Italian seismic risk maps based on code-compliant design

This paper discusses the Italian seismic risk assuming that the existing buildings portfolio is substituted by new code-conforming structures. The seismic risk is quantified, at municipality scale, via the evaluation of failure rate per building class. This requires: (i) the probability that the structures fail for a given ground motion intensity value, that is, the fragility functions and (ii) the hazard curves resulting from probabilistic seismic hazard analyses. The adopted fragility functions come from the Italian research project RINTC – Rischio Implicito delle Strutture progettate secondo le NTC, in which a large set of buildings was designed for three sites representative of different seismicity. Thus, the Italian municipalities were divided in three seismic classes and it was assumed that fragility functions from RINTC are representative of new design (residential) structures, according to a replacement criterion that was established to associate the structural typologies of the existing buildings to those considered in the project. The failure rates per building typology were computed first, combining the structural fragility functions and the computed hazard curves. Then, the failure rates were averaged over the building typologies and the percentages of soil conditions characterizing each municipality. The results, presented in the form of maps, show that the fragility of masonry structures have the main impact on the maps, which are also affected by the identification of the hazard and soil classes of the sites.