Stress monitoring of concrete using embedded optical fiber sensors

Fiber-optic sensors have been deployed successfully in the monitoring of composite structures such as aircraft. At present there is considerable interest in using these sensors to measure the curing, strain, and long-term integrity of civil structures. This study presents the use of an embedded multimode optical fiber to monitor load-to-failure testing of a reinforced concrete beam. The procedure for embedding fiber-optics sensors into a reinforced concrete beam is described as are the various and sundry details, e.g., connections and instrumentation. A key issue relatingt o this studyi s the survivabilityo f fiber-optics ensors, embeddedi n concrete structures, particularly during the curing process. This has been evaluated by monitoring the intensity transmissibility during a 28-day cure cycle. Intensity transmission measurements and optical time domain reflectometry (OTDR) analysis of the embedded fiber-optic sensors were conducted during a load-to-failure test. High correlation of the embedded fiber fault locations and stress-induced failure points in the beam was observed.