THE CONCRETE BRIDGE MAGAZINE

SPRING 2010

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.

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Challenges Numerous challenges needed to be addressed throughout the life of the project. First and foremost, meeting the project requirements meant it was necessary to ensure the final product was constructible and could be built within budget. From the beginning, discussions with contractors investigated erecting and pouring the cast-in- place deck and with fabricators to discuss issues such as formwork of the arches, reinforcing (clearances, bar bends, development lengths, etc.), and transporting the arches. From a design perspective, a bridge of this nature required a unique approach. The arch and deck were modeled in STAAD and final design completed with spreadsheets that followed load and resistance factor design and PennDOT design requirements. While each part of the design was important, two were critical. First, because of the continuous loading of the deck, the bottom chord was designed for both tension and flexure. Second, the connection of the deck to the arch was designed to properly account for both shear and torsion. F i n a l l y, g a i n i n g a p p ro v a l f o r t h e final structure before moving on to construction was challenging. The Pennsylvania Historical and Museum Commission (PHMC) was involved from the very beginning of the project to ensure that the replacement structure matched the historical attributes of the original bridge. Since the design was context sensitive, obtaining PHMC's approval fared easier than originally anticipated. PHMC did, however, require inclusion of some of the nonstructural details, such as the unique architectural end treatments. A detailed historical recordation had already been completed for the existing bridge, but the owner and designer agreed to develop a website to detail the existing bridge and display photographs of the new bridge construction and completion. Construction and Fabrication I n A p r i l 2 0 0 8 , t h e c o n s t r u c t i o n contract was awarded for a winning bid of $966,000. The county gave notice to proceed in May 2008 with a construction schedule of approximately 7 months. Newcrete Products fabricated the two precast concrete arches in their Roaring Spring, Pa. plant while site work was ongoing and the abutments constructed. The precast specialty engineer provided services to Newcrete and coordinated with Newcrete and RETTEW Associates to address concerns and make several minor modifications to simplify fabrication and transportation of the arches. Modifications included adding post-tensioning to aid in lifting and transporting the arches, adjusting clearances and development lengths to work within the tight tolerances of the arch formwork, and adding mechanical couplers for the transverse deck bars protruding from the bottom chord of the arches. On October 22, 2008, the arches were delivered to the site. The contractor worked overnight to erect them and set the deck formwork in place. The arches were set in place using a 500- ton crane and the deck formwork was hung directly from the bottom chord to avoid working in the creek water. By December 2008, Auction Road Bridge reopened to traffic. Much of the credit for the success of this unique bridge goes to Lancaster County. Their desire to preserve the heritage of yet another historic bridge was impetus for designing a context- sensitive structure that so beautifully complements its rural surroundings. Another contributor to the project's success was effective coordination among the designer, the contractor, and the precaster. As a result of these three firms working together, Lancaster County now has a new bridge that will serve the community—both in form and function—for as many years as Frank Shaw's original 1916 structure. __________ Daniel A. Rogers is senior bridge engineer with RETTEW Associates Inc., Lancaster, Pa. The replacement bridge behaves structurally identical to the original and replicates its details. The original structure built in 1922 had one lane and limited sight distance. The original end treatment is replicated in the new bridge. For more information on this or other projects, visit www.aspirebridge.org. 42 | ASPIRE , Spring 2010 Auction Road_spr10-1.indd 42 4/30/14 11:21 AM

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