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O método multigrid algébrico na resolução de sistemas lineares oriundos do método dos elementos finitos.; The algebric multigrid method for solving linear systems issued from the finite element method.

Pereira, Fábio Henrique
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 14/02/2007 PT
Relevância na Pesquisa
75.78%
Este trabalho propõe uma nova abordagem, baseada em wavelets, para o método Multigrid Algébrico (WAMG). Nesta nova abordagem, a Transformada Discreta Wavelet é aplicada na matriz de coeficientes do sistema linear gerando uma aproximação dessa matriz em cada nível do processo de multiresolução. As vantagens da nova abordagem, que incluem maior facilidade de paralelização e menor tempo de montagem, são apresentadas com detalhes e uma análise quantitativa de convergência do método WAMG é realizada a partir da sua aplicação em problemas testes. O WAMG também é testado como pré- condicionador para métodos iterativos no subespaço de Krylov na análise magnetostática e magnetodinâmica (regime permanente senoidal) pelo Método dos Elementos Finitos, e em matrizes esparsas extraidas das coleções Matrix Market e da Universidade da Flórida. São apresentados resultados numéricos comparando o WAMG com o Multigrid Algébrico tradicional e com os pré-condicionadores baseados em decomposições incompletas de Cholesky e LU.; In this work we propose a wavelet-based algebraic multigrid method (WAMG) as a linear system solver as well as a prediconditioner for Krylov subspace methods. It is a new approach for the Algebraic Multigrid method (AMG)...

Análise comparativa pelo método dos elementos finitos entre diferentes estruturas internas de capôs de veículos visando à proteção ao pedestre em caso de atropelamento.; Comparative finite element analysis of different vehicle hood inner panels, with the objective to minimize the injuries to the pedestrian in case of a running over accident.

Ferreira, Anderson Sirolli
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/03/2010 PT
Relevância na Pesquisa
85.86%
Este estudo foca uma análise comparativa de diferentes painéis internos de capôs de veículos, com o objetivo de minimizar as lesões ao pedestre em caso de um atropelamento. As lesões na cabeça do pedestre são medidas através de um modelo em elementos finitos de uma cabeça padrão de acordo com o comitê europeu de melhorias da segurança de veículos. Os valores de desaceleração obtidos nas análises são comparados com valores toleráveis de acordo com o critério HIC (Head Injury Criteria), criado pela NHTSA (National Highway Traffic Safety Administration). Baseando-se nos resultados obtidos demonstra-se a influência dos tipos de estruturas internas de capô e recomenda-se a melhor estrutura para aplicações na indústria automobilística.; This study focus on comparative analysis of different vehicle hood inner panels, with the objective to minimize the injuries to the pedestrian in case of a running over accident. The method to measure the injuries in the head of the pedestrian will be made through a finite element model of a standard head in accordance with the European committee of improvements of the security of vehicles. The values of decelerations obtained in the analysis are compared with human tolerance levels according to HIC criteria (Head Injury Criteria)...

Análise probabilística de vigas de concreto armado recuperadas à flexão, através do método de Monte Carlo utilizando um modelo de elementos finitos; Probabilistic analysis of reinforced concrete beams rehabilitated for flexure, through the Monte Carlo method using a Finite Element model

Paliga, Charlei Marcelo
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
75.89%
O objetivo deste trabalho é apresentar um modelo para análise probabilística de vigas de concreto armado recuperadas à flexão, através da utilização conjunta do método de simulação de Monte Carlo e do método dos Elementos Finitos. Para uma análise da confiabilidade, foram projetadas vigas de concreto armado seguindo as recomendações da NRR 6118:2003. Após, foi considerado que as armaduras tracionadas de flexão sofreram reduções de 10%, 20% e 30% na sua área da seção transversal, sendo, então, feita uma análise da segurança estrutural remanescente. Para o projeto de recuperação das vigas danificadas, estão apresentados os procedimentos do Bulletin 14 da fédération internationale du béton (fib) para o dimensionamento de sistemas de reforço com material compósito colado externamente às estruturas. Assim, a confiabilidade destas vigas recuperadas pôde ser estimada e comparada à confiabilidade das vigas originais. Dentro do processo de simulação, a resposta em termos da carga de ruptura das vigas de concreto armado recuperadas foi obtida através de uma análise numérica não-linear utilizando um modelo de elementos finitos. Devido à importância do deslizamento entre o substrato de concreto e o sistema de reforço estrutural...

Otimização de forma estrutural e aerodinâmica usando análise IsoGeométrica e Elementos Finitos; Structural and aerodynamic shape optimization using isogeometric and finite element analysis

Espath, Luis Felipe da Rosa
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
95.87%
Neste trabalho buscou-se consolidar aspectos referentes à otimização de problemas envolvidos na mecânica dos meios contínuos, envolvendo diferentes áreas do conhecimento, tais como: otimização matemática, diferenciação automática, análise estrutural, análise aerodinâmica, parametrização de curvas, superfícies e sólidos do tipo B-spline racionais não-uniformes (NURBS, acrônimo do inglês), análise IsoGeométrica (IGA, acrônimo do inglês) e análise por Elementos Finitos (FEA, acrônimo do inglês). Como objetivo final busca-se otimizar formas de cascas estruturais e formas de corpos aerodinâmicos imersos em escoamentos compressíveis. No que concerne à análise estrutural, esta é realizada via análise IsoGeométrica utilizando elementos sólidos para modelar cascas. Uma cinemática co-rotacional abrangente e precisa baseada na exata decomposição polar é desenvolvida, para lidar com problemas estáticos e dinâmicos altamente não lineares. Na análise estática foram implementados o método de Newton-Raphson e controle de deslocamentos generalizado, para problemas dinâmicos foram implementados o método -generalizado (G ) e o método energia momento generalizado (GEMM+ ). A análise aerodinâmica é realizada via análise por Elementos Finitos para modelar escoamentos compressíveis viscosos e não viscosos em regimes transônicos e supersônicos. Um esquema característico baseado na separação da equação de momento (CBS...

Influence of Implant Design on the Biomechanical Environment of Immediately Placed Implants: Computed Tomography-Based Nonlinear Three-Dimensional Finite Element Analysis

Pessoa, Roberto S.; Coelho, Paulo G.; Muraru, Luiza; Marcantonio, Elcio; Vaz, Luis Geraldo; Sloten, Jos Vander; Jaecques, Siegfried V. N.
Fonte: Quintessence Publishing Co Inc Publicador: Quintessence Publishing Co Inc
Tipo: Artigo de Revista Científica Formato: 1279-1287
ENG
Relevância na Pesquisa
85.79%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 06/06844-2; Purpose: To evaluate the influence of different implant designs on the biomechanical environment of immediately placed implants. Materials and Methods: Computed tomography (CT)-based finite element models comprising a maxillary central incisor socket and four commercially available internal-connection implants (SIN SW, 3i Certain, Nobel Replace, and ITI Standard) of comparable diameters and lengths were constructed. Biomechanical scenarios of immediate placement, immediate loading, and delayed loading protocols were simulated. Analysis of variance at the 95% confidence level was used to evaluate peak equivalent strain (EQV strain) in bone and bone-to-implant relative displacement. Results: Loading magnitude (77.6%) and the clinical situation (15.0%) (ie, presence or absence of an extraction socket defect, condition of the bone-to-implant interface) presented the highest relative contributions to the results. Implant design contributed significantly to strains and displacements in the immediate placement protocol. Whereas a greater contribution of implant design was observed for strain values and distributions for immediately placed and immediately loaded protocols...

Influence of Implant Connection Type on the Biomechanical Environment of Immediately Placed Implants - CT-Based Nonlinear, Three-Dimensional Finite Element Analysis

Pessoa, Roberto S.; Muraru, Luiza; Marcantonio, Elcio; Vaz, Luis Geraldo; Sloten, Jos Vander; Duyck, Joke; Jaecques, Siegfried V. N.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 219-234
ENG
Relevância na Pesquisa
85.79%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Purpose:The purpose of the present study was to evaluate the biomechanical environment of immediately placed implants, before and after osseointegration, by comparing three different implant-abutment connection types.Materials and Methods:A computer tomography-based finite element model of an upper central incisor extraction socket was constructed containing implants with either external hex, internal hex, or Morse-taper connection. Frictional contact elements were used in the bone, implant, abutment, and abutment screw interfaces in the immediately placed simulations. In osseointegrated simulations, the repair of bone alveolar defect and a glued bone-to-implant interface were assumed. By analysis of variance, the influence was assessed of connection type, clinical situation, and loading magnitude on the peak equivalent strain in the bone, peak von Mises stress in the abutment screw, bone-to-implant relative displacement, and abutment gap.Results:The loading magnitudes had a significant contribution, regardless of the assessed variable. However...

Testing and modeling of a traditional timber mortise and tenon joint

Feio, A. O.; Lourenço, Paulo B.; Machado, José S.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
75.86%
The structural safety and behaviour of traditional timber structures depends significantly on the performance of their connections. The behaviour of a traditional mortise and tenon timber joint is addressed using physical testing of full-scale specimens. New chestnut wood and old chestnut wood obtained from structural elements belonging to ancient buildings is used. In addition, the performance of different semi and non-destructive techniques for assessing global strength is also evaluated. For this purpose, ultrasonic testing, micro-drilling and surface penetration are considered, and the possibility of their application is discussed based on the application of simple linear regression models. Finally, nonlinear finite element analysis is used to better understand the behaviour observed in the full-scale experiments, in terms of failure mode and ultimate load. The results show that the ultrasonic pulse velocity through the joint provides a reasonable estimate for the effective- ness of the assembly between the rafter and brace and novel linear regressions are proposed. The failure mechanism and load–displacement diagrams observed in the experiments are well captured by the proposed non-linear finite element analysis, and the parameters that affect mostly the ultimate load of the timber joint are the compressive strength of wood perpendicular to the grain and the normal stiffness of the interface elements representing the contact between rafter and brace.

Numerical study of concrete-filled steel composite (CFSC) stub columns with steel stiffeners

Bahrami,Alireza; Badaruzzaman,Wan Hamidon Wan; Osman,Siti Aminah
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2014 EN
Relevância na Pesquisa
75.81%
Numerical study of concrete-filled steel composite (CFSC) stub columns with steel stiffeners is presented in this paper. The behaviour of the columns is examined by the use of the finite element software LUSAS. Results from nonlinear finite element analyses are compared with those from corresponding experimental tests which uncover the reasonable accuracy of the modelling. Novel steel stiffeners are used in the CFSC stub columns of this study. The columns are extensively developed considering three different special arrangements of the steel stiffeners with various number, spacing, and widths of the stiffeners. The main variables are: (1) arrangement of the steel stiffeners (C1, C2, and C3); (2) number of the steel stiffeners (2 and 3); (3) spacing of the steel stiffeners (50 mm and 100 mm); (4) width of the steel stiffeners (50 mm, 75 mm, and 100 mm); (5) steel thickness (2 mm, 2.5 mm, and 3 mm); (6) concrete compressive strength (30 MPa, 40 MPa, and 50.1 MPa); (7) steel yield stress ( 234.3 MPa, 350 MPa, and 450 MPa). Effects of the variables on the behaviour of the columns are assessed. Failure modes of the columns are also illustrated. It is concluded that the variables have considerable effects on the behaviour of the columns. Moreover...

Damage based constitutive model for predicting the performance degradation of concrete

Wang,Zhi; Jin,Xianyu; Jin,Nanguo; Shah,Abid A; Li,Bei
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2014 EN
Relevância na Pesquisa
85.78%
An anisotropic elastic-damage coupled constitutive model for plain concrete is developed, which describes the concrete performance degradation. The damage variable, related to the surface density of micro-cracks and micro-voids, and represented by a second order tensor, is governed by the principal tension strain components. For adequately describing the partial crack opening/closure effect under tension and compression for concrete, a new suitable thermodynamic potential is proposed to express the state equations for modeling the mechanical behaviors. Within the frame-work of thermodynamic potential, concrete strain mechanisms are identified in the proposed anisotropic damage model while each state variable is physically explained and justified. The strain equivalence hypothesis is used for deriving the constitutive equations, which leads to the development of a decoupled algorithm for effective stress computation and damage evolution. Additionally, a detailed numerical algorithm is described and the simulations are shown for uni-axial compression, tension and multi-axial loadings. For verifying the numerical results, a series of experiments on concrete were carried out. Reasonably good agreement between experimental results and the predicted values was observed. The proposed constitutive model can be used to accurately model the concrete behaviors under uni-axial compression...

Femoral Bone Strength and Its Relation to Cortical and Trabecular Changes After Treatment With PTH, Alendronate, and Their Combination as Assessed by Finite Element Analysis of Quantitative CT Scans

Keaveny, Tony M; Hoffmann, Paul F; Singh, Mandeep; Palermo, Lisa; Bilezikian, John P; Greenspan, Susan L; Black, Dennis M
Fonte: Amer Soc Bone & Mineral Res. Publicador: Amer Soc Bone & Mineral Res.
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
75.79%
The “PTH and Alendronate” or “PaTH” study compared the effects of PTH(1-84) and/or alendronate (ALN) in 238 postmenopausal, osteoporotic women. We performed finite element analysis on the QCT scans of 162 of these subjects to provide insight into femoral strength changes associated with these treatments and the relative roles of changes in the cortical and trabecular compartments on such strength changes. Patients were assigned to either PTH, ALN, or their combination (CMB) in year 1 and were switched to either ALN or placebo (PLB) treatment in year 2: PTH-PLB, PTH-ALN, CMB-ALN, and ALN-ALN (year 1-year 2) treatments. Femoral strength was simulated for a sideways fall using nonlinear finite element analysis of the quantitative CT exams. At year 1, the strength change from baseline was statistically significant for PTH (mean, 2.08%) and ALN (3.60%), and at year 2, significant changes were seen for the PTH-ALN (7.74%), CMB-ALN (4.18%), and ALN-ALN (4.83%) treatment groups but not for PTH-PLB (1.17%). Strength increases were primarily caused by changes in the trabecular density regardless of treatment group, but changes in cortical density and mass also played a significant role, the degree of which depended on treatment. For PTH treatment at year 1 and for ALN-ALN treatment at year 2...

Real-Time Nonlinear Finite Element Computations on GPU - Application to Neurosurgical Simulation

Joldes, Grand Roman; Wittek, Adam; Miller, Karol
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/12/2010 EN
Relevância na Pesquisa
75.81%
Application of biomechanical modeling techniques in the area of medical image analysis and surgical simulation implies two conflicting requirements: accurate results and high solution speeds. Accurate results can be obtained only by using appropriate models and solution algorithms. In our previous papers we have presented algorithms and solution methods for performing accurate nonlinear finite element analysis of brain shift (which includes mixed mesh, different non-linear material models, finite deformations and brain-skull contacts) in less than a minute on a personal computer for models having up to 50.000 degrees of freedom. In this paper we present an implementation of our algorithms on a Graphics Processing Unit (GPU) using the new NVIDIA Compute Unified Device Architecture (CUDA) which leads to more than 20 times increase in the computation speed. This makes possible the use of meshes with more elements, which better represent the geometry, are easier to generate, and provide more accurate results.

Nonlinear finite element analysis of three implant–abutment interface designs

Tang, Chun-Bo; Liu, Si-Yu; Zhou, Guo-Xing; Yu, Jin-Hua; Zhang, Guang-Dong; Bao, Yi-Dong; Wang, Qiu-Ju
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
85.89%
The objective of this study was to investigate the mechanical characteristics of implant–abutment interface design in a dental implant system, using nonlinear finite element analysis (FEA) method. This finite element simulation study was applied on three commonly used commercial dental implant systems: model I, the reduced-diameter 3i implant system (West Palm Beach, FL, USA) with a hex and a 12-point double internal hexagonal connection; model II, the Semados implant system (Bego, Bremen, Germany) with combination of a conical (45° taper) and internal hexagonal connection; and model III, the Brånemark implant system (Nobel Biocare, Gothenburg, Sweden) with external hexagonal connection. In simulation, a force of 170 N with 45° oblique to the longitudinal axis of the implant was loaded to the top surface of the abutment. It has been found from the strength and stiffness analysis that the 3i implant system has the lowest maximum von Mises stress, principal stress and displacement while the Brånemark implant system has the highest. It was concluded from our preliminary study using nonlinear FEA that the reduced-diameter 3i implant system with a hex and a 12-point double internal hexagonal connection had a better stress distribution...

Potential of in vivo MRI-based nonlinear finite-element analysis for the assessment of trabecular bone post-yield properties

Zhang, Ning; Magland, Jeremy F.; Rajapakse, Chamith S.; Bhagat, Yusuf A.; Wehrli, Felix W.
Fonte: American Association of Physicists in Medicine Publicador: American Association of Physicists in Medicine
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
75.86%
Purpose: Bone strength is the key factor impacting fracture risk. Assessment of bone strength from high-resolution (HR) images have largely relied on linear micro-finite element analysis (μFEA) even though failure always occurs beyond the yield point, which is outside the linear regime. Nonlinear μFEA may therefore be more informative in predicting failure behavior. However, existing nonlinear models applied to trabecular bone (TB) have largely been confined to micro-computed tomography (μCT) and, more recently, HR peripheral quantitative computed tomography (HR-pQCT) images, and typically have ignored evaluation of the post-yield behavior. The primary purpose of this work was threefold: (1) to provide an improved algorithm and program to assess TB yield as well as post-yield properties; (2) to explore the potential benefits of nonlinear μFEA beyond its linear counterpart; and (3) to assess the feasibility and practicality of performing nonlinear analysis on desktop computers on the basis of micro-magnetic resonance (μMR) images obtained in vivo in patients.

Analysis of Vertebral Bone Strength, Fracture Pattern, and Fracture Location: A Validation Study Using a Computed Tomography-Based Nonlinear Finite Element Analysis

Imai, Kazuhiro
Fonte: JKL International LLC Publicador: JKL International LLC
Tipo: Artigo de Revista Científica
Publicado em 01/06/2015 EN
Relevância na Pesquisa
75.91%
Finite element analysis (FEA) is an advanced computer technique of structural stress analysis developed in engineering mechanics. Because the compressive behavior of vertebral bone shows nonlinear behavior, a nonlinear FEA should be utilized to analyze the clinical vertebral fracture. In this article, a computed tomography-based nonlinear FEA (CT/FEA) to analyze the vertebral bone strength, fracture pattern, and fracture location is introduced. The accuracy of the CT/FEA was validated by performing experimental mechanical testing with human cadaveric specimens. Vertebral bone strength and the minimum principal strain at the vertebral surface were accurately analyzed using the CT/FEA. The experimental fracture pattern and fracture location were also accurately simulated. Optimization of the element size was performed by assessing the accuracy of the CT/FEA, and the optimum element size was assumed to be 2 mm. It is expected that the CT/FEA will be valuable in analyzing vertebral fracture risk and assessing therapeutic effects on osteoporosis.

Dreidimensionales Finite-Elemente-Modell von Stereozilien innerer und äußerer Haarzellen; Three-dimensional finite-element model of the stereocilia bundles of inner and outer hair cells

Müller, Roland
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
75.97%
Die Erforschung der mechanoelektischer Kopplung im Innenohr von der mechanischen Wanderwelle zum elektrischen Nervenimpuls ist mit klassischen Lösungsansätzen und Tierversuchen bis zum heutigen Tag im Detail noch nicht geklärt. Seit wenigen Jahren bietet nun die Finite-Elemente- Methode einen neuen Ansatz, besondere Fragestellungen zu lösen. Daher wurde ein drei-dimensionales Finite-Elemente-Modell von inneren und äußeren Haarzellen entwickelt, um das mechanische Verhalten zu analysieren. Die verwendeten Modellparameter zum Modellaufbau entsprechen Haarzellen mit einem Abstand von 6,2 mm vom Apex der Cochlea von Meerschweinchen mit einer charakterischen Frequenz von 1080 Hz. Das Modell der äußeren Haarzelle umfaßt den zentralen Anteil des Haarbündels mit der charakteristischen W-Form. Es wurden für das Modell des äußeren Stereozilienbündels 75 Stereozilien in 3 Reihen mit je 25 Stereozilien unterschiedlicher Länge angeordnet. Das Modell der inneren Haarzellen wurde mit 60 Stereozilien in 3 Reihen mit je 20 Stereozilien generiert. Das Modell des Bündels einer äußeren Haarzelle besteht aus ca. 23 000 Solidelementen für die Stereozilienkörper und 6870 Balkenelementen zur Generierung der Links. Das Modell der äußeren Haarzellen zeigte bei der statisch-linearen Analyse der Stereozilienauslenkung nach Kraftapplikation ab 0...

Static analysis of rubber components with piezoelectric patches using nonlinear finite element

Manna, M.; Sheikh, A.
Fonte: Techno-Press Publicador: Techno-Press
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
95.93%
In order to reduce vibration or to control shape of structures made of metal or composites, piezoelectric materials have been extensively used since their discovery in 1880. A recent trend is also seen to apply piezoelectric materials to flexible structures made of rubber-like materials. In this paper a non-linear finite element model using updated Lagrangian (UL) approach has been developed for static analysis of rubber-elastic material with surface-bonded piezoelectric patches. A compressible stain energy function has been used for modeling the rubber as hyperelastic material. For formulation of the nonlinear finite element model a twenty-node brick element is used. Four degrees of freedom u, v and w and electrical potential j per node are considered as the field variables. PVDF (polyvinylidene fluoride) patches are applied as sensors/actuators or sensors and actuators. The present model has been applied to bimorph PVDF cantilever beam to validate the formulation. It is then applied to study the smart rubber components under different boundary and loading conditions. The results predicted by the present formulation are compared with the analytical solutions as well as the available published results. Some results are given as new ones as no published solutions available in the literatures to the best of the authors' knowledge.; http://technopress.kaist.ac.kr/?page=container&journal=sss&volume=5&num=1#; M. C. Manna...

THREE-DIMENSIONAL NONLINEAR ANALYSIS OF DEEP-CORRUGATED STEEL CULVERTS

ELSHIMI, Tamer Mohamed
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
75.81%
Deep-corrugated steel culverts (with a corrugation wavelength of 400mm and amplitude of 150mm) can be used as an effective alternative for short-span bridges. Current design methods are typically based on two-dimensional finite element analysis. This thesis reports results from three-dimensional finite element analysis, with explicit modelling of the geometry of the corrugated plates (called corrugated analyses) and employing the orthotropic shell theory (called orthotropic analyses), for a specific box culvert having a 10 m span and 2.4 m rise. The results were compared to previously reported experimental data where a specific large span box culvert was tested under controlled laboratory conditions. The behaviour of the box culvert under small vertical displacement without any soil support was modelled to isolate the structure response. The box culvert was also modelled when subject to fully loaded dump truck, and when loaded using a tandem axle frame to service and ultimate loads. Both corrugated and orthotropic analyses successfully captured the response of the box culvert when backfilled and loaded using dump truck and axle frame loading. It was found that the orthotropic model overestimated the culvert stiffness at the ultimate limit state...

Metodo dos elementos finitos posicional aplicado a analise estatica de risers; Positional finite element method applied to the analysis of risers behaviour

Rafael Giovane Morini
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 31/07/2009 PT
Relevância na Pesquisa
75.78%
A dissertação é dedicada ao estudo do comportamento estrutural estático de risers rígidos montados em catenária para aplicações na exploração de petróleo em águas profundas. Estuda-se o problema de equilíbrio estático de risers, no qual é considerado o efeito do peso próprio, do empuxo, e a interação com o solo. Para tanto, utiliza-se do Método de Elementos Finitos Posicional, que é baseado em posições dos nós ao invés de deslocamento nodal, sendo que o referencial utilizado é o Lagrangiano Total. Adota-se a cinemática de Reissner para descrever o comportamento do pórtico plano, na qual são consideradas as deformaçõoes oriundas das tensões de cisalhamento. Utiliza-se o algoritmo de Newton-Raphson para a solução iterativa do problema não linear e o método de penalidades para a solução do problema de contato com o solo. São desenvolvidos estudos comparativos e de sensibilidade de alguns parametros envolvidos no problema de risers com o objetivo de avaliar a influencia do modelo do solo, das condições do contato solo-riser na região de toque sobre o comportamento estático do sistema acoplado. Os resultados são validados com resultados da literatura e por comparação de resultados obtidos com o programa Anflex...

Stress analysis of single-bolt, single-lap, countersunk composite joints with variable bolt-hole clearance

Egan, Brian; McCarthy, C.T.; McCarthy, Michael A; Frizzell, R.M.
Fonte: Elsevier Publicador: Elsevier
Tipo: info:eu-repo/semantics/article; all_ul_research; ul_published_reviewed
ENG
Relevância na Pesquisa
75.79%
peer-reviewed; Single-lap, carbon-epoxy joints with countersunk fasteners were modelled using the nonlinear finite element code Abaqus. A highly-detailed analysis of the stress distribution at the countersunk hole boundary is provided. Bolt-hole clearance, which arises due to limitations in manufacturing capabilities, is modelled extensively. Clearance levels both inside and outside typical aerospace fitting tolerances are studied and the finite element model is validated with experimental data. Plots of radial stress in each ply of the countersunk laminate show the load transfer to be severely localised, with only a few plies bearing the majority of the load. The inclusion of clearance in the model was shown to result in far higher radial stresses compared to those in the neat-fit joint model. An associated loss in joint stiffness of more than 10% was recorded for the highest clearance considered (240 mu m). Finally compressive through-thickness stresses are shown to be present at the damageable region of the countersunk hole, and increase with bolt-hole clearance. These compressive stresses, which are an indicator of lateral constraint, are seen to suppress "brooming" failure in the countersunk laminate. (C) 2011 Elsevier Ltd. All rights reserved.; PUBLISHED; peer-reviewed

Applications of response sensitivity analysis in earthquake engineering

Roth,C P; Grigoriu,M D
Fonte: Journal of the South African Institution of Civil Engineering Publicador: Journal of the South African Institution of Civil Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2010 EN
Relevância na Pesquisa
85.82%
Response sensitivity analysis as a part of dynamic finite element structural analysis has many applications to structures of realistic scale and complexity in earthquake engineering. A demonstration project, consisting of a hospital structure and piping network, is used to demonstrate the potential applications of the method to practical problems. Nonlinear finite element analysis is done to determine displacements, stresses, etc, as well as sensitivity information by the direct differentiation method. The response sensitivity analysis is used for the identification of critical parameters of the systems, optimisation, calibration and the generation of fragility curves.