[bill quotes NIST]
NIST said:
QUESTION:
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?
ANSWER:
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. Details of this finding are provided below:
Consider a typical floor immediately below the level of collapse initiation and conservatively assume that the floor is still supported on all columns (i.e., the columns below the intact floor did not buckle or peel-off due to the failure of the columns above). Consider further the truss seat connections between the primary floor trusses and the exterior wall columns or core columns. The individual connection capacities ranged from 94,000 lb to 395,000 lb, with a total vertical load capacity for the connections on a typical floor of 29,000,000 lb (See Section 5.2.4 of NIST NCSTAR 1-6C). The total floor area outside the core was approximately 31,000 ft2, and the average load on a floor under service conditions on September 11, 2001 was 80 lb/ft2. Thus, the total vertical load on a floor outside the core can be estimated by multiplying the floor area (31,000 ft2) by the gravitational load (80 lb/ft2), which yields 2,500,000 lb (this is a conservative load estimate since it ignores the weight contribution of the heavier mechanical floors at the top of each WTC Tower). By dividing the total vertical connection capacity (29,000,000 lb) of a floor by the total vertical load applied to the connections (2,500,000 lb), the number of floors that can be supported by an intact floor is calculated to be a total of 12 floors or 11 additional floors.
This simplified and conservative analysis indicates that the floor connections could have carried only a maximum of about 11 additional floors if the load from these floors were applied statically. Even this number is (conservatively) high, since the load from above the collapsing floor is being applied suddenly. Since the dynamic amplification factor for a suddenly applied load is 2, an intact floor below the level of collapse initiation could not have supported more than six floors. Since the number of floors above the level where the collapse initiated, exceeded 6 for both towers (12 for WTC 1 and 29 for WTC 2), neither tower could have arrested the progression of collapse once collapse initiated. In reality, the highest intact floor was about three (WTC 2) to six (WTC 1) floors below the level of collapse initiation. Thus, more than the 12 to 29 floors reported above actually loaded the intact floor suddenly.
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[bill issues a challenge]
So does nobody want to have a guess what NIST might have omitted in the above explanation ? Or maybe comment on the liklihood of whether that omission could have occurred accidentally ? Does the omission totally invalidate this explanation and if so who will be the first to call NIST and damand a rectification?
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[Several posters immediatly predict bill's impending "crash & burn"]
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[bill reveals his "Gotcha"]
In my opinion no analysis of the collapse can exclude the 47 upstanding massive core columns. Nor the offset descending 47 core columns in the disconnected upper block. Both upper and lower columns will chew the concrete floors that they meet into a rain of loose rubble that has little concentrated force, just like a bag of loose nails, while heavier will never drive a nail into a plank. So the overall destructive power of the descending upper block on the lower intact 90% of the building is massively diluted by comparison with a rigid and intact upper block.
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[Predictions come true.]
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Here's your "thought for the day", bill:
"Arrogant and aggressive" does NOT constitute lipstick for "ignorant's" pig.
1st error: NIST does NOT "exclude the 47 upstanding massive core columns" from their discussion.
The "47 upstanding massive core columns" are key components of the "vertical capacity of the connections supporting an intact floor". Without the upstanding massive core columns, the vertical capacity of the connections is zero.
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2nd (minor) error: NIST does NOT completely exclude the "descending 47 core columns in the disconnected upper block" from their discussion either.
While they are not tallied in this explicitly "SIMPLIFIED" analysis, they are a component in addition to the top hat assembly that makes their weight estimates "conservative".
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3rd major error: Your charmingly quaint assumption that you possess the knowledge or experience to dictate to a bunch of PhD Structural Engineers what is, and is not, significant.
NIST does not take the upstanding or descending core columns into account in this way at all and of course that is a vital and glaring omission.
So can I ask you again ?...Could this omission have been accidental ?
No, bill. It was not an accident.
NIST states explicitly that this is a "simplified and conservative analysis". It is neither necessary nor desirable to discuss all the myriad effects going on. It's the forest vs. the trees, bill. If you identify ONE point of certain failure that leads inextricably to total collapse, you're done. Additional discussion blurs focus for the non-professional.
The structural engineers have identified such a single point of certain failure: the carrying capacity of the cross truss to column connectors. They have shown that these components would have been overloaded no matter how non-traumatic any other effect might have been.
There are dozens of other effects that might be considered. All of them (including your cherished "massive core columns") are rendered irrelevant by the total failure of the connectors.
"Painting the lily & gilding the gold..."
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I DO have one bitch with this explanation. It's the "... the dynamic amplification factor for a suddenly applied load is 2 ... " comment. This is a gross understatement. Another conservative simplification. If you think that it is accurate, I'll invite you to lay on the ground, and I'll gently lower a 40 lbs cement block onto your chest. Then, with your arms strapped to your side, I'll drop a 20 lb block cement block from 12 feet onto your chest. And then I'll ask you which one you'd prefer I do 10 additional times.
But again, this is a "simplified and conservative analysis". So I won't bitch too vocally.
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Finally:
Some people would find your answer evasive Dave and a lot less than a resounding vote of confidence in the above NIST explanation of the collapse dynamic.
4th error: This was NOT NIST's "explanation of the collapse dynamic". It was one condition that was - on its own - sufficient for total collapse.
Furthermore, unlike you idjits and your teenage YouTube-ology, we don't take NIST as holy-writ. We'll actually listen to, and participate in, critiques of the report. In fact, there have been many competent critiques, such as the much-discussed Dr. Quintiere's.
So Dave gave you the option of presenting your "gotcha" moment. Meanwhile, predicting (along with the vast majority) your imminent crash & burn.
Dave was right on the money.
1. You misunderstood what NIST was saying here.
2. You baselessly attributed malevolent intentions to NIST as a result of
your misunderstanding.
3. Your "gotcha" exposé fell on its face.
4. You expressed the quaint delusion that you could "paint into a corner" anybody except yourself.
In other words, SNAFU.
tom