Prediction of the Compressive Strength of Longitudinally Stiffened Plates Undergoing Buckling Interaction

A finite element research on the ultimate strength of longitudinally stiffened plates in axial compression is presented. The longitudinally stiffened plate in compression normally buckles in one of two basic buckling modes, local or distortional. However, it may also buckle in the interacted mode between local and distortional buckling according to the section geometries. Finite element analyses demonstrated that the basic buckling mode was interacted with each other according to the stiffness of the longitudinal stiffeners and the width-thickness ratio of sub-panels. The adverse interaction between local and distortional buckling of stiffened plates can not be accounted for in the current design specifications. A simple strength formula for the Direct Strength Method (DSM) has been proposed to account for the interaction between local and distortional buckling of stiffened plates. The DSM does not need computing the effective area of each plate elements and uses the gross area of the whole plate and the design strength formula based on the various numerical and test results. The DSM proposed was compared with the test results conducted previously for verification.