Generates a uniaxial P–M interaction curve for a rectangular column using strain-compatibility.
Reinforcement is modeled as symmetric steel on two opposite faces (tension/compression faces).
Enter (Pu, Mu) to plot demand point and check safe/unsafe.
Uniaxial curve. Biaxial + second-order effects must be checked separately in final design.
For IS/EC2/NBC, “Design curve” uses design stress/strength values. (Nominal option is only for ACI.)
Total bars in model = 2 × (bars per face). Example: 4/face → 8 total.
Provided Ast will be computed from bar dia and bars per face.
Method used (quick)
- Uniaxial strain-compatibility with equivalent rectangular concrete stress block.
- Reinforcement model: total Ast split equally on two opposite faces at cover line.
- Intended for preliminary design / quick checks.
Ready
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Enter inputs to generate the P–M curve.
Provided Ast
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Steel ratio ρ
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Max axial on curve (≈ M=0)
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Peak moment on curve
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Balanced / yield point (approx.)
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M capacity at Pu (if given)
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Utilization (Mu / Mcap)
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Note: This is a uniaxial curve using a simplified reinforcement distribution (two-face model).
For real columns, consider full bar layout, biaxial bending, slenderness/second-order, and detailing rules.