Development and validation of an innovative uplift-restraining friction pendulum bearing

This paper presented an innovative uplift-restraining friction pendulum bearing (UR-FPB) to address the limitations of traditional FPBs, which are unable to withstand vertical tensile loads. The UR-FPB is composed of a friction set acting as the horizontal sliding module and an anti-uplift set acting as the vertical uplift-restraining module. Based on this configuration, the study derived the theoretical force-displacement relationships of the UR-FPB, established three solid finite element models in Abaqus, and proposed a hybrid modeling method based on OpenSees. Then the practical effectiveness of this bearing and the credibility of the theoretical analysis models and hybrid numerical models were validated. The theoretical and numerical results demonstrate that the frictional behavior of the UR-FPB in horizontal sliding is characterized by multi-stage hysteresis relationships. The numerical results on the sliding characteristics and the corresponding hysteresis relationships are highly consistent with the theoretical results. The UR-FPB has a large horizontal sliding capacity similar to that of traditional FPBs, while the design of the anti-uplift configuration does not reduce or limit this sliding capacity. Significantly, the study investigated the uplift-restraining behavior of the UR-FPB and its effect on the horizontal responses. The analysis results suggest that the UR-FPB has a good uplift-prevention capacity and this paper recommends that the design value of tensile capacity should not exceed the yield force in tension. Therefore, this novel uplift-restraining friction bearing has an expected effectiveness, which can simultaneously resist vertical tensile loads and function as a horizontal seismic isolator. The proposed hybrid modeling method may provide a useful reference to model the behavior of the UR-FPB in software used for response-history analysis.