29 Structural & Civil Engineers Cite Evidence for Controlled Explosive Demolition

[The Platypus]

It's funny how Chris has no credentials, no expertise, no education, no experience in what he is talking about and yet he continuously sits there telling others that they aren't qualified enough to know what they are talking about.

 

[The Platypus]

Most of the world's experts are not interested but that is changing, inexorably.

No it isn't. You are delusional...

 

[Christopher7]

You had two quotes. This one, doesn't exist:

My bad. I used the wrong reference

1-9 Vol.2 pg 588 [pdf 250] 9-1 Vol.2 pg 586 [pdf 248]
"As the interior columns failed. the exterior columns on the west face buckled inward at the lower floors as a result of floor pull-in forces due to the downward movement of the building core. The floor connections to the columns had not failed in this region [columns 59 & 62] because there were no fires observed on the west side on floors 10 through 14 at any time during the day, and the intact floors were able to pull the exterior walls inward."

Furthermore, I've already explained to you that the columns lost lateral support WHEN the exterior columns buckled. This happened AFTER the connections from the floor diaphragm around columns 59 and 62 were able to pull the west face IN.

You have that backwards.
"the intact floors were able to pull the exterior walls inward." - correct, however;

The core girders were supporting the floors and they would have to fail first, then the falling floors could pull the exterior columns inward.

The core girders supporting the floors were also providing north-south lateral support to column 59.

Those girders did not fail on floors 11-15 because there were no fires in that region on floors 10-14.

Columns 59 & 62 did not loose support in the north-south direction on floors 11-15.

Furthermore, there is no mention of damaged floor-to-column connections around columns 59 & 62 on any floor.
and:
Column 68 was in an elevator shaft and did not loose north-south lateral support on any floor.

 

[Cl1mh4224rd]

The core girders were supporting the floors and they would have to fail first, then the falling floors could pull the exterior columns inward.

Not if the heat caused to them to sag, shortening the horizontal distance between core columns and exterior columns, thus pulling the exterior columns inward. The outwardly visible effects of this scenario were easily observed.

 

[Christopher7]

Not if the heat caused to them to sag, shortening the horizontal distance between core columns and exterior columns, thus pulling the exterior columns inward. The outwardly visible effects of this scenario were easily observed.

You missed this:

"Those girders did not fail on floors 11-15 because there were no fires in that region on floors 10-14."

Reference:
9-1 Vol.2 pg 586 [pdf 248]
"The floor connections to the columns had not failed in this region because there were no fires observed on the west side on floors 10 through 14 at any time during the day, and the intact floors were able to pull the exterior walls inward."

The columns had to fail at the core to pull the exterior columns inward.

 

[Newtons Bit]

My bad. I used the wrong reference

1-9 Vol.2 pg 588 [pdf 250] 9-1 Vol.2 pg 586 [pdf 248]
"As the interior columns failed. the exterior columns on the west face buckled inward at the lower floors as a result of floor pull-in forces due to the downward movement of the building core. The floor connections to the columns had not failed in this region [columns 59 & 62] because there were no fires observed on the west side on floors 10 through 14 at any time during the day, and the intact floors were able to pull the exterior walls inward."

I'm happy you admitted you used the wrong reference.

You have that backwards.
"the intact floors were able to pull the exterior walls inward." - correct, however;

The core girders were supporting the floors and they would have to fail first, then the falling floors could pull the exterior columns inward.

[/B]

Okay, I'll walk you through this.

1st. The east floor fails.
2nd. As the east floor moves downwards, it introduces tension forces into the floor system. The beam-beam and beam-column connections on the west side of the building are intact. These connections transfer this pull in force to the exterior columns because the exterior columns have the stiffness to resist this force.
3rd. The exterior columns fail. When the exterior columns fail, there is no stiff lateral system to brace the columns.
4th. The interior line of columns that you are referring to fail first in NIST's model. Though the timeline for this is minisicule.

Do you follow?

 

[triforcharity]

.....That is nonsense.......
That did not happen.

Ok, then please explain this illustration to me please.
If there was not a seperate independant collapse in the west side of the building, than please explain this illustration. From NIST NCSTAR 1-9 Vol 2

Please explain the left side of the very first image. If this is not a collapse independant of the East core, than what is it???

 

[triforcharity]

....

The collapse on the east side of the building CAUSED a collapse on the west side, BEFORE the collapse itself got there. Even tho there were "uncollapsed" sections of the building in between.

How?

An exercise for the students... Pop quiz on Monday......
I hope everyone has a great 4th of July. Stay safe.

Tom

Professor Tom,

I think I would like to try to answer that question.

As the collapse occured near the East core, specifically column 79,80, and 81.

This caused the west side of the building to deflect towards the east. This deflection was said to be more than 1m or 3'3"+/-

This deflection put massive strain on the West core's vertical colums and connections. Because of the damage noted from the collapse of WTC 1, it was already structurally compromised. At some point, the stress of the horizontal deflection to the East became too much for the East core columns and beams/girders to handle, and began to fail at critical connection points.

See this illustration From NIST NCSTAR 1-9 Vol 2. Not sure of the page though.

Is that correct???

 

[tfk]

Professor Tom,

I think I would like to try to answer that question.

As the collapse occured near the East core, specifically column 79,80, and 81.

This caused the west side of the building to deflect towards the east. This deflection was said to be more than 1m or 3'3"+/-

This deflection put massive strain on the West core's vertical colums and connections. Because of the damage noted from the collapse of WTC 1, it was already structurally compromised. At some point, the stress of the horizontal deflection to the East became too much for the East core columns and beams/girders to handle, and began to fail at critical connection points.

See this illustration From NIST NCSTAR 1-9 Vol 2. Not sure of the page though.

http://i63.photobucket.com/albums/h131/triathlete247/1WTC7p83a.jpg

Is that correct???

You are on the right track, I believe.

A couple of questions to help...

First one:

1. In general, would you characterize the structure as brittle or ductile?

2. Which supported which? Floors supported columns? Or columns supported floors?

3. Do you recall Castigliano's theorem? What role might it play in the break-up?

4. Describe briefly the damage done to the structure of the building on the south wall. Think in 3D terms.

That'll do.

Have a good weekend...

Tom

PS. Beware trick questions...

 

[Grizzly Bear]

For ****'s and giggles I'll give it a try... I need some practice in something that somewhat relates to my education, and I haven't done enough writing recently

1. In general, would you characterize the structure as brittle or ductile?

It would be a bad thing if the steel itself were brittle. I'll cautiously answer ductile in the context that the steel fails when it reaches its plastic limit. Hopefully this sounds like it's moving it the right general track when it comes to the structure as a whole.

2. Which supported which? Floors supported columns? Or columns supported floors?

Both when you consider how the structure was built. The floor structure provides a load path to the columns, as well as crucial lateral stability which enables the columns to transfer their loads to the foundation and ground. However this works most effectively with the structure preferably intact

Key to the point, the floors need the columns to stand, but the same is true for the columns in this case. Since when we think of the building as a whole one cannot function properly with out the other.

3. Do you recall Castigliano's theorem? What role might it play in the break-up?

I'll flat out tell you this is a new one for me. *Looks up the theorem*
Going by what I'm seeing of the definition I would say this concerns how changes in the load paths impact other parts of the structure. Displacement would have been particularly crucial given the long span floor construction in WTC7, and the particularly large floor area each column was assigned to support. I'm not sure how far I can get into detail with this, but I should at least be moving in the right direction with this.

4. Describe briefly the damage done to the structure of the building on the south wall. Think in 3D terms.

As the internal structural failure progressed westward relative to the south face, the loads were increasingly shifted to remaining alternative load paths, until the primary structural integrity that remained was insufficient to carry the loads. When the internal structure failed, the south wall also subsequently failed.

PS. Beware trick questions...

Accounted for, and explained accordingly in my answers. I may have fallen for one of them...but I haven't had to answer questions like these in a while.

 

[triforcharity]

You are on the right track, I believe.

A couple of questions to help...

First one:

1. In general, would you characterize the structure as brittle or ductile?

2. Which supported which? Floors supported columns? Or columns supported floors?

3. Do you recall Castigliano's theorem? What role might it play in the break-up?

4. Describe briefly the damage done to the structure of the building on the south wall. Think in 3D terms.

That'll do.

Have a good weekend...

Tom

PS. Beware trick questions...

Well, I would consider this building brittle becaause of the type of construction first off. It isn't like a traditional concrete and steel building. It was predominitly steel. Adding on to that, the fact that WTC1 had taken huge chunks out of it when it (WTC1) collapsed, therefore providing added structural stress. This is noted in many reports. Specifiacally NIST NCSTAR 1-9 Volumes 1,2, and 2a.
The next reason I believe this building to be "brittle" was because there were fires over many floors that were allowed to burn over many hours. Steel is not very friendly with fire. Steel will become comprimsed at aproximitly 1100 Deg. F. With fires ragin out of control, with no firefighting effort whatsoever for many hours, the steel was bound to fail.
Also, the last reason I believe that WTC was brittle was because the FDNY waas specifically quoted as saying that they observed a bulge in the East face (I am not certain, but I believe this to be correct) and that they believed that the building was structurally compromised. I personally witnessed the bulge in the face of WTC 7, but did not witness the collapse.

"2. Which supported which? Floors supported columns? Or columns supported floors?"

Both. I believe that the columns provided the vertical support for the floors. But, the floors themselves provided the horizontal support for the columns. The columns would not have been able to stand vertically on their own without some kind of support. Same for the floors. Without the columns, obviously they would not have been in place. Unless someone has invented an anti-gravity machine that I am not awaare of.

"3. Do you recall Castigliano's theorem? What role might it play in the break-up?"

Which one, his first theorem or second?? I will assume the first because the second deals with displacement if I am not misstaken.

(BTW, I slept through most of my physics classes in HS, so I am going to try my best.)

His first theorem deals with the forces in an elastic structure. I am not sure what exactly that means, but I will take an educated guess.

It is (I believe) it means that that the component in a certain direction of deflection at the point of application of an external force is equal to the partial sum of the work of deformation to the component of the force in that direction.

Now, apply it to this.......Holy crap professor, you do know I am a fireman right??

I believe it is saying that when a beam or piece of material is forced to do something, that when it goes beyond it fail strength, it will force that material to go whichever direction that the the material that is forcing it to go.
Its the best I got.


"Describe briefly the damage done to the structure of the building on the south wall. Think in 3D terms."

Ok, I believe you are talking about the damage done by the colapse of WTC1 and the damage it imposed on WTC 7.

When WTC 1 collapsed, copious amounts of structrual steel were said to have "sliced" the SW corner of WTC 7 for about 15-20 stories. ( I don't recall the SW tower, but who the hell knows)

This was confirmed with pictures that there were in fact damage in that area. Since that area waas damaged by the collapse, than its structural integrity was compromised. Becaause the floors were holding the columns, and vice versa, the floors did not give the columns the support it needed, so in turn the floors could not recieve the support they needed. (Not sure which occured first. This is a little on the lines of the Chicken or the Egg first) This would have put that area under quite extensive amounts of stress. Now, once the East core began to collapse, it amplified the damage on the West side exponentionally. Meaning, because now it has to support more weight, and it has more Eastward deflection, its failure was imminent.



Right?? Now, rememeber, I am a fireman, not an engineer. I can build you one heck of a wood porch though!!

 

[Regnad Kcin]

Intellectual cowardice.

You will not answer the question directly.

Please answer this question directly:

How do you propose that a plot, plan, or conspiracy which would be 100% impossible to enact, not to mention cover up for all time, is possible?

Well? A simple, direct question. How do you make possible the impossible?

 

[triforcharity]

Easy answer, Strap it into a 767 and drive in into a building.

der.

 

[FineWine]

First of all, you are an anonymous poster and until you are willing to state your real name and credentials your claims have no value in the real world.

You too have "moved the goalposts" to "They haven't written papers like Bazant"

The 29 structural engineers and other professionals have gone on record as supporting CD. They have the courage and integrity to give their names and credentials. These are qualities you do not possess.

You've been caught lying again. Among your so-called "structural engineers" are a lunatic who works on oil rigs and dreams that the towers were nuked, a gentleman in his late eighties who has never read a word about the events of 9/11 that didn't appear on a loon site, and a host of people who simply are NOT structural engineers. Do you still want to prattle about "credentials"?

Not a single member of Gage's gaggle of frauds and fools has come close to explaining how the miraculous soundless explosives found their way into the towers and went off on the exact floors struck by the hijacked planes (incdientally, who hijacked those planes?).

You have done very badly here.

 

[FineWine]

Well Chris,

This is a legacy note that I wrote to you. I was gonna toss it, because I'm not going to bother debating you anymore. I've been struggling to find some redeeming feature in your character here that'd justify it. Can't find one. Especially the insulting 'tude.

So, here's some more bad news for ya regarding fall times. Trust me, I KNOW that you won't get it...

Since it appears that numbers & math discussion means nothing to you, I thought that I'd draw you a picture.

I've calculated the acceleration of the roofline of WTC7 using NIST's data (same as Chandler's) and the mathematical technique that Chandler used on the raw data - the "center difference approximation" (aka, "CDA") that I said introduced noise into the conclusions. The purpose of this is to show you HOW MUCH noise this technique puts into the analysis.

Chandler took the perfectly good position data, and performed a CDA to get velocities. He assumed that these velocities were appropriate for the midpoint in time between his position data points.

I have done exactly the same thing, only one more time. (Hey, if the technique is good once, it must be good twice, right??) I took the velocity data and applied a CDA to calculate acceleration, and assumed that acceleration would be true for the midpoint in time between the velocity data points.

Here are the results.

[qimg]http://www.internationalskeptics.com/forums/%5Bimg%5Dhttp://www.internationalskeptics.com/forums/vbimghost.php?do=displayimg&imgid=16761%5B/img%5D[/qimg][qimg]http://www.internationalskeptics.com/forums/picture.php?albumid=176&pictureid=1276[/qimg]


There are 4 plots of acceleration vs. time on this graph.

1. An object that is REALLY in free fall (red line)
2. My calculation of acceleration vs. time from a double differentiation of the position vs. time data. (blue line)
3. Chandler's reported "constant approximately G" value (heavy green straight line between 1.75 & 4.0 seconds.)
4. The Instantaneous accelerations, based on "Central Difference Approximation" applied to the calculated velocities. (light green wavy line.)

The heavy green line IS, in fact, the "linear average" of that ridiculously wavy light green line. Pretty gacky data, eh Chris?

Chris, this is the REAL results of plotting Chandler's conclusions, using Chandler's method. I simply used Chandler's method one more time than Chandler did.

So, while you're moaning & groaning that MY analysis cannot be right because it produces short term accelerations up to 108% of free fall, I will point out to you that Chandler's calculation show short term accelerations of 133% of free fall acceleration. And then 94% G, 163% G, 42% G, 132% G, 73% G, 130% G, 32% G & 111% G.

Which Chandler then took and "linearized" to 101% G.

And verbalized to "essentially free fall".

I don't suppose that ANY of this is sinking in...

Tom.

PS. BTW, Chris, this is a quote taken directly from Chandler's website: It refers to his previous calculation of the acceleration of the fall of the WTC towers.

From: http://www.911speakout.org/
Faster than Gravity (Removed)
"I removed this video because when I did additional runs at different resolutions, I always got extreme accelerations, but not the same amounts in the same places. This made me skeptical of the procedure. Finding accelerations from position data involves double numerical differentiation, a process that can amplify "noise" in the data. The raw data in this analysis is the inherently noisy positional measurement of cloudy material, and the conclusions were based on the short term variations in the acceleration. This raises the likelihood that the extreme accelerations are artifacts. The WTC7 measurements (above) do not suffer the same defect because (1) they are measuring the motion of a more definite point of solid material, and (2) the conclusions are based on long term average acceleration."

Any of that sound familiar, Chris. Can you read into Chandler's (admirably honest) statement here that there are potential sources of error (aka "artifacts") that are purely the result of mathematical technique. Have you learned that all experimental technique is not created equal?

Naahhhh. What was I thinking...??

This is hopeless . Chris didn't understand a word you wrote.l

 

[dropzone]

Is one difference between us and truthers the reaction, "I don't entirely get this math, but wait while I grab my TI-86?"

 

[triforcharity]

Hey, I even ADMITTED I slept through my physics classes in high school!! They HAD to make that class FIRST period, didn't they??? ITS A CONSPIRACY!!!!!!!!!!

 

[alienentity]

Most of the world's experts are not interested but that is changing, inexorably.

You wish.

 

[Oscar]

Finewine:

You've been caught lying again.

Correct. Why do these people do it? I don't get it.

 

[tfk]

Griz & Tri,

Both of you guys get excellent marks.

1. Brittle vs. ductile: Both. The concrete floors brittle. The steel ductile. The most difficult design case.

So you have a problem is when you have composite structures like this: The building has to flex a certain amount (earthquake, wind & thermal expansion). But they never flex the amounts that happened in the damage / heating / sagging. To say nothing of the load shifting as the building started to collapse.


2. Floors & columns. You both got this right. Each supports the other.
The floors give a tremendous amount of lateral stiffness to the columns, keeping them aligned. The columns & girders provide a flat support for the poured concrete floors. Until they sag & the concrete cracks. And then the concrete doesn't support the columns any more. Viscous circle.

3. Castigliano's Theorem. This is simply a statement of conservation of energy (actually equivalence of work & energy).
The amount of work that one does on any member (column, beam, whatever) is equal to the energy stored in that member. Work is force x deflection. For a beam loaded below the elastic limit, that's equal to W = 1/2 F*d. This amount of energy is stored in the beams. And the total amount is considerable. They're in general loaded up to about 20 - 30% of their elastic limit. With another 40% or so reserve capacity before you get to the ultimate strength.

The whole structure is locked & loaded (literally) during its construction. But the damage to the building (physical & thermal) is unlocking that stored energy in several areas.

And all those stressed members are basically giant compressed springs. When they suddenly give way, there is an enormous amount of energy that is released. This released energy & motion is a second source (in addition to just falling debris) of a lot of damage.

4. The damage on the south west wall.
I'm getting at "what caused the second collapse to start in the west core?" with this question.

I'm not thinking about the corner. This was scooped out, but doesn't strike me as a huge problem. (I could be wrong on that one, I'm going by feel.) It seems that the large deep gouge in the south wall was a serious problem tho.

Unless otherwise noted, I'll be using NCSTAR1-9A, and I'll give the pdf page numbers.

Pay attention to the areas of interest near the west core for the following...

The construction:
First get a sense of the lateral supports (both concrete and the framing) near the damaged area of the south wall.

For a typical floor's bracing, look at Fig 3-29 (pg 90). Think about this floor. Strong, somewhat ductile vertical & horizontal beams, and a strong, brittle membrane of concrete. There are several cut-outs in the concrete for the elevator & stairwells. Now look at the floors from the 2nd (fig 3-23) to the 8th (Fig 3-29).

Pay special attention to the importance of the 5th floor. This is because of the giant cut outs & lack of lateral bracing on the 4th & 6th floor. Here's an image of the 5th floor diaphragm bracing. Fig 3-45 (pdf pg 99). Notice all the triangular bracing that produces a very strong frame. (Much stronger than rectangular bracing.)

The physical damage
Now imagine what happens if, in the area of columns 66 & 69, if that 5th floor gets removed by a couple hundred tons of falling debris. Suddenly, you've got a 3 floor section with no lateral support to the outside. In the case of WTC7, it was worse, because the damage reached up to the 12th floor.

As seen here: These figures are in NCSTAR1-9 vol1
Floors 5 & 6: Fig 5-94. Remember. This destabilized the core columns from the south side for 3 stories. Because there was NO support on the 4th & 6th floor.
Floors 7
Floors 8, 9, 10 & 11 Fig 5-96 - 5-98. Massively damaged. All core destabilized towards the south.

Another view of the accumulated damage:
Fig 4-10 & 4-11. (pdf pg 123). Also Fig 3-60 shows the damage and deflections that resulted, running all the way to the roof. Deflections are going to generally correlate with stresses.

Note also that the damage to the building that NIST applied was very neat & surgical. The reality was certainly very different. I would be stunned if several of the concrete floors did not fracture (but not fall) from the outside wall to the cores.

So, when you add it up, suddenly you've got a couple of columns adjacent to the core that have lost their lateral support from the south for about 9 stories. And several of them have had their connections severed, as shown (for Floor 13) in NCSTAR1-9A Fig 4-20.

This building was fatally wounded in the collapse. It probably would have survived if the collapse on the east side did not happen. But the damage to the core, removed all safety margins.

As soon as the collapse on the east side began, the building starts shifting, loads get squirrelly, and a second collapse zone opens up in the core area behind giant gash.

There is nothing surprising or inexplicable about any of it.

Later.

Tom

PS. OK, now I'm going to bed...