A Fiber Bragg Grating Anchor Rod Force Sensor for Accurate Anchoring Force Measuring

This paper presents a novel anchor rod force sensor based on fiber Bragg grating (FBG) for accurate anchoring force measurement. A special FBG strain sensor with enhanced sensitivity has been designed and embedded in the centre line of an elastic structural body, which forms the main body of the anchor rod force sensor. The mechanical structure design and measuring principle of the proposed anchor rod force sensor have been presented detailedly. Then a sensor prototype has been manufactured and fully tested. The experimental results show that the sensor provides a sensitivity of 11.58 pm/kN with a fitting linear correlation coefficient of 0.9996 in a measurement range of 50 kN, a repeatability error of 3.26%, and a hysteresis error of 3.87%. Furthermore, good resistance to bending effects of anchor rod, good creep resistance (fluctuant value is within 2 pm), and good temperature compensation capacity (maximum value is 11 pm) have also been verified. These results promise the sensor better applicability in the health monitoring of large civil engineering structures.