South Tower tilt

[Contrite]

http://911evidencebase.16.forumer.com/viewtopic.php?t=74

This is new photography and discussion concerning the tilt and rotation of the top of the South Tower. Gordon Ross contributes to comments.

[JackRiddler]

1. Ross should expand his empirical data base.

He intensively analyzes one video and constructs a number of possible models from it. (Why are those boxes all so short and squat compared to the actual proportions of the towers?) Perhaps he needs to look at more angles of this collapse, and find some pictures of the aftermath / rubble pile.

For example, what does this picture suggest about where the top actually landed? Sorry that the lines inserted by someone else already give away an answer, but do you read a different interpretation? Furthermore, I happen to know the man who found the headstone from the 110th floor - near the corner of Church and Liberty.

[Contrite]

2. It's not Ross's work! It is that of "carcdr" at 911evidencebase.co.uk

Ross merely responds to it--noting the areas of disagreement with the model and allowing for areas where there might be complementary findings.

Here is Ross's response to "carcdr" dated February 17, 2007:

Good analysis - it all helps fill in the missing pieces.
In reference to the point made regarding how this contradicts my analysis, I do not believe that such a contradiction is present, but rather that the two studies, mine and yours, are in sympathy with each other.
I believe that the first phase of the demolition involved a severing of all the core columns at about the sixtieth floor. The evidence for this is Aman Zafar's photograph of the lower core section, from about the sixtieth storey to ground level, still standing at an advanced stage of the collapse.
This does not necessarily mean that the position of this cut was the centre of rotation of the upper section. If the cut through the core was done by way of a 45-degree cut through each of the core columns, the result would be a sideways movement of the bottom end of the broken off upper core section as it begins to move downwards.
The result of this would be an inward bowing of the columns on one perimeter face as the floors pulled inwards and downwards. This was a phenomenon noted by NIST immediately prior to collapse initiation.
The other result and the one which is pertinent to this discussion is that the centre of rotation would not be at the point where the core was severed, but rather would move towards the points F and G in your diagram. From this we can see that the two studies do not contradict, but in fact each study backs up the findings of the other.

I'll study this in more detail later and may get back to you again.
Gordon.

[JackRiddler]

3. Fine...

I was looking at carcdr's observation and finding it problematic:

The already accelerated block would be "slurped" back into the lower portion - i.e. the outer walls of the bottom portion would act like a funnel and would gradually (over distance) provide sufficient counter-force to the torque that would "right" the top block and cause it to fall straight into the footprint of the bottom portion, without tumbling off to the side. As Gordon Ross says "This can be envisaged by imagining a Christmas tree being pulled downwards through a packaging funnel. The force only has to be generally downwards to have the trunk passing through the centre and it will tend to straighten or arrest any tilt of the tree.

This doesn't appear to be what happened. It did not straighten out and fall back into the footprint. The tilting top continued tipping over, conserving angular momentum, and the topmost floor landed 400 feet away, exactly where one might expect. The rapidly spreading dust obscured all this, but this is what must have happened, as the picture above indicates.

[Contrite]

4. Ross doesn't appear to agree entirely but finds areas of agreement

Ross says:

"I believe that the first phase of the demolition involved a severing of all the core columns at about the sixtieth floor. The evidence for this is Aman Zafar's photograph of the lower core section, from about the sixtieth storey to ground level, still standing at an advanced stage of the collapse.
This does not necessarily mean that the position of this cut was the centre of rotation of the upper section.

The other result and the one which is pertinent to this discussion is that the centre of rotation would not be at the point where the core was severed, but rather would move towards the points F and G in your diagram."

Meaning that Ross believes that the first demolition was below the damage area (about the 60th floor), but that the position of the cut would not necessarily be the center of rotation of the upper section. Still, he feels that if the columns were cut at a 45-degree angle, it would cause the bottom end of the top section to fall to the side as it begins to move downwards, which would still fit carcdr's F-G models where the center of rotation is above the damaged areas.

carcdr's Bald Guess was: "If the first rotation's axis were at the center of gravity of the top portion - i.e. model F - then the top portion would fall straight down without tumbling (since this model preserves the location of the center of gravity). This would:


- make the top portion appear to tilt,

- keep the top portion "safely" within the footprint of the bottom portion (no toppling), and

- impart a downward velocity to the top portion (2 - 4 seconds of acceleration - straight down)."

Ross does not appear to answer this directly, although carcdr does employ Ross's Christmas tree example.

carcdr also says: The amount of "inward bowing" on the left depends on the position of the center of rotation - the higher the axis, the greater the inward bowing. Note that the opposite occurs on the right side - there is "outward bowing" on the right side.

And Ross answers: "The result of this" (the sideways movement as the top section moves downward) "would be an inward bowing of the columns on one perimeter face as the floors pulled inwards and downwards. This was a phenomenon noted by NIST immediately prior to collapse initiation. From this we can see that the two studies do not contradict, but in fact each study backs up the findings of the other."

This is what Ross' report says:

Perimeter column bowing

Note that the bowing identified by Nist was only on one side of each tower. It was not generalised across all of the tower.
For the example of WTC1, Nist report bowing only on the South face, storeys 94 - 100. For WTC2 bowing only on the East face, storeys 77 - 83.
Note that for both Towers only the MID-WALL perimeter columns were bowed.The corners were not visibly bowed.

If the bowing was being caused by a pure vertical movement of the upper core structure, that is with no tilt, the bowing would be present on all four sides.

Angle cut columns

Example of an Angle Cut Vertical Column
5100.jpg

However if a 45 degree cut is made in the core columns, there will also be a horizontal component to the movement of the bottom of the upper core section and a consequent tilt in the upper core section.
The floors will only transmit an inward pulling action through the floors to one wall, with a compressive action on the opposite floors and a twisting action on the floors on the adjacent sides.

It was the reaction created by a, say, 45 degree cut through the core columns which began, both the tilting action of the upper sections, and the bowing of one perimeter wall in each Tower.

Rotation of upper section.

The upper section of WTC2 appears upon first examination to tilt as one piece about a fulcrum located at the aircraft impact level. Closer examination reveals that there is a distinct bend in the line of the corner columns and the top storeys of the upper section, those which are above the bend do tilt, but in the section below, more obscured by smoke, there is less, or even no, rotational movement in the line of columns. The upper section did not necessarily display the behaviour expected by some commentators and in particular it has been said that the conservation of angular momentum was not observed.

Because the core failure occurred at a lower level than aircraft impact the core structure projecting below the impact level would give a "keel" action to the upper section as it fell. It would also give a different fulcrum position for the rotation, than has been previously examined. This may account for some questions which have been asked.

This can be envisaged by imagining a Christmas tree being pulled downwards through a packaging funnel. The force only has to be generally downwards to have the trunk passing through the centre and it will tend to straighten or arrest any tilt of the tree.