Can 15 floors crush one floor?

[Animal]

This seems to imply that something (what?) fell onto columns, and that would be a partial answer to femr2's question "What impacted what ?".

So is this your claim? That, in the actual WTC collapses, "something (or columns?) impacted columns"?
femr2 told you that he can show that columns were NOT impacted. Can you show the contrary, that they were? Do you deny that femr2 can show they were not?


This raises an obvious question: How long (over what distance or time) do buckling columns have a significant minimum resistance, and at what point, if ever, do they turn into buckled columns, have no significant minimum resistance?
You may answer this by either pointing towards applicable evidence from the actual WTC collapses (showing columns in the process of buckling), or by discussing from engineering principles, using well derived, documented, tabulated data and knowledge about the behaviour of columns experiencing impact and platic deformation.

(My amateur intuition tells me that a steel column may offer full, or even more than full, resistance, through a distance of a few % of its length; then resistance will decrease dramatically, and become effectively 0 a few % later. My intuition tells me further that this is mere theory, because columns will more typically buckle at their joints. And a couple of years reading this and other forums and appreciating the actual evidence suggest to me that column buckling played no great role during collapse progression, as it was mostly floor-to-column connections that lead the way. Let's see what your "professional" (I understand that you are not quite in the right profession, but hey...) intuition tells you. This shall be more fun.)

A column that is buckling means the load imposed have exceeded the yield point of the metal. The metal will continue to yield until the load is removed / reduced to below its yield point.

But yes, you are correct....in the towers, for the most part, it was the floor plates (designed for an approximate 100 psf live load) that faled from the impact which in turn removed the lateral support for both the perimeter and core columns, which in turn failed.

Why troofers have such a hard time grasping that simple concept is beyond me.

 

[Newtons Bit]

What it says on the axis..."connection failure"...the energy, in Joules, required to sever all connections between an OOS floor assembly from the perimeter and core.

Would have thought my words immediately beneath the graph you quoted...



...would have given you some indication, but ho hum.

The other axis is the time for progression to ground. No datapoint for connection strength/floor mass qty that don't propogate to ground.

Perhaps you ought to label your axes so people can see what units your using, as well as which measuring system.

 

[alienentity]

By the way, a one g fall is impossible in a natural collapse initiation due to buckling columns, as buckling columns have a significant minimum resistance.

Good. You've just successfully argued that the tower collapses were natural collapses because they did not initiate at g. How many years did it take for one of you to use simple logic to eliminate the glaring contradictions your movement has been making? About 6 years I think.

Richard Gage is still screeching about Freefall, perhaps you and David Chandler should send him a memo to remove that canard from the list.

Columns buckled because the structure was weakened by the plane impact and fire damage. We have the cause of the initiation, if not every detail of the interior (because nobody will ever know for sure).

Onto the OP - can the 12 floors crush one floor? By 'crush' I take it Travis means 'destroy' or 'continue to fall thru'.

The answer is obviously 'yes', particularly if the upper structure falls onto lower structure with any significant degree of misalignment, because then there's even less load-bearing capacity to resist.

As Tony notes:

The initiation occurred on the 98th floor, so it was 12 floors. It accelerated at about 5 m/s through that first story and at about 6.2 m/s^2 thereafter. So it wasn't a one g fall.

So about 6.2 m/s^2 acceleration thereafter.

Tony is trying to disqualify and disallow the upper structure fall by inserting a condition on the collapse he got from one of the Bazant papers (the 'jolt'). But that paper proposed a 'limiting case' which was designed to test the absolute strength of the structure and its ability to resist the downward momentum of the upper block collapse. It was not designed to mimic the actual impact qualities of the collapse. Tony is incorrectly trying to treat the limiting case (which sets the outer boundaries of collapse physics) as the ACTUAL collapse. (ETA the actual collapse gave the building even less chance of survival)
Thus he sets up a fallacious argument when he declares that there was no 'jolt'. It is yet another attempt at a strawman argument - to look for something which is not expected to be there and then declare suspicion upon its absence.....

I agree with the other critics of Tony's reasoning that his next objection is also invalid: his insistence that there wasn't enough tilt in the initiating moments to prevent axial impacts on the structural columns - but we already know that many of the columns seem to have buckled at initiation; ie they were INTACT on the perimeter until they failed. Thus it is impossible for them to have 'impacted' one another, and thus there cannot be a 'jolt'.

Tony takes this faulty logic to the next phase where he strangely expects a cartoon-like perfect drop of 1 story onto the next, column to column. But his argument is purely rhetorical - the collapses did not happen that way. And in any case WTC 2 differed from WTC 1 in the first moments, so the attempt to handwave only applies to one out of two. What's the point? It's a failed argument.

Sure, if you examine a verinage collapse, where hydraulics remove vertical support very uniformly, you will see a 'jolt' or sharp deceleration. But this mechanism is well understood and very obvious. Equally obvious is that the WTC collapses were natural collapses (to use Tony's term) which involved asymmetrical and gradual failures. They couldn't be more different from verinage in that respect.

ps verinage still is a natural collapse from the point of release, and still completely crushes the buildings involved, without the use of additional explosive charges.
If one applied Bazant's limiting case physics it would work in either case. The cause of initiation is not what determines whether the crushdown will be complete or not. That is a red herring and another distraction from the OP.

 

[jaydeehess]

A column that is buckling means the load imposed have exceeded the yield point of the metal. The metal will continue to yield until the load is removed / reduced to below its yield point.

Of course in this case we are also referring to columns with varying degrees of either impact damage and heat damage. Treating all columns as equal in condition is an approximation. If we treated a percentage of number of columns with a reduced percentage of steel strength we'd still have an approximation. Only if we assigned impact and heat damage to each and every column would we have a much better model. This is near impossible to do though since we just don't know which columns had what damage. we could use the NIST reports as a guideline of course....
Problem is that the 911'truthers' will then picky-picky-picky on all of these assumption and claim that there should be different assumptions, not as hot a fire, not as great an impact damage, etc.

ohh, wait,,, that's already happening.... right,,,,,,,

But yes, you are correct....in the towers, for the most part, it was the floor plates (designed for an approximate 100 psf live load) that faled from the impact which in turn removed the lateral support for both the perimeter and core columns, which in turn failed.

Why troofers have such a hard time grasping that simple concept is beyond me.

seconded

 

[Newtons Bit]

A column that is buckling means the load imposed have exceeded the yield point of the metal. The metal will continue to yield until the load is removed / reduced to below its yield point.

Your terms are incorrect. By definition, buckling occurs prior to yielding.

 

[Cl1mh4224rd]

The lateral inertia of the upper section would keep them aligned. So the only way it could happen is with enough tilt, which can be shown not to be there. Those who say the columns would have been misaligned have nothing technical to back what they say.

[...] buckling columns have a significant minimum resistance.

Significant enough to slow the collapse measurably (and supposedly contribute to its eventual arrest), but not significant enough to throw the columns out of alignment?

 

[ozeco41]

...Why troofers have such a hard time grasping that simple concept is beyond me.

It's not just troofers.

Tony is employing his usual approach to discussion - focussing on a couple of details so people lose the overall picture. Call it "cannot see the forest for the trees" if you like metaphors.

And just about everyone is falling for the trap. I have pointed to the trap and femr2 has also identified features of that trap.

This is the situation:
1) The OP asks, in effect, can a falling 15 storey top part of tower "crush" what is below.
2) After settling a few bits of ambiguity discussion continues about what happened with the WTC 1 tower. So we are supposedly discussing the "real event".
3) The scenario is "top bit falling" and the key question becomes "what impacted on what"?
4) I pointed out two simple facts of reality viz
(a)"With the top bit falling the columns had already failed or qwere in the actual brief act of failing" AND
(b) "since the top bit was falling then ends of columns had already missed impacting or were about to miss.
Both those simple facts accessible to a bit of thought which I encouraged members to engage in.
5) Third simple fact which flows from those two is:
(c) what impacts on what will be (i) OOS floors land on OOS floors; AND (ii) core falling on core lands cross beam on cross beam. No columns involved other than in a minor way. Certainly no buckling.
6) plus a few "boundary clean up issues (p) the outer perimeter of the falling top block will either fall inside the lower perimeter and add to the overload of the OOS floors OR it will fall outside the lower periemter with similar consequences - details easily explained if needed. Mere details.

Bottom line:
Column buckling was not involved and column strength was not a significant faster. Another easily explained secondary issue if raised.

AND - the process or procedural trap - Tony has succeeded in getting people chasing their logical tails round in circles. By trying to get explanations of how the impact on columns could affect outcomes when there would be no impact on columns.

Which is exactly the faulty "circular logic" error in the "Jolt which could not be missing because it never was..."

I wont go back over the last 2+ pages of posts to trace the derails and false scents...

And the message??? Try these two:

"when discussing a tree or two don't forget the forest" OR

"when you are up to your arse in alligators it is easy to forget the objective was 'drain the swamp'"

 

[Dave Rogers]

Your terms are incorrect. By definition, buckling occurs prior to yielding.

Is there a word meaning "formation of plastic hinges," which I suspect is what Animal meant by "buckling"? It seems clear to me that, once plastic hinges form, the resistance of the column is considerably modified from its behaviour prior to yielding, and that, once the plastic hinges fracture, which should happen at a fairly small angle, then the column resistance becomes negligible.

Dave

 

[Newtons Bit]

Is there a word meaning "formation of plastic hinges," which I suspect is what Animal meant by "buckling"?

Dave

Well, that's inelastic buckling. That's very different than "yielding". The stress at which an entire section buckles is far lower than the yield point. All I'm saying is that yield != buckle.

It seems clear to me that, once plastic hinges form, the resistance of the column is considerably modified from its behaviour prior to yielding, and that, once the plastic hinges fracture, which should happen at a fairly small angle, then the column resistance becomes negligible.

TM 5-1300 puts this angle at 8-12 degrees.

 

[Oystein]

...
This is the situation:
1) The OP asks, in effect, can a falling 15 storey top part of tower "crush" what is below.
2) After settling a few bits of ambiguity discussion continues about what happened with the WTC 1 tower. So we are supposedly discussing the "real event".

It is not clear to me that this is what we are "supposedly" discussing. Who is supposing this? I think the OP, depside what I supposed earlier, has replied, although muddily, with something that sounded to me as if he doesn't care, and would be satisfied with any generic building undergoing collapse for any random, even magical, initiating reason.

It is your prerogative to "suppose" we are debating the actual and observed WTC 1 collaspe, and perhaps we should.

3) The scenario is "top bit falling" and the key question becomes "what impacted on what"?

There is fun to be had when someone gives a wrong answer to this question, uses this wrong answer as one of his starting premises, adds a few more unreal premises, and STILL gets his conclusions wrong - both in terms of what really happened, and what would happen if his assumptions were true.
Interestingly, that same poster has already admitted that "15 floors can crush 1 floor", provided that a couple of conditions are satisfied. When pressed to define these conditions in terms such that it can be determined if these conditions are satisfied, he rambles on into a mix of insults, lame dodges more false assumtions and conclusions that don't follow from these assumptions (or assumptions that don't warrant the conclusions?).

... the process or procedural trap - Tony has succeeded in getting people chasing their logical tails round in circles. By trying to get explanations of how the impact on columns could affect outcomes when there would be no impact on columns.

See above: I say you try to rid some here of some fun! Tony is wrong on so many levels, why should I stick to the topic?

Which is exactly the faulty "circular logic" error in the "Jolt which could not be missing because it never was..."

The circle is a spiral downwards - it circles around wrongness, on many levels.

 

[Oystein]

I just scanned this paper which appears in the massive link list that I posted on Chris Mohr's behalf in his thread:


LU Xinzheng & JIANG Jianjing: Simulation for the Collapse of WTC after Aeroplane Impact

Abstract: Mechanical simulation and parameter discussion for the collapse of WTC (World Trade Center) after aeroplane impact are presented in this paper with the dynamic FEA software of LS-DYNA. The simulation results are very close to the real situation, which means that such type of special damage process can be recurred on the computer with proper parameter and numerical model. The results show that the direct reason for the collapse is the softening of steel under fire and the chain reaction damage of floors under the impact load of upper floors. If improve the fire resistance and the ductility of the structure, the collapse may can be avoided.
...

Conclusions
...
4) Improving the ductility of structure elements is an efficient way to avoid the chain collapse happens. In the simulation above, if the fracture plastic strain of steel structure is 0.5%, the chain collapse will take place entirely. However, if the fracture strain is improved to 1%, the impact energy of upper floors will be absorbed by the lower structures and the chain collapse will be stopped at about 100m under the airplane impact zone. When the fracture strain is improved to 5%, only part of the structure near the airplane impacting zone will be damaged, and no chain collapse will take place. Hence, if the structure has enough ductility to absorb the energy of upper floors¡¯ collapse, the chain damage will be controlled. Even though consider the influence of heap load, the towers still have much larger chance to escape from the entire collapse.

Has this been discussed?

 

[Animal]

Well, that's inelastic buckling. That's very different than "yielding". The stress at which an entire section buckles is far lower than the yield point. All I'm saying is that yield != buckle.



TM 5-1300 puts this angle at 8-12 degrees.

And that is why I pay my structural engineer the fees he well deserves.e

 

[Newtons Bit]

And that is why I pay my structural engineer the fees he well deserves.e

 

[ElMondoHummus]

I just scanned this paper which appears in the massive link list that I posted on Chris Mohr's behalf in his thread:


LU Xinzheng & JIANG Jianjing: Simulation for the Collapse of WTC after Aeroplane Impact




Has this been discussed?

At all? References to their work has been made in the past, yes; I've made them myself. But I think your question is whether they've been discussed in detail on their own merits, and to that I have to say no. Theirs was one of the early works (not even a full year after, I think) that were done without the benefit of knowledge from the NIST studies, so they don't get mentioned that much.

That doesn't mean they're not worth discussing. I'm only saying that the rare mention we've made of them has not been in the context of their own work. Rather, it's been in reference to them being examples of independent studies not linked with NIST or the US government that support the basic concepts of fire-induced collapses.

It might be interesting to consider their paper in the same way we consider Bazant's and his colleagues various works: As early works applying general engineering concepts to the then-known specifics of a real world event (As an aside: Folks, am I correct to call Bazant's works, as well as Jiang's and Lu's works as "First Order analyses"? Or am I misunderstanding and misusing the term?). Poor Jiang and Lu seem to get treated as a minor work in the grand scheme of things.

 

[ozeco41]

It is not clear to me that this is what we are "supposedly" discussing. Who is supposing this?...

Well me and several others. Including Tony Sz - who, by agreeing with me raises some interesting points of irony. Which I "suppose" you had chuckled over.

...I think the OP, depside what I supposed earlier, has replied, although muddily, with something that sounded to me as if he doesn't care, and would be satisfied with any generic building undergoing collapse for any random, even magical, initiating reason....

Agreed on "doesn't care" but keeping a rain cheque on "doesn't realise".

...It is your prerogative to "suppose" we are debating the actual and observed WTC 1 collaspe,[sic] and perhaps we should....

Yup - just as much my prerogative as others have the prerogative to choose others. And, silly me, I have identified all three (no body has disputed "three") and I have even answered all three (no body has disputed my three answers either)

...There is fun to be had when someone gives a wrong answer to this question, uses this wrong answer as one of his starting premises, adds a few more unreal premises, and STILL gets his conclusions wrong - both in terms of what really happened, and what would happen if his assumptions were true....

I hadn't missed that aspect. In fact if I go another layer up into "mets-meta- process" I could comment on a phenomenon I noticed and reported in my very first Internet post which started off with this:

The paper referenced as Engineering Reality by [some author or other] 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.

That was Nov 2007. It still happens.

...Interestingly, that same poster has already admitted that "15 floors can crush 1 floor", provided that a couple of conditions are satisfied. When pressed to define these conditions in terms such that it can be determined if these conditions are satisfied, he rambles on into a mix of insults, lame dodges more false assumtions and conclusions that don't follow from these assumptions (or assumptions that don't warrant the conclusions?)....

You need to know the "code". Insults are second level evasions and correspond to "I cannot answer your question but I'm brave enough to say so." I often get "First level evasions" shown when my posts are totally ignored. That corresponds to "I cannot answer your questions and I am certainly not prepared to continue down that track because I know that you are right" We need not define the third and fourth level evasions at this point.

...See above: I say you try to rid some here of some fun! Tony is wrong on so many levels, why should I stick to the topic? ...

To stop confusing me is one reason. The combination of engineer/lawyer must be a limiting factor - ask anyone who has come second in a debate with me.

...The circle is a spiral downwards - it circles around wrongness, on many levels.

Yes. And being partly serious - as you know I will usually target the top level error. And make comments about those discussing at levels 2>>3>>4 - the "details" which don't matter for debating purposes when the claim has failed at the "big picture' of the top level circle.

...hence the several recent references to:

1) Forest;
2a) Trees
2b) Tree;
And For same reasons as above I wont descend the hierarchy to:
3) Branches;
4) Twigs;
5) Leaves;
6) Grub eating the 457th leaf on twig 492 of branch 17 of tree 12 in THIS forest.

Your turn.

PS: BTW
1) In reality 15 storeys did collapse the lower tower in real life - leaving out use of the word "crush"
2) The Bazantian one dimension limit case model showed that 15 storeys falling would crush the lower section (with energy to spare and a couple of residual niggles from ozeco )
3) Any generic claim that 15 storeys would with certainty crush or otherwise destroy any undefined generic building is demonstrably false. BUT
4) The claim could well be true for certain specific buildings out of the set of generic buildings. So for any individual building selected out of the set of all buildings taller than 16 storeys the answer is "maybe - it depends on the building etc etc"

E&OE on that last bit -

And, obviously, I agree with the objective "have fun"

[/SmartArseMode]

 

[Dog Town]

YES!

 

[000063]

Wait......was that an attempt to answer while still dodging the question?

Strictly speaking, it was an attempt to pretend to answer while still dodging the question.

You seem to spend enough time on this subject to come up with your own calculation. So why don't you tell us?

"My daughter's birthday is next week."
"They're great girls. Which daughter, and which birthday?"
"You tell me."

The fall of the mass through a specified distance generates a certain amount of momentum, and finally it is the momentum transfer that counts.

Both of which you are ironically refusing to specify.

I am aware that some people like yourself attempt to say the columns would have missed each other. However, this is an unsupported claim. It has been proven that the upper section of the North Tower does not tilt more than 1 degree for the first couple of stories of the fall and that is nowhere near sufficient to move the columns out of alignment.

And were the columns the only collapsing parts of the floors? You know they were not. You also know that Oys statement said nothing about the columns, and that is just your straw man.

Well I guess that it is still just a matter of opinion. And that's all I'm saying. None of it has been proven on either side of the issue.

Some people, on both sides, are just asserting to be right.

That post is almost entirely free of any real content. Good job!

 

[000063]

It is incredible that you think the column flange and web areas have to hit exactly square area to area to cause a deceleration and then to top it off you have the nerve to question me. This is precisely why people like you don't get answered. Go play in a sandbox somewhere.

Straw man.

The top block fell, therefore columns across a floor area were disconnected, and nothing will ever bring them back into contact again.

Not "square-on contact", but "contact", period, you sophist.

You have no basis for saying a vertical analysis isn't legitimate. It is fully legitimate to look at the vertical descent only when it is known that there is no significant lateral movement. The upper 33 stories of WTC 7 had a significant deceleration after a 16 story fall and you have been shown that and I have explained the stiffness issue to you before.

Another straw man, and one which blows right by Femr's question about lateral movement.

It is only those with an agenda who inanely claim that no jolt would be expected and a few non-technical individuals who have gone along with it. The decelerations present in all of the measured Verinage demolitions should have shown anyone being honest about it, that may have thought different, that they were wrong.

Poisoning the well.

You haven't shown anything. You are an anonymous poster claiming he has found things nobody else has and applying back handed logic that doesn't work.

I have answered the questions you are asking many times in the past. Go find them.

I want to know if anyone has ever fallen for this tactic from any truther. "Yes, I answered those same questions at some point between me joining this forum and today. All you need to do is find it among my thousands of posts. Simple!"

You haven't shown anything. You are an anonymous poster claiming he has found things nobody else has and applying back handed logic that doesn't work.

What on Earth are you talking about Tony ? You sound exactly like Chris7, which is particularly sad....

Ironically, he's also describing Chris7.

That isn't an automatic. It depends on the strength of the structure below.

If you are following this issue much at all you would know there have been failed controlled demolitions. Some of these failures can be seen on the Internet. Why did they fail?

Red herring. Describe why they failed, describe why it's relevant, and stop with the indirect insults and well poisoning.

 

[Justin39640]

Some of these failures can be seen on the Internet.

Ah, summing up the truth movement.

 

[femr2]

had a quick look at old Sauret traces, and...a good 3 or 4 inches of Eastward lateral movement of the NW corner prior to NW corner release.

Make that 4 or 5 inches.

Lateral motion began >8s prior to NW corner release.

Very similar lateral motion for NW corner and antenna (until frame ~1088), suggesting it is not a tilting type action.