Skyscrapers are built primarily because they are convenient; one can create much real estate from a relatively small ground area.
The central support structure of a skyscraper is its steel skeleton. Steel, which is lighter and stronger than iron, makes it possible to build taller buildings. As a result, steel buildings have become more prevalent in recent years.
- Underground Substructure: The base of a skyscraper is supported by an underground substructure. The force of gravity is transferred through vertical columns to the base of the building.
- Vertical Columns: The weight of the skyscraper is supported by a group of vertical columns. Each vertical column sits on a spread footing. The column rests directly on a cast-iron plate, which sits on top of a grillage. The grillage is a stack of horizontal steel beams, lined side-by-side in two or more layers. This rests on a thick concrete pad poured directly onto the hard clay under the ground. Once the steel is in place, the entire structure is covered with concrete.
- Girder Grids: Each floor is supported by horizontal steel girders running across the vertical columns. Many buildings also have diagonal beams running between the girders, for extra structural support.
- Curtain wall: The curtain wall, which makes the outside of the skyscraper, is made of glass and concrete and needs to support only its own weight.
With the advent of the Bessemer process, the first efficient method for mass steel production, architects moved away from iron.
Fighting the Wind
Where the horizontal girders are attached to the vertical column, the construction crew bolts and welds them on the top, bottom, and side. This makes the steel structure move as one unit, like a pole, as opposed to a flexible skeleton.
Skyscrapers would not have worked without the emergence of elevator technology. Since the first passenger elevator was installed in New York’s Haughwout Department Store in 1857, elevator shafts have been an integral part of skyscraper design.
Building safety is also a major consideration in design. A building is successful only when its architects focus on structural stability, practicality, and occupant satisfaction.
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