T.Y. Lin International (TYLI), a globally recognized full-service infrastructure consulting firm, announces that the new Brookfield Floating Bridge, which crosses Sunset Lake in Brookfield, Vermont, opened to traffic on Saturday, May 23, 2015. Serving as prime design consultant for the Vermont Agency of Transportation (VTrans), TYLI performed an alternatives investigation for the replacement bridge and carried the selected alternative through final design and Plans, Specifications, and Estimates (PSE) submittal. The project transformed an aging floating structure into a state-of-the-art fiber-reinforced polymer (FRP) pontoon system with a life expectancy of 100 years.
One of only a handful of floating bridges in the world, the new Brookfield Floating Bridge is approximately 321 ft long, and located along S.R. 65, the last state-owned gravel road in Vermont. Rebuilt seven times since its original tied-log construction in 1820, the floating timber bridge is listed on the National Register of Historic Places as a contributing element to the Brookfield Historic District. Prior to today’s modernized structure, the former bridge had been built in 1936 and then rebuilt in 1978.
VTrans closed the old bridge to vehicles in 2007 and pedestrian traffic in 2008. The alternatives investigation for a new structure began in 2012, after local residents called for a reopening of the beloved landmark. Criteria for the replacement bridge included a durable, maintenance-free structure that could shoulder highly-variable ice pressure loads, even when closed during the winter months, and the integration of modular components to aid in potential major repairs.
TYLI’s preliminary design compared concrete and FRP for the pontoons used to support the floating portion of the bridge. VTrans selected the FRP alternate because dredging of the lake would not be required, and because FRP pontoons could be filled with closed-cell foam for a secondary flotation system. TYLI worked closely with the state agency to identify project needs, design parameters, and construction constraints in order to allow the fabricator to determine the most appropriate and cost-competitive methods to meet project requirements.
“T.Y. Lin International has a long history of innovation in designing unique structures under challenging environmental conditions,” said Kevin S. Ducharme, PE, TYLI Vice President. “It was an honor to partner with the Vermont Agency of Transportation on a project that represents such historical significance for the state of Vermont, as well as significant advancements in the use of fiber-reinforced polymer structures for our industry.”
The new Brookfield Floating Bridge carries a single 12-foot-wide travel lane for alternating, one-way traffic and two flanking 5-foot-wide sidewalks. The articulating approach ramps comprise glued laminated timber beams. Timber was used for the deck, railing, and ramp system to echo the appearance of local historic structures. The bearings and hinged expansion plates were uniquely designed and detailed to accommodate large movements caused by lake level fluctuations. The abutments are traditional cast-in-place concrete, with one abutment supported by a shallow footing on bedrock and the other pile-supported.
Distinguished speakers at the May 23rd Brookfield Floating Bridge Celebration included State of Vermont Governor Peter Shumlin and State Congressman Peter Welch, as well as Sue Minter, Secretary of VTrans, and Josh Olund, PhD, PE, TYLI Bridge Engineer and the designer of the new bridge. Also in attendance was 91-year-old Mim Herwig, a local resident who attended the 1936 bridge opening celebration and is related to Luther Adams, the builder of the first floating bridge across Sunset Lake in 1820.
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