Inspection of Prestressed Concrete Structural Members with Magnetic Methods

Inspection of Prestressed Concrete Structural Members with Magnetic MethodsThe methods of magnetic stray field measurement and of magnetic remanence measurment are well suited for nondestructive detection of ruptures in prestressing wires of concrete structural members. Using a yoke magnet with integrated magnetic field sensors, the members are scanned several times with varying magnetization field strength. The signal analysis is based on the comparison of measurements after different premagnetizations as well as on the determination of the correlation with idealized rebar and crack signals. The limits of detection are discussed on a case-by-case basis. The application in inspection practice is illustrated with three examples