Cable break detection in pre-stressed bridges, parking decks and girders

摘要

The Remanent Magnetism Method (RM-method) is a non-destructive method to identifyrnpotentially unsafe conditions in pre-tensioned and post-tensioned concrete structures. The RM-method identifiesfracturesrnin single pre-stressing wires, even when they are bundled with intact wires. Fractures producerncharacteristic magnetic leakage fields, which are measured with Hall-Effect sensors. The magnetic field of therntendons is measured at the concrete surface, once they have been pre-magnetized with an electromagnet.Thernparameters associated with fractured wires are the intensity of the magnetic poles, the distance between tendonrnand concrete surface and the crack width.The knowledge of these parameters allows drawing conclusionsrnabout the reduction of the cross-sectional area or the number of fractured wires in a tendon.The method hasrnbeen evaluated by the German Federal Highway Research Institute (BundesanstaltfürStra?enwesen, BASt) andrnis going to be described in a DGZfP directive (German Association for non-Destructive Testing).The test resultsrnare indicated just in time in a gray-scaled magnetic laptop picture.