Tag Archives: Gardiner Expressway

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

Gardiner structurally sound, experts say, after chunk smashes onto road

TORONTO: City crews will be examining sections of the Gardiner Expressway after a 4.5-kilogram chunk of concrete fell onto Lake Shore Blvd. W. earlier this week, hitting a guardrail and ricocheting into the road.

The slab, about four centimetres thick and over a meter long, was sloughed off the bottom of the elevated section, its steel reinforcing bars corroded by road salt.

No cars were hit and no one was injured. Two lanes of westbound traffic just east of Bathurst St. were temporarily closed.

The incident is the fourth in recent memory, but does not mean that drivers should steer clear of Lake Shore, city staff said.

“There really shouldn’t be any concern,” said Mike Laidlaw, Toronto’s acting manager of structures and expressways.

Aside from the dangers inherent in a chunk of concrete weighing almost as much as a bowling ball falling from the sky, the expressway itself is sound, experts say.

“The stuff on the outside, most of it could fall off without affecting the structural integrity,” said R. Doug Hooton, a civil engineering professor at the University of Toronto. “(The overpass) is not in danger of falling.”

Laidlaw said the city will be conducting extra inspections around the area. Toronto is also putting out a call for proposals from engineering firms for a complete inspection within two years.

City crews inspect the Gardiner yearly — “sounding” the concrete for unstable pieces and removing them with a hammer — and conduct visual inspections at least every six months.

“If they do see any areas of concern they’ll look after it immediately,” said Laidlaw.

In January 2007, a piece of concrete about the size of a basketball fell onto Lake Shore near York St. and narrowly missed hitting a car. A small piece fell near Spadina Ave. in February 1999 and near York St. in January 1997.

“It is a concern for anybody underneath of it,” said Laidlaw.

Hooton said the Gardiner was designed before Ontario began salting roads in the winter, so it wasn’t constructed to withstand the salt that seeps through the roadway and into the steel reinforcing bar.

The salt rusts the rebar which then expands, cracking the concrete and pushing the outer layer off. Repair work was done years ago to the road’s drainage system to prevent salt from seeping into the concrete.

“It’s not happening as much as it would have if they hadn’t done those repairs,” said Hooton.

Police said no one reported any damage to a vehicle and there were no injures.

By 3 p.m. Monday, city crews had cleared debris off the road and unblocked all westbound lanes on Lake Shore Blvd.

The incident called to mind a horrific accident in Quebec five years ago. Five people were killed when a 40-year-old Laval overpass fell onto a highway on Sept. 30, 2006, crushing several vehicles.

A year later, a commission report into the accident blamed shoddy workmanship, insufficient oversight and deficient maintenance.

SOURCE: http://www.thestar.com/news/transportation/article/1011934–gardiner-structurally-sound-experts-say-after-chunk-smashes-onto-road?bn=1