NIST Releases Updated FAQ's on WTC Collapse

Originally posted by MikeVet
1- oh, i'm sure about it. but, now i understand your confusion. you think that a global collapse would be initiated by a floor falling. This is incorrect. as i stated before, but you decided to edit out, the floors sagging/failing/pulling the exterior columns out of vertical alignment would only make the exterior columns more prone to buckle, which lessens steel's ability to absorb compression loads.

Ok, but this doesn't have anything to do with (a) dynamic (impact) loading of the floors, or (b) floor connections failing. Both of these are required by "traditional theory" to progressive the global collapse downward.

since it must be agreed upon that the exterior columns supported some of the vertical loads - around 50%?

Around that much but the higher perimeter columns also had much greater FoS ratings than 2.

a global collapse would be initiated when the load capacity of the columns -both core and exterior- were exceeded, and at the point of failure, the entire mass above would fall as one onto the mass below.

That is incorrect. Floors may fall, theoretically, if you want to generalize and be vague and not realistic. The columns would not telescope into themselves. Nor would they just rip apart. Buckling is buckling, and that's only for the perimeter columns theoretically. Remember none of this was ever proven.

we agree that a global collapse couldn't be initiated by a single floor falling onto a floor below, so that avenue of discussion is a pointless waste of bandwidth, agreed?

It depends on whether you want that dynamic loading or not. The buckling columns would not experience impact loading, nor loading of so many more floors than they were built for, because the columns held ALL of the floors above them on a day to day basis at just the design strength.

2- simple answer again here, even though i suspect you're looking for something much more complicated/conspiracy friendly. The core structure would "go" when their load bearing capacity was exceeded

But how do you define "go"? Does "go" mean they just start moving downwards somehow? How does it move downwards? Do you know what the formal definitions of failures in steel structures are? Like buckling, etc.? What kind of failure would be a failure that's just "downward"? It doesn't exist. There is resistance if you try to do that, MASSIVE resistance, from the moment of inertia of the entire lower column and all of its bracing and connections to the rest of the structure. That stuff doesn't just move on a whim like you think a single floor would.

3- actually the fires, if we accept your 15% calc, would only have to do 233% of the weakening that the planes did, not 400%. i'll ask again, do you have any idea, since i see your an engineering student, what a typical safety factor might be? i'd assume you have sources..... again, structural docs would be nice.

The only source I can offer is from one of the engineering teams in the 1960s suggesting the perimeter columns of the upper floors had FoS ratings of 20.

As far as this:

3- actually the fires, if we accept your 15% calc, would only have to do 233% of the weakening that the planes did

I said >15%. The real numbers are like 11% and 13% for the perimeter columns on those floors according to FEMA, and NIST did core modeling and came up with something like 7-8 core columns severed max, and this was even after changing Flight 175's impact angle.

did i interpret it right and the connections are 11x as strong as necessary?

How would I know, if I don't have the structural documents?

5- so then by your reasoning, if i give the angles, then we can agree that the building didn't collapse symmetrically?

The angles would be like 5 degrees and I would ignore you because any discerning person familiar with anything related to engineering knows how small of a margin of error 5/180 or 5/90 is. 10% is considered a reasonable tolerance for most purposes.

Really anyone with EYES can look at WTC1 fall and see that it happens evenly, that the roof line drops pretty flat the whole way across, there is no tilting or asymmetrical loading. It's as if everything were pulled at the same instant. It's really pathetic when such an obvious fact can't be grasped, and someone tries to cloud it by turning it into semantics. There is no amount of explaining you can do to explain this to me, because I already understand it simply by looking at it. When everything falls evenly, at the same time, that means, guess what?, it must have failed at the same time. To within a very small difference, such that you can hardly even tell, if you can tell at all.

[edit on 6-1-2008 by bsbray11]

Actually, if the core buckled, it would mean the supports were bent. It would depend on which way each and every core support was buckled. Inward? Outward? Sideways? Some still rigidly vertical? How far and in which direction on each for those not still rigidly vertical?

The floor that buckles may leave the top portion still attached to the building, in one direction or another, and the rest of the building may well be standing vertically reaching to the sky as always.

The following is a building dropping into its own footprint not exactly, but not unlike, WTC 7:

www.youtube.com...

This is very similar to WTC 1 and 2 without as much height, weight, and mass:

www.youtube.com...

The following is a video of a controlled demolition cutting it only from the bottom. Please note the very obvious pancake effect as it falls away from the camera:

www.youtube.com...

This one is just for levity:

www.youtube.com...

Originally posted by bsbray11

Ok, but this doesn't have anything to do with (a) dynamic (impact) loading of the floors, or (b) floor connections failing. Both of these are required by "traditional theory" to progressive the global collapse downward.

Around that much but the higher perimeter columns also had much greater FoS ratings than 2.

That is incorrect. Floors may fall, theoretically, if you want to generalize and be vague and not realistic. The columns would not telescope into themselves. Nor would they just rip apart. Buckling is buckling, and that's only for the perimeter columns theoretically. Remember none of this was ever proven.

It depends on whether you want that dynamic loading or not. The buckling columns would not experience impact loading, nor loading of so many more floors than they were built for, because the columns held ALL of the floors above them on a day to day basis at just the design strength.

But how do you define "go"? Does "go" mean they just start moving downwards somehow? How does it move downwards? Do you know what the formal definitions of failures in steel structures are? Like buckling, etc.? What kind of failure would be a failure that's just "downward"? It doesn't exist. There is resistance if you try to do that, MASSIVE resistance, from the moment of inertia of the entire lower column and all of its bracing and connections to the rest of the structure. That stuff doesn't just move on a whim like you think a single floor would.

The only source I can offer is from one of the engineering teams in the 1960s suggesting the perimeter columns of the upper floors had FoS ratings of 20.

I said >15%. The real numbers are like 11% and 13% for the perimeter columns on those floors according to FEMA, and NIST did core modeling and came up with something like 7-8 core columns severed max, and this was even after changing Flight 175's impact angle.

How would I know, if I don't have the structural documents?

The angles would be like 5 degrees and I would ignore you because any discerning person familiar with anything related to engineering knows how small of a margin of error 5/180 or 5/90 is. 10% is considered a reasonable tolerance for most purposes.

Really anyone with EYES can look at WTC1 fall and see that it happens evenly, that the roof line drops pretty flat the whole way across, there is no tilting or asymmetrical loading. It's as if everything were pulled at the same instant. It's really pathetic when such an obvious fact can't be grasped, and someone tries to cloud it by turning it into semantics. There is no amount of explaining you can do to explain this to me, because I already understand it simply by looking at it. When everything falls evenly, at the same time, that means, guess what?, it must have failed at the same time. To within a very small difference, such that you can hardly even tell, if you can tell at all.

1- FEMA did envision a collapse using the floors as the reason... etc. Is this what you're quoting? Because I'm going by what NIST says. This must be the basis of our inability to communicate. I would admit that FEMA's hypothesis to be wrong, so can we move on to a discussion about NIST's explanations about global collapse - core creep, transferring of loads to exterior columns, etc?

2- I take it FoS is an engineering term to quantify "overengineering"?

3- again with telescoping. I thought we agreed that columns would bend , buckle, and break? Buckling of the exterior columns was SEEN, so I think this is therefore proven. The core columns are indeed assumed, but I think this is logical. I think we agree that the core columns, regardless of their bracing, would buckle at some undefined point. So what is incorrect? that a global collapse would involve columns b, b, and b'ing? How else could it be described then? We agree that floors failing wouldn't be called a global collapse, neither would they be the cause of it. So what else is left?

4- So loading remain almost the same, even if a floor stripped off. i agree, and this why I've been saying it's a pointless discussion. All the floors above would remain attached and the load would be transferred down. So if the load capacity was weakened enough, the columns would fail.

5- "Go" was your term. How do you define it? I still don't see your fascination with the floors. No, I don't know the formal definitions, I explained that I'm just a layman here. A downward failure would need a combo of things, the way I imagine it. You'd need buckling, followed by bending, plastic deformation, inelastic deformation and a whole variety of things going on. Basically, in layman's terms, they'd fold up locally, like perhaps over a span of a floor or 2, in the area that would have presumably recieved impact damage/bracing removed by the planes. Folding would shorten them. Shorten them just a little and the body above begins to move downward with such momentum that it can't be stopped. Yes, there's MASSIVE resistance, but there's an even (LOL) MASSIVER amount of momentum to be halted. I don't think the rest of the structure below would have ANY effect at the point of global failure. Only the strength of the columns would be in play at that moment.

6- ok so we don't have the docs. that's why I asked you if you know what a typical "safety factor" would be.

7-I disagree with 7-8 max severed. Perhaps max on 1 floor, but when all floors are taken into account, the cummulative number is higher. And there were more that were damaged, so maybe your 15% estimate is too low? Meaning that fire would have to do less weakening.

8- Huh? But you quoted the updated NIST report in CO's thread on the new FAQ sheet. I see that you're not trusting anything NIST says then. Ok.

9- Remind me to not go into any building you design if you think 10 degrees is of no consequence !!!!! But since I see you already know the angles, why did you ask me to provide them? Totally unnecessary, IMHO.

10- yes we agree that it failed at the same time. This is the nature of a global collapse, it's not semantics, as you claim. Without a global collapse, it would NOT have fallen at all. And yes, the roof remains inline at the onset of its fall. I would expect this. If I envision setting a broom in a pipe, and then taking a sword to the pole, the bristle portion doesn't fall apart.

Originally posted by MikeVet
Because I'm going by what NIST says. This must be the basis of our inability to communicate.

NIST did not offer any kind of explanation as to how everything failed so quickly, or even as to how the global collapse progressed so many floors. They even admit this themselves. Their only goal was to investigate what initiated the collapses, ie, in a very legal and formal kind of sense of the word, what caused the collapses (which is the vague wording Congress must have used). I'm not sure what prompts them to speculate further, since they never actually did any further investigation. (Not really; I know why they do it: they're just a mouthpiece.)

3- again with telescoping. I thought we agreed that columns would bend , buckle, and break?

No, we didn't. I said those are legitimate forms of failure. Not just "straight down motion." I never said any of those things had any reason to occur.

I think we agree that the core columns, regardless of their bracing, would buckle at some undefined point. So what is incorrect? that a global collapse would involve columns b, b, and b'ing? How else could it be described then? We agree that floors failing wouldn't be called a global collapse, neither would they be the cause of it. So what else is left?

You keep dancing around a real theory for global collapse as you see it, so why don't you just come out with it? How did the floor failures happen, how did the column failures happen, and how did they relate? Which came first? Fill me in on the details.

A downward failure would need a combo of things, the way I imagine it. You'd need buckling, followed by bending, plastic deformation, inelastic deformation and a whole variety of things going on.

I have to honestly say I can't tell what you're thinking and I know what all of those mean. Pretty much all the same thing in different flavors. And heat causes expansion in steel (which causes deformations) very slowly and with heat constantly applied. What would cause an immediate failure as you see when the towers suddenly fail, would be more along the lines of a shearing type failure from dynamic loading. How the first floor managed to all drop at once just can't be explained by thermodynamics in my opinion. There is not enough time to heat and cool the steel so many times that it bends the number of times you must be imaging, if that's what you're imaging, because I really can't tell.

7-I disagree with 7-8 max severed. Perhaps max on 1 floor, but when all floors are taken into account, the cummulative number is higher. And there were more that were damaged, so maybe your 15% estimate is too low? Meaning that fire would have to do less weakening.

Ok, let me see. Am I going to listen to you, just say that you disagree with those numbers, or am I going to go with NIST, which actually modeled it with computer software to the most severe conditions they could?

9- Remind me to not go into any building you design if you think 10 degrees is of no consequence !!!!!

In demolishing a building.

Watch demolitions and see how perfectly vertical they are. Even the ones designed to be vertical aren't. They're off by certain percentages probably around 10% or less of what was intended.

But since I see you already know the angles, why did you ask me to provide them? Totally unnecessary, IMHO.

Because they're insignificant. WTC1 fell symmetrically. Disputing that is splitting hairs and the angles show it. Can we not step back, and just look at what freaking direction the building just up and starts moving in?

This is the nature of a global collapse, it's not semantics, as you claim.

It IS semantics, simply because you think that stating the term "global collapse" is proof of its existence. The word "global collapse" doesn't mean any actual theory it represents makes any sense, does it? Just like any other theory also has its own name, but that doesn't mean anything.

I want to know how everything (ie all the truss connections) failed simultaneously. That doesn't mean telling me what "global collapse" is supposed to mean. It means telling me where the hell the idea came from, what the thought process was behind it, or if there really was one.

[edit on 8-1-2008 by bsbray11]