Toronto has the most tower cranes in North America — but are they safe in severe weather?

In RLB’s last Crane Index study, Toronto had well over 100 cranes in use — the most in North America — with Calgary having over 30 of them dotting its skyline.

They’re a common, everyday sight for many Canadians. But as Haligonians witnessed when hurricane Dorian hit in September 2019, cranes can quickly deliver destructive force, if they fail.

“Wind is clearly the number one culprit,” says Doug Perovic, a University of Toronto engineering professor.

Perovic said that in an urban environment, there are several factors at play.

“You can also get wind events between buildings and there are various effects, there’s downdraft effects, the venturi or tunneling effect which gets accelerated through narrow spaces,” he said.

What often catches people’s attention on the ground during a wind storm is when they look up and see tower cranes “weathervaning” — that’s when cranes seem to be spinning uncontrollably.

But that’s normal, according to Global News meteorologist Ross Hull. It’s part of the plan to keep the structures intact during severe weather,

1:53 Downed Halifax crane malfunctioned months before storm: documents

“When a crane isn’t in use and strong winds are expected, the structures are set to weathervane,” Hull said. “They then move more freely with less surface area exposed to the most intense winds.

“But if that safety precaution isn’t taken, that’s when accidents can happen.”

Claudio Montesano, an instructor at the Operating Engineers Training Institute of Ontario in Oakville, says proper judgment and training are key for crane operators when it comes to weather.

“As the elevation goes up, the winds go up,” Montesano said, adding that students at his school practice on a specially designed simulator before dealing with real-life weather situations.

Despite the potential for strong storms, Perovic believes that tower cranes are safe but that the right crane needs to be in place for the right job.

“The onus is on the constructor to make sure that extra margin of safety is there,” Perovic said.