NORTH HERO ROUTE 2 BRIDGE DECK REPLACEMENT
Bridge No. 5, located on US-2, linking the islands of North Hero and Alburgh in Vermont. These islands are located on Lake Champlain, between the states of New York and Vermont.
This recent undertaking was carried out under the Accelbridge program. This initiative, developed by SPI Engineering in collaboration with their precast manufacturer, The Fort Miller Group, allows for rapid replacement of deteriorating bridge decks with minimal impact to the traveling public when compared to conventional bridge construction methods.
The bridge is comprised of two parabolic girders on each outer edge, with transverse floorbeams and stringers running longitudinally below the deck. It spans a length of 786 feet across seven spans, and was constructed in three separate phases – western approach, suspended span, and eastern approach. The suspended span, which sat in the middle of the bridge, was almost identical to the Colchester project. It featured a transverse opening in the center that allowed for the installation of jacks to put a camber in the bridge. In contrast, the two approach spans, which measured 343 feet each, were different from Colchester. They were secured together with two runs of post-tensioned rods that ran underneath the newly erected precast deck, and were tensioned to 250 kips (or 250,000 pounds) in order to stabilize the deck in place. The construction of Phase 2 followed the same pattern as Phase 1, and the two phases were ultimately connected using a longitudinal closure pour that spanned the entire bridge deck.
This construction project was implemented in phases, which involved demolishing the existing deck, installing four new floor beams, and 16 tie beams.
Once the original deck was removed, a subcontractor was responsible for installing grout dams on the existing steel stringers. Then, all precast panels were erected and bonded together using high-strength epoxy. Chain come-alongs and wire rope chokers were then used to tension the panels as the epoxy required a minimum of 10 psi across the face of the precast panels.
A total of one hundred twenty six (126) precast deck panels were used, with sixty three (63) panels for each phase.
This project was subject to the Incentive/Disincentive portion of the Vtrans special provisions, requiring meticulous planning and execution. Phase 1 was scheduled to commence on April 17, 2023 and be completed by July 14, 2023, with an additional incentive payment for prompt completion. Phase 2 followed linearly, beginning on July 15, 2023 and concluding by November 2, 2023. However, unforeseen design issues with the PT rod resulted in an extension for both phases.
The project successfully met all objectives and opened the bridge to two-lane traffic ahead of the scheduled I/D period dates, thanks to the collaborative effort of the Construction Group. This project marks only the second Accelbridge project completed in Vermont.
