bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of neighborhood on the longitudinal response of a building under wind action
Authors: Gregório Sandro Vieira  , Isabella Duarte Rodrigues da Cunha  , Thiarly Feitosa Afonso de Lavôr
Published: January 2025

As structures grow in height, the complexity of their design and structural analysis also increases. Specifically, the impact of wind becomes a crucial consideration in construction. This study aimed to examine how distances between adjacent buildings affect the longitudinal response of a standardized tall building, known as CAARC, under the influence of wind. Wind effect analysis was conducted in two main directions, with wind acting at 0º and 90º, considering three different neighborhood scenarios. Utilizing the force data obtained in a wind tunnel by Vieira (2016), computational analyses were performed using MATLAB software, combined with the High-Frequency Pressure Integration (HFPI) method. The results revealed that greater distances between neighboring buildings result in less impact on the analyzed building.
Nonlinear Vibrations of Wind Towers with Variable Cross Section and Elastic Foundation Under Base Excitation
Authors: Zenon Jose Guzman N. del Prado  , MANUS SAINTILMA
Published: January 2025

In this work, the nonlinear vibrations of coupled tower-nacelle-blade system, considering variable cross section and elastic foundation, subjected to base excitation (harmonic and seisme) are studied. For this, the nonlinear Euler-Bernoulli beam theory is applied to model the tower and nacelle and the elastic base is described as a Winkler model, considering contact problem. The Rayleigh-Ritz method together with Hamilton principle are applied to obtain the set of nonlinear dynamic equilibrium equations which are, in turn, solved with the fourth order Runge-Kutta method. Numerical results show the strong influence of parameters and base excitation on the natural frequencies, on the resonance curves and on bifurcation diagrams.
Remarks On the Use of Variational mode decomposition for Chaos and Nonlinear Dynamics Analysis in Fractional-Order Systems applications
Authors: Marcus Varanis  , Clivaldo Oliveira  , Jose Manoel Balthazar  , Angelo Marcelo Tusset
Published: January 2025

This study investigates the dynamics of an electromechanical device for energy generation. The device utilizes a motor with an unbalanced mass coupled to a piezoelectric substrate. The central focus of the analysis is measuring the average power generated by the piezoelectric material, which is stimulated by the motor's vibrations. We explore the fractional dynamics of the system, examining variables such as the parameter of the fractional derivative operator and the control parameter. Using techniques like bifurcation diagrams and recurrence analysis, we investigate the routes to chaos and their implications on the stability and behavior of the system. The study is enhanced by the implementation of Variational Mode Decomposition, a technique that allows us to decipher the complexities of the system's dynamics.
Numerical simulation method for masonry partition walls affected by the deflections of concrete structures
Authors: Hipólito José Campos de Sousa  , Luisa Maria Pimenta Abreu Costa Sousa  , Rui Miguel Almeida Vieira de Sousa  , Humberto Salazar Amorim Varum  , José Miranda Melo
Published: January 2025

Non structural masonry walls can be damaged when submitted to in plane loads, imposed by the vertical deflections of their support structures (e.g. concrete slabs).Given the high complexity of this problem associated to the masonry anisotropy and behaviour of interface joints wall/structure, including the difficulty of reproducing real scale prototypes for laboratory testing, the use of more generalised and time efficient models are important aspects to be considered. Therefore, a numerical simulation method and its application is presented to simulate this type of problem. This method is based on a FEM macro-model, witch includes a constitutive damage model for concrete calibrated for masonry walls and a shear-cohesion model to simulate the interface joints. This method was simulated in a case study of a masonry partition wall loaded by the vertical deflections of adjacent concrete slabs. Results obtained highlighted a high risk of damage in the masonry partitions when these are affected by the structural deflections limits referred in literature, specially if no detachment wall/structure joints and reinforcement techniques are used.
Study of the influence of construction stages on the analysis of tall reinforced concrete buildings
Authors: Mateus Martins Marinho  , Leandro Lopes da Silva
Published: January 2025

This dissertation project proposes to investigate the influence of considering construction stages in tall reinforced concrete buildings by evaluating conventional strategies, which do not take the construction stages into account, and strategies that consider them in an approximate way, including a model interpreted as a reference, known as construction effect. Nowadays, with the development of structural analysis and design programs, a change in the structural calculation is observed, moving from conventional models to those that describe the real sequence of loading and construction. Since the structure is subjected to internal forces as it is built, it is desirable for structural engineers to consider the loading being applied progressively and the evolution of the mechanical properties of materials with time. The conventional method, by considering the action of all loads on the completed structure and the modulus of elasticity of concrete at 28 days, does not reflect the reality of constructions. The main distinction between analysis strategies lies in how displacements along the height of the building are treated. In the conventional model, since the loads are applied in a single step, displacements occur simultaneously and cumulatively. On the other hand, in incremental analysis, the loads acting on a given floor do not cause displacements, or consequent internal forces, on an upper floor not yet built. Analysis without consideration of the construction stages may result in an inconsistent distribution of internal forces and may not represent the real behavior of the structure, wich may even result in inadequate design and consequent pathological manifestations and/or collapse of the structure. Therefore, it is intended to conduct a comparison between the methods of conventional analysis, axial stiffness increaser, called the approximate method, and incremental analysis, seeking to understand the main differences in terms of internal forces and the design of buildings. For this purpose, softwares for modeling, analysis, and structural design that allow the simulation of these strategies will be used.
Numerical modeling of steel deck slabs with position based finite element method and immersion techniques
Authors: Rodrigo Souza de Melo  , Chiara Pinheiro Teodoro  , Rogério Carrazedo
Published: January 2025

Steel deck slabs are an efficient construction system thanks to the deck's double role of molding the concrete in the builiding phase and resisting to flexural loads within its lifespan. Due to the high costs and semiempirical nature of experimental programs, it is important to formulate a numerical model that broadly and accurately describes the behavior of these structures. This article proposes a numerical model employing a finite element method based on positions, which naturally allows for geometrical nonlinear analysis of structures. A prismatic element is developed to represent the concrete matrix, and active face immersed elements are included to represent the steel deck. Additional immersed bar elements are also featured as reinforcement bars. The results are expected to conform with previous numerical and experimental results from literature and to allow for the proposal of new benchmarks taking advantage of the capabilities of the employed theory.
Numerical simulation of behavior of masonry mechanics made with ecological bricks
Authors: Dabdon Conceição Nascimento  , Francielly Las Casas  , Fernanda Valim  , Lucas Ribeiro do Santos  , White Jose dos Santos  , Rodrigo Barreto Caldas
Published: January 2025

Soil-cement brick masonry structures have gained prominence in developing countries due to their practicality, low cost and excellent ecologically sustainable alternative. However, the literature presents few numerical studies on masonry structures in soil-cement bricks, since most of the studies carried out focus on concrete and ceramic bricks. Therefore, in this work, the finite element model of a small wall made of soil-cement brick with structural masonry mortar joints, subjected to compression, is calibrated. The experimental analysis of these small walls was conducted at the Laboratory for Experimental Analysis of Structures at the Federal University of Minas Gerais, and the experimental results are used to calibrate the numerical simulation. The numerical model was developed in the finite element program ABAQUS CAE. A detailed micromodeling strategy was adopted, that is, the models were developed considering the individual representation of bricks and mortars, in addition to the interface between the materials. Using the proposed finite element model, a numerical investigation was conducted to verify the validation of the model concerning experimental investigations. The present study allowed us to adequately replicate the concentration of damage in the bricks, corroborating what was observed in the experimental tests.
Numerical Simulation of Three-Point Bending Test on Steel Fiber-Reinforced Concrete Specimens Using DIANA FEA
Authors: Mariane Rodrigues Rita  , Igor de Azevedo Fraga  , Ana Beatriz Carvalho Gonzaga e Silva  , Eduardo de Moraes Rego Fairbairn  , Jose Claudio de  Faria Telles  , Alexandre Landesmann
Published: January 2025

This study presents a numerical investigation of the behavior of steel fiber-reinforced concrete specimens under three-point bending tests employing different model approaches. Steel fiber-reinforced concrete has gained significant attention in the construction industry due to its enhanced mechanical properties, including improved ductility and crack resistance. Understanding its behavior under loading conditions is crucial for optimizing structural design and ensuring durability. The simulations were conducted using DIANA Finite Element Analysis (FEA) software, and the comparative analysis was design to compare their effectiveness in predicting the structural response. The simulations were validated against experimental data from laboratory tests to ensure the accuracy and reliability of the numerical predictions. Through comparative analysis, this study evaluates the performance of each modeling approach in predicting key parameters such as load-displacement response, crack mouth opening and ultimate failure mode. Insights gained from these comparisons will provide valuable guidance for selecting the most appropriate modeling technique for similar structural analyses in practical engineering applications.
On an immersed boundary technique for modeling 3D incompressible fluids laden with particles
Authors: André Sarkis Müller  , Eduardo de Morais Barreto Campello  , Henrique Campelo Gomes
Published: January 2025

This work presents results from a recently developed three-dimensional immersed boundary technique for modeling 3D particle-laden fluid problems. A classical Eulerian approach is followed to describe the fluid (assumed here as incompressible through Navier-Stokes equations). A discrete element formulation, in turn, is used to describe the particles´ dynamics. The fluid-particle interfaces are treated through Nitsches method, which is an immersed boundary technique whereby we impose the particles´ surface velocities and spins as boundary conditions to the fluid in a weak form. Here, particle-to-wall (i.e., fluid´s exterior solid boundaries) contacts are fully permitted and resolved. In order to assess the accuracy and efficiency of the developed scheme, numerical simulations of 3D unsteady flow of an incompressible fluid loaded with particles are performed and compared against benchmark solutions. This work refers to an intermediate stage of a scientific research that aims to model problems of fluid-particle interaction (FPI) with full particle-to-particle contacts in particle-laden fluids.
Quasi-conformal versus Hertz superposition: a comparison for two-dimensional contact
Authors: Lucas da Silva  , Alfredo Gay Neto
Published: January 2025

Hertz contact theory results in a relation between the normal contact force and the rigid indentation of the contact surfaces, the force is proportional to the indentation to the power of 3/2, and a semi-ellipsoidal traction distribution. It is a valid theory for non-conformal contact between smooth surfaces (curves in 2D) of elastic bodies. This force model can be derived by considering the Taylor polynomials of degree 2 at the contact point as approximations for the surfaces/curves. In the 2D case, it depends only on the curvature radii of the curves and is undefined when they are equal, the equality of radii violates the non-conformality.The Hertzian force is usually applied to the contact of solid particles as a model compensating for the small local deformations that occur in the contact region. We consider the 2D contact of a rigid convex particle with a rigid concavity enforcing the contact constraint with a barrier method, an approach that prevents overlapping of the bodies, resulting in a force that acts on the contact point. The geometries and the motion are specially designed to show the coalescence of two contact points into one. It illustrates two possible issues with convex-concave contact, the non-uniqueness of contact points and the conformality. We compare the results with a deformable finite element model for equivalent bodies and motion showing that there is a transition between a Hertzian and a non-Hertzian behavior. We conclude that a criterion for the conformality of curves must include the ever-present gap when a barrier method is used to enforce the constraint and the Hertzian force is not suitable for the coalescence of contact points.
Application of the finite element method for analysis of the influence of dynamic loads on a machine foundation on piles
Authors: Joana Campos Rodrigues  , Marco Aurélio Chaves Ferro
Published: January 2025

This work presents the fundamental concepts of structural dynamics, applied to the study of machine foundations. It discusses a method of obtaining the representative parameters of the pile-soil set considering the effect of the group acting by the proximity of the piles. In addition, this monograph is dedicated to preparing a detailed case study with the aid of ANSYS®, software based on finite elements, in order to reach the displacement values incorporated by the foundation element. These results were obtained according to normative criteria in the questions of severity of vibrations, effects on people and damage to the structure, allowing for attesting the capacity of the chosen foundation to resist the dynamic loads caused by the operation of the machine.
Application of the Immersed Boundary Method in the Study of Two Tandem Cylinders
Authors: Ismar Mascarenhas de Carvalho Filho  , Caio Lemos Peixoto Martins  , Mylena Carvalho Silva  , Andreia Aoyagui Nascimento
Published: January 2025

The study of fluid flow around various surfaces is crucial in several applications of mechanical engineering, especially in cylindrical geometries of circular section, common in structures such as bridges, wind turbines, cooling systems, and power towers. In this work, we solve the two-dimensional mass conservation and Navier-Stokes equations in the x and y variables, ignoring gravitational effects, applying the Fourier pseudo-spectral method coupled with the immersed boundary method. We define a domain with two cylindrical boundaries of diameter equal to 0.0016m and a low Reynolds number. The obtained results are promising, approaching existing literature reviews.
Implementation of a convolutional network for detection of PPE in automotive repair services.
Authors: Álvaro Severo Marcus  , Luiz Alberto Pinto  , Gustavo Maia de Almeida  , Amanda Santos Silva
Published: January 2025

This study explores the application of computer vision to occupational safety in automotive services, specifically focusing on the real-time detection of Personal Protective Equipment (PPE). The automotive service context presents unique challenges in managing the proper use of PPE, such as safety glasses, gloves, and appropriate uniforms, to ensure the safety of those involved in service execution.Identifying and monitoring the correct usage of PPE is crucial for maintaining work quality and preventing workplace accidents. The research aims to develop and implement a methodology tailored to the specific needs of automotive services, with a focus on repairing windshields, headlights, and mirrors. A detection model based on the YOLOv8 convolutional network is proposed for its simplicity and potential for integration into a portable platform.The study's objective is to achieve satisfactory precision in PPE usage detection. Additionally, it seeks to optimize the efficiency of automotive services, avoiding interruptions and delays in service delivery due to workplace accidents. The research builds on prior studies that demonstrated the effectiveness of computer vision in PPE detection in industrial and construction settings. The proposed approach includes creating a dataset and training a convolutional network with approximately 2000 images from security cameras.The research significantly enhances both computer vision and occupational safety in automotive services, reducing the number of non-compliances found in internal inspections and improving the quality and safety of the workplace. Moreover, it addresses challenges related to managing image banks and the complexity of detecting PPE. The study also examines successful experiences in other sectors that used convolutional networks for real-time PPE detection.
Validation of an in-house developed acquisition system using a commercial acquisition system and the theoretical model of a clamped beam
Authors: Vitor Frutuoso de Carvalho  , Gustavo Fernandes Costa e Silva  , Hugo Sakai Idagawa  , Renato Ludwig Pilan
Published: January 2025

Vibration analysis is a technique that allows understanding through visualization of the frequency spectrum the propagation of vibrations in which a body is receiving from external forces. At a laboratory, the type of study allows the students to learn the concepts of this invisible force that is present in all the bodies and it also helps to understand how the material characteristics and the sample specimens geometry behave in these situations. Therefore, the objective of this project is the development of a didactic kit that allows the study of modal vibrations in test specimen such as beams, without the need of a vibration analysis equipment available in the market, that, in addition to the high cost, these equipments have reserved construction characteristics, that requires specialized training to understand how it works. For this acquisition system, it developed an accelerometer, analogical low-pass filters and an esp 32 microcontroller with A/D converter. The data processing was performed with a program developed in MatLab. A clamped beam was used to validade the project, in which a frequency analysis was performed. For this validation process, the kit results were compared against the mathematical model of the beam, whose first natural frequency is around 7Hz, and a commercial hardware available in the market. With these results, it was possible to evaluate the reliability and accuracy of the acquisition system in relation to computational models. Therefore, after extensive testing, this project can be manufactured by other institutions, bringing to the students in the educational environment the capacity to understand the structure and working of the equipment, besides learning how structures behave when submitted to many different vibration modes.
Reliability and sensitivity analysis of pultruded GFRP I-sections resistance to flexural and lateral-torsional buckling
Authors: Leonardo Wendler Felchak  , Roberto Dalledone Machado  , Henrique Kroetz
Published: January 2025

Civil industry demands increasingly for materials with outstanding properties and economic viability. In this sense, Pultruded Fiber-Reinforced Polymers (FRP) profiles are experiencing great acceptability and usage in civil construction as innovative structural elements. This is due to its lightness, excellent mechanical properties-to-weight ratios, cost-effective manufacturing process, improved durability and so many other advantages. However, despite the growing application of these materials, there are scarce efforts towards development of recommendations or design standards for FRP structures based on reliability concepts. Frequently in the design of FRP frames buckling phenomena governs the structural ultimate limit state design research, because of the high strength to stiffness ratio of this material compared to conventional ones. The present work evaluates a reliability and sensitivity analysis of global buckling ultimate limit state of I-section pultruded beams, aiming to capture the effect of uncertainties related to initial imperfections, material properties and loading in the structure reliability index, and its sensitivity to modeled uncertainties.
Passenger vehicle behavior modeled by Power Flow using different mathematical tire models
Authors: Ricardo Teixeira da Costa Neto  , Bruna Rafaella Loiola
Published: January 2025

Ground Vehicles can be approached as a set of integrated subsystems, with cause-effect relationships. Through the Power Flow Modeling approach, each of these subsystems can be interpreted as a black box, and interrelated with the others in a modular way, as long as causalities are respected. This work aims to take advantage of the modularity of the automobile interpreted as a set of integrated subsystems and evaluate the influence of mathematical tire models on its acceleration and braking behavior. Each of the subsystems is mathematically modeled in individual blocks that are then integrated, without loss of causality, in MATLAB/Simulink® software. The purpose is to provide a fully modular vehicle model, taking advantage of this Power Flow feature, in an open-source code. Furthermore, Inverse Problems are applied to estimate parameter values of the Burckhardt and Dugoff mathematical models in order to obtain similar behaviors of the corresponding tire model by the Magic Formula.
Assessment of the Structural Response of Transmission Lines Steel Towers when Subjected to Nondeterministic Wind Loadings
Authors: Mariana Souza Rechtman  , José Guilherme Santos da Silva
Published: January 2025

The lattice steel towers have been widely used as supports for power transmission lines. In the current project practise, the structures dynamic behaviour usually is not considered. However, the main loading to consider in structural analysis of these steel towers is produced by wind loadings. Considering that many accidents associated to this kind of structural system occur even for wind velocities below that specified in project, its possible that most of these accidents have been produced by dynamic actions. This way, this investigation proposes an analysis methodology that can accurately simulate the coupled behaviour between the transmission line cables and the towers, when subjected to wind nondeterministic loadings, having in mind the assessment of the displacements and forces maximum values that occur in the steel towers. In this work, the investigated transmission line system, including the steel towers, conductors and shield wire types, presents two spans of 450 m associated to a main suspension tower in the centre with total height of 32.86 and other two towers at the ends. The conclusions of this research work pointed ou to relevant quantitative differences associated to the structural response, when was calculated based on a static linear analysis and compared to the results determined based on a geometric nonlinear and nondeterministic dynamic analysis.
Determination of deflection in composite slabs considering concrete creep
Authors: Lorrana da Silva Nunes  , Rodrigo Sernizon Costa  , Sarah Elza Santos Bitencourt  , Renata Gomes Lanna da Silva  , Harley Francisco Viana  , Armando Cesar Campos Lavall
Published: January 2025

The analysis of the behavior and resistance of composite steel and concrete slabs covers several parameters. Among these parameters, concrete creep plays an important role in checking deflection. Regarding the calculation of the deflection, generally, technical standards recommend that the moment of inertia of the composite section be given by the simple average of the moments of inertia of the uncracked and cracked sections. However, experimental investigations have shown that this procedure, inadequately characterizes the behavior of the composite slab, resulting in an underestimated effective moment of inertia and smaller deflection, especially when subjected to higher loads. Using research results, this work aims to present a proposal for determining the effective moment of inertia in composite slabs that considers the concrete creep representing the behavior during the loading phase until collapse.
Reliability of cold-formed sections with web holes susceptible to failure by web crippling due to concentrated force
Authors: Cláudia Márcia Canazart  , André Luís Riqueira Brandão  , Marcilio Sousa da Rocha Freitas
Published: January 2025

Cold-formed steel (CFS) are structural elements widely used in the construction industry and, in many situations, holes in the web is a design necessity, because it facilitates the passage of ducts, wiring and piping. This study evaluates the reliability of cold-formed sections with web holes subjected to concentrated force in sections without transverse stiffeners susceptible to web crippling failure. FOSM (Second Moment and First Order Method) and FORM (First Order Reliability Method) methods were used. A database was created with experimental results extracted from the literature, covering the four loading cases (end-one-flange loading  EOF, interior-one-flange loading  IOF, end-two-flange loading  ETF, interior-two-flange loading  ITF) presented in the standards used as reference, North American specification AISI S100 (2016), Brazilian standard NBR 14762 (2010) and European code EN1993-1-3 (2006). To obtain statistical data on the professional factor, one of the variables of the reliability problem, experimental results were compared with theoretical ones obtained by norm equations. Only AISI S100 (2016) standard has a criterion for considering web holes by considering a specified reduction factor for EOF and IOF. The results showed that the web holes significantly reduce the resistance of sections when subjected to the EOF loading case, while they reduce to a lesser extent in sections exposed to the IOF loading case. Analyzing the specimens subjected to the IOF loading, the results showed that another condition that influences the resistance is the fixation of the flanges to the supports. Very similar specimens groups reached the target reliability index when connected to the supports during the tests and did not reach when not connected.
Global Sensitivity Analysis of Relative Permeability and Capillary Pressure in Unsteady-State Core-Flooding Experiment
Authors: Emely da Silva Assis  , Filipe Oliveira da Silva  , Gianfranco de Mello Stieven  , Rodrigo Surmas  , Fábio Antonio Tavares Ramos  , Paulo Couto
Published: January 2025

Numerical simulation stands as a pivotal method within the petroleum industry, enabling the prediction of fluid flow in porous media. Its primary goal lies in analyzing behavior and forecasting oil production through fluid injection. However, the necessity for numerous simulations, each encompassing diverse multidimensional and compositional characteristics, presents a challenge. This leads to a significant accumulation of physical information, exacerbating the computational demands on the numerical model, particularly in terms of computational cost. To address this challenge, one potential solution is to determine the essential input parameters required for accurate oil production prediction. Global sensitivity analysis emerges as a powerful tool for this purpose, aiming to identify which input parameters exert the most significant influence on the numerical model's response, thus optimizing computation time. Unlike traditional approaches that focus on sensitivity around a single operating point, this study adopts a holistic perspective, assessing sensitivity across the entire sample space of the inputs. Specifically, this research investigates the impact of changes in parameters related to relative permeability and capillary pressure curves within a plug during unsteady-state core-flooding experiments. The key metrics under scrutiny include water saturation profiles, pressure differentials, and cumulative oil production. Sobol indices, a method for quantifying global sensitivity, are employed to assess the contribution of each input parameter's variance to the outputs' variance. The mathematical framework employed here is based on the multiphase (water/oil) Darcy equation, incorporating capillarity effects in one-dimensional longitudinal flow, incompressible flow assumptions, and constant injection flow, commonly known as the Black Oil model. The model is solved utilizing an implicit finite difference methodology with time step control, with relative permeability and capillary pressure parameterized by the LET model. The outcomes of this analysis provide valuable insights, notably in reducing the number of estimable parameters in inverse problems on a global scale. This reduction significantly diminishes computing costs, offering greater flexibility in constructing surrogate models for future simulations.
Analytical formulae for the higher-order effective coefficients of periodic laminated elastic composites with imperfect contact
Authors: Julián Bravo Castillero  , Leslie Darien Pérez-Fernández  , Fabio Carlos da Rocha  , Maria do Socorro Martins Sampaio
Published: January 2025

Analytical formulae are derived for the effective coefficients of linear elastic second-order laminate composite materials made of any finite number of linear elastic first-order layers. Imperfect contact conditions are considered at the interfaces, and small strains are assumed at the micro and macro scales. The micro-macro homogenization procedure used here is reported in Continuum Mech. Thermodyn. (2020) 32:1251-1270 wherein only numerical studies are presented. Asymptotic homogenization method results at the micro-scale level are combined with the macro-scale parameters based on the equivalence of the stored energies on the periodic cell (i.e., the energy-averaging theorem known as the Hill-Mandel condition). Some comparisons are considered for validation. To the best of our knowledge, the fully analytical application of this methodology to the case of laminate media has not been reported previously, that is, with the analytical solution of the local problems. The formulas obtained could be useful to control numerical codes in more complex periodic cells. Projects PAPIIT DGAPA UNAM IN101822, Mexico, and CNPq Universal Nº 402857/2021-6, Brazil, are gratefully acknowledged. CAPES Brazil Program (PRAPG)  Edital No 14/2023 is also recognized.
Asymptotic homogenization, domain decomposition and finite elements combined for calculating effective elastic properties of periodic fiber-reinforced composites with imperfect interfaces
Authors: Leslie Darien Pérez Fernández  , José A. Mesejo-Chiong  , Ángela M. León-Mecías  , Julián Bravo-Castillero
Published: January 2025

A methodology is presented for calculating the effective elastic properties of periodic multi-phase composites made of an anisotropic linear elastic matrix reinforced with a periodical distribution of unidirectional fibers and exhibiting spring-type imperfect contacts at the interfaces. The periodicity cell contains any finite number of parallel fibers and exhibits arbitrary cross-section. Fibers also exhibit arbitrary cross-sections and are made of a different anisotropic linear elastic material each. The methodology uses asymptotic homogenization (AH) to obtain the mathematical expressions of the effective properties and to formulate the so-called local problems on the periodicity cell on whose solutions the effective properties depend on. In order to deal with the discontinuities arising from the spring-type interfaces, the local problems are then restated via domain decomposition (DD) in a way allowing for an iterative resolution scheme in which the solution of the problem to be solve in each iteration is obtained via finite elements (FE). Results in the examples are obtained via a computational implementation of the methodology based on the FreeFEM open-source software, which allows for the variational formulation of the iteration problem to be dealt with directly.
Mechanical Characterization of Natural Fiber Ropes
Authors: Zenon Jose Guzman N. del Prado  , Elvis Yuri Mamani Vargas  , Adonai Irving Escobar Banda  , Eliot Pezo Zegarra  , Luis Fernando Paullo Muñoz
Published: January 2025

In this work the mechanical characterization of natural fiber rope is studied. For this, the festuca dolichophylla fibers are used to manufacture ropes, which are used to build a 28m span historical hanging bridge, with ancient Inka technology called Qeswachaka at the district of Quehue, department of Cusco in Peru.Twenty-four tests were performed on samples made by various diameters, varying from 30mm up to 130mm, in order to quantify its material constants using the hyperelastic theory, specifically the Neo-Hookean and MooneyRivlin models as well as fitting a polynomic curve. The findings showed that the initial part of the strength-strain curve fit very close to hyperelastic material behavior and can be applied to future modelling of real structures.
A fully-hybrid finite element formulation for general compressible-incompressible elasticity problems using de Rham compatible spaces
Authors: Giovane Avancini  , Nathan Shauer  , Philippe Remy Bernard Devloo
Published: January 2025

This work proposes a novel fully-hybrid finite element formulation for general elasticity problems, combining $H(\text{div},\Omega)$ conforming vector functions for displacement and $L^2(\Omega)$ discontinuous scalar functions for pressure. This pair is De Rham compatible, which means that within the incompressible regime, the divergence-free constrain will hold strongly at element level. As the $H(\text{div})$ spaces only present continuity of the normal displacements across elements boundaries, the tangential displacement continuity can be weakly imposed performing a hybridization of the shear stresses using $H^1(\partial\Omega_e)$ functions. From past researches conducted at LabMeC, this approach has demonstrated to pose some numerical difficulties as it leads to a saddle point problem with two constraint variables - the pressure and the shear-stresses. In this work, a second hybridization is done by approximating the tangential component of the primal displacement variable using $H^1(\partial\Omega_e)$ space. Two benchmarks are used to verify the developed numerical scheme - the classical Cook's membrane and a tridimensional cantilever beam subjected to an end shear load. Optimum convergence rate is achieved under compressible, quasi-incompressible and full incompressible scenarios.
An Analytical Frame for Predicting Residual Contact Pressure for Mechanically Lined Pipe using von Mises Criterion and Finite Strain Theory
Authors: Rongzhi Wei  , Murilo Augusto Vaz  , Xuefeng Hu
Published: January 2025

Mechanically Lined Pipe (MLP) is a bi-metallic pipe consists of an external carbon steel pipe internally coated with a thin Corrosion Resistant Alloy (CRA) lining. This CRA layer acts as a barrier against corrosive substance present in the production fluid from offshore Oil & Gas fields, while the high-strength, low-carbon steel outer pipe bears the external loads. Hydroforming expansion stands as the primary method for bonding the liner onto the external carrier pipe. The pursuit of precise and reliable theoretical models is ongoing to improve fabrication efficiency and establish a standard for subsequent failure analysis. The Tresca criterion is traditionally utilized in stress-strain analysis of MLP fabrication due to its mathematical formulation. However, it tends to provide conservative estimations of metallic structure yielding. And comparing the results of theoretical models employing the Tresca yield criterion with the mainstream numerical simulation software relying the von Mises yield criterion poses another difficulty. Hence, its suitability for analyzing MLP fabrication is subject to debate. To enhance accuracy, nonlinear theoretical analysis of MLP incorporating the finite strain theory and the von Mises yield criterion has been performed. Analytical prediction of residual contact pressure is achieved through the circumferential strain compatibility. An axisymmetric Finite Element Model (FEM) is constructed to compare against the theoretical models. Furthermore, the investigation delves into the impact of introducing an appropriate level of carrier pipe plastification on residual contact pressure.
Probabilistic Approach for Lateral Buckling Analysis in Virtual Anchor Spacing (VAS) Models of Rigid Flowlines Subjected to High Pressures and High Temperatures (HP/HT)
Authors: Rodrigo Borges Primieri  , Breno Pinheiro Jacob  , Carl Horst Albrecht
Published: January 2025

This study deals with the main topics related to the phenomenon of thermomechanical buckling of rigid flowlines laid on the seabed. It focuses on the latest versions of DNV-ST-F101 [1] and DNV-RP-F110 [2]. Additionally, the study presents a probabilistic approach for lateral buckling analyses in Virtual Anchor Spacing (VAS) of rigid flowlines exposed on the seabed, subjected to High Pressures and High Temperatures (HP/HT) in deep-water environments. The methodology includes determining the probability curves of the parameters with the greatest influence on the analysis: Pipe-Soil Interaction (PSI), friction between the pipe and sleeper (buckling mitigator), and geometric imperfections (lateral out-of-straightness). This is followed by a Design of Experiment (DoE) analysis to create a matrix composed of a representative set of load cases to be simulated using the Finite Element Method (FEM). These simulations are performed using Abaqus to obtain the probability distributions of the effective Critical Buckling Force (CBF) and Post-Buckling Force (PBF). The tolerable VAS is determined through FEM analyses applied to a dedicated load case matrix to identify the most critical failure criteria. The results are post-processed to generate response surfaces and failure probabilities for each of these criteria using the Monte Carlo Method. Finally, a case study is performed to illustrate the probabilistic approach, which requires more simulation time than a deterministic method but offers more detailed probability ranges for lateral buckling responses, potentially reducing a project's overall cost. It can be used to assess the reliability of lateral buckling responses during the detailed design phase of subsea pipelines susceptible to lateral buckling.
Stability analysis of a seabed under combined action of waves and seismic loading
Authors: João Paulo Chodacki Quiuqui  , Samir Maghous
Published: January 2025

The stability analysis of a seabed under wave and seismic loading is conducted within the framework of yield design theory using the pseudo-static method. The strength properties of the constitutive material are modeled by means of a purely cohesive condition. The loading associated with water waves is modeled through the linear wave theory, whereas the inertial forces induced by the passage of seismic waves is addressed in the framework of pseudo-static method. The material cohesion that increases linearly with dept is adopted in the analysis. A sufficient stability condition is obtained through the static approach of limit analysis, while a necessary condition is determined from the kinematic approach. The effects of seafloor surface inclination, as well as seismic intensity, are analyzed through pseudo-static coefficients. The determination of the limit load obtained through the pseudo-static approach is based on existing literature, particularly when seismic coefficients are not considered.
Bayesian parameter calibration of a one-dimensional hemodynamic model
Authors: Diovana Oliveira Mussolin  , Luis Alonso Mansilla Alvarez  , Pablo Javier Blanco
Published: January 2025

In this work, we couple a Bayesian optimization approach with a one-dimensional blood-flow model (known as ADAN86) to achieve a flexible and efficient strategy for the calibration of model parameters when in-vivo patient-specific data is available. The optimization step is addressed in the frequency domain, minimizing the discrepancies between the first harmonics of the in-vivo and predicted flow/pressure signals. The model parameters can be locally or globally perturbed, modifying the reference values in the same proportion for the whole system (global) or by region to account for the specificities of each location (local).To test the proposed strategy, two cases are considered. The first one involves parameter calibration in a synthetic patient, where some parameters are locally modified, and the optimization process is compared in local and global scenarios. The second case addresses parameter optimization in a patient with in-vivo flow/pressure data, comparing the local and global calibration approaches.The results show that the coupling between the Bayesian optimization process and the ADAN86 models yields an efficient strategy for the parameter calibration problem, which is naturally parallelizable and promising for data assimilation in computational hemodynamics.
Simulation of Blood Flow in Arteries for Functional Assessment of Coronary Disease: Implementation of Numerical Code
Authors: Sónia Isabel Silva Pinto  , Maria Carolina Fernandes  , Luísa Costa Sousa
Published: January 2025

Cardiovascular diseases are a major cause of mortality and morbidity in developed countries. Coronary atherosclerotic disease (CAD) is a degenerative process that is characterized by the development of atheromatous plaques on the wall of coronary arteries. Clinical manifestations of CAD range from stable angina, resulting from progressive plaque growth with partial obstruction of the arterial lumen (stenosis) and consequent limitation of coronary blood flow. In clinical practice, a diagnostic strategy is widely used to assess the functional relevance of CAD: the invasive assessment of myocardial fractional flow reserve (FFR).Coronary Computed Tomography Angiography (CTA) is an established non-invasive diagnostic tool for evaluating CAD. However, CTA can overestimate anatomic stenosis and is limited in that it does not provide information on the hemodynamic relevance of coronary stenosis. Thus, the implementation and numerical simulation of blood flow in arteries in the most real physiological conditions has been one of the main areas of interest of the authors [1]. The main purpose of this work is to develop and validate a computational tool for calculating the FFR and hemodynamic descriptors.In this way, to obtain the most accurate non-invasive FFR, the hemodynamic numerical tool was hardly improved to establish real conditions, specific to each patient case with CAD. Therefore, to achieve accurate pressures, Windkessel models, mainly based on the resistance of blood flow [2], were implemented considering hyperemia conditions (maximal dilation of the coronary tree), since the patient must be subjected to this condition during the catheterization to obtain the invasive FFR (reference value for validation). Moreover, the 3D patient-specific geometry of the artery was modified to simulate blood flow in hyperemic conditions. The numerical code development was performed in ANSYS® software.After validation, the authors aim to create a software for local use, allowing a comprehensive assessment of CAD in an accessible, fast, reliable, and non-invasive way. [1] Pinto, S.I.S. et al. (2020). The impact of non-linear viscoelastic property of blood in right coronary arteries hemodynamics  a numerical implementation. International Journal of Non-Linear Mechanics 123, 103477.[2] Boileau, E. et al. (2018) Estimating the accuracy of a reduced-order model for calculation of fractional flow reverse (FFR). Int J Numer Meth Biomed Engng 34, e2908.
Fracture failure representation of quasi-brittle materials using a three-dimensional dipole BEM formulation including loading rate effects
Authors: Luis Philipe Ribeiro Almeida  , Edson Denner Leonel
Published: January 2025

This study presents an alternative boundary element method (BEM) formulation for the cohesive crack propagation modelling in three-dimensional structures, including loading rates problems. Therefore, these developments enable the modelling of viscous-cohesive fracture processes. An initial stress field for representing the mechanical behaviour along the fracture process zone is proposed, which leads to a set of self equilibrated forces named as dipole. The proposed dipole-based formulation demonstrates some advantages in comparison to classical BEM approaches in this field. Among them, it is worth citing the discretisation of only one crack surface and the requirement of solely three integral equations per source point at the crack surface. Then, in addition to the accuracy, the proposed formulation is efficient in terms of computational effort, which is a bottle neck in three-dimensional problems. Cohesive laws govern the material nonlinear behaviour along the fracture process zone. The mechanical effects of loading rate over the material resistance at the FPZ are properly handled by a time dependent function, which modifies the tensile material strength and the material fracture energy as a function of the loading velocity rate. Some applications are introduced to demonstrate the adequate performance of the proposed formulation, in which the results obtained have been compared against experimental responses available in the literature.
Stress Recovery Techniques for the Modified Local Greens Function Method
Authors: Ramon Macedo Corrêa  , Marcos Arndt  , Roberto Dalledone Machado
Published: January 2025

The Modified Local Greens Function Method (MLGFM) is an integral method hybrid of the Finite Element Method (FEM) and the Boundary Element Method (BEM). The method uses the FEM to create discrete projections of the Greens functions that will be used as fundamental solutions in BEM formulation. The MLGFM has the advantage of presenting high convergence for the displacements in the domain, inherited from the FEM, and for the normal stress on the boundary, inherited from the BEM. Despite these advantages, the accuracy of the recovered stresses in the domain has not been studied in previous works. As the MLGFM is a hybrid of the FEM and BEM, techniques used in both methods will be explored in this paper to study the advantages and disadvantages of each one. The techniques that will be used here are the Least Squares procedure, the Zienkiewicz and Zhu (ZZ) recovery, both widely used in FEM, and the integral form derived from the fundamental solution used in the BEM. The techniques will be analyzed in terms of errors and computational cost of each one.