Civil Engineering Reference
In-Depth Information
0.75
(AREMA, 2008) (see also Chapter 6) for an allowable compressive stress,
F
call
,of
The bearing stiffener may be designed as a compression member using
K
=
0.839
E
h
r
ebs
≺
F
call
=
0.55
F
y
; when
F
y
,
(7.73)
; 0.839
E
6.712
E
F
y
17500
F
y
E
3
/
2
0.75
h
r
ebs
h
r
ebs
≤
F
call
=
0.60
F
y
−
F
y
≤
,
(7.74)
6.712
E
F
y
2
E
(h/r
ebs
)
2
; when
0.685
π
h
r
ebs
F
call
=
,
(7.75)
where
h
is the height of the bearing stiffener (clear distance between girder top and
bottom flanges)
I
esb
A
esb
.
r
esb
=
The allowable load on the bearing stiffener is
P
call
=
F
call
(A
ebs
)
,
(7.76)
which should not exceed the maximum reaction,
R
, or concentrated load,
P
.
7.2.6.1.5.2 Bearing Stresses
Since a part of the bearing stiffener area,
A
bs
,is
removed at the top and bottom to clear the beam or girder rolling or weld fillets,
the reduced bearing area,
A
bs
, must be considered. AREMA (2008) recommends an
allowable bearing stress for milled stiffeners and parts in contact of 0.83
F
y
. Based on
this, the reduced bearing stiffener area (area of the bearing stiffener in contact with
the flange plate),
A
bs
,is
R
0.83
F
y
.
A
bs
≥
(7.77)
7.2.6.1.5.3 Local Plate Buckling
Local buckling of bearing stiffeners is essen-
tially the problem of uniform compression on a plate free at one side and partially
restrained at the other. The maximum permissible width-to-thickness ratio is, there-
fore, the same as that established previously for local buckling of a girder compression
flange plate (Equation 7.54)
E
F
y
,
b
bs
t
bs
≤
0.43
(7.78)
where
b
bs
is the width of the outstanding leg of the bearing stiffener and
t
bs
is the
thickness of the outstanding leg of the bearing stiffener.
