The new Lees Avenue Bridge along Highway 417 in Ottawa was completely installed during a 15-hour highway shutdown on Saturday, September 6.
The replacement was achieved through the use of specialized equipment known as self-propelled modular transporters (SPMTs); a technique rarely used.The bridge is (according to the CBC) thought to be the heaviest structure to be rapidly replaced in North America. MMM structural engineering experts designed the replacement of the existing structure with a new structure specifically intended for rapid replacement.
The advantage of the rapid replacement strategy is that the bridge – which experiences high traffic volume from Highway 417 – is closed for only a short period of time, instead of for the several months that would be needed if conventional construction methodologies were being used. The new bridge was constructed in approximately four months in a construction staging area just 100 metres from its final location. The new bridge, which is 2,060 tonnes and 87.5 metres in length, has a geometry that is complex, with the two-span curved composite steel box girders being constructed on an average 5% longitudinal grade with a 4% super-elevated cross-section while spanning over a curved section of Highway 417 in Ottawa.
MMM is one of the few Canadian firms with this type of expertise. Our Bridge Engineering group drew on its previous rapid replacement experience when overseeing the structural engineering aspects of the project. This is our sixth such replacement in Ottawa, and the seventh is coming up next month with the two-span replacement at Vanier Parkway and Riverside Drive. This type of skilled design requires a specific knowledge of how the bridge will be supported, and an assurance that the design will withstand travel from the staging area to its final site. Also, it is vital to develop design details that are flexible, adaptable, and practical so there is no chance for unexpected delays to the highway reopening.
You can watch the amazing process through time-lapse video.