Post-flexural Torsional Buckling Strength in Slender CFS Compression Members

The design equations for the ultimate global buckling strength of cold-formed steel (CFS) compression members in different design standards were originally developed for hot-rolled steel (HRS) members which normally do not undergo flexural torsional buckling (FTB). The presence of post-buckling strength for CFS compression members undergoing FTB was reported in the literature which is not accounted for in design equations. There were a few attempts to incorporate the post-FTB strength to the global buckling strength equations available in North American Standard (NAS). One of the recent proposals is to introduce a modification to global buckling strength equations by introducing an additional parameter, β which represents the relative principal second moment of areas (Ix/Iy) of the cross-section. This paper demonstrates the limitations of using parameter β for modifying the global buckling equations to account for post-buckling strength.