Lateral impact behaviour of post-fire steel-reinforced concrete-filled steel tubular members: Experiment and evaluation method

Abstract

Steel-reinforced concrete-filled steel tube (SRCFST), which exhibits superior mechanical behaviour and fire resistance than traditional concrete-filled steel tube (CFST), is widely used as a main load-carrying component in different structures. Structure might experience severe damage even collapse as a result of both impact and fire in extreme events. This study reports an experimental investigation on the responses of post-fire SRCFST members under lateral impact. Impact tests on 12 SRCFST specimens after fire were conducted, and the main parameters considered include the fire exposure time, impact height, axial load ratio, and section steel type. The temperature-time curves, failure modes, impact force, midspan deflection, axial force, plastic deformation, and energy absorption are investigated. The results show that post-fire SRCFST specimens under lateral impact experience global flexural failure. As the fire duration increases, the global deformation and local buckling of the specimen become more visible, and the plateau impact force decreases while the midspan deflection increases. In addition, based on the equivalent temperature of SRCFST members and the membrane force factor method, new simplified evaluation methods are proposed for calculating the dynamic flexural capacity and maximum deflection of SRCFST members subjected to lateral impact.