Steel Structures

structures in which the members are made of steel and are joined by welding, riveting, or bolting. Because of the high strength of steel, these structures are reliable and require less material than other types of structures. Steel structures are distinguished by the diversity of their shapes and by their architectural expressiveness. Fabrication and installation of steel structures are realized through industrial methods. The main disadvantage of steel structures is susceptibility to corrosion, which requires that protective measures, such as the application of special coatings and paints, be taken periodically, thereby increasing service costs.

In modern construction, steel structures are used mainly as supporting members in buildings and larger structures that vary widely in purpose and design. Examples are residential and public buildings (including high-rise buildings), industrial buildings, especially such metallurgical plants as rolling mills and mills using blast furnaces and open-hearth furnaces, storage tanks and gas tanks, communication structures (radio and television towers and antennas), and power-engineering structures (hydroelectric, thermal, and nuclear power plants, transmission lines). Other examples include transportation structures (bridges, overpasses of railways and highways, depots, hangars), oil and gas pipelines (those suspended over large rivers, ravines, and gorges), stadiums, and pavilions.

Steel structures were first used in construction work in the 1880’s. By that time, such industrial methods for the production of cast iron (steel) as the open-hearth, Bessemer, and Thomas processes had been developed and were being applied. By the end of the century, large buildings and structures made mostly of steel were being built in Russia and abroad, among them the pavilions with suspended roofs built for the Nizhny Novgorod fair, the Brooklyn Bridge, and the Eiffel Tower.

In the USSR, the rapid growth of metallurgy provided the basis for the futher development and improvement of steel structures. Experience in the design and erection of structures was accumulated, and the areas most suitable for use were defined. Electric-arc welding became the principal method of joining structural elements. Significant contributions to the creation and development of a national school of steel-structure design were made by the Soviet scientists V. G. Shukhov, N. S. Streletskii, and E. O. Patón. Standardized steel structures are widely used in current construction practice. These structures minimize material and labor requirements at the shop and afford ready assembly in the field.

In the USSR, steel structures are fabricated primarily from low-carbon steels of improved or high strength. The structures are usually built from sections turned out by a primary rolling mill, and the sections must meet certain specifications with regard to dimensions. (The first such list of specifications in Russia was compiled by N. A. Beleliubskii in 1900.) Tubular and bent shapes are also used as primary components. In plants that manufacture metal structures, the sections from the primary rolling mill are used to fabricate various standardized structural members, as a rule, in a limited assortment of types. The products include solid members, which are subject only to bending (beams); latticed units, which are subject primarily to bending (trusses); members subject primarily to compression and bending (columns, struts); and members subject only to tension (cables). Flat-rolled products, namely, plates, strips, and sheets, are also manufactured. By combining these various structural members, a fabricating plant can produce steel structures for almost any purpose, either as completely assembled units (if the overall dimensions permit transport) or as large individual assembly units. Assembly of the individual structural members and larger assembly units is accomplished with welded, bolted, and riveted joints. In addition

Figure 1. Design for the steel frame of a twin-bay industrial building: (1) lattice, (2) column, (3) crane girder, (4) skylight, and (5) web members

to standard bolted joints there are also joints made with high-strength bolts of the friction type (subject to friction), which have a large load-carrying capacity. It is mainly bolted joints that are used in assembling separate units into a completed structure.

Figure 1 shows the design of a steel frame for a twin-bay industrial building. Here, the trusses and skylight are latticed, and the crane girders and columns above the beams are solid. Various designs, both two-dimensional and three-dimensional, are used for roofs that must span large bays. Roof trusses are mainly used for spanning bays up to 100 m, as in airplane hangars. Structural frames, which are made up of latticed units having standardized rods as web members, are used for spanning medium and large bays. Here, the units are joined together in various ways. Steel structures of the frame type are very effective; in these structures, which are usually latticed, the thrust is transmitted to a foundation. Arches, either latticed or solid, have been found to be effective for the roofs of large-span buildings. In many cases, it is advantageous to choose a suspension structure, which offers substantial savings of steel material. Suspension systems are also used for supporting pipelines over gorges, deep ravines, and large rivers. Steel structures are widely used when great heights are involved. The television tower in Kiev, for example, whose tubular structure is made of high-strength steel, is 372 m high.

In the USSR, steel structures are designed in accordance with the Construction Code, which, guided by technical and economic considerations, stipulates optimal designs, component cross sections, and steel grades. Rating, as a rule, follows the method of limit states.

Prestressed steel structures hold promise for the future, especially for suspension systems. In addition to being lower in weight, prestressed structures have an increased load-carrying capacity.