Dr. Sriram Narasimhan, a professor of civil and environmental engineering at the University of Waterloo says that while the condition of infrastructure like bridges can be rated as a whole – 75% of Canada’s bridges are rated “good” or “very good” – when tragedies like these happen it is an individual piece of that infrastructure that is failing.
“A very small percentage are vulnerable or in a bad position,” he says. “When it comes to failure it happens to one bridge. It’s also critical for us to look at the weakest links.”
For the most part, bridge maintenance and inspections in Canada are the responsibility of municipalities and provinces. Each jurisdiction lays out different requirements for when and how a bridge must be inspected. In Ontario those requirements mean an inspection at least once every two years, but that inspection might not be as thorough as one would imagine.
Narasimhan says he’s heard of examples of inspectors looking at a bridge from the side of the road and giving it a rating based on their observations from a distance. In the case of several types of bridges, steel ties or cables are reinforced in concrete, preventing the ties from being examined.
In other cases bridges constructed close to water or other structures may prevent inspectors from getting underneath to assess their condition fully — and hiring divers to do the job would be prohibitively expensive or impossible.
New technology may make inspections easier, with sensors available to monitor stress and other changes to infrastructure like bridges.
British Columbia is an early adopter of sensors using the technology in places like the Port Mann Bridge in the Lower Mainland to read seismic activity.
Sensor technology provides its own set of challenges, however. Companies that manufacture and install sensors often don’t offer to interpret the information collected by the units, making the raw data difficult to use for municipalities that may not be able to employ a data scientist full-time.
“There’s that gap that needs to be fixed,” said Narasimhan. “Very few entities offer to do it [interpret data]. It’s of no use. There’s a lack of automation.”
Cost is another significant factor affecting bridge inspections.
“These things can get pretty expensive. Maintenance is something you’re going to realize in the long run; there’s no short-term cost benefit.”
That huge expense combined with little to show for it in the short term leads some municipalities to take a “wait and see” approach.
As the infrastructure ages that “wait and see” may turn into more failures, but there isn’t necessarily one quick fix for the problem because like again humans, aging bridges can fail for any number of reasons.
“Somebody might die of cancer, somebody might die of a heart attack, somebody might die of a stroke… These bridges are all old, the reasons for failure are very different.”