Empirical Period-Height Relationship for reinforced Concrete Moment Resisting Buildings in India

Abstract

The fundamental period of vibration of buildings is the unique parameter that has a major influence on the earthquake induced lateral forces. Many design codes provide simple empirical period -height relationships for the determination of the fundamental period of vibration but using these equations time period and the resulted base shear are conservatively estimated. In most design cases the results obtained using conservative estimates formulae are largely deviating from the required engineering accuracy. Therefore a relationship is sought that will give accurate prediction of period of vibration for structural assessment of Indian reinforced concrete moment resisting frame buildings. On the basis of fundamental period of vibration of an Indian reinforced concrete moment resisting frame (RC MRF) building, obtained by finite element analysis, new equation has been proposed. In this study 21 existing reinforced concrete moment resisting frame buildings in India, with varying length, width and height are considered. The fundamental time periods of all the selected buildings were calculated using finite element method and IS 1893(Part 1) : 2002 based empirical formula. The comparison of proposed equation with Indian code shows that finite element analysis yielded 100 % higher periods as compared to the code approach.