Steel connection design
A bolted shear connection checked against every limit state that decides it: bolt shear, bearing, tearout, block shear and — when the joint is slip-critical — slip resistance. The governing state is named, not buried.
| State | Nominal (kN) | φ | Design (kN) | Utilisation |
|---|---|---|---|---|
| Bolt shear ◂ | 467.5 | 0.75 | 350.6 | 43% |
| Bearing on plate | 864.0 | 0.75 | 648.0 | 23% |
| Tearout | 864.0 | 0.75 | 648.0 | 23% |
Fnv 372 MPa, 4 bolts × 1 plane.
Rn = Fnv · Ab · n · planes · Fnv 372 MPa for A325-N, 469 for A325-X.
Rn = 2.4 · d · t · Fu · Per bolt; tearout replaces it at small end distances.
Rn = min(0.6FuAnv + UbsFuAnt, 0.6FyAgv + UbsFuAnt) · The yielding path often governs.
A clear path from inputs to results.
A bolted shear connection has five ways to fail and the design is only as strong as the weakest. This checks bolt shear, bearing, tearout, block shear and — for a slip-critical joint — slip resistance, then names which one governs.
How to use
- Set the bolt diameter, grade and whether the threads are in the shear plane.
- Enter the plate thickness and strength, and the clear end distance.
- Read the governing limit state and its utilisation against the design shear.
The formula
Reference: AISC 360-22 §J3.2, §J3.6, §J3.10, §J4.3; φ = 0.75.
Worked example
Four M20 A325-N bolts in a 10 mm plate
- Single shear plane, Fu 450 MPa, clear end distance 40 mm, 150 kN demand.
- 1
Ab = 314 mm². Shear φRn = 0.75 × 372 × 314 × 4 = 350.6 kN. Bearing φRn = 0.75 × 2.4 × 20 × 10 × 450 × 4 = 648 kN. Tearout gives the same at 40 mm.
Bolt shear governs at 43% utilisation.
Interpreting the result
Bolt shear usually governs a normal connection; tearout governs when the end distance is short, and block shear governs a coped beam or a gusset with a short tear-out path.
Assumptions & limitations
- Standard holes; oversize and slotted holes reduce capacity.
- Bearing uses 2.4·d·t·Fu (deformation is a design consideration).
- Block shear uses Ubs = 1.0, valid for a uniform tension stress.
- Threads in or out of the shear plane is selected explicitly.
Frequently asked questions
Why does thread position matter so much?
Fnv drops from 469 to 372 MPa for A325 when the threads cross the shear plane — a 21% loss.
Is slip-critical stronger?
No — it is checked at serviceability against slip, and it is usually governed by the bolt shear strength anyway.
When does tearout govern?
When the clear end distance is less than about 2d, 1.2·lc·t·Fu falls below the bearing value.
What about prying?
Prying affects tension connections; this checks shear. Use the anchor or base plate pages for tension.
Methodology last reviewed 2026-10-22. Results are informational and not financial or engineering advice — see our disclaimer.