02-03-2011, 03:38 AM
(This post was last modified: 02-03-2011, 03:39 AM by Jeffrey Orling.)
Peter Lemkin Wrote:Next, they sit there intact and obviously blown clean of most dust and all debris; then they just turn to a blur or dust, at every point, but even more obvious on the bottom portion. Then the dust slowly disapates....not easily explained by physics if one explains that it just lost structural strength and collapsed. Why would it, first of all? Why not topple over? Why not go down without looking like it turned to dust? If real dust on it, it would be a layer very very thick that couldn't have been there! I also believe the slow-mo way it vanished is odd. This has been little studied, but is, IMO, .... evidence of something very un-kosher going on.
The collapse of the Spire HAS been studied and the tall column is CC#501 on the northwest corner of the core of the north tower. It's 35' from the west facade and 60 from the north facade. It's about 936' tall, consists of 26 - 36' tall 22"x52"box columns one atop the other weighing over 935 tons. It along with the other 3 corner column of the core were the strongest columns in the towers.
Tall columns cannot support their own weight of they have a slenderness ratio of over 150. The core columns were braced at every 12 feet... until the floors collapses and stripped away their bracing and left them standing like a stack of pencils one atop the other. CC501 has an S/R ratio over 1/463 and reached to the 78th floor.
Columns which lose their bracing can become too tall - exceed the S/R ratio. When this happens they become unstable and buckle well below the mid point. The caused the column to "kick out" or kink out at the connecting point between two of the columns out of sight of the camera. The result is that the stack of columns above suddenly has nothing below it to support and it plunges at free fall like a spear wearing perhaps a million pounds straight down.
There was dust on the column which was clad in 2" thick gypsum blocks. The dust was left behind and dispersed to the SE by the 15-20 knots NW breeze and appears to slip to the left from camera positions to the north.
Some of the spire columns tipped over and did not experience Euler self buckling. Their joints held as they sway and broke free and toppled with no internal stress. CC501 experienced Euler buckling. This is not seen often because columns are braced to make them have a lower S/R than 150. As the bracing is removed from a column its load carry capacity decreases. If more bracing is added it can support more weight.
Buckling of unbraced (braces removed) columns play a large part of the WTC collapses... of the core columns.
CC501 did not turn to dust and you can see it descend for almost 25 or so stories.