Big O concrete ring dismantled as $870M project continues at Montreal Olympic Park

The massive concrete ring at the Olympic Stadium has been removed and will be replaced with a metal structure. (Patrick Beaudry/SNAPePHOTO)

The Big O’s ring has officially been removed.

The second stage of the $870 million project to replace the Olympic Stadium’s roof and technical ring was completed earlier this month, using a “tailor-made solution” never before seen, according to the team tasked with the project.

Head of construction Yann Dieulesaint said that the original plan was to dismantle the stadium in the opposite way to how it was built in 1976.

“But we quickly realized that it wasn’t going to be that simple and that, ultimately, a unique structure required a unique solution,” he said.

• READ MORE: New roof or demolition? Debate surrounding the Big O continues

Groupe Construction Pomerleau-Canam was commissioned to dismantle the existing roof, deconstruct and replace the technical ring and install a new roof.

To dismantle the ring, teams put a diamond cable saw on a mobile rig and cut the massive ring into smaller pieces.

“To use an analogy, you have to imagine that the consoles are a bit like a fishing rod,” said engineer Sebastien Lebranchu. “At the end, there will be a heavy load, which is the technical ring, like a big fish. At some point, we want to cut the fishing rod, so let’s imagine what will happen.”

What would happen is a whiplash effect.

To control that movement, crews drilled holes and attached slings through them to lift the 125-tonne pieces and place them in the centre of the stadium for dismantling.

“This is a process called core drilling,” said project lead Mathieu Pigeon. “It involves using a core drill to drill holes of the right diameter.”

The next step is to replace the former concrete ring with a metal structure covered with curved aluminum, according to the company.

“What we like is the challenge,” said Lebranchu. “That’s why we do this job, because of the technical effects, and this project it’s one of a kind.”

Here’s how much material crews have dealt with:

• 1,332 tonnes of steel (dismantled)
• 42,019 square metres of canvas (removed)
• 22,237 metres of cable (removed)