THE CONCRETE BRIDGE MAGAZINE

SUMMER 2018

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

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P R O J E C T The Chief Joseph Dam Bridge crosses the Foster Creek ravine just upstream of where it meets the Columbia River, below the western crest of the Chief Joseph Dam in Bridgeport, Wash. Since 1959, the bridge has served as an important freight route and primary access to the agricultural and recreational region upstream of the dam. In 2016, the existing bridge was replaced with what was the longest single-span precast concrete spliced- girder bridge in Washington state at the time of construction. Background Chief Joseph was a prominent Nez Perce Native American leader. The dam was named in honor of him, and the bridge was subsequently named after the dam. Before it was replaced, the existing 309-ft-long bridge consisted of a unique 130-ft-long and 20-ft-deep Howe deck- truss main span constructed with glued laminated Douglas fir members and five timber approach spans. Designed by the U.S. Army Corps of Engineers, the bridge was certainly an unusual structure, even for its time. It was constructed during an era when steel replaced wood as the preferred material. It was the only bridge of its kind designed and constructed for highway use in Washington state in the 1950s, and, for many years, it was the only Howe deck-truss bridge remaining in the Washington state bridge inventory. Because of its rare structure type, age, and association with the Chief Joseph Dam, the main span was placed on the National Register of Historic Places. Despite being retrofitted in 2003, the bridge had major structural deficiencies and needed to be replaced. After evaluating several alternatives, the designers selected a single-span precast concrete, post-tensioned spliced-girder bridge as the preferred solution to address the unique challenges of the project. Major Project Challenges The nearly 45-degree side slopes o f t h e r a v i n e , c o u p l e d w i t h t h e presence of large boulders and sharp drop-offs of the bedrock, made site access and foundation construction major challenges. Access was further complicated by strict environmental r e q u i r e m e n t s . N o s t r u c t u r a l o r construction activities were allowed in the creek between the existing piers. Despite the creek being dry most of the year, it was highly restricted because of its environmentally fragile nature. Because Chief Joseph Dam is not equipped with fish ladders, Foster Creek is the last creek along the Columbia River that naturally supports the spawning of wild salmon and steelhead. Another issue was the historical significance of the site. profile CHIEF JOSEPH DAM BRIDGE / BRIDGEPORT, DOUGLAS COUNTY, WASHINGTON BRIDGE DESIGN ENGINEER: KPFF Consulting Engineers, Seattle, Wash. PRIME CONTRACTOR: Cascade Bridge LLC, Vancouver, Wash. PRECASTER: Concrete Technology Corporation, Tacoma, Wash.—a PCI-certified producer POST-TENSIONING CONTRACTOR: DYWIDAG Systems International, Long Beach, Calif. OTHER SUPPLIERS: Structural Earth Walls: The Reinforced Earth Company, Englewood, Colo. Chief Joseph Dam Bridge Replacing the old timber truss bridge By Jason B.K. Pang, KPFF Consulting Engineers Reinforcing steel and post-tensioning ducts installed in the 100 in.-deep WSDOT "supergirder." For the end segments, the girder web was widened at the end to accommodate the post- tensioning anchorages. All Photos: KPFF Consulting Engineers. The completed Chief Joseph Dam Bridge in Bridgeport, Douglas County, Wash. 16 | ASPIRE Summer 2018

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