Total Building Collapse from a Single Column Failure

[vtbub]

How much consideration is generally given during the design phase of construction for this very scenario?

Were buildings before 9/11 in downtown areas designed to survive impact from another buildings unplanned destruction?

In hindsight, you can say that building x's biggest flaw led to a collapse and in the future, flaws a, b and c need to be addressed, but how did that work before 2001?

 

[JSanderO]

Regardless of what CAUSED the buildings to collapse. almost all the frames of the buildings broke rather neatly at the connection of one piece of steel to the next - connection failures. The connections were obviously not strong enough to deal with the dynamic forces of a collapse. And of course you need to examine the connections themselves... They were clearly much small cross sectional area than the members they connected... such as 3/4" Ø bolts and fillet welds in some cases... and were what failed and allowed the frames to come apart.

The slabs broke up and were crushed in vertical avalanches on tens if not hundreds of thousands of tons of falling debris... 70,000 cubic yards of concrete in each twin tower and 50,000 cubic yards in 7WTC. When that much concrete is falling in addition to tens of thousands of tons to steel it pretty much destroys everything in its path.

 

[ozeco41]

How much consideration is generally given during the design phase of construction for this very scenario?

Were buildings before 9/11 in downtown areas designed to survive impact from another buildings unplanned destruction?

In hindsight, you can say that building x's biggest flaw led to a collapse and in the future, flaws a, b and c need to be addressed, but how did that work before 2001?

It's not that straightforward.

The dominant factors are:
1) Steel buildings are more vulnerable to fire than concrete;
2) Whether all steel, all concrete or mixed the objectives when designing for fire and/or serious damage are:
a) Priority 1 - get the occupants out;
b) Lower priority - protect or save the building.

The key to "Get the occupants out" is adequate egress provisions and time. So "fire rating" in hours is intended to give the time - including the intention that fire fighting will start within the "window" - plus protection of vulnerable structural elements such as insulating of steel for the desired number of hours. All those aspects overwhelmed for WTC1 - WTC2 on 9/11 - the attack was way outside the design envelope.

Now what destroyed WTC7 on 9/11 was the "impact" of the collapse of WTC1 (and 2) BUT not only the impact of physical damage by falling debris and the resulting fires. Absent all the loss of resources and emergency responder losses the WTC7 fires were almost certainly controllable. BUT not in the full setting of WTC collapses as existed on 9/11. It was the indirect impacts of total loss of water and horrendous loss of emergency responders in that full setting.

The decision based on the total scenario of WTC1-2 collapse - damage to 3,4>> etc including 7 followed the priority as above - no people at risk - forget the building we don't have resources to fight the fire.

Any design intention to learn from interaction of multiple building collapses consequent on malicious human intervention is almost certain to focus on:
Priority one = get the people out. Therefore - multiple redundant egress provisions, multiple redundant fire fighting systems and possibly extended "fire rating" times.

Priority Two (or lower) - the protect the building aspects - will probably consider resistance to "collapse progression" but beyond that it is almost certain to be "wear the risk". Because ultimately protection of the buildings by increasing strength will be of limited effectiveness. "Terrorist" attacks (Any form of malicious human intervention) will be better prevented by security measures than countered after they happen by increased building strength.

 

[tsig]

JDH,
I am not the least bit paranoid. I find the single column leading to global collapse not credible. Then I tried to put forth what seems to match the evidence I am aware of... and I am not a structural nor forensic engineer nor physicist... and I assumed that those who did the investigation MIGHT have either made mistakes or simply got into a CYA thing. I have no idea. In fact I don't care. If the structural design was contributory, which is my speculation... then those associated with those decisions should be held accountable for them.

We've seen many disasters/catastrophes which involved engineering decisions at some point.. 3 Mile Island, Katrina, BP Deep Water Horizon, Bhopal, Fukushima, even Sandy... and no engineer or decision maker of a overwhelmed system was held accountable. Is this a pattern or am I paranoid?

I feel that the twin towers' design contributed to their demise... this was not mentioned and no one was held accountable. All we heard was how strong they were.... not how vulnerable they were. Is this part of the pattern or am I paranoid?

You want to find people guilty of natural disasters?

 

[JSanderO]

You want to find people guilty of natural disasters?

You are dense eh?

The natural disasters put a strain/stress on infrastructure and engineered buildings and systems which were supposedly designed to withstand all reasonable stress.

You may recall the debacle with the CitiCorp building which was erected and then one day the engineer decided to think about the impact of a 100yr storm hitting his building and did some calcs and decided the wind reinforcing / wind shear design was inadequate and they did a retro fit to the occupied building.

Engineers make mistakes. That one was caught in time.

Engineers at Chernobyl, Army Corp of Engineers for NOLA's levees, those who designed the BP Deep Water Horizon, 3 Mile Island, and of course Fukushima seemed to have dropped the ball.

No one is guilty for a specific natural disaster but we may be collectively causing the atmosphere and oceans to heat up and this BECOMES natural disasters.

Catastrophes are usually felt when engineered systems don't stand up to some sort of assault or stress. Plain and simple

 

[vtbub]

It's not that straightforward.

The dominant factors are:
1) Steel buildings are more vulnerable to fire than concrete;
2) Whether all steel, all concrete or mixed the objectives when designing for fire and/or serious damage are:
a) Priority 1 - get the occupants out;
b) Lower priority - protect or save the building.

The key to "Get the occupants out" is adequate egress provisions and time. So "fire rating" in hours is intended to give the time - including the intention that fire fighting will start within the "window" - plus protection of vulnerable structural elements such as insulating of steel for the desired number of hours. All those aspects overwhelmed for WTC1 - WTC2 on 9/11 - the attack was way outside the design envelope.

Now what destroyed WTC7 on 9/11 was the "impact" of the collapse of WTC1 (and 2) BUT not only the impact of physical damage by falling debris and the resulting fires. Absent all the loss of resources and emergency responder losses the WTC7 fires were almost certainly controllable. BUT not in the full setting of WTC collapses as existed on 9/11. It was the indirect impacts of total loss of water and horrendous loss of emergency responders in that full setting.

The decision based on the total scenario of WTC1-2 collapse - damage to 3,4>> etc including 7 followed the priority as above - no people at risk - forget the building we don't have resources to fight the fire.

Any design intention to learn from interaction of multiple building collapses consequent on malicious human intervention is almost certain to focus on:
Priority one = get the people out. Therefore - multiple redundant egress provisions, multiple redundant fire fighting systems and possibly extended "fire rating" times.

Priority Two (or lower) - the protect the building aspects - will probably consider resistance to "collapse progression" but beyond that it is almost certain to be "wear the risk". Because ultimately protection of the buildings by increasing strength will be of limited effectiveness. "Terrorist" attacks (Any form of malicious human intervention) will be better prevented by security measures than countered after they happen by increased building strength.

So, you are saying in large part that the buildings did what they were designed to do.

 

[ozeco41]

So, you are saying in large part that the buildings did what they were designed to do.

I don't think I actually said that but it is a reasonable claim.

However I would take care with the "in large part" if active truthers or trolls were in the discussion with their tendency to distort or draw false inferences.

We know that the building remained standing under an impact that was outside the original design envelope. BUT people egress arrangements and fire fighting arrangements were compromised - essentially all persons below the impact zone escaped and all at or above that level perished.

What we do not know is whether, had the impact been within or on the design envelope, the egress and fire measures would have survived AND allowed all those alive above the impact to escape successfully. I suggest that is the true test of "..what they were designed to do..." and we cannot know that. Plus the big variable in that is the uncertainty as to whether the buildings were actually designed for low speed low fuel impact of a Boeing 707 or whether that claim was a retrospective or hindsight determination.

 

[DGM]

So, you are saying in large part that the buildings did what they were designed to do.

Talk about your leading questions.

 

[ozeco41]

Talk about your leading questions.

...and the possibility that I wouldn't see it???

 

[DGM]

...and the possibility that I wouldn't see it???

I get that when I say WTC 7 performed better than design. Sometimes they don't read that I also said "considering the circumstances".

I'm sure it's always an honest mistake on their part.

 

[ozeco41]

I get that when I say WTC 7 performed better than design. Sometimes they don't read that I also said "considering the circumstances".

I'm sure it's always an honest mistake on their part.

I get the same problem with people who routinely use inference or innuendo in their own claims and read inferences into anything they read. I tend to write with legal precision - for reasons which may not be as obvious as they seem.^#

So over recent days I have been repeating the claim that "Col 79 must have failed because it was under the EPH and the EPH fell". So a single stand alone statement (assertion actually) of fact. And - to be legally pedantic - an assertion of true fact.

All the criticisms "Don't you realise ozeco that other columns and other bits of structure failed also????"

Of course I b**** (Aussie adjective) realise it. BUT my assertion as true fact was "Col 79 must have failed". That was the fact I needed in my argument. I wasn't discussing anything more remote like Columns 80, 81 or even more remote like sinking the Titanic or how many moons around Jupiter or the distance to Alpha Centauri.

Merely one of the minor barriers to objective reasoned discussion in this little sand box of fun.


# I was a pedantic pr....err....person long BEFORE I studied law.

 

[DGM]

Merely one of the minor barriers to objective reasoned discussion in this little sand box of fun.

The problem now is there is precious little sand left and that there is the cat has used as a litter box.

 

[vtbub]

I don't think I actually said that but it is a reasonable claim.

However I would take care with the "in large part" if active truthers or trolls were in the discussion with their tendency to distort or draw false inferences.

We know that the building remained standing under an impact that was outside the original design envelope. BUT people egress arrangements and fire fighting arrangements were compromised - essentially all persons below the impact zone escaped and all at or above that level perished.

What we do not know is whether, had the impact been within or on the design envelope, the egress and fire measures would have survived AND allowed all those alive above the impact to escape successfully. I suggest that is the true test of "..what they were designed to do..." and we cannot know that. Plus the big variable in that is the uncertainty as to whether the buildings were actually designed for low speed low fuel impact of a Boeing 707 or whether that claim was a retrospective or hindsight determination.

Point taken on "large part."

As much as we would all like to plan and fix accordingly based on models, you will never be able to fully anticipate the chaos that comes with an event like this.

The best thing that can come from these events is to learn from them. Ensuring that egress procedures are updated and beefing up the codes to extend the fire rating of materials in exit areas is the best way to deal with the next maniac that wants to blow up a building outside of preventing the act itself.

 

[DGM]

Point taken on "large part."

As much as we would all like to plan and fix accordingly based on models, you will never be able to fully anticipate the chaos that comes with an event like this.

The best thing that can come from these events is to learn from them. Ensuring that egress procedures are updated and beefing up the codes to extend the fire rating of materials in exit areas is the best way to deal with the next maniac that wants to blow up a building outside of preventing the act itself.

Fortunately, that is what has been done.

I have to wonder though, why the question in the first place? You must admit, it did appear to be very leading.

 

[ozeco41]

The problem now is there is precious little sand left and that there is the cat has used as a litter box.

Yes. The "party" is over. All the "Genuine Truthers" seem to have learned the truth and left the scene. Most of the technical discussion leaders have also departed - some of them still with "interesting" Bazantian or parody of Bazant style misunderstandings. My other two "secondary" or "backup" forums likewise dead.

I signed up on DebatePolitics but there is near zero interest in serious 9/11 stuff over there - and three of the four resident trolls are 6-12 month newbies who still have the energy for playing silly games. And I don't feed trolls so....

...find a new hobby time.

 

[ozeco41]

Point taken on "large part."

I thought it worth the effort to avoid misunderstanding.

As much as we would all like to plan and fix accordingly based on models, you will never be able to fully anticipate the chaos that comes with an event like this.

True.

The best thing that can come from these events is to learn from them. Ensuring that egress procedures are updated and beefing up the codes to extend the fire rating of materials in exit areas is the best way to deal with the next maniac that wants to blow up a building outside of preventing the act itself.

We are singing the same tune.

 

[vtbub]

Fortunately, that is what has been done.

I have to wonder though, why the question in the first place? You must admit, it did appear to be very leading.

Wasn't trying to ask a leading question or play gotcha, it was more of me making sure I understood what Ozeco was saying. I mostly lurk on these threads and sometimes get lost on some of the more technical explanations. (Not that he was being too technical in this case.)

My fault on trying to be too simplistic. After reading some of the head-scratching responses to those who take the time to give out detailed answers, I can see where my response could lead to others thinking I was JAQ'ing.

 

[ozeco41]

I can see where my response could lead to others thinking I was JAQ'ing.

I was a bit unsure but no problem.

 

[ozeco41]

How About We Discuss the OP?

There should still be a bit of life in this topic - if we can get back to the OP

Here goes. First let's see what JSanderO's main question was:

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?

So that is the main question - "I wonder... how universal this actually is?"

Well I doubt that it is universal at all for two sets of reasons:

The First "Set of Reasons"
We cannot seriously think that all buildings with a Column 79 are likely to fail - with Column 79 leading the failure. Even less likely in the pursuit of "universality" is any such building likely to have a pair of 110 storey towers standing nearby, struck by aircraft and collapsing ...etc So I'll give that one a miss - yes - it was "tongue in cheek".

Now before we take on the second set we need to get rid of some loose definitions otherwise we will end up chasing strawmen:

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?

OK those three hilited points are where we see ambiguity - whether intended or not the words used can mislead.

The collapse was of a building seriously compromised by fire to the extent that it failed^#. It was a form of cascade failure and no single structural member "caused" the failure. Column 79 did not cause the failure nor was it the first structural member to fail nor was it the only item to fail.

The Second "Set of Reasons" - stated as answers to JSanderO's OP questions:

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

No - it was a major component of the collapse mechanism but the manner of its failing required other component failures. Changing the floor doesn't change the reality that the Col79 failure was only one component of the collapse mechanism

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

Not likely. Risks becoming a strawman - the actual WTC7 collapse was not "caused" by Col 79 and Col 79 was not the initiator of its own failure. It didn't "lead" as in at head of chain - it followed some and came before others.

Could any single column failing on any other floor NOT lead to global collapse?

Near certain it wouldn't as a stand alone event.

(I don't suspect the failure of a column at the roof level would.)

Moot.

If so why or why not?

Not a valid generic claim....would always be building structure specific.

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?

All must be building specific. All are false stated as they are as generic claims. Remember global claims are:
1) Almost always false; AND
2) Only need one exception to falsify them.

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?

This statement is not valid as a premise..therefore this:

Should NIST have discussed this or not?

...is moot.




# Any pro CD folk can include CD - It wont change what I need to say - I will still challenge you to prove CD so whether you do it before or after in the discussion doesn't matter.

 

[JSanderO]

How About We Discuss the OP?

There should still be a bit of life in this topic - if we can get back to the OP

Here goes. First let's see what JSanderO's main question was:
So that is the main question - "I wonder... how universal this actually is?"

Well I doubt that it is universal at all for two sets of reasons:

The First "Set of Reasons"
We cannot seriously think that all buildings with a Column 79 are likely to fail - with Column 79 leading the failure. Even less likely in the pursuit of "universality" is any such building likely to have a pair of 110 storey towers standing nearby, struck by aircraft and collapsing ...etc So I'll give that one a miss - yes - it was "tongue in cheek".

Now before we take on the second set we need to get rid of some loose definitions otherwise we will end up chasing strawmen:
OK those three hilited points are where we see ambiguity - whether intended or not the words used can mislead.

The collapse was of a building seriously compromised by fire to the extent that it failed^#. It was a form of cascade failure and no single structural member "caused" the failure. Column 79 did not cause the failure nor was it the first structural member to fail nor was it the only item to fail.

The Second "Set of Reasons" - stated as answers to JSanderO's OP questions:
No - it was a major component of the collapse mechanism but the manner of its failing required other component failures. Changing the floor doesn't change the reality that the Col79 failure was only one component of the collapse mechanismNot likely. Risks becoming a strawman - the actual WTC7 collapse was not "caused" by Col 79 and Col 79 was not the initiator of its own failure. It didn't "lead" as in at head of chain - it followed some and came before others.Near certain it wouldn't as a stand alone event.Moot.Not a valid generic claim....would always be building structure specific.
All must be building specific. All are false stated as they are as generic claims. Remember global claims are:
1) Almost always false; AND
2) Only need one exception to falsify them.

This statement is not valid as a premise..therefore this:
...is moot.

# Any pro CD folk can include CD - It wont change what I need to say - I will still challenge you to prove CD so whether you do it before or after in the discussion doesn't matter.

Cut the BS... stop parsing words here, But thanks for returning to the OP.

Obviously the column didn't cause the collapse. Its "failure" was some which enabled that which was supported by it to collapse.... and apparently NIST thought that other columns around 79 failed lickity split and that turned into what they call a global collapse.

This is sort of beating around the proverbial *initiation bush*... that is to see a bunch of things when awry at / under col 79 and column 79 could not do its *normal job* and *caved* ... according the NIST... taking the entire building with it.

The OP is pretty clear at trying to ask... can a single column failure cause a high rise to collapse? Not the column... but its failure... not doing what it was designed to do.

And by extension I ask... legitimately...

Does the location in elevation of the failed column have anything to do with global collapse?

Could a single column failure in a *typical* grid of columns framed high rise suffer global collapse from a single column failure? Yea it's a generic question.

But of course to learn lessons to be applied to other and generic buildings you have to identify the key weaknesses or failures modes.

In the case of 7WTC the mechanical damage from WTC was on the SW side and did not initiate even local failures above it. It may have caused fires, but this is actually not obvious either. The impaled steel on the WFC did not cause fires, nor at Bankers Trust.

I infer that the proximate cause of the global collapse was not the mechanical damage from 1WTC. But sure it made less of the frame to collapse 7 hrs later. The proximate cause appears to be the fires and what they did to the steel, the connections and so forth over a 7 hr period. NIST seems to think the fire broke the camel's back at column 79 floor 13. Again... was this location *special*. It has been pointed out that col 79 carried the largest proportional load of any column in the building. That needs to be verified. Surely the load of column 79 at grade was more than it was at floor 13.

So inquiring minds want to know. Can a single column's failure reliably lead to a global collapse in a typical steel frame high rise? If not, why not? If so, why so.

Don't beat around the bush. Answer the questions if you can. And skip the rubbish about generalities are always false.