Charlie Thornton discussing a plane possibly hitting the WTC

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Jeffrey Orling

Senior Member
So what about Thornton saying this............Do you just dismiss that?
Gerry,

He's right of course... no plane is going to knock any skyscraper over. It's the nature of the structure and the forces. You know that...

By the way... I worked on the 74th floor of the ESB and had a window office facing south... I wonder if that was were the plane had hit a few decades earlier? If so they did a great job cleaning it up... you'd never know.
 

gerrycan

Banned
Banned
Gerry,

He's right of course... no plane is going to knock any skyscraper over. It's the nature of the structure and the forces. You know that...

By the way... I worked on the 74th floor of the ESB and had a window office facing south... I wonder if that was were the plane had hit a few decades earlier? If so they did a great job cleaning it up... you'd never know.
I remember reading that the ESB plane was a wayward B25 disorientated in foggy conditions.
So we both agree with Thornton that the impact itself wouldn't be enough to damage the WTC to the extent that the structural integrity would be compromised enough to cause collapse, so then we have the resultant fires.
This from John Skilling, who was the lead structural engineer on the twin towers.
"Our analysis indicated the biggest problem would be the fact that all the fuel (from the airplane) would dump into the building. There would be a horrendous fire. A lot of people would be killed," he said. "The building structure would still be there."
Indicates that by his analysis, the fire would also not damage the building to the extent that a collapse would occur. I believe you can view his analysis in the book 'city in the sky'. He was interviewed after the '93 attack by the Seattle Times, here
http://community.seattletimes.nwsource.com/archive/?date=19930227&slug=1687698
 

Jeffrey Orling

Senior Member
I remember reading that the ESB plane was a wayward B25 disorientated in foggy conditions.
So we both agree with Thornton that the impact itself wouldn't be enough to damage the WTC to the extent that the structural integrity would be compromised enough to cause collapse, so then we have the resultant fires.
This from John Skilling, who was the lead structural engineer on the twin towers.
"Our analysis indicated the biggest problem would be the fact that all the fuel (from the airplane) would dump into the building. There would be a horrendous fire. A lot of people would be killed," he said. "The building structure would still be there."
Indicates that by his analysis, the fire would also not damage the building to the extent that a collapse would occur. I believe you can view his analysis in the book 'city in the sky'. He was interviewed after the '93 attack by the Seattle Times, here
http://community.seattletimes.nwsource.com/archive/?date=19930227&slug=1687698
Skilling was wrong. The fires would not destroy all the steel for sure... but with the plane destruction having knocked out a large % of the axial capacity... the heat was able to do the rest to set the thing into collapse mode. This was complex and likely (guess) involved the failing of the beam stub outlookers (connections) to the belt girder leading to the inboard side of the floor system collapsing. That turned into several more problems... increased in unbraced length... and loss OF bracing . Column to column connections in the twin towers were unrestrained and more easily pushed laterally off alignment. But the collapse was driven by the collapsing floor mass outside the core we call ROOSD and inside the core (there was considerable floor area in the core at the upper floors of each of the three sections of the towers... which I call RICD (runaway inside the core destruction).

Once this got going the core columns simply lost 90% of their bracing (you can see that only rows 500 and 600 remain connected by bracing... the rest were completely unbraced by the RICD)... all the columns toppled from Euler forces.

So Skilling needs to bone up on how his tower came apart. It's been figured out...
 
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Tony Szamboti

Active Member
Skilling was wrong. The fires would not destroy all the steel for sure... but with the plane destruction having knocked out a large % of the axial capacity... the heat was able to do the rest to set the thing into collapse mode. This was complex and likely (guess) involved the failing of the beam stub outlookers (connections) to the belt girder leading to the inboard side of the floor system collapsing. That turned into several more problems... increased in unbraced length... and loss OF bracing . Column to column connections in the twin towers were unrestrained and more easily pushed laterally off alignment. But the collapse was driven by the collapsing floor mass outside the core we call ROOSD and inside the core (there was considerable floor area in the core at the upper floors of each of the three sections of the towers... which I call RICD (runaway inside the core destruction).

Once this got going the core columns simply lost 90% of their bracing (you can see that only rows 500 and 600 remain connected by bracing... the rest were completely unbraced by the RICD)... all the columns toppled from Euler forces.

So Skilling needs to bone up on how his tower came apart. It's been figured out...
It is provable that the aircraft impact knocked out no more than about 17% of the axial capacity in the North Tower. The number of severed or severely damaged perimeter columns is known and was no more than 35. The wings never made it to the core and even if the fuselage went completely through the building it was only 16.5 feet in diameter and would have been limited to taking out no more than 12 core columns based on its size and volume. So that would be 47 columns out of 283 which is 17%.

John Skilling also said that the tower structure was so robust that you could remove one exterior face and its corners completely and every other exterior column (half the columns) on the sides and it could still take a 100 mph wind. So here he is saying 118 columns could have been removed, which is about 42%, and that the building could have survived a very severe wind event. Do you think he was wrong here also? If so, can you provide some simple calculations showing why?
 
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Jeffrey Orling

Senior Member
It is provable that the aircraft impact knocked out no more than about 17% of the axial capacity in the North Tower. The number of severed or severely damaged perimeter columns is known and was no more than 35. The wings never made it to the core and even if the fuselage went completely through the building it was only 16.5 feet in diameter and would have been limited to taking out no more than 12 core columns based on its size and volume. So that would be 47 columns out of 283 which is 17%.

John Skilling also said that the tower structure was so robust that you could remove one exterior face and its corners completely and every other exterior column (half the columns) on the sides and it could still take a 100 mph wind. So here he is saying 118 columns could have been removed, which is about 42%, and that the building could have survived a very severe wind event. Do you think he was wrong here also? If so, can you provide some simple calculations showing why?
It's provable?

Prove it.

The facade was a vierendeel truss with very tall spandral plates... it was not a series of columns as you are trying to portray... the facade unlike a row of columns... acted like a diaphragm... one that both resisted wind loads (horizontal) and axial loads (floor and columns from above)

What Skilling said about the stength of the facade is irrelevant to the mechanism of collapse - ROOSD ... it did not involve the facade. The facade was the victim of ROOSD... no lateral support... tippa canoe and over they go..
 

Alienentity

Active Member
At the time the study was done (in the mid 1960's) they didn't have the math capabilities to calculate fuel loads and so on, as a modern FEA and fire analysis can do.
They made some guesstimates based on the likely speed of the aircraft, but they didn't know for certain.

The biggest motivator for them at the time was countering critics who worried that another plane was going to crash into the towers. Turns out those fears were justified, and not in a way that anyone envisioned.

The inward bowing of the perimeter columns showed that progressive failure was underway, and this was due demonstrably to impact and fire alone. This still is the hypothesis which fits the facts best. Why you must attempt to minimize what actually happened and emphasize what you imagine happened is just due to your bias.
Why not just let the facts speak for themselves and live with the consequences?
 

Alienentity

Active Member
It's provable?

Prove it.

The facade was a vierendeel truss with very tall spandral plates... it was not a series of columns as you are trying to portray... the facade unlike a row of columns... acted like a diaphragm... one that both resisted wind loads (horizontal) and axial loads (floor and columns from above)

What Skilling said about the stength of the facade is irrelevant to the mechanism of collapse - ROOSD ... it did not involve the facade. The facade was the victim of ROOSD... no lateral support... tippa canoe and over they go..
That's right - the sagging trusses and inward bowing of the perimeter are clear consequences of the impact and fire. It can never be ruled out that this was the mechanism of collapse, even if other much more complex scenarios are theoretically possible. But which explanation fits the evidence better?

The only reason Skillings is mentioned is because he tends to argue against the conventional understanding. But Leslie Robertson, on the other hand, who also was the chief engineer and knew of the impact study, says that he agrees with the impact/fire hypothesis. You have equal testimony which supports the conventional hypothesis, which is treated like garlic to a vampire by the truth community.
And Robertson is on record that he carried the calculations far enough such that
He's very clear about it.
 

Jeffrey Orling

Senior Member
A

The inward bowing of the perimeter columns showed that progressive failure was underway, and this was due demonstrably to impact and fire alone. This still is the hypothesis which fits the facts best. Why you must attempt to minimize what actually happened and emphasize what you imagine happened is just due to your bias.
Why not just let the facts speak for themselves and live with the consequences?
No this is not the explanation for the inward bowing. It's more inline with the NIST explanation which (is incorrect) and posits that the trusses pulled in the facade. Would that be all 4 sides? Where was the pull in from the trusses? Where was all that sagging? which side? Why there?
 

Jeffrey Orling

Senior Member
That's right - the sagging trusses and inward bowing of the perimeter are clear consequences of the impact and fire. It can never be ruled out that this was the mechanism of collapse, even if other much more complex scenarios are theoretically possible. But which explanation fits the evidence better?

The only reason Skillings is mentioned is because he tends to argue against the conventional understanding. But Leslie Robertson, on the other hand, who also was the chief engineer and knew of the impact study, says that he agrees with the impact/fire hypothesis. You have equal testimony which supports the conventional hypothesis, which is treated like garlic to a vampire by the truth community.
And Robertson is on record that he carried the calculations far enough such that
He's very clear about it.
Robertson appears to understand that his floor trussed supported floors would lead to a ROOSD collapse.. which it did. Both of them share in my opinion responsibility for some boneheaded decisions probably driven by PANY pressure to make the towers cheap and easy to build.

The inward bowing was from buckling not from pull in... Why buckling? Because it corresponds to the core column destruction opposite to where the IB was. This also kicked of the twist. torsion and mis alignment of the top (facade faces)... a few trusses on one floor are not going to displace the entire 40-50,000 tons of the top... or...

gimme a break. You don't believe this nonsense do you?
 

Alienentity

Active Member
Robertson appears to understand that his floor trussed supported floors would lead to a ROOSD collapse.. which it did. Both of them share in my opinion responsibility for some boneheaded decisions probably driven by PANY pressure to make the towers cheap and easy to build.

The inward bowing was from buckling not from pull in... Why buckling? Because it corresponds to the core column destruction opposite to where the IB was. This also kicked of the twist. torsion and mis alignment of the top (facade faces)... a few trusses on one floor are not going to displace the entire 40-50,000 tons of the top... or...

gimme a break. You don't believe this nonsense do you?
No this is not the explanation for the inward bowing. It's more inline with the NIST explanation which (is incorrect) and posits that the trusses pulled in the facade. Would that be all 4 sides? Where was the pull in from the trusses? Where was all that sagging? which side? Why there?
This is OT to the OP, the reason I mentioned it was because it attests to gradual failure of the structure due to fires. You may indeed feel that the mechanism is different from what I described, but again this was a response to the idea that somehow the engineers in the 1960's had the time and maths to actually figure out the implications of a plane impact and fires.

Nobody has a copy of the study, and it appears it was done to placate the fears of the tall tower critics, so it's not certain that it was realistic.
 

Jeffrey Orling

Senior Member
Actually the issues at the wtc don't apply to virtually any other high rise... the wtc were bizarre designs. Of course that is what the NIST should have revealed. But they didn't.
 

Alienentity

Active Member
Actually the issues at the wtc don't apply to virtually any other high rise... the wtc were bizarre designs. Of course that is what the NIST should have revealed. But they didn't.
This could be an excellent area for criticism - that the towers were not as safe as they could have been. I suppose nobody expected the 9/11 attacks, but hindsight is 20/40 (even hindsight isn't perfect in my world).
 

Mick West

Administrator
Staff member
The WTC were perfectly safe for their anticipated use case. If a plane half full of fuel had not flow into them at 500 mph, then they would have been perfectly fine. And structurally they were fine (well, at least not collapsing) after the impact.
 

Tony Szamboti

Active Member
That's right - the sagging trusses and inward bowing of the perimeter are clear consequences of the impact and fire. It can never be ruled out that this was the mechanism of collapse, even if other much more complex scenarios are theoretically possible. But which explanation fits the evidence better?

The only reason Skillings is mentioned is because he tends to argue against the conventional understanding. But Leslie Robertson, on the other hand, who also was the chief engineer and knew of the impact study, says that he agrees with the impact/fire hypothesis. You have equal testimony which supports the conventional hypothesis, which is treated like garlic to a vampire by the truth community.
And Robertson is on record that he carried the calculations far enough such that
He's very clear about it.
We have never seen Robertson's alleged calculations on the effects of an aircraft impact on the twin towers. Many don't know that his college education wasn't even in engineering. Much of what he has learned in engineering has been through on the job training. Look it up if you don't believe me.

I have my doubts that Leslie Robertson was even capable in 1964 of the type of calculations required to determine what effect an aircraft impact would have on the building. It is very likely that he did not know enough at the time.

It also does not make sense that Leslie would do an additional set of calculations when the study was already done with that Skilling refers to in the 1964 white paper addressing the issue.

In addition, the sagging truss theory and inward bowing of the perimeter columns alleged to have been due to it is extremely controversial and very likely to be nonsense. Calculations show the floor system outside of the core to be quite robust, with just a 3 inch deflection at 700 degrees C. The NIST FEA couldn't produce the inward bowing due to truss sagging. They needed to add an artificial lateral load on the columns to produce it.

The sagging trusses seen through the impact hole in the North Tower were caused by the pressures generated by the fuel/air explosion at impact and were not a result of fire heating the trusses and this had nothing to do with the collapse.
 
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Tony Szamboti

Active Member
Actually the issues at the wtc don't apply to virtually any other high rise... the wtc were bizarre designs. Of course that is what the NIST should have revealed. But they didn't.
No, they were not bizarre designs and you couldn't be more wrong here.

The robust exterior tube with a central core, to gain a large moment of inertia on the exterior of the building and more contiguous open space in the interior, was first conceived by Fazlur Khan and has been used on nearly all high rise buildings since the mid 1960s.

See the paragraph on tube structural systems here http://en.wikipedia.org/wiki/Fazlur_Khan
 
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Jeffrey Orling

Senior Member
The WTC were perfectly safe for their anticipated use case. If a plane half full of fuel had not flow into them at 500 mph, then they would have been perfectly fine. And structurally they were fine (well, at least not collapsing) after the impact.
The parts that weren't destroyed by the plane... YES!
 

Jeffrey Orling

Senior Member
No, they were not bizarre designs and you couldn't be more wrong here.

The robust exterior tube with a central core, to gain a large moment of inertia on the exterior of the building and more contiguous open space in the interior, was first conceived by Fazlur Khan and has been used on nearly all high rise buildings since the mid 1960s.

See the paragraph on tube structural systems here http://en.wikipedia.org/wiki/Fazlur_Khan
Name another tower which used long span floor joists

Name another tower built over a power station with massive transfer structures and 60% of the columns of the north face supported on the ends of cantilevers.

You can cite aspects of the towers which were standard practice...such as moment connections... or poured slabs... and even wind shear strategies such as hull and core... Fine.. These features are not what I was referring to as bizarre (my loaded word).
 
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Tony Szamboti

Active Member
Name another tower which used long span floor joists
The Sears Tower has 75 foot long open floors in each of its nine separate stacks. This is 25% longer than the 60 foot long open floors in the Twin Towers.

Name another tower built over a power station with massive transfer structures and 60 of the columns of the north face supported on the ends of cantilevers.
There is no basis for showing this had anything to do with the collapse of WTC 7 and your allegations to the contrary are unsupported, as is much of what you say.

You can cite aspects of the towers which were standard practice...such as moment connections... or poured slabs... and even wind shear strategies such as hull and core... Fine.. These features are not what I was referring to as bizarre (my loaded word).
Your contention that the twin tower design was bizarre is unsupported like almost everything else I have seen you say on the subject.
 

Jeffrey Orling

Senior Member
The Sears Tower has 75 foot long open floors in each of its nine separate stacks. This is 25% longer than the 60 foot long open floors in the Twin Towers.

There is no basis for showing this had anything to do with the collapse of WTC 7 and your allegations to the contrary are unsupported, as is much of what you say.

Your contention that the twin tower design was bizarre is unsupported like almost everything else I have seen you say on the subject.

Sears was a collection of 9 75 x75 squares. Did they use bar truss joists and pre assembled floors with no stone aggregrate 4" slabs?

The twin towers were billed as revolutionary for their design and building technology. They were... You should know this. Stop the BS. I suppose you are too young to remember. There are always books and the way back machine.

What I say elsewhere has no bearing on the crazy design of the towers.
 

Tony Szamboti

Active Member
Sears was a collection of 9 75 x75 squares. Did they use bar truss joists and pre assembled floors with no stone aggregrate 4" slabs?

The twin towers were billed as revolutionary for their design and building technology. They were... You should know this. Stop the BS. I suppose you are too young to remember. There are always books and the way back machine.

What I say elsewhere has no bearing on the crazy design of the towers.
There is no BS. The floor systems outside of the core were quite robust and I am sure you can't show otherwise. I am sure you don't even know what the moment of inertia was for the composite floors with trusses in the towers and are saying what you are based on your erroneous perception that they were somehow lacking because they used trusses.
 

Jeffrey Orling

Senior Member
There is no BS. The floor systems outside of the core were quite robust and I am sure you can't show otherwise. I am sure you don't even know what the moment of inertia was for the composite floors with trusses in the towers and are saying what you are based on your erroneous perception that they were somehow lacking because they used trusses.
Wrong. They weer "lacking" because they used no stone aggregate "concrete" was more like leveling grout. They used very little reinforcing as far as I can tell, the pans were 22 ga which is .03" thick. they were bearing on small seats with only 4 bolts securing them to the seat. Trusses can be fine. I don't think these could be called robust.

So what other office towers use bar trusses for office live loads?

Listen to Charles Thornton and take it up with him... if he's still alive.
 

George B

Extinct but not forgotten Staff Member
The negative personal references are not contributing to this Thread . . . I reserve the right to delete any future violations of our politeness policy . . . please maintain an objective debate referring to the facts not personalities . . . Thanks!
 

Tony Szamboti

Active Member
Wrong. They weer "lacking" because they used no stone aggregate "concrete" was more like leveling grout. They used very little reinforcing as far as I can tell, the pans were 22 ga which is .03" thick. they were bearing on small seats with only 4 bolts securing them to the seat. Trusses can be fine. I don't think these could be called robust.

So what other office towers use bar trusses for office live loads?

Listen to Charles Thornton and take it up with him... if he's still alive.
The slabs outside of the core in the twin towers were well reinforced with two layers of high strength welded wire fabric of .230" and .234" diameter 90,000 psi yield strength steel in a 4" x 10" grid. It was equivalent to a 9/16" diameter high tensile strength rebar every foot in both directions.

The floor pans were 22 gauge (.030" thick) but they had 1.5" deep corrugations and this dramatically increased the stiffness. Stiffness and resistance to bending is a function of the depth cubed. It is not just a function of the amount of material. It is also a function of depth and shape. Do you understand that? An example of how shape affects stiffness is in metal trash cans which are corrugated. See http://www.belson.com/gcls.htm, where the strongest is 23 gauge, which is a little thinner than the 22 gauge used for the fluted steel decking used to form the bottom of the slab in the towers. We all know how stiff metal trash cans are from experience. This is due to the corrugating.

The bolts on the seats saw little load as there was not a significant lateral load. Gravity loads are vertical and the stiffened seats took that load not the bolts. However, the bolts were 7/8" diameter high strength ASTM A325 bolts and were able to take about 36,000 lbs. in shear each. So 72,000 lbs. of lateral load would have been required to break them. Their strength far exceeded that required to pull the perimeter columns inward when the core was cut.

The trusses were quite robust at 32 inches deep and double trusses were used every 80 inches. When made composite with the floor slab and deck they had a moment of inertia equivalent to a W30 x 108 steel I-beam.

You are appealing to a perception that trusses are weak, the floor pans thin walled, that there were only two seat bolts, etc., without providing calculations to back up your assertions.
 
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Alienentity

Active Member
We have never seen Robertson's alleged calculations on the effects of an aircraft impact on the twin towers. Many don't know that his college education wasn't even in engineering. Much of what he has learned in engineering has been through on the job training. Look it up if you don't believe me.

I have my doubts that Leslie Robertson was even capable in 1964 of the type of calculations required to determine what effect an aircraft impact would have on the building. It is very likely that he did not know enough at the time.

It also does not make sense that Leslie would do an additional set of calculations when the study was already done with that Skilling refers to in the 1964 white paper addressing the issue.

In addition, the sagging truss theory and inward bowing of the perimeter columns alleged to have been due to it is extremely controversial and very likely to be nonsense. Calculations show the floor system outside of the core to be quite robust, with just a 3 inch deflection at 700 degrees C. The NIST FEA couldn't produce the inward bowing due to truss sagging. They needed to add an artificial lateral load on the columns to produce it.

The sagging trusses seen through the impact hole in the North Tower were caused by the pressures generated by the fuel/air explosion at impact and were not a result of fire heating the trusses and this had nothing to do with the collapse.
Tony, the quote from L.R. was from the late 2000's in a radio interview. It was not from 1964.
He started working as an engineer in about 1952 for Kaiser Engineering, and joined the engineering firm WSHJ in 1958. He was selected as one of the chief engineers for the WTC in 1966 and made a parter in 1973. Since then he's been responsible for some of the world's tallest buildings, such as the Shanghai World Financial Center.
He's one of America's most successful tall building engineers, and you're here to insinuate he doesn't know engineering.

Not only are you way off base, you're handwaving a major career as if it meant nothing.
 
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Alienentity

Active Member
Anyway, to get back to the subject of the plane impact study done in the mid 1960's, Robertson was referring to the same study that Skilling was. Nobody has that study, there are no copies of it.

Again, the point is that we know that whomever conducted the study could not have used the kind of FEA modelling which is available to us in 2014. This was 50 years ago. It is highly misleading to pretend that they KNEW exactly what the fuel and damage would do. Particularly when you consider the multifloor damage done by the much higher kinetic energy of the actual crashes. The study speed was something like 180mph.

To reiterate, Robertson attests that, after the 9/11 collapse he was able to corroborate NIST's conclusion by performing his own calculations. That's not just an idle comment, it's a valid judgement given by one of the chief engineers - that's why it has to be dismissed, of course. If you're going to quote Skillings, you should also quote Robertson.
 

Tony Szamboti

Active Member
Tony, the quote from L.R. was from the late 2000's in a radio interview. It was not from 1964.
He started working as an engineer in about 1952 for Kaiser Engineering, and joined the engineering firm WSHJ in 1958. He was selected as one of the chief engineers for the WTC in 1966 and made a parter in 1973. Since then he's been responsible for some of the world's tallest buildings, such as the Shanghai World Financial Center.
He's one of America's most successful tall building engineers, and you're here to insinuate he doesn't know engineering.

Not only are you way off base, you're handwaving a major career as if it meant nothing.
I didn't say Leslie Robertson didn't know engineering. I said his undergraduate degree from UC Berkeley was not an engineering degree. It was a general science degree and he then got involved in engineering, so much of what he learned about engineering was after his undergraduate schooling and on the job.

It has been said by a number of people that he did his own analysis of a jet aircraft impact in the 1960's, separate from the one discussed in the white paper John Skilling speaks of. Leslie's experience level at the time the towers were being designed would have been limited, so I don't believe he did a jet aircraft impact analysis in the mid to late 1960's.

You took what I said out of context.
 
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Alienentity

Active Member
Tony, you wrote
Yet by 1964 he had 12 years experience as an engineer.

Not only are you dismissing 12 years of his career, his appointment as a chief engineer, but subsequently his extremely successful career which gives him more than enough qualifications to be taken seriously when he agrees with the overall NIST conclusions.

I think I got the context right. If you can provide citations showing that he did a separate plane study in the '60's, please provide them. I've never come across any such thing.
 

Tony Szamboti

Active Member
Tony, you wrote
Yet by 1964 he had 12 years experience as an engineer.

Not only are you dismissing 12 years of his career, his appointment as a chief engineer, but subsequently his extremely successful career which gives him more than enough qualifications to be taken seriously when he agrees with the overall NIST conclusions.

I think I got the context right. If you can provide citations showing that he did a separate plane study in the '60's, please provide them. I've never come across any such thing.
I have not dismissed Leslie Robertson's extremely successful career. I am merely pointing out that it is extremely unlikely that he would have done an analysis for jet aircraft impact on the buildings, separate from the one John Skilling mentions was the basis for the 1964 white paper, for two reasons:

1. It would have been a redundant task and unnecessary.
2. Leslie would not have been well enough accomplished analytically at that point in his career to bear the responsibility for that analysis.

I am a 57 year old engineer and I have an idea of what the maturity levels are in the field. It doesn't sound like you do. Are you an engineer?

If you aren't saying Leslie Robertson did a separate jet aircraft impact analysis then this discussion is moot.

John Skilling was the head structural engineer for the World Trade Center. In a 1993 interview, Skilling stated that the Towers were designed to withstand the impact and fires resulting from the collision of a large jetliner such as a Boeing 707 or Douglas DC-8.

A white paper released on February 3, 1964 states that the Towers could have withstood impacts of jetliners travelling at 600 mph -- a speed greater than the impact speed of either jetliner used on 9/11/01. A quote from the white paper is below.

The buildings have been investigated and found to be safe in an assumed collision with a large jet airliner (Boeing 707—DC 8) traveling at 600 miles per hour. Analysis indicates that such collision would result in only local damage which could not cause collapse or substantial damage to the building and would not endanger the lives and safety of occupants not in the immediate area of impact.
 
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gerrycan

Banned
Banned
WORTHINGTON, SKILLING, HELLE & JACKSON - structural engineering firm for the towers.
Alien, do you notice what name IS NOT present?
 

Tony Szamboti

Active Member
Anyway, to get back to the subject of the plane impact study done in the mid 1960's, Robertson was referring to the same study that Skilling was. Nobody has that study, there are no copies of it.

Again, the point is that we know that whomever conducted the study could not have used the kind of FEA modelling which is available to us in 2014. This was 50 years ago. It is highly misleading to pretend that they KNEW exactly what the fuel and damage would do. Particularly when you consider the multifloor damage done by the much higher kinetic energy of the actual crashes. The study speed was something like 180mph.

To reiterate, Robertson attests that, after the 9/11 collapse he was able to corroborate NIST's conclusion by performing his own calculations. That's not just an idle comment, it's a valid judgement given by one of the chief engineers - that's why it has to be dismissed, of course. If you're going to quote Skillings, you should also quote Robertson.
I would like to see all of the calculations. They have never been released. How come?

NIST also did not do any analysis past where they say "the tower was poised to collapse". After that they depended on Zdenek Bazant and his analyses have been shown to be erroneous, and now essentially fraudulently presented, as legitimate corrections were sent to the Journal of Engineering Mechanics and they refused to publish them without being able to defend Bazant's conclusions. That story will be publicly told in full very soon, just like the NIST WTC 7 report omissions of pertinent structural features, which would have made their conclusion impossible, are now becoming public knowledge.

In addition, the NIST FEA analysis didn't show inward bowing of the exterior columns due to truss sagging. They had to add an artificial lateral load. Isn't that interesting? I am sure the FEA would have shown it if they cut the core in the model. In fact, the poster with the name Enik has shown the inward bowing of the exterior and collapse of it in a FEA with the core being cut. I know his real name and have corresponded with him and he agrees with me and others who think the core was cut to effect the collapses.
 
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Alienentity

Active Member
I have not dismissed Leslie Robertson's extremely successful career. I am merely pointing out that it is extremely unlikely that he would have done an analysis for jet aircraft impact on the buildings, separate from the one John Skilling mentions was the basis for the 1964 white paper, for two reasons:

1. It would have been a redundant task and unnecessary.
2. Leslie would not have been well enough accomplished analytically at that point in his career to bear the responsibility for that analysis.
1) I never said there was a separate study done. You did.
2) You don't know what his level of expertise was, in fact 2 years later he was made chief engineer on the towers, so historical records indicate the opposite of your claim.
I don't need to be an engineer to read this.

I am a 57 year old engineer and I have an idea of what the maturity levels are in the field. It doesn't sound like you do. Are you an engineer?
Nice try. We're talking about Robertson and your attempt to disqualify him from the discussion. I notice you show very little respect for him and his expertise. I think your bias is showing.

If you aren't saying Leslie Robertson did a separate jet aircraft impact analysis then this discussion is moot.
Bingo

A white paper released on February 3, 1964 states that the Towers could have withstood impacts of jetliners travelling at 600 mph -- a speed greater than the impact speed of either jetliner used on 9/11/01. A quote from the white paper is below.
Robertson explicitly recalls the design study was at roughly 180 mph, which is the expected speed for a jet preparing to land. It is in fact what actually happened when a plane hit the ESB.
There is no rational reason to calculate it at 600mph, and the white paper was released by a lawyer's office for the Port Authority I think, and contained no quotation from the study. The study itself has never been reproduced, so it is not certain that the whitepaper was correct.

The motivations for exaggerating the figure were simple: there was fierce public opposition to the construction of the twin towers.

Besides, in 1964 did the engineers have the technology to properly model an aircraft impact and fuel dump into the towers? I think this is very much an open question, and I can understand perfectly why you don't want Robertson's opinions and recollections anywhere near this conversation. It spoils your claims and beliefs.

I just go with all the facts, I don't try to force the conclusions. I don't think we know for certain that the study was done at 600mph, and I think Robertson's recollection is perfectly valid. It's equally likely the study was at 180mph, not 600mph. I'm not pretending to know which it was though. :)

Edit to add: Robertson even had a slogan for it, which is evidently a mnemonic. They envisioned a 'low flying, slow flying aircraft lost in fog'. Remember, that's what had previously happened, and what they could anticipate happening again.
Nobody on that design team thought a jet would be flown at (as truthers like to claim) and impossibly fast speed.

Come to think of it the impossible speed of the jets is another truther conspiracy point. Yet ironically 600mph is not odd when you're arguing the other way. Hmm
 
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Alienentity

Active Member
I would like to see all of the calculations. They have never been released. How come?
There is no obligation for him to do so. He was simply agreeing that NIST's overall conclusion was correct in his view.

I've never seen Niels Harrit's calculations, yet he's not an engineer and he claims they couldn't have collapsed without explosives. I take Robertson's views at face value. He is one of the lead engineers for the towers, he is extremely well qualified to comment.

Have you ever designed 100 story steelframe towers Tony? If not, why do you feel qualified to comment? Just having fun with you. :p

NIST also did not do any analysis past where they say "the tower was poised to collapse". After that they depended on Zdenek Bazant and his analyses have been shown to be erroneous, and now essentially fraudulently presented,
 
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Tony Szamboti

Active Member
1) I never said there was a separate study done. You did.
2) You don't know what his level of expertise was, in fact 2 years later he was made chief engineer on the towers, so historical records indicate the opposite of your claim.
I don't need to be an engineer to read this.


Nice try. We're talking about Robertson and your attempt to disqualify him from the discussion. I notice you show very little respect for him and his expertise. I think your bias is showing.


Bingo


Robertson explicitly recalls the design study was at roughly 180 mph, which is the expected speed for a jet preparing to land. It is in fact what actually happened when a plane hit the ESB.
There is no rational reason to calculate it at 600mph, and the white paper was released by a lawyer's office for the Port Authority I think, and contained no quotation from the study. The study itself has never been reproduced, so it is not certain that the whitepaper was correct.

The motivations for exaggerating the figure were simple: there was fierce public opposition to the construction of the twin towers.

Besides, in 1964 did the engineers have the technology to properly model an aircraft impact and fuel dump into the towers? I think this is very much an open question, and I can understand perfectly why you don't want Robertson's opinions and recollections anywhere near this conversation. It spoils your claims and beliefs.

I just go with all the facts, I don't try to force the conclusions. I don't think we know for certain that the study was done at 600mph, and I think Robertson's recollection is perfectly valid. It's equally likely the study was at 180mph, not 600mph. I'm not pretending to know which it was though. :)

Edit to add: Robertson even had a slogan for it, which is evidently a mnemonic. They envisioned a 'low flying, slow flying aircraft lost in fog'. Remember, that's what had previously happened, and what they could anticipate happening again.
Nobody on that design team thought a jet would be flown at (as truthers like to claim) and impossibly fast speed.

Come to think of it the impossible speed of the jets is another truther conspiracy point. Yet ironically 600mph is not odd when you're arguing the other way. Hmm
Leslie Robertson simply agrees with what NIST said publicly but has never shown any calculations. We all would agree that if things broke loose and fell far enough that a natural collapse was possible. The rub is getting it going and having it fall far enough. I don't think Leslie has looked at issues such as the lack of deceleration and the acceleration through the first story etc, which indicate charges were used to get things going.
 

gerrycan

Banned
Banned
Robertson explicitly recalls the design study was at roughly 180 mph, which is the expected speed for a jet preparing to land. It is in fact what actually happened when a plane hit the ESB.
There is no rational reason to calculate it at 600mph, and the white paper was released by a lawyer's office for the Port Authority I think, and contained no quotation from the study. The study itself has never been reproduced, so it is not certain that the whitepaper was correct.
You are guessing here I think. You need to read this book maybe......
City in the Sky, p 131......The buildings have been investigated and found to be safe in an assumed collision with a large jet airliner (Boeing 707-DC 8) traveling at 600 miles per hour. Analysis indicates that such collision would result in only local damage which could not cause collapse or substantial damage to the building and would not endanger the lives and safety of occupants not in the immediate area of impact.

From the same book - p 133

The Vierendeel trusses would be so effective, according to the engineers' calculations, that all the columns on one side of a tower could be cut, as well as the two corners and several columns on the adjacent sides, and the tower would still be strong enough to withstand a 100-mile-per-hour wind.

Also, Richard Roth, of Emery Roth and sons, stated in response to Lawrence Wien.......
THE STRUCTURAL ANALYSIS CARRIED OUT BY THE FIRM OF WORTHINGTON, SKILLING, HELLE & JACKSON IS THE MOST COMPLETE AND DETAILED OF ANY EVER MADE FOR ANY BUILDING STRUCTURE. THE PRELIMINARY CALCULATIONS ALONE COVER 1,200 PAGES AND INVOLVE OVER 100 DETAILED DRAWINGS.

Besides, in 1964 did the engineers have the technology to properly model an aircraft impact and fuel dump into the towers? I think this is very much an open question, and I can understand perfectly why you don't want Robertson's opinions and recollections anywhere near this conversation. It spoils your claims and beliefs.
Of course they could calculate it, computers are faster at it these days, yes, but that does not mean that a finite element analysis could not be produced in the mid 60s.
"THE PRELIMINARY CALCULATIONS ALONE COVER 1,200 PAGES "
The towers used many methods that have become the norm since, for example, boundary limit models etc. And as for Robertsons' recollections being included, I am all for that.
The twin towers were in fact the first structures outside the military and nuclear industries designed to resist the impact of a jet airplane.” - Leslie Robertson
little likelihood of a collapse no matter how the building was attacked.’ - Leslie Robertson


"I think Robertson's recollection is perfectly valid" -AE
Yeah, when it suits you.
 

Mick West

Administrator
Staff member
THE PRELIMINARY CALCULATIONS ALONE COVER 1,200 PAGES AND INVOLVE OVER 100 DETAILED DRAWINGS.
Yes, because they had to do it all manually. Computers in the mid-60s were basically wind-up pocket calculators. Modern computers are literally a billion times faster per $.

And how many of those 1,200 pages took plane impacts into consideration?
 

Tony Szamboti

Active Member
There is no obligation for him to do so. He was simply agreeing that NIST's overall conclusion was correct in his view.

I've never seen Niels Harrit's calculations, yet he's not an engineer and he claims they couldn't have collapsed without explosives. I take Robertson's views at face value. He is one of the lead engineers for the towers, he is extremely well qualified to comment.

Have you ever designed 100 story steelframe towers Tony? If not, why do you feel qualified to comment? Just having fun with you. :p
I am qualified to comment. I have 30 years of experience doing structural design for dynamic environments. I don't know what calculations Leslie did, but don't believe he has looked at the acceleration through the 1st story of the North Tower or the lack of deceleration at any point. I would certainly like to talk to him about it.

You clearly aren't qualified to be making the comments you are, as you don't seem to know enough about it.
 

Mick West

Administrator
Staff member
Gentlemen, we are all qualified to comment. The onus here is on the listener to decide how big a pinch of salt to take those comments with.

So perhaps we could have a little less of the appeals to authority, and more of the actual facts?
 

Alienentity

Active Member
You clearly aren't qualified to be making the comments you are, as you don't seem to know enough about it.
Tony, this isn't even valid as argumentation by the forum guidelines. You're not addressing any particular point I made.

I'm as qualified as you are to read the white paper, note Robertson and Skilling's comments and the fact that Robertson was a professional engineer for 12 years before the 1964 study was done.
Worse, you don't even know who performed the study. Or do you know which engineers did it? Please tell us!
 

Alienentity

Active Member
You are guessing here I think.
"I think Robertson's recollection is perfectly valid" -AE
Yeah, when it suits you.
Robertson said 'low flying, slow flying'. What part of that do you not understand?

Let me repeat it - 'low flying, slow flying'. Does that sound like 600 mph to you? Yes or no?
Who is ignoring Robertson now?

BTW he was made a partner in the firm in 1973. He was a chief structural engineer on the WTC project in 1966.
'Leslie Robertson was the chief engineer for the Twin Towers' BBC
'chief engineer for the Twin Towers' Journal of 9/11 Studies
'Robertson, the chief engineer' Collapse: The Science of Structural Engineering Failures

Your point was......?
 
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