Construction of the World Trade Center
Sep 13, · Overall, , tons (, metric tons) of steel were used to build what were, at the time of their construction, the largest buildings on Earth [source: Ross ]. Next, find out what happened to all that steel on Sept. 11, September 11, Author: Michael Franco. World's Tallest Twin Building. The twin towers were originally proposed to be built at a height of only feet (m). Thankfully, Dr Mahathir saw greater potential in the building as the world's tallest structures, and pressed architects and engineers to include a few more meters in .
By: Michael Franco. As you might imagine would be the case in a complex as large as the original World Trade Centermultiple different grades of steel were used in construction -- 12, in fact.
These grades began at a very common type of steel known as A36, which has a yield strength of 36ksi or jaterials per tue inchand got progressively stronger -- all the way up to steels that had buiild strengths of ksi [source: FEMA ]. The yield strength assigned to any grade of steel is the point at which it will bend and not regain its original shape. So A36 steel -- a mix of carbon and iron, like all steels -- can handle 36, pounds per square inch 36 kilopounds of pressure before it begins to deform.
In the external walls of towers one and two of the World Trade Center, the steel also varied by thickness to allow for different pressure loads at different levels. In the lower levels, the thickness was most frequently around 4 how to make a stuffed toy parrot 10 centimeters builx, while at higher floors, it could be as thin as 0.
ASTM A is what is known as a high-strength, low-alloy HSLA steel, which means that it was extra-strong, allowing less of it ot be used which makes for a lighter building. Overall,tonsmetric tons of steel were used to build what were, at the time of their construction, the largest buildings on Earth [source: Ross ].
And they're right. Towefs 's melting point is 2, degrees Fahrenheit Celsius. Yet jet fuel only burns between and degrees Fahrenheit So what happened on that September morning that caused the towers to collapse?
Even though the girders that comprised the twin towers wouldn't turn to molten steel in the jet fuel fire, they would certainly have weakened in the heat. In fact, one estimate says that they would have lost half of their ti at 1, degrees Fahrenheit It's important to also note that other items would have caught on fire in the buildings in addition to the jet fuel, and could have contributed to higher burning temperatures. But according to a multi-year study carried out by the National Institute of Standards and Technology NIST even these fires combined buile the impact of the planes would not have been enough to bring the buildings down.
Their report concluded that the real culprit was the fact that fireproofing materials were dislodged during the impact and this in turn exposed vital structural components to the heat. As these components lost strength, the floors began builf sag, pulling the weakened columns inward and leading to a chain reaction that had floor collapsing upon floor until the buildings no longer stood [source: NIST ].
Structural Engineering. What grade whay steel was used in the World Trade Center? The twin towers as they once stood how to calculate pregnancy days from last period the night sky. See more skyline pictures. Sources Banovic, S. Cite This! More Awesome Stuff.
Sep 13, · There were two main factors that greatly distinguished the two main towers of the World Trade Center from anything that had been built before them: their walls and their elevators.. Prior to the construction of the Twin Towers, skyscrapers were designed to support themselves through large internal columns spaced about 30 feet (9 meters) apart, which interrupted the flow of interior datmetopen.com: Michael Franco. The major structural material employed in the towers was A36 structural steel, although higher strength steel was used in the lower elevations of the structure. Except for some selected floors, for which normal strength concrete was employed, the composite slabs were made of a 21MPa (3ksi) lightweight concrete. Sep 07, · Photo courtesy of Paul Lioy and James Millette The collapse of the Twin Towers pulverized and then scattered into the air millions of tons of cement, steel, drywall, window glass .
By: Michael Franco. Long before the World Trade Center became synonymous with the most damaging terrorist attack in U. Upon its completion in , the two towers that rose from the acre But the construction of such mammoth structures had its challenges. The first major challenge was the building site itself.
The location selected for the project, on Manhattan's Lower West Side, had been built upon generations of landfill that had actually grown and compacted on itself so much that it had extended the Lower West Side of Manhattan into the Hudson River.
To reach a solid base of bedrock, workers had to dig down 70 feet But because of the proximity of the river, a barrier needed to be created that would keep the excavated section of the city from filling with water as fast as the earth was removed.
The answer was something that became known as the slurry trench method. A trench dug deep in the ground was filled with a slurry mixture made from water and an expanding clay known as bentonite. This slurry was denser than the surrounding dirt, so it kept the ditch from caving in. Once filled with the mixture, a steel cage was dropped in that weighed 25 tons and stretched to a height of seven stories. Concrete was then poured into the trench.
As the concrete was heavier than the slurry, it forced the clay mixture out and hardened around the cage, making a section of underground wall.
Workers then moved on to the next section. When the wall was complete, forming what became known as the "bathtub," the rest of the earth was removed from inside it without danger of flooding the newly opened space. Another concern unique to the construction of the World Trade Center was the fact that the PATH commuter rail line ran directly through the center of the construction site. Instead of interrupting service, engineers designed a protective cradle for the underground line and as a result, the train ran throughout the entire project, carrying , passengers a day [source: veritas ].
There were two main factors that greatly distinguished the two main towers of the World Trade Center from anything that had been built before them: their walls and their elevators. Prior to the construction of the Twin Towers, skyscrapers were designed to support themselves through large internal columns spaced about 30 feet 9 meters apart, which interrupted the flow of interior space.
For this project however, the engineers came up with a different solution -- the exterior walls themselves would support the bulk of the structure, and they would get a boost from one single column of beams in the center. This allowed for a much more open plan on every floor of the building, which not only had aesthetic value but had financial worth as well -- the more floor space, the higher the rent the buildings' owners could collect.
Adding to the creation of open floor plans was the design of the elevators. A classic problem in skyscrapers is that as buildings grow taller, the number of residents increases. With more residents, more elevator shafts are needed. But the more elevator shafts there are, the less floor space there is for tenants. This issue was solved in the construction of the twin towers through the use of express and local elevators. In much the same way the New York City subway system worked, express elevators would take passengers to "sky lobbies" placed on various floors throughout the building where they would then disembark and switch to local elevators to get to their required floor.
The use of this system cut the number of required elevator shafts in half, thus preserving valuable floor space. Not only was the construction of the World Trade Center unique, but the tools used to construct it were as well. To erect the tallest building in the world, "kangaroo cranes" were brought over from Australia. These mighty building machines could raise themselves up through the use of heavy-duty hydraulics, in effect growing with the building itself.
The building of the Twin Towers marks the first time such cranes were used in America. The design of the Twin Towers is often called a "tube within a tube," referring to the fact that all of the weight of the building was supported by the external walls and an internal column. Previously, the exterior walls of a skyscraper were called curtain walls -- they weren't relied upon for strength, so it wasn't imperative that super-sturdy materials were used for them.
But for towers one and two, the external walls would not only bear the weight of the interior floors, but they would also have to withstand tremendous pressure from the wind. Because the external "tube" of each tower was perforated with openings for windows, the entire web of steel could shift in strong winds, transferring the load from the windward side to the leeward side of the buildings through something known as Vierendeel action [source: FEMA ].
For the columns that comprised the walls, a mixture of 12 different types of steel with yield points between 42, pound per square inch psi and , psi were used, while the interior columns consisted of a steel known as A36, a designation which meant it had a yield strength of 36, psi.
The thickness of these columns also varied -- from as thin as 0. In all, , tons of super-strong steel which had just recently become available in were used to create the two towers [source: Gayle ].
Just inside the walls, at approximately 10, locations throughout each tower, visco elastic dampers were installed [source: FEMA ]. These were basically large shock absorbers that could bend with wind pressure and then return to their original form. Because the towers were designed to sway and adjust in the wind, these dampers helped reduce the impact of this movement on occupants. It was the first time this technology had ever been used in a high-rise [source: FEMA ].
The floors that flowed between the supporting walls and interior columns were made from 0. Overall, , cubic yards Structural Engineering. How was the construction of the World Trade Center unique? The exterior walls of the World Trade Center towers, bathed in sunlight.
See more beautiful skyline pictures. Unique Job, Unique Tools. World Trade Center Design and Materials The design of the Twin Towers is often called a "tube within a tube," referring to the fact that all of the weight of the building was supported by the external walls and an internal column. Sources veritas. Science, Engineering and Speculation. April 30, Cite This! More Awesome Stuff.
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