Cuai Dai bridge

  • Name of the owner
    Quang Ngai Province Traffic Construction Investment Project Management Unit
  • Name of the client
    DCPT Quang Ngai
  • Delivery date of the project
    October 2020
  • Partners of the project
    Designer: Britec
    Main contractor: Trung Chinh
    Stay cables:     Freyssinet Vietnam
Key figures

Cua Dai extradosed bridge project

The Cua Dai extradosed bridge project in Vietnam counted five 120m long spans supported by a total of 180 stay cables, each formed of 200m long strands.

The six extradosed spans make up the main river crossing of the 1,877 m-long bridge, which also incorporates 31 standard concrete box girder spans and has a deck width of 22 m. Provision of the bridge has cut around 18 km from the travel distance between the two coastal communities it links.

Strongly competed on this project, Freyssinet got to find a cost-effective solution to produce its 1,860 MPa Cohestrand technology. After advanced studies from our technical department, the solution that made the difference was a new manufacturing process reducing use of resin in the cable. This innovation seduced also the client for its sustainable approach.

  • 140
    Km of strands produced
  • 13.5
    Cumulative length of strand with resin filler (km)
  • 19
    Number of strands per cable
Locally cohesive strand

Looking for a substitute to resin filler

Freyssinet developed the patented Cohestrand® technology to overcome issues of force transfer and mechanical strength that a “conventional” waxed sheathed strand cannot withstand, and so avoid any slippage between the strand and its sheath. The resin binds the wires together to enable them to act as a single unit, transmitting more effectively axial forces into the saddle and the tower. But from a performance point of view, the resin filler is only necessary for the short length of strand that is confined within the saddle, where the load transfer takes place. The 200 m long strand needed for Cua Dai bridge required then only resin over a length of around 5 m in the middle of the strand which will be within the tower saddle unit. The extra cost and environmental impact of using resin across the full strand length made it difficult for Freyssinet to be competitive with other suppliers on the extradosed bridge market.

Pilot project for an innovative locally-cohesive strand

The challenged launched to our technical department on Cua Dai bridge was then to find a way of manufacturing a locally-cohesive Cohestrand technology with resin filler through the 5m saddle area of the strand and wax filler through the free length.

Freyssinet designed and successfully tested an automated injection system changing from wax to resin injection at the appropriate point on the strand. This new technique reduces the cost of manufacturing the product and optimises the use of both wax and resin filler without compromising structural performance or durability of the strand. With both functions in the same machine, management of quality control is also much more straightforward, and the entire strand can be manufactured locally.

Cua Dai bridge Vietnam under construction - locally-cohesive strand

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