Australian Steel Fy and Fu — AS/NZS 3679.1 Yield & Tensile Table
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Complete reference for yield strength (Fy) and tensile strength (Fu) per AS/NZS 3679.1:2016 (sections) and AS/NZS 3678:2016 (plates). Values used in AS 4100 limit state design.
Grade 300 and 300PLUS — Sections
| Thickness | Fy (MPa) | Fu (MPa) |
|---|---|---|
| t ≤ 11 mm | 300 | 430 |
| 11-20 mm | 300 | 430 |
| 20-40 mm | 280 | 430 |
| t > 40 mm | 260 | 410 |
Grade 350 — Sections
| Thickness | Fy (MPa) | Fu (MPa) |
|---|---|---|
| t ≤ 11 mm | 360 | 450 |
| 11-20 mm | 350 | 450 |
| 20-40 mm | 330 | 450 |
| t > 40 mm | 310 | 430 |
Grade 350/400 — Plates
| Grade | t≤12 | 12-20 | 20-40 | >40 |
|---|---|---|---|---|
| 350 Fy | 360 | 340 | 330 | 320 |
| 350 Fu | 480 | 480 | 480 | 450 |
| 400 Fy | 400 | 400 | 380 | 360 |
| 400 Fu | 500 | 500 | 500 | 480 |
Worked Example
Problem: φMsx for 410UB59.7 (Sx=1142×10³ mm³) Grade 300.
Solution: Flange t=11.4 mm > 11 → Fy=280 MPa. φMsx = 0.90 × 280 × 1142×10³ = 287.8×10⁶ Nmm = 288 kNm. Using Fy=300 gives 308 kNm (7% overestimate).
Design Resources
- [[Australian Steel Grades|/reference/australian-steel-grades/]] | [[Australian Steel Properties|/reference/australian-steel-properties/]] | [[Australian Beam Sizes|/reference/au-beam-sizes/]] | [[Australian Bolt Capacity|/reference/australian-bolt-capacity/]] | [[AS 4100 Beam Design|/reference/as4100-beam-design-example/]] | [[All Australian References|/reference/]]
FAQ
What is the design yield for Grade 300 per AS 4100? 300 MPa for t≤11mm, 280 MPa for t>11mm. Use lower value based on thicker element.
What Fu value for bolt bearing calculations? Grade 300: 440 MPa. Grade 350: 480 MPa. Grade 400: 480 MPa per AS 4100 Clause 9.3.2.1.
How does thickness affect capacity? Thicker steel has lower yield due to reduced hot-rolling ratio. Columns with flanges >40 mm may see 10-15% reduction.
Educational Use Only — This reference is for educational and preliminary design purposes only. All structural designs must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) in accordance with AS 4100:2020 and all applicable Australian Standards. Results are not for construction.
Design Applications
Common Design Scenarios
This reference covers structural design scenarios commonly encountered in Australian steel design practice:
- Strength verification: Check member or connection capacity against factored loads per the applicable design code
- Serviceability checks: Verify deflections, vibrations, and other serviceability criteria
- Code compliance: Ensure design meets all provisions of the governing standard
- Connection detailing: Verify weld sizes, bolt quantities, and edge distances
Related Design Considerations
- System behavior: consider the interaction between members and connections
- Load paths: verify that forces can be transferred through the structure to the foundations
- Constructability: check that the design can be fabricated and erected practically
- Cost optimization: evaluate alternative sections or connection types for economy
Worked Example
Problem: Verify a Grade 300 member for the following conditions:
Typical span: 6.0 m | Load: service loads per applicable code | Section: common section in this category
Design Check:
- Determine governing load combination (LRFD or ASD per applicable code)
- Calculate maximum internal forces (moment, shear, axial)
- Compute nominal capacity per code provisions
- Apply resistance/safety factors
- Verify interaction if combined forces exist
Result: Use the results from the Steel Calculator tool to verify design adequacy.
Yield and Tensile Strength of Australian Steel Grades
AS/NZS 3679.1 (hot-rolled structural sections) specifies the following minimum yield and tensile strengths:
| Grade | Thickness (mm) | Min Fy (MPa) | Min Fu (MPa) | Fu/Fy Ratio |
|---|---|---|---|---|
| Grade 300 | ≤ 12 | 320 | 430 | 1.34 |
| Grade 300 | > 12 to ≤ 30 | 300 | 430 | 1.43 |
| Grade 300 | > 30 | 280 | 430 | 1.54 |
| Grade 350 | ≤ 12 | 360 | 450 | 1.25 |
| Grade 350 | > 12 to ≤ 30 | 340 | 450 | 1.32 |
| Grade 350 | > 30 | 320 | 450 | 1.41 |
| Grade 400 | ≤ 12 | 400 | 480 | 1.20 |
| Grade 400 | > 12 | 380 | 480 | 1.26 |
Thickness Effect on Yield Strength
The reduction in Fy with increasing thickness is due to the reduced effect of work hardening in thicker sections during hot rolling. For design per AS 4100:
- Fy determination uses the nominal thickness for flange (tf) and web (tw) separately
- If tf ≤ 12 mm but tw > 12 mm, the higher Fy may be used for web capacity calculations
- For conservative design, use the lower Fy governed by the thicker element
Frequently Asked Questions
What Australian Standard governs structural steel design?
AS 4100-2020 (Steel Structures) is the primary standard for structural steel design in Australia. It covers all aspects of design including member capacity, connections, serviceability, and fire resistance. The standard uses a limit states design philosophy with resistance factors (φ) applied to nominal capacities. Companion standards include AS/NZS 3679.1 for hot-rolled sections, AS/NZS 1554 for welding, and AS/NZS 4600 for cold-formed steel.
What are the common steel grades used in Australian construction?
The most common steel grades for Australian construction are Grade 300 and Grade 350 per AS/NZS 3679.1. Grade 300 (minimum yield 300 MPa for sections > 12 mm thick) is the standard for general structural applications. Grade 350 (minimum yield 340 MPa for sections > 12 mm) is used where higher strength reduces weight. Grade 400 and Grade 450 are available for specialized applications requiring higher strength-to-weight ratios.
How does AS 4100 compare to AISC 360?
Both AS 4100 and AISC 360 use limit states design (LRFD) principles. Key differences include: AS 4100 uses a single "capacity factor" φ approach rather than separate φ for different failure modes; AS 4100 specifies distinct buckling curves for hot-rolled and welded sections; the moment capacity formula in AS 4100 uses αm factor directly rather than Cb; and AS 4100 has more detailed provisions for slender sections and combined actions. Despite philosophical differences, both codes produce similar results for typical members.