Compression and tension are forces that cause a material to be pressed together or pulled apart. You compress a chair when you sit on it. Squeezing a sponge is a compression force. Can you think of others? We think of tension in a rubber band as it stretches. But just similar to compression in a chair that you don’t see when you sit on it, you don’t see tension in the chair or in the cables holding hanging lights or plants from the ceiling. Two of the common forces that building components experience are compression and tension. Tension is a force that stretches a material. Compression is a force that causes a material to be pressed together. The two main forces that bridge components experience are tension and compression. When properly designed, a bridge or building will be built to withstand any potential load that the structure may experience.
Take a photo of yourself on one of your favorite bridges. Post your photo to the SELS website and share it with others!
Print your photo on paper and draw “force arrows” where you think the load of the bridge is being carried. Think about how the cables on a bridge carry the load of the bridge deck with tension force. Think about the bridge as “hanging” from these support cables. If your bridge does not use cables, draw force arrows to show how the load of the bridge deck is being carried by the bridge structure above the deck.
Watch the Compression and Tension video to help better understand how the forces of compression and tension affect construction materials.
Compression & Tension
Next Generation Science Education Standards
Scientific and Engineering Practices:
-Asking questions (for science) and defining problems (for engineering)
-Planning and carrying out investigations
-Structure and function
- Discuss with a friend how buildings and bridges have to be designed to resist the forces of compression and tension. What effect would compression and tension forces have on bridges or buildings?
- Think about a bridge that uses support cables. What would happen if you were able to cut through these cables?
- How do arches like the ones in the photo of the Newport Bridge below help carry the compressive load of cars and trucks from the bridge deck down to the support columns submerged in the water?