Seismic pounding fragility and risk assessment method for nonlinear adjacent structures based on subset simulation

Existing procedures to determine a minimum separation distance needed to avoid seismic pounding are based on approximations of the peak relative horizontal displacement between linear adjacent buildings, and are characterized by unknown safety levels. Thus, a performance-based probabilistic procedure for assessing risk of seismic pounding between nonlinear adjacent buildings was proposed. An efficient small failure probability method, i.e. subset simulation, was used for calculating the seismic pounding fragility of adjacent buildings. The multi-degree-of-freedom systems of equal height with substantially different dynamic properties were taken as examples to assess the rules of seismic pounding fragility and risk with and without considering nonlinear behavior of adjacent buildings at different separation distances. Moreover, the proposed method was employed to assess the performance of link elements connecting the adjacent structures, which aimed at decreasing the pounding probability. Results show that with the increase of peak ground acceleration, the seismic pounding fragility curves with considering nonlinear behavior of adjacent buildings are generally monotonic and non-decreasing but have local variations. The difference between the seismic pounding probabilities of adjacent structures with and without considering nonlinear behavior becomes larger with the increase of separation distance. When the separation distance is large, the stiffness of linking between the adjacent structures should be large enough to achieve the goal of pounding mitigation. © 2020, Zhejiang University Press. All right reserved.