EFFECT OF PLAN GEOMETRY ON STRUCTURAL ECONOMICS IN EARTHQUAKE . RESISTANT DESIGN OF RC BUILDINGS

Abstract

Building may have different plan geometry. The plan geometry may have different shapes like square, rectangular, circular, etc. The square and rectangular are most common plan geometry used in construction of RC buildings. As per IS 1893 (Partl): 2002 [7] to perform well during an earthquake, a building should posses four attributes mainly, simple and regular configuration, adequate lateral strength, stiffness and ductility. IS code provisions are same for square and rectangular plan geometries. But they may behave differently when subjected to lateral loads, and therefore, there is a need to study the structural behavior of buildings having same floor area but different plan geometries. Because of different plan geometry, the number of structural members like beam and column may be different. Therefore in the buildings having different geometry the structural cost may come out to be different keeping all other things same. Further, the accidental torsion for the building with regular plan geometry will also depend on the plan dimension, i.e., length and width. The accidental torsion is considered in the analysis. An attempt is made to study the effect of plan geometry on the structural cost. Three different types of buildings have been considered for study in this dissertation: type I building is 24 in x 24 m, type II building is 36 m x 16 m and type III building is 48 m x 12 m in plan. The floor area is 576 m2 for all the three types of building. All the three types of building have been modeled and analyzed by SAP 2000 [12] using response spectrum analysis as per IS 1893 (Partl): 2002 [7]. Each `Type' building consists of four storey, six storey, and eight storey buildings. Complete detailing of buildings has been done as per IS 13920: 1993 [8]. The structural cost of these buildings has been computed. The structural cost is the cost of the reinforcement steel and concrete required for beams and columns of the buildings. The comparison of structural cost of the three buildings of the same type is called structural economics. The structural economics of these three types of building with four, six and eight storey has been work out