Reliability monitoring of CFRP structural elements in bridges with fiber optic Bragg grating sensors

Fiber optical sensors based on Bragg gratings were used to monitor the strain in suspension or prestressing CFRP (carbon fiber reinforced polymer) cables in bridges. The sensors were either adhered to the surface of the CFRP wires for the suspension cables, or directly embedded during the production process for the prestressing cables, where the load is closer to the limit. Tests for the two applications were performed to validate the suitability of the sensing system. Results accumulated over three years on a stay cable demonstrate the reliability of those sensors.