Consulting engineer HNTB, retained to design the replacement structure, produced construction plans for bidding on March 17, 2010. HNTB’s design consisted of a 1,029-ft.-long steel multigirder New York approach and a 769-ft.-long steel multigirder Vermont approach. The approaches are linked by a unique modified network cable-tied arch structure with a 402- ft. span, making the new bridge length 2,200 feet. General contractor Flatiron Constructors was awarded the contract to build the replacement structure on May 27, 2010, for $69 million.
Erdman Anthony was hired by Flatiron to generate erection-engineering submittals to NYSDOT for approval of the seven multigirder spans, the delta frame girders, the tied arch, and the precast concrete deck panels of the arch span. The steel erection was challenging due to the frequency of high winds at the site. Each step of the erection had to account for large construction wind loads to ensure safety. Pairs of girders in the approaches were erected with diaphragms and bracing between and required large cranes to place in position. Girder erection in spans 1 and 8 also required temporary erection bents. Custom-designed angel-wing shoring supported by the new piers allowed longer girder pieces to be erected and reduced the number of girder splices.
A custom shoring system was also designed to erect the 40-ft.-deep steel delta frames. The shoring system was composed primarily of rolled shapes weighing 100 tons at piers 4 and 5 and included post-tensioning to resist overturning. The tied arch was completely erected off site on the lakeshore with all-structural steel and high-strength hangers in position. The arch staging area and erection scheme were facilitated by Erdman Anthony, who designed shoring towers and barge transfer beams. The span was floated to the site on twin barges, positioned beneath its final location, and vertically hoisted from strand jacks located near the cantilever end of the delta frames. The total weight lifted was nearly 1,000 tons, and the span was raised approximately 75 feet.
It took about 18 hours on August 26, 2011, to transport and hoist the arch. High winds from Hurricane Irene visited the site on August 28, and lashing details developed by Erdman Anthony held the span in position during that event. The bridge was opened to traffic on November 7, 2011.
Some history: The Lake Champlain Bridge, which spanned the state line between Crown Point, NY, and Chimney Point, VT, was one of the first continuous-truss road bridges built in the nation and exhibited characteristics of both a through-truss and deck-truss design. Built in 1929, the 2,184-foot bridge was found to be unsafe and was closed to traffic in 2009.
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