Fillet Weld Capacity

A fillet weld fails across its throat, and the codes turn that into an available strength: AISC 360 as 0.60 FEXX on the effective throat with φ = 0.75 (LRFD) or Ω = 2.00 (ASD), and Eurocode as fu / (√3 βw γM2).

Strength is rarely what limits a fillet. On a lightly loaded joint the minimum leg for the plate thickness usually governs, and that minimum is about cooling rate, not load. Size for both below.

Weld and load

Effective throat
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Available strength
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Same, in kip
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Utilisation
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Leg needed for the load
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Per 100 mm of weld
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Size limits — AISC 360 §J2.2b

The minimum leg (Table J2.4) is set by the thinner part joined, and need not exceed that part's thickness. Along an edge the leg may be the full thickness under 6 mm, and must stop 2 mm short of it from 6 mm up.

Minimum leg
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Maximum leg along the edge
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Your leg
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Equal-leg 90° fillets in direct shear, checked on the weld metal only — AISC also requires the base metal to be checked in shear rupture, and Eurocode's directional method can give more for transverse welds. Minimum sizes assume no qualified procedure permits smaller. A helper, not a substitute for engineering judgment or the governing code.