Engineered FBG Cable Force Sensor With Ultra-high Sensitivity

With the proposal and development of concepts such as "Internet of Things","Smart City",and "Artificial Intelligence",structural health monitoring in civil engineering has received more and more attention and application.The real-time monitoring of cable tension is an important part of cable structural health monitoring and a key parameter for measuring the safety status of cable engineering.The appearance of FBG which has unparalleled advantages,such as anti-electromagnetic interference,small size,and corrosion resistance,has attracted extensive attention from scholars of cable structure engineering at home and abroad.In order to solve the problems of the applicable conditions and insufficient sensitivity of FBG’s current application in cable force testing,such as smart cables,FBG force-testing rings,which need to be installed before the cable manufacturing process or tension.For conventional FBG strain sensors whose demodulation accuracy is disturbed by noise.The sensitivity of them are not enough to identify the current deformation when the load is small.In this paper,an ultra-high sensitivity engineered fiber grating cable force sensor is developed.Theoretical analysis,finite element simulation and calibration test have been done to prove the good performance of the cable force sensor.The strain transfer coefficient which caused by the existing of anchors and clamps is established to modify the engineering measurement results.Finally,the engineering applicability of the cable force sensor is been verified.The main research contents are as follows:(1)Development of engineered FBG cable force sensor with ultra-high sensitivity: Introduce the principle of sensor sensitization,change the structure distribution of the sensor to achieve ultra-high sensitivity,make the sensitivity adjustable,and to design suitable sensitivity of specific engineering objects.The clip-type anchorage is used in the end of GFRP which can solve the problem of poor shear resistance of GFRP,and the anchoring mechanism and parameter selection of anchorage are analyzed.(2)Fabrication and stress analysis of engineered FBG cable force sensor with ultra-high sensitivity: FBG is encapsulated by GFRP directly in order to improve the durability,engineering applicability and operability of it.The sensors are made by pultrusion molding process which is used to make GFRP bars.The overall sensitization of the cable force sensors,the internal stress state of the clip anchorage during the anchoring,the strain transmission loss due to the presence of anchorages and the clamp are analyzed by FEM..(3)Verification of engineering adaptability of engineered FBG cable force sensor with ultra-high sensitivity: The basic perceptual characteristics of cable force sensors such as sensitivity,is tested.And then steel strand tensile test is used to simulate the cable’s deformation,to verify the engineering applicability of the cable force sensords.The results show that the sensors have ultra-high sensitivity and good sensing performance.Their engineering adaptability is verified,and it can realize cable force’s real-time dynamic monitoring of cable structure engineering.