Built-up Section Calculator
Calculate area, mass, centroid, second moments of area, section moduli, radii of gyration and surface area of welded and built-up plate sections. Export the result as section XML.
Result – Welded I
Area A19,600mm²
Mass per metre153.86kg/m
Centroid (from bottom-left)150.0 / 400.0mm (x̄ / ȳ)
| Parameter | x-axis | y-axis | Unit |
|---|---|---|---|
| Second moment of area I | 2,191.413 | 90.063 | 10⁶ mm⁴ |
| Elastic section modulus Z (min) | 5,478.5 | 600.4 | 10³ mm³ |
| Elastic section modulus Z (top/right) | 5,478.5 | 600.4 | 10³ mm³ |
| Elastic section modulus Z (bottom/left) | 5,478.5 | 600.4 | 10³ mm³ |
| Plastic section modulus S | 6,124.0 | 919.0 | 10³ mm³ |
| Radius of gyration r | 334.4 | 67.8 | mm |
| Principal I1 / I2 | 2,191.413 | 90.063 | 10⁶ mm⁴ |
| Torsion constant JOpen thin-walled approximation Σ b·t³/3 | 1,853.3 | 10³ mm⁴ | |
| External surface area | 2.780 | m²/m | |
| Overall depth × width | 800.0 × 300.0 | mm | |
Method & assumptions
A = Σ Ai ; ȳ = Σ Ai·yi / A ; Ix = Σ (Ix,i + Ai·(yi − ȳ)²) ; Z = I / ymax ; r = √(I / A)
Plates are treated as perfectly joined rectangles; weld metal and corner rounding are neglected.
Plastic modulus S is found numerically from the equal-area axis. Local buckling, effective sections and weld design are outside the scope of this calculator.