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Modelling the influence of manufacturing parameters on variation of residual stresses in quenched partsSedighi, Mohammad January 1998 (has links)
No description available.
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Simulation of thermal stresses in vacuum arc remelting processWani, Nitin Yashwant January 1995 (has links)
No description available.
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Failure Analysis of the World Trade Center 5 BuildingLaMalva, Kevin Joseph 29 April 2007 (has links)
This project involves a failure analysis of the internal structural collapse that occurred in World Trade Center 5 (WTC 5) due to fire exposure alone on September 11, 2001. It is hypothesized that the steel column-tree assembly failed during the heating phase of the fire. The results of this research have serious and far-reaching implications, for this method of construction is utilized in approximately 20,000 existing buildings and continues to be very popular. Catastrophic failure during the heating phase of a fire would endanger the lives of firefighters and building occupants undergoing extended egress times (e.g., high-rise buildings), or relying upon defend-in-place strategies (e.g., hospitals). Computer software was used to reconstruct the fire event and predict the structural performance of the assembly when exposed to the fire. Results from a finite element, thermal-stress model confirms this hypothesis, for it is concluded that the catastrophic, progressive structural collapse occurred approximately 2 hours into the fire exposure.
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Uma contribuição ao estudo do comportamento termomecânico de estruturas maciças de concreto. modelagem viscoelástica linear e aplicaçõesSantos, Sérgio Botassi dos 06 April 2004 (has links)
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Previous issue date: 2004-04-06 / O estudo realizado nesta dissertação é motivado principalmente pelo interesse em se avaliar a
resposta térmica e tensional em estruturas de concreto massa nas primeiras idades
considerando a viscoeleasticidade linear do material. Neste trabalho desenvolvem-se modelos
numérico-computacionais e implementam-se os softwares PFEM_2DT e PFEM_2DAT, de
análise térmica e de tensões no domínio bidimensional, respectivamente.
Inicialmente, foi realizada uma revisão bibliográfica do problema termomecânico
considerando os mecanismos e modelos físicos para a representação do mesmo, utilizando-se
de ferramentas matemáticas e artifícios numéricos para a resolução do problema. Foram
pesquisados ainda os parâmetros influentes na análise de temperaturas e de tensões no
concreto massa, destacando-se as propriedades viscoelásticas de fluência e retração onde de
forma resumida, porém esclarecedora, foram descritos seus principais conceitos, causas e
efeitos bem como alguns dos principais modelos de representação dessas deformações
diferidas.
Por meio desses estudos teóricos e das conseqüentes implementações computacionais, foram
analisadas diferentes estruturas de concreto através dos programas computacionais
desenvolvidos e, posteriormente, realizadas comparações com resultados experimentais e
numéricos obtidos por outros pesquisadores objetivando validar os aplicativos.
Na elaboração deste software fez-se uso do novo paradigma de programação Programação
Orientada a Objetos, associado à resolução de sistemas de equações lineares pelo Método dos
Gradientes Conjugados.
Analisou-se o comportamento das temperaturas de diferentes estruturas sujeitas ao calor interno gerado no concreto sob a influência das condições ambientais, que permitem que esse
calor seja dissipado, gerando como conseqüência, distribuições de temperatura não-lineares
no interior da estrutura. Nos estudos tensionais das estruturas de concreto massa analisadas nesta dissertação pôde-se avaliar a evolução das tensões de origem térmica considerando o material viscoelástico linear,
comparando-as com a resistência à tração do material. Por fim, efetuaram-se estudos comparativos de tensões em um bloco de concreto massa utilizando os modelos elástico e
viscoelástico linear, avaliando o nível de importância e o grau de magnitude da consideração dos efeitos diferidos associados quando da análise do comportamento termomecânico de estruturas maciças de concreto em fase de construção. / The study accomplished in this dissertation is motivated mainly by the interest in evaluating
the temperature and stress field in mass concrete structures at first ages considering material s
linear viscoeleasticity. The development and implementation of numeric-computational
models are also scope of this work by means the softwares PFEM_2DT and PFEM_2DAT,
of thermal stress analysis in the two-dimensional domain.
Initially at first step, the bibliographic revision of the thermomechanical problem was
accomplished considering physical mechanisms and models for its representation, using
mathematical tools and numeric artifices for the resolution of the problem. The influential
parameters in the analysis of temperatures and stresses in the mass concrete were also
researched, standing out to the creep and shrinkage rheological properties, where in a summarized and elucidated way, its main concepts, causes and effects were described, as well as some of the main representation models of those differed deformations. Considering theoretical studies and the consequent computer implementations, different concrete structures were analyzed through the developed softwares, and compared with experimental and numeric results obtained by other researchers with the objective of validating the applications. In the elaboration of this software was made use of the new programming paradigm Object-Oriented Programming, associated to the resolution of linear systems equations for the Method of the Conjugated Gradients. The temperature field s behavior of different structures subject to the internal heat into the concrete was analyzed, under the influence of the environmental conditions, that allows the heat to be dissipated, generating as consequence, non- linear temperature distributions inside the structure.
The termomechanic problems studied in mass concrete structures were analyzed in this dissertation, where the thermal stresses behaviour could be evaluated considering the linear viscoelasticity properties of the material, comparing them with the tensile strength of the material. Finally, comparative studies of the stresses in a mass concrete block were executed using elastic models and linear viscoelasticity, evaluating the importance and magnitude
levels of the associated differed effects in the termomechanic behavior analysis of solid concrete structures in a construction stage.
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