PSI - Issue 44

Gianluca Fagotti et al. / Procedia Structural Integrity 44 (2023) 339–346 7 Gianluca Fagotti, Stefano Nodessi Proietti, Fulvio Soccodato, Nicola Alemanno, Maurizio Rotondi, Marco Mezzi, Paolo Verducci, Monia Bavicchi, Catia Ciavaglia, Luisa Cincini, Monica Finotto, Eleonora Gabbarelli, Francesca Morosi, Stefano Di Carlo/ Structural Integrity Procedia 00 (2022) 000 – 000 345

the "fixed base" scheme, corresponding to VR = 50 years for the buildings of use class II and VR = 75 years for those of use class III (religious buildings), and the SLV of the "isolated" scheme, corresponding to VR = 200 years. The construction types that are considered most appropriate are those of confined or reinforced masonry; these solutions are able to guarantee at the same time high stiffness of the structural system and better decoupling associated with the insulation system, high capacity towards the increased vertical actions associated with the vertical components of the seismic input, as well as high compatibility with the morphologies of irregular plan that characterize the aggregates. 7. Innovative techniques for seismic risk protection Currently, conventional anti-seismic design entrusts the protection of structures to their dissipative capacity with respect to seismic actions. This design approach, aimed at safeguarding life, however, does not prevent, in the presence of seismic events of a certain magnitude, neither damage to the structure (necessary for dissipative purposes), nor to damage to particularly vulnerable contents. Morover for these reasons, in recent years some innovative anti-seismic techniques have been developed, able to solve the problems highlighted above and, more generally, to considerably increase the seismic protection of the structures and their contents. Their operation is based on the drastic reduction of the seismic forces acting on the structure; the most effective of these technologies is certainly represented by seismic isolation. The technique allows to reduce the seismic input in the isolated construction (superstructure) below the damage thresholds, up to the "integral" seismic protection (absence of harmful consequences) of the building in elevation even for high intensity seismic events; in this way the buildings move as “rigid bodies” and the vibrations transmitted inside them are drastically reduced. After an initial phase in which the isolators were used to protect strategic artifacts (bridges, viaducts, hospitals, plants of significant environmental risk - nuclear and chemical, buildings containing historical and monumental assets), in this period the tendency is also to isolate residential buildings. The "ground isolation" solution for the rebuilding of the central portion of the village Castelluccio di Norcia, completely destroyed during the similar events on October 30, 2016, consists in the construction of a terraced platformof great surface development, seismically isolated from the underlying ground through the interposition of seismic isolators, on which the buildings are built. From the point of view of seismic protection, the benefits are completely similar to those achievable with conventional seismic isolation concerning the single building. Unlike the traditional insulation technique that provides for the insulation of a single building, the construction of a large insulated platform allows the construction of entire isolated neighborhoods, reducing the number of joints and limiting the criticalities associated with the not perfectly homogeneous distribution of buildings masses in elevation (Mezzi et al. 2021). A further opportunity offered by the solution is to make building ’ s construction in elevation compatible with appropriate technologies under various profiles, structural, energy and landscape, allowing application to even complex contexts. The economic assessments of the expected costs also show that the extra costs associated with the use of the “ground isolation” technique are two to three times lower than the expected costs over the useful life of the buildings rebuilt according to conventional criteria. Added to this are the benefits associated with the absence of all social, cultural and managerial consequences that cannot be evaluated economically. 8. Concluding remarks The rebuilding project of Castelluccio’s village represents an innovative model capable of integrating the criterion of reducing the seismic hazard with a plurality of objectives linked to territorial quality; the respect and enhancement of local identities, the regeneration of the affected areas through new unitary revitalization visions, the territorial’s reactivation and anthropic balances and the rebuilding not only of the buildings, but of the communities, have guided the design choice shown.