Vibration-based scour monitoring: Prototype design, laboratory experiments and field deployment

Scouring is caused by the removal of bed material surrounding the piers and abutments and can rapidly compromise the integrity of a bridge structure and cause catastrophic failure. Such failures, which occur most frequently during peak flow periods, such as flooding, are a hindrance to emergency personnel trying to enter affected areas and to individuals trying to evacuate. As a countermeasure to mitigate the effects of the bed degradation, this article presents a vibration-based scour monitoring technique. This novel approach exploits the differences between the measured lowfrequency ambient excitations of a thin, flexible plate located in the flow and the same plate located in the sediment. The underlying principle is that a flexible plate excited by the turbulent flow vibrates at significantly higher amplitude compared to an identical plate placed within sediment. Laboratory and field results obtained at various flow conditions indicate that the vibration-based scour monitoring concept is able to supply reliable information regarding both scour and refill processes. This article details the underlying monitoring concept, the design and optimization of sensors, the evaluation of sensitivity of the developed sensors to environmental conditions, and their long-term field deployment.