As Taiwan’s biggest earthquake in 25 years rocked the island nation on Wednesday, with videos of violent shakes and sways observed among some properties and structures, Taipei 101, Taiwan’s tallest building, betrayed hardly any movement against the skyline of the capital city.

The 101-story, bamboo-shoot-shaped landmark, the world's tallest building when completed in 2004, has withstood earthquakes and typhoons undamaged — including this week’s magnitude 7.4 earthquake, as measured by the U.S. Geological Survey. That's thanks to what’s been described as its many structural engineering feats, including the 730-ton, gold steel ball called a tuned mass damper that's suspended by 92 steel cables at the top of the building.

“When the building starts shaking during a seismic [event], the heavy ball is operating in the opposite direction of the movement of the building,” Timurhan Timur, a structural and digital team leader at engineering consulting firm Arup, said in an interview. “It’s like a pendulum.”

Taipei 101’s steel ball — rare among supertall buildings — is among a variety of dampers used to help “reduce the sway of the building” and “dissipate energy and reduce the effect,” Timur said, adding the Taiwan landmark is “very well designed and well constructed.”

For instance, Arup has used other types of damper designs at buildings such as 181 Fremont Tower luxury condo tower in San Francisco, he told CoStar News.

“If there’s an earthquake in Taiwan, I would run to Taipei 101” because I would feel safe there and know it’s well designed, Dennis Poon, managing principal at Thornton Tomasetti and one of the lead engineers behind the structural design and system for Taipei 101 when Thornton was hired by the building’s local design architecture firm C.Y. Lee & Partners as its international structural consultant. Taiwan’s Evergreen Consulting Engineering was the structural engineer of the record.

“When we got the job, we understand the importance of designing a supertall tower” that would be the world’s tallest building at the time, Poon, based in Thornton’s global headquarters in New York, said in an interview. “We know that Taipei itself is in a severe earthquake zone with frequent earthquakes. Also Taipei is subject to very high typhoon wind loads. … The soil is not rock solid. We had to deal with structural design challenges. … It was a challenging project at the time because it was the first. We were talking about the tallest building in the world in the earthquake zone and in the high wind zone. We had to try to find all the optimizable solutions.”

The answer: Using a structural steel brace core as the main spine of the tower and complementing it with four massive steel columns along each side of the perimeter of the building, he told CoStar News. The structure was also strengthened with outrigger steel trusses connecting the tower core with the exterior columns that's similar to the idea of a skier strethcing their arms out and grabbing a pole on each arm for stability, he said. There’s also a steel truss girder connecting the perimeter columns together to create an exterior frame of the tower for further support.

“It’s a dual structural system that’s been designed to resist wind and earthquakes,” Poon said. The system is “similar to a skier stretching their arms ... in order to provide more stability. … It was quite revolutionary at the time. … It sets the trend for a performing structural system for megatall buildings.”

In fact, since Taipei 101, Thornton went on to design many other supertalls, including China’s Shanghai Tower, with similar structural designs, Poon said.

Back in North America, these types of structural designs also have been used by other developers for properties such as the supertall and slender “pencil” towers on Manhattan’s Billionaires’ Row nearby Central Park, he said.

As to Taipei 101’s tuned mass damper, located from floors 88 to 92, Poon said its main purpose is to help mitigate and reduce any motion sickness that may be felt by the building’s tenants in the event of an earthquake or a major wind event.

The “tuned mass damper is contributing to the successful performance of the building,” Poon said.

The gold sphere ball, made of 41 layers of solid steel plates welded together, is a big tourist draw and main feature of the observation deck of the 1,667-foot, mixed-use office and retail property.

“Most dampers tend to be hidden away” and behind mechanical floors, Borys Hayda, managing principal at DeSimone Consulting Engineering, said in an interview. “It’s wonderful they celebrated the opportunity to make this golden globe so that people can watch it. … It grabs the imagination.”

In fact, the interest in the damper is such that Taipei 101’s observation deck sells a collection of damper-related souvenirs, including a line of “damper baby” cartoon characters.

“The reason you want the damper high up in the building is it’s the most efficient location,” Hayda said. “It acts as a shock absorber of the building. … It’s like a huge bungie cord at the top of the building.”

Taipei 101’s tuned mass damper helps the building withstand high winds, and up to 40% of the building’s movements are reduced, A+H Tuned Mass Dampers says on its website, adding it worked with engineering consultant Motioneering to make Taipei 101’s system. The fabrication of the components took just under a year to complete.

A+H also was involved with making tuned mass dampers for buildings such as Manhattan’s 432 Park Ave. luxury condo building overlooking Central Park; the Cambridge Crossing office building at the intersection of Cambridge, Boston and Somerville in Massachusetts; and the M City condo complex in Mississauga, Ontario, in Canada.

Among other design attributes of Taipei 101, the foundation of the building features 380 piles driven about 262 feet into the ground, according to the building website. The deepest pile extends about 100 feet into the bedrock, similar to nailing the entire building onto a solid tectonic plate, Taipei 101’s website says.

To be clear, tall buildings with dampers or other so-called dynamic modification devices remain relatively rare. According to a 2018 study, among the 525 buildings of 820 feet or greater that were completed or under construction globally, only about 18%, or 97, were equipped with dynamic modification technologies, according to the Council on Tall Buildings and Urban Habitat. The study is the group's most recent survey on that topic.

“Dampers are common for tall and slender buildings,” Hayda told CoStar News, adding DeSimone has also used tuned mass dampers at the top of some of Manhattan’s supertalls including the 125 Greenwich St. and 220 Central Park South luxury residential towers. “Typically the top of the building is the most valuable real estate. … As engineers we have to design for all types of potential risks. … It’s become an economic exercise [to study] what’s the most economical way to reduce [the effect of wind and other loads]. The space requirement of damper is not insignificant.”

For instance, dampers usually come in size that would require the equivalent of two tall stories or two and a half normal stories of a building space with 30-foot cube as a starting point, he said.

In some markets, dampers aren’t commonly used at all. For instance, while DeSimone’s structural designs factor in earthquake risk among other potential risks in New York, in Miami, where he said there’s no earthquake risk but is known for hurricanes and storms, dampers aren’t commonly used.

Miami is a “reinforced concrete town,” he said. Still, concrete has the “drawback of weighing a lot” that’s “not a good thing to resist an earthquake.” In a seismic zone, “you have to use special design and detailing … to make it as light as possible” versus making the building as heavy as possible to resist wind, Hayda said.

“Taipei 101 is a location that presents to engineers unique challenges [with risk exposures to] very high wind load and severe earthquake,” Thornton’s Poon said. “It’s a trend setter for megatall buildings that have to resist earthquake and high wind loads.”