A suspension bridge without open trusses, this bridge twisted in the breeze. One day, the bridge twisted so violently in the wind that its center span collapsed. Since then, engineers test bridge models in wind tunnels prior to construction and build their decks more stiffly. When determining what type of bridge to build, engineers evaluate terrain and length of span. In addition, bridges change as our needs and resources change.
Engineers constantly look for ways to improve bridge designs and materials.
During the recent earthquakes in California, for example, engineers analyzed highway overpasses to find ways to make them stronger. Force per unit area. The encyclopedia of how it's built. Four Winds Press. The story of America's bridges.