EVALUATION OF MODAL COMBINATION TECHNIQUES FOR DYNAMIC ANALYSIS OF MULTISTOREYED BUILDINGS

Abstract

This dissertation work includes study of different modal combination techniques for some of the multistoreyed buildings constructed in India, with the aim to evaluate the formula for modal combination given in IS: 1893-1984. The formula is based on paper presented by Arturo and Raul Husid (1963). This formula gives maximum response as a linear combination of the SRSS superposition and absolute value superposition of modal maxima. Six multistoreyed buildings ranging from 8 to 36 storeyes located in New Delhi, Bombay and Calcutta have been considered. Buildings have been analyzed by time wise mode combination using Newmark's 0 scheme, The time history analysis is considered as a basis for comparison. The spectrum compatible time history has been used for this purpose. Further the same buildings have been analyzed by Response spectrum technique.Modal combination techniques applied are absolute sum method. Square root of sum of squares method, IS: 1893-1984 code method, complete quadratic combination method double sum combination method and Professor A.K. Gupta's Method. The dynamic response quantities are compared for regular buildings. Square root of sum of squares method is seen to give much closer response to time history analysis as compared to other methods.