Gli edifici del periodo razionalista in Italia: modello per la valutazione della vulnerabilità sismica

The seismic vulnerability that characterizes the architectural heritage in Italy requires methods applicable at territorial scale, simplified but reliable for a proper risk assessment and a subsequent planning of intervention strategies. For this purpose, in the present work a method for the seismic vulnerability evaluation at territorial scale was developed in order to analyze the buildings built in Italy between 1930 and 1940, belonging to the architectural movement of Italian Rationalism. Starting from the vulnerability method, based on the European Macroseismic Scale (Grunthal, 1998; Giovinazzi and Lagomarsino, 2004), the proposed methodology provides new parameters related to specific vulnerabilities of the Rationalist architectural heritage. The analysis of these buildings, represented by a sample geographically contextualized to Liguria region (Italy), pointed out that the vulnerability is related to two main reasons. The first reason is the formal characteristics, related to the research of lightness, transparency and boldness that characterized the new architectural language which, in those years, was developing in Italy, as in the rest of Europe. At the base of the formal choices is the use of reinforced concrete, a "new" construction technology: if the use of this material was a valuable tool for the formal renovation in architecture, it is true that it is, at the same time, the second cause of the vulnerability that characterizes the buildings belonging to the Italian Rationalism. In fact, it is necessary to take into account that the construction technique was in its "first steps" at the beginning of the last century, and that, therefore, had not yet fully mastered, causing structural problems, in some cases, already from a static point of view. The scores of vulnerability, assigned to the parameters identified, have been calibrated through parametrical sensitivity analysis on a building "prototype", from a real case study, selected as representative of certain recurring characteristics in the sample. The proposed method allows to assess the vulnerability of this cultural heritage, that is higher than the vulnerability that characterized the reinforced concrete existing building with modern design.