Performance of Plain and Lipped Cold-Formed Channel Sections in Axial Compression

Cold-formed steel (CFS) members are finding increasing acceptance within the construction markets as primary structural elements. Among the members most commonly used is the open channel members that offers simple fabrication and connection. This paper throws light into the behaviour of both lipped and plain channel members with different slenderness ratios comparing with the various international codes of practice for cold-formed sections subjected to compression. The various standards includes, the Indian Standard Code of Practice for use of Cold-formed Light Steel Structural Members-IS:801, the British Code of Practice for Design of Cold-formed Sections-BS:5950 (Part 5) and the North American Standard-NAS Manual. Finite element analysis (FEA) on the post-buckling behaviour of channels under axial compression is compared with the various codal specifications. The load versus axial shortening behaviour of sections is obtained by using a non-linear FEA. The load carrying capacities of plain and lipped channels for seven different slenderness ratios are compared. Load versus axial shortening behaviour for the plain and lipped channels are also presented. The mode of failure observed is combined local buckling in the case of unstiffened element, flexural buckling about minor axis for the slenderness ratio of 30 to 100 and for sections having slenderness ratio 120 to 200 overall flexural buckling about the weak axis. FEA is useful as an alternative and complementary method to the design of CFS structures and predicts the ultimate load with reasonable accuracy.