Two developments in the 19th century paved the way for a whole new type of building: the skyscraper. The first was the development of a safe elevator. Primitive elevators of various designs had been used for centuries, and starting in the mid 19th century, steam-operated elevators were used to move materials in factories, mines, and warehouses. But these elevators were not considered safe for people; if the cable broke, they would plummet to the bottom of the elevator shaft. Then in 1853, an American inventor named Elisha Graves Otis developed a safety device that kept elevators from falling if a cable should break. This new development had an enormous impact on public confidence. And later in the century, the switch to an electric motor made the elevator a practical solution to the problem of getting up and down tall buildings.
The second development took place in Chicago. In 1871, Chicago suffered a devastating fire. In the years that followed, however, instead of recovering slowly, the city experienced explosive growth, and it quickly began to strain against its natural boundaries. By the 1880s, the available land for new buildings in this area could not keep up with demand; the only alternative was to build up. But in order to achieve the desired height, construction techniques had to change. A new method of building was developed that used a grid of steel beams and columns that were strong enough to support any stresses or forces a building might experience, including both the weight of the floor and the building contents, as well as the force of wind or even, in some areas, earthquakes. And with this new building method, the skyscraper was born and the race for the tallest building began.
Skyscrapers are the world’s tallest buildings. They first appeared in New York and Chicago at the end of the 19th century. Skyscrapers are often like small cities. They offer space for offices, apartments, shops, hotels, restaurants and other services. Tens of thousands of people live and work in skyscrapers.
Skyscrapers have 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.
A skyscraper needs careful planning before it can be built. First a big hole a few stories deep is dug into the earth. Sometimes this foundation reaches into solid rock. Then steel and concrete beams and columns are placed into it. They carry the weight of the superstructure. When the foundation is finished cranes are used to raise a steel frame up into the sky. 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.
A skyscraper must also be able to hold off strong winds. Modern buildings are able to swing a few metres in each direction, like a tree, without damaging the structure. Sometimes a steel core rises upwards from the inside of the building to give it better support. Corridors, staircases, elevators, heating systems, air conditioning and electrical systems belong to the most important inner elements of a skyscraper. Although the outside structure can be completed in a few weeks it may take years to finish the whole building. Pumps bring clean water to all parts of the skyscraper; the drainage system carries away water and waste materials. Air conditioning and heating systems control the temperature in the building the whole year round. Electrical systems provide power and communication throughout the building and wires carry electricity to each floor. Elevators are the most important systems of a skyscraper. They carry people up and down at speeds of up to 500 metres per minute.
Tomorrow we will take a critical look at the advent of skyscrapers and its threats to survival in an article titled; A race to the sky.