Australian End Plate Connection — AS 4100 Design Guide
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Reference for flush and extended end plate connection design per AS 4100:2020 Clause 9. Covers T-stub model, bolt prying action, weld design, and plate bending for moment-resisting connections.
Connection Types
| Type | Typical Moment Capacity | Use |
|---|---|---|
| Flush end plate (4 bolts) | 50-150 kNm | Light moment frames |
| Extended end plate (4 bolts) | 150-400 kNm | Moment frames |
| Extended end plate (8 bolts) | 400-800 kNm | Heavy moment frames |
| Stiffened end plate | 800+ kNm | Special high-capacity |
Design Procedure — AS 4100 Clause 9
Step 1 — Bolt design (tension + shear):
- Tension from moment: T* = M* / db (bolt group lever arm)
- Check: φNtf ≥ T* per bolt (tension capacity per Clause 9.3.2.1)
- Combined: (V*/φVfn)² + (T*/φNtf)² ≤ 1.0
Step 2 — End plate bending (T-stub model):
- Effective T-stub length: ℓeff = min(2πm, 4m + 1.25n, p, b)
- Plate moment: Mpl = T* × m / (2 × ℓeff) (per unit width)
- Required thickness: tp ≥ √(4 × Mpl / (φ × fy))
Step 3 — Weld design:
- Beam flange to end plate: full-penetration butt weld or 8 mm min fillet each side
- Beam web to end plate: 6 mm fillet each side
- Weld capacity per Clause 9.7
Worked Example: Extended End Plate
Problem: Design extended end plate for 410UB59.7 with M* = 300 kNm. Bolts: M24 8.8/TB in 4 rows. Grade 300 end plate.
Solution:
- Bolt lever arm db ≈ 420 mm (top bolt to critical compression flange)
- Bolt tension: T* = 300/0.420 = 714 kN total
- Per bolt (8 bolts): T* = 714/8 = 89 kN
- M24 8.8/TB φNtf = 0.80 × 830 × 353 = 234 kN per bolt. 89 < 234 OK
- Check prying (Clause 9.3.4): Increase bolt force by ≈20% → 89 × 1.2 = 107 < 234 OK
- End plate thickness: tp = √(4 × (107×10³ × 35) / (0.90 × 280 × 300)) ≈ 20 mm
- Specify: 300×200×20 mm extended end plate, 8-M24 8.8/TB bolts
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 prying in end plate connections? Tension in bolts induces bending in the end plate, amplifying bolt force (typically 10-25% increase). Per AS 4100 Clause 9.3.4.
When are stiffeners needed on end plates? When plate thickness exceeds 25 mm (uneconomical) or when the connection must develop the full beam section capacity.
Minimum end plate thickness? Typically 12 mm minimum for flush, 16 mm for extended. Design governed by T-stub bending per AS 4100.
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.