IIIT Hyderabad Publications
Evaluation of Empirical Expression for Fundamental Natural Period of RC Moment Resisting Frames and RC Shear Wall Buildings in India
Author: Pulkit Velani
Report no: IIIT/TH/2016/40
Advisor:Pradeep Kumar Ramancharla
Urbanization is rapidly increasing in almost every city in India. Huge infrastructure developmental plans have been laid by government and private organizations. There are quite a few codes and buildings by laws are available for construction of these buildings but many of them lack in addressing the parameters for seismic design. Some issues related to seismic behaviour are still not resolved. Researchers all over the world are continuously working towards development of latest techniques for improving earthquake safety of buildings. Among several aspects, the fundamental natural period ‘T’ of the building is one of the important parameters in the earthquake resistant design of buildings. The fundamental period will decide the base shear to be resisted by the structure. Apart from knowing the seismic demand the natural period also gives insight about the damage status of the structure. Present version of Indian seismic code gives empirical formulae for natural period. These expressions of the fundamental period is originally developed based on Californian earthquakes and adopted by many of the seismic codes around the world; including current Indian seismic code IS 1893: 2002. This research study aims to check the viability of the current provision of Indian seismic code for the approximate formulae given for RC buildings with infill walls. For this purpose, ambient vibration study has been carried out in Indian cities viz. Hyderabad, Chandigarh, Mumbai and Nanded, by placing vibration sensor on topmost accessible floor. All together there are 90 RC MRF buildings and 14 RC SW buildings were tested out of which 74 RC MRF and 14 RC SW buildings were selected for further analysis. With the regression analysis performed on the new database, a conservative empirical expression is proposed for finding natural period T of RC MRF buildings and RC SW buildings.The measured periods have been compared with the code provisions. Study found that current empirical equation holds good only for low-rise RC MRF buildings, it often overestimates the natural period for medium-rise buildings with more than thirty metre heights. In case of RC SW buildings it underestimates the natural period and there by overestimates the seismic demand of a building. Hence there is an urgent need for revision of the empirical expression.
Full thesis: pdf
Centre for Earthquake Engineering
Copyright © 2009 - IIIT Hyderabad. All Rights Reserved.