Addington Forks Underpass Structure Precast Deck Alternate, NS


Addington Forks Underpass was constructed just west of the Town of Antigonish in 2010 as part of Phase 1 of the Highway 104 Twinning Project. The bridge is a two span (35 m – 35 m) semi-continuous concrete structure with NEBT 1800 prestressed girders, a composite concrete deck, full integral piled abutments and a central in median hammer head concrete pier. The design of the structure was completed in house by NSTIR, who hired HEC before tendering the project to complete a thorough peer review of the design.

After award of the contract to Nova Construction out of Antigonish Nova Scotia, the contractor hired HEC to undertake preliminary designs of a precast deck alternate in an attempt to mitigate schedule concerns and the cost of suspended formwork for the cast-in-place deck. HEc developed two options: a full depth precast / post-tensioned option and a half depth stay-in-place soffit form option. After discussions and estimating the costs of each option, the precast half depth stay-in-place panel option was carried forward to detailed design and construction. The alternate deck design consisted of the panel design (both during construction and in service), the interconnection design between the panels and the CIP overlay, cast-in-place closures at the integral abutments, integration of the panels / deck with the pier diaphragm, levelling screws and haunch form designs, composite action / interconnection of the deck with the prestressed girders, panel set elevations, deck and membrane drain designs and the panel sizing to ensure geometric control and efficient transport / handling from the panel fabrication shop to site.

Client: Nova Construction

Value: $0.15 M (Deck Alternate Only)

Year: 2010

Role: Preliminary and Detailed Precast Deck Alternate Design, Peer Review of Bridge Design