Page 156 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

134 CORROSION CAUSES

Figure 3.3 Golden Gate Suspension Bridge (7).

statements very difficult. The corrosion problems are highly dependent on specific
structural configurations, maintenance, and operational practices and local environ-
mental conditions.
Corrosion concerns on cable-supported structures have been present from the early
design. For example, galvanized zinc coating of the wires was used on the Brooklyn
Bridge, which was completed in 1883. At that time, it was a standard practice to
coat the wire with linseed oil, circumferentially wrap the assembled cable with soft
galvanized wire laid into red lead paste, and to paint the finished cable.
Some of the oldest and well-known bridges in the United States, such as the Golden
Gate and Brooklyn bridges, are suspension bridges (Figs. 3.3 and 3.4). The mainte-
nance costs of these bridges are high. These cannot be replaced or taken out of service
for any length of time because of historic reasons or strategic location. The specific
concern with these bridges is the condition of strands. The strands are susceptible to
corrosion, stress corrosion cracking, and hydrogen embrittlement, which can result
in premature failure of the strands.
A more recent design of a cable bridge is a cable-stayed bridge as shown in
Figure 3.5. In these bridges, the integrity of the cables is critical to the structural
integrity of the entire bridge. The inspection of the cables is very difficult and these
bridges are built with due consideration of corrosion protection (W Podolny, FHWA,
Office of Bridge Technology, Personal Communication, 1999).