Posted on 09/11/2001 4:27:20 PM PDT by Looking for Diogenes
Sept. 11, 2001 |
The World Trade Center's twin towers were the tallest buildings in the world at the time of their opening in 1970. They each stood 110 stories and more than 1,300 feet tall. They are the dominant features in an enormous office complex totaling more than 9 million square feet of office space and together make up one of the most recognizable architectural landmarks in the world.
Today they were reduced to heaps of rubble after one of the worst catastrophes in U.S. history. A pair of jetliners crashed into them Tuesday morning -- at precisely the points at which they would do the most damage, according to architectural experts. The impacts created fires and, ultimately, brought about the collapse of both buildings.
Why did the buildings collapse?
According to Gregory Fenves, a professor of Civil Engineering at the University of California at Berkeley, the planes weakened the buildings' structures at key points. Fenves, working on information gleaned from preliminary TV reports, stressed that he was speculating. He said that if the planes had hit the structures higher, they could have merely damaged their tops; if they had hit lower, they would have been up against the enormous weight and resistance of the base of the buildings.
The buildings were architecturally interesting in many ways. Each structure is based on a central steel core, which is surrounded by the outside wall, a 209-foot by 209-foot cube of 18-inch tubular steel columns, set 22 inches apart. The cores and "tube walls" share the enormous physical weight of the structures and protect them against the extraordinary wind forces of buildings that tall. There are trusses that support each floor, but no other columns between the cores and outside walls. Some floors contain nearly 40,000 square feet of open office space.
News reports said the planes were jetliners, a 757 and a 767. The 757 has a 124-foot wingspan, is 155 feet long and can weigh 100 tons. A 767 is bigger, with a 156-foot wingspan and 159-foot length and can weigh a maximum of 200 tons. (A 747 is more than 200 feet long and can weigh 400 tons.)
The planes hit the buildings near the 70th or 80th floors. Their impact severely damaged the tube walls, which carried a large proportion of the buildings' weight. CNN footage of the second plane hitting a tower appeared to show that a large part of the jetliner went all the way through the building, suggesting that the interior core was also damaged.
Once a building like a World Trade Center tower loses some of its support, the building in effect goes to work, Fenves said. "The loads are trying to redistribute," he said. "The loads are figuring out how to get back down to the ground." At the same time, he noted, the fires are deforming the physical properties of the support steel.
"It's a very rugged system," he said. "It takes a long time for the collapse mechanism to develop. It's not like kicking the leg out from underneath a chair. The building is 200-foot square and there's a lot of structural system there."
But once the upper floors began to give way, terrible force was set in motion. Each floor of a building that big might weigh 6 million pounds, he said. Once impact is factored in as well, he said, the force becomes irresistible.
The disaster is a terrible echo of another disaster involving a New York landmark.
On July 25, 1945, a B-25 bomber slammed into the north side of the Empire State Building, then the tallest building in the world. A reckless pilot was flying over Manhattan in poor visibility; it was apparently an accident. Thirteen people died, mostly in fires started by burning gasoline.
The Empire State Building, Fenves noted, was built during the Depression, and made with a much heavier structural system. The bomber in that accident was also a much smaller plane, said Fenves.
The WTC buildings' official names are One and Two World Trade Center; their respective heights are 1,368 and 1,362 feet tall. They are part of a massive seven-building complex near the southeastern end of Manhattan. The center's architect was Minoru Yamasaki. The engineers were John Skilling and Leslie Robertson of Worthington, Skilling, Helle and Jackson.
The complex cost $350 million in 1966, or nearly $2 billion in today's dollars. Ground was broken in 1966, and the buildings opened in 1970, but the complete center was not finished until 1974; there are now seven total buildings, a large shopping mall, and an enormous garage. An observation deck is a popular tourist destination. Beneath the center two New York subway lines converge; there is also the Manhattan terminus of PATH commuter trains from New Jersey.
The center has been the target of an attack before. On Feb. 26, 1993, terrorists linked to Osama bin Laden planned and carried out a truck bombing in the parking garage. Prosecutors said the weapon was a 1,200-pound truck bomb. Six people died and more than 1,000 were injured in the attack. The explosion created a five-story crater beneath the building, but its structure held.
After the center opened in 1970, for several years it was feared the complex would become a real-estate white elephant. But for decades it then reigned as one of New York City's premier office buildings. A recent press release from the New York and New Jersey Port Authorities, which own the building, says that more than 430 companies from 28 countries are tenants. The authorities said that 40,000 employees work in the buildings daily, besides 140,000 daily visitors.
The World Trade Center lost its position as the world's tallest building in 1974, when the Sears Tower in Chicago opened. In 1998 the two Petronas Towers in Kuala Lumpur, Malaysia, opened; they are each more than 100 feet taller than the World Trade Center structures.
I pretty much agree with your analysis. The tricky part would be to get ID to get on the flights with. Not really that big of a problem if you are talking about people already in the country, but if you have to import the principles from overseas, it gets a bit trickier and more expensive. My estimate was for 30 people and $250,000. Not that difficult. Of course, everything needs to be compartmentalized for security's sake.
Childish revisionism by, or cited by, the author. A MILITARY PILOT lost in HEAVY FOG crashed into the building...and OF COURSE it was an accident...how effortlessly do liberals distort: it's their very nature.
Still & all, Diogenes, an interesting post.
Agreed. Anyway, they probably just aimed at the middle of what was above the surrouning landscape, that is what it looked like to me. I dont see a great deal of planning here, and any grade school kid knows that a plane taking off, is full of fuel, and when it is finished with its trip at the end of a long journey, it is close to empty. That did not indicate any great planning. The reason they they hijacked planes at when they were full of fuel, is because the planes were near the target, and they were all trying to coordinate hitting the targets at about the same time.
I still say, it only took 4 guys acting alone to pull this off, no great master mind, and no outside financing was required. A master might have been behind it, but certainly it was not necessary. Anyway, the targets are suspect, why fly 2 of the planes into one building? A master mind would have picked 4 separate and distinct targets, and if there was outside financing, then more than 4 targets would have been chosen, and the targets would have been in more than 2 cities, it would have been in at least 4 cities for maximum effect.
What happened, is more likely 4 stupid crazy guys who dont mind suicide.
Until at least the pilots, and more preferably the passengers are armed, this could easily happen again. Isreal stopped hijacking by letting the passengers be armed. When I used to fly with my revolver, I would not have let any hijacker fly my plane into a building.
Denied a STATE? After watching them celebrate the deaths of at least 10,000 Americans, I want them denied their very EXISTANCE. I want the term "Palestinian" to be used in the same way as "Assyrian" or "Babylonian" - strictly in an historical sense.
The towers each survived the impact. The structural steel is covered with fireproofing rated at 2-3 hours. The steel is also rated at twice the load it is designed to carry: i.e. the weight of everything above any point in the building. The towers were also designed as stiff tubes due to the tremendous wind load at the higher elevations.
The south tower was hit closer to the middle. I expected that tower to fall from the damaged floor up, and it should have fallen at whatever corner or side the fireproofing burned through first, thus buckling the steel and causing a collapse. That's not what I saw on TV. I saw a straight down collapse, similar to an implosion caused by demolition charges. In reality, the top of the tube should have fallen to one side.
If we say that the steel at the bottom gave way, which is possible due to the first four floors being engulfed in flames, thus the fireproofing could have been burned through and the steel weakened, I would have expected the building above to fall in a semi-intact state.But it seemed that the building disintegrated downward, as it fell. That doesn't add up. The steel in the other parts of the building had not been engulfed in flames, thus the "tube" in some parts should have been intact.
Then the north tower fell within minutes of the south tower. That tower had much less damage, and the damage was much higher up than the south tower. Yet it fell in the same pancake fashion, straight down. One tower collapsed right down to ground level, one down to twenty floors. Controlled demo charges seemed to be at work here.
My take is that the buildings were to be hit by the planes-plan A- and then plan B would be to demo the towers an hour later. Plan B would happen whether plan A succeeded or not, as plan A had more visual impact to the world then a straight demo job.
The Coffee Sugar and Cocoa Exchange
The New York Cotton Exchange
Salomon Brothers Inc
American Express Bank
Sumitomo Bank Securities Inc
Morgan Stanley
Credit Suisse Group
Commerzbank
Deutsche Bank AG
From your mouth to God's ears....thank you for putting into words what I want too!
Remember, even the sims respond better than the actual a/c and in the case of the second a/c to hit the WTC I believe you can actually see that the landing gear was down which would also effect the mobility and steerability(sp?) of the plane. Anyone who has ever flown what we in the aviation community refer to as "pigs" heavy a/c, understand the slow response time to pilot input to the flight controls. Kinda like trying to stop an a/c carrier on a dime, just ain't gonna happen. Also, the lack of a proprioceptive (sp?)sense (seat of the pants flying) points to someone who only trained on a sim and never felt that feeling in the seat of his pants that comes from severe banks or dives.
there are now seven total buildings, a large shopping mall, and an enormous garage. An observation deck is a popular tourist destination. Beneath the center two New York subway lines converge; there is also the Manhattan terminus of PATH commuter trains from New Jersey.
The author apparently copy-and-pasted this out of a tourism web site, and forgot to change the wording to past tense.
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