Out-of-plane flexural testing and stiffness response of concrete masonry walls with NSM steel reinforcement

Abstract

Near-surface mounted (NSM) reinforcement is used to retrofit masonry structures for increased strength and resiliency; however, its application to new masonry construction remains largely unexplored. Four masonry walls measuring 3.2 m tall were constructed from hollow concrete blocks to assess the potential of NSM reinforcement to increase flexural stiffness. Two of the walls were reinforced conventionally, and two were reinforced with NSM bars. Each wall had a total area of steel reinforcement of 600 mm2 and was loaded under conditions of third-point out-of-plane flexure. All four walls had similar flexural strength, ranging from 24 kNm to 26 kNm; however, the stiffness (determined using direct measurement of curvature, curvature calculated using conditions of equilibrium and compatibility, and the load displacement response) of the NSM reinforced walls was twice that of the walls with conventional reinforcement. The flexural stiffness of the masonry walls was underestimated by current Canadian design standards provisions under low out-of-plane loads.