Types of Bridges

Learn the 4 types of bridges and build models of them



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MatchCard Science Types of Bridges Worksheet

Objective: Diagram 4 different types of Bridges.

MatchCard: Download below.

MatchCard Information Pieces describe the four different types of bridges and their main parts.

Print the Types of Bridges MatchCard

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This is MatchCard #1 of the Technology Unit Study. Find more information on MatchCard Science below.

Build Index Card Models of Different Bridges

Do This BEFORE Giving Students the MatchCard

Before looking at the Matchcard, the students can experiment with ways to build bridges to make them stronger. You will need:

To make these bridge models you will need:

• A stack of index cards (3 x 5 inch will work fine.)
• A stack of books or notebooks
• Tape
• String, thread, toothfloss or yarn
• A small, light weight toy car

Build a Beam Bridge

Make two stacks of books the same size and close enough together that an index card can span the space between. There’s your beam bridge.

Drive a car across the bridge. The index card may sag a bit, but the bridge should hold. What if you added a second car? It’s probably getting a bit shakey. I wouldn’t want to be in one of those cars if it was a real bridge.

So what would you do?

Trial and Error

Let the student(s) experiment a little with the index cards and see what ideas they have for making a stronger bridge. Than we will build the next three types.

Build an Arch Bridge

To make an arch bridge you may need to raise or lower the height of your bridge by changing the number of books.

Take another index card and bend it into an arch and set it under the beam of your beam bridge. The arch will take the weight and spread it out.

Now try driving your two cars on the bridge. You will notice that the index card is stronger.

Point out that bridges may have a series of arches. Some of the arches may be on top rather than underneath the beams, but they will learn about that coming up.

Build a Cantilever Bridge

Sometimes bridges have to span long distances, for instance when crossing a wide river.

You can demonstrate this by taping two index cards together and increasing the space between your books.

You know this isn’t going to hold your cars. We need to make some pillars for support. Take another index card and fold it in thirds. Tape the edge to make a triangular pier.

Make a total of four triangular piers. (Two for each side.)

Slide a pier under each side of the middle of each index card. They are called central piers because they are in the middle of the section.

You may need to adjust the number of books to make the bridge the right height for your piers.

How well will the cantilever bridge work?

Build a Suspension Bridge

I always thought they were called suspension bridges because everyone in the car was in suspense when we crossed them. Not really. But if I had known they were called suspension bridges because the entire bridge and all those cars were being suspended from the upper beams I would have been in even more suspense.

Take your four piers from the Cantilever Bridge (above)and use them as the towers of your Suspension Bridge. Put them on either side of the bridge, with the triangle pointing away from the center of the bridge.

You may want to tape the edges of your bridge to the books to help hold them while you finish building this bridge.

Make snips in outside corner of the towers. This will help hold the string.

Using a hole punch or very sharp pencil punch holes on each side of the card in the center.

Use yarn, string, thread or tooth floss to create the cables for your suspension bridge. Cut two very long pieces. They should be long enough to go over the towers, past the books, and to the table top. Tape the strings to the table top on all four corners.

Make sure the string is threaded into the slits you cut into the edge of the towers.

Cut 4 pieces about 12 inches long. You will end up trimming them down, but this gives you plent to work with.

Thread the string through the hole and tie it with two knots.

It may help to have someone's assistance for this part. Bring the string up and loop it over the upper cable. Loop it five times around the cable, and then five times around itself. (This lashing is done instead of tying a knot. If you are using very slippery material, you may also need to tie a knot. Most materials will hold with the five loops and five lashes.

The deck is now suspended by the cables.

What is holding the weight of the car? What holds your weight when you drive across a suspension bridge?

Learn Facts About the 4 Types of Bridges

Beam Bridges

A beam bridge is the simplest form of bridge. The weight of the load is pushes straight down on the beam.

Piers are on either side of the beam and support the weight of the main beam.

Arch Bridge

Arches spread the weight more evenly allowing the beam to holder a greater amount of weight.

They are supported by abatements that are firmly anchored in the ground.

There may be a single arch or series of arches. The arches are usually below the main beam, but may also be above it.

Cantilever Bridge

The cantilever bridges are made of multiple sections in order to span large distances.

A central pier is located in the center of each section and supports the weight of that section.

Suspension Bridge

Suspension bridges are able to span wide and high distances. They often are built over waterways so ships can sail underneath.

A cable is attached firmly to the ground beyond both of the end towers and goes over the towers.

The main deck is suspended from the cable.

Trusses

A series of triangle trusses may be found on any of the types of bridges. These are triangular patterned rods that provide strength to the structure.

Bridge Projectsfor You< /h2>

Bridge Science Experiments

Bridge Building can be a great science fair project. Balsa wood strips are the perfect medium to use for a bridge experiment.

Here are some questions you might explore:

• What holds more weight: a cantilever or suspension bridge?
• How much sturdier is a beam bridge with and without trusses?
• How much more weight can the same size bridge support if an arch is used?

Bridge Poster

There are many awesome bridges and photos of bridges around the world. Consider making a poster of the different types of bridges. You will find many variations within each four of the types of bridges. How are they different and how are they the same?

• For each of the four main types of bridges, put a picture of a famous bridge.
• Add photographs you have taken of local bridges.
• Use the diagrams on the MatchCard and the Information Pieces as an InfoGraphic so your readers learn each type.

Your Local Bridge Hunt

Every time you travel by car there's a good chance you go over a bridge! Do you know what type it is?

Now, rather than barely noticing it, see if you can identify which type of bridge you are on.