Sumitomo (SEI) Steel Wire Corporation has been playing a role in bridge construction through the development of construction equipment and constituent systems, such as stay cables, tower saddles and main girder anchors for extradosed bridges(*1) that have such features as towers that are lower than those of cable-stayed bridges and increased cost effectiveness. While conventional tower saddles use a double-tube structure with a view toward cable replacement, Sumitomo (SEI) Steel Wire has developed additionally cost-effective single-tube tower saddles jointly with the Japan Railway Construction, Transport and Technology Agency and the Zenitaka Corporation. These saddles were selected for the Sannai Maruyama Overbridge of the Tohoku Shinkansen super-express line.
Since it was the first time shipping saddles for the Shinkansen super-express, Sumitomo (SEI) Steel Wire constructed a full-size test specimen(*2) in the development stage at its factory and examined stress conditions of each member under level 2 earthquake(*3) condition in order to ensure the soundness of the system against earthquakes.
In addition to the single-tube tower saddles, highly corrosion-resistant epoxy resin-coated prestressing strands(*4) were selected as stay cables for the bridge. Sumitomo (SEI) Steel Wire recently delivered the strands to a joint venture comprising Zenitaka, Asanuma, Inoue and Shida construction companies formed for a specific construction project.
Among the extradosed railway bridges incorporating products of Sumitomo (SEI) Steel Wire are the Arakogawa bridge in Aichi Prefecture, the Sannohe Bokyo bridge in Aomori Prefecture and the elevated bridge in Hirano Ward, Osaka Prefecture. Sumitomo (SEI) Steel Wire expects that the tower saddle will be adopted for railway bridges in countries abroad, as well as in Japan.