Aging Ontario bridges at risk, engineer says
Toronto's venerable bridges
There are 530 bridges under City of Toronto control, with many of the major ones having long ago passed the half-century mark.
Some of the oldest and largest include:
The Prince Edward Viaduct , which was opened in 1918.
The Leaside Bridge, opened in 1927.
The Queen St. Bridge opened in 1911.
All of these structures span the Don River and its valley and all are in the process of or have recently undergone major rehabilitations.
The elevated portion of the Gardiner Expressway was built between 1955 and 1966 and underwent an extensive rehabilitation program over the past decade.
Despite this, a basketball-sized chunk of the structure plummeted on the roadway near Lake Shore Blvd. and York St. in January, narrowly missing a car.
John Bryson, manager of structures and expressways for the city, said at the time the roadway was safe and in no danger of collapse.
In the wake of a deadly bridge collapse in Minneapolis, a top Ontario engineer says many bridges in this province are reaching the end of their intended lifespan and need significant maintenance funding to avoid a similar catastrophe here.
"It's likely we will see more tragedies if we don't make sure that we spend enough money to maintain the infrastructure," said Ghani Razaqpur, chair of the civil engineering department at McMaster University.
The official death count from Wednesday's rush-hour collapse stood at four yesterday, with 79 injuries. But more bodies had been spotted in the water and as many as 30 people still reported missing.
Federal highway officials in Washington yesterday alerted states to immediately inspect all of the 700 bridges across the country that have a design similar to the collapsed Minnesota structure, which was built in 1967.
Razaqpur emphasized that the state of the province's bridges is currently satisfactory. But he pointed out that many were built in the 1960s with a "design life" of 50 years.
"That doesn't mean they're going to fall. That means they will require heavy maintenance to keep them going," said Razaqpur, who is past president of the Canadian Society of Civil Engineers, as well as director of McMaster's Centre for Effective Design of Structures.
There are approximately 2,800 bridges under provincial jurisdiction in Ontario.
Municipalities have responsibility for approximately 13,000 bridges and large culverts. There are 530 bridges under the city of Toronto's control.
Maintaining bridges is more than just a question of spending money, Razaqpur said. He called for changes in the way bridges are inspected. Inspections are largely visually based and more high-tech techniques should be employed, he argued.
"You can go to a bridge and look at it ... but you wouldn't be able to detect all the flaws this way," he said. "That's where some of these unfortunate collapses occur."
There should be more inspections using ground-penetrating radar, which lets you see if the supporting rebar inside the concrete is damaged, he said, explaining that this technology could have helped prevent the collapse of a bridge in Montreal last fall.
It's possible that X-ray technology used in the aircraft industry to assess metal fatigue could be adapted to steel bridges, Razaqpur continued, adding that technologies could also be borrowed from the health sector.
"All of these are trying to see something that's not visible to the naked eye," he said.
According to information provided by the province's transportation ministry, the province conducts visual inspections of its bridges annually.
The province does some "non-destructive" testing such as ultrasound to determine the condition of concrete and steel.
Ministry officials say bridges older than 25 years are visually inspected every five years by engineers trained to spot structural fatigue. These inspectors will then recommend which areas of the bridges receive ultrasound scans. The province also does "destructive testing" by removing core samples from bridges to assess the condition of concrete and steel.
Again performed mainly on bridges older than 25 years, these tests occur every five to 10 years, depending on recommendations made during visual inspections conducted by engineers every two years.
Steel bridges are tested for steel fatigue every five years.
Joe Tiernay, executive director of the Ontario Good Roads Association, said he's satisfied with the condition of bridges in the province.
"We're quite confident that the bridges in Ontario are safe," he said. "Municipalities would close bridges if it came to the point that they ever felt they were unsafe," he added.
Tiernay noted that municipalities are required to inspect their bridges every two years, but he did not have details of the municipal inspection process readily available.
He questioned whether municipalities could afford to pay for more high-tech bridge inspections.
"I'm sure that X-ray technology would certainly be an improvement if it was available. But at what cost? Municipalities are struggling right now to find adequate funding to maintain the infrastructure they have," he said.
The City of Laval, the scene of two fatal overpass collapses in the last five years, dispatched a pair of safety experts to Minneapolis to lend a hand to local officials, and to study the way American authorities handle the investigation, the Star's Sean Gordon reports.
A public inquiry into the most recent collapse – which killed five and injured six in Laval last September – is ongoing.
On Tuesday the City of Montreal identified nine overpasses and bridges that will be put under increased scrutiny.
In the wake of Wednesday's events, Montreal Mayor Gérald Tremblay closed one of the structures to heavy truck traffic, and said the Minnesota catastrophe should prompt all governments to review their inspection and upkeep practices for bridges and overpasses.
With files from Joseph Hall and Associated Press