Was Column 79 the Achilles' Heel of WTC7?

[Henkka]

I just watched it and took some notes. Wow! I feel both enlightened and completely vindicated.

"In the past, no one would have ever thought that … the failure of a single connection could bring down a 47-story building. Today, we actually do believe that that might be possible. A very important technical lesson that we've learned through the World Trade Center." (45:00)

I've taken some notes, and I'll watch it again. I think this is worth a thread of its own and I'll leave my thoughts for then. But thank you, @benthamitemetric. Thank you very much. Great find!

That kind of ties into a question I wondered about earlier in the thread... That if before 9/11, you gave someone like CDI the task of demolishing WTC 7, could they have figured out they only needed to blow up column 79?

Although even if they could have figured it out, they probably wouldn't have done it like that. In controlled demolitions, you want to ensure the building comes down, without leaving it to chance. So you would much rather go for overkill rather than trying to figure out the minimum amount of charges required.

 

[Mendel]

Why is it very important to debunk the idea that firefighters did not expect fire to be able to cause the total progressive collapse of a skyscraper?

It's not important.
But it's bunk, and this is a debunking forum, hence people want to debunk it.

But according to NIST, the debris damage did not really play a role in the collapse.

So what do you think caused the large fires on six floors, if not the falling (flaming?) debris from the WTC tower?

My view remains that if they had believed that putting out the fires would have significantly reduced the probability of total progressive collapse (i.e., reduced the odds of the worst case scenario for the building) then they would have devoted more of their energies (with "greater urgency") to the task of getting water on them. I don't think they believed this, and, on my reading of the NIST report, they had no way of knowing this, so they let the fires burn, and left the building to its fate.

They had no choice in the matter, because there was no way to bring sufficient water to bear on the fires to fight them.

You argue they did not fight the fires because they believed it was pointless.
I argue they did not fight the fires because they couldn't.

Now look at the source (I excerpted the quote):

here's a press release that FDNY Chief Daniel Nigro issued on September 23, 2007 ahead of the release of the NIST report:

The reasons are as follows:

1 - Although prior to that day high-rise structures had never collapsed, The collapse of WTC 1 & 2 showed that certain high-rise structures subjected to damage from impact and from fire will collapse.
2. The collapse of WTC 1 damaged portions of the lower floors of WTC 7.
3. WTC 7, we knew, was built on a small number of large columns providing an open Atrium on the lower levels.
4. numerous fires on many floors of WTC 7 burned without sufficient water supply to attack them.

Point 1 implies the chief considered that the fires had an impact (as they commonly do with other building fires), and that contradicts your view.
Point 4 supports my view.

I'm out of this thread now.

Hmm.

Yeah, I've seen that FAQ answer before. They don't go very deeply into specifics, though. If WTC 7 was built in a way that made it remarkably less capable of surviving fires than a much older skyscraper, I feel like someone should have been held liable for that.

The building codes specify a minimum standard that different buildings exceed in different ways. As long as the minimum standard is met (which is primarily designed to allow orderly evacuation of the building), there is no legal concern, and the differences between the buildings are not legally meaningful.

One of the biggest emergency incidents seen in a dense urban setting. Two of the world's tallest buildings collapsed due to fire. A third large building was already evacuated and fully involved with fire.

Also, numerous fire trucks were burned out, fire fighters dead or injured, and challenges assessing and directing existing resources.

Although even if they could have figured it out, they probably wouldn't have done it like that. In controlled demolitions, you want to ensure the building comes down, without leaving it to chance. So you would much rather go for overkill rather than trying to figure out the minimum amount of charges required.

Exactly.
On the other hand, in a situation with spreading fire and spreading damage, you are more likely to see a "weakest link" type failure when it collapses, with the weakest link identified in hindsight from the observations of the collapse.

 

[Henkka]

So what do you think caused the large fires on six floors, if not the falling (flaming?) debris from the WTC tower?

Eh, I was clearly just talking about the physical damage caused by the debris impacts. Those impacts gouged some big holes in the southern face of WTC 7, but those couldn't have had anything to do with column 79 failing, since it was in the northeast corner of the building.

 

[Mendel]

Eh, I was clearly just talking about the physical damage caused by the debris impacts. Those impacts gouged some big holes in the southern face of WTC 7, but those couldn't have had anything to do with column 79 failing, since it was in the northeast corner of the building.

Yes.

But keep in mind that the way these fires were started simultaneously on several floors distinguishes the WTC7 situation from what you'd normally think of as an "office fire".

 

[Thomas B]

Hmm.

I really encourage you to watch that Jose Torero lecture that @benthamitemetric found. I'm working on a new OP for a thread where we can discuss the extent to which he validates what you've been dismissing as my "speculations". I'll keep reading this thread until then, but I'm not going to weigh in. I think the Torero lecture can put our discussion on much firmer ground.

 

[econ41]

I just watched it and took some notes. Wow! I feel both enlightened and completely vindicated.

An astonishing reversal given your stubborn refusal to even discuss the topic.

"In the past, no one would have ever thought that … the failure of a single connection could bring down a 47-story building. Today, we actually do believe that that might be possible. A very important technical lesson that we've learned through the World Trade Center." (45:00)

I'm predicting a spurt of quote mining.

I've taken some notes, and I'll watch it again. I think this is worth a thread of its own and I'll leave my thoughts for then. But thank you, @benthamitemetric. Thank you very much. Great find!

At last. I shouldn't need to remind you of how many times I've tried to get you to separate what went wrong under the outdated standards so we could look at what was needed for the future which is now on top of us.

AND I'll put it on record right now - the core question of how serious trauma should you design for is NOT answered by Dr Torero's identification of the need for a paradigm shift. The challenges will remain "How do we define the necessary design envelope" AND "What do we do for those situations where the trauma exceeds the design limits".

 

[econ41]

I really encourage you to watch that Jose Torero lecture that @benthamitemetric found. I'm working on a new OP for a thread where we can discuss the extent to which he validates what you've been dismissing as my "speculations". I'll keep reading this thread until then, but I'm not going to weigh in. I think the Torero lecture can put our discussion on much firmer ground.

Our "discussion" could always have been on firmer ground except for your refusal. Tho if the Torero insight does help you clear up your thinking it will be great. So please do shift the focus of your claim in a new OP - that will be a good thing. Just remember that some of us have been proposing need for change in three areas:
The two technically specific technical issues which arose from WTC 9/11 viz:
1) Improved provision for single item vulnerability to failure. (i.e. the column 79 situation)
2) Means to limit, minimise, or prevent runaway progression (i.e. the rapid progression to the global collapse of both Twin Towers)

AND the philosophically more complex issue:
3) Given the need to define a "design envelope" in some form what measures are appropriate to prevent catastrophic failure of applied trauma grossly exceeds the "design envelope". In "trade jargon" can we require "soft failure" under gross overload conditions?

And maybe we will finally be able to dispose of the emotive term "Achilles' Heel" and put the WTC 9/11 failures correctly into the evolving context.
If that means having an academic spell it out for us... great.

Bear in mind that DrToerero's comments are directed at the needed "paradigm shift" (my words to describe how he recommends a fundamental change in how the engineering of structures and regulation of fire precautions should work in integration). He does not discuss or offer suggestions for the areas of structural weakness that WTC 9/11 revealed despite the WTC buildings complying with regulations. NOR does he address the issue of "where to draw the line" for a design envelope >> which is one of the critical issues - still unresolved - for this thread. NOR the major issue of design philosophy - "What do we want to change in the situations where gross trauma exceeds what a building is designed for". THAT question is not in the scope of Dr Torero's address.

 

[econ41]

Eh, I was clearly just talking about the physical damage caused by the debris impacts. Those impacts gouged some big holes in the southern face of WTC 7, but those couldn't have had anything to do with column 79 failing, since it was in the northeast corner of the building.

Understood, correct and wrong respectively.

Let's put three issues in context:
1) The debris impact started the fires so was the first step in setting up Column 79 et al as the single point of failure.

2) The debris impact was not significant in the structural causes of the collapse. But that fact was only known in retrospect. It may have caused the "bulging" that the emergency managers monitored. So - a bit of irony - the warning signs that the managers were monitoring were actually false alarms. Such situations are not unusual for emergency management.

3) The Column 79 failure was a "single point vulnerability" for the type of fire situation which arose. (That does not mean it was the only such single point of vulnerability.)

And the relevant structural issues. The WTC7 had a strong "moment frame" incorporated in the perimeter shell. The perimeter was strong. The core was weaker. Hence the collapse was "core led" - the core collapsing first leaving the still intact perimeter shell to fall later and still mostly intact for the portion of middle to upper-level floors that was visible. The perimeter failed at the lower levels - out of sight to available video recordings. Almost certainly involving features of the design which bridged over the Con-Ed substation. @Jeffrey Orling may be intersted.

 

[econ41]

Although even if they could have figured it out, they probably wouldn't have done it like that. In controlled demolitions, you want to ensure the building comes down, without leaving it to chance. So you would much rather go for overkill rather than trying to figure out the minimum amount of charges required.

That is certainly the military practice. Demolition in a Military setting is often practised as you are pulling back. "Withdrawing" (the Military never say "retreating") You have to be sure the structure will go down to deny it to the enemy and you will not get a second chance.

However, both military and terrorist para-military demolitions do not usually care about "collateral damage" or "dropping in own footprint".

That kind of ties into a question I wondered about earlier in the thread... That if before 9/11, you gave someone like CDI the task of demolishing WTC 7, could they have figured out they only needed to blow up column 79?

I doubt it. I'm a qualified Military Engineer and when I first joined 9/11 discussion about WTC collapses one of my first mental exercises on "demolition" was "how would I do it". The obvious approach is massive charges at basement level and "blow the guts out". Hang the co-lateral damage. (Why a Military Engineer could be tasked to demolish WTC Towers is a much bigger issue. )

That was 2007. Several years later - circa 2010 - I collaborated with a couple of genuine truthers - two separate series of posts - to formulate an hypothesis for a CD that would mimic the collapse from high up the building we actually saw. A "moot" exercise since we know that fires caused the collapse and how it occurred. So CD was redundant... a story for another time. But, yes, it is plausible to mimic the actual collapses. With or without the aircraft.

Bottom Line for all three scenarios - WTC7 or 2xTwin Tower - it is easy to see the vulnerabilities in hindsight. But highly improbable that anyone could have pre-determined the "weak points". BTW that is an issue for @Thomas B's consideration as he reviews the "New Paradigm" recommended by Dr Torero. How do "you" pre-determine a weak link? Not impossible but at least a couple of grades more difficult than simply designing a building to be "safe to code".

 

[Mendel]

The collapse of World Trade Center 7: revisited
November 2020
DOI:10.14264/9f81895
Conference: 11th International Conference on Structures in Fire (SiF2020)

Article:

A fire in the mechanical room would heat columns 77 and 80 as well as the diagonals of truss 2 which connects them. As these columns lose their capacity, their load is transferred to columns 76, 79, and 81. Likewise, the exposed and partially heated truss 1 is also losing capacity due to heating thus transferring its own capacity to the core and to column 79. Given that column 79 is likely to have been heated due to a diesel fire in its location, and that it also is the most heavily loaded column, it is likely that it would have failed. From this, it was clear that failure of any one of truss 1, truss 2, or column 79 would overload the other two and lead to their failure. It was, therefore, that combined heating of truss 1 and truss 2, and potential heating of column 79 was the primary factor for global collapse of WTC 7. The initiating failure could have been either failure of column 79 or of truss 2, because a collapse event beginning at either of these two points had the potential to manifest the kink observed in the penthouse and cause its sinking as was seen in the videos.

Source: https://www.researchgate.net/publication/347108749_The_collapse_of_World_Trade_Center_7_revisited

The upshot of this paper is that column 79 was not the Achilles heel by itself.

 

[econ41]

The upshot of this paper is that column 79 was not the Achilles heel by itself.

That is necessarily true. It is a matter of definition. Most discussion has referred to Column 79 as if it was the sole cause of collapses. And referenced it as an example of "single item" failure. The reality is that Column 79 could not have been the initial trigger of the collapse process which was caused by fires. (Ironically it could have been the single item trigger of it had been taken out by explosive CD but that did not happen.)

The reality was that it took multiple bracing beam failures to weaken Col 79 - before it failed. It was the "victim" of other failures - not the cause. It would be pedantically more correct to refer to the multiple "triggers" or better still recognise that it was the subsystem of nearby columns plus Col 79 and the connecting bracing beams which together contributed to a so-called "single point" failure.

I have, in many of my posts referred to "Col 79 and associated structure..." OR "The Col 79, 80, 81 cluster..." or on a couple of occasions less formally as "Col 79 et al.." On most other occasions I have simply followed the common practice of simply referring to Col 79 as single point failure. The distinction is probably not significant in the setting of recent discussions but could become necessary if the discussion progresses.

 

[Thomas B]

@Henkka mentioned this in another thread, but I thought it might also be useful here. Explaining why NIST didn't release the data that was the the basis of the WTC7 simulation, NIST said the following:

The withheld information contains detailed connection models that have been validated against actual events, and therefore, provide tools that could be used to predict the collapse of a building. The information contained in the withheld files is sufficiently detailed that it might be used to develop plans to destroy other, similarly constructed, buildings.

https://www.nist.gov/world-trade-center-investigation/study-faqs/wtc-7-investigation

This suggests to me that they did actually find a vulnerability.

 

[Henkka]

@Henkka mentioned this in another thread, but I thought it might also be useful here. Explaining why NIST didn't release the data that was the the basis of the WTC7 simulation, NIST said the following:

The withheld information contains detailed connection models that have been validated against actual events, and therefore, provide tools that could be used to predict the collapse of a building. The information contained in the withheld files is sufficiently detailed that it might be used to develop plans to destroy other, similarly constructed, buildings.

https://www.nist.gov/world-trade-center-investigation/study-faqs/wtc-7-investigation

This suggests to me that they did actually find a vulnerability.

And not just a vulnerability in WTC 7, but one that could apply to other buildings as well.

 

[Jeffrey Orling]

Don't you think that a take away from the WTC collapses is that unfought fires in steel frames can be fatal.

 

[Thomas B]

Don't you think that a take away from the WTC collapses is that unfought fires in steel frames can be fatal.

Yes, this very much what I gathered from watching those Jose Torero talks. It's also why I think firefighters must approach skyscraper fires differently since 9/11. (I'm still thinking about starting a thread on that.)

 

[Mendel]

And not just a vulnerability in WTC 7, but one that could apply to other buildings as well.

No, that's not what they said.

What they said is that the choices NIST made in "programming" the model align with reality, so if you model a similar building the same way, you know your model is probably going to predict the collapse correctly if you identify a vulnerability.

In other words, if you are a terrorist aiming to bring down a steel frame building, model it like NIST modeled WTC7 and then play around with the model to find the easiest way to destroy it.

However, if you don't have access to the NIST model, you need to guess at some of the settings they made, and guess at some of the decisions made on how to model certain properties of the building, and then you can no longer be sure that your model reflects reality: something that collapses the model in the simulation might not work in reality, and your terror attack could fail.

This uncertainty is preserved by not publishing the NIST model in full.