Weld group
mm
mm
Forces at the load point
kN
kN
kN
Load point from the weld centroid
mm
mm
mm
Extra moments about the centroid
kN·m
kN·m
kN·m
Check
Material
Stress in fillet weld groups – line, two lines, rectangle, C-shape and circle – under shear, axial force, torsion and bending, with the critical point found along the whole weld. Checked by EN 1993-1-8 (directional and simplified) or AISC 360 (ASD and LRFD).
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The welds are treated as lines with the effective throat a (the elastic line-weld method of Shigley and Blodgett). The group's length, centroid and second moments Ix, Iy, Ixy and J = Ix + Iy are integrated exactly over each straight segment and the circle. Forces act at the load point you give, so their moments about the centroid (r × F) are added to any moments you enter. At every point along the welds – about 200 per segment, plus every end and corner – the stress vector is the sum of direct shear, torsion, axial stress and bending stress; the full Ix–Iy–Ixy matrix is used (all groups offered here are at least mono-symmetric, so Ixy = 0, but loads off the axes are still resolved correctly).
Use design (factored) loads with EN 1993-1-8 and AISC LRFD, service loads with AISC ASD. γM2 = 1.25 is the recommended value; check your National Annex. The directional method assumes a 90° equal-leg fillet joining a member perpendicular to the weld plane (a bracket, plate or tube welded to a face); for each point the worse of the two possible throat orientations is used, so its utilization is the same as or up to about 13 % lower than the simplified method's – never higher. The components shown (σ⊥, τ⊥, τ∥) are those of that governing orientation; the separate σ⊥ ≤ 0.9 fu/γM2 check uses the larger σ⊥ of the other orientation. Clauses and fu values follow EN 1993-1-8:2005 and EN 1993-1-1 Table 3.1 for t ≤ 40 mm; some National Annexes use the product-standard fu (for example S355 470 MPa). The AISC check uses the basic strength without the (1 + 0.5 sin1.5θ) increase for loads at an angle, which is conservative.
Not checked: the base metal next to the weld, the strength of the connected parts, minimum and maximum weld sizes, effective length rules and end returns, the long-joint reduction (EN 1993-1-8 4.11, welds longer than 150a), plastic or instantaneous-centre methods (which give higher capacity for eccentric loads), fatigue, and weld quality.
This calculator checks fillet weld groups – a single line, two parallel lines, a rectangle all round, a C-shape on three sides and a circle – under any combination of in-plane shear forces, a normal force, torsion and bending. Forces can act away from the weld centroid, so a bracket load with its lever arm is handled directly. It finds the most stressed point along the whole weld, shows the stress components there and checks them by EN 1993-1-8 (directional or simplified method) or AISC 360 (ASD or LRFD).
The critical point is the corner where direct shear and torsion add up; utilization 15.5 % by the EN simplified method. These numbers are reference case WELD-001 on the verification page.
The effective throat a is the height of the largest triangle that fits in the weld cross-section, measured from the root. For a 90° fillet with equal legs z, a = z/√2 ≈ 0.707 z, so a 6 mm leg gives a 4.2 mm throat. Design codes work with the throat; drawings often give the leg (z) or the throat (a) – check which.
Where the direct shear and the stress from torsion or bending add up – usually the corner or end farthest from the centroid on the side the load pushes towards. The calculator checks about 200 points along every segment plus all ends and corners, so it also finds less obvious peaks in C-shapes and circles.
Both are allowed. The simplified method compares the resultant stress with fvw,d = fu/(√3·βw·γM2) regardless of direction and is quick and conservative. The directional method splits the stress into σ⊥, τ⊥ and τ∥ on the throat and usually gives a little more capacity, especially for welds loaded across their length.
The nominal strength is Fnw = 0.60 FEXX = 42 ksi (290 MPa) for E70. With LRFD φ = 0.75 the design stress is 31.5 ksi (217 MPa); with ASD Ω = 2.00 the allowable is 21 ksi (145 MPa). Use factored loads with LRFD and service loads with ASD.
It assumes the weld stays elastic, so the first point to reach the limit governs. Real welds redistribute load, and the instantaneous-centre method in AISC tables allows for that and gives higher capacity for eccentric brackets. The elastic method is still the common hand method in Europe and safe for design.
No. The base metal next to the weld, the connected plate or member, minimum weld size for the plate thickness, weld length rules and fatigue all need separate checks. A strong weld on a thin plate can still fail in the plate.
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