Effect of Revised Seismic Design Provisions on Seismic Performance of RC Frame Buildings with and without Infills

Abstract

Indian Standard for seismic design of Reinforced Concrete (RC) frame buildings with Un-Reinforced Masonry (URM) Infills have undergone significant revisions in 2016 compared to its older version in 2002 and 1993, respectively. Two of the major revisions of BIS 13920-2016 are the inclusion of capacity design criteria to ensure strong-column weak-beam and selection of column dimension based on largest longitudinal beam rebar. The revised seismic design standard also recommends modeling guidelines for Un-Reinforced Masonry (URM) infill using the equivalent diagonal strut to take into account the complex infill-frame interaction. Under lateral loading, infills contribution to global strength and stiffness is often ignored for being treated as non-structural elements in general design practice. The present study attempts to evaluate the comparative seismic response of Special Moment Resisting Frame (SMRF) RC buildings with and without infills, designed with revised and older versions of Indian seismic standards. Capacity curves have been developed through nonlinear static pushover analysis. It has been observed that revised code provisions improve the structural performance in terms of stiffness, strength, inelastic displacement capacity, and eventually results in the desired ductile failure mechanism of the RC frames. However, considering the effect of infills as per the revised Indian standard has led to reduced inter-storey drift and ultimate inelastic deformation compared to the bare frame and the general design practice. It has been observed that the infill-frame interaction plays a key role in the overall performance as well as govern the failure mechanism of the structure as a whole.