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/306858
The twin arches support bent and spandrel columns and the double- tee deck. T h e N W M a p l e A v e n u e B r i d g e provides an east-west link for the city of Redmond, Ore., across Dry Canyon, which bisects the city. The canyon is a scenic natural feature, providing open space and recreation to local citizens. The designers and the construction team were challenged to design and build a bridge that could blend with its natural surroundings while satisfying current and future needs. City officials desired a bridge that was affordable, functional, aesthetically pleasing, and capable of being efficiently widened in the future as needs required. To meet these needs, the designers c re a t e d a c a s t - i n - p l a c e s t r u c t u re featuring three continuous 210-ft-long arch spans and two 75-ft-long post- tensioned approach spans. Each arch has a distinct contour so the arches together conform perfectly to the sloping topography of the canyon floor. A very wide range of crossing configura- tions was considered, from a sag- vertical curve on fill to a single-span profile MAPLE AVENUE BRIDGE / REDMOND, ORE. ENGINEER: OBEC Consulting Engineers in conjunction with Jiri Strasky, Consulting Engineer, Eugene, Ore. PRIME CONTRACTOR: Cascade Bridge LLC, Vancouver, Wash. CONCRETE SUPPLIER: Central Oregon Redi-Mix LLC, Redmond, Ore. AWARDS: 2008 Portland Cement Association Bridge Award Three cast-in-place arches with different shapes conform to Oregon canyon, adding beauty and functionality arch. The fill was deemed inappropriate and inconsistent with the goals of the canyon, but city officials asked that the design be given at least a cursory investigation to determine a baseline cost. Design Options Bridge options that made the final cut for consideration were a five-span bulb- tee girder, a single-span arch bridge with half-arch approaches at each end, and the three-span arch that was selected. It offered the best combination of aesthetics, economy, and scale for the site. City officials were particularly interested in the potential to achieve a "landmark" bridge appearance if they could obtain it for only a modest cost premium. I n t e r m s o f m a t e r i a l s , s t e e l w a s considered but was ruled out because it was not competitive from a life- cycle perspective. Precast concrete was determined not to offer the best solution because there would not be many repetitive structural elements. by James N. Bollman, OBEC Consulting Engineers CUSTOM ARCHES The NW Maple Avenue Bridge in Redmond, Ore., features three continuous cast-in-place 210-ft-long arch spans, each of which is different to conform to the contours of Dry Canyon below. 18 | ASPIRE , Winter 2009