An earthquake-proof tower challenge lets students test how engineering choices affect a structure during shaking. The goal is to build a lightweight model tower from materials such as spaghetti and marshmallows or straws and tape, then see if it can survive 30 seconds on a shake-table. This project matters because real buildings must handle forces from earthquakes without collapsing.
It connects physics, design, teamwork, and careful measurement in one hands-on investigation.
During shaking, the base of the tower moves back and forth while the upper parts tend to keep moving due to inertia. This creates sideways forces that can bend joints, twist frames, and make tall structures sway. Cross-bracing, a wider base, and stronger connections can help spread forces through triangles instead of weak squares.
By changing one variable at a time, students can compare designs fairly and use evidence to improve the next version.
Key Facts
- Earthquake survival time can be measured as maximum time before collapse, up to a 30 s target.
- Inertia makes the top of a tower resist sudden motion when the shake-table moves the base.
- A wider base usually lowers the chance of tipping by increasing the support area.
- Triangles are stiffer than squares because their side lengths lock the shape in place.
- Average survival time = total survival time for all trials / number of trials.
- Design efficiency can be compared using efficiency = survival time / tower mass.
Vocabulary
- Shake-table
- A shake-table is a platform that moves back and forth to simulate earthquake motion for testing models.
- Cross-bracing
- Cross-bracing is a pattern of diagonal supports that helps a frame resist bending and sideways motion.
- Inertia
- Inertia is the tendency of an object to resist changes in its motion.
- Center of mass
- The center of mass is the average location of an object's mass, where it balances as if all its mass were concentrated there.
- Variable
- A variable is a factor in an experiment that can be changed, measured, or kept the same.
Common Mistakes to Avoid
- Changing height, base width, and bracing all at once makes the test unfair because you cannot tell which change caused the result.
- Building only square frames is weak because squares can deform into leaning parallelograms during shaking.
- Making the tower very tall without widening or strengthening the base increases tipping because the center of mass is higher.
- Ignoring joint strength gives misleading results because many model towers fail at the tape, marshmallow, or connection points before the beams break.
Practice Questions
- 1 A tower survives shake-table trials of 18 s, 24 s, and 30 s. What is its average survival time?
- 2 Design A has a base width of 12 cm and a height of 48 cm. Design B has a base width of 16 cm and the same height. What are the height-to-base ratios for both designs, and which is likely more stable?
- 3 Explain why a cross-braced frame usually stays stiffer than a square frame during side-to-side shaking.