Mechanical characterization of double-wythe masonry walls with a view to in-situ testing methods

Unreinforced masonry is one of the most commonly used structure typologies for the construction of residential buildings, which is why the estimation of its mechanical parameters is of primary importance. The main techniques to acquire them are based on destructive methods, however less invasive tests have been studied in the past years in order to obtain the same parameters in-situ: the core testing method is one of those. While monotonic compression tests on single-wythe cores provided good results, tests performed on double-wythe cores have given a significant overestimation of the compressive strength, supposedly due to the excessive stiffness of the high strength mortar cap used to perform the tests, that doesn’t allow the opening of the collar joint. An experimental campaign was conducted at Delft University of Technology in order to identify a new configuration of the cap suitable to use in moderately destructive tests to retrieve the mechanical properties of masonry under compression. An initial Finite Element Analysis is performed to anticipate the behaviour of the different configurations in order to choose the right prototypes. Four different models are developed, and the most significant ones are implemented and tested in the laboratory. In particular, a configuration with high strength mortar cap is tested as a comparison with previous tests on double-wythe cores, while a configuration with a high strength mortar cap separated from the core by a neoprene sheet is chosen in an attempt to reduce the confinement in the direction perpendicular to the collar joint. Finally the results obtained from the monotonic compression tests on cores are compared with the results from destructive tests on companion wallets, which were carried out in a previous experimental campaign on the same masonry.