The Cheticamp River Bridge

Project Description

The Cheticamp River Bridge is the ideal project to showcase the extraordinary advantages of using steel box girders. The long span bridge structure, one of the longest simple span bridges in Atlantic Canada, has a sleek profile and sharp lines that follows the road profile and actually enhances the surrounding landscape, blends with the National Park setting and distinguishes the structure as the entrance to the Cape Breton Highlands.

The project objective was to remove and replace the existing four simple span riveted steel girder bridges in an efficient, cost-effective and environmentally friendly manner and to realign the approaches to NSTIR standards. Environmental concerns were also of great importance since the river is a significant salmon habitat in the region and is frequented by fisherman and nature enthusiasts.

The long simple span structure that flew over the existing abutments and piers allowed for the implementation of a phased construction method in which a portion of the existing bridge remained as a single alternating lane detour and allowed the new bridge to be built partially within the footprint of the existing structure. This eliminated impacts on private lands, minimized the environmental footprint, and allowed the construction to be completed within one calendar year while respecting the July to October limitation on in stream work.

The total steel weight in the bridge, including girders, bracing and end abutment diaphragms was 350 tonnes; the efficiency of steel weight was achieved by the trapezoidal steel box shape. Maintaining the large skew of 34 degrees reduced steel quantities and the overall cost of the bridge significantly, but it added significant complexity to the design and behaviour of the bridge. The design required sophisticated finite element modeling to verify design load effects and determine deflections for vibration control, cambers, setting elevations for the precast deck panels, and girder deflections under loads to ensure that the girders, after erection the girders flyover the existing piers.