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## Bridges by Discovery Education

### Course, Subject

Technology, Math, Science & Technology

### Grade Levels

Intermediate, 6th Grade, 7th Grade, 8th Grade

### Objectives

Students will understand the following:

1. Bridges are categorized into three primary types: suspension, beam, and arch.
2. Each is designed and built according to certain principles of engineering.

### Materials

Students will need research materials on bridge engineering, including a computer with Internet access. Each group will need the following materials:

• Twenty drinking straws
• One meter of masking tape
• Two stacks of books or blocks of wood
• Meterstick
• Jar of pennies

### Procedure

1. Divide your students into groups, provide each group with the necessary materials, and challenge each group to build a bridge that will span 25 centimeters.
2. Set the following rules:

For the two ends of the span, students will use two stacks of books or wood blocks placed 25 centimeters apart.
The only materials students may use for the bridge itself are 20 drinking straws and 1 meter of masking tape.
The straws may be shortened, bent, or cut.
No part of the bridge may touch anything between the two ends of the span.

3. Allow each group one class period to research bridge engineering. They should find out the basic principles of the three main kinds of bridges: suspension, beam, and arch.
4. Allow each group another class period to brainstorm ideas, make sketches, and choose a final design for their bridges.
5. Students will use a third class period to build their bridges with the materials provided.
6. After all bridges have been completed, have students test their bridges by seeing how many pennies they will hold. Students may modify their bridges, at this point, and then see if they will hold more pennies.
7. Have groups present their bridges and testing results to the class. Ask students to speculate about why some bridges were more or less successful than others. What factors went into the strength or weakness of each bridge? What flaws were inherent in the building materials? How were those flaws overcome?
8. Students who enjoyed this activity can try a more challenging level by increasing the span to more than 25 centimeters.

### Adaptations

Rather than requiring students to do their own research on bridge engineering, provide students with a few basic plans to choose from in constructing their bridges.

### Discussion Questions

1. Suppose all the bridges in a large city (New York City, for example) were closed. What effect would that have on that city? What are some specific ways that people would adapt to not using bridges?
2. Discuss how each of the three basic types of bridges—suspension, beam, and arch—transfers loads from the bridge to the ground. Describe where tension and compression occur on each type of bridge.
3. Many bridges are icons for their city or region. Why do you think people associate certain bridges with certain cities, while other bridges seem unremarkable?
4. Compare and contrast a beam bridge and an arch bridge. List at least three ways they are similar and three ways they are different.
5. The U.S. government requires states to inspect and rate all bridges at least once every two years. Describe ways that technology can be used to make monitoring and inspection of bridges more efficient and effective.
6. The earthquake in October 1989 in the San Francisco Bay area caused great structural damage to many of the bridges in the area. What features would you design as part of a bridge to make it better able to withstand an earthquake? Explain your ideas.

### Evaluation

You can evaluate groups on their projects using the following three-point rubric:

• Three points: worked cooperatively; carefully prepared plans and sketches; thoroughly researched principles of bridge engineering and applied principles learned
• Two points: worked cooperatively; prepared plans and/or sketches; researched and applied some principles of bridge engineering
• One point: had difficulties working cooperatively; failed to prepare plans or sketches; research insufficient; only a few principles of bridge engineering applied

### Extensions

Celebrity Bridges
Many bridges are icons for the cities or regions in which they are located. Almost everyone associates the Golden Gate Bridge, for instance, with San Francisco, or the Brooklyn Bridge with New York City. Have your students prepare posters or multimedia presentations on famous bridges from around the country and world. Students should include in their presentations descriptions of the designs and features of the bridges, including pictures or diagrams and brief descriptions of the areas in which the bridges are located. They should also include brief histories of how and why the bridges were built and the current uses and states of the bridges, including any repair plans. You might also ask them to include any famous cultural references to bridges, like quotes from poems or songs ("London Bridge is falling down," for example). An excellent starting point for finding information is Netscape's Bridge Search.

Constructing with Bridges in Mind
Some engineering principles used in bridge building are also used in the design and construction of other structures. Ask your students to research the three primary types of bridges and investigate how these engineering principles are used in the design and construction of other structures. Then have them build models of structures, incorporating one or more of these engineering principles in their designs. In addition to building models, students should write explanations of the engineering principles they discovered and the ways in which they incorporated those principles into their projects. When their models and explanations are complete, have the students present their work to the class.

### Suggested Readings

Engineers of Dreams: Great Bridge Builders and the Spanning of America
Henry Petroski. Knopf, 1996.
This book contains captivating stories about the men who designed and built the bridges that span America. See how the personalities of these engineers have played as much of a role as their technical know-how in getting bridges built. The book discusses well-known American bridges and includes a photograph and technical drawings of each one.

Bridges: A History of the World's Most Famous and Important Spans
Judith Dupre. Black Dog & Leventhal Publishers, 1997.
This magnificent, one-of-a-kind book about bridges bears witness to the creativity and intelligence of engineers. You'll find photographs and location maps for each bridge featured.

### Resource

Access this resource at:

Bridges

### Content Provider

Discovery Education

Discovery Education offers a breadth and depth of digital media content that is immersive, engaging and brings the world into the classroom to give every student a chance to experience fascinating people, places, and events. All content is aligned to state standards, can be aligned to custom curriculum, and supports classroom instruction regardless of the technology platform.

Whether looking for a digital media library service, an implementation to help you transition your classroom to a 21st century environment or to move completely to replace textbooks with digital resources, Discovery Education offers a continuum of solutions to meet your district's specific needs. In addition, we offer real-time assessment services and a variety of professional development to ensure effective implementation in the classroom. You know your needs. We know our services. Together we can create an effective solution.

And, add the vast number of additional classroom instruction opportunities available such as virtual experiences, compelling Discovery talent, free lesson plans and materials, and a variety of contests and challenges and with Discovery Education teachers are truly able to give students opportunities to soar beyond the traditional textbook for endless possibilities.

Credit: Don DeMember, science resource teacher, Kingsview Middle School, Germantown, Maryland.

### Vocabulary

composite
Definition: Made up of distinct parts.
Context: Chemists and engineers are creating strong yet lightweight composite materials that are now being used in everything from tennis rackets to airplanes.

resonance
Definition: A vibration of large amplitude in a mechanical or electrical system caused by a relatively small periodic stimulus of the same or nearly the same period as the natural vibration period of the system.
Context: The magnified sways and twisting of the Tacoma Narrows Bridge were caused by the resonance of 40-mile-per-hour winds and the natural oscillations of the bridge.

stay
Definition: A large, strong rope usually of wire used to support a mast.
Context: One of the diagonal steel stays that supported the bridge broke, but the structure remained standing.

tension
Definition: Either of two balancing forces causing or tending to cause extension.
Context: The heavy weight of concrete and steel causes a great deal of tension on the cables that support a bridge.

viaduct
Definition: A long elevated roadway usually consisting of a series of short spans supported on arches, piers, or columns.
Context: In Europe, there are still viaducts over deep valleys that were built by the Roman Empire.

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