MECHANICAL PROPERTIES OF HISTORICAL MASONRY WALLS THROUGH FLAT JACK TESTS

Many Countries in the Mediterranean area are characterized by a wide and ancient masonry building stock, whose preservation and restoration have economic, social and logistic impacts. However, the first step to protect this patrimony, is the characterization of the mechanical behavior of its masonry walls by an in-situ testing campaign. The flat jack tests are the most adopted inspection method, because, even if they require the execution of cuts on the walls, the effects of this procedure are quite limited and, thus, are compatible with the respect of the heritage protection demands. Moreover, this procedure provides valuable data on the vertical stress pattern, and the elastic modulus, that are key parameters in the vulnerability assessment procedure. The paper investigates the results of an experimental campaign performed by means of single and double flat jack tests. In detail, the investigated structures belong to an Italian zone characterized by the use of materials directly extracted on site before the construction of the structure and, thus, the mechanical parameters of these walls can be considered as reference values at local scale as they depend on the strength and stiffness of the extracted material, and on the geometry of the blocks which in many cases have conditioned the laying method and the thickness of the wall.