2.5 TOWARD AN ACCURATE TECHNICAL HISTORY OF THE WTC 7 COLLAPSE
WTC7 BUILDING MOVEMENT: INDEPENDENT MAPPING AND MEASUREMENTS OF THE EARLIEST DETECTABLE MOVEMENT THROUGH THE COLLAPSE INITIATION SEQUENCE
The collective visual record of the WTC7 collapse is examined directly and independently of all other sources, groups or individuals. The movement of the structure during the initial column failure sequence is mapped and traced back to the earliest point of detectable movement from multiple angles. Features of the initial failure sequence can be understood as a rapid succession of 7 identifiable events occurring in the following order:
1) Movement Detected from 2 Minutes before Collapse
2) Increase of rocking 6 seconds before visible collapse
3) Ejections and overpressurizations
4) Collapse of the East Penthouse
5) Collective core failure
6) Perimeter response
7) Acceleration downward
Collapse Progression and Rubble Distribution
1) Movement Detected from 2 Minutes before Collapse
The earliest detectable movement leading into the visible collapse process was never recognized in the NIST report shown in section 3.3). There is nothing within the NIST computer simulations that can explain this type of movement.
The trace process of the northwest corner using sub-pixel tracing (syntheyes) demonstrated:
This camera angle is called the "camera #3 viewpoint" within the NIST report.
The corner started to rock back and forth at about 90 seconds before the visible collapse began. The movement is detectable by overlaying frames of the video.
The blue line indicates the moment when visible collapse first begins.
2) Increase of rocking 6 seconds before visible collapse
About 6 seconds before the collapse first becomes visible the northwest corner starts to rock more intensely. This movement was detected by the NIST and they consider it to be the earliest detectable motion. The first visible movement was the collapse of the east penthouse and is indicated in the graph. Once the east penthouse begins to fall, the rocking becomes much more intense until the whole core starts to fall collectively about 4 seconds later.
The NIST measurements are posted over independent confirmation. During this rocking motion from 6 seconds before the earliest visible collapse, both sets of measurements match well.
The perimeter flexure shows quite clearly how the outer structure of the building responds to collective core failure.
This perimeter response is not recognized to exist within the NIST reports (shown in section 3.3). There is no existing model to explain the visible interaction between the core and the perimeter.
One attempt to account for the unique core-perimeter flexure observed is reproduced below. In this model the core collapses in three distinct stages. First, the east penthouse, followed by the middle portion of the core, quickly followed by the eastern third of the core:
As will be more clearly demonstrated in part 3.3, the NIST computer simulations of the collapse process cannot account for any realistic core-perimeter coupling or for the perimeter flexure which was observed during the actual collapse process
MOVEMENT AS SEEN FROM THE DAN RATHER VIEWPOINT
The mechanism of core-led, perimeter response coupling
The the three points marked on the penthouse, when traced, fall as a single interconnected unit. The core is followed by the northwest corner. The perimeter responds geometrically to the downward movement of the collective core.
Displacement and velocity profiles:
The 3 points along the penthouse (light blue, yellow, magenta) fall together. The northwest corner (dark blue) then follows after a slight delay.
As will be shown later in this section, the most accurate measurements of the displacement, velocity and acceleration of the northwest corner of the building show that the downward acceleration underwent a very rapid transition from zero to a short period which exceeded gravitational acceleration. As will be shown in section 3.3, the transition was much more rapid than the NIST reported.
Note the relation between the velocity transition of the magenta point and the dark blue point.
The perimeter response to the rapid core drop can possibly account for such a pronounced change in acceleration, including the period exceeding free fall acceleration.
Displacement, velocity and acceleration profiles of the northwest corner from the Dan Rather viewpoint:
syntheyes tracing the northwest corner Dan Rather viewpoint shown here.
The measured displacement of the northest corner and the downward velocity are shown below. The NIST measurements are shown in green next to the more accurate independent measurements. It will be explained in detail in section 3.3 why they are so different and various mistakes the NIST made while measuring.
The acceleration profile given by the NIST is in green. A much more accurate acceleration profile is given in red. Free fall acceleration is marked by a blue line:
Due to the early fall of the east penthouse, one can assume that the core and perimeter on the east side of the building were not coupled together during the building collapse. The perimeter flexure, as it responded to collective core failure, also shows that the east side of the perimeter was decoupled from the core while the center area and west side of the perimeter was tightly coupled to the collective core.
There is further evidence of this during the collapse progression process. The section of the perimeter located farthest east fell slower than the rest of the perimeter and actually folded in on top of and over the rest of the building as shown in this short slow motion video:
The resulting rubble distribution of the collapse of this 47 story building was quite compact:
There are more images of the resulting rubble at this link:
