Behaviour of cold-formed steel built-up columns: tests and numerical simulation

Abstract

This paper describes a test program on cold-formed steel built-up columns composed of two-lipped channels placed back to back. In this study, 14 specimens were tested between pins with the warping restrained end condition. The overall initial geometric imperfections are measured. The compression resistance, load-axial shortening response and deformed shapes are presented. A nonlinear finite element models were developed, and numerical analysis that includes material nonlinearity, geometric nonlinearity, contact nonlinearity and geometric imperfections was performed. The FE and the experimental results were found in good agreement in terms of ultimate compression resistance, deformed shapes and load-axial shortening curves. The Direct Strength Method (DSM) and Effective Width Method (EWM) for cold-formed steel were evaluated against the obtained test results. It is concluded that the design strengths predicted by design codes are provided conservative strength predictions for the built-up columns, and these design rules are also assessed by the reliability analysis.