Posted on 07/10/2002 6:45:51 PM PDT by blam
Date: Posted 7/10/2002
Planes May Have Almost Toppled World Trade Center Towers On Impact
The hijacked jetliners might have come close to toppling the World Trade Center Towers on impact on Sept. 11, according to new calculations by a Swarthmore College physics professor. This counters the views of most experts and a recent federally funded engineering study that concluded the planes lacked sufficient force to knock the towers down on impact. "Certainly the loss of approximately 2,830 people in a single event is a tragedy," says Professor of Physics Frank Moscatelli, a native New Yorker. "But assuming an occupancy of 40,000 to 50,000 people in the towers alone at the time of impact, we could have had a catastrophe well beyond what we actually experienced last September."
The federal report, released last month, concluded the buildings could have remained standing if not for the enormous fires that broke out after they were struck by the hijacked airplanes. The report, sponsored by the Federal Emergency Management Agency and the American Society of Civil Engineers, supports statements made on the recent NOVA special Why the Towers Fell.
But Moscatelli contends that the report's conclusions and similar expert opinions err by focusing solely on force. "You must also compare the torque, which is a physical measure of 'twist' produced by the planes with that due to the wind load the towers were designed to withstand," Moscatelli says. "Comparing the static weights of the buildings and planes is wrong. The planes were moving, and that clearly changes the problem. The buildings did not have to bear the weight of the planes; they had to stop the planes."
Moscatelli calculated that the torque applied by the planes' impact -- 7.7 million ft. tons -- actually exceeded the amount the towers were designed to resist due to wind load -- 7.4 million ft. tons. "So they could have immediately collapsed, if not for the fact that neither object is a rigid body and that the towers flexed quite a bit upon impact with the planes," he says. "If they had not at least bent temporarily, they would have been in danger of instantly toppling."
Moscatelli also determined that the 11,000 tons of force required by the towers to resist the wind barely exceeded the 7,000 tons of force required to stop the planes. "In fact, the stopping force for the plane scales as the square of its velocity, so if the plane was traveling at 564 mph these forces would be equal," he says. "This is probably why the terrorist pilots flew at such an uncommonly high speed for that aircraft, at that altitude, for that particular maneuver. They flew as if they wanted to knock them down, and I think we cannot conclude that they were so far off from doing just that."
Moscatelli previously calculated that of the three sources of energy delivered to the twin towers on September 11 -- exploded jet fuel, kinetic energy due to the motion of two aircraft, and gravitational potential energy due to the falling building material -- the last was the most devastating. This is supported by the extensive damage caused to surrounding buildings, as noted in the federal report.
"My calculations show that the largest component by far was the latter," Moscatelli says. "This is due to the large mass and height of the towers. The airplanes destroyed 20 stories of the buildings, and gravity did the rest. Their splendor was their undoing."
IMHO the intense heat of the fire is what brought down the towers. If the impact forces alone were enough to topple them, they would have fell sooner.
Their undoing was the work of evil men on a mission for evil forces. Their splendor was nothing more than an espression of our dreams and ambitions. Reach high and think big...A New Order for the Ages.
It is well for the Afghan people, who hoarded an unwelcome cancer in their midst, that the towers stood as long as they did. Our just rage would have known no bounds if a conflagration from a toppling would have occured.
What it means is that airplanes continue to be a risk for buildings.
Clearly one way to make buildings safer is to make the airplanes lighter and smaller. It should be possible for an engineer to figure out how small an airplane has to be to prevent it from toppling any buildings in New York City. Then, simply bar airplanes larger than that from any local airports.
But he's saying we're a bit lucky that the buildings didn't fall immediately on impact, with an order of magnitude more dead.
This guy must be on drugs. He is saying that if the towers were rigid bodies that did not flex they could have been toppled over. Think of a plane slamming into a solid poured concrete structure the size, weight, and dimensions of a tower
The tower are not rigid bodies and they were designed to be flexible. In fact they were so flexible the elevators would get stuck on windy days because the towers were swaying.
Plus, add to this the fact that these towers were built to withstand pressures generated by high winds that were far in excess of what was delivered by the two aircraft.
These towers were not in danger of toppling from the impacts. Not even close.
In fact, if the supports that held up the girders that supported the concrete floor slabs were designed and made as well as the central core, the buildings may have survived the heat of the fire and averted a collapse.
These girders were encapsulated in a fire retardent material that was designed to protect the steel from intense heat from a traditional fire source. However, the force of the blast upon impact of the aircraft blew away most of this material and left many of the supports vulnerable to the intense heat. When the supports gave way, so did some of the slab floors and once that started, no force in the universe would have stopped it.
You are correct. The buildings demonstrably withstood the torsion loads applied. The culprit was the steel members, which melted due to the intense heat. Once the first set of members failed, they fell down upon the next set of steel members, and that weight then fell down upon the next set, etc.
It's what called a cascade failure......
I don't believe this guy is credible. This guy is NOT a structural engineer. His "findings" that contradict engineering studies are highly questionable. And, in case anybody is wondering, I AM an engineer (mechanical).
Exactly how many scientific papers have you published, and where'd you get your Phd in Physics?
Also bunk.
The analysis supposes: "if not for the fact that neither object is a rigid body and that the towers flexed quite a bit upon impact with the planes". In other words both the target (WTC tower) and the projectile (airliner) have to be rigid for these torque calculations to accurate, let alone effective vectors.
This article is the height of unethical spectulation by a supposedly educated scientist.
Glad my children aren't students in this professors classroom.
I don't follow your argument. Flexure and fracture are two very different mechanisms. Just because a tree is moving in the breeze, that doesn't mean that it is ready to fall down.
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