Behaviour of thin-walled intermediate stiffened back-to-back columns under axial compression

Abstract

The axial load carrying abilities and the buckling behaviour of Cold-Formed Steel (CFS) Stiffened Built-up Columns (SBC) has been presented in this paper. In total, the results from 8 actual experiments and 64 finite element models in the parametric studies on CFS back-to-back channels built-up screw fastened SBCs with different cross-sections are reported. The specimens were tested with fixed end condition under axial compression. Sections with lip and web stiffeners predominantly failed due to distortional buckling mode whereas all the other sections failed due local or global flexural buckling mode or interaction of local and global modes of failure. The inclusion of intermediate stiffeners and global stiffeners supported in resisting buckling. The results obtained from this study were compared with the estimated load carrying capacities using Direct Strength Method (DSM) design equations. It was found that for built-up SBC members the method of calculating its compression capacity was over-conservative. SBC sections made of lipped channels along with longitudinal stiffeners exhibited highest load carrying ability. Providing stiffeners at the junction of flange and web portions did not radically increase in load carrying ability when compared to sections having stiffeners in the webs and lip portions. SBC sections made of lipped channels also failed in similar buckling phenomenon like in other sections but the plate element local buckling predominantly occurred at the lip portions.