The Italian Guidelines on Risk Classification and Management of Bridges: Applications and Remarks on Large Scale Risk Assessments

Bridges are essential for guaranteeing the functioning of transportation systems since their failure can cause serious threats to the safety, well-being and economy of modern communities, especially in emergency conditions. Following recent bridge failures, among which include the Morandi bridge in 2018, specific guidelines on risk classification and management, safety assessment and monitoring of existing bridges have been issued in Italy by the Minister of Infrastructure as a mandatory code. They pay particular attention to the evaluation of the residual life span of critical transportation infrastructure dating back to the 1950s and 1960s of the last century. Being a newly issued tool, the Guidelines need to be applied and tested in order to find possible drawbacks and to point out the main factors influencing their results. Therefore, in this study, after a short description of the Italian Guidelines, pointing out some differences with other approaches adopted worldwide, some advantages and disadvantages are discussed by an application to a bridge stock located in the Basilicata region (Italy). Data needed to apply the Guidelines are gathered by a purposely set up procedure that exploits existing databases on road infrastructure (OpenStreetMap) complemented by additional data retrieved by means of public image repositories (Google Street View). By accounting for the qualitative nature of the risk classification results obtained by applying the lower analysis levels of the Guidelines, a prioritization method is proposed for ranking bridges for higher assessment levels and possible interventions, as well as consequent funds allocation. The application shows that the Guidelines' approach tends to provide conservative results. In fact, even in case of bridges with low degradation levels, the final risk classification induces actions undertaken for preliminary or detailed assessment; thus, normal operation (with periodic inspections) would not be possible anymore.