Civil Engineering Reference
In-Depth Information
as a horizontal diaphragm. The approach adopted assumes the
timber deck to act as a deep beam. The long edges (supported
on wall plates or similar) are assumed to be the beam fl anges
which resist the horizontal bending moment. The decking is
the beam web which transmits the shear force to the supporting
shear walls (
Figure 15.19
).
The guidelines are as follows:
The following checks are required to be carried out:
a)
Bending strength of 'fl anges'
Fl
8whb
f
Fl
Fl
,
t d
hb
≤
,t d
t d
f
t d
,
t t d
t d
,,
,t d
,
t d
t d
8w
8whb
Where F
d
- total design force on diaphragm (N)
Span of panel - ℓ (mm)
Width of panel - b (mm)
edge beam width - w (mm)
ditto height
The span ℓ must lie between 2b and 6b.
■
The critical ultimate design condition must be failure of the fas‑
■
teners and not failure of the panels.
Edge beams should be designed to resist the maximum bending
- h (mm)
■
f
t,0,d
- design tension strength of timber edge beam
moment in the diaphragm.
The panels are fi xed to the supporting edge beams and joists. All
- k
mod
f
t,0,k
/ γ
m
■
k
mod
- modifi cation factor for load duration
(ref. Table 3.1, Eurocode 5)
unsupported edges should be connected to adjacent panels by fi x‑
ing to battens in accordance with Eurocode 5, 10.8.1.
The fi xings should be nails (other than smooth nails) or screws at
f
t,0,k
- characteristic tensile strength of timber
■
γ
m
- partial coeffi cient for material properties
(ref. Table 2.3, Eurocode 5)
a maximum spacing of 150 mm along panel edges and 300 mm
spacing along the supports.
Stiff Roof
Diaphragm
Lateral forces
on Structure
Stiff Wall
Diaphragm
Stiff Floor
Diaphragm
Figure 15.18 Lateral forces carried by two storey timber framed structure
Wind Load F
d
Edge Beam (Continuous)
Supporting Joists
Shear Wall
Shear Wall
Edge Beam (Continuous)
Edge Beam:
Width - w (mm)
Height - h (mm)
Panel Thickness - t (mm)
Figure 15.19 Plan of horizontal diaphragm
