Compressive performance of steel-reinforced concrete columns after exposure to high temperature

Abstract

Steel-reinforced concrete (SRC) columns have been extensively employed in high-rise buildings due to their superior mechanical properties, especially under fire conditions. In most cases, the fire damaged SRC columns may still be able to re-use after proper repairs. Thus, it is important and essential to investigate the residual behaviors of these post-fire SRC columns. In this study, a total of 75 SRC columns, including 60 that are heated and 15 that are unheated for comparison, are tested under axial compression. Four parameters, including the steel section ratio, the concrete strength, the sectional aspect ratio and the heating duration, are considered to examine their effects on the failure modes, bearing capacities, deformation, axial stiffness and ductility characteristics. It is demonstrated that the strength of SRC stub columns on average decreases by 13%, 20%, 25% and 37% after exposure to high temperature with durations of 30min, 60min, 90min and 120min. Increasing the steel section ratio can effectively decrease the strength loss resulted from heat exposure. While the concrete compressive strength and sectional aspect ratio exhibit little effect on the residual strength. To this end, equations for estimating the ultimate strength of SRC stub columns after exposure to fire are developed via tests. It is verified that the calculation results agree well with the experimental results.