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I think the physics term for this is "impulse", defined as a change in force over a period of time. For a constant mass (which, admittedly, this isn't), that would translate to a change in acceleration.
Not quite. Impulse is a change in momentum and has units of force times time. Tony is explicitly looking for a change in the force itself.
Impulse would be easier to look for, but it's tricky because it leads you to estimate the average acceleration -- and as noted, the average acceleration just isn't good enough for his argument. He needs to know the instantaneous acceleration at all times.
Tony there is a big difference between giving a brief summary of findings or conclusions which can be backed up if needed and "gross speculation". Please don't try the trivialising evasions, they do you no credit.
I note that you deny "simply shearing off at...the first several floors". OK accept that we don't know the detail at this stage of OUR discussion. That is no grounds for the implied "GodDidIt" false dichotomy of "it must be demolition..."
So lets go beyond those first few mostly obscured floors. Once underway the bulk of the falling mass other than the peeling off outer tube material fell inside the outer tube. And in doing so it would readily shear the floor joist to column connections. (Yes another "brief summary" )
So the falling mass was inside through most of the global collapse. If it was "outside" at the start how did it or could it change? Even explosives cannot achieve that mode change.
And I take it as given that 100% axial alignment of column on column did not occur - another "brief summary" subject to support if required.
So the video evidence shows at least one face of one top block aligned to fall inside the top block before the initial collapse plus strong logic to suggest it all fell inside AND no evidece that it fell outside PLUS no reasonable argument to support 100% axial alignment.
OK there are aboput 4-5 challenge points in there.
Tony Szamboti said:
...There is a reason Dr. Bazant said there must have been a powerful jolt. That is because he knew that would be the only way a natural collapse could continue beyond a one story collapse. You too should read the Addendum to his paper with Zhou, where he says a smaller series of jolts would not be fatal.
I am not in awe of Bazant or any other academic. His record is great but he assumes a wrong but conservative model to prove his point about "total energy". IIRC there was enough energy even given the wrong underlying assumption. So a valid conservative side argument but not a valid foundation for further analysis.
My interest is in understanding how the towers fell as the basis of explanation. I will re-read the Addendum BUT I suspect from memory and what you state that you are quote mining. The comment about a small series of jolts (OR a series of small jolts???) would be valid in the false model of collapse they assumed. They were not talking about the collapse mechanism I describe which is the one which actually happened.
Tony Szamboti said:
... The reality is that this is an untenable argument that several people here simply continue to use with no legitimate basis provided for how it could possibly transpire. To his credit Bazant realized it was impossible.
methinks you misuse both the "people" and Bazant here so I will let it pass.
Tony Szamboti said:
...Your shearing of the outer tubes argument has some merit like Bazant's jolt, but it also does not conform with observation, for the first several stories at least.
....There is a reason Dr. Bazant said there must have been a powerful jolt. That is because he knew that would be the only way a natural collapse could continue beyond a one story collapse.
Seeing you had the audacity to suggest "...You too should read the Addendum to his paper with Zhou, where he says a smaller series of jolts would not be fatal...." as if it was relevant to what I was putting forward.
In response I suggested you might be "quote mining". So I re-read Bazant and Zhou's "Addendum". They were not referring to the actual collapse mechanism THEREFORE you were quote mining.
My suggestion - already supported by many on these threads - remains that the Global Collapse occurred because the outer tube columns played a minimum role and the core columns resisted with far less that original designed strength.
Given that most of the mass either fell on the outer floors OR was not resisted by the core your "Jolt" explanation is falsified. The actual mechanism of collapse was not one that would produce or require a large Jolt.
There are still some details of my alternate which may require support in any further genuine discussion.
I fully grasp that you think there were separate impulses as the block rotated and I am saying that you can only try and use that for the initial floor collapse. The difficulty for you is to then try and explain the rest of the 114 foot measureable drop of the upper block not showing any signs of deceleration.
As the block rotates further, the difference between the leading and trailing edge height becomes greater, so the shocks are more smeared out, not less. As soon as the tilt is enough that the bottom of the top block extends over more than a single storey height, there can be no simultaneous impact. Again, simple geometry.
Additionally, the way the north face fell is hard to reconcile with your explanation of impulses being smeared. When something rotates and then falls it does not eliminate a deceleration of the raised side. I do rotational drop tests of of electronic equipment on hard benches and have had accelerometers on the vertical surface of the raised side of the box while dropping from just four inches of height, and have recorded 300g decelerations there. The reason is that the vertical surface is stiff in the direction of the load and the shock is not attenuated by deflection. The north face would have been stiff in the direction of the load caused by it's impact also.
If I were suggesting that the upper block were not behaving approximately rigidly, that would be relevant. I'm not suggesting that the vertical surface isn't stiff, I'm suggesting that different columns strike the lower block at different times. The example of a rigid box striking a surface that has an ample reserve of structural strength doesn't throw any useful light on the situation.
I don't think you have a full appreciation for how shock loads work. There really is no chance that the rotation would explain a lack of observation of a deceleration on the north face of WTC 1, if an impulse actually occurred there. The columns on both corners were intact and just nine columns on either side of the north face and east and west faces on those corners, or 18 columns per corner, were capable of supporting 25% of the full tower load above them. They would not have collapsed without a serious impulse barring some sort of weakening.
If they were capable of bearing 25% of the weight of an upper block, then a simultaneous impact would cause them to fail with a negative acceleration of 0.25g. This, added to the positive acceleration of 1.0g, would give a resultant positive acceleration of 0.75g (where positive is defined as downwards. In other words, your example supports my point.
Wrong! Deceleration is a negative acceleration. Anything less than 9.8 m/s^2 but greater than zero is just lesser positive acceleration. To transfer kinetic energy the impacting object needs to decelerate.
That's scientifically illiterate. In the presence of gravity, the impacting object needs only to accelerate at less than g.
Let's work an example. Suppose we have a block of weight M, falling on a support of ultimate strength 0.25M, under the action of gravity. Gravity exerts a force of Mg downwards. The support cannot, by definition, exert a greater force than 0.25Mg upwards. The minimum resultant force is therefore (1.0-0.25)Mg, or +0.75Mg. The resultant acceleration must therefore be positive, with a minimum value of 0.75g. No deceleration has occurred, the falling block has in fact continued to accelerate, and yet kinetic energy has been transferred to the support.
If you don't understand this, you don't understand basic Newtonian mechanics.
I think that I know what the argument that Szamboti is trying to make. He's saying that if the structure normally resisted 1.0*m*g then it can definitely resist the difference in acceleration of 0.3*m*g.
Unfortuntanely, his 0.3*m*g number is an average, not an actual peak. Furthermore, he's comparing the column capacity to the floor capacities. The former can resist 1.0*m*g (and more) of the structure above. The floor cannot.
I think that I know what the argument that Szamboti is trying to make. He's saying that if the structure normally resisted 1.0*m*g then it can definitely resist the difference in acceleration of 0.3*m*g.
Unfortuntanely, his 0.3*m*g number is an average, not an actual peak.
No, I don't think he's making that mistake; he's perfectly clear about the fact that he's looking for a minimum in the downward acceleration, rather than simply claiming that the time-averaged value is incorrect. I'm fairly certain that his error is in assuming that the value of the collision impulse at any position is equal to its spatial average, rather than the more common error amongst truthers that the impulse at any time is equal to its time-average.
I've been trying to understand how he can persist in that error, and I suspect one of his posts from yesterday gives a clue; he's accustomed to shock-testing of rigid components by dropping them on a surface with ample structural reserve. If this is informing his understanding of the WTC collapses, and he's thinking of the towers as an assembly of relatively strong floors connected by relatively weak support columns, then his analysis makes perfect sense, because the stiffness of the floors will average out the impulse from the impact of the upper block. However, the real WTC towers had floors that were very much weaker than the columns, so the load distribution between columns in an abrupt impact would have been virtually nonexistent. Therefore, the spatial dependence of impulse per unit area must have been extremely non-uniform, and shown very large excursions from its average value; and it's these excursions that gave sufficient instantaneous pressure on individual elements to induce failure. Put more simply, the columns of the lower structure couldn't resist collapse as a single unit, and hence failed separately.
Furthermore, he's comparing the column capacity to the floor capacities. The former can resist 1.0*m*g (and more) of the structure above. The floor cannot.
Again, I don't think he's neglected that point, but for the initial impact he's claiming that the lateral and rotational movement of the upper block was less than the width of a single column, so the initial strikes were column-on-column. I think he has an argument there for the core columns, but the additional buckling of the perimeter columns would complicate matters enormously.
This whole incident has inspired me to dabble in learning more advanced mathematics. I've ordered a nice course on Calculus from the Teaching Company. Does anyone have any suggestions for a self-guided Physics course besides "Look It Up On Amazon?"
This whole incident has inspired me to dabble in learning more advanced mathematics. I've ordered a nice course on Calculus from the Teaching Company. Does anyone have any suggestions for a self-guided Physics course besides "Look It Up On Amazon?"
This whole incident has inspired me to dabble in learning more advanced mathematics. I've ordered a nice course on Calculus from the Teaching Company. Does anyone have any suggestions for a self-guided Physics course besides "Look It Up On Amazon?"
This whole incident has inspired me to dabble in learning more advanced mathematics. I've ordered a nice course on Calculus from the Teaching Company. Does anyone have any suggestions for a self-guided Physics course besides "Look It Up On Amazon?"
Oh, Feynman! I was watching videos of his lectures at New Zealand, or was it Australia? It was on quantum mechanics. Oh, how my brain did crunch so nicely. I'll have to find those.
I thought it was time to bring the discussion with Tony back to this more appropriate thread, leaving the damp marine environment behind.
This excerpt from Mr. Mackey speaks to the missing jolt succinctly, I'll give it the first billing:
'..as we've also noted repeatedly, Tony's argument only works in unlimited precision. There are going to be tiny but sharp periods of deceleration, lots of them, that average to much less than one g. The time resolution needed to see this greatly exceeds what we have available.'
for a laugh, try to find the jolt in my video: (hopefully the quality will resolve - youtube issue)
Taking a look at the Balzac Vitry demolition (2007), where 3 floors were simultaneously removed, once again you can see how the collapse of WTC1 and 2 are NOT like this.
1) Note how neatly and uniformly the upper block descends, due to the precise use of hydraulics. This did not happen in the WTC tower collapses, where the initial collapses began with more gradual (and chaotic) failures.
Viewing the acceleration graphs below (presuming they are accurate) you can see how the Balzac/Vitry demo accelerated at a much faster speed right away - in less than .5 seconds it was almost 80ft/s/s. For WTC 1, the rate of acceleration began more slowly, and actually slowed during the first .5 seconds! (15ft/s/s)
2) Roughly 6 floors of the building were intact above the initial collapse floors (less than the intact floors of the WTC towers) to continue the collapse all the way. I don't know what the building construction was and how it differed from the steel frame WTC towers, so I can't compare the expected deceleration from this alone.
But clearly the ratio of height to width is not comparable between the two - the French building is rectangular, and has far fewer floors than the WTC towers.
3) Both buildings experience sharp declines in the rate of acceleration between about 1.2 seconds and 1.6 seconds. The B/V the sharpest, dipping into actual deceleration for about .5 seconds/ WTC 1 comes relatively close to deceleration, but the velocity swings are not as pronounced.
From what I can see, you have two different buildings, with different construction methods and different collapse mechanisms, resulting in somewhat different outcomes of acceleration throughout the collapses.
Especially when you consider the very rapid initial acceleration of the B/V demolition (due to simultaneous removal of columns) the difference between the two is very striking.
If anything it supports the notion that WTC 1 was NOT subjected to explosive demolition, as the failures were obviously more gradual, and the acceleration rates slower - clearly there was more structure that was slowing the descent.
The more you look, the less like CD it appears. I almost forgot to mention that the B/V building wasn't damaged asymmetrically by high-speed jets, and wasn't experiencing large fires. Or is that irrelevant?
(I believe the original graphs are from Tony Szamboti)
Oh, Feynman! I was watching videos of his lectures at New Zealand, or was it Australia? It was on quantum mechanics. Oh, how my brain did crunch so nicely. I'll have to find those.
I'm not above it. I check the community college regularly, but I only have Th-Sat off, and it's hard to get a class that can fit into that schedule.
Over the years, I've audited several courses at community colleges. I've simply picked what were interesting topics to me (outside of engineering), approached the teacher and asked if he/she'd mind if I just sat it because I was interested in the subject. I've never been turned down.
The great thing was that I was not worried about grades, or taking notes or any such thing. I could pay attention to what they said in a zero stress state. Everything made a LOT more sense than when I was trying to listen & write at the same time.
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Thanks, though!
