Non-linear time domain analysis of base isolated multi-storey building under site specific bi-directional seismic loading

The incorporation of base isolation in building construction in the region of medium risk seismicity is now an important issue. Thorough investigation is needed for buildings located in those regions, to be incorporated with base isolator and then dynamic analysis to carry over. This research provides incorporation of Lead Rubber Bearing and High Damping Rubber Bearing as base isolators in addition to focussing on the changes of structural parameters for isolating effects in those vicinities. Nonlinear models of Lead Rubber Bearing and High Damping Rubber Bearing have been built up. The design of base isolators for building construction is covered along with structural feasibility. Linear static, free vibration and nonlinear dynamic time domain analyses are performed for both isolated and non-isolated buildings under site specific bi-directional earthquake. The automated Newmark-beta time integration approach has been adopted for solution in time domain. The nonlinearities, arising due to base isolated bearings and seismic forces are duly considered. The study reveals that for medium rise building construction, isolation can significantly reduce seismic response in soft to medium stiff soil. The reduction of overturning base moment due to isolation indicates that the building becomes more stable compared to the fixed base structure. Modelled non-linear bearings have been found to be suitable to cope with the precise nonlinearities. The building experiences more flexibility even when using the same structural element configuration. In addition, the flexibility of the structure envisages some sort of savings due to reduced structural responses through incorporation of the isolator. In seismic vulnerable areas where the main concern is the mitigation of the seismic instability with the support of critical components, the study shows the effectiveness of the base isolation system in terms of lessening structural responses under seismic loading. (C) 2011 Elsevier By. All rights reserved.