“Because of the high durability properties of ultra-high-performance and high-performance concrete, this structure will stand the test of time.”

Biljana Rajlic

 

Best Bridge with Spans between 76 and 150 ft (23.2 and 46 m)

Hodder Avenue Underpass in Thunder Bay, ON, Canada

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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.

This 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 bridge spans six highway lanes and is founded on a combination of hard till and bedrock. Because the structure would be exposed to the harsh northern Ontario climate, it was necessary to choose a construction material that could stand up to extreme weather conditions, says Biljana Rajlic, vice president and engineer for Hatch Mott MacDonald in Mississauga, ON, Canada.

A precast concrete design gave Rajlic that durability and so much more. “The use of precast concrete, along with UHPC joints, provided multiple benefits,” she says. The precast, prestressed concrete solution increased structural capacity and met the design requirements while the UHPC allowed for smaller joints with improved durability, strength, and continuity. “Even after years of exposure to harsh climate and abuse from salt spray, it will still look great for decades to come.”

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 pier cap was designed using prestressed UHPC with a compressive strength of up to 29,000 psi (200 MPa), which allowed for just three pier columns and a more open appearance, says Paul Kochan, sales and marketing manager at LaFarge’s precast concrete division in Winnipeg, MB, Canada. “This creates the appearance that the pier cap is integral with the box girders while seeming to provide a frame that goes directly into the superstructure.”

Due to restricted plant height clearance, the UHPC pier column shells were cast on a 15° angle using steel formwork, which allowed the material to be placed slowly from the top of the column through an inlet funnel. To erect the UHPC shell pier columns, the original forms were shipped to the site and wrapped around the elements before concrete infill placement.

“The result is an open and slender structural form that complements the surrounding landscape rather than obstructs it,” Rajlic says.

Because the use of precast concrete eliminated the need for forming and curing on-site, the project was completed in 80% of the time that would be required for a bridge with a cast-in-place solution, Kochan says. Each girder took just 15 minutes to be erected, with 16 girders per span.

This project demonstrates that the use of precast ultra-high-performance and high-performance concrete bridge elements combined with field-cast UHPC connections gives designers an opportunity to advance bridge performance, shorten construction time, and extend the durability of these spans. The result, Rajlic says, “is a resilient, attractive structure that is built to last and an excellent model for similar precast bridge projects worldwide.”

“As the owner of the bridge, we are extremely proud of the finished structure. The use of UHPC enabled us to achieve 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,” says Ray Krisciunas of the Ministry of Transportation.

PHOTO CREDIT

PROJECT CREDITS

Owner: Ministry of Transportation of Ontario, Northwestern Region, Thunder Bay, ON, Canada
Engineer of Record: Hatch Mott MacDonald, Mississauga, ON, Canada
Precaster and UHPC Supplier: Lafarge Canada Inc., Winnipeg, MB, Canada
Contractor: Teranorth Construction & Engineering Ltd., Sudbury, ON, Canada
Total Cost: $9 million
Bridge Length: 279 ft (85 m)