Fillet Weld Shear Strength
Fillet Weld Shear Strength
Fillet welds are sized on the shear stress across their throat — the smallest plane through the weld.
The effective throat is a = 0.707·s and the shear stress is τ = F/(a·L_w). where s is the leg size, a the throat thickness, F the load and L_w the total weld length.
Inputs
s := 8 mm=8 mm
F := 60 kN=60000 N
L_w := 200 mm=200 mm
The throat is the leg size projected onto the 45° failure plane.
a := 0.707·s=5.66 mm
The shear stress is the load spread over the throat area.
tau := F/(a·L_w)=53.04 MPa
Results
Compare the throat shear with the weld metal’s design strength. Longer welds or a larger leg reduce the stress; note the leg buys throat only at 0.707 efficiency.
Assumptions & limitations
- Concentric load, uniform stress along the weld.
- Equal-leg fillet weld.
- No eccentricity or weld-group rotation.