Effect of Superstructure and Isolator Time Period on the Response of Base Isolated Structure

The response of a multi-storey space frame structure resting on laminated rubber bearing, subjected to bi-directional harmonic and seismic ground motions are studied.Afour-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 superstructure and isolator time period on the response of base isolated structure is investigated. The effect of frequency ratios, superstructure damping and number of storeys on the response of base isolated structure is also studied in this paper. 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 in the system. It is also found that the superstructure time period, isolation period, excitation frequency, superstructure damping and number of storeys have considerable influence on the response of a base isolated structure.