The existing eight span, 430 m long single-lane Fort Nelson River Bridge on Hwy 77 was constructed in 1984 and is one of world's longest ACROW bridges. The British Columbia Ministry of Transportation and Infrastructure (MoTI), the owner of the bridge, due to increasing traffic demands in the region, is pursuing the replacement of the narrow single lane superstructure with a new two lane superstructure utilizing the existing piers and abutments. McElhanney Consulting Services Limited (McElhanney) has undertaken the initial foundation evaluation, condition inspection, conceptual and detailed design of the new superstructure and rehabilitation of existing abutments and piers to accommodate the heavier and wider superstructure. The existing bridge has spans of 34 m - 37 m - 58 m - 70 m - 70 m - 70 m -58 m - 32 m with the longer spans using a double height ACROW section while the shorter spans have a single height section. The new superstructure consists of a full depth precast concrete composite deck with an out to out width of 10.0 m and three continuous lines of steel girders that vary in depth from 1.1 m to 3.0 m. The girders have been designed to be launched into place from the north end of the bridge. The abutments require additional piles and modified seats and backwalls to accommodate the wider structure. The land piers also require new steel pipe piles cast into new wider pile caps that support the existing pier shafts. As the bridge is to be constructed in extreme northern conditions, a significant amount of the bridge is shop fabricated for faster assembly on site.
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