Research On Deformation Inspection Of Bending Members Based On Distributed Optical Fiber Sensing

As the key control projects in the transportation network, the safety of Bridges in theconstruction and operation is more concerned by the people.The deformation of thebridge structures is an important performance indicator to evaluate their health status.Distributed sensing optical fiber technology become a hot research direction to replace thetraditional means of deformation monitoring because of its distributed, automation, gooddurability advantages. Deformation detection of the bending member based on distributedoptical fiber technology is investigated theoretically and experimentally in this thesis.1. It summarizes the traditional structure deformation detection methods, andanalyzes their advantages and disadvantages. The characteristics of the sensing fiber isintroduced, the advantages and the prospects of applied to structural deformationdetection are pointed out.The research situations of the distributed optical fiber sensingtechnology at home and abroad are reviewed. And the main research contents and methodsin this paper are put forward.2. Types of Brillouin scattering and the respective generating mechanism areintroduced in detail.It analyzes the characteristics of the Brillouin scattered light, Thesensing mechanism which is sensitive to both temperature and strain is expounded, Itdeduces the quantitative relations of the Brillouin frequency shift and the changes of strainand temperature. The curve smoothing method is presented to improve the signal-to-noiseratio.3. A theoretic deduce to quadratic integral method and conjugate beam method ispresented.According to the distributed optical fiber sensing technology can realize thedirection along the layout of the strain characteristics，a modified conjugate beam methodis presented. The precision of the two methods are theoretically analyzed. A new concept of real-time assessment of the flexural stiffness is proposed.4. Laying of optical fiber, temperature compensation, monitoring the position of theoptical fiber calibration are analyzed and the corresponding solution are putforward.Comparative analysis of the tight-buffered fiber and bare fiber strain detectioneffect is presented.The contrast analysis of the results of strain deformation measured byOptical fiber, the results measured by foil gauge and dial indicator and theoretical valuesare given. And the feasibility of the technical solution applied to Bending member isproposed.Finally, the new concept of flexural members flexural stiffness assessment areverified.