Wobbly Bridges

When resonance goes wrong

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Rhythmic forcing near a structure’s natural frequency can cause dangerous oscillations.
• The Millennium Bridge wobbled because walkers synchronised with its sway.
• Tacoma Narrows failed through aeroelastic flutter, a self-excited instability.

Steps

1. The Millennium Bridge
2. Tacoma Narrows
3. A sideways rhythm
4. Break step!
5. Footsteps and sway
6. Engineering it out