where Nd is the design axial load and A is the cross-sectional area of the member. /Cj0jd is the design compressive strength parallel to the grain and:

kmod ' ksys

Km where kmod is the modification factor for load duration and service classes as given in Table 2.4; ksys is a strength factor for load-sharing systems. When dealing with single column members this factor is not relevant and is taken to be unity; ym is the partial coefficient for material properties, given in Table 2.6; /c>0jk is the characteristic compressive strength of the timber or wood-based product parallel to the grain. Strength information for timber and the commonly used wood-based structural products is given in Chapter 1.

Where A.rel,y or Xrel z (or both) exceed 0.3, the member can buckle about the associated y-y and z-z axis, respectively, and for such a condition it must be demonstrated that when taking into account the effect of the related instability factors, the compressive stress in the member is less than the compressive strength of the member. This requires oc 0 d when Xrel>y > 0.3 -—— < 1 (5.11a)

kc y /c 0 d Oc 0 d when Xrel ,z > 0.3 —^^ < 1 (5.11b)

Table 5.3 Value of kc,y or kc,z based on equations (6.25)-(6.29) inclusive in EC5 with = 0.2

Strength class C14

Strength class C16

Strength class C18

Strength class C22

fc,0,k 14 N/mm2 E0.05 4700 N/mm2

fc,0,k 16 N/mm2 E0.05 5400 N/mm2

fc,0,k 18 N/mm2 E0.05 6000 N/mm2

fc,0,k 22 N/mm2 E0.05 6700 N/mm2

X Xrel kc,y (kc,z ) X

hrel kc,y (kc,z ) h

Xrel kc,y (kc,z) ^

Xrel kc,y (kc,z )

0 0

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