Development of New Steels to Reduce Life Cycle Costs of Steel Bridges and Build Application Experience

摘要

There is strong demand for reduction of the life cycle cost (LCC) for steel bridges, and the use of weathering steel is increasing. But in chloride environments, conventional weathering steel does not have enough corrosion resistance. Therefore we have researched and developed new steel for unpainted use that has excellent atmospheric corrosion resistance in chloride environments. This was achieved by Cr removal and Ti addition. The new steel which is named "Super-Ticor W" showed higher chloride corrosion resistance than the conventional weathering steel in accelerated exposure tests, that is less than 0.3 mm in thickness loss in chloride environment estimated for 50 years duration. Meanwhile, we have developed another type of new steel for painted bridges. This steel can prolong the period between repainting, especially in chloride environments. The newly developed steel is named ''Eco-View". This new steel can suppress the growth of rust from defects in paint film, and can keep painted bridges in good condition for a longer period of time. These two new steels have been applied to nearly 30 bridges. In this report, the characteristics of these new steels and applications for steel bridges are described.