Effect of soft storey in a structure present in higher seismic zone areas

Abstract

The use of unreinforced brick masonry as infill material in reinforced concrete frames is inevitable even in higher seismic zone areas. With increasing demands for architectural features in buildings, the provision of soft storey is a common practice in many multi storeyed structures throughout the world, for parking. The standard code of practice in many countries suggests higher design forces for the columns present in the soft storey. In order to understand the affect of increase in design seismic forces on the columns in a structure present in higher seismic zone areas, a study is carried out by taking pushover analysis as a tool for obtaining capacity of the structure. A comparative study between three types of arrangements; type I: structure with infill walls in all floors, type II: structure with open ground storey, type III: structure with open ground storey and columns designed for increased forces. It is observed that there is an increase in maximum load carrying capacity for the type III structure as compared to type II structure with no considerable change in behaviour of the two types of structures. It can be concluded that the increase in design forces of the columns at open ground storey may not lead to the safety as of structure type I. Keywords: Unreinforced brick masonry (URM), multi storeyed structures, higher seismic zone areas, soft storey, pushover analysis