Bridge Engineers
GRADES 6-8

Bridge Engineers

Driving Question:

How can engineers design a bridge that is both strong and efficient?

Activity Overview:

Bridge Engineers, the city needs a crossing! Students investigate how engineers design bridges for different purposes, explore how shapes affect strength, and discover why testing models matters before full-scale construction. Armed with a Bridge Design Brief, students plan and build a cardboard bridge using the ChompSaw, then load it with paperback books to test how much weight it can hold. After analyzing their results, they redesign one part of their bridge and retest to see if their improvements hold up.

Vocabulary
Exit Ticket

Learning Objectives

  • Explain why engineers design bridges in different ways.
  • Investigate how shapes affect a bridge's strength.
  • Design and build a bridge that meets specific criteria and constraints.

Slide Deck

Get the Slides

Full Materials List

Lesson Plan

Lesson Slides

Vocabulary Slides for frontloading

Design Worksheet

1 per student

Testing Log

1 per student

Exit Ticket

1 per student

Chompsaw(s)

1 per 5 students

Cardboard

1 12"x18" sheet per group

Tape

3 feet per group

Ruler

1 per group

Paperback books

Several per group

Two equal height supports (boxes, stacks of books, etc)

1 per testing station

Preview/Background Knowledge

  • Students should have a basic understanding that structures are designed to support weight and withstand forces
  • Students should be able to identify basic 2D and 3D shapes and have some understanding of how shape affects stability
  • Students should be familiar with the concept of variables and understand that changing one thing at a time helps isolate what works
  • Students should have an introductory understanding of the engineering design process: define a problem, plan a solution, build, test, and improve
Prep Instructions

Time Required for Prep: 15–20 minutes

1. Prepare the Testing Stations

  • Create one or more bridge testing stations depending on material and space constraints.
  • For each station:
    • Position two sturdy supports 14 inches (36 cm) apart.
    • Test the setup to ensure it remains stable during testing.
    • Gather identical paperback books for consistent results, or reuse the same set of books for each group.

2. Prepare Student Groups

  • Decide how many students will work together.
  • Small groups encourage collaboration while allowing every student to participate in planning, building, testing, and redesigning.

    • 3. Print Student Materials

    • Print the following materials before class:
      • Bridge Design Plan (1 per team)
      • Engineering Test and Redesign Log (1 per student)
      • Exit Ticket / Assessment (1 per student)

    4. Gather Building Materials

    • For each team, prepare:
      • One 12" x 18" sheet of corrugated cardboard
      • Approximately 3 feet of masking tape
      • ChompSaws (can be shared between groups as needed)
      • Pencil
      • Ruler

    5. Check Technology

    • Before class:
      • Open the slide deck and test all animations.
      • Confirm that any videos or interactive elements play correctly.
      • Test the document camera (if using one) for bridge demonstrations.
      • Make sure presentation materials are ready before students begin.

    6. Review Lesson Timing

    • The building, testing, redesign, and retesting portions require approximately 60 minutes.
    • If your schedule is limited:
      • Complete the Explore and Plan sections during one class period.
      • Finish the Build, Test, Improve and Retest, and Assessment sections during a second class period.
      • This allows students enough time to thoughtfully redesign their bridge using evidence from their first test, reinforcing the engineering design process.
    Extensions

    Ancient Rome Needs Your Help

    • The Roman Empire is expanding and needs a bridge for soldiers, merchants, and travelers to cross a river.
      • Students must:
        • redesign their bridge using principles of Roman engineering
        • explain which bridge type the Romans would most likely choose and why
      • Discussion Questions
        • How would the Romans make their bridge strong?
        • Which bridge type would they most likely choose?
        • Why did Romans favor arch bridges?

    Bridge Budget Challenge

    • The project is over budget — students must remove 25 percent of their cardboard while keeping their bridge as strong as possible.
      • Students must:
        • identify which parts of their bridge can be reduced without sacrificing strength
        • retest their bridge after removing material and record the results
      • Guiding Question
        • How can engineers reduce costs without sacrificing safety?

    Disaster-Proof Bridge

    • The city announces the bridge must now survive a natural disaster.
      • Choose one condition:
        • Earthquake
        • Strong winds
        • Flooding
      • Students must:
        • redesign their bridge to better withstand their chosen condition
        • explain what changes they made and why those changes help

    New Client, New Bridge

    • Students choose a new client and redesign their bridge for a different purpose.
      • Client Options
        • Pedestrian bridge or bike path
        • Highway
        • Train bridge
      • Discussion Questions
        • How would the load change for your new client?
        • Would your bridge need to look different?

    Famous Bridge Inspiration

    • Students research a famous bridge and connect what they learn to their own design.
      • Example Bridges
        • Golden Gate Bridge
        • Sydney Harbour Bridge
        • Brooklyn Bridge
        • Millau Viaduct
      • Students must answer:
        • Why was this bridge built?
        • What type of bridge is it?
        • What engineering ideas from this bridge could improve your own design?