AWWA INF53962

AWWA INF53962 Acoustic Monitoring of Prestressed Concrete Cylinder Pipe: A Case History
Conference Proceeding by American Water Works Association, 06/01/2001

Holley, Mark^Diaz, Robert^Giovanniello, Michael

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Corrosion of prestressing wire in prestressed concrete cylinder pipe (PCCP) andother structures is a widespread concern for owners and managers responsible forthese facilities. The general inaccessibility of the pipe and prestressing wiremakes evaluation difficult, costly and often inconclusive. Random examination ofprestressing wires by excavating or internal inspection of the pipe wall givesonly a very localized knowledge of the prestressing wire condition. This paperdescribes the development, testing, application and results of a continuousacoustic monitoring system used to detect and locate corrosion-induced failuresin approximately 6000 feet of 42-inch prestressed concrete pipe owned andoperated by Howard County, Maryland, Department of Public Works. A SoundPrintacoustic monitoring system was installed to assess and analyze the condition ofthis and other critical potable water conduits. The results of this evaluationand subsequent excavation to confirm deterioration measured by the system arediscussed. This technology works on the premise that when a tensioned wire fails,its stored energy is released suddenly, causing a dynamic response in thestructure. The monitoring system utilizes acoustic sensors connected on a longcable and installed inside the pipeline. These sensors detect the response of awire break at different points in the structure. Processing of data by thesite-based data acquisition system eliminates most irrelevant ambient activity.Events that meet pre-set criteria are recorded and transmitted over the Internetto a central processing facility where proprietary processing software is used togenerate reports summarizing the time, location and classification of recordedevents. Long-term acoustic monitoring can provide comprehensive information aboutthe nature and extent of pipeline deterioration so that informed andcost-effective management decisions can be made. Includes 3 references, table, figures.