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.
Issue link: http://www.aspiremagazinebyengineers.com/i/297018
The York Bridge replacement project w a s a c o l l a b o r a t i v e d e s i g n a n d construction effort between King County and the city of Redmond, Wash. It demonstrates the ability to solve tough engineering challenges while minimizing costs and being sensitive to the environment and the community. The new bridge, with its gracefully arched, cast-in-place concrete substructure and 42-in.-deep precast, prestressed concrete girders (Washington State Department of Transportation Type W42G), required rebuilding, widening, and raising the approach roadways. The existing bridge, which crossed the Sammamish River at NE 116th Street in Redmond, had become structurally deficient and functionally obsolete. Sizable flexural cracks had developed in the girders, requiring a low-posted load limit that restricted the bridge's usefulness. The bridge's piers also disrupted the river's flow and created dangerous, at-grade crossings for pedestrians and bicyclists along the trails on both sides of the river. The location also contains the multi-use 60 Acres Park recreational area that attracts large numbers of visitors, creating a traffic bottleneck. bridge lengthened, elevated The bridge was designed to be 220 ft long, which is 103 ft longer than the original bridge, and 51 ft 3 in. wide overall, which is more than 25 ft wider. The bridge and approach roads were elevated 15 ft so the trails continue uninterrupted beneath the bridge, greatly improving accessibility and safety for pedestrians, bicyclists, and equestrians. The primary goals in selecting the bridge's design and material were to minimize construction time and create an aesthetically pleasing appearance. In addition, the city of Redmond had recently completed a $14-million project downstream at NE 90th Street, and city officials were concerned that the new bridge might pale in comparison. There also were numerous agencies to work with due to the area's environmental sensitivity and the desire to maximize shoreline habitat for endangered salmon. An extensive comparative analysis was performed early in the process. Concrete always was considered to be the best material, but finding the most efficient design solution was critical. The design process also was impacted by the desire to gain as much federal funding as possible. Federal funds would cover only the costs for the lowest-cost design alternative, with other sources needed to cover any premium. Fortunately, the created design proved to be the low-cost option, as well as the most profile YORk BRIDGE / REDMOND, WASHINGTON bRIDge DeSIgN eNgINeeR: King County Department of Transportation, Seattle, Wash., and Redmond Public Works Department, Redmond, Wash. eNgINeeRINg CoNSulTANTS: AECOM (formerly Entranco and DMJM Harris), Seattle, Wash. pRIme CoNTRACToR: Mowat Construction Co., Woodinville, Wash. pReCASTeR: Concrete Technology Corp. Tacoma, Wash., a PCI-certified producer CoNCReTe SupplIeR: Cadman Inc., Bellevue, Wash. by Jim Markus and Gwendolyn I. Lewis, King County, and Kevin Kim, Jacobs Engineering Beauty on the Banks The new York Bridge in Redmond, Wash., is longer and wider than the original structure, allowing it to span multi-use trails on both sides of the river. The shape of the pedestrian lookout can be seen by the shadow on the girders. All photos: King County, Washington. Aesthetically pleasing arch design requires innovation and environmental sensitivity 26 | ASPIRE , Winter 2012 Book_Win12.indb 26 12/29/11 11:12 AM