Oddly I see no math what so ever in your link. Bazant’s is rebutted by a essay of obtuse feelings?
So now you’re quoting Ace Baker, the musician who believes that the news videos we have of Flight 175 crashing into WTC2, actually were recording no plane, but the plane image was added in real-time by the news organizations? He thinks that planes didn’t even hit the towers, that they were faked. I dealt with him over at JREF long ago, and he’s, well, unusual.
The fact that he’s so far from credible doesn’t negate what he says by itself, but it sure does say a lot about where you get your information, if you feel a need to quote him.
Ahh, the Volkswagen Mophead. Classic car.
You are absolutely correct about this. Hopefully your own statement will stir some self-reflection: you’ve demonstrated that you don’t understand the basic physics behind your own models or the relationship between the models and the more complex buildings. Moreover, the data you’ve been repeatedly asking for is useless for the calculation you want to make with it.
My personal opinion is that you’d be better off re-examining your pre-conceived ideas about structural modeling, and be open to considering new data and information rather than just LOLing and ROFLing and so forth. But then, I’m not an expert in message board communication.
So you are saying that some of the kinetic energy of the plane did not go into moving the building in the vicinity of the impact?
psik
So, basically you are saying that it didn’t need to be worked out exactly, because it was quite apparent to anyone who knows anything about physics, just what happened, and anyone who wants specifics, is just nit-picking?
Correct me if I’ve read you wrong.
Define “exactly”. For obvious reasons, the exact sequence of collapse won’t ever be known, because we don’t have comprehensive video evidence of what was happening inside the towers as they were burning. We have a number of eyewitness accounts, with the normal and expected range of inaccuracy eyewitness accounts are always prone to. Structural engineers can and did closely examine the wreckage afterward, but it was in such disarray and in such quantity that an exact sequence of collapse is at best a highly educated guess.
A general sequence of collapse, i.e. one that covers the major points and is not contradicted in any serious way by avilable evidence, has been available for NEARLY EIGHT YEARS, but if by “exact” you want to know exactly which beam broke first and where, which beam broke second and where, which beam broke third and where, all through the entire collapse, then you’re asking for an unreasonable standard of proof, and gleefully doing so because you’re deliberately asking a question nobody can answer and using this to to claim that the answer is known but being deliberately concealed.
Heck, nobody could explain exactly how a car accident happened, if the “exact” standard required accounting for every bit of metal and tracking its exact path during and after the collision to within a tolerance of one micron. My question to you is how “exact” a explanation do you need to be satisfied, assuming there is any possibility that you can be satisfied.
Not too sure about Zut, but what we’ve been saying is this:
- The data is available, all Psikey has to do is go to NYC and dig up the old blueprints on file with the Port Authority.
- We’re not going to go to NYC to do this 'cause we don’t need the information.
- Regardless, the specific information that Psikey is requesting is irrelevant in understanding why the buildings fell. For example, we don’t need to know the distribution of all molecules of hydrogen on the sun to understand why or how the star is undergoing fusion.
- We have yet to hear Psikey’s explanation of what he thinks brought down the buildings. If it wasn’t the planes, if it wasn’t the fires… then what?
On one hand, just on WTC7 alone, we have teams of experts who have run LS-DYNA simulations using a model based on 3.045 million elements, run on a high-speed Linux Beowulf cluster using 2 64bit 2.4Ghz processors/4 gigs of RAM/1.5 Terabytes of RAID 5 disk storage over an 8 week period, and on the other hand we have…
a musician and a guy who made a Youtube video using washers and toothpicks.
Now, c’mon. For those of us who aren’t structual engineers, who should we believe? The guy with the tinkertoys or the experts using JPL simulation software?
Actually, that level of precision can be known. For example, for WTC7 according to the NIST (8 meg PDF! Look at page 31, if you dare to load it), it was beam # 79 on the 13th floor which caused the collapse.
Of course. Some of the kinetic energy of the airplane was spent in severing structural support columns in half. Some of it was dissipated (sp!) when it made people into pulp.
And that’s good, but what was the second beam to break? And if you know that, then tell me what the third was. And if you know that… well, you can see where this is going. I’d like to know if ivan’s (and by extension, psikey’s) demand for an “exact” solution has a limit, or will it be an exercise in goalpost-moving where every answer leads to yet another question?
True that. They’ll probably get down to the Heisenberg level of uncertainty and then say “See?!?!? Conspiracy!”
Heisenberg, huh? Sounds Jewish…
That’s a pretty big oversimplification. As a number of us have pointed out several times in these threads, understanding what happened beyond the screamingly obvious parts (big plane crash and fire, buildings collapsed) takes a bit of knowledge. The basics are not really complicated but they’re not immediately obvious to someone with, say, high school physics as their only background. Somebody with a moderate education in physics, material science and structural engineering can explain it quite well to the layperson (as I think we’ve seen done many times).
Our everyday experience with normal phenomena simply does not scale up well to what happened to the WTC buildings and that makes it very easy for people to draw wrong conclusions or just not understand what took place on a technical level.
As far as wanting specifics, posters like Bryan Ekers and JohnT have covered that well - there’s a certain level of detail needed but there’s plenty of detail that is not needed, and in fact may be hard to come by. Knowing, for example, that 6 floors were engulfed in flames that would easily reach 600+ F (these are numbers off the top of my head, not specifics) is important in understanding what happened. Knowing to the nearest degree the exact temperature in each square foot of each floor over time is not necessary, and constantly insisting on that kind of detail (even when it’s been explained over and over that it’s unnecessary) will in fact become nitpicky.
I wasn’t explicitly saying that at the time, but yes, your statement is absolutely correct. Some of the kinetic energy goes into deforming the structure of the building; some more goes into deforming the plane itself.
Well, no, I wasn’t saying that at all, and even the most inexact restatement of what I said comes nothing close to what you posted. I have a hard time believing you’re sincerely puzzled here, and in fact I suspect you’re using my post to make some obtuse rhetorical point rather than honestly asking for clarification.
However, let me assume for a moment that you’re posting in good faith and answer your question.
I’m saying that the models psikeyhackr has constructed don’t reflect what actually happens in a full-sized building, because of some oversimplification and scale effects. It’s not that you can’t build a reasonable scale model, and it’s not that it’s a bad idea. It’s just that it’s not necessarily easy to do right.
Moreover, psikeyhackr has been pretty vocal about wanting a mass distribution of the building, in order to determine building deflection after impact. But to determine building deflection (approximately, but that’s fine), what he really needs is the structural stiffness of the building. So the thing he’s been asking for for years and years is the wrong thing.
And, even if it *were *the right thing (which it’s not), it’s not at all clear that knowing an exact distribution would result in a substantively different result, considering all the other uncertainties and the relative coarseness of the ultimate answer (“does the building fall or not?”).
Does that answer your question?
You are going into word games here.
There are two different types of deforming we are talking about here.
There is the bending and even breaking of steel which will not spring back. And there is the bending that will return to its original position. The NIST said the south tower deflected 12 inches at the 70th floor and I extrapolate that would be 14 inches at the 81st floor. The NIST then says the building oscillated for four minutes.
Now didn’t some of the kinetic energy from the plane go into producing that deflection and oscillation so don’t we need to know the mass in the vicinity of the impact to compute how much energy that took? And don’t we need to know that to compute how much energy did permanent structural damage?
psik
That wikipedia link says that Ace Baker killed himself last week. As much as I’ve spoken unkindly about him, I am saddened by his death and apparent state of despondence before it. He was apparently a talented musician, but it was pretty obvious that he had serious delusions about the 9/11 attacks (believing there were no planes at all, but images of planes were placed into live TV streams, cameras, and I guess people’s memories who saw it first-hand.
I guess if we wanted to compute the amount of the plane’s kinetic energy went into causing structural damage in the building, you would need to know that, but why would anyone need to know? There was a lot of kinetic energy dispersed into the building, and then the fires caused them to collapse. Every analysis I’ve seen indicate that the collapses would have occurred even without the structural damage, as long as something stripped the fire-resistant material off the floor trusses.
But I’ll play along with some round numbers for you. The kinetic energy in a moving object is mv[sup]2[/sup]/2. Before the crash, there was just the kinetic energy from the plane:
(45000 kg) * (245 m/s)[sup]2[/sup] / 2 = 1,350,000 kN
Now, what about the kinetic energy in the building after? This is the energy that it would have as kinetic energy as it started swaying, then this would build up to spring potential energy when it reached its peak displacement. But let’s assume that it started moving at about an inch per second, that the building weighs 500 million pounds, but since it’s fixed at the base let’s use half that energy.
(227,000,000 kg) * (0.0127 m/s)[sup]2[/sup] / 2 = 18 kN
So according to my rough numbers, there were 1,350,000 kN in the plane before the crash, and 1,349,982 kN were spent on damage while 18 kN went into moving the building.
99.999% of the plane’s energy went into damaging the building, while 0.001% went into moving it.
Now, why was this important?
I didn’t intend to play word games, although I can see why you might think so. Let me clarify. Your original question was this: “So you are saying that some of the kinetic energy of the plane did not go into moving the building in the vicinity of the impact?”
And yes, your statement is absolutely correct. Some of the kinetic energy goes into the permanentdeformation of the structure of the building; some more goes into the permanentdeformation of the plane itself. By permanent deformation, I mean actually permanently bending or breaking the steel (or aluminum, or whatever) so that it doesn’t spring back. (Which involves breaking molecular bonds, by the way, so if you’re interested in following the path of the energy flow, there you are.)
And, of course, some of the energy does go into moving the building motion.
A two-part question. The first is obvious: Of course some of the kinetic energy from the plane goes into producing that deflection. The second is, it seems, where you’re having trouble.
Consider it this way: oscillatory motion is really the transfer of energy between the kinetic form (which is a function of mass and velocity), and potential form (which, in a system with stiffness, is a function of the stiffness and the displacement).
So, in oscillatory motion, the *distance *that an object moves given a certain energy input depends on the stiffness. The *velocity *that an object moves given a certain energy input depends on the mass. As a thought experiment, imagine your tower with a really flimsy rubber base connecting it to the ground. If you hit it with a known energy, would you expect the tower deflection to be exactly the same as if the base were a completely rigid steel structure? That change of base support is a change in the structural stiffness of the system.
(This is complicated somewhat by the fact that continuous systems have multiple modes, but given the setup here I think concentrating on the first mode only is not unreasonable.)
And here’s the rub. Ignore for a moment that you’re asking for the wrong thing (mass instead of stiffness). Ignore for a moment that there are inherent uncertainties in the calculation you’re doing (which is fine, by the way, as long as you keep tabs on the magnitude of the uncertainties and their effect on the answer). Suppose you do calculate the energy that does structural damage.
So what? What can you conclude from that number? How would that lead to any further conclusion about the building?
Still waiting …
Could you please show me any evidence that the top thirty story chunk of the North Tower made it to the ground intact, then disintegrated?
Support the Iranian Green Movement
Where did I ever say that happened?
And if you are talking about an approximately 30 story chunk that would be the south tower not the north.
psik
So which analysis told you how much steel was in the fire? I have not seen that anywhere yet.
Isn’t the quantity of steel going to affect the temperature in could reach in LESS THAN TWO HOURS?
Doesn’t the weight of a frozen turkey affect the time it takes to cook?
psik