Studies On Fiber Bragg Grating Sensors In Civil Engineering And Model Tests

The field of structural health monitoring (SHM) is concerned with accurately and reliably assessing the integrity of a given structure in order to reduce ownership costs, to increase operational lifetime, and to improve safety. In civil SHM systems, fiber optic sensors (FOSs) are credited with promising sensing alternatives for several advantages such as, flexibility, embeddability, multiplexity and EMI immunity, as compared with traditional sensors. Among the optical fiber sensors based on varied principles, fiber Bragg grating (FBG) sensors are the most promising candidates to effectively replace conventional strain gages for long-term monitoring applications in harsh circumstances.The main points of this dissertation are to present the design and performance of FBG sensors, including strain, force and temperature sensors, apply the FBG sensors to the model dynamic characteristics tests and introduce the applications of FBG sensors in structural health monitoring. The layout of the paper is as follows:The chapter 1 is the introduction of structural health monitoring including concepts, importance and components and the present status of fiber Bragg grating sensor technology, which plays a key role in civil engineering. This chapter presents the sensing principle of fiber Bragg grating, introduces some kinds of sensors based in fiber Bragg gating. In addition, this chapter illustrates the main research content of dissertation.The design and performance of FBG sensors, including force, strain and temperature sensors are presented in the chapter 2. A force sensor, packaged by a cantilever beam, is designed to measure the ice force of model structure. In addition, the improved packaging methods are put forward to enhance the stability and durability of FBG strain and temperature sensors. The performance of FBG sensors are studied in detail.The chapter 3 presents the applications of FBG sensors in ice-induced vibration experiment of bridge model, the roller compacted artificial concrete dams model. The results the strain measured by FBG sensor agrees well with the theoretical result. The results prove this FBG strain sensor has the advantages of small size, high precision and flexible use, and demonstrates promising potentials. The chapter 4 introduces several engineering applications in which the FBG sensors served as key sensing element. A real-time remote structure health monitoring system in Innovation Park building is developed. The function of this system is ranging from automated data sampling, displaying, analyzing and saving to structure damage identifying and safety evaluation. In addition, the FBG sensors are applied in health monitoring of New Oil Transportation Port of Dalian including bridge and shipping berthing pillar. The FBG sensors exhibit excellent performance and higher tolerance to harsh environment in the long-term real-time health monitoring.