Design Aids

Column Design Example – Compression load only

Select a sawn timber member to carry a permanent factored axial compressive load of 12 kN:

N*c =12kN

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 = 90mmb = 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 =0.41from NZS3603 2.10

About the weak axis y-y:

Lay =800
S3 = k10.L/d or Lay / d=17.8
k8 =0.78from NZS3603 2.10
fc =18MPa
k1 =0.6for a permanent load
Φ =0.8
ΦNncx = Φ.k1.k8.fc.A =14.3kN
ΦNncy = Φ.k1.k8.fc.A =27.2kN

Example prepared by David Reid, Structural Engineer.

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