Application Of Fiber Bragg Grating Sensing Technology In Bridge Pile

Fiber Bragg gratings (FBGs) can be used as sensing elements withunique wavelength-encoding property. Their wavelengths are immune fromintensity fluctuation of light source. FBG sensors can be used asquasi-distributed sensors through the wavelength-division multiplexingtechnique as they can be embeded into the interior of structures or installedon the surface. Multipoint real-time monitoring for strain and temperature canbe achieved. Therefore, fiber Bragg grating sensors have been deployed inmany engineering applications, such as bridges, tunnels, aerospace andelectrical power systems. The application of fiber Bragg grating sensingtechnology in bridge pile is studied in this thesis. Following are the maincontents:1. The developments of FBGs, the research background and significanceare introduced. The characteristic features and application situation of FBGsensors are emphasized. Meanwhile, the sensing principle and demodulationtechnology of FBG sensors for temperature, strain and the crossed sensitivityare analyzed. That provides important theoretical foundation for design ofFBG sensors and demodulating system.2. FBG-based steel gauge, temperature sensor and strain sensor forstructural health monitoring are developed and calibration tests are carriedout. Technical parameters and reliability of these three FBG sensors areverified．3. FBG sensor demodulation method based on InGaAs array detector isinvestigated. Intuitive demodulation system for FBG sensor is designed.Based on this demodulation system, the strain and temperature information ofmonitored regions can be recorded real-timely. The wavelength range of thissystem is from1515nm to1590nm, and the number of FBG sensors of asingle channel is up to20. 4. Engineering applications of the developed FBG sensors in bridge pileare carried out. Nearly200FBG sensors were successfully installed on steeltube pile, bored pile and composite pile during the pile test of a greatsea-crossing bridge. Wavelength-division multiplexing technologies are usedfor multipoint real-time monitoring in loads test. It is testified that FBGsensors have the same response as conventional resistance strain chips andadditional multiplexing capability over the latter.