Bolt joints are formed by drilling holes in the connected elements, inserting the screws, putting on washers and tightening the nuts (Fig. 6.86). The pressure caused by the tightening generates friction between connectors, which decreases or increases along with the changes of equivalent moisture of wood or moisture of wood-based materials.
Minimal spacing and distances between bolts are specified in the norm PN-B-03150:2000 (Table 6.8).
Pressure strength of a bolt joint with wooden connectors can be calculated using the equation (PN-B-03150:2000):
|
Fig. 6.86 Example of a bolt joint: 1 bolt head, 2, 4 washer, 3 nut |
|
Distance signature |
Orientation |
Minimal distances of connectors |
|
a1 |
| to fibres |
(4 + 3|о^а|^ |
|
a2 |
± to fibres |
4d |
|
a3t |
-90° < а < 90° |
7d min 80 mm |
|
a3c |
150° < а < 210° |
4d |
|
90° < а < 150° |
(1 + 6|sinа|)d min 4d |
|
|
210° < а < 2700° |
(1 + 6^та|^ min 4d |
|
|
a4t |
0° < а < 180° |
(2 + 2^та|^ min 3d |
|
a4c |
Other values of the angle а |
3d |
|
Table 6.8 Minimal spacing and distances between bolts according to PN-B-03150:2000 |
where
fh,0,k = 0.082(1 – 0.01dq),
k90 = 1.35 + 0.015d for coniferous wood species, k90 = 0.90 + 0.015d for deciduous wood species, d diameter of bolt core,
pk density of wood.
