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Day the Earth Shook, The

Classroom Activity

Objective
To explore structural engineering through three design challenges.

• copy of "Shake, Rattle, and Roll" student handout (PDF or HTML)
• 10 index cards
• 1 sheet of graph paper
• 2 sheets of lined notebook paper
• 10 drinking straws
• 16 paper clips
• 1 metric ruler
• 1 tape measure
• 1 pencil
• 1 colored pencil
• marbles to fill shoebox top
• masking or transparent tape

1. This program presents information about some architectural features that work and those that don't during an earthquake. To give the students some hands-on experience in structural design, conduct this activity.

2. Set up the three challenges around the room with the materials and the "Shake, Rattle, and Roll" student handout (which should remain with each specific structure challenge).

3. Divide the class into three teams and assign each team to one of the structure challenges. Each team will build and test its structure and record its results.

4. When the teams are done, have them rotate so that each team is working on a new structure challenge, using the information gained from the team that already worked on that challenge. Have teams again record their data and analysis. Continue rotating until all teams have built and tested three different structures. Once this is done, bring the class back together and discuss the results. You may want to have one student record all the results on the chalkboard. Which features, if any, helped resist which challenges? Which features helped resist all challenges?

Challenge #1 High Impact: A relatively short, wide building will be more stable than a tall, narrow building. Another design feature that will help the building's stability is to concentrate most of its mass near the bottom, since a top-heavy building will tend to be unstable. Since many of the buildings in earthquake-prone cities are skyscrapers, most of them are narrower at the top than the bottom. An extreme example of this is the pyramid-shaped Transamerica building in San Francisco, California.

Challenge #2 Hillside Home: The building will be most stable if it is given a wide foundation, such as a fan of paper to skirt its bottom to provide more surface area against the side of the hill. Another strategy would be to brace the building by attaching straws to the downhill wall that angle down to the hillside surface. Again, as with the High Impact challenge, a relatively wide building will be more stable than a relatively tall, narrow building.

Challenge #3 Rolling Along: This building will be stabilized by focusing most of its mass near the bottom. A pyramid shape would be a very clever idea, and is unlikely to tip over even when it is being shaken quite rapidly. In some communities where the ground beneath buildings is quite soft, such as the Marina district of San Francisco, California, which was badly damaged in 1989, the buildings were literally shaken apart because the soft ground magnified the intensity of the earthquake. Explain that some new buildings have actually been constructed on rubber mountings that absorb the shock waves.