Lesson 4: The Breaking Point: Calculating Structural Efficiency

1. Where did the bridge fail, and was it a material failure or a design failure?

2. How does our efficiency ratio compare to our classmates?

Efficiency Ratio: The ratio of the load supported to the mass of the bridge.

Structural Failure: The point at which a member or joint can no longer support its load.

Buckling: When a member bends and fails under compression.

ENG.02.10: Evaluate the design solution.

ENG.05.02: Analyze the effects of loads on structures.

The "Big Event." Bridges are weighed, then placed on a testing rig. Sand or weights are added until the bridge snaps. Students must record the "failure point" on video to analyze later.

Purpose: To use failure as a data-gathering tool for future engineering improvements.

DOK Level: Level 4 (Extended Thinking).

Allow students to submit a video "vlog" reflection instead of a written report to explain their failure analysis.

Students must calculate their efficiency using preferred formulas

(ex: Efficiency = \frac{Load\ Supported\ (g)}{Mass\ of\ Bridge\ (g)}

Materials / Resources: Testing rig (bucket, sand/weights), slow-motion cameras (smartphones), digital scales.