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Tae Bo Workout Sent Skyscraper Shaking 107

Posted by Unknown Lamer
from the kick-punch-destroyskyscraper dept.
MiniMike writes "According to CNN: '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. Scientists recreated the event in the 12th floor gym, according to a report in the Korea Times.' I don't know which is scarier, that they made such a flimsy skyscraper, or the sight of 17 scientists doing a Tae Bo workout. Hopefully they're better at it than the scientists I've seen in the gym."
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Tae Bo Workout Sent Skyscraper Shaking

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  • by Anonymous Coward

    Heh, they accidentally hit a resonance frequency?
    After (admittedly) doing tonnes of calculations, the actual fix is typically very simple adding weights or some other form of damper to correct parts of the building).

      • by ShakaUVM (157947)

        A bunch of Koreans doing Tae Bo while listening to Snap and collapsing a skyscaper around themselves would definitely get my vote for most amusing tragedy of the decade.

    • by ehrichweiss (706417) * on Tuesday July 19, 2011 @06:35PM (#36817052)

      I wonder what the Mythbusters will say in regards to their "Marching In-step over a Bridge" episode. I was one of several to speak up and AFAIK they never addressed resonance. I said the same thing about their Tesla Earthquake Machine episode except I pointed out that these earthquake machines are used in demolition to this very day; I got the same lack of response.

      • by DeathElk (883654) on Tuesday July 19, 2011 @07:20PM (#36817364)
        They're obviously having too much fun blowing shit up to worry about responding to your points.
      • Marching in-step over a bridge...I remember that episode well..

        They built a suspension bridge. Then promptly neglected to SUSPEND the damn thing. The main cables were simply attached to the ends, but it wasn't a cable-stayed design. It was meant to be anchored to the ground! It could barely support itself much less resonate.

        MythMorons
      • Re: (Score:3, Insightful)

        by Anonymous Coward

        I wonder what the Mythbusters will say in regards to their "Marching In-step over a Bridge" episode. I was one of several to speak up and AFAIK they never addressed resonance. I said the same thing about their Tesla Earthquake Machine episode except I pointed out that these earthquake machines are used in demolition to this very day; I got the same lack of response.

        The problem seem to be that you are under the impression that Mythbusters is something other than an entertainment TV show.

        • by Shark (78448)

          The problem seem to be that you are under the impression that Mythbusters is something other than an entertainment TV show.

          Apparently [nextbigfuture.com] that's enough credentials for the US military... And I'm not trying to prove you wrong here. I'm baffled by it.

          • by digitig (1056110)
            That isn't about believing the show's results, that's about the people doing the show being genuine special effects experts who (despite how they make it look on the show) know a thing or two about safety.
          • Although the show does its best to hide it, Jamie Hyneman is actually an incredibly smart man with amazing credentials scientifically. I doubt the fact that he was a part of Mythbusters really had anything to do with his selection for the making of this armor. If you actually RTFA that you linked, it explicitly states "This is not Hyneman's first work with the military", implying they actually hired him because he was the man for the job, not just because somebody in the Army likes Mythbusters.

            • by GooberToo (74388)

              Exactly right! Mythbusters is purely for entertainment. Both of those guys readily admit it. There simply isn't enough time in a day to properly and stringently follow the scientific method for the shows they must pump out. As such, they rarely are very scientific.

              IMOHO, aside from the basic entertainment value provided by Mythbusters, their primary merit is that it allows people to understand they can apply some of the lessons learned from their science class to solve and/or explore real world problems, ev

              • IMOHO, aside from the basic entertainment value provided by Mythbusters, their primary merit is that it allows people to understand they can apply some of the lessons learned from their science class to solve and/or explore real world problems, even if you don't rigorously apply the scientific method in doing so. Science can be fun. That message alone is worth something.

                The "science is fun" message is worth loads, but the show's core concept also transmits the most fundamental tenet of science: don't believe in things just because. Try them out, test them, and discard as false the results you can't reproduce unless and until someone can show you why you weren't managing to reproduce them.

      • by GooberToo (74388)

        Thinking of Mythbusters as uneducated entertainment is a must. They get far more wrong then right. Frequently its completely bad science. Commonly they reproduce something which is well documented to have happened and their "validation" is somehow anything other than confirmed.

        If you ever watch Mythbusters expecting good science, you're doing it wrong. Mythbusters is entertainment clothed in a lab coat.

        • I agree fully. As a matter of fact it was the earthquake machine episode that turned me completely off to them since I knew for a fact that the damn machine not only existed but was in "popular" use.

          • by Kamoo (1935738)
            I tried to find some info on the machines used for demolition but the search terms I used returns this slashdot page. Could you please elaborate?
            • They're typically called "servo units"(or at least that's how they were referred to when I was around) and what they do is vibrate around 3-10 Hz for a period of time. The frequency is enough to loosen/weaken structures pretty readily, especially with the power they put into them. After a while, the demolition team can knock the place down with far fewer explosives. They also use them for "bass support" at raves which is kinda dangerous since these things can affect your health on a drastic level....but boy

    • by icebike (68054)

      Assuming synchronized rhythmic movements if 17 people (total weight probably over a ton) I would be surprised if a lot of buildings didn't sway a little depending on where the weight was being thrown about. They were located one third of the tower, and a ton is a lot of weight. By the time even a slight movement was propagated to the top floors it could be a significant movement. I doubt this is as accidental as it sounds.

      The flexibility of the building might be a key part of its earthquake protection, and

      • by cffrost (885375)

        The flexibility of the building might be a key part of its earthquake protection, and it probably doesn't need fixing.

        True points, though both safety and comfort can be improved with the addition of one or more tuned mass dampers. [wikimedia.org]

    • by dougmc (70836)

      Yes, but tall buildings sway all the time in heavy winds. I'll bet the effect was pretty small ...

  • please have video. This has got to be funny!
  • by Jah-Wren Ryel (80510) on Tuesday July 19, 2011 @05:13PM (#36816280)

    Korea's got a dramatic history [wikimedia.org] with such things. 500 people died in that one.

    • by SuperBanana (662181) on Tuesday July 19, 2011 @05:32PM (#36816478)
      The article concerns a workout which happened to hit the resonant frequency of the structure, which was properly designed. The failure you linked to had to do with criminal negligence by the owners ignoring repeated engineering and construction firms who refused to accept design changes driven by greed (and were fired for it), completely repurposed building usage leading to gross overloading of the structure's strength, and then completely incompetent handling of obvious signs of structural failure (failure to immediately evacuate the building.) For fuck's sakes, they removed columns for escalators, then cut into the remaining columns, then ADDED A STORY WITH POURED CONCRETE FLOORS *and* an air conditioning unit the building wasn't designed for. And then when the building started to fail, they just blocked off areas to hide it from customers because they didn't want to lose sales revenue.
      • Not even remotely related

        Failure to include a correctly functioning resonance damper [wikimedia.org] is still negligence.

        • Did you read the article? The resonance could only be felt on one very narrow range of floors. The whole building wasn't shaking, which is what tuned-mass and active dampers are designed for. They're for countering earthquakes, wind-induced vibrations, etc.
          • Did you read the article? The resonance could only be felt on one very narrow range of floors

            So, are you trying to imply that it wasn't a danger? Because otherwise you seem to be saying, "Oh well! Who could have expected a structural engineer to anticipate a problem like this!?"

            • Did you read the article? The resonance could only be felt on one very narrow range of floors

              So, are you trying to imply that it wasn't a danger? Because otherwise you seem to be saying, "Oh well! Who could have expected a structural engineer to anticipate a problem like this!?"

              Yes. That's precisely what he was saying: there's no reason to believe there was actually any danger. Sure, it was an unexpected issue the engineers probably never considered, but the point of the article is that it's been tested and is believed to be safe.

              The real question is, what are you trying to imply?

              • Sure, it was an unexpected issue the engineers probably never considered, but the point of the article is that it's been tested and is believed to be safe.

                Did you RTFA? The article doesn't say anything of the sort. It doesn't comment either way, but it certainly doesn't even imply "no big deal." What it does do is say that even some expert disagree with the current diagnosis.

                The real question is, what are you trying to imply?

                That having a stick up your ass about resonance is missing the forest for the trees. Bad engineering is bad engineering, no matter the form.

                • So, I'm no expert here, but is it REALLY possible to design a building which does not resonate at any frequency?

                  • Re:RTFA (Score:4, Informative)

                    by Jah-Wren Ryel (80510) on Tuesday July 19, 2011 @09:32PM (#36818392)

                    So, I'm no expert here, but is it REALLY possible to design a building which does not resonate at any frequency?

                    You need a way to dump the energy into some other form, there are multiple ways of doing that, I linked to one in an earlier post. You don't have to dump all of the energy, just enough to prevent it from becoming structurally dangerous within certain margins. I think it is entirely reasonable to expect a building to avoid shaking 19 floors because about 10 people are jumping around. It isn't like they are putting a whole lot of energy into the structure to begin with.

    • by bunratty (545641)
      The US does too [wikipedia.org].
    • by cusco (717999)
      I'm impressed. The building owner got a year in prison for every 70 dead. In the US he probably would have gotten a suspended sentence or house arrest.
  • by geekoid (135745)

    insult the scientists that are trying to determine the problem and get data.. scientist don't work out well in the gym! kek., where better then they are. kek
    .

    • Just the usual preemptive-defensive reaction of another code monkey that finally realized that his computer "science" 101 course didn't really make him a scientist. Nothing to see here, just part of the new anti-intellectual slashdot of this decade.
    • Re:yes (Score:4, Informative)

      by MiniMike (234881) on Tuesday July 19, 2011 @06:00PM (#36816778)

      OP here. The end of my submission, where I include that IAAS (scientist), was cut off, so I would like to state that I wasn't trying to convey a "where (sic) better than they are" attitude. I could have stated my intent with the last surviving sentence more clearly. While many scientists I see in the gym are in great shape, some of them are in quite poor shape and uncoordinated. The ones at that end of the spectrum are usually in the beginner group exercise classes. It is that group I was trying to reference in the post. The last sentence should have read 'some of the scientists'. Hope this clears it up.

  • The doom of resonant frequency.
    • by TheRaven64 (641858) on Tuesday July 19, 2011 @05:23PM (#36816386) Journal
      Which bridge? The Tacoma Narrows Bridge, that shook itself apart, is one famous example, but it's not the only one. The Millennium Bridge in London had a similar problem. If people walked across it at a normal walking pace, their footsteps were at the bridge's resonant frequency. Worse, when a bridge starts to resonate like that, people naturally start walking in sync with the vibrations, making it worse. It cost £5m to fix - over 25% of the original construction cost.
      • by Altus (1034)

        yea, its really more like the millennium bridge. The Tacoma Narrows bridge problem was caused by the cross wind if I recall correctly.

        • yea, its really more like the millennium bridge.

          Yes.

          The Tacoma Narrows bridge problem was caused by the cross wind if I recall correctly.

          And by a design of some windbreak structures on the sides of the bridge that caused the twisting motion of the bridge, once the resonance was being pumped up, to modulate the crosswind airflow over the bridge in a way that pumptd the resonance further.

          It was essentially a vibratory wind turbine. It failed when the wind down the narrows was finally high enough to pump ene

      • by sp0tter (1456139)
        appreciate the figures. I cannot help but wonder how exactly does one alter the resonance frequency of a structure? I take it is an expensive undertaking.
      • by dotbot (2030980)
        Interestingly, for the Millennium Bridge, it wasn't actually the frequency of people's footsteps that caused the problem. (This can be a problem when people step in time and some other London bridges have signs that troops should break time.) The main issue with the Millennium Bridge was that the resonance was lateral, i.e. side to side, which was not well known about, and there was positive feedback: small lateral movements, within normal limits, became amplified because the way people naturally correcte
  • Apparently we have learned nothing from Galloping Gertie [wikipedia.org]?

    No wait, some of us have. Mythbusters proved [wikipedia.org] that properly designed modern bridges aren't anywhere near as susceptible to forced resonance anymore.
    • I was going to post the same Wikipedia article, but then I read it and learned that the failure wasn't cause by resonance (resonance frequency of the bridge was ~1Hz, but the oscillations occurred at ~.2Hz). The Discovery channel taught me wrong but hey, at least I learned something new today.

      • Re:Whoops (Score:4, Informative)

        by HornWumpus (783565) on Tuesday July 19, 2011 @06:00PM (#36816776)

        Too bad you learned something wrong.

        Galloping Gertie was brought down by aeroelastic flutter, aka forced resonance. Aeroelastic flutter is more specific, but not a correction.

        Galloping Gertie was visibly resonant in its second harmonic, in torsion. Structures have more then one resonance frequency. All those frequencies have harmonics.

    • by Osgeld (1900440)

      Galloping Gertie was a wind problem, it acted as a wing

      • by Daetrin (576516)
        First, you and MozeeToby are both correct. However it's also true that Galloping Gertie was used for decades as an object lesson for the problems resonance can cause in large engineering works. Even though the attribution of the fault was (somewhat) incorrect, we still learned something from it that was entirely correct when applied appropriately, something that apparently _wasn't_ applied in this case.

        Second, and maybe i'm wrong here, but as best as i can understand from the complicated physics the probl
        • by EdIII (1114411)

          What I find absolutely amazing is that we can have conversations like this about frequencies and harmonics, elementary resonance, complicated resonance from multiple sources, etc. and yet we still cannot create a system where you understand the person taking your order for a simple burger and fries without having them repeat themselves and screaming into the loud speaker .

          • by c6gunner (950153)

            and yet we still cannot create a system where you understand the person taking your order for a simple burger and fries without having them repeat themselves and screaming into the loud speaker .

            Sure we can; it's called "don't go through the drive-through".

            I could name off at least 3 different ways to fix the problem you're bitching about, but nobody really cares enough to go to the expense of implementing them. The newer generations of smart-phones - with "swipe" payment and data-sharing abilities - open up some interesting possibilities, but it's still going to take time.

      • by Sulphur (1548251)

        Galloping Gertie was a wind problem, it acted as a wing

        If they had harnessed the wind, then it might have damped the bridge.

        In any event there was a cable intended to stop the problem, and it was broken.

  • Interesting. If this is true they were probably moving in sync, and accidentally matched the resonant frequency of the building. It was a similar problem with that wobbly bridge that collapsed shortly after completion, but that was resonating from the wind. Whats interesting is that they managed to do this from the 12th floor of the building. It must not have very good resonant properties. Luckily wind rarely buffets or changes at such a quick frequency, so they are safe from that, but I would really worr
  • Were these 17 people?

  • Chuck Norris once did a kung-fu workout, on January 17th, 1994 in Northridge, California.
    • by oldhack (1037484)
      I hear he's also a taekundo master, the korean kungfu. Coincidence? I think not..
  • by MetalliQaZ (539913) on Tuesday July 19, 2011 @05:31PM (#36816470)

    Scientists are bad at the gym? Is that a stereotype? Never heard that before. I know some marathon-running, rock-climbing scientists that would probably take issue with that.

    • by city (1189205)
      Surely your anecdotes will refute generations of unathletic nerdery... (braces for downmods...)
    • Gah it's one of those anti-stereotype people. You shouldn't reject humor, even mediocre or bad humor, under the grounds of playing at stereotypes. The thing with Stereotypes is only an idiot would think they are 100% accurate, but it's equally silly to not to note and laugh at things when they do tend to cover 60% or more of a particular race/profession etc... There's a few tigers that are rather friendly around humans, but it isn't insensitive to the creatures to run like hell if you see one, nor is it ins
    • by c6gunner (950153)

      Scientists are bad at the gym? Is that a stereotype? Never heard that before. I know some marathon-running, rock-climbing scientists that would probably take issue with that.

      Sure, and I know some slashdot readers who actually RTFA, but we're talking general trends here!

  • That's why (Score:2, Funny)

    by slapout (93640)

    That's why Chuck Norris and Jackie Chan don't usually workout together.

  • by Datamonstar (845886) on Tuesday July 19, 2011 @05:51PM (#36816666)
    Have they questioned this guy [suavv.com] yet?
  • ...with meat bodies?!??!!

  • Billy Blanks is no longer allowed in South Korea.

  • ... "Yo mama's so fat" jokes in 3 ... 2 ... (brace yourself) 1 ...

  • by Anonymous Coward

    There are many building codes in S. Korea and local officials want bribes to look the other way. Even if you build by the letter, they will find some technicality or make one up to delay the construction. Any delay costs lot of money so most developers just pay the bribe.

    Korea is a lovely country but sadly it is infected with corruption like most of Asia.

    P.S. I know this because my in-law is one of those corrupt official in S. Korea. She wasn't even embarrassed about it either.

  • Not the first time such things have happened:

    http://www.smh.com.au/lifestyle/wellbeing/zumba-class-has-office-all-shook-up-20110224-1b73p.html [smh.com.au]

    A Zumba class in a building only a block away from where I work caused noticeable movement in that building, so much so that some people were afraid for their safety. Of course, the building was up to code and engineers reported that nothing was wrong, but still, interesting...

  • all about how flimsy you can make your building that 17 small 150 pound males running around could topple that skyscraper down....serious architectural deficiency there!

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