9/11 Physics from Non-Experts

[rwguinn]

I have never suggested that 99.992% energy loss is reasonable. Please don't put words in my mouth. In fact, I have no idea how efficiently a large compacted mass impacting the bedrock transfers KE to seimic energy. Nonetheless I cannot believe that only 0.004% of KE is transferred.

I am not yet supporting the CD theory but I am critical of Bazant's explanation. The seismic energy issue indicates that Bazant's amount of ejected debris and/or velocity are in error.

I'm not sure how my post is off topic. It is physics. I am not an expert. It is perfectly relevant in regards to that non-experts are capable of pointing out valid issues with physical explanations given by experts.

Plkease not the bolded and italicised parts above. See any inconsistency?
You have been informed, time and time again--the Richter scale only indicates peak displacement, which is a measure of peak energy.
The total energy would be a function of the area under the curve, not the peak. But since you're not an expert, your belief overrules all science and logic, right?
If you put a recording ammeter in your electric line, it will show peaks when your air conditioner, or stove, or high power items come on. The total energy you use has little to do with those peaks--you have to get the area under the curve! That occurs over time, not instantaneously

 

[GregoryUrich]

Plkease not the bolded and italicised parts above. See any inconsistency?
You have been informed, time and time again--the Richter scale only indicates peak displacement, which is a measure of peak energy.
The total energy would be a function of the area under the curve, not the peak. But since you're not an expert, your belief overrules all science and logic, right?
If you put a recording ammeter in your electric line, it will show peaks when your air conditioner, or stove, or high power items come on. The total energy you use has little to do with those peaks--you have to get the area under the curve! That occurs over time, not instantaneously

LDEO gave the total seismic energy as 10^7 Joules. Do you have any science or logic that would support your belief?

 

[Dave Rogers]

I have never suggested that 99.992% energy loss is reasonable. Please don't put words in my mouth. In fact, I have no idea how efficiently a large compacted mass impacting the bedrock transfers KE to seimic energy. Nonetheless I cannot believe that only 0.004% of KE is transferred.

I'm not trying to put words in your mouth, rather giving you my interpretation for you to dispute, which you have - fair enough. The point I'm making is this: You're describing Bazant's explanation as "nonsense" on the basis that you "cannot believe that only 0.004% of energy is transferred." However, Bazant's calculation relies only on three parameters: mass of the towers, velocity of impact, and percentage impacting the bedrock. You've proposed that the actual mass was only 50% of Bazant's estimate, but that still only leaves 0.008% of the energy transferred. Do you believe that 0.008% energy transfer is reasonable? If not, how do you account for the discrepancy? If you can't account for it, why is Bazant's figure implausible?

I am not yet supporting the CD theory but I am critical of Bazant's explanation. The seismic energy issue indicates that Bazant's amount of ejected debris and/or velocity are in error.

OK, but you have more than four orders of magnitude to account for. Adjusting the amount of ejected debris and the velocity within physically reasonable limits will make very little difference. Let's pick some numbers - suppose 80% of debris were ejected, and the velocity was only 25m/s, meaning that the collapse must have taken longer than Bazant suggests, and the mass is half what Bazant suggests. We're now looking at about 0.06% energy transfer. Have we got to your threshold of belief yet? If not, how much energy should be transferred, and how are you going to reduce the impact energy any more? Before long the towers will be made of balsa wood and taking three hours to fall.

I'm not sure how my post is off topic. It is physics. I am not an expert. It is perfectly relevant in regards to that non-experts are capable of pointing out valid issues with physical explanations given by experts.

The trouble is, what you're doing is what I think of as the single-sided inequality. You say, "The energy transfer is too low." Your opponent says, "If it's too low, how high should it be?" You reply, "I have no idea, but it's still too low." If you have "no idea" what it should be, how do you know it's too low? It doesn't help your credibility, especially when you then present this as an example of an obvious flaw in someone else's argument. In other words, you're not pointing out a valid issue, you're simply presenting an argument from incredulity.

Dave

 

[GregoryUrich]

I'm not trying to put words in your mouth, rather giving you my interpretation for you to dispute, which you have - fair enough. The point I'm making is this: You're describing Bazant's explanation as "nonsense" on the basis that you "cannot believe that only 0.004% of energy is transferred." However, Bazant's calculation relies only on three parameters: mass of the towers, velocity of impact, and percentage impacting the bedrock. You've proposed that the actual mass was only 50% of Bazant's estimate, but that still only leaves 0.008% of the energy transferred. Do you believe that 0.008% energy transfer is reasonable? If not, how do you account for the discrepancy? If you can't account for it, why is Bazant's figure implausible?

OK, but you have more than four orders of magnitude to account for. Adjusting the amount of ejected debris and the velocity within physically reasonable limits will make very little difference. Let's pick some numbers - suppose 80% of debris were ejected, and the velocity was only 25m/s, meaning that the collapse must have taken longer than Bazant suggests, and the mass is half what Bazant suggests. We're now looking at about 0.06% energy transfer. Have we got to your threshold of belief yet? If not, how much energy should be transferred, and how are you going to reduce the impact energy any more? Before long the towers will be made of balsa wood and taking three hours to fall.

The trouble is, what you're doing is what I think of as the single-sided inequality. You say, "The energy transfer is too low." Your opponent says, "If it's too low, how high should it be?" You reply, "I have no idea, but it's still too low." If you have "no idea" what it should be, how do you know it's too low? It doesn't help your credibility, especially when you then present this as an example of an obvious flaw in someone else's argument. In other words, you're not pointing out a valid issue, you're simply presenting an argument from incredulity.

Dave

Neither I nor anyone else is saying how high it should be but the four orders of magnitude are not supported in any way by Bazant. So instead of "nonsense" I should have said it is an unsupported claim. You must admit 4 orders of magnitude begs the question. I'll look into seismic energy related to impact events.

I need to be careful using the word believe. I speak Swedish most of the time, and in Swedish it is the same word. I think.

 

[Dave Rogers]

Neither I nor anyone else is saying how high it should be but the four orders of magnitude are not supported in any way by Bazant. So instead of "nonsense" I should have said it is an unsupported claim. You must admit 4 orders of magnitude begs the question. I'll look into seismic energy related to impact events.

As far as I can see, it's your assertion that his numbers are inconsistent with the seismic data. So let's look at what Bazant is actually saying. He's calculating a kinetic energy from a mass and a velocity. If you're suggesting that his kinetic energy is incorrect by orders of magnitude, that implies a suggestion that either his mass, his velocity or both are incorrect by orders of magnitude. Where are these orders of magnitude coming from? Even you only claim that his mass is out by about a factor of two. The velocity can't be out by any more than that; note that the impact velocity is the maximum velocity experienced by the falling mass, so an impact velocity of half Bazant's value would mean the minimum possible collapse time would be over 20 seconds.

Do you see my point here? It's that, whatever the seismic data says, Bazant's result simply cannot be as far wrong as you suggest, whatever parameters you want to dispute. So, from a calculation based on a science which by your own admission you have "no idea" about, you're describing Bazant's work as nonsense. This is nothing more than mud-slinging, whatever your first language may be.

Dave

 

[Furcifer]

Yah, I'm not sure what, if any, conclusions can be drawn from the seismic data. I ran it by the crew over a PhysOrg a coupla weeks ago and there wasn't much of a reception to it. I thought the readings were more accurate, but it would appear otherwise. It was after all a relatively small seismic event.

 

[GregoryUrich]

Real nonsense

As far as I can see, it's your assertion that his numbers are inconsistent with the seismic data. So let's look at what Bazant is actually saying. He's calculating a kinetic energy from a mass and a velocity. If you're suggesting that his kinetic energy is incorrect by orders of magnitude, that implies a suggestion that either his mass, his velocity or both are incorrect by orders of magnitude. Where are these orders of magnitude coming from? Even you only claim that his mass is out by about a factor of two. The velocity can't be out by any more than that; note that the impact velocity is the maximum velocity experienced by the falling mass, so an impact velocity of half Bazant's value would mean the minimum possible collapse time would be over 20 seconds.

Do you see my point here? It's that, whatever the seismic data says, Bazant's result simply cannot be as far wrong as you suggest, whatever parameters you want to dispute. So, from a calculation based on a science which by your own admission you have "no idea" about, you're describing Bazant's work as nonsense. This is nothing more than mud-slinging, whatever your first language may be.

Dave

You're right, I shouldn't have called it nonsense on this issue yet. I take that back. I won't call it nonsense again on this issue until I have references to back it up.

Nonetheless, The Great Bazant's erroneous assumption that "crush up" does not begin until "crush down" is complete is in fact nonsense. Neither basic physics nor video evidence support it.

 

[rwguinn]

You're right, I shouldn't have called it nonsense on this issue yet. I take that back. I won't call it nonsense again on this issue until I have references to back it up.

Nonetheless, The Great Bazant's erroneous assumption that "crush up" does not begin until "crush down" is complete is in fact nonsense. Neither basic physics nor video evidence support it.

Anybody see what happened to those goalposts?
I swear, they were right there, just before GregoryUrich posted the above....

 

[Furcifer]

Nonetheless, The Great Bazant's erroneous assumption that "crush up" does not begin until "crush down" is complete is in fact nonsense. Neither basic physics nor video evidence support it.

No, it's an acceptable simplification to allow calculation. He acknowledges it in the Bazant/Verdure paper.

 

[Minadin]

You were trying to convince me that the cores were not braced, except by the main floor assemblies. Newton's bit on this very thread has now confirmed that the cores had their own independent flooring (IE CROSS BRACING) system.

You were trying to convince me that the cores were braced only by the main floor assemblies. Newton's bit agrees with me, although I was trying to get a simple yes or no answer out of him. Or you. Or anyone.

Let's try to make sure we're all using the same terms to convey the same ideas:

Cross Bracing:
________________
|X|X|X|X|X|X|X|X|
|X|X|X|X|X|X|X|X|

Note: not all bays need to be cross braced in all instances. It might only be used in the outside bays, or a couple of the inside bays, depending on the design.

Diagonal Bracing:
_______________
|/|/|/|/|\|\|\|\|\|
|/|/|/|/|\|\|\|\|\|

Note: not all bays need to be diagonally braced in all instances. It might only be used in the outside bays, or a couple of the inside bays, depending on the design.

No Bracing:
______________
| | | | | | | | | |
| | | | | | | | | |

 

[Newtons Bit]

To clarify Minadin, those are elevation views. Or for layman, the side of the building. (And don't forget chevron bracing, though I don't think WTC1&2 had those).

Flooring, does not constitute cross bracing. It laterally braces the columns against buckling (and the beams against bending forms of buckling), but that's it. It does not carry horizontal loads down to the foundation.

 

[GregoryUrich]

No, it's an acceptable simplification to allow calculation. He acknowledges it in the Bazant/Verdure paper.

It's not acceptable because it completely changes the dynamics of the situation. "Crush up" first, the most extreme alternative, results in the arrest of collapse. At the end of crush up, there is only one floors colliding with the rubble sitting on the top floor of the lower part.

What actually happened was probably something in between, but with significant effects on collapse time.

 

[rwguinn]

It's not acceptable because it completely changes the dynamics of the situation. "Crush up" first, the most extreme alternative, results in the arrest of collapse. At the end of crush up, there is only one floors colliding with the rubble sitting on the top floor of the lower part.

What actually happened was probably something in between, but with significant effects on collapse time.

.... It is physics. I am not an expert. It is perfectly relevant in regards to that non-experts are capable of pointing out valid issues with physical explanations given by experts.

So you are not an expert, but can state with absolute confidence that someone who has studied the subject for years, teaches the subject, and is an expert is 100% wrong.

[ twilight zone theme] woo woo wooo woo [/twilight zone theme]

 

[GregoryUrich]

So you are not an expert, but can state with absolute confidence that someone who has studied the subject for years, teaches the subject, and is an expert is 100% wrong.

[ twilight zone theme] woo woo wooo woo [/twilight zone theme]

Very typical of the closed minded to attack with ridicule when they have no substantial argument.

 

[beachnut]

Very typical of the closed minded to attack with ridicule when they have no substantial argument.

Even more typical of the challenge minded who have no arguments, no conclusions to just make up stuff and talk. Are you ready yet to expose your great evidence to prove something about 9/11?

What do you think about the topic of the thread, does that physics expert make sense to you?

 

[Furcifer]

It's not acceptable because it completely changes the dynamics of the situation. "Crush up" first, the most extreme alternative, results in the arrest of collapse. At the end of crush up, there is only one floors colliding with the rubble sitting on the top floor of the lower part.

What actually happened was probably something in between, but with significant effects on collapse time.

Don't get me wrong, I'm not particularly fond of it, but it is acceptable. Don't forget Greg these are mathematical approximation of a chaotic event, nothing will ever be totally encompassing. Even with an undergrad, I can sit here all day a nit pick at what is not there. If you're going to make these accusations of Bazant, you're gonna need some proof. I don't think that incorporating "crush up" during the collapse will arrest the collapse. If you're going to arrest the collapse you need to find and define equilibrium for the system. Use what ever numbers you've got and give us a figure at least, but don't try to attack Bazant like this, it makes you look bad. The burden of proof in this forum is way higher (trust me I learned the hard way)

 

[pomeroo]

I have never suggested that 99.992% energy loss is reasonable. Please don't put words in my mouth. In fact, I have no idea how efficiently a large compacted mass impacting the bedrock transfers KE to seimic energy. Nonetheless I cannot believe that only 0.004% of KE is transferred.

I am not yet supporting the CD theory

I could sell a bridge to anyone who swallows this one.

but I am critical of Bazant's explanation. The seismic energy issue indicates that Bazant's amount of ejected debris and/or velocity are in error.

I'm not sure how my post is off topic. It is physics. I am not an expert. It is perfectly relevant in regards to that non-experts are capable of pointing out valid issues with physical explanations given by experts.

Tell us when you conclude that a gigantic, mathematically-impossible conspiracy blew up the buildings. We promise to act surprised.

 

[Kent1]

Yes, I don't agree with everything in the paper. In fact there are some out right errors within the papers research. But I would suggest a discussion with some of the writers.

And yes, I have mentioned your research regarding the towers weight but I don't think your going to get very far on the seismic data.

Scott

 

[GregoryUrich]

Even more typical of the challenge minded who have no arguments, no conclusions to just make up stuff and talk. Are you ready yet to expose your great evidence to prove something about 9/11?

What do you think about the topic of the thread, does that physics expert make sense to you?

More of the same Beachnut!

I have already demonstrated a number of issues regarding the weight of the tower which is my focus right now.

1. The statistically predicted average (in-service) superimposed live load is 25% of the design live load. I have given references including NIST and no one seems to be challenging this any more and at least Mackey has accepted this. This is the single largest issue regarding weight. Read my references which I have posted previously.

I think it is very telling that none of the critics here have pointed out one issue that reduces the weight. Here are a couple I have become aware of during the time I have been discussing this here:

2. There is no floor outside the core on floors 3-6, 8, 42, and 76, and there is only a partial floor on the mezzanine (floor 2). Sources are NIST and photos from within the lobby area. Hard to contest.

3. The amount of empty space in the core is on average 28%. The average amount of floor space in the core without a permanent live load is 14%. These are calculated from the architectural drawings. So it's easy to check for anyone who doesn't believe it.

4. Floor support in the sublevels amounted to 6000 tons of steel which I have distributed throughout the building in my initial article. This further reduces P.E.

5. Most really heavy machinery (e.g. cooling, emergency power generation, steem generation was outside the footprint of the building). Again the architectural drawings--hard to argue with.

Together, 1-3 account for approximately 200,000 tons which is very close to the difference between my weight 279,000 tons and the official weight 500,000 tons.

A number of important issues have been pointed out here, which I really appreciate:

1. My SDLs in the core and on mechanical levels are not correct.

2. My variation of steel is incorrect due to the fact that floor support (i.e. trusses) should not be scaled. Nonetheless, Since Bazant uses linear scaling from the base to floor 81 it does support my linear scaling. Actually, since i used linear scaling above the 81st floor I actually put more weight higher in the building which is in favor of gravity driven collapse.

Other issues I was aware of before I started discussing this here (as I have previously pointed out):

1. I have ignored the hat truss and antenna.

2. I have assumed the mechanical level to be the same as all other levels.

I have been forthcoming regarding my methods and sources. I have accepted criticism when that criticism is backed up by evidence or good arguments. Your accusation of "no arguments" and "making stuff up" are nothing but mudslinging.

My article was being discussed here and I joined the discussion. I couldn't care less about your object of ridicule. Do you really get any satisfaction just hammering away at people who are obviously inept?

 

[GregoryUrich]

I could sell a bridge to anyone who swallows this one.
Tell us when you conclude that a gigantic, mathematically-impossible conspiracy blew up the buildings. We promise to act surprised.

You are suggesting that I couldn't stand up for my secret CD conclusion? You don't know me and your accusation is offensive.

If I do eventually conclude that a gravity driven collapse was unlikely, I'll definitely let you know.