Detection of Flaws in Reinforcing Steel in Prestressed Concrete Bridge Members

摘要

The long-range objective of the research summarized in this report is the development of a practical nondestructive (NDE) method for detecting deterioration in the reinforcement of prestressed concrete bridge structural members in situ. A detailed definition of the problem is presented and the technical approach is summarized. The basis for selecting and assessing fifteen NDE methods is reviewed, and the results of a limited laboratory investigation of the magnetic method prior to developing inspection equipment are summarized. Development of a preliminary magnetic inspection equipment is described and many records are presented from laboratory evaluations using a 20-ft. (6m) section of Texas Type 'C' beam and from field evaluations on the Sixth South Street Viaduct at Salt Lake City, Utah. Similarities between laboratory and field inspection signatures are indicated; other prominent anomalous signatures are shown which correlated with steel elements neither known to be present nor shown on the plans; still other field signatures are shown which indicated the stirrup configuration in the post-tension girders was not in accordance with the plans. Correlation investigations are described which illustrate promising electronic signature enhancement and recognition methods for discriminating between steel artifacts and deterioration. Recommendations for further development are outlined.