Development of an innovative three-dimensional vibration isolation bearing

This paper presented an innovative three-dimensional vibration isolation bearing (3D-VIB) to mitigate horizontal seismic action and rail-induced vertical vibration. The 3D-VIB was composed of a thick laminated rubber bearing acting as the vertical vibration isolation module and a friction pendulum acting as the horizontal seismic isolation module. The thick laminated rubber bearing was used as a part of the slider in the friction pendulum. The compression performance of 3D-VIB was decoupled from its shear performance by concentrating the compressive deformation into the thick rubber bearing while shear deformation occurred independently in the friction pendulum module. The bearing capacity, vertical and horizontal properties of a full-scale 3D-VIB specimen were tested. In the test, the ultimate bearing capacity of 3D-VIB was 7 times that of the design compressive load of normal service condition. The vertical stiffness of the specimen under seismic vibration and vertical rail-induced vibration were tested separately. It was found that the vertical stiffness of the specimen under rail-induced vibration was 1.55 times higher than the vertical stiffness under seismic vibration. The horizontal performance of the 3D-VIB was characterized by stable parallelogram-shaped hysteretic curves similar to that of the traditional friction pendulum system. A user-defined element was developed and incorporated into ABAQUS to simulate the mechanical behavior of the 3D-VIB under different loading conditions, and simulation results agreed with the test results. The responses of a steel structure equipped with the 3D-VIB, while subjected to earthquake ground motions and rail-induced vibrations, respectively, were analyzed and compared with the non-isolated one. The analysis results suggested that with the installation of the 3D-VIB, the maximum inter-story drift ratio of the structure under maximum considered earthquake was reduced by about 88%. The average maximum transient vibration value of the rail-induced vertical vibration at the typical points of the conventional model was 86.2 dB, while that in the 3D-isolated model was 78.6 dB, the vibration reduction was 7.6 dB.