Area, centroid, moment of inertia, section moduli and radius of gyration — general shapes, KS H-beams and bridge girder sections. Exact polygon integration (Green's theorem).
GENERAL SECTIONS
BRIDGE SECTIONS
KS STANDARD SIZE (H-BEAM)
RESULTS
Sharp-corner model: fillets/root radii are not included, so H-beam values sit 1–3% below catalogue figures that include them. Plastic modulus Zx is about the horizontal equal-area axis. Preliminary use only.
Field notes — what to watch for
For bending, the section modulus S is the number that matters, not I alone — and for asymmetric sections like a PSC girder, always check which fibre governs: the bulb pulls the centroid down, so the bottom modulus usually controls at release and the top in service. When comparing steel shapes, weight per metre is the honest denominator — an efficient section is the one with the most S per kg. Catalogue H-beam values include root fillets; this tool models sharp corners, so expect its inertia to sit 1–3% low.