When designing and detailing the reinforcement in a concrete structure, the dimensions referred to for bars and wires are based on “nominal sizes“.
The word nominal size is used in place of diameter, referring in this way to diameter of a circle with an area equal to the effective cross-sectional area of bar or wire.
For example, for a 16 bar, because of surface deformations, there are no cross dimensions measuring 16 mm. Usually, the deformed bar can be contained in a circumscribing circle 10% (with peak values of 13 or 14%) larger than the nominal size of bar.
Preferred sizes of high yield reinforcing bars are 8, 10, 12, 16, 20, 25, 32 and 40 mm. Additional sizes, not preferred, are 6 and 50. The reason for these last to being not preferred regards the availability of the material by fabricators.
The following list below provides a comparison between the nominal size and the maximum size (in red are shown the non-preferred sizes): (more…)