📋 Input Parameters
📐 Section Geometry
| Diameter D | mm | |
| Unsupported Length L (for emin, Cl. 25.4) | m | |
| Effective Length Le (for slenderness, Cl. 25.1.2) | m |
🔩 Reinforcement
| Main Bar Diameter (φ) | mm | |
| Number of Bars (N) | — | |
| Nominal Clear Cover to Ties | mm | |
| Tie Bar Diameter (φt) | mm | |
| Tie Arrangement | — |
🧱 Materials
| Concrete Grade (fck) | MPa | |
| Steel Grade (fy) | MPa |
⚡ Applied Loads (Factored)
| Axial Load Pu | kN | |
| Moment Mux (about any axis) | kNm | |
| Moment Muy (orthogonal axis) | kNm |
📊 Design Summary
| Diameter D | — | mm |
| Factored Load Pu | — | kN |
| Steel Area Asc provided | — | mm² |
| Steel Percentage pt | — | % |
| Minimum Asc (0.8% Ag) | — | mm² |
| Effective Cover d′ (= c + φt + φ/2) | — | mm |
| Reinforcement Detail | — | |
| Tie & Pitch | — | |
| Bar Periphery Spacing | — | mm |
| Applied Resultant Moment Mu,res | — | kNm |
| Design Moment Mu,des (incl. emin & slenderness) | — | kNm |
| Uniaxial Capacity Mu1 at Pu | — | kNm |
| Utilisation (Mu,des / Mu1) | — | — |
⬛ Cross-Section & Bar Layout
Main bars
Lateral ties
Cover zone
Pitch circle
⚡ Section Properties & Capacity
| Parameter | Value | Unit |
|---|---|---|
| Gross area Ag = π D²/4 | — | mm² |
| Total bar area Asc | — | mm² |
| Steel ratio pt | — | % |
| Eff. cover d′ = c+φt+φ/2 | — | mm |
| Pitch-circle radius Rp = R − d′ | — | mm |
| Puz = 0.45fckAc+0.75fyAsc | — | kN |
| Pu/Puz | — | — |
| Pub @ Cl. 39.7.1.1 balanced | — | kN |
| Mu1 at applied Pu | — | kNm |
📐 Slenderness & Design Moment (Cl. 25.4, 39.7)
| Parameter | Value | Unit |
|---|---|---|
| Slenderness λ = Le/D | — | — |
| Column type | — | — |
| Min eccentricity emin | — | mm |
| Mmin = Pu·emin | — | kNm |
| Applied Mres = √(Mux²+Muy²) | — | kNm |
| Mprimary = max(Mres, Mmin) | — | kNm |
| Ma,raw (Cl. 39.7.1, k=1) | — | kNm |
| k factor (Cl. 39.7.1.1) | — | — |
| Ma = k · Ma,raw | — | kNm |
| Mu,des = Mprimary + Ma | — | kNm |
📖 SP:16 Normalised
| Parameter | Value |
|---|---|
| p / fck | — |
| Pu / (fck·D²) | — |
| Mu,des / (fck·D³) | — |
| d′ / D | — |
📈 P-M Interaction Diagram (Strain Compatibility, IS 456 Cl. 38.1)
✅ Codal Checks — IS 456 : 2000
| Check & IS 456 Reference | Provided | Limit | Result |
|---|---|---|---|
| Enter inputs to evaluate | |||
Engineering Notes — IS 456 : 2000 : Limit-State method for solid circular columns. Capacity computed by strain-compatibility integration over the cross-section using the rectangular-parabolic concrete stress block (Cl. 38.1) and SP:16 Annex / Table A design stress-strain curves for HYSD steel. Reinforcement modelled as discrete bars on the pitch circle (not smeared) for accurate behaviour at low bar counts. Biaxial moments combined as resultant √(Mux²+Muy²) — valid for rotationally-symmetric circular sections where Mu1 is direction-independent. Additional moments for slender columns per Cl. 39.7.1, with reduction factor k per Cl. 39.7.1.1 using Pub defined by the code's strain condition (εc=0.0035, εs=0.002 at outermost tension steel) — not the peak-M point.
Scope & assumptions:
• Slenderness: Single effective length Le is assumed equivalent about both principal axes. For frame columns with differing Lex / Ley, end conditions, or sway behaviour about each axis, additional moments should be computed axis-wise and combined externally.
• Helical reinforcement: The 1.05× strength enhancement of Cl. 39.4 (which applies only to short axially-loaded columns with e ≤ 0.05D meeting the volumetric helical ratio of Cl. 39.4.1) is not applied. Treatment is conservative — strength evaluated as for a tied column.
• Seismic detailing: Confinement / hinge-zone tie spacing per IS 13920 is outside this tool's scope.
Results are for verification only; final design must be checked by a licensed structural engineer.
Scope & assumptions:
• Slenderness: Single effective length Le is assumed equivalent about both principal axes. For frame columns with differing Lex / Ley, end conditions, or sway behaviour about each axis, additional moments should be computed axis-wise and combined externally.
• Helical reinforcement: The 1.05× strength enhancement of Cl. 39.4 (which applies only to short axially-loaded columns with e ≤ 0.05D meeting the volumetric helical ratio of Cl. 39.4.1) is not applied. Treatment is conservative — strength evaluated as for a tied column.
• Seismic detailing: Confinement / hinge-zone tie spacing per IS 13920 is outside this tool's scope.
Results are for verification only; final design must be checked by a licensed structural engineer.