Impact of Concrete Masonry Unit Geometry on Masonry Assemblage Strength

An experimental investigation of 126 masonry prisms was conducted to assess the influence of concrete masonry unit web height on structural response. All prisms had the same overall geometry, were either grouted or left hollow, and included either: regular stretcher units with full-height webs, knock-out units with remaining web height conforming to typical Canadian practice, or knock-out units with remaining web height resulting in a calculated normalized web area approaching the minimum permissible in accordance with U.S. standard ASTM C90. Cracks in hollow prisms shifted from the centre of the exterior web face for those constructed with regular stretcher units to the web-face shell interface as the remaining web height decreased. The stability of the grout columns in grouted prisms reduced stress concentrations at the web-face shell interface and the effects of increased restraint with reduced height-to-thickness ratio.