Why Buildings Sway: The Science of Resonance

Tall buildings are designed to be slightly flexible because rigid structures are more likely to crack under stress. However, if a wind gust or earthquake matches the building's natural frequency, it can start to sway dangerously—a phenomenon called resonance. To prevent this, engineers install tuned mass dampers. This is a massive weight, sometimes hundreds of tons, suspended near the top of the building. When the building sways, the mass moves in the opposite direction, canceling out the building's motion.