DAMAGE WITHOUT INDICATION—DETECTION OF TENDON RUPTURE USING CODA WAVE INTERFEROMETRY

Abstract

Pre-stressing is often the decisive feature of concrete bridges. Deterioration of the tendons used to provide pre-stress is thus an immense problem. To detect potential damage, monitoring of the structures promises to be a remedy. However, since the location of damage is seldom known, conventional monitoring systems reach their limits. Then, ultrasound in conjunction with coda wave interferometry becomes promising to monitor entire structures with just a small number of sensors. To demonstrate the general feasibility of detecting tendon rupture, a pre-stressed concrete beam was experimentally investigated. Failure was artificially initiated by cutting a tendon. Ultrasonic and strain measurements recorded stress changes that occurred due to cross-section losses of the tendon. Both the process of pre-stressing and the artificially induced failure has been tracked using the coda wave technique. Based on the relative velocity change of the ultrasound, the internal state change in the (from the outside) still intact specimen could be detected and tracked. These initial results inspire further in-depth investigations into the detection of pre-stressing steel fractures.