8. Bearing strength

The design load case will be due to a combination of the self-weight of the beam plus the combined permanent and variable point loads at mid-span:

Design value of the end reaction, Reacd = Vd Reacd = 9.44 kN


Reacd 2

Design bearing stress, ac.9o.d ^c.9o.d = ——— ^c.9o.d = 1-26 N/mm2

Design bearing strength, /c.9o.d fc.90.d = kmod'med ^sys fcmk fc.9o.d = 4 N/mm2 (equation (4.23)) Ym

Factored design bearing strength, kc.9o • fc 9o.d = 4 N/mm2 kc.9o • fc.o.d (equation (4.22))

Bearing strength is OK without need to use a higher kc.9o

9. Beam deflection

Deflection due to bending and shear effects:

At the SLS the partial safety factor is 1.

As the member is made from one material, the mean value of stiffness will be used to derive the instantaneous and the creep deflection of the beam.

The greatest value of instantaneous deflection at the SLS will be associated with the largest value of bending moment at that state and will be due to the characteristic combination of the combined self-weight of the beam plus the combined dead and variable point loads at mid-span.

Instantaneous deflection due to the self-weight of the beam Minst,selfwt (Table 4.7):

Instantaneous deflection due to the point loads at mid-span Minst.point loads (Table 4.7):

_ (Gk.p + Qk.p) ■ t 1,12 F0.mean I h uinst.point. loads — ~ T T~3 ' 1 + 1,2'

4 ' E0.mean ' b ' h G0.mean uinst.point loads = 16-38 mm

Instantaneous deflection under combined self-

weight and point loads, «inst, «inst = «instselfwt + «inst.point loads «inst = 16.84 mm EC5 limitation on deflection - ^

(Table 4.6 (EC5, Table 7.2)) The deflection is satisfactory mean

Example 4.8.4 A timber floor in a domestic property has a clear span of 3.7o m between supports and a bearing length of 5o mm at each end. The structure comprises 47 mm by 2oo mm deep sawn timber joists at 4oo mm c/c, strength class C18 to BS EN 338:2oo3, and functions in service class 1 conditions. The flooring is 18 mm thick OSB/3 boarding to BS EN 12639-1:2ooi and is nailed to the joists. Although the floor structure is finished on its underside with plasterboard, no increase in the flexural stiffness of the floor will be allowed for this. The floor width is 4.o m and the floor mass, based on permanent loading only, is 35 kg/m2.

Carry out a design check to confirm that the vibration behaviour of the floor will be acceptable.

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