Carnegie Mellon University

Lesson title:  2D to 3D Truss Bridge Building

 Middle School: Bridge Building Constraints

[Note: A pdf version of this page is available; see navigation box on the right.]

Truss Bridges

Figure 1: From page 64 of Noyce, Pendred E, Engineering Bridges Connecting the World, Boston: Tumblehome, Inc., 2019


  1. Must be freestanding
  2. Bridge must not weigh more than __________*
  3. Bridge must have a road that spans 8 inches long, 3 inches wide, and has guardrails on both sides of the bridge
  4. May only use the provided resources
  5. Budget must not exceed $5000
  6. Must be able to support the weight of one or more of the following for 10 seconds without buckling
    1. Toy car (hot wheels)
    2. Four block erasers

*Must be as close to the chosen patented design as possible*

Budget Sheet:

Materials Fees

  • Construction Paper: $10.25 per sheet  
  • Scissors: $15 per scissors
  • Tape: $5 per 2 meters
  • Ruler: $10

 Construction Fees

  • Labor Cost: $45 per person in group + $6.57 per minute worked

 Disposal Fee:

  • Construction Paper: $5.27 per sheet returned
  • Construction Paper: $2.50 per sheet portion of sheet returned practices fee
  • Tape: $25 per roll returned


Activity Debrief:

Allow time for the students to discuss the activity and complete the reflection page.