Nqs

o.mean

Stiffness of each fastener at the SLS,

K ser

2. 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

Table 2.2 (UKNA to BS EN 1990:2002, Table NA.A1.1) - Category C

Factor for quasi-permanent value of f2 = 0.6 variable action, f2

Table 2.6 (UKNA to EC5, Table NA.3) Material factor for plywood, ym1 Material factor for solid timber, ym2 Connection factor, YM.connection

3. Actions

Characteristic permanent action, Gk

Characteristic variable (imposed) action, Qk

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

4. Modification factors

Factor for permanent duration loading and service class 2, kmod.perm (Table 2.4 (EC5, Table 3.1))

Factor for medium-duration loading and service class 2, kmod.med (Table 2.4 (EC5, Table 3.1))

kmod.

perm

System strength factor, ksys - not relevant ksys = 1.0

Deformation factor for timber and service class 2, kdef.t

Deformation factor for plywood and service class 2, kdef.p

5. Geometric properties

Column length, L

Effective length about the y-y axis, Le.y Effective length about the z-z axis, Le.z Spacing of each fastener, sp For the creep condition:

Le.y = 1.0 ■ L Lez = 1.0 ■ L sp = 50 mm i.e. Ley = 3 m i.e. Le.z = 3 m

The largest stress to strength ratio will be the larger of the permanent action/£mod.perm and the combined permanent and variable action/£mod.med. Let the ratio of one to the other be r:

^mod.perm YQ ' Qk + YQ ' Qk i.e. because the factor is less than 1, the variable loading produces the higher stress/strength ratio, so the factor f 2 will be associated with variable loading.

Final mean value of the modulus of elasticity parallel to the grain for timber,

E 1mean.fin

0 0

Post a comment