Embedded Files
by Maureen Williams 5/31/2015
Keywords
construction technique earthquake Earth process shake structure wave
Summary
Students learn how engineers construct buildings to withstand damage from earthquakes by building their own structures with toothpicks and marshmallows. Students test how earthquake-proof their buildings are by testing them on an earthquake simulated in a pan of Jell-O®.
Engineering Connection
Because earthquakes can cause walls to crack, foundations to move and even entire buildings to crumple, engineers incorporate into their structural designs techniques that withstand damage from earthquake forces, for example, cross bracing, large bases and tapered geometry. Earthquake-proof buildings are intended to bend and sway with the motion of earthquakes, or are isolated from the movement by sliders. Engineers come up with an idea, test it, and then re-engineer the structure based on its performance.
Learning Objectives
After this activity, students should be able to:
Identify some of the factors that make buildings earthquake-proof, including cross bracing, large "footprints," and tapered geometry.
Model an earthquake-proof structure using simple materials.
Compare a model structure with what it represents.
Understand why engineers need to learn about earthquakes.
Materials List
Each student needs:
30 toothpicks
30 miniature marshmallows
Journal
For the entire class to share:
one 8½-inch square disposable baking dishes, or one 8½ x 11-inch disposable roasting or baking pan
8 boxes Jell-O® (plus a stove, water and pan to make the Jell-O® in advance)
Introduction/Motivation
Earthquakes can cause much loss of life and millions of dollars worth of damage to cities. Surface waves and body waves from earthquakes can cause walls to crack, foundations to move and even entire buildings to crumble. Engineers continually strive to make buildings stronger to resist the forces of earthquakes.
Engineers face the challenge of designing more robust buildings to withstand earthquakes. Earthquake-proof buildings are intended to bend and sway with the motion of earthquakes, instead of cracking and breaking under the pressure. Have you ever looked at a really tall building, such as a skyscraper? What does it look like? Does it appear fragile and unstable? It might, but it is most probably quite sturdy and can withstand wind, rain and other natural elements and phenomena. Earthquake-proof buildings typically have cross bracing that forms triangles in its design geometry (like a bridge). Such buildings also typically have a large "footprint," or base, and a tapered shape, decreasing in size as the building gets taller (or simply, smaller at the top). Short buildings are more earthquake proof than tall ones. Why do you think that is? Have you ever climbed up a tree or been on top of a playground jungle gym in the wind? Do you sway more when you are up high than when on the ground? All buildings shake at the same frequency as the shaking of the Earth, but the movement is magnified as the building gets taller. Sometimes, as can be the case during earthquakes, buildings sway too much, crack and crumble and fall.
Procedure
Before the Activity
Prepare the Jell-O® the night before the activity so that it is fully set when students begin the activity. Pour the Jell-O® into eight 8½-inch square pans to be shared by four students, or in one large pan for the entire class to share.
Make one marshmallow-toothpick structure as a display example for students.
With the Students
Hand out student journals. Have students fill in the top left section of the journal with vocabulary terms. Direct students to record their activity observations as they work.
Tell students that today they are acting as if they are engineers. They will make models of buildings and conduct an experiment to test how well their structures stand up under the stress of an earthquake. Explain to them that this is similar to what some civil engineers do as their jobs.
Show students the display model of a structure.
Illustrate how to make cubes and triangles using toothpicks and marshmallows. Show students how to break a toothpick approximately in half. Explain that cubes and triangles are like building blocks that may be stacked to make towers. The towers can have small or large "footprints" (or bases).
Distribute 30 toothpicks and 30 marshmallows to each student. Explain that the Earth has limited resources, so therefore engineers also have limited resources when building structures.
For this engineering challenge, students are limited to using only the materials they have been given to make structures. They may make large or small cubes or triangles by using full-size or broken toothpicks. They may use cross bracing to reinforce their structures. (Note: For higher grade levels, give students more rules for their buildings. You can use one or more of the following rules or create your own: buildings must be at least two toothpick levels high, buildings must contain at least one triangle, buildings must contain at least one square, or buildings must contain one triangle and square.)
Place the structures on the pans of Jell-O®.
If aluminum pans are used, tap the pans on the bottom to simulate compression or primary waves. If glass baking dishes are used, shake them back and forth in a shearing motion to simulate S or secondary waves.
After students have tested their structures, have them redesign and rebuild them and finally test them again. What can they do to make it stronger? Did it topple? Should they make the base bigger? Make the structure taller or shorter? Let students design and rebuild as many times as the class period allows.
Have students draw and label the shapes in their designs (cube, triangle, etc).
Have students pretend that they are engineers who work for a civil engineering company. Instruct them to make a flyer to convince their company to let them design a better building or structure.
Safety Issues
Inform students that in a science lab or during science experiments, nothing should ever be put into their mouths. The marshmallows and Jell-O® are not for consumption. Instead, set some aside for a treat after the activity.
Troubleshooting Tips
The activity works best with fresh (soft) marshmallows. As the marshmallows sit out and dry out, they and the structures become stable and rigid.
Do not leave the Jell-O® uncovered too long, as it dries out and becomes less fluid, which affects the activity results.
Post-Activity Assessment
Journal: Have students fill in the final sections of the journal labeled, "What I've Learned," and "Questions I Have." Solicit questions from the students and let other students answer.
Re-Engineering: After students have tested their structures, they should redesign and rebuild them, then test again. What can they do to make it stronger? Did it topple? Should they make a bigger base? Make it taller or shorter? Let students design and rebuild as oftenas time allows.
Drawing the Geometry: Have students make drawings and label the shapes in their designs (cube, pyramid, triangle, etc.).
Make a Pitch! Have students pretend to be engineers and make flyers to convince a company to let them design a better building or structure.
News Broadcast:: Have student teams write news broadcasts about an earthquake that has hit their hometowns. Have the broadcast begin with something exciting to catch the listener's attention. Then tell the facts of the event. Have the teams share their news broadcasts with the class.
Activity Extensions
Have students examine the school for earthquake engineering. Does the school building encompass some of the principles of earthquake proofing?
Observe buildings in the community or nearby city. What do students observe about the structure of the buildings?
Obtain fault maps of the area by searching the Internet. Try searching under Federal Emergency Management Agency or National Earthquake Education Center. Is the area in a zone at risk for earthquakes? Does the local architecture plan for this?
References
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