Korea solves mystery of shaking skyscraper

Korean scientists think they have determined what caused a 39-story Seoul skyscraper to shake violently for 10 minutes, causing the building to be evacuated for two days. Earthquake? Nope. Gale-force winds? Sorry. Volcanic activity? Unh-uh.

No, the culprit, they say, was 17-middle-aged gym rats working off the midriff bulge in a Tae Bo class. Apparently, while dancing and boxing to "The Power" by Snap on July 5, the exercisers not only shook their booties, they shook the building. "It just happens to be that the vibration set up by the Tae Bo exercises coincided with the resonance frequency unique to the building," Chung Lan, professor of Architectural Engineering at Dankook University, told the Korea Times. "When an external vibration hits the resonance frequency of a certain object, the vibration is amplified and causes excess shaking even from slight movement." Six Architectural Institute of Korea professors and several vibration measurement experts inspected the building, a high-rise shopping mall, and carried out a simulation of the exercise class using the same number of participants. They agreed that mechanical resonance was the probable explanation. Chung said the class had a new instructor who apparently worked the group twice as hard as usual.

Resonance Frequency Causes Shaking Skyscraper

I thought it was quite interesting to see this in action. Just a few people can set a building to trembling like that!


(Mods, if I'm in the wrong forum, please move. First post and all. )

reply to post by 1FullHouse


Brilliant!! Every DJ's fantasy! Get the club jumping and bring the whole house down! Imagine if those had been 17 Americans with all that weight shifting and jiggling in unison!

This subject has always fascinated me, and I believe that Mythbusters did some experiments on a bridge surrounding the stories about soldiers marching perfectly in unison and matching the resonant frequency of the bridge. If I remember correctly, they did replicate it on a small scale model, and were allowed permission to try it out on a huge bridge in San Francisco. Apparently the authorities were totally unconcerned about this effect so allowed them to carry out any tests they saw fit.

They couldn't move the bridge to destruction, but they did show a video taken around 1940 where traffic matched the resonant frequency perfectly and violently shook it to destruction. It was incredible how much it was twisting, waving and swinging side to side, literally flipping cars into the air.

I wouldn't be surprised if the research done on this effect was used to make some kind of weapon. I can just imagine drawings of a ray gun kind of contraption that scrolls through thousands of frequencies in an effort to topple a building!

reply to post by luckythirteen


I remember that episode. I don't put much stock in to that show, as it's well.....just a TV show. Their methods do not explore all possibilities nor usually follow scientific method.

Also, isn't it one of the ongoing theories for HAARP?

And people say teslas machine based on resonant frequencys couldnt bring down a skyscraper, here we have proof that it will work, as this wasnt even done with a machine such as his but with people and music.

What can i say.

I told ya'll.

reply to post by 1FullHouse


I agree, there are some experiments where they don't explore all avenues of possibility, but as an engineer myself, I was quite happy in how they handled that from what I remember. They could of course have built an enormous weighted piston and programmed it to cycle through frequencies, but it would have detracted from the theory that it's possible through foot traffic.

I do recall seeing something developed by the military that used sound waves, but have never seen any evidence of using it to topple structures. I have read about the technology being developed to clear land mines, and to disrupt the nervous system of soldiers. It would be very interesting to see if it has been used for destructive purposes of this scale before though!

Originally posted by luckythirteen
They couldn't move the bridge to destruction, but they did show a video taken around 1940 where traffic matched the resonant frequency perfectly and violently shook it to destruction. It was incredible how much it was twisting, waving and swinging side to side, literally flipping cars into the air.

That's the Tacoma Narrows Bridge, we studied it in structural engineering classes in college. It wasn't traffic that set it off, it was high winds. And it wasn't due to resonant frequency, it was something called "aeroelastic flutter" that did it in.

Regarding the OP, something is seriously wrong with the design of that building if some people working out can set it to moving like that. It may indeed be resonant frequency, but the bottom line is that the design should incorporate features to ensure the structure is not affected by resonant frequency and the fact that it is being affected tells me Korean structural engineering leaves a lot to be desired.

Having lived there for almost 8 years and experiencing first hand the lengths the Korean business people and Govt. will go to in order to save money and pride...I don't believe this explanation one bit.

Fan Death is still believed by many to be real and the myth has been traced back to propaganda that was an effort to save electricity and has been used to account for many suicides. Family members blame Fan Death for the loss of the loved ones and it is actually reported as such in autopsy and news reports.

My wife is Korean, she loves her Country and I love her dearly. Even she had to giggle a bit at this.

Fan Death
en.wikipedia.org...

Fan death is a widely held belief prevailing in South Korea that an electric fan left running overnight in a closed room can cause the death of those inside. Fans sold in Korea are equipped with a timer switch that turns them off after a set number of minutes, which users are frequently urged to set when going to sleep with a fan on.

reply to post by 1FullHouse


I agree, since that show the Mythbusters lost me as a frequent viewer. Even though they could feel a vibration more or less equivalent to that of a truck, they just wrote Tesla's machine off in a way. It may be for security reasons so that not any TDH will try to build one or myself being a South African didn't catch their sarcasm, I prefer the former.

This proves, as Tesla's experiment in his building, it is the real thing.

S&F

* Savedone is correct on how that bridge came down.

Originally posted by qonone
reply to post by 1FullHouse

 

I agree, since that show the Mythbusters lost me as a frequent viewer. Even though they could feel a vibration more or less equivalent to that of a truck, they just wrote Tesla's machine off in a way. It may be for security reasons so that not any TDH will try to build one or myself being a South African didn't catch their sarcasm, I prefer the former.

This proves, as Tesla's experiment in his building, it is the real thing.

S&F

* Savedone is correct on how that bridge came down.

edit on 7/26/2011 by qonone because: added

Didn't both of those experiments, Tesla's and Myth Buster's, take at least a few hours to get the frequency and tremors up to speed in order for the vibrations to start feeding back? May be wrong here but an exercise class jumping up and down for a few minutes wouldn't be enough time for the vibrations to set in.

In other words, I'm not buying it.

Bunch of kids jumping up and down for a few minutes?
Ummm,. i dont agree with this at all,.
I say prove it and make it happen again.

reply to post by jude11


I understand that Tesla's machine ran non-stop, so this exercise/gym/taebo class which they're claiming is the cause is hard to swallow, i'll admit to that. I have no idea how this could have occurred. I do believe is that it is possible for the Tesla "earthquake machine" to cause a tremor.

My previous post was aimed at that specific mythbusters episode, which is understandable why, yet crapping over Tesla in their own nice way.