Finite element analysis and design of cold-formed steel built-up closed columns with flange and web intermediate stiffeners

This paper describes a finite element analysis (FEA) and design of cold-formed steel built-up closed sections with intermediate stiffeners in the flange and web under axial compression. A finite element model (FEM) was developed and validated using the available experimental results. The validated FEM can be used for further parametric study on strength of built-up closed columns. The results obtained from the parametric study are compared with the current direct strength method (DSM) in the North American specification of cold-formed steel structures for those specimens that failed by only local, distortional, and flexural buckling. It is shown that the current DSM is not quite suitable for the design of cold-formed steel built-up closed columns. Therefore, the improved design equations are proposed by modifying the current design equations used in the DSM for flexural, local, and distortional buckling. The reliability of current DSM and proposed DSM was assessed by reliability analysis.