Research And Application Of Bridge Cable Force Measuring Ring Based On Fiber Bragg Grating Sensing Technology

With the frequent occurrence of bridge accidents,people gradually pay more attention to the running state and safety of the bridge structure..As an important force component of bridges,the real-time monitoring and evaluation of cable forces can avoid the occurrence of bridge accidents,and also provide important measurement information for bridge health monitoring.Based on the sensing technology of FBG,this paper designs a cable force sensor applied to the bridge cable.From the selection of the initial cable force sensor,the program determination and feasibility analysis,to the final development of CG1-CG4.Various types of cable force sensors have been successfully applied in practical engineering,providing valuable experience for the future engineering application of such cable force sensors.The main contents of this paper include:(1)Reviewing the achievements of bridge construction in China and the bridge safety accidents occurring in our country and abroad in recent years,introduction of the current cable force measurement method,the research status of fiber Bragg grating sensing technology and its engineering application,comprehensive consideration of the existing bridge cable force measurement method of related principles,application and advantages and disadvantages,puts forward the completed design a new type of fiber Bragg grating sensor;(2)Based on the theoretical deduction,the relationship between strain,temperature and the central wavelength of FBG is obtained.Based on this,a solution to the problem of strain and temperature cross-sensitivity between two fiber gratings and single-fiber grating measurement method is proposed,which have effect of temperature on strain measurement in practical engineering application is eliminated;(3)Referring to the existing cable force sensor,a new type of fiber grating cable force sensor is designed and the force calculation is carried out on the elastic part by finite element software.Based on this,three design schemes #2、#3 and #4 are proposed and carry out finite element calculation in turn.Based on the above calculation results,the analysis and comparison of the above three design schemes show that the optimal scheme is #4 cable force sensor.According to the existing JJG 860-2015 test specification of pressure sensor(static)the feasibility test of #4 is analyzed.The test results show that #4 cable force sensor is feasible and Can meet the measurement requirements;(4)According to the feasibility test results,four kinds of cable force sensors of CG1-CG4 are designed based on #4 cable force sensor,and the force analysis of CG1-CG4 is carried out according to the feasibility test.The test results are evaluated according to linearity,sensitivity,hysteresis and repeatability in turn.At the same time,CG1 was taken as an example to carry out partial load test.according to the test data and the inference,the four types of cable force sensors CG1-CG4 perform well in the above calibration test and off-load test(0-2cm),which can meet the engineering application standards;(5)The four types of cable force sensors obtained from the above research results were applied to a cable-stayed bridge to provide hardware support for the bridge’s health monitoring system.