Study On The Monitoring Of Beam Bridge Based On FBG Macro Strain Spatial Distribution

With the increase of the service life of the bridge,the bridge has aroused people’s attention.In order to understand the use of Bridges,structural health monitoring system has been used in bridge monitoring.The field of bridge health monitoring has developed rapidly in the past few decades,thanks to the attention paid by practitioners to bridge health monitoring,and on the other hand the emergence of new optical fiber sensor technology.The shortcomings of traditional sensors in complex environments are gradually exposed.In the context of the urgent need for innovative sensors,fiber optic sensors have come to the scene from the laboratory.Due to many advantages of fiber optic sensors,such as high precision,anti-electromagnetic interference,corrosion resistance,distributed measurement,light and soft and easy to install and bury,fiber optic sensors have become an ideal monitoring element in bridge health monitoring system.In the process of using fiber optic sensors,in order to achieve global mo nitoring,a long gauge fiber Bragg grating(FBG)macro strain sensor has been developed.The FBG macro strain sensor can monitor the average strain within the coverage and expand the monitoring range.A small number of sensors can detect the overall damage of the structure.Based on the advantages of long gauge FBG macro strain sensor,the paper studies the application of long gauge FBG macro strain sensor in health monitoring.The specific content of this article is as follows:(1)The introduction part explains the background and significance of the research,the research and application of fiber grating sensing technology at home and abroad;Derived the sensing principle of optical fiber and the working principle of FBG macro strain sensor.The multiplexing technology of FBG sensing is analyzed.Three kinds of distribution techniques of fiber optic sensors in practical engineering are studied,and detailed formula derivation of three distribution methods is carried out,which provides a theoretical basis for the latter experiments.(2)The relationship between the bending stiffness and the strain of the unit is established.On this basis,the diagrammatic multiplication method is improved to be combined with the monitoring.(3)The reinforced concrete simply supported T beam was tested.The crack,curvature,stiffness and deflection of the T beam were monitored by parallel distribution of FBG macro strain sensors.The deflection values of the members are calculated by three methods(conjugate beam method,finite integral method,and diagrammatic multiplication method),and compared with the measured values of LVDT,the feasibility of three methods for calculating deformation is verified.(4)In the case of T-beam twisting,the FBG macro strain sensor monitors the development of the flange and the oblique crack of the front and rear webs in a cross-topology manner.The experimental results show that the FBG macro strain sensor can monitor the development of oblique cracks of components.