Cable-stayed bridges - Computational Analysis and Design of Bridge Structures - page 333

Cradle

Cable sheathing

Centerline of pylon

Deck

Anchor

Figure 11.9 Cradle stay system.

Figure 11.10 Cross section of a typical steel box girder.

are widely used in short-span ranges, whereas steel box girders dominate
the long-span range (Figure 11.10).
Based on NCHRP Report (National Cooperative Highway Research
Program; Tabatabai 2005), several types of cables are available for use
as stays * in cable-stayed bridges. The form or configuration of the cable
depends on its make-up; it can be composed of parallel wires (no longer
commercially available in the United States), parallel strands, parallel solid
bars (larger diameter and lower allowable stress and fatigue resistance
than comparable parallel strand stays), and single or multiple arrange-
ments of structural strands or locked-coil strands (no longer used in the
United States). Nowadays, high-strength steel strands, same as those used
in PC bridges, are commonly used for stay cables. Each strand usually con-
tains seven high-strength steel wires. Each stay cable contains a number of
strands inside and a polyethylene (PE) jacket on the outside. The number of
strands in one cable varies from as few as 10 to more than 100. The corro-
sion protection of cables is a common concern in the design of cable-stayed
bridges. Usually the strand itself can be epoxy-coated, galvanized, or greased.
The stay cable is sheathed by PE jacket, which can effectively protect the

* Stay is defined as a large strong rope usually made of wires used to support a mast.