General methodological approach for the seismic assessment of masonry aggregates

Strong earthquakes have recently shown the vulnerability of masonry structures. In Italy, most of the historical centres are characterized by adjacent masonry structures connected in aggregate that have been subjected to structural and functional changes during time. Their structural behaviour shall be studied to avoid catastrophic outcomes after seismic events. In the technical literature, many studies are available to identify the most vulnerable structures in historical centres from a macroscopic point of view, or the seismic behaviour of some typical structures was studied in detail with sophisticated numerical methods providing a specific seismic vulnerability assessment. However nowadays there is not a general and standard procedure available, mostly methodological, based on well-known analysis methods, that can be followed to evaluate the structural behaviour under seismic actions of any building aggregate, and that allows to identify effective retrofitting interventions. Moreover, national regulations typically do not provide a standard procedure that can be followed by practitioners for such kind of problems. Thus, the purpose of this paper is to suggest a protocol to be used in common design, based on a broad blend of analyses that can be carried out with commercial software. It relies in a variety of numerical analyses, spanning from simple eigenvalue simulations to full 3D pushover computations, assuming different hypotheses for the material behaviour. The suggested method has been applied and benchmarked to an ex-monastery in northern Italy and several structural considerations to provide a sufficient insight useful for practitioners are provided.