Deformation Monitoring of Reinforcement Bars with a Distributed Fiber Optic Sensor for theSHM of Reinforced Concrete Structures

This paper is concerned with the implementation of FO sensors in reinforcement bars (rebars) for strain measurement in reinforced concrete (RC) structures made of Ultra High Performance Fiber Reinforced Concrete. In the proposed technique, the FO sensor is embedded into a drilled cavity in the rebar using suitable adhesive. The measurement chain consists of an OBR interrogation unit (Optical Backscatter Reflectometer, based on relative Rayleigh measurements) paired with FO sensors. The validation of the proposed technique has been performed successfully through a series of experiments. In a first validation step, uniaxial tensile tests were carried out on steel rods instrumented with FO sensors. The second validation step was to demonstrate the feasibility of embedding FO sensors in RC structures (embedded into the groove of rebars or bonded on the rebars surface) without damaging them during pouring of the concrete. For this purpose, pullout samples were fabricated by partially embedding instrumented rebars in concrete blocks. Results obtained so far indicate that the sensors perform adequately for the strain measurement of rebars tested in tension and for the strain measurement of rebars embedded in a loaded RC structure.