Failed connection at Algo Mall showed “marine-like” corrosion

An animated video created by NORR engineers was released on March 21 that succinctly explains what they found caused the collapse of the Algo Mall in Elliot Lake, northern Ontario.

NORR also prepared a 700-page forensic report on the collapse for the Ontario Provincial Police which has also been released.

The video is directed by NORR’s Hassan Zaffarani, P.Eng., who is based in Toronto. It takes the viewer on a tour inside a virtual reconstruction of the three storey building which was built in 1980 using a steel frame supporting precast hollow core panels. At the time the design was seen as innovative.

The engineers say the collapse was due to a badly corroded weld connection between two steel angles and a column on the upper level. The connection, which they estimate had lost 85% of its original capacity due to corrosion, gave way after a single car on the parking lot travelled over it. This failure triggered the collapse of another beam, allowing 12-m x 24-m slabs to fall into the food court below, killing two women and injuring 20 others. The video also incorporates some surveillance video of two people walking over the parking lot before the roof gave way.

The narrator says that the mall “was beset with a chronic leakage problem from the day it opened,” and that “this went unabated due to the lack of a proper continuous waterproofing membrane at the parking level.” A series of owners merely attempted to seal and reseal the cracks, but the water had continued to leak onto the structural steel “carrying with it de-icing salt that accelerated corrosion rates to levels only found in marine environments.”

To watch the video, click here.

A series of witnesses will continue until the end of April to give evidence before the inquiry Commissioner Paul Bélanger on the mall’s structural failure. The second part of the inquiry will look into the controversial and failed rescue operations.

The last witness to give evidence before Easter was Robert Leistner, the former general manager and vice-president of Algoma Central Properties. He was questioned about the recommendations that had been made by Trow consulting engineers for repairing the roof’s waterproofing system in the 1990s. Trow had given two options to the owners: one was to repair and waterproof the entire structure; the other was to fix only the debonded concrete. Leistner said that the first option “wasn’t viable” at the time. The original structural engineer, John Kadlec, has already given evidence and Paul Meyer, a structural engineer hired by Algoma Central Properties, will give evidence April 4. He will be followed by engineers from Halsall, who were also at one time asked to advise on the state of the mall’s roof.

Twenty four years ago another of Canada’s most infamous structural failures occurred, also at a shopping mall. The collapse of the Save-on-Foods supermarket roof in Burnaby, B.C. on April 23, 1988, left no-one dead, but 20 people injured. In that case too, the roof which gave way supported a parking lot, but the mall was brand new and the cause was partly a beam that was undersized.