Using after-event assessments to evaluate the resilience of road networks to earthquake hazards

Recently, a previous research work by the Authors assessed the efficiency of urban and extra-urban road networks (RNs) under seismic hazards. That study highlighted how, in a use case located between the city of Turin and the nearby town of Chieri, a relatively severe drop in efficiency was reached for a moderate seismic event (Tr = 50). This is due to the expected high probability of the network’s R.C. bridges exceeding low-level damage states (DSs) at low peak ground acceleration (PGA). Nevertheless, there is a subtle but important difference between structural robustness and resilience. This lies in the target system’s ability to withstand adverse events. A robust structure is supposed to maintain its core functionalities when subjected to strong disturbances such as a seismic event – thus resisting damage. Conversely, resilience refers to the same system’s capacity to recover and re-adapt after (partial or total) failure. In this sense, RN resilience can be enhanced not only by avoiding traffic disruptions but also by swiftly restoring full or partial serviceability. Therefore, to account for this factor, the previous results are in light of a time-to-recovery perspective. This accounts not only for trespassing a certain DS threshold but also for safety redevelopment and functional recovery. The results highlight how the R.C. bridges in the tract of interest may be resilient, i.e. quickly restorable, even without being necessarily robust, i.e. fully functional in the immediate aftermath.