NASA Scientist Ryan Mackey Answers ATS Questions

For all of you that do not know. On another thread, there was a link to a paper written by a NASA scientist. This paper was written to point out the errors made by Dr. Griffin. I offered to e-mail Mr. Mackey with errors they felt may have been wrong.

I had his wrong e-mail address twice, explaining the time it took for his response. After I found the right address he replied to me in less than 4 hours.

I would like this thread to be dedicated to legitimate questions surrounding his paper.

Mr. Mackey can be reached at the jref site as he is not a member here. I will be more than happy to forward any questions you may have to him directly via e-mail, posting all his reply's promptly.

His paper can be found here:

911guide.googlepages.com...

Let's look at the criticisms one at a time:

FROM “GRIFF”:

One thing I have noticed is pages 17-19 of the pdf when he's talking about wind load. He says that the wind load is the governing factor over the live load. I hate to break it to him but wind load is considered a live load for one thing.

Then he goes on to say that the 2000% is erroneous because the columns were designed for wind load governing live load. This is false because in design, you combine ALL loads into factored loads. He even quotes NIST for this.
What he doesn't realize is that when designing a member, you design the member to hold ALL loads. He is actually shooting himself in the foot there because it shows that the columns were designed to withstand the wind loads (remember that live loads are smaller if you want to seperate them out) and could therefore hold much more gravitational load than what he is suggesting.

Response:

First of all, I am well aware of the design process, and if I wasn't, this is well laid out in NCSTAR1-1 and 1-1A.

Wind load is not considered as a live load. It is similar but not identical. In particular, the design rules allow "live load reduction" with height, which was a shorthand approach to avoid double-counting safety margin in tall structures. Wind load is not eligible for live load reduction, and therefore must be bookkept separately. Wind load is not a dead load or a superimposed load, so it is perhaps most similar to a live load, but for tall structures it is simply false to state that it is live load. In modern design practice this is irrelevant as we no longer use load factors and ultimate strength design.

The "2000%" is misleading. Let me argue by way of an example. Suppose a given assembly must support 100 tons of dead load, 25 tons of live load, and up to 50 tons of wind load. Further suppose the design rules state that the ultimate strength U = 1.5 x dead load + 2 x live load + 2 x wind load. We then must design the assembly to handle 150 tons + 50 tons + 100 tons of load or 300 tons.
Suppose we then build this structure and consider additional live load on a windless day. The actual load is 100 tons + live load + 0 wind load, so it can theoretically handle another 200 tons of live load before it actually fails. I might then say that "the structure is designed with enough margin to handle eight times its live load." This statement is true, but useless.
This is basically what's going on with the "2000%" quote that Dr. Griffin singles out. Because the wind load on the structures was so enormous -- they were the broadest building faces ever built -- the wind considerations were the primary driver of design in the perimeter. You will note that Mr. Skilling did not say, in 1964, that they were built to handle "2000% of the wind load."
Dr. Griffin singles out this quote because it sounds impressive, and then claims (with no calculations of any kind) that this number proves the structures had enough reserve capacity to withstand the impacts and fires, and to resist total collapse. He's making an enormous leap in logic, and one that turns out to be wrong.

Now, because the winds on September 11th were light, it is true that the wind-tolerant design of the perimeter columns meant much more reserve capacity than an ordinary structure might have had. Since the structure didn't need to fight the wind, the perimeter columns had perhaps a factor of 4 excess capacity on that day, as compared to the core columns, which being only sized for gravity, had only about a factor of 2 excess prior to impact (designed for 1.67, but the service live load was below the design live load). NIST did not ignore this. In fact, this excess capacity explains both why the structures stood as long as they did, and also why they failed in the manner seen.
The perimeter columns were the last things to fail. First they were hit by aircraft, diminishing their capacity by about 1/5. Then they were exposed to heat, diminishing it by another 1/5 or so. Then the core began to shift its load to the perimeter, as it was heated more and compressed, leading to load rerouting through the hat truss, which increased the actual load on the perimeter by roughly 50%. Yet still the structure held, and NIST predicted that it wouldn't have toppled at all except for the final ingredient, which was the pull-in forces as the still-attached floors failed and sagged in the heat. That led to eccentric loading of the perimeter columns, greatly reducing their effective strength.
It took all of these factors combined to lead to the collapses. This would not have been the case if the perimeter columns didn't start with so much excess capacity. Therefore, the NIST result is completely consistent with this observation. A more detailed explanation is given in NCSTAR1-6.

To answer the original question, (a) the 2000% figure quoted by Dr. Griffin is misleading, (b) wind loads and live loads are not the same, and (c) we all agree that the perimeter columns had considerable reserve capacity. Nothing Dr. Griffin has said in any way contradicts the NIST conclusions.

From Mr. Mackeys paper:

page 169:
We will use this lower value, but remark that the actual value could be considerably different, although it may never be known for certain.


FROM Jprophet:

secondly, as i mentioned before, this report also assumes that every core column and every supporting beam failed completely at exactly the same instance in time.
there is no explanation of this in the report.

Response from Mr. Mackey:

This is false. Nowhere do I make the assumption that "every core column and every supporting beam failed completely at exactly the same instance in time." This individual has both not read my report, and also has no conception of how a structure fails.
I describe my "assumptions" (actually conclusions) on pages 90-91. This passage describes in full detail how the initiating event definitely did not occur "completely at the same instance in time," but that the onset of global instability -- which took place after many individual elements reached their limits -- took about a second. Also as I describe on Page 91, we know that all supports did not fail simultaneously, because if this was so, the upper blocks would not have rotated slightly as they fell. Furthermore, on pages 101-102, I describe how the action of the hat truss and antenna on WTC 1 is also consistent with a rapid, but not simultaneous, failure of the supports.
When a structure overloads beyond its ability to reroute loads, total failure happens quickly. Overstress in one part of the structure can be transmitted to another part, failing it as well, at roughly the speed of sound in the material -- about Mach 15 for steel. One can easily simulate this effect by gradually increasing the weight on a board resting on a number of empty soda cans, supporting the board at regular intervals, until it fails. Once the first can buckles, the rest will follow very quickly if it is set up properly.
Thus, I do not assume that everything failed at once. I do, however, explain how a rapid failure -- collapse beginning in a fraction of a second -- is expected. The complainer is wrong on both counts.

also, his theory on wtc7 is completely debunked...
page 173

He is in no position to draw this conclusion. Suppose, for instance, the structure – even damaged and during collapse – was capable of supporting twice the static load, which we will call Fstatic, but that it could only do so until being deflected by 25 cm. After this, any given floor will snap, and the resistance goes to zero until the next floor is hit 300 cm below. Work, again, is force times distance. The total work done on any given floor would be 2 Fstatic x 25 cm + 0 x 300 cm = 50 Fstatic cm. If we model the structure as homogeneous, supplying instead an average force called Fdynamic that acts over the full 325 cm distance of each floor, we can estimate this average force by dividing the total work by the total distance. The total work done in both situations must be the same. Therefore, we can calculate Fdynamic = 50 Fstatic cm / 325 cm = 0.15 Fstatic, what Dr. Kurttila would call a “resistance factor” of 0.15, very close to his estimate for WTC 7.


FROM Jprophet:

wtc7 didnt fall from the top down like the other 2 buildings. that destroys this entire argument.

This is also false. Nowhere do I state that WTC 7 fell top-down, nor does my explanation above require that to happen.
The argument above is an adjustment to Heikki Kurttila's whitepaper. In it, he also does not assume that WTC 7 fell from the top down. His error is that he confuses the static strength of the structure with the dynamic resisting force as it collapses -- his calculation is basically correct, but he interprets his result improperly. His interpretation would only be correct if the structure exerted the same resisting force at all times as the structure was squashed from its original height to zero. This is not true. After the structure suffers its maximum deflection, which is small compared to the height of the structure, its resistance force is basically zero.
My argument above does not consider time. It only considers work and energy. Because of this, only the total distance matters, since work is equal to force times distance. Thus, it doesn't matter whether the structure collapses top down, bottom up, floors collapsing at random, or even all floors collapsing at once. All of these scenarios will be treated exactly the same in the argument above. Dr. Kurttila doesn't make any assumptions about the order of collapse either.

The only person who has ever proposed that WTC 7 collapsed top-down, as far as I am aware, was Dr. Kuttler in his whitepaper in the first issue of the "Journal" of 9/11 Studies. He tried to argue that WTC 7 collapsed too fast because momentum transfer between floors in a top-down collapse would slow the collapse by a few seconds. His calculation is reasonable, but his model is wrong -- as the complainer above observes, WTC 7 did not collapse top-down.

In summary, I find that none of these complaints describes an actual problem with my whitepaper. At best, they are simply confused about its contents.

Hope these explanations make sense.

Thanks,
Ryan Mackey

Originally posted by CaptainObvious
First of all, I am well aware of the design process, and if I wasn't, this is well laid out in NCSTAR1-1 and 1-1A.

Wind load is not considered as a live load.

He is WRONG!!!!!!!!!!!



Source: "Structural Analysis", Alexander Chajes, 1990, Prentice Hall

My structural analysis book from college.

It is similar but not identical. In particular, the design rules allow "live load reduction" with height, which was a shorthand approach to avoid double-counting safety margin in tall structures. Wind load is not eligible for live load reduction, and therefore must be bookkept separately. Wind load is not a dead load or a superimposed load, so it is perhaps most similar to a live load, but for tall structures it is simply false to state that it is live load.

Then why does my structures book say that wind load is a live load?

In modern design practice this is irrelevant as we no longer use load factors and ultimate strength design.

Also wrong. In modern times we use LRFD (Load Resistance Factor Design). Notice the load and factor in there? Also, modern times don't govern what was designed for back in the 60's and 70's. We used ASD (Allowable Strength Design) back then. Don't know where he gets Ultimate Strength Design from.

The "2000%" is misleading.

He could be correct, as I haven't read Griffin's paper. But, he still is not getting that wind load is designed into a member using the moment produced by the wind. This moment is designed for in the member ALONG with the other axial loads.

As far as the rest of his response, I don't have the time right now to pick it apart. But, he does seem to know a few things.

Plus, I never stated that the 2000% was correct.

er the original question, (a) the 2000% figure quoted by Dr. Griffin is misleading,

May be, maybe not.

wind loads and live loads are not the same, and

Correct but wind load IS a live load.

It's like saying a square is a rectangle by definition but a rectangle is not a square by definition.

Edit: ASD is Allowable Stress Design. Stress and strength are almost interchangeable. Just before someone tries to call me out on that.

[edit on 9/29/2007 by Griff]

[edit on 29-9-2007 by asala]

[edit on 29-9-2007 by asala]

Thanks Griff... I will send him an e-mail as soon as I get a few more points. I don't want to send him an e-mail for every one question.

A simple wikipedia search could have told him that wind loads are considered live loads.

Dead loads

Typically dead loads are considered those which are static, i.e. do not change over the course of normal operations of the object. For example, in the analysis of a staircase where the handrails are attached to the main structure but are not the subject of the analysis and so not included in the model. The dead load would be considered to be -

* Self weight of the staircase (9.81 x mass)
* Force exerted by the weight of the handrails, applied to the point of attachment to the staircase (again calculated as 9.81 x mass)

Live loads

Live loads, sometimes referred to as dynamic loads include all the forces that are variable within the object's normal operation cycle. Using the staircase example the live load would be considered to be

* Pressure of feet on the stair treads (variable depending on usage and size)
* Wind load (if the staircase happens to be outside)

Source: en.wikipedia.org...


[edit on 9/29/2007 by Griff]

Hey, CO, thanks for taking this effort on. It is very interesting reading. Could you please pass the following to Mr. Mackey?

*******************

Dear Sir,

My contentions with the NIST report due not lie within the framework of LIHOP or MIHOP. In fact, my contentions don't attach to any conspiracy theory at all. Where I take great umbrage with the NIST final report is in the fact that the conclusions drawn within the report do not align with, and at times soundly contradict, the data presented in the report. Since this investigation, analysis and resultant report were paid for by the American people, which include me, I take issue with being handed a report that reflects insufficient data collection (insufficent collection of failed members and testing on same), scientifically unsound statements (creep played a significant role in the failure of the supporting elements), and a failure model that contradicts the data they present themselves on what little testing they did perform.

What makes the incongruities of the NIST report even more exasperating is the fact NIST refuses to share their model and database with the U.S. citizens who wish to vet the process used. I noticed you state in your paper that reviews Dr. Griffin's work (a work I must admit I know little to nothing about), that while Dr. Griffin does not provide calculations to support certain accusations (calculations I fully agree are needed), you state "the NIST Report [7] is readily available, and while the report may be criticized, errors that Dr. Griffin makes regarding its contents may be factually verified with no uncertainty." While this statement is true as refers to the REPORT, it is absolutely untrue as regards the actual important information (i.e. the model, the empirical data, the assumptions, etc.) Yes, we can verify the CONTENT of the NIST report, but that content is made up of only sparse references to actual data, and by and large is INTERPRETATION of that undisclosed data.

Stepping off my soap box I get to the matter hand. One particularly ornerous incongruity is the fact that the final failure mode on the macro level presented by NIST is in unacceptable contradiction (as far as this learned reader can tell) to the failure mode of certain components analyzed. In particular, the floor truss connectors at the perimeter walls and at the central core columns of WTC 1/2. The NIST report states that the floor truss connectors at the perimeter walls were sheared in a downward motion while none of the floor truss connectors on the central columns exhibited this failure mode. This would require that the floors fall in a downward motion at the perimeter wall connection while staying attached to the core columns. Since the perimeter walls couldn't possibly have "jumped up" to cause a downward shearing motion at the connectors, and since the connectors on the core columns did not shear in a downward motion, this would require that the floor trusses and core columns move in concert - which would be in a downward motion relative to the perimeter walls. The failure mode that has been presented by NIST does not account for this situation.

I would greatly appreciate reading your thoughts on this matter, and hopefully we can visit further on other concerning mismatches I perceive within the final report. I would like to personally thank you for taking the time to respond to these thoughts.



[edit on 9-29-2007 by Valhall]

CO,

To be as unbiased as I can in this matter, I need to read Dr. Griffin's paper and pick it apart as well. I will read it as critically as I have read (what I have read....about 5 pages maybe) of Mr. Mackey's report.

Valhall,

as always, nicely written.

ps. CO, please let Mr. Mackey know that in no way is this debate hostile from my direction. I may get fired up here and there but I'm mostly a laid back guy.

Great thread! This is exactly the type of thread that ATS needs to see more of! Great Post Captain!

Ask him how the building was able to fall in just about 10 seconds? Was there zero resistance from the floor below when each floor above seem to just fall straight down?

Originally posted by kleverone
Great thread! This is exactly the type of thread that ATS needs to see more of! Great Post Captain!

Ask him how the building was able to fall in just about 10 seconds? Was there zero resistance from the floor below when each floor above seem to just fall straight down?

I hope he doesn't ask him this because the building didn't fall in "just about 10 seconds". It fell in 14 to 16 seconds (WTC 1 and WTC 2).

Should have taken a lot longer than that either way. 14 seconds, thats more than a floor a second. Way too fast.

Originally posted by kleverone
Should have taken a lot longer than that either way. 14 seconds, thats more than a floor a second. Way too fast.

Actually, it's not. I believe we calculated it out to be some where between 33% and 50% more than the accleration due to gravity alone. Which is significant. This is one of those times where I wish my account wasn't gimped up beyond what is apparently repairable so that I could find the threads where we went through this.

Oh well.


[edit on 9-29-2007 by Valhall]

Any idea where that 33- 50% acceleration is coming from? I would think that the resistance of slamming into the floor below you slow you down before it accelerated. Regardless, I do not wish to derail this thread. Just looking for some plausible answers.

Originally posted by kleverone
Any idea where that 33- 50% acceleration is coming from? I would think that the resistance of slamming into the floor below you slow you down before it accelerated. Regardless, I do not wish to derail this thread. Just looking for some plausible answers.

Sorry, I stated that in a totally confusing - well, let's just say WRONG way. It's accelerating slower than the acceleration due to gravity. It's a 33% to 50% increase in time over what you would get due to gravity alone. I'll try to find the thread where we worked the calculations on this.

Sorry for the confusing statement.

Thanks to all in here for the stars and flags...and applause. Being one of the few skeptics in here, it is nice to get a pat on the back once and a while.

Valhal... I know that Mr. Mackey is not a "huge" fan of NIST. I believe he has questioned certain aspects of it. This by no means suggests he thinks that the collapse was a C.D. I know that may turn some of you off, but this man is one of the most educated people you will find.

I was hoping Bsbray, or Labtop could add to this (thanks Griff for your input) If anyone chats with them, please make them aware of this thread.

Thanks again for all your positive responses.

C.O.

Since when is a NASA scientist a structural expert?

Am I missing something here?

reply to post by uberarcanist


Agreed!

(Mr Griff as always- you’re a tireless patriot)

I might like to ask if the free fall calculations expressed here included energy conversion for concrete floor pulverization. -Im a pancake fan.

Steel and concrete - still more durable than a jet fueled collapse theory.

Originally posted by Valhall
I hope he doesn't ask him this because the building didn't fall in "just about 10 seconds". It fell in 14 to 16 seconds (WTC 1 and WTC 2).

As much as I love you Valhall, the "official" story is 10 and 11 seconds. It's the official story that states as FACT freefall time.

thanks everyone for this civilized and very informative thread. I wish there were more of these going on instead of the usual statement + counter statement = personal attack...
Nice to see some specialists opinions on technical matters. At least we are getting somewhere this way.
Looking forward to whatever comes out of this.
respect to all parties involved
mr.Jones

edit: my remark is a bit off topic, but i thought it would be nice to voice my appreciation.
Please continue the discussion

[edit on 29/9/2007 by mister Jones]

Originally posted by CaptainObvious
Thanks to all in here for the stars and flags...and applause. Being one of the few skeptics in here, it is nice to get a pat on the back once and a while.

Don't take it personal man. People here are skeptical of everyone. That's why I like this place instead of jref where it's OK to make fun of someone who has a different view than someone else.

This by no means suggests he thinks that the collapse was a C.D.

No matter what you or Mr. Mackey believes, this was a CD. If radical Islam did it or not, it is still a CD. Why is it any different?

I know that may turn some of you off, but this man is one of the most educated people you will find.

Why? Because he believes the same as you? I have just shown that out of about 5 pages I read of his, that he is erroneous, so why is he "one of the most educated people you will find"? Please explain, because if he can say things about someone else without being totally correct, how can I take ANYTHING ELSE he has to say as being correct?

(thanks Griff for your input)

No problem. Keep up being "skeptical" if it makes you feel better. But, as for me, I know what the hell is going on. Do I have to remind you that my BF works for the State Department? Do I have to say that my BF (since I've been adamant about crap, is now being targeted after 13 years of service) might not be in the service anymore. Do you think he cares? He doesn't. He wants the government to "fire" him because of this crap. I DARE THEM!!!!!. I know my rights and so does he. Take that to heart Dick Cheney (i.e. Big Brother).

Thanks again for all your positive responses.

C.O.

No problem. Keep us updated about this. Or Mr. Mackey could actually join here (a non-biased forum to talk) or he could sit behind the jref "gang" where thinking outside the box is worthy of being chastized. Let the jrefers think about that please.

Originally posted by uberarcanist
Since when is a NASA scientist a structural expert?

Never.

Am I missing something here?

Nothing.