There's been a number of posts the last few months on the JREF forum about a european method of demolition known as "Verinage". Basically this method involves weakening a few floors and displacing the weakened floors to cause the entire top section to slam into the lower section. The thermite deniers claim videos of this method of demolition prove that the upper floors of the north tower could have destroyed the rest of the building at a rate comparible to freefall, since the time it takes for these buildings to fall is comparible to a freefall time.
However, as I touched on briefly in my Fires, Explosions, Demolitions, Collapses, Crushdowns and the World Trade Center video, the Verinage demolitions actually seem to support our claims because in all three of the videos I could find, the rate of fall appeared to slow down after the upper section impacted the lower section.
I never actually measured the rate of fall of these buildings though. Well I have now. One evening when I was making my pop culture video, I had a bit of a mad moment and decided to use Adobe After Effects to depict the Queen stealing Miley Cyrus' soul! My crude 70s Sci-Fi FX aside, in order to make that I had to learn how to use motion tracking.
When I found out that After Effects even makes a speed-time graph of the motion, I decided to motion track some points on these Verinage videos to see how the speed changed over time.
ABC Tower, Balzac, Vitry-sur-Seine
February 14, 2007
Three points were tracked and the three tracks were averaged. The graph below is the speed-time graph of the average.
Glacis, Belfort
February 21, 2008
Five points were tracked and the five tracks were averaged. The footage was stabilized first. The graph below is the speed-time graph of the average.
Broca Tower, Argenteuil
August 22, 2007
Five points were tracked and the five tracks were averaged. The footage was stabilized first. The graph below is the speed-time graph of the average.
Now I don't claim this to be in any way scientific. All three videos are at an angle and the graphs are speed-time graphs, not velocity-time graphs, so obviously there's gonna be some accuracy issues, but still I think this gives you a fairly good idea of what a section of building falling on another section of building should look like. Notice how in all three cases there's an initial acceleration and then upon impact the acceleration abruptly ceases and a deceleration trend begins. This is exactly what we would expect using basic physics and common sense. The tracks go a bit wild towards the end because of the dust clouds getting in the way, that's why I did several and averaged. Now let's look at the north tower ...
Three points were tracked. This was a bit more difficult because of the smoke. The graph below is of all three tracks together.
I think that's pretty clear! Just like Chandlers' analysis and MacQueen & Szamboti's analysis, my tracks have produced a reasonably straight line. For at least two seconds the north tower accelerated constantly, further proof of the lack of jolt.
The three Verinage demolitions are perhaps the closest real-world examples we have for comparison to the North Tower, and they clearly behave differently. The fact remains that what happened to the north tower was unprecedented, regardless of how much you wanna exaggerate the tilt!
See Also:
Another Balzac Vitry Verinage
Reflecting on the Verinage demolition method
Einsteen, Szamboti and Greening's analysis of the Balzac-Vitry demolition
(From here)
What a Gravity-Driven Demolition Looks Like
by David Chandler
Lack of Deceleration of North Tower’s Upper Section Proves Use of Explosives
by Tony Szamboti
