Types of Bridges
There are numerous types of bridges in today’s world; however there are only a few basic bridge structures. They include:
- Girder Bridge - A girder bridge is the most common and likely, the most basic of bridges. A fallen log across a creek is an example of a girder bridge. Steel girder bridges use I-beam girders and box-girders. Picture to the right is the famous Coronado Bridge in San Diego, CA.
- Truss – A truss bridge is a simple skeletal structure, typically made of an assortment of triangles. The picture to the right is a railroad truss bridge over the Flint River in central Michigan. Since most beams in a truss bridge are straight, toothpick bridge projects are perfect for bridges as they are typically easy to build and demonstrate the strength these types of bridges can support.
- Rigid Frame Bridge – In the rigid frame bridges, the girders and support piers are all one piece. These are required to support a lot of weight. The picture to the right is the George Bush Bridge.
- Arch Bridge - After girders, arches are the second oldest bridge type and one you see often. Arch bridges are perfect for stone and were developed and used extensively by the Romans. Arches are good choices for crossing valleys and rivers since the arch doesn't require piers in the center. The arch bridge to the right is the Cold Springs Bridge near Santa Barbara, CA.
- Cable Stayed Bridge- A cable stayed bridge is a continuous girder with one or more towers erected above piers in the middle of the span. From these towers, cables are connected diagonally and support the girder (the road or surface). The picture to the right is the Tatara Bridge in Japan.
- Suspension Bridge - The suspension bridge allows for the longest bridge spans. Although the suspension and cable stay bridges look similar, they are very different. Suspension bridges are in fact a very old form of bridge. In primative cultures, simply ropes and wood planks are used in a typical suspension bridge. To the right is the famous Golden Gate Bridge in San Francisco, CA