A New Methodology for the Survey and Evaluation of Seismic Damage and Vulnerability Entailed by Structural Interventions on Masonry Buildings: Validation on the Town of Castelsantangelo sul Nera (MC), Italy

Damage surveys following to the Central Italy 2016 seismic swarm have shown that retrofitting or strengthening interventions on masonry buildings may result in unexpected seismic behaviour, which may be defined as hybrid. In fact, the insertion within the masonry of single parts aimed at activating the box-like behaviour can worsen the overall response like a vulnerability added to a building’s intrinsic ones. Existing procedures for post-earthquake visual assessment do not permit the definition of the behaviour of altered masonry buildings (substitution of horizontal structures, concrete curbs, injections, etc.). The article proposes a completion of the ‘knowledge path’ of an existing survey form adding a new part specifically dedicated to structural interventions. On-site data collection is performed by a digital survey form written in Google Forms. The analysis phase takes advantage of the features available in a Geographical Information System (GIS). The application of this survey form to about one hundred buildings in Castelsantangelo sul Nera (Macerata district, Central Italy) hit by the Oct. 26 and 30, 2016 quakes also helped to define the vulnerability classes for buildings with structural interventions. Empirical results show that either poor execution or conception of interventions can lead to the highest vulnerability classes.