3.Steel Reinforcement Types and Characteristic Strength Parameters for Concrete Structure Design

Selection Specifications for Longitudinal Mild Steel Reinforcement
Longitudinal load-bearing mild steel reinforcement can adopt grades including HPB300, HRB335, HRB400, HRBF400, RRB400, HRB500 and HRBF500. For longitudinal reinforcement in beams, columns and diagonal bracing members, HRB400, HRB500, HRBF400 and HRBF500 grades are recommended as preferred options.
Note: HPB stands for hot-rolled plain steel bar; HRB stands for hot-rolled ribbed steel bar; HRBF stands for fine-grained hot-rolled ribbed steel bar; RRB stands for remained-heat-treatment ribbed steel bar. The number in the grade represents the characteristic yield strength value, consistent with standard specifications.

Applicable Grades for Stirrup Reinforcement
Stirrups are recommended to be made of HRB400, HRBF400, HRB335, HPB300, HRB500 and HRBF500 steel bars, to meet the shear resistance and confinement requirements of concrete structural members.
Note: Stirrups are transverse reinforcement used to resist shear force and restrain longitudinal reinforcement from buckling. The grade selection provisions follow standard concrete structure design requirements.

Recommended Material Types for Prestressing Reinforcement
For prestressing tendons, prestressing steel wires, steel strands and prestressing threaded steel bars are the recommended material types, which are selected according to the prestressing process and structural performance requirements.
Note: Prestressing reinforcement applies pre-compression to concrete to improve structural crack resistance. Steel strands are widely used in post-tensioned structures, while threaded bars are suitable for long-span heavy-load components.

Guarantee Rate and Classification of Steel Strength Characteristic Values
The characteristic strength values of steel reinforcement shall have a guarantee rate of no less than 95%. For ordinary steel bars, the characteristic yield strength and characteristic ultimate strength are adopted as basic strength indexes; for prestressing steel products, corresponding characteristic ultimate strength and characteristic yield strength are specified. The specific parameters of ordinary steel bars are shown in the table below.

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

Note: fyk represents the characteristic yield strength value of ordinary steel bars; fstk represents the characteristic ultimate strength value of ordinary steel bars. The unit N/mm² is equivalent to MPa, and the definitions fully conform to the referenced standard provisions.

Characteristic Strength Parameters of Prestressing Steel Products
Prestressing steel products cover medium-strength prestressing wires, stress-relieved wires, prestressing threaded bars and steel strands, with differentiated strength grades corresponding to different diameters and structural forms. The detailed strength parameters are listed in the table below.

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

Notes:

1. For steel strands with a characteristic ultimate strength value of 1960 N/mm², reliable engineering experience is required when used as post-tensioned prestressing reinforcement.

Note: fpyk represents the characteristic yield strength value of prestressing reinforcement; fptk represents the characteristic ultimate strength value of prestressing reinforcement. The symbol definitions are consistent with the referenced standard provisions.

Disclaimer

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The data in this article are derived from publicly available industry standards and engineering experience. The viewpoints presented are for reference only. For specific schemes and data in actual engineering projects, adjustments shall be made in combination with the actual conditions of the project.

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