A Simplified Approach for the Prioritization of Bridge Stock Seismic Retrofitting

Prioritization methods for bridge stock seismic retrofitting underwent to a remarkable discussion among the researchers in the past thirty years. Several approaches have been proposed that can be mainly grouped according to 1) the method employed to evaluate the condition state and corresponding structural rate of failure of the specific bridge, that can be physically based or dependent on subjective judgment, and 2) the method to assess the failure cost for each bridge which is related to social cost born by the surrounding communities that can be focused on a specific bridge or on the entire transportation network operating in the area exposed to the seismic hazard. However, the approach investigating the impact in terms of reduced efficiency of a transportation network as a result of a defined seismic input can be often extremely complex and cumbersome, as far as the computational aspect is concerned. There is therefore, a need to develop more direct and simple methods to assess the social cost related to bridge failure at the network level. In this paper, a prioritization method based on a combined approach taking into account seismic input, specific fragility curves according to several bridge features and condition state and transportation-related failure cost is proposed The method has been applied to a case study of a local bridge stock located in central Italy to demonstrate its effectiveness.