Engineering
Designing a Truss Bridge for Wind and Seismic Loads
Quick fact
During the 1940 Tacoma Narrows Bridge collapse, the bridge's torsional vibrations were so violent that they tore the deck apart—even though the bridge was a suspension bridge, the same resonant behavior threatens truss bridges. Modern truss bridges are designed to avoid any natural frequency that matches likely wind or earthquake frequencies, and they use special bracing to prevent aeroelastic flutter.
Why this is interesting
A truss bridge might look like a web of simple triangles, yet when the wind blows or the ground shakes, those triangles can start vibrating like a guitar string—and that vibration, not the static load, can bring the bridge down. How do engineers keep a lattice of steel from dancing itself to failure?