Introduction
The back mark is the distance from the back of an angle or channel web to the centre of a hole through the leg or flange. This dimension is selected taking into account, access for tightening the bolt using an appropriate spanner, being close to centroidal axis ,and provision of required edge distance The distance between centres of holes in flanges of joists, universal columns and Universal beams is selected to provide accessibility and acceptable edge distance.
All Dimensions in mm
Maximum recomended bolt sizes shown in brackets
dimensions in mm
|
Nominal Flange Wdith
|
S1
Back Mark
|
Edge Dist
|
Recommended Bolt dia
|
|
102
|
55
|
47
|
24
|
|
89
|
55
|
34
|
20
|
|
76
|
45
|
31
|
20
|
|
64
|
35
|
29
|
16
|
|
51
|
30
|
21
|
10
|
|
38
|
22
|
-
|
|
Recommended Bolt Back Marks in Angle Sections
All Dimensions in mm
Maximum recomended bolt sizes shown in brackets
| Nominal leg | S1 | S2 | S3 | S4 | S5 | S6 |
| 25 | 15 | - | - | - | - | - |
| 30 | 20 | - | - | - | - | - |
| 40 | 23 | - | - | - | - | - |
| 45 | 25 | - | - | - | - | - |
| 50 | 28 (12) | - | - | - | - | - |
| 60 | 35 (16) | - | - | - | - | - |
| 65 | 35 (20) | - | - | - | - | - |
| 70 | 40 (20) | - | - | - | - | - |
| 75 | 45 (20) | - | - | - | - | - |
| 80 | 45 (20) | - | - | - | - | - |
| 90 | 50 (24) | - | - | - | - | - |
| 100 | 55 (24) | - | - | - | - | - |
| 120 | - | 45 (16) | 50 (16) | - | - | - |
| 125 | - | 45 (20) | 50 (20) | - | - | - |
| 150 | - | 55 (20 ) | 55 (20) | - | - | - |
| 200 | - | 75(30) | 75(30) | 55 (20) | 55 (20) | 55 (20) |
Recommended Bolt Centres for Column/Beam Flanges
All Dimensions in mm
Maximum recomended bolt sizes shown in brackets
| Flange width | Min. for Accessiblility |
Maximum for Edge dist |
S1 | S2 | S3 | S4 |
| Joists | ||||||
| 44 | 27(5) | 30 | 30 | - | - | - |
| 64 | 38(10) | 39 | 40 | - | - | - |
| 76 | 48(10) | 51 | 48 | - | - | - |
| 89 | 54 (12) | 59 | 56 | - | - | - |
| 102 | 60 (16) | 62 | 60 | - | - | - |
| 114 | 66(16) | 74 | 70 | - | - | - |
| 127 | 72(20) | 77 | 75 | - | - | - |
| 152 | 75(20) | 102 | 90 | - | - | - |
| 203 | 91(24) | 143 | 140 | - | - | - |
| Universal columns | ||||||
| 152 | 65 (24) | 92 | 90 | - | - | - |
| 203 | 75 (24) | 143 | 140 | - | - | - |
| 254 | 87 (24) | 194 | 140 | - | - | - |
| 305 | 100 (24) | 245 | 140 | 120 (24) | 60 (24) | 240 (24) |
| 368 | 88 (24) | 308 | 140 | 140 (24) | 75 (24) | 290 (24) |
| 406 | 120 (24) | 346 | 140 | 140 (24) | 75 (24) | 290 (24) |
| Universal Beams | ||||||
| 102 | 50 (16) | 62 | 54 | - | - | - |
| 127 | 62(20) | 77 | 70 | - | - | - |
| 133 | 57 (20) | 83 | 70 | - | - | - |
| 140 | 69 (24) | 80 | 70 | - | - | - |
| 146 | 64 (24) | 86 | 70 | - | - | - |
| 152 | 73 (24) | 92 | 90 | - | - | - |
| 165 | 67 (24) | 105 | 90 | - | - | - |
| 171 | 72 (24) | 111 | 90 | - | - | - |
| 178 | 72 (24) | 118 | 90 | - | - | - |
| 191 | 74 (24) | 131 | 90 | - | - | - |
| 210 | 80 (24) | 150 | 140 | - | - | - |
| 229 | 80 (24) | 169 | 140 | - | - | - |
| 254 | 87 (24) | 194 | 140 | - | - | - |
| 267 | 91(24) | 207 | 140 | 90(20) | 50 (20) | 190 (20) |
| 292 | 92(24) | 232 | 140 | 100 (24) | 60 (24) | 220 (24) |
| 305 | 100 (24) | 245 | 140 | 120 (24) | 60 (24) | 240 (24) |
| 419 | 112(24) | 359 | 140 | 140 (24) | 75 (24) | 290 (24) |