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/306894
The sleek look of the new bridge was created by post-tensioning the three spans; thereby reducing the weight of the superstructure. The thin lines of the metal railing help emphasize the shallow profile of the bridge. ASPIRE , Winter 2007 | 27 A E S T H E T I C S C o m m E n T A r Y by Frederick Gottemoeller tendons were jacked from both ends of the superstructure at the same time. Approximately 125 cu yd of concrete w e r e u s e d f o r t h e s u b s t r u c t u r e units, with another 170 cu yd used for the superstructure. The project took approximately 10 months for completion. "Reinforced concrete rigid-frame bridges have long been a mainstay in the bridge world," Nenaydykh says. "They offer many advantages in comparison to their materials in terms of durability, economy, and maintenance. With increasing span lengths, conventionally reinforced concrete bridges tend to get bulkier, which can quickly add cost." The post- tensioning provided a continuous design and prevented that from happening in this case. "On the Brady Street Bridge, we used an innovative hybrid scheme, consisting of a concrete rigid-frame structure with a sleek shallow arch in the main central span," he notes. "The Brady Street Bridge serves the twin purpose of functionality and architectural expression while also enhancing the beauty of the natural surroundings," he says. "The success of this project can encourage bridge designers to make use of the best technology available to design beautiful bridges that challenge the imagination." For more information on this or other projects, visit www.aspirebridge.org. Replacing an attractive and well-loved bridge is always a challenge, particu- larly when the bridge is in a park and crosses over a well-traveled roadway. The designers of the Brady Street Bridge have taken this challenge and mastered it. The existing bridge was one of a family of similar bridges over Milwaukee's Lincoln Memorial Parkway. These bridges have curved soffts and a very open and transparent appearance. The new bridge provides both of these features. The curved sofft is created by the haunched girder design, which deepens the girder at the piers to match the forces there, while making it as thin as possible at center of the main span, where the forces are the lowest. The openness is created by removing triangu- lar sections of what otherwise would be the web of the haunched girder. The openings make the bridge lighter visually as well as reducing the self weight. The openness is reinforced by the selection of a railing design with horizontal elements. The railing is transparent from all angles, which would not be the case if it were made up of vertical pickets. The railing posts are thin and are themselves shaped to refect the forces on them. The designers are to be congratulated on creating a bridge that is effcient, economical, and elegant, which fts into and reinforces the family of bridges over the Lincoln Memorial Parkway in Milwaukee. 'There are no bearings or joints on the bridge that will deteriorate with seasonal changes.' ASPIRE_win07.indb 27 12/29/06 2:12:01 PM