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URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/513

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Autor: search.filters.author.Araújo, José Milton deData final: 2015

Resultados da Pesquisa

Agora exibindo 1 - 10 de 29
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    On stochastic finite elements for structural analysis
    (1994) Araújo, José Milton de; Awruch, Armando Miguel
    This paper considers the stochastic finite element analysis of structures resulting from random spatial variability of material properties, when they are subjected to loads of deterministic nature. Direct Monte Carlo simulation, Monte Carlo with Neumann expansion of the stiffness matrix and Taylor series expansion combined with the classical finite element approach are applied and compared with respect to accuracy and computational efficiency. Dynamic and non-linear problems are also included.
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    Optimization of newton-raphson methods in RC nonlinear analysis
    (1989) Araújo, José Milton de
    The Newton-Raphson method is used for the nonlinear analysis of reinforced concrete structures. Three extrapolation formulas for displacements are developed in order to accelerate the convergence of the iterative scheme. The computing time and the number of necessary iterations for each proposed alternative are compared.
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    An objective cracking criterion for the analysis of concrete dams
    (1996) Araújo, José Milton de; Awruch, Armando Miguel
    Cracking analysis by the finite element method may be accomplished using a continuum damage theory, but results are strongly affected by the adopted finite element mesh. A reduced tensile strength has been proposed in order to obtain objective results; however this approach may still be dependent on the adopted finite element mesh. An alternative model for concrete cracking, which is independent of the finite element mesh and especially suitable for the analysis of concrete dams, is proposed in this work.
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    Probabilistic finite element analysis of concrete gravity dams
    (1998) Araújo, José Milton de; Awruch, Armando Miguel
    A methodology for the probabilistic analysis of concrete gravity dams is presented, Concrete properties and seismic excitation are considered as random variables. The seismic excitation is considered as a non-stationary stochastic process which is artificially generated. Concrete properties have random variations over the spatial domain. Structural response is obtained employing the finite element method to solve the equations of motion of the coupled system dam-reservoir-foundation. Structural safety is evaluated with respect to the main failure modes (cracking, concrete crushing and sliding at the dam-foundation interface) using the Monte Carlo method.
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    Cracking safety evaluation on gravity concrete dams during the construction phase
    (1998) Araújo, José Milton de; Awruch, Armando Miguel
    The cracking phenomenon in concrete gravity dams during the construction phase is analysed in this work. Stresses due to the self-weight of the dam, thermal gradients, creep and drying shrinkage are computed, taking into account the different stages of the construction process. A twodimensional constitutive model considering time dependent and temperature dependent mechanical properties is adopted for the concrete. Safety against cracking is obtained using a criterion independent of the finite element mesh.
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    Probabilistic analysis of reinforced concrete columns
    (2001) Araújo, José Milton de
    The subject of this work is the probabilistic finite element analysis of reinforced concrete columns. Concrete properties are represented as homogeneous Gaussian random fields. The yield stress and position of steel reinforcement, dimensions of the column cross-section and axial load are considered as random variables. The Monte Carlo method is employed to obtain expected values and standard deviations of the rupture load. The partial safety factors method is used for columns design and structural safety is evaluated by means of the reliability index, which is obtained through simulations. The effects of main parameters on the reliability index are investigated. It is shown that the correlation length of random fields for concrete properties may have a significant effect on reliability. Therefore, simplified procedures, which do not consider spatial variations of concrete properties are inappropriate for safety analysis.
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    Considerações sobre a rigidez à torção das lajes nervuradas de concreto armado
    (2005) Araújo, José Milton de
    Neste trabalho é feita uma análise do comportamento das lajes nervuradas de concreto armado. Uma série de resultados experimentais descritos por outros autores é utilizada para verificar os modelos de cálculo usuais. A partir deste estudo, fica demonstrado que as lajes nervuradas de concreto armado possuem elevada rigidez à torção e se comportam de modo muito semelhante às lajes maciças. Assim, pode-se fazer o cálculo através do modelo de laje maciça equivalente, conforme é estabelecido nas principais normas de projeto.
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    Modelo bilinear para análise de lajes de concreto armado
    (2006) Araújo, José Milton de
    Neste trabalho apresenta-se um método bilinear para análise de lajes maciças e de lajes nervuradas de concreto armado. O modelo permite obter as deformações das lajes no estádio I e no estádio II. Para as lajes nervuradas, emprega-se o conceito de espessura equivalente. A comparação com resultados experimentais demonstra a eficiência do modelo proposto.
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    Processos simplificados para cálculo de flechas de vigas de concreto armado
    (2004) Araújo, José Milton de
    O objetivo deste trabalho é avaliar a precisão de alguns métodos simplificados para o cálculo de flechas em vigas de concreto armado. Para isto, desenvolve-se um modelo para análise não-linear, o qual é utilizado na aferição dos processos simplificados. Os métodos simplificados analisados são o método bilinear do CEB, uma fórmula prática apresentada no código modelo CEB-FIP/90 e o método do ACI, adotado na NBR-6118. Os resultados obtidos indicam que este último método não deve ser utilizado para o cálculo das flechas de longa duração das vigas de concreto armado.
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    Simplified procedures for calculation of instantaneous and long-term deflections of reinforced concrete beams
    (2005) Araújo, José Milton de
    The simplified methods of CEB and of ACI for prediction of deflections of reinforced concrete beams are analyzed in this work. Obtained results with those methods are compared with those obtained through a nonlinear analysis. Additional deflections due to creep and shrinkage are considered in the study. The obtained results indicate that the two simplified methods are appropriate for calculation of instantaneous deflections of reinforced concrete beams. The method of CEB also supplies good results when creep and shrinkage of concrete are considered. However, the method of ACI is not satisfactory for evaluation of long-term deflections of reinforced concrete beams.