Evaluation of Direct Strength Method for CFS Compression Members without Stiffeners

Abstract

The axial compressive strength of the cold-formed steel (CFS) members with edge or intermediate stiffener is affected by interaction of local, distortional and overall buckling. In order to overcome the tedious and time consuming nature of the traditional Effective Section method of evaluating strength of such members, direct strength method (DSM) has been advanced recently. However, the DSM has not been adequately evaluated for calculating the strength of compression members (such as tubular, plain channel, and I-sections) consisting of only stiffened and unstiffened elements, without either lip stiffener or intermediate stiffener. These members experience interaction of only local and overall buckling before failure. In this paper, results of a study on the suitability of DSM to evaluate the compressive strength of plain channel, I and rectangular tubular members is presented. Extensive experimental data in literature and additional data generated using currently accepted effective width method (based on better estimate of local buckling stress evaluated considering element interaction), are used in this study. It is found that DSM can be used to evaluate strength of such members also.