2/25/11 Answers from NIST to Questions by Chris Mohr, Journalist

(Comments by me have been added to this article in red)

The following written answers were provided to Chris Mohr, Investigative journalist, by NIST (National Institute of Standards and Technology) on 2/25/11 in preparation for the debate that Mohr had with AE911Truth in Boulder, CO on 3/6/11. Listen to that debate here.

From: "Newman, Michael E."
To: Chris Mohr
Sent: Fri, February 25, 2011 10:23:53 AM
Subject: Answers to Your Questions

Chris,

Below are the answers to your questions as requested. We apologize for the delay in getting these to you but we wanted to be certain that we provided you with the most complete and up-to-date responses that we could. Hopefully, these will help you as you prepare for your debate.

Thanks for your patience. Let us know if we can be of further assistance.

Best wishes,

Michael

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1) Just making sure I understand sag vs pancake etc., getting clear on the difference and why the pancake theory popularized on public TV several years ago is no longer accepted. Also is there photographic evidence of sagging steel structures and steel columns being pulled inward? I do have figure 2-12 with the lattice overlay of inward buckling. I'll be using a lot of slides and videos (as will Richard) and visuals work well for this audience.

NIST’s findings do not support the “pancake theory” of collapse, which is premised on a progressive failure of the floor systems in the WTC towers (the composite floor system—that connected the core columns and the perimeter columns—consisted of a grid of steel “trusses” integrated with a concrete slab). Instead, the NIST investigation showed conclusively that the failure of the inwardly bowed perimeter columns initiated collapse and that the occurrence of this inward bowing required the sagging floors to remain connected to the columns and pull the columns inwards. Thus, the floors did not fail progressively to cause a pancaking phenomenon.

Note that the first part of NIST's answer is simply a repeat of one of their answers at their FAQ section on the WTC investigation. As we will see, several of NIST's answers to Mohr are just repeats of points that have already been raised at their FAQ page.

The change from “truss failure and pancake collapse” to the “weakened trusses that did not completely fail causing inward bowing of the perimeter columns and a non-progressive collapse” was acknowledged in the second of two NOVA TV documentaries about Ground Zero. The first program, “Why the Towers Fell” in 2002, discussed the truss failure/pancake collapse theory postulated by the Building Performance Assessment Team study (done by the Federal Emergency Management Agency and the American Society of Civil Engineers) that was the precursor to our more comprehensive investigation (which was under way at the time the program was produced). The follow-up program, “Building on Ground Zero” in 2006, corrected their previous report with a discussion of the “inward bowing” mechanism.

In his review of NIST's FAQ page, Jim Hoffman notes NIST's likely reason for changing their collapse theory:

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In the following, NIST squirms away from the assertion that the 'collapses' of the Twin Towers were progressive collapses. It does this by describing the floor pancaking model (endorsed by earlier versions of the official story, such as FEMA, NOVA, and Eagar) as a progressive collapse, thereby implying that NIST's theory is not a progressive collapse theory.

However, regardless of whether one calls the total destruction of the Twin Towers progressive collapse or something else, it remains true that there is no historical or experimental basis for believing that collapse events near the tops of the towers could progress all the way down the towers' vertical axes to produce total collapses. Lacking such a basis, the core assumption of NIST's theory is unscientific. _______________________________________________________

Indeed, there are no examples at all of a high-rise steel-framed skyscraper totally collapsing from fire. As for the inward bowing, Jim Hoffman has noted an alternative scenario for how it could have happened, as NIST has no evidence for the kinds of temperatures needed to cause it.

The inward bowing could be caused through some type of demolition scenario.



2) Making sure I understand how to calculate the kinetic energy of the fall. Besides f=ma, what are the factors that determine how much more force gravity adds to a falling object? Richard Gage says there is not enough kinetic energy for the collapse to continue, but with the f=ma formula it seems that an object hits with 9.8 times more force just in the first second (assuming not much elasticity... and concrete and steel aren't all that elastic). By the way, I will be dropping a 25 pound dumbbell on a bathroom scale from 6 1/2 feet up. That's only half a story. In my first debate with a local 911 guy I crushed the scale completely. It's not scientific but I think it does demonstrate how even 25 pounds in free fall quickly generates enough force to crush a scale designed to measure the weight of a 300-pound object!

NIST estimated the elapsed times for the first exterior panels to strike the ground after the collapse initiated in each of the towers to be approximately 11 seconds for WTC 1 and approximately 9 seconds for WTC 2. These elapsed times were based on: (1) precise timing of the initiation of collapse from video evidence, and (2) ground motion (seismic) signals recorded at Palisades, N.Y., that also were precisely time calibrated for wave transmission times from lower Manhattan (see NCSTAR 1-5A).

As documented in Section 6.14.4 of NIST NCSTAR 1, these collapse times show that:

“… the structure below the level of collapse initiation offered minimal resistance to the falling building mass at and above the impact zone. The potential energy released by the downward movement of the large building mass far exceeded the capacity of the intact structure below to absorb that energy through energy of deformation.

Since the stories below the level of collapse initiation provided little resistance to the tremendous energy released by the falling building mass, the building section above came down essentially in free fall, as seen in videos. As the stories below sequentially failed, the falling mass increased, further increasing the demand on the floors below, which were unable to arrest the moving mass.”

In other words, the momentum (which equals mass times velocity) of the 12 to 28 stories (WTC 1 and WTC 2, respectively) falling on the supporting structure below (which was designed to support only the static weight of the floors above and not any dynamic effects due to the downward momentum) so greatly exceeded the strength capacity of the structure below that it (the structure below) was unable to stop or even to slow the falling mass. The downward momentum felt by each successive lower floor was even larger due to the increasing mass.

Here we have another rehashing of the points raised in NIST’s FAQ on the WTC. As pointed out by Jim Hoffman:

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NIST's assertion that the Tower's intact structure was "unable to stop or even to slow the falling mass" is absurd:

• It requires us to believe that the massive steel frames of the towers provided no more resistance to falling rubble than air.
• It ignores the fact that most of the rubble fell outside the towers' footprints, and hence could not contribute to crushing.
• It is unsupported by any calculation or logical argument.

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Indeed, the NIST report provides no calculations to back up this assertion. And calculations that have been done to support this notion have been addressed and refuted numerous times here, here, here, and here. NIST’s response does nothing to answer Mohr’s question.

From video evidence, significant portions of the cores of both buildings (roughly 60 stories of WTC 1 and 40 stories of WTC 2) are known to have stood 15 to 25 seconds after collapse initiation before they, too, began to collapse. Neither the duration of the seismic records nor video evidence (due to obstruction of view caused by debris clouds) are reliable indicators of the total time it took for each building to collapse completely.

This point has also been addressed by Hoffman:

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To the contrary, video records, such as this record of the North Tower's fall clearly establish upper boundaries on the times that it took for the vast majority of each tower to be destroyed.
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3) The tops of WTC I and II have been compared to pile drivers pushing the building through a natural collapse. But since both the top and bottom of the buildings were of similar structural strength, it looks to me like the bottom of the building was like a pile driver for the top as well. As the top of the building loses its structure while crashing down onto the very strong steel supports of the bottom part, how does the structural collapse of the top affect its ability to keep pushing down on the bottom of the building?

Since the stories below the level of collapse initiation provided little resistance to the tremendous energy released by the falling building mass, the building section above came down essentially in free fall, as seen in videos. As the stories below sequentially failed, the falling mass increased, further increasing the demand on the floors below, which were unable to arrest the moving mass.

In other words, the momentum (which equals mass times velocity) of the 12 to 28 stories (WTC 1 and WTC 2, respectively) falling on the supporting structure below (which was designed to support only the static weight of the floors above and not any dynamic effects due to the downward momentum) so greatly exceeded the strength capacity of the structure below that it (the structure below) was unable to stop or even to slow the falling mass. The downward momentum felt by each successive lower floor was even larger due to the increasing mass.

From video evidence, significant portions of the cores of both buildings (roughly 60 stories of WTC 1 and 40 stories of WTC 2) are known to have stood 15 to 25 seconds after collapse initiation before they, too, began to collapse. Neither the duration of the seismic records nor video evidence (due to obstruction of view caused by debris clouds) are reliable indicators of the total time it took for each building to collapse completely.

Not only is this a repeat of NIST’s FAQ page, it’s a repeat of their previous answer to Mohr’s previous question! Does NIST have the capability of originality? These points about the “pile driver” have already been addressed. As for the cores of the Towers, photographs show that the remaining portion of the South Tower’s core included only the inner 23 core columns. The 24 outer core columns are evidently missing.

As pointed out by Tony Szamboti:
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The fact that 50 to 60 story high portions of the central core remain standing for several seconds, in the collapses of both twin towers, does pour cold water on the crush down (pile driver) theory of Bazant and the NIST. What many don't know is that it was only the 23 inner core columns which remained standing, and none of the significantly larger outer 24 core columns. This was brought to light by Muhammad Columbo in 2007 and enabled mechanical engineer Gordon Ross… to be the first to fully dissect just how the towers were demolished.
The reality is that the 24 outer core columns and the corners of the perimeters were taken out to effect the demolitions of the twin towers. Gordon does a very good job of explaining this on the website he took the time to create, for just this purpose at http://gordonssite.tripod.com/id2.html
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Again, NIST’s response does nothing to answer Mohr’s questions.

4) How could the towers have collapsed almost straight down? I have good answers (building was 95% air by volume, no lateral force like an earthquake pushed it to the side, etc). Still, I can't quite answer their assertion that a mostly straight-down collapse would have required that hundreds of structural supports all fail at once, that the randomness of natural fires creates asymmetrical collapses.

In the absence of any lateral forces acting on the falling mass, gravity will cause the mass (upper stories of the building) to collapse straight down. Core members were still standing after the rest of the building had collapsed.

This point is highly misleading, as the upper section of the South Tower initially collapsed in an extremely asymmetrical fashion. And yet, the collapse became more symmetrical as it progressed. A natural collapse should usually become less symmetrical as it progresses. As pointed out by 911research.wtc7.net:

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The centered collapses meant the falling mass followed the path of maximum resistance. That's the opposite of how we expect a structure to behave when it falls apart in any kind of natural process. Even if the towers were made out of clay, we wouldn't expect them to collapse in such a dead-centered fashion. It's all the more incredible that a steel structure would shred itself by falling into itself instead of falling over.

There are many examples of steel-framed buildings undergoing unintentional collapses as a result of severe earthquakes. In contrast to the destruction of the Twin Towers, no such collapses have been vertical or total -- let alone explosive. Rather, steel-framed buildings destroyed by earthquakes have toppled.
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Again, a straight down collapse of a steel framed structure has only ever happened in a controlled demolition.

5) Do you have an explanation for the iron microspheres in the WTC dust? Controlled demolition theorists assert this is evidence of very high temperatures during the collapse, well over 2000 degrees, which leads them to thermites. The "911 debunkers" claim the microspheres are in printer toner, burnt garbage ash, concrete, etc but I can't find evidence of this.

NIST did not study the “microspheres.” The body of available evidence does not support the theory that thermite or nanothermite was used to demolish the WTC Towers or WTC 7.

This is not the first time NIST has openly admitted that they never looked for evidence of explosives or incendiaries. NIST did not find any evidence that thermite was used in the demolition of the Towers because they never looked for it.

As far as the “microspheres” that were claimed to have been found at Ground Zero, there are two arguments against their being linked to thermite or nanothermite. First, there is no "chain of custody" for the samples. They cannot be traced back to anything "used" in the towers or WTC 7, or for that matter, or to any of the these three buildings at all.

On the contrary, the chain of custody has been well established for the samples Dr. Jones has collected.

Secondly, even if the samples could be conclusively linked to one of the three WTC buildings, there are hundreds of possible sources for the samples reported. For example, the alternative theory groups have often cited a U.S. Geological Survey paper, “Particle Atlas of World Trade Center Dust Report,” as documenting the chemical signature of thermite. However, a review of the actual paper (http://pubs.usgs.gov/of/2001/ofr-01-0429/chem1/) shows that the authors state that "the trace metal compositions of the dust and girder coatings likely reflect contributions of material from a wide variety of sources. Possibilities include metals that might be found as pigments in paints (such as titanium, molybdenum, lead, and iron), or metals that occur as traces in, or as major components of, wallboard, concrete, aggregate, copper piping, electrical wiring, and computer equipment. Further detailed SEM studies of dust and beam coating samples are needed to develop a better understanding of the residences of metals in the samples. A detailed review of the materials used in construction, and the elemental composition of materials commonly found in office buildings would also be useful to understand more completely the potential sources and compositions of the materials in the dusts." There is NO mention of thermite or nanothermite as a possible source.

The idea that the spheres could have been formed from the natural materials in the buildings is absurd. As Gordon Ross has pointed out:

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If I leave margarine, flour, sugar and fruit in a cupboard, when I next open the cupboard I will not find a fruit crumble. Some mechanism is required to convert the ingredients. Similarly, if I take these same ingredients, set them alight and throw them out the window, I still will not get my fruit crumble. The mechanism must have some order.
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Similarly, Jim Hoffman has pointed out that:

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Although these elements -- aluminum, iron, oxygen, and silicon -- were all abundant in building materials used in the Twin Towers, it is not possible that such materials milled themselves into fine powder and assembled themselves into a chemically optimized aluminothermic composite as a by-product of the destruction of the Twin Towers.
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As for the microspheres, Hoffman also points out that:

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"Debunkers" have proposed that the iron-rich spheres were fly ash residues embedded in the Towers' concrete, ignoring that the iron constituents in fly ash are oxides rather than elemental iron. How will they explain away the bi-layered chips, whose red layers have iron oxide and elemental aluminum in the ratio of Fe2O3 thermite as nano-sized particles of uniform shape?
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To date, there is still no explanation for the iron microspheres or the red/gray chips.

6) For Building Seven, if column 79 had failed, weren't there redundant support structures somewhere to shift the load to, at least partially? It seems that all big buildings are designed with structural redundancies. How can one column's failure bring the whole building down? I do see an eight-second time period on the video of the Bldg 7 collapse after the east penthouse goes down. Is that when the structural load shifted momentarily before the global collapse?

The heat from the uncontrolled fires caused steel floor beams and girders to thermally expand, leading to a chain of events that caused a key structural column to fail. The failure of this structural column then initiated a fire-induced progressive collapse of the entire building.

According to the report's probable collapse sequence, heat from the uncontrolled fires caused thermal expansion of the steel beams on the lower floors of the east side of WTC 7, damaging the floor framing on multiple floors.

And yet, as others have pointed out, NIST’s estimated fuel loading for the floors they claimed failed could not have provided sufficient energy to cause collapse in the first place.

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"[R]aising those five floor beams to a temperature of 600°C would require an enormous amount of energy, far more than was available from the burning of the office furnishings underneath the floor beams." -Kevin Ryan

"NIST's collapse initiation hypothesis requires that structural steel temperatures on floors 12/13 significantly exceeded 300°C [570°F]--a condition that could never have been realized with NIST's postulated 32 kg/m2 fuel loading." -Dr. Frank Greening
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Eventually, a girder on Floor 13 lost its connection to a critical column, Column 79, that provided support for the long floor spans on the east side of the building. The displaced girder and other local fire-induced damage caused Floor 13 to collapse, beginning a cascade of floor failures down to the 5th floor. Many of these floors had already been at least partially weakened by the fires in the vicinity of Column 79. This collapse of floors left Column 79 insufficiently supported in the east-west direction over nine stories.

However, evidence shows that NIST has greatly misrepresented the construction of Building, and shows that the girder should NOT have failed.

The unsupported Column 79 then buckled and triggered an upward progression of floor system failures that reached the building's east penthouse. What followed in rapid succession was a series of structural failures. Failure first occurred all the way to the roof line-involving all three interior columns on the easternmost side of the building (79, 80, 81). Then, progressing from east to west across WTC 7, all of the columns failed in the core of the building (58 through 78). Finally, the entire façade collapsed.

This description of WTC7’s internal failures is completely inconsistent with videos of the building’s collapse, as pointed out by Dr. Frank Greening:

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"According to NIST, the global collapse of WTC 7 began 6.9 seconds after the East Penthouse collapse or about 23 seconds into the simulation. Now consider NIST’s Figures 12-66, 12-67 and 12-69 and in particular the images showing the alleged state of the core 17.5, 19.5, 20.7, 21.8, 24.1, 26.8 and 28.8 seconds into the collapse simulation. These images represent NIST’s view of what the core looked like at ~1-2 second intervals following the collapse of the East Penthouse. What is most significant about these images is that around the time of global collapse initiation NIST’s simulation shows that the eastern half of the core had completely collapsed while the western half of the core remained standing and relatively undamaged. This is quite remarkable since videos of the collapse of WTC 7 show that up to and well beyond the moment that the roofline of WTC 7 exhibited its first downward movement, the exterior of the building revealed absolutely no signs of NIST’s proposed partial collapse of the core even though the core was connected to the exterior walls of Building 7 by dozens of horizontal beams on every floor."
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7) Your official 2008 report says that Building 7 fell at 100% of free fall acceleration for over two seconds of the collapse. Even if the major support structure had collapsed, it seems there would have to be SOME resistance to the collapse. How is this possible?

In the draft WTC 7 report (released for public comment on Aug. 21, 2008), NIST stated that the north face of the building descended 18 stories (the portion of the collapse visible in the video) in 5.4 seconds, based on video analysis of the building collapse. This time period is 40 percent longer than the 3.9 seconds this process would have taken if the north face of the building had descended solely under free fall conditions. During the public comment period on the draft report, NIST was asked to confirm this time difference and define the reasons for it in greater detail. That was done for the final WTC 7 report (released Nov. 20, 2008).

To further clarify the descent of the north face, NIST recorded the downward displacement of a point near the center of the roofline from first movement until the north face was no longer visible in the video. Numerical analyses were conducted to calculate the velocity and acceleration of the roofline point from the time-dependent displacement data. The instant at which vertical motion of the roofline first occurred was determined by tracking the numerical value of the brightness of a pixel (a single element in the video image) at the roofline. This pixel became brighter as the roofline began to descend because the color of the pixel started to change from that of the building façade to the lighter color of the sky.

The analyses of the video (both the estimation of the instant the roofline began to descend and the calculated velocity and acceleration of a point on the roofline) revealed three distinct stages characterizing the 5.4 seconds of collapse:

* Stage 1 (0 to 1.75 seconds): acceleration less than that of gravity (i.e., slower than free fall).
* Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall)
* Stage 3 (4.0 to 5.4 seconds): decreased acceleration, again less than that of gravity

This analysis showed that the 40 percent longer descent time—compared to the 3.9 second free fall time—was due primarily to Stage 1, which corresponded to the buckling of the exterior columns in the lower stories of the north face. During Stage 2, the north face descended essentially in free fall, indicating negligible support from the structure below. This is consistent with the structural analysis model which showed the exterior columns buckling and losing their capacity to support the loads from the structure above. In Stage 3, the acceleration decreased as the upper portion of the north face encountered increased resistance from the collapsed structure and the debris pile below.

NIST’s response does nothing to answer Mohr’s question. This is, yet again, a repeat of the points NIST has already raised in their report and the FAQ pages. They provide no calculations to support their assertion that the buckling of the lower floors could cause the building to descend in free fall.

8.) Your report says that the Building 7 fires were scattered on several floors, that was not one huge fire. How do I reconcile this information with a global collapse of a steel framed building for the first time ever.

Debris from the collapse of WTC 1, which was 370 feet to the south, ignited fires on at least 10 floors in the building at its south and west faces. However, only the fires on some of the lower floors-7 through 9 and 11 through 13-burned out of control. These lower-floor fires-which spread and grew because the water supply to the automatic sprinkler system for these floors had failed-were similar to building fires experienced in other tall buildings. The primary and backup water supply to the sprinkler systems for the lower floors relied on the city's water supply, whose lines were damaged by the collapse of WTC 1 and WTC 2. These uncontrolled lower-floor fires eventually spread to the northeast part of WTC 7, where the building's collapse began.

As NIST itself has stated, the fires in WTC7 were likely no more severe and probably less severe than the fires in other buildings. They blamed the collapse on the fires and the construction of the building, which we have already seen NIST misrepresented.

As stated previously above, the heat from the uncontrolled fires caused steel floor beams and girders to thermally expand, leading to a chain of events that caused a key structural column to fail. The failure of this structural column then initiated a fire-induced progressive collapse of the entire building.

Again, NIST has not provided proof of either the temperatures of the fires, nor shown how their models of the building’s collapse are consistent with the videos.

9.) In Appendix C of an earlier FEMA report (http://wtc.nist.gov/media/AppendixC-fema403_apc.pdf), there is talk of sulfidized steel. Chemistry is a weak spot for me; I understand physics better. Richard Gage makes a big deal about this Appendix and his assertion that it is not dealt with in the subsequent NIST report. From the 1000 or so pages I have read of your report, I haven't found it either, and I see much more physics than chemistry in your report. That said, I have to try to find an answer to this question of how there was melted and sulfidized steel. Is there a chemist at NIST who has researched this? So far I have come up with this:

a) Sulfidized steel melts at a lower temperature than regular steel (I have read figures of both 1800 and 2200 degrees F).
b) Gypsum, which is 18% sulfur, was used as fire insulation for some of the steel beams and trusses.
c) I don't know how steel is sulfidized. Is mere proximity of steel and sulfur during a fire enough to sulfidize steel?
d) If so, could some steel have been sulfidized in the WTC fires, causing some steel to melt at the lower temperatures of the WTC fires? Or is there another explanation? Or is there no explanation yet? Except for this I have so far been able to find alternative explanations for melted steel in the rubble (such as melted aluminum from airplanes and cars in the basement garages).

The steel sections used in the other WTC buildings (WTC 3, 4, 5, 6, and 7) were conventional sections and were not marked. Thus it was not possible to conclusively trace the piece studied in the FEMA report to a particular building. It is also not possible to determine how and when the sulfidation occurred. It is important to note that NIST found that the steel only needed to heat sufficiently to lose a substantial amount of its strength and stiffness, which occurs at a temperature well below the melting point.

NIST’s claim that “it was not possible to conclusively trace the piece studied in the FEMA report to a particular building” is contradicted by Dr. Jonathan Barnett, who has said that the type of steel found could be traced to WTC7. But even if it could not conclusively be traced back to WTC7, this is still no excuse not to examine it, as it obviously came from Ground Zero.

And although, as NIST claims, it is not known when the sulfidation occurred, the FEMA investigators did suggest that it’s “possible that the phenomenon started prior to collapse and accelerated the weakening of the steel structure.”

Note that NIST still continues to talk about steel weakening, whereas Mohr’s question had to do with the steel melting. NIST has provided no explanation for the sulfidation of the steel, and any of the natural sources of sulfur in the buildings has been ruled out.

Conclusion:

NIST has done nothing to answer any of Mohr’s questions. They have simply rehashed many of their old points which have long been debunked. Hopefully Mohr will be able to see through NIST’s deceptiveness in the future.