Evaluation of Wrought Iron for Continued Service in Historic Bridges
Publication: Journal of Materials in Civil Engineering
Volume 17, Issue 4
Abstract
Doubts about the strength of wrought iron used in historic structures can be resolved with appropriate methods of evaluation. Since wrought iron is a composite material of metal and slag fibers, its performance in structures cannot be adequately evaluated by the techniques routinely used for testing structural steel. Both historic and modern test data show that wrought irons from different sources vary little in strength but greatly in ductility. Since adequate sampling for mechanical ductility tests is often difficult, alternatives based on metallurgical analysis can assist evaluation of the metal in historic structures. Test data show that more than 0.3% phosphorus in solid solution embrittles wrought iron. This level of phosphorus can be detected by optical microscope techniques. Excessive or poorly distributed slag fiber is the other principal source of inadequate ductility, and can be evaluated by metallographic examination either in place or on samples much smaller than those required for mechanical testing.
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Acknowledgments
Samples of the original wrought iron components of the Aldrich Change Bridge, built for service over the Erie Canal in 1858 were supplied to us for testing and examination through the courtesy of Jay Harding, the A.C.B. Project Committee, and James Stewart of FRA Engineering. The writers thank L.C. Whiteford, Inc., Wellsville, N.Y., for the metal from the Schoellkopf Road Bridge, the Union Concrete and Construction Corp., West Seneca, N.Y., for the samples from the Eck Road Bridge. James Stewart provided the historical data on these bridges and carried out the stress analysis for the Aldrich Bridge.
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Information & Authors
Information
Published In
Journal of Materials in Civil Engineering
Volume 17 • Issue 4 • August 2005
Pages: 393 - 399
Copyright
© 2005 ASCE.
History
Received: Aug 25, 2003
Accepted: Jun 24, 2004
Published online: Aug 1, 2005
Published in print: Aug 2005
Notes
Note. Associate Editor: David Trejo
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