Why did the country eliminate cold-rolled ribbed steel bars?

The state does not want to eliminate cold-rolled ribbed steel bars, but to update them. Because the ductility of traditional cold-rolled ribbed steel bars is low. Forty years have passed from the invention and appearance of cold-rolled ribbed steel bars to the popularization and application of products, but there is no great innovation. Low ductility has always been an industry problem that affects the promotion of this high-efficiency and energy-saving steel. A new code for construction of cold-rolled ribbed bars, JGJJ 95-2011,has been issued, and an updated product of cold-rolled ribbed bars, high ductility cold-rolled ribbed bars, has been added. This new steel grade was developed by Anyang Heli Cold Rolling Company. The tensile strength of high ductility cold-rolled ribbed steel bars is increased from 550Mpa to 600Mpa, which means that the building safety factor is improved and steel can be saved. Secondly, the elongation is increased by 50%, especially the maximum uniform elongation is increased by 1.5 times, which greatly improves the ductility and seismic performance of steel bars, effectively prevents brittle fracture of steel bars and ensures seismic safety. Thirdly, the strength design value is increased from 360Mpa to 4 15 MPa, which expands the application range of high ductility cold-rolled steel bars, not only for cast-in-place floor slabs, but also for shear walls, and large specifications can be applied to ring beams.

The tensile strength design value of CRB600H high ductility cold-rolled ribbed bar is fy=4 15MPa, which is obviously higher than that of HPB235(fy=2 10MPa), HPB300(fy=270MPa) and HRB335(fy=300MPa) and also higher than that of HRB. CRB600H cold-rolled ribbed steel bars with high ductility are mainly of fine diameter specifications and can be supplied in fixed length according to engineering requirements. They can be used as stress reinforcement and distribution reinforcement of concrete slab members, which can not only reduce the amount of reinforcement and cost, but also facilitate construction, and have remarkable social and economic benefits.

This information can be found on the industry website "Cold Rolled Ribbed Steel Information Network".