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Symmetric T-section properties calculator.

Calculate gross area, centroid, strong- and weak-axis second moments, top and bottom section moduli, and radii of gyration for a centred-web T-section.

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The centroid is not at mid-depth.

A T-section has a flange on one side of the web, so its horizontal centroid shifts toward the flange. That makes the top and bottom section moduli different even though the section is symmetric about its vertical axis.

Governing equations

For overall depth D, flange width B, flange thickness tf, and web thickness tw, the web depth is D - tf and the gross area is A = Btf + tw(D - tf). The centroid follows ȳ = ΣAy/A from the top.

Use the parallel-axis theorem for the strong-axis second moment: Ix = Σ(I + Ad2). The top and bottom moduli are Ztop = Ix/ȳ and Zbottom = Ix/(D - ȳ). The centred vertical-axis property is Iy = tfB3/12 + (D - tf)tw3/12.

Use gross properties carefully.

  • The flange is assumed to be at the top and the web is centred under it.
  • Fillets, tapers, holes, reinforcement, cracking, composite action, and effective properties are not included.
  • Use the top or bottom section modulus that matches the actual bending stress fibre and orientation.