PSI - Issue 78

Gianrocco Mucedero et al. / Procedia Structural Integrity 78 (2026) 1959–1966

1965

The median collapse intensity ( ϑ ) for the retrofitted scenarios is [2.00-4.50] times higher than those obtained in the as-built scenarios. The solutions S4 is the one reducing more the probability of collapse for a given IM level, whereas S2 is the less effective one. Economic losses were then estimated through the FEMA P-58 methodology. The building component inventory, including all the structural/non-structural elements and contents, was assumed to be the same that was adopted in previous seismic assessment studies of Italian RC school buildings (O’Reilly et al. 2018) , based on the results of in-situ surveys, which can be found in Mucedero et al. (2025). The EAL results are provided Fig. 4(b). For the as-built scenario (S0), EAL is close to 1.3%, whereas the lowest value (EAL = 0.11%) was obtained with the alternative S4; the EAL values corresponding to S1, S2 and S3 are 0.26%, 0.6% and 0.38%, respectively. The median downtime values for the re-occupancy and functional recovery states were obtained (Fig. 4(c-d)) for the considered return periods, as a function of the structural model and hazard level, implementing the same downtime assessment methodology employed for new buildings. The return periods for the SLO (45 years), SLD (75 years), SLV (712 years) and SLC (1463 years) limit states are highlighted, as these correspond to the return periods foreseen by the Italian code (MIT 2018). As expected, downtime for RO is consistently lower than that for FR across all cases. It is also demonstrated that, regardless of the adopted retrofitting solution, the median downtime estimate is consistently lower than the case of as-built (S0). For all retrofitting solutions, median downtime estimates remain very low for the SLO and SLD limit states for both recovery states, whereas for the S0 configuration, the building's median downtime to reach the functional recovery state is estimated at more than 100 days for the 75-year return period (SLD). Moreover, significantly higher downtimes are obtained for both recovery states at the SLV and SLC limit states, with the only exception of the S4 retrofitting solution for the 712-year return period, which still exhibits less than 15 days of downtime for the RO state. 5. Conclusions This study focused on the quantification of economic losses and post-earthquake recovery times of Italian reinforced concrete (RC) buildings, both new and existing ones. Four new RC residential buildings, designed according to NTC-18 for a high seismic hazard level, were assessed through a component-based loss assessment methodology using Multiple Stripe Analysis. Then, an existing RC school building from the 1960s – 70s was also analysed under high seismic hazard, adopting the same loss assessment approach. For the existing building, four distinct retrofit strategies were selected and compared in terms of median downtime (in days) to achieve re-occupancy and functional recovery states, for different return periods. In both cases, a recently proposed downtime assessment methodology was used. The results showed that, for modern code-compliant RC buildings, recovery times become particularly high for return periods exceeding the design-level intensity (475 years). For example, re-occupancy (RO) and functional recovery (FR) require between 15 and 19 months for the 975-year return period, and the assumed reconstruction time for the 2475-year return period, especially for higher-rise buildings. Moreover, the increasing contribution of indirect losses, given by the occupants’ relocation costs, to total losses, especially beyond the 475 -year return period, underscores the need to go beyond life safety as the sole design goal and instead integrate seismic design codes with downtime-based performance criteria. As regards the existing building, all the solutions demonstrated a significant reduction in the median downtime, compared to the as-built configuration. A noticeable scatter in the median downtime performance among the retrofitting alternatives was observed. For all retrofitted cases, downtimes remained very low for both re-occupancy (RO) and functional recovery (FR) states for lower return periods. In contrast, the as-built structure exhibited over 100 days of downtime to achieve FR even at relatively low return periods. Substantially longer downtimes were observed across all cases, except for one (CFRP combined with viscous dampers), which maintained the RO downtime below 15 days even for the 712-year return period. Overall, the results advocate for the integration of downtime-based performance objectives in seismic design and retrofit decision-making, aligning seismic design practices with urgent goals of sustainability, resilience, and post-earthquake functionality in

the built environment. Acknowledgements

This work was carried out within the activities of CONSTRUCT - Instituto de I&D em Estruturas e Construções (UID/04708), CERIS (UIDB/04625) and the project 2022.08138.PTDC (SERENE) with DOI identifier: