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A bridge pier is a type of structure used to support a travel surface such as a road. The bridge itself connects two points, and it is supported by piers that extend to the ground below or into the water beneath the bridge. A bridge pier design is useful for certain applications because it can be an extremely strong structure, it can be built to be quite attractive, and it will not obstruct water flow or tides if the bridge spans water. Highway bridges may also use this design because roadways can easily be built beneath the bridges, since the supports do not take up as much space as other supporting designs.
The bridge pier itself can vary in size and shape. This part of the bridge is essentially a supporting pylon, and it can be shaped like a beam, or it may feature a more sweeping shape, like a V. Generally, modern piers are made from concrete, though some can be made of stone or even metal. A bridge pier designed to be submerged in water is likely to be made of concrete, as metal can rust or otherwise corrode due to the constant exposure to moisture. Before the bridge pier can be installed into the water, the river bottom or bottom of the waterway must be dredged so the soil can support the weight of the pier and bridge surface.
Waterways are not the only locations at which a bridge pier is useful. In many cases, this design may be used when bridges must be built on dry land; highway systems commonly use such designs, as overpasses can be raised over other roadways, capitalizing on available height where more width is not available. Overpasses are very common in large cities, in which the roadways may split off into several directions at one pivotal location. Bridge piers allow these bridges and overpasses to be built without eliminating the possibility of other roadways being built beneath.
The engineer of the bridge project will need to determine which pier shape is most appropriate for the specific application. It is possible for the pier structure to be built in such a way that it will not prevent proper water flow of a river, and in other cases, it can be built to ensure the proper load bearing of a roadway. Sometimes the design must vary according to what other forces will be acting on the bridge; high winds, for example, may call for one pier design over another.