STUDY OF DEVELOPMENT OF BASE ISOLATION SYSTEM WITH ROTATIONAL INERTIAMASS

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In this research, a seismic base isolation system with a rotational inertia inertia mass and nonlinear restoring force is developed. Tha table of system is supported by ball bearings and produces restoring force by means of a rope and pulleys. Thenonlinear dynamic characteristics of this system are investigated analytically and experimentally. And also, the optimum design of this system is excuted from the point of view of minimizing the rotational moment caused by restoring forces applied to the system and of linearizing the restoring force of nonlinear hardening-type which causes the keen spikes in acceleration response of the table. The results obtained from this research are summarized as follows.1. The developted nalytical model of this system has been examined and proved to be vaild through comparison between the simulations and experiments.2. It has been proved that the input scismic acceleration from ground motion to the system was lost due to the effect of the installed rotational inertia mass.3. The waveform of acceleration obtained from the dynamic experiment showed keen spikes due to the effect of the nonlinear characteristics of the system, and this phenomenon has been clearly analyzed by the method of harmonic balance.4. The system with the optimum arrangement of pulleys and optimum inertia moment of the rotaional inertia mass was confirmed to give the desirable response through simulations and experiments.