Proposed Failure Criteria for Concrete Block Masonry under Biaxial Stresses

The available failure hypotheses for masonry under combined stresses are reviewed. The applicability of the failure theories for composite materials to masonry is examined utilizing experimental results of concrete block masonry test. Failure theories for isotropic materials are not applicable to masonry. Also, failure theories for composite materials cannot be directly applied to predict the masonry strength under biaxial stresses. Failure criteria are proposed for masonry under biaxial stresses, taking into consideration its anisotropic nature as a composite material. Two failure criteria are proposed, with each describing a single mode of failure—a shear failure along one of the criterical bed or head joint direction, and a tension failure incorporating the interaction of the block, mortar and grout. The proposed criteria are capable of predicting both the mode of failure and the strength of concrete block masonry under biaxial stresses.