Build the Bridge: Engineering a Model Span
The full design cycle, inspired by the Gordie Howe International Bridge's no-mid-channel-pier constraint.
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Standards
HS-ETS1-2 — Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems. | HS-ETS1-3 — Evaluate a solution based on prioritized criteria and trade-offs.
Why Does This Matter?
The Gordie Howe International Bridge connecting Detroit and Windsor had to span a wide, active shipping channel with no support piers allowed in the water — a real constraint that shaped its cable-stayed design. This lab gives your team the same core challenge: span a fixed gap with no mid-span support, using limited materials.
Objective
Design, build, and test a model bridge that spans a fixed gap and holds as much load as possible without touching the ground/table beneath it, then redesign based on your test results.
Materials
- 30 craft sticks or spaghetti strands per team
- 1 roll of tape and/or glue
- String (optional, for a cable-stayed design)
- 2 stacks of books or blocks (the "banks") set a fixed distance apart
- Small weights (washers, coins, or a cup and marbles) for load testing
- Ruler
Safety: Be careful with scissors and hot glue if used. Keep the load-testing area clear so weights don't fall on feet.
Procedure
- Define: As a team, list the criteria (what the bridge must do) and constraints (materials, gap distance, no mid-span support) for your design.
- Develop: Sketch at least two possible bridge designs (e.g. truss, arch, cable-stayed). Choose one to build, and explain why.
- Build your bridge to span the fixed gap between the two "banks," using only the allowed materials.
- Test your bridge by slowly adding load (washers, coins, or a weighted cup) at the center of the span until it fails. Record the maximum load held and where the failure occurred.
- Optimize: Based on where and how your bridge failed, redesign one part of it and re-test.
- Compare your final load-to-material-used ratio with another team's.
Data Table
| Trial | Design type | Materials used (count) | Max load held | Failure location/mode |
|---|---|---|---|---|
| 1 (initial design) | ||||
| 2 (redesign) |
Analysis Questions
- What criteria and constraints most shaped your design decisions?
- Where did your bridge fail first, and what does that tell you about how forces (tension vs. compression) moved through your structure?
- How is the "no mid-span support" constraint in this lab similar to the real constraint engineers faced building over the Detroit–Windsor shipping channel?
- If you had double the materials, would you build a stronger version of the same design, or switch to a different design entirely? Justify your answer.