How does NIST know that any core columns were severed between floors 93 and 98? Pls provide the evidence. The photos of videos of the poor woman later appearing leaning at some severed exterior columns and standing on floor 94 - not severed - and waving does not show any severe damages inside the WTC1 north wall at all. Look, please. Use your eyes. Use your brain. And do not just believe what some poor NIST employées invent to please their Masters in the hope to please them.
RFC: Bazant and Zhou Simple Analysis refuted
- Thread starter GregoryUrich
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How does NIST know that any core columns were severed between floors 93 and 98? Pls provide the evidence. The photos of videos of the poor woman later appearing leaning at some severed exterior columns and standing on floor 94 - not severed - and waving does not show any severe damages inside the WTC1 north wall at all. Look, please. Use your eyes. Use your brain. And do not just believe what some poor NIST employées invent to please their Masters in the hope to please them.
DavidJames
Penultimate Amazing
Okay, so some "NIST employees" are co-conspirators in the murder of 3000 people.
Care to tell us specifically who they are and what you plan on doing to bring justice.
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Pookster
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Use our eyes and brains? I saw a floor slab missing where there should've been one. You don't consider that severe damage?
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From http://wtc.nist.gov/oct05NCSTAR1-2index.htm:
In order to estimate the aircraft impact damage to the WTC towers, the following steps were undertaken:
• Constitutive relationships were developed to describe the behavior and failure of the materials under the dynamic impact conditions of the aircraft. These materials included the various grades of steels used in the exterior walls, core columns, and floor trusses of the towers, weldment metal, bolts, reinforced concrete, aircraft materials, and nonstructural contents.
• Global impact models were developed for the towers and aircraft. The tower models included the primary structural components of the towers in the impact zone, including exterior walls, floor systems, core columns, and connections, along with nonstructural building contents. A refined finite element mesh was used for the areas in the path of the aircraft, and a coarser mesh was used elsewhere. The aircraft model included the aircraft engines, wings, fuselage, the empennage, and landing gear, as well as nonstructural components of the aircraft. The aircraft model also included a representation of the fuel, using the smooth particle hydrodynamics approach.
• Component and subassembly impact analyses were conducted to support the development of the global impact models. The primary objectives of these analyses were to (1) develop an understanding of the interactive failure phenomenon of the aircraft and tower components, and (2) develop the simulation techniques required for the global analysis of the aircraft impacts into the WTC towers, including variations in mesh density and numerical tools for modeling fluid-structure interaction for fuel impact and dispersion. The component and subassembly analyses were used to determine model simplifications for reducing the overall model size while maintaining fidelity in the global analyses.
• Initial conditions were estimated for the impact of the aircraft into the WTC towers. These included the aircraft speed at impact, aircraft orientation and trajectory, and impact location of the aircraft nose. The estimates also included the uncertainties associated with these parameters. This step utilized the videos and photographs that captured the impact event and subsequent damage to the exterior of the towers.
• Sensitivity analyses were conducted at the component and subassembly levels to assess the effect of uncertainties on the level of damage to the towers due to impact and to determine the most influential parameters that affect the damage estimates. The analyses were used to reduce the number of parameters that would be varied in the global impact simulations.
• Analyses of aircraft impact into WTC 1 and WTC 2 were conducted using the global tower and aircraft models. The analysis results included the estimation of the structural damage that degraded their strength and the condition and position of nonstructural contents such as partitions, workstations, aircraft fuel, and other debris that influenced the behavior of the subsequent fires in the towers. The global analyses included, for each tower, a “base case” based on reasonable initial estimates of all input parameters. They also provided a range of damage estimates based on variations of the most influential parameters. This range included more severe and less severe damage cases.
• Approximate analyses were conducted to provide guidance to the global finite element impact analyses. These included: (1) analysis of the overall aircraft impact forces and assessment of the relative importance of the airframe strength and weight distribution, (2) evaluation of the potential effects of the energy in the rotating engine components on the calculated engine impact response, (3) influence of the static preloads in the towers on the calculated impact damage and residual strength predictions, and (4) analysis of the load characteristics required to damage core columns compared to the potential loading from impact of aircraft components.
The reports containing all the evidence can be downloaded free of charge at the above linked page.
Respectfully,
Myriad
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Yes, I am aware of these approximate simulations but I have not found any indications that, e.g. core column #501 - very strong to say the least - would have been damaged. It is fitted between two floors that would have sliced the plane as a cheese and then the column itself is very slender and would just deflect anything hitting it. 90 mm thick steel plates!
One problem is that none of the 280+ columns of the WTC1 initiation zone has been identified and analysed - damaged by plane or later 'buckled' (undefined) by heat in combination with very low compressive stresses (the mass above) and finally disappearing (how!) to allow the mass above to drop.
If you allege, as NIST, that the cause of the whole collapse is 'buckled' columns in the initiation zone, the least you need is one sample of such structural part.
Your standard of evidence is tremendously biased. Such evidence can not reasonably be expected to exist, you are denying a plausible theory by demanding implausible amounts of evidence.
Have you found an error with NISTs simulation or have you performed a superior one which indicates column 501 would not be damaged? If not you are arguing from your personal disbelief which does not hold weight.
edit: I should add to make the above a bit clearer, when I say 'can not reasonably by expected to exist' I mean that the columns in WTC1 can be identified only by a small stamping on the steel, given the tremendous forces involved that day it is plausible that such columns could not be identified. It is important to realise how much evidence you should expect to be available to select a specific theory, whether this evidence is considerable enough to accept the theory as being correct is disputable, but you cannot claim that a lack of specific columns being recovered makes the NIST theory unprovable
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NISTs theory is proved by what was witnessed on the day.
No one has managed to prove that this theory is impossible. Until they do so, there is no reason to believe that the towers could not have collapsed from the structural damage and fires alone.
No one has managed to prove that this theory is impossible. Until they do so, there is no reason to believe that the towers could not have collapsed from the structural damage and fires alone.
It is of course a combination of what can be seen/measured/estimated and what you have to assume in order to arrive at your end result. I've seen 100s of videos but not that the fireproofing was stripped. But if one can live with an incomplete explanation then that is fine.
First, find out what spray on fireproofing is like. Is it hard or soft? Brittle or malleable?
Then consider the impact of a large object with the fireproof structure; an impact so great that large steel columns are visibly severed and debris from the impacting body is seen to burst out through the wall opposite the point of impact.
Then tell me the fireproofing had a better chance of being undamaged than damaged.
Dave Rogers
Bandaged ice that stampedes inexpensively through
The explanation's complete, it's the proof that has one or two thin spots. You must be thinking of somebody else's explanation.
Dave
Dave Rogers
Bandaged ice that stampedes inexpensively through
Getting back, however briefly, to the original topic of this thread, I'd just like to comment on one paragraph of Gregory's paper.
This clearly doesn't follow.
We know, of course, that significant numbers of exterior columns were severed at the point of initial impact. Gregory is arguing that, because the collapse onset was above this level, we still have to consider buckling of these columns at the region of collapse onset. However, the downward motion of the upper block can just as easily be accommodated by a downward displacement of the section of the column between the collapse initiation zone and the point of fracture of the column. The only structural elements restraining the columns from this downward motion are the spandrels and floor connections, which are therefore being loaded in shear and bending rather than compression.
Looking at the core columns, NIST's modelling predicts serious damage to a proportion of these also, and again the downward motion can be accommodated by downward displacement of the short section between the collapse zone and the point of failure. The only elements restraining the core columns are the floor connections, whose strength against shear is virtually negligible.
Finally, NIST's fire modelling predicts reduced yield strengths for core columns which at the time of collapse were significantly heated by fire, and again this permits a failure mode where the column is severed at the point of reduced strength, below the collapse initiation zone.
There is a certain amount of double counting to be eliminated here, because the failure of the columns due to heating was itself a cause of collapse initiation. However, I would argue that, for the reasons given above, the assumption that the structure in the region of collapse initiation was able to resist collapse with 98% of its undamaged strength is a significant overestimate, and that therefore the overload ratio is higher than the paper predicts.
Dave
This clearly doesn't follow.
We know, of course, that significant numbers of exterior columns were severed at the point of initial impact. Gregory is arguing that, because the collapse onset was above this level, we still have to consider buckling of these columns at the region of collapse onset. However, the downward motion of the upper block can just as easily be accommodated by a downward displacement of the section of the column between the collapse initiation zone and the point of fracture of the column. The only structural elements restraining the columns from this downward motion are the spandrels and floor connections, which are therefore being loaded in shear and bending rather than compression.
Looking at the core columns, NIST's modelling predicts serious damage to a proportion of these also, and again the downward motion can be accommodated by downward displacement of the short section between the collapse zone and the point of failure. The only elements restraining the core columns are the floor connections, whose strength against shear is virtually negligible.
Finally, NIST's fire modelling predicts reduced yield strengths for core columns which at the time of collapse were significantly heated by fire, and again this permits a failure mode where the column is severed at the point of reduced strength, below the collapse initiation zone.
There is a certain amount of double counting to be eliminated here, because the failure of the columns due to heating was itself a cause of collapse initiation. However, I would argue that, for the reasons given above, the assumption that the structure in the region of collapse initiation was able to resist collapse with 98% of its undamaged strength is a significant overestimate, and that therefore the overload ratio is higher than the paper predicts.
Dave
These pictures of columns from the collapse initiation zone of WTC 1 have been posted by me earlier in this thread. I post them again in case you missed them.
This is exterior column 210, a part of exterior panel A209 floor 97-100.
This is core column 605A floor 98-101
In addition to the columns above this is panel A130 floor 93-96 that was struck directly by the aircraft nose:
Here is a high resolution version showing the original identification labeling, so that you personally can identify the panel:
http://wtc.nist.gov/images/WTC-003_hires.jpg
All these columns are discussed in NIST NCSTAR 1-3B og 1-3C together with other columns and exterior panels from both towers. There are several pictures of severely buckled columns in these two reports. In addition I can show you numerous photographs of buckled columns in the debris pile after the collapse.
Do not try to move the goal posts after this Heiwa.
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GregoryUrich
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I've been thinking a bit about this too. I agree that your points above are in line with a more realistic approach. The point about heating seems to be the main point of contention between the plane-fire-gravity (PFG) hypothesis and the plane-fire-CD-gravity (PFCDG) hypothesis. I think this question alone is worthy of a careful anaylsis of NIST's work because the conclusions are based on modeling rather than evidence.
Nonetheless, the strength at collapse initiation must be nearly mg because as soon as the strength falls below mg collapse will ensue. That would increase the overload ratio somewhat. However there are still other issues that may further reduce the ratio. More below.
I'm having trouble keeping the arguments within the Bazant and Zhou paradigm and making it more realistic without getting into a full blown collapse analysis. Keep in mind that the point of my paper is examining whether or not B&Z prove anything. My (hypo)thesis is that a more realistic analysis is necessary to prove the PFG hypothesis, NOT that the PFG hypothesis is incorrect.
The basic thesis of B&Z is that even with assumptions in favor of collapse arrest that the overload ratio is overwhelmingly in favor of collapse. Nonetheless they make many assumptions in favor of continued collapse. My approach has been to correct the assumptions in favor of continued collapse to make them neutral or slightly favoring arrest.
Thus to stay within the B&Z paradigm, I have corrected the collapse initiation level, but I have ignored damage below the collapse area. This is because B&Z have the upper part impacting an undamaged lower part. More realistically, the collapse initiation is on more than one floor and includes tilting: 97-98 on the north side, 96-97 on the south side, and the lower part is damaged.
There are more issues that involve the many assumptions. I will try to motivate each of the choices more carefully (similar to above) when I do a rewrite.
Not really! Nist states: "The release of potential energy due to downward movement of the building mass above the buckled columns (the cause) exceeded the strain energy that could be absorbed by the structure. Global collapse ensued (the effect) ."
No buckled columns below the building mass above have been identified or seen to 'buckle' at any time.
Downward movement of mass above cannot be correlated to 'buckled' columns below, e.g. the roof moves when all visible columns between floors 93-98 are not buckled.
Core column #501 cannot buckle under any circumstances. It is too strong. Same applies for a majority of other core columns.
The potential energy of mass above is not calculated by NIST.
The cause is not proven!
The strain energy of the structure is not calculated by NIST!
It is not shown that the potential energy exceeded the strain energy.
Regardless - it is not even shown that the potential energy of mass above was applied to the structure and that its strain energy is relevant.
Thus the effect (that we see) cannot be related to the proposed cause by NIST.
Conclusion - the effect, lack of strain energy and global collapse, could very well have been caused by something else. Don't ask me what.
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Cut by me to the last bit. H, don't weasel. You are obliged to say "what" you think it was. If you don't, even the wee tots at whom you claim your research is aimed will be entitled to holler "weasel" at you.
In other words you are claiming that if all the other exterior and interior columns failed/were removed except #501, it should alone manage to keep the upper block standing.
Dave Rogers
Bandaged ice that stampedes inexpensively through
stateofgrace
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Am I missing something here?
Are you saying the perimeter columns did not buckle?
Ok we won't .
Evidently a column damaged before the collapse (by the nose of a plane) is of no interest. Nor is a 180° bent core column above the initiation zone of interest - the structure above is assumed to be intact all the time during the collapse until it probably is 'buckled' in contact with ground. Same with the crumpled up perimeter column - that should be a square box - that was part of the mass above.
In a proper forensic analysis you sort out all the parts, mainly columns, in the rubble and line them up on some football fields for further study. Not too difficult. By looking at the fracture surfaces of the columns, you can establish how they were ripped apart. Also the shape of each column after 'buckling' can be established. You do not even have to move the goal posts.
No, the same applies to all columns. #501 is just an example. I write for children. To keep it simple.