bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of the unilateral elastic base on the backbone curves of an imperfect cylindrical panel
Authors: Frederico Martins Alves da Silva  , Jordana Lopes Morais
Published: January 2025

This work evaluates the influence of a discontinuous unilateral elastic base and an initial geometrical imperfection on the nonlinear free vibration of cylindrical panels. The Donnells nonlinear shallow shell theory is considered to describe the cylindrical panel, then the equations are discretized by the Galerkin method. The unilateral elastic base is represented by the Signum function, and the Heaviside function describes the discontinuity of the elastic base. The results show the analysis of the nonlinear free vibrations of the cylindrical panel through the backbone curves, investigating the influence of the hypothesis of contact of the unilateral elastic base and the initial geometrical imperfection of the cylindrical panel. The modal solution employed has with five degree-of-freedom, being sufficient to describe the nonlinear softening behavior of the imperfection cylindrical panel in contact with the discontinuous unilateral elastic base. The numerical results reveal that the imperfect cylindrical panel in contact with unilateral elastic base presents less structural stiffness than in contact with bilateral elastic base, with decreasing the natural frequencies. In conclusion, the backbone curves are strongly influenced by discontinuous unilateral elastic base and the imperfections of the cylindrical panel.
Nonlinear Dynamics of a Cantilever Beam under a Transversal Harmonic Follower Force
Authors: Lucas da Mata Rocha Menezes  , Paulo Batista Gonçalves  , Deane de Mesquita Roehl
Published: January 2025

The nonlinear geometric of cantilever beams is well disseminated in current literature. Normally, in this type of analysis the load does not maintain its constant slope throughout the analysis. This work addresses the case of large displacements for beams considering a follower transversal load to the deformed axis. This type of situation generates interesting nonlinearities and has several applications, for example, the wind load in wind turbine blades must be considered always perpendicular to the beam element axis. This work will also address the dynamic behavior of this structural system as well as its implications regarding stability. According results for large response its possible to observe the great influence of load level, the beam curvature suffer a abrupt change highlighting the importance of nonlinearity in this problem
Optimization of tuned mass dampers parameters using Artificial Neural Networks
Authors: Patrick de Oliveira Batista da Costa  , Daniele Kauctz Monteiro  , Daniel Barbosa Mapurunga Matos  , Letícia Fleck Fadel Miguel
Published: January 2025

Control systems are usually employed to minimize the dynamic effects on structures. These controllers must be designed according to the physical and geometric characteristics of the system and the environmental loads to which the structure will be subjected. Passive control is the most suitable for extreme events because it does not depend on an external power source to function properly. The use of a linear attenuator, such as the tuned mass damper (TMD), allows for dynamic analysis in the frequency domain, which provides a reduction in the computational cost of the analysis. Among the several methods used to determine the optimal parameters of the damper, analytical methods in their closed form can be applied to simpler structures. In structures with several degrees of freedom or complex geometry, the optimal TMD parameters, as well as its optimal position, can be acquired by methods based on stochastic optimization. This kind of problem is commonly solved in the state-of-the-art by Metaheuristic algorithms. However, in general, these procedures require high computational costs, which makes Artificial Neural Networks (ANN) a viable alternative to minimize the processing time. Thus, this paper proposed a methodology based on ANN in comparison with the Circle-Inspired Optimization Algorithm (CIOA) to determine the optimal parameter of tuned mass dampers, i.e., the damper period. Training of the neural networks was performed with a dataset of optimal TMD values, which were obtained in the frequency domain. The model developed from these results was subsequently tested on different shear-building models, including the influence of seismic excitation. The response of the structures in displacements was evaluated with the optimal values obtained through ANN and compared with the structures without the control device. In addition, the optimal parameters obtained by ANN were also compared with the closed analytical formulations. The results obtained by the neural networks were as effective as the CIOA metaheuristic algorithm but required up to 0.02% of its processing time.
Parametric study of the apparent modal parameters of crowd-footbridge systems
Authors: Igor Braz do Nascimento Gonzaga  , Michèle Schubert Pfeil  , Wendell Diniz Varela
Published: January 2025

The modal parameters of footbridges are time-variant as pedestrians walk along them, resulting in a new dynamic system comprising the isolated structure and the walking persons. This phenomenon is known as human-structure interaction (HSI) and is particularly significant for lightweight footbridges, where the effective damping ratio of the combined system is significantly higher than that of the isolated structure. This paper proposes an analytical-numerical approach to address the effects of HSI on the modal parameters of the coupled system. The effective damping ratios and natural frequency are determined by solving the eigenvalue problem of a two-degree-of-freedom mass-spring-damper system, with one degree of freedom representing the isolated structure and the other representing the equivalent model of the walking persons. The obtained results are compared with experimental measurements from the literature, illustrating the effectiveness of the proposed approach while also demonstrating its computational cost-effectiveness in comparison to existing methods.
Seismic Performance Assessment of an Unreinforced Masonry Historical Building Using Nonlinear Static Methods
Authors: Philipe Queiroz Rodrigues  , Eduardo Marques Vieira Pereira  , Fábio Fleming Leitão  , Rodrigo Bezerra Andrade  , Hugo Luiz Oliveira  , Gustavo Henrique Siqueira
Published: January 2025

Historical heritages embody the identity and evolution of a people, making their preservation paramount. Buildings from the 17th and 18th centuries constitute a significant portion of this heritage, and evaluating their behavior under potentially damaging actions is crucial for mitigating and preventing irreparable losses. Despite Brazil's location in a tectonically stable region, seismic events with the potential for considerable damage have occurred and could impact these historical structures. Among the methods for assessing the seismic vulnerability of buildings, nonlinear static methods stand out, aiming to quantify the effect of earthquakes on a structure using an incremental lateral force analysis considering nonlinearity, known as pushover analysis. This study aims to evaluate the seismic performance of an 18th-century masonry historical building using a nonlinear static method, notably the oldest one in the urban complex of the central-south region of the state of Ceará. To this end, a finite element numerical model of the main façade was developed to represent the historical building. The seismic performance of the building was then evaluated, and the expected damage to the historical building under seismic loading was quantified.
Study of the influence of physical nonlinearities of spherical caps made by Elastomeric Materials
Authors: Patrícia Fernanda Silva de Oliveira  , Renata Machado Soares
Published: January 2025

The analysis of the behavior of structural elements in terms of variations in physical and geometric influences has been the subject of study since the early days of mechanical and structural engineering research. When it comes to shells, especially those composed of hyperelastic materials, many researchers have carried out work evaluating both the influences of the type of curvature of these elements and the type of deformation expected due to hyperelasticity. This work will investigate the behavior of a spherical cap with a boundary condition established by the locking of the circumference that makes up its base and subjected to uniformly distributed loading on its surface. Two different types of material were considered, one elastic following Hooke's Law and the other hyperelastic represented by elastomeric constitutives models. The Novozhilov and Donnell-Mushtari-Vlasov (DMV) shell theories together with the Rayleigh-Ritz method are used to obtain the governing equations of the problem. The displacements will be approximated using trigonometric functions in the circumferential direction and the Legendre polynomial of the first type in the meridional direction. Linear results are obtained, such as natural frequencies, and non-linear results, such as frequency-displacement and load-displacement relationships.
Cardiac Pacemaker: Fractional Equations and Frequency Analysis
Authors: Clivaldo de Oliveira  , Murilo Cesar Filipus  , Felipe Lima de Abreu  , Rodrigo Borges Santos  , José Manoel Balthazar  , Marcus Varanis  , Gabriella O. M. Silva  , Cristhiane Gonsalves  , Ângelo M. Tusset
Published: January 2025

Understanding and researching the human body has been fundamental due to its importance for living beings. As one of the vital organs of the human body, the heart has always been of great academic relevance. One of the areas of study of the heart is the study of the electrical stimuli that provide blood pumping. These electrical stimuli come from the Sinoatrial Node (SA), known as the natural pacemaker, which transmits the stimuli to the other parts of the heart, thus allowing blood to be pumped. A model to represent the signals of a pacemaker has been developed using a relaxation oscillator, the Van der Pol oscillator, given by a second-order differential equation. In this particular study, a more comprehensive investigation is proposed by introducing fractional order differential equations. Varying the order of the system allows for a more refined analysis of the dynamic properties of the Van der Pol oscillator and, by extension, of the cardiac pacemaker modeled by it. This approach is especially relevant considering the complex and nonlinear nature of the cardiovascular system. The practical implementation of this model is carried out by means of numerical simulation, using algorithms developed in the Python programming language. This choice of platform allows for efficient and flexible analysis of the resulting signals under different conditions and system parameters. Signal analysis in the time domain is complemented by advanced signal processing techniques in the frequency domain. The Discrete Fourier Transform (DFT) and Continuous Wavelet Transform (CWT) are employed to investigate the system's response at different frequencies, providing an in-depth understanding of its stability and dynamic behavior. In addition, the graphical representation of the results using phase spaces and bifurcation diagrams provides a visual understanding of the complex interactions between the system components and their dependencies on the model parameters.
Control allocation of an arbitrary fully actuated multirotor aerial vehicle equipped with 1-DOF vectoring rotors
Authors: Davi Antônio dos Santos  , Flávia P. Nery  , José A. Bezerra
Published: January 2025

The present paper deals with the control allocation of fully actuated multirotor aerial vehicles (MAVs) equipped with an arbitrary number of only radially vectoring rotors. To tackle the problem, we first consider a control architecture in which the control allocator is cascaded with the control laws. Therefore, the latter provides the resultant force-torque commands for the former to distribute them among the available actuators, which include the spinning and the vectoring motors. We formulate the control allocator through an optimization problem in which the rotor thrust vectors represented in body-fixed frames are the design variables. In this way, the control allocation equation becomes linear since it does not explicitly include the commands for the vectoring angles, which can be immediately computed afterwards using the computed optimal thrust vectors. In the optimization problem, the thrust vectors are constrained in such a way to respect given bounds on their magnitude and vectoring angle. It is noteworthy that, considering a minimal thrust magnitude, in general, greater than zero, the thrust vectors span non-convex sets, thus making the original problem a non-convex optimization. However, instead of dealing with such convex sets, we have replaced them by convex ones, thus given rise to a convex program that approximates the original problem. The method is widely evaluated by computer simulations on a hexa-rotor with all the six rotors equipped with a one-degree-of-freedom vectoring mechanism.
Exploring the Dynamics of Wind Energy Harvesters: VIV Turbines and Piezoelectrics
Authors: Clivaldo de Oliveira  , Felipe Lima de Abreu  , Rodrigo Borges Santos  , Murilo Cesar Filipus  , José Manoel Balthazar  , Ângelo M. Tusset  , Marcus Varanis
Published: January 2025

Wind energy is recognized not only for its high generating capacity among renewable sources, but also for its growing popularity in recent years. However, conventional wind turbines, which rely on blades to capture wind energy, present significant challenges, including noise pollution, interference with bird migration and the frequent need for maintenance due to the complexity of their mechanical components. In an attempt to minimize these problems, current innovations include bladeless wind turbines (VBWT). These operate from wind-induced vibrations, mostly vortex-induced vibrations (VIV). Among the various designs that have been documented, those that exploit energy generation through electromagnetic induction and piezoelectric systems deserve to be highlighted, as they have gained increasing recognition in the academic sphere. In this context, this work focuses on carrying out a dynamic analysis of a vortex-induced vibration energy harvester (VIVEH), which will have its energy generated from a piezoelectric patch connected to a beam with non-linear stiffness due to a magnetic coupling. The system will have its equations of motion simulated using a Runge-Kutta integrator implemented in the Python programming language, where its responses will be analyzed in the time domain by studying the system's sensitivity to different wind speeds, and in the frequency domain using tools such as Fast Fourier Transforms (FFT) and Continuous Wavelet Transforms (CWT). The results focus on analyzing the influence of the beam's non-linearity and its response in the frequency and time domain for different wind speeds.
Vibration of extremely flexible beam axially tensioned by incremental force
Authors: Iago Gonçalves de Oliveira  , Alexandre de Macêdo Wahrhaftig  , Cibele Mota Menezes  , Eduardo Márcio de Oliveira Lopes
Published: January 2025

Cables can be associated with extremely flexible beams. Particularly, electrical system cables supported on transmission towers are subject to climatic conditions whose effects are capable of mobilizing their vibration modes. The first mode is considered to be of special importance due to the shape assumed by the cable when subjected to the Earth's gravitational field. Under these conditions, cable deformation is influenced by its geometric and material properties, including viscoelastic behavior, when considered, making these systems intrinsically nonlinear in terms of geometry and material. The balance of these structural parts can only be found in the deformed configuration of the system. As a rule, cables need to be pulled for proper and correct use in transmission lines. The use of a traction force modifies the rigidity of the system, causing an increase in the natural frequencies of vibration. This occurs because the force that pulls the cable mobilizes the geometric stiffness portion of the total system stiffness. In solving the vibration problem, numerical methods can be employed. To this end, the model adopted is analogous to a double-supported beam, for which the successive integration of the bending moment differential equation leads to displacements of the axis, or the elastic line, for each stage of the iterative process. These iterations are repeated until the sum of the portions equals the total axial force to be applied. The smaller the force portion in each iteration, the better the result obtained. However, the number of iterations required will be greater, making processing potentially costly from a computational point of view. To solve the proposed problem, a programming routine was developed in the Python Jupyter Notebook language that allows calculating the deformation of the structural system and the natural frequency of vibration in each iteration. The process begins with the analytical solution of the approximate elastic line under the effect of gravity and the subsequent tension in the cable, with the definition of the natural frequency of vibration following the Rayleigh method. In the end, the first natural vibration frequency of the cable was raised non-linearly from 0.358 Hz to 5.944 Hz.
Determination of stresses in welded connections of railway bridges with the finite element method and global-local approach
Authors: Karina Barth Ferro  , Hermes Carvalho  , Túlio Nogueira Bittencourt  , João Victor Fragoso Dias
Published: January 2025

Steel bridges are used due to their large spans with reduced self-weight, and therefore, are widely used for expanding the Brazilian railway network. However, due to the cyclic loading acting on the structure, and their limited damping capacity, the dynamic effects must be evaluated. In addition, due to the cyclic loading, the effects of fatigue must be considered. In bridges, fatigue failures account for most of the damage and collapse of structures. Thus, techniques are proposed for assessing their service life, considering fatigue failure effects. Fatigue life assessment can be performed considering the history of stresses acting on the structure, and obtaining stress history data using the finite element method yields more accurate results compared to normative methods, but it requires an extremely refined mesh to obtain adequate stress values. Therefore, this study presents a strategy for obtaining stress histories with the passage of a vehicle on a railway bridge using the commercial software Ansys Mechanical APDL v. 2020R1 and Python routines to assess the fatigue life of connections. A global-local methodology is proposed, in which a model of a bridge span using shell and beam elements is developed and subjected to the passage of a vehicle. Its displacement results are then transferred to a local connection model developed with solid elements, to determine stresses for future use in assessment of fatigue life.
Determination of the Drag Force Disturbance Index for Analysis of the Neighborhood Effect in Tall Buildings Subject to Wind
Authors: Gabriela Villoslada  , Thiarly Feitosa Afonso de Lavôr  , José Luis Vital de Brito  , João da Costa Pantoja
Published: January 2025

The presence of obstacles around a building can interfere with wind flow, modifying the pressures on the facades and, consequently, the resulting forces and moments. These interferences can generate protective effects or increase pressure coefficients. Therefore, it is important to study wind behavior in buildings in the presence of neighbors to better understand these effects and ensure the safety of structures. Most physical phenomena cannot be predicted with complete certainty and repeated measurements of these phenomena generate random results, with some of these results being more frequent than others. Reliability analyzes are commonly used to examine the behavior of structures subjected to such phenomena, and one of these analyzes is considering the beta reliability index, which has several representations and in this case, the determination of beta is proposed, not being considered a criterion of failure, but rather as a change in the state of the drag force. In this sense, the present work presents the determination, through reliability, of the drag force disturbance index, that is, how much the drag force is being modified depending on the presence of the neighbor, in order to evaluate the behavior of the effects of the wind from the CAARC (Commonwealth Advisory Aeronautical Research Council) standard tall building model, using experimental data generated in a wind tunnel. The standard tall building model was studied in different positions, subjected to variable drag force actions, in isolation and with the existence of different neighborhoods. Probabilistic concepts and graphs of results are presented and discussed in relation to the directions adopted by CAARC for beta variation indices. With the results found, it was observed that the existence of a neighborhood affects the average values of the data, as well as the aforementioned index, both for increase and reduction compared to the isolated building, depending on the situation. Therefore, this study presents interpretations that can help predict the behavior of tall buildings subjected to wind loads in the presence of neighborhoods.
Seismic Vulnerability Assessment Mobile Application for Rapid Visual Screening
Authors: Philipe Queiroz Rodrigues  , João da Costa Pantoja
Published: January 2025

Similar to the Federal Emergency Management Agency's (FEMA) FEMA 154 method in the United States, which provides a rapid on-site survey method for building data to assess vulnerability indices and offers the RSV App mobile electronic form, this paper proposes the development of a mobile application for the visual rapid screening method for the Brazilian community of engineers and inspectors to assess the seismic vulnerability of existing structures. The simplified qualitative method adopted in the application originates in Japan, and a similar initiative was observed in that country at the symposium "Future of post-disaster assessment for buildings"; however, such an application was not found. Considering that the evaluation is carried out on-site, the application aims to facilitate the rapid screening process and disseminate the use of the method. Seismic-V was developed based on the Dart programming language and the Flutter framework. The Android Studio Giraffe IDE (Integrated Development Environment) | 2022.3.1 Patch 3 was chosen. Among the functionalities, it allows the structural verification for the five seismic zones with soil classes recommended in NBR 15.421. The user is required to provide real structural deterioration conditions, data, and structural characteristics such as number of floors, number of pillars, and respective cross-section that will support the seismic performance sub-index. Other features will be discussed in the paper and, at the end, a comparison will be developed between the results issued by the application and those calculated manually, with a discussion of the results. The proposal is relevant given the speed of application of the method and the initial screening that helps to prioritize existing buildings in future quantitative analytical approaches.
Twisted Tall Building Structural Response Under Lateral Wind-Induced Loads
Authors: Thiago Araujo Macedo  , Carlos Eduardo Luna de Melo
Published: January 2025

The design and construction of tall structures have consistently presented unique difficulties as architectural pushes limits continuously. Such building challenges demands from engineers' innovative structural solutions. Among these problems, a particularly notable one is the definition of twisted tall buildings structural system, which demand breakthrough designs to guarantee stability, safety, and functionality. The first twisted building, Turning Torso in Sweden, is a 190m tower designed by Santiago Calatrava with a total rotation of 90 degrees and its construction was completed in 2005.Twisted tall buildings, in contrast to prismatic ones, have non-uniform floor layouts and facades that spiral upwards, resulting in a visually appealing architecture. Nevertheless, this aesthetic innovation brings benefits and drawbacks to all building subsystems. Some authors have studied that the facade spiral decrease the natural illumination, other postulated that this shape reduces the magnitude of wind loads but decreases the lateral stiffness of the building. There are few studies on the structural form and on the response of twisted tall buildings under lateral loads. In this study, the behavior of tall buildings with 120m height under wind-induced loads will be investigated and contrasted between a prismatic model and various twisted ones, increasing the angle of rotation between different stories for each model from 0.5 to 6 degree. The analysis will be performed with procedural generated models in SAP2000 using Python programming language.The wind load will be estimated for the prismatic model according to the Brazilian Code NBR 6123:2023 and will be applied to the columns nodes each floor. The same numerical value of the load will then be applied to the columns of all twisted models and the only variable will be the twist angle between stories. The objective of this study is to evaluate and compare the maximum story drift, horizontal displacement, and the ratio between cross-sectional pre-dimensioning at the bottom level of the columns according to Brazilian Code NBR 6118:2023 and the total floor area.
Analysis of Tensile Specific Deformation of Fiber Reinforced Concrete Beams via FEM
Authors: Iva Emanuelly Pereira Lima  , Aline da Silva Ramos Barboza
Published: January 2025

The use of fiber reinforced concrete (FRC) for structural purposes has been gradually increasing and this growth has resulted in the emergence of several standards. With regard to Brazil, the first standard related to the design of FRC structures was published in 2021. In this standard, the calculation aspects for sizing FRC structural elements are represented, however, the behavior of specific tensile deformations is not fully illustrated. Based on this, a study is presented regarding the determination of the tensile specific deformation at the beginning of the plastic boundary (ε_Fp) of beams fiber reinforced concrete (FRC) and beams fiber reinforced high strength concrete (FRHSC). To establish these deformations, we used works found in the literature and through numerical analysis via the finite element method (FEM), and through the mesh convergence analysis of the finite elements obtained from the ABAQUS software, the beams were analyzed. According to the study carried out, it was found that, for FRC beams and FRHSC beams, ε_Fp corresponded to a value in the order of 5.0 and 6.5, respectively. This illustrates the possibility of greater deformation occurring at the beginning of the plastic boundary for the FRHSC and shows the potential of the work to contribute to the establishment of guidelines for the structural aspects of the FRC.
Coupling of discrete and smeared cracking models applied to reinforced concrete structures
Authors: Waila Mara Ciríaco dos Santos  , Samuel Silva Penna
Published: January 2025

The nonlinearity inherent to concrete comes from the cracking process and the inelastic phenomena in the fracture process zone (FPZ). It is understood that initially, microcracks appear diffusely in the material medium, even under low-intensity loading conditions. In these initial stages, cracking develops stably, causing the structure's nonlinear response, which can still absorb loads. With the advancement of the process, the crack coalescence causes the significant growth of cracks so that a discontinuity in the material medium is observed. At this stage, propagation occurs in an unstable manner, and the structure loses the ability to absorb loads. In reinforced concrete, the manifestation of cracks occurs through multiple fronts due to the reinforcement steel that absorbs tensile forces and locally contains the crack propagation, which initially appears in regions not covered by the reinforcement steel. In more advanced stages, cracks can be observed that surpass the reinforcement steel region and propagate throughout the structure until its collapse. Over the years, two main approaches have stood out in the representation of concrete fracturing: smeared crack models and discrete crack models. Each model aims to represent the concrete response based on different hypotheses. In the smeared models, the medium is considered continuous, and the effects of cracking are represented by the elastic degradation of the material computed through constitutive models. In discrete models, the crack is represented by a material discontinuity inserted into the mesh. This work presents a strategy that combines smeared and discrete models applied to the modeling of flat reinforced concrete structures. The reinforcement steel will be represented by one-dimensional elements with elastoplastic behavior while maintaining the perfect bond between the steel rebar and concrete. In the representation of concrete fracturing, the FPZ will be represented by a scalar damage model for the continuous degradation of the material, and from a critical damage value, a discrete model, which considers multiple crack fronts, is activated by inserting a discontinuity into the mesh using a nodal duplication strategy, thus describing the final rupture process. Finally, numerical simulations will be presented to illustrate the model's performance.
Formulation of a nonlocal bimodular damage model based on mechanical properties parametrization
Authors: Livia Ramos Santos Pereira  , Matheus Moreno Fortes  , Samuel Silva Penna
Published: January 2025

Material media representation by damage models presents difficulties in the parametrization process. The damage laws are generally written as functions of mathematical variables and, in many cases, without physical meaning. This lack of connection between the evolution of degradation and the material properties requires a diversity of tests to numerically reproduce results obtained experimentally, which makes such a process slow, costly, and subjective. Based on this context, a constitutive model capable of describing the material response with damage evolution laws defined in terms of material parameters obtained from experimental tests is proposed in this paper to overcome parametrization adversities. Such a model is focused on reproducing the bimodular behavior of quasi-brittle materials, such as concrete, which respond differently to tension and compression efforts. While these materials have a significant resistance under compression, they manifest cracks when subjected to tension, collapsing due to fracturing. The current model presents a nonlocal character as a regularization technique to avoid strain localization phenomena. The nonlocal equivalent strains are calculated according to the principal strains associated with uniaxial constitutive laws and physical parameters obtained experimentally. Finally, numerical simulations are conducted to validate and verify the constitutive model performance to represent the response of concrete structures.
Massivity index and numerical analysis of concrete specimens
Authors: Bruno Barroso de Oliveira  , Eduardo de Moraes Rego Fairbairn  , Ana Beatriz de Carvalho Gonzaga e Silva  , Alfredo Quiroga Flores  , Mariane Rodrigues Rita
Published: January 2025

This study is focused on the behavior of massive concrete structures and the stresses caused by the temperature variation, which occurs along the development of the hydration reaction. However, before a heat transfer analysis takes place, it is necessary to determine if the structure is massive or not. In this scope this article studies a proposal of enhanced massivity index, which is helpful to determine what kind of analysis is more suitable for each structure element. It also presents an analysis of a concrete block, which was modeled with two different softwares, considering also two different situations. The first one considered the block was filled with concrete at once. The second considered the concrete was discharged in four steps, which lasted fifteen minutes each. That gives us an insight of the thermal effects variation according to the different possible concrete plannings. The model results were compared with experimental results, since the the block was concreted in the laboratory and monitored with thermocouples.
N-M interaction curves for timber members cross-section under ambient and high temperature
Authors: Jackson da Silva Rocha Segundo  , Dalilah Pires Maximiano  , Ricardo Azoubel da Mota Silveira  , Caroline Aparecida Ferreira  , Rafael Cesário Barros  , Luis Henrique Aragão Alves de Queiroz  , Ígor José Mendes Lemes
Published: January 2025

Widely used for structural calculation, axial force (N) - bending moment (M) interaction curves are suitable instruments for evaluating the structural elements cross-section capacity, relating the ultimate values of bending moment and axial force. Also known as resistance curves in ambient temperature and fire situation, the N-M curves become strongly dependent on the temperature field because of the physical and mechanical changes that occur in the material under elevated temperatures. Therefore, the present study aims to obtain the interaction curves of timber structural elements cross-section of commonly used members in civil construction, subjected to the action of thermal conditions (ambient and high temperatures), using a generalized numerical strategy based on the strain compatibility method (SCM) and Newton-Raphson method coupling. The adopted strategy is validated through the construction of N-M curves for timber cross-sections, subject to ambient temperature and different fire configurations and temperature distribution. The results obtained are compared with answers available in the literature.
A mixed total Lagrangian-updated Lagrangian Smoothed Particles Hydrodynamics method for geomechanics simulations with discontinuities
Authors: Daniel Shigueo Morikawa  , Mitsuteru Asai
Published: January 2025

This study presents a novel approach for simulating geotechnical problems including the initiation and post-failure behavior of discontinuities. The developed method is constituted by a mixed total Lagrangian--updated Lagrangian Smoothed Particle Hydrodynamics (SPH) method, which the main characteristic is to distinguish between internal forces within a body and contact forces from interactions with other bodies as internal stress and collision stress, respectively. Internal stress effects are calculated using total Lagrangian SPH interpolations, while collision stress effects are computed with updated Lagrangian. Fractures are simulated by employing plastic deformation as a damage measure, with fully damaged particles detached from their original body and treated as a separate particulate material, interacting via collision stress. Numerical tests confirm the method's capability in accurately modeling elastic collisions, friction forces and tension and shear fractures, validated against experimental data. Finally, we show the applicability of the proposed by simulating a real-scale landslide scenario, the Selborne experiment. This final numerical test demonstrates the capability of the method to simulate a landslide detached from the main soil mass as observed in the experiment.
A position-based PFEM formulation for free-surface non-Newtonian flows with application to fresh concrete
Authors: Luiz Fernando Honorato Teodoro  , Giovane Avancini  , Rodolfo André Kuche Sanches
Published: January 2025

This work presents a methodology for free surface non-Newtonian incompressible flows using a particle position-based formulation of the Particle Finite Element Method (PFEM) [1], motivated by the simulation of fresh concrete flow. This method is based on the Lagrangian description of the flow and represents the fluid domain by cloud of particles, with a finite element mesh being built, taking the particles as nodes, to solve the motion equations and update the particle positions. To deal with large distortions of fluid flows, such mesh is constantly rebuilt, leading to a method very robust to deal with topological changes within the fluid domain. This approach requires updating the reference configuration, enabling the use of partially or fully updated Lagrangian descriptions. The weak solution is based on the stationary energy principle considering current nodal positions and pressures as variational parameters, deviating from the common practice of employing velocity and pressure as unknowns. Furthermore, smoothed versions of the Bingham and Herschel-Bulkley viscoplastic models are chosen to represent the fresh concrete behavior, keeping stresses independent of strain history and making updating the reference for the fluid simple, without the need for considering the stress distribution in the past reference. The implicit α-generalized strategy is chosen for time integration, enabling second order convergence and ensuring good stability due to the control over numerical dissipation at high frequencies. Finally, selected 2D and 3D examples are simulated to test and verify the proposed methodology.[1] IDELSOHN, S. R.; ONATE, E.; Del Pin, F. The particle finite element method: a powerful tool to solve incompressible flows with free-surfaces and breaking waves. International Journal for Numerical Methods in Engineering, John Wiley and Sons, Ltd, v. 61, n. 7, p. 964989, oct 2004. ISSN 1097-0207.
Analysis of two-phase flows using position-based PFEM formulation
Authors: Thiago Rodrigues Carvalho  , Rodolfo André Kuche Sanches  , Giovane Avancini
Published: January 2025

The numerical simulation of flows with topological changes is quite challenging, being approached in the literature by different techniques, highlighting fixed mesh methods, generally based on immersed boundary techniques, and particle-based methods, generally based on a Lagrangian description of the flow. One approach that has proven to be efficient is the particle and finite element method (PFEM), which combines the concepts of particle methods with the finite element method. In this context, this work deals with the development and implementation of techniques for simulating two-phase flows with free surface and topological changes in an alternative formulation of PFEM, where instead of velocities as nodal parameters, particle positions are used. Initially, the domains of the two fluids are represented by a cloud of particles to which the physical characteristics of the fluid they represent are attributed, as well as the initial conditions. A mesh of finite elements is built on this particle cloud to solve the equation of motion in Lagrangian description, with the physical characteristics, as well as the velocity and pressure fields, being interpolated by the shape functions of the finite elements. To avoid large distortions, and also mesh entanglement, at each step this mesh is destroyed and a new mesh is built. Delaunay triangulation is used to construct the mesh, together with the alpha-shape method to define the contours, together with a particle relocation technique that must guarantee the quality of the mesh (avoid extremely small elements or elements with a very small volume ), as well as ensuring the conservation of the number of particles of each fluid. This formulation is tested for cases of free surface flows, such as sloshing in reservoirs, taking into account the water-air interaction, and the results are compared with results from the literature.
Assessing 3D-printed concrete process parameters through Discrete Element Modeling
Authors: Victor Hugo Morais Avancini  , Osvaldo Dario Quintana-Ruiz  , Eduardo Morais Barreto Campello
Published: January 2025

Three-dimensional concrete printing (3DCP) has emerged as a promising manufacturing technique in the civil engineering sector, offering myriad advantages over traditional construction methods. Despite its potential, challenges persist in optimizing the manufacturing stage of 3DCP, including determining optimal fresh concrete rheology, layer thickness, print path, and nozzle characteristics. In this study, we incorporate the Discrete Fresh Concrete model (DFC) into our Discrete Element Method (DEM) code to simulate the rheological behavior of fresh printable concrete during printing, aiming to explore a comprehensive range of process parameters and their combinations to enhance understanding and optimization 3DCP process. Through a series of simulations, we systematically vary some of the process variables such as concrete mix design, nozzle specifications, and printing speed to investigate their influence on the printed output quality. By the obtained results, we aim to identify the key parameters that significantly affect the process, offering insights for refining 3DCP technologies and helping guide their development. We believe methodologies of the type as shown here may be an efficient tool for advancing 3DCP technologies.
Advanced Computational Modeling with FVDAM for Homogenization of Reinforced Concrete Beams
Authors: Samuel Richard da Silva  , Diego Souza Mendonça  , Romildo dos Santos Escarpini Filho  , Francisco Patrick Araújo Almeida  , Kevin Tenório Lobo Martins
Published: January 2025

Reinforced concrete is widely used in civil engineering due to its strength, durability, and versatility. This material is heterogeneous, as it combines concrete with steel bars, giving it a tensile strength much higher than that of simple concrete. However, the computational modeling of this type of material is challenging due to the need to consider the distinct properties of the phases, generating considerable computational costs. According to Almeida (2018), the simulation process of reinforced concrete beams requires a meticulous analysis of the interactions between concrete and steel, as well as the non-linear behavior of the material under different load conditions. This complexity significantly increases the time and resources needed to perform accurate computational analyses. An alternative to modeling reinforced concrete is to replace it with a homogeneous material with properties/behaviors equivalent to those of the original heterogeneous material.The Finite-Volume Direct Averaging Micromechanics (FVDAM) method emerges as a promising and efficient alternative for obtaining the effective elastic properties of composite materials with complex microstructures. In this study, the efficacy of FVDAM in the homogenization of reinforced concrete beams was evaluated. The stiffness using this technique was compared with that obtained using the calculations presented by Pinheiro (2007). In addition, two unit cell models were compared, differentiating the shape of the fiber: square and circular (Escarpini and Almeida, 2023).In this work, it is expected to understand the influence of the fiber shape in the unit cell and compare the results of FVDAM with those of Pinheiro, in terms of stiffness, evaluating issues in the context of safety.
Assessment of the structural integrity of cement sheaths in oil wells.
Authors: Maria Clara de Lima Medeiros  , Catarina Nogueira de Araújo  , Thiago Barbosa da Silva  , William Wagner Matos Lira
Published: January 2025

This work proposes a study on the analytical modeling of the system composed of casing-cement-formation, considering the displacements and stresses acting at the interfaces, in order to assess the structural integrity of the cement sheath in oil wells. The interaction of this system is also evaluated through numerical modeling, using the commercial software Abaqus, aiming to verify the results provided by the studied analytical model. In the process of oil well construction, the cementing phase is one of the most important and demands integrity analyses and risk assessment, as poorly executed results in increased costs and operational problems. Cement failure can be modeled using the traditional Mohr-Coulomb criterion, which provides the limiting stress for shear failure. In this context, a comparative case study is presented to illustrate the proposed investigations and verify the results obtained from the following methodology: a) implementation of a discrete analytical model that estimates the mechanical behavior of the system and evaluates the integrity of the cement sheath and b) modeling of a discrete numerical model, evaluated by a static structural analysis, considering the effect of temperature and the debonding failure mode. Through a comparative analysis of the results obtained, it is noted that the two strategies used (analytical and numerical) provide very similar results. Thus, the computational implementation of the analytical solution is an important tool for the design of oil wells, allowing rapid analysis and prediction of the structural integrity of cement sheaths.
Automatic Detection of Seafloor Bedforms for 3D Bathymetric Data
Authors: Larissa Marques Freguete  , Luiz Alberto Pinto  , Alex Cardos Bastos  , GUSTAVO MAIA DE ALMEIDA
Published: January 2025

Seafloor bedforms are sedimentary structures that can reveal the local hydrodynamics conditions as they are the result of the bottom sediments' response to the dominant flow. The studying of these dynamic bottom shapes is important given that they can provide auxiliary information for the mapping of benthic habitats and can present a risk to navigation and marine structures. Mapping of the sea bottom is often done with dense and spatially extensive 3D bathymetry data (point clouds) resulting in a more precise representation of the targeted area. However, the most common praxis in this field is to rasterize the original data for the easiness in computation and lack of yet well-established methodology for 3D bathymetric data processing. As a consequence, the rasterization process causes information loss and increase of data processing time. The advantage of points clouds is that they comprise a larger volume of information in the same file, e.g. depth, intensity, RGB, and point classes, enabling a closer representation of reality and simultaneous generation of multiple products as potential habitat maps, Landscape Information Model (LIM), and denser Digital Bathymetry Model (DBM). Therefore, the purpose of this work is to apply a modified U-Net convolutional neural network for detecting and classifying bedform types in the bathymetry point cloud. The methodology will be applied to two datasets collected on the Espirito Santo Continental Shelf: Recifes Esquecidos (RE) and Doce River (DR).The following methodological steps will be carried out: (1) data collection, (2) generation of bathymetry derivatives as slope, curvature, geomorphons, aspect, and data tiling up for data augmentation, (3) image labeling, (4) model implementation including the training, validation, and testing steps, (5) calculation of models performance metrics: Intersection over Union (IoU), mean Average Precision (mAP), recall, and precision. This study will also present a performance comparison between the modified U-Net and a Random Forest (RF) forest. The selected areas are very rich in sedimentary features, so it is expected as the final product a classified points cloud in transversal, parallel, transitional, and artifacts (errors related to the surveying method) classes. It is also expected to have better performance from the non-convolutional model, RF.