Magnetic Flux Leakage Testing Method For Corrosion Of Prestressed Steel In Concrete Bridge

As more and more bridges are in building, the safety of such bridges attracts greater attention. Prestressed steel is normally placed in the tension region of concrete structural members, once corrosion appears, it will imperil the safety of bridge. There is still no appropriate inspecting method for prestressed steel in concrete bridge.The thesis researched the testing method about concrete bridge and the principle of magnetic flux leakage test, the experiment system which is used to test the prestressed steel in concrete bridge has been designed. The thesis has also finished the design of excitation device, the research of signal acquisition method and the pretreatment circuit of Hall-sensor signal. Using this experiment system, a series of experiment have been finished. Firstly , let the testing instrument inversion while the prestressed steel moving above it in different depth, the experiment indicate that 7% corrosion can be found in the depth of 65mm and 42% corrosion can be found in the depth of 200mm in such conditions. Secondly, a wooden test beam which is used to research the influence of girder has been designed, the steel which is along the magnetization direction has little influence on the testing result, but the steel which is plumb with the magnetization direction will bring periodicity disturbance, it will influence the testing result seriously. Finally, the experiment in concrete bridge test beam indicates that 50% corrosion can be found when the Lift-off is 100mm.As the span of bridge increases, the dimension of prestressed bridge is increasing and the depth of prestressed steel in bridge increases accordingly, the existing testing methods can't achieve non-destructive testing. The research of this thesis indicates that magnetic flux leakage test is a feasible method, and it offers fresh approach for test method of prestressed steel in concrete bridge.