Experimental Study on Ultimate Strength of H-Shaped Fire-Resistant Steel Columns under Fire Load

Abstract

With the advancement of metal production, a new type of steel plate, Fire Resistant Steel (FRS), has been developed to conquer inherent weakness of the conventional steel. FRS has been proven to have better mechanical properties at high temperature than those of the conventional steel. Also, the requirement of fire-protection in the fire-resistant steel can be released or relaxed in the fire condition. However, the knowledge related to the structural behavior of FR steel members under fire load is lacking. In this study, a series of H-shaped steel columns, made of FR steel, were centrally loaded to their limit states to investigate their performance under fire load. The specimens examined in this study including stub columns, and columns within inelastic and elastic ranges, according current design specifications developed at ambient temperature. Stub columns with varying width-to-thickness ratios were designed to examine the local buckling behavior of FR steel columns under fire load; while, the columns with varying slenderness ratios were aiming at evaluating the global behavior. Based on this study, it was found that the current design criteria developed at ambient temperature is capable of preventing premature failure of local buckling of FR steel columns subjected to axial compression either at ambient temperature or at elevated temperature. Due to the limited effect of residual stress in fire, the governing failure mode could be changed from inelastic global buckling at ambient temperature to local buckling at elevated temperature. At 600 degrees C, steel columns retain 60% of the ambient temperature strength if the slenderness ratio is less than 80. Design guidelines are proposed for FR steel columns under fire load.