Sliding implant-magnetic bearing for adaptive seismic mitigation of base-isolated structures

Sliding isolation system is one of the widely used base isolation systems. Traditional pure sliding base isolation systems, however, lack restoring force and possess low damping energy-dissipation capacity. To overcome these disadvantages, a novel low-friction sliding isolation system with adaptive behavior using sliding implant-magnetic bearing (IMB) has been proposed in this paper. The isolation system consists of an upper block and a base block, both having polyurethane elastomer fillings and circumferentially implanted permanent magnets. This configuration allows an alterable damping force related to the eddy currents associated with bearing movement. Meanwhile, the interactions between magnets deployed in the upper and base blocks provide a capitalized repulsive force. A quasistatic test is performed to appraise the performance of the IMB system. Theoretical analysis and numerical simulation are carried out for quantification of the repulsive force, damping force, and Coulomb friction, which facilitates the modeling of the isolator. In order to verify the mitigation performance of the IMB deployed in seismic structures, a comparative study against the sliding hydromagnetic bearing (HMB) is carried out. It is revealed that the IMB exhibits reliable frictional performance and excellent damping energy-dissipation capacity, which commits the adaptability of the IMB in protecting the structures from severe vibration induced by high-frequency earthquake ground motions. Although exhibiting similar mitigation effectiveness to the HMB, the IMB has the capacity of fulfilling a more effective deformation constraint when subjected to pulse-type ground motions.