Static Cyclic Response of Partially Grouted Masonry Shear Walls

This research investigated the shear behavior of five full-scale partially grouted masonry shear walls (PG-MWs). The walls were built using concrete masonry units, with horizontal reinforcement ratios ranging from 0.085 to 0.169%. The specimens had horizontal spacing between vertical grouted cells ranging from 610 (24 in.) to 1,219 mm (48 in.). All the specimens were tested under constant gravity load and incrementally increasing in-plane loading cycles. This research showed that there appears to be a maximum horizontal reinforcement ratio after which no additional shear capacity is achieved. As indicated by the experimental results, the maximum value appears to be approximately 0.1% for specimens with horizontal spacing between vertical grouted cells of 1,219 mm (48 in.). Increasing the horizontal reinforcement beyond this level did not increase the shear strength of the test specimens. In addition, the current provisions of the Masonry Standards Joint Committee (MSJC), the New Zealand code for masonry structures, Fattal’s model, and the strut and tie model were used to predict the shear strengths of the test specimens. The current MSJC shear equations overestimated the strength of PG-MWs with horizontal spacing between the vertical grouted cells of 1,219 mm (48 in.). A significant source of this error is from overestimating the contribution of the horizontal reinforcement. In addition, the current MSJC equations overestimated the masonry contribution to the shear strength of PG-MWs. For partially grouted walls with horizontal spacing between vertical grouted cells of 813 mm (32 in.) or less, and a horizontal reinforcement ratio of 0.085%, the MSJC shear equations are adequate. Shear equations by other codes and researchers were unconservative, as well. The strut and tie models were able to predict the shear strength of the test specimens within $\pm 16\%$.