POST-FIRE BEHAVIOR OF REINFORCED CONCRETE-FILLED SQUARE STEEL TUBULAR STUB COLUMNS UNDER AXIALLY COMPRESSIVE LOADING

To study the residual load bearing capacity after fire of reinforced concrete-filled steel tube (RCFST) short columns with rectangular section under axial pressure, eighteen RCFST short columns with rectangular section were tested under loading device after exposure to standard fire. The failure modes were observed and the residual load bearing capacity was obtained. The temperature field model of RCFST short columns under heating part was built by ABAQUS. The comparison shows that the theoretical analysis results are in good agreement with the former test results. Based on that, the parametric analysis of post-fire residual load bearing capacity of RCFST column with rectangular short under axial pressure was studied. The study reveals that the RCFST short columns have high bearing capacity; longitudinal reinforcement have better restraining effect to concrete; the reinforced filled concrete can enhance the ultimate capacity of the specimens; the heating up time and sectional dimension are the main parameters influencing the fire resistance of RCFST with rectangular columns.Based on these parameters, simplified formulas of the residual load bearing capacity after fire were put forward, and the calculated results by the formulas showed well agreement with the theoretical model results.