How Are Bridges Built Over Water?

There are a number of construction methods used when building bridges but, in general, the central road or path is lowered into place using cranes or rolled across the expanse using cantilevers after the supporting structures have been placed. Techniques often vary based on the size of the crossing, the amount of anticipated traffic and use and types of materials being used.

The Golden Gate Bridge in San Francisco is arguably one of the most iconic bridges in the world, and uses the suspension method to handle and distribute loads. This is achieved through the two large towers at either end of the bridge, and the vast amount of tensile cables. Construction of the bridge began with erecting the two towers at either end of the river, along with the main supporting cables at the highest points. Due to the high winds in the area, a suspension bridge is the ideal solution, as it offers minimal wind resistance and can bend with forces much easier than some other techniques.

Other bridge building techniques range from the essentially basic beam bridge, which is supported by substructural elements at each side of the crossing, to more complex feats of engineering, such as double decked or three-way bridges.