EFFECTS OF LOCATIONS OF BASE ISOLATORS ON SEISMIC BEHAVIOUR OF RCC FRAMED BUILDING

Abstract

The base isolation is one of the most widely implemented and accepted seismic protection systems used in earthquake prone areas. The basic principle of base isolation is to reduce the seismic demand of the structure rather than increasing the capacity of structure. It helps in increasing the natural period of the structure away from the high energy periods of the earthquake and prevents the structure from ground motions being transmitted from the foundation into the structure above. The thesis work comprises of comparing the effects of location of base isolators on seismic behaviour of Base Isolated (B.I.) building with the Non Base Isolated (N.B.I.) building. The two types of locations of isolators are considered, one at top of the basement column and other at the bottom of the basement column. The dynamic characteristics and seismic responses of B.I. and N.B.I. buildings for hard type of soil as per IS 1893 (Part I):2002 are calculated and compared. The effects of soft soil and medium soil on isolation system are also compared for a typical earthquake time history. A four storey Building is modelled in SAP 2000 and the loadings have been applied as per IS 875 (Part II):1987. The two types of earthquake time history namely Uttarkashi and Chamoli earthquake having different dominant frequency are used for the analysis. The Lead plug rubber bearings having bi-linear force-displacement behaviour is used. The design parameters and dimensions of the Lead plug rubber isolator are derived and modelled in SAP 2000. The linear and non linear seismic responses of B.I building (isolators at top and bottom) are compared with N.B.I building.