An Independent Analysis into NISTs Report on the WTC collapses - The Real Smoking Gun

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I believeI have discovered a fundamental flaw in NISTs report into the WTC collapses on 9/11. If it is correct it forms the basis for getting them to reopen the investigation into 9/11. It hasn't been checked though so please check it, if you agree with it pass it on to as many people as you can so it can be confirmed/debunked as appropriate.

An Independent Analysis Of NISTs Scientific Methods And Assumptions
NIST’s “Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Tower” (hereafter referred to as “The Final Report”) states its first objective was to “Determine why and how WTC 1 and WTC 2 collapsed following the initial impacts of the aircraft”1 (emphasis mine). To determine why and how the buildings collapsed The Final Report needs to explain the events following the initial impact until the collapse of the buildings is complete. NIST state that their approach was to simulate the behaviour of the tower using “four steps:
1. The aircraft impact into the tower, the resulting distribution of aviation fuel, and the damage to the structure, partitions, thermal insulation materials, and building contents.
2. The evolution of multi-floor fires.
3. The heating and consequent weakening of the structural elements by the fires.
4. The response of the damaged and heated building structure, and the progression of the structural component failures leading to the initiation of the collapse of the towers.”2 (emphasis mine)
Their approach appears to fall short of that which would be required to determine why and how the initial impacts resulted in the collapse of the towers as their stated approach stops at the initiation of collapse, not at the completion of it. There is no explicit explanation why they took this approach in The Final Report or in any of the supporting documents, however their footnotes state that they conducted “little analysis of the structural-behaviour of the tower after the conditions for collapse were reached and collapse became inevitable.”3 (emphasis mine – NOTE: in another footnote (footnote 13, page 82), “conditions for collapse” is replaced with “conditions for collapse initiation”, these are assumed to be one and the same). Although I can find no analysis of the structural behaviour of the tower after “the conditions for collapse” were met in The Final Report or supporting documents, this sentence implies they have made an assumption, or have unstated proof, that once the conditions for collapse are reached, the collapse that occurs must, inevitably, be the collapse that was observed. There is no justification offered for why this assumption was made and no evidence or sources given to support its validity.
However, elsewhere in The Final Report they state that their recommendation for further research into the “Prevention of progressive collapse” is “related” to 9/114 (emphasis mine). The Final Report also states that “Progressive collapse (or disproportional collapse) occurs when an initial local failure spreads from structural element to structural element resulting in the collapse of an entire structure or a disproportionately large part of it.”5 From this statement, and given the lack of explicit explanation, it can be inferred that “the conditions for collapse” were defined as the initial conditions for progressive collapse, which The Final Report states to be “an initial local failure spreads from structural element to structural element”. To check the validity of this definition it is necessary to examine the peer reviewed scientific papers modelling progressive collapse to see whether “an initial local failure spreads from structural element to structural element” does inevitably result in progressive collapse of the entire structure.
Reading the peer reviewed work on the subject of progressive collapse reveals that there has in fact only
Footnotes
1 Section E.1, page xxxv of The Final Report
2 Section E.2, pages xxxvi and xxxvii of The Final Report
3 Footnote 2, page xxxvii of The Final Report
4 Table E-1, page xliv of The Final Report
5 Footnote 19, page 206 of The Final Report

ever been one paper modelling the mechanics of the collapse of the twin towers (or any steel framed structure) after initiation of collapse, a paper called “Why Did the World Trade Center Collapse? – Simple Analysis” by Zdenek P. Bazant, Fellow ASCE, and Yong Zhou (hereafter referred to as “The Paper”). All other papers on the subject reference this paper and use it as a basis for further analysis, so if The Paper conclusively supports NISTs definition of “the conditions of collapse” then the definition can be assumed to be valid and hence NISTs conclusions are valid.
Using a simplified model the paper presents an analysis of the overall collapse of the twin towers and purports to show that the towers were doomed “if prolonged heating caused the majority of columns of a single floor to lose their load carrying capacity”6. In examining the paper I found that its internal logic was consistent and it seemed to support NISTs inferred definition. However, as stated in The Paper “an important hypothesis implied in this analysis is that the impacting upper part, many floors in height, is so stiff that it does not bend nor shear on vertical planes, and that the distribution of column displacements across the tower is almost linear, like for a rigid body. If, however, the upper part spanned only a few floors (say, 3 to 6), then it could be so flexible that different column groups of the upper part could move down separately at different times, producing a series of small impacts that would not be fatal (in theory, if people could have escaped from the upper part of the tower, the bottom part of the tower could have been saved if the upper part were bombed, exploded or weakened by some ‘smart’ structure system to collapse onto the lower part gradually as a mass of rubble, instead of impacting it instantly as an almost rigid body).”7 The paragraph is quoted in full as it has two fundamental implications directly linked to NISTs definition of “the conditions of collapse”.
The first implication is that, despite admitting that the flexibility of the upper section is dependent on the number of floors, and that it admits the upper section “could be so flexible that different column groups of the upper part could move down separately at different times, producing a series of small impacts that would not be fatal” no justification is offered as to where the threshold of flexibility is. Hence the assumption that 15 floors “is so stiff that it does not bend or shear on vertical planes, and that the distribution of column displacements across the tower is almost linear, like for a rigid body” must be proven to be true for the world trade centre towers before this paper can be proved to explain the towers complete collapse after initiation of collapse.
The second implication is that, as “the bottom part of the tower could have been saved if the upper part were bombed, exploded or weakened by some ‘smart’ structure system to collapse onto to the lower part gradually as a mass of rubble, instead of impacting it instantly as an almost rigid body”, then it must be shown conclusively that the ‘system’ suggested (but not referred to in these terms) by both NIST and The Paper, namely rising heat from the fires started by the jet fuel from the planes, did not weaken the upper section sufficiently to “collapse onto the lower part gradually as a mass of rubble” in the specific case of the world trade centre before The Paper can be proved to explain the towers collapse.
The importance of whether the upper section is rigid or not at the point of impact can be easily demonstrated by visualising a simple model. Consider a solid tower with a density equal to that of sand. If we drop a solid object with a mass of, say, 1 Kg, and the density of sand on top of that tower then it is easy
Footnotes
6 page1 of The Paper (page is labelled XVII in linked document)
7 pages 2 and 3 of The Paper (pages are labelled XIX and XX in linked document)
to see how the mechanism proposed in The Paper applies (shown in Fig. 1 in The Paper8), however if we allow 1 Kg of sand to fall on top of the same tower then it is clear that mechanism proposed in the paper does not apply.
The importance of whether the upper section of the tower was rigid at the instant of impact can also be seen when comparing the diagrams in Fig. 1.3, 1.4 and 1.5 from The Paper8 showing the stages of ‘progressive collapse’ with the visual record:



Footnotes
6 page1 of The Paper (page is labelled XVII in linked document)
7 pages 2 and 3 of The Paper (pages are labelled XIX and XX in linked document)
8 page 8 of The Paper (page is labelled XXV in linked document)

Conclusion
The crucial implied hypothesis stated in The Paper means the inferred definition of “the conditions for collapse” in The Final Report is incomplete and should have been “an initial local failure spreads from structural element to structural element, and proof that the upper section of the tower was a rigid body at the instant of impact with the lower section”.
Furthermore, if indeed there are no other demonstrable mechanisms for explaining the total collapse of the lower section of the towers then the inferred definition of “the conditions for collapse” is irrelevant. NISTs model must show that at the instant of impact with the lower section the upper section was still a “rigid body”. Anything less than this means that the mechanism for progressive collapse demonstrated in The Paper has not been shown to inevitably follow on from the model in The Final Report and the model in The Final Report would therefore be a scenario based on an unproven and, in the specific case of the twin towers, suspect hypothesis.
As The Final Report and supporting documents, in particular the WTC 1 collapse sequence as described in the supporting documents9, do not show that the upper section must have still been a “rigid body” at the instant of impact with the lower section, The Final Report does not, as it claims, explain how the twin towers collapsed from impact and fire damage alone, it is only a possible sequence of events based on an unproven and suspect hypothesis and it will remain so until they rectify the fatal flaw in the formulation of their approach.
Footnotes
9 Section E.3.1 beginning on page lii of NIST NCSTAR 1-6D


Summary of Key points
NISTs official report says global collapse is inevitable following the establishment of the conditions for collapse. This is dependent on a 2002 paper proposing a mechanism for progressive collapse of a steel structured building. However the 2002 paper also clearly states that it is based on a hypothesis that the upper section is rigid at the instant of impact with the lower section. NISTs report fails to show that the upper section is rigid at the instant of impact and there is circumstantial evidence that the hypothesis is not true in the case of the twin towers, hence NISTs report is in error when it claims global collapse is inevitable following the establishment of the conditions for collapse.

Sources
The Final Report: http://www.nist.gov/customcf/get_pdf.cfm?pub_id=909017
Supporting document NIST NCSTAR 1-6D: http://www.nist.gov/customcf/get_pdf.cfm?pub_id=101366
Other supporting documents to The Final Report: http://www.nist.gov/el/disasterstudies/wtc/wtc_finalreports.cfm
NIST information on progressive structural collapse: http://www.nist.gov/el/topic_collapse.cfm
The Paper: http://www.mae.ncsu.edu/eischen/courses/mae543/docs/BazantWTC.pdf
Selected list of Scientific papers on the progressive collapse of the twin towers: http://sites.google.com/site/wtc7lies/peer-reviewedpapersaboutthewtcimpacts,fi

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1. the 3 missing images

[BobbyBoring]

8. Great effort

But this is the wrong place as you'll see. There will be no further investigation as long as the masses believe that something that is impossible in so many ways happened the way the government said it did.

Welcome to DU and the dungeon~

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18. I'm getting more and more convinced

That they have to prove that the upper section was rigid on impact with the lower section. If you think about there was a whole hour of intense fires in the upper section that (theoretically, and this is what needs to be examined) could have weakened the structure to the point that when gravitional collapse iniitiated it pulled the upper section into smaller pieces before it impacted the lower section.

EDIT: and thanks for the welcome :)

I like being challenged on it because it helps me understand, if I'm wrong I'm wrong.

[William Seger]

2. You give no reason to think another investigation would produce a different result

You are merely asking for a more rigorous demonstration that Bazant's assumption about rigidity is correct, without giving the slightest reason for thinking it isn't correct and ignoring reasons for thinking it is. That doesn't require another investigation to settle. Unfortunately for your case, there is the documentary evidence: The numerous videos from various angles do not show any flexing or distortions that indicate the top block didn't act "essentially as a rigid block." The scenario that Bazant supposes might have lead to survival -- "different column groups of the upper part could move down separately at different times" -- simply wasn't the case.

Those videos are quite sufficient for answering your concern, but since we're here: Your link is to the original version of the paper. In a revised version, somewhat different text appears in the Addendum rather than in the body of the paper:

Second, note that the analysis that led to Eq. 1 implies the hypothesis that the impacting upper part of the tower behaves essentially as a rigid body. This is undoubtedly reasonable if the upper part has the height of 20 stories, in which case the ratio of its horizontal and vertical dimensions is about 52.8/20x3.7=0.7. But if the upper part had the height of only 3 stories, then this ratio would be about 5. In that case, the upper part would be slender enough to act essentially as a flexible horizontal plate in which different column groups of the upper part could move down separately at different times. Instead of one powerful jolt, this could lead to a series of many small vertical impacts, none of them fatal.

Second, it seems rather silly to accept Bazant's opinion of how things "could" have been different if the top block was flexible, but then reject his opinion that that wasn't the case. It would appear that you don't really have any "independent analysis" to substantiate your highly selective acceptance and rejection of Bazant's expertise.

Third, like virtually all conspiracists attempting to argue with the Bazant analysis, you overlook this:

Once accurate computer simulations are carried out, various details of the failure mechanism will undoubtedly be found to differ from the simplifying hypotheses made. Errors by a factor of 2 would not be terribly surprising. But that would hardly matter since the analysis in the paper reveals order-of-magnitude differences between the dynamic loads and the structural resistance. Crude order-of-magnitude estimates made easily by pencil suffice in this case to rule out various intuitive theories that were advanced to explain the collapse.

So, absolute rigidity is NOT nearly so "crucial" as you claim: Even if the top block had been flexible enough to reduce the impulse force by a factor of 2 (or really, anything up to a factor of 8, since the calculated overload factor was 8.7), it just wouldn't matter: Collapse was unavoidable.

And BTW, here's a later analysis by Bazant et al which doesn't mention the rigidity issue at all:
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00+WTC+Collapse+-+What+Did+&+Did+Not+Cause+It.pdf

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3. You've ignored essential points

So, absolute rigidity is NOT nearly so "crucial" as you claim: Even if the top block had been flexible enough to reduce the impulse force by a factor of 2 (or really, anything up to a factor of 8, since the calculated overload factor was 8.7), it just wouldn't matter: Collapse was unavoidable.

And BTW, here's a later analysis by Bazant et al which doesn't mention the rigidity issue at all:
http://www.civil.northwestern.edu/people/bazant/PDFs/Pa...

===================================================================================

no it isn't, neither NIST nor Bazant mentioned the most obvious 'system' for weakening the structure above the impact site, i.e. to raging fires caused by the jet fuel, heat rises you know.

The first quote you gave does clear up the question of how it was determined that the 15 floors above the impact site retain their rigidity, however as I said neither of them model or even mention the effect of the fires of the rigidity of the upper section before collapse began. That means they can't say that the conditions for initiating imapct will inevitably lead to global collapse

your last link doesn't work

[William Seger]

6. "Essential" to what?

The video evidence does not show any lack of rigidity, and you offer nothing but your own speculation as "circumstantial evidence," so sorry but I don't see anything "essential" to it. But anyway, I believe your point is well covered by Bazant's observation that a simplified analysis is sufficient when it shows there's an order of magnitude more force available than was necessary to collapse the structure. We're just not talking about a marginal situation where these minor issues would change the conclusion. In fact, a more exact analysis might well show that the overloading was even much greater than 8.7. For example, one improvement to the simplified analysis should be that, according to both the videos and the the NIST model, the initial collapse actually involved a floor pulling perimeter columns inward until they buckled, so two levels of columns failed at initiation, allowing the top block to drop for two stories instead of the one that Bazant's analysis used. Since the impact force would be increasing exponentially with the distance of the fall, that would make a huge difference. Also, Bazant's simplified analysis assumed that all of the columns developed their maximum load resistance, which would only be true if structural integrity was maintained while the columns were loaded until they buckled. In fact, in cases were falling debris broke floors away from columns first, leaving them unrestrained laterally, the buckling resistance of restrained columns was irrelevant because those columns were simply pushed aside.

Here's the corrected link to the extended analysis:
http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20Did%20&%20Did%20Not%20Cause%20It.pdf

And by the way, you are wrong that Bazant and Zhou's original paper is the only analysis, and the later paper above is not the only exception. Before collaborating on that paper, Frank Greening had done this analysis, which takes a rather different approach to reach the same conclusion. Likewise, so does this peer-reviewed analysis by Keith Seffen. And there are many others, if you would take the trouble to look before claiming that there aren't.

Furthermore, NIST finite element analysis is not the only one that's been performed. This one proposes a somewhat different mechanism for the collapse initiation, one that requires even lower temperatures than NIST's, but arrives at the same conclusion: The towers were doomed.

In short, in my opinion, your criticism of NIST and Bazant et al is much less than half-baked.

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11. I've already seen that link

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20Did%20&%20Did%20Not%20Cause%20It.pdf

I've already read that paper, it does nothing to question the previous paper as he states in his opening sentence:

"Previous analysis of progressive collapse showed that gravity alone suffices to explain
the overall collapse of the World Trade Center (WTC) towers" - i.e. the 2002 paper is correct in all circumstances

the rest of the paper is dedicated to showing that the energy expended in creating the debris seen FOLLOWING INITIAL IMPACT isn't enough to effect the progressive collapse once it has begun.

Others have already pointed out certain things on other forums and I've written a more detailed analysis showing more clearly where I have found evidence for my assertions and more clearly explaining why it's important.

I don't mind been proven wrong, in fact thats why I'm posting it, because I can't find an error.

The updated analysis will follow.

As for Seffen's paper, this is what I'm talking about with everything leading back to that hypothesis, seffen says:

"The subsequent near free-falling of these upper parts over the height of just one storey resulted in dynamical “over-loading” of the relatively undamaged lower columns by a factor of 30 compared to their static load capacity, according to Bazant and Zhou (2002)"

i.e. bazant's calculations showing the overload ratio to be 30 or greater is true in all cicumstances, but thats the exact part of bazants paper that is based on the unproven hypothesis.

My updated analysis will follow.

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13. Updated analysis

An Independent Analysis Of NISTs Scientific Methods And Assumptions

Summary of Key points

NISTs official report says global collapse is inevitable following the establishment of the conditions for collapse. This is dependent on a 2002 paper proposing a mechanism for progressive collapse of a steel structured building. However the 2002 paper also clearly states that it is based on a hypothesis that the upper section is rigid at the instant of impact with the lower section. NISTs report fails to show that the upper section is rigid at the instant of impact and there is circumstantial evidence that the hypothesis is not true in the case of the twin towers, hence NISTs report is in error when it claims global collapse is inevitable following the establishment of the conditions for the initiation of collapse.

Supporting Argument

NIST’s “Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Tower” (hereafter referred to as “The Final Report”) states its first objective was to “Determine why and how WTC 1 and WTC 2 collapsed following the initial impacts of the aircraft”1 (emphasis mine). To determine why and how the buildings collapsed The Final Report needs to explain the events following the initial impact until the collapse of the buildings is complete. NIST state that their approach was to simulate the behaviour of the tower using “four steps:

1. The aircraft impact into the tower, the resulting distribution of aviation fuel, and the damage to the structure, partitions, thermal insulation materials, and building contents.
2. The evolution of multi-floor fires.
3. The heating and consequent weakening of the structural elements by the fires.
4. The response of the damaged and heated building structure, and the progression of the structural component failures leading to the initiation of the collapse of the towers.”2 (emphasis mine)

Their approach appears to fall short of that which would be required to determine why and how the initial impacts resulted in the collapse of the towers as their stated approach stops at the initiation of collapse, not at the completion of it. There is no explicit explanation why they took this approach in The Final Report or in any of the supporting documents, however their footnotes state that they conducted “little analysis of the structural-behaviour of the tower after the conditions for collapse were reached and collapse became inevitable.”3 (emphasis mine – NOTE: in another footnote (footnote 13, page 82), “conditions for collapse” is replaced with “conditions for collapse initiation”, these are assumed to be one and the same). Although I can find no analysis of the structural behaviour of the tower after “the conditions for collapse” were met in The Final Report or supporting documents, this sentence implies they have made an assumption, or have unstated proof, that once the conditions for collapse are reached, the collapse that occurs must, inevitably, be the collapse that was observed. There is no justification offered for why this assumption was made and no evidence or sources given to support its validity.

However, elsewhere in The Final Report they state that their recommendation for further research into the “Prevention of progressive collapse” is “related” to 9/114 (emphasis mine). The Final Report also states that “Progressive collapse (or disproportional collapse) occurs when an initial local failure spreads from structural element to structural element resulting in the collapse of an entire structure or a disproportionately large part of it.”5 From this statement, and given the lack of explicit explanation, it can be inferred that “the conditions for collapse” were defined as the initial conditions for progressive collapse, which The Final Report states to be “an initial local failure spreads from structural element to structural element”. To check the validity of this definition it is necessary to examine the peer reviewed scientific papers modelling progressive collapse to see whether “an initial local failure spreads from structural element to structural element” does inevitably result in progressive collapse of the entire structure.

Reading the peer reviewed work on the subject of progressive collapse reveals that there has in fact only ever been one paper modelling the mechanics of the collapse of the twin towers (or the global collapse of any steel framed structure) after initiation of collapse, a paper called “Why Did the World Trade Center Collapse? – Simple Analysis” by Zdenek P. Bazant, Fellow ASCE, and Yong Zhou (hereafter referred to as “The Paper”). All other papers on the subject reference this paper directly (including Bazant authored papers on the subject discussing questions others have asked) and use it as a proven basis for further analysis or they state (paraphrased)“it has already been well established that at the moment of impact the steel in the lower section is overcome by an order of magnitude” i.e. The Paper is correct in all circumstances. Therefore if The Paper conclusively supports NISTs definition of “the conditions of collapse” then the definition can be assumed to be valid and hence NISTs conclusions are valid.

Using a simplified model the paper presents an analysis of the overall collapse of the twin towers and purports to show that the towers were doomed “if prolonged heating caused the majority of columns of a single floor to lose their load carrying capacity”6. In examining the paper I found that its internal logic was consistent and it seemed to support NISTs inferred definition. However, as stated in The Paper “an important hypothesis implied in this analysis is that the impacting upper part, many floors in height, is so stiff that it does not bend nor shear on vertical planes, and that the distribution of column displacements across the tower is almost linear, like for a rigid body. If, however, the upper part spanned only a few floors (say, 3 to 6), then it could be so flexible that different column groups of the upper part could move down separately at different times, producing a series of small impacts that would not be fatal (in theory, if people could have escaped from the upper part of the tower, the bottom part of the tower could have been saved if the upper part were bombed, exploded or weakened by some ‘smart’ structure system to collapse onto the lower part gradually as a mass of rubble, instead of impacting it instantly as an almost rigid body).”7 The paragraph is quoted in full as it has two fundamental implications directly linked to NISTs definition of “the conditions of collapse”.

The first implication is that, despite admitting that the flexibility of the upper section is dependent on the number of floors, and that it admits the upper section “could be so flexible that different column groups of the upper part could move down separately at different times, producing a series of small impacts that would not be fatal” no justification is offered as to where the threshold of flexibility is. Hence the assumption that 15 floors “is so stiff that it does not bend or shear on vertical planes, and that the distribution of column displacements across the tower is almost linear, like for a rigid body” must be proven to be true for the world trade centre towers before this paper can be proved to explain the towers complete collapse after initiation of collapse.

The second implication is that, as “the bottom part of the tower could have been saved if the upper part were bombed, exploded or weakened by some ‘smart’ structure system to collapse onto to the lower part gradually as a mass of rubble, instead of impacting it instantly as an almost rigid body”, then it must be shown conclusively that the ‘system’ suggested (but not referred to in these terms) by both NIST and The Paper, namely rising heat from the fires started by the jet fuel from the planes, did not weaken the upper section sufficiently to “collapse onto the lower part gradually as a mass of rubble” in the specific case of the world trade centre before The Paper can be proved to explain the towers collapse.

Studying the calculations used to determine the overload ratio’s shows that it is dependent on the mass at the instant of impact (assumed to be approximately 58000 tonnes), if the upper section was broken into, say, 3 identical pieces then the overload ratio would have to be calculated for an impact of 19333 tonnes, then another, separate 19333 tonnes, and then again.

The importance of whether the upper section is rigid or not at the point of impact can be easily demonstrated by visualising a simple model. Consider a solid tower with a density equal to that of sand. If we drop a solid object with a mass of, say, 1 Kg, and the density of sand on top of that tower then it is easy to see how the mechanism proposed in The Paper applies (shown in Fig. 1 in The Paper8), however if we allow 1 Kg of sand to fall on top of the same tower then it is clear that mechanism proposed in the paper does not apply.

The importance of whether the upper section of the tower was rigid at the instant of impact can also be seen when comparing the diagrams in Fig. 1.3, 1.4 and 1.5 from The Paper8 showing the stages of ‘progressive collapse’ with the visual record:

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Clarification or important points

In their supporting documents9 NIST do discuss other collapse hypotheses, The Paper already mentioned, Weidlinger Associates 2002 study which was to show that the two collapses were independent of each other and deals only with the collapse initiation, Maryland which they state they disagree with and two students from Edinburgh and Arup, both of which deal with cross-sectional areas and so don’t impact the implied hypothesis in The Paper. Hence my assertion that the only justification for their collapse initiation conditions inevitably leading to global collapse is Bazants 2002 paper.

The Final Reports flow chart10 also shows that only three of their studies fed into the global collapse scenario, NCSTAR 1-2 which studies specifically what the impact damage was and hence where the load above impact was redistributed to, NCSTAR 1-3 which studies the structural steel response of the additional heat and additional load caused by the redistribution to determine the point of failure of the supporting steel, again used to determine if initiation of collapse was due to impact and fire only, and NCSTAR 1-6 which determines the structural fire response to show where the fires were located around the impact site to find where the collapse was initiated. None of this research is used to determine whether the fires in the upper section were enough to weaken it to the point where the initiation of gravitational collapse was enough to break it apart before it impacted the lower section.

Further evidence of their assumption is found in NISTs FAQ released in 200710, which states:

“1. Was there enough gravitational energy present in the World Trade Center Towers to cause the collapse of the intact floors below the impact floors? Why was the collapse of WTC 1 and 2 not arrested by the intact structure below the floors where columns first began to buckle?

Yes, there was more than enough gravitational load to cause the collapse of the floors below the level of collapse initiation in both WTC Towers. The vertical capacity of the connections supporting an intact floor below the level of collapse was adequate to carry the load of 11 additional floors if the load was applied gradually and 6 additional floors if the load was applied suddenly (as was the case). Since the number of floors above the approximate floor of collapse initiation exceeded six in each WTC Tower (12 and 29 floors, respectively), the floors below the level of collapse initiation were unable to resist the suddenly applied gravitational load from the upper floors of the buildings.” (emphasis mine)

So the assumption, once again, is that the upper section remained intact, the only analysis performed is the difference between gradual application of the load and sudden application. This does not test the implied hypothesis in The Paper, it is merely the difference between the steel support slowly giving way or giving way quickly. In fact this statement suggests that (assuming 15 floors above the impacts site) if indeed the upper section did break up under the force of gravity before impacting the lower section, and each individual section to impact the lower section was less than 6 complete floors in mass, and more than 4 floors worth of material was ejected and didn’t impact the lower section, then collapse due to gravity only wasn’t possible. Given the visual evidence of both the extent of the fires above the impact site and the collapse itself I would suggest that this scenario is possible.

“10. Why didn’t NIST fully model the collapse initiation and propagation of WTC Towers?

The first objective of the NIST Investigation included determining why and how WTC 1 and WTC 2 collapsed following the initial impacts of the aircraft (NIST NCSTAR 1). Determining the sequence of events leading up to collapse initiation was critical to fulfilling this objective. Once the collapse had begun, the propagation of the collapse was readily explained without the same complexity of modeling, as shown in the response to question #1 above.” (emphasis mine)

So once again their argument is circular, their response to question one is dependent on the assumption that the upper section had not been weakened enough by the fires to suffer break up under gravity alone before it impacts the lower section, a scenario that hasn’t been shown to be the case.

Conclusion

The crucial implied hypothesis stated in The Paper means the inferred definition of “the conditions for collapse” in The Final Report is incomplete and should have been “an initial local failure spreads from structural element to structural element, and proof that the upper section of the tower was a rigid body at the instant of impact with the lower section”.

Furthermore, if indeed there are no other demonstrable mechanisms for explaining the total collapse of the lower section of the towers then the inferred definition of “the conditions for collapse” is irrelevant. NISTs model must show that at the instant of impact with the lower section the upper section was still a “rigid body”. Anything less than this means that the mechanism for progressive collapse demonstrated in The Paper has not been shown to inevitably follow on from the model in The Final Report and the model in The Final Report would therefore be a scenario based on an unproven and, in the specific case of the twin towers, suspect hypothesis.

As The Final Report and supporting documents (including the WTC 1 collapse sequence as described in the supporting documents11 and 12) do not show that the upper section must have still been a “rigid body” at the instant of impact with the lower section, The Final Report does not, as it claims, explain how the twin towers collapsed from impact and fire damage alone, it is only a possible sequence of events based on an unproven and suspect hypothesis and it will remain so until they rectify the fatal flaw in the formulation of their approach.

Footnotes

1 Section E.1, page xxxv of The Final Report
2 Section E.2, pages xxxvi and xxxvii of The Final Report
3 Footnote 2, page xxxvii of The Final Report
4 Table E-1, page xliv of The Final Report
5 Footnote 19, page 206 of The Final Report
6 page1 of The Paper (page is labelled XVII in linked document)
7 pages 2 and 3 of The Paper (pages are labelled XIX and XX in linked document)
8 page 8 of The Paper (page is labelled XXV in linked document)
9 Section 9.4.4 beginning on page 322 of NIST NCSTAR 1-6D
10 page xxxi of the Final Report
11 Section E.3.1 beginning on page lii of NIST NCSTAR 1-6D
12 section 9.4.5 beginning on page 326 of NIST NCSTAR 1-6D

Sources

The Final Report: http://www.nist.gov/customcf/get_pdf.cfm?pub_id=909017

Supporting document NIST NCSTAR 1-6D: http://www.nist.gov/customcf/get_pdf.cfm?pub_id=101366

Other supporting documents to The Final Report: http://www.nist.gov/el/disasterstudies/wtc/wtc_finalreports.cfm

NIST information on progressive structural collapse: http://www.nist.gov/el/topic_collapse.cfm
The Paper: http://www.mae.ncsu.edu/eischen/courses/mae543/docs/BazantWTC.pdf

Selected list of Scientific papers on the progressive collapse of the twin towers: http://sites.google.com/site/wtc7lies/peer-reviewedpapersaboutthewtcimpacts,fi

FAQ: http://www.nist.gov/public_affairs/factsheet/faqs12007.cfm

Weidlinger Assocites Study: http://www.wai.com/articles_pdf/webAS_abboudlevy_wtc_asceforensic_2003.pdf

[William Seger]

14. Again (and probably again and again)...

... you haven't addressed the fact that the videos show the upper block behaving "essentially as a rigid body." I don't find that behavior at all surprising considering the design: The purpose of those deep spandrel plates on the exterior walls was to create enough rigidity that the walls could act like a square beam to resist wind loading, and the "hat trusses" at the top created substantial rigidity between the exterior walls and the core columns. I would certainly expect that kind of structure to have much more rigidity than simple column-and-beam construction, and you offer absolutely nothing that makes me reconsider that expectation. Furthermore, you seem to have no response to my reasons for thinking that Bazant's simplified analysis substantially (and deliberately) overstates the ability of the building to resist collapse.

So, on the one hand, we see that the perfectly reasonable rigidity assumption by a recognized structural mechanics expert is completely substantiated by the video evidence, whereas on the other hand we have a non-expert conspiracist claiming that his totally unsubstantiated speculations constitute some kind of "smoking gun" that warrants opening a new investigation. Good luck with that.

Seffen mentioned the Bazant paper, but his own analysis arrives at the same "unavoidable total collapse" conclusion by a completely different method. In the paragraph immediately following the one you quoted, Seffen says, "This paper examines the collapse sequence by referring the behaviour to concepts familiar in studies on propagating instabilities." So, your claim that his analysis merely reflects Bazant's indicates that you didn't understand it, and it seems you have no comment on the other papers I mentioned, which also did not rely on Bazant. If I thought it would be useful, I'd try to relocate several other papers I've seem, but I get the feeling that would be a waste of time. (And by the way, the 31-times overload factor was a comparison of the kinetic energy versus the strain energy in the columns at maximum elastic compression, i.e. there was 31 times more energy than was required to begin deforming the columns. The collapse could have nonetheless been halted if the first set of columns had been able to absorb the excess energy via plastic deformation after that point. Bazant calculated that there was 8.4 times -- which I misremembered as 8.7 times, sorry -- more kinetic energy than could be absorbed by plastic deformation, so that's the critical overload factor. Bazant states that that's all a structural engineer needs to know to understand the total collapse, and you present absolutely nothing that really challenges that statement.)

All I can see in your analysis is the standard conspiracist approach of starting with a conclusion and desperately looking for reasons to pretend that your paranoid speculation is actually a rational conclusion, but then being forced to settle for rather dubious arguments while completely dismissing out-of-hand anything that doesn't fit. That approach -- the exact opposite of the scientific method -- might be still justified if you actually found something convincing, but I've given you my reasons for not seeing any "smoking gun" there. However, I don't set for myself the likely-impossible goal of convincing you, so carry on.

[errrrrrrrrrm]

17. Seffen

"The resulting impingement produced peak forces correctly identi¯ed by
Ba·zant and Zhou (2002) to be far in excess of the design capacity of these columns and hence, above
the expected value of \Pmax" (Fig. 1) that could be reasonably carried by them, even if perfect and
undamaged. These columns began to deform plastically, thereby seeding failure of this, next part of
the structure."

page 5 paragraph 1

EDIT - like I said, please keep questioning me, I'm not saying I've considered everything but the more you question me on it the easier it comes to either reject it or accept it.

[William Seger]

42. So, you're conceding that Seffen's analysis independently draws the same conclusion as Bazant's? n/t

[errrrrrrrrrm]

19. I think you've mis understood his paper

The upper section being rigid is essential for the equations to work, as m is no longer a constant, the equation that governs the initial impact* isn't linear, it's a quadratic.

*correction, the equation that calculates the maximum force applied by the upper section on impact with the lower section is a quadratic, in the equation m is a constant i.e. the mass of the whole upper section, if m isn't a constant (if the fires damaged the upper sections structure in the time prior to collapse suffiently to allow gravity to pull it apart before it impacts with the lower section) then his calculations don't work, I quote it explicity in version 3

[William Seger]

41. I think you've misunderstood what's seriously wrong with your argument

The videos show that the upper block DID act "essentially as a rigid body" so there's no point whatever in speculating what might have happened if it hadn't. Furthermore, the videos then show a total collapse that several completely different analyses explain, with exactly ZERO evidence of a controlled demolition. Your "smoking gun" is shooting blanks. You keep saying that you want someone to tell you what's wrong with your argument but then you keep ignoring the obvious answer.

[LARED]

4. Summary of key nonsense

NISTs official report says global collapse is inevitable following the establishment of the conditions for collapse. This is dependent on a 2002 paper proposing a mechanism for progressive collapse of a steel structured building.

Who says the NIST report in dependent on the Bazant and Zhoe paper? No one except you. My take is you are another CTer that misreads or poorly understands what Bazant and Zhoe wrote.


However the 2002 paper also clearly states that it is based on a hypothesis that the upper section is rigid at the instant of impact with the lower section.

Mr. Seger already responded to this claim. But it's worth repeating that videos show the upper floors acting essentially as a rigid body.

NISTs report fails to show that the upper section is rigid at the instant of impact and there is circumstantial evidence that the hypothesis is not true in the case of the twin towers,

Again connecting the NIST report with "the paper" is your conflation, and frankly is trival at best, and again it was pointed out the rigidity of the upper sections is not a key issue.

[wildbilln864]

5. you cannot....

run a VW beetle into a school bus and have the VW completely demolish the bus!

[William Seger]

7. you cannot...

... rationally compare a 110-story, 200-foot square steel and concrete structure to a VW and a school bus. Bazant's analysis is an energy-versus-strength argument that is not challenged by irrational analogies.

[zappaman]

9. and if your aunt had balls

she would be your uncle.
that's quite the analogy you have there!

[LARED]

10. Your comment is very telling

in that it betrays your lack of appreciation for the amount of kinetic energy in an object moving at 500 miles per hour.

If a VW rear ended a stationary bus fixed to the ground at around 500 miles per hour, I'm pretty confident the bus would be completely destroyed.

If a VW impacted the side of a stationary bus fixed to the ground, I am again confident the bus would very nearly completely destroyed.

Of course I am ignoring how ridiculous the analogy is.

[wildbilln864]

12. sorry dude...

that upper section of the tower wasn't falling at 500 mph! :shrug:

you can't use common sense!

[OnTheOtherHand]

27. the point was that your assertion was false

You didn't contest that point. Do you concede that your assertion was false, but not think that it matters?

[hack89]

15. But if the VW constantly gained mass while the collision happened

then the bus would be toast. Think about it.

[wildbilln864]

20. didn't happen at WTC towers!

think about that!

[hack89]

21. So the mass above the collapse zone didn't grow

as each floor was crushed in succession? The WTC collapsed one floor at at time - the falling mass grew all the way to the bottom. Surely even you can see that.

[wildbilln864]

22. surely you can see....

from this picture,


and in videos, that the crumbling building was pouring over the sides as it went down! And anti-truthers like to claim the building did not fall into it's footprint. If the building floors just piled up one on another as you say then it would have pretty much just been in it's own footprint.

[hack89]

25. So it didn't fall in it's footprint? How could have been CD then?

you do do notice that all heavy stuff like the steel beams went straight down? Remember all those pictures of that huge pile of steel? How much mass do you think all that gypsum dust in your picture really had?

[wildbilln864]

28. you're kiddin me right!?

look at the videos and the pics!

did they stack up or not in your opinion?
you really think all that is just gypsum dust? really!? :crazy: then what hit #7 300' away?


on edit: and it wasn't meant to look like a CD. It was meant to look like the planes took em down!
So there was nothing conventional about it!

[hack89]

30. So are you saying there were explosives on every floor

since there was not enough mass?

[wildbilln864]

33. no...nt

[terrafirma]

34. Could you show us

using Microsoft Paint which floors DID have the explosives?

[wildbilln864]

36. stupid question! nt

[hack89]

40. So you can't explain what happened? nt

[terrafirma]

24. Funny you say that.

I hit a school bus with a Ford Escort and both had to be towed.

That having been said, Spooked's bunny cage experiment is more applicable than your analogy.

And Spooked's bunny cage experiment wasn't applicable at all.

[wildbilln864]

26. thank you for your opinion...

incorrect as it is. :hi:

[terrafirma]

29. You're welcome

Good luck convincing people with your VW/bus analogy! :hi:

[wildbilln864]

31. wrong again!

I'm not trying to convince anyone. I want someone to convince me that I'm wrong and it really was a surprise attack and members of my government aren't really psycho murderous mofo's as it seems! I hope I am wrong and just believe in wild CTs for what ever reason. Their arguments fail though!

[terrafirma]

32. Call me crazy...

... but I doubt very much you're looking to be convinced otherwise.

Especially when you're willing form your opinions from "facts" pulled off of anonymous blogs.

[wildbilln864]

35. doesnt matter what you think...

you believe what ever you like.
As Nietzsche said, "There are no facts. Only interpretations."

[terrafirma]

37. Oooooh

That's deep.

[LARED]

39. Nietzsche, the guy that spent the last ten years of his life

in mental hospitals or under the care of his family. That guy?

Nietzsche, the guy whos' writings had great influence on Nazism.

There was some ground for this appropriation of Nietzsche as one of the originators of the Nazi Weltanschauung. Had not the philosopher thundered against democracy and parliaments, preached the will to power, praised war and proclaimed the coming of the master race and the superman--and in the most telling aphorisms? A Nazi could proudly quote him on almost every conceivable subject, and did. On Christianity: "the one great curse, the one enormous and innermost perversion... I call it the one immortal blemish of mankind.... This Christianity is no more than the typical teaching of the Socialists." On the State, power, and the jungle world of man: "Society has never regarded virtue as anything other than as a means to strength, power, and order. The State unmorality organized... the will to war, to conquest and revenge... Society is not entitled to exist for its own sake but only as a substructure and scaffolding by means of which a select race of beings may elevate themselves to their higher duties... There is no such thing as the right to live, the right to work, or the right to be happy: in this respect man is no different from the meanest worm." (Women, whom Nietzsche never had, he consigned to a distinctly inferior status, as did the Nazis, who decreed that their place was in the kitchen and their chief role in life to beget children for German warriors. Nietzsche put the idea this way: "Man shall be trained for war and woman for the procreation of the warrior. All else is folly." He went further. In Thus Spake Zarathustra he exclaims: "Thou goest to woman? Do not forget thy whip!"...) And he exalted the superman as the beast of prey, "the magnificent blond brute, avidly rampant for spoil and victory."

http://www.westernrevival.org/nietzsche.htm

[errrrrrrrrrm]

16. Version 3

Please keep the comments coming, the more you question me over it the more solid my argument seems to become.

An Independent Analysis Of NISTs Scientific Methods And Assumptions

Summary of Key points

NISTs official report says global collapse is inevitable following the establishment of the conditions for collapse. This is dependent on a 2002 paper proposing a mechanism for progressive collapse of a steel structured building. However the 2002 paper also clearly states that it is based on a hypothesis that the upper section is rigid at the instant of impact with the lower section. NISTs report fails to show that the upper section is rigid at the instant of impact and there is circumstantial evidence that the hypothesis is not true in the case of the twin towers, hence NISTs report is in error when it claims the conditions for the initiation of collapse it establishes will inevitably lead to global collapse.

Supporting Argument

NIST’s “Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Tower” (hereafter referred to as “The Final Report”) states its first objective was to “Determine why and how WTC 1 and WTC 2 collapsed following the initial impacts of the aircraft”1 (emphasis mine). To determine why and how the buildings collapsed The Final Report needs to explain the events following the initial impact until the collapse of the buildings is complete. NIST state that their approach was to simulate the behaviour of the tower using “four steps:

The aircraft impact into the tower, the resulting distribution of aviation fuel, and the damage to the structure, partitions, thermal insulation materials, and building contents.

The evolution of multi-floor fires.

The heating and consequent weakening of the structural elements by the fires.

The response of the damaged and heated building structure, and the progression of the structural component failures leading to the initiation of the collapse of the towers.”2 (emphasis mine)

Their approach appears to fall short of that which would be required to determine why and how the initial impacts resulted in the collapse of the towers as their stated approach stops at the initiation of collapse, not at the completion of it. There is no explicit explanation why they took this approach in The Final Report or in any of the supporting documents, however their footnotes state that they conducted “little analysis of the structural-behaviour of the tower after the conditions for collapse were reached and collapse became inevitable.”3 (emphasis mine – NOTE: in another footnote (footnote 13, page 82), “conditions for collapse” is replaced with “conditions for collapse initiation”, these are assumed to be one and the same). Although I can find no analysis of the structural behaviour of the tower after “the conditions for collapse” were met in The Final Report or supporting documents, this sentence implies they have made an assumption, or have unstated proof, that once the conditions for collapse are reached, the collapse that occurs must, inevitably, be the collapse that was observed. There is no justification offered for why this assumption was made and no evidence or sources given to support its validity.

However, elsewhere in The Final Report they state that their recommendation for further research into the “Prevention of progressive collapse” is “related” to 9/114 (emphasis mine). The Final Report also states that “Progressive collapse (or disproportional collapse) occurs when an initial local failure spreads from structural element to structural element resulting in the collapse of an entire structure or a disproportionately large part of it.”5 From this statement, and given the lack of explicit explanation, it can be inferred that “the conditions for collapse” were defined as the initial conditions for progressive collapse, which The Final Report states to be “an initial local failure spreads from structural element to structural element”. To check the validity of this definition it is necessary to examine the peer reviewed scientific papers modelling progressive collapse to see whether “an initial local failure spreads from structural element to structural element” does inevitably result in progressive collapse of the entire structure.

Reading the peer reviewed work on the subject of progressive collapse reveals that there has in fact only ever been one paper modelling the mechanics of the collapse of the twin towers (or the global collapse of any steel framed structure) after initiation of collapse, a paper called “Why Did the World Trade Center Collapse? – Simple Analysis” by Zdenek P. Bazant, Fellow ASCE, and Yong Zhou (hereafter referred to as “The Paper”). All other papers on the subject reference this paper directly (including Bazant authored papers on the subject discussing questions others have asked) and use it as a proven basis for further analysis or they state (paraphrased)“it has already been well established that at the moment of impact the steel in the lower section is overcome by an order of magnitude” i.e. The Paper is correct in all circumstances. Therefore if The Paper conclusively supports NISTs definition of “the conditions of collapse” then the definition can be assumed to be valid and hence NISTs conclusions are valid.

Using a simplified model the paper presents an analysis of the overall collapse of the twin towers and purports to show that the towers were doomed “if prolonged heating caused the majority of columns of a single floor to lose their load carrying capacity”6. In examining the paper I found that its internal logic was consistent and it seemed to support NISTs inferred definition. However, as stated in The Paper “an important hypothesis implied in this analysis is that the impacting upper part, many floors in height, is so stiff that it does not bend nor shear on vertical planes, and that the distribution of column displacements across the tower is almost linear, like for a rigid body. If, however, the upper part spanned only a few floors (say, 3 to 6), then it could be so flexible that different column groups of the upper part could move down separately at different times, producing a series of small impacts that would not be fatal (in theory, if people could have escaped from the upper part of the tower, the bottom part of the tower could have been saved if the upper part were bombed, exploded or weakened by some ‘smart’ structure system to collapse onto the lower part gradually as a mass of rubble, instead of impacting it instantly as an almost rigid body).”7 The paragraph is quoted in full as it has two fundamental implications directly linked to NISTs definition of “the conditions of collapse”.

The first implication is that, despite admitting that the flexibility of the upper section is dependent on the number of floors, and that it admits the upper section “could be so flexible that different column groups of the upper part could move down separately at different times, producing a series of small impacts that would not be fatal” no justification is offered as to where the threshold of flexibility is. Hence the assumption that 15 floors “is so stiff that it does not bend or shear on vertical planes, and that the distribution of column displacements across the tower is almost linear, like for a rigid body” must be proven to be true for the world trade centre towers before this paper can be proved to explain the towers complete collapse after initiation of collapse. (UPDATED: in an updated paper available on line it is stated how this conclusion was reached and so removes this question)

The second implication is that, as “the bottom part of the tower could have been saved if the upper part were bombed, exploded or weakened by some ‘smart’ structure system to collapse onto to the lower part gradually as a mass of rubble, instead of impacting it instantly as an almost rigid body”, then it must be shown conclusively that the ‘system’ suggested (but not referred to in these terms) by both NIST and The Paper, namely rising heat from the fires started by the jet fuel from the planes, did not weaken the upper section sufficiently to “collapse onto the lower part gradually as a mass of rubble” in the specific case of the world trade centre before The Paper can be proved to explain the towers collapse.

Studying the calculations used to determine the overload ratio’s shows that it is dependent on the mass at the instant of impact (assumed to be approximately 58000 tonnes), if the upper section was broken into, say, 3 identical pieces then the overload ratio would have to be calculated for an impact of 19333 tonnes, then another, separate 19333 tonnes, and then again.

More specifically The Paper states that the maximum force applied by the upper part, P, can be calculated using the equation:
mg(h+ P/C)= P^2/2C
Where h=3.7m is the height of the critical floor columns, C≈71 GN/m is the stiffness of the structure beneath, g=9.8m/s^2 is acceleration due to gravity, and m≈58×〖10〗^6 kg is the mass of the upper part, which is where the assumption that that the entire mass of the upper section impacts the lower section is of most importance.

The importance of whether the upper section is rigid or not at the point of impact can be easily demonstrated by visualising a simple model. Consider a solid tower with a density equal to that of sand. If we drop a solid object with a mass of, say, 1 Kg, and the density of sand on top of that tower then it is easy to see how the mechanism proposed in The Paper applies (shown in Fig. 1 in The Paper8), however if we allow 1 Kg of sand to fall on top of the same tower then it is clear that mechanism proposed in the paper does not apply.

The importance of whether the upper section of the tower was rigid at the instant of impact can also be seen when comparing the diagrams in Fig. 1.3, 1.4 and 1.5 from The Paper8 showing the stages of ‘progressive collapse’ with the visual record:

/>
/>
/>

Clarification or important points

In their supporting documents9 NIST do discuss other collapse hypotheses, The Paper already mentioned, Weidlinger Associates 2002 study which was to show that the two collapses were independent of each other and deals only with the collapse initiation, Maryland which they state they disagree with and two students from Edinburgh and Arup, both of which deal with cross-sectional areas and so don’t impact the implied hypothesis in The Paper. Hence my assertion that the only justification for their collapse initiation conditions inevitably leading to global collapse is Bazants 2002 paper.

Quotes from other papers on the subject include:

“To explain the collapse, it was proposed (on September 13, 2001; Bazant 2001; Bazant and Zhou 2002) that viscoplastic buckling of heated and overloaded columns caused the top part of tower to fall through the height of at least one story, and then shown that the kinetic energy of the impact on the lower part must have exceeded the energy absorption capacity of the lower part by an order of magnitude.” - What Did and Did not Cause Collapse of WTC Twin Towers in New York (Bazant, LE, Greening and Benson, Journal of Engineering Mechanics ASCE, Vol 134 2008)

“The subsequent near free-falling of these upper parts over the height of just one storey resulted in dynamical “over-loading" of the relatively undamaged lower columns by a factor of 30 compared to their static load capacity, according to Ba•zant and Zhou (2002)” – Progressive Collapse of the World Trade Center: a Simple Analysis (Seffen, 2007)

“Regardless of the load capacity of the columns, there is no way to deny the inevitability of progressive collapse driven by gravity alone if this criterion is satisfied (for the World Trade Center it is satisfied with an order-of-magnitude margin)” Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions (Bazant and Verdure, 2007)

Another paper on the subject makes the same assumption, but unlike Bazant doesn’t state the limitations:

“We consider the initiating event of a WTC tower collapse to be the failure of crucial steel support structures at the appropriate upper floor level of the building, followed by the free fall of the entire upper block of n floors through a distance” Energy Transfer in the WTC Collapse (Greening, )
The Final Reports flow chart10 also shows that only three of their studies fed into the global collapse scenario, NCSTAR 1-2 which studies specifically what the impact damage was and hence where the load above impact was redistributed to, NCSTAR 1-3 which studies the structural steel response of the additional heat and additional load caused by the redistribution to determine the point of failure of the supporting steel, again used to determine if initiation of collapse was due to impact and fire only, and NCSTAR 1-6 which determines the structural fire response to show where the fires were located around the impact site to find where the collapse was initiated. None of this research is used to determine whether the fires in the upper section were enough to weaken it to the point where the initiation of gravitational collapse was enough to break it apart before it impacted the lower section.

Further evidence of their assumption is found in NISTs FAQ released in 200710, which states:

“1. Was there enough gravitational energy present in the World Trade Center Towers to cause the collapse of the intact floors below the impact floors? Why was the collapse of WTC 1 and 2 not arrested by the intact structure below the floors where columns first began to buckle?

Yes, there was more than enough gravitational load to cause the collapse of the floors below the level of collapse initiation in both WTC Towers. The vertical capacity of the connections supporting an intact floor below the level of collapse was adequate to carry the load of 11 additional floors if the load was applied gradually and 6 additional floors if the load was applied suddenly (as was the case). Since the number of floors above the approximate floor of collapse initiation exceeded six in each WTC Tower (12 and 29 floors, respectively), the floors below the level of collapse initiation were unable to resist the suddenly applied gravitational load from the upper floors of the buildings.”

So the assumption, once again, is that the upper section remained intact, the only analysis performed is the difference between gradual application of the load and sudden application. This does not test the implied hypothesis in The Paper, it is merely the difference between the steel support slowly giving way or giving way quickly. In fact this statement suggests that (assuming 15 floors above the impacts site) if indeed the upper section did break up under the force of gravity before impacting the lower section, and each individual section to impact the lower section was less than 6 complete floors in mass, and more than 4 floors worth of material was ejected and didn’t impact the lower section, then collapse due to gravity only wasn’t possible. Given the visual evidence of both the extent of the fires above the impact site and the collapse itself I would suggest that this scenario is possible.

“10. Why didn’t NIST fully model the collapse initiation and propagation of WTC Towers?

The first objective of the NIST Investigation included determining why and how WTC 1 and WTC 2 collapsed following the initial impacts of the aircraft (NIST NCSTAR 1). Determining the sequence of events leading up to collapse initiation was critical to fulfilling this objective. Once the collapse had begun, the propagation of the collapse was readily explained without the same complexity of modeling, as shown in the response to question #1 above.” (emphasis mine)

So once again their argument is circular, their response to question one is dependent on the assumption that the upper section had not been weakened enough by the fires to suffer break up under gravity alone before it impacts the lower section, a scenario that hasn’t been shown to be the case.

Conclusion

The crucial implied hypothesis stated in The Paper means the inferred definition of “the conditions for collapse” in The Final Report is incomplete and should have been “an initial local failure spreads from structural element to structural element, and proof that the upper section of the tower was a rigid body at the instant of impact with the lower section”.

Furthermore, if indeed there are no other demonstrable mechanisms for explaining the total collapse of the lower section of the towers then the inferred definition of “the conditions for collapse” is irrelevant. NISTs model must show that at the instant of impact with the lower section the upper section was still a “rigid body”. Anything less than this means that the mechanism for progressive collapse demonstrated in The Paper has not been shown to inevitably follow on from the model in The Final Report and the model in The Final Report would therefore be a scenario based on an unproven and, in the specific case of the twin towers, suspect hypothesis.

As The Final Report and supporting documents (including the WTC 1 collapse sequence as described in the supporting documents11 and 12) do not show that the upper section must have still been a “rigid body” at the instant of impact with the lower section, The Final Report does not, as it claims, explain how the twin towers collapsed from impact and fire damage alone, it is only a possible sequence of events based on an unproven and suspect hypothesis and it will remain so until they rectify the fatal flaw in the formulation of their approach.

Footnotes

1 Section E.1, page xxxv of The Final Report
2 Section E.2, pages xxxvi and xxxvii of The Final Report
3 Footnote 2, page xxxvii of The Final Report
4 Table E-1, page xliv of The Final Report
5 Footnote 19, page 206 of The Final Report
6 page1 of The Paper (page is labelled XVII in linked document)
7 pages 2 and 3 of The Paper (pages are labelled XIX and XX in linked document)
8 page 8 of The Paper (page is labelled XXV in linked document)
9 Section 9.4.4 beginning on page 322 of NIST NCSTAR 1-6D
10 page xxxi of the Final Report
11 Section E.3.1 beginning on page lii of NIST NCSTAR 1-6D
12 section 9.4.5 beginning on page 326 of NIST NCSTAR 1-6D

Sources

The Final Report: http://www.nist.gov/customcf/get_pdf.cfm?pub_id=909017
Supporting document NIST NCSTAR 1-6D: http://www.nist.gov/customcf/get_pdf.cfm?pub_id=101366
Other supporting documents to The Final Report: http://www.nist.gov/el/disasterstudies/wtc/wtc_finalreports.cfm
NIST information on progressive structural collapse: http://www.nist.gov/el/topic_collapse.cfm
The Paper: http://www.mae.ncsu.edu/eischen/courses/mae543/docs/BazantWTC.pdf
Selected list of Scientific papers on the progressive collapse of the twin towers: http://sites.google.com/site/wtc7lies/peer-reviewedpapersaboutthewtcimpacts,fi
FAQ: http://www.nist.gov/public_affairs/factsheet/faqs12007.cfm
Weidlinger Assocites Study: http://www.wai.com/articles_pdf/webAS_abboudlevy_wtc_asceforensic_2003.pdf
Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions (Bazant and Verdure, 2007): http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/466.pdf
Progressive Collapse of the World Trade Center: a Simple Analysis (Seffen, 2007): http://winterpatriot.pbworks.com/f/seffen_simple_analysis.pdf
What Did and Did not Cause Collapse of WTC Twin Towers in New York (Bazant, LE, Greening and Benson, Journal of Engineering Mechanics ASCE, Vol 134 2008): http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20Did%20&%20Did%20Not%20Cause%20It.pdf
Energy Transfer in the WTC Collapse (Greening, ): http://www.911myths.com/WTCREPORT.pdf

[terrafirma]

23. This is like Loose Change

Only in text form.

How many versions of your theory are you planning on releasing, and can we expect them all to be made in to straight-to-YouTube videos?

[greyl]

38. Don't forget about these other responses:

http://forums.randi.org/showthread.php?t=217634