Spring 2011, Vol 13, No. 2

The shape of most of the wall sections in existing unreinforced masonry (URM) structures have L, T, and H shapes, instead of rectangle. Limited research on the effect of return wall (flange) on their seismic behavior has been reported in the literature. The primary aim of this study is to develop a deeper understanding of in-plane response of URM walls with emphasis on return walls. The URM shear walls represent existing masonry structures with poor shear strength. An Experimental program has been conducted on four specimens with aspect ratios of 0.5 and 0.7. Two specimens designed with flanges and, for comparison, another two specimens designed without flanges. All specimens tested under constant axial force corresponding to typical 3-story buildings, and cyclic reversal displacement control loading was applied in horizontal direction. Predicted shear strength based on FEMA-356 has been compared with experimental results. An analytical model has been proposed to predict lateral response of flanged URM walls. The results emphasize on the effect of flanges when seismic assessment of non-rectangular section URM walls is considered.