APPLICATION OF CABLE INSTALLATION TECHNOLOGIES WITH LINK MECHANISMS ON LONG BRIDGES IN KOREA

摘要

This paper describes cable installation technologies byrnusing link mechanisms for long bridges in Korea.rnTwo kinds of mechanisms, which have evidentlyrndifferent design concepts, were adopted to Yong-jongrnand Seo-kang bridges. The design concept was either therncompactness or the sufficient safety marginrnThe structures of link mechanisms should be designedrnwith the proper parameters of cable sheath fatigue so thatrnthey never cause a mechanical damage on the powerrncables during its lifetime.rnIn the case of Yong-jong bridge, the bending radius ofrnthe cable offset was safely set by 30 Ds, and the arc of therncable offset is restricted to the change before and afterrnoperation. The strain limit of the cable sheath was setrnlower than 0.3% of the installation standard of the KorearnElectric Power Corporation.rnFor Seo-kang bridge, in the meantime, as the installationrnspace is limited by the width of 1.5m, the link mechanismrnmust be designed to have minimum weight, minimumrnbending radius(15 D_s) and maximum accumulated sheathrnfatigue (close to 1.0 or lower).rnThe link mechanisms with cables have been installed onrnthe field after carrying out an accelerated mechanical testrnfor emulating 30 years duration and the electricalrnperformance test for cables.rnThe mechanical design was evaluated whether or not itrnworks under the given operating conditions. In order tornemulate the in-situ cable, the mechanical test wasrnperformed with 3 phase - 2 cct cables under its maximumrnampacity.rnAs a test results, since the bending radius of the linkrnmechanism is small and the sheath fatigue is close to 1, itrnis easy to know that the Seo-kang bridge was designedrnunder the concept of compactness. To evaluate thernsuitability of the design, the test results on the prototypernmechanism for Yong-jong bridge was compared with thernresults by CAE. When verifying the prototypernmechanism for Seo-kang bridge, the sheath fatigue hasrnbeen regarded as the most important factor among therntest results. Maximum daily strain was 0.2845% whichrndoesn’t exceed the design value 0.2929%. The sheathrn0.8720% was 12 % lower than the design value 0.9957%.rnIt implies that the prototype acquired 12% additionalrnsafety margin when compared to the target value (lowerrnthan 1.0).rnAfter a mechanical test for each link mechanism, anrnelectrical test, which is for checking the residualrncharacteristics, was performed in order to check whetherrnany damage occurs or the expected lifetime is reducedrnfor the power cables. The test has been performed basedrnon IEC60840. After AC and impulse tests, the test for thernlifetime (n=12, 400kV/3hours) and the impulsernbreakdown test were performed. The results of thernelectrical test for cables installed on the prototypernmechanisms showed no signs of deterioration inrnelectrical performance.rnThe link mechanisms for each bridge have been installedrnbased on the test results and have been being successfullyrnoperated since the end of 1999 and mid 2000,rnrespectively.