Cable-stayed bridges - Computational Analysis and Design of Bridge Structures - page 339

Moment distributions close to a continuous girder

(a)

Moment distributions

High stresses in cables

Compression in girder is significantly increased

(b) Axial force distributions

(c) Displacements Deflections are reduced significantly

Figure 11.16 (a-c) Ideal state of a cable-stayed bridge.

unattainable, or simply not economical. What bridge engineers define is
only one preferred state .
During the schematic design of a cable-stayed bridge, the concept of con-
tinuous girder behavior can be used to estimate cable quantities by hand.
Figure 11.17, for example, shows one erection segment of the girder. If
100% of the dead loads on one girder segment are redistributed to the pylon
by a pair of cables, the cable forces F would be

W

(11.1)

F = sin

a

where:
W is the dead loads on a girder segment
α is the cable angle