So what really holds a skyscraper up? Start with the frame. What is it made of, and what does it do? A tall building stands on a strong frame of steel beams and columns, like a skeleton. The weight of the building pushes down on its columns, and the columns are squeezed. Engineers use steel beams and columns to hold up most skyscrapers because steel is very strong.
Squeezing is only half the story. What about stretching? Compression squeezes a material, and tension stretches it. When a beam bends, one side is squeezed and the other is stretched. A truss is a frame made of connected triangles. In a truss the top is usually squeezed and the bottom stretched.
Compression squeezes a material and tension stretches it. Concrete is strong when it is squeezed, but weak when it is pulled apart. To make concrete strong when pulled, builders put steel bars inside it. The Burj Khalifa is built of reinforced concrete, which is concrete with steel bars inside. Steel bars take the stretching.
Now look down, at the ground. A building has a foundation, the part that goes down into the ground and holds the building up. Where the ground near the surface is too weak, builders use deep foundations that carry the load down to stronger layers. Piles are long, slender columns of steel, concrete or sometimes timber that are put deep into the ground.
Before steel frames, tall buildings had thick, heavy masonry walls, and that limited how high they could go. Steel changed that. Because a steel frame carries the weight, the outer wall can have many windows, which stone walls could not. Engineers use steel beams and columns to hold up most skyscrapers because steel is very strong. The weight of a building pushes down on its columns.
How do people get up to the top floor? In 1857 the first passenger elevator was installed in a New York store. It made buildings taller than four or five stories practical. Elisha Otis showed a safe elevator by having its rope cut while he stood on the platform. The platform held. His safety brake is a steel spring that grabs a ratchet if the rope breaks, which stops the platform from falling. Elevators let people ride up tall buildings, so builders could make buildings taller.
Steel frames and elevators together made the first skyscraper possible, in Chicago in 1885. The Home Insurance Building there is called the first skyscraper. It was 10 stories and 138 feet tall. The Home Insurance Company wanted a fireproof building, and masonry covered the metal frame to protect it from fire.
Here is a famous tower. The Empire State Building in New York was built in about one year. It is 1,250 feet (381 meters) tall and has 102 stories. It was the tallest building in the world for about 40 years after it opened in 1931. The Burj Khalifa in Dubai is 828 meters (2,717 feet) tall and has 163 floors. It is much taller than the Empire State Building, which is 1,250 feet tall.
Next comes wind. Wind pushes on tall buildings, and they sway a little. Taller buildings face stronger and more complicated wind forces than short ones. Every tall structure sways a little, and engineers watch sway because people on high floors can feel it.
One tower has a big answer to sway. Taipei 101 has a huge pendulum at the top that weighs 660 tonnes. It swings the opposite way from the tower, which helps cancel out its swaying. This was true in November 2026.
Words to know
- masonry: stone or brick
- compression: squeezing force
- tension: stretching force
- truss: triangle frame
- pendulum: swinging weight
- foundation: building's base
