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 λ_rel,m or the critical bending stress σ_{m, 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 k_c,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 k_crhas to be taken as k_cr= 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
f_m,k^a	28	32	36	40	44	48
f_t,0,k	21
f_t,90,k	0,5
f_c,0,k	25
f_c,90,k	8,4
f_v,k	3,4
Characteristic stiffness values
E_{0, mean}	13500	13500	13500	14300	15100	15100
E_0,05	12700	12700	12700	13700	14700	14700
E_{90, mean}	690
E_90,05	550
G_mean	1000
G_0,05	800
Characteristic density values (kg/m³)
Ρ_k	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
k_h=

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 k_c,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 k_c,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 k_crhas to be taken as k_cr= 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
f_m,k^a	28	32	36	40	44	48
f_v,k	2,5
Characteristic stiffness values
E_{0, mean}	13200	13200	13200	14000	14700	14700
E_0,05	12400	12400	12400	13300	14200	14200
Characteristic density values for softwood laminations (kg/m³)
Ρ_k	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
k_h= If h > 600 mm the characteristic strength shall be multiplied by a coefficient of k_h =

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.