Rebar is a ribbed steel bar on the surface, also known as ribbed steel bar, usually with two longitudinal ribs and transverse ribs evenly distributed along the length. The shape of the transverse ribs is spiral, herringbone, and crescent. It is expressed in millimeters of the nominal diameter. The nominal diameter of ribbed steel bars is equivalent to the nominal diameter of smooth round steel bars with equal cross-sections. The nominal diameter of the steel bars is 8-50 mm, and the recommended diameters are 8, 12, 16, 20, 25, 32, and 40 mm.