EFFECT OF ISOLATION DAMPING ON THE RESPONSE OF BASE ISOLATED STRUCTURE

The response of a multi-story space frame structure resting on non-linear base isolation system, subjected to bi-directional harmonic and seismic ground motions are studied. A four-storey space frame structure with consistent mass system having six degrees of freedom (three translations along x, y, z-axes and three rotations about these axes) at each node is considered for study. The effect of isolation damping and the excitation frequency on the response of a base isolated structure is investigated. The effect of excitation frequency, isolation period, superstructure time period and superstructure damping on the optimum isolation damping is also studied in this paper. It is shown that the above parameters have significant effects on optimum isolation damping. The response of isolated system is found to be less in comparison to the corresponding response without isolation system, implying that the isolation is effective in reducing acceleration and forces of the system.