steelWelds

Analyze and design fillet weld and butt weld connections to AS 4100:1998. Resolves combined shear and tension into force per unit length of weld and checks against the design capacity with the appropriate reduction factors.

This calculator uses an earlier code edition (AS4100:1998 (R2016)). It stays available for existing projects. For new designs, check the [Calculator Library](/docs/calculators/au) for the current edition. ## Method & scope | Property | Detail | | -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------ | | What it checks | Force per unit length, Weld capacity (Clause 9.7), Reduction factor for lap connections (k\_r), Design capacity, Utilization check, Design notes | #### Calculation method The Weld Connection (AS 4100:1998) calculator checks fillet and butt weld connections against Clause 9.7 of AS 4100:1998. Given the total shear and tension forces on the connection and the weld geometry, it resolves the demand into force per unit length and compares it to the design capacity. ##### Force per unit length The total applied shear force V\_w and tension (or compression) force N\_w 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 The resultant design force per unit length of weld: **v\*\_w = sqrt(tau\_w^2 + sigma\_w^2)** ##### Weld capacity (Clause 9.7) The nominal capacity per unit length v\_w depends on the weld type: **Fillet weld:** v\_w = 0.6 × f\_uw × t\_t × k\_r where: * f\_uw = nominal tensile strength of the weld metal (MPa) * t\_t = throat thickness of the fillet weld (mm) * k\_r = reduction factor for the length of the lap connection **Butt weld:** v\_w = f\_ub × t\_t where f\_ub = nominal tensile strength of the base metal. ##### Reduction factor for lap connections (k\_r) For lap connections, the force distribution along the weld becomes less uniform as the connection length increases. AS 4100 applies a reduction factor: * l\_w ≤ 1700 mm: k\_r = 1.10, 0.06 × (l\_w / 1000) * l\_w > 8000 mm: k\_r = 0.62 * Otherwise (1700 mm \< l\_w ≤ 8000 mm): linear interpolation For non-lap connections, k\_r = 1.0. ##### Design capacity The design capacity per unit length of weld is: v\_d = phi × v\_w The capacity factor phi for weld connections to AS 4100:1998 is: * phi = 0.8 for fillet welds (SP category) * phi = 0.9 for butt welds (SP category) ##### Utilization check **Utilization** = v\*\_w / v\_d ≤ 1.0 When the utilization ratio exceeds 1.0, the weld is overstressed. The throat thickness, weld length, or applied loading must be adjusted. ##### Design notes This calculator checks the weld at a single cross-section under uniform loading. For weld groups with moment or torsion, the peak demand location should be identified separately and the maximum force per unit length at that location used as the input. Detailing requirements (minimum throat thickness, end returns, etc.) must be verified by the engineer per AS 4100:1998 Clause 9.8. ## How to use it Open it from **Run calc** in the About this calculator panel above. 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](/docs/running-calculations/checking-results/checks-references-conditions-assumptions). Check the utilization of each governing check in the summary, then export a PDF report. See [Views and Export](/docs/running-calculations/exporting-reports/views-and-export). ## Common questions This calculator checks weld connections to AS 4100:1998 (R2016), Clause 9.7. 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 loads. Key inputs are the weld type (fillet or butt weld), throat thickness, effective weld length, weld metal nominal tensile strength f\_uw, base metal tensile strength f\_ub, total shear force on the connection, and total tension force on the connection. For lap connections, the connection length determines the reduction factor k\_r. The calculator resolves the total shear and tension forces into force per unit length components (tau\_w and sigma\_w), computes the resultant design force per unit length v\*\_w = sqrt(tau\_w^2 + sigma\_w^2), and checks this against the design capacity v\_d = phi × v\_w. The capacity factor phi and reduction factor k\_r for long lap connections are reported alongside the utilization ratio. Yes. For connections where the weld group carries both shear and axial (tension or compression) forces, the shear force component tau\_w = V\_w / l\_w and tension component sigma\_w = N\_w / l\_w are combined using the square root of the sum of squares. This approach applies to the weld at the point of highest demand along the effective length. The weld metal tensile strength f\_uw is entered directly in MPa, so any electrode classification can be used. For common Australian electrodes, E48XX corresponds to f\_uw = 480 MPa. The base metal tensile strength f\_ub sets an upper limit on the butt weld capacity. ## Next steps Complete list of Calcs.com design calculators available for Australian and New Zealand projects (AS 3600, AS 4100, AS 1720, AS/NZS 1170, and related standards). Analyze and design weld connections to AS 4100:2020, Cl 9.6. Checks fillet weld and butt weld capacity under combined shear and tension force per unit length. Design and analyze steel bolt connections to AS 4100:2020. Supports arbitrary bolt layouts with shear, tension, bearing, and friction serviceability checks. Design bolt groups under shear, tension and combined loading to AS 4100:1998 (R2016). An earlier code edition, kept for existing projects. 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