🚀 Weld Strength Calculator & Simulator
- Select Weld Joint Type: Choose between Butt Weld (for parallel member connections) or Fillet Weld (for perpendicular or overlapping connections) from the top tab.
- Configure Weld Dimensions & Electrode: Smoothly adjust the sliders to select the effective weld length (L), weld throat thickness/leg size (a), and electrode tensile strength specification (Exx).
- Apply Tensile/Shear Load: Adjust the load (P) acting on the weld joint to increase the applied pressure in real time.
- Measure Throat Stress & Safety Margin: Measure the effective shear/tensile stress occurring at the center of the joint, and monitor the safety factor (F.S.) and failure visualization according to AISC (American Institute of Steel Construction) standard allowable stresses.
📚 Review Weld Strength Mechanics Formulas & AISC Standard Allowable Strength Commentary ▼
1. Geometric Classification of Welded Joints
Welding is the most robust and integrated mechanical joining method in steel structure fabrication. Depending on the direction of the applied load and the cross-sectional shape, it is typically classified into two main types:
- Butt Weld (Groove Weld): A joint configuration where two plates are aligned on the same plane, with a V- or U-groove prepared and filled with weld metal. The main effective cross-section consists of the plate thickness itself and the weld length, resisting tensile loads.
- Fillet Weld: A method of joining where two steel plates overlap (Lap Joint) or meet in a T-joint, forming a right-triangular weld at the corner. The minimum shear strength is primarily determined by the effective throat thickness, which is the shear failure path along a 45-degree angle.
2. Formulas for Calculating Effective Throat Area
The weakest critical cross-section supporting the load acting on a weld is called the Effective Throat Area (Aw), and is mathematically defined as follows:
- Fillet Weld (Leg Size a, Weld Length L): Because the minimum distance in a triangular cross-section is the height perpendicular to the hypotenuse, the effective throat thickness is calculated by multiplying the leg size by cos(45°) ≈ 0.707.
t_throat = 0.707 × a → A_w = 0.707 × a × L [mm²] - Butt Weld (Plate Thickness t, Weld Length L): Generally, the thickness of the base metal, excluding the reinforcement, is considered the effective throat thickness.
t_throat = t → A_w = t × L [mm²]
3. Allowable Stress and Safety Evaluation of Welds According to AISC Standards
According to the American Institute of Steel Construction (AISC) standards, the strength evaluation of a weld is based on the minimum tensile strength of the electrode (Exx, e.g., E70 is 70 ksi ≈ 482 MPa), adjusted by a safety factor to determine the design allowable stress.
- Allowable Shear Stress for Fillet Welds (τ_allow): Set at 30% of the nominal electrode strength.
τ_allow = 0.30 × E_xx [MPa] - Allowable Tensile Stress for Butt Welds (σ_allow): Set at 60% of the nominal electrode strength.
σ_allow = 0.60 × E_xx [MPa]
If the design strength of the weld is less than the applied stress (Safety Factor F.S. < 1.0), there is a high risk of sliding shear failure initiating at the weld root, leading to complete structural failure. Therefore, non-destructive testing and weld size adjustments are absolutely required.