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Title: Localized and cellular buckling in stiffened plates
Author: Farsi, Maryam
ISNI:       0000 0004 5349 2942
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2014
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Nonlinear buckling behaviour of a thin-walled simply-supported stiffened panel that has uniformly spaced longitudinal stiffeners is studied. The structure is made from a linear elastic, isotropic and homogeneous material. The panel is subjected to pure compression applied at the centroid of whole cross-section. In such structures, the nonlinear interaction can occur between a global (Euler) buckling and local plate ( i.e. the stiffener or the main plate) buckling modes. The interactive buckling behaviour is usually more unstable than when the modes are triggered individually. This can lead to a significant reduction of the load-carrying capacity. The current work focuses on the case where the stiffening is only on one side of the main plate. An analytical model of a perfect thin-walled stiffened plate is formulated based on variational principles by minimizing the total potential energy. The equations of equilibrium are then solved numerically using the continuation and bifurcation software Auto to determine the post-buckling behaviour. Cellular buckling (or snaking) is revealed analytically in such a component arising from nonlinear local global interactive buckling, perhaps for the first time. In addition, the effect of varying the rigidity at the main plate -stiffener junction is studied; a rapid erosion of the cellular buckling response is revealed by increasing the joint rigidity. The initial model is then developed by including more degrees of freedom within the stiffened panel and the introduction of global and local imperfections. The results from the analytical model are validated by the finite element (FE) method using the commercial software Abaqus as well as by comparing against some experimental results taken from the literature. To obtain a greater understanding of the drivers of the structural behaviour, parametric studies are conducted for a variety of different plate and stiffener geometries as well as an investigation into the heightened sensitivity to geometric imperfections. The worst forms of local imperfection are identified in terms of the initial amplitude, number of waves and the degree of localization. The imperfection sensitivity and the parametric studies are conducted for two limiting cases, where the main plate- stiffener joint is assumed to be fully pinned or fully rigid. A framework for establishing the zone where structural designers need to consider mode interaction carefully is presented.
Supervisor: Wadee, Ahmer Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral