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Politics : Foreign Affairs Discussion Group -- Ignore unavailable to you. Want to Upgrade?

To: Bilow who wrote (203241)	9/17/2006 7:29:05 AM
From: maceng2	Read Replies (1) \| Respond to of 281500

the center structure of WTC-7 fall in on itself well before the rest of the building fell down. All this is perfectly normal in this sort of thing. We will just have to agree to disagree on that one. My ideas were that the steel columns transmitted shock waves through the steel beams to get the collapses going. Fact is though that this would have only caused local collapse at the points where the shock waves focused. They cannot explain how a whole structure just falls out of the sky influenced only by the gravitational constant. No breaking effect by the supports in place? It's just plain nuts!

To: Bilow who wrote (203241)	9/18/2006 3:45:41 AM
From: maceng2	Read Replies (1) \| Respond to of 281500

We're just lucky that we don't live in Lebanon or Iraq and get to see how tall buildings collapse more often. A telling phrase. Although explosives must be common these days, they are still very different substances from jet fuel, wood, paper, or gypsum etc. The USA has improved is ability to destroy tall buildings, but forgotten how to build 'um for some reason. So what else is happening? Just the usual wonderful news every morning... guardian.co.uk

To: Bilow who wrote (203241)	9/18/2006 6:05:56 AM
From: geode00	Respond to of 281500

I've always thought this was an interesting solution (as long as the lubricating pumps keep working) to the instability of tall buildings. en.wikipedia.org The building's upper-floor occupants suffered from motion sickness when the building swayed in the wind. To stabilize the movement, a device called a tuned mass damper was installed on the 58th floor. As described by Robert Campbell, architecture critic for the Boston Globe: Two 300-ton weights sit at opposite ends of the 58th floor of the Hancock. Each weight is a box of steel, filled with lead, 17 feet (5.2 m) square by 3 feet (0.9 m) high. Each weight rests on a steel plate. The plate is covered with lubricant so the weight is free to slide. But the weight is attached to the steel frame of the building by means of springs and shock absorbers. When the Hancock sways, the weight tends to remain still... allowing the floor to slide underneath it. Then, as the springs and shocks take hold, they begin to tug the building back. The effect is like that of a gyroscope, stabilizing the tower. The reason there are two weights, instead of one, is so they can tug in opposite directions when the building twists. The cost of the damper was $3 million. The dampers are free to move a few feet relative to the floor. LeMessurier Consultants says the dampers are located in relatively small utility rooms at each end of the building, leaving most of the 58th floor usable. According to Robert Campbell, it was also discovered that—despite the mass damper—the building could have fallen over under a certain kind of wind loading. Ironically, it could tip over on one of its narrow edges, not its big flat sides. Some 1,500 tons of diagonal steel bracing were added to prevent this, costing $5 million.