The main systems of span structures are girder, arched and hanging, split, continuous and cantilever.
The main types are by material: reinforced concrete, steel and wood.
In metal and wood, all three basic systems are possible – beam, arched and hanging; in reinforced concrete – girder and arched.
The application of the principle of prefabrication brings constructive forms from all three materials closer together.
Combined structures are widely used, for example, steel beams with a reinforced concrete slab or reinforced concrete beams with a steel truss, etc.
In bridge building, the main building material is reinforced concrete, which has advantages over other materials (durability, lower operating costs, low steel consumption, etc.).
Precast concrete is of great importance in application to the bridge, which greatly facilitates the installation of structures. Prefabricated reinforced concrete bridges are installed basically the same way as steel ones. In case of small spans, reinforced concrete spans can be supported by a crane as a whole.
The main advantage of metal is high industrialism and, in this regard, the short terms and low labor intensity of manufacturing and installation, as well as the relatively low weight of the span. Therefore, the main area of application of metal in bridge construction is more spans, where these advantages are still significant.
Figure: Elements of the metal superstructure: 1 – main trusses; 2 – carriageway, driving surface; 3 – longitudinal beams; 4 – cross beams;
5 – supporting parts.
Another area of application of metal bridge structures is movable bridges (movable, collapsible, movable and floating, for example, military, for which transportability, speed of construction, etc. are essential)