Ucd

The functions are as described in 2.3.4.1(c).

The values of kdef, for timber and some wood-related products in service class 1, 2 and 3 conditions, are given in Table 2.10, and when dealing with connections the factor must be modified as described in 2.3.2. For completeness, the modifications to kdef are as follows:

(i) Where the connection comprises timber elements with the same time-dependent behaviour, kdef should be taken to be 2 times the value given in Table 2.10.

(ii) Where the connection comprises two wood-based elements having different time-dependent behaviour, kdef should be taken to be:

kdef = 2ykdefj1 ■ kdef>2 (EC5, equation (2.13)) (10.78)

where kdef1 and kdefj2 are the deformation factors for the respective wood-based elements.

(iii) When timber is being used and installed at or near its fibre saturation point, but is to function in an environment where it was likely to dry out under load, the value of kdef in Table 2.10 must be increased by 1.0.

The use of 2kdef as the deformation factor when dealing with joints has arisen because it has been concluded that when kdef is used there is a tendency to underestimate the deflection in a joint. It is to be stated, however, that this is not fully supported by the findings from all researchers.

For structures at the ULS, the analysis procedure will depend on whether or not the distribution of the stress resultants in the members of the structure is affected by the stiffness distribution, and the methodology to be adopted for each alternative is given in 2.3.4.2. Unless the joints in the structure are designed to be pin jointed, the distribution of the stress resultants in the members will be affected by the stiffness distribution, and in a stress analysis at the ULS the final mean value of the stiffness properties in equations (2.38), (2.39) and (2.40) will be used as follows:

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