Response of space frame structure resting on non-linear rubber base isolation system

The response of a multi-storey space frame structure resting on non-linear rubber base isolation system (lead rubber bearing), subjected to bi-directional harmonic and seismic ground motions are studied. A four-storey space frame structure having six degrees of freedom (three translations along x, y, z-axes and three rotations about these axes) at each node is considered for the study. The response quantities obtained from the analysis are the acceleration, base shear, bending moment and displacements. In this study, the response of the base isolated structure is compared with the response of the corresponding fixed base structure. It is found that the base isolation system can be used effectively to suppress the dynamic response of a multi-storey space frame structure. In addition, the effects of superstructure time period, isolation period, excitation frequency, post-to-pre yield stiffness ratio and yield force on the effectiveness of the base isolation system are also inves-tigated. It is shown that these parameters have considerable influence on the effectiveness of the base isolation system in reducing the response of the structure.