Influence of Secondary Buckling on the Buckling/Plastic Collapse Behaviour of Plates

Abstract

Recently, to use the high tensile strength steel more effectively for a ship hull, some feasibility studies have been performed on a ship structural design which allows a local panel buckling. Such a design method needs an accurate evaluation of the post-buckling behaviour of plates. It is well known that a thin plate which deformed after the primary buckling may snap to another equilibrium state of a different deflection mode. This is called a secondary buckling.In the previous paper, the authors performed an elastic large deflection analysis for a rectangular plate under uniaxial compression and discussed the influence of initial deflections on the elastic secondary buckling behaviour of the plates. In this paper, elastoplastic large deflection analyses are performed using the finite element method, and the influence of the secondary buckling on the buckling/plastic collapse behaviour of rectangular plates is investigated. The dynamic effects of secondary buckling are also studied. It has been found that : (1) Dynamic analysis must be performed to simulate snap-through behaviour due to the secondary buckling exactly. However, when free from large plasticity effects, static analyses can give rational estimates of the behaviours except in the vicinity of snap-through path.(2) The influence of a secondary buckling on the ultimate strength of thin plates depends on the relationship between an initial yield strength and an elastic secondary buckling strength.(3) Ultimate strength of thin rectangular plates is sometimes attained by a secondary buckling. Secondary buckling reduces a load carrying capacity of plates even when it takes place in the post-ultimate strength range.(4) The change in the deflection behaviour owing to the secondary buckling is more complicated for the plates of larger aspect ratio.(5) Elastoplastic secondary buckling strength can be predicted by the elastically calculated equilibrium path after primary buckling.