Research On Application Of FBG Sensor In Structural Health Monitoring Of Subway Station

With excellent sensing performance and many advantages, fiber optic sensor is a new type of smart sensor developed rapidly in recent years and has a brilliant future in sensing field. In this thesis, the fiber Bragg grating(FBG) sensing technology is utilized to monitor concrete structures of subway station during the construction and service period. This thesis is arranged as follows:The package of FBG is studied. Packaged with composite laminates and appropriate structure, the FBG is protected effectively. The results of tensile and fatigue property tests reveal that packaged FBG is of high sensitivity and good linearity as well as durability. Bury the packaged FBG in the RC beam and make destroy test, the results of which show that it has good sensing property, compared with strain gauges, and is suitable for monitoring strain in the civil structure.Based on FBG sensing technology, the health monitoring hardware system of GuoMao subway station is established. FBG strain sensors are compensated by reference grating. With Wavelength Division Multiplex technology, the FBG network, which can implement distributed measurement, is established. Based on the subway station model, Optimizing location of FBG sensors is studied in statics and kinetics method respectively. The final optimizing placement of FBG sensors in subway station is determined by considering both statics and kinetics method.Based on Winsock and ADO control on Visual Basic and Microsoft Access platform, a data acquisition scheme is presented and the structural health monitoring software system of the subway station is established, enabling a large number of sensors' data acquisition and displaying of real time data and curve as well as data saving and retrieving in database. Data acquired by the software are in terms of temperature and strain instead of wavelength, avoiding the limitations of the software offered by interrogation.Temperature and strain of the subway station structure are monitored during construction period. The results show that state of structure is normal. Structural damage detection and safety evaluation methods at present are studied. Because of the superiority of local health monitoring over overall health monitoring, damage detection and safety evaluation is carried at real time in the software system based on local response of the subway station structure.