Steel · Bases, anchors & embedded plates
Base plate shear lug calculator
Lug embedded below grout: concrete bearing on the lug, lug cantilever bending and the lug-to-plate fillet welds.
Standard: AISC Design Guide 1 · AS 4100 Cl 5, 9.7 (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 |
|---|---|---|
| Design shear V* | 150 | kN |
| Lug width | 200 | mm |
| Lug depth (total) | 120 | mm |
| Grout thickness | 40 | mm |
| Lug thickness | 36 | mm |
| Concrete f′c | 32 | MPa |
| Lug grade | Grade 250 plate | |
| Weld leg (both faces) | 12 | mm |
| Weld category | SP (φ = 0.8) |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Plate yield stress fy (AS/NZS 3678) | 250.0 | MPa |
| Plate tensile strength fu | 410.0 | MPa |
| Embedded depth below grout | 80.00 | mm |
| Bearing φ0.6·0.85 f′c·2 (confined) bl he | 522.2 | kN |
| Lug moment V(g + he/2) | 12.00 | kNm |
| Lug capacity φ fy bl t²/4 | 14.58 | kNm |
| Weld resultant per mm (couple M/t + shear) | 1,708 | N/mm |
| Weld capacity per mm | 1,996 | N/mm |
- ✓ Concrete bearing
- ✓ Lug bending
- ✓ Lug welds
Method, formulas and assumptions
- Plate yield stress fy (AS/NZS 3678) = CHOOSE(1,IF(36<=8,280,IF(36<=12,260,250)),IF(36<=8,320,IF(36<=12,310,IF(36<=20,300,280))),IF(36<=12,360,IF(36<=20,350,340))) = 250 MPa
- Plate tensile strength fu = CHOOSE(1,410,430,450) = 410 MPa
- Embedded depth below grout = 120-40 = 80 mm
- Bearing φ0.6·0.85 f′c·2 (confined) bl he = 0.6*0.85*32*2*200*80/1000 = 522.24 kN
- Lug moment V(g + he/2) = 150*(40+80/2)/1000 = 12 kNm
- Lug capacity φ fy bl t²/4 = 0.9*250*200*36^2/4/1E6 = 14.58 kNm
- Weld resultant per mm (couple M/t + shear) = SQRT((12*1E6/36/200)^2+(150*1000/(2*200))^2) = 1708.3 N/mm
- Weld capacity per mm = IF(1=1,0.8,0.6)*0.6*490*12/SQRT(2) = 1995.7 N/mm
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.