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WTC Metal Fatigue. How Did Building 7 Fall?

  1. Jul 13, 2005 #1
    Building 7 was hit by no aircraft or debris. It had several small fires and amazingly collapsed in symmetrical fashion at free fall speeds.

    We saw in Madrid a building burn at intense levels for MANY hours but not collapse.

    Is there any scientific explanation for such a catastrophic structural failure in a largely steel building?

    I am concerned. Friends and family work in similar structures. It seems strange that I see little debate on such an important subject...a modern steel structure completely collapsing after a few small fires ignite.

    I have read the official reports. They summize they cannot explain the collapse.

    Does anyone know of any other reports that could shed some light on such an important subject? Does anyone here have a view on how steel could collapse in such a sudden, catastrophic manner?
  2. jcsd
  3. Jul 13, 2005 #2


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    Oh boy. Here we go AGAIN.

    That is your first error. WTC 7 got hit by quite a bit of debris by towers 1 and 2.

    So what does that have to do with WTC7? Are the two buildings even remotely similar in construction? Did it have working fire supression? WTC7 did not have working sprinklers due to a water main break. WTC7 also had critical structural members on floors 5 and 6 which were on fire. They also had the possibility of 20,000 gallons of diesel fuel feeding the fire.

    Have you read them? Did you understand them? If you are expecting answers with 100% certainty, you're not going to find one. Even the report I cite below recommends getting more data. Personally, going into a pile of rubble and determining how it fell is pretty amazing stuff. Unless you are in the position to do the same, I would suggest dropping the conspiracy theories until real proof is presented.

    I don't consider 7 hours on fire sudden.

    WTC 7 summary:
  4. Jul 13, 2005 #3
    Sorry I don't have a clue to how it collapsed the way it did, I've seen the video and it seriously looks like a controlled demolition, and I find that it's also strange that the 9/11 commision report did not even mention its collapse, or how it was possible.
  5. Jul 13, 2005 #4


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    I don't see what this has to do with metal fatigue, but anyway, this isn't something to be concerned about. If you really posted this thread out of concern over the possibility of other buildings collapsing on your friends, just remember, 7 hours is plenty of time to evacuate a building. Also, as Fred noted, the situation on 9/11 was highly unique.
  6. Jul 13, 2005 #5
    I have to disagree with Freds contention, (They also had the possibility of 20,000 gallons of diesel fuel feeding the fire.), who evidently hasn't seen the video that shows only two small fires before the collapse.
  7. Jul 13, 2005 #6


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    Two small fires? Are you kidding me? I suggest you look at the report I posted a link to. There were quite a lot of fires burning on multiple floors with photographs.
    I also recommend you look at page 5-14 which outlines where in the building the fuel tanks for the back up generator systems were located. Only two tanks were located below ground. The rest were inside the building.
  8. Jul 13, 2005 #7


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    One thing people tend to forget about this is that the damage/fires in this case would not be as visible from the outside as people tend to expect.

    Typically a fire is confined to a single floor and spreads to engulf the entire floor. That ends up looking like a "ring of fire" encircling the building. It takes a long, long time for such a fire to spread beyond the floor it starts on, but they are very impressive looking from the outside.

    With WTC7, a lot of the pictures we see are of the side of the building that appeared relatively undamaged, while most of the fire/damage stayed on the other side of the building.

    To some extent we really have to take the word of the firefighters who went in there and reported back that the building was in danger of collapse. They were inside. That almost makes the issue/resolution trivially self-evident: the fire fighters were afraid the fires would make it collapse - it collapsed - so the firefighters were probably right that it collapsed due to the fires.
  9. Jul 13, 2005 #8


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    I agree. The sad thing is that without 100% undeniable proof of what happened, interviews, photos and the like will always be questioned and fuel the conspiracy theorists.
  10. Jul 13, 2005 #9
    Wheres the link to this, and does it have links to your resource material. pg 5-20 and 5-21: According to fire service personnel, fires were initially seen to be present on non-contiguous floors on the south side of WTC7 at approximately floors 6,7,8,10,11 and 19. The presence of fire and smoke on lower floors is also confirmed by the early television news coverage of WTC7, which indicated light color smoke rising from the lower floors of WTC7.
  11. Jul 13, 2005 #10


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    The bottom of post 2. That's the official report on its collapse.
  12. Jul 13, 2005 #11
    Building 7

    G'Day Russ.

    I worked for many years in "Fire Assay"...that is melting stuff in 1300c firnaces to see what was in them.

    I also transfered into Shotfiring where I got to blow things up on a regular basis including packing plastic type explosive - "Power Gel" - around objects to blast them apart and make the way clear for large vehicles.

    You soon learn the power of explosives as you can make them cut like a knife through objects of any sought.

    Anyway...i watched that building fall. What cant be explained to me is it's symmetrical collapse. How could metal POSSIBLY fail in such a symmetrical fashion? I note that the central core went first as is evident by the video and the "penthous" failing first.

    I know what heat does Russ. I know that a few fires, which were only just visible, whether fueled by a bit of deisel or not, are EXTREMELY unlikely to "weaken" support core structures to that extent in THAT short a time.

    Large metal beams can dissapait heat easily. If it was that easy to "melt" or "weaken" metal to such a point then I guess we can dispense with the well insulated metal furnaces i used to use and the high pressure natural gas feed and just chuck some deisel on top of the samples I used to melt.

    Please keep your arrogant and paternalistic tone to yourself.

    You find the fact that finding out how such a large metal structure collapsed...is somehow a waste of time and bothersome?

    I guess you must work at NASA as they seem to have the same attitude when it comes to probing into the causes of things.

    I am interested in hearing from people involved in the metal trade, particularly those involved in fatuige testing metal materials...if they come here.

    I appreciate your input Russ but can you please bottle the paternalistic tone.

    I want to know how that building collapsed. We saw other buildings TRASHED by WTC debris which were kind enough to remain standing and indeed retain there structural integrity enough to be rebuilt.

    I know what the heat requirements are to weaken metal and join points.

    And as for your claim that the reports mentioned 5-6 floors had CRITICAL structural members which were on fire, this in NO way explains the symetrical and catastrophic collapse of WTC 7. In NO WAY does this explain it.

    In fact they cant explain it Russ. Thats the point. All your arguments are null and void as in the end the reports DO NOT claim to know the cause.

    "They" cannot help. Can anyone else here?
  13. Jul 13, 2005 #12
  14. Jul 13, 2005 #13
    Building 7 & Firefighter reports.

    Dear Russ,

    This is off point but it is one you have made with some certainty.

    You claim fire fighters in Building 7 reported that the fires were such that the building was in danger of collapsing.


    You seem to trust the opinion of firefighters.

    In that case we seem to have a problem of sorts with your logic.

    It is WELL reported and ON THE RECORD that firefighters in the towers reported small fires that would be easily contained and extinguished. It is also ON THE RECORD that not ONE firefighter believed there was ANY chance of those buildings collapsing. Minutes later the first of the Towers suffered a catastrophic collapse.

    Which will it be?

    Or will you simply be picking and choosing your line of thought to suit yourself?

    And by the way...i do not appreciate being accused of being a "whacky conspiricy theorist" because I WANT TO KNOW how those buildings collapsed. ESPECIALLY BUILDING 7.

    And why we're on the subject of fire fighters opinions, you are aware of the fact the the premiere firefighting magazine called the report..."a half baked farce".

    I demand answers. Thats why I'm here.

    And here I edit again...to question your logic...what exactly was burning in those buildings to make large steel girders buckle? To make bolts the size of my fist and weld joints split and crack? Carpet? Wooden furniture? Deisel?

    Diesel is a relatively LOW volatility fuel but if it were feeding those fires we would have seen a fire ball in short order...agreed? Or is there some other laws of the Universe you wish to postulate?

    As for Building 7 being PELTED by debris...please direct me to the photographs and video showing large scale structural damage to Building 7?

    I dont know what you rqualifacations are Russ but mine are pretty good. Especially the qualifacation as a free thinking human with an expansive frontal lobe able to spot "over intellectualized bulldust" when I see it.
    Last edited: Jul 14, 2005
  15. Jul 14, 2005 #14


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    It would appear that fires burned for 7 hrs - not exactly a short time. The center of the building has numerous elevators and stairwells, so those could provide some central cavity for fire propagation and perhaps air to feed the fire.

    I think it is also important to realize that prior to the event, there is apparently not record of a collapse of a steel building due to fire, so I doubt there is much research on the subject.

    Pages 5-15 and 5-16 discuss some issues related to fuel oil for emergency generators. At the time of the report some tanks had not been retrieved.

    page 5-23

    and -
    page 5-20.

    see then - section - 5.5.4 Sequence of WTC 7 Collapse page

    Presumably with weakened core structure, the building started to collapse, falling mass from above caused a chain reaction (similar to WTC 1 and 2) which caused collapse of lower floors. The collapse of the penthouses indicates loss of core integrity.

    Regarding -
    This seems inconclusive at best.

    Diesel fuel may have fed some of the fire, but it is not volatile, and it may have been released gradually. So it does not seem necessary to have a fireball.
  16. Jul 14, 2005 #15


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    why do people trivialize these things so much?

    Is there anyone who really thinks hte US government, with possibly 2 billion people watching on, would demolish a building in plane sight and lie?
  17. Jul 14, 2005 #16


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    I don't think the OP was asking or inferring that anyone intentionally brought down WTC 7 after the fact.

    The OP seems to ask how - given relatively small fires - the building could have collapsed so symmetrically. That is also what experienced structural engineers have asked, and probably many are still trying to understand what happened.

    Clearly the buildings in question experienced situations beyond design. And in fact, one will find that the 'normal' design process is often deficient in addressing beyond design situations, which are considered quite rare.

    I should have pointed out that the buckling of the building coincided with the longest members, and that is where one would expect it to fail - i.e. no surprise there.

    The other point - structural analysis, and particularly predictive analysis is very complex. There are very few who do it very well.
    Last edited: Jul 14, 2005
  18. Jul 14, 2005 #17


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    BORING!!!! Please tell us what your background is in the structural mechanics of buildings is. Please tell us that you have studied the layout of all of the support structure to that building. Please tell us that you have some professional credentials at all. I look at the moon and stars every night. I guess that means I have 30+ years experience as an astrophysicist or astronamer.

    Ok....you say you understand about how the central core of the building gave way first, but you don't understand how it happened symmetrically. Since you are using intuition and nothing else, I will too. Doesn't it seem intuitive that if the center of something gives that the remainder will give at the same time? To me it makes sense, but I am not a structural engineer.

    I think we've beaten this horse to death. If you consider 20,000+ gallons a bit of diesel, then ok. However, the report shows multiple pictures and eyewitness accounts of more than a just a few in number and burned for more than 7 hours. Please debate this further based on your video clip you keep mentioning. If this video is all you have to go on, your one leg is shaky to say the least.

    Do your furnaces help to disipate the load of an entire building? Please show me a free body diagram showing the forces on a building support and then the ones a furnace has to encounter. This is a complete apples and oranges comparisson.

    The only arrogance I see is people that come up with conspiracy theories based on zero experience in a field, with no feel for the magnitude of what happened and their own intuition that is baseless, but yet feel the need to question and arm chair quarterback the experts doing the actual work.

    That was not said anywhere. Please cite where anything remotely close to that was said. What was said was that the information is sketchy at best and that more work needs to be done.

    Resorting to emotional responses instead of the facts presented is not a way to make yourself seem credible.

    I just posted a link to the official report which was created by just such a group of people.

    You are not alone in wanting a 100% positive answer.

    So if one other building made it, then all of the others should have too?

    You've thrown down the gauntlet here. Please provide your data and reasoning behind this statement of "fact." Please come down from the mountain top and explain why all of the experts that were on site, that collected data and that know that building are wrong.

    They have provided the most probable causes. Theirs is an educated guess. That is understood. That does not make the argument void. The official release has data and eyewitnesses to back them up. What do you have?

    There are two DRASTIC things flawed with yours and other's line of reasoning:

    1) You have based all of your assumptions on seat of the pants guess work and a single video clip.

    2) WHY?!?!? Why would they deliberately destroy the building? You have no solid theory as to why they would do such a thing.
  19. Jul 14, 2005 #18


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    Fred covered most of it, but a few points:
    It wasn't quite symmetrical: the report discusses/shows a "kink" in the building indicating a failed structural member initiated the collapse. After the collapse begins, however, and except for that little "kink", symmetrically is the only way such a building can collapse.
    Ok.... well, engineers and firefighters disagree with you. It is, of course, your prerogative to form your own conclusions, but despite the fact that I'm a mechanical engineer, I don't consider myself qualified to come up with my own: I'll cede to the real experts - the ones who wrote the report and the ones who decided to abbandon the firefighting efforts.
    I studied metal fatigue in materials engineering. I asked before: what does any of this have to do with fatigue? A building is a static structure.
    That's a distortion. They cannot be 100% certain of the cause, but they can be pretty sure - perhaps 90% certain on most issues. When you say "do not claim to know the cause" that implies that they have no idea. That isn't the case at all.
  20. Jul 14, 2005 #19


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    AFAIK, no firefighers were able to get to the floors with fires on them, so its pretty obvious that they wouldn't have had any fires to report. So there isn't any contradiction there.
  21. Jul 14, 2005 #20


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    Regarding my tone, the only thing I posted with any tone to it was this:
    That is intended to imply that your concern, would be a very unique one. I've never seen it before. Yes, it also implies that I question whether the concern is real, but given its unusual nature, that's a fair question.

    You threw a comment about being called a "whacky conspiracy theorist" at me, but I never used the term. Fred made some offhand remarks about it, perhaps your replies were meant for him - since you didn't quote anyone or respond directly to any specific arguments made, its impossible to tell.

    Regarding Fred's tone, there are, almost exclusively, two types of people who bring up the mode of collapse of the buildings on 9/11: Those who just don't know and are asking how it happened (those types are rare and they've never even heard of WTC7). And those who are pushing conspiracy theories. The tone of your first post looks like the typical 'I'm-really-only-looking-for-answers' first post bait of a conspiracy theorist looking for a fight. The fact that you so quickly jumped to over-the-top hostility,that you are utterly dismissive of the official reports (without citing specific parts), that you "demand answers" but refuse to accept the ones given, and that you didn't respond to specific arguments of others also fits that mold.

    So here's the deal: either change your tone and the approach to your arguments or this thread won't be allowed to continue.
    Last edited: Jul 14, 2005
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