The health condition assessment of long-span structures (i.e., shells, beams and pipes) has always been important for tracking the service safety state. Effectively monitoring the large-scale deformation of these structures can be adopted to diagnose the structural performance and identify the possible damage. To improve the measurement accuracy and durability of the sensors, improved packaging design for optical fiber sensing element is expected to enhance the monitoring feasibility and stability. Therefore, flexible silicone elastomer packaged quasi-distributed optical fiber sensor is proposed and tested on the structures under static and dynamic loads. Comparison analysis on the bending strain measurement with bare fiber Bragg grating (FBG) and packaged FBGs in series has been conducted. Parametric reflection method is theoretically proposed for the packaged sensor subjected to bending action. Simulation analysis has also been performed to validate the effectiveness of the proposed sensor and the corrected calibration coefficient deduced from the theoretical analysis. Results show that the flexible packaged optical fiber sensor has stable performance for measuring the bending induced compressive or tensile deformation of the structure. Suggestions on the parametric reflection methods under different working cases have also been given. The proposed parametric reflection method can accurately calibrate the quasi-distributed and distributed optical fiber sensors. The study can promote the precise and feasible application of distributed optical fiber sensors in bending strain measurement.
 

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