Thread steel is a surface ribbed steel bar, also known as ribbed steel bar, usually with two longitudinal ribs and uniformly distributed along the length direction of the transverse ribs. The shape of transverse ribs is spiral, herringbone and crescent. Expressed in millimeters of nominal diameter. The nominal diameter of ribbed bar is equivalent to the nominal diameter of round bar with equal cross section. The nominal diameter of reinforcing bars is 8-50 mm, and the recommended diameters are 8, 12, 16, 20, 25, 32 and 40 mm. Ribbed steel bars mainly bear tensile stress in concrete. Ribbed steel bars have greater bonding capacity with concrete due to the role of ribs, so they can better withstand the role of external forces. Ribbed steel bars are widely used in various building structures, especially large, heavy, light thin-walled and high-rise building structures.