Construction of Stranderd-Armstrong Bridge was complicated

A new bridge across the Rideau River in the south end of Ottawa was being hailed as a landmark at its opening on Saturday, July 12.

Ottawa’s mayor and hundreds of people were at the official opening of the Strandherd-Armstrong Bridge. It crosses the river south of the airport, connecting the communities of Barrhaven and Riverside south by linking Strandherd Drive to Earl Armstrong Road.

The mayor is so enamoured with the space-truss, triple arched structure he called it Ottawa’s “Eiffel Tower” and compared its importance to Sydney’s Opera House.

The bridge has a 143-metre span, with eight lanes in total, including two dedicated to transit. It also has bicycle lanes and sidewalks in both directions.

Delcan, now Parsons, designed the bridge, while Harbourside Engineering Consultants of Charlottetown, P.E.I. were engineers for the contractor Horseshoe Hill Construction. Harbourside did the conceptual, preliminary and detailed construction and erection engineering.

Erecting the bridge was complicated. The Rideau River is a designated UNESCO world heritage site, which meant the construction’s environmental impact had to be strictly controlled. The navigation channel also had to remain open from May to October, during which no overhead work could take place from Friday to Monday.

Since traditional construction methods were not possible, Harbourside Engineering designed an innovative erection method which allowed 90% of the steel superstructure to be erected on temporary supports on the east approach and then launched into place across the river.

Harbourside Engineering explains that after the arch segments were welded and the deck was suspended, the ends of the arches were tied together with a “bow string” horizontal post-tensioned cable system. The arches were then supported on railcars and the steel superstructure was rolled across on a temporary launch structure. Once the arches and deck were in position, a series of manouvres were carried out, including placing the structure onto thrust blocks, removing the temporary “bow string,” and installing the short approach spans.

The project cost a total of $50 million and was funded partly by the federal and provincial governments. As the third crossing over the Rideau in the south end of the city, the bridge was first proposed two decades ago and was originally conceived to carry a light rapid transit (LRT) line.

While it is expected that the bridge will ease traffic going downtown and reduce commuter times, its critics are disappointed that it does not carry an LRT. Critics also say it will route more vehicles onto Prince of Wales Drive, which is already congested.