9/11 Physics from Non-Experts

[Furcifer]

Interesting. I could be wrong, of course, and I don't have the expertise to evaluate those LIDAR images. But "intact" is sometimes a relative term in such cases, and I wonder if the 4-7 story height you read about is above street level (which would bring it close to surmounting most of the debris pile) or above foundation level. It's not surprising that the lower stories of the core remained upright within the debris pile. I was thinking, rather, of lateral compression and/or displacement. If the base stories of the core structure were compressed laterally to even a relatively small degree, its ability to stably support any freestanding core above it would become doubtful.

Respectfully,
Myriad

Yes, and from what i can tell from the collapse videos, this may have happened 2 or 3 times during the collapse. The collapse wave broke the exterior truss connections, the exterior columns fell away (peeled) from the building, then the trusses swung free and snapped away from the core. What remained of the core was freestanding until the collapse wave was some 30-40 stories further down. At this point the damage from the falling debris (the lateral forces), coupled with gravity, took down the core. This process may have been repeated several times. From the video, the 75 story section of core on WTC may have broke about around 40-45th floors, then again at the 20-25th floor and again at 4-7th floors. The first estimate is based on a crude estimate of when the collapse wave passes and the the core begins to move and fall, which appears to be 3 seconds. The rest is pure conjecture on my part, based solely on assuming the increasing thickness of the exterior and core plate towards the bottom of the building and the similarities to WTC1 (the pictures i have seen show a 40-50 story tall section of the core standing in WTC1)

 

[Furcifer]

I have assumed a substantial deformation to the core based on the upper mass giving it a substantial working over as it passed and the torsional effects of the trusses as they swung away from the exterior. These trauma events and gravity alone should have been more than sufficient to collapse the standing core.

Retraction: NIST NCSTAR 1-3C pg. 118
The torsional effects of the trusses were not a factor. The dang things sheared off according to NIST. By all accounts the floors offered very little resistance to the collapse wave.

 

[Pookster]

I don't see how this can mean anything else:

Quote:
Blanchard: A review of all photographic images clearly shows about 95% of falling debris being forced away from the footprint of the structure...

Concluding:... These facts indicate that a relatively small amount of structural support debris actually landed straight down in the towers foot prints...


Anyway, I reject this claim.

I don't know if anyone else has addressed this, but I don't see how it can mean what you think it does. I don't believe Blanchard asserts that 95% of the mass of the towers fell outside the footprint of the towers either. From the quote you posted, he states that a relatively small amount of structural support debris actually landed straight down in the towers foot prints. I agree with Blanchard on that. But I believe that is far from him asserting 95% of the mass of the towers landed outside of the footprint.

The quote also refers to a review of the images showing 95% of the falling debris falling outside the building's footprint. I agree with this as well, recognizing that we can't see the bulk of the debris falling within the building's perimeter walls. But of what we can see, 95% of it is falling outside the footprints. The majority of what we can see is the perimeter walls falling themselves. I believe you're reading things into Blanchard's quotes that just aren't there.

 

[beachnut]

Don't forget conservation of momentum.

You mean like Dr Jones of Scholar for 9/11 truth does? Darn, at least you are not dumb enough to join the Scholars for truth, you just posted a letter. There is hope for you yet, as you pursue the facts behind 9/11. Got Facts?

 

[chriswgood71]

Hey, I've got a wacky idea...why don't one of you actually respond to the challenge and create a more realistic model and show why you are all correct. I am still trying to find one that makes sense and replicates at least some of the variables you all cling to as making such attempts totally foolish and incompatible with reality. Or are you all just skeptics and not really capable of creating things to be tested or ridiculed? I am beginning to think no one that fills up this forum with posts is capable of actually doing anything about all the stuff you talk about and pat yourselves on the back about how well you each can dissect and pick apart any lay persons attempt to demonstrate what happened on 9/11. Please, I appeal to any intellect (or wannabe) show us the real world model that behaves just like the the 3 buildings did on 9/11? Anyone, anyone, anyone. I am still waiting. Thanks...but I am still waiting.

 

[I Am He]

chriswgood71

In other words, I have no idea what you people are saying and I can not add anything constructive to this thread myself.

Is that right??

I Am He

 

[rwguinn]

Hey, I've got a wacky idea...why don't one of you actually respond to the challenge and create a more realistic model and show why you are all correct. I am still trying to find one that makes sense and replicates at least some of the variables you all cling to as making such attempts totally foolish and incompatible with reality. Or are you all just skeptics and not really capable of creating things to be tested or ridiculed? I am beginning to think no one that fills up this forum with posts is capable of actually doing anything about all the stuff you talk about and pat yourselves on the back about how well you each can dissect and pick apart any lay persons attempt to demonstrate what happened on 9/11. Please, I appeal to any intellect (or wannabe) show us the real world model that behaves just like the the 3 buildings did on 9/11? Anyone, anyone, anyone. I am still waiting. Thanks...but I am still waiting.

Invent an artificial gravity machine so we can scale it, and we'll build you all the models you want.
Lacking that, there are no materials anywhere which can be used to scale the effects of area, volume, modulus of elasticity, strain at yield and rupture.
If you could read, and if you could comprehend that mathematics are used to describe reality, you would understand what we have been saying. As it stands, no physical model, short of full scale, can duplicate the full scale reality. That is why we use mathematical (Finite element) models to show the reality.
Go read and understand some of the papers presented by Dr. Greening, Bazant, Benson, and others. When you are capable of discussing them intelligently, come back and we'll talk, m'kay?

 

[Myriad]

I've got many photos of the tower cores before, during, and after collapse here:

Tower core construction photos, plans, column specs, drywall installation

Thanks for that link, Gravy. A very useful compilation, even without He Who Probably Shouldn't Be Named Too Often around.

Based on the information there, it appears that my conjecture about the bases of the cores being distorted or pinched by the forming debris piles is not supported by the available evidence. It remains a somewhat plausible possibility in my opinion, but short of detailed computer modeling of the debris striking the substructure and the ground I don't see any way to demonstrate that the base of the core within the debris piles would have been any more damaged than other parts of it higher up, even if that were actually the case. Therefore I withdraw the idea.

Sorry about the delay in acknowledging this point. (Studying the images on Gravy's link is what "inspired" this post of mine on the comic strips thread. Analytical detachment regained, for now.)

Respectfully,
Myriad

 

[Furcifer]

Thanks for that link, Gravy. A very useful compilation, even without He Who Probably Shouldn't Be Named Too Often around.

Based on the information there, it appears that my conjecture about the bases of the cores being distorted or pinched by the forming debris piles is not supported by the available evidence. It remains a somewhat plausible possibility in my opinion, but short of detailed computer modeling of the debris striking the substructure and the ground I don't see any way to demonstrate that the base of the core within the debris piles would have been any more damaged than other parts of it higher up, even if that were actually the case. Therefore I withdraw the idea.

Sorry about the delay in acknowledging this point. (Studying the images on Gravy's link is what "inspired" this post of mine on the comic strips thread. Analytical detachment regained, for now.)

Respectfully,
Myriad

Aww, don't give up so easily. There seems to be a lack of information concerning the core, especially what happened to it in the last few seconds of the collapse IMO

 

[R.Mackey]

Hey, I've got a wacky idea...why don't one of you actually respond to the challenge and create a more realistic model and show why you are all correct. I am still trying to find one that makes sense and replicates at least some of the variables you all cling to as making such attempts totally foolish and incompatible with reality. Or are you all just skeptics and not really capable of creating things to be tested or ridiculed? I am beginning to think no one that fills up this forum with posts is capable of actually doing anything about all the stuff you talk about and pat yourselves on the back about how well you each can dissect and pick apart any lay persons attempt to demonstrate what happened on 9/11. Please, I appeal to any intellect (or wannabe) show us the real world model that behaves just like the the 3 buildings did on 9/11? Anyone, anyone, anyone. I am still waiting. Thanks...but I am still waiting.

Shifting the burden of proof.

On the "true weight" question, I still stand by my summary post here.

On the larger question of a "real world model," the NIST report remains the standard to beat. It is far more complex than anything I could put together on my own, and nobody has yet demonstrated a significant flaw. Criticism has been levied, of course, even of the constructive kind, but any claims that it is wrong are speculation at best.

In other words, I'm not sure what you're waiting for.

 

[A W Smith]

sorry not scalable. take your chicken wire and go home

Hey, I've got a wacky idea...why don't one of you actually respond to the challenge and create a more realistic model and show why you are all correct. I am still trying to find one that makes sense and replicates at least some of the variables you all cling to as making such attempts totally foolish and incompatible with reality. Or are you all just skeptics and not really capable of creating things to be tested or ridiculed? I am beginning to think no one that fills up this forum with posts is capable of actually doing anything about all the stuff you talk about and pat yourselves on the back about how well you each can dissect and pick apart any lay persons attempt to demonstrate what happened on 9/11. Please, I appeal to any intellect (or wannabe) show us the real world model that behaves just like the the 3 buildings did on 9/11? Anyone, anyone, anyone. I am still waiting. Thanks...but I am still waiting.

Conversely. Scale an Ant up to human size and get back to me when it can still lift 50 times its own weight. Deal?
http://www.ftexploring.com/think/superbugs_p1.html

 

[beachnut]

Hey, I've got a wacky idea...why don't one of you actually respond to the challenge and create a more realistic model and show why you are all correct. I am still trying to find one that makes sense and replicates at least some of the variables you all cling to as making such attempts totally foolish and incompatible with reality. Or are you all just skeptics and not really capable of creating things to be tested or ridiculed? I am beginning to think no one that fills up this forum with posts is capable of actually doing anything about all the stuff you talk about and pat yourselves on the back about how well you each can dissect and pick apart any lay persons attempt to demonstrate what happened on 9/11. Please, I appeal to any intellect (or wannabe) show us the real world model that behaves just like the the 3 buildings did on 9/11? Anyone, anyone, anyone. I am still waiting. Thanks...but I am still waiting.

I used the real models to show how aircraft impacts, and fires can make building fall. Where were you on 9/11, that you missed the real thing? Sorry, it was done on the real thing you should have paid attention. WTC tower fell due to aircraft impacts and fires. You model is funny, as are all the others. Scale models only work if you do the hard engineering behind to get at the factors you are interested in. I think your video was a great parody for physics, you could use it as a project for physics students or a science fair project.

I think you should do another one, with jet fuel. Good luck. (you can model the jet fuel with charcoal lighter fluid, any ideas? )

 

[GregoryUrich]

Main issue regarding total weight

Shifting the burden of proof.

On the "true weight" question, I still stand by my summary post here.

On the larger question of a "real world model," the NIST report remains the standard to beat. It is far more complex than anything I could put together on my own, and nobody has yet demonstrated a significant flaw. Criticism has been levied, of course, even of the constructive kind, but any claims that it is wrong are speculation at best.

In other words, I'm not sure what you're waiting for.

I think we agree that the main issue is live loads:

Mr Mackey:

5. Does Mr. Urich correctly handle live loads?

This is open for some debate. We are agreed on how much load the Towers could handle; instead, it comes down to how much stuff we believe it did handle.

Roughly speaking, the design live load is about 100 psf, with some reduction figured due to live load reduction practices, and some additions in high-traffic areas. Mr. Urich and I agree that the actual strength of the structure was tested to be much higher than this, with an additional safety factor of ~ 2.5. The issue is just how close we think the design load was to the actual load experienced at time of impact.

Mr. Mackey again:

Mr. Urich is positing that the actual load was about 25% of the design load, and he has assembled some simple calculations explaining his basis. I and several others feel his calculations are serious underestimates, and besides do not account for the variety of functions carried out in the Towers. Given the enormous real safety factor that would result if the design load was so heavily padded, the fact that surveys were regularly carried out to make sure the Towers weren't overloaded, and the Towers were occasionally modified in places to accomodate heavier loads, I believe the actual load was much higher, perhaps 75% or more of the design load.

This is difficult to prove either way without a far more detailed look at the Tower contents. Furthermore, this factor accounts for perhaps 170,000 tons, which is by itself enough to close much of the argument.

Don't forget that the regular surveys were most likely focused on local overloading than global overloading, the latter of which has a statisical likelihood << 0.01 (the likelihood of local overloading).

From NIST NCSTAR1-2 pg 106:

Journal of Structural Division 1974, R. K. McGuire et al., "Live Load Effects in Office Buildings".

In the chapter, "Results of live load survey - Variance of sustained load", the mode is given as 0.45 kPa and 90% of the samples are less than 1.0 kPa. The average appears to be around 0.55 kPa = 11.5 psf. This would indicate that my use of 25 psf live load for the area outside of the core is more likely an overestimate than an underestimate.

Unless anyone can present more recent developments that would contradict this I think we should accept it?

 

[Belz...]

Hey, I've got a wacky idea...why don't one of you actually respond to the challenge and create a more realistic model and show why you are all correct.

Well, seeing as this has already been done, reviewed, and accepted, opposing hypotheses now have the burden of proof.

Or are you all just skeptics and not really capable of creating things to be tested or ridiculed?

Appeal to emotions.

I am beginning to think no one that fills up this forum with posts is capable of actually doing anything about all the stuff you talk about and pat yourselves on the back about how well you each can dissect and pick apart any lay persons attempt to demonstrate what happened on 9/11.

Well, I can't. I'm just a computer programmer. I don't do collapse models. What I do is this:

If (User = Wrong)
GOTO Deride
End if

I am still waiting. Thanks...but I am still waiting.

That's because you're still in the same post.

 

[GregoryUrich]

Hey, I've got a wacky idea...why don't one of you actually respond to the challenge and create a more realistic model and show why you are all correct. I am still trying to find one that makes sense and replicates at least some of the variables you all cling to as making such attempts totally foolish and incompatible with reality. Or are you all just skeptics and not really capable of creating things to be tested or ridiculed? I am beginning to think no one that fills up this forum with posts is capable of actually doing anything about all the stuff you talk about and pat yourselves on the back about how well you each can dissect and pick apart any lay persons attempt to demonstrate what happened on 9/11. Please, I appeal to any intellect (or wannabe) show us the real world model that behaves just like the the 3 buildings did on 9/11? Anyone, anyone, anyone. I am still waiting. Thanks...but I am still waiting.

There are already many highly regarded researchers presenting work supporting gravity driven collapse. Since most people here are in agreement with this work, why would they need to reproduce it. For example, here is the latest from Bazant et al.:

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20Did%20%26%20Did%20Not%20Cause%20It%20-%205-2007.pdf

It's true, that it is easier to dissect and pick apart someone elses work than to create your own model. Nonetheless, the people here for the most part are knowledgable and provide valid criticism. They are not always correct (see my previous post) but they are focused on evidence and proper physics.

Why not take a shot at dissecting the above article? A good place to start is:

1. Bazant uses a mass for the upper part that is at least 60% higher than the statistically predicted actual mass.

2. Bazant again neglects momentum transfer.

3. Bazant assumes that the upper part is totally immune to the forces affecting the lower part when in fact the upper part can not exert a force greater than the upper part itself is subjected to. Or rather, "crush up" begins at the first collision during collapse.

 

[Furcifer]

There are already many highly regarded researchers presenting work supporting gravity driven collapse.
Why not take a shot at dissecting the above article? A good place to start is:

1. Bazant uses a mass for the upper part that is at least 60% higher than the statistically predicted actual mass.

2. Bazant again neglects momentum transfer.

3. Bazant assumes that the upper part is totally immune to the forces affecting the lower part when in fact the upper part can not exert a force greater than the upper part itself is subjected to. Or rather, "crush up" begins at the first collision during collapse.

1. Although it is the currently accepted mass, right Greg

2. Is this true? I will have to take a closer look at the paper. Is this another case of the effects being negligible in the overall equation or is it simply innocuous in the differential equation?

3. What are the effects of Zone B? Or better yet what is the COR of Zone B? Is there even a "crush" up on WTC1? Professor Jones would suggest otherwise.

 

[Arkan_Wolfshade]

I fear I don't have time to look through the paper, atm. What is the mass that is used to represent the upper part?

 

[GregoryUrich]

1. Although it is the currently accepted mass, right Greg

2. Is this true? I will have to take a closer look at the paper. Is this another case of the effects being negligible in the overall equation or is it simply innocuous in the differential equation?

3. What are the effects of Zone B? Or better yet what is the COR of Zone B? Is there even a "crush" up on WTC1? Professor Jones would suggest otherwise.

1. If you want to argue against FEMA (1/2 of Bazant's PE), NIST (references Culver) and McGuire et al. Did you miss this?

3. What do you mean by zone B?

 

[GregoryUrich]

I fear I don't have time to look through the paper, atm. What is the mass that is used to represent the upper part?

They vary the popular total mass of 500,000 tons over the height of the building. I did a quick check and it's around 52 x 10^6 kg. The 500,000 tons value is probably based on in-service loads = 100% of design load. See also this.

With realistic in-service live loads it would be closer to 20 x 10^6 kg.

 

[Arkan_Wolfshade]

They vary the popular total mass of 500,000 tons over the height of the building. I did a quick check and it's around 52 x 10^6 kg. The 500,000 tons value is probably based on in-service loads = 100% of design load. See also this.

With realistic in-service live loads it would be closer to 20 x 10^6 kg.

Yes, I understand you take issue with the 500,000 #. However, what I am asking is what is the number (or %) that they use to represent the upper portion in their work (expecting some # < 500,000/100%).