Abstract
At present, prestress detection is a worldwide problem. Corrosion has an important impact on the accuracy of the stress detection results of prestressed tendons. Once the steel strands in service is corroded, stress corrosion will occur, which seriously affects the safe operation of the prestressed structure. Based on the LC electromagnetic resonance circuit to detect the prestressing force of steel strands, this research has been successfully applied to the detection of the corrosion rate of steel strands, which lays the foundation for the nondestructive detection of the healthy state of steel strands in the existing structure. In this study, the steel strands were regarded as an external inductor embedded in the LC resonance circuit. After the steel strands was corroded, its electromagnetic characteristics would change, and this change was manifested by the resonance frequency. In this paper, the regular change of the resonance frequency caused by the change of the inductance of the steel wire after corrosion was explained theoretically, and a theoretical model of the relationship between the electromagnetic resonance frequency and the corrosion rate was established. In this study, it was proved through experiments that the LC electromagnetic resonance method can accurately detect the overall corrosion degree of bare steel stranded wires, and a fitting formula for corrosion detection of steel stranded wires was established. Through the analysis and exploration of the test data and test phenomena, it has been found that the action mechanism of the stranded wire decreases with the increase of the corrosion rate and the inductance thereof, which leads to the increase of the resonance frequency. The discovery of these laws will provide an improved basis for the prestress detection of in‐service steel strands by LC resonant circuits and make the method to be further applied to practical engineering.
Highlights
Prestressed structure has the characteristics of reducing structural cracks and improving the bearing capacity of the structure
It can be seen that the data from six experiments show the same law. at is, the corrosion rate of steel strands has a positive correlation with the square of its resonance frequency. e above phenomenon is in accordance with the relationship between the corrosion rate of the steel strands and the square of the resonance frequency as shown in formula (11). is proves that the theoretical relationship between the corrosion rate of steel strands and the resonance frequency derived in 2.2 is correct. rough data analysis and Figure 8, the following conclusions can be drawn
(1) As the corrosion rate η of the steel strands increases, the resonance frequency f obtained by the LC resonance circuit will increase
Summary
Prestressed structure has the characteristics of reducing structural cracks and improving the bearing capacity of the structure. Huo et al use a piezoelectric ceramic transducer to linearly correlate the peak value of the stress wave with the times reversal operation of the stress wave, indicating the feasibility of using time reversal to monitor the corrosion of steel bars [6]. Sriramadasu et al [9] continuously monitors the corrosion state of steel bars in concrete beams by generating and receiving ultrasonic guided waves from piezoelectric wafer sensors attached to the steel bars. Sriramadasu et al [10] used the ultrasonic guided wave to detect the wave packet of the corrosion center of the steel bar and used the two different wave packets to propose the damage index method, which can be successfully used to monitor the pitting degree and strength of the steel bar
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