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.Know More
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.Learn more in Architecture
For medium distances of between 500 and 2,500 feet, cable-stayed bridges have the advantages over suspension bridges of requiring less steel cable and being less expensive and quicker to build. In addition, instead of being limited to two towers as suspension bridges are, cable-stayed bridges can be built with any number of towers.Full Answer >
The problem with iron bridges was that the material was not as reliable as carbon steel, so it was replaced starting in the late 1800s and was completely unavailable for bridge building by the early 1900s. Bridges in the late 1700s were made of cast iron, but, by the early 1800s, cast iron gave way to wrought iron.Full Answer >
An interesting fact about beam bridges is that the world's longest bridge is a beam bridge called the Lake Ponchartrain Causeway; it is nearly 24 miles in length. Beam bridges are not normally used for long distances because they weaken when the supports are far apart. A long stretch is actually composed of multiple beam bridges that have been put together using a process known as daisy chaining.Full Answer >
One of the most famous beam bridges in the United States is the Manchac Swamp Bridge in Louisiana. It cost approximately $7 million to complete each mile of the bridge, according to USA Today.Full Answer >