Structural Performance of Cold-Formed Steel Unstiffened and Edge-Stiffened Channel Section Beams

An experimental program and numerical study on the structural performance of cold-formed steel unstiffened and edge-stiffened channel section members under major axis bending are presented in this paper. Channel sections with plain flanges and single-fold lips as well as double-fold inward and outward return lips were investigated. In total, 16 four-point bending tests were conducted on channel section specimens of steel grades G450, G500, and G550. The experimental results, including moment-curvature responses, failure modes, and bending capacities, were obtained and used for the calibration of a nonlinear finite-element model. Subsequently, based upon the validated finite-element model, a parametric study was carried out to examine the flexural behavior of thin-walled channel section beams. Underpinned by the results of 16 experiments and 222 numerical analyses obtained from this study together with 19 test data reported in the literature, it was revealed that the strength predictions determined by the direct strength method (DSM) in AISI S100 were overall conservative for the plain channel section beams, while generally unconservative for the edge-stiffened channel section beams. Additionally, the DSM-based approaches with consideration of local-distortional interaction were found to underestimate the nominal flexural strengths of the thin-walled channel section members with edge stiffeners. Hence, modified DSM formulas were recommended in this study to accurately predict bending capacities of the cold-formed steel unstiffened and edge-stiffened channel section beams under major axis bending.