bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance-based design optimization of steel structures subjected to seismic actions
Authors: Surrogate Models  , Seymour M. J. Spence  , André T. Beck
Published: January 2025

Finding an optimal design for a structural system subject to seismic actions to minimize failure probability, repair costs, and injuries to occupants, significantly contributes to the resilience of buildings in earthquake regions. This research presents a comprehensive framework for the performance-based design optimization of steel structures, incorporating the Performance-Based Earthquake Engineering (PBEE) methodology delineated in FEMA P-58 [1]. A selected set of ground motions, consistent with the seismic hazard intensity of interest, and a nonlinear finite element model, established using OpenSees, enable the assessment of the system's dynamic response. To address the computational complexity related to evaluating the probability of failure of the system during an optimization iteration when using the PBEE methodology for assessing performance, this study introduces metamodeling techniques as a substitute for the original high-fidelity nonlinear finite element model. In particular, Kriging is employed to approximate both the median and standard deviation of the Engineering Demand Parameters (EDPs) in the design domain. The parameters of the Kriging metamodels are derived from nonlinear dynamic analyses performed using the original high-fidelity model and an optimal sampling plan obtained through Latin Hypercube sampling. Under the assumption of a lognormal distribution, the metamodel is then used to generate a large number of simulated demand sets necessary for the Monte Carlo procedure adopted by FEMA P-58 to calculate the distribution of probable losses for any given value of the design variable vector. Additionally, the median and standard deviation of the fragility function modeling collapse are also approximated by a Kriging metamodel, in which the parameters are derived from an Incremental Dynamic Analysis (IDA) for any given value of the design variable vector. The scheme is illustrated in a full-scale case study consisting of the performance-based optimization of the buckling-restrained braces of a steel seismic force-resisting system in terms of expected losses and construction costs. The study demonstrates that the proposed risk-based optimization scheme effectively balances construction costs with expected financial losses from earthquakes, thus enhancing the seismic performance of the system.[1] Applied Technology Council, & National Earthquake Hazards Reduction Program (US). (2012). Seismic performance assessment of buildings. Federal Emergency Management Agency.
Reliability analysis in the design of cold-formed steel built-up I sections by modified Direct Strength Method
Authors: Júlia Nogueira Mauad  , André L. R. Brandão  , Marcilio Sousa da Rocha Freitas
Published: January 2025

Cold-formed steel (CFS) framing is an economical and efficient structural solution, as it provides high strength and low self-weight. Built-up sections, formed by combining two or more CFS members, can reduce instabilities and obtain more versatility. An approach adopted in standards from several countries for the design of CFS bars is the direct strength method (DSM), which allows calculation of axial force from elastic buckling loads, considering global, local and distortional buckling modes. Currently, there are proposals to modify the DSM for the design of built-up sections, aiming to better fit experimental and numerical data. This study aimed to investigate these modifications of original DSM formulae by applying them to a database of experimental compression tests on built-up I, or back-to-back, sections. Using the database results, it was possible to calculate the professional factor (P), obtained from the ratio between experimental and theoretical results. To obtain reliability indices (β) related to theoretical methods, the professional factor was evaluated as a continuous random variable, according to data grouping by section type, failure type, and all one. The reliability index (β) was obtained using FOSM, FORM and Monte Carlo Simulation (MCS) reliability methods for load combinations from AISI S100 (LRFD and LSD) and NBR 14762.
Reliability Analysis of Serviceability Limit States of Beams in a Benchmark Reinforced Concrete Building
Authors: Jonathan Henrique Cordeiro Nunes  , Eduardo Toledo de Lima Junior  , Flávio Barboza de Lima
Published: January 2025

The construction system of reinforced concrete entails inherent uncertainties concerning its execution method, as well as physical, chemical, and biological phenomena, along with the loads acting on buildings. Hence, understanding and characterizing random variables in designing reinforced concrete structures is pivotal for devising effective solutions that meet safety and performance requirements. In this context, limit state equations are employed for structural analysis and design, addressing different failure modes, while concepts of probability and statistics are utilized alongside reliability methods to ascertain the probability of failure and assess the structural integrity of the elements. Within this framework, this study endeavors to implement models for evaluating the reliability levels of reinforced concrete beams in a 2-storey building, considering the limit states of excessive deflection and crack width, and incorporating the effects of shrinkage and creep, according to NBR 6118:2023. The probabilistic assessment of the designed beams is performed by using the First-Order Reliability Method (FORM), whose results are validated and compared with those obtained through the Monte Carlo simulation method. The findings indicate a conservative design of the beams for the failure modes addressed, as the reliability indices are in line with values stipulated by international standards in most cases analyzed. Although this, some critical beams subject to higher loads approached the allowable limits more closely, presenting a narrow safety margin. This study aims to contribute to the advancement of integrating reliability analyses into reinforced concrete structural projects.
3D Topology optimization considering multiple loading
Authors: Herbert Martins Gomes  , Bruno Cuthi Mattia
Published: January 2025

Topological optimization looks for determining the ideal material distribution within a design domain (2D/3D) in order to optimize structural performance following imposed design constraints. This material distribution can vary continuously, resulting in complex shapes that are lighter than the original structure and take better advantage of material strengths. Incorporating multiple loads into topology optimization increases the complexity of the problem, as it requires simultaneous consideration of different types of loads and their interactions with the structure in problems that have several degrees of freedom. This can include the analysis of load combinations due to self-weight, other load combinations or even dynamic or thermal loads. This work aims to develop and implement a 3D structural topological optimization model that takes these multiple loads into account using MATLAB program language. Practical examples of optimization cases considering multiple loads are presented, as well as comparisons with existing results in the literature, in order to demonstrate the accuracy of the proposed algorithm.
Geometrically Nonlinear 3D Topological Optimization: An Efficient MATLAB Code for the SESO Method
Authors: Hélio Luiz Simonetti  , Valério Silva Almeida  , Luttgardes de Oliveira Neto
Published: January 2025

The study of Topological Optimization (TO) in three-dimensional structures with geometrically nonlinear formulation is scarce. This work aims to apply TO in elasticity problems extended to consider geometric nonlinearity, using the total Lagrangian formulation. To achieve this goal, we developed a numerical model in MATLAB, employing the finite element method with hexahedral elements. We used the TO method Smoothing Evolutionary Structural Optimization (SESO) in conjunction with the Method of Moving Asymptotes to accelerate the optimization procedure, especially in the calculation of sensitivity factors. SESO is based on a bidirectional heuristic, systematically removing and adding elements with lower compliance compared to the maximum compliance of the structure. The results show that Smoothing - Evolutionary Structural Optimization Geometrically Non-Linear (SESO-GNL) is robust and efficient in solving classic problems from the literature.
Multi-material topology optimization of 2D structures using the SESO and SIMP method with reliability
Authors: Márcio Maciel da Silva  , Francisco de Assis das Neves  , Hélio Luiz Simonetti  , Marcilio Sousa da Rocha Freitas
Published: January 2025

Topology optimization is essential for the efficient distribution of structural form within the desired design domain, ensuring that structural elements are positioned to resist the requested forces and the specific boundary conditions for which they were designed. Therefore, the main objective of the article is the multimaterial topological optimization of a variety of two-dimensional structural problems, based on literature benchmarks, such as Michell structures and the MBB beam. These problems are approached considering a multi-material perspective, to distribute different materials throughout the structure, thus seeking their optimal solution. The methodology was generated based on the use of the finite element method for structure analysis and computing techniques were implemented for multi-material topology optimization (M.T.O.), Smoothing-ESO (SESO), and Solid Isotropic Material with Penalization (SIMP) via MATLAB. Furthermore, a reliability analysis is incorporated to deal with uncertainties, using Reliability-Based Topology Optimization (RBTO) with the First-Order Reliability Method (FORM), dealing with the random variables involved, such as geometry, modulus of elasticity, volume fraction, compliance, and loading, such as normal and lognormal probability distributions. The results obtained show a satisfactory convergence between the two topological optimization methods studied, thus highlighting the potential for applying these techniques to various structures as an effective tool in the search for economic efficiency in structural design.
Dynamic Modeling of Suspension with Air Spring
Authors: Carlos Cesar Augusto Itacaramby  , Marcus Vinicius Girão de Morais
Published: January 2025

The present work aims to model a ¼ vehicle semi-active suspension, using a combination of air spring and magneto-rheological damper. The modeling of the magneto-rheological damper will be based on the Wang model, which will be calibrated through experimental tests. The air spring model will be employed to compare performance between discrete mechanical models and the thermodynamic model. Various semi-active control strategies, such as bang-bang type skyhook/groundhook and PID, will be explored for comparison with existing selective passive systems on the market. The study of the air suspension with magneto-rheological damper will be evaluated from the perspective of comfort and drivability, following standardized parameters (ISO 2631:1978).
Performance comparison of an Inerter Suspension
Authors: Vítor Machado de Toledo  , SUZANA MOREIRA AVILA  , Rafael Rodrigues da Silva  , Evandro Leonardo  , André Murilo
Published: January 2025

Recent enhancements in automotive suspension systems have significantly increased vehicle safety, comfort, and dynamics. The inerter integration is an innovation, improving stability and comfort by dampening vibrations. As a two-terminal inertial element, the inerter creates a resistance force proportional to the relative acceleration between the terminals, quantified by the inertance constant in kilograms (kg). This research investigates the dynamics of a passenger vehicle using a 14 Degrees of Freedom (DOF) vehicle model that includes an inerter, alongside traditional springs and dampers. Comparisons are drawn between this comprehensive model and quarter-model and half-transversal car models. Employing VI-CarRealTime and MATLAB/SIMULINK for simulations, the study seeks to elucidate the enhancements in suspension performance attributable to the inerter across different road conditions.
Assessment of the Dynamic Structural Behaviour of Steel Wind Towers when Subjected to Wind Loadings
Authors: André Victor da Silva Castilho  , Francisco José da Cunha Pires Soeiro  , José Guilherme Santos da Silva
Published: January 2025

This research work investigates the structural response of a steel tower supported by an octagonal reinforced concrete foundation designed to accommodate a 2 MW wind turbine. The wind tower finite element model was developed based on the use of the Finite Element Method (FEM), utilising the ANSYS computational program, and considering the wind loadings on the rotor and tower, and the soil-structure interaction effect, aiming to obtain a realistic representation of the structure dynamic behaviour. In this investigation, given the stochastic nature of wind load modelling, a statistical analysis of the structures dynamic response was conducted in order to determine maximum values for displacement and stresses. Initially, the static and dynamic analyses have demonstrated that, incorporating geometric nonlinearities leads to a minor increase in the structural response concerning to the translational horizontal displacements and von Mises stresses. Additionally, a parametric study was performed, considering wind loads obtained through several basic wind velocities, with the objective of assessing the dynamic structural behaviour of the steel tower based on the of horizontal displacements, von Mises stresses, and also the fatigue service life. The results revealed that within the operational limit of the turbine, the investigated wind tower complies with the limit states specified in current wind tower design standards. However, for higher basic wind velocities, the steel wind tower structural design no longer meets these requirements.
Dynamic Structural Analysis of Steel-Concrete Composite Highway Bridges Based on Monte Carlo Simulations
Authors: Marilene Lobato Cardoso  , Guilherme Santana Alencar  , José Guilherme Santos da Silva
Published: January 2025

The highway bridges are subjected to several random dynamic loadings of different intensities, among which the vehicles traffic is one of the most present. This type of loading generates displacements and stresses amplitudes that vary in intensity along the time, causing stress cycles on the bridge structural elements. When a structural element is subjected to these stress ranges, serious problems related to the fatigue phenomenon can occur. It is well known that an efficient analysis methodology to assess the fatigue service life caused by the road traffic is based on a dynamic analysis considering a coupled vehicle-pavement-bridge system. This way, this research work proposes an analysis methodology based on Monte Carlo simulations aiming to determine the fatigue service life of steel-concrete composite high way bridges. The main characteristics of the bridge and the vehicle are defined as random variables and the vehicle-pavement-bridge dynamic interaction effect is considered. Furthermore, the simulations are carried out considering two levels associated to the pavement degradation. The dynamic response of a typical simply supported steel-concrete composite highway bridge with straight axis and spanning 40 m is investigated. After that, the results calculated through the proposed analysis methodology, considering a large sample of the vehicle-pavement-bridge combinations, make it possible to assess which parameters of the vehicle-pavement-bridge system presented the most relevant influence on the fatigue service life of the investigated highway bridge.
Geometric nonlinear analysis of planar frames constituted of nonprismatic Timoshenko-like elements referred to their noncentroidal axis
Authors: Protáze Mageveske Netto  , Francisco Célio de Araújo
Published: January 2025

This paper proposes a geometric nonlinear formulation to solve 2D frames modeled with Timoshenko-like elements defined by their noncentroidal axis. The kinematics of deformation of the element and the cross-sectional constitutive relationships are referenced to any given axis. Thus, the element axes may be any simple straight-line segments intersecting the element's cross-sections at any position. Knowing the element's centroidal axis is of no relevance. As a consequence, the interaction between axial and flexural effects must be consistently taken into consideration. The methodology consists of using a flexibility-type method based on the principle of virtual forces to determine the structural property coefficients. Such a method is convenient for determining the exact solutions of nonprismatic Timoshenko beams because they avoid solving awkward differential equations governing the frame elements. In addition, the exact Timoshenkos shape functions (TSFs) for nonprismatic elements result as a by-product of the formulation. Thus, the exact deformed shape of the element may be determined at any load level in the nonlinear analysis. Polynomials of different orders may be used to interpolate the variable rigidities along the element length. Moreover, we adopt boundary integrals to compute the cross-sectional rigidities along the element, which facilitates the modeling of cross sections of complex shapes. Regular, low-order Gauss-Legendre quadratures are required to evaluate all integrals involved in the analyses. The proposed formulation is validated by comparing our responses with the ones determined by using highly refined 3D ANSYS models. Nonlinear equilibrium paths, stresses, and internal forces are observed in the comparison of results.
Study of the influence of geometric imperfections and residual stresses on the stability of steel columns subjected to axial compression
Authors: Mariana Mohana Rodrigues da Silva  , Evandro Parente Junior  , Marcelo Silva Medeiros Junior
Published: January 2025

Steel columns are known to provide strength, durability, flexibility, and greater speed of construction. Although being industrially produced under rigorous quality control, steel columns usually present small geometric imperfections and residual stresses that arise during the manufacturing process. These imperfections and residual stresses play a major role on the columns` final compressive strength. Acknowledging the complexities and high cost involved in experimental investigation of these effects, this research was geared towards assessing the influence of the geometric imperfections and residual stresses on the strength of steel columns subjected to axial compression. For this purpose, computational models of I-beam steel columns were developed and analyzed using the Finite Element Method. Initially, a linearized elastic buckling analysis was carried out to determine the critical loads (eigenvalues) and buckling modes (eigenvectors). Following this, nonlinear analyses were conducted considering materially and geometrically nonlinear effects to evaluate the columns strength considering the geometric imperfections with different amplitudes and the shape of the first buckling mode. The elastoplastic model without hardening was adopted to represent the material nonlinearity. Finally, nonlinear analyses were carried out considering different levels of residual stresses for each geometric imperfection amplitude. The results show that the geometric imperfections and residual stresses have a strong influence on the load carrying capacity steel columns leading to a column curve close to the curve adopted by NBR 8800:2008. Therefore, both geometric imperfections and residual stresses should be properly considered in advanced analysis procedures for steel structures.
A defect correction technique for the MPFA-H scheme in single-phase heterogeneous and anisotropic flow problems media
Authors: Marlon Miguel Barbosa da Silva  , Phillipe Caetano Gomes da Silva  , Darlan Karlo Elisiário de Carvalho  , Pedro Victor Paixão Albuquerque  , Paulo Roberto Maciel Lyra
Published: January 2025

The numerical simulation of fluid flow in porous media is a technical tool of fundamental importance in the oil industry and a significant challenge for numerical algorithms. Standard reservoir simulators use the classical Two-Point Flow Approximation (TPFA) technique to discretize diffusive fluxes. However, it fails to give proper results for complex reservoirs with highly anisotropic and heterogeneous media and does not allow the use of unstructured meshes. It is essential to adopt efficient numerical methods and computational strategies to overcome such limitations and optimize the numerical simulations of these flows. In this context, the cell-centered Multipoint Flux Approximation with Harmonic Points (MPFA-H) method is a robust and accurate alternative. Furthermore, enforcing the discrete maximum principle (DMP) is essential to avoid non-physical extremes, such as negative pressures or saturations. In our work, we investigated and implemented a slope limiting coupled with MPFA-H to impose these conditions. Finally, we evaluate benchmark problems extracted from the literature to verify our implementation.
A Treatment for Overlapping Fractures in the Context of Mixed Finite Elements for Flow in Fractured Porous Media
Authors: Nathan Shauer  , José B. Villegas S.  , Philippe R. B. Devloo
Published: January 2025

Accurately modeling flow in discrete fracture networks (DFNs) can be important for several fields of engineering such as groundwater management, petroleum engineering, and geotechnical engineering where these DFNs can play a key role in the flow patterns in a formation. These fracture networks are often complex and can have fractures in very close proximity, which, in turn, can lead to challenges in creating fitting meshes for finite element analyses. This work proposes a methodology to handle overlapping fractures in the context of simulating flow in fractured porous media using a Mixed Finite Element Method formulation. With this capability, fractures in close proximity can simply occupy the same geometric location in the mesh, which avoids the creation of elements with poor aspect ratio. In this work, the porous media flow is modeled with traditional Darcy's equations and the fractures and their interaction with the porous media are modeled using the Discrete-Fracture-Matrix (DFM) representation. A mixed finite element formulation is adopted to solve the flow problem in both porous media and fractures, which has key features such as local mass conservation and improved velocity approximation. The mesh generation is done using the DFNMesh algorithm, which is a mesh generator for DFNs that can handle overlapping fractures by using pre-defined user settings. The proposed methodology is analyzed using a set of numerical examples, which show the importance of the treatment even for very simple cases and that it can handle overlapping fractures and provide accurate results for the flow in complex fractured porous media problems.
Modeling the propagation of hydraulic fractures in reservoirs with natural fracture networks using high aspect ratio interface elements
Authors: Lucas Guarnieri Barbosa  , Pedro Rogério Cleto  , Murilo Camargo  , Osvaldo Luís Manzoli
Published: January 2025

The application of hydraulic fracturing in unconventional reservoirs is a technique widely used to overcome the problem of low permeability in porous media. However, there are complex factors involved in understanding this technique, since the propagation of hydraulic fractures can be impacted by factors such as the state of stress in situ and the distribution of natural fractures, which may have different lengths, inclination angles and aperture values. Thus, based on the continuum mechanics and using the finite element method, this paper seeks to simulate the effect of hydraulic fracturing in porous media with a complex natural fractures network under the influence of different stress states. The modeling of the problem considers a fully coupled approach for solving the hydro-mechanical problem, with the Darcys law governing the fluid flow in the porous media and by the classical cubic law inside the fractures. For the representation of natural and hydraulic fractures, High Aspect Ratio Interface Finite Elements (HAR-IEs) associated with a suitable tensile damage model are used and inserted into the regular mesh via the Mesh Fragmentation Technique (MFT). The results obtained are validated with the literature and show that the model is capable of reproducing the complex scenarios of propagation and interaction between multiple fractures.
A micromechanical approach for homogenization of elastic multiphase periodic composites
Authors: Severino Pereira Cavalcanti Marques  , Eduardo Nobre Lages
Published: January 2025

This work presents a micromechanical model for the linear elastic homogenization of composites with periodic microstructures. The model is constructed for composites with an arbitrary number of phases and geometric shapes of the inclusions, differently from the most homogenization approaches available in the literature. In addition, no restriction is made with respect to the mismatch between the properties of the constituent phases and volume fractions of the inclusions. The model formulation is based on the Eshelby equivalent inclusion method and corresponds to an extension of a procedure originally derived to evaluate the effective elastic moduli of periodic composites with only two constituent phases. The fluctuating elastic fields within of the repeating unit cell (RUC) are represented by Fourier series, resulting in Lippmann-Schwinger integral equations involving the unknown eigenstrain fields of the inclusions. These integral equations are solved by using a straightforward approach that employs a scheme of partition of the domain of each inclusion. Applications to composites with different arrays of coated fibers and constituent materials are presented to show the efficiency of the model.
Asymptotic Homogenization Method with fictitious multilayers applied to the mesoscale characterization of concrete beams
Authors: Fabio Carlos da Rocha  , Leonardo Fellipe Prado Leite  , Elyakim Aguiar Santana  , Julián Bravo Castillero  , Leslie Darien Pérez Fernández  , Maria do Socorro Martins Sampaio
Published: January 2025

The escalating complexity of engineering challenges necessitates the utilization of increasingly efficient materials, often met through the adoption of composite materials as a viable solution. Concrete stands out as one of the most prevalent composite materials in civil engineering, evolving through alterations in its constituent components as researchers pursue enhanced durability, workability, and sustainability. However, traditional theories treating concrete as a homogenous isotropic material prove inadequate for predicting the mechanical properties of these innovative concretes, primarily due to the excessive costs associated with experimental analyses. Consequently, this study introduces a high-order zig-zag multilayer theory incorporating the asymptotic homogenization method. The variational formulation of a unified beam kinematics was used to carry out a multiscale analysis through the asymptotic expansion of the unknown variables. This methodology facilitates the transformation of a beam composed of heterogeneous materials into an equivalent homogeneous. The findings of the formulation proposed agree with established numerical and experimental formulations documented in the literature, even when employing a one-dimensional beam theory.
Asymptotic homogenization of energy-limited nonlinear microperiodic composites with imperfect interfaces to model failure of masonry structures under uniaxial compression
Authors: Roberto Martins da Silva Décio Júnior  , Leslie Darien Pérez-Fernández  , Julián Bravo-Castillero
Published: January 2025

In this work, a masonry prismatic structure made of alternating layers of mortar and bricks is modeled as a periodic two-phase elastic composite with one-dimensional heterogeneity along the layering direction. The prediction of its mechanical behavior (failure mainly) is important to estimate the allowable stress and stiffness used in the masonry design. At the mortar-brick interfaces, both ideally perfect contact and spring-type imperfect contact are considered. In order to model both classical and failure behaviors simultaneously, a nonlinear constitutive relation, which results from limiting the classical Hookean energy by inserting it into the so-called softening hyperelasticity energy representation, is adopted. The model is a two-point boundary value problem, which is stated by subjecting the resulting mechanical equilibrium nonlinear differential equation to the contact conditions at the interfaces and the mixed boundary conditions corresponding to uniaxial compression in the layering direction. The masonry structure exhibits separation of scales, as its size is generally much greater than the size of the mortar-brick periodicity cell, so its mechanical properties are rapidly oscillating, and also the equivalent homogeneity is guaranteed, justifying the application of the asymptotic homogenization method. Here, the effective law, that is, the constitutive relation of the equivalent homogeneous structure, is obtained via the asymptotic homogenization method. Finally, comparisons with experimental results from the literature are provided, which show qualitative agreement and that the model with imperfect contact is more accurate than the one with perfect contact.
Computational homogenization of masonry using the finite-volume direct averaging micromechanics theory
Authors: Rafael Leandro Costa Silva  , Severino Pereira Cavalcanti Marques
Published: January 2025

This paper presents a study focused on determining effective elastic properties of masonry made up of bricks and mortar joints arranged in periodic arrays. The brick and mortar are treated as linear elastic materials, with a bond pattern consisting of stacked bond and running bond. The overall effective elastic moduli are evaluated by a computational unit cell-based micromechanical procedure. The formulation employs a discretization of the masonry unit cell which is examined using the finite-volume direct averaging micromechanics theory (FVDAM). The homogenization approaches are carried out considering plane stress (PS) and generalized plane strain (GPS) states, as well as a tridimensional version of the FVDAM theory (3D-FVDAM). The results provided by these three conditions of analysis (PS, GPS, 3D-FVDAM) are compared in order to verify their limitations and applicability in the elastic homogenization of periodic masonry with different geometric features.
Analysis of the Creep Curve Reinforced Concrete Beams in Eurocode 2 via the Three-Parameter Model
Authors: Mateus Moura Barretto  , Alexandre de Macêdo Wahrhaftig
Published: January 2025

Creep is characterized by progressive deformation that occurs in concrete structures when exposed to constant loads during their operation. Factors such as air humidity, temperature, the initial consistency of the concrete, and the strength of the concrete after curing are decisive for the advancement of this phenomenon and the resulting deformation over time. In reinforced concrete beams, these deformations can increase the final deflection corresponding to the serviceability limit state, as well as cause the failure of the system at the ultimate limit state. The three-parameter model is suitable for describing the viscoelastic nature of many solids and is frequently used to study the phenomenon in various scientific fields. In this work, the creep model could be considered in two ways: first, the mathematical model for creep predicted by Eurocode 2 (European Standard EN 1992-1-1), and second, a three-parameter viscoelastic model whose parameters are adjusted to match the results obtained with the use of Eurocode. A three-parameter mathematical model was developed to accurately represent the creep curve of Eurocode 2 using computational modeling. In this context, this study seeks to understand the effects of creep in reinforced concrete structures through numerical modeling using a three-parameter model of a simply supported beam designed for usual building loads. A basic literature review on creep in concrete structures was conducted, followed by a structural analysis at different times during the commonly accepted life expectancy of these structural systems. In the simulation, the three-parameter model was used as an alternative to the creep calculation prescribed in Annex B of EUROCODE 2. During the analysis process, curves representing the investigated phenomenon were generated, considering different ambient temperature values, with the results presented in the form of graphs and tables. The adopted structural element was a rectangular reinforced concrete beam, simply supported at the ends. The adopted load was uniformly distributed. With this, it was possible to assess the displacements over time, enabling the evaluation of creep deformations at different stages of time under the influence of temperature and ambient humidity.
Finite Element Analysis of a Steel Catenary Riser Transporting Gas-Liquid Slug Flow
Authors: Igor Fortuna Lima da Silva  , Carlos Eduardo da Silva  , Leandro Gazoni  , José Luis Drummond Alves  , Jian Su
Published: January 2025

Steel catenary risers (SCRs) are main offshore structures that transport produced oil and gas from the seabed to floating units such as floating production storage and offloading (FPSO) units. This work analyzes the dynamic behavior of a steel catenary riser transporting internally a gas-liquid slug flow. A finite element formulation for computing elastic large displacement in planar and spatial frames, with consistent numerical implementation, is presented using Updated and Total Lagrangian approaches. To account for geometric changes as external forces are applied, the nonlinear solution is linearized in steps, each representing a load or time step. However, nonlinear terms are included to calculate the stiffness matrix due to the presence of large deformations. The Newmark numerical integrator was used, coupled with the Newton-Raphson method. The two-phase slug flow is model as a homogeneous mixture with timewise and spatially varying density. Numerical results are in good agreement with available experimental data in literature. The effects of the slug flow parameters on the dynamic behavior of the steel catenary riser are investigated.
Structural analysis of beams on masonry: comparison between analytical and computational modeling
Authors: Khrys Kathyllen da Silva de Medeiros  , Romilde Almeida de Oliveira
Published: January 2025

Structural masonry stands out in building projects as an efficient and versatile solution due to its function not only in sealing environments, but also in supporting and resisting different types of loads, in addition to presenting fast construction. The stiffness of masonry plays a crucial role in the global behavior of the structure, as it contributes to the safety and resistance of the set, thus obtaining a more robust and resilient system. Thus, this work aims to study analytically and computationally beams on masonry using elastic supports in the calculation of bond beams used in structural masonry. In the end, the analysis highlighted the influence of masonry stiffness on the elastic line and the distribution of sectional forces in the beam. Comparison with the numerical model in the Ftool software validated the analytical results and provided a detailed visualization of the beams behavior and the masonry that supports it. In this context, the study in question constitutes an excellent application of concepts with an interesting use to the technical community and the computational modeling proved essential to deepen the structural analysis in question.
Analysis in Mooring Chain Links Tensioned on Curved Surface
Authors: Evilly Raquel Henrique da Silveira  , Michele Agra de Lemos Martins  , Fábio José Coutinho da Silva Filho  , Eduardo Nobre Lages  , Mauro Costa de Oliveira
Published: January 2025

The development of offshore energy resources, specifically oil and gas, is increasing. Consequently, there is an increasing demand for state-of-the-art technologies and concepts to enhance productivity in this sector. One critical component of deep and ultra-deep water floating platforms is the mooring system, which requires rigorous design considerations. The motivation behind this lies in the substantial repair costs associated with unexpected failures. Structural failure in anchor chain links is primarily attributed to fatigue damage. While extensive studies have explored this phenomenon, the impact of mooring equipment with curved surfaces  responsible for guiding or restricting the upper end of mooring lines  on chain link behavior remains somewhat overlooked. In this study, we investigate the effects of ungrooved curved surfaces on the fatigue life of tensioned offshore mooring chain links. Using Finite Element Analysis (FEA), we analyze the behavior of mooring chain links when subjected to tension on curved surfaces. Our findings identify stress hotspots and calculate the corresponding Stress Concentration Factors (SCFs). Notably, the presence of curved surfaces significantly influences stress distribution and fatigue life. Additionally, we explore the effects of varying nominal stress levels applied during assembly and changes in the radius of the curved surface. These results have important implications for the design of mooring systems used in oil and gas exploration and production.
Assessing the feasibility of suspended BOP transportation and its impact on fatigue life
Authors: Ana Claudia Reis Orsolon  , Fabrício Nogueira Corrêa  , Breno Pinheiro Jacob
Published: January 2025

The sailing of the drilling rig along with its subsea equipment, such as, the drilling riser and the blowout preventer (BOP), from one well to another using traditional methods is a time-consuming operation. Typically, this process involves lowering and retrieving the BOP after drilling, followed by moving the rig to another well to be drilled, and again lowering the BOP and subsequently retrieving it. This method becomes even more time-consuming in ultra-deep waters, where recent oil field discoveries have taken place, as the deeper the water depths, the more time is required for such operations. Considering the high costs associated with renting and operating drilling rigs, operators are looking for ways to make these processes more efficient. One promising alternative is the method of navigation with the BOP suspended at a certain distance from the seabed, eliminating the need to retrieve the entire drilling riser and BOP, resulting in significant optimization of the process of transferring the drilling rig and its subsea equipment between wells.During the navigation of the BOP, hydrodynamic and inertial forces are exerted on the suspended riser column and the subsea BOP. In this present work, analyses of fatigue resulting from the effects of waves and vortex-induced vibration resulting from current speed and navigation, will be conducted for different lengths of the riser column. The results of these analyses will be presented, and the software used to obtain these results will be Orcaflex and Shear7.
Coupled in-line and cross-flow vortex-induced vibration responses of a fluid-conveying riser with variable tension in shear flow
Authors: Zhenhua Li  , Yangye He  , Chengbin Liu  , Yujin Yuan  , Junfeng Zhao  , Jian Su
Published: January 2025

When seawater streams around risers, it causes vortex-induced vibrations (VIV), which occur in two forms: in-line (IL) and cross-flow (CF). Accurate prediction of coupled IL and CF VIV behaviors is essential for designing risers. To investigate the VIV of marine risers used in deep-sea oil and gas transportation, this study analyzed the coupled CF and IL VIV characteristics of the riser with axially time-varying tension under the combined effects of internal flow and oceanic linear shear flow. The work established the vibration control equation for the riser considering internal flow velocity, axial top tension, and bending stiffness, which is based on Euler-Bernoulli beam theory. The double Van der Pol diffusion wake oscillator model was used to simulate the vortex-induced forces from the ocean currents, and the internal fluid was considered as a single-phase incompressible liquid. Using the Generalized Integral Transform Technique (GITT), the coupled system of nonlinear partial differential equations was further transformed into a system of nonlinear ordinary differential equations for numerical solution. A parametric study was conducted to analyze the impact of current velocity, internal flow velocity, and diffusion term on the VIV responses, including structural displacement, structural frequency, displacement envelope, and displacement evolution. Numerical results indicate that the vibration modes of the riser are influenced by both CF and IL directions, and the effect of IL can not be ignored. The diffusion term has a significant impact on the vibrations of the riser. The number of vibration modes of the riser is mainly influenced by the increasing current velocity, and for a given current velocity, the vibration of the riser becomes chaotic when the dimensionless internal fluid velocity increased within a certain range.
Dynamic Analysis of Fixed Offshore Structures for Wind Turbines
Authors: Elias Duarte Oliveira  , Flávio de Souza Barbosa  , Marcos Vinícius Rodrigues  , Elson Magalhães Toledo
Published: January 2025

Offshore wind power presents itself as an alternative for complementing and diversifying the Brazilian energy matrix. In this context, fixed jacket-type platforms, widely used by the oil industry, are alternatives for supporting offshore wind turbine towers. However, the unique characteristics of these structures, such as their large dimensions, high centers of mass, and eccentricities of assemblies, as well as the random nature of the loads acting simultaneously on the structure, such as ocean waves, winds, and currents, are challenging components for the engineering of structures built in the marine environment. This article presents some of the main computational models for dynamic structural analysis of fixed offshore wind turbines. In the applied methodology, the sea state is modeled based on second-order Stokes wave theory, where fluid kinematics are calculated from the analysis of random waves in the frequency domain, using the Pierson-Moskowitz spectrum. The aeroelastic-dynamic forces and interactions acting above the free surface were simplified through the adoption of values prescribed in the literature. Finally, structural analysis is carried out using the finite element method, with the jacket bars modeled using plane frame elements. The results obtained in terms of dynamic properties, as well as structural responses, were compared with those extracted from recent works, thus confirming the validity of the chosen methods and consolidating the results for the development of future work.
Influence of velocity on conductor casing driving via Material Point Method
Authors: Raniel Deivisson de Alcantara Albuquerque  , Jennifer Mikaella Ferreira Melo  , Juliana Souza Baioco  , Breno Pinheiro Jacob  , Beatriz Ramos Barbosa  , João Paulo Lima Santos  , Mávyla Sandreya Correia Tenório  , Fábio Sawada Cutrim  , Rafael Dias
Published: January 2025

The conductor is the first casing settled in an oil well and it has important functions regarding the initial phase of well construction. Some of its functions are to bear loads from the wellhead, bear the surface casing during its cementation, and insulate unconsolidated formations. The soil response to the conductor settlement is an important factor, for a poor settlement may cause excessive wear on the wellhead equipment or even the loss of the well. Therefore, a simulation of the self-weight phase of a conductor driving was conducted to enhance knowledge about the soils state during this process. The soil was modeled as soft clay, and the mechanical behavior was described by the Mohr-Coulomb model. As the conductor driving results in large displacements in a short period, the traditional Finite Element Method (FEM) is unable to model this system. Therefore, the Material Point Method (MPM), which is a modification of FEM, was used to model the conductor-soil system. Three conductor velocities were simulated and the resultant force in the casing outer surface was analyzed. The soils stress state, displacement, and velocities were studied.
Monetary risk analysis of operating corroded offshore pipelines
Authors: Andréa Raffaella Avelar Pimentel Vila Nova  , Juliana von Schmalz Torres  , Silvana Maria Bastos Afonso da Silva  , Nadège Bouchonneau
Published: January 2025

The offshore oil and gas exploration activity involves a high degree of complexity, being characterized by high extraction costs and long distance to the coastline, turning the use of pipeline essential to guarantee the flow of production. However, one of the main mechanisms of pipeline degradation is corrosion, which results in compromising the integrity of the structure. Therefore, risk analysis is necessary to avoid the consequences of pipeline failure, which could lead to environmental and human tragedies. The objective of this study is to quantify and analyze the risks of operating corroded offshore pipelines, assisting in the decision-making process. To this end, it is important to predict the mechanical behavior of the pipe, to reduce the probability of failure and ensure continuity of operations. A case of study is carried out and presented to verify the operating condition of a corroded pipeline, using semi-empirical methods, finite elements and new methods, obtaining effective answers to assist pipeline operators in decision making.
Transport Studies of the Innovative Vertical Buoy Supported Risers System
Authors: Magnus Carvalho de Vilhena Prata  , Fabricio Nogueira Corrêa  , Christie de Vilhena Prata Machado  , Breno Pinheiro Jacob
Published: January 2025

The current expansion of offshore oil and gas exploration in increasingly deeper water depths leads to an option of utilization of hybrid riser systems. These systems are characterized by the combination of flexible jumpers and Steel Catenary Risers (SCRs), interconnected by a floating submerged structure. Among the offered types of hybrid riser systems, one of them employs a Buoy Supported Risers (BSR) as an intermediate element between the flexible jumpers and the SCRs. Although the hybrid riser system utilizing the BSR manages the advantages associated with both types of risers, providing a very effective ultradeep waters riser system, the use of the BSR entails high costs, complexity, and considerable risk during the transportation and installation stages of the buoy. In this way, new alternatives regarding the use of hybrid risers are welcome. In this context, this work presents the innovative proposal of a Vertical Buoy Supported Risers (VBSR) that may offer greater viability when compared to the traditional horizontal concepts, resulting in benefits for hybrid riser systems and, consequently, for oil and gas exploration activities in deepwater environments. The benefits of vertical configuration of the BSR, in relation to the conventional horizontal one, are more focused on transport and installation risks reduction, although also presents vantages in operational phase. In this work, the presented study is focused on the transport stage of the VBSR. Therefore, an evaluation of the VBSRs static and dynamic responses during transportation in intact and damage scenario are presented here.