Engineering Skyscrapers

Once students understand how forces act on different materials and shapes, they use that knowledge to help them design skyscrapers that resist different forces related to weight and high winds in this lesson.

• Engineers have to make sure that any skyscraper they build will be strong enough to withstand all of the forces acting on it.
• Wind is a major concern in skyscrapers because as the wind blows, it applies a pushing force against structures in its path.
  
  

• How are skyscrapers different from other buildings?
• How does the height of a skyscraper make it challenging for engineers?
• How does a skyscraper use shapes and materials to resist the downward pull of gravity?
• What forces other than gravity and wind act on the materials of a skyscraper?
• How are skyscrapers designed to support their weight?
• How can wind cause a skyscraper to bend?
• How does the central core and the cross supports help protect skyscrapers from different forces?
  
  

Misconception: If an object is at rest, there are no forces acting on it.

Fact: There are forces everywhere. When an object is at rest, all of the forces acting on it are balanced.

Misconception: A force is necessary to keep an object moving. 

Fact: An unbalanced force changes an object’s motion. An object that is already in motion will continue moving until acted on by an unbalanced force, such as friction.

Misconception: Only moving objects have energy. 

Fact: Nonmoving objects have stored potential energy.

Bending : when forces cause tension to happen on one side of an object or material and compression to happen on the other side

Compression : when forces push the ends of an object toward each other

Material : any kind of matter that makes up objects

Shear : when forces push one part of a structure one way and another part the opposite way

Skyscraper : a tall building with many stories that can contain many people in a vertical space

Structure : anything that is made up of parts and can support and withstand all of the forces that act on it

Tension : when forces pull the ends of an object in opposite directions

Torsion : when forces cause an object to twist

The Weight of the Skyscraper

Before engineers build a skyscraper, they have to do research. They need to know what forces will act on it. The skyscraper will have to be strong enough to withstand all of those forces.

Many challenges face engineers who design skyscrapers. First, every floor pushes down on the walls and floors below. People in a skyscraper add more weight to it. As this weight pushes down, the ground pushes back. This causes compression. As materials compress, they can also bend.

The skyscraper has to be very strong so it can withstand all of these forces. Engineers use steel beams to resist these forces. Steel is a strong material. It won’t crack or break in response to strong compression or tension.

The Structure of a Skyscraper

The first part of the skyscraper to be built is its foundation. The foundation connects skyscrapers and other buildings to the ground.

The foundation supports the weight of the structure. A skyscraper needs a deep foundation because it is so heavy. In a regular house, the foundation is less deep. This is because it has less weight pushing down.

Many skyscrapers also have a central core. This is the stiff “backbone” within the skyscraper. It is the central vertical beam that holds the skyscraper in place. The central core is often made of concrete and steel. It supports most of the skyscraper’s weight. The combination of concrete and steel don’t change their shape easily when forces act on them.

For the hands-on activity of this lesson, students apply what they know about the forces that act on structures to design and build skyscrapers that resist different forces related to weight and high winds. Students use information from a scenario to help them define the main problem facing the city of Boston, which needs engineers to design a skyscraper with five floors that resists the forces caused by high winds in the city and the weight of a school on the top floor. Students identify the criteria and constraints of the problem. Then, they create visual models of their prototype skyscraper solutions. Once they have built a prototype, they carry out a procedure for testing it to see how well it solves the problem. Students collect and analyze data on how well their skyscraper prototypes withstand weight and high winds, using their data to identify possible failure points that they can improve upon.