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Unformatted text preview: 98 PCI JOURNAL 2004 PCI DESIGN AWARD WINNER This article describes the design and construction of the Old 99 (Riverside) Bridge, an 850-ft-long (260 m), 72-ft-wide (22 m), five-span, post-tensioned, spliced-girder bridge spanning over the Skagit River in Washington State. In 2004, this bridge won a PCI Design Award. The bridges superstructure consists of recently developed Washington State Department of Transporation W95PTG supergirder sections. These precast concrete girder sections were transported to a staging area close to the site, where they were spliced into single pieces that produced maximum spans of 180 ft (55 m). After delivery to the site, the post-tensioned girders were erected on top of the piers with no intermediate temporary supports. High-performance concrete (HPC), with design strengths of 7.5 ksi (52 MPa) and 10 ksi (69 MPa), was specified for the cast-in-place splices and precast supergirder segments, respectively. The use of HPC allowed a high initial post-tensioning force to be applied to the precast concrete girders. Special attention was paid to the lateral stability during erection and time-dependent camber of the assembled girders. Design and Construction of the Old 99 Bridge An HPC Spliced-Girder Structure Khashayar Nikzad, Ph.D., P.E. Principal/Partner TranTech Engineering, LLC Bellevue, Wash. Theo Trochalakis, Ph.D., S.E. Principal TranTech Engineering, LLC Bellevue, Wash. Stephen J. Seguirant, P.E., FPCI Vice President and Director of Engineering Concrete Technology Corp. Tacoma, Wash. Bijan Khaleghi, Ph.D., P.E. Concrete Spet Bridge and Structures OfFce Washington State Department of Transportation Olympia, Wash. JanuaryFebruary 2006 99 T he Old 99 (Riverside) Bridge links the twin cities of Mount Vernon and Burlington in north- western Washington ( Fig. 1 ). The bridges superstructure consists of three 180-ft-long (55 m) interior spans and two 150-ft-long (46 m) end spans. These spans are supported by the recently de- veloped Washington State Department of Transporation (WSDOT) W95PTG precast concrete supergirder sections, which serve as longitudinal stringers. The superstructure is semi-integral at the abutments and hinged longitudinal- ly at the interior piers. Figure 2 shows plan, elevation, and cross-sectional views of the Old 99 Bridge. The Skagit Valley is located between the Cascade Mountains (to the east) and the Pacific Ocean (to the west). Strong atmospheric currents produce a pro- longed rainy and windy winter season and massive accumulations of snow in the mountains. The river is prone to flooding in the winter from rain and in the spring from melting snow in the mountains. This flooding results in large quantities of debris drifting past the bridge site, including large logs....
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