Why Suspension Bridges Must Move — And When It Turns Dangerous

Why does a suspension bridge move under traffic—and when can that movement become dangerous? Explore how suspension bridges carry enormous loads through their decks, towers and cables, why expansion joints leave room for temperature changes, and how wind can turn controlled movement into destructive twisting. The 1940 Tacoma Narrows Bridge collapse reveals the stakes. Discover how aerodynamic forces and torsional flutter helped bring down “Galloping Gertie,” and why bridge engineering depends on understanding motion as well as strength.