AustraliaAS 4100:2020
Analyze and design fillet weld and butt weld connections to AS 4100:2020. Resolves combined shear and tension into force per unit length of weld and checks against the design capacity with weld quality and reduction factors per Cl 9.6.
The Calcs.com Weld Connection Calculator to AS 4100:2020 enables the easy analysis and design of weld connections to AS 4100:2020, Cl 9.6.
Method & scope
Calculation method
The Weld Connection (AS 4100:2020) calculator checks fillet and butt weld connections against Clause 9.6 of AS 4100:2020. The calculator resolves total applied shear and tension forces into force per unit length of weld and compares the resultant demand against the design capacity.Force per unit length
Total applied forces are distributed over the effective weld length l_w:- Shear force per unit length: tau_w = V_w / l_w
- Tension force per unit length: sigma_w = N_w / l_w
Weld capacity (Clause 9.6)
The nominal capacity per unit length v_w depends on the weld type: Fillet weld (SP quality): v_w = 0.6 × f_uw × t_t × k_r RHS fillet weld: v_w = 0.6 × f_uw × t_t × k_r (with a modified capacity factor) Butt weld: v_w = f_ub × t_t where:- f_uw = nominal tensile strength of the weld metal (MPa)
- f_ub = nominal tensile strength of the base metal (MPa)
- t_t = design throat thickness (mm)
- k_r = reduction factor for lap connection length
Reduction factor for lap connections (k_r)
For lap connections, the reduction factor k_r accounts for non-uniform force distribution along long welds:- l_w ≤ 1700 mm: k_r = 1.10, 0.06 × (l_w / 1000)
- 1700 mm < l_w ≤ 8000 mm: linear interpolation
- l_w > 8000 mm: k_r = 0.62
Capacity factor (phi)
The capacity factor phi depends on the weld type and quality category per AS 4100:2020:- SP fillet weld: phi = 0.8
- SP butt weld: phi = 0.9
- GP weld category: phi = 0.7
Utilization check
Utilization = v*_w / v_d ≤ 1.0 If the utilization ratio exceeds 1.0, the weld is overstressed. Adjustments can be made by increasing the throat thickness, increasing the weld length, or reducing the applied loading.Scope and limitations
This calculator checks a single weld cross-section under uniform force per unit length. For weld groups carrying bending moment or torsion (such as in eccentric connections), the peak demand at the most stressed point in the group should be determined first and entered as the governing input forces. Minimum weld sizes and end return requirements per AS 4100:2020 Clause 9.7 must be verified separately.How to use it
1
Open the calculator
Open it from Run calc in the About this calculator panel above.
2
Enter your inputs
Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See Checks, References, Conditions and Assumptions.
3
Review the results and export
Check the utilization of each governing check in the summary, then export a PDF report. See Views and Export.
Common questions
What design code does this calculator use?
What design code does this calculator use?
This calculator checks weld connections to AS 4100:2020, Clause 9.6. It evaluates the design force per unit length of weld against the capacity per unit length for fillet welds and butt welds under combined shear and tension loading per the current Australian standard.
What are the key inputs?
What are the key inputs?
Key inputs are the weld type (fillet weld, butt weld, or RHS fillet), throat thickness, effective weld length, weld metal nominal tensile strength f_uw, base metal tensile strength f_ub, weld quality category (SP or GP), total shear force on the connection, and total tension force on the connection.
What does the calculator check and output?
What does the calculator check and output?
The calculator computes the design force per unit length v_w = sqrt(tau_w^2 + sigma_w^2) and compares it against the weld design capacity v_d = phi × v_w. Outputs include the shear component tau_w, tension component sigma_w, resultant demand v_w, nominal capacity v_w, reduction factor k_r for lap connections, capacity factor phi, and the governing utilization ratio.
Can it handle fillet welds under combined shear and bending?
Can it handle fillet welds under combined shear and bending?
Yes. When the weld carries simultaneous shear and tension or compression (as is typical in beam-column connections, bracket plates, and gusset plates), the shear and tension force per unit length are resolved using the square root of the sum of squares formula. This gives the resultant weld demand at the critical cross-section.
What weld electrode classifications are supported?
What weld electrode classifications are supported?
The weld metal tensile strength f_uw is entered directly in MPa, so any AS/NZS 2980-classified electrode can be used. Common values: E48XX = 480 MPa, E55XX = 550 MPa. The weld quality category (SP or GP) affects the capacity factor phi per AS 4100:2020.
Next steps
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