07.36: Strength of combined sigma cold formed section columns

Abstract

ABSTRACTThe high strength‐to‐weight ratios of cold‐formed steel framing systems make them competitive in modern construction markets. Generally, Cold‐formed steel sections are shaped to suit the particular application. Lipped channel sections are the most used sections, however, sigma sections need more effort in fabrication but they have high strength‐weight ratios compared with the lipped channel sections. In this paper, the strength of pined‐pined columns composed of combined back to back sigma cold formed sections is studied numerically by a non‐linear finite element analysis. Four nodes isoparametric shell element that allows both geometric and material non‐linarites is used. The effect of geometric imperfections is included in the model. The boundary conditions considered allow the columns ends to rotate about the major and minor axis. The parameters studied include, the cross section proportions such as the flange, web, and lip dimensions as well as the connectors spacing. The two sections are assumed to be connected through their webs. Further, several columns heights are considered to study the different modes of failure. The numerical model is validated by experimental study carried out by the authors. Findings reflect that sectional (local/distortional) buckling governs the failure shape of short columns. Finally, the results have been compared with the predicted strengths determined by the Eurocode‐3 and the American specifications (AISI, DSM).