Research on joint models of welded flange-bolted web connection for progressive collapse analysis of steel frames

Based on progressive collapse-behavior test results on a cold-formed RHS column to an H-beam sub-assemblage with a welded flange-bolted web connection, the whole process performance of the joint was reasonably reproduced through high fidelity finite element modeling by using ABAQUS software, including the beam bottom flange fracture under a middle column removal scenario. A simplified joint model was further proposed based on the component method and back-stepping method, which can reflect a force evolving process and discontinuous deformation such as fracture and a post-fracture path with a cost-effective solution. Incorporating this joint model, the dynamic nonlinear progressive collapse analysis was carried out on a five storey by four bay steel frame. It is found that the joint fracture imposes a significant impact on the structural vertical response and sufficient attention should be therefore paid on the behavior evaluation for progressive collapse.