Civil Engineering Reference
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yield strength of the flanges, and where
b
f
t
f
t
w
h
w
f
yf
f
yw
c
=
a
0.25
+
1.6
.
(4.88)
Worked examples of checking the shear capacity of a slender web are given in
Sections 4.9.5 and 4.9.6.
4.7.5.3 Transverse stiffeners
Provisions are made in EC3 for a minimum value for the second moment of area
I
st
of intermediate transverse stiffeners.These must be stiff enough to ensure that
the elastic buckling stress
τ
cr
of a panel can be reached, and strong enough to
transmit the tension field stiffener force. The stiffness requirement of EC3 is that
the second moment of area of a transverse stiffener must satisfy
I
st
≥
0.75
h
w
t
w
,
(4.89)
when
a
/
h
w
>
√
2, in which
h
w
is the depth of the web, and
I
st
≥
1.5
h
w
t
w
/
a
2
(4.90)
when
a
/
h
w
≤
√
2.TheselimitsareshowninFigure4.29,andareclosetothoseof
equations 4.27 and 4.26.
The strength requirement of EC3 for transverse stiffeners is that they should
be designed as compression members of length
h
w
with an initial imperfection
2
equation 4.27
1
equation 4.89
equation 4.26
equation 4.90
0
0
1
2
3
Value of
a/d
Figure 4.29
Stiffness requirements for web stiffeners.
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