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In the early stages of a project to construct the Pohang-Yeongdeok Expressway in eastern South Korea, a challenge was identified in the way the construction of one of the multi-span bridges was being planned – with the concrete superstructure being prefabricated in lengths corresponding to each span, and then stitched together with reinforcement and concrete at each pier. Unusual about the approach taken was that the continuous superstructure formed by the concreting together of the individual spans required to be supported, at each side of the superstructure, by a single bearing. This presented a particular challenge for the design of the bearings, which consequently had to support the uneven loading arising throughout the construction process. Most drastically, each bearing would be required to carry a load of 1600 kN at one side of the bearing before any load was applied at the other side, but a state of consistent even loading would only be achieved several months – or up to a year in some cases – after the first elements of superstructure were installed. This was particularly challenging because the bridge’s design called for the use of seismic isolators to support the superstructure, protecting it in case of an earthquake, and isolators of the curved surface slider (pendulum) type were specified – a type of isolator that offers no resistance to rotation in normal circumstances.
mageba RESTON®PENDULUM isolator bearings were selected for use on three of the project’s multi-span highway bridges – Bangseok No. 1, Bangseok No. 2 and Seojeongri Cheon. These were to be of the Duplo type, with two curved surfaces facilitating translation and simultaneous lifting of the supported structure during an earthquake. To address the specific challenge of the proposed bridge construction method for Seojeongri Cheon Bridge, a solution had to be developed and validated at short notice. Our local engineers in South Korea, working closely together with their colleagues in mageba’s Shanghai design and manufacturing facility and with the client, came up with the solution that is illustrated in the attached pictures. The bearings were designed with additional support elements between the upper and lower connection plates, one at each corner, to keep the connection plates parallel in spite of any uneven loading that might arise. These were designed with inclined sliding surfaces as shown to facilitate their easy removal when they are no longer needed – an elegant solution that has since been patented. Congratulations to our teams in South Korea and China for developing and validating this solution so quickly to meet the project’s special needs – always willing to go the extra mile for their clients!
Bridge designers: HONG-IK ENGINEERING & CONSULTANTS CO., LTD., KYONG DONG ENGINEERING CO,.LTD., SOOSUNG ENGINEERING CO.,LTD., Dream ENG CO., LTD.
Main contractor: DL E&C CO., LTD.
Owner: Korea Expressway Corporation