Structural behavior of centrally loaded steel columns at elevated temperature

A series of experimental studies is conducted to examine the behavior of SN490 steel column subjected to axial load in the fire condition. This experimental work is aimed at examining the effect of the width-to-thickness ratio of flanges, the slenderness ratio of steel columns and residual stresses on the ultimate strength of an SN490 steel column at a specified temperature. From these studies, it is found that the column strength decreases with the increase of width-to-thickness ratio and slenderness ratio. Column behavior is sensitive to width-to-thickness ratios and the slenderness ratio at temperatures below 550 ∘C. However, the influence of width-to-thickness ratios and the slenderness ratios is not severe when the temperature is higher than 550 ∘C. When the temperature is above 550 ∘C, the column strength deteriorates rapidly. It is also found that the failure mode of steel columns changes from inelastic global buckling at room temperature to inelastic local buckling at elevated temperature, due to the release of residual stress in a fire. Based on the results of this study, local buckling criteria and column strength at specified temperatures are suggested.