The rapid and complete destruction of the World Trade Center Twin Towers, ostensibly by causes other than controlled demolition, was an unprecedented event in the history of high-rise construction.
Although theoretically possible, collapses of heavily constructed buildings like the Twin Towers had never occurred prior to September 11, 2001, without the use of explosives. The reason for this is that they are built with significant reserve strength. The construction of each floor is designed to support several times the actual load above it.
The only way a collapse of a structure with significant reserve strength can continue is for the static load to be amplified in what is called dynamic loading. Dynamic loading occurs when the impacting object decelerates. For instance, if during an impact the falling object decelerates at twice the rate of gravity, it will impart a load on the object it strikes that is three times its static load. This occurs due to an additional force with an acceleration value twice that of gravity being added to the static load. This amplified load is represented by the equation F = mg + m(deceleration), where mg is the static load and the m(deceleration) term is the additional load due to dynamic effects. Dynamic loading was postulated in a paper written by Dr. Zdenek Bazant of Northwestern University and used in the National Institute of Standards and Technology (NIST) report on the World Trade Center collapses. However, Dr. Bazant had not performed any actual measurements to support his theory.
Actual measurements of the descent of the North Tower were performed independently in 2008 by physics instructor David Chandler of Fresno, California, and Professor Graeme MacQueen of Hamilton, Ontario. Both found no evidence of deceleration at any time during the descent. In fact, the upper section of the North Tower continuously accelerated, at approximately 2/3 of g (free-fall) during the measureable first nine stories of the building’s collapse.
The contradiction caused by the lack of deceleration of the upper section of the North Tower with the dynamic loading event postulated, but never measured for, by Dr. Bazant or NIST, is discussed in a published paper entitled “The Missing Jolt,” which can be found online at the Journal of 9/11 Studies and in the Technical Articles section of AE911Truth.org.
The lack of deceleration is indeed a startling revelation, because it shows that the falling upper section did not actually impact the lower section with enough force to destroy it, and therefore explosives must have been used to destroy the lower section as the upper section continued its constant acceleration downward and visibly disintegrated on its own without impacting the lower section.
Proof that the necessary deceleration is observable in a collapse, in which the momentum and kinetic energy of an upper section actually break the columns in the lower section, is found in the demolition of several buildings in France. In recent years demolition engineers there have devised a system known as the Verinage technique, where they demolish buildings without the use of explosives. This technique uses hydraulic rams to break all of the columns in a couple of stories near the center of the building. The loss of vertical support in these stories then causes the upper section to fall unimpeded through a pre-determined distance before impacting the intact lower structure. Watch this video of one of these demolitions – of the Balzac-Vitry building.
In all known measurements of these “Verinage” demolitions, the descent of the roofline shows definitive proof of deceleration of the upper building sections as they impact the lower structure, as seen in the velocity graph of the Balzac-Vitry building demolition below.
Now compare the above velocity graph of the Balzac-Vitry demolition to the velocity graph of the North Tower (WTC 1) “collapse.”
The same measurement methodology is used in both cases.
There is clearly no deceleration in the fall of the upper section of the North Tower. A “natural” collapse, where explosives were not used, could not have occurred without deceleration. Therefore, this verified scientific data proves that explosives must have been employed to remove the structural columns – and thus to bring down the World Trade Center North Tower.
It stands to reason that if the North Tower was brought down surreptitiously with explosives, then the South Tower must have been as well. Its destruction was similarly explosive, rapid, and thorough, though with a few differences in the features of its destruction.
*This “Constant Acceleration” primer is based on the article “Lack of Deceleration of North Tower’s Upper Section Proves Use of Explosives,” which can be read at http://www.ae911truth.org/en/news/41-articles/403-lack-of-deceleration-of-north-towers-upper-section-proves-use-of-explosives.html