Seismic risk assessment for the Italian residential masonry built stock and effectiveness of different mitigation strategies

Italy is one of the countries most subject to seismic risk, not only because of high seismicity, but also because of its significant exposure and vulnerability. These aspects can determine very high social and economic costs for the country. In order to have a good estimate of risk indicators such as economic losses, casualties and usability of buildings in the aftermath of an earthquake, some computation tools that perform damage and risk assessments can be utilized. Particularly, this work uses the Italian Risk MAps (IRMA) platform developed by Eucentre, which can produce maps of conditional damage (with a selected return period) or unconditional damage (with an observation time window) to evaluate seismic risk in Italy. IRMA allows the combination of hazard and exposure data included in the platform with vulnerability models. In this case, a vulnerability model for residential masonry is implemented within the platform to obtain the as-built risk evaluation. Moreover, a retrofitted vulnerability model is also derived, obtaining fragility curves that consider the main seismic retrofit interventions that can be performed on masonry buildings. By comparing the as-built risk evaluations with the mitigated ones, it is possible to highlight the entity of the benefit after a retrofit and compare it to its cost, at territorial scale. This analysis allows the assessment of the economic effectiveness of different seismic mitigation strategies.