bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative study of strategies for creep simulation in the calculation of second-order effects in reinforced concrete columns
Authors: Lucas de Siqueira Paes Teixeira  , Leandro Lopes da Silva  , Juliano dos Santos Becho
Published: January 2025

This dissertation project aims to investigate the effects of creep in reinforced concrete columns, considering different strategies. With the democratization of computer access and the evolution of structural models, most part of building projects developed nowadays relies on more comprehensive structural models, which incorporate non-linear behaviors in their analysis, either through simplified or refined approaches. However, despite the evolution of these models, the simulation of the effects of creep is an aspect that still needs improvement. Creep is defined as the phenomenon of increasing deformations in concrete over time when subjected to constant stress. The topic is especially relevant in reinforced concrete columns, where the phenomenon can cause increased forces as well as increased second-order moments. The complexity of the creep phenomenon leads to simplified methods dominating the scenario, although there is still a shortage of studies on practical methodologies applicable in projects. In this context, the main objective of this work is to conduct a comparative analysis between commonly employed methods in practice for simulating creep with more refined models. The strategies considered are the Approximate Method of Additional Eccentricity e_{cc}; Standard-Column Method coupled with M, N, 1/r Diagrams considering creep effects through extended stress-strain curve; General Method coupled with M, N, 1/r Diagrams also considering creep effects through extended stress-strain curve; and Mathematical Model with analytical incorporation of the time variable. This study aims to formulate algorithms, to produce different models and simulations, to compare the results obtained by the different analyzed methods, and, if necessary, to propose practical solutions to achieve more reliable results. In this way, this study seeks to highlight both the effectiveness and limitations of the analysis strategies considered, aiming to contribute to the improvement of safety in implementing these strategies, especially those presented by Brazilian standards.
Eco-resilient (ECORE) concrete constructions: a new challenge and a new concept
Authors: Pierre Rossi
Published: January 2025

This paper presents a new concept concerning the development of eco-resilient concrete constructions, that is to say constructions with a reduced carbon footprint and which can withstand mechanical stress and physico-chemical attacks worsened by climate change. After a critical analysis of current research and development policies in the field of concrete construction, a new global approach is proposed which should allow this concrete construction profession to better respond to the challenges caused by global warming. This approach is based on two strong ideas: 1) the use of fiber concretes in combination with passive or active reinforcements in all constructions susceptible to crack 2) the use of numerical models based on non-linear finite element calculations in order to optimize the design of eco-resilient concrete constructions.
Heterogeneity Modelling of Concrete Structures by Nonlocal Damage Models
Authors: Matheus Moreno Fortes  , Samuel Silva Penna
Published: January 2025

The behavior of structural concrete is usually represented by considering the homogeneous material media and its macroscopic properties. The problem can be represented in more realistic models considering the material as a heterogeneous multiphase media. In representing heterogeneity, either a direct or indirect description of the phases can be considered. The direct approach considers the phases to be geometrically described in the discrete model. In the indirect approach, phases are represented by homogenizing their physical properties or by the random distribution of points in the domain with material parameters corresponding to each phase. In the physically nonlinear analysis using the Finite Element Method, a constitutive model capable of differentiating the response to tension and compression and computing the gradual cracking process of the concrete is necessary. Furthermore, these models must be coupled with regularization mechanisms to deal with numerically induced localization problems, such as the nonlocal approach. Given the above, this work proposes a model for representing the heterogeneity of concrete aiming at the physically nonlinear analysis of structures. Two phases will be considered to describe the heterogeneity: the cement matrix and the coarse aggregates, which will be incorporated into the discrete model using a hybrid method, which combines characteristics of direct and indirect methods. For material media degradation, a non-local damage model will be adopted with appropriate constitutive laws for each constituent material. Finally, numerical simulations will be presented to evaluate the model's characteristics.
Seismic Analysis of Nonlinear Reinforced Concrete Frame Structures
Authors: Mauro Schulz  , José Vittor Siqueira Cóco
Published: January 2025

Seismic structural analysis attracts significant interest in Brazil, even though much of the country exhibits low seismicity. Some regions in northwestern Brazil, such as most of the state of Acre and the southwest of the state of Amazonas, present ground motion accelerations that require dynamic analysis for earthquake loading. The construction of some special structures, such as nuclear power plants, requires the consideration of their seismic responses, regardless of their location. The internal forces provided by the Response Spectrum Method, in the frequency domain, are not always suitable for the design of reinforced concrete structures. The behavior of concrete is different under compression and tension. The sum of the modal absolute values through SRSS (Square Root of the Sum of Squares) and CQC (Complete Quadratic Combinations) approaches provides maximum absolute internal forces. However, negative or positive values indicate compression and tension, and reinforcement design is greatly influenced by whether stresses are compressive or tensile. The purpose of this research is to present a methodology for the seismic dynamic analysis of nonlinear framed structures, in the time domain, in which the equilibrium is rigorously examined at the end of each time step. The constitutive models adopted for the cyclic behavior of concrete and steel are discussed. A Timoshenko beam element suitable for this nonlinear analysis is presented. A time integration algorithm, based on Newmark's implicit method, is developed using the element's implicit stiffness matrix that considers the nonlinear behavior of the material. Equivalent nodal forces are calculated from accelerograms of known earthquakes. The adoption of the classic Rayleigh damping model is discussed. The numerical implementation is detailed. Examples are presented and conclusions are drawn.
A Comparison of Mesh Simplification Strategies for Realistic Grains
Authors: Danilo Menezes Santos  , Alfredo Gay Neto
Published: January 2025

In recent years, the Discrete Element Method (DEM) has emerged as a powerful tool for studying granular materials. In a DEM simulation, the objective is to reproduce the grain-to-grain interactions, and by working at this scale, the method can provide new insights into granular behavior. In the early stages of DEM, the particles were represented by disks and spheres. Currently, many codes have been developed to incorporate new ways to represent the grain shape more accurately. However, this process is not simple, taking into account that more realistic shapes bring the necessity of more complex algorithms for contact detection. Furthermore, to represent realistic grains through some ways like polyhedrons, a large number of entities (i.e., points, faces, and edges) are necessary, which increases the computational costs, making the simulation infeasible in some situations. To circumvent this problem, an alternative commonly used with polyhedrons is to reduce the number of entities in the mesh, decreasing the computational costs of simulation and the level of fidelity to the real grain shape. Due to the importance of this pre-processing stage, this paper compares three strategies for mesh simplification, analyzing the impact in shape descriptors, and the computational costs involved entities in DEM simulations, when varying their level of representation of 30 realistic grains.
Contact enforcement methods comparison in DEM context: application for railway ballast shear test
Authors: Guilherme Nunes Bassegio  , Alfredo Gay Neto
Published: January 2025

In the Discrete Element Method (DEM) analysis one has to represent the mechanical contact between particles, which is a need in a model representation in a certain geometric scale. This can be done by numerous methods and assuming distinct interface laws. In this work, two distinct contact enforcement methods are compared: the classical penalty-based and the barrier method. The former is available in Rocky DEM commercial software and the latter is implemented in the academic code GIRAFFE. Both methods are compared with respect to their capabilities, advantages and limitations. A classical shear box test is used as a comparison basis. The granular material tested is a sample of railway ballast. Discussions on aspects of convexity or concavity of particles are also made, such as their influences in overall mechanical results.
Shear strength reduction in triaxial compression of confined granular materials due to vibrations using the discrete element method
Authors: Rodrigo Bezerra Andrade  , Georg Koval  , Gustavo Henrique Siqueira
Published: January 2025

When subjected to external forces, the mechanical behavior of granular materials may range from static to dynamic. Unconfined granular beds, for example, are easily fluidized by vibratory loading. Under confinement, this type of material may also exhibit observable effects due to vibrations regarding their volumetric and strength behaviors. In this paper, the shear strength and dilatancy of dry confined granular materials subjected to vibrations are investigated using discrete element simulations of a triaxial cell. The material is first subjected to isotropic compression. Then, with controlled lateral stresses and imposed vertical motion, shear and compressive stresses are applied to a cubic sample. Additional harmonic displacements of the walls induce vertical and horizontal vibrations in the system during the shear tests. Finally, the impact of the amplitude, frequency, and direction of the vibrations on the angles of internal friction and dilatancy of the material is analyzed and compared to observations from the literature.
Simulation of 3D concrete printing using an implicit formulation of the moving particle semi-implicit method
Authors: Daniela dos Santos da Mata Gomes  , Melina Rocutan  , Lucas Soares Pereira  , Fabio Kenji Motezuki  , Liang-Yee Cheng
Published: January 2025

Additive construction techniques, such as 3D Concrete Printing (3DCP), offer significant advantages, as reduced material waste, optimized construction times, and the possibility to create complex shapes that would be difficult to achieve through conventional methods. Despite the advances in 3DCP, some challenges persist due to the still incipient development to predict the printing results. The fresh properties of the material play a crucial role. Therefore, in addition to experimental studies, numerical modeling emerges as a valuable tool to investigate the dynamic aspects of the extrusion process in 3DCP. However, the numerical modeling of 3DCP is challenging due to the complex rheological behavior of the self-supporting concrete, which typically exhibits high values of apparent viscosity at low deformation rates. To address these challenges, we adopted the moving particle semi-implicit (MPS) method, which is a particle-based simulation technique suitable for modeling free surface flows and materials undergoing large deformations. As a Lagrangian approach, MPS discretizes the computational domain into particles that move according to the governing equations of fluid motion. The conventional formulation of the MPS presents numerical restrictions when dealing with highly viscous fluids. To assure numerical stability, the semi-implicit approach requires very low time steps, resulting in high processing costs. In this way, this study adopts an implicit algorithm that allows for significantly larger time steps, resulting in reduced processing time compared to the conventional semi-implicit formulation. To validate the implicit algorithm, simulations of non-Newtonian flow between parallel plates were validated using analytical solutions, demonstrating better accuracy at lower Bingham numbers. The 3DCP simulations were conducted to describe the flow of fresh mortar using the Bingham-Papanastasiou constitutive model. The geometry of the 3D model includes the extrusion nozzle and a planar surface where concrete is printed. The numerical investigation involved simulations with different nozzle heights (Hn), printing speeds (V), and extrusion volumetric fluxes (U). The cross-sectional shapes of the extruded layers were compared with experimental data, showing qualitative agreement. The results demonstrate the potential of the implicit MPS method for modeling 3DCP processes.
Analysis of Soil-Structure Interaction in Raft Foundation Using Grid Analogy
Authors: Márcio Farias Italiano de Araújo  , Christian Carneiro de Oliveira  , João Carlos Cordeiro Barbirato
Published: January 2025

Anticipating the behavior of structural elements to be designed is an inherent necessity in Civil Engineering. Within the realm of foundation structures, this need is no exception. In this context, it is pertinent to state that structural analysis softwares represents a significant advancement in this field. Its utilization enables the attainment of precise and often complex results through a variety of analysis methods. Consequently, the Grid Analogy method, through its numerical application, offers a simplified and effective approach to analyzing two-dimensional plate elements by treating them as grid elements. This study focuses on analyzing the soil-structure interaction in raft foundations, using an approach based on the Grid Analogy Method. This is achieved through an adaptation of the LAGI software, developed in Python, aimed at the structural analysis of slab floors, which now includes support for analyzing rafts supported on soil, serving as a flexible base for the structure. The Grid Analogy is employed as a technique that facilitates modeling for soil-structure interaction analysis, providing relatively accurate results and enabling a deeper understanding of raft behavior under different loading conditions and soil characteristics. Practical applications are utilized to validate the implementation of the modeling, along with comparison of results obtained from other structural analysis software. These results, which include internal force diagrams emphasizing maximum bending moments and displacements with their values, underscore the effectiveness of the adopted approach and present an innovative alternative for analyzing a crucial area within Structural Engineering.
Assessment of Strategies for Numerical Modeling of the APB in Oil Wells
Authors: Gabriele Karolyne Melo Lins  , Catarina N. A. Fernandes  , Thiago B. da Silva  , Gleide K. M. Lins  , William W. M. Lira
Published: January 2025

This study aims to study and compare numerical modeling strategies for reproducing the phenomenon of Annular Pressure Build-up (APB) in vertical oil wells, in order to contribute to the development of procedures with higher accuracies. APB occurs due to the tendency of confined fluids filling the annular region between casings to expand in response to thermal variations within the well. This phenomenon is critical in the petroleum industry, especially in deepwater environments, where greater temperature and pressure differentials are present. APB leads to increased stresses on well casings, which can cause structural failures and, in extreme situations, could in human, environmental, and economic losses. Therefore, studying the origins and effects of this phenomenon and considering them during the well design phase are essential to ensure safety and efficiency. Motivated by the significance of the topic and the challenge of reproducing APB analytically, several authors have sought to model the phenomenon and its effects using finite element-based computational software like Abaqus. To achieve the proposed objective, the methodology adopted includes: a) literature review of existing strategies for APB modeling; b) definition of a simplified scenario for reproducing selected strategies; c) comparison of methodologies and results obtained from each; and d) discussion on discrepancies, gaps, and potential improvement opportunities. This study evaluates two modeling strategies in Abaqus, both utilizing fluid cavity interaction to model fluid behavior within a plane axisymmetric analysis. The difference lies in the approach to thermal expansion. While one calculates APB directly from thermal variation, the other does so by introducing an equivalent mass flow. Furthermore, the strategies will be compared not only in terms of results and accuracy, but also with regards to computational cost, aiming to identify the most efficient approach for modeling the phenomenon. Despite methodological differences, both approaches yield similar results, with the second providing the flexibility to model fluids with different behaviors. Thus, this study contributes to understanding and optimizing APB modeling, aiding in the development of more robust and efficient strategies for predicting the effects of this phenomenon.
Comparative analysis of wellbore closure in salt rock formations considering primary creep
Authors: Elisama Quezia Silva Santos  , Catarina Nogueira de Araújo Fernandes  , William Wagner Matos Lira  , João Paulo Lima Santos  , Antônio Paulo Amâncio Ferro
Published: January 2025

This study presents a comparative analysis of vertical wells wellbore closure behaviour considering constitutive models with and without the incorporation of primary creep in salt rocks. In the context of drilling wells in the pre-salt region, one aspect that can jeopardise the operation is the phenomenon of creep, as time-dependent deformations accumulate and can lead to irreversible drilling column entrapment due to wellbore wall closure. Because of the complexity of drilling in salt formations, vertical trajectories are usually adopted in this region. During the design stage, well closure simulations are necessary to predict undesirable scenarios and thus assist in the appropriate selection of drilling fluids and the planning of reaming operations. Therefore, it is crucial to employ constitutive models capable of adequately representing the behaviour of salt rocks in these simulations. The constitutive model traditionally adopted for Brazilian rocks is the so-called Double-Mechanism of deformation. This model describes only the secondary creep stage, which is dominant over longer periods of time. This study focuses on comparing the differences between the results of well closure simulations with the Double-Mechanism and with the EDMT model (Enhanced Double-Mechanism using a Transient Function), which incorporates primary creep into the Double-Mechanism of deformation, thus being able to better represent short-term deformations. To achieve this objective, a case study is employed with the modeling of a synthetic well, using data consistent with real pre-salt wells. Elastic and viscoelastic parameters of saline rocks are obtained from the literature. The numerical simulation is performed using the finite element method. The well closure profiles of a well section obtained over time are compared. In the comparative analysis, the importance of primary creep in the well wall closure is further discussed by comparing critical time windows for restricting the passage of drilling equipment.
Modeling of Creep Closure of Salt Rocks Drilled by Directional Wells
Authors: Carlos Mikael Alencar Tenorio  , Catarina Nogueira de Araújo Fernandes  , João Paulo Lima Santos  , William Wagner Matos Lira  , Themisson dos Santos Vasconcelos
Published: January 2025

This paper presents a strategy for three-dimensional modelling of directional wells penetrating salt rocks, aiming at predicting the closure of these rocks due to creep. One of the major challenges in oil production in the pre-salt region is drilling through thick layers of salt rocks. During drilling, these rocks deform in the direction of the wellbore closure due to creep. The accumulated deformation of the wellbore wall over a given time interval can lead to the restriction of the drilling string's passage and even its irretrievably trapped. Directional wells in salt regions present an even greater complexity, as changes in inclination alter the stress distribution around the well, changing the configuration of the deviatoric stress, with no symmetry around the well's central axis (as in vertical wells). This paper discusses a strategy for modelling directional wells in salt regions using the commercial software Abaqus. This software implements the Finite Element Method, including its three-dimensional formulation, and allows modeling of creep deformation of materials, enabling the implementation of constitutive models different from traditional ones through subroutines. The adopted constitutive equation is the most recurrent in the literature to describe the creep phenomenon in wells through Brazilian salt rock. To verify the developed strategy, a vertical well is modelled, and the obtained results are compared with those presented by axisymmetric modeling, already consolidated in other works developed by the group. After verification, directional wells are modelled and studied, and their behavior is discussed regarding the observed displacement and stress fields, mainly along the region near the wellbore wall. This work contributes to the understanding of the creep behavior in salt rocks when drilled by directional wells, and discusses some strategies that can contribute to the stability of the rock formation, aiming at the safe and efficient construction of wells in salt regions.
Pre-processing for isogeometric analysis of laminated composites
Authors: Murilo Almeida Oliveira  , Elias Saraiva Barroso
Published: January 2025

Composites are materials resulting from the mixture of two or more components, usually a polymer matrix reinforced with synthetic fibers, used to build stronger structures capable of withstanding heavy loads and unfavorable environmental conditions. Laminated shells are made of layers of fiber-reinforced composite material, stacked in a specific sequence to ensure good structural performance. The analysis of these structures is predominantly done using the Finite Element Method, a conventional approach used to solve these problems, approximating both the displacements and the geometry of the structure using polynomial functions. A more recent alternative is Isogeometric Analysis (IGA), which uses rational functions to approximate the displacements and geometry of the structure. This ensures that the geometry of the problem is exact, regardless of the level of discretization used. The aim of this work is to study the use of NURBS surfaces in the context of isogeometric analysis of laminated structures. The theoretical and practical aspects of these representations will be studied, with emphasis on the pre-processing stage of the numerical analysis. In this context, the pre-processing of the numerical model of the composite material structure is carried out in the academic software FEMEP (Finite Element Method Educational Computer Program), written in the Python language. The software's graphical interface has been extended to handle models of laminated composite plates. The numerical model is processed using the FAST tool, where the pre-processing program writing routines have been implemented. In the post-processing stage, the simulation results are visualized using the Nlpos tool. The system developed was used in examples of laminated plates, demonstrating the system's capabilities.
Topology optimization of spatial frames
Authors: Sarah Maria Schroeder  , Eduardo Lenz Cardoso
Published: January 2025

The pursuit of improving projects, such as optimizing resources and material usage, has led to an increased interest in structural optimization techniques. Among the various options available in the literature, the topology optimization stands out, allowing the design of structures with extreme behavior and significant material reduction, while adhering to constraints on the mechanical behavior of the structure. This study aims at implementing the topology optimization for spatial frames, with the goal of reducing volume with stress and displacement constraints. The mathematical formulation and computational implementation were developed by the authors and are available on github. The results show significant reduction on material usage while respecting the functional constraints
Machine Learning aided Phase-Field Method in Constitutive Modeling of Concrete Structures
Authors: Adalberto Horácio de Oliveira Mendes  , Hugo Mouro Leão  , Saulo Silvestre de Castro  , Roque Luiz da Silva Pitangueira
Published: January 2025

Phase-field modeling has emerged as a promising approach for modelling crack propagation. Different from Griffiths theory, which deals with discrete cracks, phase-field modeling transforms cracks into diffusive entities that propagate within a defined region, regulated by a length scale parameter. This methodology introduces a phase-field variable as a novel nodal degree of freedom, governed by an additional equation integrated into the model. This variable quantifies the damage of the material at each point, with zero representing intact material and unity indicating complete damage.However, the practical implementation of phase-field modeling presents significant computational challenges. Its requirement of very refined meshes makes the process computationally expensive. In this context, machine learning techniques can be used to simulate the constitutive model and ensure that the process enhance efficiency. The article aims to use the machine learning technique to train a neural network capable of simulating the constitutive behavior of a phase-field model. The validation of this approach will be carried out by comparing its results with those obtained through finite element numerical analysis. All simulations will be conducted using the INSANE software.
Local-distortional-global buckling interaction os lipped channel steel cold-formed columns
Authors: Eduardo de Miranda Batista  , Gustavo Yoshio Matsubara
Published: January 2025

It is well-established that axially loaded thin-walled steel cold-formed members are susceptible to elastic buckling. This has been a focal point of numerous research studies, leading to insights into various buckling interaction cases, including local-global (LG), local-distortional (LD), distortional-global (DG), and local-distortional-global (LDG) interactions. This investigation specifically focuses on the triple buckling interaction LDG, building upon the authors' previously proposed design solution for LD buckling interaction. The study was conducted using experimental and finite element method (FEM) column results, creating a comprehensive database to validate the proposed solutions. The first research step involved verifying the accuracy of the shell FEM model by calibrating with experimental results of lipped channel (LC) columns developing the LDG buckling. Once the FEM model's accuracy was confirmed, a parametric study was conducted to support the development of the proposed LDG design solution for LC columns. The proposed design equations adhere to the core principle of the direct strength method, capable of incorporating all single buckling modes (L, D, and G) and their combinations (LG, LD, and LDG). Comparisons were made using LRFD-based reliability analysis, which confirmed that the proposed solution is reliable, easy to apply, and aligns with the usual design principles and parameters found in current codes and standards for steel cold-formed structures. Additionally, DG and LDG design approaches from other authors are mentioned and discussed in the context of the findings of the present investigation.
Numerical analysis of circular hollow section bar with stiffened flattened ends
Authors: Ana Amélia Oliveira Mazon  , Arlene Maria Cunha Sarmanho  , Lucas Roquete Amparo  , Fábio Nogueira da Silva Costa
Published: January 2025

Circular hollow sections are usually used in long-span roof truss systems due to the advantages they offer. One of the typology for connecting elements in such structures involves the flattening of bar ends, in order to provide a simpler and more economical connection. A new flattening typology called stiffened flattening is proposed, characterized by a non-flat geometry, with the creation of stiffeners in the lateral edges of the bar flattened ends. A theoretical, numerical and experimental study was carried out on the behavior of a plane truss composed of circular hollow sections, in which diagonal bars have stiffened flattening ends. The diagonal connecting system with the chord members uses connecting plates. The plates are welded to the chords and the diagonals are connected to latter through a single bolt. This work presents the numerical analysis of a circular hollow section bar with stiffened flattening ends subjected to compression. This is a study of the behavior of an isolated bar compressed from the truss, which corresponds to the most requested diagonal composed by circular hollow sections with stiffened flattening ends. The numerical analysis using finite elements method was developed through ANSYS software with the Parametric Design Language (APDL), in which parameters such as geometry, material, element type, definition of the finite element mesh, boundary conditions and application of compression loads are specified. A non-linear analysis was performed using shell element on the bar with stiffened flattened ends. The numerical analysis result satisfactorily represented the structural behavior of the isolated circular hollow section bar with stiffened flattening ends. It was possible to observe the buckling effect of the compressed circular hollow section bar and the effect of the axial load eccentricity due to the stiffened flattening of bar ends.
Web shear buckling capacity of a stiffened Z-purlin: reporting of experimental tests
Authors: Almir Benedito de Lima Júnior  , Diego Fernandes Moreira  , José Luis Vital de Brito  , Guilherme Santana Alencar
Published: January 2025

Over the last few years there was a growing demand for structural solutions with lower steel consumption in the design of portal frames. It is considered that cold-formed steel (CFS) represents a consumption of 30 to 40% of steel in the entire structure, due to its great applicability in roof systems. Purlins with Z-sections have capabilities to achieve greater spans than other sections due to the continuity provided by overlapping connections. Greater spans require higher sections, thus increasing the susceptibility to local buckling of the web when the purlin is subjected to bending. Therefore, there is the need to introduce web stiffeners with complex geometry, providing better structural performance to local buckling strength. However, this also introduces complex web behaviour in the presence of shear, as result it requires advanced analytical, experimental and numerical studies to assess the web shear buckling mode of failure of such sections. In this context, as a first incursion in this field, the authors report in this paper some experimental tests of a new stiffened web cold-formed Z-section in the Brazilian market aiming the web shear buckling mode of failure. Consequently, an experimental setup of simply-supported purlins with short spans under 3-point bending are carried out. The flanges were locked to investigate the structural behaviour of CFS under predominantly shear. The resistances are compared between experimental data and direct strength method (DSM) as prescribed in the AISI S100. The results were evaluated providing a rich understanding of the structural behaviour of the CFS Z-sections with stiffened web and complex geometry.
Finite element analysis of steel shear frames with composite reinforced concrete infill walls and welded bolts as shear connectors
Authors: Marinés Pérez Ramírez  , Pablo Uribe Bárcenas  , Carlos Alberto Bermúdez Mejía
Published: January 2025

In the composite walls stiffness system of reinforced concrete walls with composite boundary members, boundary members resist most of the moment due to seismic loading. In contrast, the reinforced concrete (RC) wall provides shear resistance. The SRCW system comprises partially restrained steel frames with reinforced concrete infill walls. The steel columns and beams act as boundary members to resist gravity loads and most of the overturning moment due to seismic loading, while the reinforced concrete (RC) infill wall acts as shear-resisting web. The RC infills increase the lateral stiffness dramatically compared to a bare steel frame, thus avoiding excessive drift and reducing the seismic demands on the steel frames. In that way, why not use just steel shear frames instead of partially restrained steel frames with reinforced concrete infill walls? This paper presents a numerical study of the behavior of a composite structural system consisting of steel shear frames with reinforced concrete infill walls (SFRCW). The composite interaction is achieved using welded bolts as shear connectors along the steel frameinfill interfaces. Welded bolts were used as shear connectors because they are frequently used in Colombia due to their ease of installation. The SFRCW system may be particularly appropriate for low-to-moderate-height structures. In addition, the steel shear frame will support gravity loads at the construction stage, allowing progress in height. The system can also be used to strengthen existing steel buildings. The relatively light steel frame constructed using shear connections maximizes the system's economy.This study compared the behavior of the SFRCW with columns acting in their weak and strong axes and with different numbers of shear connectors. It also compared the behavior of the bare steel moment frame, bare steel shear frame, and reinforced concrete wall. The numerical models show interesting results.
Nonlinear finite element analysis of steel-concrete composite beams with cellular I-section under hogging moment
Authors: Carlos Humberto Martins  , Vinicius Moura de Oliveira  , Lucas Mognon Santiago Prates  , Alexandre Rossi  , Felipe Piana Vendramell Ferreira
Published: January 2025

Adopting hybrid cellular I-sections can favor optimizing steel consumption, as the higher steel grade is localized only in the compression tee. In addition, continuous steel-concrete composite cellular beams allow the construction of longer spans due to the combination of higher bending stiffness of the cellular I-section and its connection with the concrete slab, further the continuous of the beam, which provides a better distribution of the bending moment diagram. However, due to the hogging moment on the support regions, the steel-concrete composite beam can present lateral instability of the compression flange accompanied by web distortion, named Lateral-DistortionalBuckling (LDB). No investigations have evaluated the behavior of steel-concrete composite beams with hybrid cellular I-section under hogging moment. This way, the present study aims to assess the behavior of the structure in question using a nonlinear finite element model via ABAQUS software. The investigation consists of verifying the beams' failure mode, considering plastic behavior or LDB, and the effectsof different combinations of steel grades for the hybrid I-section, and further comparing the use of hybrid and homogeneous steel profiles on the composite beams.
Protection of Columns in Buildings: against accidental impact, fire and progressive collapse
Authors: Luiz Eduardo Gonçalves de Mattos  , Jose Caio Couto Bezerra Carneiro  , André Teófilo Beck
Published: January 2025

Civil structures must be designed to withstand demands throughout their lifespan, ensuring adequate safety levels. However, accidental events, such as fires and vehicular impacts, present high uncertainty regarding intensity, location and occurrence probability, potentially exposing the structure's lack of robustness and representing significant risk. A column loss, for example, can trigger progressive collapse. To prevent disproportionate damage, reinforcements or safety devices can be used. However, traditional reinforcements can be expensive and impractical, especially in existing buildings. In this context, an optimized structural protection device is proposed for reinforced concrete columns, capable of inhibiting or reducing damage caused by impacts and fires and reducing the likelihood of collapse due to falling slabs. The device consists of cellular structures, known for their energy absorption and thermal insulation properties. Using multi-objective optimization techniques, compromise points that composes Pareto fronts are explored. Through case studies, these points are evaluated and promoted to optimal solutions in scenarios that require specific mechanical and thermal capabilities to ensure the columns integrity against the mentioned hazards, coupled with optimized material consumption. A cost-benefit analysis based on risk minimization is also presented, aiming to reduce expected failure costs and failure probabilities in adverse scenarios. Supported by positive results, it is concluded that of the cellular protection device emerges as a good alternative to traditional structural reinforcement techniques, standing out for its versatility, effectiveness, and potential for application with reduced costs.
Structural reliability analysis of a laminated plate using the Reissner-Mindlin model and the finite element method
Authors: Lucas Miranda de Macedo  , Paulo de Tarso Rocha Mendonça  , Wellison José de Santana Gomes
Published: January 2025

The use of anisotropic laminated plates as structural elements has become increasingly common due to their ability to emphasize desired mechanical characteristics and reduce undesired ones, based on the laminate stacking sequence.Although the application of structural optimization methods to define the optimum laminate stacking angle is common in the literature, an analysis of the influence of this angle on the behavior of the plate and the approximate identification of its failure mode is relevant when seeking to increase laminate efficiency. In addition, taking into account the uncertainties that affect the structural response of these elements is still under development and open to discussion. Structural reliability is a suitable tool for dealing with these uncertainties. This article aims to analyze the influence of the stacking angle on the probability of plate failure, taking into account the probability distributions of the variables involved. In order to make a comparative analysis, different Structural Reliability methods are adopted, such as FORM and the Monte Carlo method, and several failure criteria - Tsai-Hill, Tsai-Wu, Hoffman and Maximum Stress. The analysis is based on a case study of a laminated plate subjected to transversal static loading. The plate is considered to be made up of orthotropic laminae in oblique directions. The structure is modelled using the Finite Element Method, using the Reissner-Mindlin kinematic theory in the linear elastic regime. The aim is to verify and discuss the influence of the stacking angle on the level of structural safety of laminated plates.
A compliance-based topology optimization approach using conservative convex separable approximations and PSB Hessian estimation
Authors: Ricardo Albuquerque Fernandes  , Adeildo Soares Ramos Junior
Published: January 2025

In topology optimization, methodologies for updating design variables, such as the widely-used Optimality Criteria (OC), play a pivotal role in efficiently addressing problems with monotonically decreasing objectives subject to certain design constraints. However, despite its effectiveness, the OC method is derived from first-order optimality conditions. These conditions may not fully capture the nuances of more complex optimization problems, potentially leading to suboptimal or inefficient solutions. In this work, we use conservative convex separable approximations (CCSA) of the objective function, alongside with a PSB method for estimating the diagonal terms of the Hessian matrix. Three variations are considered: quadratic, logarithmic, and square-root approximations. This approach aims to enhance the efficiency and effectiveness of objective minimization in topology optimization problems subject to a volume constraint. To demonstrate the efficacy of the aforementioned methodology, several case studies are presented and evaluated using both the OC method and the CCSA update scheme. The obtained results and performance metrics are compared, providing clear evidence of the advantages offered by the proposed approach.
Exploring Topology Optimization in Geotechnical Engineering
Authors: Aldemar Pontes de Siqueira Neto  , Xiaodong Huang  , Josué Labaki
Published: January 2025

Despite recent advancements in utilizing topology optimization in geotechnical engineering design, practical applications primarily focus on simple foundation design. In the view of this, this study aims to explore the application of topology optimization methodology to various geotechnical design problems. The optimization takes place in a finite portion of the soil, modeled via Finite Element Method (FEM) which is coupled with the rest of the semi-infinite soil, modeled via Indirect Boundary Element Method (IBEM). The optimization is carried out considering a linear bi-material interpolation through the three field Floating Point Topology Optimization (FPTO) method. Numerical results for the optimized foundations of plates, bridges and linings are presented and discussed.
Topology Optmization Applied to Problems with Local Fatigue Constraints Based on Augmented Lagrangian Method
Authors: Carlos Eduardo Lino  , André Luis Ferreira da Silva  , Emilio Carlos Nelli Silva
Published: January 2025

Fatigue is the most usual failure mode of any mechanical structure subject to loading. There are several methods to predict the structure life, and different approaches can be applied to extend this life. From the point of view of materials engineering, new materials can be proposed to deal with this issue. However, developing and producing these materials can be expensive. A different approach consists of optimizing the design using some optimization algorithm, determining the optimized material distribution that ensures a higher fatigue life. This work proposes to use topology optimization to design structures subjected to permanent loads to increase the component life. The objective is to minimize the volume, considering fatigue constraints. The works in the literature deal with fatigue constraints using aggregate methods, which are common in problems considering stress constraints. Our proposed approach uses a norm of the stress field to represent the stress constraint. However, stress and fatigue are local phenomena. Thus, in this work, the Augmented Lagrangian method is used to deal with the large number of constraints in the problem. This approach, previously used in stress-constraints problems, makes treating fatigue as a local phenomenon. The Modified Goodman method is used to measure local fatigue. This method considers a sensitivity factor that accurately estimates fatigue life. Numerical examples show the efficiency of the proposed method.
Assessment of the Human Comfort of Pedestrian Footbridges Utilising Probabilistic Response Spectra
Authors: José Guilherme Santos da Silva  , Paula de Oliveira Bezerra Diniz  , Jorge Maurício de Souza  , Amanda Borges Oliveira  , Gilvan Lunz Debona
Published: January 2025

Nowadays, the design of pedestrian footbridges is associated to light weight structures with low natural frequencies and low structural damping rates. These facts have generated slender footbridges, sensitive to human dynamic excitations, and consequently changed the serviceability limit states associated to the design. Thus, the current design codes and technical guides recommend the use of deterministic models to assess the dynamic structural behaviour of footbridges. On the other hand, the pedestrian walking is related to a stochastic phenomenon and the dynamic force generated at each step depends of the weight, the step frequency and the step length of each pedestrian. This way, this investigation aims to develop a probabilistic approach to assess the steel and steel-concrete composite footbridges dynamic behaviour, based on the use of design response spectra. To do this, the developed analysis methodology has considered the stochastic nature of the pedestrians walking, in order to evaluating the structural response having in mind excessive vibrations that may cause human discomfort. Based on the use of probabilistic methods, it becomes possible to determine the probability of the footbridges peak acceleration values exceeding or not the human comfort criteria. The results obtained in this research work reveal that the peak acceleration values calculated through the deterministic methods can be overestimated in project situations.
Comparison between different sets of interpolation functions for Timoshenko frame elements
Authors: Rodrigo Bird Burgos  , Matheus Barros do Amaral
Published: January 2025

The objective of this paper is to discuss, in the context of a second-order geometric non-linear analysis, the differences in results considering different sets of interpolation functions for frame elements. The usual way to obtain interpolation functions for Timoshenko frame elements is using cubic Hermitian polynomials since they are the solution for the fourth-order differential equation which represents the bending behavior of the infinitesimal element. When dealing with more complex problems (geometrical and/or physical nonlinearities), the usual strategy is to subdivide the elements, which circumvents the limitation of the interpolation functions. Since discretization can sometimes be unwanted, especially for undergraduate students who still do not grasp this concept, a solution which overcomes this is interesting from a didactic point of view. This work proposes the use of different sets of shape functions to interpolate displacements, rotations and bending moments along the elements length, to account for the nonlinearities that arise from the change in geometry during loading. Shape functions obtained directly from the solution of the differential equation of an axially loaded deformed infinitesimal element and traditional Hermitian polynomials are used. Comparisons were made against analytical and numerical solutions using the two-cycle approach. Initial results indicate the ability of the formulation to capture the nonlinear behavior without the need to over discretize the domain.