Civil Engineering Reference
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Figure 8.7
Warping stresses in a box girder.
Lateral ties (struts)
(a)
Solid diaphragm
(b)
Cross frame
Top bracing system
(X-type)
Top bracing system
(single diagonal type)
(c)
Figure 8.8
(a-c) Bracing system terminology.
large torques with relatively low shear flows. The shear low around the
circumference of the box follows a consistent direction (clockwise or coun-
terclockwise) at any given location along the length of the girder. As a result,
when combined with vertical shear in the webs, this shear flow is always
subtractive in one web and additive in the other.
In addition, box girders are subjected to cross-sectional distortion when
subjected to eccentric loading such as overhang loads and eccentrically
applied live loads. This cross-sectional distortion results in out-of-plane
(transverse) bending stresses and longitudinal warping normal stresses
in the webs and full-width flanges of the box cross section. These bend-
ing stresses may be estimated by using a beam-on-elastic-foundation
(BEF) analogy method (Wright et al. 1968), which was further improved
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