Concrete Column Design
Reinforced concrete columns per ACI 318-19 — rectangular tied and circular spiral sections under axial load with uniaxial or biaxial bending. Full P-M interaction by strain compatibility, Bresler reciprocal and PCA load-contour biaxial checks, non-sway slenderness magnification (§6.6.4) and detailing limits — with the interaction diagram and demand point. US units (kips, kip·ft, psi, in).
Axial-flexure interaction Ch. 22 · biaxial
| φPn,max | 1,115.9 k | 0.65·0.80·Po |
| φMnx at Pu | 324.9 k·ft | |
| Demand Mx | 300.0 k·ft | |
| Bresler φPn | 739.3 k | Pu 700.0 |
| Utilisation | 0.95 |
Detailing §10.6 / §25.7
| ρg (0.01–0.08) | 2.00% | Ast 8.0 in² |
| Bars / min | 8 / 4 | |
| Tie spacing | 18 in |
Section properties Rect
| Ag | 400 in² | |
| Po (nominal) | 2,146 k | §22.4.2.2 |
| Ec | 4,031 ksi |
ACI 318-19 (LRFD). Rectangular tied and circular spiral columns — uniaxial & biaxial P-M interaction (Ch. 22 strain compatibility, Bresler reciprocal / PCA load contour), non-sway slenderness magnification (§6.6.4) and detailing limits (§10.6/§10.7/§25.7). Sway (Δ) magnification, second-order frame analysis, shear/tie design for shear, and connection/splice design are not included. Factored demands and effective length are user inputs. A licensed P.E. review remains required.