Cold-formed steel columns undergoing local-distortional coupling: Behaviour and direct strength prediction against interactive failure

This paper reports the results of an investigation on the structural behaviour and Direct Strength Method (DSM) design of cold-formed steel columns affected by local-distortional coupling interaction, aimed at extending findings unveiled earlier for lipped channels to other cross-section shapes, namely, hat, zed and rack-sections. Following a brief presentation of the most relevant aspects concerning the post-buckling behaviour and strength of columns with those cross-section shapes and identical local and distortional critical buckling stresses, the paper addresses the assembly of a significant column ultimate strength data bank, concerning fixed-ended hat, zed and rack-section columns undergoing strong local-distortional interaction and exhibiting several geometries (cross-section dimensions and lengths) and yield stresses. Then, these ultimate strength data are used to assess the performance of the existing DSM approaches to design columns against local-distortional interactive failures. It is shown that a novel DSM design approach, recently developed and validated in the context of cold-formed steel fixed-ended lipped channel columns affected by local-distortional interaction, can also be successfully applied to hat, zed and rack-section columns under the same circumstances (i.e., exhibiting similar interactive failures).