BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to a method for preventing corrosion of a cable for use in bridges, specifically, a method for preventing corrosion of a cable including a plurality of bundled wires and a covering tube which covers the plurality of wires.

Background Art

As a bridge passed over straits, rivers and the like, there has been known a bridge including a main cable and a bridge girder suspended from the main cable via hanger ropes. Such a bridge, being exposed to wind and rain and direct sunlight, is likely to be influenced by an environment in which the bridge is disposed (specifically, influenced by change of seasons or change of weather). Hence, the use of bridges for a long period of time requires various measures.

For example, Unexamined Japanese Patent Publication Nos. H8-177012 and H10-159019 disclose methods for preventing corrosion of a main cable including a plurality of bundled wires and a covering tube which covers the wires. These methods involves supplying dry air into the covering tube to flow the dry air between the wires to thereby protect them from corrosion.

However, it has been found that simply flowing dry air between wires is not sufficient to suppress corrosion of the plurality of wires.

SUMMARY OF INVENTION

An object of the present invention is to provide a method capable of suppressing corrosion of a plurality of wires forming a cable.

In order to achieve the object, the inventor of the present application has focused on a relationship between a corrosion progress speed of a wire and an oxygen concentration of air existing around the wires, thereby having attained the knowledge that flowing a gas with an oxygen concentration lower than that of air between the plurality of wires to allow the plurality of wires to exist under an atmosphere with an oxygen concentration lower than that of air makes it possible to suppress corrosion of the wires.

Meanwhile, an excessively low oxygen concentration affects workers who conduct maintenance of bridges. Besides, generating such a gas involves increased costs. It is necessary not only to simply reduce an oxygen concentration but also to take the above circumstances into consideration.

Provided is a method for preventing corrosion of a cable including a plurality of bundled wires and a covering tube which covers the plurality of wires, the method including: a step of mixing a low-oxygen gas with an air, the low-oxygen gas having an oxygen concentration lower than an oxygen concentration of the air, to thereby generate a mixed gas; and a step of supplying the generated mixed gas into the covering tube to flow the mixed gas around each of the wires.

