SEISMIC ANALYSIS OF R/C FRAMED BUILDINGS

Abstract

The present thesis has been undertaken to carry out some studies on the elastic seismic response of framed buildings. The buildings are modeled as a discrete, lumped-mass multi-degree of freedom (MDOF) system. The time period and maximum responses of the fixed base buildings subjected to ground motion due to seismic excitation are obtained by 3 different methods , i) 2-D Dynamic Analysis , ii) Response Spectrum Method recommended by IS:1893-1984 , -ii) Pseudo-Static Method. In the first method mode superposition method, which is suitable for frames, has been used along with average acceleration spectra of IS code, for seismic loading. Combination of modal maxima of response is achieved by the popularly used square root of sum squares(SRSS). For the second method, 1-D modal analysis (so called response spectrum method by IS code) which is partly based on dynamic analysis have been used. In this case the modal responses are combined by the formulae suggested by IS code and the square root of sum of squares (SRSS). In the third method seismic coefficient method of IS:1S9,-1984 has been used to find the equivalent lateral loads. The results of the building examples obtained by three methods are compared to see up-to what extent the seismic coefficient and response spectrum method overestimates the response quantities of buildings Next the seismic provision of 1981 BSL OF Japan, 1984 IS of India, 1988 UBC of U.S.A., 1985 NBC of Canada and 1984 NZS of New Zealand, for multistorey buildings are presented and compared factor wise. It is found that, in general, the provisions of five countries can be related to, one another in terms of components. A study has also been carried out regarding the distribution of base shear along the height of building according to provisions of the above codes and the pattern of distribution has been compared with the pattern obtained by dynamic analysis.