9/11 Structural Engineer's poll 19

[WARose]

A former colleague of mine who is a structural engineer (now retired and with apparently too much time on his hands ) discusses various conspiracy theories on the net. One of them is the 9/11 theory that holds that the buildings that fell on that day did so due to a controlled demolition. (A theory he feels is “nonsense”.)

You've probably heard followers of this theory called “Truthers” (or worse). In any case, aside from telling my friend that he is/was apparently a member of the CIA (and trying to say he wasn't even a structural engineer), apparently another angle of argument is to say that the profession is somehow afraid to talk about it (noting a lack of support in journals, etc) or that my friend somehow doesn't know what the profession talks about. That got me wondering how much this is discussed beyond my (and his) experience. So the question I have as sort of a poll for structural engineers:

Is the controlled demo theory something that is a regular topic of conversation with your colleagues?

AND (if the answer to the above question is “yes”) Do you feel compelled to view it one way or the other?

Speaking for myself, I cannot think of a single time it has come up (except in conversations with my retired friend mentioned earlier). I've certainly discussed the failures on that day with other structural engineers as an example of progressive collapse. But not much beyond that.

However, public awareness on the topic (I would call it misinformation) seems to have done nothing but grow over the years......and will likely grow more in the years to come.....so I thought I'd ask fellow structural engineers for their thoughts and ideas as to be better equipped to answer the public’s concerns in the future.

 

[mtu1972]

I am also retired and according to my wife have too much time on my hands. I've never heard of this conspiracy theory and do not think it should have any credibility. There have been numerous reports and articles of how the failures happened. My recollection is that the fires, because of the amount of jet fuel, were a big factor to the progressive collapses.

On that morning, one of our drafters came into my office to tell me a plane had crashed into one of the WTC buildings. My response was - "A plane hit the Empire State Building a long time ago and it was OK". Turned out it was a small plane.

When he came back a while later with the report that the second building was hit, we spent a good part of the day, taking turns watching TV in the conference room, and keeping the entire office updated.

Our lives were changed forever that day! And 15+ years later we are still in recovery.

gjc

 

[Lomarandil]

It is not a topic of conversation with my colleagues. It does come up from time to time within certain circles of my friends.

I can't say it's ever been presented to me in any way that can be described other than "laughable".

 

[TheTick]

Most of the truthers' arguments seem to center around the combustion temperature of jet fuel (kerosene), and how that's not hot enough to melt steel.

No discussion about heat building up in a confined space.

No discussion about the burning magnesium from the airframe.

No discussion about how steel weakens as it is heated even if it doesn't melt.

 

[IRstuff]

Just goes to show that post-truth and post-fact are not new; it's only the degree and the number of people involved that seem to be increasing

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[ornerynorsk]

There are aspects of that day that will never pass the smell test. The physical evidence has all since been remelted and turned into macadam, and the snippets and video segments suggesting anything but a foreign-hatched plot have faded into oblivion in most people's memories. The truther's rabid testimony is akin to ramblings of schizophrenic madmen, effectively sabotaging any sane dialogue that might be had on the subject. Ridicule and scoffing become the defense mechanisms of those who cannot mentally process the unthinkable implication. This is JFK, in that the top-tier planners and organizers behind it got away with it, be they Arabs or not.



It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[JohnRBaker]

I've never heard of this conspiracy theory...

I find that very hard to believe. It has been talked about all over the net as well as being at least given lip-service, if not outright support, by certain so-called 'journalists' at places like Faux News and other Right-wing media outlets.

As for the Empire State building incident, it was not exactly a "small plane" but rather a B-25 bomber. Granted, it may have been "small" compared to the 767's that hit the Twin Towers, but relative to the size of the Empire State building itself, it was still a large aircraft. I think the big difference was that the B-25 was attempting to land in Newark after a flight from New England and therefore was not full of fuel as were the 767's that had just taken off on transcontinental flights. Also, the stone facade of the Empire State building probably prevented the complete fuselage, including the fuel tanks, from actually penetrating through the side of the building thus limiting the fire and subsequent heating threat to the actual superstructure of the building.

And for the record, I think this whole "9/11 Truther" movement is a bunch of crap. This is just another classic example of what can happen when a nation is attacked by a group utilizing asymmetrical means.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[mtu1972]

JohnRBaker - I must be oblivious but I truly had not heard any of this. I get my news from the major networks and MSNBC, Time magazine, and a Sunday newspaper. From a technical standpoint I get information from ASCE, Structure magazine, and Modern Steel Construction. I don't recall any reporting of a conspiracy theory.

Note: A quick internet search has just shown me that these theories have been in place since just after the incident. I can't believe I never stumbled on this over the last 15 years.

I do believe that the Bush administration may have overlooked some clues, but I can't accept some covert conspiracy theory.

Visited NYC last summer for the first time and one of our stops was the WTC Memorial. Like my Italian grandmother used to say, "I may be slow to learn, but I never forget". I will be doing more searches regarding this.


gjc

 

[WARose]

I must be oblivious but I truly had not heard any of this. I get my news from the major networks and MSNBC, Time magazine, and a Sunday newspaper. From a technical standpoint I get information from ASCE, Structure magazine, and Modern Steel Construction. I don't recall any reporting of a conspiracy theory.

Don't feel bad mtu1972. There is pretty much a underground conspiracy industry out there. You can find all kinds of crazy web sites claiming all sorts of things.

Thanks for the replies so far guys. Keep them coming.

JAE, Buggar, Kootk, etc if any of you are reading this.......I'd like your input as well (i.e. some of my favorite posters on the structural boards).

 

[SwinnyGG]

As for the Empire State building incident, it was not exactly a "small plane" but rather a B-25 bomber. Granted, it may have been "small" compared to the 767's that hit the Twin Towers, but relative to the size of the Empire State building itself, it was still a large aircraft. I think the big difference was that the B-25 was attempting to land in Newark after a flight from New England and therefore was not full of fuel as were the 767's that had just taken off on transcontinental flights. Also, the stone facade of the Empire State building probably prevented the complete fuselage, including the fuel tanks, from actually penetrating through the side of the building thus limiting the fire and subsequent heating threat to the actual superstructure of the building.

The B25 actually did punch a hole through the side of the facade of the building.

http://a.abcnews.go.com/images/US/gty_esb_bomber_crash_1945_ss_jp_120308_vblog.jpg

14 people were killed, 11 of them inside the building. One of the B25's engines punched a hole in the opposite side and landed on the roof of a building about a block away.

During that incident the B-25 was on landing approach, flying in heavy fog, and was probably moving very slowly.

A B-25 also only weighs about 20,000 lb empty. Much smaller than most people think.

 

[JohnRBaker]

Perhaps, but I suspect that the wings, where most of the fuel would have been stored, were sheared off, even if the main fuselage penetrated the building facade. Granted, one engine did end-up inside the building, but the other ended-up on the roof of another building a couple of blocks away indicating that NOT all of the plane slammed into the side of the building, that at least part of one wing, with the engine attached, missing the building completely. And if that B-25 had been fully loaded with fuel, and had been flying at closer to normal speed, like the 767's were, and it had hit fully and squarely on the side of the building, perhaps a bit lower down, it could have done significantly more damage than it did, perhaps even to the extent of compromising the overall structural integrity of the superstructure, maybe even to the point of causing a catastrophic collapse.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[WARose]

I think another big difference was the fact the Empire State Building wasn't built with the "tube" design philosophy. Not saying anything is wrong with the approach, but it doesn't quite have the ability redistribute things in such a situation.

World Trade Center 7 (which certainly wasn't hit by a plane) had a "tube" design approach as well......but it was a bit odd in terms of it had a number of cantilevers (and other systems) to redistribute the vertical load. The building's layout (in plan view) overshot it's foundation (which was placed years prior the building being built). The result was that a lot of vertical load had to be redistributed from some of the upper floors down to the foundation. Perhaps this made the building more susceptible to the fire that brought it down.

 

[MacGruber22]

the profession is somehow afraid to talk about it

THAT is an argument for controlled demolition theory? Firstly, that basic argument is part of a boiler plate tactic from people trying to muddy the waters of clarity. If they can get you on a tangent that cannot be readily disproved, then they have already won without being correct.

Secondly, there hasn't been much discussion, because 99.9% of structural engineers respect the general findings from the original NIST, ASCE, & FEMA reports. These reports aren't from some single cockamamie engineer who reads infowars.com articles all day. They consist of many layers of peer reviewed information, qualitatively and quantitatively. Is everything in those reports likely to be without flaw? - no, of course not. Of course, the doubters prey on errors, ambiguity, etc. and treat them as evidence that brings the whole system down.

We are in an age where any bozo with an internet connection is an "expert" at everything. The real experts, of whom are intimately familiar with the nuances of the circumstances at hand, are shrugged off as "insiders" and inherently corrupt. The conspiracy theorists (CT's) take advantage of these ideas and implant them as a priori. No matter the quantity/quality of evidence and rigor of corroboration, the CT's rely on tenants rooted in mistrust and respond with a barrage red herring arguments.

"It is imperative Cunth doesn't get his hands on those codes."

 

[Comcokid]

I am not a structural engineer. However, as I watched the unfolding events of 9/11 on a TV at work I clearly recalled curious statements made by a Civil Engineering professor in an elective course some 20+ years earlier. The course was an optional 'elective' course in 'Mechanics of Materials'.

One was a statement about multi-floor steel frame buildings, that should one level collapse with more than 3 or 4 floor levels above it then typically the entire building will pancake. The other was a statement about the issues of fire damage to steel structures and the very specialized experience needed by a structural engineer to evaluate the structure afterwards, which impressed upon me the complex changes that can occur in steel under such conditions.

I have chanced upon the conspiracy theory videos on the internet but don't personally know of anyone who takes them seriously. But as an engineer I mostly interact with rational objective-thinking people who don't suffer from a paranoid world-view. Most of the conspiracy videos out there are made by those who like to troll on the fear of others rather than those who really believe in such stuff.

 

[SwinnyGG]

Perhaps, but I suspect that the wings, where most of the fuel would have been stored, were sheared off, even if the main fuselage penetrated the building facade. Granted, one engine did end-up inside the building, but the other ended-up on the roof of another building a couple of blocks away indicating that NOT all of the plane slammed into the side of the building, that at least part of one wing, with the engine attached, missing the building completely. And if that B-25 had been fully loaded with fuel, and had been flying at closer to normal speed, like the 767's were, and it had hit fully and squarely on the side of the building, perhaps a bit lower down, it could have done significantly more damage than it did, perhaps even to the extent of compromising the overall structural integrity of the superstructure, maybe even to the point of causing a catastrophic collapse.

You misunderstood.

The plane hit the building full on. Splat.

The fuselage punched a relatively clean hole right through the wall of the building. This is visible in all of the photos. Both wings left big gashes. There's not a huge number of photos available that show a lot of the facade, so its impossible to say for sure what happened to the wings themselves- I suspect they mostly disintegrated. Not a lot of mass there, as you stated.

One of the engines hit an elevator shaft and fell to the bottom. The other engine went THROUGH the building, punched another hole in the far wall, and came to rest inside of/on top of another building a little less than a block away (not a couple of blocks- 1 single block.)

This means the second engine fell about 900 feet while traveling forward only 250-300 feet- so when it exited the building it was not going very fast. But it did go through the building. All of the news accounts agree on that, and the photos that show the impact zone do as well- the engine on a B-25 is not very far from the fuselage. If the plane had hit the building in such a way that one engine could completely miss the building and be launched free, the fuselage would have basically had to impact the corner of the building, and it did not.

The fire also burned on 11 floors of the building. This was not a small fire contained on the two floors that were hit.

 

[JohnRBaker]

I stand corrected

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[hokie66]

Any controlled demolition conspiracy theory about the WTC collapse is complete rubbish. I know a lot of engineers, and not one would even suggest such a thing. The WTC towers collapsed because of conspiracy of terrorists.

 

[WARose]

[blue](MacGruber22)[/blue]
THAT is an argument for controlled demolition theory? Firstly, that basic argument is part of a boiler plate tactic from people trying to muddy the waters of clarity. If they can get you on a tangent that cannot be readily disproved, then they have already won without being correct.

Quite true. I've seen them make a variety of arguments over the years (relative to our discipline)......among them (pardon if any of them seem so preposterous as to not warrant even mentioning):

1) No skyscraper has ever collapsed from fire before. (Some will go as far to say no steel structure has ever collapsed from fire.)
2) The collapse in the WTC Towers 1&2 should stopped after some point. That is: the collapse should have been arrested after crushing a relatively small number of floors.
3) The NIST (or whomever) didn't properly model the buildings or do a proper investigation. One specific complaint in that regard is apparently they didn't "model" some shear studs and stiffeners in WTC 7 that the Truthers feel would be critical to restrain thermal expansion.

My critique:

1) As far skyscrapers go: that's not entirely accurate. The Windsor Tower (in Madrid) was gutted by fire and had the steel portion of the upper building collapse. Interestingly enough: the core of that building was made of reinforced concrete and that portion survived the fire.

As far as smaller steel buildings go....that of course happens all the time: the Kader Toy Factory (in Singapore), Dogwood Elementary (in Virginia), Mumbai North Platform, etc being notable examples.

To me, a worthwhile comparison would be a building built with the "tube" design approach being hit by a 767 going at nearly 500 mph. IOW: There aren't too many comparisons to make. (None to my knowledge.)

2) I've run some numbers for the collapse and I frankly don't see what the argument is. After the collapse initiated, we are essentially talking a overwhelming force hitting the floors below......and it snowballs from there. Based on some I've listened to, it's like they are expecting the steel to "crumple up" (for the lack of a better way to put it) and that would end it. I came out with the sections buckling before plastic deformation could take place (on the sections I looked at). (Dynamic buckling came up in a project of mine some months back, so I've had to get reacquainted with the concepts recently.)

3) Frankly, I don't get what they are saying here. I've never included shear studs and/or stiffeners in a (overall) model of a building in my life. One argument I looked in on some time back, a Truther was claiming that a web/flange stiffener was going to somehow stop a girder from growing (axially) in thermal expansion.

So the arguments range from some you feel you need to run some numbers on.......to the downright crazy.

[blue](MacGruber)[/blue]
We are in an age where any bozo with an internet connection is an "expert" at everything. The real experts, of whom are intimately familiar with the nuances of the circumstances at hand, are shrugged off as "insiders" and inherently corrupt. The conspiracy theorists (CT's) take advantage of these ideas and implant them as a prior. No matter the quantity/quality of evidence and rigor of corroboration, the CT's rely on tenants rooted in mistrust and respond with a barrage red herring arguments.

Yep, could not have put it better myself.


Happy New Year to all!

 

[zeusfaber]

I've been swithering for a couple of days over whether to post these links.

[URL unfurl="true"]https://xkcd.com/966/[/url]

[URL unfurl="true"]https://xkcd.com/690/[/url]

Not a subject to joke about lightly, but sometimes humour is what it takes to get people to engage their critical faculties.

A.

 

[hokie66]

Thanks for the new word to my vocabulary, zeusfaber. I'm sure I will have a use for "swither" at some stage.