Post-fire seismic performance of concrete-filled steel tubular column to steel beam joints with blind-bolted connections: Experiment and simulation

During the life-cycle of a building, the structure might be subjected to multiple hazards such as fire, earthquake and impact. Compared with the traditional structure design methods based on a single type of disaster load, the structure subjected to multiple and coupled disaster loads would be more dangerous and worth to be investi-gated. In this paper, the post-fire seismic behavior of concrete-filled steel tubular (CFST) column to steel beam joints with blind-bolted connections subjected to coupled fire and cyclic loads were investigated. A total of ten post-fire hysteresis joint tests were designed and conducted, and the testing parameters included heating time, post-fire column load ratio and thickness of fire protection layer. The test results indicated that the joint failure mode changed from column failure to connection failure when the post-fire column load ratio ranged from 0.3 to 0.6. Generally, the blind bolts in the panel zone of this joint specimen showed acceptable working performance in fire, but gap between the stee tube and beam end plate might be formed during the post-fire cyclic loading process. Finite element analysis (FEA) models were established to simulate and discuss the post-fire seismic performance of this type of blind-bolted CFST joints under the coupled fire and loading process. Finally, a simplified post-fire hysteretic relationship model for this type of joint was proposed.