Civil Engineering Reference
In-Depth Information
5.2.1.1.2 Criteria for Maximum Shear Force (with Loads Applied to the
Superstructure through Transverse Members)
A series of concentrated loads applied through longitudinal members (stringers) to
transverse members (floorbeams) to the steel beam or girder is typically assumed in
the design of open deck through spans. Ballasted deck superstructures that transfer
load to the beams or girders by closely spaced transverse members without stringers
may be treated as outlined in Section 5.2.1.1.1.
The maximum shear force,
V
BC
, in panel BC in a simply supported span of length,
L
, traversed by a series of concentrated loads (with resultant force at a distance,
x
T
)
is
(Figure 5.3)
P
L
+
P
BC
c
s
p
.
V
BC
=
P
T
x
T
L
−
(5.4)
The maximum shear force in panel BC may be determined by considering a constant
P
T
moving from
x
T
to
x
T
+ Δ
x
T
is a small increment of movement of
load assuming no change in concentrated forces on the span or within panel BC. In
that case, the change in shear force,
x
T
, where
Δ
Δ
V
BC
, in panel BC, is
P
T
L
−
P
BC
s
p
Δ
V
BC
=
Δ
x
T
.
(5.5)
When
P
T
/
L
P
BC
/
s
p
, maximum shear in panel BC occurs as the change in shear
changes sign (positive to negative). Therefore, the maximum shear occurs in panel
BCwhentheaveragedistributedloadonthespan,
P
T
/
L
,equalstheaveragedistributed
load in panel BC,
P
BC
/
s
p
.
When
s
p
=
=
L
/
n
(where
n
is the number of equal length panels)
P
T
n
−
P
BC
Δ
x
T
s
p
Δ
V
BC
=
(5.6)
©
b
P
T
P
L
P
BC
Direction of
movement
d
c
B
C
A
s
p
x
T
a
L
/2
L
/2
FIGURE 5.3
Concentrated moving loads applied to the superstructure at transverse members.
