Fun & Easy Science for Kids

# All About Bridges: Importance and Types

Remember the story of the Three Billy Goats Gruff? They needed to cross a river to get to the green grass on the other side. Of course, the mean troll played a big part in the story, but what about the bridge? If there hadn’t been a bridge, there would have been no story. And, those poor little goats would have gone hungry.

A beam bridge is made by building two piers or towers. Boards are placed over the piers to make a bridge. Keep reading all about bridges below.

Bridges have always been important because they allow people to travel over canyons, rivers and streams. There are over 500,000 bridges in the United States. Some bridges are small, while other bridges span 7,000 feet or more. Bridges seem like a simple invention, but they’re actually quite complex. Engineers who build bridges must think about the distance to be covered, as well as the type of traffic that will cross the bridge. A bridge for cars and trains must be stronger than a simple bridge for foot travel.

A truss bridge is stronger than a beam bridge because the trusses help distribute some of the weight. The trusses run horizontally between each beam.

## Fun Facts about Bridges for Kids

• Have you ever built a bridge? Stretching a log over a stream is a simple type of bridge. Dropping stones in a creek to pass is also a type of bridge.
• You might have seen beam bridges over small rivers and creeks. A beam bridge is made by building two piers or towers. Boards are placed over the piers to make a bridge. The boards press down on the piers, so these types of bridges aren’t very strong. They are usually pretty short.
• What would happen if you reinforced a beam bridge with metal poles pieced together in a pattern of squares or triangles? You’d have a truss bridge. A truss bridge is stronger than a beam bridge because the trusses help distribute some of the weight. The trusses run horizontally between each beam.
• Arch bridges are very strong. Ancient Romans made arch bridges out of stone. These bridges were made of columns joined by arches.
• Suspension bridges like the San Francisco Bay Bridge use a completely different approach. Tall towers are built. Then long metal cables attached to the towers suspend the road in place. Piers and trusses are usually built underneath for additional support. The Chinese built the first suspension bridges in 300 A.D. They used twisted bamboo fibers instead of steel cables.

Suspension and Arch bridges are very strong type of bridges.

### Bridge Vocabulary

1. Reinforce: strengthen
2. Complex: complicated

Suspension bridges like the San Francisco Bay Bridge use a completely different approach.

Watch beautiful bridges in this video:

A video all about bridges around the world.

### Bridge Q&A

Question: How safe are bridges?

Answer: Bridges are very safe as long as they are properly constructed and maintained. Some bridges can even withstand sever earthquakes and other natural disasters, but not all can. Some bridges might be ancient and not as strong as more modern ones, should disaster strike.

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### MLA Style Citation

Declan, Tobin. " Facts About Bridges for Kids ." Easy Science for Kids, Jun 2018. Web. 19 Jun 2018. < http://easyscienceforkids.com/all-about-bridges/ >.