REVIEW OF COLLAPSE FEATURES OF WTC1, WTC2, AND WTC7 WITH FOCUS ON THE QUALITIES OF CONFINEMENT AND REGULATION
5.2: THE CASE OF WTC2
Please recall the order of events leading up to and during the WTC2 collapse sequence from section 3.2. Features of the initial failure sequence can be understood as a rapid succession of 8 identifiable events occurring in the following order:
Action above the 75th floor:
1) Deformations: Inward bowing of the east face
2) Earliest visible movement: 81, 82nd fl spandrels pull in sharply (along east and north walls)......................
3) Earliest ejections, 78th fl ejections: .....................
4) East wall separates into upper and lower parts, East wall upper portion is pulled inward and behind the lower portion
5) Tilting begins
Flash and destruction of NE corner, floor 90
Failure sequence of the north and south perimeter walls over tilt of __ degrees
Action along the 75th floor:
6) 75th fl east face row of ejections
7) 75th fl west wall north and south quarter of MER panels ejected from building with flooring still attached. NW and SW MER corners are destroyed, west wall upper portion falls out and over lower portion. Release and fall of upper portion. Tilting levels out.
2) EARLIEST VISIBLE MOVEMENT: 81, 82nd fl spandrels pull in sharply (along green and blue lines)
First, green and blue lines pull inward and down sharply.
Second, 7 distinct ejections form along the 78th floor (marked by red ovals).
Third, the east face breaks along the staggered purple line into upper and lower sections. The 2 yellow panels remain attached to the lower section. The rest of the perimeter above the staggered purple line is pulled behind the lower portion, and tilting begins.
The NIST does not mention within their reports or seem to notice how the north wall is pulled in along with the east wall. Just as in the case of WTC1 and WTC7, the motion indicates that the perimeter seems to be responding to failure within the core.
In all 3 collapsed buildings, the NIST does not acknowledge that the perimeter deformation is most probably a response to partial or collective core action.
3) EARLIEST EJECTION PATTERNS: 78th floor east face ejections
Two sharply distinct rows of ejections form along the east face separated by about 3 floors. The first sharply distinct row of ejections that appears is along the 78th floor. They are distinct from the row of 75th floor ejections which follow and they are visible from very far away as is demonstrated at this link:
It is identical to the purple staggered line shown in item #2 (earliest detectable motion) with the addition of 2 perimeter panels, shown as the off-colored panels in this illustration.
The relationship between the ejection locations and the staggered break line of the uppermost edge of the lower portion is shown in this graphic:
The ejections appear from the 7 red ovals along the 78th floor. Those are the 7 lowest points of the staggered break line.
Because these ejections are distinctly visible from far away, It is easy to know when the 81st and 82nd floor spandrels begin to pull inward and when the east wall separates into upper and lower portions by using the appearance of these ejections as a reference event. Examples will be given later in this section.
All the events so far happened before tilt becomes visible. The 81st and 82nd spandrels pull in to the point where the upper and lower portions are split into upper and lower sections and the first emergence of the 78th floor ejections all happen before tilting first becomes visible.
5) TILTING BEGINS
There is a clear westward displacement of the lower portion of the building as the upper portion was tilting. There is also a clear point at which the lower portion begins to return to its original position.
End of the *flat period*...frame 6873 on the graph, when the lower portion begins to return, is at this moment:
This is the moment when the tilting upper portion, which was still held together to the lower portion through bending elements, completely separates from lower portion and begins to fall onto it unrestrained by a hinge.
The complete action through the portion of tilting in which the lower part of the building is being pushed outward to the west (to the right) is shown below from 2 viewpoints. During this tilting process the upper portion must still be attached to the lower portion through a bending hinge. The latter image is the moment the final connections break:
These gifs show the complete range over which hinged tilting occurred in WTC2. The hinge fails in the latter images and the lower portion ceases to be pushed west as a result
At this point the building is tilting up to the point that the coupling or final connection between upper and lower portion is becoming completely severed. 2 distinct activities are witnessed along the 75th floor just at the moment the connecting hinge is being completely severed.
Just after the upper and lower portions are severed a strong row of ejections were seen to emerge from the east face along the 75th floor (event 6). Shortly after this the MER panels were ejected from the west face with the 75th floor beam flooring still attached (event 7).
Up to this moment only the 78th floor ejections were expanding and visible.
6) 75th FL EAST FACE ROW OF EJECTIONS AND SEPARATION OF UPPER AND LOWER PORTIONS:
This gif consists of 4 images. the first 2 images are the same as the ones shown just before. The 2 additional images show the distinct row of 75th floor ejections emerging.
The gif consists of 4 images, 2 of the 78th floor row of ejections and 2 of the 75th floor row.
78th floor ejections
Image 1: Moment the 78th fl row of ejections are noticable
Image 2: Moment just before forceful 75th row ejections emerge
75th floor ejections
Image 3: The 75th fl ejections are distinct
Image 4: Further downward movement.
The upper tilting portion becomes completely separate from the lower section just before the 75th row of ejections first emerge. The emergence of the 75th floor ejections mark the final destruction of a bending hinge.
The 78th floor ejections first become visible just as the upper and lower portions of the east wall separate and tilting begins, so the emergence of the ejections signify a transition in the physical mechanism of collapse initiation. Likewise, the emergence of the 75th floor row of ejections has physical significance; the transition from hinged tilt to collective falling.
7) SPLITTING OF THE WEST FACE:
WEST WALL MER PANELS EJECTED WITH BEAM FLOORING ATTACHED
The west face MER panel is shown in the graphic as a red rectangle. The 75th floor beam flooring between the perimeter and the core is shown in yellow. Those portions seem to have remained together still attached when they were ejected from the west face of the building.
The perimeter MER panels colored in the graphic below fell along the marked trajectories. There was beam flooring from the 75th floor Mechanical equipment rooom (MER) still attached to the west face MER sheets of panels.
The marked panels are trackable using the visual record.
From the video clip:
A large sheet of perimeter panels becomes visible with a large extended object extending from behind.
The extra-strong MER panel sections are distinctly leading the falling debris in images taken from the west during collapse. The red trajectory and the blue sheet of panels are marked.
Flooring is visible still attached to the MER panels sheet marked in blue. Edges of the flooring are marked.
This is a diagram of the beam flooring layout with the corresponding sections marked.
The emergence and fall of the west face MER perimeter is visually reconstructed:
8) DROPPING OF THE UPPER PORTION WITHIN THE LOWER PORTION
The upper portion falls completely behind the lower east perimeter wall and thrusts the lower wall outward:
Note the 78th floor row of ejections and the 75th floor row of ejections are clearly distinguishable. The earliest emergence of the 78th floor row of ejections means the 81st and 82nd east face and north face spandrels have been pulled inward, the east wall has split into upper and lower portions and the upper portion is starting to tilt.
Tilt increases through a bending hinge until the 75th floor row of ejections forcefully emerge. That is when the bending hinges fail and the upper portion collectively begins to fall onto the lower portion.
The same; 78th floor ejections followed by the 75th floor ejections. The pattern is unmistakable.
COLLAPSE PROGRESSION REVISITED: ORDERED DECONSTRUCTION (DECOMPOSITION) OF THE LOWER PORTION
WTC twin towers collapse progression was already described in section
The exact same ejection pattern is seen along the 75th floor slab when the aircraft first impacts the building:
and again on the north face, west side:
The following link gives the layout of venting and equipment on the 41st and 75th floor from which the lines of ejections emerge. There is no venting in the regions where the ejections emerged
: Mechanical Equipment Room (MER) Layout and Structure
2 images from the video are shown below. The 2 ejections are observed to emerge from the east face at the same time, though they are separated by about 20 floors.
Moments later the 41st floor east face ejection begins to emerge:
ORDERED DECOMPOSITION OF THE PERIMETER WALLS
Recorded Motion of the Perimeter Walls
Of all 8 perimeter walls on the twin towers, the most well-ordered and highly organized collapse was of the WTC2 east face. As shown in the graphic above, the east wall broke cleanly into 3 large sheets; upper, middle and lower The break point is along the upper edge of the MER panels, along the lowest bolted collections just above the MER levels.
One such upper edge was already shown during the 4th event described and is drawn as a purple staggered line in figure __.
There was remarkable order in the deconstruction and falling of the entire east face as 3 massive sheets.
Motion of the east wall is visually reconstructed here:East Wall
The west wall broke apart in a quite different way. Large portions of the extra-sturdy 75-77th floor MER perimeter were ejected from the building with beam flooring still attached. The motion of the west wall is visually reconstructed here: West Wall
The collapse fronts move down the east face earlier than they move down the west face. This means the panels to the east will be stripped of support earlier than the panels to the west. This can create a twisting motion of large sheets of perimeter panels as they fall away from the building to earth, landing at an angle to the footprint like this:
The motion of the south wall is reconstructed here: South Wall
The motion of the north wall is reconstructed here: North Wall
ORDERED DECOMPOSITION OF THE CORE
Details of the core sections that temporarily survived the collapse viewed from the northeast.
The images available at this link allow the interconnected columns to be identified with certainty
