Strategies to enhance seismic performance of reinforced masonry shear walls

Better understanding of the structural behaviour of concrete and masonry structures is facilitated through experimental testing. Although some experimental testing of reinforced masonry (RM) rectangular walls is reported in literature, little experimental data is available on RM walls with flanges or with boundary element. Unlike those pertaining to rectangular walls, seismic design provisions of flanged and end-unconfirmed masonry walls are not available in North American masonry design codes.;High levels of ductility accompanied by relatively small strength degradation were observed in all walls in general with a significant increase in ductility and displacement capabilities for the flanged and end-confirmed walls compared to the rectangular ones. The drift levels attained at 20% strength degradation by the rectangular, the flanged, and the end-confined walls were 1.0%, 1.5%, and 2.2%, respectively. The ductility values of the flanged and end-confirmed walls were, respectively, 1.5 and 2.0 times that of their rectangular wall counterparts. In addition to the enhanced ductility, a saving of more than 40% in the amount of vertical reinforcement was achieved using the proposed alternative strategies while maintain the lateral resistance. The relationship between the energy dissipation and the ratio of the post-yield to the yield displacement was found to be almost linear for the test walls. Wall stiffnesses degraded rapidly to about 60% of their gross stiffness at very low drift levels (0.1% drift). Measured compressive strain at the wall toes were almost double those specified in both North American codes. Extent of plasticity over the wall height was about 75% of the wall length. Equivalent plastic hinge lengths, needed in wall displacement predictions, using theoretical curvatures and experimental displacement ductilities varied between 17% and 40% of the wall length at ultimate load for all the tested walls. The test results indicated that higher seismic force modification factors should be assigned to the flanged and end-confirmed RM shear walls compared to values currently assigned to rectangular walls.;The data presented in this study is expected to facilitate better understanding of RM wall behaviour under in-plane load to researchers, practicing engineers, and code developers. This study aimed at presenting the flanged and end-confirmed categories as cost-effective alternatives to enhance the seismic performance of mid-rise RM construction in North America.;In the current study, the response of seven half scale fully grouted RM shear walls, all with the same length but different end configurations and aspect ratios is investigated. The goal of the study was to evaluate and document the enhanced ductile behaviour of rectangular RM shear walls when flanges and boundary elements are structurally connected at the wall ends. Another goal was to extract specific seismic performance parameters of reinforced concrete-block rectangular, flanged and end-confirmed shear walls based on quasi-static experimental results. Finally, nonlinear dynamic analysis was conducted on the test walls to quantify seismic force modification factors used in seismic design.