Use this circular weld group properties calculator to calculate the geometric properties of a circular fillet weld group. The calculator determines weld length, effective throat thickness, total effective throat area, centroid position and polar moment of inertia.
This calculator calculates the geometric properties of a circular weld group. Circular weld groups are commonly used for pipe attachments, bosses, round plates, nozzles, collars and welded circular connections.
The calculator provides:
These results are commonly used as the starting point for circular weld group stress calculations involving direct shear, eccentric loading or torsion.
Total weld length / circumference:
Effective throat thickness:
Total effective throat area:
Equivalent throat area formula:
Centroid location:
Unit-line polar moment of inertia:
Throat polar moment of inertia:
| Symbol | Description | Units |
|---|---|---|
| r | Radius to weld centreline | mm |
| h | Fillet weld size | mm |
| a | Effective throat thickness | mm |
| L | Total circular weld length | mm |
| A | Total effective throat area | mm² |
| x̄, ȳ | Centroid position relative to centre of circle | mm |
| J | Unit-line polar moment of inertia | mm³ |
| Ja | Throat polar moment of inertia | mm&sup4; |
Enter the circular weld group dimensions and click calculate.
| Result | Meaning |
|---|---|
| Total weld length | The circumference of the circular weld group measured around the weld centreline. |
| Effective throat thickness | The theoretical effective throat thickness of the fillet weld, calculated as 0.707 times the weld size. |
| Total effective throat area | The effective weld area based on the circular weld length and effective throat thickness. |
| Centroid position | For a complete circular weld group, the centroid is located at the centre of the circle. |
| Unit-line polar moment of inertia | A weld group property used in torsional stress calculations when welds are treated as lines. |
| Throat polar moment of inertia | The polar moment adjusted for effective throat thickness. |
This calculator determines geometric properties for a complete circular fillet weld group. It does not calculate final weld stress, resultant stress, utilisation or pass/fail strength checks.
| This Calculator Includes | This Calculator Does Not Include |
|---|---|
| Weld circumference | Applied force inputs such as Vx or Vy |
| Effective throat area | Applied moments or torsion inputs such as M or T |
| Centroid location | Resultant weld stress calculation |
| Unit-line polar moment and throat polar moment | Pass/fail weld strength check |
| Complete circular weld group properties | Partial circular welds, intermittent welds or non-circular weld groups |
For a simple direct shear weld strength check, use the Fillet Weld Strength & Size Calculator.
This calculator is intended for a complete circular fillet weld group. The weld radius should be measured to the centreline of the weld. The total weld length is calculated from the circumference of the circular weld group.
The effective throat area is calculated from the total weld length and the effective throat thickness. The polar moment of inertia is calculated using the standard circular weld group property formula for welds treated as lines.
For circular weld group stress calculations involving applied shear loads or torsion, a separate circular weld group stress calculator should be used.
To calculate the effective throat area of a simple straight fillet weld, use the Weld Throat Area Calculator.
For further weld strength formulae and weld group properties, see the RoyMech reference page: Weld Strength Formulae and Weld Group Properties.
A circular weld group is a weld arrangement where the weld follows a circular path. It is commonly used for pipe attachments, bosses, nozzles, collars, round plates and circular welded connections.
The total weld length for a complete circular weld is calculated from the circumference:
where r is the radius to the weld centreline.
The total effective throat area is calculated as:
where a is the effective throat thickness. Since a = 0.707h, this can also be written as:
For a complete circular weld group, the centroid is located at the centre of the circle.
For a circular weld group treated as a line, the unit-line polar moment of inertia is:
No. This calculator calculates circular weld group geometric properties such as weld length, throat area and polar moment of inertia. These properties can then be used in later weld stress and strength calculations.