Post-earthquake fire performance of square concrete-filled steel tube columns

It has been shown that fire disaster normally occurs following an earthquake disaster, which might cause even more serious losses than the earthquake itself. This study investigates the post-earthquake fire performance of concrete-filled steel tube (CFST) columns. The experimental programme contains two parts - quasi-static tests and fire tests. During the quasi-static tests, the square CFST columns were loaded under constant compressive force and cyclic horizontal force, until reaching different degrees of seismic damage. Afterwards, the pre-damaged columns were loaded under a constant axial compression ratio (i.e. ratio of the applied compressive load to its bearing capacity) of 0.3 at elevated temperatures. The fire resistance time and failure modes of these pre-damaged CFST columns were reported. Finite element (FE) models were developed and validated against the test results; a total of 48 numerical results were generated in the parametric study using the validated model. In the parametric study, the influence of key parameters including the thickness of steel tube, the yield strength of steel tube, the axial compression ratio and pre-damage degrees on the fire resistance of square CFST columns were analysed. The experimental and numerical results are used to propose design rules for the fire performance of square CFST columns with different degrees of seismic damage.