Example 5.7.2 A 47 mm x125 mm sawn timber member of strength class C18 to BS EN 338:2003 functioning under service class 2 conditions in a timber truss is subjected to a characteristic permanent tensile axial action of 2.5 kN and a characteristic variable medium-term tensile axial action of 3.0 kN. The member is effectively pin jointed at each end to accommodate end fixings, 8% of the cross-sectional area is removed at one end and 10% at the other end. The effect of bending of the member due to its self-weight can be ignored. Check that the member complies with the requirements of EC5 at the ULS.

1. Geometric properties

Thickness of the member, t1 t1 = 47 mm

Net area of the member - based Anet = 0.9 ■ A on the minimum area -(100% - 10%), Anet

2. Timber properties

Table 1.3, strength class C18 (BS EN 338:2003(E), Table 1)

Characteristic tensile strength /t-0-k = 11 N/mm2

parallel to the grain, /t 0 k

3. Partial safety factors

Table 2.8 (UKNA to BS EN 1990:2002, Table NA.A1.2(B)) for the ULS

Permanent actions, yG Yg = 1-35

Variable actions, yq Yq = 1-5

Material factor for solid timber, yM

4. Actions

Characteristic permanent tensile action, Gk

Characteristic variable medium term action, Qk

Design tensile action for the critical load combination, Nd (Table 2.8, equation (c) using the unfavourable condition)

5. Modification factors

Factor for medium-duration loading and service class 2, £ (Table 4.1 (EC5, Table 3.1))

Size factor, kh (Table 2.11; EC5, equation (3.1)) (the equation incorporates a dimensional correction factor for Mathcad)

System strength factor, ksys - not relevant kh =

0 0

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