고정식 해양구조물의 동특성 및 구조손상 평가를 위한 실험 연구

Abstract

It is greatly crucial to monitor the structural dynamic characteristics such as natural frequencies and mode-shapes especially for tidal current power plants under strong tidal current environment because changes in dynamic characteristics are directly associated with structural integrity conditions. From the previous observation through long-term measurement for Uldolmok tidal current power plant structure, it was shown that the natural frequencies are fluctuated with certain cycle periods, i.e. twice a day and twice a month as changes of tidal height and tidal current velocity, and also it was reported that the construction work had a lot of trouble especially in connecting jacket support structure and its pile foundation. Therefore there is a necessity to investigate the reason of the fluctuation of natural frequencies and the integrity of pile foundation. In this study, a lab-scale experimental study was conducted using a circulating water channel. The natural frequency was extracted from measured acceleration by using frequency domain output-only modal identification method, i.e. peak-picking method. And then the experimental model was also verified with numerical model using ABAQUS. As a result, it was shown that the fluctuation of natural frequencies was governed by the decrease in stiffness at the foundation. It can be explained that the damage at foundation is much more crucial than the effect of added massare directly associated with structural integrity conditions. From the previous observation through long-term measurement for Uldolmok tidal current power plant structure, it was shown that the natural frequencies are fluctuated with certain cycle periods, i.e. twice a day and twice a month as changes of tidal height and tidal current velocity, and also it was reported that the construction work had a lot of trouble especially in connecting jacket support structure and its pile foundation. Therefore there is a necessity to investigate the reason of the fluctuation of natural frequencies and the integrity of pile foundation. In this study, a lab-scale experimental study was conducted using a circulating water channel. The natural frequency was extracted from measured acceleration by using frequency domain output-only modal identification method, i.e. peak-picking method. And then the experimental model was also verified with numerical model using ABAQUS. As a result, it was shown that the fluctuation of natural frequencies was governed by the decrease in stiffness at the foundation. It can be explained that the damage at foundation is much more crucial than the effect of added mass