Column Design Example – Compression load only
Select a sawn timber member to carry a permanent axial compressive load of 12 kN:
| N*c = | 12 | kN |
Say the column is 2.4m long and restrained about the strong axis at the ends, and restrained about the weak axis @0.8 crs
Using MSG8 timber, actual size of 100×50 is 90×45:
| d = 90mm | b = 45mm |
Need to satisfy N*c <= ΦNncx and N*c <= ΦNncy
About the strong axis x-x:
| k10. L = | 2400 | |
| S2 = k10.L/d or Lax / d= | 26.7 | |
| k8 = | 0.41 | from NZS3603 2.10 |
About the weak axis y-y:
| Lay = | 800 | |
| S3 = k10.L/d or Lay / d= | 17.8 | |
| k8 = | 0.78 | from NZS3603 2.10 |
| fc = | 18 | MPa |
| k1 = | 0.6 | for a permanent load |
| Φ = | 0.8 | |
| ΦNncx = Φ.k1.k8.fc.A = | 14.3 | kN |
| ΦNncy = Φ.k1.k8.fc.A = | 27.2 | kN |
Example prepared by David Reid, Structural Engineer.
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