Civil Engineering Reference
In-Depth Information
Figure 18.29
Effect of unsymmetrical loading on suspension bridge with cables curved in plan
wind loads. However it is still advisable for the deck to retain bending and torsional
strength and stiffness to control the dynamic behaviour of the cables.
As the cables have a horizontal parabolic curvature, they also apply a distributed
horizontal force to the deck equal to 8
Fh
/
L
2
units/m, where
F
is the force in the cables,
h
is the sag of the cables in the horizontal plane, and
L
is the span, Figure 18.29 (a).
When all vertical loads are equally shared between the cables, these horizontal
forces are balanced. However, any eccentric vertical load on the deck will increase the
tension in one set of cables with respect to the other, increasing the vertical sag of the
more heavily loaded cable. As a result of the different tensions in each set of cables,
the horizontal forces applied to the deck will be unequal, giving a net lateral force,
