# Structural bolt capacities (AS 4100)

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Design capacities of single M12 to M36 structural bolts to AS 4100:2020 in the bolting categories of Table 9.2.1: 4.6/S (AS 1111 or AS 1110 bolts), 8.8/S, 8.8/TB and 8.8/TF (AS/NZS 1252.1), and the 10.9 categories added in 2020, with ply bearing, hole sizes, pitch and edge distances.

## Grade 4.6 and 8.8 bolts (one bolt, one shear plane)

| Bolt | 4.6/S (f_uf = 400 MPa) – φN_tf (kN) | 4.6/S (f_uf = 400 MPa) – φV_f N (kN) | 4.6/S (f_uf = 400 MPa) – φV_f X (kN) | 8.8/S and 8.8/TB (f_uf = 830 MPa, M12 800 MPa) – φN_tf (kN) | 8.8/S and 8.8/TB (f_uf = 830 MPa, M12 800 MPa) – φV_f N (kN) | 8.8/S and 8.8/TB (f_uf = 830 MPa, M12 800 MPa) – φV_f X (kN) | 8.8/TF friction – N_ti (kN) | 8.8/TF friction – φV_sf (kN) |
|---|---|---|---|---|---|---|---|---|
| **M12** | 27.0 | 15.1 | 22.4 | 54.0 | 30.2 | 44.8 | – | – |
| **M16** | 50.2 | 28.6 | 39.9 | 104.2 | 59.3 | 82.7 | 95 | 23.3 |
| **M20** | 78.4 | 44.6 | 62.3 | 162.7 | 92.6 | 129.3 | 145 | 35.5 |
| **M24** | 113.0 | 64.3 | 89.7 | 234.4 | 133.4 | 186.1 | 210 | 51.4 |
| **M30** | 179.5 | 103.0 | 140.3 | 372.5 | 213.7 | 291.1 | 335 | 82.1 |
| **M36** | 261.4 | 150.6 | 202.0 | 542.5 | 312.5 | 419.1 | 490 | 120.0 |

N: threads intercept the shear plane; X: they don't (plain shank). φV_f is for one shear plane with k_r = 1.0; multiply by the number of shear planes. φV_sf is per effective interface with μ = 0.35 (clean as-rolled surfaces) and k_h = 1.0 (standard holes). S: snug tight; TB and TF: fully tensioned (Table 9.2.1). Grade 8.8 bolts less than 16 mm in diameter (M12) have f_uf = 800 MPa (Table 9.2.1, Note 2).

## Grade 10.9 bolts (one bolt, one shear plane)

| Bolt | 10.9/S and 10.9/TB (f_uf = 1040 MPa) – φN_tf (kN) | 10.9/S and 10.9/TB (f_uf = 1040 MPa) – φV_f N (kN) | 10.9/S and 10.9/TB (f_uf = 1040 MPa) – φV_f X (kN) | 10.9/TF friction – N_ti (kN) | 10.9/TF friction – φV_sf (kN) |
|---|---|---|---|---|---|
| **M12** | 70.1 | 32.6 | 58.3 | – | – |
| **M16** | 130.6 | 61.7 | 103.7 | 130 | 31.8 |
| **M20** | 203.8 | 96.3 | 162.0 | 205 | 50.2 |
| **M24** | 293.7 | 138.7 | 233.2 | 295 | 72.3 |
| **M30** | 466.8 | 222.2 | 364.7 | 465 | 113.9 |
| **M36** | 679.7 | 325.0 | 525.1 | 680 | 166.6 |

With threads intercepting the shear plane, grade 10.9 bolts take k_rd = 0.83 for their lower ductility (Cl. 9.2.2.1). Check availability and the Table 9.2.1 notes before specifying 10.9 bolts.

## Ply in bearing

Design bearing capacity of the ply per millimetre of ply thickness, φV_b/t_p = 0.9 × 3.2d_f f_up (kN/mm), for common ply tensile strengths f_up (MPa):

| Bolt | 410 (Grade 250 plate) | 430 (Grade 300 plate, C350L0) | 440 (Grade 300 sections) | 450 (Grade 350 plate) | 480 (Grade 350 sections) | 500 (C450L0) |
|---|---|---|---|---|---|---|
| **M12** | 14.2 | 14.9 | 15.2 | 15.6 | 16.6 | 17.3 |
| **M16** | 18.9 | 19.8 | 20.3 | 20.7 | 22.1 | 23.0 |
| **M20** | 23.6 | 24.8 | 25.3 | 25.9 | 27.6 | 28.8 |
| **M24** | 28.3 | 29.7 | 30.4 | 31.1 | 33.2 | 34.6 |
| **M30** | 35.4 | 37.2 | 38.0 | 38.9 | 41.5 | 43.2 |
| **M36** | 42.5 | 44.6 | 45.6 | 46.7 | 49.8 | 51.8 |

Tear-out near an edge also limits the ply: φV_p = 0.9a_e t_p f_up, where a_e is the distance from the edge of the hole to the edge of the ply, measured in the direction of the force, plus half the bolt diameter (Cl. 9.2.2.4). Use the smaller of φV_b and φV_p.

## Holes, pitch and edge distance (mm)

| Bolt | Standard hole | Oversize hole, max. | Short slot, max. length | Long slot, max. length | Min. pitch | Min. edge distance (Table 9.5.2) – Sheared or hand flame cut edge | Min. edge distance (Table 9.5.2) – Rolled plate, flat bar or section: machine cut, sawn or planed edge | Min. edge distance (Table 9.5.2) – Rolled edge of a rolled flat bar or section |
|---|---|---|---|---|---|---|---|---|
| **M12** | 14 | 20 | 22 | 30 | 30 | 21 | 18 | 15 |
| **M16** | 18 | 24 | 26 | 40 | 40 | 28 | 24 | 20 |
| **M20** | 22 | 28 | 30 | 50 | 50 | 35 | 30 | 25 |
| **M24** | 26 | 32 | 34 | 60 | 60 | 42 | 36 | 30 |
| **M30** | 33 | 38 | 40 | 75 | 75 | 52.5 | 45 | 37.5 |
| **M36** | 39 | 45 | 47.9 | 90 | 90 | 63 | 54 | 45 |

Hole sizes from Cl. 14.3.2: standard holes are d_f + 2 mm up to M24 and d_f + 3 mm above; oversize holes up to the larger of 1.25d_f and d_f + 8 mm; slots are the standard hole width, with short slots up to the larger of 1.33d_f and d_f + 10 mm long and long slots up to 2.5d_f. Oversize and slotted holes need hardened or plate washers, and Cl. 14.3.2 limits where they may be used. Base plate holes may be up to 6 mm larger than the anchor bolt, with a plate washer at least 4 mm thick where the hole is 3 mm or more oversize. Minimum pitch is 2.5d_f (Cl. 9.5.1). Edge distances are measured from the centre of a standard hole; for other holes, from the nearer edge of the hole plus d_f/2 (Cl. 9.5.2).

## Bolt areas (AS 1275, mm²)

| Bolt | Thread pitch (mm) | A_o plain shank | A_s tensile stress | A_c minor diameter |
|---|---|---|---|---|
| **M12** | 1.75 | 113 | 84.3 | 76.2 |
| **M16** | 2 | 201 | 157 | 144 |
| **M20** | 2.5 | 314 | 245 | 225 |
| **M24** | 3 | 452 | 353 | 324 |
| **M30** | 3.5 | 707 | 561 | 519 |
| **M36** | 4 | 1018 | 817 | 759 |

## Formulas (AS 4100:2020)

- **Shear** (Cl. 9.2.2.1): φV_f = φ0.62f_uf k_rd k_r(n_n A_c + n_x A_o), φ = 0.8 (Table 3.4). k_rd = 1.0 except for 10.9 bolts with threads in the shear plane (0.83). k_r = 1.0, or for a bolted lap connection of length l_j 1.075 − l_j/4000 between 300 and 1300 mm and 0.75 beyond (Table 9.2.2.1).
- **Filler plates** (Cl. 9.2.2.5): fillers more than 6 mm and less than 20 mm thick in total multiply V_f by 1 − 0.0154(t − 6), e.g. 0.908 for 12 mm.
- **Tension** (Cl. 9.2.2.2): φN_tf = φA_s f_uf, φ = 0.8.
- **Combined shear and tension** (Cl. 9.2.2.3): (V\*_f/φV_f)² + (N\*_tf/φN_tf)² ≤ 1.0.
- **Ply in bearing** (Cl. 9.2.2.4): φV_b = φ3.2d_f t_p f_up ≤ φa_e t_p f_up, φ = 0.9.
- **Friction-type (8.8/TF, 10.9/TF)** (Cl. 9.2.3): φV_sf = φμn_ei N_ti k_h, φ = 0.7 (Cl. 3.5.5), with N_ti from Table 15.2.2.2, μ = 0.35 for clean as-rolled contact surfaces and k_h = 1.0 for standard holes, 0.85 for short slotted and oversize holes and 0.70 for long slotted holes. It limits slip at the serviceability limit state; the bolts must also be checked at the strength limit state (Cl. 9.2.2).

Design aid only, not a substitute for a qualified engineer or for AS 4100 itself. See the [disclaimer](https://steelinfo.au/disclaimer/) and [data sources](https://steelinfo.au/sources/).

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