Fillet Weld Check (Eurocode 3)
Perform a quick stress check for a weld following Eurocode 3.
Parameters explained
| Parameter name | Symbol | Unit | Info text |
|---|---|---|---|
| Weld length | L | mm | Overall length of the fillet weld. The effective length used in calculations may be subject to reductions (e.g., for end craters or long weld effects). |
| Plate thickness | t | mm | Thickness of the plates being joined. A minimum plate thickness of 4 mm is recommended. |
| Throat thickness | a | mm | Effective throat thickness of the weld. This is the critical dimension for strength calculations (min. 3mm is recommended). For equal leg 90° welds, a ≈ 0.707z (where z is leg length). |
| Length reduction factor | βred | - | Factor applied to account for non-uniform stress distribution in long welds (e.g., βLw1 for connections > 150a or βLw2 for welds > 1.7m on transverse stiffeners). Applied if weld length reduction is specified. |
| Applied forces | Fx,Ed, | kN | Design force components along the defined X, Y, Z input axes. These are resolved into normal (σ⊥) and shear (τ⊥, τ∥) stresses on the weld throat. |
| Applied moments | Mx,Ed, My,Ed, Mz,Ed | kNm | Design moment components about the defined X, Y, Z input axes. These are resolved into normal (σ⊥) and shear (τ⊥, τ∥) stresses on the weld throat. |
| Yield stress | fy | N/mm² | Nominal yield strength of the weaker of the two parent materials being joined. |
| Ultimate tensile stress | fu | N/mm² | Nominal ultimate tensile strength of the weaker parent material. This value is critical for determining the weld's design strength. |
| Correlation factor | βW | - | Correlation factor for fillet welds, dependent on the steel grade of the parent material (e.g., S235: 0.8, S275: 0.85, S355: 0.9). Refer to EN 1993-1-8, Table 4.1. |
| Partial safety factor | γM2 | - | Partial safety factor for the resistance of welds. Typically 1.25 according to EN 1993-1-8, but always verify the value specified in the relevant National Annex. |
| Parallel shear stress | τ∥ | N/mm² | The calculated shear stress component in the weld's throat plane acting parallel to the longitudinal axis of the weld. |
| Perpendicular shear stress | τ⊥ | N/mm² | The calculated shear stress component in the weld's throat plane acting perpendicular to the longitudinal axis of the weld. |
| Perpendicular normal stress | σ⊥ | N/mm² | The calculated normal stress component acting perpendicular to the plane of the weld's throat. |
| Design weld resistance (combined stress) | - | - | The weld must satisfy the condition: √(σ⊥2 + 3(τ⊥2 + τ∥2)) ≤ fu / (βWγM2). This is the primary check for combined stresses according to EN 1993-1-8. |
| Design weld resistance (normal stress limit) | - | - | The normal stress perpendicular to the throat must also satisfy: σ⊥ ≤ 0.9 fu / γM2, according to EN 1993-1-8. |
| Unity check | UC | - | The ratio of the calculated design stress (or combination of stresses) to the design resistance. A value less than or equal to 1.0 indicates that the weld design is acceptable under the given loads. |