Resisting the Twisting

Since the modern suspension bridge was invented in the early 1800s, one of the biggest challenges engineers have faced has been preventing these flexible structures from moving too much in the wind. A storm on December 1, 1951, caused the Golden Gate Bridge to twist and vibrate enough to cause some minor damage, so it was retrofitted from 1953 to 1954. The retrofit added new bracing across the bottom, connecting the two steel trusses that support the roadway deck. This change increased the bridge's twisting, or torsional, stiffness. In a scale model of a 500-foot, 152-meter length of the bridge without the roadway on top, the original design used side trusses and top framing that formed an upside-down U-shape, while the retrofitted design added bottom bracing to create a closed cross section.

San Francisco, California · United States