Steel · Cold-formed & secondary steel
Purlin cleat under uplift calculator
Purlin cleat welded to a rafter: bolt shear from wind uplift and downslope load, cleat bending at the weld toe.
Standard: AS 4100 Cl 9.3 · cleat plate bending (simplified)
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 |
|---|---|---|
| Uplift reaction per purlin W* | 9 | kN |
| Downslope component | 2 | kN |
| Bolt line to weld toe | 60 | mm |
| Cleat width | 100 | mm |
| Cleat thickness | 10 | mm |
| Cleat grade | Grade 250 plate | |
| Bolts | 2 | |
| Bolt size | M12 | |
| Bolt category | 4.6/S |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Bolt diameter df | 12.00 | mm |
| Bolt tensile strength fuf | 400.0 | MPa |
| Tensile stress area As | 84.30 | mm² |
| Core area Ac (threads) | 76.20 | mm² |
| Shank area Ao | 113.0 | mm² |
| Plate yield stress fy (AS/NZS 3678) | 260.0 | MPa |
| Plate tensile strength fu | 410.0 | MPa |
| Bolt shear (resultant per bolt) | 4.61 | kN |
| φVf (threads in) | 15.12 | kN |
| Cleat moment W* e | 0.540 | kNm |
| Cleat capacity φ fy b t²/4 | 0.585 | kNm |
- ✓ Bolts
- ✓ Cleat bending
Method, formulas and assumptions
- Bolt diameter df = CHOOSE(1,12,16,20,24,30,36) = 12 mm
- Bolt tensile strength fuf = IF(1=1,400,830) = 400 MPa
- Tensile stress area As = CHOOSE(1,84.3,157,245,353,561,817) = 84.3 mm²
- Core area Ac (threads) = CHOOSE(1,76.2,144,225,324,519,759) = 76.2 mm²
- Shank area Ao = CHOOSE(1,113,201,314,452,707,1018) = 113 mm²
- Plate yield stress fy (AS/NZS 3678) = CHOOSE(1,IF(10<=8,280,IF(10<=12,260,250)),IF(10<=8,320,IF(10<=12,310,IF(10<=20,300,280))),IF(10<=12,360,IF(10<=20,350,340))) = 260 MPa
- Plate tensile strength fu = CHOOSE(1,410,430,450) = 410 MPa
- Bolt shear (resultant per bolt) = SQRT(9^2+2^2)/2 = 4.6098 kN
- φVf (threads in) = 0.8*0.62*400*76.2/1000 = 15.118 kN
- Cleat moment W* e = 9*60/1000 = 0.54 kNm
- Cleat capacity φ fy b t²/4 = 0.9*260*100*10^2/4/1E6 = 0.585 kNm
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.