Technology meets Tradition: Extradosed Bridge in Japan

The Sannai-Maruyama Overpass is a bridge for the Shinkansen Japanese bullet train that crosses the National Beltway No.7 through Aomori City at the northern tip of Honshu, Japan’s main island. The bridge is part of the longest bullet train line in Japan, the Tohoku-Shinkansen Line. This line connects Tokyo to the northern city of Hachinoe and is currently being extended.

The bridge is located next to the Sannai-Maruyama Site, a 4,000 to 5,500 year-old ancient settlement dating back to the Jomon Period. Sannai-Maruyama is one of the largest National Historical Sites in Japan. Given the need to harmonize with these surroundings, the design selected was a four-span continuous extradosed bridge. With an overall bridge length of 450m and a main span of 150m, this will be the bridge with the longest span on any of the Shinkansen lines.

The bridge features saddles in the pylon in which the strands run through a curved steel pipe. The reliability of the structure was carefully verified before the start of construction through loading tests using a full-scale mockup.

Sumitomo, DSI’s licensee in Japan, supplied 66 Type XD-E27 Extradosed Tendons consisting of 27 epoxy-coated prestressing strands in a HDPE pipe that was subsequently grouted.

Construction was completed in December 2008. The new section of the Tohoku-Shinkansen Line between Hachinohe and Shin-Aomori will become operational in December 2010. Thanks to the extension of this bullet train line, Tokyo will be linked to the six prefectural capitals of Tohoku, a region in north-eastern Japan.