Effect of Base Isolation on the Seismic Performance of Hill Buildings

RC buildings constructed on hill slopes pose complex structural behaviour as compared to conventional buildings resting on a plain ground. The hill buildings come under the category of irregular buildings, which are asymmetric in elevation as well as plan at different floor levels, due to which the centre of gravity and stiffness at subsequent floor levels always vary and cause additional torsional moments in the buildings. Further, the length of the columns in hill buildings also varies pertaining to steep slopes, resulting in variation of lateral stiffness in all columns. Moreover, the base isolation systems have shown a profound effect to reduce the seismic vibrations in the buildings. Thus, in this study, the influence of a commonly used base isolation system, i.e. Laminated Lead Rubber Bearing (LLRB) on the seismic performance of two hill building configurations, viz. stepback and setback-stepback, was investigated. All the configurations have been modelled using a finite element software, and examined by Response Spectrum analysis and Non-linear Static Pushover analysis. The dynamic parameters obtained from the numerical study were discussed as variations in storey shear, base shear, time period, drift, maximum top storey displacement values and plastic hinge development pattern in the building structure. finally, the vulnerability and suitability of the different configurations against seismic excitations were compared.