Analytical study of the effect of LRB isolators positioning at the base and inter-story levels on seismic response of RC buildings

In this study, the effect of isolators positioning at three Levels and different arrangements on seismic response of RC buildings are investigated. For this purpose 18 RC building of 4, 8 and 12 story with and without lead rubber bearing (LRB) isolators were selected. The LRB isolators positioned at three Levels and five different arrangements were modeled in Opensees software. The near field and far fault earthquakes were added to the frames and incremental dynamic analysis was performed. The fragility curves base on inter-story drift ratio as well as the IDA curves base on maximum inter-story drift ratio, maximum base shear, maximum roof displacement and acceleration versus peak ground accelerations (PGA) were plotted and compared. The results showed that among the isolated structures, the isolator positioning at the level of below the first floor (type 1 and type 2) had the best performance in reducing responses. The positioning type 1 (MSI-1) resulted the best decreasing in inter-story drift ratio and base shear. In addition, this type of isolator had the best increasing the PGA according to median fragility between the different types of the positioning levels. The recommended type of isolator had the best performance, especially in high rise buildings in severe damage levels.