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앵커 충돌 위치 변화에 따른 아치형 해저케이블 보호 구조물의 과도동적해석
우진호(Jinho Woo),나원배(Won-Bae Na) 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.5
This study presents of finite element simulation of an arch-type reinforced concrete under anchor collision. For the analysis, a dynamic finite element program, ANSYS AUTODYN, was used to examine the damage contour, displacement and stress of the arch-type submarine power cable protector. The RHT concrete material model are used for concrete modeling. Five collision points were considered. From the analyses, the effects of the collision location on the results (displacement and stress) were analyzed.
앵커 충돌 위치 변화에 따른 아치형 해저케이블 보호 구조물의 과도동적해석
우진호(Jinho Woo),나원배(Won-Bae Na) 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5
This study presents a finite element simulation of an arch-type reinforced concrete under anchor collision. For the analysis, a dynamic finite element program, ANSYS AUTODYN, was used to examine the damage contour, displacement and stress of the arch-type submarine power cable protector. The RHT concrete material model are used for concrete modeling. Five collision points were considered. From the analyses, the effects of the collision location on the results (displacement and stress) were analyzed.
아치형 해저 케이블 보호 구조물의 앵커 충돌 수치 시뮬레이션
우진호(Jinho Woo),나원배(Won-Bae Na),김헌태(Heon-Tae Kim) 한국해양공학회 2009 韓國海洋工學會誌 Vol.23 No.1
In 2006, Jeju Island in South Korea experienced a crisis, no electricity for three hours anywhere in the entire island. This incident was caused by a domino effect that occurred after one of the submarine power cables connecting the island to Haenam, a coastal city on the mainland, was damaged by an external load, probably from a ship anchor or a steel pile being used in marine farming. This study presents a collision analysis if a new submarine power cable protector called arch type reinforced concrete. For the analysis, a dynamic finite element program, ANSYS AUTODYN, was used to examine the displacement and stress of the submarine power cable protector using different material models (RHT concrete model, Mohr-Coulomb concrete model). In addition, two reinforcing bar spacings, 75 mm and 150 mm, were considered. From the analysis, the effects of the parameters (concrete model and spacing) on the results (displacenJent and stress) were analyzed, and the relations between the damage and parameters were found.
수치 시뮬레이션을 이용한 동파력을 받는 벌집형 유공케이슨의 안정성 해석
우진호(Jinho Woo),나원배(Won-Bae Na),강윤구(Yoon-Koo Kang) 한국해양공학회 2010 韓國海洋工學會誌 Vol.24 No.1
This study presents a stability analysis procedure for caisson structures and a case study for a honeycomb slit-caisson. CADMAS-SURF was used to calculate the wave pressures based on an irregular wave with a 50-year period and the data for three regular waves obtained from a target site. Then, the irregular and regular wave pressures were used to obtain the dynamic responses (stresses) of the caisson structure using an explicit time integration program, ANSYS/LS-DYNA. Finally, the DNV code was used for structural and fatigue stability analyses.
유체-지반-구조물 상호작용을 고려한 이중 원통형 슬릿 케이슨의 내진해석
우진호(Jinho Woo),나원배(Won-Bae Na),강윤구(Yoon-Koo Kang) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
Recently, it is emphasized to consider fluid-soil-structure interaction in seismic analyses for caisson structures to acquire more robust design practice. This study presents a seismic analysis of a double cylinder-type slit caisson by considering fluid-soil-structure interaction. In the analysis, The fluid was assumed by the added mass, the double cylinder-type slit caisson was modelled by solid and shell elements. Three seismic waves were considered for the analyses such as Hachinohe, Ofunato, and artificial sesmic waves. Then, seismic waves were used to obtain the dynamic responses (displacements and stresses) of the caisson structure using an explicit time integration procedure in ANSYS.
앵커 충돌 및 끌림에 의한 원통연결 보호구조물의 최대 응답 해석
우진호(Jinho Woo),나원배(Won-Bae Na) 한국해양공학회 2010 韓國海洋工學會誌 Vol.24 No.5
This study presents the results of collision and lift analyses of a cylinders-connected protector under stock anchor colliding and dragging. For the analyses, the terminal velocity of the stock anchor was obtained first, and, then, the velocity was used to calculate the falling distance of the stock anchor in air. In addition, two other falling distances were considered for purposes of comparison. From the finite element analyses, using ANSYS, the maximum responses obtained from the stock anchor colliding and dragging were obtained and compared for different collision distances (3, 5, and 8.83 m) and dragging angles (0, 3D, 60, 90°). Then, the maximum displacements and stresses were discussed, along with the strength and dimensions of the protector. Finally, conclusions were made for the maximum responses.
단면 겹치기 접착 조인트에 존재하는 비대칭 결함 탐지를 위한 탄성파 유한요소 시뮬레이션
우진호(Jinho Woo),나원배(Won-Bae Na) 한국해양공학회 2009 韓國海洋工學會誌 Vol.23 No.6
This study presents a finite element simulation of elastic waves for detecting anti-symmetric damages in an adhesively-banded single lap joint. Plane strain elements were used for modeling adherents (aluminum) and adhesives (epoxy). Three types of damage were introduced: thickness reduction, elasticity deterioration, and voids in the adhesive layers, and two excitation and reception arrangements (ER1 and ER2) were used to investigate the detectability of the damage. The simulation showed that symmetrically located damage, such as a thickness reduction, can be detected by one excitation and one reception arrangement (ER1) and anti-symmetric damages, such as elasticity deterioration and voids, can be detected by modified two-point elastic wave excitation (ER2). Compared with the ER1 arrangement, the ER2 arrangement does not require a baseline signal for damage detection; hence, an efficient method of anti-symmetric damage detection in an adhesively-bonded single lap joint is proposed.
우진호(Jinho Woo),나원배(Won-Bae Na) 한국해양공학회 2010 韓國海洋工學會誌 Vol.24 No.6
This study presents free vibration analyses of perforates steel plates with various cutouts. Four different parameters (shape, size, curvature radius ratio, and rotation of cutouts) were considered to investigate the effects of those parameters on the free vibration characteristics, such as natural frequencies if the perforated steel plates. Three different shapes if cutouts are circle, square, and triangle, and the considered sizes are 5, 10, 15, 20, and 25 ㎜. For the triangular and square cutouts, the characteristic radii of the inscribed circles if those cutouts were defined. In addition, the curvature radius ratio was defined as the ratio of curvature radius if bluntness and the characteristic radius. Then, total seven different curvature radius ratios (0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1) were considered. To investigate the rotation effect of the cutouts, it was considered four rotations (0°, 15°, 30°, and 45°) for the square cutouts and three rotations (0, 15, and 30) for the triangular cutouts. All the free vibration analyses were conducted using a general purpose finite element program. From the analyses we found that the most influential parameter for the free vibration response of the perforated plates is the size of cutout. The other factors such as the shape, curvature radius ratio, and rotation are minors; they mainly change the natural frequency as long as the size effect is accompanied.
수중강판의 결함 및 열화 검출을 위한 탄성파 유한요소 시뮬레이션
우진호(Jinho Woo),나원배(Won-Bae Na) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.3
This paper presents the results of finite element simulations of elastic wave propagation in an underwater steel plate and the verification of a proposed method utilizing elastic wave?based damage detection. For the simulation and verification, we carried out the following procedures. First, three?dimensional finite element models were constructed using a general purpose finite element program. Second, two types of damages (mechanical defects and deteriorations) were applied to the underwater steel plate and three parameters (defect location, defect width, and depth) were considered to adjust the severity of the applied damages. Third, elastic waves were generated using the oblique incident method with a Gaussian tone burst, and the response signals were obtained at the receiving point for each defect or deterioration case. In addition, the received time domain signals were analyzed, particularly by measuring the magnitudes of the maximum amplitudes. Finally, the presence and severity of each type of damage were identified by the decreasing ratios of the maximum amplitudes. The results showed that the received signals for the models had the same global pattern with minor changes in the amplitudes and phases, and the decreasing ratio generally increased as the damage area increased. In addition, we found that the defect depth was more critical than the width in the decrease of the amplitude. This mainly occurred because the layout of the depth interfered with the elastic wave propagation in a more severe manner than the layout of the width. An inverse analysis showed that the proposed method is applicable for detecting mechanical defects and quantifying their severity.