KEVOS® MAKEOS · Fabrication
Fillet Weld Strength
Can these fillet welds carry the load, and what leg size is needed?
Throat thickness, load capacity of fillet welds on the throat with an allowable shear stress, utilisation under a load and the minimum leg size required.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Leg size | mm | Leg length of an equal-leg fillet weld. |
| Effective length of each weld | mm | Effective length of each weld, excluding craters and start-stops. |
| Number of welds sharing the load | welds | Number of welds of this size carrying the load. |
| Allowable shear stress on the throat | MPa | Allowable or design shear stress on the weld throat from your design code and electrode (e.g. AS 4100 / AS/NZS 1554 or AWS D1.1). |
| Applied load | kN | Load on the weld group, assumed shared uniformly in shear. |
Method and formulas
- Throat a = 0.7071 × leg (equal-leg, 90° fillet).
- Capacity = a × L × number of welds × allowable shear.
- Minimum leg = F ÷ (0.7071 × L × number × allowable shear).
- Example: two 6 mm fillets 100 mm long carry 123.04 kN at 145 MPa.
Limitations
- Uniform shear on the throat; eccentric loads add bending and torsion to the weld group.
- Base metal capacity, fatigue category and weld quality must be checked to the code.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size fillet welds for a bracket or lug
- Check an existing weld after a load change
- Compare weld length and leg size
Who it is for
- Structural and mechanical engineers
- Welding supervisors
- Fabrication estimators
What you get
- Throat thickness
- Weld capacity
- Utilisation
- Minimum leg size for the load
Interpreting the result
- Use code-specified design strengths and capacity factors for structural work.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1476–1486, 1469–1475. Topic reference; no source tables or recommended settings are reproduced.
- AS/NZS 1554.1 Structural steel welding — Welding of steel structures; AS 4100 Steel structures
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