Generalised Beam Theory to Analyse the Buckling Behaviour of Thin-Walled Steel Members with “Branched” Cross-Sections

This paper presents the derivation and illustrates the application of a Generalised Beam Theory (GBT) developed to analyse the buckling behaviour of a class of thin-walled steel members displaying (open) "branched" cross-sections. Following a very brief review of the conventional GBT, the modifications that must be incorporated into its cross-section analysis procedure, in order to handle the "branching" points, are described and discussed in detail. Particular attention is paid to the choice and characterisation of the appropriate warping and flexural "elementary functions". The derived equations are then used to study the local and global buckling behaviour of simply supported columns and beams with a singly symmetric I-section. The GBT results are validated through a comparison with numerical values obtained from finite strip and finite element analyses (the latter employ shell elements to discretise the members).