Concrete · Materials & serviceability

Moment–curvature (RC section) calculator

Full M–φ response of a rectangular RC section: cracking, first yield and ultimate, with curvature ductility.

Standard: Fibre section · Hognestad concrete · bilinear steel

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Diagram for the worked example

Concrete: Hognestad parabola, f″c = 0.9f′c, ε0 = 0.002; steel elastic–perfectly plastic, Es = 200 GPa
For each top strain the neutral axis is found by bisection on ΣN = 0
Mcr = 0.6√f′c·Ig/(D/2); tension stiffening and confinement are ignored

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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.