Ensuring reinforced concrete masonry (RCM) has adequate shear strength is an important aspect of structural design. This is particularly true for masonry beams without stirrups as shear failures in these elements can be brittle, occurring with little to no warning. As such, the design provisions used to determine shear strength must be accurate, safe, and rational. The objective of this paper is to analyze shear design provisions of current design codes to assess their reliability and predictive capabilities. A database of 104 shear tests reported in the literature on RCM beams without stirrups was assembled, and the failure shear stresses of these beams were predicted using four different masonry design codes. The codes analyzed include CSA S304.1-04 (Canada), ACI 530-08 (US), AS 3700-2001 (Australia), and BS 5628-2:2005 (UK). A fifth set of shear design provisions was chosen as well -the General Method of shear design from the CSA A23.3-04 code for reinforced concrete. The study showed that the average Vexp/Vpred ratios for the masonry codes ranged from 1.06 to 1.53, with the lowest value associated with the BS 5628-2:2005 code. However, high coefficients of variation for all four masonry codes indicated that low material strength reduction factors are required in order to apply the design codes with appropriate levels of safety. Interestingly, the CSA A23.3 general method had the lowest coefficient of variation of all five codes, and the third lowest average ratio of tested to predicted strength. Further analysis indicated that the general method can account accurately for the effects of both longitudinal strain (due to variations in steel area and MA/ ratio) and size (due to changes in effective depth). It is concluded that RCM beams exhibit similar behaviour in shear as reinforced concrete beams, and that their shear strengths can be more accurately predicted using the CSA A23.3 code for concrete than current masonry codes.

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Conference Annual Conference of the Canadian Society for Civil Engineering 2010, CSCE 2010
Sarhat, S.R., & Sherwood, E.G. (2010). Effective shear design of reinforced masonry beams. Presented at the Annual Conference of the Canadian Society for Civil Engineering 2010, CSCE 2010.