Carbon fiber strengthening system aids swing-span bridge

January 25, 2018
The Umpqua River Bridge in Oregon was kept in service while structure strengthening occurred in several locations.

The Umpqua River Bridge along the Oregon Coast Highway (U.S. 101) in Reedsport, Ore., is a swing-span bridge flanked by two tied reinforced concrete arches on each side. The bridge was opened in 1936 and was added to the National Register of Historic Places in 2005. Due to the age and deterioration of the bridge, along with increased loading, the structure required strengthening in several locations. The goal of the Oregon Department of Transportation (ODOT) was not only to strengthen the deck and beams to support today’s truck loadings, but to keep the bridge in service during construction.

A detailed analysis of the existing bridge structure revealed the several deficiencies that required attention. ODOT designed and specified an FRP solution for the flexural deficiencies in the decks of the tied-arch spans and interior concrete girders of the approach spans.

ODOT required the positive moment regions of the decks spanning between floor beams to be strengthened using a near-surface mounted (NSM) technique and provide a strength equivalent to #4 steel rebar at 15 in. off center. To provide the specified strength RenewWrap carbon fiber bars were bonded into shallow slots cut into the deck soffit. Pioneer Waterproofing, the FRP installation contractor, worked from scaffolding suspended from the bridge over the river to provide full access to the underside of the bridge. Pioneer developed an innovative method for quickly and accurately cutting the slots, which was one of the most challenging aspects of the project.

For the positive moment regions of the interior girders of the approach spans ODOT required additional strength equivalent to one #11 steel rebar. Pioneer installed the RenewWrap CF600 carbon fiber strengthening system to the bottom of the girder to meet ODOT’s requirement. The CFRP was coated to provide UV-protection and an aesthetic finish.

As a result, the Umpqua River Bridge will continue to serve the local community and to maintain its historic significance.

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