Study On Corrosion Monitoring System Of Reinforced Concrete Based On Fiber Bragg Grating(FBG)

Structural failure of reinforced leads to huge economic losses and rebar corrosion is one of the most important causes of structural failure.In recent years,optical fiber sensing technology has become a hot issue among domestic and foreign research fields due to its excellent durability,anti-electromagnetic interference,high sensitivity and corrosion resistance.However,the traditional optical fiber sensing technology has its problems in application of concrete structure monitoring,such as temperature interfered and short service life,which make it hard to meet the needs of full-life monitoring,especially the crucial late phase of monitoring after the crack’s generation.Therefore,in response to problems above,a new sensing system,with high engineering value,which eliminates temperature interference and meets the monitoring requirements of various stages of steel bars has been developed.Main work carried out in this paper is as follows:(1)Recent research progress of optical fiber sensing technology is introduced.Advantages and disadvantages of traditional rebar corrosion monitoring technology are summarized and analyzed,as well as the development direction of new fiber grating sensor.A multiple alarm point analysis process is introduced.Firstly,the deformation alarm point is obtained through finite element simulation,while the grating wavelength spacing is about 0.4037 nm.Secondly,the acceleration rust warning point is set,while the grating wavelength spacing is about 0.8223 nm.Finally,the extreme corrosion warning point is set based on structural mechanic,while the grating wavelength spacing is about 4.3260 nm.(2)Based on the traditional FBG monitoring,using the special grating structure-HF partial corrosion method,a grating sensor suitable for full-life rebar corrosion monitoring is proposed,which eliminates the interference of temperature on measurement signal.The measurement of a single strain variable is available.With a monitoring strain of 3600 με,a sensitivity of 0.0013 nm/με can be achieved,meeting the needs of full-life monitoring of rebar corrosion.Based on this analysis scheme,the performance of the sensor is evaluated by accelerated electrochemical corrosion test.The actual monitoring range of the corrosion monitoring sensor was found to be 3462 με.According to Faraday’s law of electrolysis and the loss model of rebar structure,the measurement accuracy of the sensor was obtained,ranging between 71% and 95%.(3)Based on the corrosion prediction regression analysis,the process of monitoring model establishment and standardized corrosion trend prediction system is formed.The evaluation criteria of the corrosion prediction model are formulated.Combined with reinforced concrete corrosion data,the feasibility of the corrosion trend prediction model is verified.Based on the multi-warning point theory proposed in this paper,the calibration is in line with the actual steel limit corrosion warning point,which guides the maintenance of the reinforced concrete structure.