| In the service process of CFRP reinforced concrete bridge,it is often affected by load and environment and other adverse factors,which accelerate the performance degradation of CFRP-concrete bond interface and significantly reduce the bearing capacity and service life of the structure.Therefore,it is very important to detect the damage of the bond interface of CFRP reinforced bridge,and the piezoresistance method(EMI)is very important.It has a unique advantage in the detection of peeling damage of structural thin plates.In this paper,EMI structural health monitoring technology,combined with mechanical performance monitoring means,is used to monitor the performance of the bond interface of CFRP strengthened concrete bridge under various loads and environments,which provides a reference for the durability research of the bond interface of CFRP and concrete.The main research work and conclusions are as follows:(1)The principle of EMI structural health technology is studied,and the specific method of EMI damage detection technology is proposed.This paper describes the piezoelectric reaction of piezoelectric materials,studies the basic principle of piezoelectric impedance structure technology,demonstrates the feasibility of piezoelectric impedance method to detect the damage of CFRP bond interface,proposes to analyze the durability of CFRP strengthened beam bond interface by combining the piezoelectric impedance method and strain monitoring,and compares and analyzes the two interface performance evaluation indexes of RMSD value and CFRP strain value,The damage law of CFRP-concrete interface is demonstrated.(2)The damage test of CFRP strengthened concrete beam under overload fatigue was carried out to study the change of interface performance of CFRP during overload fatigue.The test results show that the piezoelectric impedance curve can identify and locate the peeling damage of CFRP plate in the process of the test beam overload.The RMSD value of the impedance can be used to quantitatively analyze the damage condition of the test beam,and the EMI technology is more sensitive to the detection of the slight damage of the structure than the strain gauge.The strain,deflection and rigidity of the test point in the middle of CFRP will increase with the times of overload,and the concrete in the compression area will increase with the times of overload The strain hardly changed.(3)The static load tests of CFRP strengthened concrete beams and reference beams after overload fatigue were carried out to study the influence of overload fatigue damage on the interface performance of CFRP.The test results show that the piezoimpedance method can detect the crack development and the peeling failure process of CFRP plate in the static load of the test beam.Through the RMSD value of the impedance,the bond interface performance of the overload damaged beam is lower than that of the reference beam.After the overload fatigue,the ultimate bearing capacity,ductility,deflection and the maximum strain of the CFRP plate span of the overload damaged beam are reduced,and the performance of the overload damaged concrete compression area is lower impact.(4)The interface damage monitoring test of CFRP during the dry and wet cycles and the static load test of CFRP strengthened concrete beams after the dry and wet cycles were carried out to study the influence of the dry and wet cycles on the strengthened beams and the overload damage on the interface performance of CFRP bonded beams.The test results show that the piezoresistance method can monitor the corrosion and aging damage of CFRP bonding interface during the dry and wet cycles,and the damage at the end of CFRP is larger than that in the middle;the impedance of the beam after the dry and wet cycles changes greatly,which shows that the piezoresistance method can distinguish the existing damage of the strengthened beam;the dry and wet cycles have little effect on the ultimate bearing capacity of the strengthened beam,but will reduce the ductility and CF The overload damage has little effect on the ultimate bearing capacity of the hygrothermal beam,which will significantly reduce the ductility of the hygrothermal beam,and has a negative impact on the interface bonding performance of the hygrothermal beam. |
