Progressive collapse behavior and capacity of FPB-isolated 3D structures subjected to internal isolator removal

• Published in: Structures (Oxford) Vol. 80; p. 109799
• Main Authors: Zhang, Jingcai, Li, Yingna, Zhang, Chunwei, Huang, Yonghu, Wang, Shuhang, Qiao, Hailun, Lin, Yongye, Cheng, Liang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2025
• Subjects: Friction pendulum bearing (FPB); Lateral restraint; Progressive collapse; Seismic isolation; Progressive collapse; Seismic isolation; Friction pendulum bearing (FPB); Lateral restraint
• ISSN: 2352-0124; 2352-0124
• DOI: 10.1016/j.istruc.2025.109799

The friction pendulum bearing (FPB) can effectively reduce the horizontal seismic response of structures. However, the horizontal stiffness of the isolation layer is significantly reduced, leading to changes in the progressive collapse mechanism of the structure when the FPB is damaged. This work focuses on the progressive collapse mechanisms and structural responses of three-dimensional (3D) reinforced concrete (RC) frame structures isolated by FPBs under internal isolator removal. To this end, this paper conducts a series of detailed finite element analyses using a validated numerical model, whose results have been experimentally verified through tests and show good agreement with the measured data. The characteristics of load-deformation histories were analyzed, focusing on the responses of the beam spanning the failed isolator, edge columns, corner columns, and the supplementary resistance provided by horizontal constraints. The effects of the FPB friction coefficient and equivalent radius on structural behavior were also evaluated. The results show that FPBs hinder the development of compressive arching action (CAA) and catenary action (CA), but have very limited influence on the flexural mechanism of the beam spanning the failed isolator. The supplementary resistance of FPB-isolated structures is substantially lower than that of fixed-base structures. Thus, FPBs significantly reduce the structural capacity to resist progressive collapse, and the friction coefficient and equivalent radius exhibit negligible effects on the progressive collapse resistance of FPB-isolated structures.