WTC2 E Face Perimeter Pulls in, Breaks Along Bolt Seam
WTC2 E Face Perimeter Pulls in, Breaks Along Bolt Seam
High resolution video shows that the line of perimeter columns along the east face of WTC2 which bent inwards during the earliest moments of collapse initiation broke along bolt connections after being pulled in.
There is no evidence that the perimeter buckled inwards. There is substantial evidence that the east perimeter broke into an upper and lower sheet cleanly along a zig-zag line of bolt connections with no permanent column deformation or buckling. The action of the break is shown:
We extract the most informative frame images from frames 11650 to 11760 of the high resolution version of the WTC2 compilation video here. This corresponds to the 4 second interval, 6:29 to 6:33 in the video. The high resolution download is here
These images show:
1) Increased inward bending until frame 11070
2) The visible columns become straight again after that point. This means that the tension that caused the columns to bend has disappeared. The upper columns have broken, or "snapped" from the lower visible columns.
3) The visible columns were never bent past their elastic limit before "snapping" from the upper columns. The bending caused little permanent deformation and the columns quickly straightened up again when the cause of tension was removed.
Part 2 of this presentation, using other portions of the same video compilation linked earlier, will show
4) When this lower sheet of columns fell away from the building a few moments later, it's entire upper edge was clearly visible from multiple angles, showing that the break between upper and lower happened completely along bolt lines in a zig-zag pattern over 3 floors.
All columns along the top edge appeared very straight as they fell from the building. There was no evidence of a single buckled columns along the top edge of the falling sheet.
All images are in chronological order.
Frame 11653
frame 11659
frame 11665
frame 11671
frame 11679
frame 11690
frame 11695
frame 11702
In the image above the bending reaches a maximum inward displacement.
In the following images we see the visible columns quickly straighten.
There is no longer the evidence of increased inward bending. Instead, there is a release of tension as the visible columns break away from their connections above.
Please observe as the visible columns return to their former (straight) shape.
frame 11707
frame 11716
The image below shows the columns once again quite straight.
As they return to their former shapes and positions we see an open space, a empty hole is left where the upper columns once were.
frame 11736
frame 11741
In the last image in our short but educational presentation we see the camera has zoomed out allowing us to see how the upper sheet of columns has folded into the building and inside the lower straight visible columns.
Notice the obvious difference in angle between the upper and lower right corners of the building. The upper part is folding within the lower part.
frame 11756
Part 2 of this presentation will identify the line along which the east perimeter "snapped" into upper and lower. I will show that it was a clean, unbuckled break completely along bolt lines.
The two images below, of the top edge of the lower sheet moving outwards, show a small taste of what the type of break I mean. The first image shows how clean and unbuckled the break was, while the second image hints that the pattern stretched across the entire east face, from the NE to the SE corners of the building.
The upper edge of the sheet is marked in the graphics:
It is the first stepped pattern of bolted connections above the 75-77 Stiff MER panels.
The orange line marks a row of welded and bolted conections. They prove much stringer than the connections along the stepped pattern shown.
