The deadly 7.4 magnitude earthquake that hit Taiwan on Wednesday and killed at least 9 people also damaged more than 100 buildings across the island, according to the National Fire Agency (NFA). About half of them were near the epicenter in Hualien County, where four structures partially collapsed.
Just 80 miles away in the capital, Taipei, buildings also shook violently during Taiwan’s strongest earthquake in 25 years. But in a triumph of modern engineering, Taipei 101, once the world’s tallest skyscraper, emerged undamaged from the island’s latest seismic event.
Images from the earthquake show the 1,667-meter-tall tower shaking slightly, its structural flexibility helping to resist the earthquake’s powerful motion. This move perfectly demonstrated that the skyscraper’s most important defense against earthquakes is the material from which it is built – reinforced concrete.
The material combines the compressive strength of concrete with the tensile strength of steel, making the building flexible enough to shake but also strong enough to withstand the high winds and typhoons that frequently hit Taiwan. (The principle that buildings can withstand seismic forces by moving with Opposition to, rather than against, them has been the basis of traditional architecture in earthquake-prone East Asian countries for centuries, from Japanese pagodas to Chinese palaces.)
But high up in the tower, another technological innovation helps protect the 101-story skyscraper, a massive sphere-like device known as a tuned mass damper.
giant counterweight
The golden steel sphere, suspended by 92 thick cables between the 87th and 92nd floors, can move approximately 1.5 meters in any direction. As a result, it acts like a pendulum, counteracting (or “damping”) the swinging movements.
“Super Tall: How the World’s Tallest Buildings Are Reshaping Our Cities and Lives.” “It’s actually a huge counterweight,” Stefan Al, author of the book, explained in a phone interview. “In the case of Taipei 101, this is 660 tons. This looks really heavy, but if you compare it to the total weight of the building, you’ll see that it’s just a fraction.
“When a building starts to shake (the tuned mass damper) will move in the opposite direction. “In the case of Taipei 101, it is suspended…so as the tower swings, it will fall behind and move in the opposite direction, absorbing kinetic energy,” Al said, explaining that hydraulic cylinders between the ball and the building convert this energy into energy. the heat then dissipates.
The tuned mass dampers are installed in 11 skyscrapers around the world, including the “super-thin” Steinway Tower in New York and Dubai’s sail-shaped Burj al-Arab. Al said the device provides significant protection against violent movement caused by “harmonic vibration” that could cause structural failure during an earthquake.
“(It’s) when buildings start vibrating in their own resonance,” he said, comparing the phenomenon to a tuning fork. “This could lead to collapse as (the building) would start to shake faster and faster.”
Tuned mass dampers, also known as harmonic dampers, are “tuned” to resonate at the same frequency as the building; but wavelengths start earlier or later, helping to dissipate potentially destructive energy.
The stability they provide can also reduce the uncomfortable and even nauseating effect that swaying in high winds can have on building occupants.
structural support
Designed by Taiwanese firm CY Lee & Partners, Taipei 101 was the world’s tallest building from 2004 to 2007, when it was surpassed by Dubai’s Burj Khalifa. An observation deck overlooking the groundbreaking tuned mass damper is now a popular visitor attraction, especially when it moves during strong winds.
But the massive sphere isn’t the only design feature that helps stabilize the tower, which sits near a major fault line.
First, the skyscraper sits on extremely deep foundations; that is, 380 reinforced concrete and steel piles drilled into the bedrock below. Above them, the building’s core is connected to a series of “mega-columns” placed around its perimeter via massive steel support beams.
The high-rise complies with anti-seismic building codes, which are as stringent as one might expect on an island located along the “Pacific Ring of Fire” that runs along the edge of the Pacific Ocean and causes major seismic and volcanic activity. From Indonesia to Chile.
But while the design has also undergone extensive digital modeling and “shake table” testing (where scale models are tested on a device that mimics earthquake motion), it remains to be seen how a building like Taipei 101 would respond to a stronger or more recent seismic event. theoretical to some extent.
“Even though we have computer simulations, there’s something about the physical that we can’t really get from digital simulations,” Al said. “Despite our technological advances, we’re still testing (designing) in wind tunnels and on shaking tables.”
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