5.Total Elongation at Maximum Force and Elastic Modulus of Steel Reinforcement

Basic Requirements for Total Elongation at Maximum Force
For both ordinary steel bars and prestressing reinforcement, the total elongation at maximum force δgt shall not be lower than the specified limit values. This index reflects the ductility performance of steel materials, ensuring sufficient deformation capacity of structural members before failure and enhancing structural safety under extreme loading conditions.
Note: δgt represents the total elongation of steel reinforcement at maximum force, which is a core ductility indicator. The limit definitions fully conform to the referenced standard provisions.

Table 1 Limit Values of Total Elongation at Maximum Force for Steel Reinforcement (%)

Ductility Gradient and Seismic Performance Requirements
Ductility performance varies across steel grades. Plain hot-rolled bars have the highest elongation capacity, while heat-treated ribbed bars have relatively lower ductility. Seismic-grade steel bars marked with 'E' have stricter total elongation requirements to ensure better energy dissipation capacity under seismic action. Prestressing reinforcement generally has lower ductility limits than ordinary bars due to its higher strength grade.
Note: Grade E steel bars are seismic-grade reinforcement with stricter ductility and strength uniformity requirements. The graded limit values follow the standard classification in the referenced specification.

Elastic Modulus Provisions for Steel Reinforcement
The modulus of elasticity Es for ordinary steel bars and prestressing reinforcement shall be selected according to the standard graded values. This parameter is a fundamental index for structural deformation calculation, crack width analysis and prestressing loss estimation. The specific values for each steel type are shown in the table below.

Table 2 Modulus of Elasticity of Steel Reinforcement (×10⁵ N/mm²)

Note: Es represents the modulus of elasticity of steel reinforcement. The unit ×10⁵ N/mm² is equivalent to ×10⁵ MPa. The definitions and values are consistent with the referenced standard provisions.

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