Saturday, March 03, 2007

Tower talk- Are there surprising things to discover?

Are there surprising things to discover. We all no the answer is yes, everyday. Yet consprirasists linger like Wilkes Boothes in the wings saying it can be so and here is a little germ of truth that I will blow on and conjure confusion.

Had a discussion about Twin Towers on fire as hijacked planes hit with Jeff Hull. Caused me to revisit some PBS sites, and some overheard conversation with Failure Student Henry Petroski. I caught up with him in Tampa about three weeks after 911..when flying was really spooky..and heard him discuss failures of engineering [his specialty] and remember the [software] engineers around him discusing the recent great conflagaration....

Let's be base: What happened to the towers was not anticipated. Most structural engineers were surprised when the World Trade Center towers collapsed. Suprise is always possible as there are always new things to learn. Structural engineers are not dealing with a completely closed systems and they are always learning new things or variations on themes.
What was unique here? The objective of the plane hijackers was not to avoid the towers. Was to hit them head-on. Was to hit them on with almost the maximum amount of jet fuel. Because this building was super tall..one was able to go at it...if it had been one among similar buildings..if it had been smaller.. the effect, even given the plane hijackers specific objective might have been more diffuse..
What has been surprising in the study of the collapse of the towers.. Henry Petroski was asked...he responded.... Among the most interesting results of engineering failure analyses of the collapsed towers has been the incontrovertible evidence that fire and the heat that accompanies it can trigger the collapse of a structure...
The building was designed to take the impact of a Boeing 707, though engineers apparently did not take into consideration the plane's fuel load. Temperatures of the fuel fire may have reached 2,000°F.
Understand: No evidence has turned up that the fires burned hot enough to melt any of the steel [I had thought that some of the less virile steel {level 3 or 4 in the steel pecking order, tressing steel, say} might have] .. but eventually the steel lost 80 percent of its strength because of the intensity of the fire. And this was very logical key to dissolution observed of towers.
Because anything incendiary is susceptible to the maneurivings of relatvistic opionion freaks .. I think it is improtant to be sure about the validity quality of sources.l Petroski me thinks is a valued source...

From a Petrowsi interview:

Among the most interesting results of engineering failure analyses of the collapsed towers has been the incontrovertible evidence that fire and the heat that accompanies it can trigger the collapse of a structure the way they did in New York. There had been fires in skyscrapers before, but none had collapsed, because the fire and the attendant structural damage was confined to a floor or two and thereby localized in their effect and the structural damage they caused. In the case of the World Trade Center, the massive structural damage due to the impact of the hijacked airplanes, in combination with the intense heat of the resulting fires, produced a theretofore incredible combination of forces on the buildings. Such combinations of forces are, obviously, no longer incredible.



See
http://www.pratt.duke.edu/news/?id=749

also
http://www.pbs.org/wgbh/nova/wtc/dyk.html

and don't forget
http://www.pbs.org/wgbh/nova/transcripts/3311_wtc.html

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