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).
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.
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