SLIDING ISOLATION USING VARIABLE FREQUENCY BEARINGS FOR

In order to overcome the low-frequency resonance problem that a conventional sliding isolation system may encounter when subjected to an earthquake with near-fault characteristics, a sliding isolator with variable frequency is proposed in this study. The isolator is similar to a typical friction pendulum system (FPS), but the sliding surface has been made of an axially symmetric surface with a variable curvature, rather than a spherical surface with a constant radius, so the isolation frequency becomes a function of the isolator displacement. A polynomial function has been employed to define the geometry of the sliding surface. A parametric study has been conducted to decide the optimal values of the polynomial function. Since the isolation frequency of the proposed isolator is not a constant, the low-frequency resonance due to long-period components of a near-fault earthquake can be prevented. Numerical study has demonstrated that, when subjected to a long-period pulse-like earthquake, the proposed isolator is able to simultaneously reduce the isolator drift and structural acceleration, as compared with those of a conventional FPS system