Design and strength classes - Glued laminated timber made of beech

The characteristic strength, stiffness and density properties for glued laminated timber made of beech shall be taken from Table 4.
For the calculation of the relative slenderness for bending λrel,m or the critical bending stress σm, crit in accordance with DIN 1052:2008-12, Section 10.3.2, the fifth percentile value product of the characteristic stiffness values may be multiplied by a factor of 1.3.

For the verification of the compression perpendicular to the grain stresses in accordance with DIN 1052 a coefficient of kc,90 =1 shall be taken into account for all cases. The rules given above are also applicable for a design according to DIN EN 1995-1-1. Additionally kcr has to be taken as kcr = 1.

Table 4: Characteristic strength, stiffness and density properties for Glued laminated timber made of beech of varying strength classes (in N/mm2)

 

GL 28h

GL 32c GL 36c GL 40c GL 44c GL48c
Characteristic strength values
fm,ka

28

32

36

40

44

48

ft,0,k

21

ft,90,k 0,5
fc,0,k

25

fc,90,k

8,4

fv,k 3,4

Characteristic stiffness values

E0, mean

13500

13500

13500

14300

 15100

 15100

E0,05

12700

12700

12700

13700

 14700

 14700

E90, mean

690

E90,05

 550

Gmean

 1000

G0,05

 800

 Characteristic density values (kg/m³)

Ρk

 650

a   If the laminations are subject to flat-wise bending in the case of beams of height < 600 mm, the characteristic strength may be multiplied by the coefficient

kh =            

Hybrid beams made of beech/spruce

The characteristic strength, stiffness and density properties for glued hybrid beams made of beech/spruce shall be taken from Table 5. For strength- and Stiffness properties not covered by Table 5 the values shall be taken as values for GL 24h according to DIN 1052: 2008-12, Table F.9.

For the verification of the compression perpendicular to the grain stresses in accordance with DIN 1052 a coefficient of kc,90 =1 shall be taken into account for the design of the beech laminations for all cases.

In addition, the compression perpendicular to the grain stresses of the softwood core laminations shall be verified whereby a stress propagation of 45° in the outermost laminations must be assumed. The coefficients kc,90  in accordance with DIN 1052 for the different cases of support may be used.

For the design of joints the provisions of DIN 1052 or DIN EN 1995-1-1the provisions for hard- and softwood (in the case of hybrid beams) apply accordingly. The rules given above are also applicable for a design according to

DIN EN 1995-1-1. Additionally kcr has to be taken as kcr = 1.

Table 5: Characteristic strength, stiffness and density values for hybrid beams made of beech/spruce of differing strength classes (in N/mm2)

 

GL 28
hyb

GL 32
hyb
GL 36
hyb
GL 40
hyb
GL 44
hyb
GL48
hyb
Characteristic strength values
fm,ka

28

32

36

40

44

48

fv,k 2,5

Characteristic stiffness values

E0, mean

13200

13200

13200

14000

 14700

 14700

E0,05

12400

12400

12400

13300

 14200

 14200

 Characteristic density values for softwood laminations (kg/m3)

Ρk

380

a   If the laminations are subject to flat-wise bending in the case of beams of height < 600 mm, the characteristic strength may be multiplied by the coefficient

kh =           

If h > 600 mm the characteristic strength shall be multiplied by a coefficient of

 

kh =        

Openings in glued laminated timber made of beech or hybrid beams made of beech/spruce are not permissible.

When using mechanical fasteners the regulations stipulated by DIN 1052 or technical approvals for the appropriate fasteners must be observed. The facilitation given in DIN 1052:2008-12, 12.5.2(10), may not be applied to glued laminated timber made of beech or in the outermost laminations of hybrid beams made of beech/spruce.