Seismic response of six-storey base isolated building subjected to earthquakes of different characteristics

Seismic base isolation is now an accepted practice, in many parts of the world, for controlling the earthquake response of important buildings. For low to moderate height buildings, natural rubber bearing is often considered suitable because of its durability, easier fabrication and better control of flexibility and damping The effects of earthquake characteristics and of bearing characteristics such as variation of damping and post-yield stiffness of isolation system, on effectiveness of base isolation. have not been studied throughly. In this analytical study, effect of these parameters are studied for a six-storey reinforced concrete building base isolated by rubberbearings, Five earthquakes, recorded at different sites in India, are considered in this study. It is observed that response of the base isolated building is reduced significantly as compared to fixed base building for the ground motions in which dominant frequency is in the range of 2 Hz to 5 Hz, while the reduction in response is not substantial for ground motion possessing frequency close to 0.5 Hz. It is found that isolation damping is effective in reducing base displacement. The choice of post-yield stiffness and damping of isolators is observed to be crucial as their larger values may result in increased forces.