Research On Bridge Stress Monitoring System Based On Fiber Bragg Grating

Fiber Bragg grating sensor(FBG)has been widely used in bridge health structure monitoring due to its unique advantages such as high sensitivity,high precision,small size and light weight,easy reuse and embedded smart materials.Firstly,the simulation models of FBG under uniform axial stress and temperature are built by using ANSYS finite element software,and the simulation analysis is carried out,the simulation results show that for FBG with a central wavelength of 1550 nm,the strain sensitivity coefficient calculated by finite element method is 1.201pm/??,and the temperature sensitivity coefficient is 10.1306pm/?,which is in good agreement with the theoretical calculation.Secondly,two FBG temperature sensors with enhanced sensitivity were prepared by the combination of tube packaging and polymer packaging,and the fiber grating demodulation platform was built by Bayspec FBGA demodulation module and C# language,on this basis,the water bath method was used to conduct the temperature rise and temperature drop perception experiment for the two packaged FBG.The experimental results show that the FBG temperature sensitivity of the grapheme aqueous dispersion package is 21.5pm/?,which is close to the 2 times of naked grating,the FBG temperature sensitivity of the multi-wall carbon nanotube package is 27.7pm/?,which is close to the 2.7 times of naked grating.Before the stress monitoring of bridge structures,the optimal layout criteria of sensors in the health monitoring of bridge structures are briefly introduced,and the problems of stress,crack and shear force based on static sensors are discussed.Taking a simply supported girder bridge as the mathematical model,the optimization objective function is derived.Finally,the layout theory is applied to an actual bridge with a small span.The sensor layout is optimized by combining the finite element stress analysis results of the bridge with the actual characteristics of the bridge.At the same time,the long-gauge FBG sensor is used for the related stress monitoring,and finally the strain data is collected for analysis.The feasibility of the scheme is verified,and the long-gauge FBG sensor can monitor the overall stress of the bridge structure.