Seismic Reliability Analysis of Base-Isolated Buildings

Seismic base isolation is achieved via inserting flexible isolator element between the foundation and superstructure which lengthens the vibration period and increases the energy dissipation. Values adopted for uncertain parameters in earthquake engineering deviate from their nominal values. The stochastic response analysis of the base-isolated building is studied considering uncertainties in the characteristics of the earthquakes. Artificial acceleration time histories developed using probabilistic ground motion model are used in the study. The uncertainties in peak ground acceleration, frequency content, and time duration are considered to develop 5,000 artificial acceleration time histories. A bilinear model of the isolator described by its characteristic strength, post-yield stiffness, and yield displacement is used, and the stochastic response is calculated by using an ensemble of generated earthquakes. The study also presents the results of seismic reliability analysis of the five-storey base-isolated building. The first-order reliability method (FORM) and Monte Carlo simulation (MCS) method are used to evaluate the probability of failure associated with the top floor acceleration response of the building. The top floor acceleration response statistics are used in the performance function considering 0.3 g as a maximum allowable acceleration, and the probability of failure is evaluated. The probability of failure evaluated using the FORM is fairly in good agreement with the value obtained by the MCS.