Experimental investigation of cross-sectional bending capacity of cold-formed steel channels subject to local-distortional buckling interaction

This paper describes an experimental program carried out at the University of Sheffield to investigate the interaction of local and distortional buckling in cold-formed steel lipped channel beams. The channels were arranged in a back-to-back configuration and a total of six tests, including three different cross-sectional geometries, were completed. The specimens were tested in a four-point bending configuration with simply supported boundary conditions while being laterally braced at the loading points. The beams failed in the constant moment span by interaction of local and distortional buckling. The geometric imperfections of the channels were recorded before the test using a specially designed measuring rig employing laser sensors. Tensile coupons were also extracted from the flat portions and the corner regions of the cross sections in order to determine the material properties. Comparisons showed good agreement between the experimental results and the predictions of European design guidelines and current North American provisions, whereas other DSM formulations based on the NLD and NDL concepts resulted in rather conservative predictions.