Acceleration of the falling top blocks.

[ozeco41]

Ah, my mistake. Could you just remind me what/whose collapse model you're discussing? Thanks.

Mostly the "what actually happened" model where you can access the evidence as readily as any of us.

A couple of members have touched on aspects drawn from theoretical models. Those theoretical models can be useful if they help ou understanding of "what actually happened".

BUT naturally the "what actually happened" model should take precedence.

 

[ergo]

Mostly the "what actually happened" model where you can access the evidence as readily as any of us.

A couple of members have touched on aspects drawn from theoretical models. Those theoretical models can be useful if they help ou understanding of "what actually happened".

BUT naturally the "what actually happened" model should take precedence.

Interesting. The "What Actually Happened" model. Who are the authors of this new WTC collapse model, and where has it been published? Thanks.

 

[ozeco41]

You seem to have given this subject some thought....

So have I.

...Can you tell me, what began the first downward acceleration?

It was a feature of a cascade failure in the impact and fire zone which reduced the strength of that part of the tower to less than was needed to support the top storeys above that level.*

...What was the force that initiated the first movement downward?

You may be asking the wrong question here. The answer to the question as written is "Gravity" as Oystein has already said. Possibly you are looking for details of the mechanism which initiated collapse?





* Note: That statement is neutral to any claims of CD by explosives, incendiaries, energy beams or any other technology. If there was CD it must have formed part of the cascade failure which was observed.

 

[ergo]

It was a feature of a cascade failure in the impact and fire zone which reduced the strength of that part of the tower to less than was needed to support the top storeys above that level.

Not to put words in WTC Dust's mouth, but I think what she's asking is: what caused the "cascading floor failure" in the impact zone?

 

[Animal]

Quote:
3. The "bathtub" was only partially damaged. It wasn't destroyed by the force of the falling building material.

Not sure if this is correct or not, but since you've got a terrible track record, I'm calling it wrong anyway.

The "bathtub" was built around the perimeter of the site......made to withstand the pressure from the water of the Hudson River. The fact that it was not destroyed in the collapse is not a surprise whatsoever..

Why is it even as issue?

 

[ozeco41]

Not to put words in WTC Dust's mouth, but I think what she's asking is: what caused the "cascading floor failure" in the impact zone?

That would be my guess too.

 

[DaveThomasNMSR]

Interesting. The "What Actually Happened" model. Who are the authors of this new WTC collapse model, and where has it been published? Thanks.

Since you apparently have some reading comprehension issues, why not take a few minutes and just watch the YouTube version? After all, "YouTube" = "Published" in the truther fantasy world, yes?

 

[DaveThomasNMSR]

Right. And again, where can we read the official version of this collapse model? Where, for example, can engineers find this explanation? Thanks.

I've published notes on my model here.

When the towers began to collapse, large parts of the inner cores (called “the Spires” in 9/11 Truth circles) were actually left standing, briefly, before they, too, toppled over. The perimeter walls were largely forced to peel outward in large sections, producing the iconic images of Ground Zero with which we’re all familiar.

Of course, it's a very simplified model, but it does convey the essence of what happened. Quite different from truthiness, in which the only thing of importance is to express dubiousness with the last word.

 

[Tony Szamboti]

That agrees with most of what I've figured out, also. Plus, the impacts are enough to make collapse inevitable over a wide range of stiffness parameters, etc.

Dave, you haven't figured anything out and you have to know it.

It is clear that you just back substituted a velocity loss and kinetic energy loss to account for the difference between David Chandler's North Tower measurements and freefall, without calculating what the real loss would have to be.

Your Skeptical Inquirer analysis has the upper section in freefall between impacts and goes from 19.3 to 18.0 mph over a 0.002 second duration at first impact.

That is wrong in several ways:

1. Even giving you freefall between stories after the first impact, you can't get it during the initial fall through the first story, as you have nothing to bring the average down. The measurements show the upper section was accelerating at about 5.11 m/s^2 during the initiating story drop, while your 19 .3 mph would require freefall (9.81 m/s^2) to get to before the first impact. This exposes a fallacy in your logic.

2. The actual velocity at first impact, with a 5.11 m/s^2 acceleration, would be 13.7 mph (6.13 m/s) at 1.2 seconds into the fall after traveling downward for 3.7 meters. The kinetic energy with that velocity would have been 0.5 x 33 x 10e6 kg x (6.13 m/s)^2 = 0.62 GNm. If the column energy dissipation capacity was even as low as Zdenek Bazant said, at 0.5 GNm, then it would have lost 0.5/0.62 = 80% of its kinetic energy.

3. Even giving you your provably wrong freefall through the first story you have the velocity going from 19.3 to 18 mph after first impact, which means it only lost 13% of its kinetic energy. The kinetic energy at 19.3 mph (8.63 m/s), of a 33 x 10e6 kg mass upper section, would have been 1.2 GNm. So even using Bazant's column energy dissipation numbers and your errorneous freefall generated velocity through the first story fall you would still lose 0.5/1.2 = 41% of the kinetic energy at first impact. How do you possibly come up with just a 13% kinetic energy loss? Oh, you didn't do that calculation because you just substituted in what the loss needed to be to account for the difference between freefall and Chandler's measurements.

Your calculations do not consider the column energy dissipation capacity and are essentially meaningless with no explanatory power.

 

[newton3376]

Dave, you haven't figured anything out and you have to know it.

It is clear that you just back substituted a collision duration and kinetic energy loss to account for the difference between David Chandler's North Tower measurements and freefall.

Your Skeptical Inquirer analysis has the upper section in freefall between impacts and goes from 19.3 to 18.0 mph over a 0.002 second duration at first impact.

That is wrong in several ways:

1. Even giving you freefall between stories after the first impact, you can't get it during the initial fall through the first story, as you have nothing to bring the average down. The measurements show the upper section was accelerating at about 5.11 m/s^2 during the initiating story drop, while your 19 .3 mph would require freefall (9.81 m/s^2) to get to before the first impact. This exposes a fallacy in your logic.

2. The actual velocity at first impact, with a 5.11 m/s^2 acceleration, would be 13.7 mph at 1.2 seconds into the fall after traveling downward for 3.7 meters.

3. You have the velocity going from 19.3 to 18 mph after first impact, which means it only lost 13% of its kinetic energy. The energy dissipation capacity of the columns was a minimum of about 1.7 GNm and even if half the columns were gone (which they weren't as most of the damaged columns were on the north face and only about 15 to 20% were out of action per NIST) it would still be 0.85 GNm. The kinetic energy at 19.3 mph (8.63 m/s), of a 33 x 10e6 kg mass upper section, would only have been 1.2 GNm. So even with a half gone structure your kinetic energy loss would have been 0.85/1.2 = 71%. Even Zdenek Bazant says the column energy dissipation capacity was 0.5 GNm and there you would lose 0.5/1.2 = 41%. How do you possibly come up with just a 13% kinetic energy loss? Oh, you didn't do that calculation becuae you just substituted in a loss to account for the difference between freefall and Chandler's measurements. Your calculation does not consider the column energy dissipation capacity and thus has no explanatory power.

4. Now let's get to the real velocity at initiation, based on measurements, and prior to first impact, of 13.7 mph. The kinetic energy with that velocity would have been 0.5 x 33 x 10e6 kg x (6.13 m/s^2)^2 = 0.62 GNm. If the column energy dissipation capacity was even as low as Bazant said, at 0.5 GNm, then it would have lost 0.5/0.62 = 80% of its kinetic energy.

Tony.....

PLEASE PLEASE PLEASE tell me that you understand Dave Thomas's "model" of the collapse he has posted on the internet...

Tell me you understand the limitations, the approximations, and why it is not a "coincidence" that many of his answers are close to what Bazant got with the more detailed calculation...

You are heading down a road you probably should not.....much like when you talked about forces on this forum and completely screwed up the vector math. Your statements above are not well thought out....

Think Tony think.....with the "rough" model that Thomas used...considering a series of impacts with each impact followed by a period of freefall....and using the very simple momentum/force calculations....how on earth could Thomas get values so close to what Bazant got with the more detailed calculation?

How is that possible?

***Hint: It's because in general the collapse WAS a series of impacts with periods of essentially freefall in between***

 

[Tony Szamboti]

Tony.....

PLEASE PLEASE PLEASE tell me that you understand Dave Thomas's "model" of the collapse he has posted on the internet...

Tell me you understand the limitations, the approximations, and why it is not a "coincidence" that many of his answers are close to what Bazant got with the more detailed calculation...

You are heading down a road you probably should not.....much like when you talked about forces on this forum and completely screwed up the vector math. Your statements above are not well thought out....

Think Tony think.....with the "rough" model that Thomas used...considering a series of impacts with each impact followed by a period of freefall....and using the very simple momentum/force calculations....how on earth could Thomas get values so close to what Bazant got with the more detailed calculation?

How is that possible?

***Hint: It's because in general the collapse WAS a series of impacts with periods of essentially freefall in between***

Thomas' analysis doesn't match Bazant's. Bazant's Wg/Wp = 8.4 or 12% loss due to column energy dissipation is for a two story drop. Bazant's kinetic energy loss for a one story drop would have been 24% and Thomas' is 13%.

Bazant also erroneously used freefall through the first story and he used nearly twice the actual mass of the upper section in his kinetic energy calculation and if he hadn't his loss would have been much larger. The 41% loss I showed Thomas would have gotten with Bazant's column energy dissipation was also with the actual mass of the upper section of 33 x 10e6 kg not Bazant's fallacious values of 58 or 54.18 x 10e6 kg.

The North Tower fall has been measured. We know its actual velocity and acceleration through the first story. We also know the actual mass of the upper section was 33 x 10e6 kg, not the 58 x 10e6 or 54.18 x 10e6 kg that Bazant uses in his papers.

Both Dave Thomas' and Zdenek Bazant's analyses are completely and unambiguously in serious error and when these errors are corrected the results are the opposite of what they say. It is a little complicated and I can see why people, who haven't given it much thought, would go along with it. However, these two have been promulgating nonsense.

 

[ozeco41]

...Of course, it's a very simplified model, but it does convey the essence of what happened....

And quite suitable to "convey the essence" of what happened in the the "what actually happened" model i.e. the real world collapse. Yes there are a couple of details I would nowadays express differently but your model in pictures is identical with the model in words I used through 2007-8-9. I have since refined my explanations but the originals stand as my understanding as I published it at that time and are still valid as means to "convey the essence" of what happened.

...Quite different from truthiness, in which the only thing of importance is to express dubiousness with the last word.

As demonstrated by the mixture of partial truths and nonsense Tony has posted which shows no progress of understanding from the foundation errors of "Missing Jolt".

For ergo's benefit the post by Tony is a mish-mash of bits cribbed from different theoretical scenarios and added to some real world measurements. It reminds me once again of my first comment on some of Tony's early work which I posted in November 2007.

This recent post by Tony Szamboti...

...is typical of many which look impressive in detail to the non-engineer. The complex calculations may even be correct but the base premises are faulty and the resulting conclusions can readily be demonstrated to be totally wrong.

Once again he's got the model or mechanism wrong...

...whether or not he can nit-pick a detail in DaveThomas' work.

 

[ozeco41]

Bazant also erroneously used freefall through the first story....

Yes!
So what actually happened? What bits fell where?

Can you relate the events sequence of "initiaion" ("transition" if you want it) and "progression"?

At what stage in your explanation did column strength become essentially irrelevant?

etc etc....

And why is Bazants energy calculation of any relevance in what actually happened?

... and he used nearly twice the actual mass of the upper section in his kinetic energy calculation....

If we accept that:

...Zdenek Bazant's analyses are completely and unambiguously in serious error and when these errors are corrected the results are the opposite of what [he says]. Stop defending the nonsense which has been promulgated by [him].

so give us your explanation so we can either:
A) Agree and learn from your insights;
B) Correct minor errors you may make; OR
C) Disagree totally and tell you why to the necessary level of detail.

 

[DaveThomasNMSR]

Thomas' analysis doesn't match Bazant's. Bazant's Wg/Wp = 8.4 or 12% loss due to column energy dissipation is for a two story drop. Bazant's kinetic energy loss for a one story drop would have been 24% and Thomas' is 13%.

Bazant also erroneously used freefall through the first story and he used nearly twice the actual mass of the upper section in his kinetic energy calculation and if he hadn't his loss would have been much larger. The 41% loss I showed Thomas would have gotten with Bazant's column energy dissipation was also with the actual mass of the upper section of 33 x 10e6 kg not Bazant's fallacious values of 58 or 54.18 x 10e6 kg.

The North Tower fall has been measured. We know its actual velocity and acceleration through the first story. We also know the actual mass of the upper section was 33 x 10e6 kg, not the 58 x 10e6 or 54.18 x 10e6 kg that Bazant uses in his papers.

Both Dave Thomas' and Zdenek Bazant's analyses are completely and unambiguously in serious error and when these errors are corrected the results are the opposite of what they say. It is a little complicated and I can see why people, who haven't given it much thought, would go along with it. However, these two have been promulgating nonsense.

Had you actually read my article (I am not Zdenek Bazant, BTW), you might have noticed this:

Each floor of the towers contained over two million kilograms of mass. The gravitational potential energy of a standing tower with twelve-foot floors extending upward 110 stories can be calculated straightforwardly; it comes to over 420 billion joules of energy, or the equivalent of 100 tons of TNT per tower. This energy, which was released completely during the collapses, is more than the energy of some of the smaller nuclear weapons in the U.S. arsenal, such as the W-48 (72 tons TNT)

So, I posited an upper section of 14 floors (WTC1), 28 million kg total, around half of what Bazant used.

 

[DaveThomasNMSR]

Dave, you haven't figured anything out and you have to know it.

It is clear that you just back substituted a velocity loss and kinetic energy loss to account for the difference between David Chandler's North Tower measurements and freefall, without calculating what the real loss would have to be....

I'm not "back substituting", I am applying conservation of momentum. Your description is pure strawman, as anyone who reads my detailed calculations knows.

Kindly don't put words in my mouth.

 

[Oystein]

Dave, you haven't figured anything out and you have to know it.

It is clear that you just back substituted a velocity loss and kinetic energy loss to account for the difference between David Chandler's North Tower measurements and freefall, without calculating what the real loss would have to be.

Your Skeptical Inquirer analysis has the upper section in freefall between impacts and goes from 19.3 to 18.0 mph over a 0.002 second duration at first impact.

That is wrong in several ways:

1. Even giving you freefall between stories after the first impact, you can't get it during the initial fall through the first story, as you have nothing to bring the average down. The measurements show the upper section was accelerating at about 5.11 m/s^2 during the initiating story drop, while your 19 .3 mph would require freefall (9.81 m/s^2) to get to before the first impact. This exposes a fallacy in your logic.

2. The actual velocity at first impact, with a 5.11 m/s^2 acceleration, would be 13.7 mph (6.13 m/s) at 1.2 seconds into the fall after traveling downward for 3.7 meters. The kinetic energy with that velocity would have been 0.5 x 33 x 10e6 kg x (6.13 m/s)^2 = 0.62 GNm. If the column energy dissipation capacity was even as low as Zdenek Bazant said, at 0.5 GNm, then it would have lost 0.5/0.62 = 80% of its kinetic energy.

3. Even giving you your provably wrong freefall through the first story you have the velocity going from 19.3 to 18 mph after first impact, which means it only lost 13% of its kinetic energy. The kinetic energy at 19.3 mph (8.63 m/s), of a 33 x 10e6 kg mass upper section, would have been 1.2 GNm. So even using Bazant's column energy dissipation numbers and your errorneous freefall generated velocity through the first story fall you would still lose 0.5/1.2 = 41% of the kinetic energy at first impact. How do you possibly come up with just a 13% kinetic energy loss? Oh, you didn't do that calculation because you just substituted in what the loss needed to be to account for the difference between freefall and Chandler's measurements.

Your calculations do not consider the column energy dissipation capacity and are essentially meaningless with no explanatory power.

To help you figure out where your train of thought goes wrong, I highlighted a few phrases. Hope that helps.

 

[ozeco41]

To help you figure out where your train of thought goes wrong, I highlighted a few phrases. Hope that helps.

Beat me to it.

That was my next step - if I decided to assist Tony further.

 

[Oystein]

Beat me to it.

That was my next step - if I decided to assist Tony further.

I am actually a little curious about who among the debunkers gets it

 

[ozeco41]

I am actually a little curious about who among the debunkers gets it

We would probably both be disappointed if we knew.

 

[WTC Dust]

Two questions, under your theory, what initiated the very first downward motion? Also, why didn't you mention it was dust that obscured your view?

Forget any (free)fall drop. It doesn't matter much how the top starts moving, all that matters is that it does start moving and attains a downward velocity / momentum sufficient to overcome the "first collision". If that momentum is gained in 0.5 seconds of freefall at g or 1 second of acceleration increasing linearly from 0 to g or 2 seconds of 0.25g or whatever, all that matters is that a minimum momentum arises.

As soon as the moving block starts impacting major components at rest - we typically think "floor slabs", and if this initial momentum suffices, those components will be overwhelmed, and movement will continue at an average of 0 < a < g

So Bazant says "drop"? Maybe he doesn't mean that literally, or maybe he shouldn't.

That doesn't invaldidate the rest of his work.


I don't actually know where this idea of a "terminal velocity" originated; it seems that the motion is difficult to observe at least for the lower third of the towers, for that is cloaked in dust plumes. Did they look at ejections from just below the collapse front disturbing the plumes?


Different solutions are possible
- crawl back towards the trunk
- support the limb
- ...?