An adaptive friction isolation system for seismic response control of buildings
Yadong Li, Hasan Ozek, Osman E. Ozbulut
Abstract
Abstract This paper proposes an adaptive friction isolation system (AFIS) composed of shape memory alloy (SMA) cables and double friction pendulum bearings (FPBs). Double FPBs with different friction coefficients enable two-level response characteristics that are advantageous at frequent and design basis hazard levels, while SMA cables with initial slack provide adaptive response at maximum considered earthquake hazard level. SMA cables are arranged vertically and they limit excessive isolation displacement by providing hardening effects and additional energy dissipation capacity. They also improve the stability of FPBs under severe earthquakes. Based on the experimental response of FPB and SMA cables, a high-fidelity finite element model of AFIS is first established in ABAQUS. Then, to study the effectiveness of the AFIS in controlling seismic response of structures, a simplified model of the AFIS is developed in OpenSees and nonlinear time history analyses of a seven-story steel frame building isolated with AFIS are conducted. The results show that the AFIS can satisfactorily meet displacement demands under frequent and moderate earthquakes, while it effectively reduces the excessive displacement of the building under severe earthquakes. In particular, the AFIS considerably improves the performance of the isolated building under pulse-like near-fault earthquakes.