Vibration Analysis of Base-Isolated Table Installing Rotational Inertia Mass. Study on Optimization for Arrangement of Pulleys and Inertia Moment of Rotational Inertia Mass.

Abstract

In this paper, the optimum design of the seismic base-isolated table with a rotational inertia mass (R.I.M.) is executed from the point of view of minimizing the rotational moment caused by restoring forces applied to the table and of linearizing the restoring force of nonliear hardening-type which causes the keen spikes in acceleration response of the table. For the first time, a planar optimum arrangement of pulleys is obtained under the above condition. Although this planar optimum arrangement of pulleys succeeds in making the rotational moment of the table zero and linearizes the nonlinear restoring force as well as possible, the weak nonlinear hardening-type characteristics of the restoring force still remain. Then, the optimization of inertia moment of the R.I.M. exists and can be obtained, because the R.I.M. rotates according to the movement of the rope installed between pulleys and produces the spikes in acceleration if too large an inertia moment is selected. Finally, the table with this optimum arrangement of pulleys and inertia moment of the R.I.M. is confirmed to give the desirable response through simulation and experiment.