PERFORMANCE ASSESSMENT OF A SEMI-ACTIVE FRICTION PENDULUM SYSTEM UNDER BIDIRECTIONAL EXCITATION

The use of seismic isolation devices to reduce the damage in structures under seismic motion has been studied for decades. The traditional approach aims to achieve a long period in the isolated system, away from the acceleration-sensitive region of the response spectrum. However, this approach may not be so practical for certain designs in regions near an active fault where the response spectrum is characterized by low-frequency (LF) content, which may produce large displacement in the isolation system. For a friction pendulum system (FPS), this large displacement can lead to the isolators reaching their ultimate displacement, causing impact with the restraining rings and increasing the energy transfer into the superstructure, which some recent studies have linked to an increased probability of collapse. To improve the response of the FPS under low-frequency earthquakes motion (LFE), this study explores the performance of a semi-active control strategy termed Semi-active Friction Pendulum System (SFPS), which is composed of FPS isolators with smart dampers. The damping properties of these dampers can be modified in real-time (in milliseconds) with a very low power consumption based on the instantaneous FPS response. The investigation focuses on implementation of the SFPS in a 3-story building. The design of a SFPS is optimized for a 3-story building. First, an ideal smart damper with realistic conditions in the control law is considered, and the response of the SFPS with an ON-OFF phase control is evaluated. The bidirectional behavior of the SFPS is then investigated under a set of LFE. Finally, the paper concludes with a discussion on the performance of the SFPS aimed toward improved future implementation.