Full-scale Distributed Monitoring Technology Of Optical Fiber Brillouin And Its Applications In Civil Engineering

Critical civil infrastrucuture can be characterized by large size and surface area, high cost, harsh environment, long service period, etc. Their damages have complicate mechanism, multi-affecting factors, noticeable time-dependent evolution and they are hard to be localized. To date, qualified full-scale monitoring technique is in urgent need for structural health monitoring of critical civil infrastructure. This dissertation focuses on the topics of full-scale monitoring technique including highly-performanced optical Brillouin sensor, collinear system by combining Fiber Bragg Grating (FBG) and Brillouin Optical Time Domain Analysis/Reflectometry (BOTDA/R) sensing technology, and fully-distributed smart sensor by combining Fiber Reinforce Polymer (FRP) and optical fiber sensor. The content of this work mainly contains:Firstly, the principle of optical Brillouin sensing technoloy has been introduced. Its strain-temperature coupling effect has been discussed in details and a novel absolute temperature compensation for strain measurement is put forward and experimentally validated.Secondly, the sensing characteristics of BOTDA/R based optical sensors such as their shear strength, axial tensile ultimate strain of series of coating Brillouin sensing optical fiber are investigated by large numbers of comparison tests. The compared optical fiber sensors include common Corning optical fiber, carbon coating optcial fiber, polymide coating high-temperature optical fiber and FRP coating optical fiber. The results provide basic guide for the selection among various kinds of sensing optical fibers in field application.Thirdly, a novel intelligent collinear optical sensor system (named BOTDA/R-FBG system) is developed by combining the full-scale distributed Brillouin sensing system and local high-precise Fiber Bragg Gratting (FBG) sensing system. The impact of FBG to Brillouin sensing signal has been studied. To improve the accuracy of the novel sensor, two data processing techniques such as wavelet denoising method and Lorentz fitting algorithm are applied. Besides, the feasibility of long period fiber grating(LPFG) based corrosion sensor and the probability of collinear system by combining LPFG and Brillouin sensing technique has been studied as well. Forthly, in regard to various requirments of installation, series of full-scale distributed Brillouin sensors and collinear BOTDR/FBG sensors are developed. Besides, a long-term monitoring method for cable-based structure is developed by combining collinear sensor and the stay cable/steel strand together. Thus, a corresponding long-term prestress monitoring technique has been put forward and validated experimentally.Finally, based on the full-scale measuring technique, structural damage detection has been investigated systematically. This work includes: damge mornitoring such as large deforamtion, cracks and steel sliding detection of six RC beams under static loads based on BOTDA/R sensors and collinear sensors; the feasibility study for the mornitoring of in-service oil pipes based on Brillouin sensing technique; the BOTDA/R sensor application in civil defense project in Guanzhou City and casing pipe project in Daqin Oilfield for the monitoring of the strain increment at the hot position and casing damage at construction and in-service stages.