Seismic Performance Parameter Quantification of Shear-Critical Reinforced Concrete Masonry Squat Walls

In North America, the design of reinforced masonry (RM) shear walls as a seismic force-resisting system (SFRS) is very conservative in terms of quantifying the wall’s shear strength and ductility capacity. In the current study, eight full-scale squat RM walls were tested at McMaster University under quasi-static reversed cyclic loading to quantify their shear strength, idealized displacement ductility, drift-damage relationships, lateral stiffness degradation, and hysteretic damping. The test walls demonstrated shear-strength capacities up to 200% of those predicted by the Canadian Standards Association’s (CSA) masonry design code. In addition, the results demonstrated that the Canadian shear strength expression was, on average, 32 and 34% more conservative than the Masonry Standards Joint Committee (MSJC) and the New Zealand Standards (NZS) design codes for masonry, respectively. Moreover, the simplified modified compression field theory (SMCFT), adopted directly from the Canadian concrete design code, gave the most accurate predictions of the tested walls’ shear strength compared with masonry code expressions. Using bilinear idealization, the wall displacement ductility levels were found to range from 3.8 to 9.0 with corresponding equivalent viscous damping ratios of 8.7–19.2%, respectively. Design-oriented expressions were developed to relate the lateral stiffness degradation to ductility and drift levels. The wall drift-damage relationships were presented in fragility curve format for two predefined damage states. In general, the study attempts to shed some light on the behavior of this understudied SFRS (i.e., RM squat walls) to facilitate its adoption in the next generation of performance-based seismic design codes in North America.