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Total Building Collapse from a Single Column Failure

RedIbis said:
Without including the stiffener in its model, how do we know it would not have prevented the walkoff?
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I'll stick with two points I made in my previous post:
1) We cannot know with any certainty either way;
2) Because we cannot be sure of the local physical context.

However - sort out the double negative construct ("would not have prevented") - the claim in the paper is:
With the inclusion of these critical features, NIST’s probable collapse sequence must be ruled out unambiguously. It is the unanimous opinion of the structural engineers who have carefully studied this matter that an independent engineering enquiry would swiftly reach the same conclusion...
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The first of those claims is false. The second claim is wrong. If it is true that their hand picked small group of engineers was unanimous - they were unanimously wrong.

So the "burden of proof" lies with them as claimants.

AND they have not made out their claim. It is unproven - the identical status as the same claim made by T Szamboti on this forum and as I described it in my previous post.
 
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david.watts said:
Good answer. After all, there might be one Tom, Dick, and/or Mary that might see that their entire model is (de)bunk.
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"Engineers" that claim they can't check the NIST because they don't have the data, are not qualified to know if it's "bunk".

Are you claiming the data needed to create the model was not in the report?
 
DGM said:
The appearance of a conflict can be used to dismiss the whole argument.
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So... some truthers argue therm*te, some argue explosives and some argue DEW. Therefore none of the arguments are valid and there is no more conspiracy theory!
 
JSanderO said:
OP:

Total Building Collapse from a Single Column Failure
NIST makes the case that the failure of column 79 on floor 13 apparently caused by a girder walking off its beam seat at column 79 led pretty quickly to the collapse of the entire building leaving nothing standing at all.

I wonder... how universal this actually is?

Would column 79 failing at floor 29 have caused the global collapse?

Would any other single column failing on any floor lead to global collapse?

Could any single column failing on any other floor NOT lead to global collapse? (I don't suspect the failure of a column at the roof level would.) If so why or why not?

Is this single column failure applicable to any multi story high rise? Would it have to be steel framed? Would it have to be a minimum building height? Would there have to be a minimum number of floors above the failed column?

If the single column failure global collapse outcome is not more or less universally applicable what was it about 7 WTC's design and column failure at floor 13 that allowed for a single column failure to lead to global collapse?

Should NIST have discussed this or not?
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Seems to me to all be good points and questions.

Has anyone given you any responses?
 
david.watts said:
Seems to me to all be good points and questions.

Has anyone given you any responses?
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Why dont you read the thread David? Lots of answers or partial answers.


They are fair questions as first draft. They need to be more specific - especially the premises in the leading paragraphs.

My answers:
1) That is not the NIST claim;
2) It is not likely to be universal BUT the premised scenario is not properly defined so no definitive answer is possible;
3) No - unless we specify the full scenario. You do not get "single column failure" in isolation bereft of a structural context involving other members of the structure.
4) Ditto.
5) Must be yes. The question calls for a global requirement - "Any single column failure would result in total collapse". Clearly not so...then apply the negative to get the logic polarity right way round.
6) No followed by three x "Situation specific"
7) Falsely premised question. Based on poor word choice then misinterpretation. Col 79 did not fail solo to cause the collapse. Col 79 was caused to fail as part of a major structural trauma. Clear those issues THEN the part about "what was it about 7 WTC's design" may be relevant.
8) Why should NIST have discussed it? You need to comprehend where JSanderO is coming from. It has been subject of lengthy discussions. My conclusion there is no basis to support that NIST should have discussed "it".
 
IMHO...this critical connection ripped itself apart. The bottom two 7/8" diameter bolts ripped thru a large piece of the bottom girder flange and probably a large part of the web too. This local failure probably released 40-80 tons of force, built up by the temperature gradient. At this point there was no remaining girder support left to bear on the column support plate.

I wish NIST had done a more detailed non-linear finite element analysis of this critical connection and proposed failure.
 
MileHighMadness said:
IMHO...this critical connection ripped itself apart. The bottom two 7/8" diameter bolts ripped thru a large piece of the bottom girder flange and probably a large part of the web too. This local failure probably released 40-80 tons of force, built up by the temperature gradient. At this point there was no remaining girder support left to bear on the column support plate.
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That is a full grade closer to coming to grips with likely reality than all the arguments which presume pristine conditions.

...but I'm staying away from the detail - too much "forests v trees" or "alligators v swamps" thinking.

IMNSHO :blush:

MileHighMadness said:
I wish NIST had done a more detailed non-linear finite element analysis of this critical connection and proposed failure.
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Nah. Too much misuse of FEA by both sides on this forum. ;) (Yes - I'm showing the frustrations of a manager of engineers who had perennial problems with getting them out of the details to remember "drain the swamp")

NIST doing it would only feed more fuel into the "NIST wuz rong" arguments. The main need is to:
Understand why it collapsed NOT "prove NIST right/wrong".
 
So... can a single column failure lead to a collapse of an entire 47 story building?

Please describe how that happens.
 
JSanderO said:
So... can a single column failure lead to a collapse of an entire 47 story building?

Please describe how that happens.
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Column fails --> Load redistributes eccentrically --> chain reaction failure of floor slabs --> chain reaction failure of adjacent columns --> continues until the structural system goes critical. That's roughly how it happens. WTC7 was known to have had significant floor spans due to its design, which likely didn't help.

If that doesn't answer your question you're going to have be more specific. It's bad practice to assume that such a collapse scenario is improbable. The relevant issue (since it already happened) is the sequence of events and understanding what vulnerabilities in the design made it more susceptible.

PS: The "single column failure" is little more than a best guess based on exterior analysis of the collapse, and simulation based on knowing the building's construction. Nevertheless the general point stands; It's basic structural systems understanding that when something fails, the loads have to be redistributed to adjacent structure, and that remaining structure must have the capacity to prevent further spread in order that the building maintains its integrity. If the adjacent structure is vulnerable because of its design and can't arrest further failure, then under the right set of circumstances the building can have a million columns in its system and still failure because of a small initiating collapse.
 
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JSanderO said:
So... can a single column failure lead to a collapse of an entire 47 story building?

Please describe how that happens.
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Well? If you play the game of JENGA, and you pull out just one wrong wooden piece...down she comes! :crazy:
 
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JSanderO said:
So... can a single column failure lead to a collapse of an entire 47 story building?

Please describe how that happens.
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Sander that question is too vaguely defined to be answerable as you have been told several times.

The ambiguity has two main alternatives:

1) If you mean that something causes a column to fail without any context of other trauma THEN it is both highly unlikely AND situation specific.

2) If you mean failure of a single column in the full context of other trauma then you need to define both the context and what you mean by "lead"

For example there is zero doubt that Column 79 failed in the WTC7 collapse. It is near certain that Col 79 failed in Euler buckling due to removal of bracing over several storeys. In that setting Col 79 could be described as a key feature of the collapse. Using "leading" is misleading - it neither "leads" in the sense of "happening before" - "leading the way" NOR "leads" in the sense of being the single causal event.
 
:blush: Ooops - I wasn't explicit enough in the previous.

alternative "1)" should read something like this:
1) If you mean that something causes a column to fail without any context of other trauma AND that the failure of ONLY that single column causes global collapse THEN it is both highly unlikely AND situation specific.
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Redundancy would almost certainly redistribute loads succesfully from a single column "failure" in most buildings.

The more important question being "How do you get single column failure in a building with no other structural trauma?" with two obvious possibilities - removal by deliberate human intervention OR removal as consequence of accident - eg Motor Vehicle Impact. It is scarcely credible that single column removal could ever cause collapse in such a scenario BUT - as I have said several times through this thread - it will be situation specific. It cannot be a global truth (AKA that collapse is inevitable) for reasons which should be obvious.

It should also be obvious that neither of those two interventions - esp the MVA - are likely to remove columns over multiple storeys - thereby significantly limiting the possibility of more global collapse being caused by the single failure.
 
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ozeco41 said:
Sander that question is too vaguely defined to be answerable as you have been told several times.

The ambiguity has two main alternatives:

1) If you mean that something causes a column to fail without any context of other trauma THEN it is both highly unlikely AND situation specific.

2) If you mean failure of a single column in the full context of other trauma then you need to define both the context and what you mean by "lead"

For example there is zero doubt that Column 79 failed in the WTC7 collapse. It is near certain that Col 79 failed in Euler buckling due to removal of bracing over several storeys. In that setting Col 79 could be described as a key feature of the collapse. Using "leading" is misleading - it neither "leads" in the sense of "happening before" - "leading the way" NOR "leads" in the sense of being the single causal event.
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Ozzie,

You accepting the cause of the failure being floor collapse and then lengthening of the unbraced length.

That wasn't the question. I did not suggest a column of multiple stories which had lost its lateral bracing. I asked if a single column failure (one story) could lead to a total building collapse?
 
JSanderO said:
Ozzie,

You accepting the cause of the failure being floor collapse and then lengthening of the unbraced length.

That wasn't the question. I did not suggest a column of multiple stories which had lost its lateral bracing. I asked if a single column failure (one story) could lead to a total building collapse?
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That is not true Sander - you didn't specify one story - this was the question you asked:
So... can a single column failure lead to a collapse of an entire 47 story building?
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I identified lack of definition in three areas:
A) Did you mean one storey or more?
B) Was the failure part of a more general trauma as was WTC7 OR do you mean the specific situation of ONLY the column failure; AND
C) I identified the ambiguity of the word "lead"... which I take to mean "initiating or causing" global failure. Col 79 did not do that for the WTC7 collapse - a foggy use of terminology I have identified on previous occasions.

My answer to the question "if a single column failure (one story) could lead to a total building collapse?" still is blocked by two of the three ambiguities. Sure I could give the logically correct answer "Yes" but given where you are coming from if I did that it would be grossly misleading to other readers. (My equally legitimate answer would be "almost certainly no but I cannot prove no". That is probably just as confusing for other members.)

So let me expand my answer to make it explicitly clear:
1) For an unspecified building AND with no other surrounding trauma the failure of ONE column in ONE storey is extremely unlikely to initiate or cause global failure.

BUT
2) It is situation specific. I have no way of knowing that there is not one building somewhere in the world which has a built in vulnerability. So I cannot justify the global negative answer "No!"

Then again you limit it to 47 Storey buildings which does reduce the target group somewhat. :boggled:
 
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