Memorial Bridge 1923-2012

Memorial Bridge 1923-2012. . , Photo 1 , The memorial bridge was constructed between 1920 and 1923 and demolished in 2012. It was the second bridge built across the fast and deep waters of Portsmouth Harbor. The 1923 bridge was the first vertical lift bridge constructed in the eastern United States. When it was completed it had the longest lift span and highest lift towers in the nation. It was the prototype for many later and larger lift bridges throughout the country and inspired the 2013 lift bridge. Funded in equal parts by the United States, Maine, and New Hampshire, the construction of the 1923 bridge was the culmination of a long campaign to replace a dilapidated 1822 toll bridge, located upstream. The vertical lift design was selected as the least expensive type of movable bridge design that could accommodate the large ships that needed to pass upstream of the bridge. The new free bridge provided direct access to the Portsmouth Naval Shipyard (in Kittery, Maine) for New Hampshire workers. It was dedicated on August 17, 1923, as a memorial to those who served in World War I.

Photo 2 , A Key Transportation Corridor The opening of the original Memorial Bridge brought the newly created U.S. route and its interstate traffic through the center of Portsmouth. As memorial bridge became a vital Eastern Seaboard transportation link, additional bridges across Portsmouth Harbor became necessary. Another vertical lift bridge was completed upstream as a part of the Route 1 bypass and further upstream, the high-level Piscataqua River Bridge was completed in 1973.

Photo 3 , J.A.L. Waddell and Vertical Lift Bridges Memorial Bridge was designed by J.A.L. Waddell (1854-1938) the prominent bridge designer of the area who claimed over 1,000 bridges He was the developer of vertical lift bridges in the United States and holder of patents on most aspects of the operation of those bridges. Based on the success of the Memorial Bridge and two other contemporary bridges, Waddell’s was adopted for locations throughout the world where spans greater than 300 feet were required.

Photo 4 , Bridge Plaques In 1924 bronze plaques and sculptural elements were added to the south portal of the 1923 Memorial Bridge. These included a plaque honoring World War I sailors and soldiers, United States and New Hampshire seals, and an eagle with outstretched wings. They were reinstalled on the 2013 bridge.

Photo 5 , 1923 Bridge construction and operation The extreme tides and currents of the Piscataqua River made the construction of the Memorial Bridge particularly challenging. Contractors for the substructure, Holbrook, Cabot, and Rollins, used watertight caissons for the extensive underwater excavation necessary to construct the deep bridge piers. The American Bridge Company, contractors for the bridge’s superstructure, assembled the spans on the Boston and Maine Railroad’s Market Street Wharf in Portsmouth. When complete, the spans were floated in at slack tide on barges built by tugboats. Ninety years later, the trusses for the 2013 Memorial Bridge were moved into place in the same manner to rest on the original 1922 piers. To permit the passage of tall boats, Memorial Bridge’s center span rose between its flanking towers. Steel pulleys, or sheaves, at the tops of the towers carried steel cables which connected the ends of the lift span to counterweights that exactly countered the weight of the span. Electric motors raised or lowered the span using a separate set of cables.

Photo 6 , 2013 Memorial Bridge The 2013 Memorial Bridge was designed by Theodore P. Zoli III of HNTB Corporation and constructed by Stephen A. DelGrosso of Archer Western Contractors. Like the 1923 bridge, it too introduced important engineering and construction innovations. It was the first truss bridge built without gusset plates connecting its major members-instead using identical steel sections that are spliced together. It also introduced cold bending of steel to truss bridge construction, a submarine building technique pioneered by the US Navy. Its zinc coating, which provides a longer-lasting protective surface than paint, also innovative. Finally, the original 1922 granite piers were rehabilitated using new micropile technology.