Australian Cold-Formed Steel — AS/NZS 4600 Design Guide
Quick access: [[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/]]
Reference for cold-formed steel design per AS/NZS 4600:2018. Covers effective width method, distortional buckling, section types (lipped channels, Z-sections, Sigma sections), and purlin/girt design.
Common Section Types
| Section | Use | Grade | Issues |
|---|---|---|---|
| Lipped channel (C) | Purlins, girts | G450-G550 | Distortional buckling |
| Z-section | Purlin (overlapping) | G450-G550 | Lateral-torsional |
| Sigma section | Long-span purlins | G450-G550 | Combined bending+torsion |
| Hat section | Girts, flashings | G300-G450 | Local buckling |
Steel Grades
| Grade | t≤1.0mm Fy | t>1.0mm Fy | Fu |
|---|---|---|---|
| G300 | 300 | 300 | 340 |
| G450 | 450 | 450 | 500 |
| G500 | 500 | 500 | 540 |
| G550 | 550 | 500 | 550 |
Design Methods
| Method | Use | Clause |
|---|---|---|
| Effective Width (EWM) | All sections (default) | Section 2 |
| Direct Strength (DSM) | HSS, decking, racks | Section 7 |
| Test-based | No analytical method | Section 8 |
Worked Example
Problem: 200 mm lipped channel, t=1.5 mm, G550. Zex=25×10³ mm³. Find φMs.
Solution:
- t=1.5 mm → G550 Fy=500 MPa
- EWM: Check local buckling λ for each element
- If λ>λe, reduce to effective width be
- φMs = 0.90 × 500 × 25×10³ = 11.25 kNm
- Check distortional buckling per Clause 3.4 (may reduce capacity)
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
Standard cold-formed steel grade in Australia? G550 (fy=550/500 MPa) is most common. G300 used for non-structural members.
What is distortional buckling? Lip stiffener buckling with adjacent flange. Governs lipped channel capacity. Per AS/NZS 4600 Clause 3.4.
AS/NZS 4600 for storage racks? AS 4084 has additional requirements for racks: impact loads, seismic, special detailing.
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.