Civil Engineering Reference
In-Depth Information
Fx
(a)
1
0
Mz
(b)
4
0
Figure 3.19
(a, b) Influence surface of a tied-arch bridge.
As an example shown in Figure 3.19, influence surface is a function of planar
coordinates. Based on the influence line loading method introduced in Section
3.4.2, the influence surface loading method can be developed with certain
assumptions.
The deck of a bridge with an irregular shape may be divided into dif-
ferent traffic areas. Figure 3.20a, for example, shows the plane view of
a generic bridge deck. On a plane, traffic regions may be overlapped as
seen in interchanges. A region on a plane can be defined by its center-
line, left width, and right width, and both widths are constant along
the entire region. Although the centerline of a region may be curved in
reality as regions Ω
2
and Ω
3
shown in Figure 3.20a, it is assumed that
Left width
of a region
Regions may be overlapped
on the plane
Ω
3
Ω
2
Ω
1
Left width of a region
Centerline of a region
Ω
2
Centerline of a region
Right width of a region
Centerline of a region
Right width
of a region
(a)
Multiple traffic regions
Ω
i
......
... ...
Influence lines interpolated transversely from surface
(b)
Unfold a region to a rectangle along its centerline
Figure 3.20
(a) Multiple traffic regions and (b) unfolding region to rectangle.
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