Timber · Connections
Nailed timber joint (AS 1720.1 Sec 4) calculator
Nailed timber-to-timber or steel-plate-to-timber joint. Lateral design capacity Nd = φ·k1·k13·k14·k16·k17·n·Qk with the characteristic nail capacity Qk for the joint group and nail diameter (enter from AS 1720.1 Table 4.1 or the fastener supplier), reduced for short penetration; withdrawal capacity; minimum end, edge and spacing distances for driven or pre-bored nails, and whether the nail pattern fits the member.
Standard: AS 1720.1-2010 Cl 4.2 nails: Nd = φk1k13k14k16k17·n·Qk · Table 4.3 spacings
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 |
|---|---|---|
| Nail diameter | 3.15 | mm |
| Characteristic lateral capacity Qk per nail | 0.94 | kN |
| Characteristic withdrawal per mm penetration | 0.012 | kN/mm |
| Number of nails | 12 | |
| Rows across the grain | 3 | |
| Penetration into the main member | 40 | mm |
| Shear planes | Single shear | |
| Side member | Timber (k16 = 1) | |
| Nails into | Side grain (k13 = 1) | |
| Holes | Driven, not pre-bored | |
| Load duration k1 | 0.8 | |
| Capacity factor φ (category 2) | 0.8 | |
| Member depth across the grain | 140 | mm |
| Design lateral load N* | 6 | kN |
| Design withdrawal load (0 = none) | 0 | kN |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| k13 / k14 / k16 | 1 / 1 / 1 | |
| Penetration factor (pen/10D ≤ 1) | 1.00 | |
| Lateral design capacity Nd | 7.22 | kN |
| Withdrawal design capacity | 3.69 | kN |
| Minimum end distance | 63 | mm |
| Spacing along / across the grain | 63 / 32 | mm |
| Edge distance | 16 | mm |
| Width needed for 3 rows | 95 | mm |
| Joint length needed | 252 | mm |
- ✓ N* ≤ Nd — 83 %
- ✓ Withdrawal
- ✓ Rows fit in the member depth — 95 vs 140 mm
- ✓ Penetration ≥ 10D for full capacity
Method, formulas and assumptions
- Nd = φ·k1·k13·k14·k16·k17·n·Qk (Cl 4.2.3); k17 = 1 for nails, k13 = 0.6 into end grain, k14 = 2 for double shear, k16 = 1.1 through steel side plates.
- Qk depends on the joint group (J1–J6) and nail diameter: take it from AS 1720.1 Table 4.1(A)/(B) or the fastener manufacturer; the default is indicative only.
- Spacings (Table 4.3): driven: end 20D, along 20D, across 10D, edge 5D; pre-bored: 10D, 10D, 3D, 5D.
- Nails in end grain must not be relied on for withdrawal.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.