911 WTC collapse, page 2
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reply posted on 19-11-2003 @ 08:54 AM by astrocreep
Well, as someone educated in materials engineering and construction, I won't argue any points about whether Bush knew or who flew the planes but I can tell you that no other forces were needed to bring the buildings down.

We've seen fire cause the collapse of steel buildings before not that it melts the beams in the literal sense but intense heat cause metal fatigue and the added pressure of load trying to redistribute after key memebers were destroyed pushed stresses and strain beyond tolerance. If building 7 burned for 7 hours, then its withstood most fire rated material's expectation by 6 hours probably because its retardant system wasn't damaged that badly and likely kept it under control for a little while. The key with towers one and two was the likely destruction of the fire retardant system on the floor which collapsed. Even if the floors below were 100% in tact when the weight above fell upon them, there was no way they could withstand that. Likely the siesmic readings were from the instant that all that load was transfered to rock (consolidated glacial till in that area) before it overloaded the transfer device which was the structure itself.

Now, I won't get into elasticity/reslient modulus and compressive/tensile/and elongation properties of steel or masonry but they all play an important role in explaining the failure of the structure. There are limits to what we can get materials to do and we must work with those principles when we design a building or bridge and we know that if these properties are surpassed, failure is a real possibility.



reply posted on 4-12-2003 @ 09:16 PM by dexxy
wtc7.net...

At 5:20 PM, September 11th, 2001, a 47 story steel frame skyscraper in Manhattan underwent a swift, systematic, straight-down collapse. In a matter of seconds, the immense 600-foot tall structure was transformed into a small pile of rubble lying almost entirely within the building's original footprint.

The building is variously known as Building 7, WTC 7, or 7 World Trade Center. Despite its address, it was across the street from the superblock containing the rest of the World Trade Center, and was of a different architectural style and age than the 6 other WTC buildings.

The cause of the collapse has never been determined. FEMA's Building Performance Study, the only government document that addressed the collapse of Building 7 in any detail, stated:

The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time. ... Further research, investigation, and analyses are needed to resolve this issue.
By the time FEMA's report was published, the remains of Building 7 had been almost entirely destroyed, nearly all of the structural steel having been expeditiously removed and shipped to blast furnaces overseas. Without the physical evidence of the structural steel, such research, investigation, and analyses would be impossible.
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