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To: carl a. mehr who wrote (143709)	9/18/2001 5:40:57 PM
From: Mick Mørmøny	Read Replies (1) \| Respond to of 186894

The ever Intelligent and not so humble Carl: Why read a book by someone who took him eight (8) years to write? Darton could have gone back to school and took structural civil engineering and maybe, just maybe, he could build a better skyscraper himself. This is how the Twin Towers crumbled, according to Prof. Raymond Cook. BREAKDOWN: UNH professor explains exactly what brought each tower down Raymond Cook, a professor of structural civil engineering at the University of New Hampshire, provided a grim but fascinating look at the last hours of the World Trade Center’s twin towers, destroyed in Tuesday’s terrorist attacks. He explained from a structural engineering perspective what caused the towers to crumble as they did. While the horrific image of the buildings crumbling will remain with Americans forever, Cook said the country should not forget that both towers remained standing after the cataclysmic impact of a jetliner — 47 minutes for the south tower; one hour and 44 minutes for the north tower. And that gave thousands of people inside the doomed buildings critical time to escape. “You’ve really got to be in admiration of the engineers and the architects and the construction workers that built the World Trade Center because both towers performed unbelievably well under completely unforeseen circumstances,” Cook said. “It performed remarkably well. A huge airline slammed into it and it stood, and then another airplane slammed into another one, and that stood. That’s fantastic,” Cook said. “You’ve got to hand it to the architects and engineers that did this.” Cook said the twin towers were designed like giant tubes, with most of the support columns on the outside of the building. The design is meant to make it hard for the building to topple over in hurricane winds or an earthquake. Here’s what brought each tower down: -- The airplane, filled with jet fuel for a cross-country trip, impacts the building in a huge fireball, breaking into tiny pieces and spilling fuel everywhere. -- Some of the vertical support columns are destroyed. The remaining columns, designed to withstand at full capacity a worst-case scenario like a hurricane or earthquake, continue to support the floors above. -- The spilled fuel starts an intense fire. Many in the building start to evacuate, through the stairwells in the central core of the building, which has somehow survived. -- Despite insulation, steel beams and columns begin to heat up. Even if sprinkler systems work on the damaged floors, they likely do little against the intense fire. -- As the steel softens, the columns buckle, first in the core of the building, where the most intense heat is. -- The first intact floor above where the plane hit begins to bow downward, in a trampoline-like effect. That pulls in on the exterior columns, and everything above collapses downward into the center of the building. -- The weight of the floors above, combined with the impact of the collapse, causes the columns beneath the first intact floor under the impact area to fail. -- This sets up a “progressive collapse,” where, floor by floor, the interior columns fail, the floor sags and pulls in on the outer columns, and everything collapses inward. (The same principle is used by experts in building implosions.) -- Meanwhile, the air pressure on every floor builds up as the floor above collapses, which blows out the windows, sending drywall, papers and everything else inside the building outside. -- The collapsing debris ends up crashing into the basement of the tower. Cook believes anyone involved in structural engineering would advocate rebuilding the towers. “The best memorial to the thousands of people that died here is to rebuild them, and build them taller and stronger, and dedicate them to the people that died. That’s showing that the United States and our supporting countries worldwide are defiant and strong. We’re not going to let this get us down.”