Mestrado em Engenharia Civil (EEC)
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Navegando Mestrado em Engenharia Civil (EEC) por Por Orientador "ALMEIDA, Sylvia Regina Mesquita de"
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Item Otimização de estruturas reticuladas planas com comportamento geometricamente não linear(Universidade Federal de Goiás, 2006-10-20) ASSIS, Lilian Pureza de; ALMEIDA, Sylvia Regina Mesquita de; http://lattes.cnpq.br/1855764480221018The aim of this work is to present a formulation and corresponding computational implementation for sizing optimization of plane frames and cable-stayed columns considering geometric non liner behavior. The structural analysis is based on the finite element method using the updated lagrangian approach for plane frame and cable elements, which are represented by plane truss elements. The non linear system is solved by the Newton-Raphson method coupled to load increment strategies such as the arch length method and the generalized displacement parameter method, which allow the algorithm to transpose any critical point that happen to appear along the equilibrium path. In the optimization process the design variables are the heights of the crosssection of the frame elements, the objective function represents the volume of the structure and the constraints impose limits to displacements and critical load. Lateral constraints impose limits to the design variables. The finite difference method is used in the sensitivity analysis of the displacement and critical load constraints. The optimization process is carried out using three different optimization strategies: the sequential quadratic programming algorithm; the interior points algorithm; and the branch and bound method. Some numerical experiments are carried out so as to test the analysis and the sensitivity strategies. Numerical experiments are presented to show the validity of the implementation presented in this dissertation.Item Busca da superfície de ruptura crítica na análise tridimensional de estabilidade de taludes(Universidade Federal de Goiás, 2010-08-24) SOARES, Patrícia Maria de Carvalho; GITIRANA JUNIOR, Gilson de Farias Neves; http://lattes.cnpq.br/4710728908810849; ALMEIDA, Sylvia Regina Mesquita de; http://lattes.cnpq.br/1855764480221018The main objective is to develop, implement and evaluate a method to search for surfaces in order to determine the three-dimensional critical surface, corresponding to the lowest factor of safety of the embankment. They are also objectives of this study to evaluate the influence of the strength and elastic parameters the geometry of the slope safety factor and the 3D shape and position of the failure surface, as well as to evaluate the relationship between 2D and 3D safety factors. It was implemented an optimization routine in FORTRAN that performs the search for critical failure surface, whose safety factor is calculated by SAFE-3D program. The SAFE-3D program uses voltages coming from an elastic stress analysis performed by FlexPDE program, which uses the finite element method and provides the shear and normal stresses acting on the slope necessary to calculate the safety factor. For the analysis has been adopted as the ellipsoid shape of the rupture surface. The search method implemented examines safety factors obtained for a finite set of solutions and design variables as the coordinates of the center of the ellipsoid and the size of its three semi-axes. The search algorithm is implemented in successive tests of the factor of safety by SAFE-3D program, varying the position and dimensions of the ellipsoid for the determination of lower safety factor of slope. It was analyzed two examples of slopes, a symmetrical slope which varied the parameters of soil strength and the angle of the slope face and the other was the historic case of slipping Lodalen. The methodology implemented was successful in finding the critical failure surface, achieving consistency in results. The Poisson's ratio was very influential in the results of the safety factors of three-dimensional critical surfaces. It was also observed that there is less difference between the safety factors when keeping the shear stress unacceptable when these tensions are eliminated there is a closeness among the factors of safety.