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Corrosion likely culprit in roof collapse

The partial collapse of a shopping mall roof last weekend was likely the result of a combination of factors the most likely cause was corrosion of the reinforced concrete, said Mark Green, a Queen’s University engineering professor.

On Saturday afternoon a section of the roof at the Algo Centre Mall (Kingston, Ontario) collapsed.

A section of roof about 12 metres by 24 metres fell.

The roof supported a parking lot and at least two vehicles fell into the mall when the roof came down. Because the roof served as a parking lot, corrosion could have been an even greater issue because of the salt used to clear the surface of ice during winter.

Green said it was also possible that the design of the building may have included an aspect that made it more susceptible to collapse.

Twenty-two people were injured in the collapse.

Police also said at least 30 were missing.

In 2010, mall owners Eastwood Malls Inc. spent about $1 million to repair leaks in the roof that had been ongoing for several years.

But hints of a catastrophic collapse may have been easily overlooked, Green said.

“The warning signs may not have been that obvious,” he said.

In April 2010, a section of the parking garage at Confederation Place hotel in Kingston collapsed, damaging about 20 vehicles and closing the hotel for several days for repairs.

In 2006 a bridge in Laval collapsed, killing five people. That bridge had been inspected shortly before it fell, Green said

That bridge collapse prompted inspections of other bridges in Quebec and Green said he expects buildings similar in age and design to the Algo Centre to undergo additional inspections in the coming weeks.

On Monday a small piece of concrete fell off the Gardiner Expressway hitting a car below.

SOURCE: http://www.thewhig.com/2012/06/25/corrosion-likely-culprit-in-roof-collapse-expert