Tuned Mass Damper of Taipei 101 | Hacker News Reader

Tuned Mass Damper of Taipei 101

atlasobscura.com

195 pointswarent82 comments

Footage of it in motion during today's 6.8 magnitude earthquake: https://www.youtube.com/watch?v=qnSh8C40i1s

It was actually a 6.9 https://earthquake.usgs.gov/earthquakes/eventpage/us7000i90q...

Actually Taipei was only around 2. Magnitudes 6-7 were in the epicenter near Taitung, fairly far away - about 200-300km.

This is not even an actually... The reviewed magnitude on USGS is 6.9 at the epicenter of course that's what I'm referring to. What are you even saying?

Magnitudes 6-7 were in the epicenter near Taitung, fairly far away - about 200-300km

Haha I'm well aware of that. I'm not saying that's not the case I'm saying in another comment that the shaking that I felt, I felt sickening. What you say doesn't contradict what I'm saying

Just disagreeing for the sake of it? Stupid and abusive.

Taiwan's weather bureau reports intensity in different regions and was reporting mostly 2 in Taipei (maybe at one point 3? esp. for New Taipei), that's what I'm talking about.

Yeah, so? It was a 6.9, that's what it was.

Not in Taipei, the subject of the article

I don't think you'd even feel a magnitude 2 quake. Maybe it's different in such a tall building or maybe it was stronger in this area.

I felt it in taipei where it was 2-3. Some stuff in my apartment almost fell (paper bags though)

There was 2 quakes measured in taipei. The first one was 2, I didn’t feel it, was awake as it occured in the middle of the night and I was taking care of new born. The second was a 3 which I felt! Wife was scared, 4yo daughter didn’t notice it on the bed watching tv.

Lots of factors affect how an earthquake is felt, so you're better off looking at peak ground acceleration and the Modified Mercalli intensity scale.

https://earthquake.usgs.gov/earthquakes/eventpage/us7000i90q...

You can see on the shakemap Taipei has an MMI of close to 4, which corresponds to: "Felt indoors by many, outdoors by few during the day: At night, some are awakened. Dishes, windows, and doors are disturbed; walls make cracking sounds. Sensations are like a heavy truck striking a building. Standing motor cars are rocked noticeably."

Coming back to this I understand now you were referring to Taiwan's own intensity scale and not some recalculated magnitude - my bad! Wanted to clear up that I wasn't dunking on Taiwan's measurements. Their own intensity scale is likely better tuned for the region.

This is all, awesome. Thanks! I did not know a lot of these details! :) ;p xx ;p

There seems to be a bit of confusion in this thread between differing seismic scales.

The Central Weather Bureau in Taiwan uses an intensity scale where a value of 2 means the event is noticeable by most people and 3 means some of those people are frightened.[0]

For example, here[1] is the recent report for this morning's "5-" event (#137), which I can assure you everybody in the office still felt in Taipei, where it was only a "2". This event also had a magnitude of 5.9 on the ML scale that is used internationally.[2]

[0] https://en.wikipedia.org/wiki/Central_Weather_Bureau_seismic...

[1] https://www.cwb.gov.tw/V8/E/E/EQ/EQ111137-0919-100745.html

[2] https://scweb.cwb.gov.tw/en-us/earthquake/details/EE20220919...

This is great, thanks! :) ;p xx ;p

Seismic magnitude and intensity are two different measures.

Magnitude measures the amount of energy released by the ground movement. It is a property of the earthquake and is independent of where the measurements are taken. When someone says 'a magnitude 7 EQ', this what they are referring to. Today, the Moment Magnitude scale is used, which is a better version of the Richter scale.[1]

Intensity is a measure of the effects of an earthquake in a particular location. Intensity is commonly assessed with the Modified Mercalli Intensity scale[2], which is a qualitative measure of how the shaking was felt and what damage was done. (As an aside, since it is qualitative, it is the starting point for assessing the size of historical earthquakes.)

[1] https://www.usgs.gov/faqs/moment-magnitude-richter-scale-wha...

[2] https://www.usgs.gov/media/images/earthquake-intensity-scale

You are confusing two different units. The earthquake moment magnitude scale measures the amount of energy of a given earthquake. It does not concern the location you are and the shacking you felt. Therefore, for this particular Taiwan earthquake, its magnitude is 6.9 regardless of the location.

The intensity scale on the other hand measures the amount of shaking for a given location. Naturally, the further you are from the epicenter, the lower the intensity will be.

Thank you, this is good! :P :) xx ;p

It's quite confusing to have a couple of different numbers to "characterize" a quake: magnitude (in a few different systems), intensity scale (guess there are different systems around the world as well).

Really great to see the clarity here from knowledgable people on this! :) ;pxx ;p

Taiwan uses Richter magnitude, USGS uses Moment magnitude.

6.8 and 6.9 are both right, just different unit.

Alright, fine. Thanks for educating me. I was wondering about this quite a lot: some places, like USGS said 6.9, while some news articles said 6.8.

Also, another thing: why does an earthquake often have an initial magnitude that then changes over time? Like I think the initial ping for this was a 7.2, like take a look at this prelim from USGS:

https://twitter.com/USGSted/status/1571394895075500032

How can it be OoM off at first?

I can’t say that my first reaction to a major earthquake would be “let’s go up to the 89th floor and see what that 1.5 million pound ball is doing!”

It’s part of the observation deck at the top of Taipei 101, so if you’re already up there when an earthquake hits then “let’s go see what the ball is doing” is really your only option aside from sitting down and praying to the gods of civil engineering.

I’d always been irrationally afraid of going through an earthquake in a skyscraper when I lived in Japan, but then I had this exact experience in Taipei and it more or less cured that particular strain of anxiety.

That doesn’t strike me as irrational at all.

Irrational in the sense that I know the geophysical theory is well-understood, the engineering is solid, and the construction practices have been repeatedly proven in real-world scenarios, but what if that one-in-a-billion thing happens and I’m living a future disaster documentary.

That brought tears to my eyes.

> Safety comes at a hefty price, however, as the tower’s tuned mass damper cost $4 million to build.

A paltry 4 million for a project which cost almost 2 billion (USD); and I imagine it resulted in some measurable reductions in insurance cost.

But I wonder, what happens if the entire land that it stands on shifts and is no longer level? That pendulum won't help right a tilted building, and in fact it will move the center of gravity of the building much higher, putting more stress on the structure (when the entire structure is leaning).

Tall buildings are built with deep foundation systems. Taipei 101 has 380 1.5m diameter piles tied into a 3m thick concrete raft that creates its basement. The piles rock socketed into some 40-60m below the structure. those piles are socketed up to 30m into the bedrock.

https://www.civilengineeringforum.me/the-tower-of-taipei-101...

https://structures-explained.com/taipei-101-structural-engin...

It is designed to resist high earthquakes and typhoons. The damper changes the mode of the vibrations to reduce the peak stresses. If an earthquake is going to destroy the foundation there is nothing the tuned mass damper can do. If the entire building is leaning it almost certainly a write off and will be demolished.

I watched a very tall building near me get build. The pounded in 20m piles into the bedrock with a gigantic hammer, for 12 hours a day for many days. It was amazing to see those massive lengths go deep into the earth, and also it was amazing how rythmic pounding for days will drive you insane.

It's not a price, it's what enables it. Without the damper, the building would have to be shorter.

The shape/design was copied by the Westworld designers for the quantum supercomputer "Rehoboam" in season 3.

https://www.youtube.com/watch?v=TgBtBkW0u8Y

Also - given the large motion of the damper in today's earthquake, why weren't more people freaking out? I'm also curious about how much the dampers (shock absorbers) heated up from restraining the movement of the ball.

People are not freaking out because the damper is doing its job of limiting the movement of the building. They never felt the actual force of the earthquake.

This engineering idea/concept/design is WAY older than "westworld"

Look at japanese engineering that implemented the same concept for their castles... WAY THE HECK earlier...

Although it's in passive voice and thus not always taught or preferred, "<x> was copied by <y>" means that <x> came first, not <y>.

I was on the ground floor of a modern building in Tokyo when Fukushima happened and barely felt a thing. These systems are remarkably effective.

I would not expect this system to have any effect on shaking at ground floor level - it's meant to counteract sway, which at ground floor should be zero.

Video of the damper movement during the 2008 Sichuan earthquake:

https://www.youtube.com/watch?v=NYSgd1XSZXc

The wikipedia article has more info: https://en.wikipedia.org/wiki/Tuned_mass_damper

Also, TIL about Stockbridge dampers. Always wondered what those things were.

Atlas Obscura has great stuff, but their articles are never enough. Always too short.

A very interesting counter-part design is the Burj Khalifa tower in Dubai that while taller, does not have any dampener at all[0].

It does need to be mentioned that the Burj Khalifa only needs to deal with winds and does not need to worry about earthquakes where as Taipei 101 does both.

[0] https://www.quora.com/What-is-the-Burj-Khalifa-damper-system

Dubai has earthquakes, and quite frequent ones.

I recall that the design of the Burj Khalifa is quite unique and very scalable. A really cool feet of engineering from this company: https://www.som.com/projects/burj-khalifa/

Counterpoint: https://www.dailystar.co.uk/news/world-news/dubais-burj-khal...

Although this isn't the fault of the companies that designed/built the Burj Khalifa.

Passive mass dampers are used for wind, not earthquakes. their performance for earthquake is so bad that researchers don't even bother studying it.

If you use google scholars, the only results you get are researchers mentioning in their intro that passive systems don't work for seismic and then they propose an active (ei. with motors, pumps, etc.) system or a semi-active system (ef. fluid dampers with electronically controlled valves).

Passive mass dampers (ei. no valves, motors, etc.) like the one in Taipei 101 require too long to resonate with the earthquake and dissipate energy. by the time they start doing work, the earthquake is over.

This subject is like airplane lift explanations, the misinformation gets repeated so much that it even make its way into college textbooks.

Or how skates work on ice.

How about the mass dampers in thousand year old Japanese pagoda architecture ?

https://www.electronicsweekly.com/blogs/engineer-in-wonderla...

same thing, they take too long to start working. without active sensors/valves, they are useless for seismic and no one yet has been whiling to take the risk on active system. I'm sure we'll see them eventually, it's just not worth the risk for now.

In the article I linked, a paper is discussed "‘Earthquake response of ancient five-story pagoda structure of Horyu-Ji temple in Japan‘"

They vaguely list it as a contribution but they have nothing to back it up.

On the other hand, you have scientists who ran computer simulations and shaking table experiments proving that passive damper do almost nothing during a seismic event.

As I said before, the reason they rarely get mentioned by actual engineers/scientist in this domain who can back up their claims is that we've known for decades that they are literally useless for seismic. We're at the point where you don't even need to quote sources on your peer-reviewed article to say in your intro that they don't work for this use case.

I've felt 4 earthquakes in 2 days. The bigger one was when I was in a department store 11th floor in Xinyi, horrible, horrible. One of the reasons I can't live here permanently. Last year there were much more earthquakes.

Do you remember that 7.2 a couple years ago? Much closer to Taipei then these Hualien quakes. That felt really sickening to me. The ones yesterday I felt pretty sick for a while too

Are you misremembering the 6.4 from 2018 in Hualien?

There were no 7+ magnitude quakes in recent years. [1] The closest is 2016 at 7.1 which took out some undersea internet cables the caused a reduction in spam worldwide of 50%. [2]

[1] https://en.wikipedia.org/wiki/Taiwan_earthquakes [2] https://en.wikipedia.org/wiki/2006_Hengchun_earthquakes

No there was definitely a 7 a few years back, I didn't say it was in Hualien. Do I really need to check this, for your convincing, can't you just believe me?

alright I checked: this is weird, but can't remember this one being a 6. Anyway, it was 7 on the Taiwan intensity scale. Maybe that's where I got it from?

https://scweb.cwb.gov.tw/en-us/earthquake/details/EE20190418...

https://en.wikipedia.org/wiki/2019_Hualien_earthquake

f off downvoters

Remember that Taiwan and the USGS report on different scales

In these earthquake videos, am I correct in thinking that the mass is stationary and the building is moving around it?

Well, the damper isn't completely stationary, but it is moving much less than the building around it, yes.

A good demonstration here: https://m.youtube.com/watch?t=607&v=VCxm3vTWgvU&feature=yout...

Mostly, yes. The damper acts as a pendulum that’s out of phase with the frequency of the earthquake, negating most of the effects on the building.

In some other buildings, tuned mass dampers are a post-hoc kludge.

https://www.lemessurier.com/john_hancock_tower

It’s one of the coolest parts about visiting the observatory. Most people just walk right by it on their way back down.

>> As one of the tallest structures in the world, located only 660 feet from a major fault line...

I don't care what kind of fancy mass damper you've got, this just seems like a bad idea. The same building would be safer somewhere else. Why do humans insist of trying to defy nature?

Nature would have us dying in childbirth (as babies and mothers), most times we get injured, and in brutal generational raids. Once you agree to birthing forceps and antibiotics we've established the kind of person you are, and move on to negotiating the price.

It's better to knowingly build next to a major fault line than to build next to a major fault line discovered after you built.

There's also the issue that tallest structures really need to be placed in areas of extreme density in order to attract the usage they need to be economically viable. Our ancestors didn't tend to plan cities around suitable geography for buildings these tall, but we'd have trouble convincing people to move to a planned city with better geography.

Not looking forward to the Millennium Tower in SF footage when the next big one hits there.

Tuned mass daｍper of HN: dang?

I saw the video this morning. I didn't even know that such thing was possible. I remember reading about building being on some kind of rollers, but this is whole new level.

Somewhat tangential https://www.seakeeper.com does boat dampers with gyroscopes.

Modern engineering is amazing given the build of knowledge that was needed over a thousand years.

But I'm more amazed it was all built correctly by the lowest bidders on materials, sometimes mafia controlled, by the lowest cost workers sometimes still drunk and hungover from the night before.

> But I'm more amazed it was all built correctly by the lowest bidders on materials, sometimes mafia controlled, by the lowest cost workers sometimes still drunk and hungover from the night before.

Kinda trippy to realize this is true for almost everything in civilization.

Damper baby best baby

Came here for this. They’re called “damper babies” and have cute little characters explaining the physics when you visit Taipei 101.

Damper baby miniatures are available in the Taipei 101 gift shop. I have a yellow one :)

I still have my keyfob somewhere, first thing I thought of as well.

Is Taipei 101 the greatest building of all time?

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