Investigation on post-impact fire resistance of square-cased circle steel tube-reinforced concrete columns

The steel tube-reinforced concrete (ST-RC) column is widely used in high-rise buildings. However, its performance under multi-hazard scenarios, such as impact followed by fire, is not well understood. This study numerically investigates the post-impact fire resistance of square-cased circle ST-RC columns using ABAQUS. A typical ST-RC column is designed and its performance under combined eccentric load, impact, and fire scenarios is analyzed. The study reveals that impact significantly compromises the fire resistance of the ST-RC column. Parametric studies are conducted to investigate the influence of various factors on the post-impact fire resistance of ST-RC columns. Key factors influencing the post-impact fire resistance of square-cased circle ST-RC columns are identified, including load ratio, section size, slenderness ratio, external concrete strength, section core area ratio, section steel ratio, load eccentricity, impact velocity, and impact mass. A simplified calculation formula is proposed to estimate the fire resistance of ST-RC columns under post-impact fire scenarios.