Test and development of SMA-based negative stiffness isolation device

Abstract

Although shape memory alloy (SMA) wires/cables can improve the re-centering capacity of traditional isolation devices to prevent residual displacement, pounding, or falling of girders, they also raise the forces in the substructure since the stiffness of the device is increased. In this paper, quasi-static lateral shear tests of an SMA-based negative stiffness isolation device were conducted at first to reduce the increased forces of the substructure. The mechanical properties and the failure modes of the SMA-based negative stiffness isolation device are studied. Next, the SMA-based negative stiffness isolation device is updated based on its failure modes. Finally, the mechanical properties of the improved device were numerically studied. The results show that the new SMA-based negative stiffness isolation device can partially reduce the force responses of the substructure in addition to keeping excellent re-centering capability. Moreover, it can also limit the excessive displacement of bridges to prevent the girders from falling.