Abstract
This paper presents the results of a study of a nondestructive evaluation technique, the Magnetic Field Disturbance (MFD) system, for detection of flaws in the reinforcing and prestressing steels of prestressed concrete bridges. This work included development of an improved MFD signal processing technique, a series of laboratory experiments, and tests of prestressed bridge beams in the field. A description of the principles of the MFD system and of various signal processing and interpretation techniques is provided. It was found that when a flawed bar or cable is within 6 in. of the surface of the concrete beam, it is possible to detect and locate flaws with a minimum size equivalent to a 5% loss of a cross-sectional area of the steel.