NONLINEAR DYNAMIC BEHAVIOUR OF BASE-ISOLATED BUILDINGS WITH THE FRICTION PENDULUM SYSTEM SUBJECTED TO NEAR-FAULT EARTHQUAKES

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.

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Finite Element Formulations and Theoretical Study for VCFPS

Seismic Engineering ◽

10.1115/pvp2003-2117 ◽

2003 ◽

Author(s):

C. S. Tsai ◽

Tsu-Cheng Chiang ◽

Bo-Jen Chen

Keyword(s):

Finite Element ◽

Base Isolation ◽

Ground Motions ◽

Base Shear ◽

Pendulum System ◽

Near Fault ◽

Base Isolator ◽

Friction Pendulum ◽

Finite Element Formulations ◽

Friction Pendulum System

The friction pendulum system (FPS), a type of base isolation technology, has been recognized as a very efficient tool for controlling the seismic response of a structure during an earthquake. However, previous studies have focused mainly on the seismic behavior of base-isolated structures far from active earthquake faults. In recent years, there have been significant studies on the efficiency of the base isolator when subjected to near-fault ground motions. It is suggested from these studies that the long-duration pulse of near-fault ground motions results in significant response of a base-isolated structure. In view of this, an advanced base isolator called the variable curvature friction pendulum system (VCFPS) is proposed in this study. The radius of the curvature of VCFPS is lengthened with an increasing of the isolator displacement. Therefore, the fundamental period of the base-isolated structure can be shifted further away from the predominant period of near-fault ground motions. Finite element formulations for VCFPS have also been proposed in this study. The numerical results show that the base shear force and story drift of the superstructure during near-fault ground motion can be controlled within a desirable range with the installation of VCFPS. Therefore, the VCFPS can be adopted for upgrading the seismic resistance of the structures adjacent to an active fault.

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