Cold-Formed Purlin Design Calculator
Lipped C or Z cold-formed steel purlin design by the Direct Strength Method to SANS 10162-2 (an adoption of AS/NZS 4600). Member moment capacity from local (Mbl), distortional (Mbd) and global (Mbe) elastic buckling, cold-formed web shear buckling, combined bending + shear and serviceability deflection — with a cross-section diagram and a printable clause-by-clause calc sheet. The distortional buckling stress uses the Lau & Hancock closed form of AS/NZS 4600 Appendix D, validated against published CUFSM finite-strip results within 3%. Yield stress and section dimensions are editable user inputs.
Inputs
Section & loading
Design result
| Design line load w* | — |
| Design moment M* | — |
| Design shear V* | — |
| Yield moment My = fy·Zf | — |
| Local Mbl (fol) | — |
| Distortional Mbd (fod) | — |
| Global Mbe | — |
| Section moment capacity φbMb | — |
| Area A | — |
| Ix (full) | — |
| Zf (full) | — |
| fod · Lcr,d | — |
| λl / λd | — |
| Governing (bending) | — |
| Shear φvVv | — |
| Deflection δ (limit) | — |
Design checks
Step-by-step calculation
Purlin schedule — all members
This isn't a toy calculator
The distortional buckling here is the Lau & Hancock closed form of AS/NZS 4600 Appendix D, validated against published CUFSM finite-strip results within 3% — the same standard STATIX holds across analysis, design and connections. A full 3D suite with native CBFEM is planned.