Civil Engineering Reference
In-Depth Information
An example of the analysis of the shear flow distribution in the I-section beam
shown in Figure 5.12a is given in Section 5.12.6. The shear flow distribution
is shown in Figure 5.12b. It can be seen that the shear stress in the web is nearly
constant and equal to its average value
V
z
d
f
t
w
,
τ
v
(
av
)
=
(5.22)
whichprovidesthebasisforthecommonlyusedassumptionthattheappliedshear
is resisted only by the web.Asimilar result is obtained for the shear stress in the
web of the channel section shown in Figure 5.14 and analysed in Section 5.12.7.
When a horizontal shear force
V
y
acts parallel to the
y
axis, additional shear
stresses
τ
h
parallel to the walls of the section are induced. These can be obtained
from the shear flow
s
τ
h
t
=−
V
y
I
z
yt
d
s
.
(5.23)
0
which is similar to equation 5.17 for the shear flow due to a vertical shear force.
A worked example of the calculation of the shear flow distribution caused by a
horizontal shear force is given in Section 5.12.8.
V
z
d
f
t
f
b
V
z
d
f
t
f
b
v
t
=
v
t
f
2
=
I
y
w
2
I
y
V
f
t
w
S
C
d
f
y
V
w
t
f
v
f
a
2
0
2
t
f
b
d
f
t
f
b
d
f
t
w
V
z
V
z
b
v
t
=
+
2
bt
f
+
d
f
t
f
w
2
8
I
y
I
y
z
(a) Shear flow due to shear force
V
z
(b) Shear centre and flange and web shears
Figure 5.14
Shear flow distribution in a channel section.
Search WWH ::
Custom Search