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나원배,우진호,김동하 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.2
Submersed rock-berm structures are frequently used for protection of underwater lifelines such as pipelines and power cables. During the service life, the rock-berm structure can experience several accidental loads such as anchor collision. The consequences can be severe with a certain level of frequency; hence, the structural responses should be carefully understood for implementing a proper structural health monitoring method. However, no study has been made to quantify the structural responses because it is hard to deal with the individual behavior of each rock. Therefore, this study presents a collision analysis of the submersed rock-berm structure using a finite element software package by facilitating the smoothed-particle hydrodynamics (SPH) method. The analysis results were compared with those obtained from the Lagrange method. Moreover, two types of anchors (stock anchor and stockless anchor), three collision points and two different drop velocities (terminal velocity of each anchor and 5 m/s) were selected to investigate the changes in the responses. Finally, the effect of these parameters (analysis method, anchor type, collision point and drop velocity) on the analysis results was studied. Accordingly, the effectiveness of the SPH method is verified, a safe rock-berm height (over 1 m) is proposed, and a gauge point (0.5 m above the seabed) is suggested for a structural health monitoring implementation.
Parametric density concept for long-range pipeline health monitoring
나원배,윤한삼 국제구조공학회 2007 Smart Structures and Systems, An International Jou Vol.3 No.3
Parametric density concept is proposed for a long-range pipeline health monitoring. This concept is designed to obtain the attenuation of ultrasonic guided waves propagating in underwater pipelines without complicated calculation of attenuation dispersion curves. For the study, three different pipe materials such as aluminum, cast iron, and steel are considered, ten different transporting fluids are assumed, and four different geometric pipe dimensions are adopted. It is shown that the attenuation values based on the parametric density concept reasonably match with the attenuation values obtained from dispersion curves; hence, its efficiency is proved. With this concept, field engineers or inspectors associated with long-range pipeline health monitoring would take the advantage of easier capturing wave attenuation value, which is a critical variable to decide sensor location or sensors interval.
나원배(Won-Bae Na) 전남대학교 수산과학연구소 2020 수산과학연구소논문집 Vol.28 No.2
It is not easy to properly manage the fishery resources mainly because we do not know how the invaluable resources act with social, economic, and environmental fluctuations in detail. Nonetheless, we have installed artificial reefs (underwater man-made structures) in the coastal waters and tried to take advantages over. One of the main trials is large artificial reef projects over the world, launched from the 70s and 80s, to promote fisheries. Accordingly, we have accumulated some aftermath (hoping it is not totally mess we made) such as issues accumulated and resolutions related. This study summarizes how the issues have been risen to the surface and how relevant resolutions have been constructed from the surface not only to defend the original sin that we made but also promote the future works on which we have to focus, especially emphasizing the so-called attraction-production debate and its solution.
Finite Element Analysis of Geometrically Nonlinear Cable Nets
Na,Won-Bae,Cho,Hyun-Man,Ryu,Yeon-Sun 釜慶大學校 1998 釜慶大學校 論文集 Vol.3 No.2
본 연구에서는 범용유한요소프로그램을 이용한 케이블망의 비선형정적해석을 제시하였다. 해석모델로는 등매개변수 케이블 요소로 이루어진 유한요소모델을, 비선형해법으로는 다중증분과 평형반복을 갖는 혼합법을 사용하였다. 하중으로는 집합하중과 자중을, 구조형식으로는 접시, 완장, 현수형의 케이블망을 고려하였다. 해의 수렴을 위해서 전처리단계에서는 초기변형율을, 해법단계에서는 자동하중분할을 도입하였다. 해석결과는 종전에 주어진 결과와 비교되어 본 연구결과의 정확성과 효율성이 증명되었다. 또한 수치해석의 경험으로부터, 케이블망의 기하학적 비선형해석의 성공적인 수행을 위해서는 미소초기변형율을 도입해야 한다는 것을 알았다.