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Post by JayUtah on Oct 19, 2005 14:34:06 GMT -4
BTW IIRC "center of gravity" is not a term that is normally used by anyone other than non-scientists.
Not true at all. Center of gravity and center of mass are defined differently, but in many applications they equate to almost the same geometric point. Center of mass is the locus of concentration for an object's mass for inertial purposes, and for most applications of force it is a key geometrical consideration for the object's response to that force.
Center of gravity is the locus of an object's weight, which takes into account the special nature of gravity as a force defined by a tensor field, especially where large objects are concerned. Objects that are large enough, or in an eccentric enough gravitational field, so that different parts of the object are subject to different gravitational force, have a center of gravity different from the center of mass.
Chances are that the center of mass and the center of gravity of the top of the WTC towers differ only by a negligible distance.
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lenbrazil
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Post by lenbrazil on Oct 19, 2005 19:13:54 GMT -4
Jay or anybody else did you find anywhere in the NIST report, where they said the steel reached temperatures over 600 C? This would be still be sufficient because that's over 1100 F at which steel loosed 50% of it's strength according to the expert quoted in PM
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Post by JayUtah on Oct 19, 2005 19:43:05 GMT -4
Yes, somewhere in the middle is a summary of the thermal models of the structure in which some steel elements reached temperatures of 600 C or thereabouts. Different models were run with different initial assumptions. The empirical samples did not show evidence of steel heating beyond 600 C and the models did not predict heating beyond 675 C. The 1,000 C estimate, again, is for the gas layer in some portions of the buildings, not for the steel. The gas estimates derive from the fluid dynamics portions of the computer models.
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lenbrazil
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Post by lenbrazil on Oct 19, 2005 20:14:51 GMT -4
Yes, somewhere in the middle is a summary of the thermal models of the structure in which some steel elements reached temperatures of 600 C or thereabouts. Different models were run with different initial assumptions. The empirical samples did not show evidence of steel heating beyond 600 C and the models did not predict heating beyond 675 C. The 1,000 C estimate, again, is for the gas layer in some portions of the buildings, not for the steel. The gas estimates derive from the fluid dynamics portions of the computer models. ?? I asked about steel tempretures over 600. You said "Yes" but the rest of your answer sounds like a "No"
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Post by JayUtah on Oct 20, 2005 10:16:28 GMT -4
Sorry, the answer is yes -- the NIST report gives heat transfer models that show some steel reaching and exceeding 600 C.
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lenbrazil
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Post by lenbrazil on Oct 20, 2005 14:06:34 GMT -4
Sorry, the answer is yes -- the NIST report gives heat transfer models that show some steel reaching and exceeding 600 C. You said up to 675 C anything exceeding that? How sure were they that it got that hot? Do remember the chapter/page numbers? Also Turbonium says that the report never says that the structural damage caused by the impact of the planes had a role in the collapse of the towers. I don't believe this is true. Do you know where in the report it says this? P.S. Congratulation to me [I've now made it to Earth - Marsward ho!]
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Post by JayUtah on Oct 20, 2005 17:10:25 GMT -4
You said up to 675 C anything exceeding that?
In one set of output, which is a 3D rendering of the steel structural sytem of each tower at T+6000s, the temperature legend only goes to 675 C. The software automatically generates these scales as color-coded references. A significant portion of the steel depicted is between 600-675 C on the color chart. None is depicted as hotter, and with the way the data are presented, it would be impossible to do so.
In another set, which is a 2D structural plan color-encoded for temperature at different points in time, the legend peaks at 800 C, and very little of the steel depicted has reached that temperature. A handful of columns is consistently at around 600 C.
There is a large amount of tabular data, one in particular showing which kinds of structural elements exceeded 600 C. Not surprisingly, the trusses and core columns seem most likely to exceed 600 C.
How sure were they that it got that hot?
As sure as a computer model can be validated. Much of Chapter 6 discusses the computer models and the means used to validate them. No one is ever able to measure temperatures in any actual structural fire, although instrumented full-scale tests produce empirical results. All temperature profiles for actual fires have to be reconstructed in some manner after the fact.
I am involved in creating these kinds of models for other purposes, and they are only useful to the customers if they are accurately predictive. Customers are not really willing to spend $1,000,000 on one of my products if it's just going to produce guesswork. The same kinds of models are used to predict, for example, heat flow paths in engine structures so as to provide optimal materials margins.
The WTC fires resulted from initial conditions that cannot necessarily be determined with great accuracy. And since initial conditions affect final results significantly, the NIST researchers parameterized their models in various ways to examine a reasonable range of possible outcomes.
Do [you] remember the chapter/page numbers?
I went back to double-check, so I have exact references. The graphical depictions of some of the model output is on pp. 137-138 of the draft NIST report (pp. 191-192 in the PDF page-numbering).
Also Turbonium says that the report never says that the structural damage caused by the impact of the planes had a role in the collapse of the towers. I don't believe this is true. Do you know where in the report it says this?
It doesn't. The report mentions several times that the relative roles of impact and fire were to be assessed. Nowhere I've read in the report concludes that the impacts and the resulting structural damage did not contribute to the collapse. In fact, this is stated most clearly in Chapter 8 (Principal Findings, pp. 177ff.) A sample:
It is difficult to image how, in light of this kind of language, someone could contend that the report argues that the aircraft impact had "no role" in the overall collapse scenario. Perhaps there is confusion over the findings that the aircraft impacts alone would not have inflicted sufficient damage, and that the buildings were observed stable after the impacts.
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lenbrazil
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Post by lenbrazil on Apr 6, 2006 23:36:50 GMT -4
How can I check if someone who claims to be really is an Architect in West Virginia? I tried the AIA database but it only shows firms and offices so individual architects who work for firms don't show up. I tried the sites of the state AIA chapter and licensing board but they didn't have searchable databases. The person in question is Ted Elden a.k.a Henry Theodore Elden Jr. who is listed on st911 as an "architect/communicator" I exchanged some e-mails with him and asked if he was licensed and he replied that he was " (a) registered Architect, NCARB, AIA" there are no Eldens listed in the NCARB database and it's possible to join AIA without being an architect if you work with one, In this case I think he works with his dad, he it seems is a wedding photographer. www.abodia.com/architecture/index.htmwww.abodia.com/photography/about_us.htmEDITED TO ADD I went back to the site of the state board he is listed as having a lisence but being "inactive".
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Post by Ranb on Apr 8, 2006 3:38:27 GMT -4
Maybe this has been mentioned before, but some people are using total building height to determine how fast it fell. Wasn't the pile of rubble that the towers collapsed into rather high? Wouldn't this result in a shorter drop for parts of the buildings? Thanks.
Ranb
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lenbrazil
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Post by lenbrazil on Apr 8, 2006 9:32:18 GMT -4
Maybe this has been mentioned before, but some people are using total building height to determine how fast it fell. Wasn't the pile of rubble that the towers collapsed into rather high? Wouldn't this result in a shorter drop for parts of the buildings? Thanks. Ranb The pile was about 60 feet/20 meters high. Thus unless I'm missing something free fall time would have been 9 and not 9.2 seconds. As to the architect I mentioned above, he is it turns out a legitimate architect and even got a master's degree from a well respected school (Carnegie-Mellon). I asked him about his experience with tall building design and he only mentioned one "Our VA Hospital design was $ 5 million construction project, 8 ? stories." His use of 1st person plural and uncertainty about it's height leads me to believe his dad and the other architects/engineers employed by their company designed that. I asked him about tall/steel framed buildings he was the architect for and he hasn't answered yet despite already having sent we 2 e-mails since I asked
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Post by PhantomWolf on Apr 8, 2006 22:38:54 GMT -4
I was looking at some footage the other night, one of the towers still appeared to have 6-7 floors standing after the collapse, so that pile wouldn't exactly be small.
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Post by truthseeker on Apr 11, 2006 18:44:41 GMT -4
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Post by scooter on Apr 11, 2006 19:58:20 GMT -4
If you read the actual report (not the 91sft stuff) you will see that the fire damage did NOT extend beyond the 11th floor. Some cabling in conduits burned within the conduit up and down a few floors, but there was no fire outbreak in the office areas beyond floor 11. Funny how a roaring inferno is implied in this fire, but on 9/11, with the same materials burning, PLUS JP-4, on several floors , it's a small fire...(even though the firefighter consensus was it was unfightable...quickly became an evacuation and rescue operation).
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Post by truthseeker on Apr 11, 2006 20:10:49 GMT -4
I was more interested in the steel temps.
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Post by PhantomWolf on Apr 12, 2006 2:51:06 GMT -4
I'd also note that the 1975 fire didn't involve structural damage to the surroundings, nor the removal of the fire retadant and insulation material from the explosion of a plane crash.
This is just another case of the CT's ignoring that Fire alone didn't bring down the towers, it was a Plane slamming into the building + a large fire.
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