The application of carbon fiber reinforced polymers (CFRP) is one of the effective retrofitting and strengthening methods that is used worldwide and is starting to be used in Turkey as well because they have high strength and high modulus in the fiber direction, have very low coefficient of thermal expansion when compared to concrete and steel and are known not to corrode. Since FRPs are lightweight, their mass can be neglected when compared to concrete and steel. However, before proposing this material as an alternative for strengthening and retrofitting applications their long-term behavior should be understood because they are applied on to concrete by several layers of epoxy-based adhesives, which can be affected by change in humidity, temperature and load. Therefore, behavior of CFRP-strengthened structures in varying temperature and humidity conditions must be investigated. In this dissertation, behavior of CFRP confined cylindrical and prismatic concrete specimens having square cross-section were investigated under sustained compressive loads, dry and wet heating-cooling cycles, and outdoor exposures under direct sunlight, to determine the possible changes in their mechanical properties. Sustained loads were applied as the 40% and 50% of their confined axial load capacity. In addition to the sustained loads, specimens were subjected to 200 heating-cooling cycles between -10&deg / C to 50&deg / C. In order to understand the change in behavior of CFRP confined concrete specimens better, they were divided in six groups. A single effect was investigated in each group. After aging tests mechanical properties of the specimens were recorded via monotonic uniaxial loading. It was observed that temperature cycles had little effect on behavior but sustained loads changed the shape of the axial stress-strain diagram and resulted in a dramatic decrease in ultimate strain. Based on the test results and also using the data of similar studies available in the literature, strength and strain models considering the exposures as independent parameters were established and finally axial stress-strain curve was tried to be predicted.

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[pt] A maioria dos métodos de laboratório disponível para a avaliação das tensões horizontais in situ é aplicável somente a solos normalmente adensados ou levemente sobreadensados. A avaliação do estado de tensões efetivas in situ de solos rijos sobreadensados e, conseqüentemente o desempenho tensão-deformação desses solos, envolve um considerável grau de incertezas devido à dificuldade na determinação da tensão lateral de campo. Apresenta-se, neste trabalho, resultados de um estudo experimental de laboratório que teve por objetivo: obter informações de compressibilidade do material e do comportamento tensão- deformação em condições não drenadas, e avaliar a tensão lateral efetiva in situ de um solo da Formação Guabirotuba, que se situa na Bacia Sedimentar de Curitiba. Propõe-se uma nova metodologia experimental para a determinação da tensão lateral de campo, tendo em vista que as metodologias apresentadas na literatura não são adequadas para solos rijos e sobreadensados. Na primeira fase deste estudo foram realizados ensaios de caracterização completa, análise mineralógica e de microscopia eletrônica. Após a caracterização física do material, passou-se ao estudo do comportamento tensãodeformação e resistência com a execução de ensaios triaxiais e edométricos. Foram executados ensaios triaxiais não drenados com corpos de prova adensados isotropicamente, e ensaios de adensamento com velocidade constante de deformação de um solo intacto da Formação Guabirotuba e de um solo da mesma Formação, porém laterizado. O método proposto para a avaliação da tensão lateral de campo está baseado no conceito de superfícies de escoamento, ou seja, a história de tensões de um solo está relacionada com seu comportamento tensão-deformação-rigidez, e, portanto, pode ser determinado através desta. Foram executados ensaios triaxiais com trajetória de tensões controlada, de acordo com a metodologia proposta, em amostras indeformadas desta Formação. / [en] Most of the available laboratory methods for the evaluation of the in situ horizontal stresses are usually applicable only to normally consolidated or slightly overconsolidated soils. The assessment of the in situ effective stresses state of rigid, overconsolidated soils, and consequently of their stress-strain performance , involves a considerable degree of uncertainty due to the difficulty in the determination of the field lateral stresses . This thesis presents the results of an experimental study performed in the laboratory to gather information on compressibility and undrained stress-strain characteristics, and to determine the in situ effective lateral stress of a soil from the Guabirotuba Formation, at the Curitiba Sedimentary Basin, in the South of Brasil. The first stage of the study comprised characterization tests, mineralogical analysis and electronic microscopy evaluations. After the physical characterization of the material, it was carried out the study on the stress-strain-strength behaviour through undrained triaxial tests and oedometric tests with constant rate of deformation. Unweathred and latherized soil samples from the Guabirotuba formation were used in such investigations. As the methodologies presented in the literature are not appropriate for rigid, overconsolidated soils, a new experimental technique for the determination of the in situ lateral stress was proposed. The proposed method is based on the concept of yield surfaces. The stress history of a soil is related to its stress-strain behaviour and, therefore, can be inferred through monitoring changes of the soil rigidity under a given stress path. Following the proposed methodology, stress-path controlled triaxial tests with internal measurement of axial strains were performed in undisturbed samples of the Guabirotuba Formation, providing an assessment of the field lateral stress of the material. / [es] La mayoría de los métodos de laboratorio disponibles para la evaluación de las tensiones horizontales in situ puede ser aplicado solamente a suelos normalmente adensados o levemente sobreadensados. La evaluación del estado de tensiones efectivas in situ de suelos duros sobreadensados y, consecuentemente el desempeño tensión deformación de esos suelos, involucra un considerable grado de incertezas debido a la dificuldad en la determinación de la tensión lateral de campo. En este trabajo se presentan resultados de un estudio experimental de laboratorio realizado con el objetivo de obtener informaciones de compresibilidad del material y del comportamiento tensión deformación en condiciones no drenadas, y evaluar la tensión lateral efectiva in situ de un suelo de la Formación Guabirotuba, situada en la Bacia Sedimentar de Curitiba. Se propone una nueva metodología experimental para la determinación de la tensión lateral de campo, considerando que las metodologias presentadas en la literatura no son adequadas para suelos duros y sobreadensados. En la primera fase de este estudio fueron realizados ensayos de caracterización completa, análisis mineralógica y de microscopia electrónica. Después la caracterización física del material, se pasó al estudio del comportamiento tensión-deformación y resistencia con la ejecución de ensayos triaxiales y edométricos. Fueron ejecutados ensayos triaxiales no drenados con cuerpos de prueba adensados isotrópicamente, y ensayos de adensamento con velocidad constante de deformación de un suelo intacto de la Formación Guabirotuba y de un suelo de la misma Formación, pero laterizado. El método propuesto para la evaluación de la tensión lateral de campo está basado en el concepto de superfícies de vaciado, o sea, la historía de tensiones de un suelo está relacionada con su comportamiento tensión-deformación-rígidez, y, por tanto, puede ser determinado a través de ésta. Fueron ejecutados ensayos triaxiales con trayectoria de tensiones controlada, de acuerdo con la metodología propuesta, en muestras indeformadas de esta Formación.

Com o crescente uso de estruturas de membrana tensionada, as relações tensãodeformação do tecido utilizado em sua fabricação devem ser bem entendidas. Deste modo, esta dissertação apresenta um estudo sobre o comportamento mecânico de um tecido arquitetônico PTFE-vidro, ressaltando seu complexo mecanismo de deformação que engloba efeitos de anisotropia, não-linearidade física, troca de ondulações, histerese, remoção do espaçamento entre os fios e variação de temperatura. Diferentes métodos para modelagem do material foram estudados, com ênfase no modelo de material ortótropo representado por um funcional energia de deformação hiperelástico. Além disso, vários protocolos para ensaios de tração em tecidos recobertos foram analisados e uma série de ensaios biaxiais com amostras cruciformes foram realizados no Centro de Pesquisa e Desenvolvimento da Birdair, Inc. Um determinado funcional energia de deformação foi então ajustado aos dados de campo obtidos nestes testes, cujos resultados foram então comparados diretamente aos dados obtidos em campo e a um ajuste direto de uma superfície suave tensão-deformação. A performance do modelo ajustado não se encontra ainda em um patamar de aplicação industrial, entretanto este estudo permite um entendimento global dos mecanismos de deformação do tecido PTFEvidro, fornecendo também uma massa de dados consistentes que podem ser utilizados em situações práticas. / Considering the growing use of tensioned membrane structures, the stress-strain relation of the fabric used on its construction must be well understood. This dissertation presents a study of the mechanical behavior of a PTFE coated fiberglass fabric, emphasizing its complex strain mechanism which is influenced by the material anisotropy, physical non-linearity, crimp interchange, hysteresis, removal of yarn spacing and changes in temperature. Different material models were studied, focusing on an orthotropic material model represented by a hyperelastic strain energy function. Also, different test protocols were reviewed and a series of biaxial tests on cruciform samples were performed at the Birdair, Inc.s Research and Development Center. A strain energy function was adjusted to the collected data and than its results compared to the data itself and to another stress-strain function directly adjusted to the data. The performance of the strain-energy function chosen is not on a level of industrial application; however this study gives a global understanding of the PTFE coated fiberglass strain mechanism and also provides a consistent database that may be used on real situations.

This dissertation presents a numerical study using molecular dynamic simulations that interrogates the polymer structure as it is strained continuously in time and correlates it with the stress developed in it. We investigate the role of external control variables such as temperature, strain-rate, chain length, and density. At temperatures higher than glass transition, stress anisotropy is reduced even though bond stretch is greater at higher temperatures. There is a significant increase in stress level with increasing density. At faster rates of loading stress anisotropy increases. Deformation is mostly due to bond stretch and bond bending rather than overall shape and size. Stress levels increase with longer chain length. Cross-linkers beyond a critical value of functionality cause increased constraint on the motion of monomers and uniaxial stress developed increases. Stacking of chains also plays a dominant role in terms of excluded volume interactions. Low density, high temperature, low values of functionality of cross-linkers, and short chain length, facilitate chain uncoiling and chain slipping in crosslinked polymers. Uniaxial stress in linear polymers, on the other hand, is only mildly in uenced by temperature. Sinusoidal strain loading clearly reveals the viscoelastic nature of polymers. Internal structural parameters of the chains such as bond length, bond angle show hysteresis during loading and unloading. However, parameters representing overall size and shape of chains do not display any hysteresis. Small size magnetic particles and their small volume fractions in polymers show no signi cant e ect of applied external magnetic eld on anisotropic stress. Stress increases with lowering temperature, increasing density, decreasing volume fraction of magnetic particles, and increasing chain length

This diploma thesis deals with stress-strain analysis of inferious limb fixator type Poldi VII and tibia, whereupon is applied. In work is discribed creation of a geometry model of fixator and tibia, her discretization, loading and solving. Tibia was load by torsional moment and his magnitude was 10Nm. Then was perform a numerical solution in FEM system ANSYS Workbench 11.0. Further was effect biomechanical study about osification of broken part. Tibia was load by force, which evokes upright standing on both limbs.

This diploma thesis deals with the determination of lifetime and computational modeling of stress strain states arising in the body of the steam turbine valve. Due to the high temperature of the inlet steam, the creep of the material which fundamentally affects its final lifetime is also considered in the calculation. The lifetime is evaluated by four different procedures using the finite element method via the ANSYS software. The results are compared at the end of this work. One of the chapters is focused on solving the problem of the creep in the ANSYS software environment.

This master’s thesis deals with the analysis of stress, fatigue and the assessment of frost effects in program ALIZE as it is prescribed in norm NFP 98-086 and comparing with the regulation TP 170 Designing roadways of roads and program LayEps.

This diploma thesis deals with stress-strain analysis of healthy and save tooth. Defor-mation and stress of tooth system with a part of jawbone was solved by calculating method, FEM in computing system ANSYS Workbench 11. Stress-strain analysis of save of tooth was performed in twenty-five ways describing various classes and sizes of cavity, filling material and model of connection between the filling and the tooth.