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Newsletter "SEI NEWS" 2012

Home > Company Information > SEI WORLD > Back number > Vol.414

[Newsletter "SEI NEWS" Vol.414]

Super-High-Tension Prestressed Concrete Strand 15.7 mm in Diameter

Enjoys Increased Use on Arterial Expressways!

Epoxy coated and filled prestressed concrete strand

Compared with the conventional 15.2 mm prestressed concrete strand (1,860 MPa class) specified by JIS, the super-high-tension prestressed concrete strand 15.7 mm in diameter demonstrates 20% higher stress level (2,230 MPa class) and 28% higher load level, and is used to reinforce bridges and other structures, as the strongest prestressed concrete strand in the world.

In 2011, the Japan Prestressed Concrete Engineering Association established specifications for super-high-tension prestressed concrete strands and concrete structure design and construction methods incorporating this type of steel strand and issued Guidelines for PC Structure Design/Construction Using High-Strength Prestressed Concrete. With usage established by the guidelines, our expectations are high for increased popularity of super-high-tension prestressed concrete strand.

The present product prestresses *1 a concrete structure more effectively, requiring fewer strands, than the conventional strand type. It brings about various advantages as described later on.

Starting in 2004 in the Akiba Bridge (client: NTT Urban Development Corporation; construction company: Kajima Corporation), this strand has been selected steadily in a number of structures. More recently, we delivered this product to the Uratakao Bridge on the Metropolitan Inter-City Expressway (client: Central Nippon Expressway Co., Ltd.; construction company: special construction consortium between Kajima Corporation and Hazama Corporation), as the first case of selection of the strand on expressways, and to the Matoba Viaduct on the New Tomei Expressway (client: Central Nippon Expressway Co., Ltd.; construction company: Sumitomo Mitsui Construction Co., Ltd.), which is scheduled to go into service in early summer this year. More specifically, shipped to these sites were epoxy coated and filled prestressed concrete strands *2 that offer excellent corrosion resistance.

The strand has also been planned to be used for expressway bridges in the near future. Expectations are high for this product to substantially contribute to all kinds of infrastructure development in Japan and abroad.

 
 

Full view of Uratakao Bridge

 

 Prestressed concrete cables installed in narrow space inside Uratakao Bridge girder

 
 

Matoba Viaduct on New Tomei Expressway

 

Prestressed concrete cables installed inside Matoba Viaduct girder

 
Point 1. Resource and energy saving

An environmentally friendly strand promising to save construction labor, resources and energy.

Point 2. Shortened construction period

Reduces cable quantity requirements and consequently, construction period.

Point 3. Reduced construction cost

Shortened construction period and reduced resources owing to downsized and lightened girders lead to construction cost reductions.

Notes:
*1 Prestressing:
Prior application of a compressive stress to a concrete girder. Tightened by a tensioning device and fixed by dedicated fittings at both ends, prestressed concrete strands apply a compressive stress to a concrete structure to prevent deformation of concrete members caused by their own weight and the load of the traffic.

*2 Epoxy coated and filled prestressed concrete strand:
Prestressed concrete strand provided with a high-quality epoxy powder coating on its surface and also in spaces between strand wires. This corrosion-resistant steel exhibits exceptionally high resistance to corrosion compared with the conventional prestressed concrete strand.

Sumitomo (SEI) Steel Wire Corp.

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