Challenging interpretations coming from flat jack tests applied to irregular masonry patterns

The article considers three different historical architectures, located in Tuscany, Piedmont and Liguria regions. All the buildings were constructed with irregular stone masonry. In Italy, in fact, small villages are very diffused and are often located in rural areas, where local building techniques have developed over the centuries. The architecture of these areas has been influenced by local craftsmen and building resources offered by the place. The frequent lack of studies and documentation on buildings in these contexts makes an important challenge even more difficult: characterizing the behavior of masonry to facilitate effective interventions. These masonry typologies were analyzed through single and double flat jack tests to assess the mechanical properties of each structure. In such masonry, even locating the cut hosting the flat jack presents a challenge, and results often differ from those commonly obtained in more regular constructions. The contribution aims to show some solutions to obtain and process the data to derive the mechanical parameters necessary for characterizing historic masonry, even when it has a pattern of uncrafted stones of different sizes, with brick wedges, and where the use of mortar is abundant. By providing supporting literature, based on experimentation that explain some possible phenomena, authors provide a useful procedure for professionals who wish to take advantage of this testing technique even when facing complicated irregular masonry, which is very common in rural areas of Italy.