B500B vs SD390/SD490 (Japan): Reinforcing Steel Standards Compared

Why Compare B500B and SD390/SD490?

Japan’s JIS G 3112 reinforcing bar grades SD390 and SD490 are widely referenced in Japanese-influenced construction markets across Asia — including infrastructure projects in Southeast Asia and parts of the Pacific where Japanese engineering practice or Japanese-origin financing shapes material specifications. For project engineers and procurement teams evaluating EU-origin B500B against JIS grades, a clear technical comparison is a practical starting point.

SD390 and SD490 are deformed (ribbed) reinforcing bar grades under JIS G 3112, with nominal yield strengths of 390 MPa and 490 MPa respectively. B500B under EN 10080/DIN 488 targets 500 MPa yield with explicit high-ductility requirements. This page compares the two systems on mechanical properties, chemistry, ductility, and documentation. It is a technical reference only — not formal equivalence or cross-certification. Any material substitution must be validated by a qualified structural engineer and approved by the relevant project authority.

Standard Overviews

JIS G 3112 — SD390 and SD490

JIS G 3112 is the Japanese Industrial Standard for steel bars for concrete reinforcement. The “SD” prefix denotes “Steel Deformed bar.” Key grades include SD295A, SD345, SD390, and SD490. SD390 specifies a yield strength of 390 MPa minimum (upper limit 510 MPa) and tensile strength ≥ 560 MPa. SD490 specifies yield ≥ 490 MPa (upper limit 625 MPa) and tensile strength ≥ 620 MPa. The standard specifies both lower and upper bounds on yield strength — a feature that influences seismic design under Japanese building codes (AIJ guidelines, Building Standard Law). Elongation requirements are expressed as percentage elongation after fracture (A) over a gauge length of 5d or 8d, varying by diameter. SD490 is a high-strength grade used where reduced bar cross-sections are advantageous.

EN 10080 / DIN 488 — B500B

B500B under EN 10080 (DIN 488 in Germany) requires f_yk ≥ 500 MPa (no upper bound specified in the characteristic value), k = f_t/f_y ≥ 1.08, and Agt ≥ 5.0 %. CE marking and EN 10204 3.1 Mill Test Certificates are mandatory for EU commerce. B500B is the standard grade for Eurocode 2 Class B ductility applications across Europe and many international markets.

Yield Strength: B500B vs SD390 and SD490

The most immediate difference is yield strength. SD390 (390 MPa) falls 22 % below B500B’s 500 MPa minimum, meaning more steel cross-section would be needed to achieve the same structural capacity under Eurocode 2 design. SD490 (490 MPa) is closer but still approximately 2 % below B500B’s 500 MPa. For design purposes under JIS and AIJ guidelines these grades are well-established, but they do not map directly onto Eurocode 2 design tables for B500B.

A distinctive feature of JIS G 3112 is the upper bound on yield strength (510 MPa for SD390, 625 MPa for SD490). This bilateral control reflects Japanese seismic design philosophy: excessively high yield strength can shift failure modes in ductile moment frames. EN 10080 B500B specifies only a lower characteristic yield bound; upper bound control is handled separately under seismic design using B500C (which adds an upper k limit: 1.15 ≤ k < 1.35).

Ductility: Elongation Methods and Values

JIS G 3112 specifies elongation after fracture (A) measured over a 5d or 8d gauge length — values of A ≥ 16 % (SD390, dia ≤ 32 mm) and A ≥ 12 % (SD490) appear high but use the fracture-gauge method. EN 10080 B500B uses Agt (total elongation at maximum force, uniform elongation) ≥ 5.0 % — a different measurement convention. These numbers are not directly comparable; a material with Agt ≥ 5.0 % can have A well above 12 % because the fracture-gauge method includes additional post-necking deformation. Both standards produce ductile reinforcing bars suitable for structural concrete, but under different design code frameworks.

Weldability and Chemistry

JIS G 3112 SD390 and SD490 impose controlled carbon and alloy content to permit welding, though the exact C_eq limits and welding procedures follow Japanese Welding Society standards, which differ from DIN EN ISO 17660. German B500B (C_eq ≤ 0.50, DIN 488) is fully compatible with DIN EN ISO 17660 structural welding, the reference standard for reinforcement welding in EU and many internationally-specified projects. The EN 10204 3.1 MTC documents heat chemistry for each cast — enabling project welding engineers to verify compliance without additional testing.

Documentation and Export

German B500B exported by Steel Rebar Germany is supplied with:

• EN 10204 3.1 Mill Test Certificate — heat number, full chemical analysis, mechanical test results per cast
• CE Marking / Declaration of Performance — EN 10080 conformity
• Certificate of Origin — German origin, chamber of commerce issued
• Packing list & weight certificate — seaworthy bundles ~2 t, container-ready

This documentation package supports project QA and customs clearance in most international markets. Learn about our export and delivery process.