Acoustic Emission Monitoring Technology Of Key Members Corrosion Damage For The Cable-Stayed Bridge

Elegant design, low cost, good performance of stiffness and wind resistance make the cable-stayed bridge as one kind of bridges widely accepted by us. Nearly all the cable-stayed bridges are built in the marine environment, which has much kind of aggressive ion such as chloride ion. Chloride and other corrosive ion make a serious corrosion to the critical members of cable-stayed bridges such as cable and reinforced concrete. Thus, it is imperative to investigate and monitor the corrosion of these critical members. Comparing with other Nondestructive Testing methods, acoustic emission (AE) testing has higher sensitivity, real-time monitoring and integrated monitoring. Using AE testing in the monitoring of corrosion is very favorable. In this paper, corrosion monitoring work using AE technology is carried out as follows:First, the factors of distortion in the AE wave propagation process are analyzed, and the advantages and disadvantages for AE parameters and waveform analysis are shown respectively. In addition, the wavelet analysis technique is used to remove noise signals which mixed in AE signals. It is found that the selection of wavelet basis, decomposition times, threshold selection and optimization method for the useful feature extraction and noise separation of AE signals is very favorable, and it is validated that the effectiveness of wavelet denoising by the simulation analysis.Second, the most serious difficulty of AE technology-wave effect of AE signal will be given an in-depth study, combining the guided wave theory and good use of software of Matlab to program dispersion curves of different propagation modes. According to the objects tested in experiments (cable and steel), tress wave propagation in different conditions is simulated using finite software of ANSYS. The result of simulating of passive film rupture process in corrosion by two-dimensional Fourier transform demonstrated the effect of waveguide dispersion. At last, the method of using two-dimensional Fourier transform to indentify damage is given.Finally, the corrosion test accelerated by direct current to cable and reinforced concrete is made, using AE system to collect and storage signals generated in the corrosion process all the time. Finally, select some appropriate signal processing methods to analysis and study the law of corrosion. The accelerated experiments show that AE technology plays a good dynamic real-time monitoring to the whole process of inaction, onset and deterioration of corrosion. Selecting appropriate signal processing methods can minimize the wave effect. It is effectively that useful AE signals are extracted from the strong noise environment by the wavelet analysis. The AE signals have obvious features in different corrosion stages. In this paper, the AE characteristics and evaluation methodology are propounded in different damage stages. The examination results provide some guidance for bridge's corrosion monitoring in the actual operation.