Tesi sul tema "Limit analysis"
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BARROS, GUILHERME COELHO GOMES. "TOPOLOGY OPTIMIZATION CONSIDERING LIMIT ANALYSIS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29908@1.
Testo completoCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Este trabalho apresenta uma formulação puramente baseada em plasticidade para ser aplicada à otimização topológica. A principal ideia da otimização topológica em mecânica dos sólidos é encontrar a distribuição de material dentro do domínio de forma a otimizar uma medida de performance e satisfazer um conjunto de restrições. Uma possibilidade é minimizar a flexibilidade da estrutura satisfazendo que o volume seja menor do que um determinado valor. Essa é a formulação clássica da otimização topológica, que é vastamente utilizada na literatura. Não obstante fornecer resultados interessantes, condições adicionais devem ser levadas em consideração para viabilizar sua aplicação prática. O projeto estrutural aborda dois aspectos principais: (i) a estrutura não deve colapsar, suportando os carregamentos aplicados (critério de segurança); e (ii) deverá se sujeitar a um valor máximo aceitável de deformação (critério de aceitabilidade). Consequentemente, a otimização topológica clássica deve ser modificada de forma a encontrar a distribuição de material correspondente ao menor volume possível tal que o critério de segurança seja verificado. O referido critério de segurança pode ser definido como limitar as tensões elásticas ao critério de plastificação em todo o domínio. Esta definição resultou em um novo ramo de pesquisa: a otimização topológica com restrições de tensões. Por outro lado, entende-se que o projeto estrutural plástico é preferível quando um projeto ótimo é almejado, uma vez que permite um maior aproveitamento da resistência do material. Dessa forma, este trabalho aborda a incorporação do projeto estrutural plástico à otimização topológica como método mais vantajoso do que a otimização topológica clássica e a com restrições de tensões. A formulação proposta é uma extensão da análise limite, que fornece uma estimativa da carga de colapso de uma estrutura diretamente por meio da programação matemática, assegurando a eficiência computacional da metodologia proposta. De forma a verificar a otimização topológica plástica e comparar a topologia final com as obtidas através da otimização topológica clássica e da com restrição de tensões, são apresentados exemplos numéricos.
This work presents a full plastic formulation to be applied within topology optimization. The main idea of topology optimization in solid mechanics is to find the material distribution within the domain so that it optimizes a performance measure and satisfies a set of constraints. One might seek to minimize the compliance satisfying that the volume is less than a given value. The aforementioned formulation is the standard topology optimization which has been used widely in literature. Although it provides interesting results, additional requirements must be taken into account when practical application is concerned. Structures are designed considering two main aspects: (i) the structure must not collapse, supporting the applied loads (safety criterion); and (ii) its displacements must be lower than a prescribed bound (serviceability criterion). Consequently, the standard formulation shall be modified, finding the material distribution corresponding to the minimum volume such that the safety criterion is met. Said safety criterion may be defined as restraining the elastic stresses to the yield criterion in the entire domain. This definition has resulted in a new branch in this research field: the stress constrained topology optimization. On the other hand, it is understood that the plastic design criterion is preferable when optimization is intended, since it fully exploits the material strength. Therefore, this work addresses the incorporation of the plastic design criterion into topology optimization as a more advantageous method than standard and stress constrained topology optimization methods. The proposed formulation is an extension of limit analysis, which provides an estimative of the collapse load of a structure directly through mathematical programming, ensuring computational efficiency to the proposed methodology. Lastly, numerical examples are shown to verify plastic topology optimization and the final topology is compared with those provided by standard and stress constrained topology optimization methods.
Rabiei, Nima. "Decomposition techniques for computational limit analysis". Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/284217.
Testo completoEl análisis en estados límite es una herramienta relente en muchas aplicaciones de la ingeniería como por ejemplo en el análisis de estructuras o en mecánica del suelo. La teoría de estados límite asume un material rígido con plasticidad perfecta para modelar la capacidad portante y los mecanismos de derrumbe de un sólido sometido a una distribución de cargas estáticas. En este contexto, el problema en estados límite considera el continuo sometido a una distribución de cargas, tanto volumétricas como de superficie, y tiene como objetivo hallar el máximo multiplicador de la carga que provoca el derrumbe del cuerpo. Este valor se conoce como el máximo factor de carga, y puede ser calculado resolviendo un problema de optimización no lineal de dimensión infinita. Desde el punto de vista computacional, se requieren pues dos pasos: la discretización del problema analítico mediante el uso de espacios de dimensión finita, y la resolución del problema de optimización resultante. Este último paso representa uno de los mayores retos en el proceso del cálculo del factor de carga. El problema de optimización mencionado puede ser de gran tamaño y con un alto coste computacional, sobretodo en el análisis límite tridimensional. Técnicas recientes han permitido a investigadores e ingenieros determinar cotas superiores e inferiores del factor de carga. A pesar del atractivo de estos resultados, su aplicación práctica en ejemplos realistas está todavía obstaculizada por el tamaño del problema de optimización resultante. Posibles remedios a este obstáculo son el diseño de técnicas de descomposición y la paralelizarían del problema de optimización. El objetivo de este trabajo es presentar una técnica de descomposición que pueda reducir los requerimientos y el coste computacional de este tipo de problemas. Con este propósito, se explotan una propiedad importante del problema de optimización: la función objetivo contiene una único escalar (el factor de carga). La contribución principal de la tesis es el replanteamiento del problema de optimización como la intersección de dos conjuntos, y la propuesta de un algoritmo eficiente para su resolución iterativa.
Fishwick, Rupert John. "Limit analysis of rigid block structures". Thesis, University of Portsmouth, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310412.
Testo completoPACHAS, MAURO ARTEMIO CARRION. "LIMIT ANALYSIS WITH LARGE SCALE OPTIMIZER AND RELIABILITY ANALYSIS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31860@1.
Testo completoCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
O presente trabalho tem por objetivo desenvolver um otimizador eficiente de grande escala, que permita a aplicabilidade prática da Análise Limite Numérica pelo MEF, para resolver problemas reais da Engenharia Geotécnica. Para isto, foi desenvolvido um otimizador para o programa GEOLIMA (GEOtechnical LIMit Analysis) (Carrión, 2004) baseado no algoritmo de Pontos Interiores, computacionalmente mais eficiente que os otimizadores comerciais existentes. Pelo fato das propriedades do solo serem de natureza aleatória, a possibilidade de aplicar Análise de Confiabilidade com a Análise Limite pelo método FORM em problemas geotécnicos é pesquisada também. Sendo a grande vantagem do método FORM a possibilidade de se aplicar para funções de falha quaisquer e variáveis com distribuição quaisquer. Inicialmente, são apresentados os fundamentos da teoria de Análise Limite e sua formulação numérica pelo MEF (Método dos Elementos Finitos). A seguir, é investigada a possibilidade de se usar otimizadores comerciais para resolver o problema matemático resultante da aplicação de Análise Limite com o MEF e são descritos os fundamentos teóricos do otimizador implementado baseado no algoritmo de Pontos Interiores. Um resumo dos fundamentos teóricos da Análise de Confiabilidade é apresentado. É descrito o processo de cálculo pelo método FORM e dois exemplos de aplicação são realizados. Finalmente, análises de diferentes problemas resolvidos com o otimizador implementado são apresentados indicando o grande potencial da Análise Limite Numérica, na solução de problemas reais da Engenharia Geotécnica.
This work has, as its main objective, the development of an efficient and large scale optimizer, that allows the practical application of Numerical Limit Analysis (NLA) with Finite Element Method (FEM) to solve real problems in Geotechnical Engineering. For that purpose, an optimizer was developed for GEOLIMA (GEOtechnical LIMit Analysis) program (Carrión, 2004), based on Interior Points algorithm, computationally more efficient than the existing commercial optimizers. Due to the fact that soils have random properties, the possibility to apply Reliability Analysis with Limit Analysis using the FORM method was also investigated. Initially, Limit Analysis theory was presented together with its numerical formulation using the FEM. In sequence, the use of commercial optimizers was investigated in order to solve the resulting mathematical problem. Subsequently, the theorical foundations of the developed optimizer, based on the Interior Points algorithm were described. A summary of Reliability Analysis was also presented together with a description of computational procedures using FORM and two examples were developed. Finally, analyses of different problems solved with developed optimizer were presented. The obtained results demonstrated the great potential of Numerical Limit Analysis (NLA), in the solution of real problems in Geotechnical Engineering.
Liu, Ying, e 劉影. "Limit equilibrium methods for slope stability analysis". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B42576684.
Testo completoLi, Haorong 1969. "Preliminary forming limit analysis for advanced composites". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37741.
Testo completoAhmed, Husham. "Limit analysis of structures : novel computational techniques". Thesis, University of Sheffield, 2005. http://etheses.whiterose.ac.uk/14871/.
Testo completoLiu, Ying. "Limit equilibrium methods for slope stability analysis". Click to view the E-thesis via HKUTO, 2002. http://sunzi.lib.hku.hk/hkuto/record/B42576684.
Testo completoVasquez, Elizabeth Danielle. "Designing anisotropic friction through limit curve analysis". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123249.
Testo completoCataloged from PDF version of thesis.
Includes bibliographical references (page 26).
Friction is an essential component of robotic manipulation which is highly dependent on contact surfaces. In practical applications, these surfaces are often anisotropic, a property that has been known to produce interesting movements in nature and uncertainty in human applications. Therefore, control of anisotropic frictional surfaces could result in more precise movement in manipulation, locomotion, and other facets touched by frictional contact. To arrive at such controllability, frictional force was collected across a spectrum of anisotropic micro-textures, and a limit curve was generated. Experimental data was analyzed in accordance to friction laws such as limit curve and maximum-inequality principle (MPI). Qualitative observation and residual sum of squares (RSS) was used to detect lack of normality and non-convexity within each limit curve. This lack of both normality and convexity contradicts MPI and suggests that an alternative model is necessary. Additionally, the anisotropic frictional behaviors observed advances the feasibility of "designing" micro-textures capable of controllable anisotropic friction.
by Elizabeth Danielle Vasquez.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering
Bourne-Webb, Peter John. "Ultimate limit state analysis of embedded retaining walls". Thesis, Imperial College London, 2004. http://hdl.handle.net/10044/1/7862.
Testo completoPACHAS, MAURO ARTEMIO CARRION. "THREE-DIMENSIONAL DETERMINISTIC AND NON DETERMINISTIC LIMIT ANALYSIS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5750@1.
Testo completoO presente trabalho tem como objetivo estudar o comportamento de estruturas geotécnicas mediante o uso de Análise Limite Numérica. Para isto foi desenvolvido o programa GEOLIMA (GEOtechnical LIMit Analysis) com base na teoria de Análise Limite Numérica utilizando o Método de Elementos Finitos (MEF), considerando problemas bidimensionais e tridimensionais. Devido ao fato das propriedades do solo serem variáveis aleatórias, a Análise Não Determinística também foi considerada mediante o uso do Método Estatístico Linear e do Método de Monte Carlo. Inicialmente, são apresentados os fundamentos da teoria de Análise Limite Determinística e sua formulação mista pelo Método de Elementos Finitos. A seguir são apresentados os fundamentos de Análise Não Determinística, onde os métodos Estatístico Linear e Monte Carlo são descritos. As fases de desenvolvimento do GEOLIMA são descritas de forma resumida e a validação é feita mediante a comparação de resultados obtidos com soluções analíticas ou outras soluções. A seguir, uma aplicação em 2D é apresentada com a finalidade de ilustrar a Análise Limite Determinística e Não Determinística mediante o método Estatístico Linear e o método de Monte Carlo. Finalmente, duas aplicações em 3D são apresentadas: um problema relativo à frente de escavação de um túnel e um estudo de painéis de mineração. Os resultados deste trabalho indicam a viabilidade de usar Análise Limite Determinística e Não Determinística no estudo de problemas geotécnicos.
The present work has the purpose of studying the behavior of geotechnical structures by means of numerical analysis. For this, program GEOLIMA (GEOtechnical LIMit Analysis) was developed based on the theory of Numerical Limit Analysis using the Finite Element Method (FEM), considering bidimensional and three-dimensional problems. Due to the fact that the properties of the ground are generally random variables, Non Deterministic Analysis was also considered by means of the Linear Statistical and the Monte Carlo Methods. Initially, the fundamentals of Deterministic Limit Analysis and its mixed formulation are presented. Then, the fundamentals of Non Deterministic Theory are presented, and the Linear Statistic and the Monte Carlo Methods are described. The development phases of GEOLIMA are briefly described. Its validation is made by comparing the results obtained with analytical solutions or other solutions. Following, a 2D application is made with the purpose of illustrating Deterministic and Non Deterministic Limit Analysis. Finally, two 3D applications are presented: a problem related to the excavation of a tunnel front and a problem related to mining panels. The results of this work indicate the viability of using Deterministic and Non Deterministic Limit Analysis in the study of geotechnical problems.
Babiker, A. F. A. "Limit analysis using a non-associative flow rule". Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/5577/.
Testo completoCalhoun, Grayson Ford. "Limit theory for overfit models". Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3359804.
Testo completoTitle from first page of PDF file (viewed July 23, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 104-109).
Dunne, Helen P. "Finite element limit analysis of offshore foundations on clay". Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:ba9c9beb-e055-4f46-a9f9-b2d10bd292b7.
Testo completoSANTOS, FERNANDA DANTAS. "LIMIT ANALYSIS AND OPTIMUM DESIGN OF REINFORCED CONCRETE BEAMS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4423@1.
Testo completoÉ apresentada uma metodologia para a determinação da carga de colapso e uma outra para o dimensionamento ótimo em vigas de concreto armado. Para a determinação da carga de colapso a metodologia utiliza a análise limite e o modelo da Treliça Clássica de Mörsch. A formulação do problema é obtida a partir dos teoremas limites de plasticidade, que permitem escrever o problema da análise limite na forma de programação linear (PL) e o programa LINGO é utilizado para resolvê-lo. Para o dimensionamento ótimo o mesmo modelo da treliça de Mörsch é utilizado e a formulação do problema também recai num problema de programação linear que pode ser resolvido pelo programa LINGO. A solução fornece tanto as áreas das armaduras longitudinais como dos estribos. Os exemplos apresentados ilustram a validade e eficiência da formulação proposta. Os resultados obtidos são analisados e comparados com os resultados experimentais e com os obtidos com o uso de outra metodologia. Finalmente são apresentadas as conclusões e sugeridas propostas para trabalhos futuros.
Methodologies for the determination of the collapse load and for the optimal design of concrete beams are presented. For the collapse load determination the methodology makes use of the limit analysis and of the classical truss model of Mörsch. The formulation of the problem is based on the limit theorems of plasticity which allow the limit analysis problem to be expressed as a linear programming problem (LP) which is solved by the program LINGO. For the optimal design, the same truss model of Mörsch is used and the formulation also leads to a linear programming problem which can be solved by the program LINGO. The solution yields both the longitudinal reinforcement and the stirrups. The examples presented illustrate the validity and efficiency of the proposed formulation. The results obtained are analysed and compared to the experimental ones and to those obtained using other methodologies. Finally, conclusions are drawn from the results and suggestions are given for future researches in the field.
Visram, Abeed. "Asymptotic limit analysis for numerical models of atmospheric frontogenesis". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/23219.
Testo completoHeng, Johnny Wong Liang. "Ultimate limit state analysis of externally post-tensioned structures". Thesis, University of Sheffield, 1997. http://etheses.whiterose.ac.uk/14442/.
Testo completoHawksbee, Samuel John. "3D ultimate limit state analysis using discontinuity layout optimization". Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/3944/.
Testo completoBian, Jian. "Ultimate flexural limit states analysis of prestressed concrete sleeper". Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/63660/1/Jian_Bian_Thesis.pdf.
Testo completoOdero, Geophrey Otieno Mr. "Limit Cycles and Dynamics of Rumor Models". Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etd/1236.
Testo completoMok, Kit Ying. "Central limit theorem for nonparametric regression under dependent data /". View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?MATH%202003%20MOK.
Testo completoHuerga, Encabo Hector 1989. "Analysis of transcription mechanisms that limit type I interferon responses". Doctoral thesis, Universitat Pompeu Fabra, 2018. http://hdl.handle.net/10803/666035.
Testo completoTrần, Thanh Ngọc. "Limit and shakedown analysis of plates and shells including uncertainties". Doctoral thesis, Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200800256.
Testo completoDie Zuverlässigkeitsanalyse von Platten und Schalen in Bezug auf plastischen Kollaps oder Nicht-Anpassung wird mit den Traglast- und Einspielsätzen formuliert. Die Lasten, die Werkstofffestigkeit und die Schalendicke werden als Zufallsvariablen betrachtet. Auf der Grundlage einer direkten Definition der Grenzzustandsfunktion kann die Berechnung der Versagenswahrscheinlichkeit effektiv mit den Zuverlässigkeitsmethoden erster und zweiter Ordnung (FROM/SORM) gelöst werden. Die Sensitivitätsanalysen in FORM/SORM lassen sich auf der Basis der Sensitivitäten des deterministischen Einspielproblems berechnen. Die Schwierigkeiten bei der Ermittlung der Zuverlässigkeit von strukturellen Systemen werden durch Anwendung einer speziellen Barrieremethode behoben, die es erlaubt, alle Auslegungspunkte zu allen Versagensmoden zu finden. Die Anwendung direkter Plastizitätsmethoden führt zu einer beträchtlichen Verringerung der notwendigen Kenntnis der unsicheren Eingangsdaten, des Berechnungsaufwandes und der numerischen Fehler
O'Neil, Joshua Robert. "Analysis of periodically-forced turbulence in the rapid distortion limit". Texas A&M University, 2004. http://hdl.handle.net/1969.1/3141.
Testo completoDarwich, Wael. "Novel Computational Implementations for Ultimate Limit State Analysis and Design". Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522049.
Testo completoBaldwin, Richard P. "Aircraft engine reliability analysis using lower confidence limit estimate procedures". Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23522.
Testo completoIn this thesis, a spreadsheet model was developed to compute the lower confidence limit (LCL) for the reliability of a complex weapon system using a personal computer. the LCL is an estimate of the lowest reliability a system is expected to have at a given point in time with a given level of confidence. The reliability model is based on a Weibull distribution for the system component failure times. the reliability LCL procedures has been extensively validated and determined to be quite accurate when the expected number of failures is at least 10. This model is capable of supporting :LCL decisions in support of the Component Improvement Program or new weapon system procurement where reliability growth analysis is used as a decision support tool. This procedure also provides program managers and engineers with a method to perform LCL analysis and thereby reduce their dependence on contractor supplied reliability data.
SHENG, CHANG PI. "ANALYSIS AND SYNTHESIS OF LIMIT CYCLE FREE RECURSIVE DIGITAL FILTERS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1990. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=14161@1.
Testo completoThis thesis presents a method for analysis of zero-input limit cycles due to quantization, in digital filters realized with floating point arithmetic. Conditions for absence of limit cycles are easily derived by computational calculus. The method of analysis is applicable to generic structures of any order. Following this, a method is presented a method for the synthesis of digital filters realized with fixed point arithmetic, that are free from zero-input limit cycles due to quantization, using the concept of structurally passive networks. The structures synthetized present sub-filters structurally LBR or BR in the feedback loop. Second order structures are synthetized and studied. It is proved that some of these stuctures are also free from zero-input limit cycles due to overflow and stable to forced response.
BORGES, LAVINIA MARIA SANABIO ALVES. "FORMULATION AND SOLUTION OF LIMIT ANALYSIS WITH NONLINEAR YIELDING SURFACE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1991. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19422@1.
Testo completoCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O objetivo deste trabalho é apresentar as formulações variações para o problema de análise limite e o desenvolvimento do processo de resolução, que envolve o método dos elementos finitos e as técnicas de programação matemática. As formulações variacionais são apresentadas em três versões: estática, cinemática e mista. Estas formulações são derivadas a partir da proposição das relações constitutivas na forma de pseudo-potenciais conjugados. Esses princípios são discretizados através do método dos elementos finitos. São propostos dois algoritmos iterativos de programação matemática para a solução do problema. Os algoritmos podem ser aplicados tanto para o comportamento plástico descrito por funções de escoamento lineares como não lineares. Nas aplicações numéricas são analisados corpos em estado plano de tensão, deformação e com simetria de revolução.
The aim of this work is to present variational formulations for the limit analysis problem and solution procedures using the finite element method and mathematical programming techniques. The variational formulations are presented in three versions: static, kinematical and mixed. These formulations are derived from the proposition of the constitutive relationship in the form of conjugate pseudopotencials. Finite element discretizations are proposed for each of the three continuous problems. Two iterative mathematical programming algorithms are prosed to solve the problem. These algorithms can be applied to the plastic behavior described by a set of linear or non-linear yield functions. Limit analysis in plane strain, plane stress and axissymetric solids are considered in the numerical examples.
Degwitz, Fernando G. (Fernando Guillermo) 1980. "Numerical upper and lower bound limit analysis for braced excavations". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30131.
Testo completoIncludes bibliographical references (leaves62-63).
This thesis reviews limit theorems and their applications for stability problems in geotechnical engineering. Rigorous numerical solutions of limit analyses can be obtained through finite element discretization of the soil mass and formulation of the limit theorems within a linear programming framework. The current research uses a formulation proposed by Sloan et al. (1988) and extended in a recent Ph.D. thesis by Ukritchon (1998) to include soil-structure interactions. The thesis details the input and output required for numerical limit analysis and presents an example application for the stability of a broad excavation for the MUNI Metro Turnback project in San Francisco. This well documented case study involves a 13 M deep excavation within a deep deposit of May Mud that was supported by an SPTC wall with three levels of cross-lot bracing. The numerical limit analyses calculate factors of safety, FS = 1.03 - 1.36, against basal instability. The factor of safety used in the original design (FS = 1.2) is contained in this range. The results illustrate that numerical limit analysis offers a practical alternative to limit equilibrium methods in evaluating the stability of braced excavations.
by Fernando G. Degwitz.
M.Eng.
Trần, Thanh Ngọc. "Limit and shakedown analysis of plates and shells including uncertainties". Doctoral thesis, Bericht ; 2/2008, 2007. https://monarch.qucosa.de/id/qucosa%3A18876.
Testo completoDie Zuverlässigkeitsanalyse von Platten und Schalen in Bezug auf plastischen Kollaps oder Nicht-Anpassung wird mit den Traglast- und Einspielsätzen formuliert. Die Lasten, die Werkstofffestigkeit und die Schalendicke werden als Zufallsvariablen betrachtet. Auf der Grundlage einer direkten Definition der Grenzzustandsfunktion kann die Berechnung der Versagenswahrscheinlichkeit effektiv mit den Zuverlässigkeitsmethoden erster und zweiter Ordnung (FROM/SORM) gelöst werden. Die Sensitivitätsanalysen in FORM/SORM lassen sich auf der Basis der Sensitivitäten des deterministischen Einspielproblems berechnen. Die Schwierigkeiten bei der Ermittlung der Zuverlässigkeit von strukturellen Systemen werden durch Anwendung einer speziellen Barrieremethode behoben, die es erlaubt, alle Auslegungspunkte zu allen Versagensmoden zu finden. Die Anwendung direkter Plastizitätsmethoden führt zu einer beträchtlichen Verringerung der notwendigen Kenntnis der unsicheren Eingangsdaten, des Berechnungsaufwandes und der numerischen Fehler.
Lamendola, Joel E. "Limit Cycle PIO Analysis With Simultaneously Acting Multiple Asymmetric Saturation". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36767.
Testo completoMaster of Science
Almada, Monter Sergio Angel. "Scaling limit for the diffusion exit problem". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39518.
Testo completoGholami, Ghadikolaei Iraj. "Data analysis of continuous gravitational waves". Phd thesis, Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1880/.
Testo completoDiese Dissertation besteht aus zwei Projekten: Im ersten Projekt wird die Optimierung einer hierarchischen Strategie zum Auffinden von 'unbekannten' Pulsaren beschrieben. Der erste Teil besteht dabei aus einer semi-kohärenten und der zweite Teil aus einer kohärenten Optimierungsstrategie, wie sie in Projekten wie Einstein@Home verwendet werden kann. In beiden Ansätzen erwies sich eine 3-Stufensuche als optimale Suchstrategie für 'unbekannte' Pulsare. Für das zweite Projekt entwickelten wir eine Software für eine kohärente Multi-IFO (Interferometer Observatory) Suche. Zum Validieren der Software verwendeten wir sowohl simulierte Daten als auch Hardware induzierte Signale von Pulsaren aus dem vierten 'LIGO Science run' (S4). Wir erwarten nicht, mit der aktuellen Empfindlichkeit unserer Detektoren echte GW- Signale aufzunehmen, können jedoch obere Grenzen für die Stärke der Gravitationswellen-Signale bestimmen. Diese oberen Grenzen geben uns an, wie schwach ein gerade noch detektierbares Signal werden kann. Ferner benutzten wir die Software um eine obere Grenze für bekannte, isolierte Pulsare zu bestimmen, wobei wir Daten aus dem fünften 'LIGO Science run (S5) verwendeten.
Tran-Cao, Tri Civil & Environmental Engineering Faculty of Engineering UNSW. "Collapse analysis of block structures in frictional contact". Awarded By:University of New South Wales. Civil & Environmental Engineering, 2009. http://handle.unsw.edu.au/1959.4/44574.
Testo completoAlizadeh, Ramin. "A new upper limit on the electron anti-neutrino rest-mass". Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236237.
Testo completoNgo, Ngoc Son Civil & Environmental Engineering Faculty of Engineering UNSW. "Limit and shakedown analyses by the p-version fem". Awarded by:University of New South Wales. Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/23463.
Testo completoShi, Jinhua. "Limit and shakedown analysis of structures by the finite element method". Thesis, University of Strathclyde, 1996. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21253.
Testo completoARAUJO, LUIZ GONZAGA DE. "NUMERICAL STUDIES OF THE STABILITY OF GEOTECHNICAL MATERIALS THROUGH LIMIT ANALYSIS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2084@1.
Testo completoO presente trabalho apresenta um estudo de problemas de estabilidade, freqüentemente,encontrados, em Engenharia Geotécnica, através da técnica da Análise Limite associada ao Método dos Elementos Finitos (MEF).Inicialmente, faz-se uma revisão das formulações da Análise Limite, via MEF,encontradas, com maior freqüência, na literatura técnica especializada.Uma formulação mista que é descrita em detalhe na tese foi escolhida para implementação. Extensões das formulações da Análise Limite de meios contínuos são propostas para contemplar características de maciços rochosos fraturados. É proposto,também, um procedimento numérico para tratar de problemas de estabilidade de meios que exibem fluxo plástico não associado.As implementações realizadas foram validadas através de problemas cujas soluções podem ser obtidas por via analítica.Finalmente, um número considerável de problemas de interesse em Engenharia Geotécnica é estudado utilizando a implementação realizada. Os resultados destes estudos sugerem a viabilidade da utilização da técnica estudada na solução de problemas práticos de Engenharia Civil.
This work presents a study of stability problems often encountered in Geotechnical Engineering, through the use of Limit Analysis in conjunction with the Finite Element Method (FEM).Initially, a literature survey of the most often found formulations in Limit Analysis through the FEM is carried out.A mixed formulation of Limit Analysis was chosen for implementation and its details are fully described. Extensions of the formulation to deal with stability problems in fractured rock media are also proposed and described. A numerical procedure to take into account the effect of non associative plastic flow is proposed.The implementations carried out were validated through problems to which analytical solutions could be found.Finally, a considerable number of problems of interest to Geotechnical Engineering is studied with the implemented formulation. The results of these studies suggest that Limit Analysis can be considered as a viable tool in the solution of practical problems in Geotechnical Engineering.
Dujc, Jaka. "Finite element analysis of limit load and localized failure of structures". Cachan, Ecole normale supérieure, 2008. http://tel.archives-ouvertes.fr/tel-00505153/fr/.
Testo completoThe dissertation deals with limit load and limit ductility analysis of structures by the finite element method. When structure is at its limit load, several structural components behave inelastically, while in the critical parts of the structure, due to localization of inelastic strains, failure of material appears. Localized effects in brittle materials are related to appearance and formation of a large (macro) crack, while failure in ductile materials is governed by localized shear bands. The study of limit load is thus related to modeling both standard inelastic material effects, as well as modeling of localized failure of material, often reffered to as material softening. Standard inelastic material effects are in this work described with elastoplastic, elastoviscoplastic and nonlinear elastic material models. All the material models are defined at the level of stress-resultants. Several mathematical approaches and numerical algorithms for modeling localized effects are at hand, but they are often inefficient or inaccurate. Therefor, we use an up-to-date approach, based on a finite element method with embedded discontinuity. We derive new finite element formulations with a quite complex kinematics of the basic elements, as well as rather complex description of discontinuous displacement fields. We derived several finite element formulations for analysis of different structural components. First we present a finite element for limit load analysis of reinforced concrete plates. Stress-resultant elastoplastic and elastoviscoplastic plate finite element formulation along with a unified computational procedure that covers both formulations are presented next. Further, a nonlinear shell finite element, based on a two-surface yield function, that includes both isotropic and kinematic material hardening is presented. The last two finite elements derived in this work are intended to model the localized failure in planar beams and 2D solids. The embedded discontinuity in rotations was built into elastoplastic Euler-Bernoulli beam finite element, and a procedure, based on a precomputed analysis of a part of a structure, by using a refined numerical model, is proposed to obtain the beam constitutive model parameters. Finally, we derive an elastoplastic quadrilateral two-dimensional finite element formulation with embedded strong discontinuity, whose kinematics can model linear jumps in both normal and tangential displacements along the discontinuity line. Numerical simulations show, that the derived finite elements, along with the accompanied numerical algorithms, are an efficient and a rather robust tool for limit load and failure analysis of structures. Among other examples, we present a simulation of crack growth in brittle material and a simulation of shear band failure in ductile material. All the computer codes of the finite element formulations presented in this work have been generated through the symbolic programming of the finite element computer code and the expression optimization in AceGen computer program. The performance of these elements has been presented in numerous numerical examples, all performed by the AceFem computer program
Warren, Sean N. "Limit equilibrium stability analysis utilizing geotechnical data at Mount Baker, Washington /". abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1461537.
Testo completo"December 2008." Includes bibliographical references (leaves 109-112). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2009]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web. Library also has electronic version on CD-ROM
MORALES, MARLENE SUSY TAPIA. "RELIABILITY ANALYSIS OF SATURATED-UNSATURATED SOIL SLOPES USING LIMIT ANALYSIS IN THE CONIC QUADRATIC SPACE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23211@1.
Testo completoCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Este trabalho tem por objetivo a avaliação da estabilidade de taludes de solo quando sometidos a processos de infiltração de chuva, utilizando conceitos de Análise Limite e Análise de Confiabilidade. Primeiramente, determina-se a variação da sução no solo, para isto, emprega-se o Método dos Elementos Finitos e o Método de diferenças finitas na solução da equação de Richards. O modelo de Van Genuchten (1980) é utilizado para a curva característica. Na solução da nãolinearidade, emprega-se o método Picard Modificado. A instabilidade de taludes é estudada mediante o método de Análise Limite Numérica com base no Método de Elementos Finitos e o critério de Mohr Coulomb como critério de escoamento. A solução do problema matemático será realizada no espaço cônico quadrático com o objetivo de tornar a solução mais computacionalmente eficiente. Considerando as propriedades do solo como variáveis aleatórias foi incluída a determinação do Índice de Confiabilidade utilizando as formulações dos métodos de Monte Carlo e FORM (first order reliability method). Inicialmente são introduzidos conceitos básicos associados ao fluxo saturado-não saturado. A seguir são apresentados alguns conceitos. Sobre Análise Limite e sua formulação pelo Método de Elementos Finitos. Finalmente são introduzidos os fundamentos da Análise de Confiabilidade. Análises de confiabilidade das encostas de Coos Bay no estado de Oregon nos Estados Unidos e da Vista Chinesa no Rio de Janeiro Brasil, são apresentadas devido a que estes taludes sofreram colapso quando submetidos a processos de infiltração de água de chuva. Os resultados deste trabalho mostram que a falha das encostas ocorre quando o índice de confiabilidade atinge um valor perto de dois.
This thesis aims to perform a reliability analysis of the stability of 2D soil slopes when they are submitted to water infiltration due to the rains.The time variation of the soil matric suctions is calculated first. The Finite Element Method is used to transform the Richards differential equation into a system of nonlinear first order equations. The nonlinearity of the problem is due to the use of the characteristic curve proposed by van Genuchten (1980). The Modified Picard Method is applied to solve de time-dependent nonlinear equation system. The responses of the flux-problem are transferred to the stability problem in some instants using the same time-interval (normally days).To estimate the stability of the slopes, limit analysis is used. The limit analyses are performed based on the Inferior Limit Theorem of the Plasticity Theory. The problem is defined as an optimization problem where the load factor is maximized. The equilibrium equations are obtained via Finite Element discretization and the strength criterion of Mohr-Couomb is written in the conic quadratic space. Therefore, a SOCP (Second Order Conic Programming) problem is generated. The problem is solved using an interior point algorithm of the code Mosek.Since the soil properties are random variables a reliability analysis can be performed at each instant of the time-dependent problem. In order to perform the reliability analyses, Response Surfaces for the failure function of the slope are generated. In this work, the Stochastic Collocation Method is used to generate Response Surfaces. The Simulation Monte Carlo Method and the FORM (First Order Reliability Method) are used to obtain both the reliability index and the probability of failure of the slopes.Reliability analyses of the Coos Bay Slope in the state of Oregon in USA and in the Vista Chinesa Slope in Rio de Janeiro, Brazil, are presented because they collapse due to rainfall infiltration. The results show that the soil slope fails when the related reliability index is close to two.
Yuan, Xiaoping. "Extensional collapses in the overpressured frictional upper crust based on limit analysis". Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE009/document.
Testo completoThis manuscript develops a 2D kinematic approach of Limit Analysis to examine the extensionalfailures in the brittle, upper crust resulting from fluid overpressures and normal faulting. There aremany interesting topics related to the extensional deformation such as (1) the roles of fluid pressure,topographic process, material and fault properties on the stability of extensional structures; (2) theformation of low-angle and listric normal fault; (3) the deformation pattern due to slip on a low-anglefault; and (4) the influence of fault softening and sedimentation processes on this deformation pattern.This mechanical approach applied to wedge prototypes is validated by the critical Coulomb wedge(CCW) theory, and it generalizes the CCW theory to investigate the complex topography on theMejillones peninsula, Northern Chile. Additionally, this approach is also applied to investigate gravityinstability of Niger Delta by linking down-slope compressional to up-slope extensional failures througha deep detachment. We predict much higher fluid overpressures than that of the CCW theory. Finally,this Limit Analysis methodology is applied to investigate the shape of normal fault linking a lowdetachment to the surface. The application to Niger Delta implies that the formation of very low-angleand strongly listric faults results from a shallow fluid-retention depth. The sequential version of LimitAnalysis opens new ways to envision the structural evolution through time resulting from normalfaulting. The simulations show that the normal fault rotates during extension, forming a region of Footto-Hanging Wall (FHW) where the material in the footwall is sheared upon entering the hanging wall.The creation of the FHW region is illustrated by sandbox experiments and field examples
田淑敏 e Suk-man Tin. "The application of probability limit theorems to problems in DNA sequence analysis". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B31211896.
Testo completoPrasad, Anamika 1979. "Development of user interface for numerical limit analysis of geotechnical stability problems". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/85751.
Testo completoTin, Suk-man. "The application of probability limit theorems to problems in DNA sequence analysis /". [Hong Kong] : University of Hong Kong, 1994. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13637708.
Testo completoShukla, Himanshu. "Nonlinear Analysis and Control of Aeroelastic Systems". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71468.
Testo completoPh. D.
Roberts, Lance Alan Misra Anil. "Reliability-based design and analysis of deep foundations at the service limit state". Diss., UMK access, 2006.
Cerca il testo completo"A dissertation in engineering and geosciences." Advisor: Anil Misra. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Jan. 29, 2007. Includes bibliographical references (leaves 200-206). Online version of the print edition.
Pénisson, Sophie. "Conditional limit theorems for multitype branching processes and illustration in epidemiological risk analysis". Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00570458.
Testo completoImamovic, Ismar. "Ultimate load limit analysis of steel structures accounting for nonlinear behaviour of connections". Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2373/document.
Testo completoThis thesis deals with the ultimate load limit analysis of steel frame structures. The steel frame structure has a very ductile response and a large potential to dissipate energy, which is crucial in the case of earthquakes. The ductility in the response of the structure comes from the behavior of the material itself and the behavior of the semi-rigid structural connections. The semi-rigid connections between beams and columns can significantly influence the response of the structure, sometimes up to 30%. In this thesis, we propose a methodology for modeling steel frame structures with included connection behavior. The idea is to model the behavior of the structural connections by the beam elements positioned in the corners of the steel frame structure. Other members of the steel frame structure, steel beams, and columns, will be modeled with nonlinear beam elements. This research consists of two parts. The first part deals with the behavior of the structural steel connections. In the second part, we present the development of the nonlinear beam element capable of representing the ductile behavior of steel structural elements, beams and columns. In the first part of the thesis, we define constitutive parameters identification procedure for the coupled plasticity-damage model with eighteen unknowns. This constitutive model is very robust and capable of representing a wide range of problems. The identification procedure was used in the preparation of experimental tests for three different types of structural steel connections. The experimental tests have been performed for two load cases. In the first, the load was applied in one direction with both the loading and unloading cycles. From the experimental measurements, we have concluded that the response of the experimental structure can be represented by the plasticity model only because no significant change in the elastic response throughout the loading program was observed. Therefore, we have chosen an elastoplastic geometrically exact beam to describe connection behavior. The hardening response of the beam is governed by bilinear law, and the softening response is governed by nonlinear exponential law. The identification of the parameters has been successfully done with fifteen unknown parameters identified. The two types of the experimental structures were also exposed to the cyclic loading. Measured experimental data shows complex connection behavior that cannot be described by the plasticity model alone. Namely, after changing load direction stiffness of the connection decreases. This suggests that the damage model should be incorporated in the constitutive law for the connections behavior as well. Therefore, we propose a new coupled plasticity-damage model capable of representing the loss in the stiffness of the connection with the changing of the load direction. At the end of this part, we also give the constitutive parameters identification for the proposed model. The second part of the thesis deals with the theoretical formulation and numerical implementation of the elastoplastic geometrically exact beam. The hardening response of the beam includes interaction between stress resultant section forces (N, T and M), and the softening response of the beam, which is governed by the nonlinear law. This type of the beam element is capable of representing the ductile behavior of a steel frame structure, and it takes into account second order theory effects. Performed numerical simulations show that the proposed geometrically nonlinear beam element is very robust and is able to provide a more precise limit load analysis of steel frame structures. By using proposed methodology for modeling steel structures, we are able to obtain the real distribution of section forces, including their redistribution caused by forming of the hinges and the connections behavior
Zhu, Pengcheng. "A novel Q-limit guided continuation power flow method for voltage stability analysis". Thesis, Brunel University, 2008. http://bura.brunel.ac.uk/handle/2438/5360.
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