Opportunity
The Ministry of Transportation Ontario (MTO) is engaged in an ambitious four-lane highway development project in the Northwest Region. This includes the construction of about 19 miles (30 kilometers) of new highway and as many as 30 structures in what the MTO calls “extremely rugged terrain, ranging from deep swamps to massive rock cuts.”
As part of this effort, the MTO needed a partial cloverleaf interchange at the intersection of Highway 11/17 and Hodder Avenue in Thunder Bay. The structure would span six lanes of traffic and would be the first grade-separated interchange in the region. It would have to withstand severe weather and salt splash from the highway.
What’s more, the Hodder Avenue Underpass would be the closest bridge to the Terry Fox Memorial just outside Thunder Bay, making it important to build an aesthetically appealing structure. The monument honors Terry Fox, a college athlete who lost his leg to osteosarcoma and set out in 1980 on a Marathon of Hope to raise money and awareness for cancer research.
Solution
HMM, a joint venture of Mott MacDonald and Hatch, was retained as the Engineer of Record. The joint venture was responsible for all structural engineering design work, including the following.
- Detailed designs for bridge superstructure, substructure, and accessories
- Detailed layout plans for precast elements
- Shop drawing review and construction liaison during construction and precast fabrication
According to the Precast/Prestressed Concrete Institute (PCI), The Hodder Avenue underpass in Thunder Bay is proof that the extensive use of ultra-high-performance concrete (UHPC) in a modular construction project delivers versatility, durability, and design excellence.
The underpass is the first structure in North America to incorporate precast UHPC pier cap and pier column shells along with precast high-performance concrete box girders, parapet walls, and approach slabs. All field connections were field cast using UHPC, resulting in smaller, simpler joints with superior durability.
The use of UHPC also enabled the design team to create a clean, open frame with sleek, elegant lines to meet the owner’s aesthetic goals. This look was achieved through the use of a pier cap beam incorporated into the superstructure that spans continuously over the three pier column shells. Each shell has an octagonal shape, which transitions from a smaller constant dimension at the bottom to a flared, larger dimension toward the top. The pier cap cantilevers at the ends with an inverted T shape to provide ledges upon which the box girders sit.
The box girders were connected using Ductal brand elements, eliminating the need for a deck or topping slab to distribute the load.
Outcome
“As the owner of the bridge, we are extremely proud of the finished structure,” said Ray Krisciunas of MTO. “The use of UHPC enabled us to obtain our intended objective of an open, aesthetically pleasing, and welcoming bridge, which was also economical and durable. It will now form the baseline design for a number of other planned overpasses on this section of the Trans-Canada Highway.”
The use of precast elements made it possible to eliminate all the formwork on the bridge’s overhang. This enhanced safety for construction workers, who did not have to work above live traffic.
Because the use of precast concrete made it unnecessary to form and cure concrete on-site, the project was completed in 80% of the time required with conventional methods. Each of the 16 girders per span was erected in only 15 minutes.
Awards
In September 2013, PCI gave the project its Design Award in the “Main Span 76–150 Feet” category as well as the prestigious Harry H. Edwards Award. The Edwards award showcases “fresh, uninhibited concepts that hold the potential to move the industry to the next generation of technology.”
Judges for the Harry H. Edwards Award said the Hodder Avenue Underpass was chosen for its cutting edge, innovative solution to a typical freeway bridge. They said it could be a cornerstone for the future of rapid bridge replacements across North America.
In December 2013, the project received awards for “Structural Design Innovation” and "Material Development and Innovation" from the Ontario Concrete Awards. (See video.) According to the organization, “The innovative design and construction method taking advantage of the superior properties of UHPC effectively achieved the owner’s requirement for enhanced quality, durability, and esthetics. The result is a resilient and elegant bridge structure that is built to last.”