Research On Corrosion Damage Testing Method Of Bridge Cable Structure Based On Magnetic Field Gradient Tensor

As the preferred type of long-span bridges,cable-structured bridges have been widely used at home and abroad.However,the cable-breaking accidents represented by cable-stayed bridges and the frequent cable-changing projects show that the assessment and mechanism of cable corrosion damage in cable-stayed bridges are insufficient.Cable service life of cable-stayed bridge will be greatly shortened due to the combined action of corrosion environment and complex stress.At the same time,the non-destructive detection method of cable is still a difficult problem due to the hidden corrosion inside the cable.How to eliminate the above hidden dangers has become a hot research topic for researchers all over the world.Firstly,through salt spray corrosion acceleration and electrochemical corrosion tests,the corrosion damage of stay cables during service is simulated.Then,the relationship between corrosion weight loss,tensile strength and magnetic field strength of strands with corrosion deepening is studied through tensile test of parallel steel wire before and after corrosion and measurement of magnetic field gradient tensor.In addition,through the finite element analysis of parallel steel wires,the relationship between the stress distribution of cable members and the corrosion pit layout of the model is studied.Finally,the data of weight loss,tensile strength and magnetic field strength are fitted by MATLAB software in cubic polynomial interpolation,and the evaluation table of corrosion damage of cable structure based on magnetic field strength is obtained.Based on the actual operation of the bridge cable replacement project,the corrosion damage assessment method of the cable obtained from the experiment was further tested.The main results of this study are as follows:(1)By salt spray corrosion and electrochemical corrosion,the corrosion of the bridge caused by PE sheath cracking in the actual operation process was simulated.It was found that the corrosion rate was not linear because of the effect of surface compounds on galvanized steel wire.(2)Through the tensile test of the specimens before and after corrosion,the change trend of the tensile strength of the specimens with different corrosion degree is summarized.(3)Parallel wire ropes with different rusting states were tested by triaxial fluxgate magnetometer,and the relationship between weight loss rate,tensile strength and magnetic field strength was established,and the three-dimensional surface function of(CS-M)is plotted.Finally,a cable corrosion damage evaluation table based on magnetic field gradient tensor was established.