November 7, 1940 · Tacoma Narrows, Washington

Why Bridges Collapse

⚠ RESONANCE REACHED — STRUCTURAL FAILURE IMMINENT
Bridge Status
Stable
Amplitude / Structural Limit
Wind Frequency
0.5 Hz
Natural Frequency
0.2 Hz
Max Deflection
0.0 m
Resonance Ratio
2.50
Collapse Risk
Low
0.5 Hz
Medium
Low (1940s)

Adjust the wind frequency toward the bridge's natural frequency (0.2 Hz). Watch what happens as they match — this is resonance. Every structure has a natural frequency. When external forces match it, energy accumulates. The Tacoma Narrows Bridge collapsed in just 4 hours of wind.