Secondary Moment Effects on Slender Reinforced Masonry Walls

Slender masonry walls can be an effective loadbearing component of buildings that require high ceilings such as warehouses and gymnasiums. This type of construction is also efficient in terms of material usage and over-all construction costs. The proven long-term durability of existing masonry buildings makes this construction material an attractive option; however, the limited experimental testing on slender walls in out-of-plane flexure combined with high axial loads have led to conservative prescriptive restrictions on their design in Canadian and U.S. standards. The experimental testing presented herein aims to advance knowledge on Reinforced Masonry (RM) walls and introduces a novel method of reinforcement for new masonry wall construction. This novel method consists of applying Near-Surface Mounted (NSM) steel reinforcement rather than conventional embedded reinforcement. The first phase of the research included numerical Finite Element (FE) analysis and experimental testing of 3 m tall RM walls subjected to four-point out-of-plane loading; the second phase consisted of experimental testing of 8 m tall slender (slenderness ratio kh/t = 42) RM walls subjected to combined axial loading and four-point out-of-plane loading. For both phases, the flexural stiffness (EI) of the walls was assessed through multiple approaches (using reinforcement strain, surface strain, and out-of-plane displacement data), and compared to the stiffness calculated using the current Canadian masonry design standard (CSA S304-14) formulation. The equation for the effective flexural stiffness in the current design standard was observed to underestimate the stiffness response in most loading conditions, however it does not provide a consistently accurate value. An alternative method for calculating flexural stiffness was therefore proposed, which accounts for loss of stiffness from repeated loading, or accidental overload, as well as the effect of applied axial loads. Throughout this dissertation, the performance of RM walls with conventional embedded reinforcement is compared to the performance of walls with NSM steel bars. RM walls with NSM steel reinforcement exhibited higher flexural stiffness, and displacement ductility comparable to or exceeding that of RM walls with conventional reinforcement. In addition, a design example illustrated how NSM steel reinforcement can be beneficial for the design of walls with large secondary moment effects.

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