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

[Heiwa]

Again, not as much detail as I'd like but at least it's an unambiguous answer. So, to sum it up, it follows form your axiom that in every collapse where a smaller part drops onto a larger part of any structure, this is what happens after the initial drop from any height (assuming no bounce of course):

1. local failures

2. no rubble!!

3. collapse stops

Is this a correct summary or did I misrepresent your position in any way?

?? In 'every collapse' there is evidently collapse! Topic is however Why a one-way Crush down is not possible!

A small part of a structure dropping on the bigger part of same structure is to start with not a collapse! It is just a 'drop'.

What happens then, at contact, are an impact, energy is applied, forces develop, etc. No collapse, so far. The forces definitely produce deformations; the structures may bounce and/or local failures will develop. It all depends on the potential energy applied.

When the energy is exhausted (transformed into heat), the process stops.

Do you seriously believe that at little part can one way crush down a big part?

 

[BigAl]

In order to continue destruction you have to add
more energy, e.g. by controlled demolition.

An unproven assertion about a hypothetical building.

What you assert can't happen (to a hypothetical building is less interesting than explaining what did happen to the WTC towers which in the million words you have typed you have made no attempt to do.

 

[twinstead]

The fact remains that what I have seen by the examples given by members of this forum, and by watching the collapses of the WTC themselves, what Heiwa claims is impossible, is indeed not only possible, but has been observed and studied by structural engineers.

Therefore, in my mind, until I hear differently by some reliable source, Heiwa has been shown to be wrong. Now, the ball is in YOUR court, Heiwa; convince somebody who actually has some RESPECT from the world's major engineering or academic organizations or please just change the subject.

 

[Heiwa]

An unproven assertion about a hypothetical building.

What you assert can't happen (to a hypothetical building is less interesting than explaining what did happen to the WTC towers which in the million words you have typed you have made no attempt to do.

Hypothetical building? What are you talking about? Anyway, any structure of a hypothetical building is such that dropping a small top part of the building on the greater bottom part cannot produce a one-way crush down of the latter as per Björkman's axiom.

So let's agree that WTC 1 was not a one-way crush down.

So, what could it have been?

 

[Dave Rogers]

Any conclusion of the form "No [X] exists" is extremely difficult to defend, and can be discarded at once on the production of a single verified example of X. I would therefore like to submit for your consideration the collapse of a multistory building in construction at Bailey's Crossroads, Fairfax County, Virginia, USA, in March 1973.

http://www.djc.com/news/co/11155170.html

The 24th floor concrete was being poured at the same time as the shoring was removed from the 22nd floor, which had been curing for two weeks. The 22nd floor was unable to bear the weight of the 23rd and 24th floors, and so collapsed on to the 21st. Although the 21st and lower floors were sufficiently cured to withstand the static weight of the upper structure - they had done so for a week - they were unable to withstand the dynamic loading from the collapsing 22nd, 23rd and 24th floors, and this resulted in a progressive collapse of the entire structure.

No doubt you will argue that the building was incomplete. This is irrelevant to your "axiom", as the structure was capable of supporting its own weight prior to the collapse. In fact, as it was the removal of shoring from the 22nd floor that rendered it unable to resist the weight of the 23rd and 24th floors, it is clear that in this instance the weight of two floors - less than 10% of the total - caused a complete crush-down of a 22-floor lower structure.

A counter-example having been produced, The Björkman's axiom is shown to be spurious.

Dave

ETA: In keeping with the previous post, shall I convey your congratulations to the families of the 14 construction workers who were miraculously resurrected the day you dreamed up your axiom?

Bump for Heiwa, who seems to be ignoring it. Heiwa, are you going to:

(a) Explain why floors 23/34 collapsing a 22-storey lower structure of the same construction doesn't disprove your axiom, which specifically claims that this cannot happen?
(b) Pretend that this collapse never happened and that the article is a fabrication?
(c) Ignore any real-world information that challenges your beliefs?

or

(d) Admit you were wrong all along and this proves it?

Regards,

Dave

 

[tuc0]

?? In 'every collapse' there is evidently collapse! Topic is however Why a one-way Crush down is not possible!

A small part of a structure dropping on the bigger part of same structure is to start with not a collapse! It is just a 'drop'.

What happens then, at contact, are an impact, energy is applied, forces develop, etc. No collapse, so far. The forces definitely produce deformations; the structures may bounce and/or local failures will develop. It all depends on the potential energy applied.

When the energy is exhausted (transformed into heat), the process stops.

Do you seriously believe that at little part can one way crush down a big part?

Hmm and I thought we were so close. If it's the word collapse that bothers you please suggest a different one. 'Drop' isn't clear enough and you talk about 'collapse arrest' yourself. Surely, there can only be a collapse arrest if there is a collapse or am I wrong? Not every collapse needs to be a one-way crush down to be considered a collapse, as I'm sure you'll agree.

"It follows from your axiom that in every drop where a smaller part drops onto a larger part of any structure, this is what happens after the initial drop..." See? That doesn't seem to be a very elegant or clear sentence.

 

[BigAl]

Hypothetical building? What are you talking about? Anyway, any structure of a hypothetical building is such that dropping a small top part of the building on the greater bottom part cannot produce a one-way crush down of the latter as per Björkman's axiom.

So let's agree that WTC 1 was not a one-way crush down.

So, what could it have been?

http://wtc.nist.gov/

 

[Heiwa]

Bump for Heiwa, who seems to be ignoring it. Heiwa, are you going to:

(a) Explain why floors 23/34 collapsing a 22-storey lower structure of the same construction doesn't disprove your axiom, which specifically claims that this cannot happen?
(b) Pretend that this collapse never happened and that the article is a fabrication?
(c) Ignore any real-world information that challenges your beliefs?

or

(d) Admit you were wrong all along and this proves it?

Regards,

Dave

Well, this Bailey Plaza was again, like Ronan Point, just local failures at the corner of a structure under construction; as most elements were still hanging on to the structure after failure, you wonder about the few supporting elements that failed, etc, etc, etc. No rubble was formed, no part C was dropping on part A.

It has thus little relevance to topic.

 

[rwguinn]

An unproven assertion about a hypothetical building.

What you assert can't happen (to a hypothetical building is less interesting than explaining what did happen to the WTC towers which in the million words you have typed you have made no attempt to do.

Add more energy.
So what does he think M*g*H is?

 

[Heiwa]

Add more energy.
So what does he think M*g*H is?

Evidently M*g*H of the upper part cannot one-way crush down the lower part! You need >1000X the energy for that.

 

[Dave Rogers]

Well, this Bailey Plaza was again, like Ronan Point, just local failures at the corner of a structure under construction; as most elements were still hanging on to the structure after failure,

Is any of this actually true, or have you simply looked at the single post-collapse picture and made it all up? The article was fairly clear that this was a failure of the supporting structure, and your definition of the word "corner" doesn't exactly seem to be the conventional one.

No rubble was formed, no part C was dropping on part A.

Part C was floors 23 and 24. Part A was floors 1 to 22. Part C fell on part A. And how, in this universe, do you imagine that a 24-storey concrete structure collapsed without creating any rubble? Did it vanish in mid-air, like you seem to think the rubble from the WTC did?

It has thus little relevance to topic.

(a), then. Sorry, but that's not good enough. This is a clear and obvious example that proves that crush-down is possible. Therefore, the premise of this thread is disproven.

Dave

 

[Klimax]

Evidently M*g*H of the upper part cannot one-way crush down the lower part! You need >1000X the energy for that.

But you cannot treat the lower section as a single thing!!!

If you were talking about old european house,then I'd somewhat understand you,but this structure we talk about is very different!

 

[Heiwa]

(a), then. Sorry, but that's not good enough. This is a clear and obvious example that proves that crush-down is possible. Therefore, the premise of this thread is disproven.

Dave

Sorry, Bailey Plaza = local failures to an unfinished structure, Ronan Point = explosion causing local failures to a structure. In no case a one-way crush down took place.

 

[Grizzly Bear]

Do you seriously believe that at little part can one way crush down a big part?

Yes. If one floor is hit with the impact load of three, and fails there can be 1, 20, 100, 200, or 500 floors underneath and they too will fail. Because in a progressive collapse such as Ronan point, the building isn't resisting the impact as a unit; only individual floors are subjected to the strain at any given time. So instead of having the overall strength of the lower 50 , 100 or 150 floors resisting the impact simultaneously, you have only one at any given time offering resistance.

 

[Klimax]

Evidently M*g*H of the upper part cannot one-way crush down the lower part! You need >1000X the energy for that.

Fail. You cannot treat structure bellow to be hit as a single solid thing!

 

[Dave Rogers]

Evidently M*g*H of the upper part cannot one-way crush down the lower part! You need >1000X the energy for that.

Not by your own calculations, where you had to pretend MgH/2 vanished in order to reach the conclusion that collapse would arrest. And anyway, dropping the top part from two miles would easily provide >1000X the energy, and yet you seem to think that even that wouldn't crush down the lower part.

Dave

 

[aggle-rithm]

Evidently M*g*H of the upper part cannot one-way crush down the lower part! You need >1000X the energy for that.

Once again, you seem to be pulling base-10 round numbers out of thin air. How did you arrive at this figure?

 

[Heiwa]

Fail. You cannot treat structure bellow to be hit as a single solid thing!

?? The structure below, part A, is exactly the same as the structure above, part C, with the exception that A carried C before (and not the other way around). That is clear from all my papers.

So A is slightly stronger than C. Or C is weaker than A. You agree?

Don't suggest that you can one-way crush down a stronger structure, part A, with a weaker one, part C.

 

[tuc0]

Edited by Gaspode: 

Edited for civility - moderated thread

?? The structure below, part A, is exactly the same as the structure above, part C, with the exception that A carried C before (and not the other way around). That is clear from all my papers.

A never carried C because in the undamaged structure there is no A and no C.

So A is slightly stronger than C. Or C is weaker than A. You agree?

Nope. 'Weaker' and 'stronger' are completely wrong concepts.

Don't suggest that you can one-way crush down a stronger structure, part A, with a weaker one, part C.

OK.

And since you didn't reply to my previous post, I take it you concede that you were wrong. That's great. You have still far to go but each tiny step is important.

 

[aggle-rithm]

Sorry, Bailey Plaza = local failures to an unfinished structure, Ronan Point = explosion causing local failures to a structure. In no case a one-way crush down took place.

Are you going to modify your axiom to exclude unfinished structures? It seems that if the axiom were correct, all that would be necessary would be for the lower part to be sturdier than the upper part for collapse to be arrested. And the fact that the unfinished structure is standing is proof of that.

Also, I can pretty much guarantee that there are some unfinished structures that are sturdier than some finished structures...especially very old finished structures that are on the verge of collapse. Does your axiom exclude those as well?