The critical condition is due to combined axial stress and bending about the y-y axis, functioning as a beam and with wind as the dominant variable action. The studs are OK as the combined compression and bending ratio is less than unity.

7. Bearing strength of the sole plates

For this condition, the greatest vertical load arises with the vertical variable load as the only variable load case:

Design bearing load per stud, N3d = 3.67 x 103 N

N3d 2 Design bearing stress on the CTc.9o.d =--^c.9o.d = 0.77 N/mm2

plate, CTc.0.d Ab

Design bearing strength, fc.9o.d = kmodmed k°.90—fc.90.d = 1.35 N/mm2 fc 90.d (ignoring enhancement of kc.90 allowed in EC5)

The bearing stress is less than the bearing strength; therefore the 38 mm by 125 mm plates, strength class C18, will meet the ULS bearing compression strength requirement of EC5.

Example 5.7.8 A stud wall in a domestic property with the same layout as shown in Figure E5.7.6 has an overall height of 2.4 m. The studs are spaced at 600 mm centre to centre and battens are fitted at mid-height. Studs are 44 mm by 100 mm section, class C18 to BS EN 338:2003, and the wall functions in service class 2 conditions. Each wall stud supports a characteristic permanent action of 0.4 kN, a characteristic medium-duration variable action of 1.8 kN and a characteristic lateral wind action of 0.85 kN/m2. Sheathing material is fixed on both faces and provides full buckling restraint about the z-z axis of the studs.

Determine the increase in the instantaneous lateral deflection of the wall at the serviceability limit states (SLS) under the characteristic combination of actions, taking wind loading as the dominant variable action.

1. Geometric properties

Stud length, L

Effective length of a stud for buckling about the y-y axis, Le.y(Table 5.2) Width of a stud, b

Depth of a stud, h

Lateral spacing of each stud,


2. Timber strength properties

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

Fifth-percentile modulus of E0 05 = 6.0 kN/mm2 elasticity parallel to the grain,


Mean modulus of elasticity parallel £0,mean = 9.0 kN/mm2 tO the grain, £0,mean

Mean shear modulus, G0>mean G0>mean = 0.56 kN/mm2

3. Partial safety factors

Table 2.2 (UKNA to EN 1990:2002(E), TableNA.Al.1) - Category A

Combination factor for a variable action f 0

Combination factor for a wind action, fo, w

4. Actions

Characteristic permanent compressive action, Gk

Characteristic medium-term compressive variable action, Qk

Characteristic variable (wind) action, Wk

Variable lateral action, Fser

Permanent vertical action, Nserdl

Variable vertical action, Nserll

Characteristic combination for vertical load with wind as the dominant action, GVLw

Characteristic lateral wind loading with wind as the dominant action,


5. Deflection of the stud wall at the SLS

The critical design load case at the SLS will be due to the combination of permanent, unfavourable wind (dominant) and unfavourable medium-term variable action:

Nserll = Qk

Maximum permitted out of straightness of a stud, S0 (EC5, Section 10)

Euler load of a strut about the y-y axis, PE (equation (5.42))

0 0

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