July 19th, 2011
07:51 AM ET

Scientist: Tae Bo workout sent skyscraper shaking

Seventeen people performing a vigorous Tae Bo workout caused tremors that forced the evacuation of a South Korean skyscraper earlier this month, the building's owners say.

Prime Group, owner of the 39-story TechnoMart commercial-residential high-rise in Seoul, said 17 middle-aged people were working out to the pop song "The Power" by Snap on July 5 when their movements set the upper floors of the tower shaking for 10 minutes, according to a report from the Korea JoongAng Daily.

Scientists recreated the event in the 12th floor gym, according to a report in the Korea Times.

“We observed the vibrometer while performing the same kind of aerobic exercise that was performed at the time of the shaking which occurred on July 5. We noticed that the shaking was felt in the upper floors while the exercise was being performed while no other place showed signs of tremor,” Chung Lan, a professor of architectural engineering at Dankook University, told the Korea Times.

“It just happens to be that the vibration cycle caused by Tae Bo collided with the vertical vibration cycle unique to the building,” Chung told the Korea Times. The action amplified the building's vibration and caused the shaking, he said.

Chung was one of six professors from the Architectural Institute of Korea who inspected the building and recreated the Tae Bo exercise.

Tae Bo is a mixture of boxing and tae kwon do.

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Filed under: South Korea • World
soundoff (322 Responses)
  1. Greg

    Reminder: do not buy a building made in Korea

    July 19, 2011 at 12:09 pm | Report abuse |
    • BS

      This has nothing to do with the quality of the building. It's a phenomena called "resonance". No way they could have predicted that an exercise class would exactly match the buildings natural resonance frequency.

      July 19, 2011 at 12:19 pm | Report abuse |
    • johnnyph12

      Greg, you gave me the biggest laugh today! I needed that!!

      July 19, 2011 at 12:23 pm | Report abuse |
    • dave

      wasn't really that funny. cnn commenters need better jokes

      July 19, 2011 at 12:30 pm | Report abuse |
    • ean

      Yeah it is called resonant frequency but structural engineers are supposed to design buildings such that there are multiple reonant frequencies thus problems like this don't occur. I would imagine at the very least some retrofitting is called for.

      July 19, 2011 at 12:38 pm | Report abuse |
    • mojojo

      gave me a laugh too!! =D

      July 19, 2011 at 12:41 pm | Report abuse |
    • Sorin

      @ BS: They can predict the resonances – it is called mechanical engineering. There are computer programs out there that would do that for you, you just need engineers who know how to use them.
      They should not design a building with resonances at such low frequencies. Or find a way to dampen them. The design is flawed.
      Do not buy Korean buildings – Greg is right.
      On second thought – I remember some American bridge collapsing not too long ago in Milwaukee (?)... I guess there can be incompentence world wide. Do not buy American bridges.

      July 19, 2011 at 12:42 pm | Report abuse |
    • Truth

      No more sweating to the oldies.....

      July 19, 2011 at 12:44 pm | Report abuse |
    • Tom

      That's nothing compared to the martial arts class I took from Chuck Norris. It took one day: January 17th, 1994 in Northridge, CA.

      July 19, 2011 at 12:48 pm | Report abuse |
    • Ken

      It has everything to do with the building design. GOOD designers understand resonance and the plan for it in the design. They put items into the design specifically designed to break up or halt the propagation of such waves of energy. But not this building. Since exercise on the 12th floor causes the upper floors to vibrate (with little noticed in the middle floors) the building has a major flaw. The upper floors must be structured so energy passing in from below deflects into the box, and then resonates back and forth with no place to go or easily disapate. I promise you that in an earthquake of any significant magnitude, the upper floors of this building would shake, vibrate, collapse, and cause the failure of the whole structure. And I can also promise you they are already vigerously working on designing corrections to the structure, as they are very aware of this danger and are not pointing it out to the public.

      July 19, 2011 at 12:53 pm | Report abuse |
    • D

      The funniest comment on any article that i've read in a while.... lmao. For those of you trying to combat his comment with scientific reasoning – IT WAS A JOKE. LIGHTEN UP!!!!!!!!

      July 19, 2011 at 12:55 pm | Report abuse |
    • jdawg

      @Tom
      Nice... i got it. 🙂

      July 19, 2011 at 2:18 pm | Report abuse |
  2. Rob

    “It just happens to be that the vibration cycle caused by Tae Bo collided with the vertical vibration cycle unique to the building,” Chung told the Korea Times.

    Is this intersection of this vibration the same phenomena that amplifies the effect of earthquakes on some buildings so that buildings within a certain height suffers the most damage while the taller and shorter buildings come out unscathed?

    July 19, 2011 at 12:11 pm | Report abuse |
    • mcg

      yes

      July 19, 2011 at 12:27 pm | Report abuse |
    • Jessica

      Yes

      July 19, 2011 at 12:28 pm | Report abuse |
    • kpm

      You've raised a very good analogy there, Rob. In an earthquake, the ground motion will be most damaging to the buildings whose flexural natural frequencies most resemble the frequency of the ground motion. In this instance, the vertical input frequency matched a vertical natural frequency in the structure.

      July 19, 2011 at 12:36 pm | Report abuse |
    • Canadian Genius

      Also during an earthquake, fat middle-aged Koreans get bounced around at a certain frequency.

      July 19, 2011 at 12:41 pm | Report abuse |
    • J

      Yes, this is why almost all modern buildings have some sort of tuned mass damper in them. Some have literally very large/heavy blocks of concrete on springs or a semi-restrictive bearing system that counteract the motion of the building, some have tuned base isolation systems (again similar to large springs) and some have variably spaced mass dampening systems which counteract several frequencies. Pretty interesting stuff. Search for "tuned mass damper".

      July 19, 2011 at 3:52 pm | Report abuse |
  3. Stephen

    Sounds like solid construction.

    July 19, 2011 at 12:16 pm | Report abuse |
  4. Epiphany

    And who said Billy Blanks can't still shake things up?

    July 19, 2011 at 12:17 pm | Report abuse |
  5. JustImagine

    ...if fat Americans would have been doing it. The building would have collapsed.

    July 19, 2011 at 12:19 pm | Report abuse |
    • Paul

      Hey, I resemble that remark...

      July 19, 2011 at 12:22 pm | Report abuse |
    • Mr. T. Bag

      Good thing Americans don't exercise... ha! But that's why our buildings cost so much - double cement and rebar, just in case...
      There should be a fat-tax!

      July 19, 2011 at 12:25 pm | Report abuse |
    • Yup it's me!

      Well, it just so happens that we (Fat Americans) do not exercise, so this never would have been a problem;)

      July 19, 2011 at 12:33 pm | Report abuse |
    • roflcopter

      LOL! true true.

      July 19, 2011 at 12:38 pm | Report abuse |
  6. Rick Springfield

    Nikoli Tesla gets his ultimate revenge.

    July 19, 2011 at 12:22 pm | Report abuse |
    • Ed

      I thought this exact same thing! Glad to see that great minds think alike.

      July 19, 2011 at 12:28 pm | Report abuse |
    • Bob

      Tesla was actually very afraid that someone could use resonance as a form of terrorism. Someone with a half decent engineering degree could quickly hobble together an inexpensive device to generate a dynamic cycle that would match any building's natural frequency... It might takes months before the effects would be felt but once started almost impossible to stop in time.

      July 19, 2011 at 12:30 pm | Report abuse |
    • Know It All

      Mythbusters already tried that on a bridge and pronounced it plausable.

      July 19, 2011 at 1:33 pm | Report abuse |
  7. Mr. T. Bag

    Interesting... I hear the Korean Hyundai and Kia do the same thing...

    July 19, 2011 at 12:22 pm | Report abuse |
    • dave

      only when the obese drive em... ie alabama, mississippi, georgia, etc.

      July 19, 2011 at 12:32 pm | Report abuse |
    • smashly

      @dave- you must live in one of those states. I bet it's Mississippi.

      July 19, 2011 at 2:23 pm | Report abuse |
  8. Police

    @JustImagine... you have no imagination. I'm sure whatever retard 3rd-world country you're from couldn't build a building above one story.

    July 19, 2011 at 12:23 pm | Report abuse |
  9. Smith

    This happens all the time. The wrong terminology is being used. It's called resonant frequency vibration. Any building architect or civil engineer is very familiar with this situation. Not exactly something you need Scientists to investigate

    July 19, 2011 at 12:23 pm | Report abuse |
  10. boltman

    Nikolas Tesla worked on this princaple its called "natural frequencies" and everything from that building to your keyboard has one. It just so happened that this group happened upon this building specific frequency by accident.

    Read more at http://www.abovetopsecret.com/forum/thread351060/pg1

    July 19, 2011 at 12:25 pm | Report abuse |
  11. I love Sandra

    Terr0rists will use this form of "attack"!

    July 19, 2011 at 12:25 pm | Report abuse |
  12. Kevin

    This is why fat people need to exercise on the ground floor!

    July 19, 2011 at 12:27 pm | Report abuse |
  13. Chr

    LOL

    July 19, 2011 at 12:35 pm | Report abuse |
  14. gemax

    I just f`rted and a picture fell off the wall.

    July 19, 2011 at 12:36 pm | Report abuse |
    • mojojo

      LOL!!!!!

      July 19, 2011 at 12:43 pm | Report abuse |
  15. hornman4u

    Gee, I wonder if the Israelites used the Tae Bo workout to bring down the walls of Jericho???

    July 19, 2011 at 12:37 pm | Report abuse |
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