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/297009
When the Sibley Pond Bridge required replacement, the project team used innovative design and the first use of the Precast/Prestressed Concrete Institute (PCI) Northeast Extreme Tee double-tee (NEXT D) beam section with full-depth integral deck, to open the bridge more than 10 months ahead of schedule. The NEXT D section had been newly developed by PCI Northeast in response to the Federal Highway Administration's (FHWA) nationwide i n i t i a t i v e f o r a c c e l e r a t e d b r i d g e construction. The 790-ft-long, two-lane bridge consists of ten 79-ft-long spans arranged in two 5-span continuous units. The bridge carries U.S. Route 2 between Canaan and Pittsfield, Maine, over a shallow pond. The pond's upper layers of organic material increase in depth towards its middle, and is underlain with glacial till and granite bedrock. Fixity is provided at each end of the bridge through semi-integral abutments. Each of the nine intermediate piers are supported on single rows of four steel-pipe piles that flex as the structure expands and contracts around a single expansion joint located at the center of the bridge. By limiting cast-in-place concrete construction to the pier diaphragms and 8-in.-wide closure strips between beam flanges, the NEXT D beams were rapidly erected using a gantry crane that rolled sideways from the old bridge and across the new piers. Durability was enhanced by using 8 ksi compressive strength, self-consolidating, precast concrete that included a corrosion inhibitor. C l o s e c o l l a b o r a t i o n b e t w e e n t h e contractor, the beam designer, the precaster, and PCI Northeast took place during the project's early stages to optimize the final design details of these new beam sections. This collaboration facilitated maximum efficiencies in precasting, erection by a custom-built gantry crane, and the quality necessary for a 100-year service life as specified by the owner. Design Considerations The replacement bridge was placed on a tangent alignment, partially overlapping the existing bridge near the abutments, but with sufficient width to maintain access to the old bridge during construction. The bridge was laid out with 10 equal 79-ft-long spans so that piles from the new bents would be well clear of those from the existing bridge with its 26-ft-long spans. Early in the proposal phase, the contractor submitted an alternative technical concept to move Route 2 traffic to the south onto an at-grade detour roadway that followed a former alignment of the route. This required a 60-ft-long temporary bridge over the pond inlet. This detour relocated traffic safely away from the work area and enabled the existing bridge to be profile SIBLEy POND BRIDGE, ROUTE 2 / CANAAN AND PITTSFIELD, MAINE BRIDGE DESIGN ENGINEER: Parsons Brinckerhoff Inc., Manchester, N.H., and Boston, Mass. PRIME CoNTRACToR: The Lane Construction Corp., Bangor, Maine CoNCRETE SuPPlIER: The Lane Construction Corp., Bangor, Maine PRECASTER: J.P. Carrara and Sons, Middlebury, Vt., a PCI-certified producer The 790-ft-long, two-lane bridge consists of ten 79-ft spans arranged in two 5-span continuous units spanning over a shallow pond. Photo: Lane Construction. by G. Keith Donington and Hany L. Riad, Parsons Brinckerhoff Design-build bridge replacement project in Maine uses Northeast Extreme Tee Sibley Pond Bridge, Route 2 34 | ASPIRE , Fall 2013 P R O J E C T Book_Fall13ASPIRE.indb 34 9/6/13 12:05 PM