The base isolation technology has been recognized as a very effective tool for controlling the seismic response of a structure during earthquakes. However, it is suggested from recent studies that the earthquakes with long predominant periods results in significant seismic responses of the base isolated structure. In view of this, a new base isolator called the Directional Optimized-Variable Curvature Friction Pendulum System (DO-VCFPS) has been proposed in this study. The radii of the curvature of the trench concave surface and the spherical sliding surface are lengthened with increasing the sliding displacement. Therefore, the isolation period can be shifted further away from the predominant periods of ground motions. Furthermore, by using the series connection of a trench concave surface and a spherical sliding surface, the isolation period is a function of the angle between the directions of the resultant displacement. In order to prove the efficiency of the proposed device, the finite element formulations of the DO-VCFPS have been derived in this study. The numerical results show that the combination of the advantages of the Variable Curvature Friction Pendulum System (VCFPS) and the Directional Optimization Friction Pendulum System (DO-FPS) can improve the disadvantages of a base isolated structure with fixed isolation period.
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