Australian Connection Design — AS 4100 Clause 9 Complete Guide
Quick access: [[Australian Steel Grades|/reference/australian-steel-grades/]] | [[Australian Steel Properties|/reference/australian-steel-properties/]] | [[Australian Beam Sizes|/reference/au-beam-sizes/]] | [[Australian Bolt Capacity|/reference/australian-bolt-capacity/]] | [[AS 4100 Beam Design|/reference/as4100-beam-design-example/]] | [[All Australian References|/reference/]]
Comprehensive guide for structural connection design per AS 4100:2020 Clause 9. Covers bolted and welded connections with complete worked example for an end plate moment connection. Integrates bolt capacity, weld design, block shear, and plate bending.
Connection Types Overview
| Connection Type | Load Transfer | Common Application |
|---|---|---|
| Shear connection (bolted/welded) | Vertical shear only | Beam-to-beam, beam-to-column |
| Moment connection (bolted/welded) | Shear + moment | Moment frames |
| Tension connection (bolted) | Axial tension | Bracing, hangers |
| Compression connection (bearing) | Axial compression | Column splices |
| Pin connection | Rotation + shear | Trusses, linkages |
Complete Design Check Summary — AS 4100 Clause 9
| Element | Capacity | Check | Clause |
|---|---|---|---|
| Bolts | |||
| Bolt shear (threaded) | φVfn = φ × 0.62 × fuf × (An/As) × kr | V* ≤ φVfn | 9.3.2.1 |
| Bolt shear (shank) | φVfn = φ × 0.62 × fuf × As | V* ≤ φVfn | 9.3.2.1 |
| Bolt tension | φNtf = φ × 0.80 × fuf × At | T* ≤ φNtf | 9.3.2.2 |
| Combined + tension | φVf = (1 − T*/φNtf) × φVfn | Combined | 9.3.2.3 |
| Bearing (connected ply) | φVb = φ × 3.2 × df × tp × fup | V* ≤ φVb | 9.3.2.2 |
| Tearout | φVb = φ × ae × tp × fup | V* ≤ φVb | 9.3.2.3 |
| Plates | |||
| Tension (gross yield) | φNt = φ × fy × Ag | N* ≤ φNt | 7.1 |
| Tension (net section) | φNt = φ × 0.85 × fu × An | N* ≤ φNt | 7.2 |
| Block shear | φVb = φ × (0.5×fu×Ant + 0.6×fy×Agv) | V* ≤ φVb | 9.2.4 |
| Plate bending | φMp = φ × fy × Zp | M* ≤ φMp | 5.2 |
| Welds | |||
| Fillet weld (GP) | φvw = φ × 0.6 × fuw × tt | V* ≤ φvw × Lw | 9.7.3.10 |
| Butt weld (full pen) | φNw = φ × fy × tw | T* ≤ φNw | 9.7.2.4 |
Worked Example: Complete End Plate Connection
Problem: Design bolted end plate connection for 410UB59.7 to column. M*=250 kNm, V*=120 kN. Use 8-M24 8.8/TB bolts, Grade 300 end plate, E48XX welds.
Solution:
Step 1 — Bolt design:
- Tension per bolt: T* = 250/(8×0.210) = 149 kN per bolt
- M24 8.8/TB: φNtf = 0.80×830×353 = 234 kN > 149 OK
- Prying factor 1.2: 149×1.2 = 179 < 234 OK
Step 2 — Combined check:
- Shear per bolt: V* = 120/8 = 15 kN
- (15/107)² + (149/234)² = 0.02 + 0.41 = 0.43 ≤ 1.0 OK
Step 3 — End plate bending (T-stub):
- Critical bending at bolt line, m=35 mm
- Required tp = 35 × √(2×149×10³/(35×0.9×300)) = 20 mm → specify 20 mm plate
Step 4 — Weld design:
- Beam flange: Full-pen butt weld (develops full flange force)
- Beam web to end plate: 8 mm FW fillet each side
- Weld capacity: 8 mm fillet = 1.33 kN/mm. Web length ≈ 300 mm each side
- Capacity = 2×300×1.33 = 798 kN > V*=120 OK
Step 5 — Block shear:
- Check plate block shear through bolt holes and plate edge
- φVb = 0.90×(0.5×440×Ant + 0.6×300×Agv) ≥ shear force OK
Design Resources
- [[Australian Steel Grades|/reference/australian-steel-grades/]] | [[Australian Steel Properties|/reference/australian-steel-properties/]] | [[Australian Beam Sizes|/reference/au-beam-sizes/]] | [[Australian Bolt Capacity|/reference/australian-bolt-capacity/]] | [[AS 4100 Beam Design|/reference/as4100-beam-design-example/]] | [[All Australian References|/reference/]]
FAQ
What is the most common connection type in Australian steel buildings? Double-angle web cleat (shear connection) for beam-to-beam. End plate connections for beam-to-column moment connections. Both designed per AS 4100 Clause 9.
How is combined bolt tension and shear checked? Per Clause 9.3.2.3: (V*/φVfn)² + (T*/φNtf)² ≤ 1.0. The interaction is quadratic, so pure tension or pure shear governs close to capacity.
What is block shear and when is it critical? Block shear is a combined tension+shear failure along a bolt hole perimeter. Critical for gusset plates, end plates, and shear tabs at short edge distances.
Educational Use Only — This reference is for educational and preliminary design purposes only. All structural designs must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) in accordance with AS 4100:2020 and all applicable Australian Standards. Results are not for construction.