Stochastic optimal design of novel nonlinear base isolation system for seismic-excited building structures

Abstract

A novel nonlinear isolation system is numerically investigated by employing a stochastic response evaluation and experimentally studied with a small-scale preliminary prototype. The stochastic response of isolated building structures is first derived using a nonstationary random process and time-dependent equivalent linearization, regarding the nonlinear restoring force behavior of the proposed isolator. A parametric study is then performed to evaluate the potential influences of earthquake excitations properties and the optimum force ratio of the isolator that adopts the widely used Kanai–Tajimi model. According to the insights from the parametric study, the optimal design for nonlinear isolation is proposed based on a stochastic optimization procedure with the convergence of different performance objectives. The stochastically optimized isolation system is numerically studied by first comparing the present nonlinear isolator and conventional bearings. The present isolator is systematically illustrated to perform advantageously compared with conventional passive isolators in terms of base drift and structural acceleration through a relatively large group of 40 recorded seismic motions. To further investigate the efficiency of the nonlinear isolator, a benchmark building for smart base-isolation is adopted, and a comparison of the results indicates comparable performances between the proposed passive isolator and the classical active isolation system. Furthermore, an original design of the base isolation system simulating an energy dissipation mechanism is presented with favorable force-deformation behavior from experimental testing on small-scale prototypes.