Inputs
mm
mm (in bending dir.)
mm to bar centroid
MPa
MPa
distributed in 2 layers
mm
Load Point Check
kN (compression +)
kN·m
Method & assumptions
- Strain compatibility: εc,max = 0.003, β1 per ACI 318.
- Whitney stress block; bars at d′ from compression face, total area split evenly into 2 layers (top & bottom).
- Pn,max capped: tied 0.80·P0, spiral 0.85·P0; P0 = 0.85·f'c·(Ag−Ast) + fy·Ast.
- φ varies: 0.90 if εt≥0.005, 0.65 (tied) or 0.75 (spiral) if εt≤εy, linear interp between.
- Diagram traced by sweeping neutral axis depth c from 0 → ∞ (and tension-controlled side included).
Results
Ag—
Ast (total)—
ρg—
P0 (pure compression)—
φPn,max—
Pure flexure φMn,0—
Balanced point φPn,b / φMn,b—
Demand checkInside