Composites Enhance Timber Bridges

by J. J. Dagher, P.E., Dir.; Univ. of Maine's Advanced Engineered Wood Composites Ctr., Prof. in the Civ. Engrg. Dept.,
Melanie Bragdon, Grad. Student; Civ. Engrg. Dept. at the Univ. of Maine,

Serial Information: Civil Engineering—ASCE, 2001, Vol. 71, Issue 8, Pg. A2-A10

Document Type: Feature article


Two relatively new technologies are available for reinforcing or strengthening timber bridges with fiber-reinforced polymers (FRPs). The first consists in reinforcing the tension side of glue-laminated (glulam) girders or decks with unidirectional FRPs. With this technology engineers can significantly increase the flexural strength of the girders, particularly when low-grade laminating stock is used. The second method consists in posttensioning stress-laminated timber decks with transverse glass FRP (GFRP) tendons. Three demonstration bridges recently constructed in Maine using different aspects of these technologies will put these techniques to the test. An FRP-glulam girder bridge in Medway, Maine, uses horizontally laminated girders; a vehicular pier in Milbridge—which has an FRP-glulam deck—uses vertically laminated deck panels. Both the girders and the deck panels are reinforced on the tension side. The third bridge, also in Milbridge, features a stress-laminated deck posttensioned with GFRP tendons instead of steel. The university is monitoring the bridges and will compare their stress losses with other stress-laminated bridge decks. So far, the results are quite favorable, and the university plans to make reports available to the Federal Highway Administration, the studies' chief sponsor, so that guidelines for using these technologies may be written.

Subject Headings: Composite bridges | Wood and wood products | Wood bridges

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