Shake table tests of steel moment resisting frame with self-centering SMA-based isolators

This paper investigates a steel moment resisting frame (MRF) with a novel type of self-centering (SC) base isolators, wherein superelastic shape memory alloy (SMA) U-shaped dampers (SMAUDs) work as core components. A two-story steel MRF model equipped with two SMAUD-based isolators was designed and built in the laboratory, and a series of shake table tests were conducted to examine the dynamic behavior and seismic performance of the frame. Throughout all the tests, no interventions, such as repair or replacement of frame or isolator members, were done. Shake table test results demonstrated that the SMAUD-based isolators could withstand multiple strong earthquakes with stable SC behavior. The utilization of SMAUD-based isolators provided effective protection for the frame, enabling it to restore its original position with minimal structural damage. A numerical model of the tested steel MRF with SMAUD-based isolators was also built. The results obtained from the numerical analyses agreed with those of the shake table tests satisfactorily. A comparative study of the seismic performance between the MRF with SMAUD-based isolators and the MRF with traditional steel U-shaped damper-based isolators was also conducted in the shake table tests. The results showed that SMAUD-based isolators not only inherit the isolation function of conventional isolators to protect the frame but also possess an SC ability to eliminate residual isolator deformation effectively. Moreover, SMAUD-based isolators demonstrate remarkable resilience to withstand multiple strong seismic events without any need for repair or replacement.