Earliest detectable deformation of roof is progressively concave
The feature titled Antenna base shifts eastward 9.5s before collapse
shows us that the earliest detectable antenna movement leads into visible collapse initiation as a eastward ad downward hook motion, pulling in the upper west wall as it shifts east.
We also can see both the 104th fl fire along the SW corner remain stationary as the antenna moves and the guy wire connecting the antenna to the middle of the E face lose tension, meaning the antenna is sinking into the perimeter roofline, in images linked at the bottom of this page.
We can see visible antenna sagging in the NBC NW view here:
60 frames per second means this covers close to two seconds leading into the more visible initiation sequence. Notice that the fire on the SW corner, west face, floor 104 shows no significant movement during this time. It is not moving with the antenna. You can verify this by placing your mouse pointer over the fire as a still reference point. You will notice it does not move.
Also notice that the window washer unit at the NW corner roofline is not moving with the antenna. There is very little doubt that the antenna is moving independently of and down within the perimeter from frames 120 to 210.
We can also verify early concave deformation by measuring how 4 key points converge over the initial column failure sequence. Core and perimeter do not rotate together as an interconnected rigid body hinging about a rotation axis. Tis is shown next.
Confirmation of concave deformation of roof: Drop movement of antenna compared to 3 key roofline anchor points on the NE, NW and SW corners of the perimeter
Points from both views are traced and plotted below:
Sauret viewpoint, NE corner, NW corner and large antenna drops compared
The antenna begins to move downward in frame 130. The NW corner doesn't begin to be displaced downward until around frame 210.
NW NBC viewpoint: Large antenna drop compared to SW corner drop
We only care about the lines marked "real fire" and "real antenna".
Just as the gif that leads this section shows, the antenna movement is detectable at least 80 frames (in 60 fps video) before significant NW or SW corner movement from the NW NBC projection.
104 fl fire drop raw
Downward movement of the antenna is measured well before the SW corner is observed to move.
NBC NW viewpoint multiple measurements of large antenna, NW corner and SW corner drops
taken separately and stretched, , show the same downward movement of these 3 points relative to each other:
NW corner drop
Large antenna drop
SW corner drop (104th fl fire)
Static point for comparison
Another measurement of the large antenna, SW corner fire and NW corner washer drops
from the NW NBC viewpoint shows once again that the antenna was moving downward before the SW and NW corners of the building.
(notes: Black - Antenna
Red - Washer
Purple - SW Fire
59.94 fps - Resolution Doubled. 1 pixel on the graph is 0.5 pixels on the original video.
All measurements are consistent with one another. All measurements from both viewpoints show early antenna movement when compared to any point on the perimeter of the building. All drop measurements and all visual evidence shows the antenna sinking into the perimeter of the building during the earliest detectable movements.
Here is my previous graph with the addition of a trace of the following region...
As you can see, downward antenna movement preceeds downward movement of the impact region.
Comparing antenna drop to 4th key roofline anchor point on middle of E face:
The antenna leans east and moves downward relative to the small antenna and the roofline. The guy wire looses tension. The small antenna remains stationary:
The slacking of the guy wire attacking the antenna to the middle of the east face shows the measured distance between the endpoints of the guy wire decreased. Once again, we see evidence of the antenna sinking into the roofline, this time by comparing points on the antenna and middle east perimeter walls.
Further visual evidence of roof deformation during the earliest motion
The antenna falls towards the east and downward and the window washer on the NW corner is pulled inward. The small antenna and the east side of the north perimeter remain stationary. Deformation of the roof is the only explanation. The gif flashes between the images from around frame 120 and 210.
The east side of the north roofline remains stationary as the antenna falls downward toward the east.
The small antenna falls after the large one does
relation of small to large antenna prior to 9-11-01, seen from the roof of WTC2 from the south,
Global deformation movement from frames 120 to 220
Sauret projection of global deformation movement from frames 120 to 220:
we look from the Sauret projection at the whole building above floor 92, flashing between frames 120 and 220 (just over 1.5 sec interval). Remember that the NW corner starts to accelerate downwards around frame 224.
In order to see the degree and direction of local deformation at any point, just hold your pointer still over that point and notice the degree of wiggle.
1) The east corner of the building stays pretty still. The whole portion below floor 98 stays pretty still.
2) The NW corner window washer actually wiggles east-west. Almost no downward displacement, but observable eastward displacement.
3) Notice that the whole west corner above floor 98 is being pulled inwards. The pull-in first becomes noticable just above floor 98 and grows much stronger in the top few floors.
4) From this projection, the antenna is moving downwards and hooking to the east. It is as if it is falling and slightly pivoting. It seems as if it's eastward angle increases slightly over this interval.
Notice how the antenna fall seems directly related to the pull-in of the window washer on the NW corner. As if the building is being pulled downward from the eastern side of the core, pulling the antenna down with a slight pivot and the NW corner with it.
The outer columns of the building provide an excellent grid that allows us to see how the whole upper west side is being pulled over to the east, but the east side of the building remains still.
This simple visual tool allows you to verify that the tendencies documented in the drop and drift curves shown to you represent very real movement that grows into visible deformations. Movement from as early as Sauret frame 140 is visible to the naked eye.
Diagram of movement consistent with all observables:
Example of perimeter-led failure representing a convbex roofline deformation:
Created on 10/16/2010 01:44 PM by admin
Updated on 06/05/2011 06:16 PM by admin