Nonlinear behaviour of back-to-back built-up cold-formed steel channel columns under compression - finite element modelling and parametric study

Abstract

This paper presents a numerical investigation on the behavior and design of back-to-back built-up cold-formed steel channel columns subjected to axial compression. Numerical models were developed using general purpose finite element (FE) package ABAQUS, and have been verified using experimental data reported by the authors recently (Ting et al. (2017). Developed finite element models included material nonlinearities as well as initial geometric imperfections. Axial strength of columns, failure modes, deformed shapes at failure, load-displacements were predicted from the finite element analyses and obtained comparisons with test results showed considerable match. A comprehensive parametric study consisting of 204 models, has been carried out covering a wide range of thickness and slenderness for the considered back-to-back built-up columns. Axial capacities obtained from the numerical study were used to assess the performance of the current AISI& AS/NZS standards when applied for cold-formed back-to-back built up columns; obtained comparisons showed that AISI& AS/NZS standards are un-conservative for stub and short columns sections which were failed by local buckling whereas standards were over-conservative for the strength of intermediate and slender columns which were failed mainly by overall member buckling.