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Old April 16th, 2007, 12:09 PM   #1
hkskyline
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Skyscraper Dampers

Water to tame wind atop new skyscraper
By Tom Avril
Philadelphia Inquirer Staff Writer

It's a great big bathtub in the sky, but hold the soap.
A 300,000-gallon, double-chambered tank of water is going in near the top of the Comcast Center - a creative solution by engineers to keep Philadelphia's tallest building from swaying too much in the wind.

The massive, sealed concrete container, which workers will start installing within weeks, will be the biggest "liquid-column damping" system in North America - and likely the world.

The tank isn't needed for structural safety, just for comfort, said engineers at Motioneering, the Canadian firm that designed it. The system is tuned so that if the building moves back and forth a few inches in high winds, water will slosh in the opposite direction - putting a damper on any unsettling motion for people on the upper floors.

"This is almost like a large waterbed," said John Gattuso, senior vice president for the developer, Liberty Property Trust.

At least a dozen such tanks have been installed since they came into vogue in the 1990s, but other kinds of dampers have been used for several decades. As architects have designed their skyscrapers to be ever loftier and more slender, engineers have resorted to a variety of means to keep the willowy wonders in check.

Some - such as Taiwan's Taipei 101, the world's tallest building - use a giant pendulum. Others use huge chunks of steel attached to springs.

Another option is simply to make a structure stiffer, as the Eagles are doing with the ramp that swayed on several occasions as fans left Lincoln Financial Field.

But a damper is an elegant design solution for today's svelte skyscraper. The key is that the pendulum or water moves back and forth at the same "natural frequency" as the building it's in - but in the opposite direction.

The Comcast Center, for example, is expected to oscillate once every seven seconds when deflected by the wind, Motioneering's Guy Ferguson said. The water will slosh in the opposite direction in the tank's twin U-shaped chambers.

The motion of the water, pendulum or other mass helps offset any wind-induced acceleration felt by people in the building.

In addition, energy from this motion is absorbed by some sort of attached device, such as a hydraulic cylinder, and dissipated as heat. Otherwise, the building would rock longer. A car's shock absorbers work on the same principle.

In water tanks like the Comcast Center's, the energy is dissipated by vertical steel vanes, or louvers, that impede the back-and-forth flow of water.

Engineers expect tall buildings to give a bit, and the Comcast Center will be no different. A 75-m.p.h. wind would move the top floors about 18 inches, said Anjana Kadakia, project manager for Thornton Thomasetti, the firm that did the structural engineering.

The damping system doesn't prevent this kind of deflection. Rather, it makes the motion subside more quickly. If you imagine the building's movement as a wavy line on a graph, the wave would flatten out sooner on a building with a damper.

In high winds, the tank should reduce by about one-third the acceleration that a person would feel on the upper floors, said Ferguson, project manager for the water tank.

Engineers around the world have begun to choose water for some damping projects in part because it is cheaper than steel, and because pumping water to the top of a building is easy. In areas prone to earthquakes, the water also can be used as a backup supply for sprinklers, said Leighton Cochran, president of the American Association for Wind Engineering. The Philadelphia tank will not serve that purpose, however.

The developer of another building with a water-tank damper, One Wall Centre in Vancouver, was somewhat skeptical of the idea - at first.

"I've been up there many times on a windy day, especially when we were getting it finished, to see if this thing actually works," said Bruno Wall, president of Wall Financial Corp.

Now his top-floor tenants say the building never sways enough to make a ripple in their morning cup of coffee.

"It makes a remarkable difference," Wall said.

The Wall building is about half the height of the 975-foot Comcast Center. Its tank contains 460 tons of water.

The Philadelphia tank will hold 1,300 tons, and has piqued the interest of the local engineering community. Kadakia spoke at the Union League on Thursday about the tank and other design features, addressing a dinner meeting of the Engineers' Club of Philadelphia and the local section of the American Society of Civil Engineers.

Because there's no sunlight in the sealed tank, algae won't be a problem.

Some tall buildings, such as Chicago's Sears Tower, have no dampers, said John Zils, structural engineer for that project. Older buildings tend to be thicker and stiffer and don't need them. And in New York the buildings shield one another from the wind, said Cochran, of the wind engineering association.

For buildings in earthquake zones, hydraulic dampers are sometimes used to offset vibrations. Water-tank dampers aren't ideal for that purpose, and are used merely to make people feel at ease.

And that's no small thing, said Cochran, a principal of CPP Inc. in Colorado.

"As one of my clients said to me once," he quipped, "people who can afford the top floor or penthouse also can afford a pretty good lawyer."

--------------------------------------------------------------------------------
Contact staff writer Tom Avril
at 215-854-2430 or [email protected].

Find this article at:
http://www.philly.com/inquirer/local...kyscraper.html
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Old April 17th, 2007, 02:27 PM   #2
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wow .. thts cool info ..
thnx fer sharing ..
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Old April 17th, 2007, 08:39 PM   #3
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has anyone a pic from the Damper they use at Citycorp Center in NY?
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Old January 17th, 2008, 09:41 AM   #4
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Windy City Wonder
25 October 2007
New Civil Engineer

TRUMP TOWER - Clever engineering has meant that North America's tallest residential building will be solid as a rock despite its windy location. Jessica Rowson reports.

Nestled among the forest of skyscrapers on the Chicago skyline, the 92 storey Trump Tower is currently notching its way up to become the city's second tallest building. The 415m tower will be completed in January 2009.

The stepped concrete building, has been designed to refect the height of nearby buildings by architect and engineer for the project Skidmore, Owings & Merrill (SOM). The first step aligns with the 130m high Wrigley Building, the second the 179m high Marina City Towers, and the third the 212m high IBM Plaza, known as 330 North Wabash.

As important as these steps – also known as setbacks – are architecturally, they also have an important engineering role as they each contain an outrigger stability system. These 5.3m deep by 1.7m wide concrete monoliths transfer lateral loads between the perimeter columns and the central core.

SOM associate partner Robert Sinn explains that the lateral shear resistance of the core and overturning resistance of the perimeter structure are mobilised by linking them at discrete levels using outrigger trusses or beams.

He adds that this means just a few heavier vertical elements are needed on the perimeter to keep the building stable, freeing up the facade.

The outrigger beams take up a storey height and are heavily reinforced. In some areas conventional bars are even replaced by an equivalent area of steel plate to ease congestion. Contractor Bovis Lend Lease is using self compacting concrete to penetrate densely reinforced areas.

Surprisingly, the tall building does not require dampers to limit its movement. This is because of the stabilising effect of the heavy concrete core and columns and the setbacks. The asymmetric setbacks change the cross section of the building, so changing the frequency of wind passing it. This means that vortices, which would cause the building to move more, cannot build up.

Any massive building needs massive foundations. The building sits on 30m long piles founded on bedrock. A permanent steel liner, which seals the excavation, cuts through 18m of stif clay and 12m of boulders and fractured rock to form a socket in solid rock.

On completion the Trump Tower will hold the record for the world's highest residential building, but only for a year. After that it will be dwarfed by the 610m, 150 storey Chicago Spire.

FOUNDATIONS

A 3m deep piled raft was poured continuously over a period of 22 hours. The concrete was poured using conveyor belts so that minimal labour and very few vibrators were needed. the temperature had to be carefully controlled as the concrete cured due to the raft thickness.

If the differential temperature across the depth was too large, stresses would set up and lead to micro cracking.

FINITE ELEMENT ANALYSIS

Engineers had to deal with the inherent problem of the uneven load distribution of a massive, asymmetrical building and its tendancy to move sideways under its own weight. The solution was to carry out a time-based finite element analysis on the structure so that movements could be predicted and compensated for during construction. Bovis Lend Lease used these results to make millimetre adjustments at every storey to bring the building back to plumb.

Non-linear analysis predicted the short and long term displacement of Chicago's Trump Tower, which included the effects of creep and shrinkage. If no horizontal correction had been made during construction, the roof could have moved 300mm out of line, due to the combined effects of gravity, creep (timedependent deformation) and shrinkage.
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Old November 16th, 2008, 06:02 AM   #5
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Taipei 101 Damper

















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Old August 24th, 2015, 01:00 PM   #6
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Canadian wind dampers hold sway over world's tallest condos
How Canadian engineers help Manhattan's sky-dwellers combat motion sickness

CBC News
Aug 24, 2015

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 Bryan 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.

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.

The rest : http://www.cbc.ca/news/business/cana...ndos-1.3199389
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Old August 26th, 2015, 08:17 AM   #7
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hkslyline, please, post mass dampers about other buildings, I beg...
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