SEISMIC RETROFITTING OF STRUCTURES BY CONVENTIONAL METHODS

Abstract

Earthquakes that occurred recently have exhibited many vulnerability issues of different buildings. This is mainly caused due to the changes in the ground motions lately .These existing buildings which were designed and constructed according to the earlier codes, may not satisfy the requirements of the present seismic codes making them to be prone to the earthquakes with moderate to extensive damages and sometimes also leads to complete collapse. Thus, it is important to prevent the unacceptable seismic hazards to life and property of the people. For the better performance of these structures. Rehabilitation in form of seismic retrofitting plays an important role. Preparedness and awareness are the key role in mitigating a disaster and thus for the protection of the structures and preventing the loss of life, Retrofitting of the seismic deficient existing structures is a must. This present work deals with Seismic retrofitting of a G+6 storied Reinforced Concrete building located in the seismic zone IV those constructed using two design philosophies. One that is designed using IS 456:2000 and other using the Earthquake codal provisions of 1S1893:2002 (part -I) along with the ductile detailing provided in IS 13920:1993.This study also comprises of the evaluation of the building under gravity along with the lateral loads and providing them with a proper retrofitting method on the basis of study of the damage probability index derived from fragility curves. This work can be broadly divided into two steps. First the evaluation of the building by calculating the capacity of each member and building as a whole along with the calculation of resistance of the building towards the demand and thus arriving at the performance point of the building. Secondly, based on the evaluation, to locate the damage that a building undergoes in a particular seismic zone and to provide the excess amount of resistance in the form of stiffness of the building towards the demand, with the provision of steel bracings and the shear wall .The location of the shear wall plays an important role and thus provided on the exterior sides of the frame and the steel bracings as x' diagonal struts.