9/11 Physics from Non-Experts

[LashL]

<snip>The core was mostly air as 99 elevator shafts were placed there.

A small nitpick. There were not 99 elevator shafts in the core. There were 99 elevators, but far fewer shafts than that as many of the elevators were stacked, three in a single shaft, in three zones.

Also, don't forget about all of the machinery and equipment that was also housed in the core. In particular, those giant (and very heavy) elevator hoists that took up half the width of the 81st floor.

<snip>You guys aren't very careful.

Ahem.

 

[jaydeehess]

Yes, absolutely. But Loose Ends leads to Loose Change.

At least Mr.Urich is better than F_net=0

 

[Furcifer]

I see he's cherry picking the questions he chooses to answer as well. His linear approximation will decrease the overall mass of the exterior and core steel by 40%.

 

[GregoryUrich]

Good-bye for now

What makes you think I'm having comprehension problems?

I've already showed you your sources of error, and I've already explained why your conclusions -- including that every blasted thing apart from structural steel and concrete fits into a mere 27 lb / ft² -- are preposterous.

I understand you've cherry-picked the NIST report, avoided a proper accounting of many materials that aren't calculated as part of the floor load, and invented a safety factor of 4, which I suspect you've cribbed from Gordon Ross. This is all wrong, and it reflects in your final answers.

Really, there's not much more to say.

You don't comprehend that I have no safety factor other than the building code. I still don't think you get that. NO SAFETY FACTOR. BUILDING CODE. Just because the design and building code says you can put 100 psf on every square foot doesn't mean that happens. Your own strucural analyst confirms 25% of design load as normal load.

You don't even get you own characterization of my model correct.

Outside the core:
Superimposed dead load = 8 psf
Actual live load = 25 psf (the design is 100 psf (code), THE FLOORS ARE NEVER MAXIMALLY LOADED)

Inside the core:
Superimposed dead load 8 psf
Actual live load = 12.5 psf (the design is 50 psf, THE FLOORS ARE NEVER MAXIMALLY LOADED)

If anyone missed it, THE CORE IS AIR AND STEEL FRAMING with 99 elevator shafts. My load in the core is grossly over-exaggerated. I could spread it over a bunch of items like gypsum and all, but I've already said that.

I've answered all your questions and continually get accused of lying or missrepresenting data. With the exception of Newton, I find you guys to be quick to jump to conclusions and slow to provide your own data. Good-luck anyway. I still have hope some of this might sink in.

 

[jaydeehess]

THE CORE IS AIR AND STEEL FRAMING with 99 elevator shafts.

It is not 99 elevator shafts.
There are more elevators than shafts but most of them are 'zone' elevators. Only 2 elevators go from bottom to top IIRC.

The floors of the core are also concrete on top of steel beams.

 

[slyjoe]

OK, we have a question of fact here. LashL says 99 elevators, not 99 elevator shafts. GregoryUrich says (for about the 3rd time), there were 99 elevator shafts. Seems there is a definite disconnect. So, which is correct? GregoryUrich, do you see why people are skeptical of your data?

ETA: and jaydeehess beat me to it!

 

[Newtons Bit]

But twice as heavy?

-Gumboot

ETA. A solid clay brick has a density of 2000kg/m³. Structural concrete is 2400kg/m³. Steel is 3 or 4 times as dense.

Clay brick also has a compressive strength of less than 1000psi (concrete masonry is around 3000psi and sometimes higher). Steel is anywhere from 36,000psi to 50,000psi for common stuff, and the WTC had even higher strength. Steel may be denser, but it's many many times stronger.

Plus the brick was just a facade and not structural.

 

[rwguinn]

You don't comprehend that I have no safety factor other than the building code. I still don't think you get that. NO SAFETY FACTOR. BUILDING CODE. Just because the design and building code says you can put 100 psf on every square foot doesn't mean that happens. Your own strucural analyst confirms 25% of design load as normal load.

You don't even get you own characterization of my model correct.

Outside the core:
Superimposed dead load = 8 psf
Actual live load = 25 psf (the design is 100 psf (code), THE FLOORS ARE NEVER MAXIMALLY LOADED)

Inside the core:
Superimposed dead load 8 psf
Actual live load = 12.5 psf (the design is 50 psf, THE FLOORS ARE NEVER MAXIMALLY LOADED)

If anyone missed it, THE CORE IS AIR AND STEEL FRAMING with 99 elevator shafts. My load in the core is grossly over-exaggerated. I could spread it over a bunch of items like gypsum and all, but I've already said that.

I've answered all your questions and continually get accused of lying or missrepresenting data. With the exception of Newton, I find you guys to be quick to jump to conclusions and slow to provide your own data. Good-luck anyway. I still have hope some of this might sink in.

You have been presented with data. You chose to ignore it. You have been presented with facts. You chose to ignore them. What started as a fals dichotomy (Lying or misrepresenting) had a 3rd option--that you were uninformed.
You behavior has eliminated the third option, leaving the other two as high probabilities.

 

[R.Mackey]

You don't comprehend that I have no safety factor other than the building code. I still don't think you get that. NO SAFETY FACTOR. BUILDING CODE. Just because the design and building code says you can put 100 psf on every square foot doesn't mean that happens.

Yes, but Gregory, you're assuming the building code contains a safety factor of four. It does not.

Your own strucural analyst confirms 25% of design load as normal load.

If you're referring to Minadin's comments, how did you figure that?

If anyone missed it, THE CORE IS AIR AND STEEL FRAMING with 99 elevator shafts. My load in the core is grossly over-exaggerated. I could spread it over a bunch of items like gypsum and all, but I've already said that.

No, it is not. Try 36 elevator shafts. With enormous winches, motors, rails, counter-weights, and of course the elevator cars themselves -- three sets per shaft, express elevators excluded. You haven't properly accounted for the core, so I don't see how you can claim it is "grossly exaggerated."

I've answered all your questions and continually get accused of lying or missrepresenting data. With the exception of Newton, I find you guys to be quick to jump to conclusions and slow to provide your own data. Good-luck anyway. I still have hope some of this might sink in.

Look, you came here asking for critical review. You have it. Your figures, by your own admission, are sharply at variance with every other figure on record. That alone should give you some pause.

If you don't like our review, fine. That's your problem. If you really want to know what's going on with your assumptions, I suggest you take your paper in person to a civil engineering department, show it to at least three professors, and see what they have to say. I also suggest you sit in on a building design and construction review to learn more about actual loads in skyscrapers.

If you choose to follow this path, please return to let us know the results. I'd be interested, since I do not work with buildings. As I stated before, I don't know just how far off you are, only that your conclusions make no sense.

If you choose not to follow this path, then there's little anyone can do to help you.

 

[SYLVESTER1592]

On being pointless...

Show my numbers are fudged. Go on, it's your turn to do some work.

<br />
<br />

Half again as much? 279,000 tons x 1.5 = 418,500<br />
<br />
Twice as much floor space == 20% more?<br />
<br />
Will Sylvester accuse you of &quot;fudging the numbers&quot; or call you a fraud? I doubt it.

<br />
<br />
Ridiculous, now we have to write your paper for you? Do your own work and defend your paper. The total amount of debris proposed will be 1.7 million tons as that is the lowest number I can find. I’m not even considering the dust cloud which must have added a substantial amount to this number. You are however adding water (which is speculative). Loss of mass in the debris cloud substracted from your numbers will make the difference even greater and move my numbers closer to the amount of debris collected. Was there a debris cloud? Yes there was… Was there water?, 1 hour of firefighting, mainly trying to get to the appropriate floor and a bathtub that had damage, but didn’t break. A few feet down the soil was saturated which prevented digging (or else the site would get flooded). So no, no large amount of water was in the debris. You are either stretching the truth or have not proven it yet…
The amount of mass that that can roughly be attributed to the buildings:

WTC1: 500.000 tons total mass above and below the surface
WTC2: 500.000 tons total mass above and below the surface
WTC3: 125.000
WTC4: 125.000
WTC 5: 125.000
WTC 6: 125.000
WTC 7: 250.000

I’ll accept those numbers for the calculations. You have conveniently added a subterranean mass, when this is included in the total mass of the towers (500.000 tons is the total mass according to Eager in JOM, 53 (12) (2001), pp. 8-11.), this mass you give is something I question. I believe all the references give a total mass not just the part above ground.

As for Gumboot, I do believe we were discussing your paper, If you think he is wrong then it’s your responsibility to correct him. I see he did accept your comment, so you can’t say we’re really unfair. If I think someone else in this forum is wrong I most certainly will address it. I think you have had time to investigate this in detail, but still pull something like this. We did not have the amount of research put into this to refute all of the statements on the spot. As I said your paper is the issue of this forum at this moment.

A total from the presented numbers is roughly 1.750.000 tons. It’s funny how this exactly matches up with the debris, don’t you think?...

As mentioned before:”The material expenditures on the towers were enormous; 192,000 tons of steel, 425,000 cubic yards of concrete, 43,600 windows with 572,000 square feet of glass, 1,143,000 square feet of aluminum sheet, 198 miles of ductwork and 12,000 miles of electrical cable.”
425,000 cubic yards of concrete would add up to:

If we use a specific gravity of concrete: Concrete, Limestone w/Portland 2.37 148 ( the lowest I can find quickly)
425000*0.7645*2.37 = 770042 tons (this divided by two exceeds your numbers)
192.000 tons of steel.
If we add those and devide it by two we already exceed your number and come closer to the reported weight. We have not even added the rest yet, maybe also lose some 10% material during construction? OK…

(770042+192000/2)*0.9= 432919 tons just cement and steel… This is still to much for your estimation.

You want to move some of this weight to the basement? Fine? 432919-254000= 178919 tons for the 6 floor basement. That’s 29819 tons per floor and 29819/2309= 12,91 times as much as the floors above surface.

I know it was strengthened, but this is a bit much. I will leave all the rest out to compensate for being generally unfair in your opinion and any overestimation I’m making. Your numbers still don’t add up with the reported use of materials and the reported debris.

The quick clean up had a reason, you can find it at FEMA if you didn’t figure it out already:

http://www.fema.gov/pdf/government/grant/pa/9523_13.pdf


The fact that your numbers are a lot smaller than any reported numbers requires an explanation, not a mere statement of the calculations. You can refute my numbers all day long, but the question is to what extent your numbers are right. And after requesting and waiting for an answer for an extended period of time, I’m told I’m confused, unfair and what not… I’m not the one publishing a paper. If you can take all of this into account in your calculations and show me a better matching explanation without exaggeration, I’ll be fair and give up this point. It has no consequence for the collapse and does not prove or disprove any conspiracy either. Being pointless, is not what I’m objecting to… I asked for a satisfying answer and get a question. Be honest and address the discrepancies presented to you. If you still think I’m being unfair, then submit your letter to a proper journal and we’ll see…


I also found a link to the paper in JOM:
http://www.tms.org/pubs/journals/JOM/0112/Eagar/Eagar-0112.html

 

[jaydeehess]

So the calculation of the mass of a tower is for what purpose? To come up with a P.E. value and thus a value on the energy available for destruction?

Well, the columns themselves contain their own ability to self destruct once the lateral ties between perimeter and core are severed. It is obvious to even a simpleton that the perimeter could not stand on its own for much height at all. (I hope its obvious) So what of the core? It is just possible that if one were to magically cause 10 levels of perimeter, office floors and such to disappear that the resulting ten storey core section sticking up above the rest of the building could stand on its own but it would be very unstable.

But that is not what occured. Instead the top dozen or more levels fell as a block onto the lower portion, ripping away the flooring from several levels on each of the upper and lower sections of the building. This created a very unstable core that was being pounded by thousands of tons of material and it also created a huge amount of very heavy loose debris that would also then be impacting more floors and overwhelming them.

When a floor was hit by debris it would immediatly sag under the impact and mass then tear away from the truss seats only to be pounded into the next floor and adding to the falling loose debris.

If one just takes the opportunity to envision this all occuring it is hardly surprisding that the concrete was greatly broken up and that the steel snapped largely at the connections between 30 foot sections.

 

[Furcifer]

"FEMA decribes a variation in thickness of exterior column plates from 4 inches at the base to 1/4 in the upper stories. This indicates a ratio of 16 to 1 for structural steel from bottom to top. The mass of the steel can be scaled linearly as a function of floor number from the bottom to the top..."

No, it can't. This statement cannot be supported with documentation. It is a supposition on your part which leads to a very high degree of error in your calculation.

 

[jaydeehess]

"FEMA decribes a variation in thickness of exterior column plates from 4 inches at the base to 1/4 in the upper stories. This indicates a ratio of 16 to 1 for structural steel from bottom to top. The mass of the steel can be scaled linearly as a function of floor number from the bottom to the top..."

No, it can't. This statement cannot be supported with documentation. It is a supposition on your part which leads to a very high degree of error in your calculation.

Of course the difference could be shown by calculating the mass of it if reduced thickness by 1/4 inch every 6.875 floors starting at the ground (16 different thicknesses). This would yeild (if my calcs are the correct) 6.25% more mass than a continuously varying thickness from bottom to top.

 

[Furcifer]

Of course the difference could be shown by calculating the mass of it if reduced thickness by 1/4 inch every 6.875 floors starting at the ground (16 different thicknesses). This would yeild (if my calcs are the correct) 6.25% more mass than a continuously varying thickness from bottom to top.

From the blueprints however, the core dimensions stayed the same until the 66th floor. So lets start there and taper up. I mean if we are gonna extrapolate we may as well base it in what we know, not what we guess.
At least in the core. I'm having trouble finding the dimensions on the exterior, i suspect they started at about the same point, but this is supposition on my part and i hold myself to a high standard. Pouring over the blueprints is hard work.

 

[Slayhamlet]

1 short ton (normal US/english ton) == 2000 lbs
1 metric ton == 1000 kg == 2205 lbs

Those of us with a high school education prior to Reagan learned the metric system to prepare us for interaction with the rest of the world. Reactionary Raygun turned the clocks back on progress.

I learned the metric system in fifth grade. That was 1994-95. We used metric measurements for just about every science class I ever took in high school. I remember having to memorize all sorts of conversion formulas in physics class. It was a pain in the ass, but we did it. So obviously you don't know what you're talking about.

And "Raygun"? How juvenile is that? Certainly not my favorite President, but don't you think it would be better to criticise the man for the bad things he actually did?

 

[Mancman]

NIST gives a value of 31,000 usable sq ft per floor == 3,410,000 sq ft per tower. The empire state building has 2,734,122 sq ft of rentable space. So the WTC tower has only 20% more rentable space. The empire state building is a conventional structure and the facade is stone. The WTC tower was a tube/core structure which is much more efficient and gives more strength with less weight. There are a number of innovative features of the wtc tower design that allow it to weigh less.

There is alot of info on this all over the net. Why aren't you guys investigating your own questions before wasting my time?

Yes, the facade is stone.

A few pages back I stated that all of the indiana limestone in the building amounts to about 13,000 tons. Or about 3.6% of the mass of the building.

The steel frame of the ESB is only reported to weigh 60,000 tons. What else could be in it that makes it so heavy?

 

[Furcifer]

The steel frame of the ESB is only reported to weigh 60,000 tons. What else could be in it that makes it so heavy?

localized gravitational phenomenon. see "Hardfire Debate pt.1" Fetzer: "antimatter"

 

[bje]

I have answered a lot of questions my friend. To be honest your questions are lower priority for me because you aren't very careful and do not acknowledge when you are wrong.

Steven Jones and his crew have been questioning that "unanswered question strategy" lately, but I am not aware that "priority" was part of that discussion. Could you clarify that for us?

 

[Myriad]

One basic misconception. I am calculating actual load not design/code/permitted load. There is 75% reserve. What the building can carry is never what the building does carry. Think of your home. Think of your office. Nothing is loaded to the max permitted by code. If it is it is usually modified so that there will still be some reserve strength.

Ah, there's that mythical safety factor of 4 again. Not correct, not supported, and irrelevant for this calculation.

Sorry, you're just plain wrong.

Okay, let me see if I can understand this argument. I'm very confused, and I hate being confused, even more than I hate soundling like an idiot, so I'm going to risk sounding like an idiot in order to try to sort this out.

There's some Very Important Number, let's call it for the moment the "VIN Load," which represents the load a building floor is rated for, according some Very Important Piece Of Paper which is created somewhere in the course of erecting a big honking building.

Mr. Urich is claiming that the VIN Load represents the most the building can withstand without Bad Things Happening. So that, if the VIN Load is 100 lbs, then the building can support 100 lbs. and if you put 101 lbs there, it's likely to have a boo-boo. Therefore it's forbidden to put more than 25 lbs. in the building, in order to leave a fourfold safety factor.

(BTW, I'm not so confused that I don't understand that I should be saying pounds per square foot, not just pounds; I'm using plain pounds to simplify the phrasing of the examples.)

Mr. Mackey is claiming that the VIN Load represents the load that the building is designed and expected to carry in normal expected use (or perhaps, at the high end of an estimated range of loads for various expected uses). Therefore, if the VIN Load is 100 lbs, you can put 100 lbs there, and no boo-boo will happen because if the Important Piece Of Paper says 100 lbs, the building must be constructed to actually support considerably more than that (though that safety factor is not necessarily x4).

Is this an accurate summary?

What is the actual correct term for the thing I'm calling the "VIN Load"?

What is the important piece of paper that authoritatively establishes it for any given building?

Are you both referring to the same Very Important Number as I've implied above, or is part of the confusion a disagreement about which Very Important Number to use?

I hope you can help me with this. Thanks.

Respectfully,
Myriad

 

[rwguinn]

Okay, let me see if I can understand this argument. I'm very confused, and I hate being confused, even more than I hate soundling like an idiot, so I'm going to risk sounding like an idiot in order to try to sort this out.

There's some Very Important Number, let's call it for the moment the "VIN Load," which represents the load a building floor is rated for, according some Very Important Piece Of Paper which is created somewhere in the course of erecting a big honking building.

Mr. Urich is claiming that the VIN Load represents the most the building can withstand without Bad Things Happening. So that, if the VIN Load is 100 lbs, then the building can support 100 lbs. and if you put 101 lbs there, it's likely to have a boo-boo. Therefore it's forbidden to put more than 25 lbs. in the building, in order to leave a fourfold safety factor.

(BTW, I'm not so confused that I don't understand that I should be saying pounds per square foot, not just pounds; I'm using plain pounds to simplify the phrasing of the examples.)

Mr. Mackey is claiming that the VIN Load represents the load that the building is designed and expected to carry in normal expected use (or perhaps, at the high end of an estimated range of loads for various expected uses). Therefore, if the VIN Load is 100 lbs, you can put 100 lbs there, and no boo-boo will happen because if the Important Piece Of Paper says 100 lbs, the building must be constructed to actually support considerably more than that (though that safety factor is not necessarily x4).

Is this an accurate summary?

What is the actual correct term for the thing I'm calling the "VIN Load"?

What is the important piece of paper that authoritatively establishes it for any given building?

Are you both referring to the same Very Important Number as I've implied above, or is part of the confusion a disagreement about which Very Important Number to use?

I hope you can help me with this. Thanks.

Respectfully,
Myriad

you are essentially correct. The Design load, in the case you use, is 100 lb. Design load gives a positive margin.
Margin is described as (Allowable/actual)-SF. THis value should always be >0.0.
In other words (yours, to be precise), at design load, you are still that safety factor away from boo-boo.