Identification of seismic failure modes of URM infilled RC frame buildings

Reinforced Concrete (RC) framed buildings with Un-Reinforced Masonry (URM) infills are the most popular structural systems for multistory buildings in many parts of the world. These buildings have shown poor performance during past earthquakes and suffered severe damage or collapse, even under moderate earthquakes. It is a general practice to ignore the infills in design, as their interaction with frame results in complex modes of failure, rendering their simulation a challenging task. Despite significant research effort dedicated to such buildings, the understanding of seismic behavior of infilled frames is still not adequate and guidelines for their modeling and analysis are lacking in the design codes. This paper takes a stock of available earthquake damage survey reports, experimental studies, analytical models and design codes to identify various failure modes of such buildings. The paper also presents a review of available models for estimating the strength of infills and frame members in various failure modes. Based on the review, an analytical study has been carried out to identify the governing failure modes of infills and frame members with an objective to develop guidelines for simulation of seismic behavior of infilled frames.