Detection of tendon breaks in prestressed concrete structures using coda wave interferometry

Tendon breaks significantly threaten the safety of prestressed concrete structures. Failure of embedded tendons does not necessarily indicate as surface cracks, demonstrating the need for early detection methods. This paper presents a novel ultrasound-based approach for detecting and localizing tendon breaks using coda wave interferometry. Already few embedded ultrasonic transducers form a robust monitoring network able to detect subtle changes in the structure. To demonstrate the feasibility of detecting tendon breaks, a post-tensioned concrete beam was fabricated at Ruhr University Bochum, Germany. A break of a centric and eccentric tendon was artificially created by drilling from the outside. Both were successfully detected and localized through characteristic changes in the ultrasound results without any evidence of damage on the concrete surface. Measurements with fiber optic sensors validate the ultrasonic findings and provide insights into the re-anchoring behavior after tendon failure.