#### Want to get students excited about civil engineering? Introduce them to some of the field’s most spectacular and imaginative creations—bridges! Not only will these hands-on activities help them appreciate the technical know-how involved in bridge design, but they’ll also discover first-hand how creative engineering can be.

## Shape It Up (Grade Level 3-4)

Time: 45 minutes

The purpose of this activity is to help students discover which shapes are the strongest and most stable for building bridges. Students will also explore the importance of testing, one of the key steps in the engineering design process. To introduce the activity, tell students that bridges and other structure are made up of a lot of shapes they’re familiar with. Show them a few different images of bridges and ask them to point out the shapes they recognize—can they spot triangles, arches, squares, and rectangles? Students will begin the activity by testing three common shapes—a square, a triangle, and an arch—to determine for themselves which is the strongest. (Most will judge the triangle as strongest, though some may choose the arch, which is also strong. It will quickly become apparent to them that the square is weakest.) Then they’ll put their knowledge to the test by building a bridge out of one of the shapes. To pass inspection, the completed bridge must be strong enough to support at least one small toy.

### Materials & Directions

For a group of 10 students:

- images of a variety of bridges, from books (e.g., Bridges Are To Cross, by Philemon Sturges) or online (ASCEville and Building Big)
- large package of index cards (500 cards)
- tape (roll for each pair)
- small 2- or 3- inch toys or objects (2 or 3 per pair)
- 1 ruler (to measure length of bridge)

1. Have students work in pairs and emphasize the importance of teamwork—it’s a great way to generate ideas and come up with effective building techniques.

2. Explain the goal of the activity: Can you build a bridge out of index cards and tape, using just one shape? Will your bridge be strong enough to support the weight of several small toys?

3. Ask students to tape together one square, one arch, and one triangle out of index cards. Show them the illustration above or else assemble a set of shapes yourself to serve as a model.

4. Have students test each shape for strength and stability, by pushing down on them and rocking them side-to-side.

5. Ask them to choose one shape to build their bridge with. Explain that because the material they are using is weak (thin index cards), they’ll have to rely on the shape to help provide strength.

6. Have students design and build their bridges, following these rules:

- Use only one shape to build with.

- The bridge must be at least 12 inches long.

- You can add a flat roadway on top of the bridge, made from index cards, if you want.

- You can tape shapes together.

- You cannot tape the bridge to the surface you're working on.

- You cannot lay a shape on its side.

7. When they’re finished building, have students test their designs by adding a small toy to the top of the bridge. Can the bridge support it? Can it support even more toys? If not, ask them to redesign their bridge—or to start over using a different shape. Finally, ask the group as a whole to rank the three shapes from strongest to weakest.

### National Science Education Standards, Grades K-4

**A: Science as Inquiry:** Abilities necessary to do scientific inquiry

**B: Physical Science:** Properties of objects and materials

**E: Science and Technology:** Abilities of technological design; understanding about science and technology

**G. History and Nature of Science:** Science as a human endeavor

## Truss Me! (Grade Level 5-6)

Time: 45 minutes

The purpose of this activity is to explore how engineers use trusses to strengthen bridges. Begin the activity by showing students images of different truss bridges, and explain how they work: A truss, in many cases, is made of a series of straight steel bars that form triangles or other stable, rigid shapes. The trusses create a strong framework that distributes the weight of the bridge and its load from single point over a wider area. Trusses can transform a simple beam bridge (a beam with two supports) into a much stronger and stable bridge. Have students point out the triangles in the photographs you’ve shown them and emphasize that there are many variations and varieties of truss bridges—this style of bridge offers engineers great opportunities to express their creativity while building a strong and sturdy bridge.

Weight pushes straight down on a beam bridge, causing it to bend. A truss bridge is stronger than a beam bridge because the trusses create a strong framework that distributes the weight from single point over a wider area. Trusses can be used above or below the deck and come in a variety of geometric patterns.

### Materials & Directions

For a group of 10 students:

- images of different styles of truss bridges, from books (e.g., Bridges That Changed the World by Bernhard Graf; The World’s Most Amazing Bridges by Michael Hurley) or the Internet (A Gallery of Truss Bridges or Types of Truss Bridges)
- 3 packages of plastic drinking straws per bridge (not the bendable kind)
- 5 rolls of tape
- 10 scissors
- 5 rulers
- stacks of books (4-8 books per pair)
- paper or plastic cups (1 package)
- 100+ pennies (5 sets—one per pair)

1. Have kids work in pairs, emphasizing the benefits of teamwork.

2. Explain the goal of the activity: Can you build a foot-long truss bridge with just 20 straws? Will your bridge be sturdy enough to support the weight of at least 100 pennies?

3. Students begin by creating two small piles of books 12 inches apart, measuring with the ruler. Their bridge will span these two piles.

4. Pass out scissors, tape, and 20 straws to each pair of students. Have kids design and build their bridges, following these rules:

- Only 20 straws can be used.

- Straws can be cut or bent.

- Books must be 12 inches apart.

- The bridge cannot touch anything except the books it rests on.

- The bridge cannot be taped to the books.

5. When the bridges are completed, have students test their strength. They’ll place a cup on the bridge, and fill it with pennies, one by one. Can the bridge support 100 pennies? If not, have them redesign their bridge. Can it support even more pennies?

### National Science Education Standards, Grades 5-8

**A: Science as Inquiry:** Abilities necessary to do scientific inquiry

**B: Physical Science:** Properties of objects and materials; motions and forces

**E: Science and Technology:** Abilities of technological design; Understandings about science and technology

**G: History and Nature of Science:** Science as a human endeavor

## Tension and Suspense! (Grade Level 7-8)

Time: 45 minutes

The purpose of this activity is to introduce students to suspension bridges and how they function. Students will then build their own, discovering first-hand how suspension bridges distribute weight. Begin by showing students images of suspension bridges, which are among the strongest and longest of bridges. Identify their different parts and explain how they work: The deck (or road) is suspended from vertical hangers that are attached to two massive steel cables. These cables are draped over two towers and secured into solid concrete blocks, called anchorages, on both ends of the bridge. When weight (like cars) push down on the road, the cables and hangers holding it up transfer the weight to the towers, which support most of the bridge’s weight.

### Materials & Directions

For a group of 10 students:

- images of suspension bridges, from books (e.g., Bridges That Changed the World by Bernhard Graf; The World’s Most Amazing Bridges by Michael Hurley) or the Internet (search for “famous suspension bridges” on Google images)
- 20 chairs with backs (2 per bridge)
- 5 sets of corrugated cardboard, each about 3 ft. long (may need to tape 2 or 3 separate sheets together)
- 10 rolls of duct tape
- 2 rolls of string (to share among the group)
- 5 hole punchers
- 10 scissors
- 1 yard or meter stick
- 10 sets of paper and pencil
- 40 or 50 books, which will be used as weights

1. Have students work in pairs. Encourage them to rely on the power of teamwork to come up with ideas and solutions.

2. Begin by giving students a demonstration of how a beam bridge supports weight. Suspend a 3-foot-long piece of cardboard between two chairs, allowing about 3 inches of each end to rest on the chair seats. Explain that this is a beam bridge, the simplest of all bridges: a horizontal beam supported by two piers at the ends. Tell students you’re going to test how much weight this bridge can hold. Put one book on it, and ask them what’s supporting the weight of the book (the piers and the beam). How many books do they think it can hold? Have a volunteer add books one-by-one until it collapses.

3. Tell kids that their goal is to design and build a suspension bridge that’s much stronger than the simple beam bridge. Ask kids how they will know if their bridge is stronger than the beam bridge (it will support more books).

4. Pass out the the materials. Have students use paper and pencil to sketch out their designs. Mention that suspension bridges are among the world’s most beautiful and admired bridges—students’ bridges should not just function well but should showcase their creativity!

Then share the building rules:

- Each bridge must have a deck, towers, cables, hangers, and anchors.

- Only 3 inches of the deck can rest on the seat of each chair.

- Don’t tape the deck to the chairs.

- Don’t tape the cables to the towers (tops of chairs).

- You can tie the cables to the chair legs, which serve as the anchors.

5. Have students build their bridges. The first stages of construction might look like this:

6. Encourage them to test their bridges as they build. They can try putting one book on the deck. Is the bridge sturdy and strong? Are the cables and hangers helping to support the weight? If not, ask them to redesign.

7. When students finish, have them pile books on the deck, one at a time. How many books can the bridge hold? Is it stronger than the beam bridge? Why? (By supporting the deck of a typical beam bridge with a system of cables and transferring the deck's weight to sturdy towers at either end, a beam bridge becomes a much stronger suspension bridge.) Tug on the cables—what’s supporting the weight of the bridge? What would happen if the anchors gave out?

### National Science Education Standards, Grades 5-8

**A: Science as Inquiry:** Abilities necessary to do scientific inquiry

**B: Physical Science:** Properties of objects and materials; motions and forces

**E: Science and Technology:** Abilities of technological design; understandings about science and technology

**G: History and Nature of Science:** Science as a human endeavor