Ile de Ré Viaduct

Ultrasonic inspection and Acoustic Monitoring of the Ile de Ré Viaduct 

The Ile-de-Ré Viaduct in France experienced in 2018 a failure on one of its external prestressing tendons. The bridge owner awarded to Sixense and Freyssinet the mission to secure the structure, inspect ultrasonically the existing tendons, monitoring acoustically their potential failure and replace the broken tendon.

EverSense® Acoustic monitoring and cable replacement are well experienced skills of Sixense and Freyssinet. However, before Ile-de Ré Viaduct, EverScan® ultrasonic inspection of anchorages has only been done on individually sheath waxed strands of stay cables but not on grouted bare strands of prestressing tendons. On prestsressing tendons the risk of failure has clearly been identified and located in the first meter away from the tip of the strand in the anchorage zone, which is further away than stay cables application.

Then Sixense and Gustave Eiffel University (UGE, formerly IFSTTAR) worked on the extension of the ability of the well known ultrasonic USCAN® technology in order to apply it on grouted strand and up to 2 m away from the anchorage.

For this project 85 anchorages have been inspected by USCAN® and 170 acoustic sensors were installed prior to the replacement of the broken tendon. USCAN® measurement resulted in identifying 3 anchorages in bad condition with potential failure. The worst tendon has been removed for replacement. Visual inspection of removed anchorage piece confirmed the blind measurement of USCAN® and showed the ability of the technology to detect failure and corrosion in strands near anchorages.

This emergency job was made in less than 6 months. Today the viaduct is under high acoustic monitoring by Sixense teams for any detection of wires breaking.