Nonlinear Dynamics (2006) 43: 329–342 DOI: 10.1007/s11071-006-8327-6 c  Springer 2006 Seismic Evaluation of Multi-Storey RC Frame Using Modal Pushover Analysis S. CHANDRASEKARAN ∗ and ANUBHAB ROY Department of Civil Engineering, Institute of Technology, Banaras Hindu University, Varanasi-221 005, India; ∗ Author for correspondence (e-mail: drsekaran@sify.com) (Received: 7 May 2004; accepted: 26 May 2005) Abstract. The recently developed pushover analysis procedure has led a new dimension to performance-based design in structural engineering practices. With the increase in the magnitude of monotonic loading, weak links and failure modes in the multi-storey RC frames are usually formed. The force distribution and storey displacements are evaluated using static pushover analysis based on the assumption that the response is controlled by fundamental mode and no mode shift takes place. Himalayan-Nagalushai region, Indo-Gangetic plain, Western India, Kutch and Kathiawar regions are geologically unstable parts of India and some devastating earthquakes of remarkable intensity have occurred here. In view of the intensive construction activity in India, where even a medium intensity tremor can cause a calamity, the authors feel that a completely up-to-date, versatile method of aseismic analysis and design of structures are essential. A detailed dynamic analysis of a 10-storey RC frame building is therefore performed using response spectrum method based on Indian Standard Codal Provisions and base shear, storey shear and storey drifts are computed. A modal pushover analysis (MPA) is also carried out to determine the structural response of the same model for the same acceleration spectra used in the earlier case. The major focus of study is to bring out the superiority of pushover analysis method over the conventional dynamic analysis method recommended by the code. The results obtained from the numerical studies show that the response spectrum method underestimates the response of the model in comparison with modal pushover analysis. It is also seen that modal participation of higher modes contributes to better results of the response distribution along the height of the building. Also pushover curves are plotted to illustrate the displacement as a function of base shear. Key words: dynamic analysis, higher mode contribution, modal pushover analysis, pushover curves, response spectrum analysis (RSA) 1. Introduction Design of earthquake-resistant structures is possible using the current state-of-the-art methods in struc- tural engineering but it is not possible to predict the magnitude (intensity) and direction that would be expected on a structure due to earthquake-induced motion. No algorithm has been developed on this front due to the high degree of complexities involved in the process. Earthquake ground motions create inertia or imaginative lateral forces to act at different storey levels along the height of the buildings in a particular direction. Vertical forces are also created in a similar manner but are of less interest. Himalayan-Nagalushai region, Indo-Gangetic plain, Western India, Kutch and Kathiawar regions are geologically unstable parts of India. Some devastating earthquakes of remarkable intensity have oc- curred in this region, which has stimulated the importance of seismic strength assessment of buildings proposed to be constructed in India. Therefore it is essential to understand the seismic analysis of buildings by a much simpler procedure that could lead to accurate and reliable results. Although seis- mic effect on structures are quite complex, the response of many type of structures can be predicted with a greater degree of accuracy by subjecting them to a single set of static forces applied at all floor levels.