Failure mode in WTC towers

[Furcifer]

Maybe he needs that extra foot to count with because in the initial collapse of the North Tower a fall of 12 feet in 2 seconds isn't what was observed.

Nor did the antennae. You have your fantasies so let Dave have his. The thing is Dave's fantasy is as a result of your fantasy. Your fantasy stems from ignorance.

 

[Newtons Bit]

There you go again with the pinned supports and no sidesway inhibition. To act like a pinned connection the end of the column would need to be able to rotate .04 radians or 2.25 degrees. That was not possible in the towers with the sidesway inhibiting beams with composite floor slabs restraining any rotation at both ends. You also fail to take into account the great inertia a massive building like the towers would have had. I'll show the little exercise on finding slenderness ratio factors again for those who might want to see why I say you are not correct again.

http://cnx.org/content/m10746/latest/

In the exercise column AB would represent the perimeter columns and columns CD and FG would represent core columns. The mass and inertia of the building would ensure a behavior represented by anchor points A, C, F, and J.

Your figure is a frame which is the same as frame DEHG in the exercise, which does not represent the configuration of any of the columns in the towers.

By the way, bluster isn't becoming of an engineer.

Tony, that frame is a MOMENT frame. All connections are fixed. Notice how the beam to column connection is at a right angle and the base to column connection is a right angle. I don't understand how you can look at something that is clearly defined as a moment frame and then call it pinned.

The difference between this and that example you choose to mine is that in your example there is a pinned connection to a brace or a wall at point J. Your example, is not that of a moment frame, it is of the gravity columns in a structure with a braced frame or a wall.

Get it into your head. Go pick up some engineering modeling software, you can get a demo of risa 2d here: http://www.risatech.com/risa-2d.asp Put in a frame with all fixed connections and see what happens. Or is Risa in on the conspiracy too?

I'm starting to get the feeling that you know that you are wrong, but won't admit it so that the poor schmucks who read this might feel that the truther position isn't the complete idiocy that it is.

 

[Newtons Bit]

My bolding



neither is a lack of comprehension of the basics...

and, like, dude--it ain't bluster when you're right...

I'm starting to get the idea that all of his engineering ideas come from an "idiots guide to engineering". Wait, that can't be right either. I'm sure if he read something like that he'd have a better understanding of it than he does.

 

[Max Photon]

Questions for the engineers about heated top chords

I have some questions for the engineers (because I don't know the answers).

What would be the effect of heating to Tc a couple of feet of the top chords:

1. by the truss seats?
2. by the channel rails?

What would be the effect on the floors?

What would be the effect on the perimeter columns?


Thanks.

Max

 

[Tony Szamboti]

Tony, that frame is a MOMENT frame. All connections are fixed. Notice how the beam to column connection is at a right angle and the base to column connection is a right angle. I don't understand how you can look at something that is clearly defined as a moment frame and then call it pinned.

The difference between this and that example you choose to mine is that in your example there is a pinned connection to a brace or a wall at point J. Your example, is not that of a moment frame, it is of the gravity columns in a structure with a braced frame or a wall.

Get it into your head. Go pick up some engineering modeling software, you can get a demo of risa 2d here: http://www.risatech.com/risa-2d.asp Put in a frame with all fixed connections and see what happens. Or is Risa in on the conspiracy too?

I'm starting to get the feeling that you know that you are wrong, but won't admit it so that the poor schmucks who read this might feel that the truther position isn't the complete idiocy that it is.

I understand that the floor loads are eccentric to the columns but they are precluded from applying moments to the columns due to being resisted by the horizontal beams in a structure such as the towers. That is what Timoshenko and Gere are stating in the sentence I quoted earlier. Your diagram was not representative of what is truly occurring.

I have modeling software at work and I can tell you that if I modeled a complete floor of the towers those columns would not have deflections due to bending moments applied by the uniformly distributed floor loads. The stresses and any deflections would only be due to axial compression. Modeling is not a do all and be all and your model was not appropriate. You know the old saying "garbage in garbage out".

 

[Tony Szamboti]

Nor did the antennae. You have your fantasies so let Dave have his. The thing is Dave's fantasy is as a result of your fantasy. Your fantasy stems from ignorance.

You are right the antenna came down a lot faster than 12 feet in 2 seconds. It's drop distance has been measured vs. time by breaking apart the Sauret video and with that it's acceleration and then velocity have been determined. There will be a paper coming out on that in the near future.

 

[rwguinn]

I'm starting to get the idea that all of his engineering ideas come from an "idiots guide to engineering ignorance". ...

fixed that for you
ETA:
Realcddeal,
Draw the freebody diagrams of each connection. (I generally hate it when people say that, but in this case, it's back to basics...) You will see that N1, N2, N4, and N5 are all carrying Moments

 

[Newtons Bit]

I understand that the floor loads are eccentric to the columns but they are precluded from applying moments to the columns due to being resisted by the horizontal beams in a structure such as the towers. That is what Timoshenko and Gere are stating in the sentence I quoted earlier. Your diagram was not representative of what is truly occurring.

No, you didn't quote the mad Irishman. You just said he stated something. That's not quoting. Okay, well maybe it is in the truther universe. I'd like to see the actual full-context of that statement.

I have modeling software at work and I can tell you that if I modeled a complete floor of the towers those columns would not have deflections due to bending moments applied by the uniformly distributed floor loads. The stresses and any deflections would only be due to axial compression. Modeling is not a do all and be all and your model was not appropriate.

And you would be wrong.

You know the old saying "garbage in garbage out".

And this apparently applies to the things you read as well.

 

[Max Photon]

The key WTC collapse initiation question is: How was the structural steel heated?

Beachnut:

Now when you go posting stuff like this I have a problem:

"Please show an example of thermite taking down a building...... lets see the large core columns cut with thermite, in a way that leaves no thermite residual or proof like we have on 9/11. No proof after the act. Kind of means thermite was not used"

Why do I have a problem with this? Because when you address your words to Gregory Urich (as if he has pushed some kind of thermite theory), I do not believe you could show me where GU has been a proponent of thermite; so why use this line of argument?

That's Beachnut's typical, multi-layered, low-caliber flak attack.

Not only is he misrepresenting Gregory, but he is also making the assumptive close that if thermite were used, then thermite was used for cutting steel (still?).

NIST blame the collapse of WTC 1 & 2 on heat weakening of the structural steel, as others such do but with very different heat sources in mind.

So, Beachnut you have to agree, we are merely quibbling about how the steel was heated are we not?

All I can say is there are plenty of CHEMICAL possibilities you are missing......

Beautifully put.

1.) NIST blames the collapse of WTC 1 & 2 (& 7) on heat-weakening of structural steel.

2.) We are now quibbling about how the steel was heated.


This is the key WTC collapse-initiation question:

How was the structural steel heated?


Max

 

[Furcifer]

You are right the antenna came down a lot faster than 12 feet in 2 seconds. It's drop distance has been measured vs. time by breaking apart the Sauret video and with that it's acceleration and then velocity have been determined. There will be a paper coming out on that in the near future.

If there is any existing proof that the antenae did not fall independantly of the upper block it's the Sauret video. There's absolutely, positively, no movement of the antennae relative to the upper block.
Are you confused or joking?

 

[Furcifer]

This is the key WTC collapse-initiation question:

How was the structural steel heated?


Max

Well we solved it then. Fire.

 

[Heiwa]

If there is any existing proof that the antenae did not fall independantly of the upper block it's the Sauret video. There's absolutely, positively, no movement of the antennae relative to the upper block.
Are you confused or joking?

The antenna does not punch a hole in the roof, if anybody believes that. But the roof drops at least 25 meters while the perimeter columns in the initiation zone below floor 98 are still intact. Explain that! What structure is damaged between floor 98 and the roof - the solid upper block that shall initiate the collapse?

 

[DGM]

The antenna does not punch a hole in the roof, if anybody believes that. But the roof drops at least 25 meters while the perimeter columns in the initiation zone below floor 98 are still intact. Explain that! What structure is damaged between floor 98 and the roof - the solid upper block that shall initiate the collapse?

What happened to the hat truss and the floor truss to core column connections above the A/C damage to cause this drop?

 

[Furcifer]

The antenna does not punch a hole in the roof, if anybody believes that. But the roof drops at least 25 meters while the perimeter columns in the initiation zone below floor 98 are still intact. Explain that! What structure is damaged between floor 98 and the roof - the solid upper block that shall initiate the collapse?

On my screen is moves about 3cm, as the upper block tilts and falls. 3cm appears to be about 1 floor. You're looking at one corner(right) of the building obviously. The antennae tilts in the direction of the most damage(left).
Yes, the upper block looks to be taking the brunt of the initial 3cm decent in the left corner, but not so much in the right (forgive me, I forget which corner is which NE, SE feel free to correct me)

The upper block was most certainly not "solid". I think you mean "ridgid".

 

[Apollo20]

A little bit of trig!

Heiwa and realcddeal:

In order to measure the relative drops of the antenna and the roof line of WTC 1 you MUST consider the tilting of the upper block. This means you must look at videos taken from any direction but due north of the tower since WTC 1 tilted to the south as it dropped.

The videos that show both the north face AND the west face of WTC 1 allow the rate of tipping of the upper block to be measured and we can then estimate that the antenna was about 3 degrees off vertical about 2 - 3 seconds into the collapse. This is quite significant in any calculation of the APPARENT vertical drop of WTC 1.

A little trig shows that for an upper tilting block of height h meters, with a tilt angle theta degrees, and a roof line drop of x meters,

x = h[1 - cos(theta)]

Now consider a point on the antenna located at a height A meters above the roof line and consider the width of the tower to be w meters, then if a is the antenna drop,

a = [ A + h ].[ 1 - cos(theta)] + w/2 sin(theta)

This shows that a is always greater than x so that the antenna will always APPEAR to drop more than the roof line.

And by the way, in using any video to estimate drop distances you also need to factor in the foreshortening introduced by the camera viewing angle.

 

[Tony Szamboti]

No, you didn't quote the mad Irishman. You just said he stated something. That's not quoting. Okay, well maybe it is in the truther universe. I'd like to see the actual full-context of that statement.



And you would be wrong.



And this apparently applies to the things you read as well.

It sounds like you aren't considering that the beams act like solid guy wires, in that they take out the moments from the column. Your diagram needed to include the beams adjacent to that frame which are then tied to the remaining massive structure whose inertia will act like an anchor. If you had beams on either side of that frame they would have been in tension removing the moment from the columns. You aren't showing the whole picture.

As for the quote from Timoshenko and Gere I have the fourth edition and it is in Chapter 11 in section 11.5 "Columns with eccentric axial loads" on the last paragraph of page 760. It will probably be at the end of that section in other editions. I will quote them exactly

"In the case of a column fixed at both ends against rotation, the concept of an eccentric load acting at the end of the column has no meaning. Any moment applied at the end of the column is resisted directly by the supports and produces no bending of the column itself."

 

[Tony Szamboti]

Heiwa and realcddeal:

In order to measure the relative drops of the antenna and the roof line of WTC 1 you MUST consider the tilting of the upper block. This means you must look at videos taken from any direction but due north of the tower since WTC 1 tilted to the south as it dropped.

The videos that show both the north face AND the west face of WTC 1 allow the rate of tipping of the upper block to be measured and we can then estimate that the antenna was about 3 degrees off vertical about 2 - 3 seconds into the collapse. This is quite significant in any calculation of the APPARENT vertical drop of WTC 1.

A little trig shows that for an upper tilting block of height h meters, with a tilt angle theta degrees, and a roof line drop of x meters,

x = h[1 - cos(theta)]

Now consider a point on the antenna located at a height A meters above the roof line and consider the width of the tower to be w meters, then if a is the antenna drop,

a = [ A + h ].[ 1 - cos(theta)] + w/2 sin(theta)

This shows that a is always greater than x so that the antenna will always APPEAR to drop more than the roof line.

And by the way, in using any video to estimate drop distances you also need to factor in the foreshortening introduced by the camera viewing angle.

Dr. Greening, tilting and foreshortening was taken into consideration in the measurements I was mentioning, which will be the subject of a new paper on the issue.

 

[DGM]

Dr. Greening, tilting and foreshortening was taken into consideration in the measurements I was mentioning, which will be the subject of a new paper on the issue.

Tony:
Maybe you can tell me. What happened to the hat truss system and the floor truss to core connection to allow the antenna to drop without the parameter columns being effected?

 

[Tony Szamboti]

Well we solved it then. Fire.

There is no physical evidence of high steel temperatures. Why not?

 

[Tony Szamboti]

Tony:
Maybe you can tell me. What happened to the hat truss system and the floor truss to core connection to allow the antenna to drop without the parameter columns being effected?

If you have been following what I have been saying you will realize that I believe the central core columns were taken out at the collapse zone and below and this would have caused a huge plate load in the roof plate and hat truss due to the unsupported core pulling down on it from the center. This would have caused the upper areas to drop, center first.