The performance of reinforced concrete (RC) infilled frames during earthquakes shows that the behaviour is very much dependent on the performance and mode of failure of the infill masonry walls. The concrete frame may fail as a consequence of the infill wall failure before reaching the bare frame load resistance levels. Even though frameinfill interaction has sometimes led to undesirable structural performance, recent studies have shown that a properly designed infilled frame can be superior to a bare frame in terms of stiffness, strength, and energy dissipation. The objective of this paper is to present a new finite element model based on prescribed failure planes in the infill panels, where Drucker-Prager failure criterion is used to simulate the behaviour of masonry. Interface elements are
used to describe the behaviour of masonry panel along the prescribed failure planes. The elasto-plastic behaviour of mortar and cracked masonry along the failure planes are considered in the analysis. The proposed model was incorporated in a generic nonlinear structural analysis program for static and dynamic analysis of masonry infilled reinforced concrete frames. Simulations of experimental force-deformation behaviour of large scale infilled frame are performed to validate the proposed model.
A low cost and effective scheme has been developed for retrofitting masonry-infilled reinforced concrete (RC) frames.
Three ¾ scaled models of single bay, single story non-ductile RC frames with un-reinforced masonry (URM) infill panels were tested under horizontal cyclic loading and a constant vertical load. The experimental results indicate that an un-retrofitted specimen suffers corner crushing and abrupt shear failure in the columns at a very small drift ratio of
0.50%. The retrofitted masonry panel is separated from the columns so that no shear is transferred to them. Steel brackets are provided to transfer the interactive forces between the RC frame and URM panel. The peak lateral load decreases approximately in proportion to the area reduction ratio of the panel with desirable gradual drop in capacity whereas the drift capacity increases to about 1.50%. The retrofit scheme compares favorably with others incorporating either heavy mesh reinforcement or carbon fiber reinforced polymer.
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