The Study On Concrete Crack Monitoring And Experiment Based On Distributed Optical Fibers

Mastering the crack development of concrete structure can provide valuable reference for the judgment of concrete structure working condition,so as to avoid the possible safety and usability problems.Since the massive use of reinforced concrete as building materials,crack problem has been much attention.Crack is an important reference index and the control object reflects the concrete security work,in the relevant specification of concrete structure crack control have clear requirements.However,the real-time crack monitoring methods need to be improved,it is necessary to study effective and reliable monitoring methods of concrete cracks.In this paper,through theoretical calculation and ABAQUS simulation,the strain transfer of different fibers under the different conditions are analyzed,and use ABAQUS to simulate the development of concrete cracks.Furthermore,the strain transfer of distributed optical fiber sensor for crack monitoring is studied,and the relationship between crack width and fiber strain is proposed.In this paper,based on the principle of BOTDA distributed optical fiber sensing,a series of optical fiber groups are used to calibrate the relationship between the frequency shift variation and crack width.In this paper,the oblique fiber group is arranged on the reinforced concrete beam to monitor the crack occurrence and expansion process,quantitative analysis of the crack width is carried out.According to the experimental research and result analysis,the main conclusions are as follows:(1)The strain transfer coefficient of the distributed fiber optic sensor decreases with the increase of the distance of the strain center,and decreases with the increase of the thickness of the epoxy resin.Different ways of embedding impact on distributed optical fiber strain transfer.(2)The strain characteristics of the distributed optical fiber at the crack position are: the slip phenomenon occurs in the area around the crack,and the strain occurs uniform.(3)The angle between the distributed optical fiber and the crack affects the measurement result.In the quantitative analysis of cracks,it is necessary to reduce the influence of angle.(4)When the distributed fiber optic demodulator is used to collecting data.By reducing the local strain peak value,it will affect the qualitative judgment of the crack.