Distortional buckling of cold-formed steel channels bent about the minor axis

The direct strength method (DSM) is an alternative design method to the effective width method in calculating the bending moment capacity of cold-formed steel members. The DSM uses elastic buckling moments with an appropriate strength curve to calculate the design moment capacity and avoids tedious plate by plate calculations to determine the effective width. However, the current DSM design moment equations have been calibrated for channel and zed sections bent about the major axis and may not be appropriate for cold-formed steel channels bent about the minor axis. In this paper, elastic finite strip buckling analysis, linear buckling and non-linear finite element analyses on cold-formed steel channels bent about the minor axis with the lips in compression are described. The elastic finite strip buckling analysis is used to investigate the buckling modes while the non-linear finite element analysis calculates the ultimate moment for these members. The aim is to compare the ultimate moments calculated by the non-linear finite element analysis with the current DSM design equations. A new DSM design equation is presented for the distortional buckling of cold-formed steel channels bent about the minor axis with the lips in compression.