Study on working stress measurement method for steel bars inside RC bridges based on self-magnetic flux leakage spatial signals

The measurement of the working stress of steel bars in concrete depends on an embedded sensor, which is difficult to replace once it is damaged. Innovatively, the magnetic characteristic "spatial difference parameter" was used to quantify the working stress of steel bars inside reinforced concrete (RC) bridges, which completely avoided the shortcomings of embedded sensors. The correlation between the stress of steel bars and the magnetic parameters was analyzed based on experimental results from nine steel bars. To be more suitable for practical engineering, the influences of the parameter lift-off value (LOV) and the initial stress value (ISV) on the experiment results were discussed. The results showed that the relative error of the measurement was almost less than 20%. The LOV and ISV did not significantly reduce the accuracy of the measurement results, which provided a good foundation for the application in the stress measurement for the actual RC bridges.