Defining parameters for buckling checks of plated structures in finite element sofware packages.

Abstract

Plated structures are widely used in many engineering structures. Most designs are poor in resisting compressive forces. Usually, the buckling phenomena observed in compressed conditions take place rather suddenly and may lead to catastrophic structural failure. Therefore it is important to know the buckling capacities of the plates and stiffeners in order to avoid premature failure. However not every model and/or analysis is suitable for an accurate buckling assessment by a FEM analysis. Buckling is a complicated phenomenon. Many properties and parameters influence the buckling strength. Most of the time, details such as imperfections, material properties or residual stresses are not included within the model. Hence, the lack of a satisfying analysis is tried to resolve with a combination of linear FEM results and standards. In the standards, just as in most literature, the behaviour of a panel is simplified by subdividing it into individual sections; plate fields and beam-columns. This study mainly aims to define the conversion of linear FEM stress results into input design stresses needed to check buckling of plated structures with the standards. The report first contains an in-depth research into what problems arise with different buckling modes and the parameters that define these problems. Furthermore several proposals for implementation of the standards are explained; plate buckling, local stiffener buckling, flexural stiffener buckling and torsional stiffener buckling. A more extensive part is about the validation of the plate buckling implementation. Linearization of in-plane stress distributions on plate fields is researched. Results show an overall allowable and good implementation method by subdividing the real stresses into longitudinal stress gradient, transverse stress gradient and remaining shear portions.