Dynamic response of planar frame sub-structure isolated by friction pendulum bearings subjected to a middle column removal scenario

The aim of this study is to investigate the dynamic response of planar frame sub-structure isolated by friction pendulum bearings subjected to a middle column removal scenario. The study presents and evaluates the dynamic structural behaviors, load transfer mechanisms, progressive collapse resistance, and dynamic increase factor (DIF) results of FPBs-isolated planar frame. The study explores the influence of the equivalent radius and friction coefficient of the FPB, as well as the peripheral constraints of the failed column. The results show that the compressive arching action (CAA) and catenary action (CA) cannot be fully developed for buildings isolated by FPBs due to the significant reduction in the lateral stiffness of the isolated layer caused by FPBs. The structural responses of planar frame isolated by FPBs are much larger than those of corresponding fixed-base buildings. The DIF of buildings isolated by FPBs initially decreases and then barely changes with an increase in the stabilized vertical displacement of the failed column. The presented fitted formula for DIF of planar frame isolated by FPBs describes the obtained results well. The friction coefficient and equivalent radius of FPBs show very limited influence on the dynamic response of planar frame isolated by FPBs under progressive collapse, but reinforcing the peripheral constraints of the failed column can enhance the progressive collapse resistance of isolated planar frame.