Assessment of bonded patch bridge repairs using acoustic emission and acousto-ultrasonics

Composite patch repairs are being increasingly used throughout bridge structures in the UK. These patches offer a convenient and strong repair providing that the bond used to adhere the patch to the structure retains its integrity. Acoustic emission (AE), a passive approach and Acousto-Ultrasonic (AU), an active approach offer two methodologies for monitoring the structural bond and ensuring the patch repair remains effective. An experimental program was developed to assess the suitability of using AE and AU for monitoring the bond. Two concrete beams were manufactured and pre-cracked in three point bending prior to being repaired using a bonded composite patch. Two static tests were then completed to assess the performance of the two techniques for monitoring the bond. Results were compared with strain gauges adhered to the bonded patch and visual observation. For active monitoring a baseline of signals were captured at a known load and post damage a further series was captured at the same load. The signals sets were then compared using a cross correlation function technique. A simple accumulative acoustic energy analysis was then completed for the passive data. Results demonstrated that both techniques can be utilised to monitor the bonded structure. By comparing the results with those recorded by the strain gauges and visual inspection it was possible to demonstrate the successful effectiveness of the techniques for detecting global damage but specific debonding events would require further investigations.