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Mechanics
Circular Section Properties
Enter values in the stated units. Example inputs are provided to help you explore the method.
Results
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Method & assumptions
- Concentric circular opening; zero inner diameter selects solid. A = π(Do² − Di²)/4; Ix = Iy = π(Do⁴ − Di⁴)/64. A circle has the same centroidal second moment about every in-plane diameter.
- All dimensions in metres. Axes pass through the centroid: x horizontal, y vertical. Centroid coordinates are measured from the bottom-left of the outer bounding box. These are area properties, not mass moments of inertia.
- Sx = Ix/(outer height/2), Sy = Iy/(outer width/2); rx = √(Ix/A), ry = √(Iy/A). The section modulus has dimensions of length cubed, but is not a volume of material.
- Polar area moment Jp = Ix + Iy. It equals the Saint-Venant torsion constant for a circular solid/annulus, not for a rectangle. No rounded corners, eccentric void, strength rating, local buckling or design-code check is included.