단기 및 장기계측자료를 이용한 가거초 해양과학기지의 모드특성 분석

Abstract

In order to study ocean and meteorological issues related to the global climate change and global warming, Korea has been operating several ocean research stations (ORS) in remote ocean area including Ieodo ORS since 2003, Gageocho ORS since 2009 and Sochengcho ORS since 2014. In 2011, the Gageocho ORS was attacked by Typhoon Muifa and it was severely damaged to its structural members including several observation devices. After that, the Gageocho ORS was rehabilitated with 5 m heightening considering the extreme wave height with 100 years of return period, and the dynamic response measurement system was also instrumented to investigate the structural characteristics of jacket-type offshore structures and to assess the structural integrity of the Gageocho ORS. In this study, the structural dynamic characteristics of the Gageocho ORS were investigated using the short-term and long-term measurement data including acceleration and inclination. As aresult, natural frequencies of lower two bending modes and one torsional mode were estimated as 1.79, 1.82, 2.65 Hz, respectively. It was also found that the damping ratios in the first mode could be more consistently obtained with lower level of variation when the acceleration response was larger. The damping ratio was estimated as about 0.7%. It is expected that the present results obtained from short- and long-term monitoring can be used to build the essential database for