An earthquake-proof building test is a hands-on way to see how engineers design structures that stay standing when the ground shakes. In this project, a pan of jello acts like a shake table because it wiggles and carries motion into small model buildings. Students can build three designs from marshmallows, toothpicks, and spaghetti, then compare how each one moves.
The goal is not to make a building that never moves, but to make one that bends, sways, or slides safely without collapsing.
The three designs can show important earthquake-engineering ideas: rigid frames, flexible frames, and base isolation. A rigid building may feel strong, but it can crack or tip if it cannot absorb motion. A flexible building can sway and spread forces through its shape, especially if it uses triangles or cross braces.
A base-isolated building has a special layer at the bottom that reduces how much shaking reaches the upper structure.
Key Facts
- Earthquake shaking moves the ground side to side, up and down, or in rolling waves.
- Force depends on mass and acceleration: F = ma.
- A lower center of mass usually makes a building harder to tip over.
- Triangles and cross braces help frames resist bending and twisting.
- Base isolation reduces shaking by letting the base move separately from the building above.
- A fair test changes only one design feature at a time while keeping materials, height, and shaking time the same.
Vocabulary
- Shake table
- A surface that moves back and forth to model how the ground shakes during an earthquake.
- Base isolation
- A design method that separates a building from strong ground motion using a movable or flexible base.
- Center of mass
- The point where an object's weight is balanced in all directions.
- Cross bracing
- Diagonal supports that make a frame stronger by forming triangles.
- Stability
- The ability of a structure to stay upright and keep its shape when forces act on it.
Common Mistakes to Avoid
- Making one building taller than the others, which makes the comparison unfair because taller models often tip more easily.
- Using different amounts of materials for each design, which changes mass and strength instead of only testing the design idea.
- Shaking the jello by hand differently each time, which is wrong because stronger or longer shaking can make one building seem worse by accident.
- Judging only whether the building falls down, which misses useful data such as sway distance, broken joints, leaning, and how quickly it recovers.
Practice Questions
- 1 A model building has a mass of 0.20 kg and the jello shake table gives it an acceleration of 3 m/s². What force acts on the model? Use F = ma.
- 2 Three buildings are tested for 10 seconds. Building A sways 6 cm, Building B sways 3 cm, and Building C sways 9 cm. Which building has the smallest sway, and how much less does it sway than Building C?
- 3 A rigid model, a flexible braced model, and a base-isolated model all stay standing, but the rigid model has two broken joints. Which design would you recommend improving for a real earthquake zone, and what evidence from the test supports your choice?