Steel grades for reinforced concrete have been adjusted
(1) Include 500 MPa steel bar. Considering the actual demand of 500 MPa grade steel bar application, on the basis of a large number of experimental research and pilot project application, 500 MPa grade 500 MPa is included in the Design Code for the first time, and detailed requirements are put forward for its design calculation and reinforcement structure. However, considering the lack of relevant test data, the fatigue design parameters of 500 MPa steel bars have not been included.
(2) Include fine grain reinforced bar. On the basis of previous material and structure studies, three kinds of fine grain reinforced bars, HRBF335. HRBF400 and HRBF500, were included. However, considering the actual problem of welding fine grain steel bar, the Code of Design proposes that the welding of fine grain steel bar should be determined by test.
(3)以HPB300钢筋替代HPB235钢筋。根据标准《钢筋混凝土用钢 第1部分：热轧光圆钢筋》( GB 1499. 1-2008)的规定，考虑到推广高强钢筋的需要，建筑工程中淘汰HPB235光圆钢筋，全面推广应用HPB300钢筋。
(3) Replace HPB235 steel bar with HPB300 steel bar. According to the national standard "Steel for Reinforced Concrete Part 1: Hot Rolled Round Reinforcement Bar" (GB 1499.1-2008), considering the need to promote high-strength reinforcement, HPB235 round reinforcement bars were eliminated in construction projects, and HPB300 reinforcing bars were comprehensively promoted and applied.
(4)保留了RRB400钢筋。《设计规范》保留了RRB400钢筋品种，但规定不宜焊接。可理解为此钢筋即为新修订的《钢筋混凝土用余热处理钢筋》( GB 13014-1991)中的不可焊余热处理钢筋RRB400，RRB400W钢筋虽未列入，但如有可靠焊接依据，也可应用。HRB500钢筋由于（GB 13014-1991）产品标准修订未及时完成，暂未纳入。
(4) RRB400 reinforcing bar was retained. The RRB400 steel bar is retained in the Design Code, but it is not suitable for welding. It can be understood that the reinforcing steel bar is RRB400, which is a non-weldable waste heat treatment reinforcing steel bar in the newly revised GB 13014-1991. Although RRB400W reinforcing steel bar is not included, it can also be applied if there is reliable welding basis. HRB500 reinforcing bar has not been included in the revised product standard (GB 13014-1991).
Note: 1. For stirrups used for calculating shear, torsion and punching shear capacity, the tensile design strength FYV is chosen according to the value of fy, but its value should be smaller than 360N/mm2:
2. As indirect reinforcement for local compression and stirrups for confined coagulation of compressive members, the tensile design strength FY is selected according to the values in the table.
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