Canadian Consulting Engineer
Montreal highway structures found crumblingEngineering
A civil engineering professor at McGill University found serious problems with the highway infrastructure of downto...
A civil engineering professor at McGill University found serious problems with the highway infrastructure of downtown Montreal during an investigation for a report published in the Montreal Gazette.
M. Saeed Mirza, P.Eng. is a structural engineering specialist who joined the university’s department of civil engineering in 1966. He is currently chair of the Canadian Society for Civil Engineering technical committee on the rehabilitation of infrastructure.
Asked by the Gazette to identify what he considered some of the most dangerous structures in the city, Mirza took the reporter to four sites. The results were reported in an article written by William Marsden, entitled “Design, build, forget: a flawed formula.” It appeared in the June 16 edition of the newspaper.
Mirza rated the safety of the four structures on a scale of 1 to 10 and said anything under 5 was unsafe. He gave the worst score of 3.5 to a column supporting the Ville Marie Expressway downtown near Green Avenue. Mirza found “huge cracks that spread from the middle of the pillar upward and outward.” Having identified it as a “classic shear failure,” Mirza said it could have been caused by a movement and was serious. Around the same time as Mirza was doing the field investigation, sections of the Ville-Marie Expressway at Green Avenue and at Fort Street were closed to heavy trucks for a period because of the safety concerns.
The other structures that Mirza and the reporters showed deterioration, though it was not quite so serious. All three scored 6.5. Typical was the Angrignon Boulevard overpass on Highway 20, the main east-west route in from the Ontario border. There they found severely corroded support columns, “with large chunks of concrete falling off from top to bottom” and rusting rebar exposed all the way up the side. Mirza decided moisture was getting into the column and causing the corrosion, partly because the concrete cover was thinner than it would be today (25-50 millimetres, versus 55 millimetres today). As well he found that the design of the joint above the column was not helping matters because it allowed water inside the column and there was not enough provision for drainage.
“On all these spans,” Mirza said, “drainage has been a major problem.” He added harsh words for engineers: “Unfortunately, engineers are to blame. We like to say we design everything perfectly. We do all kinds of excellent calculations. But when it comes to construction it’s not right.”
Drivers in Quebec are especially sensitive to the poor state of the province’s infrastructure after an overpass in Laval collapsed last September, killing five people travelling below it. The Laval overpass has been rebuilt and was reopened in June, but the inquiry into the cause of the bridge collapse is still proceeding.