Web Distortion and Flexural-Torsional Buckling

摘要

The mode of elastic buckling of an I-section member is usually classified as being either local or lateral. However, in a member with a slender, unstiffened web, a combined buckling mode may occur in which the web distorts and reduces the member's torsional resistance, and consequently its resistance to lateral (or flexural-torsional) buckling. In this paper, an approximate analysis of the effect of web distortion on the elastic flexural-torsional buckling of a simply supported I-section member is presented. This analysis leads to a closed form interaction equation, relating the critical uniform moment and axial load acting on the member. The buckling moments and loads determined from this equation are compared with the results of a more sophisticated finite strip analysis, and are shown to be of high accuracy. The effects of different member cross sections on distortional buckling are investigated.