Corrosion assessment of bridge cables

It was found from field surveys that cables were heavily corroded in Japanese suspension bridges, which were under severe corrosion environments due to the water and high temperature inside the cable. Corrosion environments depended on the wire positions inside the cables. Wires were continuously wet at the side of the cable, wet at night and dry during the day on the top, highly humid at the center, and soaked in the water at the bottom. Accelerated corrosion tests showed that the side wires were most severely corroded, the bottom wires were also significantly corroded, but the upper and center wires were not corroded. These phenomena agreed with the actual cable corrosion. The tests also showed that galvanized steel wires did not corrode when they were kept with a relative humidity below 60%, but became corroded with the higher relative humidity. Galvanized steel wires at different corrosion levels were produced, and their mechanical properties were investigated. Actual tensile strength of corroded wires did not decrease with corrosion levels, whereas the elongation and fatigue strength decreased sharply after the zinc layer was partly depleted and the steel started to corrode. Fatigue strength also decreased after the zinc layer was partly depleted. The fatigue strength of corroded wires in wet environments was lower than that in dry environments. The crack initiated from the corroded parts on the wire surface, where stresses concentrated due to the surface roughness caused by corrosion. In wet environments, the progress of crack was promoted by the hydrogen which was produced by the cathodic reaction of corrosion.

• Introduction

• Corrosion Resistant System for Suspension Bridge Cables

• Environment Inside the Cable

• Corrosion Simulation of Galvanized Steel Wires

• Effect of Relative Humidity

• Specimens at Different Corrosion Levels

• Tensile Strength and Elongation

• Fatigue Strength

• Conclusion

• References