Maintenance of Seto-Ohashi bridges

The Seto-Ohashi Bridges are located in the center route of three routes that connect Honshu, Japan's main island, and Shikoku. They consist of three suspension bridges, two cable-stayed bridges, and one truss bridge on the strait and some viaducts on the islands in the strait. They are highway-railway combined bridges whose overall length is approximately 10 kilometers. This paper describes current major maintenance issues of the Seto-Ohashi Bridges that have served for 18 years since the opening. The heavy duty coating system is used for steel structures to prevent corrosion. An all-over repainting program started with a modified paint system for 1,800,000 square metres of repainting area. To protect the cable wires of the suspension bridge from corrosion, a dry air injection system was installed. The interior of the cables is dehumidified by dry air. In order to prevent corrosion on the steel caissons of the undersea foundations, an electro-deposit method is applied. By passing an extremely weak current between a steel caisson and an anode placed in seawater, an anti-corrosion layer is formed on the surface of the caisson. To prolong pavement life, a micro-surfacing method was selected. With this method, a thin layer is formed on the existing pavement, which refreshes the road surface. (a) For the covering entry of this conference, please see ITRD abstract no. E214938.