Acoustic emission monitoring of a reinforced concrete structure by applying new fiber-optic sensors

A novel fiber-optic sensor has been developed based on a newly found principle, the 'Doppler effect in a curved light waveguide'. Excellent performance of the circular loop sensor has been obtained. The circular loop sensor can detect the sum of principal strain rate with extremely high sensitivity and very wide frequency range. The sensitivity of the sensor was experimentally examined and the theoretical value was confirmed. The sensor was applied to damage detection in a reinforced concrete structural model of a railway girder. The protected sensor system was developed in order to improve the survivability during the structural test. In total 25 sensors were applied to the structural model. The developed fiber-optic sensors have shown almost equivalent sensitivity to conventional PZT sensors and much wider frequency range than resonance type PZT sensors. Initiation and propagation of cracks in the reinforced concrete have been analyzed by using the new fiber-optic vibration/acoustic sensing system.