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V 1.41
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911Research.WTC7.net site last updated:3/21/13
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Background Attack Aftermath Evidence Misinformation Analysis Memorial

The Shockwave Theory

Theory Attempting to Explain Destruction Outracing Rubble

According to the shockwave theory, the "gigantic impact forces" caused by the tower's top falling into the intact structure below the impact zone sends a shockwave through that structure, breaking it up even before the falling top reaches it.

The most conspicuous exposition of this theory was an article entitled World Trade Center - Some Engineering Aspects published on the website of the University of Sydney's Department of Civil Engineering website. Versions of this article are widely copied on the web, and it is excerpted in Muslims Suspend Laws of Physics! first published on October 21, 2001, suggesting that the Sydney article was published soon after the attack. A version of the article archived on the Web archive contains the following excerpt:

This photograph shows the south tower just as it is collapsing. It is evident that the building is falling over to the left. The North Tower collapsed directly downwards, on top of itself. The same mechanism of failure, the combination of impact and subsequent fire damage, is the likely cause of failure of both towers. However, it is possible that a storey on only one side of the South Tower initially collapsed, resulting in the "skewed" failure of the entire tower.

The gigantic impact forces caused by the huge mass of the falling structure landing on the floors below travelled down the columns like a shockwave faster than the entire structure fell. The clouds of debris coming from the tower, several storeys below the huge falling mass, probably result from the sudden and almost explosive failure of each floor, caused by the "shockwave".

[emphasis added]

1  

In later versions of the article, the passage has been changed to remove the shockwave theory, while other copies retain the shockwave theory. 2  

This photograph shows the south tower just as it is collapsing. It is evident that the building is falling over to the left. The North Tower collapsed directly downwards, on top of itself. The same mechanism of failure, the combination of impact and subsequent fire damage, is the likely cause of failure of both towers. However, it is possible that a storey on only one side of the South Tower initially collapsed, resulting in the "skewed" failure of the entire tower.

While the ways the two towers fell were slightly different, the basic cause is similar for both - a large number of columns were destroyed on impact, and the remaining structure was gradually weakened by the heat of the fire. Not much significance should be taken from the fact that one tower fell in 45 minutes and the other in 90 minutes.

The gigantic dynamic impact forces caused by the huge mass of the falling structure landing on the floors below is very much greater than the static load they were designed to resist.

3  

References

1. World Trade Center - Some Engineering Aspects, civil.usyd.edu.au,
2. World Trade Center: why did it collapse?, nyc-architecture.com,
3. World Trade Center - Some Engineering Aspects, [cached]

page last modified: 2005-10-31