Compression perpendicular to the grain in supports
Design of compression perpendicular to the grain in supports is based on the chapter 6.1.5 of EN 1995-1-1:
The design compressive stress in the contact area perpendicular to the grain is calculated using the formula (6.4):
\sigma _{c,90,d}=\frac{F_{c,90,d}}{A_{ef}}
where: | σc,90d |
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Fc,90,d |
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Aef |
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Final verification corresponds to the expression (6.3):
\sigma _{c,90,d} \leq k_{c,90} f_{c,90}
where: | σc,90d |
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kc,90 |
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fc,90 |
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The following rules are used for determination of the factor kc,90:
- The value 1.5 is used for solid timber providing that the distance from the nearest joint is longer than 2h (where h is the height of supported member).
- The value 1.75 is used for glued laminated timber providing that the distance from the nearest joint is longer than 2h (where h is the height of supported member). The length of the support shall be shorter than 400mm.
- The value 1.0 is used in other cases
Different procedures are used for certain national annexes:
SS EN 1995-1-1 (Sweden)
Following values of partial factors are used for verification of pressure perpendicular to the grain:
\gamma _{M}=1.0 ; k_{mod}=1.0
This procedure can be used in cases when increased deformations in supports have no significant impact on the system’s stability and mechanical resistance. Otherwise, the procedure according to EN 1995-1-1 shall be used.
NS EN 1995-1-1 (Norway)
Verification of pressure perpendicular to the grain is based on "Rapport 86: Compression perpendicular to the grain, a recommendation" (released by Norsk Treteknisk Institutt in February 2013).
Following values of the characteristic compressive strength perpendicular to the grain fc,90,k are used for verification of pressure perpendicular to the grain:
Grade | C14 | C18 | C24 | C30 | GL28h | GL28c | GL30h | GL30c | GL32h | GL32c |
fc,90,k [MPa] | 4.3 | 4.8 | 5.3 | 5.7 | 5.3 | 5.3 | 5.5 | 5.5 | 5.7 | 5.7 |
The factor kc,90 is calculated according to this table:
l1 < 150mm | l1 < 150mm | ||
a ≥ 100mm | a < 100mm | ||
l ≥ 150mm | 1.0 | 1.0 | 1.0 |
150mm > l ≥ 15mm | 1.0 | 1,0+(150-l)/170 | 1,0+a(150-l)/17000 |
15mm > l | 1.0 | 1.8 | 1,0+a/125 |
where: | l1 |
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l |
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a |
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