Civil Engineering Reference
In-Depth Information
fi xed with 3.2 diameter screws at 300 mm centres has f
p,d
=
1.27 kN/m and similar sheets fi xed on opposite sides of the tim-
ber frame has a value of 2.19 kN/m. The typical plasterboard
separating wall construction of a minimum 30 mm thickness
of plasterboard in at least 2 layers has a value of 2.19 kN/m.
From
Figures 19.22
and
19.23
it can be seen that at the lee-
ward corner there is a vertical reaction. The value of this reac-
tion is given by
where
W
v,t,d
is the total design vertical load acting on the wall dia-
phragm in kN
M
d,,dst, base
is the design destabilising moment from design
wind load taken about the base of the diaphragm in kNm
M
d,stb
is the design stabilising moment from the vertical loads
taken about the leeward corner of the diaphragm in kNm
L is the length of the diaphragm in m.
Note that to arrive at the maximum value for F
c,d,leeward
it
may be neccessary to consider favourable and unfavourable
actions.
Then F
c,d,leeward
≤ F
cR,d
where F
cR,d
is the sum of the design
compressive capacities of the studs in kN within 0.1L of the
leeward corner of the diaphragm. The design compressive cap-
acity of a stud is the lower of the design axial strength and
the design end bearing strength of the stud on the horizontal
framing member.
F
c,d,leeward
= 0.8 W
v,t,d
[(M
d,,dst, base
/ M
d,stb
) + 0.6 / L]
v
q
F
H
V
R
f
w1d
f
pd
19.8.8 Frames and arches
For plane frames and arches a second order linear analysis
should be made of the structure with initial deviations in geom-
etry as shown in
Figure 19.24
.
F
c,d, leeward
V
HD
Figure 19.23 Wall type C
l
a
h
(a)
lll
0.0025
lll
α
-
α φ
α
-
α φ
α
-
α
-
(b)
lll
0.0025
l
l
1
l
1
0.0025
h
0.0025
lll
α
÷
φ
α
-
α φ
0.0025
lll
(c)
Figure 19.24 Examples of assumed initial deviations (a) for a frame or arch; (b) subject to symmetrical loading; (c) asymmetrical loading (BSI, 2004).
Permission to reproduce extracts from BS EN 1995-1-1 is granted by BSI
