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Leaked FEMA/ASCE Draft Report On WTC Collapse
securitas writes "The New York Times obtained a copy of the World Trade Center draft report by the Federal Emergency Management Agency and the American Society of Civil Engineers about the engineering failures that caused the towers to collapse. Among the findings: 'Fireproofing, sprinkler systems and the water supply for hoses were all disabled and the fires generated heat equivalent to the energy output of a nuclear power plant' reports the NYT (Yahoo link). Amazingly, if it wasn't for the fire (or another secondary catastrophic force), the towers would have remained standing."
Face it, no building could have survived a planeload of burning jet fuel that was busy eating its way through the building, with dozens of floors above adding weight to the weakening structure. And for all those people bemoaning the lack of a rooftop water supply for the sprinklers: consider the fact that the fire trucks at airports are not loaded with water, but with foam. You need foam, not water, to effectively put out burning jet fuel. Otherwise, the water would evaporate into steam before it had a chance to extinguish the flames.
Really, it's amazing that they stood as long as they did. Of course, knowing the limitless bounds of greed, people are still going to try to find someone to sue. "I want a bazillion dollars because the contractor didn't design the building to resist the destructive impact of a 767 and a plane-load of burning fuel!" Sheesh.
:Peter
TLC ran an interesting program about a month ago that went into detail about why the structures collapsed (beyond the obvious, crash, fire, etc).
The looked at factors like the blast having blown the fire protective coating off the steel and the way the building was designed with the majority of the load being carried by the steel skeleton on the perimeter of the buildings, as opposed to columns within. The achilles heel was reported to be the steel trusses running under the floors connecting the outer steel to the core.
The heat from the fire caused these trusses to weaken and fail, leaving the outer steel frame without the stabilizing and load-transfering benefit. By the time the first floor had begun to collapse, there was so much inertia in the falling portion of the structure that it was inevitable that the each floor below would fail under the crushing pressure.
They interviewed the cheif structural engineer and he said that they had designed the structure to withstand an impact from the largest airliner of the day, the 707... flying at low speed and lost in the fog. They didn't anticipate a modern widebody, loaded with enough fuel for a coast-to-coast flight crashing into the buildings at full speed.
He said that even if they took all that into account, he doesn't think there could have been any way to design the buildings to withstand that. The fact that the structures stood as long as they did is actually a testament to the good overall design (so the program said, anyway).
There is much cruelty in the universe, John.
Yeah, we seem to have the tour map.
Another famous New York Landmark also suffered an airplane collision. Now granted the airplane that hit the side of the Empire State Building was not the same size as the two that hit the World Trade Center, the B25 did quite a bit of structural damage. Enough damage in fact, that if simply the collision caused the Trade Center collapse, then the Empire STate (the plane did hit somewhere between the 78th and 79th floors)building should have also collapsed. In actuality the reason that the Trade Center collapsed and the Empire State building did not, is one of metallurgy. The thousands of gallons of jet fuel that were burning in the Trade Centers got hot enough to anneal the structural steel. When that happened the sheer mass of the floors above the impact zone collapsed triggering the chain reaction. Had the Jets that hit the Trade centers been nearly empty of fuel (ie. getting ready to land, instead of just taking off) the buildings would have survived the impact.
The following excerpt is from "Empire: A Tale of Obsession, Betrayal, and the Battle for an American Icon", copyright © 2001, available from John Wiley & Sons. It describes the impact of the B25 that hit the Empire State Building in 1945.
"Army Lieutenant Colonel William Smith Jr., a 27-year-old veteran of 34 bombing missions over Germany, had been flying a twin-engine B-25 bomber from Bedford, Massachusetts, to New York's LaGuardia Airport, and had secured permission to continue to Newark, New Jersey.
The fog was blinding. When he dropped down out of the clouds, he found himself approaching a forest of skyscrapers. In a panic, he banked away from the Grand Central Building, then from another tower on Fifth Avenue, only to find himself bearing down on the biggest one of all.
In desperation, he pulled up hard, twisting. The 10-ton (9-tonne) bomber plowed into the office of War Relief Services of the National Catholic Welfare Conference on the 78th and 79th floors, 913 feet (278 meters) off the street, tearing a gaping hole in the Empire State Building's north side."
The full article describing the impact in 1945 can be found here: Empire State Building Collision.
Except that if you consider that the first tower to come down was the second hit, and that it was hit below the 70th floor, it becomes quite clear that the asbestos that was there did little to help.
I don't think you can make a rational statement one way or the other, since we are dealing with two different crashes which probably cut different beams and spilled fuel in different patterns. Also, the beams on the 70th floor were bearing a lot more weight. So, they required less heat before they lost their cohesion.
As for all the people slinging accusations of greed, I agree that's bollox.
The WTC was designed to withstand an 8.0 earthquake. It handled the impact of the planes just fine. This hardly seems like the work of companies that were cutting corners. That the slurry wall holding back the Hudson river held is simply amazing considering it contained the epicenter of a minor earthquake. If that had broken, we would be looking at a huge lake there today. No recovery efforts would have been possible until a new slurry wall was built, and that would have taken months.
That said, I do have to question the use of "trusses". On the Discovery Channel they quoted a fireman who said that they always say "don't trust the truss" because they have a tendancy to melt quickly. Perhaps there should be a review of what types of trusses can be used in all new construction. Would it have been possible to build the WTC's wide-open design with heavier cross beams instead of trusses?
As bad as all this is, I'm sure we can learn from it. What will buildings of the future use for fire suppression? How about active cooling systems for structural components? Perhaps insulation can be coated with a material that is resistant to blast waves so that the material will be retained. From now on, architects will be thinking more about explosions and huge incendiary bombs. Perhaps they will improve design, thus resulting in safer buildings for everyone.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?