Development And Applications Of Cable Tension Sensor Based On Fiber Bragg Gratings

In civil engineering structural health monitoring field, all kinds of sensors based on Optical Fiber Bragg Grating (FBG) become one of the best core in the application prospect. Comparing with traditional cable force sensor, FBG cable force sensor characterized by its low weight, small size, the signal is not interfered electromagnetically. And Optical FBG cable force sensor especially apply to the bad environment of long-term real time monitoring. However the FBG sensing technology in China remains in the phase of laboratory research. Against this background, this technique in civil engineering has been carried out extensive applied research relying on the project of Dalian Stadium structural health monitoring. In this paper, the FBG sensor technology are deeply investigated, and a new type of FBG cable force sensor is developed. It brings good economic benefit and social benefit in the project of Dalian Stadium structural health monitoring. The layout of the paper is as follows:The present research situation of cable force health monitoring is introduced in the chapter 1, it focuses on the advantages and development state of the fiber Bragg grating sensor, points out the significance of cable force health monitoring, in addition, this chapter illustrates the main research content of dissertation.The FBG sensor mechanism is presented in the chapter 2. The self-developed miniature FBG strain sensor is based on friction and end-bearing piles, and the sensor strain characteristic is proved by calibration test. Also, the sensor strain sensitivity coefficient can be changed by adjust the parameters in the package process, which not only protect bared fiber grating, but also change the FBG sensor sensitive coefficient according to the practical engineering needs.The chapter 3 presents the development of new fiber grating cable force sensor. According to the bare fiber grating's characteristics, its strain sensitivity is far more than the pressure sensitivity, the FBG cable force sensor is developed based on holding both ends. The cable force can be measured through measuring the surface strain of anchor cable head. The calibration test shows that, the sensor's linear correlation is very well. Finally, the eccentric tension and temperature compensation have been improved.The chapter 4 introduces engineering applications in which the FBG cable force sensors served as key sensing element. The layout project of sensors and project of cable tension are introduced in detail. The working state of the tension cable has been mastered by analyzing the monitoring results, which provide valuable reference material for designing,monitoring and protecting of the large structure with cable.