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Posted 27 March 2017
On Friday, 3 March 2017, BergerABAM’s Boeing North Bridge project was awarded the Precast/Prestressed Concrete Institute’s (PCI) “Best Special Solution” award in its Transportation category. Presented at the PCI Convention and National Bridge Conference (8 February to 4 March 2017) in Cleveland, Ohio, the award highlights those projects that use innovative solutions to meet the challenge of unique structures.
The Boeing Company uses the North Bridge over the Cedar River to transport completed aircraft from the assembly facility to Renton Municipal Airport, where the planes undergo final inspection before they are sent to clients. Approximately two planes cross the bridge per day.
The original bridge was determined to be structurally and seismically deficient and needed to be replaced. The design and construction schedule needed to be accelerated to meet Boeing’s anticipated increased production rate of its aircraft.
Further, the project had a number of construction constraints that needed to be considered. The project had to allow uninterrupted aircraft manufacturing operations. This meant allowing aircraft coming from the factory to cross the river; accommodating the environmental fish windows, which restricted when in-water work could be conducted; accommodating airport operations, which limited the time and height of the construction equipment that could be used; monitoring work conditions during wet winter weather; and limiting noise.
In response to the accelerated schedule and site constraints, BergerABAM used accelerated bridge construction techniques that cut six weeks from the total project schedule and allowed the project to get the in-water work conducted within the allotted fish window.
The new three-span, steel-plate-girder bridge contains full-depth precast deck panels with concentric transverse pre-tensioning and longitudinal post-tensioning. The precast deck panels were integrated with the steel-plate girders using ultrahigh performance concrete. The intermediate piers consisted of two column bents that used a dropped precast cross beam, precast columns, and cast-in-place drilled shafts. The connection details between substructure/foundation components used details developed as part of the Highways for Life program, which focused on development of a precast bent system for use in high seismic region, with the goal to minimize on-site construction time while providing a durable, low-maintenance bridge. The Boeing North Bridge represents one of the first commercial use of this technique in Washington State.