Influence of chord compactness and slenderness on axial compression behavior of built-up battened CFS columns

Abstract

This study presents the behavior of built-up cold-formed steel (CFS) columns under axial compression loading. Two CFS unstiffened channel sections arranged in the toe-to-toe configuration are used as the chord members interconnected by the batten plates. An extensive parametric study has been conducted on 230 numbers of built-up battened CFS columns using a finite element software ABAQUS. The numerical models developed have been calibrated against the test results available on CFS battened columns with plain channels in the back-to-back arrangement reported in the literature. The main parameters varied in the numerical models are the width-to-thickness ratios of chords, overall column slenderness ratios, and the toe-to-toe spacing of chords. The behavior of built-up columns is studied in terms of peak axial compressive strengths, mode of failure, post-peak resistance, and lateral drift. The chord width-to-thickness ratios have a predominant effect on the peak axial stresses of short columns, and a meager effect on long columns. Also, large lateral displacements can be avoided by restricting the overall column slenderness to 75. Numerical results are compared with the design strengths predicted by North American Standards (NAS) and Eurocode (EC3). Both these standards are found to be un-conservative in predicting the axial strengths of short built-up columns in the range of 15–30%. Finally, the design recommendations are proposed for built-up battened CFS columns with channel chords in toe-to-toe configuration, which are verified through reliability analysis as well.