Moderated Continuation - Why a one-way Crush down is not possible

[Dave Rogers]

I explained it to you here and have done some simple calculations on the 911 free forum concerning this a month or so ago. Haven't you seen that post?

No, I haven't been following that forum lately, and all you've done here is present your conclusions. There are some engineers round here who might like to see and comment on how you arrived at those conclusions.

Dave

 

[Tony Szamboti]

So, in case anyone's keeping score...

Heiwa is jerking people's chains, mindlessly quoting his "axiom" over and over again and not caring whether it's right or wrong.

Bill is his clueless sycophant, following his every thought like an enraptured puppy.

Meanwhile, Tony is trying desperately to bend reality in order to accommodate his cherished beliefs.

And, every so often, Heiwa is rescued from a tough spot by a few other truther pals who come in wielding their verbal billy clubs to disrupt the discussion.

In other words...we're exactly where we were fifty pages ago.

What a colossal waste of time.

I would agree that these discussions are a waste of time and energy. It has been irrefutably shown that there is not a chance that those buildings collapsed due to natural causes and a new investigation should have been initiated quite some time ago. The only reason it hasn't been done is political. The stonewalling on this by those in power is surreal.

 

[Tony Szamboti]

Yet you concede it would be vulnerable to a mere 40mph wind. Not my idea of "self-supporting" at all.

And would you admit that mention of "bracing" or (even worse) "fully braced" in a technical context could easily mislead the casual reader?

There is a difference between gravity and wind loads and the stresses they generate.

I wasn't misleading anybody. The central core had it's own integral bracing and was not dependent on the floors outside of the core for lateral support. That is not true of the exterior columns.

 

[Tony Szamboti]

No, I haven't been following that forum lately, and all you've done here is present your conclusions. There are some engineers round here who might like to see and comment on how you arrived at those conclusions.

Dave

It is 7:19 AM where I am in New Jersey and I have to head to work right now, but I will look for that post tonight and link it here, or I'll show the calculations here.

 

[A W Smith]

a chain (or core column) is no stronger than its weakest link.

The core was not self supporting as the columns were not fully root welded to the root of their cross section. this is evident in the wreckage which shows clean core column breaks at their ends. I hope your "calculations" allow for these weak connections Tony. Otherwise you are going to look very foolish. Again.

 

[BigAl]

I would agree that these discussions are a waste of time and energy. It has been irrefutably shown that there is not a chance that those buildings collapsed due to natural causes

Impact by 150 tons of airplane at 500MPH and the resulting fire is hardly "natural causes".

None of the handwaving you and Heiwa do about hypothetical structures considers that the buildings that collapsed on 9/11 were not the buildings that existed on 9/10/2001 or buildings that bear much relationship to the buildings that the designers designed. If nothing else, the new buildings contained 100+ tons of load in very unplanned-for distributions that probably locally exceeded floor loading.

The off-the-cuff opinion expressed by Mr. Guthard is specific to the WTC towers and one h*ll of a lot better informed. All of your blather about what can't happen to a hypothetical building doesn't help in the analysis of what did happen.

Recently, Henry Guthard, 70, one of Yamasaki's original partners who also worked as the project manager at the [WTC] site, said, "To hit the building, to disappear, to have pieces come out the other side, it was amazing the building stood. To defend against 5,000 (sic) gallons of ignited fuel in a building of 1350 feet is just not possible.

Report from Ground Zero page 188.
http://snurl.com/j54gc
​

 

[Gamolon]

I don't think you can tell us whether the core is self supporting or not and back your claim that I am clueless when I say it was self-supporting. It's obvious you are using a silly little excuse to cover for it. Boy, you are really acting like an adult here Funky.

Do you have any calculations that support your "self support" claim that you can post here so people can look at them? I'm curious as to how you came to this conclusion.

 

[Gamolon]

Tony,

Did you find that quote from Skilling yet?

 

[Grizzly Bear]

There is a difference between gravity and wind loads and the stresses they generate.

I wasn't misleading anybody. The central core had it's own integral bracing and was not dependent on the floors outside of the core for lateral support. That is not true of the exterior columns.

It's roughly a half truth...

In Robertson's design, the downward weight of the building was also supported by large steel columns around the building's inner core, which is where he placed elevator shafts, emergency stairs and other building services. But the tall vertical columns of the inner core and outer walls were like freestanding stilts until Robertson tied them together with floor trusses.

source

 

[Dave Rogers]

That's a horrible piece of journalese. Of course, no truther would ever be dishonest enough to suggest that it represented a serious engineering account of the process by which the towers were actually constructed, would they?

Dave

 

[bill smith]

So, in case anyone's keeping score...

Heiwa is jerking people's chains, mindlessly quoting his "axiom" over and over again and not caring whether it's right or wrong.

Bill is his clueless sycophant, following his every thought like an enraptured puppy.

Meanwhile, Tony is trying desperately to bend reality in order to accommodate his cherished beliefs.

And, every so often, Heiwa is rescued from a tough spot by a few other truther pals who come in wielding their verbal billy clubs to disrupt the discussion.

In other words...we're exactly where we were fifty pages ago.

What a colossal waste of time.

That's not quite accurate actually. It has been proven in the last 20 pages or so with 100% certainty that Bazant's 'rigid part C' did not exist and that Part C was in fact in an advanced state of disintegration PRIOR to any contact with the Lower 90% of the building. That is the end of Bazant and effectively the end of the only government hypothesis in town. Leaving of course the only other hypothesis- that of controlled demolition to take a strong lead.

We can go over the proof again if you like ?

 

[Dave Rogers]

That's not quite accurate actually. It has been proven with 100% certainty that Bazant's 'rigid part C' did not exist and that Part C was in fact in an adanced state of disintegration PRIOR to any contact with the Lower 90% of the building. That is the end of Bazant and effectively the end of the only government hypothesis in town. Leaving of course the only other hypothesis- that of controlled demolition to take a strong lead.

Sadly, I think your mind really works like that.

Dave

 

[Grizzly Bear]

No, I haven't been following that forum lately, and all you've done here is present your conclusions. There are some engineers round here who might like to see and comment on how you arrived at those conclusions.

Dave

Tony doesn't need to bother... I searched for it myself and I believe the post he's referring to is here: http://the911forum.freeforums.org/would-the-cores-fall-over-without-the-perimeter-walls-t38-45.html

Don't forget that the spires consisted of only the inner 23 core columns and none of the significantly stronger outer columns. One also needs to remember that the moment of inertia of the full core with the outer core columns intact, irrespective of their individual strength, was much greater also.

In general, the greater the moment of inertia the taller a self supporting structure can be without buckling being a concern. The critical force required for elastic buckling is

Fcr = (Pi**2 x modulus of elasticity x moment of inertia) / (Effective Length Factor x length)**2

As the central cores were 137 feet x 87 feet any possible buckling would occur about the 87 foot minor axis. Inelastic buckling would require more force so the above equation is the least amount of force which could buckle the core.

Moment of inertia of a rectangular column is I = 1/12 x width x depth**3

In the case of the full core the width would be 137 feet and the depth of the column 87 feet and the length 1368 feet + approximately 72 feet for the sub levels for a column length of 1440 feet.

For a column fixed at one end and free at the other the Effective Length Factor = 2.0

A simple calculation for a 1440 foot high x 137 foot wide x 87 foot deep column of steel shows the critical buckling load to be on the order of 37 billion lbs.. Since the entire tower weighed no more than 1 billion lbs., using the worst case estimate, I think it is safe to assume that the full central core can be shown to be self supporting with a significant margin of safety.

One can try to argue that the cores were hollow and that the moment of inertia would be less. The reality is that it would not be much less and one can prove that to one's self by doing a moment of inertia calculation for pipe vs. solid of the same outside diameter, or rectanglar tube vs. solid. This is why communication towers are constructed with pipe, as pound for pound pipe is stronger than solid. The way it is stronger is in resistance to bending due to a much greater moment of inertia for a given mass. The key is to ensure that there is no local buckling and that the pipe has enough area to take the overall compressive stress. The columns of the central cores of the twin towers were sized for an average compressive stress of 11,000 psi and to allow bracing at 12 foot intervals to preclude local buckling.

Another way to get an intuitive feel for it is that the central core would be the proportional equivalent of a free standing column of steel 10.5 inches high x 1 inch wide x 5/8 inch thick. Would anyone doubt that this column could be self supporting with a fixed base?

It looks like he treats the core system as a single column... I'd have to look back on my structures notes to check the equations and see if they're right, but the treatment of the core system as a single entity sticks out as a major error IMO. I might could crunch a few of the numbers myself if I find some of my old structures notes, but I don't know how accurate I can be with the model without knowing effectively how high a column with a particular cross-sectional area spanned, since they were not uniform for the entire height of the building. This wouldn't be much a problem when factoring in the braced condition of the intact structure, but determining the strength of the unbraced assembly is another matter.

 

[bill smith]

Sadly, I think your mind really works like that.

Dave

I often learn more from what you delete than from what you leave Dave.lol

 

[Dave Rogers]

It looks like he treats the core system as a single column... I'd have to look back on my structures notes to check the equations and see if they're right, but the treatment of the core system as a single entity sticks out as a major error IMO.

It's an enormous error, as I can rather trivially show with a reductio ad absurdam. The calculation does not, at any point, consider the cross-sectional area of the columns; the only numbers entered are for the length and breadth of the entire assembly. Therefore, if the assembly were made from four solid square columns each of 1mm x 1mm section at the corners of a 137 by 84 foot rectangle, according to Tony's argument this assembly (with sufficient cross-bracing) would be able to support a load of 37 billion pounds. Since this is utterly absurd, it follows that it is an absurd assumption that a rectangular array of columns has the same load-bearing capacity as a rectangular column of the same outside dimensions as the array.


Dave

 

[A W Smith]

Tony doesn't need to bother... I searched for it myself and I believe the post he's referring to is here: http://the911forum.freeforums.org/would-the-cores-fall-over-without-the-perimeter-walls-t38-45.html



It looks like he treats the core system as a single column... I'd have to look back on my structures notes to check the equations and see if they're right, but the treatment of the core system as a single entity sticks out as a major error IMO. I might could crunch a few of the numbers myself if I find some of my old structures notes, but I don't know how accurate I can be with the model without knowing effectively how high a column with a particular cross-sectional area spanned, since they were not uniform for the entire height of the building. This wouldn't be much a problem when factoring in the braced condition of the intact structure, but determining the strength of the unbraced assembly is another matter.

As I suspected. But even worse. Tony treating the core footprint as a solid section of steel. Ignoring the fatal flaw that the core was no stronger in a light breeze than the sum of the square inch area of all its column to column weldments. The core column joints are not even staggered. It was never ever designed to be free standing. In a wind it would snap at the welds like spaghetti!!

whats worse the further down the core you go the less weld area per any given column cross section. Perhaps Tony the "engineer" can show us how the connection at the base of this quarter mile high core column could resist overturning?

 

[tfk]

OK, part C drops on part A and applies 1 GJ energy. At impact 0.5 GJ energy is used to deform parts C and A elastically (the temperature of associated structure is raised 0.05°C).
Thus there remains 0.5 GJ energy to produce local failures in interface C/A. The local failures are assumed to be broken columns punching holes in the floors. As there are about 300 columns that can punch holes in the floors of parts C and A the 0.5 GJ is not sufficient to do that. Destruction is thus arrested at once.

.

OK, part C drops on part A and applies 1 GJ energy.

.
Why are you unable to quote your own paper correctly?

Your "WTC1 - the Case for Collapse/Crush down Arrest" says:

"It is suggested that the first crush down can be initiated by a 0.5 m drop of part C, thus the initial potential energy, PE
0, applied is 0.5 x 54.06x10⁶ x 9.82 = 265.44x10⁶ J." (PE = h m g)

This is, of course, some of your typical sloppiness.

The Kinetic Energy that the upper block gained in its fall is NOT determined by "what energy would crush an object below". Difficult to believe that you could write and then publish something this ill-considered.

As you know, the KE that it has gained is equal to the PE lost, which is determined by its mass & the height that it HAS fallen. Which in this case is about 3.6 meters. So the right answer (using your mass number) is PE is 3.6 m x 54x10⁶ Kg x 9.81 m/sec² = 1.9 GJ.

And yet you produce 1 GJ here. Sloppy.
.

The local failures are assumed to be broken columns punching holes in the floors.

.
Bad assumption. But it is a starting point.
.

As there are about 300 columns that can punch holes in the floors of parts C and A the 0.5 GJ is not sufficient to do that.

.
Wrong. There are about 100 columns that can punch holes. 50 up & 50 down. If you'd paid attention in class, instead of daydreaming of your impending glory, you would have gotten this right.
.

At impact 0.5 GJ energy is used to deform parts C and A elastically

.
Baseless assertion. "Fail"

Tell me your assumptions. Which parts are undergoing deformation, what are their loads & deflections.
Show that you haven't blown some trivial number that would not make your elastic absorption be 0.001 GJ.
.

Thus there remains 0.5 GJ energy to produce local failures in interface C/A.

.
Baseless assertion. "Fail"
.

Destruction is thus arrested at once.

.
I would like to point out that your analysis makes zero sense.
IF, as you say, "the columns punch holes in the concrete floors" (as is certainly true), well then the concrete floors did NOT arrest the fall. Unless you contend that the 50,000 Metric ton upper block can stand on air.

If it did punch holes, then you must consider the NEXT group of parts that comes into contact. If that one is shown to fail, then you must consider the NEXT one after that. And so on.

And you must continue this process UNTIL you come to some parts that do NOT fail. Then, AND ONLY THEN, can you say that the collapse will be arrested.
___

Thus far, your high-falutin' Structural Damage Assessment rates an "F".

I've been trying to help you raise your grade. You don't seem to want to do the work necessary.

But this is the part that really matters.

You must CORRECTLY calculate how much kinetic energy the upper block has acquired at each collision.
You must identify the parts that fracture, and calculate how much energy that they can absorb.
... [Big hint here: Do not consider the columns to be 1 story high. This will give you wrong answers.]
You must identify the parts that ultimately do NOT fracture. And show that their total energy absorption capacity is greater than the remaining kinetic energy in the upper block.

Then, and only then, can you say that the block will stop.

I am running out of patience with you, young man. Your constant antics in class are holding everyone back.

Tom

 

[Grizzly Bear]

As I suspected. But even worse. Tony treating the core footprint as a solid section of steel. Ignoring the fatal flaw that the core was no stronger in a light breeze than the sum of the square inch area of all its column to column weldments. The core column joints are not even staggered. It was never ever designed to be free standing. In a wind it would snap at the welds like spaghetti!!

Every time I'd been tasked with calculating the safe loads of a column the first step was usually to look at charts which specified the cross sectional area A = x in², and a value for r_x & r_y

We then used these values in the following equation:
(KL/r_x) and (KL/r_y)
All length measurements used were converted from feet to inches by multiplying the L (length in ft) by 12 inches.

The largest of the two values, r_x and r_y were used to find the value F_a, which in my structures was found by reference the steel tables and matching to the values that corresponded.

P=F_a*A

where P = the maximum safe load of the column

I've only worked with calculations for wide flange steel cross-sections, and the ones I did using the process above didn't specifically require finding the moment of inertia (although for specific sizes these values are given in a reference table). For simply determining the safe load carrying capacity of the individual columns I'm not sure why he felt it explicitly necessary to calculate for the MOI, but at the very least as Dave mentioned he doesn't indicate anything about the cross-sectional area of the columns which is extremely important to determining the load carrying capacity.

This is a sample of what I've worked with:

 

[funk de fino]

No a child can't just see whether the core was self-supporting or not.

Do the calculations if you can or shut your trap.

You claim it could have stood, you do the calculations. You cannot just say you think it would have stood. I am saying it could not and so does everyone esle. Disprove them Tony, here is your big chance.

What does fully braced mean Tony?

Will you admit your claim about the evidence NIST had was false?

I think you are referring to a guy named Christophera in regards to this imaginary documentary you keep bringing up. He claimed there was a documentary that showed the core was concrete.

No, I am sure that you claimed to have seen a documentary that you said had someone admitting it was a demolition. Are you denying this?

If I am wrong I will apologize.

 

[tfk]

That's not quite accurate actually. It has been proven in the last 20 pages or so with 100% certainty that Bazant's 'rigid part C' did not exist and that Part C was in fact in an advanced state of disintegration PRIOR to any contact with the Lower 90% of the building. That is the end of Bazant and effectively the end of the only government hypothesis in town. Leaving of course the only other hypothesis- that of controlled demolition to take a strong lead.

We can go over the proof again if you like ?

.
Bill,

You gotta stop this. It's just not fair.

YOU... proved ... BAZANT ... wrong ...??!!

Sure thing, billy. And after you're done with your proof, you're going to put on your jammies & cape & fly into space to push aside the asteroid that is approaching the earth. And then have a nice evening with Lois Lane... Don't forget to wear your glasses so that she doesn't recognize you ...

Heck, bill. Even the chihuahua is in convulsions of laughter, pointing his paw at your post. Kibbles & Bits are flying out of his nose...

"Hey, Brutus, Watch it. The keyboard..."

Wait a second, the Chihuahua wants to type something:
The Chihuahua says:

Who is the stupid biped??

His post = (Stupid.Stupid x 10^Stupid)^StupidStupid

.
Darn it, bill. The damn dog was laughing so hard while he was typing that now I'm wiping Purina Chihuahua Chow off my screen.

Gross...

Bill, I DO appreciate your attempt at farce. At absurdity. At burlesque. But some of the "opposing thumb-less" members of my household are just not ready for it.

Please refrain from this in the future. The clean up is a bear...

Tom

PS. "No, Brutus. "A bear..." is just an expression. There is no REAL bear ... Aw, DAMN!! The carpet..!!!"

PPS. Thanks a LOT, bill...