Timber · Columns & studs
Timber combined bending & compression calculator
Interaction (M/φMx)² + N/φNcx ≤ 1 and M/φMx + N/φNcy ≤ 1 for a rectangular member.
Standard: AS 1720.1 Cl 3.5
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Design moment | 4 | kNm |
| Design compression | 20 | kN |
| φMx (bending capacity) | 7.5 | kNm |
| φNcx (major axis) | 110 | kN |
| φNcy (minor axis) | 60 | kN |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| (M/φMx)² + N/φNcx | 0.466 | |
| M/φMx + N/φNcy | 0.867 | |
| Limit | 1.00 |
- ✓ Interaction 1
- ✓ Interaction 2
Method, formulas and assumptions
- (M/φMx)² + N/φNcx = (4/7.5)^2+20/110 = 0.46626
- M/φMx + N/φNcy = 4/7.5+20/60 = 0.86667
- Limit = 1 = 1
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.