VARIATIONS IN PERFORMANCE IN EXTREME EVENTS WITH SELECTION OF ISOLATION TYPE

While collapse mechanisms for conventional buildings have received considerable attention, they are less well understood for isolated buildings. Regardless of the type of bearing used, it is anticipated that the performance of isolated structures will be comparable under defined ground motion levels. Nevertheless, the probability of building collapse is directly dependent on the bearing failure characteristics, which vary by bearing type. Utilizing various isolation systems while adhering to the same design guidelines may result in varying probabilities of collapse. In this study, the probability of collapse of a three-story buckling-restrained brace frame isolated with double-concave FP bearings or lead rubber bearings is compared. At maximum displacement, various designs are considered, including the use of moat walls versus allowing bearing failure (or impact of the restraining flanges for FP bearings). In the absence of the moat wall, the system-level failure using both bearing types is triggered by exceeding defined displacement capacities. In contrast, with the moat wall, the system-level failure is dominated by either axial component-level failures or excessive yielding of the superstructure. However, when the moat wall restricts ultimate displacement, the disparity in collapse probabilities is small.