Prefabricated Steel Bridges, 321 steel bridge, steel bridge, readiness steel bridge, steel bridge in rivers around the world have been widely used. Prefabricated Steel Bridges initially by the British Donald Bailey (Donald Bailey) engineers early in the design of World War II in 1938, it is also known as Bailey bridges. Bailey bridges between two main truss beams through contact, in the above configuration stringers and deck beams by the strut and tie material to secure it, and stand as a bridge. Wooden deck, the rest is steel materials, also known as steel bridge. Both sides of the main truss by a single row, double or triple rows are arranged in parallel, but also to double and triple truss frame to increase the carrying capacity. This bridge can be erected Bailey bridge, pontoon and railway bridge. Bailey bridges with steel modular design, with excellent exchange connectivity, it can short length, to wide-narrow, erect fast, the economy is good. Because of its convenience, many countries in the world which uses a lot of steel temporary bridge erected temporary or semi-permanent bridge, its applications extend from purely military purposes in the field of civil highway bridge, since its inception generally praised by users. During World War II, a large number of fabricated steel bridge is used in Europe and the Far East battlefield, repair a bridge or temporary bridge erected. The United States from England in 1941 to buy a patent, manufacture fabricated steel bridge, named M1 type; improved after (carriageway widened 12%), named M2 type. After World War II, many countries introduced a fabricated steel bridge, and have been widely used in civilian. In China, fabricated steel bridge has been great development, and setting production in 1965, is now widely used in national defense combat readiness, traffic engineering, municipal water conservancy projects.