Seismic risk assessment of residential buildings in Italy

Abstract

The last National Risk Assessment NRA for Italy was developed at the end of 2018 by the Department of Civil Protection (DPC) in response to the specific requirement of the Sendai Framework for Disaster Risk Reduction 2015–2030 to periodically adjourn the assessment of disaster risk. The methodology adopted to perform seismic risk assessment and build national seismic risk maps was specifically developed to comply with the recent Code for Civil Protection, issuing that, in addition to a solid scientific base, risk assessment should be characterized by a wide consensus of the scientific community. As a result, six research units belonging to two Centers of Competence of the DPC, namely ReLUIS (Network of university laboratories for seismic engineering) and EUCENTRE (European Centre for Training and Research in Earthquake Engineering), collaborated under the guidance and coordination of DPC to produce the recent updating of national seismic risk maps for the residential building stock. This paper describes the methodology adopted to develop the consensus-based national seismic risk assessment and presents the main results in terms of expected damage and impact measures (unusable buildings, homeless, casualties, direct economic losses).

Towards the updated Italian seismic risk assessment: exposure and vulnerability modelling

“…In 2018, the seismic risk scenario for the National Risk Assessment (DPC 2018) was evaluated with the platform IRMA (Borzi et al 2020), by combining the ones obtained by using different vulnerability models (Rosti et al 2020a, b;Lagomarsino et al 2021;Donà et al 2020;Zuccaro et al 2020;Borzi et al 2020) and assigning to them the same weight (Dolce et al 2020).…”

“…Indeed, the IRMA platform evaluates the damage for each ISTAT type by combining with the introduced percentages the damage of the 5 reference vulnerability classes. This approach is conceptually coherent with the EMS, because it assumes that in the specific building type there are structures belonging to different vulnerability classes and vice versa (for further details see Dolce et al 2020).…”

“…The fragility curves adopted by the 2018 risk assessment (Dolce et al 2020) have values of the dispersion between 0.5 and 0.8; usually, greater values are associated to the more ductile sets of fragility curves. The derivation of fragility curves, both from empirical damage data or mechanical-based models, leads to values of the dispersion that are different for any damage level.…”

“…After the first studies on the Italian seismic risk (see Dolce et al 2020 for a review), in 2018 the DPC supported a research project involving its centres of competence such as ReLUIS (Network of University Laboratories for Earthquake Engineering) and Eucentre (European Centre for Training and Research in Earthquake Engineering), to prepare an updated version of the national seismic risk assessment (NRA) by considering the better knowledge reached so far. To this purpose, the IRMA platform (Borzi et al 2008; released by Eucentre was purposely set up and used to analyse different vulnerability/exposure models and convoluting them (Dolce et al 2020) with the MPS04 hazard model made by INGV (national Institute of Geophysics and Volcanology) in 2004 (Stucchi et al 2011. Fragility curves for the building types mostly present in the Italian building stock according to the ISTAT 2011 census were obtained from different approaches, mainly empirical methods based on the Da.D.O.…”

“…steel, timber and mixed structures) or not identified types amount to about 12%. The NRA provides results in terms of mean annual losses in terms of expected repair/reconstruction costs (direct economic losses), number of unusable buildings/dwellings, homeless, dead and injured (Dolce et al 2020).…”