Cold-formed steel lipped channel columns at elevated temperatures

The main objective of this paper is to study the behaviour and design of cold-formed steel lipped channel columns at elevated temperatures using finite element analysis. The effects of initial local and overall geometrical imperfections have been taken into consideration in the analysis. Failure loads and load-shortening curves of lipped channel columns were investigated in this study. The finite element analysis was performed on lipped channel columns compressed between fixed ends over a range of column lengths for various temperatures. The nonlinear finite element model was verified against experimental results of lipped channel columns at normal room temperature and elevated temperatures. Three series of columns were studied using finite element analysis to investigate the strength and behaviour of lipped channel columns at elevated temperatures. The column strengths predicted from the finite element analysis were compared with the design strengths calculated using the effective width and direct strength methods by substituting the reduced material properties. It should be noted that the current effective width and direct strength methods are developed based on cold-formed steel structural members at normal room temperature. In this study, the suitability of the effective width and direct strength methods for cold-formed steel lipped channel columns at elevated temperatures is investigated. It is shown that the effective width and direct strength methods are able to predict the cold-formed steel lipped channel column strengths at elevated temperatures. In addition, the ratio of the failure loads of the columns at elevated temperatures to that at normal room temperature is also studied and compared with the prediction proposed by other researcher.