Experimental and numerical investigation on the lateral impact responses of CFST members after exposure to fire

The impact load acting on structure can cause a completely different structural response from the static load, and structure may be subjected to both impact and fire in extreme events, leading to severe structural damage or collapse. This paper reports the lateral impact responses of concrete-filled steel tubular (CFST) members after fire. Nine CFST specimens with different parameters, i.e., the fire duration time, impact heights, and boundary conditions, were tested using an electric furnace and a drop hammer impact system. The failure modes, impact force, midspan deflection, and energy absorption were investigated and compared. Results reveal that post-fire CFST members exhibit global bending failure under lateral impact, and increasing the fire duration time reduces the impact resistance of CFST members, with lower peak and plateau impact forces but larger deflection. The finite element (FE) model of post-fire CFST members under lateral impact was developed and calibrated against the test results to further analyze the impact responses. In addition, simplified methods were proposed for the evaluation of dynamic flexural capacity, plateau impact force and maximum deflection of CFST members subjected to lateral impact.