EVALUATION & COMPARISON OF SEISMIC DESIGN FORCES FOR BUILDINGS WORKED OUT BY VARIOUS CODES

Abstract

The present thesis work compares the seismic provisions of 1984 "Criteria for Earthquake-Resistant Design of Structures" (IS) of India, 1991 "Uniform Building, Code" (UBC) of U.S.A., 1981 "Earthquake-Resistant Design Methods for Buildings" (SJ) of Japan, 1992 "Code of Practice for General Structural Design and Design Loadings for Buildings" (NZS) of New Zealand and 1989 "National Standard of People's Republic of China'- (GBJ) of China regarding the determination of base shear, distribution of the base shear along the height of building, fundamental time period and method of Modal analysis. For comparison a numerical study has been carried out of a 6 storeyed symmetrical building by Pseudo-static approach and 3-D Dynamic analysis. The base shear, pattern of it's distribution and fundamental time period determined as per the codal provisions of these 5 countries has been compared with that obtained by 3-D dynamic analysis. Regulations regarding P-A effects and storey drift limitations of 17 countries mentioned in the World List -1992 have been studied. Actual storey drifts and it's limiting values have been obtained for the above mentioned building example according to these regulations. This has been done for a comparitive study with the drifts obtained by 3-D dynamic analysis. A detailed study has also been carried out to compare the provisions of a 20 countries regarding torsional eccentricity. For numerical purpose an asymmetrical building has been analysed and the design eccentricity between the centre of mass and centre of rigidity has been determined according to the empirical formulae suggested by these countries. Stress has also been laid upon highlighting the provisions embodied in the codes of these countries regarding the accidental eccentricity. The work presented also emphasises upon studying the development of the Indian Standard codal provisions regarding buildings. Amendments done to these provisions in the subsequent revisions of the Indian Standard have been spotted out. It can be concluded that the basic philosophy involved in the drafting of the codes of these countries is same, yet is regulations there are differences_ The difference) are only in the degree and not in the basic structiure of the code.