Design Aids

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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