Beyond Structural Safety: Downtime-Based Performance Criteria as Future Design Objectives for Italian Buildings

Despite the wide recognition of the social and economic consequences associated with seismic downtime, current seismic design codes, including the Italian one, still predominantly focus on ensuring life safety, implicitly accepting damage and functional disruption after moderate to severe earthquakes. This study analyzes the response of reinforced concrete (RC) residential buildings, seismically designed as per current Italian regulations, in terms of economic losses and temporal recovery trajectories to achieve different recovery states. Four RC frame buildings, assumed to be located in a zone of high seismic hazard in Italy, were designed according to the Italian NTC-18 code and then assessed through Multiple Stripe Analysis. Economic losses were quantified using a component-based approach whereas earthquake-induced downtime was estimated employing a recently proposed analytical framework. Five recovery states were considered, namely full recovery, functional recovery, re-occupancy, shelter-in-place, and stability. Repair and reconstruction costs, specifically derived according to the Italian bulletin price for construction, were used in addition to those proposed in the FEMA p-58 US guidelines, as well as delays and impeding factors that affect the initiation of the repair actions. Based on the outcomes, the analyzed buildings are likely to be fully recoverable or at least re-occupiable after events with low return periods. However, for events with high return periods, buildings are expected to suffer irreparable damage, making re-occupancy highly unlikely. The results underline the need to introduce multi-performance design criteria that address downtime-related objectives, ensuring that buildings maintain serviceability after frequent seismic events and re-occupancy after moderate to severe earthquakes.