Failure mode in WTC towers

[rwguinn]

The moments are extremely low in the tower sections. There are also essentially no deflections due to them, otherwise these slim structures would quickly buckle and fail.

You aren't providing anything but your opinion. Even though he is wrong at least NB tries to show backup for his thoughts.

That's the purpose of a Truss, dude.
Let's see that shear and moment diagram...

 

[Tony Szamboti]

Well, you have been proved wrong on just about everything you've posted on this forum, but my sources have unearthed some stunning information. It seems that Roberts is a dual-citizen of the U.S. and Brooklyn! Just like the proverbial broken clock, you managed to get one right.

Is it true that you are really an Israeli? That's what "they" say, you know.





There may be no "supposed," but there's a helluva lot of "doubt."





Not much mystery here. I state over and over that I have zero credentials and no background whatever in engineering. I am capable of observing what happens when a charlatan such as yourself tackles people who are the genuine article. You receive very specific corrections that you simply ignore. Max Photon and Ace Baker are completely ineducable, too, but you seem to expect people to take you seriously.




The results of the thread are in: You got smashed flat again. You have no idea of what you're talking about. And you never did get around to telling us--

WHO FLEW THE PLANES???

I'll answer one of your lambrained questions before getting away from you obviously biased dorks. I am 1/2 italian, 1/4 polish, 1/8 german, 1/16 jewish, and 1/16 austrian and I am an American citizen only. However, I was accused of being racist on this site for asking Roberts if he was a dual citizen.

 

[Tony Szamboti]

That's the purpose of a Truss, dude.
Let's see that shear and moment diagram...

Hey dude, I have shown some of my work here. Unfortunately, I can't say the same for you. You have no problem asking other people for it though. Buzz off.

 

[Gravy]

Why don't you do your little model with adjacent and anchored horizontal beams coming off the top of the frame? That would be representative of the tower columns and guess what? Your columns won't be deflecting due to bending moments in them.

I have had enough of you guys for one night. You are so wrong here it is pathetic and having people like Roberts and Wieck stick there noses in where they aren't knowledgeable is pathetic also.

Come on Ron's show, Tony, so I can dust you in an engineering debate...and I hardly know anything about engineering, while you have a degree in it!

If you're so sure I can't handle it, then come on the show and make a fool of me for everyone to see.

See you soon, ain'tgineer?

 

[Norseman]

Such a snow avalanche has nothing in common with the WTC1 collapse, even if the upper block of WTC1 had a uniform density similar to that of compressed snow (180 kgs/m3) that sticks together - snow crystals interacting. But this is what the authorities and university professors want us to believe. Potential energy is always potential energy. But is it?

Wrong again Heiwa. The initiation mechanism of many snow avalanches are a very good example of progressive collapse. Like what you see in the picture below:

Source

A local weight increase fractures the snow crystals in the weak layer, the load is transferred to the next crystal that also fractures and so on, collapsing the weak layer. Just like what happened on floor 98 in WTC 1 when the columns of the south exterior wall no longer were able to carry their weight and failed. And of course snow avalanches can also be triggered by temperature increases weakening the structural strength of the snow.

Whether a weak snow layer collapse will develop into an avalanche or not is dependent on the slope angle and the friction force. A skier can trigger a whole mountainside in this way. Think about it Heiwa, a less than 100 kg skier can trigger a several million kg snow avalanche with just one small step.

And to much snow on the roof can collapse it, look at those steel beams and columns:
http://capretzer.com/images/forensics/snowLoadCollapse.jpg
(Original context)

(Notice that even in this one story building, the columns have spray on fire proofing. But heat weakening was certainly not the problem in this case.)

 

[rwguinn]

Hey dude, I have shown some of my work here. Unfortunately, I can't say the same for you. You have no problem asking other people for it though. Buzz off.

Translation (twoofer to reality, III edition)
"I don't have a clue what you are asking for, and have absolutely no intention of finding out"

 

[pomeroo]

I'll answer one of your lambrained questions before getting away from you obviously biased dorks. I am 1/2 italian, 1/4 polish, 1/8 german, 1/16 jewish, and 1/16 austrian and I am an American citizen only. However, I was accused of being racist on this site for asking Roberts if he was a dual citizen.

It's safe to assume that no one has the slightest interest in your ethnic heritage. Your preposterous "question" about dual-citizenships suggested that you are another twoofer anti-Semite. Jew-hating loons concocted this stupid canard to smear members of the Bush administration who have Jewish-sounding names by implying divided loyalities.

Let us know when you've figured out--

WHO FLEW THE PLANES.

 

[Gravy]

WHO FLEW THE PLANES.

My Israeli brethren.

Hey, Tony:

Boo!

 

[Tony Szamboti]

Yup, you got him. His comment was exactly 180 degrees out of phase with reality.

Tony, let me try to help again, in the sincere hope that you start learning and thereby help illuminate others in your circle. The diagram that Newton's Bit put forth describes the problem perfectly -- contrasting the ideal "pinned" versus real eccentric-loaded cases. Consistently you've followed the ideal model.

This doesn't work. In the ideal model, you have those ideal pinning blocks above and below. These blocks can oppose any lateral force and any moment by definition. They're ideal, that's what it means.

In the real system, it doesn't work that way. The moments and side forces are distributed to other real members, i.e. the column above through the splice, to the floor truss, and also to the floor truss connection. The floor trusses, you will recall, were bolted, not tied off like a guy wire. There is going to be limited but real opposing moment there. The rest of the moment can only be transmitted to the column above. The connection between them does resist this moment. And in general, there are two floors connected in the middle of each single column.

Because we're dealing with a real situation, not an ideal situation, you cannot treat the WTC model as an ideal truss system, where only axial forces matter, or as an ideal double-pinned series of columns, where end moments can be dissipated up to infinity. It just isn't so. The real system is a moment frame, and that means moments -- not just axial forces -- are transmitted to different members.

This is very basic, and I trust you've seen it before. Denial of such obvious facts enhances neither your credibility nor your reputation.

Ryan, the moments which the tower columns would have experienced, due to gravity loads were so low they could be ignored. It is no different than your steel creeps forever but essentially it can be ignored it is so low. I am saying that horizontal beams supporting the top of the frame NB showed would eliminate the bending deflections his diagram shows in the columns. You know darn right well that is true.

I can't believe I am hearing this. I even showed the Timoshenko and Gere point about it. You guys are unbelievable.

 

[Gravy]

Ryan, the moments which the tower columns would have experienced, due to gravity loads were so low they could be ignored. It is no different than your steel creeps forever but essentially it can be ignored it is so low. I am saying that horizontal beams supporting the top of the frame NB showed would eliminate the bending deflections his diagram shows in the columns. You know darn right well that is true.

It's a good thing those buildings weren't damaged! That could have meant trouble!

 

[pomeroo]

Come on Ron's show, Tony, so I can dust you in an engineering debate...and I hardly know anything about engineering, while you have a degree in it!

If you're so sure I can't handle it, then come on the show and make a fool of me for everyone to see.

See you soon, ain'tgineer?

I dunno--an engineer vs. a non-engineer. It sounds so unfair. Hey, LET'S DO IT!!!!

What's that, Tony? Mark would be too easy? C'mon, take a shot. No guts, no glory.

 

[pomeroo]

Ryan, the moments which the tower columns would have experienced, due to gravity loads were so low they could be ignored. It is no different than your steel creeps forever but essentially it can be ignored it is so low. I am saying that horizontal beams supporting the top of the frame NB showed would eliminate the bending deflections his diagram shows in the columns. You know darn right well that is true.

I can't believe I am hearing this. I even showed the Timoshenko and Gere point about it. You guys are unbelievable.

On the subject of unbelievable guys, you predictably ignored the question I asked in post # 538. Inquiring minds and all that.

 

[R.Mackey]

Ryan, the moments which the tower columns would have experienced, due to gravity loads were so low they could be ignored. It is no different than your steel creeps forever but essentially it can be ignored it is so low.

This is called the Fallacy of the Unevaluated Inequality, and it's one of the more interesting ones. In other words:

• You admit that there are moments, after all
• But you claim you can neglect them -- they are "so low they can be ignored."
• Yet you provide no evidence of this. You neither compute those moments, nor establish a threshold of significance.

But at least you admit there are moments.

As-built, the moments are significant but within the capacity of the structure. Deformation is minor.

After impact and heating, and after the eccentric load increases due to floor pull-in, you can't neglect them any more. That, by the way, is what we're talking about.

I am saying that horizontal beams supporting the top of the frame NB showed would eliminate the bending deflections his diagram shows in the columns. You know darn right well that is true.

I can't believe I am hearing this. I even showed the Timoshenko and Gere point about it. You guys are unbelievable.

NB's diagram does have horizontal beams at the top of the frame. Those beams, in the WTC case, are the floor trusses. They don't eliminate bending deflections. You know darn right that your statement is nonsense.

 

[Gravy]

I dunno--an engineer vs. a non-engineer. It sounds so unfair. Hey, LET'S DO IT!!!!

What's that, Tony? Mark would be too easy? C'mon, take a shot. No guts, no glory.

That could be hugely embarrassing for both of us, with a real live Engineer for Truth and Peer Reviewer for the illustrious J.O.N.E.S. bearing down on us!

 

[Gravy]

Wow: learned a new fallacy. Thanks, Ryan! (Or did you just make that up?)

 

[pomeroo]

That could be hugely embarrassing for both of us, with a real live Engineer for Truth and Peer Reviewer for the illustrious J.O.N.E.S. bearing down on us!

As some of us have noticed, I'm no stranger to embarrassment.

 

[rwguinn]

Could you answer a serious question from a non-engineer? Is it possible for someone to be graduated from an engineering school and know as little as Tony does? In your opinion, does he understand that he can't sell this nonsense to real engineers, and if he does understand, what could his purpose be?

Unfortunately, Yes, it is possible to graduate ann know as little as Tony. An enginnering degree does not bestow analytical ability or critical thinking.
We all come out thinking we know a lot, and that the "old school" had better watch out.(I know a few folks working for me for whom that will be true in a couple of years--very, very good!) But there are many things I was exposed to in school that didn't make sense until years later--the old "So that's what Professor Cobble was talking about! Son of a *****!"
Just is it is possible to have a degree in biology and believe in creationalism (as opposed to evolution), it is possible to get a technical degree and rely on "gut feel". (there is also the "cheat your way through to a better paying job", but we'll ignore that--they usually get found outt fairly quickly, if not before they graduate)
Such folk seldom get very far, and quite often abandon the field after a few years of getting nowhere (because of "the system" or some such nonsense )

 

[R.Mackey]

Wow: learned a new fallacy. Thanks, Ryan! (Or did you just make that up?)

No, I did not, it's standard. But it's quite entertaining. In this example, it's related to Special Pleading ("Yeah, there are moments, but we can just ignore them..."), but also cast as a False Dilemma ("The moments either affect the structure or they don't," whereas in fact the effect is much more linear).

At the heart of it, sadly, is a fundamental misunderstanding of statics. This is pretty basic engineering.

 

[Newtons Bit]

I can't believe I am hearing this. I even showed the Timoshenko and Gere point about it. You guys are unbelievable.

No, again you fail (intentionally) to understand the difference between a fixed-fixed member and a moment frame. Timoshenko says that a moment applied at the top support of a problem like this has no moment:

This is true. However in a moment FRAME, there is moment in the column. Like this moment frame.



The reason for this, is that the reaction of the beam is eccentric to the column. As it pertains to the WTC, the exterior connection looked something like:




It's shear idiocy to say that a connection similar to that won't induce moment from unbalanced eccentric reactions.

 

[Newtons Bit]

This is called the Fallacy of the Unevaluated Inequality, and it's one of the more interesting ones. In other words:

• You admit that there are moments, after all
• But you claim you can neglect them -- they are "so low they can be ignored."
• Yet you provide no evidence of this. You neither compute those moments, nor establish a threshold of significance.

But at least you admit there are moments.

As-built, the moments are significant but within the capacity of the structure. Deformation is minor.

After impact and heating, and after the eccentric load increases due to floor pull-in, you can't neglect them any more. That, by the way, is what we're talking about.



NB's diagram does have horizontal beams at the top of the frame. Those beams, in the WTC case, are the floor trusses. They don't eliminate bending deflections. You know darn right that your statement is nonsense.

In reality, the bending moments are small enough to not be a serious issue (except in VERY eccentric shear connections). It is however relevant to my point about how the column spliced will break in bending due to axial failure. But then, he started off by saying that there would be zero bending moments in the column, which is ********.