The main aim of the work is the design and implementation of an integrated procedure for the identification of optimum action plans (satisfying expenditure constraints) on a road transportation system to minimize the impact produced on it by extraordinary events, in particular earthquakes. The attention is focused particularly on post-emergency situations related to effects on transportation networks caused by extraordinary events; the effects are considered with reference to bridges. Addressing the transition from physical effects to functional effects (relating to mobility) on the single infrastructure element calls for a commitment which has appeared challenging in view of the strongly innovative content involved. The analysis process consists in different steps. At the first step an effort must be made in order to acquire knowledge about the characteristics of the set of infrastructures (bridges) and about a set of possible seismic scenarios. By using fragility curves of bridges, the damage state of the network links (in which bridges are included) can be obtained. By making a series of hypotheses on how a bridge damage state can influence links’ functionality, a set of “damaged” (lower capacity) road network models has been carried out. At the next step of the process, interaction between transportation supply and demand, by way of static or dynamic traffic assignment models, allows to measure the performance of the system, or rather, its overall response to extraordinary events using suitable performance indexes. Then, the network risk curve (probability of the seismic action vs. transportation system performance indexes) is derived. At the end of the process a cost-effective retrofit strategy has been identified. The procedure has been applied to a test network at regional scale in the north-east of Italy.
