4-6

DURATION
30

COLLECTION
Hands-On Lessons

# Engineering a Bridge

This lesson will involve your students in geometry and measurement as they work as civil engineers to design and build their own bridge.

OBJECTIVE
Students will be able to:

• Identify how geometry affects bridge design and function and apply that knowledge to the design and construction of a bridge.

MATERIALS
Elmer's Foam board, Popsicle sticks, pipe cleaners, bendable rods, Elmer's Glue All, paper, pushpins, weights
Engineering a Bridge PDF

SET UP AND PREPARE
Content Introduction
When engineers design a bridge, they must consider how the bridge will be used, how long and wide it should be, and how much weight it has to hold. There are four main types of bridges:

1. Beam bridges are made of horizontal beams supported by piers at each end.
2. Truss bridges are a combination of triangles made of steel.
3. Arch bridges are made up of arches supporting the bridge and are naturally strong.
4. Suspension bridges are long bridges, such as the Golden Gate Bridge.

Essential Questions
Use these essential questions to help guide students' thinking:

• How does geometry help engineers build bridges?
• What do we need to build a successful bridge?

Vocabulary
Type of bridges: beam, truss, arch, suspension
Additional vocabulary: arch, beam, deck, column, fixed arch, footing, portal, strut

Introduction (5-10 minutes)
Explain to students that they are going to be engineers today as they design their own bridges.
Show students various bridges. What do they all have in common? What are some differences? Which bridge is the strongest? Look at the shapes that are used to construct each bridge. Which shape is the strongest? Which is the weakest? Why might you use each type of shape to build a bridge?

DIRECTIONS

Craft Component: Bridge Engineering (20 minutes)

• Divide students into groups of three to four.
• Pass out Elmer's foam board, glue, markers, Popsicle sticks, and other materials to each group.
• Challenge students to use what they learned about bridges to build a bridge that will hold the most weight.
• If students finish early, they can write a hypothesis of how much weight they think their bridge can support and their rationale.
• Students can also use pushpins and paper to label the various parts of their bridge.

Structural Test (5-10 minutes)
Have each group present their bridge and test it using increasingly heavy weights. As each group presents their bridge, students discuss which elements of bridge construction they incorporated and why.

Whiteboard Component Activities

• As students test their bridges, record the data on your whiteboard using the Engineering a Bridge PDF. Record the type of bridge, elements of the bridge (arch, beam, deck, column, fixed arch, footing, portal, strut), number of popsicles, maximum weight that each bridge held, weaknesses, and strengths of the bridge. Then create multiple ways to show the same information. Discuss why you might want to use each representation.
• Have students imagine that they are going to build an actual bridge using their small bridge as a model. Have students draw their bridge on graph paper, converting their models to show a full-scale drawing of their bridge. (Some students may need assistance establishing a way to convert centimeters or inches to meters or feet.)
• Project images of famous bridges onto the whiteboard. Have students label the parts of a bridge using bridge vocabulary.

Resources
Index of famous bridges: http://www.famousbridge.com/
PBS webography of bridges: http://www.pbs.org/wgbh/buildingbig/bridge/webography.html

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