Mr. Chandler,
I'm sorry for the length.
I'm not sorry for the tone. If I hit "irritatingly condescending", then I hit my mark.
I still question the Fig., page, and document reference. I downloaded a fresh copy of the document of that exact title and nothing related to freefall is on that page. The table of figures in the front only goes up to 12-69. If the reference you cite is real, please point me to the correct document.
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You are downloading the Draft version which did not have the update. Get the Final version.
Go to this page:
http://wtc.nist.gov/NCSTAR1/NCSTAR1-9index.htm
At the bottom of the page, you will find
• NIST NCSTAR 1-9: Volume 1: Chapters 1 - 8 *
• NIST NCSTAR 1-9: Volume 2: Chapters 9 - Appendix E *
Click on the link for "Volume 2: Ch 9 - App E"
Page 603 (pdf page 265) of this document has NIST's Fig 12-77.
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I think it is rather significant that NIST redid their analysis based on my work. Don't you?
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No, sir, I don't.
They most certainly did NOT "redo their analysis based on your work". In a 1,000 page report (NCSTAR 1A, 1-9 & 1-9A inclusive), they added two pages and one bullet point that explained your contribution.
Frankly I do not think that this was "significant". The fact that it did not change any of their conclusions demonstrates (to me, anyway) that it did not rise to the level of "significant".
Nonetheless, you did make a contribution. I was an interesting detail.
NIST calculated their acceleration over two stages, and found an average acceleration of 1.4G. You drilled down a little deeper, and found that there were two very different stages of acceleration: what NIST later referred to as Stage 1 (variable acceleration) & Stage 2 (0.98G).
And you pointed it out to NIST & to the world. Thus far, you'd done everything right.
But then, sir, you did two things that were wrong.
The first was a relatively minor error. You discovered two fundamentally different behaviors in the two stages of collapse. Then you ignored the first stage. This is just as grievous an error as NIST's, except that you cannot claim ignorance of the existence of the two regimes. Objects in true free fall, and structures that have their support blown by demolition charges, do NOT exhibit a gradual (2 seconds worth) increase in acceleration. They fall at G "right now!" Ergo, that wall did NOT fall "in free fall". Structures made from ductile materials that are undergoing a buckling type failure DO exhibit a gradually increasing ("Stage 1" type) acceleration.
The second error, below, is where the wheels really came off of your cart. You started hurling accusations of incompetence and fraud at experts who are far more knowledgeable and experienced than you. With the sole basis of your accusations being your flawed analysis.
Their original work was either so shoddy or so fraudulent that letting it stand apparently became untenable. That's how I read it, anyway.
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Well, sir, that may be how you read it. But from my seat, you need to get your ego in check.
You discovered an elaboration on one small detail out of the enormous effort in figuring out why WTC7 collapsed. Congratulations. Seriously, you found this & deserve credit for it.
You're a high school physics teacher. Congratulations again. You perform daily a valuable task in helping youngsters learn the basics of science & physics.
But you are frankly incompetent in the field of structural engineering, structural mechanics and failure mechanics of large buildings. The ULTIMATE analysis ain't physics. It's engineering. It's messy. Things in the real world don't fall in a vacuum, they don't have zero friction, they don't behave like rigid bodies or perfect gasses.
You looked at one tiny little detail of a huge puzzle. You did not have to beat your results against the FEA model results, etc. You did not have to UNDERSTAND your results in the larger context of the full collapse. You took your 0.1% piece & reported them. Again, congratulations.
And yet, you felt entitled to declare "shoddy or fraudulent" a bunch of the world's best structural engineers, who have spent their careers working in the messy real world and who did have to understand the full context of the collapse. Sorry, champ. When you started making these accusations, you stuck your appendage into the meat grinder and began to happily crank away. And only later noticed an uncomfortable feeling.
You are not the only smart guy around. And you are inept at integrating your observation into the larger context of the collapse of the building. Others, with more pertinent backgrounds, saw your correct & incorrect conclusions immediately.
You have been dealing in physics-type absolutes. You slide casually & carelessly from "fell at almost G", to "fell, for all intents, at G", to "fell at G". You then opine that "for something to fall at G, there has to be zero resistance". The correct phraseology is "for it to have fallen at approximately G, there has to be approximately zero resistance."
And, as I have drummed into about 20 baby engineers that I've helped mold in my career, "unless you know the cold, hard numbers as well as the nerdy error bands, you don't know Jack." Without an error analysis, you do NOT know how "approximately close to G" you can claim. Without a solid background in structural dynamics, you do not know "how approximately close to zero" can be the resisting force generated by a structure in the process of buckling.
You thought that your results proved something that was impossible in a gravity driven collapse of a building. And, in the pristine physics terms that you've phrased it ("it fell at gravitational acceleration'), it might be impossible. But once you throw in the real world's messiness, then your "impossible event" turns into "not surprising at all".
All of the above is trivial. It is simply the reasons that your "aha" moment is going to fizzle. These are the reasons that, with respect to your conclusion of "controlled demo", you are simply wrong.
But, we're all adults. We'll all get thru this. The guys at NIST are older engineers. That means that they've got hides like rhinos. The fact that they know that they are right, and that your accusations of incompetence and/or fraud are baseless, constitutes a first rate armor against such slings & arrows. The fact that it is an academic putz who is making the baseless assertion is merely the cherry on top of this sundae.
And you can get thru this too. If you do it right!! If you simply stop where you are, and go find a COMPETENT structural engineer to help you fill in the blanks that you do not presently understand. If you take this path, you'll come out a better person. A bit humbled, but more appreciative of the incredible level of competence that exists amongst professional engineers who have risen to the top of their professions. And, if you have a sense of decency & justice, you'll write an apology to a bunch of honest, honorable guys whose integrity you have slandered.
If you continue on the same path you've been on, you're heading for a public whooping. Probably just like you've been getting. Because Mother Nature is a cold hearted witch. Right is right, wrong is wrong, and it always comes out in the end. You'll be left attempting to defend the indefensible. And looking foolish in the process.
So, all of the above will sort itself out.
But it is the lessons that you are teaching your students that chaps my ass.
Teaching them to think for themselves, to question authority, to challenge dogma is mandatory. And incredibly valuable when it is done right. And a part of teaching that right is to teach them respect & admiration for expertise, hard work, rigor & demonstrated achievement.
You are setting a horrible example. You are teaching them suspicion, distrust &, frankly, baseless paranoia. And you are teaching them that it is acceptable to accuse perfect strangers of massively unprofessional, and borderline treasonous, behavior, based on one's own guesswork.
You do your students a massive disservice.
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I am not concerned with "credit" per se, but I am concerned with getting the record straight. When you say, "Chandler didn't have to do this work at all" the implication of your words, in the original context, was that NIST had already measured what I measured ...
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First, let me explain (better) the point that I was trying to emphasize in the paragraph from which this sentence is excerpted. Which is that "both you and NIST have obtained exactly the same result".
Your 0.98G is an average acceleration over one particular time interval (1.75 to 4.0 seconds).
NIST's 1.4G is an average acceleration over a different time interval. (0.0 to 4.0 seconds)
Neither one is "the right acceleration", which would be the instantaneous acceleration.
Yours is closer to the truth, because you have accurately identified two separate regimes, and analyzed one independently of the other.
I hear in your comments phraseology that implies that you & NIST got different results. This is simply not the case. I find your suggestion that "the REAL acceleration is 0.98G but NIST reports 1.4G" to be misleading. THIS is the point that I was trying to make in that paragraph.
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Nonetheless, I did make an incorrect statement. I saw NIST's results before I found yours, and thought that you had duplicated their work. I understand now that you did it first.
So, in that post, I need to strike the sentence "Chandler didn't have to do this work at all." And change "Chandler replicates NIST" to "NIST replicates Chandler", giving you credit & priority.
Tell me where anyone has been giving you a bad time about this & I'll happily post a correction.
I would point out that this was one comment out of about 20. Do you have any comment on the rest of the post that did not deal with credit or priority?
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... [your implication that] I was being sloppy in my own research, rehashing the obvious, and making a mountain out of a molehill. This is exactly the way others in the JREF forum and Screw Loose Change have interpreted your words.
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And now, David, welcome to MY classroom.
You chose to walk in here when drifted out of your classroom & posted your work to the public.
It is not high school. It is not college. It is not academia. It is the real engineering world. There are ONLY TWO grades: A+ and F. And everything that is not an A+, is an F. What score does it take to get an A+? 100%. What do you call a "99 out of 100"? An F. Failure. NOBODY wants to talk about the 99 things you got right. EVERYBODY wants to talk, in detail, about that other one thing.
Next point: everything that you do in here is subject to cold, harsh, PUBLIC criticism. Including people telling you that you "don't know WTF you are talking about". Calling you "a moron". And, while it ain't nice & it ain't fair, even commenting on "yo mama", just to see how you hold up under pressure. Remember what I said about engineers' thick hides?
There is ONLY ONE metric for how well you do. It is not "how hard you tried". It is not "you used the right approach, but made just a little math error." It's not "do I get partial credit".
The only metric that matters is "did you get it completely right"?
Do you think that I'm grading too hard?
Do you think that I'm being mean?
Do you think that I'm not being sufficiently concerned with your self-esteem?
Well, if you do...
... THEN GET THE **** OUT OF MY CLASSROOM...!
Go back to high school where you can make mistakes and nobody gives a rat's azz. Where tests are graded on a curve. Where the teacher corrects your tests & gives you your grades in private. Where you get to start over every semester. Where you can impugn the integrity & competence of another person, and tenure or academic politesse is gonna cover your butt from retribution.
Now, you objected to my "implied" comment of your sloppiness. Well, here we don't "imply". We say. Clearly.
So let me be clear regarding my opinion of your rigor, sloppiness, etc.
1. Your priority. You did it first. A+
2. Selecting your video. A+ (if it was uncompressed). C (if it was compressed).
3. Selecting your analysis program. A+
4. You started out with a weakness in your scaling, but you recovered. A+
5. Taking your data points. A
(I can think of two techniques right off the bat that would improve your data set.)
6. Reporting your raw data (position vs. time). D.
7. Your analysis method: C
You chose to use the calculated quantity (velocity) vs time and report the average slope.
Plotting position vs time, generating an interpolation equation that fit the data points, and differentiating that equation twice will give you substantially better results.
8. IIRC, you did not do a regression, but picked your endpoints, and let the program draw the slope of the curve. Usually, I'd mark you down for this, but I'm feeling lenient. And your curve doesn't look too bad. C (an A+ analysis on C data gives you a C grade.)
And now I look for your error analysis. And it is not to be found. F.
And this is where I'd stop reading, shake my head & chastise you for wasting my time. And tell you to come back when your project is REALLY finished. You don't like it? Tough. Personnel is on the first floor if you want to quit.
By the way, you would also have gotten an F for:
9. "lack of familiarization with ALL pertinent background subjects"
10. "failure to run your conclusions by real experts"
And the biggest F of all, of course, comes for arriving at the "WRONG ANSWER".
Not the answer to the intermediate question: "Did the wall come down at approximately G?"
But the answer to the real ultimate question: "Is this acceleration (including error bounds) incompatible with NIST's explanation of a gravity driven, progressive collapse?"
You'd also get a red flag for "doesn't play well with the other engineers". This flag is completely cancelled if you consistently get the right answer. You aren't starting off well, and I'd have a private chat with you about that.
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You might disabuse your own crowd of their mistaken perceptions based on your words.
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As I said, let me know where you find that, and I'll post a correction.
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No way. If I make an occasional appearance it is because I have something to say or some record to set straight. I'm responding here to what I perceived as a civil post on your part. However, I don't find it stimulating, entertaining, or even tolerable to subject myself to an environment where verbal abuse is the norm.
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This IS the way the engineering world operates, David. You can toughen up and play here. Or go back into the sheltered haven of high school. Your choice.
Now, I do understand & empathize with the fact that the Internet world at large has a bunch of crazies. I've had nuts stalk me with comments that probably mirror the ones you've gotten. (Although I've gotten "psychotic" and "paid shill for the Neocons" instead of, I suspect, "traitor".)
You clearly are someone who believes what you have said. I'm sorry that you've had to go thru the not-so-tender mercies of the crazies.
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I do in fact enjoy intellectual sparring with people who hold contrary views, when conducted in an atmosphere of honesty and mutual respect, or at least bare civility.
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"Intellectual sparring" is one thing. "Getting the right answer" is something entirely different. I'd suggest that you pay more attention to the latter.
"Civility" is a rare luxury.
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--David Chandler
(That's who I really am. Who are you???)
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I'm an engineer who learned, thru painful experience at a young age, not to go into the sandbox of a bunch of smart, experienced engineers and publicly kick sand in their faces.
And someone who luckily learned that it ain't worth the hassle to expose myself to the crazies.
I hope that it all quiets down for you someday. I hope that you'll take my advice and talk to a couple of QUALIFIED structural engineers.
Tom
PS. This IS what passes for "civil" in my circles, David.
