Calculation of timber connections

The timber connections ensure the link between several parts in a traditional way (usually by contact like oblique thrust, dovetailed scarf or Mortise and Tenon), or through fasteners (bolts, pins, tips, screws, etc.) or metal connectors.

Spacing and end/edge distances	Angle α	Minimum spacing or distance
Spacing a1 (parallel to grain)	0° ≤ α ≤ 360°	(4 + |cos α|) ⋅ d
Spacing a2 (perpendicular to grain)	0° ≤ α ≤ 360°	4 ⋅ d
Distance a3,t (loaded end)	-90° ≤ α ≤ 90°	max(7 ⋅ d; 80mm)
Distance a3,c (unloaded end)	90° < α < 150°	(1 + 6 ⋅ sin α) ⋅ d
	150° ≤ α ≤ 210°	4 ⋅ d
	210° < α < 270°	(1 + 6 ⋅ |sin α|) ⋅ d
Distance a4,t (loaded edge)	0° < α < 180°	max[(2 + 2 ⋅ sin α) ⋅ d; 3 ⋅ d]
Distance a4,c (unloaded edge)	180° ≤ α ≤ 360°	3 ⋅ d

with :

1. crushing wood in element 1
   
2. crushing wood in element 2
   
3. crushing wood in both elements
   
4. crushing wood in element 1 and plastic hinge in the fastener
   
5. crushing wood in element 2 and plastic hinge in the fastener
   
6. crushing wood in both elements and plastic hinges in the fastener
   

7. crushing wood in the external elements 1
   
8. crushing wood in the internal element 2
   

10. crushing wood in the external elements 1 and plastic hinge in the fastener
    
11. crushing wood in all elements and plastic hinges in the fastener
    

The characteristic load-carrying capacity of a steel-to-timber connection depends on the thickness of the steel plates. Steel plates of thickness less than or equal to 0,5d are classified as thin plates and steel plates of thickness greater than or equal to d with the tolerance on hole diameters being less than 0,1d are classified as thick plates. The characteristic load-carrying capacity of connections with steel plate thickness between a thin and a thick plate should be calculated by linear interpolation between the limiting thin and thick plate values.

1. crushing wood in element 1
   
2. plastic hinge in the fastener
   

3. crushing wood in element 1
   
4. crushing wood in element 1 and plastic hinge in the fastener
   
5. plastic hinges in the fastener
   

• interpolation between a and c, crushing wood in element 1
  
• interpolation between a and d, crushing wood in element 1 and plastic hinge in the fastener
  
• interpolation between b and e, plastic hinges in the fastener
  

6. crushing wood in element 1
   
7. crushing wood in element 1 and plastic hinge in the fastener
   
8. plastic hinges in the fastener
   

10. crushing wood in the internal element 2
    
11. plastic hinges in the fastener
    

12. crushing wood in the internal element 2
    
13. plastic hinges in the fastener
    

The rope effect increases the resistance to lateral effort with more or less importance depending on the type of organ and its ability to withstand axial stress.
The contribution to the load-carrying capacity due to the rope effect in equal to 25% of the characteristic axial withdrawal capacity of the fastener. For bolts, it should also be limited to 25% of the part of the equation from Johansen theory.

For one row of n bolts parallel to the grain direction, the load-carrying capacity parallel to grain should be calculated using the effective number of bolts n_ef where:

where :

• a₁ is the spacing between bolts in the grain direction
• d is the bolt diameter
• n is the number of bolts in the row

For loads perpendicular to grain, the effective number of fasteners should be taken as n_ef=n.

For angles 0°<α<90° between load and grain direction, n_ef may be determined by linear interpolation.

• Net cross section tensile failure
• Block shear failure
• Splitting failure

See the features of Timber Connections
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