Monitoring of scour critical bridges using changes in the natural frequency of vibration of foundation piles - A field investigation

The highly publicised failure of the Malahide Viaduct Railway Bridge in Ireland in 2009 was attributed to erosion of the supporting soils, commonly referred to as foundation scour. This is a widespread geotechnicalstructural problem that has been identified as the main cause of failure of bridges in the United States. Monitoring scour is of significant importance to ensure the continued safe operation of the ageing bridge asset network. Most of the current monitoring regimes rely on expensive underwater instrumentation that is often subject to damage during times of flooding, when scour risk is at its highest. In this paper, a novel scour monitoring approach based on dynamic measurement techniques is described. The investigation involves the mounting of accelerometers on the structure of interest, which may be used as a non-intrusive monitoring scheme above the waterline. A significant advantage of this method over traditional scour monitoring approaches is that the structure itself is used to monitor the scour damage.