The Value of Different Monitoring Systems in the Management of Scoured Bridges

Bridge scour is a leading cause of failure for bridges over waterways and is very difficult to detect accurately. Due to the large number of bridges on typical networks and the limited availability of financial resources within asset agencies, decision-makers must prioritize certain structures when it comes to management in the event of flooding. In response to the notable challenges associated with scour detection, methods that can monitor the actual performance of a scoured bridge have become popular in recent years, especially dynamic Structural Health Monitoring (SHM). One such approach relies on monitoring changes in the natural frequency of a bridge structure due to the occurrence of scour, which represents a change in the structural boundary conditions and therefore results in a change in modal behavior. A further reduction of the uncertainty involved in the problem can be obtained by monitoring the scour depth. The decision to install a monitoring system on a bridge must be balanced by the financial benefit of doing so, as limited resources often need to be carefully rationed. The Value of Information (VoI) from Bayesian decision analysis can be used to compute the benefit of installing a permanent monitoring system (scour or structural monitoring system). The VoI can be defined as the expected reduction in management cost related to informed decision-making, that is when the decision is aided by the newly acquired information. A case study is presented whereby different monitoring systems are considered to be installed on a typical bridge to support emergency management during a flood. A comparison of the relevant benefits, accounting for multiple flood events and scenarios, is carried out to identify the optimal monitoring strategy.