[pt] Este trabalho focaliza a análise elasto-plástica de componentes mecânicos e estruturais. Especial atenção é dada a formulação da equação constitutiva. A relação constitutiva em taxas é equacionada na forma de potenciais generalizados onde utiliza-se o conceito de subgradientes. Para tal, são introduzidos conceitos básicos da termodinâmica sendo usadas variáveis internas para descrever os mecanismos dissipativos. São apresentados pseudo-potenciais em incrementos finitos de tensões e deformações que incorporam a admissibilidade plástica e são capazes de descrever o descarregamento elástico local desde que não haja plastificação seguida de descarregamento no passo. Esta forma é utilizada na obtenção-de Princípios de Mínimo para a análise elasto-plástica. A discretização espacial é feita utilizando o Método dos Elementos Finitos. São considerados algoritmos para a solução de tal problema. São incluídas aplicações numéricas a problemas planos e a flexão de placas. / [en] The elastic-plastic analysis of structural components is considered. The formulation of the constitutive equations is specially focused. The constitutive relation for rates is derived from pseudo-potentials by using the sub-gradient concept. Internal variables are introduced to describe dissipation mechanisms and thermodynamical concepts are used in order, to obtain the corresponding potential relationships. Generalized potentials are also presented for the approximate constitutive relation in terms of finite increments of strain and stress. This formulation incorporate plastic admissibility constraínts and it is also able to describe local elastic unloading except the case when it follows plastic yielding in the true incremental process. This form of the constitutive equation is used next to obtain minimum principles for the elastic-plastic analysis. Spatial discretization is performed by means of the Finíte Element Method. Some algorithms are discussed for the solution of the variational formulations considered. Numerical applications are presented for plane problems and plate bending.

In this investigation, the primary objective was to study the nonlinear behavior of unbraced two-bay concrete frames and to determine the extent to which ultimate load theory or limit design can be applied to these structures. The frame behavior was investigated analytically by two methods. In the first method the frame stability equation was derived assuming that members of the frame possess an elasto-plastic moment-curvature relationship. This stability analysis was also carried out by another model consisting of a column attached to a linear spring and carrying the total frame load. The second method was through a computer program which took material and geometric nonlinearities of concrete frames into account. A model concrete frame, with a scale factor of approximately one-third was considered. Variable parameters were loading condition, column reinforcement ratio, and beam to column load ratio. For each frame, the gravity loads were increased proportionally until 75% of the frame ultimate capacity under gravity loads was reached. Then; while these gravity loads were held constant, lateral load was applied and increased to failure. The overall geometry, 21-in high columns and 84-in long beam, were kept the same for all of model frames investigated. The computer study and the stability model analysis indicated that all frames remained stable until four plastic hinges (two in each bay) formed, thus producing a combined sway mechanism. Based on the scope of this study, it appears that limit design may be employed for unbraced reinforced concrete structures.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 77-79. / by Ying-Yee Lam. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaf 113. / by Bak Kong Low. / M.S.

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O objetivo da análise estrutural é determinar os efeitos das ações em uma estrutura, com a finalidade de efetuar verificações de estados limites últimos e de serviço (NBR 6118:2003 Projeto de estruturas de concreto). A análise estrutural consiste numa das principais etapas do projeto estrutural de um edifício, pois compreende a escolha dos modelos teóricos, que devem representar adequadamente a estrutura real, e do tipo de análise, com relação ao comportamento dos materiais. Visa-se, com este trabalho, aproximar o meio técnico do acadêmico, e tornar mais acessível a parte da NBR 6118:2003 que trata da análise estrutural. Neste trabalho consideram-se os modelos estruturais mais utilizados, no cálculo de edifícios, e os principais conceitos relativos aos diferentes tipos de análise permitidos pela norma. Em seguida são realizados exemplos de elementos lineares, pelos diferentes tipos de análise, com ênfase na redistribuição de esforços, empregando-se análise linear com redistribuição ou análise plástica. Ressalta-se a importância da consideração de seção T nas vigas e os ajustes necessários quando da consideração de uma envoltória de carregamentos. Tem-se ainda um exemplo de um edifício de oito pavimentos, que visa demonstrar as diferenças nos esforços ou nos deslocamentos obtidos com modelos estruturais distintos / The structural analysis objective is to determine the actions effects in a structure, with the purpose of verifying the ultimate limit states and serviceability (brazilian code NBR 6118:2003 - Design of concrete structures). The structural analysis is one of the main parts of a building structural design, since it involves the choice of theoretical models that represent appropriately the real structure, and the type of analysis due to the materials behavior. This work intends to shorten the distance between design engineers and the academic world, providing a clearer vision of the NBR 6118:2003 structural analysis approach. This work considers the most common structural models used for buildings, and the theory concerning the different types of analysis permitted by the brazilian code. It presents simple examples of linear elements computed by different types of analysis, emphasizing the moment redistribution possibility, either with the linear analysis with redistribution or the plastic analysis. The importance of considering T-beam with moment redistribution is made clear, and lines of direction to consider alternate position of live loads are given. The last example presents an eight store building, and its differences relative to efforts and displacements, obtained by distinct structural models

O objetivo da análise estrutural é determinar os efeitos das ações em uma estrutura, com a finalidade de efetuar verificações de estados limites últimos e de serviço (NBR 6118:2003 Projeto de estruturas de concreto). A análise estrutural consiste numa das principais etapas do projeto estrutural de um edifício, pois compreende a escolha dos modelos teóricos, que devem representar adequadamente a estrutura real, e do tipo de análise, com relação ao comportamento dos materiais. Visa-se, com este trabalho, aproximar o meio técnico do acadêmico, e tornar mais acessível a parte da NBR 6118:2003 que trata da análise estrutural. Neste trabalho consideram-se os modelos estruturais mais utilizados, no cálculo de edifícios, e os principais conceitos relativos aos diferentes tipos de análise permitidos pela norma. Em seguida são realizados exemplos de elementos lineares, pelos diferentes tipos de análise, com ênfase na redistribuição de esforços, empregando-se análise linear com redistribuição ou análise plástica. Ressalta-se a importância da consideração de seção T nas vigas e os ajustes necessários quando da consideração de uma envoltória de carregamentos. Tem-se ainda um exemplo de um edifício de oito pavimentos, que visa demonstrar as diferenças nos esforços ou nos deslocamentos obtidos com modelos estruturais distintos / The structural analysis objective is to determine the actions effects in a structure, with the purpose of verifying the ultimate limit states and serviceability (brazilian code NBR 6118:2003 - Design of concrete structures). The structural analysis is one of the main parts of a building structural design, since it involves the choice of theoretical models that represent appropriately the real structure, and the type of analysis due to the materials behavior. This work intends to shorten the distance between design engineers and the academic world, providing a clearer vision of the NBR 6118:2003 structural analysis approach. This work considers the most common structural models used for buildings, and the theory concerning the different types of analysis permitted by the brazilian code. It presents simple examples of linear elements computed by different types of analysis, emphasizing the moment redistribution possibility, either with the linear analysis with redistribution or the plastic analysis. The importance of considering T-beam with moment redistribution is made clear, and lines of direction to consider alternate position of live loads are given. The last example presents an eight store building, and its differences relative to efforts and displacements, obtained by distinct structural models

The increasing demand for more sustainable construction has led to the development of new structural systems that include wood as building material. Cross laminated timber (CLT) has been identified as a potential system to address this need and to provide alternative options in the range of low- to medium-rise construction. The appeal in using CLT as a shearwall is driven by the combination of the rigid panels and small dimension fasteners, which allows for significant energy dissipation in the structure. However, there is currently no reliable analytical model to accurately predict the behaviour of multi-segment CLT shearwalls. The current study aims to develop an analytical model capable of predicting the elastic and plastic phases associated with the behaviour of multi-panel CLT shearwalls. The model describes the wall behaviour as a function of the connectors’ properties in terms of stiffness, strength and ductility. This dependency means that the only input required in the model is the behavioural parameters of the connections. The proposed model contains six cases with a total of 36 different failure mechanisms. Two final wall behaviours were developed, and it was found that behaviour (i.e. single wall) could be achieved if the yielding in the hold-down occurred prior to yielding in the panel joints. Inversely, the other behaviour (i.e. coupled panels) was achieved if the yielding in the vertical joint occur prior to yielding in the hold-down. The analytical model was validated using a numerical model, and the results of the comparison showed very close match between the two models. The study proposed simplified design provisions with the aim to optimize the walls ductility (CP behaviour) or strength and stiffness (SW behaviour).

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