Experts blames flaw in design on collapse of Twin Towers

posted by ewing2001 on Thursday June 05, @01:00PM

http://www.nypost.com/news/regionalnews/476.htm
New York Post
EXPERT BLAMES FLAW IN DESIGN OF WTC

June 5, 2003 -- LONDON -

"...A vulnerability in the structure of the World Trade Center towers may have contributed to their collapse after the Sept. 11 attacks, a leading structural engineer said yesterday.

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A combination of events, including the collision of the aircraft into the buildings, a weakening of the structure by the physical impact, the thickness of fire-proofing insulation and the fires, have been blamed for the catastrophe.

But Dr. Asif Usmani, a structural engineer at the University of Edinburgh’s School of Engineering and Electronics, told an engineering conference the Twin Towers seem to have been "unusually vulnerable" to a major fire. "There was a vulnerability in the design of the structural system. It is not materials. It is not about fire protection. It is about the design of the structure," he told Reuters.

In a computer-based analysis of the buildings, Usmani studied the structure of the towers that collapsed after they were hit by two hijacked planes in attacks by Osama bin Laden’s al Qaeda terror network. "We are not analyzing the event. We are saying, ‘Let’s look at the structure itself and see if it has anything unusual that makes it more vulnerable to fire than other structures,’ " he explained. Usmani said the towers’ exterior and internal columns, which make up the core of the building, were joined by a very long and thin expanse of floor. Supporting the floors were lightweight trusses which, when exposed to fire, expand. But because of the way the towers were built, the trusses did not have anywhere to expand without buckling.

"This was good for constructing a building very quickly, and they were strong enough to carry all the loading that was put on them. But when there is a fire underneath the trusses and the steel gets hot . . . it expands quite a lot - and those expansion forces can be quite high if the restraints to expansion are high," he added..."

Plaguepuppy on the latest "expert" report

"...Actually this is very old stuff, just a re-statement of one of several lines of speculation about how the collapse might have happened that have been around since the beginning. The trusses were relatively light weight, but were also quite strong, and in no way represented a quick and dirty way of building the towers.

There are obvious advantages to keeping things as light as possible consistent with strength, since the weight-bearing portions will have to be made bigger if the floors weigh more. What was done instead was to use intelligent design rather than sheer mass of steel, in a manner similar to airplane design. By using built-up trusses instead of solid supports similar strength is achieved with much less steel. And by creating an egg-crate like interlocking grid of these trusses, all attached along their top edges to the corrugated steel pan under the concrete, a very strong floor-truss unit is created.

As to thermal heating, there is still no evidence than any of this supposed failure mode can be seen in the actual collapses, and I seriously doubt that enough fuel existed in the offices to generate high enough temperatures for a long enough time to cause that much expansion. The collapses started long after all the kerosene had burned off, and the office fires should have begun to run out of fuel, yet somehow we are to believe that the floors just kept getting hotter and hotter.

In the version described in the FEMA report the floors are strong enough to push out the outside walls, causing them to buckle and fall outward, something that simply can't be seen in any of the pictures. This kind of floor failure would also lead to a progressive "records on a spindle" kind of collapse as the impact of falling floors shears off the attachments of the next floor hit. But that would create a very different picture, with the central core left mostly intact as the floors slid down, and the outer walls gradually falling outward in large sheets. Instead we see the entire structure, core, outer walls and all, crumbling away at almost exactly the same point as the demolition waves travelled down the towers..."

Plaguepuppy is one of the most popular Collapse specialists in the investigative 911Skeptic-Scene. Together with Eric Hufschmidt, Jeffrey G. Strahl, Endemion, Dulce Decorum, Jeff "2MuchBS", The Webfairy, Dirk Eastman and a few others most of them teamed up in some mailing lists and at the 911-Folder at democraticUnderground.com

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