On the buckling of longitudinally stiffened plates, part 1: Modal analysis by the constrained finite element method

Abstract

Abstract In this paper the elastic buckling of longitudinally stiffened plates are discussed in the light of modal deformations. Though in the analysis and design of cold-formed steel members it is a widely used approach to decompose the deformations into global, distortional, local and other deformation modes, this approach has not been used for stiffened plates yet. In this paper a large number of stiffened plates are analysed with varying the plate width and thickness, the type, size and number of stiffeners. The investigated plates are subjected to uniform or linearly varying uniaxial compression as well as shear loading. Linear buckling analyses are performed by enforcing various combinations of constraints, by using the constrained finite element method (cFEM). Regular unconstrained analyses are also completed, and the buckled shapes are identified with the help of cFEM, by calculating the participations from the characteristic deformation types. The results and tendencies are systematically and comprehensively evaluated. The completed studies reveal that though the geometric parameters and the load type have effect on the results, in the buckling modes with significant stiffener displacements the role of distortional and global modes is always crucial. This finding might have implication on the design, too. This question is discussed in detail in a companion paper, in which the Eurocode-based design of uniformly compressed stiffened plates with closed stiffeners are investigated.