Structural Load Capacity Calculator
Calculate the axial compressive load capacity of steel or concrete columns using standard structural engineering formulas (AISC / ACI 318).
Results will appear here.
Formulas Used
Steel Column — AISC LRFD (Chapter E):
- Elastic Buckling Stress: Fe = π²E / (KL/r)²
- Limit slenderness: 4.71√(E/Fy)
- Inelastic: Fcr = 0.658^(Fy/Fe) × Fy when KL/r ≤ 4.71√(E/Fy)
- Elastic: Fcr = 0.877 × Fe when KL/r > 4.71√(E/Fy)
- Nominal: Pn = Fcr × A
- Design: φPn = 0.90 × Pn
Concrete Column — ACI 318-19 (Section 22.4.2):
- Tied: Pn = 0.80 [0.85 f'c (Ag − Ast) + fyt Ast], φ = 0.65
- Spiral: Pn = 0.85 [0.85 f'c (Ag − Ast) + fyt Ast], φ = 0.75
Assumptions & References
- Steel calculations follow AISC 360-22 LRFD method, Chapter E (Compression Members).
- Concrete calculations follow ACI 318-19, Section 22.4.2 (Axial Strength).
- Steel column is assumed to be a doubly-symmetric compact section with uniform cross-section.
- Effective length factor K is already incorporated into the input KL (effective length).
- Concrete column is assumed to be short (no slenderness effects); long columns require moment magnification per ACI 318-19 Chapter 6.
- ACI 318-19 limits longitudinal steel ratio to 1% ≤ ρ ≤ 8%.
- All units: forces in N (inputs in MPa and mm²); results displayed in kN.
- No reduction for sustained loads, creep, or second-order effects is applied.