Earlier this month, a rebuilt version of the Sarah Mildred Long Bridge – spanning the US 1 Bypass over the Piscataqua River between Portsmouth, N.H., and Kittery, Maine, re-opened to traffic in time for Memorial Day.
The structure was built in 1940 to replace a crossing that dated back to 1822. In 2016, the bridge was demolished as part of a project called the Three Bridge Agreement. Due to the multi-functional aspects of this movable bridge and its 100-year design life, the bridge has the distinction of being the most expensive infrastructure project in state history. The cost to replace the 80-year-old lift-span totaled $165 million.
The bridge features vertical clearance for larger ships and a steel box lift span capable of carrying vehicle and railroad traffic above the steel superstructure. It is first bridge of its kind in the U.S. to shoulder four precast 200 ft. tall concrete towers that support a 300 ft. long structural steel box girder lift span.
When engineers needed to stabilize the structure during severe weather and high winds, they turned to FRP. Cianbro Corp., the project’s contractor, selected Composite Advantage to design and fabricate two sets of FRP wind fairings. Each was engineered to house an internal walkway to accommodate inspection and maintenance activities. The L-shaped FRP wind fairings—the first such product for Composite Advantage and only the second time FRP has been used for this type of application—attach to the top and bottom of the lift span structure.