Bailey Bridge

Prefabricated steel highway bridges are a type of modular bridge that can be quickly erected and are primarily used for emergency repairs.  These bridge components have the following characteristics:
1. They are made of high-strength steel and are fully welded. The main beams are generally detachable lightweight trusses, assembled in three-dimensional or planar units, connected by single pins or bolts. They are lightweight, making transportation and disassembly convenient.
2. The components are interchangeable and can be reused multiple times.
3. The combination of the bridge's main beams can be adjusted according to the span and load capacity.

Since World War II, several major countries have standardized and produced their own bridge repair equipment. For example, the former Soviet Union's "PMM" had an upper-supported, triangular truss main beam with three-dimensional assembly units. Japan's "Type 99" military bridge also used a triangular truss main beam with three-dimensional assembly units, primarily for railway bridge repair. This equipment can still be seen in my country's railway departments and some highway construction units, where it is often used as construction equipment. As early as the beginning of World War II, in 1938, Britain and the United States adopted the "Bailey bridge," a steel truss bridge designed by British engineer Donald Bailey, as a military bridge for the Allied forces. This bridge was widely used in Europe and the Far East during World War II, and was further improved and developed after the war.

My country's prefabricated highway steel bridges were standardized and put into production in the 1960s, originally called the "321" highway steel bridge. The state arranged for three designated factories to produce them, with an annual output of approximately 1500-2000 tons, stored throughout the country. This equipment played an important role in disaster relief (such as the Tangshan earthquake) and border self-defense counterattacks. In 1992, during peacekeeping operations in Cambodia, Chinese engineering troops used domestically produced "321" highway steel bridge components on Highway 6, repairing bridges at a rate of one bridge every two days, completing the erection of six highway bridges on a 217 km road section within 15 days, receiving high praise from the United Nations peacekeeping forces. The "321" highway steel bridge produced in my country is similar to the British "Bailey bridge," with the main beams also being lattice trusses, but the dimensions are different. The Bailey bridge uses imperial units, while the "321" highway steel bridge uses metric units, and these two types of equipment cannot be mixed. Workers on some construction sites in my country often refer to the domestically produced "321" highway steel bridge trusses as "Bailey trusses."

Bailey bridge components in my country have undergone continuous updates and evolution to adapt to the needs of more applications. The gradually emerging HD200 type Bailey bridge further improves the bending and shear resistance of the steel bridge, developing towards larger spans and heavier loads. In the housing sector, it can be combined into an aerial frame structure, serving as a construction platform, and gradually climbing upwards through the coordination of hydraulic jacking structures. As a cast-in-place support structure, the Bailey bridge components are modified into an upper-bearing structure, supplemented with beams, supports, and other materials, which can be used for formwork and concrete pouring.