가거초 해양과학기지 장기 진동 모니터링 및 모델 개선

Abstract

In order to study ocean and meteorological issues related to the climate change, Korea has been operating several ocean research stations (ORS) in remote ocean area including Ieodo ORS since 2003, Gageocho ORS since 2009 and Sochengcho ORSsince 2014. In 2011, the Gageocho ORS was directly attacked by Typhoon Muifa and its structural members and several observation devices were severely damaged. After this event, the Gageocho ORS was rehabilitated with 5 m heightening considering the 100-year extreme wave height, and the vibration measurement system was also instrumented to monitor the structural vibrational characteristics and to assess the structural integrity of the Gageocho ORS. In this study, the modal characteristics of the Gageocho ORS were identified and investigated using the long-term measurement data. As a result, natural frequencies of lower two bending modes and one torsional mode were reliably estimated as around 1.78, 1.82, and 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 uncertainty when the acceleration response was larger. The damping ratio was estimated as about 0.7%, 0.6%, and 0.5% for lower three modes, respectively. A preliminary finite element (FE) model was constructed using the design drawings and the several candidate baseline FE models were manually built considering different structural conditions