A skyscraper is a tall building that has a steel skeleton that supports its floors and walls. In big cities, where land is limited, skyscrapers are popular because building up instead out means you can put a bigger building on a smaller piece of land.
Before builders learned how to construct skyscrapers, buildings had to have very thick walls on the lower floors to bear the weight of the whole structure. If they were too tall they would collapse from the weight.
Two important developments made taller buildings possible. First, the process of producing strong steel beams inexpensively, essential for holding up tall buildings. And second, the introduction of the safety elevator, ensuring passengers a safe trip to upper floors.
Skyscrapers are built in two parts. The foundation is the part below the ground and the superstructure is the part above the ground. Both sections hold the weight of the building. When the foundation is finished cranes are used to raise a steel frame up in the air and the pieces of this frame are bolted together. As it moves upward other workers lay floors and hang in the outside walls. The complete structure of the skyscraper must be finished before the inside systems can be installed.
Designing a skyscraper takes a lot more than the steel beams and deciding how many floors to build. Skyscrapers have to be strong, safe and convenient for the occupants. Architects, contractors and builders use special technology and materials to make sure the building has the flexibility to resist high winds and earthquakes. Modern buildings are able to sway a few feet in each direction, without damaging the structure.
The construction of bigger and taller buildings is going on around the world. So how high can they go? Maybe the sky is the limit.