Suspension bridges support their deck via vertical hangers hung from main cables that drape between towers in a catenary-like curve, transferring load into tension carried all the way down to massive anchorages. Because the deck is a long, flexible ribbon suspended in air, wind and traffic loading make it oscillate both vertically and laterally, and engineers must ensure this natural sway stays well clear of resonance. The most infamous case, the Tacoma Narrows Bridge, twisted itself apart in 1940 under sustained ~64 km/h wind due to aeroelastic flutter, reshaping how bridges are designed ever since. Modern long-span bridges use aerodynamic deck profiles and tuned mass dampers to keep sway controlled and comfortable for traffic.

• Main cables follow a parabolic/catenary curve carrying deck load through vertical hangers
• Golden Gate Bridge's 1280 m main span can move several meters laterally in storms
• Tacoma Narrows Bridge collapsed in 1940 from flutter at roughly 64 km/h wind speed
• Long-span bridge natural sway frequency is typically about 0.1–0.3 Hz
• Design wind speeds for major suspension bridges often exceed 200 km/h
• Tuned mass dampers add counter-oscillating weight to suppress resonant sway
• Deck segments are usually aerodynamically shaped box girders to resist flutter