Experiment Study On Deflection And Crack Of Engineering Structure Based On FBG Strain Sensors

The sensing element is one of the key factors in a structural health monitoring. Fiberoptic sensor has made it the first choice in Structural Health Monitoring (SHM) systemwith its unique characteristics compared to the other conventional sensors.This thesis focuses on the research of a kind of fiber optic sensor, namely fiber Bragggrating sensor, to spreading its application in civil engineering, two experimental studieswill be described in this thesis.The first one, the experiment study on monitoring cracks of simply-supportedreinforced concrete beam based on quasi-distributed fiber Bragg grating strain sensors.This experiment was done to make people know when and where the crack of reinforcedconcrete component under load appears in SHM. By the analysis to the classical SFM,author confirmed the feasibility of this experiment. The results of experiments reveal thatwith the help of quasi-distributed fiber Bragg grating strain sensors, people can perceivewhen the first crack of reinforced concrete component appears by observing the graph ofeach Bragg grating and fix the position of the first crack via analyzing the degree of stainvariation.The second one, the experiment study on monitoring the deflection ofsimply-supported steel I-beam based on long-gage fiber Bragg grating strain sensors. Inthe large-scale bridge healthy monitoring, neither traditional contacted deflectionmeasuring devices (such as dial indicator) nor non-contact deflection measuring devices(such as laser DME) can apply to long-time engineering monitoring project, measure theaverage stain of any segment of structure. This experiment was be done to study theseproblems. The results of experiments reveal that the long-gage fiber Bragg grating strainsensors are used to measuring the deflection of engineer component, the results are nearto what dial indicator measure and its performance stabilizes, being suitable forlong-term engineer monitoring.Fiber Bragg grating sensor is widely applied to civil engineering, due to its specialadvantages, it is believable that it is bound to displace the place of traditional electricalsensor in some occasions. Consequently the studies on it have the excellent realisticengineering value.