Distributed Strain Monitoring Of Reinforcement Bars Using Optical Fibers For Shm

This paper is concerned with the implementation of Optical Fibers (OF) in reinforcement bars (rebars) for strain measurement in reinforced concrete (RC) structures. The measurement chain consists of an OBR interrogation unit (Optical Backscatter Reflectometer, based on relative Rayleigh measurements) paired with OF sensor. In the proposed technique, the OF is embedded into a U-groove in the rebar using suitable adhesive. The validation of the proposed technique has been performed through a series of experiments. In a first validation step, tensile and flexural tests were carried out on steel rods instrumented with OF sensors. The second validation step was to demonstrate the feasibility of embedding OF sensors in RC structures (embedded into the groove of rebars) 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 steel rods tested in flexure and for the strain measurement of rebars embedded in a loaded RC structure.