CAPACITY OF THE REMANENT MAGNETISM METHOD TO DETECT FRACTURES OF STEEL IN TENDONS EMBEDDED IN PRESTRESSED CONCRETE

Sudden collapses of structural components due to fractures of the pres tressing steel have occurred. The paper describes the successful appli cation of a nondestructive testing method to identify defective struct ures. The remanent magnetism method makes it possible to localize frac tures of single prestressing steel bars in posttensioned tendons. The tendons need not be accessible at any point, not even at the jacking e nds. The ferromagnetic properties of the prestressing steel are used i n this process. Characteristic magnetic leakage fields are caused by f ractures. The magnetic field, measured at the concrete surface along t he projection of the tendon profile, allows conclusions concerning exi sting fractures. Also the extent of damage (number of broken steel bar s) can be evaluated. (C) 1997 Elsevier Science Ltd.