In the United States, there are 600,000 bridges used for various applications. These bridges are designed to support different kinds of weight loads from cars, pedestrians, pipelines to the ancient viaducts. Although bridge application is one of the categorization points, there are other important categories which distinguishes bridges around the world. Railway bridges have been in existence since the mid-19th century and before the development of metallic structures, ancient bridges were made of either stone or wood.
The early built bridges were articulate constructed to feature some of the remarkable architectural despite being made from wood. However, after the introduction of iron and steel in bridge construction, modern designs have been adopted and some common examples include arch, beams, spans, girders and truss bridges. These modern steel railway bridges are constructed based on pre-defined requirements of their functionality, which is what defines the type of structure to be built.
Due to the high-quality materials and exceptional construction used to design ancient stone-arch bridges, most of them are still in regular use and are recognized by authorities such as National Historic Landmarks or National Register. Bridge construction is a capital intensive project and it’s often conducted by governments. Stone bridges are the most durable and beautiful but they are also expensive. For this reason, earlier bridges widely use wood to lower construction costs prior to the introduction steel and iron.
In the early 1800s, steel became more popular and readily available causing the introduction of more robust and impressive different types of bridges. In this period, new bridge variations such as arch and cantilever truss were constructed. The period also saw strong and durable railway bridges being constructed linking major towns and cities. Modern railroad bridges widely vary in their designs but the most commonly used design is the span plate girder. These bridges relatively economical than other bridge designs and they are widely applied on short to medium span bridges.
Railway bridges are an important element of the railroad infrastructure in that it facilitates transportation of goods from one point to another even in very rugged terrains. However, according to railroad statistics, over 200 million railway trips happen on daily basis across deficient bridges in the nation’s 102 largest metropolitan regions. In conclusion, it is very important that new bridges are built to support the current depleting railroads and also to maintain a smooth flow of goods within regions.