Civil Engineering Reference
In-Depth Information
web plate thickness is
R
0.75
F
y
(L
B
+
t
w
≥
for end reaction,
R
,
(7.70a)
k)
P
0.75
F
y
(L
B
+
t
w
≥
for interior concentrated load,
P
,
(7.70b)
2
k)
where
L
B
is the length of bearing.
Steel railway girders will generally require bearing stiffeners due to the high mag-
nitude loads. However, in situations where concentrated loads may not cause web
crippling in accordance with Equations 7.70a or 7.70b, it is often advisable to install
at least nominal stiffeners, in any case (an example is given in Akesson, 2008). Bear-
ing stiffeners must be connected to both flanges and extend to near the edge of the
flange. Bearing stiffeners are designed for the following criteria:
• Compression member behavior (yield and stability).
• Bearing stress.
• Local plate buckling.
7.2.6.1.5.1 CompressionMemberBehaviorofBearingStiffeners
The bear-
ing stiffener is designed as a compression member with an effective cross section
comprising the area of the stiffener elements,
A
bs
, and a portion of the web,
A
wbs
.
The effective area,
A
ebs
, and effective moment of inertia,
I
ebs
, of the bearing stiffener
cross sections shown in Figure 7.16 are
A
ebs
=
2
A
bs
+
A
wbs
=
2
A
bs
+
12
t
w
for end reaction,
R
,
(7.71a)
y
2
t
w
I
ebs
=
2
I
bs
+
2
A
bs
¯
+
for end reaction,
R
,
(7.71b)
A
ebs
=
2
A
bs
+
25
t
w
for interior concentrated load,
P
,
(7.72a)
y
2
2.08
t
w
for interior concentrated load,
P
.
I
ebs
=
2
I
bs
+
2
A
bs
¯
+
(7.72b)
__
y
A
bs
;
I
bs
t
w
A
bs
;
I
bs
25
t
w
12
t
w
Concentrated load
at interior of girder
Concentrated load
at end of girder
FIGURE 7.16
Bearing stiffener effective cross section.
