Failure criteria for grouted concrete block masonry under biaxial compression

Grouted concrete block masonry (GCBM) exhibits distinct directional properties. By the phenomenological approach, totally 86 tests on 3 kinds of macro-element were conducted for different principal stress ratios under plane stress, and 4 standard specimens were tested in shear. The anisotropic failure criteria are obtained in terms of normalized principal stress space. Comparisons of failure curves for 3 kinds of macro-element are made and it is found that the biaxial compressive strength when the applied stress direction and the material axis coincide is much greater than when the applied stress is inclined to the material axis. By the failure criteria and coordinate transformation, the law relating strength to orientation is obtained. It shows that the degree of anisotropy is affected by the difference of applied stresses. It behaves strongly only when one principal stress predominates and gradually becomes weak as the difference between the two principal compressive stresses decreases. The masonry seems to be isotropic in equal biaxial compression. The work conducted in this paper provides a basis for further theoretical study of the behavior of GCBM under biaxial stress.