Mendel
Senior Member.
Is this different in the CD scenario? How?
Would the WTC Twin Towers have collapsed from fire alone, without plane impact?
- Thread starter econ41
- Start date
The essential thing about "impaling" is that it lets the columns do some of the work. You're right that the floor connections will still be strained, but a lot of the mass will now stop moving, caught on the columns, taking a lot of the energy out of the system. The top block will be crushed up (on one side) while the bottom section is crushed down (on the other).
This actually happens in Mick's wooden model.
While the floor connections were not built to handle all that mass, the columns, of course, were. So you'd expect the process to stop when the columns have skewered enough floor pans (thus carrying their weight).
I'm not sure I understand the question. In the CD scenario, as I understand it, a "timed series of charges" goes off down through the building "ahead of the collapse front" severing the columns.
That is, the columns are not destroyed by "verinage". The (induced) column failures are the cause, not an effect, of the collapses.
econ41
Senior Member
Except it did not happen as shown by the video record.
econ41
Senior Member
That was one of the early truther claims. In fact the David Chandler version of it in a video with David's voice-over commentary was the first of his claims that I rebutted about 2009-10. If I had realised that these long disproven claims would be recycled a decade later - I would have considered keeping records.
Vivid imagination faces problems when the recorded video evidence in the public domain is clear. Now if we could eliminate the video record....
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econ41
Senior Member
So you disagree with this Nov 2007 explanation:
Think it through a bit further. The collapse in simplest overview needs:
(a) Something to start the Top Block falling; and
(b) a mechanism to keep it progressing.
AND - IF CD was needed - THEN there had to be CD at the initiation stage.
BUT the laws of physics apply whether or not there was CD. (Something that a lot of truthers forget.)
So gravity could not avoid causing damage - on a component by component basis. IF "Beam 264" had been cut by explosives - gravity could ignore it. But if it had not been cut by explosivs and it needed to be cut for collpase to continue - gravity would have to do the dirty deed.
All interesting musing from which some conclusions emerge:
Since there was no need for explosive help any CD actually performed was redundant. So the evil terrorists or "inside jobbers" who did the deed would be very disappointed. Having performed a totally unnecessary CD and left ZERO evidence of it - they couldn't brag about their success.
Imagine the CV when going for the next job of "Senior Experienced Terrorist" or "Supervisor of Inside Jobs" and the CV says "Perfomed the most succesful CD ever and it had ZERO effect because it wasn't needed"...
I agree with @Henkka that what you're doing here is begging the question. It is precisely because it did not happen that way that truthers propose demolition ... and it's also, of course, the reason that I'm confused. If the buildings had remained standing or only partially collapsed I'd be less confused and the truthers wouldn't have been suspicious.
Okay, but you would think experts in this field would be extremely interested in having the correct explanation be reflected in the mainstream, no? Like with any other scientific topic, I feel like I can pretty safely trust that the mainstream explanation presented on sites like Wikipedia is broadly correct. For example, why the Tacoma bridge collapsed or something like that. But in order to truly understand the WTC collapses, I should ignore what is said in the mainstream, and instead log onto Metabunk.com and ask users econ41 and Gamolon. That's a bit silly.
Yeah, sorry about that... This is how you explained it to deirdre:
Correct me if I'm wrong, but these trusses were designed to carry the weight of all the stuff put on that floor, like the furniture, the people etc, right? So they were like a single shelf on a bookshelf, designed to carry a number of books but not some crazy amount of weight. The entire mass of one of the upper blocks would easily exceed that I'm thinking, so the floor would fail at some point as you kept increasing the mass.
I think "disagree" is the wrong word. ROOSD doesn't make sense to me. I have explained a number of times what I would need to get my mind fully around it. (Load-path diagrams and math.) And you have not obliged. Since you are, indeed, not obligated to do anything, that's where we're at.So you disagree with this Nov 2007 explanation:
In any case, I usually don't disagree with ideas I don't understand.
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FatPhil
Senior Member.
Specifically, many of the tallest modern buildings have tuned mass dampers to counter it.
Source: https://www.youtube.com/watch?v=f1U4SAgy60c
benthamitemetric
Senior Member
Yes, that's right. Do you understand that this is what NIST's simple calculation demonstrates?
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Gamolon
Active Member
I'm going to ask you the same questions I asked Henkka upthread.
Why does your logic/understanding above fail in the video below? Explain why the collapse is not arrested after three floors/levels. Why is there no deceleration of the top section when it impacts the lower section?
Gamolon
Active Member
Gamolon
Active Member
Can you explain what you mean when you say the "mass dissipating"?
In Mick's model the structure is tied together only by the floor connections. It's easy to see why those connections fail after he shifts the top section. And it's easy to see why that process is unstoppable in his model.
I can't believe that the WTC was built that way, i.e., to be held together exclusively by the floor connections. So there's just a lot of the WTC structure that is not represented in Mick's model. I believe those elements could have played a role in slowing the collapse.
I have yet to see (and I've tried to build) a model that incorporates them and collapses. But it must be possible.
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Yes, falling off to the sides or down through the empty spaces (shafts) of the cores.
benthamitemetric
Senior Member
Where your thought experiment fails the sniff test is in another of NIST's very conservative assumptions: They show the mass of the top block's floor systems alone (ignoring the mass of the support columns in the top block) is enough to overload each lower floor system. So once the collapse is underway, for it not to propagate you would need the portion of the falling mass that is comprised only of floor systems to lose more mass per floor sheared that it gains by the accretion of the sheared floor. That is beyond unrealistic. And, again, we're ignoring here the momentum gained by the falling mass as it passes from floor to successive floor. This isn't even a close call and I hope you're beginning to see why.
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Gamolon
Active Member
Are you saying that if Mick's model had all the pieces "tied together", the collapse would then arrest after three floors?
Gamolon
Active Member
Based on your comment above, you understand how the debris from above could overload a floor and shear it from the perimeter and core columns? Is this correct?
I am just talking about the floor area around the core and inside the perimeter façade at this point.
Adding econ's picture below as the mechanism for this failed floor.
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I think it's important to emphasize that I understand all of these things. That is, I understand that this is the theory NIST has proposed and how that mechanism is supposed to have worked. What I don't understand is why a building would be made this way. It seems like arranging dominoes in that video @Mendel has been emphasising, where small causes can have enormous consequences. Or, indeed, like building a bookcase (let alone a skyscraper) in that rickety way Mick did.
deirdre
Senior Member.
what sides? there is an outer wall.
i'm still lost on this bit of your explanation.
what i picture, and excuse the analogy:
Jack is the floor we walk on and the trusses/joists beneath the floor.
Jill is the core and the outer mesh walls.
Jack fell down and broke his crown. He is rolling down the hill.
Jill is still on top of the hill watching. Eventually as her body shakes from laughing, she looses her stablity and then comes tumbling AFTER.
(i could be wrong, but that's how i've always seen it. so i dont get how stuff is pouring off the sides or down the core because Jill doesnt come tumbling down until later)
Gamolon
Active Member
It wasn't "made that way".
It encountered an extreme circumstance. That's like saying the Titanic was made to sink from hitting an iceberg.
deirdre
Senior Member.
that i can relate to that. that's why i would never go in the Twins, (now that i see how they were built) and i will never walk over one of those glass bridges or swim in one of those roof top pools.
add^ or be in the building with a rooftop pool that could come crashing down on my head
Gamolon
Active Member
I think Thomas B is saying that he can see debris piling up and failing the first floor, but the debris pile lessens due to portions of it falling off as it progresses downward until there is not enough debris to fail the remaining floors.
I've talked a bit about it with Mick on another thread but we didn't really get anywhere. The model would have to be very different. It would need to have a basic column structure that would stand up in three dimensional space under pretty serious lateral loads without the floors in place. (Like the "box" that the engineers in the video @Henkka posted on this thread talked about.)
Mick (and others here) don't think that's how the WTC towers worked. I haven't yet convinced myself they're right about that. To the extent that I can do the math, both the shells and the cores seem well beyond any danger of Euler self-buckling without lateral bracing from the floors. (Also, remember that the floors brace the perimeter against the cores and the cores against the perimeter.)
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benthamitemetric
Senior Member
Well, I don't think a reading of your comments in this thread demonstrates that you do understand why the buildings as designed collapsed as they did. In fact, you are repeatedly contesting that the buildings as designed could collapse as they did (without some secret extra help from some sort of unspecified controlled demolition device). As I've shown, however, it's not even a close call that the building as designed was doomed to collapse as it did once the initial collapses occurred.
It would be different if you were arguing that the towers should have been built a different way to be more resistant to collapse, but that is not what you have been arguing. So we are still stuck on why you think the towers, as they were actually built, would arrest a collapse when we can easily see the forces involved here would overwhelm any floor.
And don't think you can just deflect and hide from my last point with this throwaway about "understanding it". If you disagree with it, then state why with specificity. If not, then--congratulations--you finally understand why the collapses could not be arrested by the lower floors and why the controlled demolition theories about the towers are absolute nonsense.
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Gamolon
Active Member
Why without the floors in place? That's not how the the towers were design.
Gamolon
Active Member
You didn't answer the question. If Mick's model had everything tied together, would it arrest after three floors?
Like I say, that was the sticking point when I talked to Mick about it. I don't have new arguments and I understand the old ones. No need to go through that again.
Yes.
I think the middle ground here is that I think it should have been a bit more of a scandal that they collapsed. If it had been presented as the result of a serious design flaw right from the beginning, I'd be more comfortable with it.
deirdre
Senior Member.
it wasnt a serious design flaw. like that one engineer said, noone imagined a terrorist purposefully flying a plane into the building at full speed.
just like noone imagined Adam Lanza would shoot out a window int he front of the elementary school and murder a bunch of 7 year olds.
benthamitemetric
Senior Member
Do you understand now that there was no conceivable way for the lower floors as designed and built to arrest the collapses once they began?
Like I say, I've always understood how the argument (in, e.g., NISTFAQ#18) works.
benthamitemetric
Senior Member
Stop deflecting. That's not what I asked: Do you understand now that there was no conceivable way for the lower floors as designed and built to arrest the collapses once they began?
Gamolon
Active Member
So what exactly wasn't tied together/connected in Mick's model in that video?
I guess I just don't understand this emphasis on the floor trusses, as if they were what was holding up the building. In my mind, the entire weight of the upper block wouldn't be applied to the floor below, because the core columns would be providing resistance. It reminds me of this 3D animation that I believe was presented in a 2002 documentary purporting to explain the collapses. They animated the floors "pancaking", but just left the core standing there, strangely:
The trusses had no vertical support below, and were just designed to hold a thin layer of concrete, and then furniture and people on top of that. So I don't find it surprising that you can do a bit of math showing that if six or more floors came down on one floor, it would fail. But in order for those floors to come down at all, wouldn't the core have to fail first?
I wanted to check what exactly NIST said about the core in their FAQ, and there's not much... Here for example is question #11, which purports to be a quick explainer on why the building collapsed:
It does talk about "columns" in general, but does not explicitly talk about the core at all, focusing instead on the trusses pulling on the perimeter columns. But there's also question #21:
Okay, so they seem to be saying the core columns were "yielding and buckling" from the heat. But even if that were happening, it would only be at the impact zone. Immediately below that, the core columns were stone cold and good as new. So if the core columns yielded at the impact zone, I would maybe expect the upper block of the South Tower to start tipping over, not come straight down through the undamaged structure.
I'm also a bit lost on how the core columns get so hot anyway... NIST says there the fires were around 1,000 degrees Celsius, and when steel gets that hot, its strength reduces to about 10 percent of its room temperature value. But just because you have 1,000 degree fires going on in the vicinity of steel columns, that does not mean the columns themselves become 1,000 degrees hot. Google tells me a campfire is about 900 degrees Celsius, but everyone knows you can hold your hand quite close to a campfire without your hand also becoming 900 degrees. The core columns were in the... well, core, and the fires were mostly in the office spaces, ie outside the core. And all of these processes would be so uneven... Some columns would be closer to the fires than others, some would have more of their fire proofing intact, and so on. So I don't think that all 47 core columns could be evenly heated, and the ones in the middle likely wouldn't heat up much at all.
This became pretty longwinded, but I guess to summarize, you and NIST both seem particularly focused on the floor trusses. Whereas for me, it's the core that seems practically indestructible, and that's what is giving me a hard time understanding how the observed collapse could happen without "assistance".
If you're looking for me to concede some kind of point I think you'll have to give me some time. I still don't understand (to my own satisfaction) how the buildings collapsed.
Efftup
Senior Member.
Isn't this the entire point of this thread though? The OP question is whether it would collapse JUST from the fire (if you could magic the fuel into the those floors) without the plane impact. I always assumed that the damage from the airliner was important as it caused beams to buckle and therefore the loads are not distributed as designed even before fire further weakened the structure. ( I am also surpsrised as this is the first time I have heard anyone calculating a 707 at 600mph hitting the WTC. I have previously seen Robertson's calculations of 180mph and that is a HUGE difference)
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