ELASTOMERIC BASE ISOLATION SYSTEM FOR SEISMIC MITIGATION OF LOW-RISE STRUCTURES

Seismic base isolation is a passive way of achieving seismic response control by introducing isolators between foundation and super structure. Isolator performs three functions: horizontal flexibility, energy dissipation and rigidity against normal lateral loads. Lead Rubber bearing isolators performs these functions efficiently. By reducing the horizontal stiffness of the system, it increases the time period of the structure and decreases the spectral acceleration of the structure. The superstructure acts like a rigid body, thus inter storey drift is reduced. Such type of isolators are used in practice in India, yet a proper design procedure based on IS code is unavailable. The paper presents design procedure for LRB adopting the procedure of IS 1893:2002 (Part-1) for earthquake resistant design of buildings. The design procedure requires different input parameters like fundamental period and damping of the fixed base structure, axial load on the column, seismic zone, type of soil and shore hardness of rubber. Using this methodology, case study has been done using SAP2000. Building displacement, acceleration and inter-storey drift are compared for model with and without base isolator. Comparative study of linear and non-linear base isolators has also been carried out. Linear and non-linear time history analysis has been done using El Centro earthquake.