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Post by rodin on Jul 20, 2009 8:42:53 GMT -4
The outer columns would provide little resistance to the collapse, The 40 odd feet would be free fall since the two stories there would have collapsed quickly with no resistance, after that the only resistance in the south wall is from the columns separating at the joints. With the north wall, the wall we see, it actually fell southwards, not straight down, it ended up folded over the top of the pile. In fact we know that the building didn't fall into its own footprint because it hit several surrounding buildings when it collapsed. On top of this we really can't say how close to free fall the collapse was (note that free fall is an acceleration, not a speed or a velocity) because we don't have any film that records the end of the collapse. We can guess, and our guess is that it was close to what an object in free fall would have taken, but not exactly, and when you have any delay, no matter how small, then you have resistance. The question you need to find the answer to is how much resistance woulkd the columns have created before the joints failed. While I am sure we have a few people here that could tell you exactly how to do that, I'd suggest that the answer is going to be in the ms, and over 40 stories that only adds up to a fraction of a second, something almost impossible to measure from the videos. You know I am beginning to think you are spinning a line not seeking truth. The observed wall in the video I used showed no appreciable sideways movement in the plane of observation (along the edge of the building). Furthermore I was able to observe substantially more than 330 feet falling down at freefall speed with no buckling. Of course I know g is an acceleration of 32 feet sec-2. It is not necessary to see the final part of the collapse to determine if free-fall was a measurable element of the collapse. I think you know this, and therefore your comment... we really can't say how close to free fall the collapse was (note that free fall is an acceleration, not a speed or a velocity) because we don't have any film that records the end of the collapse. ...is made either from a lack of quality analytical thinking, or you are promoting a lie.
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Post by gwiz on Jul 20, 2009 9:27:38 GMT -4
You know I am beginning to think you are spinning a line not seeking truth. The observed wall in the video I used showed no appreciable sideways movement in the plane of observation (along the edge of the building). Furthermore I was able to observe substantially more than 330 feet falling down at freefall speed with no buckling. You don't seem to be aware of the collapse process for the whole building, either. The NIST simulation shows that, following the collapse of the internal structure, the outer walls failed around floors 5 to 7, out of shot below all the video coverage, and the part of the walls above the failed area then had several floors of effectively minimal resistance into which they fell more or less as a unit. This unit then failed from the bottom up as it hit the lower stub of the building. There would not be any reason for the upper part of the walls to show signs of buckling in the videos.
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Post by gillianren on Jul 20, 2009 13:36:09 GMT -4
No, I wondered if this forum was a spin-off of BAUT allowing a wider constituency of topics Nope. Started with completely opposite intentions, in fact.
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Post by rodin on Jul 20, 2009 13:51:09 GMT -4
This unit then failed from the bottom up as it hit the lower stub of the building. There would not be any reason for the upper part of the walls to show signs of buckling in the videos. OK I get the story - all stories above 7 fell into gap then impacted the ground level where, as each successive floor hit, the support columns at that level gave way, is this correct. Because if support columns gave way at higher floors than stub impact level we would have seen this as a disintegration of the wall, which obviously fell intact until impact?
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Post by gwiz on Jul 20, 2009 14:17:15 GMT -4
OK I get the story - all stories above 7 fell into gap then impacted the ground level where, as each successive floor hit, the support columns at that level gave way, is this correct. Because if support columns gave way at higher floors than stub impact level we would have seen this as a disintegration of the wall, which obviously fell intact until impact? That's the general picture. Something similar happened with the towers, with the parts well above and below the impact levels initially staying intact during the collapse, with a zone of destruction moving down the lower part. Due to the amount of debris concealing the view, it's not clear from the video what is happening at the base of the upper part, it is presumably getting damaged from the bottom up.
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Post by echnaton on Jul 22, 2009 15:25:04 GMT -4
I don't care if there was nothing at all connected to the wall in question. It fell pretty much straight down, at free fall speed. Even if the only thing left standing was that wall, it could not have done this unless all resistance was simultaneously removed at every level. So tell us rodin, since you are saying that the offered reason for the collapse is not consistent with the speed of the walls falling, how fast should they have fallen in that scenario? Its really kind of boring to just say "this can't be right" without offering something concrete to back it up.
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