bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient Market Hypothesis in Brazilian and American Markets: A Study Using Time Windows
Authors: Rodrigo Coimbra Pereira Alves  , Arthur Rodrigo Bosco de Magalhães  , Charlene Cassia de Resende
Published: January 2025

Financial markets play a fundamental role in contemporary societies, directly influencing social well-being. Traditionally, economists have sought to understand the underlying processes driving the dynamics of these markets. However, in recent decades, there has been a significant increase in the contribution of researchers from various disciplines, including physics, mathematics, and computer science. In this context, econophysics has emerged, employing typical physics methods to study systems commonly investigated in economics and finance.Financial markets are recognized as complex systems, whose behavior can be observed through indicators such as prices and trading volumes. However, the statistical characterization of these time series remains an ongoing challenge, as does understanding their emergence from microeconomic relationships.The Efficient Market Hypothesis (EMH) suggests that future price time series in financial markets contain little useful information for prediction, making it extremely difficult. In this study, we conduct analyses of financial time series to investigate this expectation. We use a return trend prediction model based on differential equations with a focus on time segmenting. The accuracy of this model can provide insights into the presence of the information suggested by the EMH in financial time series.
Social4Science: Mapping Trends and Patterns in Discussions of Scientific Publications on Social Media
Authors: Thiago Magela Rodrigues Dias  , Emerson de Sousa Costa  , Rafael Gonçalo Pereira Ribeiro  , Patrícia Mascarenhas Dias
Published: January 2025

With the growing use of social media, it has become increasingly important to understand how scientific publications are disseminated and discussed on these online platforms. Analyzing this data on the interaction and circulation of scientific research has been investigated in altmetrics studies and can provide valuable information on how science is perceived and shared by the general public. This work aims to propose a platform for collecting and analyzing social data related to scientific publications, with a focus on the video-sharing platform YouTube. By collecting data from YouTube, the platform seeks to understand how scientific publications are disseminated and discussed on social media. In the solution developed, called Social4Science, it is possible to obtain social data from YouTube and correlate it with scientific data from publications. This approach makes it possible to identify trends and patterns in discussions about scientific publications on social media. The results obtained show that the proposed platform is very promising in providing a deeper understanding of the interaction between science and the public, and also opens up possibilities for future studies on this subject.
The Prediction of Bond Strength Between Thin Steel Bars and Concrete Using an Adaptative Neuro-Fuzzy Inference System
Authors: Vanderci Fernandes Arruda  , Gray F. Moita  , Eliene P. Carvalho  , Marco A. A. Grossi
Published: January 2025

In reinforced concrete, the solidary behaviour between steel and concrete means that tensile, compressive, bending, or torsional stresses are transferred from one material to another due to adhesion. Tests such as pull-out and beam tests, proposed by the EN:10080 standard, can be used to verify this behaviour; however, the difficulties inherent in destructive tests, as well as the non-linearity and number of variables involved in this issue, make it pertinent to use alternative methods. Using a database with experimental results from pull-out tests, the aim is to create an alternative technique to these tests. Hence, this work proposes the use of an Adaptive Neuro-Fuzzy Inference System (ANFIS) to predict the maximum adhesion load in pull-out tests. An ANFIS is a hybrid model made up of two techniques: Artificial Neural Networks (ANN) and Fuzzy Logic. The central idea in a Fuzzy Inference System is that the techniques work in parallel, with the neural network used to adjust fuzzy logic parameters. The combination of ANN and Fuzzy Logic is a useful approach to obtain the benefits of these systems in a single model, namely Neuro-Fuzzy. The Neuro-Fuzzy Inference System implemented in this work consists of four input variables: the surface of the bar, the diameter of the bar (ϕ), the compressive strength of the concrete (fc), and the length of the anchor (Ld). The output is the maximum adhesion force at the steel-concrete interface. The performance metrics obtained in this work will be evaluated against those obtained by other computational methods carried out earlier by our research group. The study indicates an alternative to the destructive tests that are widely carried out, overcoming their limitations considering the safety coefficients used in engineering.
A NURBS-based isogeometric formulation for geometrically nonlinear analysis of shells
Authors: Matheus Pascoal Martins de Sousa  , Elias Saraiva Barroso  , Evandro Parente Junior  , João Batista Marques de Sousa Junior  , Joaquim Bento Cavalcante Neto
Published: January 2025

Due to their high slenderness, shell structures are vulnerable to collapse caused by loss of stability, hence nonlinear analysis is crucial to ensure a safe design. The advantage of isogeometric analysis (IGA) to exactly describe the geometry of the problem independently of the degree of discretization and allow easy refinements has led to its increasing application in shell analysis. However, IGA does not remove the shear and membrane locking presented by fully integrated shell elements based on Reissner-Mindlin's theory. Thus, several alternatives have been proposed in the literature to solve the locking problem, such as mixed formulation and reduced integration. This work aims to study the effectiveness of different reduced integration schemes to eliminate or alleviate locking in the context of stability and geometrically nonlinear analysis of Reissner-Mindlin shells based on the degenerated solid approach. The proposed formulation is applied to the stability analysis of plates and shells, where critical loads and nonlinear equilibrium paths are evaluated and compared to solutions available in the literature or obtained by the Finite Element Method. Excellent results were obtained, demonstrating that a very accurate and efficient approach for nonlinear analysis of plates and shells can be achieved by using high regularity basis functions obtained by k-refinement and an appropriate reduced integration scheme. This approach not only avoids locking but also reduces the computational cost of nonlinear analysis of shells.
Analysis of crack propagation due to fatigue using the Stable Generalized Finite Element Method (SGFEM)
Authors: Rafael Marques Lins  , Felipe Justino de Lima Lopes  , Mariano Andrés Arbelo
Published: January 2025

This work aims to present a combination of the stable generalized finite element method (SGFEM) and of the displacement correlation method (DCM) for analyzing 2D crack propagation problems due to fatigue. The SGFEM allows to model fracture mechanics problems without excessive refinement and/or concern of the mesh-to-crack alignment. Additionally, this method maintains the numerical conditioning under control. The DCM, in turn, is computationally very efficient when compared to traditional energy based methods (like J integral) and herein is even improved by means of a linear least square extrapolation. The maximum circumferential tension criterion and well-known propagation laws available in literature are adopted for considering the crack propagation. Experimental and numerical benchmark examples are proposed and the obtained results are compared against results provided by a commercial software widely adopted in the aeronautics industry.
Comparative Analysis of Solutions in the Optimal Design of Composite Flooring Systems for Different Beam Topologies
Authors: Elcio Cassimiro Cassimiro  , Luciano Dal Secco Silveira Amorim  , Chayana Morgner Gomes Silva  , Sayonara Maria de Moraes Pinheiro
Published: January 2025

With the advancement of civil construction, there has been an increase in the utilization of composite steel and concrete systems, often employing full-web profiles for the beams. However, other solutions such as cellular beams and truss beams remain relatively unexplored. The objective of this study is to conduct a comparative analysis of the optimal design of composite floors using different beam topologies, namely: full-core beams, cellular beams, and beams composed of tubular trusses. The objective function will be to minimize CO2 emissions resulting from the materials used in the floors. To solve this optimization problem, the Ant Colony Algorithm (ACO) will be employed. A comparative analysis will be conducted between the solutions proposed in the literature for floors utilizing full-core beams and those obtained with cellular beams and beams composed of tubular trusses, to determine the most environmentally efficient solution.
Multi-objective structural optimization of ground stuctures considering dynamic and stability behaviors and automatic member grouping
Authors: Afonso Celso de Castro Lemonge  , José Pedro Gonçalves Carvalho  , João Paulo Borsato de Carvalho Parêdes  , Patricia Habib Hallak
Published: January 2025

This paper aims to formulate the many-objective structural optimization problem to find the optimal design of ground-structure systems. The objective functions are the weight of the topologically optimized ground structure (to be minimized), the compliance (to be minimized), the different number of discrete cross-sectional areas (to be minimized), the first natural frequency of vibration (to be maximized), and the first load factor concerning the global stability of the structure (to be maximized). It is worthwhile to emphasize that minimizing the number of distinct cross-sectional areas of the optimized ground structure makes finding the best member grouping possible. As a result, the smaller the number of different groups, the greater the weight of the structure, and the greater the number of groups, the smaller the structures weight. Also, minimizing compliance, maximizing the first natural frequency of vibration, and maximizing the critical load factor directly impact the structures mass. The constraints are defined as the maximum allowable stress in the bars, and when the natural frequency of vibration or the critical load factor is not set as one of the objectives, they become part of the set of constraints. DE-based multi-objective algorithms are adopted to solve the proposed optimization problem. Benchmark problems are analyzed, and Pareto fronts are obtained, showing the non-dominated solutions. Multi-criteria decision-making (MCDM) is adopted to extract solutions from the Pareto front according to the preferences of the decision-maker (DM) used in the ground-structure system. The complete data for each extracted non-dominated solution, including its optimized topology, is provided.
Topological optimization with support structure filter for additive manufacturing
Authors: Nora Nei Jesica Oliveira Santana  , Lorran Ferreira Oliveira  , Adeildo Soares Ramos Júnior
Published: January 2025

Topological optimization proves to be an important tool for analysis and design of projects, seeking the best structural performance within criteria such as stiffness, strength, economy, and stability. However, manufacturing optimized structures by traditional methods is not always feasible, due to the complex and unconventional configuration of the geometry. Additive Manufacturing (AM) emerges as a solution, allowing the production of objects layer by layer, without the need for molds. However, angles greater than 45° formed in the geometry may require support material to avoid failures and deformations during printing, increasing material costs and manufacturing time. This study combines topological optimization with AMfilter, a support structure filter for AM developed by Langelaar (2016). Using the open-source MATLAB® code of 88 lines developed by Andreassen et al. (2010), in which AMfilter is integrated during the numerical analysis of the topological optimization problem. The objective is to evaluate the effectiveness of topological optimization with the implementation of AMfilter, through simulations of printing the optimized models, highlighting the potential cost reduction benefits. The results demonstrate a decrease in the use of supports, and in some cases, their complete elimination, making this methodology efficient in the cases examined in this study.
Damage identification using Bayesian derivative method
Authors: Michael Leone Madureira de Souza  , Ney Roitman  , Daniel Alves Castello
Published: January 2025

Structural Health Monitoring (SHM) is one of the most challenging topics in structural dynamic analyses. This challenging characteristic comes from several uncertainties related to boundary conditions, damping description, material properties, and unknown excitation inputs. In this regard, formulating damage identification strategies based on the Bayesian framework is a feasible alternative to conjugating prior information, computational models, and measured data. Nevertheless, building metrics based on comparisons between experimental and computational dynamic features of structure leads to difficulties in determining the likelihood model. In this context, the present work brings an approach for damage identification that considers a metric for the inverse problem, which contains information about the relative difference of natural frequencies. The lack of knowledge about the likelihood structure is tackled using the Approximate Bayesian Computation (ABC), where draws from the approximate posterior are obtained using the Sequential Monte Carlo Approximate Bayesian Computation (SMC-ABC). The feasibility of this approach is assessed considering data from an experimental set-up composed of an aluminium beam containing lumped masses at some positions. The present strategy estimates the position and magnitude of the lumped masses attached to the supported beam. The central role of these lumped masses is to simulate structural anomalies. The inference process considers uncertainties related to structural damping by calibrating several concurrent structural models whose differences reside in the model damping. Finally, the strategy provides the probability of each concurrent model at the end of the process.
Finite Element Model Updating using Bayesian Optimization Algorithm
Authors: Cássio Buss Mainardes  , Sergio Henrique da Silva Carneiro
Published: January 2025

Structural engineering projects require reliable information about parameters of the designed systems that convey precise predictions about the behavior of the system under different load cases. These predictions are derived from numerical engineering models containing real structure geometry and parameters, resulting in responses using the well-established Finite Element Method (FEM). However, due to the presence of uncertainties and assumptions made during the construction of the model, the resulting response may not well represent the real structural behavior. Thus, the established approach involves supplying the numerical model with experimental data to reduce numerical-experimental error, improving the correlation between numerical and observed structural behavior of the system, in a process called Finite Element Model Updating (FEMU). Overall, engineers have developed many different approaches to solve this problem, mainly consisting of sampling or optimization algorithms, applying these methods in FEMU, damage detection, and optimization of sensor placement. The focus of this paper is on the implementation of the Bayesian Optimization Algorithm (BOA) to solve FEMU problems. BOA is a derivative-free optimization algorithm that aims to minimize the number of evaluations of the objective function by trading some computational resources for the construction and optimization of a cheaper auxiliary function, which evaluates the best point to evaluate next. This can be beneficial when heavy sampling of the optimization function can be very time-consuming or when limited evaluations are available, rendering sampling methods and some heuristic algorithms inefficient. To assess the behavior of the algorithm, many cases are analyzed from lower evaluation time to higher complexity cases and then compared with other methods, such as Bayesian Inference, Particle Swarm Optimization, and Genetic Algorithm. The first case is to optimize test functions, followed by some FEMU applications on an uncertain boundary condition beam and finally, a honeycomb plate, in which evaluation of the objective function is more expensive. Results show that BOA can attain good results in a short amount of time when applied to FEMU for low dimensionality problems compared with well-established methods. Overall, this paper reviews FEMU methods and proposes the implementation of a novel approach, demonstrating its effectiveness in solving model updating problems.
Identification of Single and Multiple Damage in Beams Using Natural Frequencies and Bayesian Data Fusion
Authors: Giovanna Fujimura Soares  , Hugo Eduardo García Sosa  , Sergio Henrique da Silva Carneiro
Published: January 2025

Monitoring the changes in geometric or structural properties of systems during their operation to evaluate the presence of damage is a well-established process entitled Structural Health Monitoring (SHM). It is one of the most widely discussed topics in mechanical, aerospace, and civil engineering, and exhibits an increasing importance in many other fields. SHM has a crucial relevance in determining the remaining useful life of a structure, which is essential in avoiding catastrophic failure. However, these analyses can be complicated and sometimes require destructive methods in order to achieve accurate results. Nonetheless, vibration-based methods have shown promising results as non-destructive approaches, relying primarily on variations of the modal parameters. In addition, previous studies demonstrated that natural frequencies are easily determined and provide great accuracy of results. The present work proposes the identification of single and multiple damages in beam-like structures using measures of natural frequencies. First, the beam is modeled using three different methods with increasing complexity. The first model is built in Ansys® APDL module with 100 elements using BEAM188 element type, and damage is introduced as a stiffness reduction in a particular element; the second model is constructed as a beam with solid elements, and damage is presented as a local reduction in stiffness; the third one is also built with solid elements, but with the damage mechanically introduced in the beam. The results for the natural frequencies are obtained via simulation. Then, an experimental setup is assembled in order to acquire results for the beam's natural frequencies and compare them to the values obtained via numerical analysis. These results are further processed by employing a Bayesian data fusion algorithm to predict the location of damage. Three possible damage locations are examined with varying intensities, ranging from a decrease in local stiffness from 10% to 50%. Different types of beam supports are also investigated. The results demonstrate that the algorithm successfully detects single and multiple damage and locates it with great accuracy under various types of supports.
Development of an educational software for the assessment of natural slope stability
Authors: Claudio Horta Barbosa de Resende  , Roberto Juan Quevedo Quispe  , Karl Igor Martins Guerra  , Celso Romanel  , Deane de Mesquita Roehl
Published: January 2025

The analysis of natural slope stability is critical for reducing or mitigating potential catastrophic risks associated with landslides. This kind of disaster not only generates substantial economic and material losses but also creates significant threats to human safety. Landslides occur when forces acting down-slope exceed the soil strength of slopes. In particular, critical factors such as the slope gradient and the thickness of the soil layer can increase such forces, making a slope prone to sliding. Another cause for landslides is rainfall because it can increase the forces acting in the slope (such as the soil weight) or reduce the soil strength (such as the soil cohesion and friction angle), in particular under unsaturated conditions. The deterministic approaches based on numerical or limit equilibrium methods are used to check slope stability through the computation of the Factor of Safety (FOS). However, the impact of the slope geometric features, soil properties or rainfall cannot be assessed unless sensitivity studies are carried out, making difficult the learning process of slope stability. Therefore, in this study, we introduce an educational software for the quick assessment of FOS in natural slopes. The application allows the analyses of FOS considering input data such as 3D declivity maps, soil thickness, soil properties and rainfall intensity. The application boasts user-friendly navigation and delivers real-time results, enabling sensitivity analyses of the safety factor concerning parameters, alongside risk appraisal and prognostication of local condition changes following rainfall episodes.
Educational interactive graphics tool for teaching Mohr Circle
Authors: Luiz Fernando Martha
Published: January 2025

Mohr Circle is a two-dimensional graphical representation of the transformation law for the Cauchy stress tensor. The components of the Cauchy stress tensor at a specific material point are known with respect to a coordinate system. Mohr Circle graphically determines the stress components acting in a rotated coordinate system, i.e., acting on a differently oriented plane passing through that point. The e-Mohr program is an interactive graphics tool that explains the Mohr Circle to Solid Mechanics (Strength of Materials) students in engineering courses. The program demonstrates how the Mohr Circle works for plane stress states, allowing users to interactively manipulate the plane's orientation where the stress tensor components are calculated. Furthermore, e-Mohr involves determining a point in the Mohr Circle called the pole or origin of the planes. Any straight line drawn from the pole will intersect the Mohr Circle at a point representing the state of stress on an inclined plane in the same orientation (parallel) in space as that line.
Analysis of dynamic response on aircraft runway and taxiway bridges
Authors: Baddyo Karppeggyane Santana Pereira da Silva  , Reyolando Manoel Lopes Rebello da Fonseca Brasil
Published: January 2025

This paper presents a computational analysis of the dynamic responses of an aircraft bridge subjected to a moving mass and corresponding load in conditions of taxiway and runway, moving through its entire length. It aims to understand the dynamic behavior of the bridge and to determine its transversal response. The Euler-Bernoulli beam model is here, discretized in finite elements and a dynamic algorithm was applied, using numerical integration by Newmarks Method for the solution of ordinary differential equations to obtain the transversal displacements of the structure in the time domain, to evaluate its responses comparing the results with different velocities, damping ratios, and the effect of contribution of moving mass. The main objective is to apply the results obtained with the method to obtain displacements due to moving masses and corresponding loads contributing to the design of aircraft bridges with reliability.
Enhancing UAV Propulsion: Insights into Toroidal Propeller Dynamics through CFD Simulations
Authors: Patricia Habib Hallak  , Nícolas Lima Oliveira  , Afonso Celso de Castro Lemonge
Published: January 2025

Toroidal propellers have emerged as a transformative breakthrough in aeronautical propulsion, promising enhanced efficiency, maneuverability, and notably, noise reduction. Utilizing Fluent/ANSYS for computational fluid dynamics (CFD) simulations, this study endeavors to delve into the performance dynamics of toroidal propellers in aeronautical applications, with a specific focus on assessing thrust generation, efficiency, and acoustic pressure, especially pertinent in the context of unmanned aerial vehicles (UAVs).The simulations meticulously modeled the intricate airflow dynamics around toroidal propellers, using Fluent/ANSYS's steady, turbulent flow solver, incorporating parameters such as airspeed, propeller rotational speed, and toroidal rotor geometry. The comprehensive three-dimensional computational domains accurately represented the propeller geometry and airflow interactions, facilitating a nuanced analysis of performance metrics.Through comparative analyses of toroidal propellers against a conventional design, aerodynamic advantages emerged, notably in noise reduction. The unique closed-loop structure of toroidal propellers minimizes drag effects from swirling air tunnels, significantly attenuating the propeller's acoustic signature. These findings represent a pivotal step forward in our understanding of toroidal propeller aerodynamics, underscoring their immense potential in UAV applications. Moreover, they serve as a compass for future design refinement and practical integration into aeronautical engineering practices. With the groundwork laid for experimental validation and real-world deployment, the prospect of using toroidal propellers in both commercial and military aviation appears increasingly tangible.
Model Updating in Dynamic Finite Element for Damage Detection on an Aircraft Wing
Authors: Leon Vale Lobo  , Reyolando Manoel Lopes Rebello da Fonseca Brasil  , Edilson Morais Lima e Silva
Published: January 2025

SHM is a fundamental area for aerospace engineering. Within this broad area, there are non-destructive ways to assess integrity. This paper presents an approach to damage detection through optimization of a finite element model, where the design variables are the characteristics of the sections forming the components of the structural system, and the objective function is the dynamic parameters: natural frequencies and modal shapes. This allows for the detection of damage that caused alterations in the modal parameters of the structure through an optimal combination of design variables that generate responses obtained in the modal analysis of the damaged structure once the model is calibrated. The practical application used is damage detection in a simplified model of an aircraft wing.
Exploring the Influence of Heterogeneity on Determination of a RVE for Concrete Structures
Authors: José David Salviano dos Santos Montes Almeida  , Saulo Silvestre de Castro  , Hugo Mouro Leão  , Roque Luiz da Silva Pitangueira
Published: January 2025

The mechanical behavior of a heterogeneous material is strongly influenced by the response of its constituents (and their respective interactions) at lower scales. This fact accounts for the nonlinearities observed at the macroscale, and consequently, the challenges in formulating constitutive models capable of providing accurate predictions in a practical application context. Essentially, there are two primary ways to represent a heterogeneous material, either through Phenomenological Models at a Single Scale or through Multiscale Models. Multiscale models represent the most robust approach to depicting a heterogeneous material. In these models, the connection between macro and meso levels is typically made through the concept of a Representative Volume Element (RVE). The RVE is the smallest sample of the material that can statistically represent the mechanical behavior of the material. Typically, in multiscale model applications, it is assumed that an RVE exists and that its size is initially prescribed. However, the appropriate determination of an RVE for quasi-brittle materials remains a subject of study. This paper discusses the determination of RVEs for concrete using normalized graded aggregate curves. For this purpose, numerical simulations were performed using the Finite Element Method, employing constitutive models based on Phase Field theory. Throughout the study, issues related to the size of the RVE and the determination of ergodic properties are discussed. The influence of the aggregate gradation curve on the mechanical behavior of the RVE and the influence of the aggregate-mortar interface are also examined. Finally, the difficulties encountered in determining the RVE in a practical application context are presented.
Machine Learning based Analysis of RVE in Concrete Structures
Authors: Saulo Silvestre de Castro  , José David S. S. M. Almeida  , Hugo Mouro Leão  , Roque L. S. Pitangueira
Published: January 2025

In the numerical modeling of structural elements, particularly utilizing the finite element method (FEM), multiscale models represent the most robust approach for analyzing heterogeneous materials such as concrete. These models incorporate information from multiple scalestypically, macroscopic and mesoscopicto more accurately capture the material's response and its impact on structural behavior. In this context, each material point in the numerical model is associated with a Representative Volume Element (RVE), which is the smallest statistically representative portion of the material. During the analysis of a multiscale model via FEM, each integration point in the model requires the execution of an independent computational model that simulates the RVE and is processed in parallel to the main model (on the fly process). Deformations originating from the macroscale are applied to the mesoscale models, and the responses obtained are then reintegrated into the macroscale. This approach results in significant demand on processing resources and time, which can limit its practical application in large-scale projects or situations requiring rapid responses. This article propose the representation of the RVE through a Machine Learning model (ML) capable of simulating the mechanical behavior of the material. This approach eliminates the on the fly processing. Throughout the text, examples of RVEs represented by ML models are presented, and their specificities are discussed. Finally, the advantages and disadvantages of this methodology are examined.
2D nonlinear Acoustic Wave equation in heterogeneous fluid
Authors: Renan André Peres  , Antônio Manoel Ferreira Frasson  , Carlos Friedrich Loeffler  , Fábio Pavan Piccoli  , Julio Tomás Aquije Chacaltana
Published: January 2025

In this work, the non-linear equation of Acoustic Wave propagation in a heterogeneous fluid (CHACALTANA et al., 2015; PERES et. al., 2023) is solved in two dimensions by Finite Element Method (FEM). The Weighted Residual Method (Petrov-Galerkin) and linear and parabolic approximation basis functions are used to minimize the residue in each element. Ricker-type pressure source (CHACALTANA et al., 2015; PICOLLI et al., 2020) and the sinusoidal type are used to generate the P-wave. Reflective Neumann (natural) and non-reflective ABC (Absorbing Boundary Condition) boundary conditions based on the non-reflective boundaries of Reynolds (1978) were implemented. The numerical code is written in Fortran 95 language and the Octave graphical interface is used to analyze the results. The GMSH mesher (v. 4.8.4) is used to represent the continuous domain by a set of discrete points that group together form a non-uniform mesh of triangular elements. Numerical tests on square and circular geometries are performed to verify the implementations of the Neumann and ABC boundary conditions. Finally, a good agreement is found between the results of numerical simulations when compared with existing results in the literature.
Effects of modal coupling on the nonlinear dynamics of hyperelastic circular cylindrical shells
Authors: Renata Machado Soares  , Daniella Maria Oliveira Aguiar  , Frederico Martins Alves da Silva
Published: January 2025

The nonlinear dynamics of a simply supported circular cylindrical shell is analyzed using an analytical model that considers both physical and geometric nonlinearities. The material that composes the shell is assumed as homogeneous, isotropic, hyperelastic and incompressible, being described by the Mooney-Rivlin hyperelastic constitutive law. The geometric nonlinearity is introduced into the analytical model by applying the Sanders-Koiters nonlinear shell theory. The Rayleigh-Ritz method and Hamilton's principle are employed to obtain the nonlinear equilibrium equations. For that, the energy density function is expanded in Taylor series up to the fourth order and the transversal displacement field is described in Fourier series that considers both asymmetric and axisymmetric modes. This works focusses on evaluating the influence of the asymmetric and axisymmetric modes, selected in the modal solution of the transversal displacement field, on the frequency-amplitude relationships of the shell and resonance curves. It can be observed that the asymmetric modes provoke nonlinear hardening behavior of the hyperelastic shell. On the other hand, when the axisymmetric modes are added, there is a significant change in the nonlinear behavior of the hyperelastic shell - which indicates the importance of this modal coupling in the nonlinear dynamic analysis.
Experimental and numerical modal analysis of the steel frame
Authors: Carlos Natã Zenatti  , Paulo Rogerio Novak  , Giovanni Bratti  , Rúbia Mara Bosse  , Gustavo de Miranda Saleme Gidrão  , Robson Trentin  , Diego Rossetto
Published: January 2025

In engineering, it is extremely important to direct research towards the identification and understanding of dynamic behavior in structures, as dynamic loads are present in all types of structures, including civil construction. Dynamic loads can range from the interaction of the wind with the structure to people's footsteps and car movements, and cause vibrations. These vibrations can cause damage to the structure and users, depending on their intensity and duration. For this, the structures are dimensioned and designed to support all the efforts required, this includes vibrations and other dynamic actions. Thus, the present work aims to determine the dynamic properties of a steell frame through a numerical and experimental modal analysis.The steel frame is made of cold-rolled A36 steel. The profiles of the columns and beams are formed by cold rolled profiles forming sections of the type closed stiffened double u-profile and hat profile, respectively. The beams are joined to the columns by rigid connections. The dimension of the steell frame is 2m in height by 1m in width and length, approximately. Numerical analysis was performed by the Finite Element Method using shell elements. In the experimental analysis, the structure was excited by an impact hammer and the vibration response was measured by piezoelectrics accelerometers. The frequency domain method Rational Fractional Polynomial (RFP) was used to estimate the natural frequencies, mode shapes and damping factor. There was a good agreement between the experimental results and the numerical values obtained by the proposed procedure.
Local and distortional buckling of thin-walled laminated lipped channel columns
Authors: Marcelo Freires Pinto  , Pedro Sanderson Bastos Barros  , Evandro Parente Junior  , João Pedro Barbosa Pontes  , Luiz Antônio Taumaturgo Mororó
Published: January 2025

The great versatility in manufacturing and handling, as well as the mechanical capacity in structural applications, lead to the increase in the application of composites in various engineering applications, including aerospace industry, automotive industry, renewable energy, and civil construction. Due to the high strength and stiffness of fiber reinforced composites, they are mostly used to manufacture thin-walled structural components. It is already known that buckling plays a significant role in the design of thin-walled structures subjected to compressive loads, such that failure can occur with stresses much lower than the material mechanical strength. Thus, the design of many structural components is carried out considering constraints related to stability along with traditional criteria of strength and stiffness. This work focus on the stability analysis of laminated lipped channel columns. These columns present three main buckling modes: local, distortional, and global. It is important to note that the buckling loads of laminated open-section columns with arbitrary layup can be accurately computed using the Finite Element Method. However, the application of this approach to trace the signature curve of composite columns with channel sections is cumbersome and presents a high computational cost. Therefore, this work presents a simple, efficient, and accurate methodology to evaluate the local and distortional buckling load of laminated channel columns applying the Rayleigh-Ritz method. The accuracy of the proposed approach is assessed comparing the results obtained using the Finite Strip Method, Finite Element Method, and experimental data available in the literature.
Nonlinear normal modes to analyze the nonlinear forced vibrations of cylindrical shells with internal resonances
Authors: Frederico Martins Alves da Silva  , Jonathas K. A. Pereira
Published: January 2025

In this work, the nonlinear normal modes are applied to analyze the nonlinear forced vibrations of a simply supported cylindrical shell with internal resonances. The nonlinear equilibrium equations are obtained considering the Donnell's nonlinear shallow shell theory. The modal solution to the transversal displacement field, used to discretize the equilibrium equations, is obtained by perturbation techniques that consider an internal resonance between the linear vibration modes. The discretized equations of the reduced order model are obtained using an invariant manifold approach. The nonlinear dynamic behavior is analyzed from the resonance curves that are obtained by the continuation method. The resonance curves are obtained for both full and reduced order models, and these results are compared to determine the level of a harmonic load that can be reliably represented by a reduced order model. Several multi-modes are considered to assemble the best nonlinear normal modes basis that contains the most important information of the interactions that occur between the modes of the transversal displacement field. Time responses and phase portraits, with mapping Poincaré sections, are also used to analyze the nonlinear dynamic behavior of the cylindrical shell and to check the accuracy of the reduced order models.
Theoretical Analysis of Human Rhythmic Jumping on Oscillating Floors
Authors: Phablo Veríssimo Inácio Dias  , Zenón José Guzman Nuñes Del Prado
Published: January 2025

This study investigates the dynamic interaction between a human jumper and a concrete rectangular plate under cyclic vertical jumps. The plate is described using Von Kármans nonlinear relations, while the jumper is modeled as a spring-mass-damper (SMD) system with a harmonic force acting on the humans center of mass to represent the propulsion force during jumping. The mechanical system is described by a set of piecewise smoothtouch nonlinear differential equations, allowing the loss of contact between the jumper and the plate during jumps. The results show that the jumper exhibits complex dynamics, including periodic and chaotic responses, depending on the systems parameter combinations. Additionally, the SMD model can affect the mechanical behavior of the plate by coupling the jumpers vibration modes with the structures, creating new resonance frequencies and redistributing the vibrational energy.
A Parametric Study of Intervening Factors in Vibration Mitigation in Wind Towers Controlled by TLCDs
Authors: Almir Pinheiro Mesquita Júnior  , Rodolfo S. Conceição  , Lineu José Pedroso
Published: January 2025

Wind turbine support towers are tall and slender structures, because of this, they have low natural vibration frequencies, which make them susceptible to vibrations due to wind, earthquakes and/or other dynamic actions. These vibrations can cause sensory discomfort and structural damage, causing collapse by amplification of structural responses or the failure of some structural components due to fatigue. Therefore, it is interesting to implement vibration control devices to attenuate the vibrations. This work analyzes Tuned Liquid Column Dampers (TLCDs) as a passive structural control. The mathematical formulations of the wind tower motion equations are presented for structural systems with a single, and with several degrees of freedom, under bending effects, and for the incompressible fluid column (TLCD). Initially, the tower and TLCD systems are studied separately, and later in a coupled manner, within a wide range of parameter values, an aspect that allows the construction of response maps representing the ratio of attenuated and non-attenuated structural response. A simplified way of optimizing parameters of a TLCD model in the time and frequency domain under harmonic excitation is proposed to improve the performance of TLCDs, as well as simulations on wind towers with many degrees of freedom, dimensions, and real conditions.
Aesthetic Integration of Structural Elements: Joaquim Cardozos Legacy in Modern Architecture
Authors: Leonardo da Silveira Pirillo Inojosa  , Márcio Augusto Roma Buzar  , Marcos Ritter De Gregório
Published: January 2025

In established architectural projects, the structure serves as a guiding parameter, meaning architecture is designed simultaneously with the structure. "Once the structure is complete, the architecture is already present, simple, and beautiful" (NIEMEYER, 2002). In modern Brazilian architecture, the role of structure in the composition of buildings is particularly noteworthy. Structural elements are often incorporated in an apparent manner, directly linked to the building's aesthetics. Engineer Joaquim Cardozo's works highlight several structural elements with these features, including the arches of the Alberto Torres Rural School in Recife (1935), the shells of the Igreja de São Francisco de Assis in Pampulha (1943), and the columns of the Igrejinha Nossa Senhora de Fátima in Brasilia (1957). In this study, we analyze these and other structural elements calculated by Joaquim Cardozo, using the software SAP2000. Our goal is to identify the significant contribution of the engineer and his structural solutions to modern Brazilian architecture, while also highlighting the relationship between structural systems and architectural aesthetics.
AI-based automation for structural design of buildings
Authors: Nicholas Nunes Raymo  , Luiz Fernando Bazzo de Freitas  , Arthur Pastorelli de Mello  , Gabriel Emidio Lage
Published: January 2025

With the recent advancement of technology and computational empowerment, processes that were executed manually have the potential to be automated. In Civil Engineering, this is being seen through the implementation of technologies such as Building Information Modeling (BIM), Generative Design, Machine Learning and Artificial Intelligence. The objective of this work is to develop a computational system aiming to optimize the development of architectural and structural projects, implementing technologies such as artificial intelligence and generative design to automate and systematize processes inherent to the project pre-dimensioning phase when designing a building. Initially, the user interacts with an AI-based chatbot interface which allows the definition of a buildings main characteristics, such as number of stories, apartments per story and minimum areas. The system has access to a database that contains different architectural BIM models and will filter them in order to provide the best option according to the user specifications. The selected model is processed by a Dynamo script in Autodesk Revit that automatically creates and allocates structural elements, e.g. beams, columns, slabs, and foundation. The script considers the intersection between walls and building corners, also positioning columns in wider spans avoiding doors and windows. This structure is converted into an analytical model, so it can be exported to Autodesk Robot Structural Analysis where another Dynamo script is executed, which contains loads determined by technical standards as the Brazilian ABNT NBR 6118:2023 for concrete design. This script analyzes bending moments, shear effects and axial forces of the structural elements and, through limiting parameters, sends messages to Autodesk Revit, stating if a structural element needs to be modified to attend applied loads. This process runs continuously until all elements are adequate. Using this technology, enterprises specialized in architectural and structural projects will save time, since allocating and pre-dimensioning structural elements are processes that are executed manually. Therefore, engineers are then able to focus on greater challenges involved in structural analysis and architects can simulate the dimensions of elements more accurately. There are still many processes in Autodesk Revit and Robot Structural Analysis that can be automated, and these will be further developed as a sequence of this study.
Comparative Analysis of Constitutive Models for Concrete Using the Finite Element Method: Microplane Model, Menetrey-Willam, and Concrete Damaged Plasticity
Authors: Adriana Elisabete Limberger Januario  , Vinicius Vaz  , Luan Reginato  , Luiz Fernando Zubeldia Dal Posso
Published: January 2025

The nonlinear physical behavior of concrete can be represented by models from the theory of plasticity with associated damage. In the commercial software ANSYS and ABAQUS, three distinct models are available that can represent the mechanical behavior of concrete, considering the uniaxial and biaxial states under compression and tension, named the Microplane Model, Menetrey-Willam Model, and Concrete Damaged Plasticity. This article aims to present the theory regarding these models, examples of application, and sensitivity analysis of the plastic and damage parameters in numerically simulated cylindrical specimens. Finally, there is a comparison of the use of these models in a reinforced concrete beam simulated with cyclic loading.