Numerical analysis on fire behaviour of concrete-filled steel tubular columns after lateral impact

Fire often occurs accompanied by explosion or impact, which may cause more severe damage to the structures due to the combined action of different disasters, while very limited studies on the fire behaviour of structural members with impact damage are reported in literature. This paper presents a numerical investigation on the fire behaviour of concrete-filled steel tubular (CFST) columns after lateral impact. A finite element analysis (FEA) model coupling the lateral impact and fire is developed and calibrated. The full-range analysis on the fire behaviour of CFST columns with impact damage is carried out, i.e., the impact responses, distribution of internal force, midspan deflection, fire resistance, and stress development. Different parameters affecting the fire resistance of CFST columns with impact damage are also investigated. The results show that the lateral impact engenders a significant adverse influence on the fire performance and development of failure deflection of CFST columns, and may lead to a significant sudden destruction with no observable deformation process in fire. The fire resistance of CFST columns significantly reduces due to the evident residual deflection and local damage induced by the lateral impact. As the impact velocity and impact weight increase, the fire resistance of CFST columns significantly decreases, while the gap between the residual and failure deflections gradually shortens. A dual adverse effect caused by the axial load on the fire resistance of CFST columns with impact damage occurs when the axial load ratio exceeds 0.3.