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Why did the girders buckle? Forensic engineer points out two suspects

As the search continues for the culprit that crippled construction on the bridge over Groat Road, one forensic engineer says the city should look at multiple factors that may have conspired to cause the damage.

On Friday, the city closed Groat Road so crews could install girders on the 102nd Avenue bridge. The closure was supposed to last a few days. But Monday morning, workers discovered four massive steel girders had buckled, meaning Groat Road would be blocked off for an additional three weeks.

The failure has infuriated commuters and put the city on the defensive. Speculation abounds, putting the blame on everything from the design of the bridge to the quality of the steel.

Yasser Korany, a forensic structural engineer with Origin and Cause Inc., hasn’t had a first-hand look at the girders. But after looking at photos of the damage, his experience tells him the real answer lies elsewhere.

“It is more likely that sequence of events during the construction, combined with unlucky timing of extreme wind conditions, caused this to happen,” he said.

Kornay said while the design of the bridge needs to be reviewed, he said it did not seem to be “technically challenging.”

High winds forced construction crews to shut down work on the bridge for 12 hours on Saturday. Kornay said gusting winds could combine with the weight of the massive steel beams to cause them to buckle.

“Under very strong winds, they are under very intense lateral pressure, and if they are not braced at the top as the photographs suggest, that would make them vulnerable for failure,” he said.

Kornay said projects under construction are more vulnerable to wind damage, which is why girders are often braced.

The city’s supervisor of special projects, Barry Belcourt, said the city and contractors were “embarrassed” by what happened.

He said investigators are looking into what caused the girders to fail — including whether they were properly braced and if high winds played a factor.

Source:: http://www.cbc.ca/news/canada/edmonton/groat-road-bridge-failure-may-have-come-from-wind-lack-of-bracing-engineer-1.2999331?cmp=rss

      

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