SEISMIC BASE ISOLATION DESIGN FOR MEDIUM RISE BUILDINGS

Abstract

Earthquake protection of buildings using base isolators- has received considerable attention in recent times. The basic concept is to decouple the superstructure from the damaging effect of horizontal component of earthquake from foundation by introducing flexibility at the support. The fundamental principle of base isolator is to modify the response of the building without transmitting these motions into the building and to elongate the time period of the structure thus reducing the force on the structure. In the present study plan of two types of four storey reinforced concrete frame structure middle income group (MIG) and high income group (HIG) residential building have been considered. The residential buildings are proposed to be constructed in an upcoming power plant site in Haryana. The 3D modelling and analysis of both types of structure with fixed base and base isolator has been made. The structural components should not completely collapse after the earthquake and the non structural components should be operational after the earthquake. For operational performance of non-structural components, the drift limit for residential buildings should be within 1%. The performances have been evaluated using Non-linear static analysis. The performance point evaluated using push-over analysis has ensured the hinges to be below Intermediate Occupancy level and the inter story drift has also been limited to 1%. Non linear time history analysis of both MIG and HIG buildings with fixed and isolated base has been carried out. The detailed design of lead plug bearing has been carried out. For convenience only one type of isolators are used for both the type of buildings. Design of isolator is completed with the design of bolts which will connect the isolators with the foundation and structure. Numerical analysis of base isolated buildings has been carried out to estimate its seismic behaviour. A comparison has also been made between the fixed base and base isolated buildings.