Concrete · Beams
RC beam (flexure + shear) calculator
Singly reinforced rectangular beam: tension steel, ductility and shear with stirrups.
Standard: AS 3600-2018 Cl 8.1, 8.2
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Span (simply supported) | 7 | m |
| Width b | 300 | mm |
| Depth D | 600 | mm |
| Cover | 40 | mm |
| Stirrup diameter | 10 | mm |
| Main bar diameter | 24 | mm |
| Stirrup spacing | 200 | mm |
| f'c | 32 | MPa |
| fsy (main) | 500 | MPa |
| fsy.f (stirrups) | 500 | MPa |
| Dead load (excl. self-wt) | 20 | kN/m |
| Live load | 12 | kN/m |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| d | 538 | mm |
| w* | 47.4 | kN/m |
| M* | 290 | kNm |
| V* | 166 | kN |
| Ast required | 1,386 | mm² |
| Provide | 4 N24 (1,810 mm²) | |
| φMu | 369 | kNm |
| ku | 0.257 | |
| φVuc (concrete) | 92.4 | kN |
| φVu (with stirrups) | 289 | kN |
| φVu.max (web crushing) | 912 | kN |
- ✓ Flexure M* ≤ φMu
- ✓ Ductility ku ≤ 0.36
- ✓ Shear V* ≤ φVu
- ✓ Asv ≥ Asv.min — 157 vs 54 mm²
- ✓ Bars fit in one layer
Method, formulas and assumptions
- w* = 1.2(G + 25bD) + 1.5Q = 47.4 kN/m; M* = w*L²/8, V* = w*L/2
- Rectangular stress block α2 = 0.802, γ = 0.850, φ = 0.85
- Ast,min = 0.20(D/d)² f'ct,f/fsy · bd = 273 mm²
- Simplified shear (Cl 8.2.4.3): kv = 0.15, θv = 36°, dv = max(0.72D, 0.9d) = 484 mm
- Vuc = kv bv dv √f'c; Vus = (Asv fsy.f dv / s) cot θv; φ = 0.75
- Vu.max = 0.55 f'c bv dv cotθ/(1 + cot²θ)
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.