PSI - Issue 78

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

1961

downtime-based performance objectives in seismic design and retrofit decision-making. To this end, the research methodology employed is briefly summarised as follows: • New seismically designed Italian buildings : an in-plan building layout similar to those used in previous research studies (ref.) on the seismic risk assessment of residential RC buildings in Italy, was selected. Four different building heights were considered, namely 6, 12, 18, and 24 m, representative of 2-, 4-, 6 and 8- storey buildings. The assumed location is of high seismic hazard (L’Aquila), with a soil type A (Vs,30>800m/s). The seismic design was performed according to NTC-2018 (MIT 2018) using an available commercial software, ProSap (PROSAP 2017), meeting code requirements for both Damage Limitation (SLD) and Life Safety (SLV) limit states. More details are available in Mucedero et al. (2025b). • Existing case-study building : an Italian school building, constructed in the ‘ 60s and located in Isola del Gran Sasso d’Italia (high seismic hazard level), was analysed. Following the identification of the main structural deficiencies of the as-built structure through nonlinear static analyses, four seismic retrofit measures (SRMs) were considered: S1 - local strengthening with carbon FRP (CFRP); S2 - global strengthening with concentric steel braces; S3 - CFRP strengthening combined with concentric steel braces, and S4 - CFRP strengthening combined with viscous dampers. For all SRMs, a seismic gap between the URM infills and the RC frames was introduced to reduce column-infill interaction. The design of the interventions was carried out using pushover analysis, while the seismic performances of the retrofitted building configurations were assessed through nonlinear dynamic analysis, following a multiple-stripe analysis (MSA) approach. More details on case-study building can be found in Couto et al. (2024) and Mucedero et al. (2025). • Loss assessment : the component-based loss assessment methodology, as foreseen in FEMA-P58 (FEMA 2018) was employed for both new and existing buildings. The analysis was carried out using the PELICUN tool (Zsarnoczay et al. 2024), considering 200 realisations for each return period. A comprehensive inventory of the building components, i.e. structural and NSEs, was defined for the newly designed buildings based on typical quantities associated with residential buildings. In particular, the building floor plan was furnished to reflect a representative apartment layout, from which the various quantities were derived. For the existing school building, the components building inventory was adopted from the study by O’Reilly et al. (2018), which was derived from in-situ surveys. • Downtime estimation : the methodology proposed by Molina Hutt et al. (2022) was employed. The process begins with assessing the extent of damage using the FEMA P-58 methodology, followed by evaluating the post-earthquake usability of the building through five distinct recovery states: stability (S), shelter-in place (SiP), re-occupancy (RO), functional recovery (FR), and full recovery (F). Each state corresponds to the condition of the building, including both structural and non-structural elements, and is associated with a specific repair class, indicating the minimum level of repair required to achieve that state. Recovery states are assigned based on specific damage criteria detailed in Molina Hutt et al., (2022). Once the recovery state for a given earthquake intensity is identified, a temporal recovery trajectory is estimated, outlining downtime for each repair phase and accounting for potential delays and impeding factors that may affect repair initiation. In the Italian context, the repair or reconstruction process is generally funded by public loans. Unlike other countries, such as the US or New Zealand, only about 5% of the residential buildings in Italy have earthquake insurance coverage (IVASS 2024). It is thus reasonable to assume that the financing delay is primarily due to time required to secure public loans; accordingly, only this type of delay is included in the downtime estimation. Interested readers are referred to Molina Hutt et al. (2022) for further details on the downtime assessment methodology.

3. New Italian RC buildings 3.1. Collapse fragility and loss assessment results

The seismic performance of the new RC buildings was analysed through multiple-stripe analysis (MSA). To do so, probabilistic seismic hazard analysis and disaggregation analyses for different return periods were run using the OpenQuake engine (Pagani et al. 2014), based on the ESHM20 (Danciu et al. 2024) seismic source model and