Fort Point Arch

At the south San Francisco end of the suspension bridge, a large steel arch carries the roadway deck over Fort Point, the brick fort below. Fort Point was completed in 1861, long before the Golden Gate Bridge was constructed in the 1930s, and chief engineer Joseph Strauss preserved the historic fort by spanning over it with an arch bridge. An arch experiences compression, or pushing forces, while a suspension bridge is its structural opposite: its curving cables are in tension, experiencing pulling forces. The upside-down picture of those cable curves looks like an arch, and the compression forces in the arch are the opposite of the tension forces in the suspension bridge cables. Those cables pull on anchorages at the two ends of the bridge, and the anchorages embedded in the earth must supply outward reaction forces to withstand the inward pull created by the cable tension. The steel arch spans 318 ft over historic Fort Point.

San Francisco, California · United States