Hardfire: Szamboti / Chandler / Mackey

[alienentity]

During the debate you brought up the fact that the NIST report does not show a factor of safety of 3.00 to 1 for the core columns or a .333 DCR. However, the NIST does not provide backup data for their claim of what the DCR for the core columns actually was.

The 3.00 to 1 factor of safety for the core columns was calculated using Gregory Urich's mass analysis, the publicly available core column cross sections, an estimate of the perimeter cross sections at a given story based on weight from Urich's analysis, and the fact that the columns on each story were designed to have the same unit stress to preclude differential deflections and floor warpage between the core and perimeter. I estimated the 98th floor perimeter columns to have a 15.6 sq. inch cross sectional area, which would then have an average wall thickness of .289 inches for an approximate 14 inch square column. While it does not give the actual wall thicknesses of the perimeter columns over the height of the towers, the NIST report does say that the wall thickness of the perimeter columns never drops below .250 inches.

You should look at it yourself.

Yes but how do you explain the fact that Leslie Robertson, arguably the most experienced and knowledgeable engineer on the planet vis-a-vis the WTC towers, accepts the fire/gravity collapse from an engineering POV?

Surely, if anyone were to smell a rat, it would be he. Quite the opposite of you, he regards the controlled demolition theory as 'preposterous'.

You cannot argue that he doesn't know what he's talking about. It boggles the mind that you guys could ignore one of the main designers of the towers....

 

[twinstead]

Yes but how do you explain the fact that Leslie Robertson, arguably the most experienced and knowledgeable engineer on the planet vis-a-vis the WTC towers, accepts the fire/gravity collapse from an engineering POV?

Surely, if anyone were to smell a rat, it would be he. Quite the opposite of you, he regards the controlled demolition theory as 'preposterous'.

You cannot argue that he doesn't know what he's talking about. It boggles the mind that you guys could ignore one of the main designers of the towers....

It's easy. Robertson is In On It.

 

[GlennB]

Tilt clearly seen in these:
http://www.youtube.com/watch?v=V1bfPaRRK90
http://www.youtube.com/watch?v=53taT7FSFIk

Ah yes,so it is!
I wonder how many such videos and stills Szamboti has denied in the pursuit of his 'theory'.

 

[Macgyver1968]

It's easy. Robertson is In On It.

Hehe...I left a dead horse's head in his bed...with a note that says "You don't know nothin'."

 

[R.Mackey]

During the debate you brought up the fact that the NIST report does not show a factor of safety of 3.00 to 1 for the core columns or a .333 DCR. However, the NIST does not provide backup data for their claim of what the DCR for the core columns actually was.

Just because they don't run the full calculation for you doesn't mean it's wrong. You can only say it's wrong if you provide superior numbers, which you attempted to do:

The 3.00 to 1 factor of safety for the core columns was calculated using Gregory Urich's mass analysis, the publicly available core column cross sections, an estimate of the perimeter cross sections at a given story based on weight from Urich's analysis, and the fact that the columns on each story were designed to have the same unit stress to preclude differential deflections and floor warpage between the core and perimeter. I estimated the 98th floor perimeter columns to have a 15.6 sq. inch cross sectional area, which would then have an average wall thickness of .289 inches for an approximate 14 inch square column. While it does not give the actual wall thicknesses of the perimeter columns over the height of the towers, the NIST report does say that the wall thickness of the perimeter columns never drops below .250 inches.

And, again, you're assuming compressive fracture instead of buckling failure, which is wrong, or you're assuming pinned connections, which is also wrong. Been over this with you repeatedly and told you so again during the debate. NIST doesn't make these mistakes and is therefore entirely credible.

It's also irrelevant, once you understand how the collapse began, and that the columns really can't effectively resist the upper load -- it doesn't hit them, it hits the floors. The columns see eccentric loads and also see their supports smashed away, so using their intact strength is optimistic to the point of uselessness.

I explained that during the debate, as well.

I have had it up to here explaining, re-explaining, and re-re-re-re-explaining to the Truth Movement. That includes you. Henceforth, I'm not going to bother with those who can't get past their Irreducible Delusions, as I've threatened to do for years.

 

[Tony Szamboti]

Just because they don't run the full calculation for you doesn't mean it's wrong. You can only say it's wrong if you provide superior numbers, which you attempted to do:



And, again, you're assuming compressive fracture instead of buckling failure, which is wrong, or you're assuming pinned connections, which is also wrong. Been over this with you repeatedly and told you so again during the debate. NIST doesn't make these mistakes and is therefore entirely credible.

It's also irrelevant, once you understand how the collapse began, and that the columns really can't effectively resist the upper load -- it doesn't hit them, it hits the floors. The columns see eccentric loads and also see their supports smashed away, so using their intact strength is optimistic to the point of uselessness.

I explained that during the debate, as well.

I have had it up to here explaining, re-explaining, and re-re-re-re-explaining to the Truth Movement. That includes you. Henceforth, I'm not going to bother with those who can't get past their Irreducible Delusions, as I've threatened to do for years.

The DCRs given by the NIST appear to be in a similar but opposite format to the Margin of Safety value where Factor of Safety is involved in the calculation.

Margin of Safety is computed as (allowable load/actual load x factor of safety) - 1. In the DCR sense this would be (actual load x factor of safety/allowable load).

The NIST used a factor of safety of 1.67 to 1.92 against yield and buckling for the core columns.

If the NIST used a 500,000 ton mass for the towers, like Dr. Bazant did, then a typical DCR for the core columns they gave of 0.86 would convert to a factor of safety of approximately 3.00 using Gregory Urich's mass analysis.

Using the core and perimeter cross sections at any given story and Gregory Urich's mass analysis, I get a unit stress of approximately 11,000 psi. The buckling stress for the least radius of gyration direction on each core column is approximately 3 times that, even using an effective length factor of 1.0, which some like Newtons Bit insist is the value to be used for the end conditions involved.

 

[triforcharity]

None of that really matters.

Why waas there NO TILT, (as you claim) but yet, it can be seen in many videos??

Do you NOT think that fire+steel+no firefighting=MAJOR PROBLEMS=COLLAPSE??

 

[911kongen]

When can we see the debate?

 

[R.Mackey]

Margin of Safety is computed as (allowable load/actual load x factor of safety) - 1. In the DCR sense this would be (actual load x factor of safety/allowable load).

The NIST used a factor of safety of 1.67 to 1.92 against yield and buckling for the core columns.

If the NIST used a 500,000 ton mass for the towers, like Dr. Bazant did,[...]

NIST didn't "use" a factor of safety here, nor did they "assume" a 500,000 ton mass. The calculations come from their model of the Towers, where both of these were computed from the materials and their dimensions directly. Your convoluted chain of assumptions did not happen.

You're just plain wrong. Add this to the stack of things you refuse to understand. I really don't see why I need to respond to this at all.

 

[Tony Szamboti]

NIST didn't "use" a factor of safety here,

The total cross sectional area for the core columns at the 98th floor was 2,645 sq. inches and for the perimeter 3,682 sq. inches, while the mass above (per Gregory Urich's mass analysis) was 68,295,000 lbs.. This gives a unit stress of 10,794 psi. For the ASTM A36 core columns, with a buckling stress of approximately 95% of the minimum 36,000 psi yield stress, that works out to about a 3.00 to 1 safety factor for buckling.

During the debate you said a factor of safety of 3.00 was equivalent to a DCR of .333, and it is in a straight conversion. However, quite often factor of safety is incorporated into the calculation as part of the demand similar to the Margin of Safety calculation, so I am wondering if you aren't familiar with this methodology.

If they didn't involve the factor of safety in the DCR calcuation then how do you explain the NIST showing a DCR of 0.86 for the core columns? If you just do a straight conversion to factor of safety this is the equivalent of a 1.16 factor of safety, and we know that isn't what would have been used.

It would be nice if you would explain yourself and stop just appealing to the authority of the NIST. You might not be following what they are saying, which would be understandable as it isn't explained.

 

[twinstead]

It would be nice if you would explain yourself and stop just appealing to the authority of the NIST. You might not be following what they are saying, which would be understandable as it isn't explained.

The man has done an EXCELLENT job of explaining himself and the NIST, especially for the engineering challenged such as myself. There really IS no better explanation of what probably happened to that building than the NIST report. R.Mackey appears to understand that more than you do.

I would like to see a scenario that fits the available evidence better--I'm all for second opinions--but I just haven't seen it.

 

[Tony Szamboti]

Nice derail, Tony.
So you admit the towers had tilt, and you are boxed in. Can't refute it, so change the subject.
You must think we are as stupid as the average troofer...

This thread is about the debate and Factor of Safety and DCR was brought up in the debate by Ryan. So I guess I don't understand your derail comment.

As for the tilt, I think those who insist it tilted at onset need to show that, with a frame by frame analysis, as it was not done for them by the NIST. All that is in the report is a still from video from 2 to 3 seconds into the collapse of WTC 1, when the tilt was obvious, and an assertion that it tilted and then descended.

Why don't you do an analysis to show you can actually do more than write wisecracks on an Internet forum?

 

[carlitos]

With all apologies Mr. Szamboti, I don't follow this as closely as I should. Do you have an alternative explanation for the collapse of the WTC towers? If so, could you post a link? Thanks in advance.

 

[Furcifer]

The total cross sectional area for the core columns at the 98th floor was 2,645 sq. inches and for the perimeter 3,682 sq. inches, while the mass above (per Gregory Urich's mass analysis) was 68,295,000 lbs.. This gives a unit stress of 10,794 psi. For the ASTM A36 core columns, with a buckling stress of approximately 95% of the minimum 36,000 psi yield stress, that works out to about a 3.00 to 1 safety factor for buckling.

As convoluted as this is it appears to be right. At least with my limited knowledge of things.

Let's assume you and I know what's going on here, and we've both come to the same conclusion. What you have above is still based on static conditions. The same code gives a safety factor of 12 to 15 for steel under repeated stress (for yield and ultimate respectively)

That means the loading after collapse initiation was too great. Agree?

Prior to that, the safety factor absorbed the damage and the fires until it was overcome.

That's all there is to it. A greater safety factor would have allowed for more time before collapse. It would have taken an even greater safety factor to arrest the collapse after initiation.

 

[Hokulele]

As for the tilt...

If the tilt wasn't present at the onset of the collapse, what would induce it?

 

[R.Mackey]

Tony. NIST's figures are from their SAP2000 model. Not your first-principles analysis, which is WRONG.

Last time I'm telling you this. Start your own thread if you want to keep repeating nonsense.

 

[rwguinn]

Tony. NIST's figures are from their SAP2000 model. Not your first-principles analysis, which is WRONG.

Last time I'm telling you this. Start your own thread if you want to keep repeating nonsense.

I really like the fact that we can now figure "Buckling Strength^TM" as a percentage of yield, regardless of L/d, or any slenderness factor.
Will sure make my life easier--but I don't think the DER's will buy it. They're pretty set in their ways. Will an argumentum ad Tony work, ya think?

 

[Furcifer]

I really like the fact that we can now figure "Buckling Strength^TM" as a percentage of yield, regardless of L/d, or any slenderness factor.
Will sure make my life easier--but I don't think the DER's will buy it. They're pretty set in their ways. Will an argumentum ad Tony work, ya think?

I'm sure you've gone over this before, but a little more explanation of l/d and slenderness ratio would be cool for the rest of us willing to learn a thing or two.

I see what TS is talking about, and I know there is more to it than that, but without a little more education I'm fumbling with a response.

As Ryan said, he's looking at first principles. I can see that. What I don't know is the good stuff that goes beyond that.

I know repeating yourself is a drag, but it really is of benefit to those of us that can't immerse ourselves in it other than the few hours a days we peruse the internet.

 

[rwguinn]

I'm sure you've gone over this before, but a little more explanation of l/d and slenderness ratio would be cool for the rest of us willing to learn a thing or two.

I see what TS is talking about, and I know there is more to it than that, but without a little more education I'm fumbling with a response.

As Ryan said, he's looking at first principles. I can see that. What I don't know is the good stuff that goes beyond that.

I know repeating yourself is a drag, but it really is of benefit to those of us that can't immerse ourselves in it other than the few hours a days we peruse the internet.

I don't want to contribute to Tony's derail (or at a minimum, sleight-of-hand via distraction, but Newtons Bit has expounded at length elsewhere. short story- for a given cross-section, a short length will hold a lot more compressive load without buckling than a long one of the same cross-section will.
"Buckling Strength" cannot be approximated as % of Yield.

 

[R.Mackey]

I'm sure you've gone over this before, but a little more explanation of l/d and slenderness ratio would be cool for the rest of us willing to learn a thing or two.

I know repeating yourself is a drag, but it really is of benefit to those of us that can't immerse ourselves in it other than the few hours a days we peruse the internet.

The reason we're not going to cover it here is because it's off-topic, and because Tony has already had it explained to him repeatedly.

You can start a new thread if you want, but the most productive use of your time would be to search for posts by Newtons Bit, where this has been hashed out in detail.

The core error, in brief, is Tony's utterly random and completely indefensible claim that buckling would occur at 95% of linear yield. When buckling occurs is a function of geometry, and there is no geometry in his first principles analysis. NIST's analysis is a full-on finite element simulation of the as-built structure, and is therefore credible. No argument Tony's proposed against it even makes it past the giggle test.

ETA: When two engineers give you the same answer independently, it's usually right.