The Geoga Bridge is part of the Busan-Geoje Fixed Link, an 8.2-km long connection between the coastal city of Busan and Geoje Island. Freyssinet stay cable system was selected for its cable anti-vibration solution and most sustainable technology to contribute to ensuring durability of a structure subject to harsh weather conditions

  • Owner
    GK Fixed Link Corporation (public-private partnership)
  • Client
    Busan Metropolitan City
  • Delivery date
    2010
  • Partners
    General contractor: Daewoo
    Consultant: COWI
    Engineer: DM / COWI International

Key figures

The Geoga cable-stayed bridge is meant to withstand strong winds, large swell waves, and strong tidal currents. Not only did we design, supply, and install the stay cable system but we also participated in the construction of the towers and precast slabs of the deck.

As part of a major highway development project, the South Korean government has initiated in partnership with the GK Fixed Link consortium the construction of the Busan-Geoje connection. The link consists of 3 major structures:

  • 3.2 km of immersed tunnel, bored at a 48-m depth,
  • A symmetrical cable-stayed bridge with 2 pylons consisting of a main span of 475 m freeing up a navigation gauge of 52 m – Lot 2,
  • A symmetrical cable-stayed bridge with 3 pylons made up of 2 main spans of 230 m – Lot 1
  • 165m
    Height of the bridge towers (metres)
  • 1,600t
    Total strand weight (tonnes)
  • 160
    Total number of cables
  • 250m
    Longest stay cable (metres)
Geoga bridge - Temporary stay cables

Temporary stay cables to secure the deck segments

Work began in April 2009 with the lifting and installation of a first 650-tonne segment, using a 3,000-ton offshore crane. A major challenge with the coordination and preparation of the different phases was to secure the segment with Freyssinet temporary stay cables and free the crane.

The current segments, with a unit weight of 330 tons, were then implemented by successive cantilevering using a lifting goat. To mitigate the meteorological risk during construction, each segment was assembled in 3 distinct phases of short duration:

  • lifting and bolting of the prefabricated steel structure (90 tons),
  • installation of shrouds,
  • lifting and installation of prefabricated concrete panels and jointing of the precast concrete slabs (6 x 40 tons).

Beyond contributing to the construction of the steel-concrete composite deck of the two-pylon bridge, we were also in charge of the fabrication and erection of the concrete pylons of both bridges, Lot 1 and 2.

1,600t. of stay cable strands to support the structure

The deck of the two-pylon bridge was a 975 m long floating structure, only supported by the Freyssinet PSS cable system. Located in the open sea, the structure was exposed to the harsh conditions of the Pacific Ocean, which was a major challenge both in the construction phase and throughout the service life of the structure. Performance of the system and sustainable technology provided were essential requirements to ensure durability of the structure.

Our cable system comprised 160 stay cables, with units 27, 31, 37, 48, 55, 61, 75 and 91. Cables were subjected to fatigue and watertightness tests to ensure endurance of the whole system.

To meet the restrictive wind stability criteria, 16 wind stability tie-down cables were used for the construction phase. Freyssinet stay cables were fitted with the latest damping technology to reach logarithmic decrement of respectively 4% and 6%. To this end, 132 internal radial dampers (IRD) and 28 external hydraulic dampers (EHD) were used.

A provision for dissipative cross tie cables was planned to cover all future risks on the longest cables (200 to 250 m).

Geoga bridge - positive impact

A positive impact

In addition to the technical challenges, the site had to meet the constantly evolving safety and quality standards in force at Freyssinet. The Busan-Geoje worksite gathered all the Freyssinet technics and expertise in terms of cable-stay installation while using the upgrade version of cable-stay construction control.

Being part of such an ambitious project has been extremely rewarding, considering its positive impact in terms of cost savings and environmental preservation: the road shortens the distance between Geoje Island and Busan by about 60 kilometers, and reduces the travel time to one hour, resulting in less traffic pollution.

Balanced cantilever construction
Back span segment closure
Back span cable-stay installation
IRD damper system
Main span longest cable with EHD dampers
Completion of Geoga bridge construction

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