An improved interactive buckling analysis of thin-walled columns having doubly symmetric sections

Abstract

A comprehensive mode interaction analysis is presented for thin-walled columns having doubly symmetric cross-sections and carrying axial compression. It is shown that as a result of interaction of overall bending with the primary local mode, a “secondary” local mode having the same wavelength as the primary, is triggered. The problem is therefore viewed as one of interaction of three modes: viz. the overall (Euler) buckling mode and the two local modes. The analysis is based on Koiter's theory of mode interaction and employs finite strips to describe local buckling deformation. The column is treated as being loaded by a prescribed end compression at the centroid and a suitably prescribed end rotation to maintain concentricity of load application. Examples are presented to compare the results of the present theory with the currently available analytical results and to examine the behavior of typical cross-sections. Of particular interest is the considerably reduced imperfection-sensitivity of columns with well-separated critical stresses in comparison to that reported earlier in published literature.