The New Fiber Bragg Grating Tilt Sensor Design And Bridge Deflection Test

Recently, Fiber grating sensors have got rapid development and been applied widely in health monitoring of civil engineering. Compared with the traditional sensors, fiber grating sensors have distinct advantages of absolute measure, moisture resistance, strong corrosion resistance, simple structure, good reliability, strong anti-interference and easy to constitute to spread the feeling network, etc. The technologies of fiber Bragg grating (FBG) strain sensors and temperature sensors have got further mature, but the FBG inclination sensors are still in initial stage. Based on this, from the view of practical application in civil engineering, two new FBG inclination sensors have been developed in this thesis according to FBG sensors principle, and relevant performance tests have been studied which have certain engineering purpose. The main work includes:1. Based on the basic formula of FBG reflected wavelength, the strain and temperature sensing characteristics, sensing error, and the coupling characteristics of the strain and temperature have been deduced and analyzed.2. Two new FBG inclination sensors have been developed based on the FBG strain sensing properties and the design method of resistance strain inclination sensor, and the mechanical analysis and temperature compensation analysis have been carried out with its feasibility demonstrated theoretically.3. In the data of static tests, it is shown that the correlation coefficients of the two new sensors are over 0.999 with fine linearity and repeatability. The inclination sensors with the FBG sensing elements have high sensitivity and resolution ratio which reaches to 322 pm/deg, and the sensitivity can be further improved by increasing the length of the pendulum or using heavier pendulum.4. It is introduced in detail the application prospects of the inclination sensors in bridge deflection measurement, and the method of bridge deflection measurement using the least squares method by angles is proposed. Compared with the traditional methods, this method can save time and reduce the dependence upon the environmental conditions. Finally the accuracy has been verified by numerical simulation.