Reinforcement for Reinforced-concrete Structural Members

an internal, component part of reinforced-concrete structural members, designed to strengthen concrete that is subjected to tensile (more rarely to compressive) stresses.

The material generally used for this purpose is flexible steel reinforcement (in the form of separate rods or welded mesh and framework); sometimes rigid reinforcement is used (rolled I-beams, channels, and angle brackets). Plexiglass, bamboo, and other materials may also be utilized as reinforcement. The following types of reinforcement are distinguished: operative, embedded in reinforced-concrete structural members in accordance with design calculation; and installation and distributive, which are designed to form frameworks and grids together with operative reinforcement and which are embedded in accordance with structural considerations.

The great diversity in kinds of structural members has made it necessary to manufacture special reinforcement steels, which must have various strength characteristics and the necessary elastic properties. The most widespread reinforcements used are the rod type (hot-rolled, hardened by heat treatment and by drawing), which is subdivided into seven classes depending on its strength (it is produced in diameters of 6 to 90 mm); and the wire type (made in the form of wire in diameters ranging from 3 to 8 mm), strands, cables, and welded and gauze grids. Tensioned reinforcement, which is made from reinforcement steel having a high critical tensile strength (900 meganewtons per sq m [90 kg forces per sq mm] and higher), is utilized in prestressed structural members. Improvement in the bonding of the reinforcement to the concrete has been achieved by adding an effective periodic profile to the reinforcement’s surface (see Figure 1).

Figure 1. Reinforcement for reinforced-concrete structural members: (1) and (2) reinforcement with periodic profile, (3) wire with periodic profile, (4) seven-wire strand, (5) double-strand cable.