Seismic fragility evaluation of typological masonry aggregates for local collapse mechanisms

The paper presents a study on the seismic fragility of masonry aggregates by considering both global and local collapse mechanisms. Within the framework of urban-scale vulnerability analyses, studying the seismic behavior of the building stock of historical centers represents an intricate challenge, in which the complexity of the urban fabric and the heterogeneity of the structural systems converge. When come to aggregate buildings, additional complications arise, mainly related to the identification of a reliable structural model. An acceptable compromise for the seismic fragility evaluations and damage predictions can be performed through simplified approaches, accounting for several uncertainty sources (e.g., geometrical and mechanical parameters). Within this context, a methodology aimed at estimating the seismic fragility of masonry aggregates is proposed, based on the combination of multi-source data and mechanical analyses. First, an exposure analysis is conducted to collect typological features characterizing existing structural configurations, by exploiting data from freely accessible databases (e.g., census, regional technical cartographies) and information given by typical building inventory collection forms. Afterwards, mechanical models are generated and analyzed, accounting for different uncertainty sources. Finally, fragility curves are computed considering the possible occurrence of local collapse mechanisms. The method is tested on a case from the municipality of Foggia, in Southern Italy showing interesting results for a row masonry aggregate.