Interaction of Local, Distortional, and Global Buckling in CFS Lipped Channel Compression Members

Abstract

The strength of thin-walled cold formed steel (CFS) lipped channel compression members may be governed by yielding, local, distortional, or global buckling or any possible interaction among these buckling modes. The interaction between buckling modes reduces the strength of thin-walled members to values below its strengths as affected by any one of the independent buckling modes. The direct strength method (DSM), which significantly simplified the evaluation of design strength of CFS members, recognizes this reduction in strength caused by interaction of buckling modes, but explicitly handles local-global interaction only. A simple and accurate interaction equation that accounts for interaction between all possible buckling failure modes for CFS lipped channel compression members is proposed in this paper. The method requires the use of modified DSM equations for evaluating the strength under the different independent buckling modes (local and distortional). The proposed interaction equation is validated with both experimental as well as numerical results.