The $200 million bridge is the first built over the Mackenzie River, Canada’s longest river, and is the largest bridge project undertaken in the Northwest Territories. The bridge provides year round service for cars and trucks along Highway 3, connecting Yellowknife in the Northwest Territories with Highway 1 in the South.
The remote location, severe winter conditions of up to -40 degrees Celsius and ambitious construction schedule, required new thinking regarding design and erection. Ecological, lightweight bridge design principles and innovative design methods such as Assembly Line Design Approach, Failure Mechanism Concept and Fuse Design Philosophy were applied. This led to 20% cost savings for steel and 30% for concrete. It also resulted in the world’s longest continuous superstructure, with a length of 1045 metres and expansion joints only at the abutments.
The symmetrical superstructure consists of two vertical Warren trusses connected by Chevron cross frames and wind braces at top and bottom chord levels. The articulation scheme utilizes disk bearings at the piers and abutments. The bearings guide the superstructure in the transverse bridge direction but allow longitudinal movements due to temperature changes. Two steel A-pylons located at the tallest piers flank the navigation channel located in the bridge centre. The eight piers of the bridge are founded on concrete spread footings which are cast into the Mackenzie River bed using cofferdams. Classified as an Extradosed Bridge System, the “open” steel box girders have significant bending stiffness and are only locally reinforced with stays and “king posts.” The Deh Cho Bridge has a very different structural behaviour than similar looking cable-stayed bridges.
The superstructure design was optimized to maximize prefabrication and allow a fast-paced erection technique. The top priorities were robustness, durability and the ease of inspection and maintenance. The goal was to achieve the highest returns on investment over the next 75 years of service.
The Deh Cho Bridge project is a lighthouse of the bridge engineering discipline. It also provides evidence that modern progress in an industrialized society is possible in a responsible manner and in harmony with Canada’s Aboriginal people and Mother Nature.
Owner: Government of the Northwest Territories
Structural Engineer: Sargent & Associates Engineering Ltd., Infinity Engineering Group Ltd.
Project Manager / General Contractor: Ruskin Construction Ltd.
Fabricator: Rapid-Span/Structal JV
Detailer: Tenca Steel Detailing