Dynamic measurements for assessing bridge response to foundation scour

Hydraulic actions are considered one of the main causes of bridge collapse worldwide. Among them, foundation scour plays an important relevant role. However, the assessment of foundation conditions is a difficult task, especially for existing bridges. Indeed, a complete characterization is often hindered by the limited accessibility and, in some cases, by the lack of available information on both the structural and the geotechnical design. On the other hand, an effective identification of foundation scour can be crucial for an accurate prediction of the long-term bridge performance, also for the planning of possible retrofit interventions. This paper presents the results of an experimental study carried out on a road bridge in Piedmont, severely affected by foundation scour and under strict surveillance by the Metropolitan City of Turin. Dynamic measurements were collected on the superstructure and the foundations. This enables to get an insight into the modal response of the deck and to detect asymmetries in the foundation behavior due to the presence of scour. This study demonstrates the potential of in situ measurements as a tool for the characterization of scour conditions of existing bridges and thus for the improvement of the resilience of transportation infrastructures