Concrete · Beams
Continuous beams and slabs: AS 3600 simplified moment coefficients calculator
Design moments and shears from the AS 3600 coefficients for continuous beams or one-way slabs of near-equal spans, with the conditions for using the method.
Standard: AS 3600-2018 Cl 6.10.2 simplified method · Fd = 1.2g + 1.5q
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 |
|---|---|---|
| Clear span Ln | 6 | m |
| Dead load g (per m, or kPa for slabs) | 25 | kN/m |
| Live load q | 12 | kN/m |
| Number of spans | More than two spans | |
| Discontinuous end | Integral with spandrel beam | |
| Longer / shorter adjacent span | 1.1 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Fd = 1.2g + 1.5q | 48.00 | kN/m |
| Fd·Ln² | 1,728 | kNm |
| Negative at exterior support | 72.00 | kNm |
| Positive in end span | 123.4 | kNm |
| Negative at other interior supports | 157.1 | kNm |
| Positive in interior spans | 108.0 | kNm |
| Shear at first interior support 1.15FdLn/2 | 165.6 | kN |
| Shear elsewhere FdLn/2 | 144.0 | kN |
| Negative at first interior support | 172.8 | kNm |
- ✓ Live load q ≤ 2g
- ✓ Adjacent spans differ by ≤ 20 %
Method, formulas and assumptions
- Fd = 1.2g + 1.5q = 1.2*25+1.5*12 = 48 kN/m
- Fd·Ln² = 48*6^2 = 1728 kNm
- Negative at exterior support = CHOOSE(2,0,1728/24,1728/16) = 72 kNm
- Positive in end span = IF(2=1,1728/11,1728/14) = 123.43 kNm
- Negative at other interior supports = 1728/11 = 157.09 kNm
- Positive in interior spans = 1728/16 = 108 kNm
- Shear at first interior support 1.15FdLn/2 = 1.15*48*6/2 = 165.6 kN
- Shear elsewhere FdLn/2 = 48*6/2 = 144 kN
- Negative at first interior support = IF(3=2,1728/9,1728/10) = 172.8 kNm
- Also required: loads essentially uniformly distributed, members of uniform section, and (for slabs) one-way action. Otherwise analyse with the continuous beam or frame tools.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.