Km

where kmod, ksys, km are as defined in 4.5.1.1 and:

fc,90,k is the characteristic compressive strength perpendicular to the timber grain. Values for the compressive strength of timber and wood-based structural products are given in Chapter 1.

kc,90 is a factor that takes into account how the loading is being applied, the risk of the member splitting and the strain deformation of the member. The value normally used for kc 90 is 1.0 but higher values can be adopted if certain conditions apply. Where

(a) Bearing over a rigid support at beam end i l---</-

(a) Bearing over a rigid support at beam end i l---</-

(c) Bearing under a concentrated load at beam end

Fig. 4.14. Bearing (compression) failure perpendicular to the grain.

(c) Bearing under a concentrated load at beam end

(b) Bearing over a rigid support along beam length
(d) Bearing under a concentrated load along beam length

Fig. 4.14. Bearing (compression) failure perpendicular to the grain.

contact extends over the full member width, and the support conditions are in line with the requirements given in EC5, the value can be increased up to a maximum of 4.0, but, as previously stated, at this value the compressive deformation will be approximately 10% of the member depth and must be taken into account in the design.

For the case where a beam of breadth b and depth h rests on isolated supports or where a member is supported continuously, the factor is calculated as described in the following sections. Other types of bearing conditions are given in EC5, 6.1.5.

In the proposed draft amendment to EC5, summarised in Appendix C, 6.1.5, a major change is proposed for the validation of compression strength perpendicular to the grain. The proposal simplifies the design procedure given in EC5 and will remove the option to be able to design for a large compressive strain condition.

4.5.3.1 Bearing stress when the member is resting on supports Consider a beam to be supported as shown in Figure 4.15:

(i) When the distance from the end of the beam to the face of the support, a, is

< h/3, kc,90 = ^2.38 - (l + (EC5, equation (6.4)) (4.24)

(ii) When a > h/3 and at internal supports, h kc,90 = |^2.38 - —J + 6^) (EC5, equation (6.5)) (4.25)

where I is the contact length of the bearing surface in mm.

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