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.
If there was indeed state support of this act (down to technical guidance, logistics, what have you), the US Government might be able to confiscate that nations financial assets that are deposited/invested through US institutions (that was done during the Tehran Embassy hostage crisis). Thus used for compensation. Question: would there have to be a Declaration of War, or other Act of Congress, in order to sieze assets in such a manner? (don't get into asset forfeiture in the War on Drugs, this is another matter)
I did not realize this, and appreciate the insight.
........Freudian slip???
If we declare war tomorrow, does that exclusion apply to today's destruction? IDK. If not, then some insurance companies are likely to go belly up by the end of the month. Something to think about when the markets open again.
Time and might and right are on our side. Let's do it slow, and let's get 'em all.
A reflexive opposition to spending Government money hurts the conservative cause.
If you live in New York, you should know by now that there are many people who were on floors ABOVE the crash points who were able to escape to ground level before the towers collapsed.
Bin Ladin and his family made a fortune in Saudi Arabia doing civil engineering for the Saudi government. He is a civil engineer himself by training, and his family got into some huge projects and he likely got to know people of Bechtel's caliber too.
When he started to get political, the Saudi government and his family pleaded with him to come back and do some more family projects. He knows civil engineering forwards and backwards and I'm sure has contacts just as well-versed.
That said, I think it's a little too difficult to muscle those planes to the precise locations, they just aimed for the middle, if they aimed farther down they would run the risk of hitting other buildings in the way. The massive amounts of jet fuel and the fire made the destruction inevitable.
I think the towers were chosen deliberately because of the 1993 prior bombing attack on them.
Believed to Be Safe, the Towers Proved Vulnerable to the Intense Heat of a Jet Fuel Fire [NYT]
These buildings met and exceeded all building codes, and they underwent continuous life safety upgrades over their 35 year existence.
The one thing the PA does well is spend a lot of money on safety.
Somebody should have warned rescue workers about the possibility of collapse after that time.
So you don't need to hit ident huh, why when you pull into airspace around major airports and you get put into a holding pattern do they tell you to climb to yada yada and squak 1233 and hit indent?
It's truly shocking that the structure failed in such a major way, but I'm not sure it was secondary explosions, as I saw or heard no evidence of that on the videotapes.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.