4.Design Strength Values of Steel Reinforcement for Concrete Structural Design

Basic Adoption Rules for Steel Reinforcement Design Strength
For ordinary steel bars, the design values of tensile strength and compressive strength shall be selected according to standard graded values. For prestressing reinforcement, corresponding design values of tensile and compressive strength shall be adopted. When members are reinforced with different types of steel, each type shall apply its own design strength value.
Note: fy represents the design value of tensile strength for ordinary steel bars; fy' represents the design value of compressive strength for ordinary steel bars. fpy and fpy' represent the tensile and compressive design strength values for prestressing reinforcement respectively. The definitions conform to the referenced standard provisions.

Table 1 Design Strength Values of Ordinary Steel Bars (N/mm²)

Special Provisions for Axially Compressed Members and Transverse Reinforcement
For axially compressed members using HRB500 or HRBF500 steel bars, the design compressive strength value of the reinforcement shall be taken as 400 N/mm². The design tensile strength value of transverse reinforcement shall adopt the value of fy from the table; however, when used for shear, torsion and punching bearing capacity calculation, the value shall be capped at 360 N/mm² if it exceeds this limit.
Note: Axially compressed members refer to members bearing axial compressive load along the centroidal axis. Transverse reinforcement refers to stirrups and ties used for shear resistance and reinforcement confinement. The 360 N/mm² cap rule strictly follows the referenced standard provisions.

Graded Design Strength and Conversion Rules for Prestressing Reinforcement
Prestressing reinforcement is classified into medium-strength prestressing wire, stress-relieved wire, steel strand and prestressing threaded bar, each with corresponding design strength values matching different characteristic ultimate strength grades. When the characteristic strength value of prestressing reinforcement does not conform to the table provisions, the design strength value shall be converted proportionally.
Note: Proportional conversion means calculating the design value according to the ratio between the actual characteristic strength and the standard characteristic strength in the table. This conversion rule is specified in the standard notes.

Table 2 Design Strength Values of Prestressing Reinforcement (N/mm²)

Note: When the characteristic strength value of prestressing reinforcement does not comply with the provisions of this table, its design strength value shall be converted proportionally.

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