Timber · Columns & studs

Timber column (compression) calculator

Compression capacity with slenderness coefficient S, stability factor k12 and the material constant ρc.

Standard: AS 1720.1 Cl 3.3

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
Breadth (minor)	90	mm
Depth	140	mm
Effective length (minor axis)	2.4	m
Characteristic compression f′c	22	MPa
Capacity factor φ	0.85 cat 2
Duration k1	0.8 (5 months)
Moisture k4	1
Temperature k6	1
Material constant ρc	1
Design compression N*	45	kN

Diagram for the worked example

Slenderness S = le/b = 2.4*1000/90 = 26.667
k12 = IF(1*26.667<=10,1,IF(1*26.667<=20,1.5-0.05*1*26.667,200/(1*26.667)^2)) = 0.28125
φNc = φ k1 k4 k6 k12 f′c A = 0.85*0.8*1*1*0.28125*22*90*140/1000 = 53.014 kN

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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.