Behaviour Characteristics of Concrete Masonry

Abstract

<p>The lack of understanding the behaviour of concrete masonry and the complex interaction existing between its components (block, mortar, and grout) at failure may be the cause of the continued use of the code's working stress method. This approach could underestimate the potentials of masonry as a construction material. It is the main objective of this investigation to provide a better understanding of concrete masonry behaviour under different in-plane load conditions (compression, tension, shear and biaxial stresses) considering the anisotropic nature of masonry as a composite material. This understanding was gained through a combined experimental and analytical investigation.</p> <p>In the experimental study, 323 masonry assemblages were tested under compression normal and parallel to the bed joints, splitting tension at different orientations from the bed joints, shear along the bed joint with different levels of precompression, and off-axis compression and tension to produce biaxial states of stresses along the bed and head joints. The test material variables were mortar type, grout strength, and bed joint reinforcement.</p> <p>Analytical strength formulas, based on a "strength" approach, are proposed to express, in quantitative terms, the assemblage compressive strength normal to the bed joints, tensile strength normal, diagonal, and parallel to the bed joints, and shear strength along the bed joint with and without precompression. The applicability of the failure theories for both isotropic and composite materials to masonry were examined. Failure criteria are proposed to predict the strength and the failure mode of concrete masonry under biaxial stresses taking into account the anisotropic nature of masonry as a brittle composite material. Design code provisions (CSA S 304) for plain masonry are reviewed.</p>