이어도 종합해양과학기지의 진동 계측자료를 이용한 구조물 동특성 분석

Abstract

To study the ocean and meteorological issues related to global climate change and global warming, Korea is operating several ocean research stations (ORS), including Ieodo ORS, Gageocho ORS, and Sochengcho ORS in remote ocean area. In 2003, the Ieodo ORS was first constructed and in operation, and a lot of scientific studies were carried out using the observation data at Ieodo ORS. After the Gageodo ORS was attacked by Typhoon Muifa and was severely damaged to its structural members, ORSs were equipped with vibration measurement systems to monitor their structural integrities. In the case of Ieodo ORS, the vibration measurement system was instrumented in 2016. In this study, the structural dynamic characteristics of the Ieodo ORS were investigated using the vibration measurement data, including acceleration and tilt. As a result, three natural frequencies of two bending modes and torsional mode were estimated as 1.315 Hz, 1.390 Hz, and 1.590 Hz, respectively, and these natural frequencies were compared with those estimated using measurement data in 2005 and 2006 by Kim et al. (2006). It was found that the natural frequencies were decreased as about 2-3.8% due to the combined effect of structural degradation and the increase of mass of equipment. Long-term measurement data were also analyzed to obtain the variation of dynamic characteristics according to the environmental effects such as temperature and excitation force. It was also found that the dynamic characteristics of Ieodo ORS are not affected by temperature and tidal level while they are significantly affected by the level of excitation force, i.e., the amplitude of vibration responses can be used to account for the effect of excitation force indirectly.