# Bridges and Stability

Updated on November 8, 2014

## Education Fun = #1

Bridges make great examples of structure and stability in our world. Lessons in strength, design and failure can all be learned while studying bridges - take a look for yourself.

As a homeschooler I have created various different unit studies to help my children to learn and have fun. Now, I hope to help other kids do the same by sharing the unit studies and lesson ideas with others.

## What is a bridge

Bridges are one of the earliest forms of architecture. They are built to cross over something like a river, another road, a railroad track etc. Not only do bridges support their own weight but they also can hold the weight of whatever crosses it. (train, cars, people). There are special forces at work to help the bridge hold this weight. Compression and tension are the push and pull forces that help keep bridges stable.

## Anatomy of a bridge

To understand bridge construction better you need to know the words used to describe the parts of a bridge.

Deck - where you walk or drive

Supports - the parts that hold the bridge up

Span - distance between supports

Foundations - what supports rest on

Abutments - supports at the ends of beam and arch bridges

Piers - supports in the middle of beam and arch bridges

Towers - middle supports of a suspension bridge

Cables- steel ropes that supports suspension bridge

Hangers - run from the cable to the deck

There are three main types of bridges: the beam, the arch, and the suspension.

The beam is one of the simplest forms of bridge. In its basic form, it could be just a plank or a log crossing a stream. It is made of two or more supports (piers) which hold up a beam. Beam bridges usually cover relatively short distances.

An arch bridge is a semicircular structure with abutments on each end. The design of the arch, the semicircle, naturally diverts the weight from the bridge deck to the abutments. The shape of the arch itself is all that is needed to effectively dissipate the weight from the center of the deck to the abutments.

A suspension bridge is one where cables (or ropes or chains) are strung across the river (or whatever the obstacle happens to be) and the deck (where the traffic flows) is suspended from these cables. Modern suspension bridges have two tall towers through which the cables are strung. Thus, the towers are supporting the majority of the roadway's weight.

## Photo Gallery

Click thumbnail to view full-size

## London bridge is falling down

London Bridge began its life as a wooden beam bridge, built by the Romans in 43 A.D. It was built, destroyed, rebuilt and destroyed again. Destroyed by flood, fire and Vikings the story of London Bridge is much like the nursery rhyme.

London Bridge is falling down

Build it up with wood and clay

Wood and clay will wash away

Build it up with bricks and mortar

Bricks and mortar will not stay

Build it up with iron and steel

Iron and steel will bend and bow

## Cross the Bridge puzzle

A man has a hen, a fox and some corn. He must get them all across the bridge. But the bridge is too narrow and wobbly that he can only carry one thing at a time. How can he get them safely across without the hen eating the corn or the fox eating the hen?

Venice, Italy has 450 bridges spanning the canals that are the city’s streets.

Look at pictures of Venice and then paint one yourself – make sure there is a bridge in your picture!

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• traveller27

7 years ago

Interesting pics - great idea for a lens.

• Evelyn Saenz

7 years ago from Royalton

Lots of neat ideas and info on bridges.

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