Spanning the St. Lawrence River, the $4.2 billion Samuel De Champlain Bridge is an engineering marvel. With sustainability and performance as priorities, designers of the 2.1-mile-long bridge used precast concrete to tackle many design and construction goals for this project.
The bridge is a replacement structure crossing a vast span of the river, and developers faced a rigorous 48-month schedule from design to bridge opening. “It was very aggressive,” says Marwan Nadar, design manager for T.Y. Lin International. “Even if we worked every day of the 48 months, it would be a very difficult challenge.”
The team also faced brutal Canadian winters in a location where construction projects can be shut down for three to four months due to weather conditions.
“We needed to think holistically about a design that could be built year-round, and allow for very large pieces to accelerate construction,” he says. Precast concrete was the obvious answer. “It lent itself to the design of repetitive blocks that could be created in a controlled environment and shipped to the site for placement.”
Giant lego set
The new bridge was built downstream from the old bridge to prevent traffic congestion on the heavily traveled thoroughfare. Serving as a gateway, the three-corridor bridge design includes two three-lane corridors for vehicular traffic, a transit corridor capable of accommodating a light-rail transit system, and a multiuse path for pedestrians and bicyclists.
To meet the schedule, the project team used large-scale precasting modular construction methods and creative erection sequencing techniques. Precasting allowed work to continue year-round and made it possible to cast and erect the pieces in parallel, rather than in series, Nadar says.
The total design is made up of three independent superstructures:
- A 1736 ft asymmetrical cable-stayed bridge signature span, with a slender single tower and vertical clearance of 126 ft above the high-water level.
- A 2500-ft-long east approach with a maximum span of 357.6 ft.
- A 6706-ft-long west approach with a typical span of 263.7 ft.
“It was like a giant Lego set,” says Richard Munday, project director for BPDL/SSLC. The pieces was precast off site by multiple precast producers and then delivered by truck or rail in sequence for rapid assembly. Eight total casting lines were used to produce 38 to 51 panels per week, creating an incredibly efficient system, he says.
To further accelerate deck construction, the superstructure utilized over 9600 full depth precast concrete bridge panels with integral precast concrete barriers on the approach spans, and a 385-ton tower upper cross-beam component, which is a key structural and architectural feature.
Precast concrete spread footings were cast on site in a certified temporary precasting facility, which meant work to continue through cold winter periods. It also reduced the amount of in-water work, allowing the foundations to be erected in an accelerated fashion with a higher level of safety and reduced risk of pollution in the river ecosystem.
It is one of the many sustainable features that helped the project secure a Platinum Award under the Envision rating system of the Institute for Sustainable Infrastructure. “Precast concrete was a very environmentally-friendly choice for this project,” Nadar says.
The bridge, which was completed on schedule, will support up to 60 million vehicles each year, making it one of the busiest bridges in Canada. “The city of Montreal is very proud,” Nadar says. “It’s a great-looking bridge.”