Optimization of lip length and aspect ratio of thin channel sections under minor axes bending

• Lips in cold-formed sections reduces the premature local buckling of members.
• AISI Specifications overestimated ultimate strength for B/t ratio higher than 130.
• Cold-formed sections of B/D ratio less than 0.6 can reach full moment capacity.
• Flange width to lip length ratio should not exceed 5.0 for B/t ratio less than 130.
• FE analysis successfully predicted the flexural response of cold-formed sections.

Cold-formed steel members are used as structural members in a wide range of applications because of their simpler fabrications and high strength-to-weight ratios. Though high width-to-thickness ratio of such sections make them vulnerable to local buckling under compressive stresses, past studies have shown that these members possess inelastic reserve strengths at the ultimate stage under flexural loading. This study explore the influence of width-to-thickness ratio, lip lengths and depth-to-width (aspect) ratio on the ultimate flexural strengths of cold-formed channel sections bending about their minor axes. Finite element (FE) analyses have been conducted on 216 numbers of channel sections with varying geometric properties to investigate their ultimate resistance and mode of failure under flexural loading. The ultimate flexural strengths of these sections are theoretically predicted using the current code provisions and are compared with the exact values obtained from FE analyses. An experimental investigation has also been performed on five specimens of channel sections with and without lips to validate the FE analyses results. Based on the analysis and experimental results, the limiting values of lip lengths, aspect ratios, and width-to-thickness ratios of channel sections are discussed.