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/306189
The Northeast 36th Street Bridge and roundabout intersection in the city of Redmond, Wash., located 15 miles northeast of Seattle, was completed and opened to traffic in December 2010. The new bridge, a landscaped lid offering many pedestrian amenities, provides an overcrossing of State Route 520, which includes the well-known "floating bridge" that connects Redmond, the home of Microsoft World Headquarters and the University of Washington campus. The new 414-ft-long bridge measured along the travelled way, connects two sides of the expanding Overlake neighborhood in Redmond, over SR 520, and adjoins a recently expanded Microsoft campus. The two arterials connected by the Northeast 36th Street Bridge are some of Redmond's most congested roadways. The new bridge will help to alleviate bottlenecks on nearby interchanges and the impacts o f t h e p ro j e c t e d p o p u l a t i o n a n d employment growth in the Overlake area. Without the new bridge, the existing connections over SR 520 would be overwhelmed. The project is expected to reduce vehicle miles travelled by approximately 135,000 miles per year. In keeping with Redmond's designation a s t h e " b i c y c l e c a p i t a l o f t h e Northwest," the Northeast 36th Street Bridge is optimized for pedestrian access and bicycle connections. It provides one traffic lane in each direction, bike lanes, sidewalks, and intersection improvements. It also accommodates the future Sound Transit Link Light Rail alignment and a connecting pathway that offers pedestrian access to the nearby Transit Center. Double-Diamond plan The bridge passes diagonally over SR 520 and, according to Redmond's project manager, Dennis Apland, "is the product of a lot of clever engineering." The roadway crosses the highway at a 44-degree angle, rather than the more typical 90 degrees. The project is essentially two offset adjoining landscaped lids—a unique and innovative solution that prevented the project from becoming a much more costly tunnel project. The length of each lid along SR 520 is approximately 300 ft, just shy of the length that would trigger expensive fire suppression and ventilation systems for a tunnel designation. The double-diamond design allowed the bridge to be built using standard construction methods, producing a much more cost-effective project overall. This solution also yielded minimal construction impacts on the major highway below. profile NORTHEAST 36TH STREET BRIDGE Ov ER SR 520 / REDMOND, WASHINGTON br IDgE DESIgN ENgINEEr: BergerABAM, Federal Way, Wash. gENErAL CoNTrACTor: Tri-State Construction Inc., Bellevue, Wash. prECASTEr: Concrete Technology Corporation, Tacoma, Wash., a PCI-certified producer rEINForCEMENT SuppLIEr: Pacer Steel Inc., Pacific, Wash. brIDgE DESCrIpTIoN: Two spans (150 and 164 ft by 300 ft wide) providing a traveled way bridge length of 414 ft supported on cast-in-place concrete abutments and a concrete center pier by Robert L. Fernandes, Ross A. French, and S. Ping C. Liu, BergerABAM Creating a Level Playing Field The signature design of the Northeast 36th Street Bridge is the unique double- diamond shape, approximately 50,000 ft 2 landscaped lid spanning SR 520. All photos: BergerABAM. A bridge And A PArk buiLt over busy FreewAy 18 | ASPIRE , Fall 2011 Book_Fall11.indb 18 9/29/11 11:59 AM