| Cable-stayed bridges have become one of the main bridge types of long-span bridges due to their strong spanning ability,beautiful line shape,and strong economy.Real-time monitoring of cable force is an important indicator reflecting the operating status of cable-stayed bridges.Smart cable is an important development direction to obtain the status of stay cables.The current smart cable solutions proposed at home and abroad have their limitations and cannot meet the demand for long-term and stable monitoring of stay cables.This paper proposes to implant a fiber grating sensor in the cable to directly measure the strain of the cable to obtain the cable force.This method has significant advantages in durability and reliability,and can make the cable a self-sensing ability.Smart cable technology.Based on the application background of cable force monitoring,this thesis uses a combination of theoretical derivation,finite element simulation and experiment to analyze the strain transmission law and related influencing parameters of the fiber grating sensor(FBG sensor)attached to the surface of the high-strength steel wire.Cross test to obtain the optimal combination of size parameters of the glue layer,and analyze the influence of the twist angle of the semi-parallel steel wire cable and the cable specification on the transmission efficiency of the strain.The main research contents are as follows:(1)The strain transfer mechanics model of surface-adhesive FBG sensor is established.Based on the shear-lag theory,the FBG sensor strain transfer theory formula and minimum sticking length are deduced,and the strain transfer law of fiber grating and the geometrical and physical parameters of the adhesive layer are studied.Influence on the strain transmission efficiency of FBG sensors.(2)Using ANSYS Workbench software to carry out the finite element simulation of the surface-mounted FBG strain sensor,based on the controlled variable method,the adhesive length,the thickness of the adhesive,the thickness of the upper and lower layers of the adhesive layer,the elastic modulus of the adhesive layer,and the Poisson’s ratio of the adhesive layer are studied for the FBG sensor.The effect of strain transfer efficiency,and the comparison between the finite element simulation results and the theoretical derivation results verify the validity of the theoretical derivation.(3)The MTS material testing machine was used to conduct a static tensile test on the high-strength steel wire with the FBG sensor attached to the surface,and the linearity,repeatability and strain transmission efficiency of the FBG sensor were studied.Based on the orthogonal experimental analysis method,the optimal combination of adhesive layer parameters is obtained,and the correlation between the three is verified by combining theoretical derivation and finite element simulation.(4)Based on the shear-lag theory(shear-lag theory),a theoretical formula for strain transfer of a fiber grating sensor attached to the surface of the outermost steel wire of a semi-parallel steel cable is derived,and based on the optimal combination of glue layer size parameters,theoretical derivation and finite element simulation are used In combination,the influence of cable twist angle and cable specification on variable transmission efficiency is studied,and the fiber grating sensor and the cable are deduced.The strain transfer coefficient between semi-parallel steel wires. |
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