Strengthening Timber Bridge Beams Using Carbon Fiber
Publication: Journal of Structural Engineering
Volume 131, Issue 1
Abstract
This research project demonstrates how advanced composite materials can be used to strengthen existing timber bridge beams in order to increase the load capacity of the bridge. Many times, the timber bridges were not designed to withstand the heavy truck traffic that they are currently carrying, and are therefore replaced in favor of modern concrete or steel bridges. Current methods of strengthening timber bridges are not always practical or economical and so these bridges are simply replaced at a high cost to the public. This project investigated whether applying composites in the form of either a fabric wrap or laminate strips to timber beams would increase the load capacity of the beams. Bidirectional carbon fabric was the primary strengthening material used. A total of 10 solid-sawn Douglas Fir timber beams were taken from a timber stringer bridge in Yuma, Ariz. that was replaced in 1999. Seven of the 10 creosote-treated beams were reinforced with carbon fiber and then tested for bending strength, shear strength, and stiffness. Three of the beams were tested as unreinforced control specimens. The results show that applying carbon fabric to the timber beams provides significant increases in the bending and shear capacity, and nominal increases in the stiffness of the beams. Allowable stress modification factors are conceptually discussed that could potentially be used by engineers to determine the safe load-carrying capacity of beams reinforced with carbon fiber. However, a statistically significant number of timber beams strengthened with carbon fiber need to be tested to arrive at definitive stress modification factors.
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Acknowledgments
The writers wish to acknowledge the funding of this research by the National Science Foundation, Grant No. CMS-9257344, Dr. John B. Scalzi, Program Director. The results and conclusions presented here are those of the writers and do not represent the views of the National Science Foundation. The writer Ted W. Buell would also like to thank his father, Ted B. Buell, for his willingness to help in any way needed. His expertise in woodworking and general carpentry, as well as his encouragement, made this project a success.
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Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 131 • Issue 1 • January 2005
Pages: 173 - 187
Copyright
© 2004 ASCE.
History
Received: Jun 21, 2002
Accepted: Jun 23, 2004
Published online: Jan 1, 2005
Published in print: Jan 2005
Notes
Note. Associate Editor: David V. Rosowsky
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