A Reassessment of the CSA S304 Chi-Factor for Design of Reinforced Concrete Masonry Members: Large Scale Experimental Investigation

An experimental investigation was conducted that consisted of 12 pairs of reinforced masonry specimens, in which the two specimens were constructed with their longitudinal axes oriented parallel and perpendicular to the laboratory floor, respectively. This work was conducted to reassess the need for the Χ-factor accounting for the direction of compressive stresses in masonry members in relation to the direction used to establish their masonry assemblage strength included in CSA S304-14 – Design of Masonry Structures. Parameters investigated included block size and reinforcement ratio. Test results suggest that the Χ-factor can be eliminated from future editions of CSA S304 but should be considered with caution: a review of the literature and the current tests show that, in some cases, voids may develop between the exterior webs of adjacent blocks and so may be the source of the reduction in the magnitude of the equivalent rectangular compressive stress block.