The role of the masonry quality evaluation in historic constructions: the case of St. Paul hospital of Savona, Italy

The lack of monolithic behaviour can be the worst structural defect of a masonry wall and this can happen in case of poor quality, for instance when the wall is made of multiple leaves, well ordered but not mutually connected. This causes the wall to become more vulnerable with the separation of the leaves especially when external forces act in the horizontal direction. Serious mistakes can be made in the structural evaluation of a historic stone masonry if the definition of the masonry typology, following the present Italian seismic code, is incorrect. In several cases a masonry texture can appear irregular from the facade with small irregular stones of different dimensions while the cross section shows a well-interlocked masonry with long stones used as connection among the leaves. The latter example is the case of the XIX cent. ex-hospital of Savona, a three storey masonry building. Here a comparison among the quality surveys (direct inspection of the whole cross section), non-destructive tests (pulse sonic velocity and flat jack tests) and the destructive tests (diagonal tests) results was carried out showing a reliable mechanical behaviour despite the appearance of the masonry texture. The results of the experimental investigation will be presented and discussed in the paper, and an attempt will be made to suggest improvement to the masonry typology table of the Italian Code.