Theory And Application Study Of Coaxial Cable Bragg Grating Sensors

Strain or deformation of the structure is an important parameter for monitoring and control of structure. Extreme loads of local of Structure cause structural damage, failure. The current strain sensor of the lower range, generally can’t meet the large deformation (greater than5%) measurements, that lead to the lack of structural health monitoring of the whole process of structures (especially after the injury) deformation measurement data, so the development of the service can adapt to harsh environments and with a more high resolution large strain sensor engineering has become one of the topics most challenging structural health monitoring. In this paper, inspired by the FBG, novel coaxial cable distributed large-strain sensors and related smart parts will be developed based on the fact that the coaxial cable shows the functionalities of both the distributed sensing and tolerance of large-strain. Moreover, a gauge length-adjustable data-taking method for coaxial cable distributed sensor is proposed, covering both global and local quantitative information of structures. Finally, CCBG smart steel strand is developed by combining the half rigidity CCBG sensing unit with the steel strand.The specific researches include:1) Firstly, the fundamental physics is elaborated by the model coupled theory and the basic principles of the transfer matrix, and the relationship between the signal of the center frequency and the structure of CCBG is obtained.2) Secondly, the strain&temperature sensing mechanism of CCBG is deduced theoretically, the strain and temperature sensing characters are studied by the strain-temperature calibration in Lab, and the sensing coefficients of CCBG are obtained.3) Then, based on gate function in time domain of vector network analyzer, the uneven strain monitoring by CCBG and the corresponding demodulation method are put forward, which has the performances of global-local monitoring and highlight local damage.4) Finally, considering the requirements for the whole process prestressed monitoring of prestressed structures, CCBG smart steel strand is developed by combining the half rigidity CCBG sensing unit with the steel strand, and its mechanics, sensing character is also studied.