Twinning of Jindo Grand Bridge, Republic of Korea

During the early 1980's Rendel Palmer & Tritton (now practicing as High-Point Rendel-HPR) was responsible for the full detailed design and supervision of construction of a major cable-stayed bridge linking Jindo Island to the South West corner of the Korean Peninsular, for the Ministry of Construction & Transportation. This bridge, with a 344m main span and 70m side spans, was not only one of the world's longest cable stayed spans at the time, but more significantly, the slenderest, being just l lm wide. As a consequence, considerable effort was expended on ensuring the aerodynamic stability of the design, both during construction and in service. The bridge was opened to traffic in 1984.

Early in 2000, the same Client commenced the process of increasing the traffic capacity of the crossing and issued the documents for a Turnkey Competition to design and construct an additional crossing near the existing two-lane structure.

Two local design companies, Yooshin Corporation and DM Engineering, together with High-Point Rendel, were engaged by Hyundai Engineering & Construction, to carry out the necessary engineering services for this Turnkey Competition, and if successful to provide the further engineering services for completion of construction. For the tender submission the services included site investigation and route option studies, followed by wind tunnel testing, simulations, preliminary design and a full set of preliminary design drawings.

The dualling of this very slender bridge posed some challenges. Not only was the aesthetic treatment of the new crossing of paramount importance, but the option selected, the addition of a near identical and very slender bridge deck immediately adjacent to the existing bridge, required careful study in terms of its aerodynamic behaviour.

The Turnkey Competition was won by the Hyundai group submission. The chosen form of the new bridge is a 70 - 344 - 70m span configuration with steel ‘A’ frame towers. A particular feature of the twinning concept is the detailed consideration of aesthetics. This paper describes some of the important features of the existing bridge and their impact on the form of the new bridge. It describes how the new bridge differs from the existing and the measures taken to harmonise the two together. The paper outlines the aerodynamic investigations and the proposals for ensuring aerodynamic stability of the twin bridges.

• The site

• The existing bridge

• Developments since opening.

• The second crossing

• Selection of new bridge location

• Form of new bridge

• Differences in detailed design

• Aerodynamic modelling