Why do some buildings collapse in the same quake? Resonance explained | Curious Engineering #02

Instructor: Dr. Süleyman Burak ÇELİK

You don't need a huge force to bring down a building; you need the right frequency. In this episode we see what a structure's natural frequency depends on, how the phase lag between ground and building turns from 0° to 180°, and why at exact resonance the amplitude grows by 1/(2ζ) — 25 times at 2% damping. Then three buildings side by side in the same earthquake: only the one whose frequency matches comes down, as in Mexico City in 1985. Three defences: damping, seismic isolation, and tuned mass dampers like the 660-tonne sphere in Taipei 101. Along the way we correct a famous misconception: the Tacoma Narrows Bridge failed by aeroelastic flutter, not resonance.