Simplified approach to integrate seismic retrofitting prioritization with social cost evaluation: a case study in central Italy.

In the last three decades, bridge stock seismic retrofitting prioritization has become one of the cult topic for scientific discussions in the bridge management strategies. More recent methods are focusing on the evaluation of the generalized failure cost, of a specific bridge derived from direct and indirect costs induced to the users/residents of the area exposed to the seismic hazard as a consequence of bridge collapse. However, when these approaches have to be applied to large transport networks, appear still very complex and computational demanding, and therefore simplified methods to evaluate the impact in terms of social cost related to the reduced efficiency of a transportation network due to potential bridge failure, are required. In this work, a simplified method for seismic retrofitting prioritization on a bridge stock is proposed, which is based on a “blended” approach considering specific fragility curves according to several bridge features and condition state, seismic inputs and generalized failure costs related to the transportation network. The effectiveness of the method has been showed on a case study of a local bridge stock placed in central Italy and the obtained results have been compared with those provided by more refined transport simulation models, on one hand, and by more traditional prioritization approaches, on the other. It is highlighted that this method can be very useful for transportation network managers within a limited budget scenarios, in case of lack of information about possible earthquake-induced impacts on a transportation network efficiency.