Split Thread Was global collapse of WTC inevitable?

[ergo]

Since the thread's going to **** anyway, I'll take issue with this:

This is more or less the common description of events:
1) Airplane strikes tower, does some damage, starts some fires.
2) Fires are not fought allowing more damage to accumulate.
3) The accumulating damage causes load shedding and load redistribution.
4) The load redistribution events build up into a cascading sequence which weakens the impact and damage zone.
5) The damage reaches the point where there is insufficient remaining strength to support the "top block".
6) The impact zone ceases to support the Top Block.
7) The Top Block starts to fall and from that instant "global collapse was inevitable"

So that is my description and, as far as I am aware, it aligns with NIST on the key points which matter.

Look at your last key point. The entire rest of the collapse, which is hardly "inevitable", you simply handwave into one sweeping statement, exactly the way NIST did. And you yourself have elsewhere agreed that Bazant's description of "global collapse ensues" does not really match the reality. So you sweep the entire crux of the argument under the rug with one inane statement: "The Top Block starts to fall, and from that, instant global collapse was inevitable". You don't bother mentioning that the top block disintegrates. You don't bother mentioning how collapse could ensue when there is no upper block driving it, and certainly not why this would be "inevitable". Yet you fault Major Tom for wanting to draw specific attention to the detailed sequence of events that you want to blindly stuff into a single, inane statement. This is your analysis?

Split from: WTC 1 Features List, Initiation Model.

Posted By: Gaspode

 

[ergo]

The building never COULD have toppled.

Why not?

 

[ozeco41]

Since the thread's going to **** anyway, I'll take issue with this:




Look at your last key point. The entire rest of the collapse, which is hardly "inevitable", you simply handwave into one sweeping statement, exactly the way NIST did. And you yourself have elsewhere agreed that Bazant's description of "global collapse ensues" does not really match the reality. So you sweep the entire crux of the argument under the rug with one inane statement: "The Top Block starts to fall, and from that, instant global collapse was inevitable". You don't bother mentioning that the top block disintegrates. You don't bother mentioning how collapse could ensue when there is no upper block driving it, and certainly not why this would be "inevitable". Yet you fault Major Tom for wanting to draw specific attention to the detailed sequence of events that you want to blindly stuff into a single, inane statement. This is your analysis?

Come off it ergo - what a disconnected rage and I won't address all the false claims. The core issue is that I listed a sequence of stages. Like the Chapters Headings in the contents page of a book. I have all the content of those chapters if and when needed. So no it is not an analysis. And who said I faulted Major_Tom? All I did was post the stages which should include and encompass Major_Tom's list.

And if you check with Major_Tom's postings you may find that he agrees with the global collapse. He has posted a lot of detail under the acronym "ROOSD" which fits very well with my explanations published at about the same time.

So no need to defend Major_Tom until and indeed if I ever disagree with him.

 

[ergo]

If I understand ROOSD correctly, and I may not, it would not be compatible with a core-led descent. In ROOSD, the supposed floor overload has the floors collapsing between the perimeter and core (at the ridiculous speed of 6 per second). In a core-led collapse, you have the core sinking first, so floor overload is irrelevant. You would still need active destruction of the core all the way down. This would not be gravity driven.

Of course, Major Tom and femr may have different ideas.

 

[alienentity]

Look at your last key point. The entire rest of the collapse, which is hardly "inevitable", you simply handwave into one sweeping statement, exactly the way NIST did.

That's incorrect. It's an observation of fact based on complex physics. It's definitely not handwaving to make a factual statement.

The details are available to those who are interested.

If I declare that, as the sun rises, so it must also set; am I handwaving anything? Of course not. Once the upper block was moving, collapse was inevitable.

 

[ergo]

Absolutely false. You would have to suspend Newton's Third Law, whether it's an intact upper block, which it isn't, or a mass of rubble, which it also largely isn't.

 

[ergo]

You would still need active destruction of the core all the way down. This would not be gravity driven.

Actually, it might be more accurate to say all the way up, as it may indeed have begun in the basement, with other events occurring at various levels up from there.

 

[ozeco41]

If I understand ROOSD correctly, and I may not, it would not be compatible with a core-led descent. In ROOSD, the supposed floor overload has the floors collapsing between the perimeter and core (at the ridiculous speed of 6 per second). In a core-led collapse, you have the core sinking first, so floor overload is irrelevant. You would still need active destruction of the core all the way down. This would not be gravity driven.

Of course, Major Tom and femr may have different ideas.

The discussion topic which Major_Tom is leading is about 'collapse initiation' using his words and broadly equivalent to 'initial collapse' using my terminology. So steps 4,5 and 6 of my original list which you misunderstood.

ROOSD is about collapse progression in MT words or 'global collapse' in the terminology I use. That would be step 8 of my list if I had included it.

As far as I understand MT he is not talking about core collapse leading throughout the global collapse stage. It is not an impossible concept but remember that a many storey spire of core columns was left standing.

Your comment about "at the ridiculous speed of 6 per second" is unclear. That is about the rate of collapse which happened so I take it you are not claiming that it didn't happen. Some would argue that demolition was needed to achieve that rate. That is clearly not so with even a casual engineering glance at the available loads/energies and the mechanism which actually happened. ROOSD does not require demolition. Nor does my explanation which is similar to ROOSD and could be seen as a broader brush approach to ROOSD.

Then your comment "You would still need active destruction of the core all the way down. This would not be gravity driven" is an assertion (or two if you parse the sentences that way) which can readily be shown to be false.

 

[ozeco41]

Actually, it might be more accurate to say all the way up, as it may indeed have begun in the basement, with other events occurring at various levels up from there.

Good to see you starting to form your own hypothesis there ergo.

 

[triforcharity]

Absolutely false. You would have to suspend Newton's Third Law, whether it's an intact upper block, which it isn't, or a mass of rubble, which it also largely isn't.

Really? So why do engineers write papers on how to arrest a collapse in a tall building?

Like this one.

Use of high-efficiency energy absorbing device to arrest progressive collapse of tall building
Zhou, Q., Yu, T.X. 2004 Journal of Engineering Mechanics 130 (10), pp. 1177-1187

And this one on what caused the collapse?

Progressive collapse of the World Trade Center: Simple analysis
Seffen, K.A. 2008 Journal of Engineering Mechanics 134 (2), pp. 125-132


Oh, BTW, both of those papers appear in a respectable, properly peer-reviewed journal.

 

[femr2]

Since the thread's going to **** anyway, I'll take issue with...

This thread is focussed upon initiation.

I have been through the basics of ROOSD with you before, to seemingly no avail.

That you think the thread is going to **** is no excuse for you to **** all over it with off topic banter. I am sure many folk will gladly spend countless pages telling you that you are wrong time and time again, to no avail.

I suggest you create a new thread.

I suggest the recent discussion is split out by mods.

 

[femr2]

Ergo,

Our previous discussion on the topic began around the page 21 mark on thread "Applicability of Bazant's model to the real world".

I suggest a re-read.

 

[ergo]

ROOSD is about collapse progression in MT words or 'global collapse' in the terminology I use. That would be step 8 of my list if I had included it.

As far as I understand MT he is not talking about core collapse leading throughout the global collapse stage. It is not an impossible concept but remember that a many storey spire of core columns was left standing.

My apologies. If this is the case, then I tend to agree with the bee dunkers, as in, who cares?

Your comment about "at the ridiculous speed of 6 per second" is unclear. That is about the rate of collapse which happened so I take it you are not claiming that it didn't happen. Some would argue that demolition was needed to achieve that rate. That is clearly not so with even a casual engineering glance at the available loads/energies and the mechanism which actually happened. ROOSD does not require demolition. Nor does my explanation which is similar to ROOSD and could be seen as a broader brush approach to ROOSD.

Any top driven collapse is going to arrest anyway. For a "natural" top-driven collapse to propagate at the rate of 6 floors per second is completely unrealistic and therefore ridiculous. It's shocking that femr and Major Tom support this utterly ridiculous notion.

Then your comment "You would still need active destruction of the core all the way down. This would not be gravity driven" is an assertion (or two if you parse the sentences that way) which can readily be shown to be false.

By whom?

 

[triforcharity]

Any top driven collapse is going to arrest anyway. For a "natural" top-driven collapse to propagate at the rate of 6 floors per second is completely unrealistic and therefore ridiculous. It's shocking that femr and Major Tom support this utterly ridiculous notion.

Really? Then why do engineers write lengthy papers like this??

Use of high-efficiency energy absorbing device to arrest progressive collapse of tall building
Zhou, Q., Yu, T.X. 2004 Journal of Engineering Mechanics 130 (10), pp. 1177-1187


And have them published in respectable, peer-reviewed journals, if it couldn't happen?

Arguments from personal beliefs rock!!

 

[ergo]

Really? Then why do engineers write lengthy papers like this??

Use of high-efficiency energy absorbing device to arrest progressive collapse of tall building
Zhou, Q., Yu, T.X. 2004 Journal of Engineering Mechanics 130 (10), pp. 1177-1187

Yes, Zhou? Bazant's lackey? What does he say here? What "energy absorbing device" does he talk about? Where are all these other papers about how Newton's Third Law fails us when planes crash into buildings? Or even when planes don't crash into buildings?

 

[willhaven]

Any top driven collapse is going to arrest anyway.

What about these?

 

[GlennB]

Any top driven collapse is going to arrest anyway.

You've been reading Heiwa's website haven't you?

The only known cure is to find a Man in Black and ask him to wave a light-pen in front of you.

 

[ergo]

You've been reading Heiwa's website haven't you?

With all due respect to Heiwa, you don't need Heiwa to understand that a top-driven collapse (of a smaller something through its larger counterpart) won't work. However, I do credit him for bringing that point to public and popular understanding. It is not some kooky "Heiwa" theory. It is a description of Newton's Third Law in a gravitational collapse. It's elementary. It should be idiot-proof, but apparently it's not.

 

[Grizzly Bear]

Yes, Zhou? Bazant's lackey? What does he say here? What "energy absorbing device" does he talk about? Where are all these other papers about how Newton's Third Law fails us when planes crash into buildings? Or even when planes don't crash into buildings?

I suppose according to the normal logic of newton's third law - according to you - Ronan Point also violated it.

Speaking of which, there's an article you should read from the Steel Designer's manual:

Accidental loading
A series of incidents in the 1960s culminating in the partial collapse of a systembuilt tower block at Ronan Point in 1968 led to a fundamental reappraisal of the approach to structural stability in building.

Traditional load-bearing masonry buildings have many in-built elements providing inherent stability which are lacking in modern steel-framed buildings. Modern structures can be refined to a degree where they can resist the horizontal and vertical design loadings with the required factor of safety but may lack the ability to cope with the unexpected. It is this concern with the safety of the occupants and the need to limit the extent of any damage in the event of unforeseen or accidental loadings that has led to the concept of robustness in building design. Any element in the structure that supports a major part of the building either must be designed for blast loading or must be capable of being supported by an alternative load path. In addition, suitable ties should be incorporated in the horizontal direction in the floors and in the vertical direction through the columns. The designer should be aware of the consequences of the sudden removal of key elements of the structure and ensure that such an event does not lead to the progressive collapse of the building or a substantial part of it. In practice, most modern steel structures can be shown to be adequate without any modification.

Somehow, I don't think the ability to withstand an airplane impact meant it was invulnerable to have a 30-story top section falling on it.

 

[Carlos]

ergo

The mass of 15 intact floors and 15 destroyed floors are the same.

Mass doesn't disappear.