Steel · Connections: bolts & welds
Load-bearing web stiffener calculator
Bearing yield of web plus stiffener pair, and buckling of the stiffener with the effective web strip as a column of length d1.
Standard: AS 4100 Cl 5.14
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 |
|---|---|---|
| Concentrated load R* | 900 | kN |
| Web thickness | 9.1 | mm |
| Clear web depth | 428 | mm |
| Web fy | 320 | MPa |
| Stiffener outstand (each side) | 85 | mm |
| Stiffener thickness | 12 | mm |
| Stiffener fy | 300 | MPa |
| Stiff bearing width bbf | 160 | mm |
| Flange restraint | Restrained against rotation (le = 0.7 d1) |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Stiffener area | 2,040 | mm² |
| φRsy = 0.9(1.25 bbf tw fy + As fys) | 1,075 | kN |
| Web strip each side 17.5 tw/√(fy/250) | 107.0 | mm |
| Effective area | 3,987 | mm² |
| I of stiffener section | 5,744,957 | mm⁴ |
| r | 37.96 | mm |
| Effective length | 299.6 | mm |
| λn = (le/r)√kf √(fy/250) | 8.65 | |
| αa | -5.12 | |
| λ = λn + αa·αb | 6.09 | |
| η | 0.000 | |
| ξ | 109.8 | |
| Slenderness reduction αc | 1.00 | |
| φRsb = 0.9 αc Ae fy | 1,077 | kN |
- ✓ Yield
- ✓ Buckling
- ✓ Outstand ≤ 15 ts √(250/fy)
Method, formulas and assumptions
- Stiffener area = 2*85*12 = 2040 mm²
- φRsy = 0.9(1.25 bbf tw fy + As fys) = 0.9*(1.25*160*9.1*320+2040*300)/1000 = 1075 kN
- Web strip each side 17.5 tw/√(fy/250) = MIN(17.5*9.1/SQRT(320/250),428/4) = 107 mm
- Effective area = 2040+2*107*9.1 = 3987.4 mm²
- I of stiffener section = 12*(2*85+9.1)^3/12 = 5.745e+6 mm⁴
- r = SQRT(5.745e+6/3987.4) = 37.958 mm
- Effective length = IF(1=1,0.7,1)*428 = 299.6 mm
- λn = (le/r)√kf √(fy/250) = 299.6/37.958*SQRT(1)*SQRT(300/250) = 8.6464
- αa = 2100*(8.6464-13.5)/(8.6464^2-15.3*8.6464+2050) = -5.1156
- λ = λn + αa·αb = 8.6464+-5.1156*0.5 = 6.0886
- η = MAX(0,0.00326*(6.0886-13.5)) = 0
- ξ = ((6.0886/90)^2+1+0)/(2*(6.0886/90)^2) = 109.75
- Slenderness reduction αc = MIN(1,109.75*(1-SQRT(1-(90/(109.75*6.0886))^2))) = 1
- φRsb = 0.9 αc Ae fy = 0.9*1*3987.4*300/1000 = 1076.6 kN
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.