Behaviour and design of cold-formed normal- and high-strength steel SHS and RHS columns at elevated temperatures

Abstract

The behaviour of cold-formed normal- and high-strength steel columns with square and rectangular hollow sections (SHSs and RHSs) at elevated temperatures was investigated numerically in this paper. A finite element model was developed and validated against experimental results for the cold-formed steel SHS and RHS stub and long columns tested at ambient and elevated temperatures. Parametric studies were subsequently conduced on cold-formed normal- and high-strength steel SHS and RHS columns with various cross-section slenderness and member slenderness at elevated temperatures ranging from ambient to 800 °C. Based on the numerical results and experimental results reported in literature, the applicability of existing design approaches in European and North American standards to the columns at elevated temperatures was evaluated. The evaluation shows that the approaches in standards provide quite conservative strength predictions for the cold-formed normal- and high-strength steel SHS and RHS columns at elevated temperatures except for the overestimation of cross-sectional resistance obtained based on the North American standard. Modified design approaches were proposed to improve the accuracy of strength predictions and can be safely applied to generate designs for the columns under various elevated temperatures.