Saturday, December 20, 2008

Skyscrapers: How and Why they are Built

· The main reason that people build skyscrapers is because they are very convenient. They serve to fit a lot of floor space in a comparatively small amount of ground surface because of their immense height.
· The challenge in building a skyscraper is building vertically and fighting the downward pull of gravity. As the building gets taller and taller, there is more of a downward force all of which is supported by the base of the building. This is similar to the construction of a pyramid. The reason they are built as they are is because they had to build a wider, sturdier base in order to support all of the weight bearing down from the rest of the pyramid.
· The advancement of iron and steel production was a huge reason that constructing skyscrapers became a reality in the United States. Prior to that, no buildings were more than a few stories tall.
· Iron and steel beams that were relatively lightweight, could support much more weight than brick and concrete while taking up significantly less space.
· Skyscrapers are supported by their steel skeleton. Their weight is supported by a group of vertical steel columns. Each individual floor of the structure is supported by horizontal steel girders between the vertical columns. Many buildings also have diagonal steel beams to supply extra support.

· By building this grid, called the super structure, all of the weight is transferred to the vertical columns in which there is a downward force at the base which is supported by the substructure.
· A skyscrapers substructure supports the vertical beams in a cast-iron plate which sits on top of a grillage (stacks of horizontal beams laid side by side). The grillage sits on top of a level concrete surface. Once this substructure is completed, it is entirely covered with concrete to ensure stability.
· Skyscrapers were not only made possible by the advancement of steel production, but also after the introduction of elevator technology. After you build something a few stories tall stairs are problematic. In most skyscrapers, elevator shafts are placed in the core of the building so they can supply additional support to the structure.
· Skyscrapers have become more and more popular in the world today as the demand for location grows but availability of land decreases. Skyscrapers make it possible to fit a large amount of building space in a small amount of land area.
· The first ever skyscraper was built in Chicago, Illinois in 1885. It was called the Home Insurance Building and it was 10 stories high and 138 feet tall.
· Today, the largest skyscraper is the Burj Dubai in Dubai, a city of the United Arab Emirates. Although it has not yet been completed, it has 160 floors and stands at a whopping 2320 feet, nearly 17 times the height of the first skyscraper.

Burj Dubai

Home Insurance Building

· When demolishing a skyscraper, explosives are the most commonly used methods because they are both efficient and safe. More often than not, skyscrapers are surrounded by other buildings so you can’t just simply knock it over or blow it up…most demolition is done through a process called implosion.

· An implosion is an inward collapse of the building so that it all crumbles down on top of itself and does not disturb the buildings surrounding it.

· In order to pull off a proper demolition, you must place explosives on the supporting beams so and several floors of the skyscraper so that the building can no longer support itself and collapses floor by floor until it is reduced to nothing more than a pile of rubble.

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