Prestressing Steel Technology Supported the Shin-Meishin Project

One of the main arteries that connect major cities in the eastern and western parts of Japan is the Meishin Expressway between Nagoya and Kobe. This important transportation infrastructure underpins the economic activities and everyday life of Japanese people but has suffered chronic traffic congestion due to the growing traffic volume and there has always been a risk that the only trunk line could be cut off in case of disasters and other emergencies. To solve these issues, a new major road was planned, namely the Shin-Meishin Expressway, which will be 174 km long. This big project duplicates the expressway and creates a "double network" connecting the Kansai and Chubu Regions to reduce traffic congestion and serve as an alternative route in emergencies, which will secure smooth transportation. It can also shorten the traveling time to improve economic efficiency and contribute to local communities.

The project to construct the Shin-Meishin Expressway has used a large number of prestressing steel and related products supplied by Sumitomo (SEI) Steel Wire Corp*¹. (hereinafter referred to as "Sumitomo Electric" collectively). Sumitomo Electric obtained a license for long-span prestressed concrete bridge construction technologies from Dyckerhoff & Widmann AG (Dywidag) of Germany to introduce them to Japan in the late 1950s and developed a business related to prestressing steel and related products during the period of rapid economic growth. Then, the Company worked to further improve the strength and created the world's strongest prestressing steel strand with approximately 20% higher strength than conventional JIS (Japanese Industrial Standards)-compliant types*². A key point was that the strength of the prestressing steel strand was enhanced while the diameter was almost the same with that of conventional ones. Their functions were also improved. An example was the development of highly durable (corrosion-resistant) prestressing steel and related products, which are coated with epoxy resin and polyethylene (PE) resin at a factory in advance to dramatically enhance the long-term reliability.

The anchoring process is also important, in which tensioned prestressing steel and related products that efficiently transmit the compressive force to concrete are anchored to a bridge. It is a great advantage of Sumitomo Electric that it can offer a total solution from prestressing steel strands to the anchorage system (a group of parts for the anchoring).

*1 Sumitomo (SEI) Steel Wire Corp. was separated and became independent from Sumitomo Electric Industries, Ltd., in October 2002 to start operation as a comprehensive manufacturer of specialty steel wire products. While Sumitomo Electric sells the products outside of Japan, Sumitomo (SEI) Steel Wire is in charge of manufacturing, development and domestic sales.

*2 JIS-compliant prestressing steel strand has the strength of 1,860 MPa, which is equivalent to the strength of a prestressing steel strand of 15.2 mm in diameter to withstand the weight of about 25 passenger cars. The world's strongest prestressing steel strand has the strength of 2,230 MPa, which can be manufactured by only several companies worldwide.

For this project, Sumitomo Electric provided a super-high-tension system, which consists of the world's strongest prestressing steel strand and the anchorage system mentioned above. Since the prestressing steel strand has a similar diameter to that of ordinary ones but has higher strength, the number of the cables, which are made by stranding the prestressing steel strands, can be reduced and the anchorage system can also be deployed properly in a limited space. In addition, epoxy resin coatings and other highly durable rust prevention treatments are applied to the prestressing steel strands.

This super-high-tension system has been adopted in the construction of Mukogawa Bridge, Aigawa Bridge and Youbaizan Viaduct of the Shin-Meishin Expressway. It has been highly valued for the construction of the long span bridges and greatly helped save labor and reduce the bridge weight.