Seismic Performance Quantification of Reinforced Masonry Structural Walls with Boundary Elements

The design of reinforced masonry (RM) structural walls subject to high inelastic curvature demands can often be hindered by prescriptive requirements in design codes regarding the ratio between compression zone depth (c) and wall length (ℓw). A possible solution to this would be the detailing of a confined boundary element at the critical wall toes to increase the curvature ductility capacity of the plastic hinge region. The Masonry Standards Joint Committee (MSJC) code currently prescribes the possible use of such boundary elements for the special reinforced masonry shear walls category. However, the MSJC provides no relevant prescriptive detailing guidance, leaving the onus on the designer to specify appropriate detailing to ensure the desired performance. The results of an experimental program designed to develop a confinement scheme based on conventional masonry construction practices are reported in this paper. Five half-scale RM walls, detailed with confined boundary elements containing a double layer of vertical reinforcement enclosed by stirrups, were tested under reversed cycles of quasi-static loading. The walls, detailed to represent typical low- to medium-rise construction, varied by their height, length, and aspect and vertical reinforcement ratios. Test results are reported in terms of force-based seismic design parameters, such as the wall strength, stiffness and ductility characteristics, as well as displacement and performance-based seismic design parameters for the next-generation of seismic codes in North America. Overall, the performance of the walls indicates that the selected boundary element detailing is a designer-friendly means of addressing the need for lower c/ℓw ratios and higher curvature levels as indicated by the MSJC.