DEMIN - Departamento de Engenharia de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/510
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3 resultados
Resultados da Pesquisa
Item Nonlinear resonance analysis of slender portal frames under base excitation.(2017) Muñoz, Luis Fernando Paullo; Gonçalves, Paulo Batista; Silveira, Ricardo Azoubel da Mota; Silva, Andréa Regina Dias daThe dynamic nonlinear response and stability of slender structures in the main resonance regions are a topic of importance in structural analysis. In complex problems, the determination of the response in the frequency domain indirectly obtained through analyses in time domain can lead to huge computational effort in large systems. In nonlinear cases, the response in the frequency domain becomes even more cumbersome because of the possibility of multiple solutions for certain forcing frequencies. Those solutions can be stable and unstable, in particular saddle-node bifurcation at the turning points along the resonance curves. In this work, an incremental technique for direct calculation of the nonlinear response in frequency domain of plane frames subjected to base excitation is proposed. The transformation of equations of motion to the frequency domain is made through the harmonic balance method in conjunction with the Galerkin method. The resulting system of nonlinear equations in terms of the modal amplitudes and forcing frequency is solved by the Newton-Raphson method together with an arc-length procedure to obtain the nonlinear resonance curves. Suitable examples are presented, and the influence of the frame geometric parameters and basemotion on the nonlinear resonance curves is investigated.Item Nonlinear analysis of two-dimensional steel, reinforced concrete and composite steel-concrete structures via coupling SCM/RPHM.(2017) Lemes, Igor José Mendes; Silveira, Ricardo Azoubel da Mota; Silva, Andréa Regina Dias da; Castro, Paulo de Tarso AmorimThis paper presents a numerical methodology based on Euler-Bernoulli theory to simulate the steel, reinforced concrete and composite structures 2D nonlinear behavior. The displacement-based numerical formulation uses the principles of the Refined Plastic Hinge Method (RPHM) to simulate the concentrated plasticity at the corotational finite element nodal points. In order to present a more realistic simulation of the axial and flexural stiffness degradation, the RPHM is coupled with the Strain Compatibility Method (SCM), where the materials constitutive relations are used explicitly. The SCM is also applied in determining the structural elements’ bearing capacity. Moreover, the present approach is not limited to a specific cross-sectional typology. Also addressed are residual stress models; these are introduced explicitly in subareas of steel profiles generated by a two-dimensional cross-sectional discretization. It should be emphasized that this study considers full interaction between the materials. Finally, the results obtained are compared with numerical and experimental findings available in the literature.Item Nonlinear equilibrium and stability analysis of axially loaded piles under bilateral contact constraints.(2015) Silveira, Ricardo Azoubel da Mota; Maciel, Felipe Vieira; Silva, Andréa Regina Dias da; Machado, Fernando Carlos Scheffer; Nogueira, Christianne de LyraThis paper presents a nonlinear stability analysis of piles under bilateral contact constraints imposed by a geological medium (soil or rock). To solve this contact problem, the paper proposes a general numerical methodology, based on the finite element meth-od (FEM). In this context, a geometrically nonlinear beam-column element is used to model the pile while the geological medium can be idealized as discrete (spring) or continuum (Winkler and Pas-ternak) foundation elements. Foundation elements are supposed to react under tension and compression, so during the deformation process the structural elements are subjected to bilateral contact constraints. The errors along the equilibrium paths are minimized and the convoluted nonlinear equilibrium paths are made tracea-ble through the use of an updated Lagrangian formulation and a Newton-Raphson scheme working with the generalized displace-ment technique. The study offers stability analyses of three prob-lems involving piles under bilateral contact constraints. The anal-yses show that in the evaluation of critical loads a great influence is wielded by the instability modes. Also, the structural system stiffness can be highly influenced by the representative model of the soil.