Mitigating Pounding and Enhancing Seismic Resilience in Adaptive Base Isolation Systems Incorporating Passive Gap Dampers

ABSTRACT

Seismic pounding against moat walls (MWs) may occur in seismically base‐isolated buildings equipped with insufficient isolation clearances, especially during strong pulse‐like earthquakes. Serious MW pounding significantly amplifies the story drifts and floor accelerations of the superstructure, impairing structural isolation effectiveness. Hence, various passive gap dampers (GDs) have been developed in isolation systems to provide adaptive deformation mitigation, accommodating multiple earthquake intensities. This study comprehensively investigates the seismic performance of adaptive base‐isolated systems incorporating various GDs during strong earthquakes. Three typical types of passive GDs, that is, steel, shape memory alloy (SMA), and viscous GDs, were considered. An analytical model was developed for the inelastic two‐degree‐of‐freedom system incorporating GDs. Parametric response analyses were numerically conducted by varying the types and design parameters of GDs and the pulse period ratios of ground motions. The results demonstrate that adaptive systems with GDs exhibit superior deformation mitigation in the isolation layer during pulse‐like earthquakes, compared with conventional systems without GDs. The comparisons of various GDs indicate that steel GDs characterized by full energy dissipation are effective in decreasing the maximum force in the isolation layer and maximum deformation of the superstructure, while the insufficient self‐centering capability may increase the deformation responses and the risk of MW pounding in the isolation layer, during pulse‐like earthquakes. In contrast, SMA GDs with superelastic effect and medium energy dissipation achieve better mitigation in the maximum and residual deformations of the isolation layer, decreasing the risk of MW pounding. On average, steel and SMA GDs exhibit comparable maximum deformation and acceleration of the superstructure. Viscous GDs exhibit significantly higher maximum shear force and energy dissipation during pulse‐like ground motions. Therefore, compared with hysteretic GDs, viscous GDs may achieve superior deformation mitigation in the isolation layer, while increasing the maximum deformation and acceleration of the superstructure, during pulse‐like ground motions. Design recommendations are proposed for adaptive isolation systems incorporating various passive GDs, advancing the seismic design for mitigating MW pounding and enhancing seismic resilience.