Blog Post

World's First FRP Floating Bridge, world record in Brookfield, Vermont

May 10, 2024

Brookfield, Vermont, United States--The 97m long, 6.7m wide, US$2.4-million single-lane Brookfield Bridge in Brookfield, Vermont, designed by T.Y. Lin International (San Francisco, CA, US), has replaced a 1978 version that carried state Route 65 traffic over Sunset Lake and sets the world record for being the World's First FRP Floating Bridge, according to the WORLD RECORD ACADEMY.

"In the central Vermont town of Brookfield (pop. 1,292), the world’s first floating fiber-reinforced polymer (FRP) bridge has replaced a 1978 version that carried state Route 65 traffic over Sunset Lake," the Composites World says.

"Designed by T.Y. Lin International (San Francisco, CA, US), it is the eighth version of a floating log bridge built in 1820 after a resident fell through winter ice and drowned while crossing the lake nearly two centuries ago. It has since been the focal point of the town’s life.

"Construction of the new 97m long, 6.7m wide, US$2.4-million single-lane Brookfield Bridge began in April 2014 and was complete before its opening, Memorial Day weekend 2015."

"One of only a handful of floating bridges in the world and listed in the National Register of Historic Places, the first Brookfield Floating Bridge was constructed in 1820. After the seventh-generation structure was closed in 2007 due to leaking flotation devices and deteriorating timber, local residents lobbied that the important local attraction - which only carries about 110 vehicles each day – be rebuilt.," the TYLin Group says.

"TYLin engineers successfully overcame numerous project challenges, including the incorporation of four major structural materials (FRP, timber, concrete, and steel), the lack of design standards for FRP and floating bridges, and a 100-year design life mandate, which proved difficult in an aquatic environment.

"The Brookfield Floating Bridge opened on time and on budget. The bridge measures approximately 321 feet long and carries a single lane of alternating traffic and two flanking, 5-foot-wide pedestrian sidewalks."

"Fibre-reinforced polymer composites (FRPs) offer various benefits for bridge construction. Lightweight, durability, design flexibility and fast erection in inaccessible areas are their unique selling points for bridge engineering," the MDPI says.

"FRPs are used in four bridge applications: (1) FRP rebars/tendons in concrete; (2) repair and strengthening of existing bridges; (3) new hybrid–FRP bridges with conventional materials and (4) all–FRP composite new bridges made entirely of FRP materials."

"The Brookfield Floating Bridge was originally built in 1820 and has been rebuilt several times since. The proposed flotation system for the current structure consists of ten FRP pontoons joined to form a monolithic float," the Vermont Agency of Transportation says.

"The top-side of the structure is constructed entirely of timber to match the aesthetic appearance of the original construction. The project incorporates four major structural materials (FRP, timber, concrete, and steel) and project-specific design criteria for FRP and floating bridges.

"Material properties of a given FRP laminate are difficult to predict and often require physical testing to substantiate design values. Fabric type, orientations, fiber volume, and resin type each influence a laminate’s strength and stiffness and in different loading orientations."

"Project Highlights:

TYLin developed project-specific design criteria to address unique loading conditions, serviceability constraints, and other aspects, relying heavily on research papers, guides, and draft design codes prepared under American Society of Civil Engineers (ASCE) specifications.
The flotation system consists of ten 11-foot-wide and 51-foot-long FRP pontoons, tied together into a monolithic float through the use of high-strength rods and steel splice plates.
Historic constraints required the use of timber for the deck, railing, and ramp system to echo the appearance of previous structures. The articulating approach ramps are composed of glued laminated timber beams.
The bearings and hinged expansion plates were specially designed and detailed to accommodate large movements caused by lake level fluctuations.

(Source: TYLin Group)

"The Brookfield Floating Bridge is a floating bridge that carries Vermont Route 65 across Sunset Lake. The Floating Bridge was originally built in 1820 and has been rebuilt eight times since," the Brookfield Historical Society, VT, says.

"Additional information about the bridge may be found in such publications as the The History of Brookfield, Vermont (2010 Edition)."

"Engineering News-Record mentioned the University of Maine in an article about the world’s first composite floating bridge in Brookfield, Vermont," The University of Maine says.

"The 318-by-20 feet, single-lane bridge employs a fiber-reinforced polymer (FRP) flotation system with a 100-year design life, according to the article. The $2.4 million bridge is set to be completed by Memorial Day weekend.

"Since design codes for FRP bridges do not exist, the team worked with UMaine and the Vermont Agency of Transportation (VTrans) to develop a set of criteria, the article states."

"The Floating Bridge over Sunset Lake in Brookfield, Vermont, has been a landmark for local residents for nearly two centuries – longer than state transportation agencies have existed and even before the invention of cars," the Vermont Agency of Transportation says.

"During winter months, residents near the lake would travel back and forth across the ice to avoid a longer trip around the shoreline. Unfortunately, during a warm spring day in 1819, one resident tragically fell through the ice and died.

"The following winter, logs were laid on top of the ice and bound together to make a more robust crossing. As the ice melted, the logs floated, creating a makeshift water crossing during warmer months, which is now known as the original “Brookfield Floating Bridge."