FINITE ELEMENT FORMULATIONS AND EXPERIMENTAL STUDY FOR DIRECTION OPTIMIZED-FRICTION PENDULUM SYSTEM

摘要

The Friction Pendulum System (FPS) invented by V. A. Zayas in 1987 has been widely used in the seismic engineering all over the world. The efficiency for upgrading the earthquake-proof capability of a fixed base structure has been proved either from theoretical studies or experimental efforts. However, the seismic responses of the FPS-isolated structure are always significant as subjected to near fault earthquakes and strong ground motions with long predominant periods. In order to overcome the drawback of the FPS, a new base isolator named as the Direction Optimized Friction Pendulum System (DO-FPS) has been proposed in this study. The proposed device is mainly composed of a spherical sliding surface, a trench concave surface and an articulated slider. By using the special design, the isolation period is a function of the angle between the directions of the resultant displacement. Therefore, the undesirable phenomenon of resonance could always be prevented. In order to verify the functionality of the proposed device, the shaking table tests of a three story steel structure with DOFPS base isolators have been performed. The test results reveal that the proposed device can effectively upgrade the seismic resistibility of a conventionally fixed base structure. Furthermore, the comparisons between the numerical and the experimental results show that the theory proposed in this study could predict the nonlinear behavior of the DO-FPS with good accuracy.