the increase of uncertainties in the parameters of the devices, better performances and decrease in the
response variability are achieved by using other design variables in the optimization.

The effect of geometric stiffness on vibration frequencies of bulkhead frames of pressurized aircraft fuselages

2024-05-27T19:48:55+00:00

Aircraft fuselages are structured by, among other elements, planar portal frames called bulkheads.
Among their main loads, is the internal pressurization, which causes considerable traction efforts. It is well known,
from the Matrix Structural Analysis theory, that the stiffness of frame elements is composed of two parts, the
elastic stiffness and the geometric stiffness. The latter depends on the level of axial forces acting on the members.
If in traction, it increases stiffness, and, consequently, raises the frequencies of free vibration of the structure
related to it. This effect is widely explored in so-called tensile structures, such as inflated blimps. If of compression,
it decreases the total stiffness and lowers the frequencies, leading, in the limit, to the buckling of the element. In
this work, a bulkhead portal frame of a fictitious aircraft is numerically analyzed, demonstrating that the presence
of high levels of traction that such structures support, due to internal pressurization, considerably increase their
frequencies.

Graphics Post-Processing for Thermal Analysis via CS-ASA/FA

2024-05-27T19:51:19+00:00

Structural analysis aims to determine structural behavior, and whether it meets all the design's goals,
such as adequate strength and stiffness for combinations of loading conditions within the serviceability limit and
ultimate limit states. Stresses, deformations, and displacements are examples of response that act according to the
boundary conditions imposed on the structure. The process of this analysis has three basic steps: create the model,
the calculation, and analysis of the results. To facilitate this process, a a numerical method software was used for
preprocessing, processing, and post-processing, providing a more realistic and efficient analysis. In this context,
the aim of this article is to present the development of a post-processing for the module CS-ASA/FA. This module
performs a thermal analysis in a transient regime of common cross-sections in civil construction, which are
fundamental for the analysis in a fire situation. A graphics post-processing gives the analyst a major reduction in
the required effort to visualize the results, facilitating the interpretation of the data generated by the analysis
program. It developed the post-processing graphics using an interactive environment denominated GiD, and its
implementation in CS-ASA/FA creates a new result file to attend the GiD’s demands for input files and satisfactory
graphic presentation.

Pore network evaluation of the hydrophysical properties of carbonate rocks (coquinas)

2024-05-27T19:54:46+00:00

Carbonate rocks often show nontrivial flow behavior because of their multimodal pore structure. The
pore size distribution and pore space topology, the latter describing also how pores are interconnected, can provide
much information about the hydraulic behavior of these rocks. Pore Network Modeling (PNM) is an effective
method for evaluating petrophysical parameters, including especially the permeability. Pore networks can be
generated directly from microCT images to obtain such information as the pore-size distribution, the pore body
and pore throat radii distributions, and relevant coordination numbers. The purpose of this paper is to combine
microCT, nuclear magnetic resonance (NMR) and mercury intrusion (MICP) techniques to obtain information
about petrophysical properties that are not easily measured directly. We were especially interested in comparing
microCT, NMR and MICP results, assessing the multi-porosity nature of the coquinas, correlating the permeability
with porosity, and obtaining capillary pressure–fluid saturation (Pc-S) relationships. Results were to provide
important information about the generally highly heterogeneous nature of carbonate rocks, with as ultimate goal
to improve petroleum recovery from oil-bearing carbonate reservoirs. For our study we used four coquina samples
from the Morro do Chaves Formation, considered a close analogue of Brazilian Pre-Salt facies. The samples were
subjected to routine core analysis, NMR, MICP and microCT scans. The samples had very similar porosities
(between 10 and 16%), but different absolute permeabilities (between 5 and 245 mD). Results indicated good
correlations, especially between the NMR and microCT data. We further used the mercury intrusion results to
obtain estimates of the Pc–S curves. As an example, sample 136.85 showed excellent cross-correlation between
the NMR and MICP data, and a well-defined curve of the MICP-derived Pc–S functions for air-water. Plots of the
mercury intrusion data and the fitted van Genuchten hydraulic functions indicated a double porosity pore structure.

Graphic Preprocessor for Thermal Analysis via CS-ASA/FA

2024-05-27T20:01:27+00:00

The structural analysis aims to determine the structure behavior and if it meets all the design's goals as
adequate strength and stiffness for combinations of loading conditions in the ultimate limit states and service.
Stresses, deformations, and displacements are examples of response that act according to the boundary conditions
imposed on the structure. The process of this analysis has three basic steps: create the model, the calculation, and
the analysis of the results. To facilitate this process, a software with preprocessing, processing, and post processing
uses a numerical method for more realistic and efficient analysis. This work presented the development of a
preprocessor for the computational module CS-ASA/FA. This module realizes a thermal analysis in a transient
regime of common cross-sections in civil construction, which are fundamental for the fire analysis. The basic idea
is to produce an intuitive environment, easier and efficient for modeling and releasing a numerical thermal analysis.
Thus, for the elaboration of the preprocessor, used the graphical interactive environment, GiD. Performed
implementation and modifications in GiD’s problem type configuration satisfactorily to attend the demands of
input data files for the CS-ASA/FA program.

Numerical analysis of floating structures using a fluid-structure interaction model for free surface flows and anchored bodies

2024-05-27T20:45:48+00:00

The present work is dedicated to the numerical simulation of Fluid-Structure Interaction (FSI)
problems involving floating bodies subjected to the action of free-surface flows, where the structure may or may
not be anchored through mooring cables. The numerical model proposed here may be utilized in several practical
applications, such as: ships hydro-aerodynamics, stability of oil extraction platforms, efficiency of wave energy
converters, stability of floating bridges, floating houses and buildings. In the present model, the fluid equations
are discretized using the Characteristic-Based Split (CBS) method in the context of the Finite Element Method
(FEM). For the treatment of multiphase free-surface flows, the Level Set Method is used, where the fluid is
considered as a biphasic medium. The structure is kinematically described using a rigid body approach and the
mooring cable is modeled using an elastic material with geometric nonlinearity and the Nodal Position Finite
Element Method (NPFEM). The system of equations of motion is discretized in time using the implicit
Newmark and α-Generalized methods. Problems involving floating bodies with and without anchoring are
simulated to demonstrate the applicability and accuracy of the proposed numerical model.

Reliability of built-up cold-formed steel columns designed by the direct strength method

2024-05-27T20:50:54+00:00

Built-up cold-formed steel (CFS) columns are composed of two or more sections that are joined together
with welds, bolts or screws. The use of built-up sections may be an option at certain locations in a CFS-framed
building when higher axial capacity or local frame rigidity is required. This paper presents a study of the reliability
of built-up cold-formed steel columns. Reliability indexes are evaluated by First Order Reliability Method (FORM
method) for usual nominal live-to-dead load ratios. The reliability analysis used to assess the safety level of design
specifications included the model error and other random variables such as strength parameters, geometric
parameters, dead and live loads. For the statistical study of the model error variable, column test results obtained
from literature were compared to the resistant capacities obtained by the direct strength method (DSM). A total of
266 column tests were selected in order to ensure representativeness of the buckling modes and section types. A
lack of uniformity of reliability indices was observed in the analyzes organized by instability mode or by section
type. It was found that the all-data case leads to unsatisfactory results, with the reliability index lower than the
target value.

Linear and non-linear analysis of space trusses subjected to wind actions and temperature variation

2024-05-27T20:53:23+00:00

The structural analysis seeks to determine the behavior of a structure when subjected to external actions
and makes it possible to obtain its responses in terms of stresses, strains, or displacements, for example. Most
engineering structures present a linear elastic behavior, however, some complex structures, such as arches and tall
buildings, may present a non-linear behavior, requiring tools that allow considering such effects to obtain more
realistic results. In this context, the present work proposes a comparative analysis between linear and non-linear
responses in space trusses through a computer program developed in Fortran language. The structure studied is a
metallic lattice dome subject to self-weight loading, wind action, and temperature variation, considering the
technical specifications of the ABNT NBR 6120:2019 and ABNT NBR 6123:1988. To describe the behavior of
the structure it was used the finite element formulation for bar element and the geometric nonlinearity due to
normal forces. The results showed that the internal forces on the bars can vary up to 850% between the analyzed
cases.

Nonlinear Dynamic Analysis of Composite Laminate Plates Subjected to Explosive Loading

2024-05-27T20:58:21+00:00

Explosive loads have been the target of study in recent years due to the catastrophic effects that this
type of loading can cause in civil engineering structures. This phenomenon is characterized by the release of energy
in short time intervals, causing a peak of overpressure and, in sequence, a suction process, or overpressure. Due to
the high impact, this episode can generate catastrophic effects on structures, such as partial or total collapse, and
in severe cases, several deaths. At the same time, laminated plates are structural elements that are being studied
for their characteristic of improving the physical properties of the primary materials used in their composition.
Thus, this work aims to present a study on laminated plates, present in literature, subjected to blast loads to
reproduce the results. In the sequence, an evaluation of their behavior when the negative phase is not considered
is verified, to understand how this portion of the loading influences the final behavior of the structure. Finally, a
parametric study of the laminated plates is performed to determine, for each structure, equations of correlation
between the maximum displacement obtained by the structure and characteristic parameters of the shock wave. In
the calculation process, for each example present in the literature, a plate theory is used, considering second-order
effects. The differential equations are obtained according to the Total Minimum Potential Energy, in their solution,
the Galerkin method is employed, and, finally, to obtain the displacements the Runge-Kutta numerical method is
used.

Topology Optimization of Periodic Materials employing the Finite- Volume Theory

2024-05-27T21:00:33+00:00

This paper presents a computational tool for designing composite materials with periodic
microstructures for optimal effective elastic properties. The effective elastic properties of the periodic porous
material are evaluated through a combination of the homogenization method and finite-volume theory analysis.
The finite-volume theory results are employed in the topology optimization procedure, combining this technique
with the dual optimization algorithm of convex programming. In this approach, to find the optimal microstructural
topology for the periodic unit cell, specific linear combinations of the components of the effective elastic tensor
are considered to obtain extreme elastic properties, such as the maximum shear or bulk modulus under a prescribed
volume constraint. Some numerical examples involving materials with periodic porous microstructures are
analyzed, and the results demonstrate the finite-volume theory formulation’s performance for the optimal design
of composite porous materials.

Infering the passenger’s trip purpose in the Smart card data using data mining techniques, an case study of the Belo Horizonte Brazilian city

2024-05-27T21:03:12+00:00

Planning a quality public transport system starts with collecting data about passenger demand. Tradi-
tional data collection forms are expensive and do not precisely represent the travel demand. On the other hand,

secondary data collected passively, for long and continuous periods, and at low cost is emerging as a new oppor-
tunity, such as Smart-cards data. However, these data are also limited and miss important information, such as

trip purpose. Knowing the trip purpose of public transport passengers is essential to ensure integrated planning
between transport and land use and to guarantee higher quality of the public transport service and attract more
users, thus contributing to the mitigation of excessive use of the car and its impacts. In this context, the process
of Knowledge Discovered in Databases can be used to extract knowledge from these secondary data, improving
their applicability in travel demand models. Under this perspective, this study contributes to the enrichment of
Smart cards data from the public transportation system of the Metropolitan Region of Belo Horizonte by infering
the passengers’ trip purposes using data mining techniques.

Analysis of reinforced concrete beams with opening using incompatible mode elements and strut-and-ties model

2024-05-28T11:54:22+00:00

The need to reduce the execution time has led to the negligence in the process of compatibility project.
One of the consequences is the need to drill holes in beams for the passage of ducts and piping. This practice
occurs without criteria for analysis and structural design. Openings in beams performed without an accurate
analysis result in reduced strength considered in the design, instability and compromised safety. In the regions of
openings, usually called “Regions D”, the Bernoulli hypothesis becomes invalid and, therefore, the strut-and-ties
model associated with the finite element method has been used. This work proposes to analyze the distribution of
stresses in beams with opening using classical finite elements and enhanced with incompatible modes. Precise
results of internal efforts allow an adequate arrangement of reinforcements and fulfillment of safety in the ultimate
and service limit states. In order to validate the performance of the elements implemented for the analysis of
structures with discontinuities, the results obtained are compared with those found in the literature and calculated
using a commercial package. The results obtained attest to the quality of the implemented formulation.

Development of a modular analyzer using low-cost microcontrollers

2024-05-28T11:57:02+00:00

In the industrial sector, the monitoring and evaluation of machinery in continuous operation has vital
importance, principally considering the high competition and the pursuit of high-quality products without
increasing the cost of manufacture. Although, the lack of appropriate maintenance increases the possibility of
problems such as undesirable vibrations, which cause a lack of performance, several flaws in primary and
secondary systems, and unexpected downtime on their applications, increasing the manufacturing cost.
Predictive maintenance is applied to anticipate and identify these issues before that lead to the unplanned
downtime of the equipment. To apply this kind of maintenance, some analyzers are used to keep updated the
condition of the machinery, with information such as vibrations amplitudes, temperatures, and rotation velocities.
However, analyzers have a high initial cost, this does not mean a huge problem for large industries, but for small
and medium-sized ones, especially for those that go through periods of economic instability, it can be an
investment out of reality.
Taking advantage of the current expansion of low-cost microcontrollers and sensors, the objective of this paper is
to apply these programmable open-source to develop a modular data acquisition device, initially focusing to
acquire vibration and rotation speed signals with low-cost sensors. The raspberry pi 3b+ was used for that
application, and an algorithm was developed to collect and process data captured by compatible sensors, and
then applied to an experimental test bench.

Analysis of temperature treatments and manufacture methods of superelastic niti bending springs with complex-shape

2024-05-28T11:59:19+00:00

The application of smart materials in mechanical systems has been increasing, due to these materials
presenting a capacity to reduce undesirable vibrations with a small increase of mass in the system. The most
applied material is the Shape Memory Alloys (SMA), which change their characteristics with variations in
temperature or mechanical stress. SMAs have two effects: shape memory effect (SME); which changes its phase
with temperature variation, and superelasticity (SE); which modifies its phase with the change in mechanical stress.
For the SMA-SE, properties such as damping capacity and complex stiffness are relevant for application in systems
with undesirable vibrations, principally considering some external parameters such as temperature, frequency, and
amplitude can change the properties of the material. However, if the SMA-SE device has a complex shape, more
procedures are needed to achieve it. Thus, complex-shaped devices tend to be more liable to changes in the starting
properties of the material during the process of obtaining the sought shape, due to the forming process. Therefore,
focusing on obtaining balanced properties, such as damping capacity, complex stiffness, and transformation
temperatures on the SMA-SE devices, several parameters should be considered during the manufacturing, such as
time and temperature of the treatment, cooling speed, and the method of material forming. This paper aims to
evaluate types of heat treatments, application of mechanical forming, and different types of cooling applied in the
manufacture of superelastic NiTi bending springs with complex-shape, to obtain balanced properties for
application in the rotating system to intend to reduce vibration in a passive form.

Dynamic Analysis of an Aluminum Spur Gear pair

2024-05-28T12:01:35+00:00

Dynamical systems are those that show evolution with respect to time and are generally described by
ordinary differential equations with their respective initial conditions. However, the equations of motion obtained
are often difficult to solve analytically, which makes it necessary to use one of the methods of computational
numerical simulation. This work presents the dynamic modeling of a spur gears pair, considering the torque input
of an electric motor. The system is modeled analytically using Newton-Euler equations of motion resulting in a
system of equations with four degrees of freedom. The mathematical model results in an ordinary second-order
differential equation and is solved using the fourth and fifth order Runge Kutta methods, implemented in MATLAB
software; the parameters inertia, damping and gear stiffness are considered. Dynamic system simulations are
performed to observe the dynamic behavior in different scenarios. The results clearly show the differences obtained
between the transient and steady regimes and the short period of disturbance of the system.

Steel shuttering optimum geometry in construction stage for steel- concrete composite slabs

2024-05-28T12:05:21+00:00

The use of profiled steel sheeting in steel-concrete composite slabs stands out for its economic and
environmental advantages, since they are easy to install, fast in construction and reduce material waste. However,
this system is still little used in Brazil and one of the reasons may be associated with the restricted supply of steel
formwork geometries available in the national market. Therefore, this article determines the optimal structural
solution for steel shuttering geometry of composite slabs focused on the construction phase, considering the
minimization of steel consumption in the manufacturing process. The steel formwork design was performed by
applying the Effective Width Method (EWM), which is a traditional and analytical method present in several
optimization studies of cold formed steel structures. Finally, the optimization process was performed by Particle
Swarm Optimization (PSO) in the software MATLAB®. In addition, four different commercial geometries will
be analyzed at this stage in order to contribute to the development of new market models of shapes. The solution
reduced steel consumption by 34.65% on average for formwork with intermediate stiffeners and 26.16% for
sections without stiffeners.

Reinforcements in Structural Masonry Prisms: A Numerical Study of Static and Dynamic Characteristics

2024-05-28T12:08:39+00:00

Structural masonry is one of the oldest structural systems explored and currently has great relevance
due to its economic competitiveness. Still, the need for structural reinforcement in this system is ever more
common, either by restoring older structures or by changes in the behavior of static and dynamic loads on the
systems. Thus, it becomes more necessary to know the dynamic characteristics of structural masonry walls,
including those with structural reinforcements. This need occurs because of the wall’s slenderness and also since
these structures are subject to dynamic loads such as those caused by winds and earthquakes - which may be
unforeseen additional loads due to recent changes in their territorial scope. Thus, this paper observes three different
numerical models referring to concrete structural masonry prisms. The first type of prism was an Unreinforced
Masonry (URM), the second was a Reinforced Masonry (RM) with a steel bar and grout, and the third type is
reinforced by Fiber Reinforced Cementitious Matrix (FRCM). Therefore, the responses of the numerical models
of the prisms to static loads were observed, using a load prediction for the models, in addition to an analysis of the
vibration modes and the respective excitation frequencies.

A refined plastic-hinge-based formulation for advanced analysis of CFST columns: a co-rotational proposition

2024-05-28T12:12:19+00:00

The present work aims to propose a lumped plasticity-based numerical formulation for the non-linear
analysis of concrete-filled steel tubular (CFST) columns. The study is divided into two main parts: cross-sectional
analysis and global structural analysis. The local analysis is made by means of the strain compatibility method.

Thus, the moment-curvature relationship is evaluated by an incremental-iterative process. Through of this method-
ology, the limits of uncracked, cracked, elastic, inelastic and bearing capacity are determined for various axial

efforts. Thus, the NM diagram is calculated with three curves and five regimes to describe the cross-section flex-
ural stiffness. For the precise evaluation of this numerical procedure, the materials constitutive relationships are

explicitly considered. For the global analysis, the co-rotational-based approach is used to describe the finite ele-
ment formulation allowing large displacements and rotations in the numerical model. This approach is coupled to

rotational pseudo-springs at the ends of the finite element, where the gradual loss of stiffness was determined by
combining the normal force and bending moment (NM) in the cross-section. The numerical results were compared
with experimental results [15]. In average, the results found present an error of 0.1% in relation to the data obtained
in the laboratory, demonstrating the accuracy of the proposed numerical formulation.

Optimization of metallic truss using genetic algorithms via CS-ASA/MATLAB® softwares coupling

2024-05-28T12:16:03+00:00

Optimization consists of finding the best solution for a given objective, under given constraints. In
Engineering, the application of optimization algorithms has greatly developed in the last decades, but it faces
fundamental difficulties connected to the complexity of the mathematical models to be solved. In this last context,
optimizing structures tries to achieve a reduction of the structural cost, under the restriction of not compromising
efficiency and safety. This work aims to apply a heuristic optimization method — genetic algorithms (GA) — for
the determination of optimal aluminium truss structures, considering design constraints associated with minimum
areas and the maximum allowable stress. In this way, a computational routine is implemented in the MATLAB®
program, using the GA with the advanced structural analysis program, based on the Finite Element Method, named
CS-ASA (Computational System for Advanced Structural Analysis). MATLAB® manages all stages of the process,
from the internal call of the CS-ASA to carry out the structural analysis, to the application of the optimization
function, with the evaluation of the objective function and design constraints. Besides the analyses and comparison
with literature, it is shown how numerical strategies to make the process less computationally expensive influence
the total processing time.

Wave propagation analyses considering a truly-explicit time-marching formulation

2024-05-28T12:19:30+00:00

This work discusses a truly-explicit time-marching formulation to analyse wave propagation models,
which is based on locally-defined adaptive time-integrators and time-step values. The discussed technique

considers single-step displacement/velocity recurrence relations, providing an easy to implement, truly self-
starting methodology. The stability limit of the discussed approach may become larger than that of the central

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

Numerical simulation of fluid-structure-soil interaction on the CAARC standard tall building

2024-05-28T12:22:19+00:00

In the present work, the effects of the wind action over a tall building are evaluated considering the
influence of soil-foundation interaction. The numerical model is developed in this work from a partitional coupling
scheme, in which the physical media involved are solved sequentially, and may present independent discretization
and solution methods. The Finite Element Method (FEM) is adopted for the spatial discretization of all physical
media, where linear hexahedral elements with underintegration techniques are used. Load transfer between soil
and structure is performed by a three-dimensional contact algorithm based on the penalty method and infinite
elements are employed at the boundaries of the soil computational domain to avoid the reflection of waves to the
region of interest. Due to the high computational demand, a hybrid parallelization model based on CUDA-OpenMP
techniques is employed to accelerate the processing time associated with the present simulations. Numerical results
obtained from aerodynamic and aeroelastic analyses are compared with numerical and wind tunnel measurements

reported by other authors. It was observed that the building response to the wind action was influenced by the soil-
foundation interaction, where a good agreement was obtained with respect to the reference results.

Three-Dimensional Phase-Field FEM Modelling for Fracture

2024-05-28T12:24:56+00:00

The study of crack growth is very important in Structural Engineering to prevent catastrophic collapses.
This task becomes easier through developing software to model and to study the crack propagation, the crack path
and the prediction of where these pathologies will emerge in a solid. A promising approach, which lately has been
largely used, is the Phase-Field modelling, that transforms the sharp crack of Griffith’s criterion into a smoothed
crack that spreads on a certain region of the domain. Our research group, located in the Structural Engineering
Department (DEES) of the Federal University of Minas Gerais (UFMG), has been studying the Phase-Field
modelling since 2019. The computational implementations have been done in INSANE (INteractive Structural
ANalysis Environment), an object-oriented software developed by DEES. The two-dimensional modelling of
Phase-Field was previously implemented by Leão [1] in which has been proven the benefits of that approach in
the study of crack propagation. This paper presents the expansion of Phase-Field FEM models for the 3D version,
where it is possible to evaluate the cracks in solids. Preliminary results using 3D modelling are compared with
those published in the literature.

Comparative analysis of composite slab steel formwork design by Direct Strength and Effective Width Methods

2024-05-28T12:27:59+00:00

Among the different methods used to analyze the behavior of a cold-formed profile section subjected to
bending moment, the Direct Strength Method (DSM) and the Effective Width Method (EWM) have become
popular in the design of these structures. Although recently both methods have been approached in the area of
optimization for different geometries and applications and, also, in the comparison with experimental results, there
is a lack of studies that contemplate the design of composite slab formwork considering the construction phase in
which the resistant section is that of profiled steel sheet. Thus, this article aims to compare the Direct Strength and
Effective Width methods when used to dimension steel formwork sections for composite slabs. In the application
of the DSM, to obtain the critical moments through the analysis of elastic stability, the computational program
CUFSM was used, whose methodology used is the finite strip method (FSM). The design process was carried out
on the MATLAB® computational platform and the analysis started from 4 different geometries, produced for
commercialization in the Brazilian market. EWM has proven to be a more conservative approach for geometries
with stiffeners and DSM for geometries without stiffeners.

Settlement analysis of an oil storage tank considering inclined subsoil layers

2024-05-28T12:30:47+00:00

Oil storage tanks are usually designed and built in coastal regions where the subsoil is characterized by
stratigraphic intercalations of fine sands, silts, soft clays and marine sediments. The loading applied by thank is
generally of small magnitude, but the occurrence of differential settlements, due to compression of the soil, may
seriously damage the main tank components, including pipes and connections for oil supply. The main objective
of this study is a numerical evaluation of a tank foundation with respect to slightly inclined subsoil layers,
comparing the results with measured data from field hydro tests. The consideration of slope variation in the subsoil
layers has a direct influence on the settlement, especially with respect to the clay layers. This study also highlights
the importance of several factors that affect the foundation behavior and may be helpful for engineers to make
appropriate decisions from a technical and economical point of views.

Semi-empirical equation for determination of stress concentration factors (SCF) in tubular joints of fixed offshore platforms subjected to axial forces

2024-05-28T12:33:56+00:00

Considering the importance of studying fatigue failure in offshore structures, the stress concentration
factor (SCF) is one of the most relevant parameters for its evaluation, obtained through equations that vary
according to the geometry of the tubular joint; the type of joint in question; and the load to which it is subjected.
Even though numerical research on KT-type tubular joints is widely discussed in the literature, this article applies
the symbolic regression method in order to evaluate and discuss existing equations. Through a parametric study in
finite elements, using the ANSYS software, with a variation of KT joints subjected to an axial load, it is possible
to obtain the SCFs, using a specific point for analysis. Thus, through the use of dimensionless geometric
parameters, the parametric equations for the SCFs are obtained, using the symbolic regression method. Based on
these equations, it will be possible to make a comparison with existing equations and verify the possibility of
improving the values of SCFs.

Experimental and Numerical Investigation of Buckling of Structural Insulated Panel under In-Plane Loading

2024-05-28T12:36:10+00:00

Structural insulated panels (SIP) are booming in the construction industry as an alternative to traditional
materials. These panels considerably improve construction times compared to conventional wet systems. Its
implementation in varied designs results in versatile structures with more comfortable and cooler interior
environments, which translates into significant energy savings for its inhabitants. These panels are a composite
material. They are typically comprised of two outer layers and a core layer. The outer layers are formed by wooden
flakes mixed with a phenolic and polyurethane adhesive pressed at high temperature and pressure. The core middle
layer is formed by high-density expanded polystyrene and bonded to the outer layers by high-strength adhesives.
Various mechanical tests are usually carried out on isolated panel modules in order to ensure their good structural
behavior. This study reports the results of one of them, and it is focused on analyzing the structural behavior of an
isolated module subjected to in-plane compression. The research is based on experimental measurements carried
out on a panel to determine its maximum loading capacity and deformation. A numerical analysis is implemented
by modeling the panel with a multipurpose finite element code. Linear buckling analysis (LBA) and geometric
nonlinear analysis (GNLA) allowed the evaluation of buckling loads and nonlinear behavior. Modeling results are
compared to the experimental results in order to validate the features and behavior of the model so it can be used
in future analyses involving three-dimensional configurations created from the combination of multiple panels

Influence of geometry on the strength of shear keys based on numerical analysis

2024-05-28T12:39:52+00:00

Shear keys are present in several precast elements, such as foundation sockets and beam-column
connections. In the literature, several analytical formulations are observed to predict its resistance. However, the
formulations do not consider the entire geometry of the shear keys. In this paper, numerical models in finite
elements were used with the software ABAQUS® to calibrate the shear keys tested by Zhou et al. (2005) and
Faleiros Júnior (2018). The influence of the key geometry and the concrete strength was evaluated through a
parametric analysis and compared with the analytical formulations. The results showed which geometric
parameters have more influence on the strength of the keys. Furthermore, the results indicated that analytical
formulations are inappropriate for some geometries.

Structural reliability of strengthened reinforced concrete beams: comparative study of different design methods

2024-05-28T12:43:39+00:00

There are some methods in the literature for the design of concrete jackets for beams and they differ in
the way they represent the structural behavior of the beam cross-section. As a consequence, it is possible to obtain
different results for a flexure strengthened beam. This scenario raises doubts about what are the consequences of
adopting different hypotheses. In the present study, two methods from the literature for strengthening design with
jackets were compared. The first considers a monolithicy factor that reduces the beam resistance, while the second
considers the compression steel contribution to resistance. The strengthened sections were analyzed using the First
Order Reliability Method. Information about the random variables limit state functions involved were obtained
from the literature. Ten experimental strengthened beams available in the literature were selected to apply the
design methods and to perform the reliability analysis. The strengthening design and reliability analysis routines
were implemented in the Matlab environment. The results indicate that the first method, the one that considers a
monolithicy factor, results in a larger steel reinforcement area for the strengthening. Also, the reliability analyses
shows that the different parameters considered in each design method have a significant impact in the reliability
index.

Numerical evaluation of the strength of graphene-reinforced metal matrix composites

2024-05-28T12:45:47+00:00

This work evaluates the overall strength of graphene-reinforced metal matrix composites employing a
computational homogenization procedure. The simulations are carried out using the finite element method and
are based on unit cells representing an aggregate composed of a metallic matrix, obeying the von Mises criterion,
which is reinforced with high strength and stiff plane inclusions mimicking graphene. Uniaxial displacement
boundary conditions are imposed. The macroscopic stress components are calculated from the reaction force
obtained from the simulations and assumed to be the mean stress component in that direction after reaching an
asymptotic response. The study considers different volume fractions and orientations of the reinforcement, thus
addressing the effects of such material features on the macroscopic yield behavior.

SHALLOW WATER EQUATION MODEL AND DISSOLVED OXYGEN TRANSPORT IN A BUBBLING AERATION SYSTEM IN THE BAY OF ASUNCION ́

2024-05-28T12:49:52+00:00

The presence of oxygen in natural water bodies is essential for the organisms responsible for photo-
synthesis, oxidation-reduction and the decomposition of organic matter. Thus, it is important to study and analyze

the distribution and concentration of dissolved oxygen (DO). This work presents a model for DO transport in a
bubbling aeration system in the Bay of Asuncion for surface water treatment. The mathematical model considers ́
DO advection-diffusion-reaction equation, as well as wind shear and bottom drag for water flow, in 2D Shallow

Water equations (SWE). The kinetic model of oxygen absorption is obtained from a prototype of bubble aera-
tion system for several air-flows. The equations are solved using OpenFOAM® software, and simulations of the

bay of Asuncion are performed with mesh independence tests. The results obtained without the aeration system ́
are compared with field measurements of DO concentrations. Finally, the effects of the aeration system on the
improvement of water conditions in the bay of Asuncion are analyzed and presented ́

Evaluation of Methods for Optimizing Structural Design Parameters in Oil Wells

2024-05-28T12:53:42+00:00

Present work focuses on the optimization of the conductor casing length and sensitivity analysis of the
cement top of surface casings ensuring that global structural design criteria are met. These criteria include: 1)
bearing capacity of the conductor casing, 2) displacement of the wellhead system, and 3) surface casing triaxial
factor of safety. The implementation uses several optimization techniques to evaluate the performance and
accuracy of the parameters while minimizing the criteria. Assessment of the mechanical behavior of the soil-well
coupling is done using finite element software and it serves as a data source for the optimization techniques. The
implemented software is treated as a “black box” and global criteria are evaluated based on the simulation results.
The finite element software is used by an oil company, which also gave specific data about well design as case
studies. The case studies are used to evaluate which optimization method provided the best results and processing
time for each case. This kind of study on optimization techniques aims to support the decision-making process on
well casing design to evaluate the integrity of structural casings. Previous results show consistent accuracy among
casing length and cement column parameters for the employed methods.

Formulation for the local contact problem between smooth convex NURBS particles

2024-05-28T12:59:15+00:00

The paper presents a formulation for the local contact problem between smooth convex particles whose
boundaries are defined by a set of non-uniform rational B-splines surfaces. By assuming a master-to-master
approach for the contact and an optimization scheme, the maximum penetration between particles is a minimum
of an objective function that gives a constrained distance between surfaces. This objective function is defined with
the aid of the Minkowski sum, configuration space obstacle and support mapping, which are concepts usually
employed on computer graphics. A numerical example shows the good behavior of the method in handling contact
between generic particle shapes. Comments on the numerical problems that can arise when generating particle
boundaries with multiple patches are also presented.

Efficient Optimization of Engineering Problems using Multi-Fidelity Models

2024-05-28T13:02:05+00:00

Optimization methods can be employed to find the optimum design of engineering structures. Due
to their ease of implementation and robustness, bio-inspired optimization algorithms have been widely applied
to solve complex optimization problems. However, these methods require a large number of expensive function
evaluations. For a more efficient process, surrogate models can be used to provide a cheaper estimate of the
structural responses. These models are built from a small set of true responses, and their approximated surface
assists in the selection of promising trial designs. Efficient Optimization can be performed by iterately improving
the model by the addition of new points in regions of interest, thus improving the accuracy of the model near
the optimum location. In this work, we study the use of Multi-Fidelity models for the Efficient Optimization of
engineering problems. Kriging and Hierarchical Kriging models are employed, and the selection of new points is
performed using variations of the Expected Improvement and Probability of Improvement criteria. The obtained
results are compared in terms of accuracy, the number of evaluations, and computational efficiency. Results show
that Multi-Fidelity approaches are able to find optimal results using fewer high-fidelity evaluations.

Agrophotovoltaic system in Alagoas – Design contribution and performance analysis of support structures for photovoltaic solar panels

2024-05-28T13:23:24+00:00

Agrophotovoltaic (APV) systems are widely used nowadays. They are shown as a sustainable strategy
transition to renewable energies and are a "dual-farming" technique combining photovoltaic and crop cultivation.
The sugarcane energy sector is the main economic activity in Alagoas. The electrical transmission structure and
the available cultivated area offer optimal symbiotic conditions for implementing these systems. This work
proposes a structure to support the photovoltaic solar panels and their loads as well as the flexibility to adjust the
angle of the panels and modify the distance between the individual structures. The estimates of the structural loads
were carried out through the combinations of the predicted actions, such as the weight of photovoltaic solar panels
and structural elements and the action of the wind, considering the most unfavorable situation in the structure
sizing. Structural analysis and design were carried out considering the Service Limit State (SLS) and the Ultimate
Limit State (ULS) through the structural analysis based on the finite element method, SAP2000, considering the
Brazilian standards. All results are within limits established in the Brazilian National Standards Organization,
Associação Brasileira de Normas Técnicas (ABNT) in Portuguese.

Numerical modeling of dynamic behavior in a bi-axial hollow slab

2024-05-28T13:25:31+00:00

Bi-axial hollow slab is a technology that reduces the amount of concrete by replacing it with plastic
spheres with voids on their inside in areas where it does not perform substantial structural function. This technique
leads to material economy and self-weight saving, without considerable inertial loss. As a result, this method
is increasingly becoming more present in the matrix of Brazilian construction methods, due to its efficiency in
technical, economic and environmental aspects. One of the main loads that a structure is subjected to is dynamic
excitation caused by human interaction, such as walking, jumping and running, which are characterized by being
periodic and low frequency. With that, the spread of this technology depends on a reliable numerical modeling
that describes these behaviors, so that structural designers can have confidence in their work. As a relatively new
technology in Brazil’s business, the lack of commercial software that has computational models of cross sections
with spherical voids makes it difficult to popularize this constructive method. In this context, this work aims to
develop a mathematical model that describes the structural dynamic behavior of the hollow slab. To that end, four
finite element models were created, and their dynamic properties of vibration modes and natural frequencies were
compared to an experimentally tested hollow slab specimen. The models I, II, III and IV were elaborated with
frame, shell-thin, shell-layered and solid element, respectively. The results presented in this paper show that the
vibration modes were similar, but with different values of natural frequencies compared with the specimen. The
lowest variation was obtained by the model IV, with a 0,60% difference for a 6,7 Hz frequency relative to the
first mode of the experimental hollow slab. Models I, II and III varied by 8,92%, 1,34% and 43%, respectively.
Therefore, it can be concluded that, among the numerical models analyzed in this work, the one that best describes
the modal behavior of a bi-axial hollow slab it’s the model IV, with finite shell-layered elements, although model
II presents good precision too. This opens up a possibility for reliable modeling of the dynamic behavior of this
type of slab.

Topology Optimization of Plane Trusses Employing the Progressive Directional Selection Method.

2024-05-28T13:28:47+00:00

More and more, inspiration is sought from nature to solve complex problems in modern society.
Whether observing the morphological characteristics of animals and plants or even the behavior of living beings
in the environment they live. The naturalist Charles Darwin studied this behavior in depth and proposed a theory
that explains how life became what it is today, the Theory of Natural Selection. The theory of natural selection of
the directional type inspires the topological optimization method proposed in this work. The Progressive
Directional Selection (PDS) method seeks to optimize a structure by selecting the parts that contribute the most to
support the mechanical loads and eliminating the parts that contribute the least in different stages of removal.
Numerical applications of PDS were performed in two-dimensional truss structures, starting from a ground
structure. The matrix analysis of plane trusses and the direct stiffness method are employed to analyze the plane
truss in the linear regime. The obtained optimal topologies are structurally stable and efficient and very similar to
the results of other topological optimization techniques presented in the literature. The results demonstrate that
this method can be employed for the topological optimization of two-dimensional trusses.

Modeling and Analysis of Fractures in Concrete Beams Using DBEM and the BEMCracker2D Program

2024-05-28T13:31:57+00:00

In its remarkable progress, Fracture Mechanics, equipped with Computational Mechanics, explained
the huge lack of structural norms in the face of structural failures conceived in fragile materials, still allocated
under stresses below the design limit stress. Generally, such failures result from events ranging from structural
weaknesses to the occurrence of failure by the brittle fracture mechanism. In this context, this work is equipped
with concepts related to Fracture Mechanics, in particular, to Linear Elastic Fracture Mechanics, LEFM, to
Boundary Element Method, BEM, and to Double Boundary Element Method, DBEM, and seeks to implement and
attest the BEMCRACKER2D software as an effective tool to predict the propagation of multiple critical shear
cracks in simple concrete elements, with the consent of discontinuities along their interfaces. As a methodology
for this finding, at first, the necessary adjustments will be made in the BEMLAB2D graphical interface so that it
is possible to model cracks with several segments. Subsequently, simulations of propagation of shear cracks in
plain concrete will be carried out, in which their results will be used to evaluate their respective Stress Intensity
Factors in light of Integral J, as well as the direction and propagation path obtained through software, in the
application of the Maximum Circumferential Stress criterion, MCS, and fatigue crack propagation, resulting in the
comparison with other works already consolidated in the application of predictive analysis of similar cases.

Phase-field model for pressurized fractures simulation

2024-05-28T13:34:15+00:00

The present work investigates the numerical simulation of pressurized fracture, using the phase-field
strategy, and its implementation. A simplified approach to hydraulic fracture with phase-field already available in
the literature, is implemented in the open-source software INSANE (INteractive Structural ANalysis Environment)
developed at the Structural Engineering Department of the Federal University of Minas Gerais, taking advantage of
its object-oriented structure. Within this simplified model, inertial and leak-off effects are neglected, the reservoir
is considered impermeable and the fluid incompressible, leading to a fracture system where the fluid pressure
is constant. The pressure load is applied directly on the fracture surface influencing its behavior. Numerical
simulations performed with the finite element method are presented, aiming to illustrate the model as well as to
evaluate the initial results found with regard to the behavior of the crack subjected to pressure load.

Artificial Neural Networks applied to assess the impact of PM2.5 on hospital admissions for cardiovascular diseases

2024-05-28T13:36:40+00:00

The high emission of atmospheric pollutants in large urban centers causes several harms to population
health. Thus, it is necessary to evaluate the negative impact of its concentration to assist in decision-making and
public policies by government agents. Several modeling techniques have been used to assess the effects of air
pollution on human health. However, due to their greater flexibility in analyzing the complex nonlinearity of
environmental data, Artificial Neural Networks (ANN) have been shown to be the most attractive approach for
solving such data modeling problems. This work aimed to compare the performance of two artificial neural
networks, Multilayer Perceptron (MLP) and Extreme Learning Machine (ELM) in estimating the number of
hospital admissions for cardiovascular diseases due to the concentration of fine particulate matter (PM2.5) in
Joinville, Brazil. Daily PM2.5 concentration and meteorological variables were considered as input variables. MLP
network was able to achieve better performance to estimate hospital attendance because of these environmental
conditions after three days of PM2.5 exposure. The results demonstrate that ANN can be used to predict hospital
admissions due to air pollution levels or adverse meteorological conditions and therefore, be used to guide
government public policies on air quality and health risk assessment.

Approximating the operator of the wave equation using deep learning

2024-05-28T13:42:02+00:00

Deep operator networks (DeepONets) have demonstrated the capability of approximating nonlinear
operators for initial- and boundary-value problems. One attractive feature of DeepONets is their versatility since
they do not rely on prior knowledge about the solution structure of a problem and can thus be directly applied to
a large class of problems. However, convergence in identifying the parameters of the networks may sometimes be
slow. In order to improve on DeepONets for approximating the wave equation, we introduce the Green operator
networks (GreenONets), which use the representation of the exact solution to the homogeneous wave equation in
term of the Green’s function. A comparison between the GreenONets and the DeepONets is shown on a series of
numerical experiments for homogeneous and heterogeneous medias.

Use of Artificial Intelligence as an Assistant in Fashion Consulting

2024-05-28T13:44:44+00:00

Several people have difficulty acquiring clothes. This is since she does not know her personal style.
According to experts there are seven universal styles that are: Classic, Sporty, Contemporary, Romantic, Sexy,
Creative and Dramatic. So, if a person cares about the image she is passing on to the world she needs a fashion
consultancy. However, a fashion professional is not popular or as affordable, as it can be an expensive service for
the end consumer. Therefore, this project aims to implement a platform where fashion professionals such as
Fashion and Image Consultants offer the service. In addition to this modality the project will contain an intelligent
agent that can be used as a fashion consultant. To training the artificial intelligence model data was collected
through forms made available on the Internet and disseminated to certain populations such as schools and colleges.
In this first phase, only 500 samples were obtained, and the model reached 95% accuracy, but it will be necessary
to obtain a larger amount of data. After all, the identification of the correct style of a person is something complex,
248 characteristics were detected. In the next step will be collected more data and other machine learning models
will be tested.

Vibration of tall buildings under wind loads

2024-05-28T13:50:59+00:00

The evaluation of the dynamic response of tall buildings exposed to wind loads is an important complex
subject that is usually treated through different simplify method which are addressed in this study. The first one is
Mario Franco’s “Synthetic Wind Method”, which allows simulating the fluctuation of the wind from the
superposition of harmonics obtained from a power spectrum of wind speed. It was also studied methods for the
assessment of dynamic torsional moments caused by turbulent wind, and its influence on the total dynamic
response of tall buildings. The torsional dynamic wind loads were simulated trough literature available power
spectra. All load methods were addressed on case studies which involved two different tall buildings modelled on
commercial software’s based on Finite Element Method. It was observed that reliability of the obtained results
depends strongly on the choosing of the method appropriate for the buildings geometry. Also, the disregarding the
floating torsional moments due to wind load in the dynamic analysis of tall buildings can lead to major error in the
human comfort analysis.

Design of optimum viscoelastic dynamic neutralizers by response reanalysis

2024-05-28T13:57:57+00:00

In the past decades, response reanalysis techniques have been widely used to predict the dynamic effects
of localized structural modifications, for they offer the advantage of circumventing the need to reprocess the whole
set of information relative to the system of concern at each modification stage. Some recent works addressed the
issue of evaluating the effects of inserting a viscoelastic dynamic neutralizer into a primary system by means of
reanalysis, but none of them tackled the problem of finding the optimum modal parameters for the device based
on these techniques. In this context, the present work aims to investigate the use of two response reanalysis
techniques - in matrix formulation - to iteratively predict the response of the modified system after alterations in
the parameters of a single-degree-of-freedom neutralizer, which provides a convenient method to find the optimal
modal characteristics for the device. The considered primary system consists of a cantilever steel beam, the
vibrations of which are meant to be kept under control. A finite-element model for the beam is implemented and
a combination of a genetic algorithm and a local Nelder-Mead technique is used to ensure that global minimum
vibration levels are achieved. The results show promising evidence for generalizing the use of the technique to
multiple-degree-of-freedom devices and for applying the method to specific, large scale systems, such as overhead
transmission line conductor cables.

Numerical Study of the Relationship Between Bit Stick-Out and Drill Bit Size in Deepwater Jetting Drilling

2024-05-28T15:12:58+00:00

Jetting is a common technique for conductor casing driving in cohesive soils. This installation method
shows faster results with less cost. However, even nowadays, the jetting operation relies on the experience and
expertise of the drilling team for a successful performance. Therefore, to have a clear picture of jet excavation,
computational fluid dynamics (CFD) approaches have been applied as a safe and economical alternative compared
to field tests. This paper presents a numerical simulation of jetting operation for conductor casing in cohesive soil.
Since the main operation parameters are pump rate, the ratio of bit-to-conductor dimensions and bit stick-out, this
work investigates the relationship between the bit stick-out and drillbits of different magnitude. For simulation of
the soil-jet interaction, a two-phase Lattice-Boltzmann model (LBM) combined with the Volume of Fluid (VoF)

method was used to track interface behaviour. The soil is represented as a viscous fluid and described by Herschell-
Bulkley viscosity model. The model is calibrated for a well in the Brazilian Pre-Salt. Therefore, this study purposes

a follow-up analysis of the jetting process on Brazilian wells to advance understanding of the interaction between
its different parameters and their effect on the operation performance.

Artificial swimmers in concentration gradients: Simulation and learning

2024-05-28T15:17:16+00:00

The coupled problem of hydrodynamics and solute transport for artificial microswimmers is studied,
with the Reynolds number set to zero and Peclet numbers (Pe) ranging from 0 to 100. The adopted method is ́
the numerical simulation of the problem with a finite element code based upon the FEniCS library. Details of the
second-order treatment of the time-evolving geometry are presented and shown to be essential for the basic physics
to be respected. The code is first applied to compute the effective solute intake of several artificial swimmers
as functions of the Peclet number. The results confirm that no significant gain in solute intake is achieved by ́
swimming if Pe is smaller than 10. We also consider the swimmers as learning agents inside a fluid that has
a concentration gradient in the far field. We couple the simulations with reinforcement learning processes and
investigate the ability of the agents to learn to move towards the region of higher concentration. The results
demonstrate that microscopic organisms need to solve a challenging learning problem to migrate efficiently when
exposed to chemical inhomogeneities.

Numerical solution of single-phase flows in karstified heterogeneous carbonate rocks

2024-05-28T15:21:46+00:00

Oil reservoirs in carbonate porous media are usually composed of several structures such as matrices,
fractures and cavity systems, which impact properties like porosity, permeability and fluid transport behavior [1].
In this context, the problem of flow through a reservoir in the presence of karsts is rather challenging, and therefore
the predictive capabilities related to the flow and transport processes remain severely limited. In this work, we
perform simulations of a quarter of a five spot problem in a domain Ω ⊂ R
2

to numerically describe an incom-
pressible single-phase flow in a karstified carbonate rock. The methodology is based on the geometric treatment

and simulation data proposed in [2], and on the application of the Karst Index (KI) concept presented by [3]. The
use of the KI follows a similar approach to the application of the Well Index presented in [4]. Given the lack of
knowledge of the precise geometry of karst network shape, we test different arrangements with branching (such as
in [2, 5]). The mathematical model used includes equations that describe the fluid flow through a conduit, and a

mass conservation equation for each component. The domain is discretized by cartesian grids with different con-
figurations of homogeneous and high-contrast heterogeneous media, while the governing equations are discretized

by conservative finite volume methods. Results are verified in terms of conservation of mass. We compare the
generated results by using Darcy’s law changing the parameters of the conduit to assess its influence on the overall
simulation.

Human-Structure Interaction during jumping on Rectangular Plates

2024-05-28T15:26:27+00:00

In this work a Spring-Mass-Damping system (SMD) of one degree of freedom is used to represent the
human-structure interaction during jumping on a thin rectangular plate under a time-dependent base excitation.
The plate is considered simply supported and its strains relations are described by the Von Karman nonlinear
theory. A parametric analysis using the piecewise-smooth contact dynamics theory is performed to study the
influence of loss of contact during the flight phase of jumping cycles. The different stable jumping strategies of
the human body for incremental values of the human damping ratio are found. Obtained results show that,
depending on the values assumed for the biodynamic parameter, chaotic responses, hysteresis and coexisting
attractors can be observed in the bifurcation diagrams when the human degree of freedom is controlled.

Design of a composite steel-concrete multi-storey building with high- strength steels and built-up sections

2024-05-28T15:29:16+00:00

One of the main advantages of the composite steel-concrete structures is the feasibility to explore the
combined potential of the materials, i.e., steel in tension and concrete in compression. The construction system
allows two materials to be used together in beams, columns, and slabs to obtain a building with excellent structural

performance. Therefore, this project aimed to evaluate the reduction of the self-weight of the structure of a multi-
story (G+7 story) building using steel-concrete composite structures together the use of high strength steels, such

as the ASTM A572 grade 65 (yield strength of 450 MPa). A complete building project of real building available
in the literature was used to be the comparison parameter for this study. Originally, the design present in the
literature adopted European rolled profiles with European S355 steel, which has yield strength similar to the ASTM
A572 grade 50 (yield strength of 345 MPa). A complete finite element model of the building was developed using
the finite element program Autodesk Robot Structural to carry out static and quasi-static structural analyses.
Design verifications were implemented and conducted in Visual Basic for Applications (VBA) and MS Excel®
macros using Brazilian design standards (NBR 8800 and NBR 6118) for ultimate-limit and serviceability states.
This paper is included in the context of an undergraduate final project work and present the state of the ongoing
research. At this first phase, the use of high-strength steel allowed the reduction of some built-up sections and
hence the total weight of the structure.

A numerical study of cardiac pacemakers with relaxation oscillators

2024-05-28T15:31:52+00:00

The cardiac pacemaker is an important device for the proper functioning of the human cardiac system.
A modeling to represent the signals from the operation of a pacemaker has been done using a relaxation oscillator,
the Van der Pol oscillator, given by a second order differential equation. This paper aims to demonstrate the
development of a cardiac pacemaker model based on the modified Van der Pol oscillator to simulate it numerically,
in order to analyze the signal in the time domain, as Phase Portrait, and in the frequency domain, as Fourier
Transform and Wavelets Transforms, in order to identify the stability of the oscillator and its response in the
frequency domain. The numerical integrations performed in this paper were done with the fourth order Runge
Kutta method.

Model updating using hierarchical Bayesian strategy and error scale factor employing B-WIM calibration data

2024-05-28T15:35:22+00:00

Data collected during the calibration process of bridge weigh-in-motion (BWIM) systems can be applied
both for evaluating the behavior of the structure and for updating models and parameters. These model update
techniques aim to adjust parameters of a structural model making predicted responses closer to the experimental
behavior. Bayesian modeling is well applied to the present problem, as it makes possible the combination of
previous knowledge and experimental data, allowing better parameter estimates. However, in some civil
engineering applications the updated parameters may contain inherent variability during the experimental process,
due to external factors such as environmental conditions, and may have considerable changes during the process.
To consider this inherent variability, a hierarchical Bayesian model was adopted. Sampling from Markov Chain
Monte Carlo (MCMC) methods is applied. It was also observed that there is an increase in variability with
increasing vehicle weight. The introduction of this effect to the model was then studied, comparing 2 ways of
considering this variation, both as a linear function of the expected signals for a given vehicle, and using the area
under this predicted signal. Results for both numerical simulations and real bridge calibration data indicate that
the hierarchical Bayesian approach proposed for the model update, including the scale factor according to vehicle
weight, is able to perform properly, providing confidence intervals for predicted signals by unseen vehicles that
best fit within the observed strains.

Sensor Placement Optimization for Numerical Model Reduction using Genetic Algorithm

2024-05-28T15:38:59+00:00

Numerical reduction techniques are crucial for numerical and experimental model compatibility.
Besides reducing computational costs, finite element (FE) models generally have significant number of degrees of
freedom (DOFs) when compared to experimental models. Therefore, sensor placement techniques based on
effective independence (EI), condition number of the modal matrix (CN) and the sum of the off-diagonal terms of
the modal assurance criteria (off-MAC) matrix aim to provide optimal sensors position setup for future accurate
experimental tests. Thus, this work presents a comparative study among the mentioned sensor placement
techniques for selecting the candidate numerical DOFs to reduce the free-free beam FE model through the Guyan
technique. In addition, it is applied genetic optimization algorithm (GA) under CN and MAC techniques to reach

optimal solutions. A sensitivity analysis of the optimal responses from CN and MAC was held, along with an F-
test, which ranked the relevant DOFs for sensor placement. The results showed that root-mean-square-error

(RMSE) between the reduced FE and full FE models was less than 5%. MAC values were above 0.86. Finally, it
was identified that the three methods need a DOF’s selection of spatial constraints to circumvent possible problems
of the modes poor spatial resolution of the reduced FE model.

Numerical analysis of geosynthetic-reinforced embankments on soft soils

2024-05-28T15:43:58+00:00

This paper analyzes, through numerical modeling in finite element software, the behavior of an
embankment reinforced with geosynthetics on soft soils. The results presented and discussed allowed us to
establish conclusions regarding the behavior of settlement, horizontal displacement, excess pore pressure, tension
and deformation in the geosynthetic as a function of time, depth and horizontal distance. In summary, the numerical
analyses presented satisfactory behavior and the results show that the insertion of geosynthetics does not influence
the response of some analyzed variables, except for the horizontal displacement. However, the use of geosynthetics
aims to increase the global stability of the soil mass through contact interactions and reduce embankment
deformation. The contributions of this work to the understanding of the behavior of geosynthetic reinforced
embankments on soft soils are highlighted.

Computational tool for design of steel elements in fire situation with and without fire protection material

2024-05-28T15:49:09+00:00

At high temperatures, steel presents changes in its mechanical properties, which can cause severe
accidents. Due to this, fire safety engineering has two objectives: the preservation of life and the reduction of
property losses. Among the measures that can be adopted to increase the fire resistance time of a structure, the
application of passive fire protection materials stands out. Despite the importance of these materials, information
about their fire behavior and their thermal properties are still limited, causing, currently in Brazil, the material
thickness to be determined based on fixed critical temperature values. Therefore, in this paper, a computational
tool was developed to help the design of fire protection materials in steel structures. The tool was developed in
Visual Basic for Applications language and performs the design of steel columns and beams at room temperature
and in a fire situation, with or without fire coating materials. The computer program considers protective materials
such as spray-applied mortar, gypsum board, and intumescent paint. The results obtained by the developed tool,
when compared with the literature, were satisfactory, indicating that the tool is a reliable and useful instrument for
the correct design and specification of protection materials.

DESIGN OF INJECTOR PLATES FOR HYBRID ROCKET MOTORS TEST BENCH WITH GASEOUS OXYGEN

2024-05-28T15:51:58+00:00

Hybrid rocket motors have been intensively studied in universities because of their many advantages
compared to other chemical rocket motors. They are safe, simple to handle, present low cost, environmental
cleanliness, and throttling features. Because of these reasons, hybrid motors injection plate is a primary item. There
is a lot of available experimental data about the atomization of particles for liquid injection. However, for laboratory
applications, in which liquid oxygen is more expensive and challenging gaseous oxygen is desirable. From this
point of view, the present study is motivated by the lack of literature about injection plates for compressible fluids.
This paper presents an analytical and numerical design of injectors for gaseous oxygen. In the analytical study
section, continuity, ideal gas, and atomization equations present in literature have been used to design a showerhead
injection plate for the desired pressure drop. The numerical study made it possible to model a viscous flow through
the designed injection plate, resulting in slightly higher pressure drops than isentropic analytical results since the
theoretical results do not account for viscous losses. This numerical model validation enabled the design of more
complex injection plates, such as hollow-cone, pressure-swirl, and vortex ones.

A Hybrid Algorithm based on Stationary and Krylov methods for Nonsy- mmetric Linear Systems

2024-05-28T15:55:25+00:00

Iterative Krylov methods, like Generalized Minimal Residual (GMRES) and Full Orthogonalization

Method (FOM), are normally used for the solution of sparse and nonsymmetric linear systems from Computa-
tional Mechanics problems. In practice, restarted versions, are used to reduce storage and orthogonalization costs.

However, numerical experience shows that these methods may present stagnation or slow convergence. The Sta-
tionary method is older, simpler to understand and implement, but usually not completely effective. Contrarily, the

Krylov method has a more recent development and is more effective than the former, but the analysis is usually
harder to understand with difficulties in selecting its parameters. A cycle of a proposed hybrid method consists
of n Stationary iterations of Richardson followed by m × k iterations of the restarted GMRES, where n, m and
k are values much smaller than the dimension of the non-symmetric matrix. Such cycles can be repeated until
convergence is achieved. The advantage of this approach is in the opportunity to allow better performance of its
individual properties. This combination of methods is competitive from the point of view of helping to accelerate

convergence with respect to the number of iterations for some linear problems. We are going to present compu-
tational experiments to show the advantages and the main problems raised from the perspective of the proposed

hybrid method.

Sensitivity analysis and parameter identification to railway bridge structural model updating

2024-05-28T15:58:29+00:00

One of the major challenges in the management of infrastructure systems is to ensure their safety and
structural integrity throughout its useful life. This is due to the fact that the material and structural properties loss
and the eventual failure of these structures has catastrophic consequences. In that context, this project aims to
contribute to the application of methods that allow the safety and structural integrity assessment of railway bridges
based on experimental modal data. The objective is to apply the sensitivity analysis of a real railway bridge
structure using finite element model update to its unknown structural parameters. For this purpose, the Sobol‘
indices are studied to describe how the variability of the model response is affected by the variability of each input
parameter or combination thereof. Usually, these indices are computed by Monte Carlo simulation. However, they
are practically not applicable to CPU-intensive models such as finite element models. An alternative approach to
overcome this scenario is the use of surrogate models to speed-up the calculations, such as a polynomial chaos
expansion, a robust framework to compute Sobol’ indices. Thus, for the sensitivity analysis of this paper, it brings
a connection between these approaches. Finally, the role of the parameter identification is discussed, based on the
results of the sensitivity analysis.

Reliability analysis of cold formed steel members with plain C-lipped and SupaCee section in shear

2024-05-28T16:42:30+00:00

This article presents a procedure for the reliability assessment of cold-formed steel members with plain
C-lipped and SupaCee® sections in shear. The SupaCee® sections contain additional return lips and web stiffeners

which enhance the bending and shear capacity of the sections. The development of the DSM for designing of cold-
formed sections in pure shear is available in North American (AISI) and Australian (AS/NZS 4600) standards.

However, the Brazilian standard does not provide the application of the DSM for shear case. A test database of 23
cold-formed steel members in shear was assembled and test-to-predicted statistics were obtained for the Direct
Strength Method (DSM). The reliability indexes, resulting from the reliability analysis, were determined using the
First Order Reliability Method (FORM), First Order Second Moment (FOSM) and Monte Carlo Method (MCM).
It was found that the DSM safety level, adapted to the Brazilian standard, satisfies the target reliability index of
2.5 if a resistance factor of 1/1.2 is used.

CHARACTERIZATION OF DISTURBANCE IN ELECTRIC POWER SIG- NALS: A MACHINE LEARNING APPROACH

2024-05-28T16:45:02+00:00

Voltage variation in electrical networks is one of the problems that arise when it comes to electronic equip-
ment that is sensitive to voltage variations. As a way of classifying voltage variation phenomena, such as Voltage

Sag or Swell, this paper aims to use artificially created voltage signals in the time domain, which represent each
electrical fault, which will be analyzed in the frequency domain with techniques of time frequency analysis (TFA)

and entropy analysis, among other Features. Subsequently, with classic methods from the Machine Learning lit-
erature, classify the general electrical signals and identify the respective faults. As a working tool, the Python

language is used, as it is easy to implement and learn, in addition to being widely documented. Additionally, the
scikit-learn librarie is used, which are widely tested and documented in the literature.

Interactive graphic software for structural analysis of slabs using Grid Analogy with consideration of column’s stiffness

2024-05-28T16:48:02+00:00

For the dimensioning of reinforced concrete slabs, the appropriate determination of internal forces and
displacements is vital. These parameters are subject of structural analysis and, in the case of slabs, the equation
that mathematically describes such elements’ behavior is the Lagrange Differential Equation, which analytical
solution has a high degree of complexity, that increases considerably depending on the boundary conditions
involved. However, in modern days, thanks to the computational revolution, numerical solutions for this problem
have become more and more feasible and accessible, and are now widely used as basis for the structural analysis
of slabs. Among the several viable methodologies used with this purpose, this paper describes the use of the Grid
Analogy Method as the core method for developing a Python interactive-graphical software focused on the
structural analysis of concrete slabs. Furthermore, based on the observation that a solidarization process occurs in
the slab-column interface regions, the effect of the direct employment of the columns’ bending stiffnesses on the
stiffness matrix of the structural system is also analyzed. For verification matters, the recorded grid analogy results
are compared with data present in the Literature, while the influence of the columns’ stiffness is studied by
comparing the results of the analysis of the same structure with and without this consideration. The results were
very satisfactory, both numerically and regarding the graphical environment created, that can be used for handling
the structural model design and presenting the results of internal forces and displacements.

CONCRETEGRID: A COMPUTATIONAL TOOL TO ANALYSIS AND DESIGN OF STRUCTURAL GRIDS IN REINFORCED CONCRETE

2024-05-28T16:50:58+00:00

The structural solution in grids is widely used in civil construction, as in building floors and bridge
boards, due to its large bearing capacity. The grids are structural systems composed of a set of linear elements
(beams) belonging to the same plane, designed to resist the solicitations coming from not coplanar actions to this
system. Its large bearing capacity is due to the stiff connections between the beams that compose the structural
grid, allowing the loads applied to a single beam to be redistributed to the others, so that all elements work together.
Therefore, the stiffness relationship imposed by the nodes, be related to bending or torsion, implies in a formulation
adapted to the impact on the structure's behavior, in efforts and displacements. In this context, we present the
application ConcreteGrid, a computational tool developed in Python programming language for analysis, design
and verification of grid elements in reinforced concrete structures. The computational implementation allows the
user to define the structure of interest with its loads, providing the analysis of displacements and acting efforts,
considering the dimensioning of the longitudinal and transversal reinforcements of the grid beams, as well as the
verification of the reinforcements in terms of satisfying the criteria of ultimate. The validation of the presented
tool is performed through the analysis of applications available in the literature, proving the relevance of the
formulation used and the computational implementation performed.

NUMERICAL STUDY OF A MULTI-DEGREE OF FREEDOM STRUCTURE UNDER THE INFLUENCE OF WIND EXCITATION.

2024-05-28T16:53:05+00:00

Nonlinearity is always present in the most diverse real structures, so the more reliable the computational
numerical modeling of these structures, the more one must consider the nonlinearities present. This paper aims
to study the nonlinear dynamics of a structure under the action of wind force based on a structure with multiple
degrees of freedom (shear building) with the addition of a duffing spring, which introduces nonlinearity to the
system, where the external force will be implemented through the wind force applied to one of the floors of the
structure. The entire analysis will be performed through the numerical integration of the ordinary differential
equations, thus obtaining the response in the time domain, and through transforms, such as the continuous wavelet
transform (cwt), extract the signal in the frequency domain, allowing to observe phenomena that are not possible
to observe in the time domain, thus having a complete analysis of the system behavior.

OPTIMIZATION OF A PRESTRESSED CONCRETE WIND TURBINE TOWER USING DIFFERENTIAL EVOLUTION

2024-05-28T16:56:42+00:00

Optimization procedures are being increasingly used in wind tower structure design in order to provide
more efficiency. In the face of recent advances, towers are getting bigger in order to perform better by providing
better winds for the turbines. Thus, prestressed concrete towers emerge as an excellent solution. This work aims
to apply and evaluate the Differential Evolution algorithm in order to reduce costs and improve the performance of
prestressed wind towers. The Finite Element Method is used for structural analysis. The algorithm is evaluated in
terms of accuracy and computational efficiency.

A numerical model with an explicit representation of steel fibers for modeling SFRC beams subjected to torsion

2024-05-28T16:59:26+00:00

A numerical model with a discrete and explicit representation of steel fibers is used for modeling steel
fiber reinforced concrete (SFRC) beams subjected to torsion. The numerical model is a combination of a fiber
cloud, cement matrix, and the fiber-matrix interaction. It is well known that the addition of steel fibers to concrete
increases the torsional and rotational strength, in addition to greater cracking control. In this context, this work
aims to assess the capability of the numerical model to simulate experimental tests available in the literature of
SFRC beams under torsion with steel fiber rates of 25 kg/m3 and 50 kg/m3. The results demonstrated that the
numerical model proposed is appropriate to represent the failure process of beams under torsion and the numerical
tool can be very useful in future studies in combination with analytical equations proposed by standard codes.

Fuzzy Controller for a Battery and Ultracapacitor Hybrid Energy Storage System Vehicle

2024-05-28T17:01:59+00:00

With the increase in transportation electrification, one of the biggest challenges is to improve battery
performance and autonomy. A battery normally has a high energy density with a low power density, while an
ultracapacitor has a high power density but a low energy density. Therefore, this paper has proposed associating
more than one storage technology generating a Hybrid Energy Storage System (HESS), which has a battery and
ultracapacitor, whose objective is to improve the electric vehicle (EV) driving range. When batteries and SC
are associated, the power management complexity increases considerably. In this work, a fuzzy logic power
management control for the HESS is developed for the best use of the regenerative energy released for charging
the capacitors and minimizing battery wear in urban driving cycles. Therefore, it is necessary to determine the
correct power distribution between the storage devices to enhance the system efficiency by saving the battery from
excessive efforts. The topology used considers bidirectional converters, coupled to the bus and connected to the
electric motors which propel the EV. For the simulations, Matlab and Simulink software is used, where it is possible
to analyze the dynamic behavior of the electric vehicle.

Employment of Artificial Intelligence in Fish Fraud Identification

2024-05-28T17:05:56+00:00

Acquiring fish for consumption whether in restaurants, supermarkets or fishmongers can become a
frustrating task from the moment it is perceived that the species at hand is not the expected fish. Added to this is
the fact that fraud always aims to deceive to make a profit. There are some applications that aim to identify fish
species; however, they have no specific focus on certain species. With this, the user applies to all species of fish
and ends up disappointed with the inefficiency of the application. This project aims to implement an application
that uses artificial intelligence to identify certain species of fish. The main point of the application are fish species
and cannot be used for ornamental fish. The method used was to obtain images and configuration of models of
artificial neural networks for image recognition. During the tests the implemented model reached 75% accuracy.
The model had difficulty recognizing three species accurately, it was the case of Merluza fish that was confused
with Salmon and Trout. It is believed that this occurred due to the low number of samples, but in short, the model
achieved satisfactory results.

A Fourier stability study for an explicit numerical scheme applied to the fractional diffusion equation with dimensional correction

2024-05-28T17:12:39+00:00

This paper presents a study of stability analysis for the generalization of the fractional diffusion equa-
tion FDE with constant coefficient, when the dimensional correction parameter τ is inserted in the model. The

numerical approach chosen is an explicit finite difference scheme inspired by the classical forward Euler method.

The fractional temporal order derivative adopted in the equation is the Riemann-Liouville one, which is approxi-
mated by the Grunwald-Letnikov operator. The stability analysis is conducted with the application of the Fourier ̈

method, allowing to show that the proposed explicit scheme is conditionally stable. A numerical experiment is
also presented with displayed results so as to back up the theoretical conclusions and to point the influence of the
dimensional correction parameter.

Global buckling of thin-walled laminated composite columns

2024-05-28T17:15:18+00:00

The search for lighter and larger structural components makes the use of fiber-reinforced laminated
components increasingly slender. However, the increase in slenderness makes the structure more flexible, which
can cause stability problems and large displacements. As a result, buckling has a great influence on composite
material column designs, so their failure can occur with stress lower than the strength of the material. In this
way, the evaluation of the stability of these structures is of great importance because it allows for predicting the
load capacity. However, one of the main objectives of the industry is to replace experimental tests with numerical
simulations, since in tests of composite material structures, numerous and expensive tests are usually required.
Therefore, this work aims to study of global buckling of laminated composite channel-section columns. Two
approaches are employed in this context. The first approach consists of a three-dimensional beam finite element

for stability analysis of thin-walled laminated composite. Regarding the second approach, it relies on the Rayleigh-
Ritz framework assumes that the axial strain is neglected, and the column only buckles according to the minor

axis of bending, evaluating the behavior of channel-section columns, with different layups when subjected to
compressive loads. Both strategies are based on a fully coupled constitutive matrix, and the results obtained were
compared with shell finite elements.

Modal analysis of a simply supported beam subjected to a moving mass

2024-05-28T17:17:55+00:00

This study presents a computational analysis of the dynamic behavior of a simply supported beam
subjected to a moving mass and corresponding load that travels along its entire length with different speeds. The
first analysis aims to understand the behavior of the structure and to determine transversal response of the structure.
Here, a discretized simply supported beam model was developed, based on the Finite Element Method, using
numerical integration by Newmark’s Method for the solution of ordinary differential equations and obtaining the
displacements of the structure in the time domain, to evaluate its behavior due to moving masses and loads. The
analysis is made in different velocities and damping rates aiming to find the maximum transverse response, and
comparing with the static response to find the maximum amplification coefficients. This article aims to evaluate
the frequencies and vibration modes associated with the maximum displacements found and its relation with the
different velocities applied.

Comparison between predictions of the annual cyclic response of a semi-integral abutment using finite and discrete element methods

2024-05-28T17:20:00+00:00

This work compared predictions of the annual cyclic response of a semi-integral abutment retaining a
granular backfill using the Finite Element Method (FEM) and the Discrete Element Method (DEM). Finite element
(FE) and discrete element (DE) models were developed based on the field data collected from an instrumented and
monitored semi-integral abutment. A 15-node triangular FE mesh was used to discretize the backfill in the
simulation with FEM while spherical particles were used to represent the backfill in the simulation with DEM. A
± 5-mm lateral displacement was imposed on the abutment to simulate the effects of expansion and contraction of
the bridge superstructure due to annual temperature variations. The cyclic sequence of imposed lateral
displacements was chosen to simulate the abutment lateral movements after the bridge construction completion in
the summer season. Results showed that a good agreement was found between the numerical simulations using
FEM and DEM. Lateral earth pressures on the abutment and vertical displacement of the backfill surface increased
with annual cycles for both methods. Values of peak wall reaction ratio were similar in both methods while higher
values of settlement were observed using DEM compared to FEM.

The importance of linear search for the bound-constrained solver for phase- field modeling of fracture in quasi-brittle materials with FEM

2024-05-28T17:22:36+00:00

The propagation and emergence of cracks are widely explored in fracture mechanics. A study that
has increased with the advancement of computer technology is the phase-field for crack modeling. This model
approaches the crack as continuous and diffuse, placing a damage variable in the problem and a variable with the
crack band size. There are different ways to control crack irreversibility, such as the bound-constrained solver
and the historical solver. The bound-constrained solver allows you to choose any crack geometry function and
energy degradation while the historical solver needs to be a specific crack geometry function. In this article, the
importance of linear search for bound-constrained solver results will be discussed through numerical simulations,
showing that the line search is necessary to avoid numerical instabilities as well as a correct load peak. Numerical
simulations were processed in INSANE software (INteractive Structural ANalysis Environment). This work uses a
bound-constrained solver from the PETSc library, connected to INSANE through a JNI.

Nonlinear geometric analysis of orthotropic laminated plates and shells with zig-zag effect

2024-05-28T17:26:08+00:00

In this study, a positional Finite Element Method (FEM) formulation is applied to simulate orthotropic
symmetric laminated plates and shells. Alternatively to the traditional FEM, the positional formulation uses a total
Lagrangian description based on generalized vectors and nodal positions, providing an inherently nonlinear
geometric formulation. However, basic kinematics are not able to satisfy a continuous stress distribution along the
laminate thickness. The stress discontinuity is related to the emergence of a zig-zag displacement profile in the
transverse direction caused by mechanical properties changing between adjacent laminas. Therefore, the proposed
formulation introduces new degrees of freedom to regularize the classical Reissner-Mindlin kinematics and

reproduce the zig-zag effect. In addition, the mechanical model uses Green-Lagrange strain and the Saint Venant-
Kirchhoff constitutive law, which allows moderate strain. A numerical example is employed to validate the

proposed formulation and demonstrate its quality when compared with literature results.

FIRESTEEL: A COMPUTATIONAL TOOL FOR THE STUDY OF STEEL ELEMENTS IN FIRE SITUATION

2024-05-28T17:28:10+00:00

Fire is the occurrence of uncontrolled fire, an extremely dangerous phenomenon that can affect the
safety of buildings, sheltered heritage and living beings. By causing the temperature increase, the action of fire
triggers physicochemical transformations that degrade the properties of materials and interfere with the integrity
and behavior of structural elements, which can compromise the resistance capacity of the structure as a whole.
This phenomenon is particularly important in the case of steel structures, as the elements usually used are generally
light, slender and with an open cross-section, characteristics that tend to favor the quick heating of the parts. In
this context, it is essential to study the evolution of the temperature in steel as a function of the temperature
variation of the gases, as well as the consequent degradation of the resistance capacity of the structural elements.
Once the problem is established, this work presents the FireSteel application, a computational tool developed in
Python language that allows the evaluation of the thermal evolution, the verification of the resistant force and the
determination of the critical temperature in structural steel elements in fire situation. For this, FireSteel has a
customizable data entry that gives the user the freedom to select the data they want to obtain. The calculations
were made in accordance with the Brazilian technical standards currently in force and the results were validated
based on information available in the technical literature.

Numerical modeling of a reduced scale mooring line experimental investigation for load attenuation evaluation

2024-05-28T17:30:28+00:00

Oil platforms are migrating into deep waters, where the maintenance of its position represents an
engineering challenge. It has become usual to adopt mooring systems composed of chains that extend from the
floating unit to the foundation element and, along its length, have an embedded segment in the seabed, shaped as
an inverse catenary, capable of attenuating the acting forces. Several studies have been conducted to improve the
understanding of soil-chain interaction and estimate the expected attenuation level according to each problem’s
characteristics. Investigations in this area can be developed under experimental approach, normally on reduced
scale, or under numerical approach, which allows the simulation of a wide range of scenarios. Therewith, the
present work aims to simulate experimental tests in 1:40 geometric scale that reproduce the segment of a mooring
line embedded in soil, using a numerical finite element model built in a commercial software (ANSYS). The model
considers soil elements as a perfect elastoplastic material, chain elements as an elastic material with tension only
behavior and pair of target and contact elements which simulates the interface between soil and chain. The obtained
results are discussed by means of stress distribution in soil and percentages of load attenuation.

A position-based Space-Time formulation for geometrically nonlinear problems

2024-05-28T21:17:11+00:00

Space-Time finite element methods has been developed over years for solving a series of time-dependent

problems like elastodynamics, fluid-structure interaction, fluid flows, advection-diffusion equations and heat trans-
fer problems. The core of this approach is the treatment of time as a dimension of the finite element problem,

leading to space-time finite element discretizations. Single-field or two-fields formulation are possible, where the
first one uses only displacement as unknowns, while the second uses both displacements and velocities as variables.
Some challenges that appear in the Space-Time FEM are the increased size of the equation systems as the precision

in time is increased and the 4D meshes representation. Nevertheless, this approach can lead to higher order accu-
racy in time and direct dynamic spatial re-meshing. On the other hand, time-marching methods are well-known

numerical time integrators that have been applied to discrete systems of differential equations obtained from dif-
ferent spatial discretization techniques, including FEM. Most of them deal with approximations for displacements

and velocities, and the discrete system of differential equations are solved at each discrete time level taking into
account the variable fields from the last time step and the current boundary conditions. Moreover, they can be
formulated to present unconditional stability, to present controlled dissipative properties and different orders of

accuracy. As a disadvantage, dynamic re-meshing procedures are not directly feasible, as it demands the projec-
tion of past time step fields over the new mesh, including projection errors. This work presents a position-based

Space-Time FEM formulation for two-dimensional solids with large displacements, using a total Lagrangian de-
scription. This formulation is naturally isoparametric and designed directly over the large displacement assumption

making the geometric non-linearities intrinsically considered. In order to verify the potential of the formulation, a
comparative analysis with the time-marching method alpha-generalized is carried out.

Numerical formulation for advanced analysis of semi-rigid steel-concrete composite frames

2024-05-28T21:58:42+00:00

The present work aims at the implementation and validation of a displacement-based two-dimensional
numerical formulation including several sources of non-linearities in steel-concrete composite frames, such as
second-order effects, plasticity and beam-to-column semi-rigid connections. The co-rotational-based approach
is used to describe the finite element formulation, allowing large displacements and rotations in the numerical
model. Rotational pseudo-springs are used at the ends of the finite element, where the gradual loss of stiffness
is determined by combining the normal force and bending moment (NM) in the cross-section. The limiting of
the uncracked, elastic and plastic regimes are defined in the NM diagram. In the cross-sectional analysis, the
Strain Compatibility Method (SCM) is used to capture the axial strains in the section components. In this way, the
constitutive models of the materials are described by continuous functions. The semi-rigid connections are also
simulated by the rotational pseudo-springs at the finite elements ends, and the connection behavior is given by
its moment-rotation relationship. A multi-linear model for beam-to-column connections is used. To validate the
proposed numerical formulation, the results obtained are compared with numerical and experimental data available
in the literature. Since the model proposed here starts with the concentrated simulation of nonlinear effects, an
examination of the finite element mesh refinement is also carried out.

Topological optimization of composite truss beams considering CO2 emissions

2024-05-28T22:02:03+00:00

In order to provide more sustainable solutions to the construction of composite truss beams, the present
work proposes a formulation to optimize dimensional, geometric and topologic parameters aiming to minimize
CO2 emissions. Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) are used to solve the
optimization problem considering the choice of steel profiles, characteristic strength of concrete, formwork,
number of panels and truss total height. The methodology is applied to a problem where three different models of
truss are considered - Pratt, Howe and Warren - and an analysis of the best solution’s emissions composition is
made. In conclusion, results shows that the better result to the optimization problem was obtained in the Warren
model and both optimization algorithm presents consistent solutions.

A study on using an immersed boundary technique for modeling 3D incompressible fluids with internal fluid-body interface

2024-05-28T22:04:11+00:00

This work investigates the outcomes of using an immersed boundary technique for the mixed finite
element formulation of tridimensional incompressible fluid flows governed by the Navier-Stokes equations with

internal fluid-body interfaces. A classical Eulerian approach is followed to describe the fluid. A Newton-
Raphson scheme is devised to solve the resulting non-linear equations within a time step. The fluid-body

interface is treated by the Nitsche’s method, which is an immersed boundary technique whereby the fluid
boundary conditions over the contact with the bodies are imposed weakly. In order to ascertain the accuracy and
efficiency of the adopted method, numerical simulations of tridimensional flows of an incompressible fluid are
analyzed and compared against reference solutions. This work refers to an intermediate stage of a PhD research
that aims to model problems of fluid-particle interaction (FPI) and particle-laden fluids.

Numerical investigation on tornado-like flows and immersed bodies using vortex models

2024-05-28T22:06:28+00:00

A study on the characteristics of real and experimentally simulated tornado flows is carried out in this
work using a numerical formulation based on the model of Vatistas et al. [1]. The flow governing equations are
discretized using an explicit two-step Taylor-Galerkin scheme and a finite element formulation is used for spatial
discretization, where eight-node hexahedral elements with reduced integration are used. Tornado flow fields are
reproduced numerically from a velocity profile model by Vatistas et al. [1], where time-dependent boundary
conditions are used to account for tornado vortex translation. Turbulence modeling is performed using Large
Scale Simulation (LES) with the Smagorinsky sub-grid scale model and the computational code is parallelized
using CUDA FORTRAN directives for processing on graphics cards. An experimentally generated tornado flow
field is reproduced using the model implemented here and a cubic building model subjected to different tornado
flow conditions is also analyzed. Results demonstrate that the velocity profile models are able to satisfactorily
reproduce the tornado flow fields and the corresponding aerodynamic forces on immersed bodies.

Numerical analysis of an unreinforced embankment on soft soil

2024-05-28T22:08:53+00:00

The present work analyzed, through numerical modeling, the behavior of an unreinforced embankment
on soft soil. The simulations were performed in the Abaqus software, from which the Mohr-Coulomb failure
criterion was established for the granular material of the embankment and the Modified Cam Clay model for soft
soils. As result, the paper presents and discusses the behavior of settlement, horizontal displacement, excess pore
pressure, and effective stress variation as a function of time, horizontal distance, and depth. The adopted numerical
model and the observed behavior patterns are satisfactory so that the results of this study can assist in the analysis
of the performance of embankments on soft soils.

Reliability study of the ductility of reinforced concrete beams based on the NBR 6118 (2014)

2024-05-28T22:12:41+00:00

Semi-probabilistic methods are the procedures used in most structural design codes to try to ensure the
safety of structures. However, there are several uncertainties related to the structural models, as well as
uncertainties in the loads, in the geometric properties of the elements and in the mechanical properties of the
materials employed. Therefore, it becomes necessary to apply probabilistic methods to verify safety, and structural
reliability methods appear in this scenario as a way to calculate probabilities of failure taking into account the
uncertainties involved. Several studies were developed about the reliability related to the strength of reinforced
concrete beams. However, reliability analyzes focusing on the ductility of these structural elements are still rare in
the literature. In the present paper it is intended to determine the level of reliability related to the ductility of
reinforced concrete beams designed in accordance with the Brazilian code for the design of reinforced concrete
structures (NBR 6118). For this, an analytical model which tries to adequately represent the non-linear behavior
of the beams is implemented. To evaluate the structural reliability, a limit state function based on strains in the
tensile rebar is presented. A code in MATLAB is developed, in which the Monte Carlo simulation is implemented
and a beam is evaluated for a rage of concrete strength from 20 to 90 MPa. From this study, it is concluded that in
some cases the reliability related to ductility can be considered low.

A boundary element formulation for two-step thermoelastic analysis without internal cells

2024-05-28T22:14:56+00:00

Uncoupled (two-step) thermoelastic analysis is addressed by a new boundary element method formula-
tion that eliminates the use of internal cells. The first step is a steady-state thermal analysis. The second step is a

mechanical analysis, which uses the temperature field obtained in the first step as part of the applied loads. Domain
integrals in temperature, displacement and stress boundary integral equations are transformed to boundary by the

radial integration method. The radial integration method is a simple and powerful method based on a pure mathe-
matical treatment, which transforms any domain integral into a boundary and a radial ones. The radial integral is

independent of geometry and no discretization is necessary for its evaluation, while the boundary integral can be
solved using the existing boundary mesh. Since temperature has been evaluated only at discrete points, namely the
boundary nodes and a set of internal points, the moving least square procedure is used to calculate temperature at
numerical integration points during evaluation of radial integrations of the second step. The moving least square
is a technique usually adopted to generate shape functions in Meshfree methods. Two representative examples are
presented to demonstrate the accuracy and robustness of the proposed formulation.

NEW STUDIES ON META-MODELING FOR LAZY-WAVE STEEL CATENARY RISERS

2024-05-28T22:16:56+00:00

Offshore production systems are very complex structures involving safety and economic aspects. For
these reasons, several research is done to reduce these costs. At design phase, riser layout and its configuration are
a key factor as this is a high-cost component and suffers from the action of environmental loads and dynamic
movements of the floating unit where it is connected. This component is mathematically modeled, and calculations
are performed using the Finite Element method to assess the structural feasibility and optimization algorithms can
be used to determine the viable configuration with the lowest associated cost. The problem with this methodology
is that the analysis of different configurations in an optimization process demands a very large computational
power, consequently a very high processing time. Previous works have demonstrated that meta-models such as
ANN - Artificial Neural Networks can be used to replace the finite element procedure in the evaluation of riser
configurations. In this work, novel developments were studied considering two approaches, first the optimization
process starts and after a specified number of generations, the training of the meta-model is carried out and from
that point the optimization uses the meta-model as a method of evaluation. The second approach has the first part
the same as the previous one, however, after the first training, re-trainings are carried out, incorporating new
individuals to the knowledge of the meta-model during the optimization process itself.

A stochastic gradient descent approach for risk optimization using the Chernoff bound

2024-05-28T22:19:42+00:00

We propose a method for solving Risk Optimization (RO) problems based on the Stochastic Gradient
Descent (SGD) methods. SGD is used to minimize the expectation of functions. We approximate each limit state
function in the RO problem using the Chernoff bound, thus recasting the original RO problem as an expectation
minimization problem. The Chernoff bound approximation requires the evaluation of Monte Carlo sampling,
which could be expensive. However, once the Chernoff bound parameters are set, they can be used to cheaply
approximate the probabilities of failure of each state limit for several iterations. We propose a heuristic approach to
tune the Chernoff bound parameters after a distance from the last update. Moreover, we decay the update distance
each iteration, thus guaranteeing that the probabilities of failure approximations are accurate as SGD converges
to the optimum solution. We present numerical results supporting the efficiency of our approach to different RO
problems with applications in structural engineering. Comparisons of SGD equipped with our Chernoff bound
approximation against particle swarm optimization using sample average approximation validate the efficiency of
the proposed approach.

Thermal And Structural Behavior of Cold-Formed Steel Frame Under Fire Condition

2024-05-28T22:22:54+00:00

The Light Steel Frame building system is composed of structures manufactured in cold-formed profiles
of light and galvanized steel. With the union of these profiles structural and non-structural frames are assembled,
such as floor and wall beams, slabs, among other components. Over the metallic structure, a coating is applied by
cement boards, drywall, smartsid, or vinyl siding. These plates can contain acoustic, thermal and fire-resistant
coating layers. Because it has a metal support structure, LSF buildings receive great influence in fire situations,
since high temperatures modify the physical and mechanical properties of steel. The present paper aimed to
evaluate the behavior of a structural panel of the steel frame type, covered with gypsum plasterboards, in a fire
condition, analyzing the influence of temperature increase on the mechanical properties of the structural profiles
that constitute it. To achieve this objective, numerical analyses were performed with the commercial software
ANSYS, where the instability modes, the loadbearing capacity and the influence of the thermal action on the frame
were evaluated. With the result of the analyses, it was possible to obtain the fire resistance of the structure.

NUMERICAL ANALYSIS BASED ON HEAT TRANSFER IN THE DRYING PROCESS OF SOLID BRICKS

2024-05-28T22:25:07+00:00

Being the ceramic a widely used material and with great economic importance, its process of drying has
been studied due to the occurrence of numerous phenomena, beyond a high energy consumption that happens in
this stage of manufacturing. The use of numerical simulation technologies can alter the operating conditions and
geometric of the drying object, all of this at low cost and relatively easy. Therefore, this job was carried out with
the purpose of studying the drying process of massive ceramic bricks, considering it a solid means by
Computational Fluid Dynamics (CFD), under the following experimental conditions: drying temperature of 60 °
C and 80 ° C, initial moisture content of 0.001734 and 0.00158 (kg / kg, bs) and relative humidity of 10.1% and
5%, respectively. The massive brick drying phenomenon was studied isolately, considering the drying model by
liquid diffusion. The results of the temperature and volumetric fraction of water inside the brick obtained by the
ANSYS CFX software package ® 19.2. Comparing the moisture and temperature simulated with experimental
data can validate the numerical results, estimating the coefficient of mass diffusion and coefficient heat transfer
from the surface of material. The results obtained in simulations show with the existence of important temperature
and humidity gradients, which areas can shed cracks and deformations.

BEHAVIOR EVALUATION OF THE FLUID DYNAMICS OF A DRYING PROCESS TO OBTAIN ROOF TILES

2024-05-28T22:28:10+00:00

Currently, several researches have been developed on the drying of ceramic materials, most of which
are carried out experimentally. This process requires high investments and energy consumption, resulting in high
costs for companies in the sector. The drying process can be defined as a unit operation that consists of removing
water from porous materials through heat transfer. So, aiming at a better cost benefit, it is common to use
theoretical solutions that allow, with relative ease of replication and low cost, to change operational and geometric
conditions of the dryer or drying object. In this sense, this work aims to predict the drying process of a ceramic
tile in a kiln via computational fluid dynamics (CFD). To carry out the simulations, the commercial package Ansys
CFX® 22.R1 was used. For a drying temperature of 82,7 °C, the results of drying and heating kinetics, product
moisture content, oven air velocity and pressure are displayed and analyzed. A comparison between predicted and
experimental data of the average moisture content of the tile throughout the process was performed and a good
agreement was obtained

Sensitivity Analysis of Hydraulic Fractures for Well Stimulation in Shale Gas Reservoirs

2024-05-28T22:31:02+00:00

Unconventional reservoirs are formations incapable of producing significantly and economically
without the use of massive stimulations, due to low porosity and permeability values. Despite these restrictions,
the unconventional resources were responsible for the increase in the volume of gas production in the US, mainly
with Shale Gas. Among the forms of stimulation of oil wells, hydraulic fracturing is the most used. This technique
consists of injecting a pressurized fluid into the formation until the rock breaks. In this context, the proposed article
aims to evaluate a Shale Gas reservoir with a horizontal well and multiple transverse fractures, where the main
geometric parameters – length, fracture height and spacing between fractures - were combined with different
values to obtain the productivity of these configurations. Furthermore, with the same reservoir properties and
fracture geometric parameters, the permeability was studied for 3 different values, to compare the influence of
permeability on production. The purpose of this study is to, in the future, develop a computational tool capable of
predicting the ideal dimension and spacing of fractures that maximize the recovery factor of Shale Gas reservoirs.
For now, the simulations aim to evaluate the fracture parameters that most influence productivity, through a
correlation matrix.

Computational modeling of a mass concrete structure using a post-cooling system

2024-05-28T22:33:13+00:00

The thermal cracking of young concrete, associated with the high costs and safety requirements of in-
frastructure works, has been a concern of the engineering community since the first applications of mass concrete.

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

high initial stresses, but also because deleterious phenomena such as delayed ettringite formation (DEF) have been
shown to be associated with the existence of thermal fields in the early ages of cementitious material. In this sense,
this work will present the simulation of the construction of a mass concrete structure, on a mesoscopic scale, in
which the temperature of the material is reduced during hydration by the circulation of water in pipes embedded
in the formwork by a postcooling system. The simulation was based on data obtained from the construction of a
concrete slab, previously builded and tested in the laboratory of FURNAS (Goiania/GO). The computational mod- ˆ
eling was performed using the finite element method (FEM), in a parallel environment, developed in FORTRAN
programming language, by PEC/COPPE/UFRJ.

A fem-based approach coupled to path-following strategies for non-linear anaylis of steel-concrete cross-sections

2024-05-28T22:35:50+00:00

The present study aims at the non-linear analysis of steel-concrete composite cross-sections. The strain

compatibility method (SCM) is used to describe the sections deformed shape in each step of the incremental-
iterative solution process. Four-node quadrilateral finite elements (FE) are implemented to compose the FE mesh

of the analyzed sections. For the full analysis of the moment-curvature relationship, the SCM is coupled to path-
following strategies (adapted generalized displacement technique and adapted minimum residual displacement

method) to go beyond the critical bending moment points in the construction of the relations that describe the

complete cross-section mechanical behavior. Concomitantly, the strain-control strategy is implemented as an al-
ternative numerical approach and used for comparison, since the bending moment limit points do not prevent the

complete construction of the cross-section equilibrium path. The constitutive relationships are addressed explicitly,
as well as the residual stresses present in the steel sections. To validate the proposed numerical formulation, the
results obtained are compared with the numerical and experimental data available in the literature.

Optimization of 3d ground-structures with constraints of overlapping bars

2024-05-28T22:38:23+00:00

The ground-structure is a manner of representing solid geometries in an optimization problem. Opti-
mizing mass in ground-structures truss models means leaving the geometry with bars where the main stress chains

occur, i.e., searching for its performance. In real-world applications, describing geometry as a ground-structure
might be beneficial since the results are composed of bars and might be easier to manufacture. Also, depending on
the length of the bar, it might represent multiple elements in a continuous traditional mesh, which will likely reduce
the computational cost of the design’s analysis. The solutions from traditional optimization processes with meshes
consisting of polygonal elements and ground-structure approaches should be quite similar, as this last method has
been largely used lately in literature. This work deals with topology optimization of 3d ground-structures truss
models with constraints of non-overlapping bars and maximum material volume. The algorithm chosen is the
Differential Evolution (DE) coupled with the Adaptive Penalty Method (APM) to handle the constraints.

Thermal analysis of timber cross-sections via CS-ASA/FA

2024-05-28T22:41:04+00:00

When exposed to high temperatures, such as in a fire situation, the physical and resistance characteristics
of the materials employed in the structure deteriorate as the temperature increases. This fact promotes a
considerable loss in the bearing capacity and stiffness of the structural system. The verification of a structure
exposed to fire depends primarily and principally on the thermal analysis of the cross-section of the structural
element. This analysis permits the determination of the temperature variation or temperature range in the element
from the boundary conditions provided by the fire model adopted. Timber, being an anisotropic material, with
irregular fibers, presence of knots and flammable, and widely used in civil construction, becomes a target for the
study of realistic behavior in fire. As such, this study has the objective of performing a thermal analysis in a
transient regime utilizing the finite element method on timber cross-sections that are employed in civil construction
through use of the Computational System for Advanced Structural Analysis/Fire Analysis (CS-ASA/FA module).
Two cross-sections were analyzed, and the results obtained were very satisfactory. Therefore, it is possible to
conclude that the CS-ASA/FA module can yield the necessary information when a thermo-structural analysis is
performed for the evaluation of strength and stiffness losses of the structural material when exposed to fire.

Preliminary model for evaluation of surgical guide in the periacetabular os- teotomy procedure through finite element evaluation, optimization in Ge- netic Algorithms and topological optimization

2024-05-28T22:44:28+00:00

It consists of a preliminary model to evaluate the surgical guide, a tool used in the periacetabular
osteotomy procedure, a highly complex surgery used in the correction of hip dysplasia. A code (”script”) capable of
generating static, simplified and two-dimensional models in finite elements in the software ”ABAQUS”, optimizing
parameters using Genetic Algorithms and performing topological optimization, was developed to evaluate the
guide. The parameters evaluated in the Genetic Algorithm are height of the guide, radius of the screw used to
fix the guide in the bone, distance of the screw in relation to the chisel, clearance between guide and chisel, and
inclination of the chisel. The topological optimization consists in changing the modulus of elasticity in regions
that present the lowest stress values. Through the results obtained, it was possible to minimize the maximum stress
in the guide, obtain better theoretical parameters for the procedure, and obtain a guide that fits better to the bone.
The results obtained through this preliminary study are good indications for the construction of an optimal guide
of great utility in the surgical procedure, in addition to serving as a basis for more complex studies.

A meshfree approach for geometrically exact shear-deformable beams

2024-05-28T22:47:10+00:00

Besides the finite element method (FEM), a number of numerical methods have been proposed in the
literature for the analysis of geometrically exact shear deformable beams, developed to improve the convergence

properties and the shear-locking behaviour exhibited by the finite element method. This paper illustrates some pre-
liminary results obtained with the application of a meshfree method of the family of Smoothed Point Interpolation

Methods (SPIMs) to the analysis of a geometrically exact shear deformable beam. Among the possibilities of shape
functions creation, the so-called edge-based approach with polynomial basis is extended for this one-dimensional
model. A classic example is solved numerically to validate the code. The resulting nonlinear system of equations
is treated by a Newton-like algorithm with load control.

Simulation of wheel defects and train unbalanced loads for smart detection based on wayside monitoring systems

2024-05-28T22:49:21+00:00

Implementation and Validation of a 6-Degree-of-Freedom Nonlinear Model for an Aircraft

2024-05-28T22:56:28+00:00

Aircraft dynamic modeling at SAE Brazil Aerodesign competition has become a fundamental part of
the project to compute the payload and performance characteristics of the aircraft. With each year, the airplanes
become more refined and the analysis for the project, more complex. The need to evaluate in more detail the
behavior of the aircraft arises to ensure flight handling quality and verify that the mission requirements have been
fulfilled, even before building a prototype, specially since the beginning of the COVID-19 pandemic. Thus, in
alternative of the 3 degrees of freedom linear models described in the literature, it is proposed the use of a more
complete model, with 6 degrees of freedom, to describe with more fidelity the flight dynamics of the aircraft. The
implementation, written in Python, computes the movement of the airplane with twelve state variables in each
instant of the analysis, which is done by numerical simulation with either Euler’s or Runge Kutta’s method. It was
observed that the developed software can be used to estimate handling quality parameters with the aeronautical
regulations and, as a result, refine the project towards a more competitive aircraft capable of ranking the team
higher at the national competition.

Geomechanical damage evaluation of fractured carbonate rocks scenarios related to the Brazilian Pre-salt via finite element analysis

2024-05-28T22:59:14+00:00

The structural configuration of the Brazilian Pre-salt oil system took place in a Rift tectonic formation
environment. The presence of faults, joints, breccias, fractures, and microfractures makes the system complex.
Natural discontinuities impact reservoir fluid production because they may be a highly conductive primary flow
pathway in naturally fractured reservoirs. Several factors affect the pathway conductivity, such as the fracture's
state, size, stiffness, and geometry. Moreover, fluid-rock interaction also controls the reservoir fluid production
dynamics due to the hydro-mechanical effects. Our work analyzes the geomechanical behavior of fractures in
naturally fractured carbonate reservoirs. We apply finite elements methods (FEM), the embedded strong
discontinuities methodology, and Barton's constitutive model. The methodology discretizes coarser meshes in the
domain and shows the impact of the fracture aperture as a function of the normal fracture stiffness. The results
show that initial fracture normal stiffness directly impacts the fracture deformability during production, especially
near the wellbore.

A Hybrid–Stabilized FEM Method Applied to Heat Conduction Equation

2024-05-28T23:01:22+00:00

In this work, it is performed a numerical analysis of a totaly discrete formulation for the transient heat
conduction problem. This formulation is constructed by using a discontinuous hybrid stabilized finite element
method in space combined with a high order finite difference approximation (Crank-Nicolson method) for the
temporal dependency. The computational methodology used to solve the formulation is a static condensation
scheme resulting in a global system related only with the Lagrange multiplier associated with the trace of the
temperature at the edges of the elements and local problems that are solved for the temperature. In doing so, the
number of the degrees of freedom of the global system is reduced. Numerical results are presented confirming the
optimal rates of convergence obtained in the numerical analysis.

Parametric optimization of an off-road car suspension system aiming for a compromise between comfort and safety

2024-05-28T23:05:06+00:00

This work addresses the the parametric optimization of an off-road car suspension system. The aim is

to find a compromise between comfort and safety while respecting functional constraints such as maximum de-
flections for the suspension and the tires, as well as the tendency of oversteering on cornering. The vertical vehicle

dynamic is used to evaluate both the comfort and safety criteria for different operational conditions: uniform recti-
linear movement; braking; curves; and longitudinal acceleration. Tires were subjected to base excitation, obtained

from the Power Spectral Density (PSD) of the road profile. The tendency to oversteer on cornering was measured
by comparing the frontal and rear torsional stiffness. The Finite Element Method (FEM) was implemented to solve

the transient equilibrium problem needed to evaluate the comfort and safety criteria as well as the functional con-
straints. The design variables considered in the parametric optimization were the springs and tires stiffness, and

dampers damping. The optimization algorithm used was a modified version of the Particle Swarm Optimization
(PSO). Results show that it is possible to obtain a feasible final configuration minimizing the objective function,
thus improving both safety and comfort criteria.

Robust Topology Optimization of Resonant Structures Considering Uncer- tainty in the Excitation Frequency

2024-05-28T23:07:08+00:00

This article addresses robust continuous topology optimization of resonant structures under uncertain

excitation frequency. The harmonic dynamic response is evaluated by a density-weighted norm and the optimiza-
tion problem is solved by using the Method of Moving Assymptotes. The formulation is assessed by using a

common benchmark problem. Results show that the proposed formulation leads to the design of resonant struc-
tures with improved robustness. Results also show that the mechanism used by the optimizer to improve robustness

depends on the magnitude of the target excitation frequency: at lower frequencies, a low-energy resonance is used
to create an interval around the target frequency with minimized dynamic response variations whereas at higher
frequencies, a pair of high-energy resonances is located at the neighborhood of the target excitation frequency to
create the same effect and improve the dynamic robustness.

High-Order discontinuous boundary elements: Formulation, convergence and performance analysis on 3D elasticity

2024-05-28T23:24:26+00:00

The Boundary Element Method (BEM) is known for its ability to accurately approximate difficult engi-
neering problems in elasticity, such as stress concentration, contact problems, etc. Due to its inherent complexity,

element order has been historically kept as low as possible in the literature, being most of the time restricted to lin-
ear and quadratic elements, as they present an already adequate precision. Due to Green’s function singularities, a

large part of the BEM integration process is performed with high-order Gaussian quadratures, such that increasing
element order is, in many cases, more efficient than mesh size refinement. Moreover, it was recently highlighted
that the singularity subtraction method may impose the usage of high-order elements. This work’s objective is
to investigate the possible effects of employing a p-refinement on some selected benchmark problems. For that
purpose, we present a newly developed library and its formulation for computing arbitrary order shape functions
considering continuous or discontinuous, and Lagrangian or Serendipity type QUAD elements. This library (as
well as the BEM code) is written in GNU Octave, where the shape functions are automatically generated and tested
using a Computer Algebra System. This process avoids the manual implementation of these functions which in
general is cumbersome and prone to errors. The meshes for the benchmark cases are generated using GMSH,
which can generate arbitrary-order QUAD elements. Solution convergence is analyzed in terms of the L2 error
norm. The continuous versus discontinuous element subject is also briefly discussed.

Inference of the modal parameters of a walkway through the clustering and bootstrap techniques association

2024-05-28T23:26:41+00:00

Monitoring the behavior of a structure in operation is essential for the early detection of changes that
may compromise its integrity. This is possible from the identification of its modal parameters, estimated through
the modal analysis of the response signals (continuous in time) of the structure to the actions that act on it. Because
they are estimated, the parameters obtained have uncertainties that significantly interfere with the reliability of
structural monitoring, and therefore their quantification is essential. The principles of systems identification and
experimental estimation have provided, in the last decades, innovative tools for the understanding and control of
vibrations, design optimization, performance evaluation and structural integrity (Rainieri and Fabbrocino [1]).
Several studies have also ratified the efficiency of continuous monitoring of structures in assessing their integrity
(CHENG et al. [2] and SAISI et al. [3]). Thus, there is a need for study and continuous improvement of monitoring
and structural identification systems in order to ensure the safety of existing structures. The objective of this work
is to apply, in response signs of a pedestrian walkway submitted to people walking, a modal analysis methodology
that provides more robust estimates and with lower levels of uncertainty of its modal parameters, through the
association of Data- driven Stochastic Subspace Identification (SSI-DATA), bootstrap and clustering techniques.
Finally, the results found for the uncertainties of the estimated parameters are discussed.

Three-dimensional finite element analyses of monopiles in cohesive soil for offshore wind turbines

2024-05-28T23:29:01+00:00

In the vast majority of offshore wind farms, monopile-type foundations are the most used in the
construction of wind turbines, however, there are limited guidelines available for analysis and design of
foundation/support structures. Although it is a simple structure, its behavior under loads of wind, waves and
currents is very complex. As there is no design standard for offshore monopiles, offshore wind turbines are
designed based on the API standard, which has only been designed for small diameter monopiles; but, for the wind
industry, diameters greater than 4 m are used. Consequently, monopiles are commonly designed for an extreme
load scenario. For this reason, in this article a three-dimensional finite element analysis of the mechanical behavior
of offshore monopiles under vertical, horizontal and moment loads placed in cohesive soils is carried out, since
these soils, by presenting high plasticity, decrease their load capacity and increase their properties. A Modified
Drucker-Prager/Cap model (MDPC) and Mohr-Coulomb model (MC) is used to study the soil and its response to
complex loads. The results of the numerical simulations are presented and compared with the results of the vertical
bearing capacities predicted by the American Petroleum Institute (API) code method and the lateral displacement
at the pile top with the p–y curve method and the LAP GEOCALCS software. The analysis indicates that the
MDPC model has a better prediction of the load-displacement response than the MC model. The prediction of the
stress in the monopile in both models are very similar. The API method underestimated the lateral displacements
of the monopile at large forces and the LAP software predicts a flexible behavior of the monopile.

Numerical study on fiber-reinforced concrete using finite element method

2024-05-28T23:31:43+00:00

Different techniques have been recently developed to increase the tensile and shear strength of reinforced
concrete elements in addition to improving their durability. Fiber-reinforced concrete (FRC) has been the target
of many studies, since it presents a higher tensile strength and toughness when compared to regular concrete,
thus reducing crack growth, and increasing the concrete’s durability. In this study, a finite element analysis was
carried out to simulate the behavior of FRC and normal concrete beams under four-point loading conditions. A
parametric study was set to evaluate the influence of the the steel fibers concentration and stirrups ratios. The
ABAQUS Concrete Damaged Plasticity (CDP) model was used to describe the material’s constitutive behavior.
The ultimate bending capacities of the beams simulated were compared against the models proposed in the ABNT
NBR 16935:2021. Experimental results from the literature were compared to the results were found to be in
accordance with the finite element simulations and with the ultimate flexural capacity analytical solution proposed
by the NBR standard. The study showed that the finite element simulation method using the CDP model predicts
load-displacement curves slightly more stiffer than the experimental results nevertheless in good agreement with
the analytical models proposed by NBR 16935:2021.

A neural network model with finite element method for steel beams design

2024-05-28T23:34:54+00:00

This work aims to create an artificial neural network model to assist steel beam design either beam profile
and its connection with the column. The input data for the model are the beam length and the applied distributed
load. The output data are the beam profile, the connection angle profile, and the number and diameter of connection
bolts. We selected for training 10 W-type profiles, 3 angle-type profiles, and 2 bolt diameters. The data for training
the neural network has been acquired from the design results according to the Brazilian standard NBR-8800:2008
criteria. The bending moment and shear forces have been calculated from beam internal stresses. The internal
stress diagrams have been obtained from the finite element method (FEM) results. The beam analysis with the
FEM has been carried out with a flat shell quadrilateral element (plane stress plus Kirchhoff-Love plate effects)
for profiles and a three-dimensional frame element for bolts. All nodes at the hole edge and the bolt element in the
same plane are coupled. The modeled neural network has been evaluated with its confusion matrix and its accuracy
in indicating configurations that attend the design criteria. The results show a good prediction performance and
errors obtained are acceptable when compared to the level of safety factors of structural engineering.

Study of Ballistic Parameters for Projectile Range Extension

2024-05-28T23:36:45+00:00

The external ballistics of an artillery shell requires an understanding of aerodynamics in compressible
flow. In this context, computational fluid dynamics (CFD) techniques are used because real tests with ammunitions
are more expensive than numerical simulations. The purpose of this study is to simulate the use of downstream hot
mass flow injection, which is technically called base bleed, because it increases base pressure to an optimal value
that reduces base drag, which is the main component of the total aerodynamic drag. The compressible, stationary
and two-dimensional axisymmetric flow around the projectile is simulated and analyzed. For the simulations,
the SST k-ω turbulence model is used, based on the Reynolds means (RANS). The results are compared with a
specific commercial program for application in weapons ballistics. The main results are the velocity, pressure and
temperature fields; in addition to obtaining drag coefficients for different situations of boundary conditions.

Representative computational mechanical simulation of a penstock reinforced transition block

2024-05-28T23:38:46+00:00

This work describes the numerical-computational mechanical simulation of a hydroelectric plant wa-
ter intake (penstock) transition block, in reinforced concrete, evaluated according to the premises of ABNT NBR

6118/2014 standard. The computational mechanical simulation performed, based on the finite element method

(FEM), discretized the block in three-dimensional tetrahedral solid elements and the reinforcement in three-
dimensional single-line elements. Author based the analysis on loads in service, i.e., safety coefficients have

not been used to reduce the resistance of the material or to increase the self-weight and hydrostatic loads. Author

have carried out a results analysis of the block concrete using the Willam-Warnke criterion of failure. In the rein-
forcement, author have used the safety factor as a function of the resistance of each bar. The results showed the

block has enough structural integrity to not suffer structural failures in service.

Analysis of the critical crack size and operational factors in tensile armors of flexible pipes.

2024-05-28T23:40:25+00:00

Oil & Gas companies have been looking for new hydrocarbon deposits in deep and ultradeep waters.
However, this scenario has shown numerous challenges related to exploiting these natural resources, forcing the
offshore industry to invest in new technologies to resist extreme environmental conditions and increase operational
safety. Therefore, understanding how to evaluate crack behavior in offshore structures is essential as it helps predict
the equipment’s service life, reduces the cost related to inspecting, and avoids accidents. Hence, this work studies
crack propagation in tensile armors of flexible pipes considering corrosive environments. The cross-section of the
analyzed tensile armors was assumed to be rectangular, and the nonlinear material response was represented with
the Ramberg-Osgood model. Finally, two-dimensional (plane-stress) finite element (FE) models were constructed
to evaluate the effect of cracks in these armors. The FE models estimated the energy release rate (J−integral)
and stress intensity factor (KI ) when cracked armors were under operational loadings. The BS7910 standard’s
equations calculated the fracture parameters as well. Then, the responses obtained with both models helped to
elaborate on the failure assessment diagram (FAD) level 1. These analyses allowed an understanding of the wire’s
capacity for several crack sizes and operational loadings.

Thermomechanical analysis of early age concrete by computer modeling

2024-05-28T23:43:00+00:00

This study describes a procedure for the analysis of concrete structures where thermal properties are
investigated in a finite element model to predict the temperature and stress profile elements due to the hydration
process at early ages. An exponential function is used to determine the degree of hydration of the concrete; the
temperature-dependent thermo-physical parameters are considered, and the external heat loss by convection. The
commercial software ABAQUS was used to carry out the study and FORTRAN subroutines were developed to
allow solution-dependent material properties in the calculation of thermal stress (taking into account the rising of
Young's modulus). The main data are obtained from the literature and adjusted for this specific study, to predict
the evolution of temperature and the tensile tendency of a concrete structure in the initial hours. The numerical
results obtained in this work are well correlated with the literature values. The results show the thermal-stress
behavior of a concrete block during the early age, taking into account the variation of elasticity modulus and also
the weather conditions of Curitiba.

BIODYNAMIC MODELING OF THE HUMAN ACTIONS IN THE DYNAMIC ANALYSIS OF FOOTBRIDGE

2024-05-28T23:45:28+00:00

Civil structures such as footbridges and floors are commonly subject to dynamic loads due to human
activities such as walking, running and jumping. Currently there are several light and slender structures with low
natural frequencies, which are susceptible to human actions, generating discomfort and structural safety risks
problems. In most cases the human induced loads on footbridges are considered as equivalent static loads or as
moving loads. This paper presents a biodynamic modeling of human walking or running on footbridges,
considering people as a simple spring-mass-damper system. The dynamic analysis was based on the finite element
method and implemented using Scilab open-source software for numerical computation. The results showed that
crowd load can significantly change the responses in relation to the moving load because of the addition of mass
and damping to the system and due the dynamic interaction between structure and people.

A Multiscale Model to Simulate the Bone Remodeling Process

2024-05-28T23:47:53+00:00

Bone tissue is a living material under constant activity. Bone response to an external stimulus application
causes renewal of its local properties by the bone remodeling process. The synchronized activities of three bone
cell lineages are related to the process. The osteoblast lineage is responsible for bone formation, while the
osteoclasts are responsible for the resorption process. Finally, the osteocytes cells provide mechanosensitivity to
the bone tissue. An important factor for controlling the cell activity is the OPG-RANKL-RANKL pathway.
Another characteristic of the bone tissue is its multiscale behavior. The behavior at the microscale influences the
properties at the macroscale. In this sense, this study aims to develop a model for simulating the bone remodeling
process. This model considers mechanical, chemical, and biological variables, and the bone multiscale. We use
the finite element method to analyze the remodeling process by using Abaqus and Matlab software. The biological
model considers the interactions between osteoblasts and osteoclasts. Also, the model considers the control
performed by the OPG-RANKL-RANKL pathway. We determine the mechanical stimulus at the microscale using
a representative volume element (RVE). This stimulus interacts with chemical factors. This interaction controls
the bone cell evolution that changes the RVE's volume fractions. Thus, the volume fractions evolution influences
the mechanical properties at macroscale (density and elastic modulus). The BR model allowed characterizing the
structural morphology of a human femur. We observed its main characteristics.

Design, simulation and validation of a viscoelastic damper for structural vibration reduction

2024-05-29T01:02:42+00:00

Passive dampers are used to reduce structural vibration levels in a wide range of applications. Rubber
is still one of the most widely used materials. However, to simulate the viscous-elastic properties, complex
dynamic models are frequently required. In this project, we designed, synchronized, and built a viscous-elastic
damper for use on a steel frame structure. FRF was used to identify the structure's initial modes, and vibration
levels were measured using a shake table and an impact hammer. To describe and simulate the entire system, Finite
Element Models were developed. To linearize the viscous-elastic damper behavior we built a sample and tested it
to estimate equivalent proprieties values. Based on those equivalent properties, the mass and shape of a new sample
were adjusted to synchronize the frequency and optimize the damper effect. The resulting geometry was fabricated
and applied at the structure. The structure was excited over again and the vibration levels were compared to
previous results. The results show a 48.7 percent reduction in vibration levels with only a 8.3 percent increase in
mass (damper mass). The experimental tests and simulation comparison also demonstrates good agreement.

NUMERICAL SIMULATION OF THERMOCAPILLARY FLOW 2D AND 3D: A BI-PHASE SMOOTHED PARTICLE HYDRODYNAMICS APPROACH

2024-05-29T01:05:32+00:00

This work presents a Smoothed Particle Hydrodynamics (SPH) method for modeling the heat transfers,
natural convection, and thermal Marangoni effects at the interface with density variation and bi-phase fluid flows
in two and three dimensions. A capillary interface (surface tension) scheme was implemented with the Continuum
Surface Force (CSF) model and the approximation of the SPH to the Navier-Stokes equations for delimiting stable
interfaces and smooth bi-phase to allow the simulation of flows between liquid-liquid and liquid-gas. Moreover,
the solution strategy with SPH for the combination of temperature gradient (heat transfers), gravity, and surface

tension, as required for modeling the Marangoni forces, is verified with related cases of study. Problems of ther-
mally driven flow and Bernard convection in cavities are studied to validate the heat transfer and convection. The

solutions are displayed in respect of temperature, velocity fields, and Nusselt number, with different Rayleigh
numbers (Ra) regimes (103 ≤ Ra ≤ 106

). Thus, the bi-phase method applies the thermo-capillary flow, in the
migration rises a droplet due to a surrounding fluid with a linear temperature gradient. In these cases, different

aspects of the dynamics of the thermo-capillary flow were considered for verification. Finally, the numerical ex-
amples show that the SPH and CSF proposal is efficient, reliable, and with good precision in modeling inter-facial

flow problems under hydrodynamic and thermal influences.

A position-based Space-Time formulation for geometrically nonlinear problems

2024-05-29T01:10:42+00:00

Space-Time finite element methods has been developed over years for solving a series of time-dependent

Development of a computational routine in Fortran language for analysis of plane and space trusses using the finite element method

2024-05-29T01:13:09+00:00

Computational tools applied to the teaching and learning of structural analysis have been increasingly
developed and improved to optimize computational time and cost. The method to solve the analysis, the language
to be chosen, the organization of the algorithm, as well as the programming paradigm adopted, are factors that
must be taken into account in numerical analysis. Thus, this paper aims to study the behavior of 2D and 3D trusses
in the linear-elastic range using a code developed with Fortran programming language, showing the importance
of computational application and numerical methods in civil engineering. To solve this problem, the bar finite
element formulation was used. Three different benchmark examples were analyzed and verified with a commercial
software, one plane truss and one space truss. The results of these structures in stresses and displacements were
compared with MASTAN2, proving the efficiency of the built algorithms to solve the studied problems.

NUMERICAL-EXPERIMENTAL ANALYSIS OF THE PERFORMANCE OF AN EARTH-AIR HEAT EXCHANGER (EAHE)

2024-05-29T01:18:29+00:00

Studies have been searching for new ways to lower energy demand in air conditioning conditions
because heating and cooling make up a sizeable component of global energy consumption. As a result, discussions
about building energy efficiency and the active and passive solutions needed in thermally inefficient design
projects have increased in recent years. Soil may be used as a renewable energy source, and the employment of
passive solutions in these projects has proven beneficial for energy savings. Due to its high thermal capacity, the
soil can act as a large thermal reservoir, largely independent of the climatic conditions of the surfaces, adding or
removing heat from the ambient air inside the buildings. This study investigates the effectiveness of an earth-air
heat exchanger (EAHE) in heating or cooling air in various environments. The system, which includes 100 mm
diameter Polyvinyl Chloride (PVC) ducts, 2" galvanized steel pipes, and a fan for airflow control, was built on the
premises of the Federal University of Technology of Paraná (UTFPR) Campus Ponta Grossa. The pipes were
insulated to prevent heat loss along the way, and a series of k-type thermocouples were inserted along the EAHE,
the ground, and the environment. Temperatures were recorded hourly over four days in January 2022 using a data
acquisition system. From the data of the experiment, a numerical analysis was performed to evaluate the
temperature variation, heat removed, and to calculate the coefficient of performance of the heat exchanger and
compared with the experimental results. Despite the thermal gains of radiation in the system and in the ground,
the consequent increase in the inlet temperature of the exchanger, and the relatively low COP, positive results were
obtained in the removal of heat from the environment, factors such as the high power of the fan and the climate in
the region were crucial to ensuring that results did not improve.

Numerical Simulation of Oil and Water Displacements in Petroleum Reservoirs using a Multipoint Flux Approximation Method Coupled to a Flux Corrected Transport with a Flow Oriented Formulation

2024-05-29T01:22:07+00:00

The numerical modeling of multiphase and multicomponent flow in oil reservoirs poses a great
challenge and demands the development of robust and computationally efficient numerical formulations. Common
reservoir simulators are based on the combination of the classical Two Point Flux Approximation (TPFA) for the
discretization of diffusive fluxes and the First Order Upwind (FOU) method for the discretization of the advective
fluxes in the fluid flow equations. In certain cases, particularly for high mobility ratios between the injected and
the resident fluids, the numerical solution may strongly depend on the alignment between the flow and the
computational grid, this is known as the grid orientation effect (GOE). This effect is linked to the anisotropic
distribution in the truncation error associated to the numerical approximation of the transport term. Another
problem occurs when non monotonic solutions are obtained whenever using highly distorted meshes. Besides, the
standard TPFA method may not converge at all to an adequate solution when the grid is non k-orthogonal. In this
context, in the present paper, our main goal is present a full cell centered finite volume formulation for the
numerical simulation of oil-water displacements in oil reservoirs using a segregate formulation in general
unstructured and non k-orthogonal 2D meshes. For the discretization of the diffusive fluxes, we use a Multipoint
Flux Approximation based in Harmonic Points (MPFA-H) and for the discretization of the transport term, we
present a modified version of the 2nd order Flux Corrected Transport (FCT) approach to reduce artificial numerical
diffusion and we also use a Flow Oriented Scheme (FOS) in the computation of the low-order approximations
used in our modified FCT scheme. The FOS philosophy consists in using weights that are properly adapted to the
flow direction, turning our scheme into a truly multidimensional approximation in order to reduce GOE. Our
strategy was tested against one benchmark problem available in literature, producing very accurate results with
reduced artificial numerical diffusion and GOE.

Risk analysis in corroded buried pipelines

2024-05-29T10:31:14+00:00

Transporting fluids such as oil and gas through corroded pipelines presents economic, human and

environmental risks. This work aims to make a qualitative and quantitative analysis of these risks, based on DNV-
RP-G101 (2010). To measure it, it is necessary to analyze the failure probability through structural reliability

methods. Programming was made using MatLab software. For the use of the FORM and Pure Monte Carlo,
statistical data of random variables such as thickness and diameter of the pipe, internal pressure and defect depth
are used. The failure function is defined here by the difference between the failure pressure and the acting pressure
in the pipeline. For this, the failure pressure is calculated applying the method proposed by the practical
recommendation manual, the DNV-RP-F101 (2015). In possession of the failure probabilities, which are obtained
in the reliability methods, it is made the risk analysis of the buried corroded pipelines. Therefore, it is possible to
analyze and compare results obtained in this analysis, aiming a greater safety with less cost.

Collapse strength of worn casing tubes from wear log inspection

2024-05-29T10:34:58+00:00

Oil wells are drilled by depth intervals with different diameters, which usually get smaller when it gets
deeper. When the bottom of a phase is reached by the drill bit, it needs to be cased, cemented, and tested. The inner
wall of the casing string will always be subject to the drill string’s intense contact and rotation. The friction will
remove material from the casing tube, reducing its strength. The current deep wells with directional trajectories
and severe tortuosity increase the casing wear making its assessment even more relevant for structural integrity
purposes. This work proposes a methodology to estimate the collapse strength of worn casing tubes using
inspection data of oil wells integrated with nonlinear Finite Element Analysis (FEA). The methodology starts by
identifying wear grooves from an ultrasonic log (US) by applying a strategy from the literature. Then, an equivalent
cross-section geometry is proposed, in which the identified wear grooves are inserted, emulating the most likely
original geometry, since the inspected shape is deformed. Although inner radius and thickness data for many cross
sections of the casing string also become available with the inspection, the boundary conditions are not known,
e.g., pressure and temperature. Due to this, FEA performed with this scanned geometry will result in an unrealistic
estimate of the tube strength. The 2D numeric simulation is performed in Abaqus with the equivalent geometry to
estimate the residual strength of the worn casing tube. A nonlinear approach is necessary because the collapse of
a tube is an instability problem. It is observed that the stress concentration in the groove wear zone reduces the
resistance. The results show that the multiple wear grooves observed from the inspection can significantly reduce
the strength of the tube. However, most works found in the literature are concerned with only one wear groove in
their modeling, since the inspection data is not accurately interpreted. A case study is presented to demonstrate
this contrast.

Three-dimensional numerical simulation of the dynamic behavior of slopes of the Costa Verde cliff - Armendariz Sector

2024-05-29T10:37:57+00:00

In this research, slope stability was evaluated in dynamic terms, specifically in the Armendariz descent,
by means of three-dimensional numerical analysis using the finite element technique and finite differences, where
the parameters were calibrated for static and dynamic conditions by means of large-scale tests and wave
propagation, respectively. For the estimation of the parameters under static conditions, the elastic-plastic response
trajectory of the large-scale direct shear test was taken into account and compared with the numerical model with
the same test characteristics until the soil parameters were found by curve fitting (comparison with the response
of the in-situ test). For the estimation of the parameters under dynamic conditions, comparisons were made
between the dynamic responses, in terms of accelerations, recorded instrumentally with the three-dimensional
dynamic wave propagation analysis, considering the soil stratigraphy and the geometric configuration of the
slopes.

USAGE OF THE NEURAL NETWORK TO PREDICT MEAT TENDER- NESS APPROACH

2024-05-29T10:40:21+00:00

Meat tenderness is one of the main qualitative attributes sought after by consumers when purchasing
beef. Among the various properties of meat, tenderness is one of the most appreciated by the public that buys this
type of food. The tenderness of the meat is influenced by several factors in the constitution, from genetic, food,
and environmental factors is the tenderness evaluated in the post-mortem of the animal is a direct and objective
measure to be quantified. This property is obtained through mechanical tests already known in the literature, by
obtaining the shear force necessary to break the set of muscle fibers of the tissue examined. In this way, this paper
estimates the tenderness of the meat in a non-destructive way through the use of computational techniques using
machine learning, such as the use of artificial neural networks, to quantify the dependence of variables that can be
obtained without the destruction of the sample, but that obtain a satisfactory approximation in obtaining the shear
force of the analyzed beef tenderloin samples. Thus, to evaluate the tenderness parameters, measurements made
from tests were used for the values of PH, sample color, hot carcass weight, loin eye area, breed, sex, infrared and
ultraviolet images, and shear force of fillet samples. In this way, the objective of the neural network was to find the
dependence of the variables on the shear force necessary to break the fibers of the sample. For this, a cross-data
model known as Random Forest was used for training neural network was performed based on the present data, and
an average error of 20% was obtained compared to the value obtained for the shear force through the mechanical
test. It was observed that the shear force prediction values are directly influenced by the number of variables to be
introduced in machine learning, as well as the number of observed samples.

Numerical Simulation of Multiphase and Multicomponent Fluid Flow in Petroleum Reservoirs Using a Fully Implicit Formulation

2024-05-29T10:43:14+00:00

Of the many techniques and tools used for estimating oil and gas production in the recovery processes,
compositional simulation model is important for problems with complex phase behavior, as in the application of
Enhanced Oil Recovery (EOR) methods. The solution of the compositional model involves spatial and time
discretization schemes and approaches for handling the coupling of fluid flow and phase behavior. Several solution
algorithms arise from combining the different selection of primary variables and decoupling techniques. In this
work, we present a Fully Implicit (FI) formulation using cartesian grids for the compositional reservoir simulation
based on Equation of State. For the diffusive terms of the equations that describe the mathematical model, we
discretize by the Two-Point Flux Approximation (TPFA) finite volume method, while in the advective terms, we

apply the first-order upstream weighting. So far, the implemented model considers isothermal flow, up to three-
phase flow, and that there is no mass transfer between water and hydrocarbon phases. Physical dispersion and

capillary pressure effects are neglected. Our FI formulation is evaluated by solving a benchmark problem found
in literature and the results are promising, providing a basis for future implementation of a non-isothermal model
to simulate EOR problems, such as steam injection.

Analytical and numerical comparison of bearing capacity of strip foundation on slopes

2024-05-29T10:45:51+00:00

Several engineering projects such as buildings, transmission towers and bridge abutments are founded
in areas adjacent to a slope. When this occurs, the behavior of the foundation is affected by presence of the slope,
which modifies its bearing capacity and failure mechanism of the ground, being substantially different from that
developed by footings on horizontal geomorphologies. In 1957, Meyerhof was a pioneer in developing a theory to
determine the bearing capacity of a foundation in areas adjacent to a slope, and his work was complemented by
several researchers in later years and is still under study today. This paper presents a comparison of the available
methods developed by different authors to estimate the bearing capacity of a strip footing at the top of the slope.
In addition, the calculation of the bearing capacity is determined using the finite element method with the Abaqus
program. Finally, a parametric numerical study is carried out on the effects of slope height, distance to the footing
crest/width and soil strength parameters and slope angle are found to be the most influential. In the end it is
concluded that the analytical solutions have limitations, and the numerical model turns out to be faster and the
changes can be better appreciated.

Mechanical model comparison using Sobol’ indices

2024-05-29T10:48:45+00:00

Models are mathematical representations capable of describing phenomena in different scenarios. Usu-
ally, two or more models are available for the same phenomenon, which leaves the choice of the most suitable

model to the user. In practice, simplified models can be as precise as more refined ones and, simultaneously, less

demanding in terms of computational power. In this work, we present a novel approach for measuring the discrep-
ancy between models when considering the randomness of the variables. We first define a uniformly distributed

random variable that chooses which model is employed to evaluate the response. A global sensitivity analysis
(GSA) is then performed by determining Sobol’ total index of the response with respect to this variable. The result
reveals the importance of choosing between one model or another and indicates the level of discrepancy between
them in the stochastic context. Two numerical examples are presented, indicating the kind of insight the proposed
approach produces.

Limit Plastic Analysis of a Structural Concrete Block Wall

2024-05-29T10:52:25+00:00

At this paper, it is searched the maximum collapse load of a structural concrete block wall. Simulations
are made considering the removal of resistant material, such as the installation of a door or openings motivated by
modifications at the architectural project. A mathematical programming using the Coulomb and Von Mises criteria
is used at the limit plastic analysis assuming the basic hypothesis of associated plasticity. It is used a polyhedral
representation of the yielding surface studying the convergence of the results in relation of the chosen number of
planes at each representation. It is used the hybrid finite elements formulation. Numeric examples are shown for
the structural concrete block wall case, considering different finite elements meshes and the obtained results are
compared with those of the analytical analysis that exists at the criteria adopted by the Brazilian concrete block
structure project Standard - NBR 10837. Keywords: structural concrete block, hybrid finite elements, limit plastic
analysis. Theme: research and testing.

Numerical Modelling of Skin Tumor Diagnostics through Dynamic Thermography

2024-05-29T10:55:09+00:00

Dynamic thermography has been clinically proven to be a valuable diagnostic technique for skin tumor
detection as well as for other medical applications such as breast cancer diagnostics, diagnostics of vascular
diseases, fever screening, dermatological and other applications. Thermography for medical screening can be done
in two different ways, observing the temperature response under steady-state conditions (passive or static
thermography), and by inducing thermal stresses by cooling or heating the observed tissue and measuring the
thermal response during the recovery phase (active or dynamic thermography). Both methods have been used for
medical applications; however, recent research on dynamic thermography has shown many advantages over static
thermography. The numerical modelling of heat transfer phenomena in biological tissue during dynamic
thermography can aid the technique by improving process parameters or by estimating unknown tissue parameters
based on measured data. This paper presents a nonlinear numerical model of multilayer skin tissue containing a
skin tumor, together with the thermoregulation response of the tissue during the cooling-rewarming processes of
dynamic thermography. The model is based on the Pennes bioheat equation and solved numerically by using a
subdomain boundary element method which treats the problem as axisymmetric. The paper includes computational

tests and numerical results for Clark II and Clark IV tumors, comparing the models using constant and temperature-
dependent thermophysical properties, which showed noticeable differences and highlighted the importance of

using a local thermoregulation model.

Core flood in porous micromodel made of glass

2024-05-29T10:59:20+00:00

Research using microdevices related to the flow in porous media are widely developed by the oil
industry, aiming to understand the behavior of fluids, the interactions between the phases and the porous structure,
and to increase the hydrocarbon recovery factor from the reservoirs. The objective of this work was to reproduce
core flood test that was done on a rock but using a microdevice and the same fluid from the Brazilian pre-salt.
Complex porous mesh micromodel was obtained through simulation, made of glass, and aged with crude oil, thus
changing its wettability for oil wetting. Synthetic desulfated seawater (DSW) was injected as secondary recovery,
at room temperature, with a flow rate of 1cm3/h and a bump flow of 2cm3/h. The experiment was recorded with
high resolution images and a computer simulation was performed for the DSW velocities inside the micromodel.
As a result of the image analysis, the recovery factor was calculated, which after the injection of 100 pore volumes
was approximately 11,21 %. With the increase in flow, 7,92 % more oil was produced. With this, the fabricated
microdevice has shown that it can be used to better understand fluid distribution and oil production in a core flood
test.

Adaptive Importance Sampling for Reliability Analysis

2024-05-29T12:57:56+00:00

Several numerical schemes have been proposed in the last decades to address the problem of reliability
analysis (i.e. evaluation of the probability of failure). Among these, a very popular method is Importance Sampling
(IS), where the probability distribution employed for sampling is different from that of the random variables. It is
known that by appropriate choice of the sampling distribution it is possible to reduce the variance of the estimate
and thus obtain more accurate results. However, it is often difficult to known beforehand what is an appropriate
sampling distribution for IS in practice. In order to avoid this difficulty, in the last years researchers developed
Adaptive Importance Sampling (AIS) techniques. The idea of AIS is to take an initial sampling distribution, draw
a sample, evaluate the required statistical moments and then improve the sampling distribution using some update
rule. In this work we compare some of the existing AIS techniques in the context of Reliability Analysis.

Numerical Analysis of an Embedded Pile in Fractured Rock

2024-05-29T13:03:03+00:00

The determination of the load capacity of deep foundation elements is complex and requires the
definition of a good physical and mathematical model that expresses an adequate approximation of the installation
process, interaction mechanisms and the failure mode. In particular, piles embedded in rocks add difficulty to
predictions due to scarcity of specimen tests of the rock to define appropriate stress-strain relations, and
information about rock integrity in field. To overcome these issues, the Brazilian national practice of deep
foundations uses semi-empirical methods to predict load capacity validated with loading tests. In this context, the
present work presents a load capacity analysis of a deep foundation element embedded in rock using finite element
approach which is directly compared with axial compression static loading test, and semi-empirical predictions.
The pile was modeled considering elastic behavior, soil layers and fractured rocks were modeled considering the
elastoplastic model of Mohr Coulomb. Interaction mechanisms were modeled considering a normal rigid contact
behavior and penalty for tangential behavior. Results of two analyzes were presented in the paper: an analysis
defined considering a set of parameters derived based on in situ investigation (Standard Penetration Test - SPT
and Cone test - CPT) and; a parametric analysis to investigate the influence of the interaction coefficient. The
results presented contribute to the understanding of the behavior of embedded piles in situ and aims to help in the
definition of suitable models for prediction in future works.

Cooperative transport of objects by multi-robots

2024-05-29T13:05:53+00:00

Coordinated transport of objects by robotic swarms can be advantageous when the object to be trans-
ported is too large and/or too heavy to be effectively handled by a single robot alone. This type of operation

requires coordination and synchronization of the pushing forces, which are to be exerted by the robots in order for
the object to be transported successfully. In this paper, a new algorithm called Cooperative Object Transport is
proposed. The algorithm has four stages. The first stage implements the object search done by the swarm robots.
The second stage of the algorithm starts when a robot finds the object. It then recruits the other robots. During
the third stage, each robot first computes and then goes towards the location where it must position itself around
the object to cooperate in the pushing actions required for executing the transport properly. When the positioning
of all robots around the object is completed, the fourth stage of the algorithm begins. From then on, the robots
start alternating between pushing and re-positioning actions in order to keep the object moving along the expected
transport trajectory. This procedure is executed until the object is actually homed. In this work, the implementation
of the object search stage is inspired by the strategy used by ant colonies during their foraging for food sources,
depositing pheromones along the traversed paths. The proposed algorithm is implemented in GRITSBot swarm
robots, using Robotarium. We evaluate the impact of ant foraging strategy on the overall collective transport task
in swarm robotics, comparing it to a random object-seeking strategy. The achieved results prove that the proposed
algorithm is effective yet efficient in finding the shortest path while looking for an object. This allows for an
efficient execution of the transport stage of the sought object from its original location to the intended warehouse.

Gaussian Adaptive PID control (GAPID) and the Fuzzy logic PID control (FLPID) Tuned by Particle Swarm Optimization for a speed control in a BLDC motor

2024-05-29T13:08:41+00:00

The usage of Brushless Direct Current Electric Motors (BLDC) is each time more frequent in indus-
trial appliances such as the automobile segment. In such application the BLDC motor is exposed to many types

of charge disturbances which makes the conventional control methods, such as proportional–integral–derivative
controller (PID), not reaching its variables with precision in cases of sudden perturbation and variation of the

parameters. Thus, the PID controller might have its performance improved with the application of adaptive tech-
niques which collect data from the operating system environment and make adjusts based in the condition where

it is found. In this case, two techniques are chosen: the Gaussian Adaptive PID Control (GAPID) and the Fuzzy
logic PID Control (FLPID), choosing its parameters is not an easy task, although they can be obtained through the
usage of optimization techniques, such as the Particle Swarm Optimization (PSO), ensuring a better performance
and robustness of the GAPID and FLPID compared to the linear PID by load and gain sweep tests, achieving
fast response and minimal variation. This paper aims to accomplish the comparison between different control
techniques for the speed control in a BLDC motor and its practical implementation in a ESP32 microcontroller.

A Variational Full-Network Constitutive Model with Anisotropic Damage and Viscoelasticity Induced by Deformation for Biological Tissues

2024-05-29T13:13:22+00:00

Rubberlike materials, such as soft biological tissues, may exhibit high nonlinear inelastic responses
when subject to large strains. Also, anisotropic inelastic behaviors induced by deformation are observed in the
literature. The anisotropic behavior associated with coupled inelastic effects has been a major challenge in the
constitutive modeling of materials. Then, this paper presents a variational full-network model capable of
representing coupled anisotropic damage and viscoelasticity responses induced by deformation. The proposed
model combines the advantages of the full-network and variational frameworks, resulting naturally in a set of
scalar minimization problems. The inelastic scalar variables at each material point are related to the quadrature
points directions used in the full-network integration scheme, and their evolution is assessed graphically in a very
intuitive way. A numerical inflation test of a plate is presented to explore the ability of the proposed model to
represent anisotropic damage and viscoelasticity and maintain accuracy for large deformations and increments.

Automatic segmentation of breakouts in acoustic borehole image logs using convolutional neural networks

2024-05-29T13:16:01+00:00

Breakouts are collapsed zones on borehole walls caused by compressive failure. The identification
of breakouts in wellbores is fundamental for estimating the stability of the well and to obtain the magnitude of
the maximum horizontal stress present in the rock formation. Traditionally, professional interpreters identify and
characterize breakouts manually, which can be considered a very time-consuming task due to the massive size of
the borehole data. Due to the complexity of the structures of interest and several noisy artifacts in the image log,
traditional image processing methods are not very effective in solving the problem. The U-Net proposed by Olaf
Ronneberger et al. is a convolutional neural network model commonly used in medical image segmentation that
has been applied on several areas. This architecture is composed of two parts: the encoder, which is used to capture
the image context, and the decoder, which is used to allow a precise location using transposed convolutions. A
series of changes in this architecture has been proposed to improve the network’s capacity to extract features in
multiple scales and improve the skip connections between encoder and decoder. The DC-UNet (Dual Channel
U-Net) is one of the U-Net based models designed to overcome some limitations of the original network. In
this work, we present the application of DC-UNet for breakout segmentation in wellbore’s amplitude image logs.
Furthermore, we also discuss the problems related to the inaccuracy of the data’s annotated masks and the image
pre-processing strategies applied to reduce their effects.

Cubic nonlinear stiffness and quadratic nonlinear piezoelectrical coupling on the dynamic behaviour of an aeroelastic energy harvesting system

2024-05-29T13:23:19+00:00

Nonlinear aspects of energy harvesting have been extensively investigated in the last 10 years for two

main reasons: improve the accuracy of the mathematical models of systems that inherently present nonlinear be-
haviour, and to intentionally introduce nonlinear behaviour to the system in order to improve the harvesting perfor-
mance. In this paper, we show the contributions of cubic nonlinear stiffness and quadratic nonlinear piezoelectrical

coupling on the dynamic behaviour of an aeroelastic energy harvesting system. To analyse each case analytically
the method of multiple scales is used. The application of nonlinearity can make systems difficult to solve. Multiple
scales is an analytical method to provide an approximate expression of the response of a system. This method work
for small periodic finite movements in the vicinity of a equilibrium. One of the advantages of this method is that
it allows solving equations in the presence of damping and nonlinearity. Numerically, the response is calculated
using a 4th order Runge-Kutta method. The amplitude related to plunge, pitch and voltage degrees of freedom as
function of the wind speed is analysed for different values of cubic and quadratic nonlinearity. The results indicate
that amplitude decreases when cubic nonlinear stiffness and quadratic nonlinear piezoelectrical coupling increase.
It is important to observe that the results show good agreement in the LCO amplitudes only near the bifurcation.

Dynamic analysis of prestressed concrete beams in service

2024-05-29T13:28:13+00:00

The study and improvement of research related to the structural dynamics are more relevant to each
development leap of new techniques and materials used in constructing new buildings. These buildings have been
designed with a bolder look due to advanced technical regulations for using concrete and steel with high strength.
These constructions have become more susceptible to actions that can generate significant vibrations in the
structure and make them increasingly efficient, which requires intelligent vibration control. Allied to these factors,
the evolution of theoretical models allows an accurate analysis of the system, which architects and structural
engineers widely explore. The dynamic analysis of concrete beams submitted to these actions is justified because
these elements undergo a high degree of bending during service, resulting in a significant stiffness loss by cracking.
The prestressing applied to these structures has become an effective and widely used technology, avoiding, in most
cases, the development of tensile stresses, allowing the maintenance of stiffness necessary for vibration control
during service. This work investigates the dynamic structural behavior of a reinforced concrete beam during its
service. Its behavior is studied due to vertical loads in operation and axial loads from the prestressing action.
Besides, the influence of the fundamental dynamic parameters in beam behavior is verified due to these actions.
The results obtained are compared with the recommendations prescribed in the national and international codes.

Implementation of a non-intrusive approach using a global-local strategy for the Generalized Finite Element Method

2024-05-29T13:31:48+00:00

In general, the standard finite element method available in most commercial software faces difficulties
solving complex structural problems. The Generalized/eXtended Finite Elements Method (G/XFEM) is a powerful
tool for the solution of the class of problems involving discontinuities and singularities such as crack propagation
analysis. In recent years, several investigations have been proposed to make G/XFEM available in the industry
routine. A trend is the complementary bundling of commercial FEM codes with in-house G/XFEM codes,
requiring non-intrusive coupling between these two types of software. This work presents the implementation of
a non-intrusive coupling of multiscale iterative analysis by G/XFEM using global-local enrichment functions
(IGL-GFEMgl). The problem is decomposed into three scales. Commercial FEM software may perform the global
simulation, but here, the same in-house software is used to evaluate these results. G/XFEM global-local code
handles meso and local scale in the INteractive Structural ANalysis Environment (INSANE), an open-source
software developed at the Federal University of Minas Gerais. The meshes of the two bigger scales are conform
and the coupling between them is straightforward established. The Iterative Global-Local (IGL) strategy accounts
for displacement compatibility and force balance at the interface between global and mesoscale. Numerical
examples are presented to evaluate the performance of this strategy.

AERODYNAMIC LOAD IN SILO DESIGN

2024-05-29T13:34:11+00:00

Metal silos are thin structures composed mostly of steel sheets intended for grain storage. When empty
and exposed to wind action, they are susceptible to the phenomenon of instability, thus characterizing the critical
state of the structure. The instability of these profiles occurs from the formation of vibration modes leading to loss
of local stability. To guarantee the integrity of the structure, transverse stiffeners are added, increasing the rigidity
of the steel profiles. The present work consists in the modeling of a park of metallic silos submitted to the
aerodynamic action of the wind for the analysis of the structural behavior will be considered the formation of
vortices and turbulences in the empty structure, submitted only to its own weight, as well as, with the pressure
coming from of your storage. For this, the structure was modeled in software based on the finite element method.
The knowledge of the dynamic forces in light profile structures is essential to guarantee the integrity of the silos.

Aerodynamic Modeling of Generator Towers

2024-05-29T13:39:41+00:00

The energy produced from wind turbines is the result of a modern technology applied to the force of the
wind to obtain electrical energy. The towers are large structures that guarantee clean and renewable energy and
continue to expand in Brazil, with a promising scenario. According to the [1], in 2020 there was a 14.89% growth
in power compared to December 2019. In the same year, 66 new wind farms were installed in the country and
another 14 were repowered, totaling 2.30 GW of new capacity. The wind towers can reach up to 130 meters in
height and are made of metallic or concrete material, both prefabricated and assembled in the wind farms. In this
case, the present work aims to model a wind tower, using finite element software, in order to verify the influence
of aerodynamic phenomena, especially the Flutter phenomenon in the wind turbine blades and its consequences
on energy production. It is expected to obtain in the final result, how vibration phenomena affect the yield of
electricity production in wind farms.

TRANSMISSION TOWER: COMPUTATIONAL MODELING AND ANALYSIS OF THE SIMULATION OF WIND EFFECTS.

2024-05-29T13:43:12+00:00

In Brazil there is a great need for electrical transmission towers, due to its large territorial dimensions,
as well as the great distances between energy production sites and high consumption centers. In this perspective,
the use of this important type of structure tends to be usual. The objective of this work is to perform a graphical
and computational modeling of a self-supporting lattice structure. Then, the aerodynamic analysis of these
structures is carried out simulating the structural effects of random loads due to wind actions. For the transmission
tower model chosen, the finite elements of the truss model were considered, straight, connected by perfect joints.
In the simulation, the towers located in the city of Foz do Iguaçu - PR were considered. From this modeling, the
wind effects produced bending and torsion in the structure, as well as axial forces in the bracing members, which
prevented high horizontal displacements, proving that the adopted model meets the design criteria. It was also
evaluated that the structural failure, in an eventual episode of overload due to wind, should occur by buckling of
internal elements, where the application of structural reinforcements will be proposed.

Increasing the Overall Efficiency of Hydro Power Plants by Using Virtual Prototyping in the Design of High-Performance Hydromechanical Assets

2024-05-29T13:48:59+00:00

Intake racks play a very important role in the prevention of accidents and premature failures in
Hydroelectric Power Plants. As a primary function, the racks act as filters, preventing the passage of large
particulates and debris to the hydraulic turbine. However, intake rack designs, historically, do not take into account
extensive analysis, and there are many cases of failures in these structures, which despite appearing simple, require
adjustments to the actual operating conditions, in addition to the operational complexity of these devices. Thus,
the use of novel techniques, virtual prototyping focused on numerical simulations of CFD (computational fluid
dynamics), FEA (finite element analysis) and FSI (fluid structure interaction), allows the development of
optimized designs for these assets. In conjunction, the use of FEA allows the evaluation of the new intake rack
geometry considering, through FSI coupling, the dynamic pressure exerted in each specific region of the
component, and no longer average values as used by standard but for the entire component, allowing a more global
and assertive view of the mechanical stresses induced by its operation.

Optimization of steel castellated and cellular beams using finite element method and genetic algorithms

2024-05-29T13:51:27+00:00

The quest to consume resources more consciously and effectively encourages the use of optimization
processes. In this sense, the present study aims to employ computational optimization techniques to determine the
maximum strength of open-web steel beams, for two groups of different cut lines, one generating beams with holes
in the hexagons-shape and another in ellipse format. From these two models of cut lines, a set of parameters is
defined that establish different configurations for the cut line in an analyzed I-shaped profile, for example: distance
between holes; position along the web height; hole dimensions; among others. A computational routine is
implemented to generate, from the analyzed I-shaped profile and for certain parameter values, a finite element
mesh. The load capacity of the castellated and cellular beam is defined through a nonlinear analysis using the finite
element program FEMOOP and a three-node triangular finite element in plane stress state. This element was
chosen due to the need for a very refined mesh in the discretization process of the different possible configurations
of cut lines, therefore, the finite elements are small and do not require high degree interpolating functions. The
optimization process consists of defining, for a given I-shaped profile, which configuration of the cut line produces
a castellated or cellular beam with greater load capacity. The implemented routines are validated from numerical
and experimental models found in the literature, and it is expected, from an analysis of the beams found in the

populations obtained by the evolution of the genetic algorithm, an increase in the load capacity of the analyzed I-
shaped profile.

Classification of seismic facies using seismic multi-attribute

2024-05-29T13:53:55+00:00

Seismic interpretation is a fundamental process for hydrocarbon exploration. This activity consists
of identifying geological information through the processing and analysis of seismic data. With seismic data’s
rapid growth and complexity, manual seismic facies analysis has become a significant challenge. Mapping seismic
facies is a time-consuming process that requires specialized professionals. The objective of this work aims to
apply multiattribute classification using a deconvolution neural network to map the seismic facies and assist in
the interpretation process. We calculate a set of seismic attributes using Opendtect version 6.6 software from the
amplitude data contained in the Facies-Mark Dataset. They are: Energy, Pseudo Relief, Instantaneous Phase, and
Texture, all selected by an interpreter. The results showed that the attributes obtained a satisfactory result, reaching
85.15%, and the attributes together with the amplitude obtained 85.73%, while the amplitude, which is the most
commonly used data in seismic classification, obtained 81.23%, based on the FWIU metric. In a direct comparison
between the model with data augmentation and with attributes, the second performed better.

Study of Approximate Solutions for The Number Partitioning Problem

2024-05-29T13:58:27+00:00

The number partitioning problem (npp) is important because it is a combinatorial optimization NP-hard
problem and one of the canonical cases of NP-complete decision problem described in the literature. An exact
formulation for the decision problem is presented through dynamic programming approach. However, since the
npp is NP-complete, the dynamic programming algorithm has pseudo-polynomial complexity time which works
well for small instances. Also, several heuristic methods are used to approximate the exact solution for the problem.
In this paper, following the Ising formulation described in the literature, the npp optimization problem is formulated
as a cost Hamiltonian in terms of spin variables. Additionally, we discuss solutions for this formulation by two
quantum heuristics for a limited number of qubits. In the first one, we use a Quantum Approximate Optimization
Algorithm procedure based on some given ansatz to make a search for approximate solutions. In the second one,
we use an evolutionary technique ansatz-free with evolutionary quantum gate circuits. Both procedures show the
good features of the Ising model formulation for easy instances of such a problem.

A Computational Model for the Analysis of Uplift Pressures and Fluid Flow in the Jucazinho RCC Dam

2024-05-30T14:42:25+00:00

The Jucazinho dam is of the Roller Compacted Concrete (RCC) type, completed in 1998. The first flood
was in 2004 with a 1,4m thick spill, causing deterioration of part of the dissipation basin. This situation triggered
investigation services to assess the structural integrity of the structure. It was found that the drainage gallery
presented several pathological manifestations arising from the water seepage through the concrete monolith. In
2017, there were maintenance and consolidation services throughout the dam structure, paying particular attention
to cracks and the rehabilitation of the dam gallery. Several studies were carried out on the dam: (i) verification of
the quality of the materials used throughout the structure; (ii) exceptional seismicity actions that could cause major
problems preventing its use; (iii) global stability analysis. But the effects of seepage flow in the concrete were not
deeply analyzed. These considerations justify the occurrence of existing manifestations and serve as a reference
for monitoring the dam's safety. In order to analyze the water seepage that occurs in Jucazinho dam, the 2D Finite
Element Method (FEM) was used using the ABAQUS software, considering: (i) flow through porous media with
coupled fluid diffusion and stress analysis; (ii) finite elements with combined displacement and pressure degrees
of freedom; (iii) the solver of non-symmetric equations; (iv) steady-state analysis. Following these considerations,
this article presents a brief review of the literature on the subject and the knowledge of the physical parameters of
the dam. Subsequently, it introduces the physical and mathematical formulations that characterize the problem to
be studied in Jucazinho dam. With the numerical simulations the following results were achieved: (i) the
equipotential and flow lines inside the monolith; (ii) the displacements and stresses for the fully coupled analysis.
These parameters are important for future investigations and safety monitoring of the Jucazinho dam. Reference
simulations performed without fluid flow in the confined medium demonstrate that the values obtained differ
completely from the simulations that considered the water seepage inside the concrete, reaffirming the importance
of considering flow analysis coupled with stress analysis.

Optimized analysis of T, Circular and Rectangular cross-sections of reinforced concrete under biaxial bending

2024-05-30T14:45:40+00:00

He analysis of polygonal reinforced concrete sections subjected to biaxial bending is of great interest in
civil construction. Generally, its dimensioning is done through design charts, generating a section that is often
uneconomical. Therefore, this work aims to implement an algorithm capable of optimally distributing a number
of steel bars in a T, rectangular or circular cross section in such a way that it is safe and efficient for a combined
loading of moment and axial force. it is also the objective of this work, the development of a graphical interface
that stores the data provided by the user and performs the optimization and detailing of a cross section. This
algorithm uses the sequential linear programming method, where a nonlinear problem of determination of the
resistant efforts of the section is linearized, having its optimal point defined at each step using the Simplex method.
The development of this graphical interface took place through the Visual Studio Community software, using the
C# programming language. The implemented algorithm also allows considering the dimensions of the T, circular
and rectangular section as a design variable, defining an optimized section through an objective function given by
the cost of materials. Using numerical examples available in the literature, one can prove the efficiency of the
algorithm presented in this work. The results obtained were also evaluated through the axial force-moment
interaction curves, being able to observe that the optimized sections did not present slack in relation to the applied
efforts.

Wave propagation in one-dimensional diatomic metastructure with high- static-low-dynamic stiffness

2024-05-30T14:47:56+00:00

In this work, we explore wave propagation in a one-dimensional diatomic periodic structure with high-
static-low-dynamic stiffness (HSLDS) characteristics, which is a geometric nonlinearity. A diatomic chain consists

of two different masses per unit cell, and diatomic periodic structures can present interesting dynamic characteris-
tics, in which waves can attenuate within frequency bands that are called bandgaps. A periodic structure consists

fundamentally of identical components, the cells, connected in a way that characteristics of mass, stiffness, and or
damping are spatially repeated, and present interesting characteristics for vibration attenuation that are not found
in classical structures. These characteristics have been explored for automotive and aerospace applications, among
others, as structures with low mass are paramount for these industries, and keeping low vibration levels in a wide
frequency range is also desirable.

We use closed-form first-order approximation via perturbation analysis to study wave propagations by disper-
sion relations of the infinite structure considering the effect of nonlinear terms. We verify the nonlinear bandgap

seen via the dispersion relation by comparing it to the transmissibility of a finite structure. We use the disper-
sion relation to analyse how some parameters can influence the bandgaps, such as the mass ratio between the cell

elements and amplitude.

Numerical Study of the Effect of Cutting Parameters on the Orthogonal Cut of Inconel 718 Alloy

2024-05-30T14:50:03+00:00

This work aims to study the effects of cutting parameters, such as feed per tooth and cutting speed, in tradi-
tional machining process. For this, a bi-dimensional orthogonal cut model was used to represent the problem on

a commercial finite element tool. The Johnson and Cook plasticity model was assumed to describe the behavior
of the work material in terms of yield strength and damage level. Inconel 718 alloy was used as the base material
due to its great importance in engineering. This material imposes challenges when machined and it is well known
for its low machinability. With the simulations, a qualitative analysis was made regarding the effects of the cutting
parameters on chip formation.

Dimensioning of sheet bending process trough ductile damage

2024-05-30T14:53:37+00:00

This work seeks to dimension the sheet metal bending process through the control of ductile damage.
For this, the material parameters of a 6101-T6 aluminum alloy are used. The process is simulated on a commercial
finite element tool as an elastoplastic problem with ductile damage. Parameters such as sheet thickness and
geometry of forming tools are evaluated. Thus, possible problems associated with the process are analyzed, such
as cracks in the bending regions, fractures and deformations. Three sheet thicknesses are evaluated, more
specifically 1, 2 and 3 mm. For the 3 mm sheet, a new geometry of the forming tool was proposed in order to
smooth the entire process. Three parts were modeled for analysis: two parts for forming the sheet, called tools "A"
and "B", and the sheet. Tool “A” works like a punch, tool “B” works like a mold. The problem was modeled
considering plane strain state. The tools used for the sheet bending process are modeled as rigid bodies, whereas
the sheet is modeled as a deformable solid.

Numerical Simulation of a Forged Inconel 718 Alloy Indentation Process

2024-05-30T14:57:53+00:00

This work proposes the numerical simulation, through the finite element method, of an indentation test in the
forged Inconel 718 alloy. Hardness tests are performed on the alloy, under three levels of strength. At the same
time, process simulations are carried out to determine the same print obtained experimentally. The effect of spring
back and the possible use of the method in the parametric identification of hardening properties of the alloy are
evaluated, when there are small volumes of materials for mechanical characterization.

Numerical Simulation of the Deep Stamping Process

2024-05-30T15:00:18+00:00

The process of stamping is largely used when manufacturing a variety of structural and mechanical
components, composed basically of a die, a punch, and a blank holder. The CAE finite elements software,
Abaqus, allows the modeling, simulation, and analysis of the stamping process thus showing the influence the
punch displacement speed has over the maximum stress in the material. By the end of the analysis, including mesh
convergence studies, it is easy to observe that greater speeds result in greater stress levels of the workpiece and
larger deformations of its intended geometry. The study found that optimal punch speed levels for manufacturing
small aluminum cups lie between ranges of 40 to 60 mm/s.

Fully explicit FEM formulation for NMR simulations using the Dufort- Frankel method

2024-05-30T15:03:59+00:00

In this paper we present a fully explicit finite element implementation for the simulation of the T2
relaxation and T1 recovery process in nuclear magnetic resonance experiments. We consider 2D domains defined
by images. We propose the combination of a lumped mass matrix and stable time-marching schemes to achieve
a fully explicit and stable simulation even with large time steps. The time-marching scheme we consider is the
Dufort-Frankel method which allows for large time-steps even for problems in the fast diffusion regime. We show
that the use of the lumped mass matrix adds a negligible amount of numerical error in comparison to the error
introduced by the discretization. We also show that this method compare favorably to the Explicit Euler in terms
of necessary number of time steps in order to achieve a reasonable threshold of numerical error.

Numerical solution of axisymmetric shells under bilateral contact constraints

2024-05-30T15:07:23+00:00

In structural analysis, the possible geometrical configurations of the structure are fundamental for the
choice of the coordinate system to be used and, consequently, for the determination of solutions. The structural

problem description through an appropriate coordinate system allows us to visualize aspects that would not neces-
sarily be observed in another coordinate system. In this sense, the correct specification of the coordinate system

is important and necessary. The most general coordinate system, of which all others are particular cases, is the
general curvilinear coordinate system. Simultaneously, differential equations are widely used to model problems
in structural engineering. In the solution of a differential equation, the finite difference method plays an important
role, promoting the discretization of space by a mesh of discrete points, with the unknown functions and their
derivatives being replaced by approximations at the grid points through difference quotients. In particular, the

analysis of contact problems between a structure and a deformable foundation is an essential task in civil engineer-
ing, with crucial use in different support systems. Undoubtedly, thin axisymmetric shells are structural elements

widely used in structural engineering, especially when interacting with elastic or inelastic means. The main objec-
tive of this work is to develop a computational tool for the study and analysis of problems under bilateral contact

constraints, involving axisymmetric shells and elastic means, using the approximations derived from Sander’s the-
ory for slender shells. General equations applicable to any coordinate systems are developed. As an application

example, a slender cylindrical shell supported on soil (elastic foundation) is used.

Identification of horizons in seismics using convolutional neural network

2024-05-30T15:10:42+00:00

Seismic structural interpretation is an essential step in exploring and producing hydrocarbon reserves.
This interpretation requires identifying geological features such as facies, horizons, and faults in the region of
interest. The manual identification of these features is a time-consuming task. Convolutional neural networks
(CNN) are widely used in computer vision problems, yielding excellent results in many situations, including the
seismic interpretation process. This work studies supervised convolutional neural networks to segment horizon
lines delimiting seismic facies based on seismic amplitude. We evaluate our proposal using the F3 block with the
seismic facie annotations. In the original dataset annotations, the labels were annotated areas for each seismic
facies, so this set of annotations was changed from a multiclass problem to a binary, considering only the boundary
between one seismic facie to its neighbor. The horizon prediction uses the ResUnet network, a combination of
Unet with residual blocks, designed to obtain high performance with fewer parameters. Some loss functions are
analyzed to optimize the segmentation result. Generalized dice loss and Focal Tversky loss functions yield best
results in our experiments. The Dice metric reached an index above 50% with the Focal Tversky loss function,
showing promising results.

Image-based detection and classification of screws and nuts using deep learning

2024-05-30T15:13:30+00:00

Object detection in images has been one of the biggest challenges for computer vision researchers. This
paper presents a case study on screws and nuts detection and classification. The identification of screws is not a
trivial task. There are about 1,500 unique bolts, and in some cases, the differences between the two pieces involve
only tiny details, making identification difficult for untrained people. The experiments used an MVTec Screws
dataset with 384 images of bolts and nuts on a wooden background. The classification problem consists of 10
classes that differ in the length and width of the screws or nuts diameter, the color of the metal, and the shape
of the screw head, tip, or thread. Objects in some images are separated, in others ones, objects are together or
overlapped. For screws and nuts detection and classification, the network YOLOv4 and the Darknet framework
were used for training and inference. Performance was evaluated considering detection and classification after
4,200 epochs run. The results in detection, in terms of IoU and mAP, scored 77.79% and 97.79%, respectively. In
classification tasks, all classes reached above 99% F1-Score.

Prediction failure in electric motors bearings using vibration signals and Long Short Term-memory neural networks

2024-05-30T15:17:03+00:00

Bearing failures modify the vibration regime of electric motors. The acquisition and analysis of these
signals may provide important information about the operating condition of these components. In this context, the
use of failure prediction techniques can ensure the rolling bearings will be always in good operating condition,

ensuring the production processes continuity and avoiding accidents. This paper investigates the subject of fail-
ure prediction in rolling bearings from vibration signals using Long Short-Term Memory (LSTM) networks. The

experimental was carried out on the vibration signals from the data set IMC. The method consisted of building 6

models in different training settings by using either raw data or 13 statistical descriptors in time domain. Perfor-
mance evaluation was accomplished by means of accuracy, precision, sensibility, sensitivity and F1-Score. The

best result (92% of accuracy, 94% of precision, 86% of sensibility, 94% of specificity and 89% of F1-score), indi-
cates the use of LSTM aiming to predicting failures in rolling bearings can improve the reliability of production

systems, by anticipating preventive actions and reducing the need for corrective maintenance.

COMPUTATIONAL MODELING AND NUMERICAL SIMULATION OF NEW WHEELCHAIR SEAT-BACK SYSTEMS TO IMPROVE COMFORT AND POSTURAL ADEQUACY FOR CHILDREN WITH MOTOR DISABILITIES

2024-05-30T15:19:36+00:00

Physical or motor disability may be considered a body structure or function disorder that interferes with
the movement and locomotion of the individual, and this may impact several activities such as school and work.
The current work focused on the development of assistive technology and postural adequacy areas, aiming the
social inclusion of children with motor disabilities in the educational system in the Pernambuco state. In this work,
a computational model was developed to represent the current seat-back system used by children. In order to
simulate representative loading conditions, it was used temperature digital data collected in the seat-back system
through the thermography technique. Those data have been transformed into pressure maps and implemented as
mechanical loads in the computational model. Numerical simulations were then performed using the commercial
software COMSOL Multiphysics®. The results of the simulations were analyzed to identify critical stress
concentration zones and high contact pressure in the actual seat-back system, which can possibly lead to bedsores
and discomfort. The next step of the work was to propose new seat-back systems, improving better posture and
comfort to the children. Therefore, new mathematical models were implemented in the software to test and
evaluate the performance of different foams.

Soft Faults Diagnosis in Analog Circuits Using Optimization Inspired by Bat Behavior

2024-05-30T15:25:41+00:00

Open-circuit or short-circuit faults, as well as faults in discrete parameters are the most used models in
the simulation method before testing. As the response of an analog circuit to an input signal is continuous, failures
in any specific circuit element may not characterize all possible component failures. There are three important
features in diagnosing analog circuit faults: faulty component identification, faulty element value determination,
and circuit tolerance restrictions. To solve this problem, a fault diagnosis method is proposed in this work using
a bat-inspired algorithm, where the nonlinear equations of the circuit under test are used to calculate the circuit
parameters. The fault diagnosis is transformed into an optimization problem. The bats represents the values of

faulty components and applied to the transfer functions of accessible nodes. the objective is to minimize the dif-
ference between the responses obtained in the real circuit and the response simulated by the optimization process,

identifying which circuit component has the potential to present the failure. The proposed methodology is capable
of diagnosing simple faults and is proven with the Biquad Tow-Thomas Filter.

Numerical solution of the liquid film model for intermittent gas-liquid flows

2024-05-30T16:08:51+00:00

Multiphase flows occur in several industrial sectors, such as oil and natural gas production and transport.
Its understanding gives several technical and economic advantages. Gas-liquid flows are often grouped into three
main patterns: dispersed, separated, and intermittent. A succession of liquid pistons (aerated or non-aerated) and
elongated gas bubbles parallel with a thin liquid film that repeats itself over the pipe in a non-periodic way describes
the intermittent or slug flow. These flows can occur in a steady state considering the unit cell concept. Thus, the
hydrodynamic parameters of this kind of flow can be estimated using several models developed based on this
concept. This work aims to solve numerically one of the models more complete for film profile estimation using a
fourth-order Runge-Kutta method. A computational code is being written in MATLAB to implement the film profile
model and the empirical correlations for estimating the closure parameters. The numerical results obtained for the
film and piston lengths were compared with experimental data from the literature to validate the model solution
employed. In addition, liquid film (or elongated gas bubble) profiles were plotted graphically for visualization and
comparison with descriptions presented in the literature.

STAYED BRIDGE: COMPUTATIONAL MODELING AND ANALYSIS OF THE SIMULATION OF WIND EFFECTS

2024-05-30T16:12:39+00:00

Cable-stayed bridges can present damage to their components because they are constantly subjected to
the action of the winds. This type of structure was a great advance in engineering, making it possible to build more
economical bridges, as they were able to overcome large spans without the need for several supports or a large
structure in arches. At the same time, it made the problem of wind forces more important, because it is a light and
slender structure, it ends up suffering serious aerodynamic effects, which in more extreme cases can lead to
collapse. Using finite element software, a model bridge located in the municipality of Foz do Iguaçu-PR, subjected
to the effects of the natural action of the winds of this region, was analyzed to verify the behavior of the stays and
the vibrations transmitted by them to the decks, verifying possible ruptures caused by fatigue and the possibility
of the occurrence of rupture caused by the resonance of the components, thus obtaining expected results in terms
of their resistance capacity to a stress situation.

PREDICTING LOAD CAPACITY OF PRECAST CONCRETE PILES USING SPT AND ARTIFICIAL NEURAL NETWORK

2024-05-30T16:16:04+00:00

One of the great challenges of foundation engineering is the calculation the bearing capacity of piles
because it requires, in theory, the estimation of soil properties, its changes by the execution of the foundation and
the knowledge of the soil-pile interaction mechanism. The semi-empirical methods of Aoki-Velloso [1] and
Décourt-Quaresma [2] are the most widely used to estimate the bearing capacity of concrete piles in Brazil.
However, these methods were developed for a group of soils from a specific region, so it is necessary to adjust
them to adequately represent the soil-pile interaction mechanism in soils from regions different from those initially
studied. In the geotechnical engineering, Artificial Neural Networks (ANN) have shown potential in determination
of the bearing capacity of deep fundations. In this paper, an ANN model is implemented to predict the bearing
capacity of precast concrete piles based on data from 126 Standard Penetration Test (SPT) and their respective
load tests results, static and dynamic pile testing. Based on the results obtained, the ANN model may represent a
promising solution for the design of precast concrete piles.

MACHINE LEARNING APPLICATION TO ASSESS A PROCESS CON- TROL OF A CATALYTIC CRACKING UNIT

2024-05-30T16:18:58+00:00

Catalytic cracking is extensively applied in the downstream oil and gas industry to process an oil charac-
terized by a high value of API degree, in other words, petroleum with a high percentage of heavy hydrocarbons,

resulting in many products with smaller molecular weight. The biggest challenge of this process is the evaluation
and control of catalyst deactivation, a phenomenon characterized by inducing the inactivity of disponible porous

regions of the catalysts that take place the chemical species transfer or reagent to inside the porous, after the chem-
ical reaction discharge to external medium products with a less molecular chain. One alternative workable in this

industry is a continuous regular substitute of deactivated catalyst, using the chemical or pyrolysis reactivation and
returning to the chemical process. To ensure the efficiency is crucial to determine the substitute frequency and
the amount of reactivated catalyst to maintain the maximum yields of the process. To analyze aspects of catalyst
deactivation, a system control project that aims to ensure the conversion obtained at the reactor and the flow of
the reactivated catalyst is required. Since both variables are explicitly important to the problem, it is possible to
define the optimal set-point for system control by monitoring these variables. So, a strategy based on ratio control,

that uses mathematical modeling to obtain the set-point to the conversion and flow of the reactivated catalyst, clas-
sification as control and manipulate variables, respectively. Thus, get the suitable ratio in accord at the set-point

of the process. As a way of evaluating and optimizing the flow of catalyst employed, after the projected control
system, it will apply a model of machine learning, Support Vector Machine (SVM), a supervised method that with
a data set prescribe a hyperplane and assess each point of distance on relation this plane for determining which
class best representing the data. This work aims to study which variables influence the deactivation catalyst and
suggest ways to mitigate and control them.

Efficient backcalculation procedure for asphalt pavements using the Finite Element Method

2024-05-30T16:22:21+00:00

Backcalculation is a procedure used to estimate stiffness properties (resilient modulus) of asphalt
pavement layers through non-destructive tests. The resilient modulus of each pavement layer is adopted as the one
that produces the simulated deflections closest to the deflections obtained in field tests. This paper presents an
efficient backcalculation approach based on the minimization of the sum of squared errors between the measured
field deflections and deflections obtained using an axisymmetric linear elastic layered model for the pavement
with finite and infinite elements. The resulting nonlinear least squares problem is solved using the Gauss-Newton
(GN) and the Levenberg–Marquardt (LM) methods. The gradients of deflections with respect to the material
parameters used by the optimization methods are computed accurately and efficiently by the finite element code.
The two methods are compared in terms of accuracy, robustness, and computational efficiency for pavement
structures with different characteristics.

Geometrically Nonlinear Isogeometric Analysis of Functionally Graded Solids

2024-05-30T16:25:45+00:00

Functionally Graded Materials (FGM) are composites with a gradual and continuously varying com-
position. Given the constituents, the volume fraction is evaluated by a mathematical function and the effective

properties by a homogenization method. Composite structures made of FGM are commonly analyzed using Fi-
nite Elememt Method (FEM). Isogeometric Analysis (IGA) is an alternative to FEM where the displacement field

is approximated using the same basis functions employed in geometric representation, as B-Splines or NURBS.
This work presents an isogeometric formulation for geometrically nonlinear analysis of functionally graded solids
based on trivariate basis functions. Numerical results are evaluated for small and large displacements problems,

and excellent results are obtained in all examples and gradations studied. Furthermore, the results showed that us-
ing higher order functions leads to faster convergence, requiring fewer degrees of freedom in comparison to lower

order functions.

2D contact simulation of fretting specimens using IGABEM

2024-05-30T16:53:58+00:00

In this paper, the isogeometric boundary element method (IGABEM) is used for determining tractions
in contact problems. We simulate contact between a fretting pad and a metallic specimen, a usual experimental
configuration. The results are compared with standard boundary elements method and analytical results. The
analysis consists of evaluating tractions during one loading cycle, which includes normal and shear loads. After,
the results are validated using analytical formulae. Lastly, a performance comparison between each method is
presented.

Soil-Cement Mechanical Characterization Using Acoustic Vibration

2024-05-30T16:57:37+00:00

The execution of small and medium-sized foundations (for houses, townhouses, sheds, etc.), has often
been proven unfeasible because the use of semi-empirical equations results in low load capacity values, generally
leading to the use of piles. However, this is not always an economical alternative, due to the low level of loads on
the pillars. There are alternatives for improvement such as the use of cement. The mechanical characterization of
these materials is needed; therefore, the use of acoustic vibrations appears as a non-destructive and economical
technique. This technique is used for materials such as concrete and hasn’t been often applied in the soil area. In
this work, the feasibility of mechanically characterizing the dynamic modulus of elasticity and damping ratios is
studied for soil-cement-compacted (SCC). The experimental program consists of carrying out acoustic tests on
SCC specimens with cement dosage of 6, 9 and 12% in relation to the total weight of the mixture.

NUMERICAL ANALYSIS OF STRUCTURAL MASONRY PANEL USING MACROMODELING AND SIMPLIFIED MICROMODELING

2024-05-30T17:00:42+00:00

The structural masonry is among the oldest construction techniques, but over time it was replaced by
concrete and steel constructions. Recently, the number of buildings executed in structural masonry is increasing,
mainly due to the social interest housing programs, leading at the same time the increase of the cases of structural
pathologies, highlighting the need of additional studies and research in this area. Unlike frame structures, where
the walls are used only as enclosure elements, in structural masonry the panels are load-bearing structures and can
be represented by some of their 5 possible distinct elements (block, mortar, grout, interface and reinforcement) or
by panels of a single homogenized material. The representation of the panel by distinct elements generates
difficulties but is essential for local analysis of stresses and load distributions in the panels what permit to evaluate
the structural performance of this constructive technique and emergence of the building pathologies (damage and
crack pattern). In this work, the modeling and analysis of a structural masonry panel was carried out using the
Ansys software based in the Finite Element Method (FEM), applying the simplified micromodeling and
macromodeling techniques. The panel was analyzed in a two-dimensional way, being detailed the expressions for
stress and strain that govern the problem, as well as the properties of the equivalent material considering the
orthotropy applied in the macromodeling technique (homogenization). The panel analyzed was detailed as a
structural masonry wall, formed by solid blocks of concrete and having a concrete beam as a supporting element.
For analysis, a linear load was applied to the panel, being evaluated in this work, in a comparative way, the panel,
containing opening and the panel without opening. The panel modeling was performed using the PLANE42
element in state of plane stress, what is bi-linear Lagrange element (4 nodes) and two degrees of freedom per node.
Through the results obtained in this work, it was possible to evaluate that the wall and beam set works in a similar
way to the arch, with compressive stresses on the wall and tensile stresses on the beam being predominant, with a
concentration of stresses also being observed for the area of the panel close to the support. It was also possible to
verify that the presence of the opening in the panel causes a high concentration of tensions at the top and at the
bottom, justifying the use of the joint reinforcement at lintel bearing. When comparing the stress results obtained
between the micromodeling and macromodeling technique, it was observed that the homogenization technique has
convergent results on the global behavior.

Computational modelling of tendons: poromechanical approach for microscales

2024-05-30T17:03:24+00:00

Fluid flow effects on the microstructure of soft biological tissues are of fundamental importance in

understanding mechanobiological processes, such as in mechanotransduction. Since these tissues are highly het-
erogeneous and have a large microstructural hierarchy, investigations of macroscopic behavior by incorporating

microstructural effects can be performed using multiscale techniques. This work aims to bring additional discus-
sion related to the micromechanics of fibrous biological tissues such as tendons. For this purpose, technical aspects

involving the first-order multiscale formulation developed by the authors are discussed, presenting advantages and
limitations of this type of model. Some results related to a multiscale framework that considers hydro-mechanical
coupling are presented and discussed, aiming point out some features of the formulation.

Computational method for estimating the emissivity of human skin under different conditions: dry skin, sweaty and with lotion

2024-05-30T17:06:54+00:00

With the emergence of the Covid-19 pandemic, sanitary barriers that use infrared thermography have
become more relevant as a means of combating the spread of this type of disease, as it is a non-contact diagnosis
method. A crucial factor when working with thermography is the emissivity of the analyzed surface, a base
parameter that thermal imagers use to estimate the temperature. For human skin, researchers generally adopt the
emissivity value of 0.98. However, this value considers only the condition of dry skin in its natural state. Therefore,
it is necessary to estimate the emissivity of the skin in other conditions, such as sweating skin, which are common
in passersby of sanitary barriers. In this paper, the authors present an experimental procedure to obtain the forehead
emissivity of volunteers by using the electric tape method and a developed a computer program algorithm based
on Planck's Law of Thermal Radiation to enhance this method. Both approaches, the electrical tape method with
and without the developed algorithm, were applied to thermographic images of thirty-six volunteers. Both methods
obtained similar results, showing that it is possible to use the developed algorithm with the electrical tape method,
enabling emissivity estimates to be more efficient.

Recent advances in numerical modeling of massive concrete structures

2024-05-30T17:10:36+00:00

This paper presents recent advances in numerical modeling of massive concrete structures resulting
from the conclusions of the Technical Committees of RILEM TC 254-CMS "Thermal cracking of massive
concrete structures" and RILEM TC 287-CCS ‘‘Early-age and long-term crack width analysis in RC structures’’,
committees chaired by the authors. The TC 254-CMS Committee met for 7 years (2013-2019) and involved the
participation of approximately 30 researchers and professionals from different continents. In addition to several
meetings, symposia and participation in Conferences, the Committee has published a book on the state-of-the-art
and also some articles in specialized journals that indicate procedures pertinent to the construction of massive
structures that are of fundamental importance for designers and constructors. Therefore, in the present paper,
several conclusions about the best practices in numerical modeling of the problems related to the hydration of
early-age concrete will be addressed. The concept of massivity index will also be discussed which determines the
need to analyse a structure considering the hydration effects at the early ages.

SHM APPLIED TO THE REHABILITATION OF HISTORIC STEEL BRIDGE

2024-05-30T17:13:27+00:00

The historic Imperial Dom Pedro II Bridge, located in Bahia, Brazil, underwent a major rehabilitation
program that began in 2018. All tensioned diagonals, made of puddled iron, were replaced with new components,
made of stronger steel. This paper presents a numerical model of the Dom Pedro II Bridge capable of reproducing
structural performance before and during the replacement work. Numerical results were verified by the
experimental data derived from monitoring systems installed in the bridge on several occasions. The differences
observed from the numerical results could be justified by the bridge’s age and maintenance condition. In general,
the numerical results were fairly similar to the measured data, indicating the numerical solution could be used to
assess other sequences of tensioned diagonal replacements. It was concluded that the replacement work improved
the safety of the bridge, and the proposed modeling process may be suitable for other sequences of replacements,
including other steel truss bridges.

A Study of Thermal Cracking in The Buttresses Blocks in Itaipu Dam: Thermochemical-Mechanical Numerical Analysis

2024-05-30T17:16:21+00:00

The Itaipu hydropower plant is a world leader in clean and renewable energy. One of the main structures
is the right bank dam, which is composed of buttress blocks. It was built in 1978 and in 1980 the first cracks were
already observed. The thermo-mechanical model, which predicts an increase in temperature inside the concrete
mass due to the hydration of the cement, explains the thermal stresses in these dam blocks. In order to validate this
model and verify if those cracks in Itaipu buttresses are thermal cracks, the block was modeled in DamThe software
in 3D simulating the D38 block. The 3D simulation achieved results that are close to those observed in the field
regarding the position of cracks in the blocks and the temperature developed inside the blocks, compared to the
temperatures observed in the thermometers. The model, already verified in previous works, was validated, as it
was able to predict the temperatures and the tendency to crack. This indicates that it is a reliable program for
designing structures and anticipating undesirable cracks in massive concrete structures. It was also noticed that
the cracks have a thermal origin and may have a mechanical contribution, but not exclusively.

Artificial neural networks applied to heat exchangers problems: a review

2024-05-30T17:18:54+00:00

Artificial Neural Networks (ANN) are computational algorithms inspired by the nervous system of
animals. They are powerful tools to predict patterns and behaviors for problems in different fields of study. Heat
exchangers are devices created to improve heat transfer that are hard to model by conventional methods but are
highly important in many applications. ANN have been used to model heat exchange problems, thus, helping to
predict and analyze patterns and behaviors not easily predicted by traditional methods. This review discusses the
application of ANN to heat exchanger problems, evaluating the improvement in the field over the last decades. To
achieve this goal, the number of publications was first analyzed, and the studies were divided into groups according
to the research goals. It was also analyzed the number of publications each year. It was considered the keywords:
"artificial neural network" and "heat exchanger" in the Science Direct platform. One hundred nine papers were
found, and around 50% were published in the last five years. 68% of the articles focused on the evaluation of the
ANN rather than utilizing it to optimize heat exchangers, showing that the method is still in development even if
it has become more important in the last decade.

Numerical modeling of the linking damage zone between geologic faults

2024-05-30T17:21:42+00:00

Brittle fault zones are geological structures formed by a core and a damage zone that impact the fluid
flow within geological formations. The fault core is usually responsible for the compartmentalization of several
reservoirs acting as barriers while the damage zones may enhance the fluid flow. Both components present low
seismic resolution that does not allow an appropriate characterization of those regions. Recent works based on the
Finite Element Method (FEM) have focused on the characterization of damage zones adjacent to a geological fault.
However, the interaction of two or more faults may create linking damage zones and preferential flow paths or
barriers to fluid flow. This paper presents a methodology for the numerical modeling of damage zones resulting
from the interaction between two geologic faults. Several scenarios of different relative distances between two
faults are analyzed to understand the effect of linking damage zones.

An as-built digital twin visualization and generation tool using with three- dimensional CAD models and 360o images of industrial facilities.

2024-05-30T17:24:48+00:00

Today, many companies use digital twins as part of their activities. Digital 3D models enable planning,
data extraction, simulations, and training on local conditions. However, an incorrect digital twin may induce errors
that offset all possible advantages of the digitalization process. On the other hand, an information-rich digital twin
allows simulations and data extraction to be faithful to reality. Enriching the data of a digital twin is a process
that takes time, expert analysis, costs, and equipment, making the update process difficult. Photos, 360o images,
and 3D models can be used to support evaluation and updates. However, differences between pictures and models
yield confusion when transferring and connecting information. This work presents a tool that explores the benefits
of combining 360o images of industrial facilities with three-dimensional CAD models to generate a correct as-built
digital twin. This tool has an interface capable of displaying three-dimensional models of an industrial plant in
conjunction with 360o photographs, allowing the user to navigate an augmented reality environment. GPS or simple
annotations in the 360o images allow an easy manual camera calibration interactive process. The tool proposes an
effective interaction to make annotations in the CAD models and the 360o photographs.

Soil-Structure Interaction Analysis of a Wind Turbine Spread Foundation: a Case Study.

2024-05-30T17:27:08+00:00

Wind is a renewable source of energy, and its use occurs through the conversion of translational kinetic
energy into rotational kinetic energy, through the use of wind turbines to generate electricity. The present work
deals with the consideration of Soil-Structure Interaction (SSI) in a specific case of a wind turbine tower supported
on an “insulated footing” surface foundation. That said, a case study will be presented, which aims to analyze the
interaction of the wind tower foundation with the soil, verifying the use of additive materials to concrete, and the
SSI. To carry out the study, the computational tool, Diana FEA finite element modeling software, was used, which
allows the modeling and analysis of the structure by the finite element method. The results obtained in this work
allowed to enrich the discussion on soil-structural interaction.

Passive control of plate vibrations: dimensional optimization of constrained layers by using kriging surrogate

2024-05-30T17:31:06+00:00

Plate structures are slender and flexible structures and can be subject to vibrations. Vibrations can cause
problems such as acoustic discomfort, mechanical fatigue failure, and/or reduced performance. Thus, it is
necessary to use forms of control that aim to reduce and avoid vibration. One method is the passive vibration
control using constrained layers (CL). This method stands out due to easily and simplicity of application. In this
control form, the vibrating structure receives a layer of viscoelastic material (VEM) and a material layer, usually
metallic. For efficient vibration control, it is necessary to determine the optimal parameters of the CL. Thus, this
work aims to present a methodology for optimizing the vibration control of a plate using CL and Kriging's
surrogate. Considering the width and length of the VEM fixed, the design variables of this problem are the
thickness of the constrained layer (VEM) and constraining layer (metallic layer). The CL kept dimension and
shape fixed during the optimization process. The objective function evaluated is the Euclidean norm of a
component of the matrix function of inertance. As a result, we obtained optimal thicknesses of VEM and restrictor
layers for effective control of the second and third vibration modes.

Determination of the critical length of elastic buckling by distortion in Z-profiles stiffened under centered compression using artificial neural networks

2024-05-30T17:34:28+00:00

NBR 14762 (ABNT, 2010) does not have a defined method to determine the critical distortional
buckling stress, making it difficult for designers to verify the PFF strength. Because of this, researches were
developed in order to solve this problem. However, there are difficulties in the methods developed in the literature.
An alternative to overcome such difficulties is the use of the critical length associated with the distortional mode
in order to help in the determination of the distortionary critical elastic stress. In this sense, this article aimed to
determine an equation for the critical length associated with the distortional mode of cold-formed profiles with Z
section stiffened under centered compression and with bi-articulated support with free warping. For this, Artificial
Neural Networks (ANNs) were trained. Such ANNs were validated using experimental and numerical results
available in the literature and some equations were generated. The equations obtained through the adopted ANN
obtained good correlations with the literature.

Analysis of lateral displacements of a reinforced concrete tower of telecommunication systems under wind action in urban contexts

2024-05-30T17:37:28+00:00

Most of the existing reinforced concrete towers existing in Brazil intended for supporting
telecommunications systems were installed in the 1990s shortly after the “Telebrás” systems were privatized by
the Brazilian government. Currently, there is substantial growth expected in the internet sector with the appearance
of 5G in the country, and for that, there should be a new demand for the structural engineering involved. In this
context, the main objective of this work is to computationally assess the lateral displacements produced by the
wind in a reinforced concrete tower considering the geometric nonlinearity and concrete creep. For this, a useful
life horizon was defined which allows the structure to age within the estimated time for its operation. A non-linear
analysis based on the finite element method is used to operate the calculations. The loading characterizing the
problem includes the structure’s self-weight and the wind action in urban contexts. The wind forces were obtained
through a Computational Fluid Dynamic, which considers the aerodynamics of the structure and existing devices.
Herewith, it was possible to evaluate aspects related to the serviceability requirements throughout its useful life
and recommend updating existing systems in order to guarantee the quality of the service provided.

Numerical Modeling in Reinforced Concrete Tie Rods

2024-05-30T17:40:13+00:00

Concrete is a fragile material when subjected to tensile stresses, however, it is possible that a
substantial contribution can be perceived in the design of reinforced concrete elements under tension, even in the
post-cracking stage. In plain concrete, when the tensile strength is reached, cracks appear that progress until the
material ruptures, this is a localized behavior known as “strain softening”. Different from plain concrete,
reinforced concrete does not show softening due to the transfer mechanisms of tensile forces existing at the
steel-concrete interface, so tensile stiffness is a phenomenon that occurs exclusively in reinforced concrete
structures. The steel-concrete adhesion is directly related to energy absorption, which allows the redistribution of
stresses between the materials after cracking, contributing to an increase in the strength and stiffness of the
reinforced concrete element in an effect known as tension stiffening.

Nonlinear modeling of a bamboo bio-concrete beam

2024-05-30T17:42:41+00:00

Concrete is one of the most consumed materials in the world, so it is essential to promote the
sustainable development of this material. For this, it is possible to obtain environmental benefits through the
substitution of cementitious materials and/or aggregates. Bamboo is a material that has been used in several
studies as an aggregate in the production of bio-concrete, through the pressing procedure or conventional
techniques for manufacturing concrete. One way to evaluate the quality of this material is by analyzing its
mechanical behavior, either by experimental procedures or numerical modeling. The objective of this study is to
perform numerical simulations of a bamboo bio-concrete beam imposing different cracking models and tensile
laws, and compare the numerical results to the experimental ones collected from the literature. The results
indicated that the Rotating cracking model represented better the experimental load versus deflection curve than
the Fixed crack model. Furthermore, all tensile laws showed consistent results by varying only their intrinsic
characteristic of tensile softening.

Numerical modeling of mass concrete structures: practical applications and relevance to society

2024-05-30T17:46:30+00:00

Computational analysis has become crucial in almost all disciplines of our society, together with theory
and experimental analysis. In civil engineering, the thermal cracking of young concrete, associated with the high
costs and safety requirements of infrastructure works, has been a concern of the engineering community since
the first applications of mass concrete. It happens that several massive concrete structures such as hydroelectric
and nuclear power plants, thick foundations, bridge pier columns and caps, thick walls, and tetrapods breakwaters
may experience cracking induced by the generation of heat during hydration reaction (hardening). Considering
the nature of this type of work, whose risk, cost, and predictability of behavior are extremely important factors for
our community, accurate models are necessary to guarantee the success of the project. In this sense, this work will
considerer the most commonly used numerical method – Finite Element Method (FEM) - in practical applications
for numerical modeling of concrete structures developed by PEC/COPPE/UFRJ in several engineering works,
showing its impact and importance for society.

Collection and Processing of Data on Brazilian Technical Production in Engineering Areas

2024-05-30T17:50:08+00:00

The main objective of this article is to present a strategy for the identification and extraction of data
from Brazilian patents from researchers working in the areas of Engineering, such as title, abstract, filing date,
publication date, inventors, owners, among others. Such a strategy will allow the construction of a local database
of the Brazilian technical production of individuals working in the engineering areas, enabling analysis of the large
volume of data in a shorter time, since the analysis will be local and not in online repositories of patents. Therefore,
the proposed solution will allow to minimize several restrictions imposed by online repositories, among them it is
possible to mention the limit in the volume of data access and internet connectivity. In this study, the National
Institute of Industrial Property (INPI) and the international patent repository Espacenet, of recognized international
relevance, will be used as the main repositories. The obtained results allow us to verify how this type of production
has evolved over the years, considering the technical production of individuals who work in the various areas of
Engineering.

Elastic-Viscoplastic analysis of Reissner’s plates by the Boundary Element Method

2024-05-30T17:52:30+00:00

This work presents a formulation for elastic-viscoplastic analysis of plate bending by the Boundary
Element Method (BEM). It is employed Reissner’s theory, in which transverse shear strains are considered and
so, it holds for thin and thick plates. Basic formulation of Reissner's plate bending theory is presented, with the
consideration of physical nonlinearity. The related integral equations are shown for displacements at internal and
boundary points and also for moments and shear resultants at internal points. The theory for considering
viscoplasticity is presented, as well as the procedures for the solution of these equations by the BEM. This process
offers an alternative method of solution for elasto-plastic problems, when steady-state condition is reached. For
the numerical implementation, quadratic boundary elements of linear geometry and constant internal cells, also of
linear geometry, are employed. These cells are only necessary where the existence of inelastic strains is expected.
Numerical examples are presented and the obtained results are compared with solutions found in literature.

On-bottom roughness analysis for repurposing of gas export pipelines in Brazilian coast

2024-05-30T17:54:27+00:00

This work describes the on-bottom roughness analyses performed for the repurposing of two gas export
pipelines in Brazilian coast for conditions out of original design premises, as well as the assessment of a lateral
buckle identified in one of them. The main aspects of the employed methodology are presented, followed by their
results. The importance of these analyses in a repurposing context is also discussed.

Collaboration in Technological Development: an Analysis Based on Patent Proposition Networks

2024-05-30T17:57:43+00:00

Analyzes of scientific collaboration networks have been widely explored for some time in research in
different areas of knowledge, in view of their ability to identify how groups of researchers have carried out their
work collectively. Such studies make it possible to identify how collaboration between individuals occurs through
analyzes based on social network metrics. In this context, new studies have been proposed in order to analyze
collaboration in the development of technical products, with data on patents being studied in most studies. This
type of analysis is relevant because it makes it possible to understand the process of collaboration in proposing
new inventions. In this work, a general characterization of the group of individuals analyzed is initially presented,
and after that, a global and temporal analysis of the collaboration network in the patent proposal of Brazilian
individuals with CVs registered on the Lattes Platform is carried out. For this, all patents registered in the curricula
of these individuals were used for the identification and characterization of collaboration networks. As a result, it
is possible to see how collaboration in the proposed inventions of the analyzed set has been intensified over the
years, with emphasis on the institutions and areas of activity of each inventor.

Analysis of the modal response of a structure considering the periodic foundation effect

2024-05-30T18:00:26+00:00

The densification of the areas of urban structures has caused structures in general that are increasingly
approaching road traffic and this scenario, with which the structures are presented in these environments as being
the environment caused by the flow of traffic. studies that predict structures designed by traffic but do not address
technical/intelligible isolation isolation from manipulation/insulation intelligibility. The vibrations generated by
the impact cause discomfort to building users in addition to causing damage to buildings, including cracking or
even more serious problems such as the collapse of the structure. Research shows that it can isolate the use
of periodic structures as vibrations of a structure. The idea is that these periodic structures work like a filter,
absorbing as frequency bands, not passing this vibration on to the rest of the structure. Periodic structures are
being used in several areas of engineering, however, with limited use in civil engineering. In this context, this
work intends a numerical modeling in finite elements of a structure with a periodic type foundation, to study the
vibrational construction of the foundation, in comparison with a simple foundation structure. In other words, the
model is based on the development of the soil-structure coupling of finite elements, adopting the contour structure
as a basis for the study between conditions as foundations as well as between the foundation and the foundation.
Numerical modeling in finite elements was performed in the free and open source software FreeCAD version 0.19
with analysis performed in the solver Calculix. The modal response will be used to verify the filtering of the
structure’s vibrational response.

Performance analysis of random forest and support vector machine models in predicting pore pressure from well-log data

2024-05-30T18:03:18+00:00

Pore pressure (PP) prediction is critical for well drilling operations and oil reservoir characterization
and management. Recent advances in the development of Machine Learning (ML) models have led to a growing
application of these methods for pore pressure prediction using well log records. In this work, we have evaluated
the performance of two ML models for the task of PP prediction, one based on Random forest (RF) and another
based on Support vector machine (SVM). The study used geophysical logs (Gamma-ray, Sonic, and Density) of
stratigraphic wells drilled in the offshore Sergipe Basin, NE Brazil, to predict the PP in the regional sedimentary
column of the basin. The values obtained by the ML models were compared with values of PP obtained by
classic approaches used in the industry to establish the actual accuracy of the methods tested. We divided the
data used in the study in training and testing into the proportion of 70% and 30%, respectively. We also used the
metrics Mean square error – MSE and R-squared to evaluate the performance. The MSE of the SVM model was
about one order of magnitude greater than that obtained by the RF in the training data. The validation data
showed a similar result. This behavior appeared for different training data sizes, which shows the invariability of
the relative performance of the models related to the amount of data used. Another aspect observed was the
scalability of the models. The results show that the RF model presents a linear behavior concerning the model
fitting time as a function of the amount of data, while the SVM model has an exponential behavior. Finally, in
the test data, the RF model presented better results in all evaluated metrics, with an MSE of about 90%, which
was lower than that obtained by the SVM model. By comparing the values predicted by the models and the
actual values, the RF model has an r-squared of 0.99, while the SVM model has an r-squared of 0.96. Thus, the
performance of the RF model was superior to that of the SVM in all treated aspects.

A rate-dependent and unconstrained phase-field model for brittle fracture

2024-05-30T18:06:30+00:00

This work deals with the formulation and numerical implementation of a rate-dependent model for
brittle fracture that allows for damage healing. The model formulation, which is carried out within the framework
of continuum mechanics, relies on the introduction of an extra independent kinematical descriptor, the phase field,
along with the corresponding force system, the microforce system. The governing equations of theory are obtained
by supplementing the standard and extra force balances with a constitutive theory consistent with a mechanical
version of the second law of thermodynamics. A particular version of the theory is singled out to provided a
regularization of a standard theory constrained by the assumption of damage irreversibility. The model shows a
derivation of an ”optimal” kinetic modulus function from an ”optimal” penalization of rate-independent model in
the literature, which made it capable to avoid healing at a level previously unknown for rate-dependent models of
that type. A few simulation results are shown for different problem parameters previously explored by other works.
To solve the equations of the model, we use the finite-element method, for spatial discretization, and a backward
Euler scheme, for the time integration, in a Python implementation aided by an open-source computing platform
FEniCS.

Classification of Skin Lesions using CNN

2024-05-30T18:09:31+00:00

Various computational methodologies can be found in the specialized literature, with different
applications, among which the classification of skin lesions in dermoscopic images stands out in this work.
Although the initial analysis of skin lesions was performed using a set of visual rules known as the ABCDErule
(Asymmetry, Borders, Lesion Color, Diameter, and Evolution), the performance of this visual analysis is
influenced by factors such as lighting variation during image capture, the presence of artifacts that cause noise,
and the specialist's eye strain during image analysis. A mistaken initial analysis can delay the development of an
adequate treatment plan, affecting the effectiveness of this treatment. In the task of computational recognition of
elements in an image, the Convolutional Neural Network (CNN)stands out. In this context, this work presents the
results of the application of CNN ResNet for the identification of melanomas. To carry out this work, TensorFlow
and a database with 9144 images were used. The results were promising, reaching approximately 75% accuracy.

COMPUTING DEFLECTIONS OF TOPOLOGICALLY OPTIMIZED BEAMS

2024-05-30T18:13:10+00:00

In civil engineering, computing deflections is a fundamental step in the structural design process.
However, most structural optimization codes do not directly compute or evaluate displacements in the resulting
optimized structures. In that context, this work presents the basis of an approach to compute and analyze
deflections (vertical displacements) in optimized beams. Using Matlab®, we implemented an extension to the
FEM-based 99 Line Topology Optimization Code (Sigmund, 2001), which is able to compute deflections and plot
deformed shapes of optimized structures, allowing users to analyze deformation during the design process. We
also compared maximum deflections of optimized versus nonoptimized beams. According to results, for constant
boundary conditions, optimized beams present smaller maximum deflections.

Numerical modeling of composite steel-concrete beams with truss type shear connector

2024-05-30T18:16:51+00:00

Numerical analysis, when properly calibrated, presents itself as an important tool for the study and
development of new technologies. The truss type shear connector appears as a technically and economically viable
alternative, however its use in composite steel and concrete beams still needs to be studied and analyzed. For this
reason, in the present work, a non-linear three-dimensional model of composite steel and concrete beams with
lattice shear connector was developed, seeking to analyze the efficiency of the alternative connector. The
methodology used in the modeling was validated through experimental studies in the literature.

Optimal power flow considering non-smooth generation cost function and emissions using AMPL and Knitro solver

2024-05-30T18:19:15+00:00

The Optimal Power Flow (OPF) problem aims to analyze the planning and operation of electrical power
systems and has been widely used due to the benefits that can be obtained. This work analyzed the application of
language AMPL (Modeling Language for Mathematical Programming) and the Knitro commercial solver, to solve
the Economic and Environmental Dispatch (EED) problem, modeled as an OPF. In the proposed OPF modeling
were considered equality constraints such as active and reactive power balance and inequality constraints such as
generator, transformer and Shunt VAR compensator constraints that represent the operational and physical limits
of the system. The problem was implemented as single and combined objective functions aiming minimize the
generation cost with and without valve point effect and emissions. These characteristics make the problem more
complex, nonlinear, and non-convex. Additionally, a simple heuristic was proposed to deal with the discrete
characteristic related to the value of transformer taps. The IEEE 30-bus test system was presented to illustrate the
application of the proposed problem. Finally, the obtained data were compared with the literature and the
superiority of the approach was demonstrated.

Identification of Text Relevance in Service Desk Systems using Machine Learning Classifiers

2024-05-30T18:21:28+00:00

Service Desk systems form a wide source of useful information for organizations, which consists of
historical support requests. Such information can serve as a reference for responding future requests. Standardized
search tools, such as keyword searches in support request histories, are infeasible in large datasets and may provide
answers unrelated to a problem of interest. This manuscript aims to compare the performance of machine learning
algorithms in classifying support requests as relevant or not. We define as relevant the support requests that have

the potential to serve as a basis for responding to others. We will develop a filter to remove non-relevant informa-
tion from the dataset of historical support requests to provide a finite low-cardinality set of recommendations for

future support and assistance. In the performed tests, Naive-Bayes, Adaptive Boosting, Random Forest, Stochastic
Gradient Descent, Logistic Regression, Support Vector Machine, and Light Gradient Boosting Machine classifiers
were used. The classifier with the best performance (Random Forest) presented maximum average accuracy close
to 80%, and recall, F1-score, and AUC values all greater than 80%.

Epidemiologycal SIR model to study ’infodemics ́ about child vaccination

2024-05-30T18:24:29+00:00

Technological development has made the internet increasingly accessible in recent decades. However, despite

the benefits, overexposure to the dissemination of information has become a social concern. The rapid dissemina-
tion of information with fewer criteria plagued by rumours and fake news has compromised its accuracy, clarity

and reliability. The process of rapid and massive dissemination of unreliable information has been called an info-
demic because it behaves an epidemic. Google Trends is a tool developed to show the relative number of searches

for a given term of interest available on the Google platform. In this work, we apply the classic SIR model of
mathematical epidemiology to study the case of the time series of the frequency of searches on the controversial

term ‘childhood vaccination’. The aim of the approach is to assess how accurately the simple form of the epidemi-
ological model can describe the infodemic process. The matter is treated as complex open system and the model

parameters like infection and recovery rates from infection are supposed to vary but keeping stable along intervals
of engagement and disengagement. We show that the model parameters can provide useful information about the
social phenomenon in periods of social media engagement and disengagement in controversial news.

Topology optimization of 3D truss structures considering stress, displace- ment and buckling constraints

2024-05-30T18:27:18+00:00

This work addresses the development of 3D optimal trusses using the topology optimization method.

The aim is to minimize the total volume with local stress and displacement constraints as well as buckling con-
straints. The augmented Lagrangian method is also implemented to solve the optimization problem. The formu-
lation and the implementation are assesed by means of some benchmark problems found in the literature. Results

also show the importance of properly selecting the material parametrization.

Python Language Applied to Flutter Analysis in a VANT‘S 3D Wing.

2024-05-30T18:29:18+00:00

Flutter is one of the most well-known dynamic aeroelastic phenomena, known for its destructiveness
and frequently associated with thin structures and less rigid materials, and has been widely used in the evolution
of the aeronautical industry. The SAE Aerodesign competition simulates the design of UAVs - Unmanned Aerial
Vehicles - and includes the study of the probability of aeroelastic phenomena in the project to qualify students
and enthusiasts in the field. Aiming to enlarge access to Flutter analysis occurrence by students and produce an
efficient study of the Flutter Critical Speed, the Python language was applied to create a program able to interact
with the Aerodynamics through the Panel Method and the structural behavior by the Grid Method and return the
Critical Speed calculated according to Method K, generating the V-G Diagram of the aeroelastic behavior of the
plane. The wing of the UAV designed by Araras Aerodesign team in the system with two degrees of freedom was
used as an example. The code was efficient in generating the expected result, checked according to the literature,
and compared with commercial software.

Numerical modeling for deformation analysis of a cantilever beam

2024-05-30T18:31:49+00:00

The tireless quest for better living conditions makes people use technological resources as manners to
balance a work/economy/safety relationship. Those technological resources have been applied more frequently in
engineering. This is due to development of simulation software in order to provide greater economic viability in
engineering projects. The considerable growth in the infrastructure market, further promoted the application of
beams in projects, linked to this is the concern with the deformations that are caused to them. In this sense, the
deformation suffered by a beam was evaluated via structure analysis using the ANSYS Mechanical software. The
beam is at one extremity and supported by fixed support at the other extremity. To obtain the values of
deformations a beam was developed in ANSYS, and after, the deformation was found through finite element
methods. To verify the methodology effectiveness proposed in this study the numerical results were compared to
data obtained in the tests and theoretical calculations. Through the values obtained, it was concluded that the values
obtained in the simulation present deformations very similar to the tests and the theoretical calculation.

Evaluation of the mechanical behavior of concrete wall panels with functionally gradation fiber content by finite element method

2024-05-30T18:36:35+00:00

Concrete is a material with brittle rupture behavior when subjected to efforts that result in tensile
stresses, generating internal micro-cracks, facilitating the action of aggressive agents and reducing its useful life.
With the demands of improving the durability and mechanical performance of structures, the functional gradation
of concrete properties with the use of fibers has been presented as a promising alternative. With the recent
publication of NBR 16935, in addition to contributing to durability, fibers can be used to totally or partially replace
steel reinforcement, especially in structural elements where the distribution of internal tensile stresses is not well
defined, as in the case of of wall panels and other slender pieces subjected to compression. The production of
concrete wall panels with functionally gradation of fiber content allows a more efficient use of materials,
distributing the fibers only in the regions that can present a real contribution, enhancing their physical and
mechanical properties due to their presence. This work seeks to evaluate the mechanical behavior of functionally
graded fiber concrete wall panels through modeling and computer simulation. The model was implemented in the
commercial software ANSYS, which is based on the finite element method. Different configurations of the
functional gradation of the fibers were simulated along the thickness and in different regions. Each configuration
of the functional gradation in the panels were simulated in static and buckling analyses. For calibration of the
parameters of the materials of each layer, the values present in the literature for different types and fiber contents
were adopted. Finally, the numerical results obtained were compared with experimental results from the literature
to validate the proposed model. The functional gradation of fiber content did not compromise the strength of the
panels and the model adopted presented an acceptable correspondence with the experimental results found in the
literature.

PARAMETRIC OPTIMIZATION OF QUARTER VEHICLE SUSPEN- SION MODEL BY RESPONSE MAP TECHNIQUE

2024-05-30T18:39:10+00:00

This work aims to set the suspension optimal parameters of a quarter vehicle model, using an exhaustive
parametric optimization technique. The objective function minimizes sprung mass rms acceleration considering
a Gaussian white noise road profile for a fixed sprung/unsprung mass ratio with different control strategies for a
semi-active suspension system.

Convolutional Neural Networks Implementation on a Network-on-Chip Platform

2024-05-30T18:41:42+00:00

Delivering more throughput to a given computational system or device may be crucial when using
computational intelligence-based approaches as a design preference for a growing set of applications. On the other
hand, these approaches are frequently under rigorous constraints regarding processing time, power consumption
and required memory. One of the main topics of interest in computational intelligence is machine learning. It deals
with computational methods and models based on observational data. In machine learning, the machine develops
the ability to continually learn with data, in an attempt to predict and recognize patterns as humans do. Deep neural
networks use several hidden layers to achieve pattern recognition. The main difference between traditional neural
networks and deep neural networks is the amount of network layers. A convolutional neural network is a deep
learning model, usually used to classify and recognize patterns in image and video-based applications. One of
the most known designs for convolutional neural network is LeNet-5. It allows manuscript characters recognition.
This kind of neural network consists of an input layer, that receives the image, a series of layers, that implement
image operations for characteristics mapping, and a last layer, that consists of a classification neural network, using
the characteristics map and provides the classification result as output. The network structure consists of a series
of paired convolutional layers followed by pooling layers. The output is classified by a fully connected layer. A
convolutional layer is used to allow image characteristics mapping. A pooling layer is responsible for reducing
the matrixes dimensionality and data complexity. Our work aims at investigating the use of parallel processing for

the implementation of a convolutional neural network on a multiprocessor system-on-chip. It exploits a network-
on-chip platform for communication between the processing elements. Mainly, our work consists of grouping

the network operations into conceptual units called tasks. These tasks are the workload to be distributed between
the processing units, which will operate in a parallel manner. As a case study, we implement LeNet-5 on the
multiprocessor system-on-chip MEMPHIS platform. We demonstrate that the distribution of the convolutional
neural network workload over a set of processing elements leads to significant performance gain over the serial
implementation.

Crack Detection In Concrete Using Artificial Intelligence With Deep Learning

2024-05-30T18:44:15+00:00

Artificial Intelligence (AI) is a field that has been drastically changing not only several areas of
knowledge, but it also brings high expectations regarding the future of professions. While there are projections of
great growth in demand for data scientists, there is the possible threat to unqualified labour, where AI can offer a
low-cost alternative. Deep Learning is a subset of Machine Learning, which is a field dedicated to the study and
development of machines [1], which can be seen as a stage of AI. Also called Deep Neural Network, refers to
Artificial Neural Networks (ANN) with multiple layers. In recent decades, it has been considered one of the most
powerfull tool, and has become very popular in literature as it is able to deal with a great amount of data. Interest
in having deeper hidden layers began recently to overcome the performance of classical methods in different fields,
especially in pattern recognition [1]. Neural networks are used in many areas, such as search algorithms on search
engines, content recommendation algorithms, autonomous cars, speech recognition (audio), natural language
recognition (text) and computer vision (images). The use in image recognition is mainly done with Convolutional
Neural Networks. Thus, the present work intends to apply Convolutional Neural Networks for the detection of
cracks in concrete structures through image processing, especially the obtained with drones. The detection of
cracks by visual inspection can be a very laborious process, depending on the number of cracks and the difficulty
of access, in addition to relying heavily on the subjectivity of the observer. Thus, several methods have been
proposed to automate this process, which consist of image processing techniques. However, the implementation
of these techniques is difficult when there are adverse conditions, such as changes in different textures [2]. It is in
this sense that the use of neural networks brings the expectation of being a method appropriate in relation to the
stability in the detection, even considering variations in the conditions for acquiring images, such as lighting, angle
of acquisition, texture, dimensions, among others. This expectation is mainly due to the ability to automatically
learn the characteristics relevant to the detection of cracks, whereas there are adverse conditions in the learning
data.

Calibration and validation of the numerical model of a freight wagon based on dynamic tests under operating conditions

2024-05-30T18:47:14+00:00

This work presents an efficient methodology for the calibration and validation of a freight wagon
numerical model by an iterative methodology based on experimental modal parameters identified in a dynamic
test under real operating conditions. The dynamic tests involved the use of a minimalist on-board monitoring
system, which did not cause any interference in the vehicle's operational logistics. The identification of the
vehicle's dynamic properties was made through the application of operational modal analysis techniques to the
data collected during the vehicle circulation. A 3D numerical model of the freight wagon was developed and
calibrated using an iterative methodology through a genetic algorithm and based on the identified modal
parameters. The applied methodology proved to be effective and robust in estimating three numerical parameters,
besides a significant upgrade in the natural frequencies compared to the model before calibration. Finally, the
dynamic response of the model was validated by means of a direct comparison between numerically simulated
results, based on a vehicle-track interaction analysis, and experimentally collected time history responses.
Comparisons revealed an excellent agreement between the experimental and numerical time series after
calibration, especially for the frequency range covered by the identified modes.

Degradation prediction of in-service railway bridges supported by Semi-Markov process

2024-05-30T18:52:49+00:00

This article describes a model for predicting the degradation of in-service railway bridges based on a
semi-Markov continuous time process. This model relies on the history of inspections of 588 bridges located on a
heavy-haul railway line in Brazil, between 2016 and 2020. A dedicated computational tool developed in Matlab
allows the automated data processing. A parametric study is performed to understand which factors derived from
the bridge structural characteristics, as well as operational and environmental factors, most influence the
deterioration model. The type of material proves to be a decisive factor and therefore two specific prediction
models are stablished, one for concrete bridges and other to steel bridges. The prediction models have an efficiency
equal to 93.7%, for concrete bridges, and 95.1% for steel bridges.

Numerical analysis of punching shear in concrete reinforced flat slab using damaged plasticity model

2024-05-30T18:55:33+00:00

Due to high shear stresses in the slab-column connection, reinforced concrete flat slabs may be

vulnerable to punching shear failure. In this paper, nonlinear finite element analyses of a reinforced concrete slab-
column connection under static loading were conducted using ABAQUS software and the concrete damage

plasticity (CDP) model. The material parameters of the CDP model were calibrated based on experimental results
of punching shear strength of a reinforced concrete flat slab presented in the literature. Failure mode and cracking
pattern at ultimate load were evaluated, indicating that the calibrated model adequately predicts the punching shear
response of the slabs.

Numerical analysis of structures with a GFRP application in a transmission line tower

2024-05-30T18:57:28+00:00

This work aims to investigate through numerical simulations the mechanical behavior of the glass fiber
reinforced polymeric (GFRP) line post structures. It is presented a numerical validation of the mechanical
properties of the composite material, in order to ensure the representativeness of the model. Additionally, in order
to understand the impact of parameters change, such as fibers orientation, layer thickness, and resin type in the
structure model, the structure mechanical response curves is evaluated. Therefore, a parametric analysis is made
to provide an understanding on the structure response characteristics such as load versus displacement, stress
versus deformation, buckling modes, as well as the cause and effect relationship in the results obtained. The
orientation of the fibers showed to be the most important parameter on the mechanical behavior of the structure,
as well as the number of layers, a factor observed as being one of the most relevant in the verifications of the
buckling modes.

Vibration correlation technique applied to cylindrical and conical shells—an overview of the recent developments

2024-05-30T19:00:40+00:00

Traditional buckling experiments of imperfection-sensitive structures like cylindrical or conical shells
may result in the permanent failure of the specimen. Yet, for validating the numerical models and, consequently,
the design of aerospace barrel structures, to perform a qualification test is a crucial step. There is, therefore, interest

in non-destructive experimental procedures for predicting the buckling load of these structures from the pre-
buckling stage, allowing the use of the same specimen in further qualification tests. An example of these

methodologies is the Vibration Correlation Technique (VCT), which allows determining the buckling load without
reaching the instability point through a sequence of vibration tests performed at different load levels. In this review,
focus will be given to the VCT applied to cylindrical and conical shells, revisiting the analytical foundation
supporting its applicability together with experimental and numerical results of simplified downscaled barrel
structures with different design details and test conditions, highlighting its non-destructive characteristic. The state
of the art corroborates the robustness of the VCT when applied to imperfection-sensitive thin-walled structures;
however, more test results, especially for real-scale barrel structures, are needed for expanding the experimental
database and confirming the application of VCT to predict the buckling load these structures.

Hybrid models for time series forecasting of the dam monitoring data

2024-05-30T19:03:56+00:00

Time series forecasting is a result that contributes to analysis and decision-making and can be applied
in several areas of knowledge. In the area of dam structural safety, this practice is little explored, although the
equipment used in the monitoring feeds an extensive database. This work aims to apply a hybrid methodology for
forecasting time series, integrated into the processing of data collected by monitoring instruments of a concrete
dam. Wavelet Decomposition will perform the time series processing, then to separate the series components, an
Autoregressive Integrated Moving Average model will be fitted. Residuals resulting from this
mathematical/statistical model will be modeled through Artificial Neural Networks of Radial Basis Functions. The
linear combination of these models will generate the time series forecast itself. The combination weights will be
defined by solving a nonlinear programming problem. The investigated approaches will be compared and selected
according to the smallest mean absolute percentage error measure. The partial series models do not need to have
high performance for the prediction proposed to be satisfactory. The proposed approaches for predicting the test
set have MAPE of less than 0.57%, while ARIMA and ANN-RBF models used separately reached values of up to
4.33%. The results indicate gains in forecasting assertiveness, aiding decision-making, which aims to create
preventive measures to ensure dam safety.

Forecast of time series earned by the Piezometer through Method Multiple Kernel Sarima Support Vector Regression Wavelet

2024-05-30T19:06:54+00:00

In this study time series predictions were made from measurements of the instrument called piezometer
(PS), located in the key block (I10) of stretch I of the Itaipu hydroelectric dam. The results show that the forecasting
performance attained by the method called SARIMA Support Vector Regression Wavelet of Multiple Kernels
(SSVRWMN) was notably superior to predictive methods SARIMA, SVR, and SARIMA-SVR combined.
Comparing it to the second-best result (namely, the SVR method), the relative reduction was approximately 39.1%
in the mean square error (MSE) accuracy measure.

Application of a hybrid method for forecast time series in concrete deformation in a counterstruct dam

2024-05-30T19:11:55+00:00

The concrete deformations have been researchers study object in the structural safety of dams process.
These deformations, which occur over time, are influenced by various physical and environmental factors. One of
the environmental factors that affect the deformations of concrete is the ambient temperature. In this paper, a
hybrid method called SARIMAX-NEURAL is presented for prediction of concrete deformations that are
influenced by ambient temperature. This hybrid method was defined as a linear combination of predictions from
Box & Jenkins methodology models and Deep Learning neural network models with Long Short-Term Memory
architecture. Historical data of concrete deformations were measured by rosettes strain installed in a buttress block
in the Itaipu dam for a period of 34 years. The proposed hybrid method, which considered the effect of ambient
temperature on the deformations of concrete, effective results presented in comparison with the individual methods
in which the effect was not considered to ambient temperature. The predictive accuracy gains were between 25%
and 60%.

Fragility curves and failure models based on lumped damage mechanics applied to reinforced concrete frames under seismic loads

2024-05-30T19:15:24+00:00

This paper presents a methodology to apply the Lumped Damage Mechanics (LDM) in the Perfor-
mance Based Earthquake Engineering (PBEE) approach, to evaluate the seismic vulnerability of reinforced con-
crete frames. The lumped damage model represents the evolution of damage and plasticity lumped in inelastic

hinges at the nodes of the elements. The method allows the estimation of material nonlinear effects due to shear

and bending moment under static, cyclic and dynamic loads, considering fatigue and hardening. Incremental dy-
namic analysis using artificial earthquakes are performed to calculate the fragility curves of the RC frames with

LDM. The paper proposes a procedure to identify and characterize collapse mechanisms from the local internal
variables of damage, using system reliability theory. The main results show that LDM can be efficiently applied
to PBEE and it is possible to use the internal variables of damage as engineering demand parameter (EDP) in the
vulnerability analysis.

Thermometer Data Forecast for a Buttress Block of the Itaipu Dam

2024-05-30T19:18:37+00:00

The article presents the temperature forecast of thermometers installed in a buttress block of the Itaipu
dam, more specifically the D-38 block. The models used were ARIMA (Autoregressive Integrated Moving
Averages) and Holt-Winters (simple exponential smoothing), additive and multiplicative. Temperature data from
three thermometers were used: TI-D-001, TS-D-003 and TS-D-004. The analyzes were carried out with the help
of free software, R. The series with quarterly periodicity from 2008 to 2017 were considered for the modeling,
with forecasts for the quarters of 2018, which were compared with the real data. The modeling that presented the
best result, for the TI-D-001 and TS-D-004 instruments, was the additive Holt-Winters whose information criterion
AICc obtained the lowest value and, in addition, presented the lowest MAPE in relation to the ARIMA model ,
which makes it the most suitable model. As for the TS-D-003 instrument, the model that best fitted, according to
the AICc criterion, was the multiplicative Holt-Winters, but for the 2018 quarters, it presents MAPE superior to
those of the ARIMA model.

Influence of different factors related with the train-bridge interaction system in the stability of high-speed trains subjected to strong winds

2024-05-30T19:22:55+00:00

Strong crosswinds are one of the most critical sources of excitation that may impact with the train
runnability and safety. However, there are a significant number of characteristics related with the train-bridge
system that are rarely addressed which may influence the train’s performance when subjected to this kind of
actions. The present work aims to fill this gap, by individually studying the impact of such characteristic, such as
the bridge lateral stiffness and the track condition, in the runnability of high-speed (HS) trains moving over bridges
subjected to crosswinds. The Arroyo de Las Piedras Viaduct, a high pier viaduct belonging in the Spanish HS
network, was used as case study. The study concluded that the bridge’s lateral behavior has a negligible impact in
wind-induced derailments, while the track condition, considered in this work with four quality levels, proved to
significantly influence the train’s running safety, especially at higher speeds. This is due to the fact that the Nadal
and Prud’homme indexes strongly depend on the wheel-rail lateral impacts, which become more pronounced for
higher speeds and under poorer track conditions.

Integrated Methodology for Fatigue Life Prediction of Existing Metallic Railway Bridges

2024-05-30T19:28:40+00:00

In general, bridges are large structures modelled at the global scale in order to avoid computational
limitations. The fatigue assessment of these structures using such a type of modelling is not possible based on local
mechanical quantities due to the inherent difference between the size of bridges and the local nature of fatigue
phenomena. Currently, the most important standards propose S-N relations for nominal stresses to overcome this
multiscale problem, requiring an inherent approximation between the local characteristics of the investigated detail
and those at the basis of a relatable S-N curve, which may be particularly conservative for complex connections
of bridges in service with ancient construction technologies. Aiming to reduce unnecessary safety margins, local
fatigue approaches based on submodeling techniques leveraged by modal superposition principles are proposed to
implement local methods using fatigue quantities evaluated considering the real response of the mechanism of
loading transference. A complementary relation can then be established between the global conservative normative
approaches, applied to identify the fatigue-critical details, and such local fatigue approaches, defined as advanced
calculations stages. Therefore, an integrated methodology for fatigue life prediction of existing metallic railway
bridges is proposed, suggesting different phases of analyses at multiple scales. A real case study is investigated to
demonstrate the added value of this multiphase calculation strategy.

Tuned liquid column damper modeled by pressure based eulerian approach using isoparametric quadrilateral finite element

2024-05-30T19:31:48+00:00

This paper model sloshing in 2D tuned liquid column damper (TLCD) using a pressure based Eulerian
approach. The fluid domain is discretised by isoparametric quadrilateral 4-nodes (Q4) finite elements coded in
MatLab. A TLCD was modelled with rigid contours and a free surface to study uncoupled liquid reservoir. It is
performed free and forced (harmonic) analysis to determine dynamic parameters. The numerical results were
validated using experimental Alkmin’s results presenting acceptable errors (inferior of 1.7% relative error) with
less than 5k elements. The present numerical implementation presents a good agreement with analytical solution
and experimental results.

USE OF THE INERTER DEVICE IN AUTOMOTIVE SUSPENSIONS: PARAMETRIC STUDY

2024-05-30T19:38:22+00:00

The inerter appears as an innovative mechanical device capable of generating a resistance force
proportional to the relative acceleration between its two terminals, so that the proportionality constant is called
inertia and, like an element of mass, is measured in kilograms. (kg). Its properties support the purpose of
suspension systems to promote the reduction of vibration levels and the maintenance of stability and adherence of
a vehicle in front of a series of road profiles, as they allow the addition of inertia to a dynamic system without a
significant increase in mass. In this work, a parametric study of the properties of an inerter spring damper (ISD)
suspension coupled to a 1⁄2 vehicle model is carried out using the response map technique. The influence of
stiffness, damping and inertia parameters on vibration levels are evaluated for a random road profile. The response
maps are derived from the frequency domain model comparing the performance of the passive inert suspension
system and the conventional passive system. The analysis consider the main performance indicators of these
systems in terms of comfort, stability and adherence and simulations were carried out in MATLAB software.

A position-based Space-Time formulation for geometrically nonlinear problems

2024-05-30T19:41:23+00:00

Space-Time finite element methods has been developed over years for solving a series of time-dependent