Analytical modeling and seismic performance of a novel energy dissipative kinematic isolation for building structures

Abstract

The idea of separating the structure from the horizontal motion of the ground using kinematic bearings that may uplift and rock under severe ground excitations can be considered equally as a seismic isolation technique. However, the seismic demand reduction on the superstructure due to the uplift of the kinematic bearings presents an inversely proportional relation to the stability of the system. For this reason, the performance of kinematic isolation is moderate. To address this issue; the present study examines a novel high-performance kinematic isolation characterized by increased seismic demand reduction and enhanced stability. The proposed configuration comprises of slender enough concave kinematic bearings, positive post-uplift stiffness, and supplemental viscous dampers. To investigate the seismic behavior of the proposed arrangement; the nonlinear equations of motion are first derived. Due to the positive stiffness, the kinematic story serves as conventional seismic isolation, resulting in period elongation, and thereby the dynamic characteristics of the base isolation are evaluated. To this end, the system's equations of motion are linearized and analytical expressions regarding the vibration period and damping ratio are proposed. Furthermore, dynamic time history analyses are performed, and the effect of the dynamic characteristics of the kinematic story on the overall seismic response is investigated. Finally, the seismic performance of three typical isolated structures is evaluated. The study concludes that the proposed expressions of the nominal vibration period and damping ratio efficiently describe the dynamic properties of the system. Moreover, combining slender enough concave kinematic bearings with supplemental viscous dampers results in a high-performance seismic isolation system.