The high profile failure of the Malahide viaduct in Dublin in late 2009 was attributed to erosion of the supporting soils around the bridge piers, commonly referred to as foundation scour. This is a widespread geotechnical-structural problem, where foundation scour has been identified as the number one cause of bridge failure in the United States. Monitoring scour is of paramount importance to ensure the continued safe operation of the ageing bridge asset network. Most monitoring regimes rely on expensive underwater instrumentation that is often subject to damage during times of flooding, when scour risk is at its highest. Scour causes a rapid reduction in foundation stiffness and can lead to complete failure of one or more sub-structural components of a bridge. In this paper, a novel scour monitoring approach based on dynamic measurement techniques is described. The investigation is based on using accelerometers mounted on the structure of interest to detect losses in foundation stiffness due to scour, which manifest itself as a change in vibration characteristics. Experimental and numerical analyses were performed to validate the potential of this new monitoring framework. A significant advantage of this monitoring method over traditional approaches is that the structure itself is used to monitor the damage. Therefore, if failure is likely, it is assumed that the dynamic characteristics will indicate such and remediation works may be implemented.
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