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.

Each plate is a rectangle: x, y = bottom-left corner; w = width; h = height (mm). Plates may touch but not overlap.

#	Name	x	y	w	h	Delete
1
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3

Reset

Export as section XML Designation

Upload the file to data/sections/BUC/ to add it to the library (status CALCULATED).

Preview to scale. Cross-hair = centroid.

Result – Custom Plate Assembly

Area A13,800mm²

Mass per metre108.33kg/m

Centroid (from bottom-left)150.0 / 200.8mm (x̄ / ȳ)

Parameter	x-axis	y-axis	Unit
Second moment of area I	574.893	55.705	10⁶ mm⁴
Elastic section modulus Z (min)	1,947.7	371.4	10³ mm³
Elastic section modulus Z (top/right)	1,947.7	371.4	10³ mm³
Elastic section modulus Z (bottom/left)	2,862.4	371.4	10³ mm³
Plastic section modulus S	2,534.6	621.5	10³ mm³
Radius of gyration r	204.1	63.5	mm
Principal I1 / I2	574.893	55.705	10⁶ mm⁴
Torsion constant JOpen thin-walled approximation Σ b·t³/3	1,226.4		10³ mm⁴
External surface area	1.972		m²/m
Overall depth × width	496.0 × 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.