Assessing progressive collapse behavior and resistance of FPB ‐isolated 3D RC frames triggered by edge column failure

Abstract

Friction pendulum bearings (FPBs) mitigate lateral seismic effects on buildings via reducing the lateral stiffness of the isolation storey. However, this substantial reduction alters structural response characteristics and the evolution of resistance when progressive collapse occurs due to bearing failure. The progressive collapse response patterns and resistance development processes of 3D RC frames with FPB isolation under edge bearing failure are investigated. The mechanical responses and underlying causes of beams spanning failed bearings, edge bearings, and internal bearings are comprehensively assessed. Additionally, parametric analyses are performed to clarify the effects of equivalent radius and friction coefficient of bearings on progressive collapse resistance. The results indicate that in the compressive arching action (CAA) stage, compared with fixed‐base structures, structures with FPB isolation have lower resistance. But FPBs significantly delay the collapse process, enhance structural deformation capacity, and extend the time taken for the structure to enter the catenary action (CA) stage. In CA stage, the resistance development in the isolated structures is not as full as that in fixed‐base structures. The resistance provided by lateral constraints is significantly weakened, contributing minimally to the total resistance, which primarily stems from the beam's flexural mechanism and CA. Neither the equivalent radius nor the friction coefficient of FPBs significantly affects the progressive collapse resistance of FPB‐isolated structures.