Historical brick-masonry subjected to double flat-jack test: Acoustic emissions and scale effects on cracking density

The results obtained varying the size of the masonry prism involved in the double flat-jack test are described. In these tests, not only the deformations have been acquired, but also the acoustic emissions (AE) events, in order to get information about local cracking in the specimens. In addition, a meso-scale numerical model of the test is presented, where every brick of the masonry is modeled in details. Discrete cracks can arise both in the mortar joints and in the brick units. A good correlation is found between the amount of cracking simulated numerically and the experimental AE events for different prism sizes. The model is also able to catch the decrease in the compressive strength with increasing size. Although a quantitative relation between the AE events and the amount of cracking is not easy to obtain, we have been able to prove that the two quantities are simply proportional to each other when increasing specimen sizes are considered, whereas both of them are not proportional to the same sizes, but rather obey a power-law.