Australian Gusset Plate — AS 4100 Whitmore Section Design
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/]]
Reference for gusset plate design per AS 4100:2020 and AISC Steel Construction Manual principles. Covers Whitmore effective width, block shear, gusset buckling, and connection design to braces.
Whitmore Effective Width Method
The Whitmore section defines the effective width for tension resistance at 30° spread from the first bolt row:
Leff = 2 × tan(30°) × Lg + Lb
Where:
- Lg = distance from first to last bolt row
- Lb = bolt group width
- Leff = Whitmore effective width
Tension check: φNt = φ × fy × Leff × tpg ≥ N* Where tpg = gusset plate thickness
Design Checks Summary
| Check | Formula | Clause |
|---|---|---|
| Tension yield | φNt = φ × fy × Ag | 9.2.1 |
| Tension fracture | φNt = φ × 0.85 × fu × An | 9.2.2 |
| Block shear | φVb = φ × (0.5fuAnt + 0.6fyAgv) | 9.2.4 |
| Buckling (compression brace) | φNc = φ × αc × Ns | 6.3 |
| Weld (gusset to beam/column) | φvw = φ × 0.6 × fuw × tt | 9.7 |
| Bolt bearing/tearout | φVb = φ × 3.2 × df × tp × fup | 9.3.2.2 |
Typical Gusset Plate Geometry
| Brace Size | Plate Thickness | Bolt Rows | Plate Size (mm) |
|---|---|---|---|
| 150UC | 12 mm | 2 | 250×250 |
| 200UC | 16 mm | 3 | 300×350 |
| 250UC | 20 mm | 3 | 350×400 |
| 310UC | 25 mm | 4 | 400×500 |
| CHS 114.3 | 12 mm | 2 | 250×300 |
| CHS 168.3 | 16 mm | 3 | 300×400 |
Worked Example
Problem: Gusset plate for 200UC brace, N*=800 kN tension. 3 bolt rows (Lg=200 mm), bolt group width Lb=100 mm. fy=300 MPa, tpg=16 mm.
Solution:
- Whitmore width: Leff = 2×tan30°×200 + 100 = 2×0.577×200 + 100 = 331 mm
- Tension yield: φNt = 0.90 × 300 × 331 × 16 = 1,430 kN > 800 OK
- Block shear check through critical path
- Gusset buckling (if brace is compression): Check slenderness L/r ≤ 50 per AISC recommendation for gusset design.
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 Whitmore section? The effective width of the gusset plate resisting tension, determined by a 30° spread angle from the first to last bolt row. Critical for tension capacity.
How is gusset buckling checked? Using the unbraced length of the gusset edge (typically L/r ≤ 50 recommended). Conservatively check as a compression member per AS 4100 Clause 6.3.
What is the minimum gusset plate thickness? 10 mm minimum, 12-16 mm typical for buildings. Governed by bolt bearing, tension capacity, and buckling resistance.
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.