Masonry properties determination via splitting tests on cores with a rotated mortar layer

Abstract

The in situ evaluation of the masonry mechanical properties is a very complicated task. Since in general extracting a significant masonry specimen is not possible at all, alternative methods look for the solution by combining the properties of mortar and bricks. The evaluation of the existing mortar is however a not very simple issue. A viable alternative is based on the use of brick cores including a central mortar layer lying on a symmetry plane. In fact these specimens can be extracted very easily by cutting cores spanning two bricks at least. The obtained core is then subjected to a splitting test with a set up providing a 45° inclination of the mortar layer with respect to the loading plane. This type of test is similar to a diagonal wallet test and induces a mixed compression – shear stress state in the central mortar layer. By using a Mohr –Coulomb failure criterion the test result can be interpreted in order to obtain all the mechanical properties of the masonry. In particular, by assuming a friction angle based on the compression to tension strength ratio of the mortar, the cohesion can be evaluated, and by using appropriate formulas, all the other constitutive parameters in turn. In the paper a numerical model with a Mohr Coulomb plasticity constitutive law is compared with a Damage Mechanics model by using the experimentally evaluated brick and mortar parameters. Both models give accurate splitting load evaluation but the one based on damage mechanics is also capable to predict the splitting crack evolution area.