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Earlier this month, we introduced UrbanToronto's newest feature, called 'Explainer.' This weekly series provides an overview of the terms used in the architecture, design, construction, and real estate industries. Every Wednesday, a cross-post from our sister site, SkyriseCities, offers an easily digestible breakdown of industry terminology. This week we explore how tall buildings deal with sway through the motion or vibration control technology known as damping.
As new buildings continue to grow taller, the wind that sways them grows stronger. Swaying can impact comfort and safety for those in the building, necessitating engineering solutions to counteract the effects. Nonetheless, many 20th century skyscrapers, such as Chicago's Willis Tower, are bulky enough to mitigate the effects of wind without added vibration control. Meanwhile, the close proximity of some of Midtown Manhattan's towers mitigates the wind impacts on individual structures. However, an increasing number of today's taller, thinner towers—and particularly those built near fault lines—require new technology to combat swaying.
Also known as a harmonic absorber, a tuned mass damper is a device designed to reduce the effect of mechanical vibrations. For tall buildings, a slosh tank—essentially a "big bathtub in the sky"—can be installed near the top of a tower to counteract the swaying caused by earthquakes and wind. As the structure begins to sway, the water in the tank sloshes in the opposite direction, dampening the sensation of movement. This is the technique most often used in Toronto's tall buildings.
Much like a car's shock absorbers, the various technologies used in towers—which sometimes include magnets, or steel mounted to giant springs—smooths out potentially jarring motions.
The recently published SkyriseCities Explainer provides an in-depth look at one such installation, with a description of the world's largest steel body tuned mass damper. Housed near the top of Taipei 101, the 660-tonne pendulum seen above reduces the impacts of wind.
As buildings climb higher and higher, new structural challenges often present themselves. Skyscrapers, especially in Asian cities, continue to reach new heights and break records despite rising on or near vulnerable fault lines. To combat potential structural failures caused by earthquakes and strong wind, various vibration control technologies can be instituted in a building.
For the rest of the story, follow the link to SkyriseCities.com.
