Fire Resistance Study of Axially Loaded High Strength Steel Columns

Abstract In this paper, an analytical method was presented to investigate the fire resistance of axially loaded high strength steel columns. By introducing the mechanical properties of high strength steel at elevated temperature, the critical stress and critical temperature of high strength steel columns subjected to axial compression, and the width-to-thickness ratio for the flange and the web at elevated temperature are deduced, based on the stability theory of the columns and plates at normal temperature. Analysis of the stability factor, the critical temperature of high strength steel columns under axial load and the width-to-thickness ratio has been performed. The results showed that the stability factor and critical temperature for mild steel are not applicable for high strength steel. The stability factor for high strength steel is smaller than that for mild steel and at the same load ratio (bigger than 0.5), the critical temperature for high strength steel columns is lower than that for mild steel columns, and for the slender columns, the width-to-thickness ratios for high strength steel columns are bigger than that for mild steel for stub columns but for the slender columns, there is little difference. To validate the proposed analytical method, finite element studies were carried out and good agreement has been found between the results of proposed method, finite element analysis and experiments. Parametric studies are conducted to investigate the influence of modeling initial stress, initial imperfections, slenderness, section size and mechanical properties, on the fire resistance of high strength steel columns.