Steel · Members & beams
SHS / RHS beam: bending & shear calculator
Section modulus and compactness of a rectangular hollow section in major-axis bending, web shear capacity and deflection under UDL.
Standard: AS 4100 Cl 5.2, 5.11 (cold-formed RHS limits)
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 |
|---|---|---|
| Width b | 100 | mm |
| Depth d | 200 | mm |
| Thickness | 6 | mm |
| fy | 350 | MPa |
| Span | 5 | m |
| Design UDL | 12 | kN/m |
| Service UDL | 8 | kN/m |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Ix | 17,939,072 | mm⁴ |
| Zx | 179,391 | mm³ |
| Sx | 222,432 | mm³ |
| Flange λe (b − 2t)/t √(fy/250) | 17.35 | |
| Web λe | 37.07 | |
| Ze (compact λf ≤ 30, λw ≤ 82; linear to λy 40/115) | 222,432 | mm³ |
| φMs | 70.07 | kNm |
| M* = wL²/8 | 37.50 | kNm |
| φVu = 0.9·0.6 fy·2(d − 2t)t | 426.4 | kN |
| V* | 30.00 | kN |
| Deflection | 18.15 | mm |
| L/250 | 20.00 | mm |
- ✓ Bending
- ✓ Shear
- ✓ Deflection
Method, formulas and assumptions
- Ix = (100*200^3-(100-2*6)*(200-2*6)^3)/12 = 1.794e+7 mm⁴
- Zx = 2*1.794e+7/200 = 1.794e+5 mm³
- Sx = 100*200^2/4-(100-2*6)*(200-2*6)^2/4 = 2.224e+5 mm³
- Flange λe (b − 2t)/t √(fy/250) = (100-2*6)/6*SQRT(350/250) = 17.354
- Web λe = (200-2*6)/6*SQRT(350/250) = 37.074
- Ze (compact λf ≤ 30, λw ≤ 82; linear to λy 40/115) = IF(AND(17.354<=30,37.074<=82),MIN(2.224e+5,1.5*1.794e+5),IF(AND(17.354<=40,37.074<=115),1.794e+5+MIN((40-17.354)/10,(115-37.074)/33,1)*(MIN(2.224e+5,1.5*1.794e+5)-1.794e+5),1.794e+5*MIN(40/17.354,1))) = 2.224e+5 mm³
- φMs = 0.9*350*2.224e+5/1E6 = 70.066 kNm
- M* = wL²/8 = 12*5^2/8 = 37.5 kNm
- φVu = 0.9·0.6 fy·2(d − 2t)t = 0.9*0.6*350*2*(200-2*6)*6/1000 = 426.38 kN
- V* = 12*5/2 = 30 kN
- Deflection = 5*8*(5*1000)^4/(384*200000*1.794e+7) = 18.146 mm
- L/250 = 5*1000/250 = 20 mm
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.