Lach Huyen Bridge (Photo courtesy of Sumitomo Mitsui Construction)

Offshore bridge supporting the Vietnamese economy Demand for high corrosion resistance and a shorter construction period

Vietnam is one of the countries maintaining especially high GDP growth every year among the emerging economies in Asia. Many foreign firms have advanced to the northern part of Hanoi, its capital, in recent years. In response to the economic development, a project to construct an international deep-water port was launched in the Lach Huyen district of Hai Phong City, funded by the Japan International Cooperation Agency (JICA). The project also involved the construction of Lach Huyen Bridge as part of the access road. We interviewed Mr. Kazuhiro Nishimura from Sumitomo Mitsui Construction, who was responsible for the construction together with a local construction company.

"Lach Huyen Bridge is the longest offshore bridge in Vietnam with a bridge span of over 5.4 km. The prestressing steel strand used for the bridge had to have high corrosion resistance because it was located at sea. The demand was satisfied by the corrosion-resistant prestressing steel strand of Sumitomo Electric. With corrosion resistance and robustness provided by double coating, the strands greatly helped reduce the construction period and save labor with no need to inject grout (rust prevention materials such as cement milk and resin) or connect PE pipes on site."

Nevertheless, there was a major problem to be solved before their transportation to the actual site and introduction of the technology.

A challenge of cable processing on site
Patient and persistent efforts led to the solution

When prestressing steel strands are delivered to construction sites in Japan, the steel material manufacturer cuts them to a certain length and bundles multiple strands to create a cable at plant. However, the cost efficiency of this method is very poor when the products are transported to Vietnam. After repeated examinations, we adopted a method of delivering uncut products to Vietnam and then cutting and processing them locally. Shiyouji Kusano from Sumitomo Electric went to Vietnam and trained the local staff.

"A challenge was the prevention of damage to the surface of PE and epoxy coated and filled steel strands at the stages from processing to install into the girder. A cable wound around a wooden drum was cut into 60 m pieces and then bundled to create 19 cables on site. In fact, the operators in Vietnam had no experience of bundling corrosion-resistant PE and epoxy coated and filled steel strands and then installing them. I trained them persistently to help them understand the need to prevent the cables from being damaged with a corner of concrete. We also made various efforts to secure facilities and equipment for processing 60 m cables on site."

These patient manual efforts supported the creation of a new artery for the Vietnamese economy.

Future prospect of the prestressed concrete technology
Disseminate the high-performance prestressing steel strand developed in Japan around the world

In addition to bridges, the prestressed concrete technology has been used for large LNG tanks, water and sewage treatment tanks, railroad concrete sleepers, ground anchors, etc. Since the technology can provide pillar-free large space, it is also used for gymnasiums, halls and other buildings, as well as for shafts for wind power generators, these days.

Masato Yamada, who supervises the entire prestressing steel business in Sumitomo Electric, said:

"Improving the soundness of the infrastructure constructed in the past and extending its life, based on the latest technologies, is our social mission. To this end, we will work to enhance the functions and value of prestressing steel and related products and also package related technologies to provide a total solution, while promoting the development of other uses."

We are promoting overseas activities at the same time.

"Infrastructure in developed countries is becoming increasingly degraded while demand for development is soaring in developing countries. In response, we have been promoting global development through such activities as the establishment of manufacturing facilities in three US locations and Indonesia. While claiming that high-performance prestressing steel strands can help extend the life of infrastructure, we also promote the strategy to establish the high-strength and high-corrosion-resistance prestressing steel strand, optical fiber sensors, etc. created with the technological development capabilities of Sumitomo Electric as global standards."

Sumitomo Electric aims to spread highly functional prestressing steel products developed in Japan to the world and is confident that the efforts will support the development of infrastructure worldwide and thereby help people in the world live an affluent life.