AS 1720.1 – Timber Beam k₁₂ Calculator
Calculate beam slenderness coefficient S₁ and lateral stability factor k₁₂.
Calculation sequence:
Beam geometry + restraint condition → S₁ → ρbS₁ → k₁₂
Beam geometry + restraint condition → S₁ → ρbS₁ → k₁₂
1. Timber Material
Selected from the embedded material table.
2. Beam Geometry
Enter the distance between effective lateral
restraint points. If restraints are only at
the beam ends, use the distance between those
restraints.
3. Lateral Restraint Condition
Calculated Stability Factor
1.000
No stability reduction.
4. Calculation Details
| Parameter | Calculated value |
|---|---|
| b | – |
| d | – |
| Lay | – |
| ρb | – |
| S₁ | – |
| ρbS₁ | – |
| Applicable k₁₂ equation | – |
| k₁₂ | – |
5. k₁₂ Stability Equations
X = ρbS₁
If X ≤ 10:
k₁₂ = 1.0
If 10 < X ≤ 20:
k₁₂ = 1.5 − 0.05X
If X > 20:
k₁₂ = 200 / X²
Important:
correctly identify the actual beam lateral restraint
condition. End restraints only should not be treated
as continuous lateral restraint.