Civil Engineering Reference
In-Depth Information
(a)
(b)
(c)
Figure 8.3
Steel/concrete composite box girders. (a) Single box. (b) Multibox (twin-box).
(c) Multicellular box.
Horizontally curved box girders applicable for both simple and continu-
ous spans are used for grade separation and elevated bridges where the
structure must coincide with the curved roadway alignment. This condi-
tion occurs frequently at urban crossings and interchanges and also at
rural intersections where the structure must conform to the geometric
requirements of the highway. Horizontally curved bridges will undergo
bending and associated shear stresses as well as torsional stresses due to
the horizontal curvature even if they are subjected only to their own gravi-
tational load. The bridge can be treated as a series of interconnected beams
where the beam theory can be used for the behavior of the individual ele-
ments. Figure 8.4 shows the general behavior of an open box section under
gravity load showing separate load effects. An arbitrary uniform load on a
simple-span box girder (Figure 8.4a) contains bending and torsional load
components that have corresponding bending and torsional effects, which
will be described further in Sections 8.1.1 and 8.1.2.
8.1.1 Bending effects
The bending load (Figure 8.4b), causes the section to
1. Deflect rigidly (longitudinal bending)
2. Deform (bending distortion)
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