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Architecture & Engineering


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2001 Awards

January 17, 2002

National Gold Award: Northeast 90th Street Bridge

Photo by Vince Streano
Category: Structural Systems
Engineer: Entranco
General Contractors: Atkinson Construction
Architects: LMN
Owner: City of Redmond
Description: Entranco led a multidisciplinary team through planning, design and construction of the 90th Street bridge. Entranco provided the structural, utility and roadway design for the bridge as well as the environmental documentation and permitting.
 
Because of LMN’s unique architectural concept, advanced structural engineering techniques were employed. Precise three-dimensional computer renderings were created to solve numerous complex geometric issues, including integration of leaning arches with the vertically curved box girder to assist in the construction of arch forms.
 
Innovative construction methods were used to minimize bridge deflections while maintaining the proper vertical roadway alignment. Construction was sequenced, with arches and integrated exterior webs constructed first. Variable width, truss-supported sidewalks were constructed to cantilever off the sides of the bridge.
 
The bridge is the first arch bridge in the state in which the arches are out of the vertical plane — the shallow concrete arches lean 30 degrees from vertical. The entire bridge was constructed without post-tensioning, saving money for the client and simplifying the engineer’s job.
 
Juror Steve Arai called the project a “wonderful blend of architecture and engineering. A fairly straightforward municipal bridge project became a very attractive solution.”


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