Canadian Consulting Engineer

Thick concrete slab structures under scrutiny in Quebec

Consulting engineering firms in Quebec have been asked to help the Quebec Ministry of Transport to inspect 135 stru...

July 30, 2007  Canadian Consulting Engineer

Consulting engineering firms in Quebec have been asked to help the Quebec Ministry of Transport to inspect 135 structures that resemble the Concorde overpass that failed last September in Laval. A 20-metre fallen section of the overpass fell and crushed to death five people on Highway 19 below.
The actions came after Pierre-Marc Johnson, the head of the commission looking into the collapse of the Concorde overpass, passed on concerns to the Quebec government about similar structures. According to Transport Quebec, the concerns are “regarding structures with thick concrete slabs that do not have sufficient steel reinforcement to counter shear cracking.”
On July 5 the Transport ministry identified 332 structures with thick concrete slabs, and following preliminary investigations designated 135 of those which need more detailed analysis. The Ministry had brought in consulting engineering firms to do the inspections “in order to finish the work as quickly as possible.”
The inspections are to include coring and structural analysis calculations.
Since July 10, the Quebec Transport Ministry has also banned trucks carrying excess loads from using 135 structures that are similar to the Concorde overpass until the engineering inspections are done. The overpasses being investigated are located throughout the province, including in Montreal, Laval, Quebec City, the Eastern Townships, the Chateaugay Valley and in the Outaouais.
The Ministry has told cities with 100,000 inhabitants or more also to conduct investigations into similar structures.
The Johnson Commission has heard various arguments about what caused the 35-year old structure north of Montreal to fail last year. The theories include flawed design, construction shortcuts, and poor repair work done 15 years ago. The commission will reconvene in August for final arguments.



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