Continuous acoustic monitoring of grouted post-tensioned concrete bridges

The paper describes the first UK site installation of a monitoring system that detects the fracture of wires in post-tensioning tendons by listening with acoustic sensors attached to the surface of the concrete. Trials have shown the system to work reliably for grouted and ungrouted tendons. Acoustic events from other sources such as road traffic are discarded using software and hardware filters at the unattended site. Data from possible wire-fracture events are sent off site for final identification and positioning. The system is running continuously on site, on a viaduct, with close to 100% up-time. In open and blind trials on the viaduct, 41 out of 44 wire break or facsimile events were correctly located and identified and a further two were correctly located. The system can assist in the management of bridges where the posttensioning system is at risk from corrosion. (C) 2001 Published by Elsevier Science Ltd.