WTC: Rate of Fall (rate of crush)

[Mick West]

Here's another illustration of how much the centre of mass shifted in the South Tower at the onset of destruction. Certainly more than 1/100th the width of the building.

I does not appear to move at all. If anything the top of the building rotates around the center of mass, which moves only straight down. Remember the center of mass is half way up the "block", not in the middle of the bottom.

 

[Jazzy]

Here's another illustration of how much the centre of mass shifted in the South Tower at the onset of destruction. Certainly more than 1/100th the width of the building.

You aren't showing the "center of mass". You don't know where that is, because you cannot know where disconnections took place. It seemed to me to be the furthest point from where the shots were taken. But I could be wrong.

What you meant was "where I reckon the center of mass is". And I reckon - so what? What does it matter where you reckon that "center of mass" was, and why do you think that's in any way relevant?

 

[jomper]

I does not appear to move at all.

Are you saying you actually can't see the top section of the South Tower moving significantly off the perpendicular at the onset of destruction? I'd estimate it's at least fifteen degrees -- with reference to the animation I posted earlier -- but if you're saying you can see only rotation within the perpendicular described by the tower and no lateral movement, perhaps you could clarify that.

 

[jomper]

What does it matter where you reckon that "center of mass" was

I guess it matters about as much as wherever you think it was.

I'm sorry Jazzy, but your repeated failure to answer this simple question (in a thread Mick has now locked) has undermined my confidence in you as a person worth having a discussion with.

 

[Pete Tar]

The lines the you overlayed are accurate for the top, but not for the bottom as it falls. The right bottom edge of the shape is obscured by smoke, so it can't be determined that the shape you overlayed is accurate and projects out to the degree you suggest at that point.

 

[jomper]

I don't claim authorship of that animation. However, the degree of lateral movement of the top section of the South Tower at the initiation of destruction is relevant to the degree of "crush" it can be said to have exerted on the structure below. Here is another example. Although the top section of the building is falling towards the camera, the foreshortening perspective makes it clear just how much lateral movement there was.

 

[Mick West]

I don't claim authorship of that animation. However, the degree of lateral movement of the top section of the South Tower at the initiation of destruction is relevant to the degree of "crush" it can be said to have exerted on the structure below. Here is another example. Although the top section of the building is falling towards the camera, the foreshortening perspective makes it clear just how much lateral movement there was.

No, it does not.

If the block rotates about the center of mass, then the effect is exactly the same. The center of mass (center of gravity) does not need to move much at all laterally, just down.

 

[jomper]

If it does. That's why I asked you the question at post 603 -- can I ask how you'd answer that?

 

[jomper]

Here's yet another angle.

 

[Pete Tar]

Is the implication the top part cannot have initiated the rest of the collapse because it was 'off-center' too much?
So what started the collapse?

 

[Mick West]

If it does. That's why I asked you the question at post 603 -- can I ask how you'd answer that?

Are you saying you actually can't see the top section of the South Tower moving significantly off the perpendicular at the onset of destruction? I'd estimate it's at least fifteen degrees -- with reference to the animation I posted earlier -- but if you're saying you can see only rotation within the perpendicular described by the tower and no lateral movement, perhaps you could clarify that.

Obviously it is rotating. I'm just saying the center of mass if not moving much laterally:

 

[Mick West]

And maybe you could explain what you think this all means?

 

[MikeC]

just by way of possibly interesting, possibly not, a hotel in Christchurch New Zealand that was damaged in the earthquakes of a couple of years ago collapsed this week while being demolished - but it wasn't supposed to - the workers had to run for it and no-one was injured.

It was being demolished from the top when 1 section suddenly totally collapsed, and then the adjacent sections also collapsed. I am not sure whether it is steel or concrete construction tho - haven't been able to find that out - I suspect reinforced concrete because that was the common material when it was built.

Story and video

 

[jomper]

Obviously it is rotating. I'm just saying the center of mass if not moving much laterally:

I have no objection to the point you are making with this diagram -- but the point I was making is that there was significant lateral movement in the upper section of the South Tower in the early onset of destruction: considerably more than 1/100th of the width of the building, which was your initial (albeit relatively ad hoc) suggestion. That's the point of the animated gif I posted, represented at smaller scale by the "tipping" behaviour of the model posted at 590. Clearly I am suggesting that this lateral movement would not have been arrested in the descent of the upper section and should increasingly have moved the centre of mass of the falling block off the centre of the structure below as it fell.



On a side note I find your diagram -- while obviously not intended to take account of the increasing strength of the structure as one proceeds "down" the building -- does represent how remarkable it is that the falling section can be said to have maintained enough integrity to destroy the increasingly strong structure below without itself being destroyed in the process before it reached the ground, slowing, stopping, or "falling off", as appears to begin to happen here. One can sympathise with those who feel this is in violation of Newton's Third Law, wouldn't you agree?

It is lamentable and peculiar that NIST and others did not even attempt to model this supposed dynamic effect of momentum, which is after all the most shocking aspect of the attack on the Towers, even in highly simplified terms comparable to the diagram you have made. I imagine this problem will be addressed in the future as modelling technology such as this becomes increasingly advanced and affordable, married to increasingly powerful home computers that can account for scale and the square cube law.

 

[Jazzy]

your repeated failure to answer this simple question (in a thread Mick has now locked) has undermined

I answered it. Repeatedly. I'm sad you feel your confidence is undermined.

Clearly I am suggesting that this lateral movement would not have been arrested

Now, you are. But there is no real lateral movement. There is a rotational movement brought about by one side of the tower failing first. This was resisted by the floors sliding down the internal columns, which although they had structurally failed, were still intact.

how remarkable it is that the falling section can be said to have maintained enough integrity to destroy the increasingly strong structure below without itself being destroyed in the process before it reached the ground

I don't remember much intact tower top lying about Gzero.

slowing, stopping

We have covered how a reduction in acceleration doesn't mean slowing down.

or "falling off", as appears to begin to happen here

Column failure by buckling doesn't mean they snap at all. The tower top was falling down its intact internal column stack. Collisions with the core would have occurred much more frequently with the cross-members than the columns themselves.

One can sympathise with those who feel this is in violation of Newton's Third Law, wouldn't you agree?

No.

It is lamentable and peculiar that NIST and others did not even attempt to model this supposed dynamic effect of momentum

It wasn't part of their brief to explore the natural consequences of the collapse. Just what brought the collapse about.

which is after all the most shocking aspect of the attack on the Towers

Pardon me?

I imagine this problem will be addressed in the future as modelling technology such as this becomes increasingly advanced and affordable, married to increasingly powerful home computers that can account for scale and the square cube law.

I look forward to your research in this field.
.

 

[Jazzy]

Presumably you follow Bazant et al in believing the top section crushed itself "up" once it had crushed everything below it.

Nothing to do with Bazant. I don't remember much intact tower top lying about Gzero.

the falling section can be said to have maintained enough integrity to destroy the increasingly strong structure below without itself being destroyed in the process before it reached the ground

That doesn't address the problem I have described.

 

[Mick West]

WTC7 fire investigation off-topic stuff removed.

 

[Mick West]

On a side note I find your diagram -- while obviously not intended to take account of the increasing strength of the structure as one proceeds "down" the building -- does represent how remarkable it is that the falling section can be said to have maintained enough integrity to destroy the increasingly strong structure below without itself being destroyed in the process before it reached the ground, slowing, stopping, or "falling off", as appears to begin to happen here. One can sympathise with those who feel this is in violation of Newton's Third Law, wouldn't you agree?

I certainly sympathize with them, as they are laboring under a misconception which prevents them from progressing in their understanding.

The top did not maintain integrity, however the damage done to the top is not symmetrical to the damage done to the bottom while falling, as the "top" accumulates what amounts to a multiply-floor thick and heavy shield of rubble, which grows very rapidly. Whereas the bottom remains just bare individual floors.

 

[Mick West]

And while the core columns are increasingly strong, the floor connections are not. Hence you get the "spire" effect as the floors are stripped from the stronger lower core columns.

 

[jomper]

And while the core columns are increasingly strong, the floor connections are not. Hence you get the "spire" effect as the floors are stripped from the stronger lower core columns.

I see. I suppose the large volumes of material we see being laterally ejected with great force as the wave of destruction travels down the structure are of negligible mass by comparison to the accumulating mass of the rubble shield which is crushing everything beneath it so rapidly. Would that be correct?

The spire we see briefly standing at the end of the event is very spindly and not central to the structure, so are you certain it does indeed represent the remainder of the core columns? Whether it does or not, why would you expect the increasingly strong core columns not to remain standing if the mechanic of destruction was as you describe?

If the spindly spire we see remaining was indeed the remains of the strong core columns (which seems improbable to me as I've said, but never mind) what do to think is happening to it to cause it to fall - some seem to think it almost evaporates - after the rest of the structure was completely destroyed around it?

Please don't say you think it dustified ;-)

 

[Jazzy]

I see. I suppose the large volumes of material we see being laterally ejected with great force as the wave of destruction travels down the structure are of negligible mass by comparison to the accumulating mass of the rubble shield which is crushing everything beneath it so rapidly. Would that be correct?

The "large volumes of material we see being laterally ejected with great force" were snapped external columns which had just failed by buckling and had either folded or separated from their place in the external structure. Their outward speed would be proportional to the speed of the downward collapse at that moment. All the effects of the external disintegration were minimized to a degree by their explosive outward separation. Except that some pieces hit other buildings and caused massive damage.

The spire we see briefly standing at the end of the event is very spindly and not central to the structure, so are you certain it does indeed represent the remainder of the core columns?

They couldn't have been anything else. The structure was minimal. If not the outside, then the core was all that remained. It may have been strongly built, but wasn't capable of resisting tens of thousands of tons of steel doing 120 mph. Only some of its vertical columns remained, and by themselves they couldn't possibly have remained standing.

Whether it does or not, why would you expect the increasingly strong core columns not to remain standing if the mechanic of destruction was as you describe?

They were slender columns subject to Euler's Law of Buckling Instability. They failed because without cross-ties they lacked sufficient stability.

If the spindly spire we see remaining was indeed the remains of the strong core columns (which seems improbable to me as I've said, but never mind) what do to think is happening to it to cause it to fall - some seem to think it almost evaporates - after the rest of the structure was completely destroyed around it?

It buckled.

Please don't say you think it dustified ;-)

Ambient smoke and video image compression algorithms did the rest.
.

 

[jomper]

The spire we see briefly standing at the end of the event is very spindly and not central to the structure, so are you certain it does indeed represent the remainder of the core columns?

They couldn't have been anything else.

How can you be so sure?

why would you expect the increasingly strong core columns not to remain standing if the mechanic of destruction was as you describe?

They were slender columns subject to Euler's Law of Buckling Instability. They failed because without cross-ties they lacked sufficient stability.

They were under zero axial load, so that makes no sense.

These are the core columns. Not minimal structures. If that spire was indeed part of them, then the cores were almost completely destroyed through a mechanic Mick has not explained.

If the spindly spire we see remaining was indeed the remains of the strong core columns, what do to think is happening to it to cause it to fall?

It buckled.

Again, it was clearly under zero axial load, so why would it buckle?

 

[Mick West]

Again, it was clearly under zero axial load, so why would it buckle?

It (or rather "they") buckled near the bottom, the axial load was the columns themselves. They individually buckled under their own weight (although the lateral pushing of falling debris would certainly not have helped).

 

[jomper]

It (or rather "they") buckled near the bottom

That's speculation on your part isn't it? It's similar to speculation that buckling occurred at WTC 7 at a low level which, in the video footage, is obscured by dust/surrounding structures -- meaning no direct visual evidence exists to support the assertion.

Here are the rather hackneyed and misinterpreted few frames of the last moments of the spire again.



Certainly if what is recorded here is the spire buckling at a low level and falling broadly through the perpendicular, one would expect the spire to be laid in some condition on top of the debris, would you agree?

Is there any photographic evidence of the spire existing in any condition in the wreckage? I have not seen any -- perhaps you imagine it shattered on impact with the ground?

the axial load was the columns themselves. They individually buckled under their own weight.

So what you are saying is there were a set of 47 massive cross-braced columns built like this:



...which were reduced to just this (which in fact looks to me like an interior box column outside the northwest corner of the core area)...



...through a mechanism you can't explain.

After all, you said:

the core columns are increasingly strong, the floor connections are not. Hence you get the "spire" effect as the floors are stripped from the stronger lower core columns.

So where are these stronger lower core columns?

Added to that speculation, you imagine this remaining piece of what you believe was once the core was unable to support even its own weight after the collapse, when previously it helped to support 110 stories of skyscraper.

Is that correct?

 

[Jazzy]

That's speculation on your part isn't it? It's similar to speculation that buckling occurred at WTC 7 at a low level which, in the video footage, is obscured by dust/surrounding structures -- meaning no direct visual evidence exists to support the assertion. ...through a mechanism you can't explain. After all, you said: "the floor connections are not. Hence you get the "spire" effect as the floors are stripped from the stronger lower core columns." you imagine this remaining piece of what you believe was once the core was unable to support even its own weight after the collapse, when previously it helped to support 110 stories of skyscraper. Is that correct?

No. Mick's answer was not speculation at all.

Your argument from incredulity is completely vitiated by your ignorance. It is itself speculative, because you appear unable to appreciate what STRUCTURAL STABILITY means.

We cannot educate you. It's a task you must set yourself. http://en.wikipedia.org/wiki/Buckling
.

 

[jomper]

No. Mick's answer was not speculation at all.

Your argument from incredulity is completely vitiated by your ignorance. It is itself speculative, because you appear unable to appreciate what STRUCTURAL STABILITY means.

We cannot educate you. It's a task you must set yourself. http://en.wikipedia.org/wiki/Buckling
.

Bare assertion, ad hominem and a failure to appreciate the rudiments of the Socratic method. What you are saying is you cannot answer the question. Jazzy: I was addressing myself to Mick. You're going on ignore because I know you're going to get abusive again.

 

[jomper]

Obviously it is rotating. I'm just saying the center of mass if not moving much laterally:

Here is another famous photograph which shows the movement of the top section of the South Tower was significantly more off the perpendicular than the above diagram implies.

 

[jomper]

Meanwhile, this video effectively exposes the bunk in the MIT "model" we have often seen invoked here on Metabunk, as for example here in this very thread by Jazzy, and again by myself here -- when we discovered

It's one of my favorite videos.

But it seems to be bunk: this is certainly an impressive effort at some real-world experimental modelling. Debunking of the MIT effort at the end.

 

[Mick West]

Meanwhile, this video effectively exposes the bunk in the MIT "model" we have often seen invoked here on Metabunk, as for example here in this very thread by Jazzy, and again by myself here -- when we discovered


But it seems to be bunk: this is certainly an impressive effort at some real-world experimental modelling. Debunking of the MIT effort at the end.

The video maker seems to fail to understand that it's illustrating the principle of buckling, not modelling the towers.

 

[thedude953]

the problem with the buckling theory was and still is there is no explanation for the simultaneous collapse of all points at the same time to allow for the process to start and continue the way it did. I totally get and agree that if it were to happen that way where the columns and steel buckled to the point of giving way and then allowing the floors to pancake onto each other and collapsing, its been shown that this is possible and the gravity and force would allow the buildings to fall. but the heat and impact was not evenly distributed, impact was from one side and fires spread from there. but the only thing that would create this simultaneously on all choke points to allow the perfect collapse is coincidence. ok now that's possible the columns could have given way in that way so it could fall perfectly or near perfectly, but then you get into the argument of it happening three times....it just gets to the point of ridiculousness just like the entire story as a whole. of course the people arguing the point already think that things like finding the hijackers passport seems realistic so I guess I may be wasting my time here but for all three of them to fall in the same way with the same theory...little weird that's all i'm getting at

 

[Mick West]

the problem with the buckling theory was and still is there is no explanation for the simultaneous collapse of all points at the same time to allow for the process to start and continue the way it did. I totally get and agree that if it were to happen that way where the columns and steel buckled to the point of giving way and then allowing the floors to pancake onto each other and collapsing, its been shown that this is possible and the gravity and force would allow the buildings to fall. but the heat and impact was not evenly distributed, impact was from one side and fires spread from there. but the only thing that would create this simultaneously on all choke points to allow the perfect collapse is coincidence. ok now that's possible the columns could have given way in that way so it could fall perfectly or near perfectly, but then you get into the argument of it happening three times....it just gets to the point of ridiculousness just like the entire story as a whole. of course the people arguing the point already think that things like finding the hijackers passport seems realistic so I guess I may be wasting my time here but for all three of them to fall in the same way with the same theory...little weird that's all i'm getting at

When some columns fail, then the load is transferred to other columns. At which point one of two things can happen:

A) They don't fail, in which case the building is not collapsing. Goto A.
B) They do fail, at which point an even greater load is IMMEDIATELY transferred to the adjacent columns. Goto B.

 

[Jazzy]

the only thing that would create this simultaneously on all choke points to allow the perfect collapse is coincidence.

This is not true, and demonstrates a failure to understand what you see. Jomper shares this bunk with you.

In a static structure on the point of failure the loading at any point is ALWAYS unfixed as soon as the situation is no longer static. The four-column model demonstrates just how easily the four columns fail together. They can only do so because they are handing across to each other what they can no longer tolerate. Whether it is four columns or two hundred connected by spandrels the same principles operate.

To claim coincidence is to admit that you fail to understand what you see.

little weird that's all i'm getting at

A little weird because you haven't grasped what's happening. Don't join Jomper if you can help it.

The science behind vertical column instability and buckling is two hundred and sixty years old. People study hard in further education to grasp it, and learn to pass examinations using it.

Jomper hasn't been one of them.

 

[jomper]

The video maker seems to fail to understand that it's illustrating the principle of buckling, not modelling the towers.

You missed the part about the columns and spandrels from 10m 20s? Without spandrels or core columns in that little model it's got about as much explanatory power as wet clay.

 

[Mick West]

You missed the part about the columns and spandrels from 10m 20s? Without spandrels or core columns in that little model it's got about as much explanatory power as wet clay.

No I didn't. He's misunderstanding what the model is explaining. It's about how individual columns react.

Have a look at this:
http://www.sharpprintinginc.com/911...op=view_page&PAGE_id=269&MMN_position=525:525

 

[thedude953]

the transfer of energy to the columns would happen in succession since we all can agree it wouldn't happen instantly to all columns for no reason, I cant remember the number of columns I but it was a huge amount of core columns, even if the columns buckled this would have happened in a way we could see, we have video of these collapsed buildings severely slowed down and you still cant tell, you guys again are proving how it could happen but giving no reason why It would happen this way, the videos and the evidence do explain how the collapse COULD happen, just not how it made sense that it happened this way with three separate instances. guys please watch the videos do the research mick and jazzy are clearly dodging and avoiding basic points because of there clear point of view.
as I have said before on these threads jazzy does nothing but dodging actual points by using facts that don't really apply to what the spectacle issue really is. and claiming coincidence means nothing about understanding, sorry I think you are just out of touch with reality. I am questioning both sides, you are just ignoring what the real issue is.

 

[thedude953]

This is not true, and demonstrates a failure to understand what you see. Jomper shares this bunk with you.

In a static structure on the point of failure the loading at any point is ALWAYS unfixed as soon as the situation is no longer static. The four-column model demonstrates just how easily the four columns fail together. They can only do so because they are handing across to each other what they can no longer tolerate. Whether it is four columns or two hundred connected by spandrels the same principles operate.

To claim coincidence is to admit that you fail to understand what you see.


A little weird because you haven't grasped what's happening. Don't join Jomper if you can help it.

The science behind vertical column instability and buckling is two hundred and sixty years old. People study hard in further education to grasp it, and learn to pass examinations using it.

Jomper hasn't been one of them.

this was not a four column this was MULTIPLE COLUMNS this is nonsense and you are ignoring what the issue is, I have already agreed to the basic point you have made but again you have dodged what the problem with your argument is. you will now respond with more nonsense and jargon that will not apply and try to make it seem like I don't understand. unfortunately I am just being realistic.

 

[Mick West]

the transfer of energy to the columns would happen in succession since we all can agree it wouldn't happen instantly to all columns for no reason, I cant remember the number of columns I but it was a huge amount of core columns, even if the columns buckled this would have happened in a way we could see, we have video of these collapsed buildings severely slowed down and you still cant tell, you guys again are proving how it could happen but giving no reason why It would happen this way, the videos and the evidence do explain how the collapse COULD happen, just not how it made sense that it happened this way with three separate instances. guys please watch the videos do the research mick and jazzy are clearly dodging and avoiding basic points because of there clear point of view.
as I have said before on these threads jazzy does nothing but dodging actual points by using facts that don't really apply to what the spectacle issue really is. and claiming coincidence means nothing about understanding, sorry I think you are just out of touch with reality. I am questioning both sides, you are just ignoring what the real issue is.

By the "real issue" here, you mean the time of initiation of full collapse?

How long should it have taken? And why?

How long did it take? And how did you measure it?

 

[jomper]

No I didn't. He's misunderstanding what the model is explaining. It's about how individual columns react.

Have a look at this:
http://www.sharpprintinginc.com/911...op=view_page&PAGE_id=269&MMN_position=525:525

Yes, I've been dipping in and out of that site for a while now. It's a very impressive body of research, but it seems particularly weak in its claim to "reassess the question of demolition" at WTC 7 -- in fact I could not find any "reassessment" of this issue anywhere, so if you did please point me to it -- and many of the conclusions are merely broad criticisms of false dichotomies, aren't they?

Nevertheless it says things which I think are true, for example:

The truther movement is not responsible for the lack of an accurate description of the collapse progression modes of the largest structural failures in memory. Truthers are not responsible for the falsification of the technical history of each collapse.

Content from External Source

and

NIST basically fabricates descriptions of early building movement and claims their proposed initiation mechanism matches all observables. Various people then rally behind the NIST reports with a zeal similar to what one might observe at a sporting event.

Content from External Source

Would you agree with these statements?

There is also no evidence in the photographic archives of the spire on the rubble anywhere that I could see, to return to a point I made earlier that you have not addressed.

But to return to the MIT "model" we were discussing: all you have here is a model that represents nothing except the fact that buckling can occur. Yes, buckling happens if you put lots of weight on top of a little column. But the "model" in the video makes no attempt to represent the construction features of the towers or represent how they were actually supported, so it models nothing of any relevance to the question of what happened to them. It is simply banal.

And in any case the MIT model is bebunked as a mere postscript to the impressive physical experiment that forms the bulk of that video, and it is this physical experiment that appears to debunk the assertion that impact/fire and gravity could cause the total destruction of the towers. As its creator observes, it is remarkable that this kind of modelling has not been attempted by research institutions in the years since the disaster. I'm quite looking forward to this:

 

[Mick West]

There is also no evidence in the photographic archives of the spire on the rubble anywhere that I could see, to return to a point I made earlier that you have not addressed.

Why would there be? If it had failed at the bottom, then the entire spire would have separated.

The entire series of disputes here really hinges on the problem of scale, and the square cube law.

 

[Mick West]

Certainly if what is recorded here is the spire buckling at a low level and falling broadly through the perpendicular, one would expect the spire to be laid in some condition on top of the debris, would you agree?

No, I don't. I expect it collapse like a house of cards. Because it lacks the support for withstand such an event.

Scale.