Abstract
Abstract
Cold formed steel sigma sections are a part of highly optimized family of steel sections. The presence of folding lines along their webs makes them safe for resisting buckling. However, when the CFS beams are exposed to concentrated transverse loads, it increases their vulnerability to web crippling, resulting in a decrease in their moment capacity. To evaluate the performance of CFS sigma sections in applications involving concentrated loads, a finite element analysis-based investigation has been done to understand their behaviour under combined bending and web crippling loading. Out of the four web crippling load cases specified by the AISI code, only the IOF loading case was considered for the study since the IOF case involves concentrated loading at mid-span. Three sets of FE analyses were done to estimate the capacity of the CFS sigma section under pure bending, pure web crippling and combined bending and web crippling. A comprehensive numerical study has been conducted to select the optimum parameters that affect the combined bending and crippling capacity of the sigma section. The adequacy of interaction rules specified in three major cold-formed steel design standards, North American Specification (AISI S100), Australian/New Zealand Standard (AS/NZS 4600), and Eurocode 3 Part 1.3, which are developed primarily using CFS Z and C sections as a basis, has been evaluated. An empirical relation to predict the combined bending and crippling capacity of the CFS sigma section was proposed using the MARS algorithm, and its appropriateness was checked. The proposed empirical relation can be used as a design tool to predict the combined bending and web crippling capacity of the CFS sigma section for the given set of parameters.