Posted on 10/22/2002 12:13:03 AM PDT by kattracks
NEW YORK (AP) -- A new report commissioned by the leaseholder of the World Trade Center site has concluded that the twin towers did not collapse because of flaws in their structural design.
The study, reported Tuesday by The New York Times, said the damage caused by the planes, and the fires that broke out as a result, caused both buildings to fall during the terrorist attacks.
The report's analysis contradicts the findings of an earlier federal investigation, which said the World Trade Center's unconventional design contributed to their collapse. The federal study said the towers' weak floor supports gave way during the attacks, triggering a collapse of the entire building.
The Manhattan engineering firm that analyzed the collapse, Weidlinger Associates, used a computer program to recreate the terrorist attacks. The engineers found that the fires and the overwhelming heat that spread through the towers made the collapse inevitable, the Times said.
Larry Silverstein, the owner of the trade center property, paid for the study as part of his $4 billion insurance lawsuit.
Silverstein has argued that that two planes hit the twin towers in separate occurrences, entitling him to a $7 billion double payment. The insurance companies in the suit say he should be paid half that amount.
Copyright 2002 Associated Press. All rights reserved.
Thats why building codes specify that vertical shafts be fire rated and pipe penetrations, gaps between curtainwalls and slabs, etc. be sealed with fire stopping to prevent flue effects and fire jumping floor to floor.
The WTC's biggest problem was you had an instantaneous acre sized fire on several floors with multiple penetrations into the building, destroying the compatmentation that was designed to halt the spread of a normal fire. You also had aviation kerosene as an accelerant pouring into the building.
I recently attended a briefing on the entire forensic engineering study of the WTC Attack given by the head of the commissioned study team.
The jet fuel itself wasn't so much a fuel source causing the fire to burn hotter as it was an ignition method that caused the fire to be non-typical.
A third of the fuel burned outside the structures, in fire balls and explosion, a third ran down inside creating incidental fires, and a third spread through out the floors involed with impact like charcoal lighter fluid.
Thus, that last third, caused the entire contents of those floors to begin burning at the same time. Like charcoal lighter, it burned off in twenty minutes or less. The subsiquent fire was non-typical because it wasn't progressive, proceeding form an ignition point. Instead, great temperatures above typical developed because of entire floor burn progression was happening at the same time.
The structuures preformed beyond their design and were designed ahead of their time. Different uses of fire-proofing were the only things that would have prolonged the callapse, but only by minutes. Hardened core systems would have made a difference to victims above the fire, but that is the issue in any highrise.
But a thousand lives or more could have been saved by having fire escape stairs at the corners of the building. Not to mention Halon extinguishers. I could live with a slightly larger ozone hole.
I'd venture to guess a few thousand had an even worse day.
The abstract given out with the talk states in its Conclusions: " Despite tragic loss...the World Trade Center and surrounding buildings performed very well, considering the severity of events to which they were subjected. It was the overwhelming conclusion of the BPAT that rather than changing our building design and construction practice to better resist events like those of September 11, buildings can best be protected from aircraft attacks by providing improved aircraft security."
Additionally: "The twin towers incorportated extensive continuity, redundancy and overstrength in their structural design, which enabled them to survive the aircraft impact without immediate collapse. Most other buildings do not possess this combination and extent of redundancy, continuity and overstrenght and would not have performed as well. Most other building would have collapsed immediately upon aircraft impact."
Prior to the failure of the nearby WTC-7 there was no record of fire-induced collapse of any fire protected steel frame structure of this size. Fire Protection of certain connections on WTC-7 and WTC-5 would have greatly reduced the possibility of collapse from the fire. But we must remember, that those buildings were permitted to burn without the fire being fought due to loss of life, the circumstances, their state of evacuationand damage, and risk. This was a very non-typical condition.
This appears to me to be a grievous misrepresentation of the FEMA study whose 25 person team did the definative analysis. As these buildings were constructed by the Port Authority they didn't have the same Fire Marshall and City Code permitting that a typical project had and when those agencies were questioned, wild speculation as to causes was allowed to be repeated in the press. The real studies, by the professionals and industry experts showed exactly the opposite to those off-the-cuff armchair comments at the time.
They would know the building. They would have generated superior emergency preparedness conditions. They could be on site observing all sorts of equipment and infrastructure repairs to make sure proper fire procedures were adhered to. They would drive home the importance of adhering to fire procedures when alarms go off.
In a large building, it might not be a bad idea to require this around the clock on site fire personnel as part of the business licensing process.
These large buildings are essentially mini-cities. It doesn't seem all that unreasonable to provide on site fire services.
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