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The De La Concorde Disaster
by Alexandre Darche
On September 30th, 2006, around 11:30am, a representative for Transport Québec was sent to investigate a falling block of concrete from the de la Concorde overpass on AutoRoute 19 between Montreal and Laval. After a brief visual inspection and sound analysis, the overpass was deemed in need of further inspections sometime in the coming days. The de la Concorde overpass collapsed just half an hour later, killing 5 and injuring many.
Further inquiries showed that the subpar inspection system played an important role in this tragedy. Repercussions were seen across Quebec where over 300 structures required a structural overhaul, including portions of the Turcot Interchange in downtown Montreal, now being rebuilt as part of a $3 billion-dollar project.
Today, visual methods have easily been surpassed in efficiency and reliability by algorithmic and software-based inspections. This technology has also become available enough that is a very reasonable step to take in ensuring the integrity of the structure. Many structures across the world are ageing quickly and are approaching the end of their service life.
The de la Concorde disaster could have been prevented with proper periodic monitoring (image: de la Concorde Overpass)
Modern structural health monitoring methods require the collection of various kinds of data taken during regular structural operations to build a proper understanding of the structure. The data is then turned into parameters to assess the current integrity of the structure. Sensequake's very own 3D-SAM software does just this by applying filters and its patented algorithms to sieve the important properties needed for analysis such as the natural frequencies, mode shapes and damping ratios. A proper assessment, however, is heavily reliant on a good analysis to understand the meaning of the collected information and interpret the origin of the data collected.
Governments are increasingly considering overhauling older infrastructure for safety concerns (image: Turcot Interchange)
For the data to hold valuable meaning, it needs to be, ideally, compared over time to monitor the information. Tests should be conducted after any major damage, blast loading or structural renovation to ensure no major changes have been accidentally made to its integrity. In the case of the de la Concorde overpass, it was determined that the structural integrity was lowered due to renovations done in 1992. If these methods were used before and after the renovations, this structural failure may have been avoidable.
Tragic events like this are the backbone behind why Sensequake prides itself in the preventative work we do on structures daily. The importance of structural health monitoring is often overlooked in our society and should be made more important as we begin to live more and more in cities with ageing infrastructure.
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