Canadian wind dampers hold sway over world's tallest condos
How Canadian engineers help Manhattan's sky-dwellers combat motion sickness
New York real-estate brokers often talk about a living space's "vibe." But not like this.
"I've never felt the building move," Halstead Property's Brian Lewis mused last week from the airy 60th-floor condo he's selling for $8.95 million US for Law & Order actor Christopher Meloni.
"I almost want it to sway a little now," Lewis joked, gazing out at a helicopter vista over Central Park. "It's imperceptible."
That's good news for RWDI, the Guelph, Ont., engineering firm responsible for cushioning those wind vibrations.
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Canadian damping technology is becoming a necessary amenity for prestige developers seeking to stretch the limitations of architecture without causing physiological discomfort to its occupants, many of whom are among the world's richest tenants.
Increasingly, when high-rise builders need to counteract sway, they call Canada.
Canadian engineers are "widely respected by international architects who are building all around the world," says Carol Willis, director of New York's Skyscraper Museum.
Were it not for the Canadian-designed "damping system" implemented near the top of Meloni's high-rise at the 70-story Park Imperial complex, that gentle creaking would have been much more unsettling for the building's well-heeled tenants, who have included music mogul Sean "Diddy" Combs, Canadian actor Donald Sutherland and writer Deepak Chopra.
Like a pendulum
"The basic problem is, when buildings get this tall, how do you counteract sway so that the natural motion, acceleration, frequency and movement in the wind doesn't hit a point that makes people feel seasick or afraid?" Willis explains.
For many prestige property developers, including the designers behind the Park Imperial, the solution is a pendulum-like system of counterweights pioneered by RWDI and demonstrated for effectiveness by marine and fisheries researchers in Newfoundland.
Chicago's 257-metre-tall Park Tower houses a damping system designed by RWDI, as do Manhattan's One57 Residences, a stick-thin skyscraper topping out at 306 metres, and 432 Park Avenue, the tallest residential building in the world at 426 metres high.
The Shanghai Tower, which rises to 650 metres, also houses one of the firm's dampers involving weights and, in this case, powerful magnets.
RWDI served as wind consultants for New York's Freedom Tower, Dubai's Burj Khalifa, the forthcoming 1,000-metre-plus Kingdom Tower in Jeddah, and Toronto's One Bloor West, slated to become the tallest building in Canada after the CN Tower at 318 metres.
"They're basically the world leaders in wind engineering," says Kevin MacLean, a structural engineer with the Toronto-based consultancy Read Jones Christoffersen Ltd.
"As structural engineers, there's only so much we can do to increase a building's stiffness by playing with its mass."
So as ever thinner buildings shoot skyward, they need an increasingly sophisticated system of counterweights to keep them from bending like reeds.
The weight of 32 buses
"This is almost becoming a craze, these tall and slender towers," says Mike Montgomery, a principal with Toronto's Kinetica, which also designs damping systems.
"There's probably six or seven buildings in Toronto with these damping systems, but the ones in New York are absolutely spectacular because of the size."
At certain elevations, super-slim office and residential towers become susceptible to vibrational energies from wind turbulence.
Gales reaching 80 km/h have been known to gently rock New York high-rises back and forth by several inches, adding another potentially nauseating factor to the already stomach-dropping views.
In wind storms, some buildings could take up to 15 seconds to cross back to the centre. So dampers are sized to match the frequency of a building's vibration.
"You can have these counterweights that are as heavy as like 32 TTC buses, but effectively really small, and all steel," Montgomery says.
As for what it would feel like to be in a 75th-floor penthouse tilting to and fro without any damping effect?
"It would be an awfully extreme case to be throwing up," says Jon Galsworthy, a principal with RWDI. "But it would certainly be uncomfortable, especially to the layperson who doesn't know these buildings are supposed to move at all."
Designed for the offshore
When strong wind hits a skyscraper, the turbulence "excites" a tuning-fork action on the structure, Galsworthy says.
"When a building starts to move, that makes the damper want to move. And if you design the damper properly, it will lag behind the building."
The dampers can cost millions of dollars and weigh hundreds of tonnes, and they help to create a pullback or drag effect on the building, generating enough force of their own to offset the turbulence pushing the structure's framework.
"The result is you can reduce the motion by about a half," Galsworthy says.
RWDI regularly invites international developers to Newfoundland, where they can experience the building sway for themselves at a simulator at Memorial University's Fisheries and Marine Institute in St. John's.
"We've had people from New York, from the U.K., from Shanghai. They fly in on their private jets," says Maria Halfyard, a researcher with the institute's Full Mission Ship's Bridge Simulator, a state-of-the-art lab often used for training off-shore oil workers and marine transporters in sea-sickness trials.
Condo developers will bring in interior decorators to "stage" the simulation room with curtains and furniture, then Halfyard might cue up a 360-degree projection of a Manhattan, Chicago or London skyline. Hydraulic jacks replicate the oscillations.
"I can bring up the 144th floor of a skyscraper, then put in a one-year storm, a 10-year storm, and show them what it feels like with the dampening system, and what it's like without it," she says.
"We're not the ones building the damping systems, but it's kind of neat to know we had a little bit to do with how a building in New York is moving when it's finished."
The dampers themselves are often invisible, although the Taipei 101 skyscraper displays an RWDI damper, a 728-tonne steel pendulum, as a tourist attraction.
Visitors can watch the steel orb swing in the opposing direction of typhoon winds.
Several new Toronto condos employ "tuned slosh dampers" that rely on water flowing back and forth in a huge tank, rather than steel weights, to dissipate energy.
Montgomery, with Kinetica, patented a different damping system currently used in Toronto's Y+C condo complex at Yonge and College Streets.
Kinetica's model involves sandwiching a rubbery "visco-elastic" material between steel plates distributed throughout a building's structure.
"Instead of relying on a counterweight, ours have little shock absorbers," he said.
Although there isn't a magic ratio, any structure rising eight or nine times its width will more than likely need dampers.
In the case of 432 Park Avenue, which will be the tallest residential building in the Western hemisphere when it's completed, Galsworthy says the height-to-width ratio exceeds 15:1. The One57 building in Manhattan is 23:1.
It doesn't bother Galsworthy that dampers are usually unseen features in marquee high-rises, even if they serve an important purpose.
"This is generally a new or foreign concept to the layperson. It's not something they feel every day," he says. "What matters is that it gives them a sense of comfort in investing, and in making their building feel better."