• 대한조선학회논문집
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• 제53권5호
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• pp.388-399
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• 2016

A motion analysis of an underwater towed cable is a complex task due to its nonlinear nature of the problem. The major source of the nonlinearity of the underwater cable analysis is that the motion of the cable involves large rigid-body motion. This large rigid-body motion makes difficult to use standard displacement-based finite element method. In this paper, the authors apply recently developed nodal position-based finite element method which can deal with the geometric nonlinearity due to the large rigid-body motion. In order to enhance the stability of the large-scale nonlinear cable motion simulation, an efficient time-integration scheme is proposed, namely predictor/multi-corrector Newmark scheme. Three different predictors are introduced, and the best predictor in terms of stability and robustness for impulsive cable motion analysis is proposed. As a result, the nonlinear motion of underwater cable is predicted in a very efficient manner compared to the classical finite element of finite difference methods. The efficacy of the method is demonstrated with several test cases, involving static and dynamic motion of a single cable element, and also under water towed cable composed of multiple cable elements.

• Structural Engineering and Mechanics
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• 제34권6호
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• pp.719-738
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• 2010

The aim of this paper concerns with the nonlinear analysis of cable-stayed bridges including the vibration effect of cable stays. Two models for the cable stay system are built up in the study. One is the OECS (one element cable system) model in which one single element per cable stay is used and the other is MECS (multi-elements cable system) model, where multi-elements per cable stay are used. A finite element computation procedure has been set up for the nonlinear analysis of such kind of structures. For shape finding of the cable-stayed bridge with MECS model, an efficient computation procedure is presented by using the two-loop iteration method (equilibrium iteration and shape iteration) with help of the catenary function method to discretize each single cable stay. After the convergent initial shape of the bridge is found, further analysis can then be performed. The structural behaviors of cable-stayed bridges influenced by the cable lateral motion will be examined here detailedly, such as the static deflection, the natural frequencies and modes, and the dynamic responses induced by seismic loading. The results show that the MECS model offers the real shape of cable stays in the initial shape, and all the natural frequencies and modes of the bridge including global modes and local modes. The global mode of the bridge consists of coupled girder, tower and cable stays motion and is a coupled mode, while the local mode exhibits only the motion of cable stays and is uncoupled with girder and tower. The OECS model can only offers global mode of tower and girder without any motion of cable stays, because each cable stay is represented by a single straight cable (or truss) element. In the nonlinear seismic analysis, only the MECS model can offer the lateral displacement response of cable stays and the axial force variation in cable stays. The responses of towers and girders of the bridge determined by both OECS- and MECS-models have no great difference.

• 문화기술의 융합
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• 제10권4호
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• pp.473-481
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• 2024

본 논문은 윈치드럼과 함께 구성되어 있는 수중 케이블의 거동을 해석하기 위해 개발된 조출 모델링을 소개한다. 케이블의 수중 거동은 장력만 영향을 준다고 가정한다. 이러한 가정은 직진 거동을 하는 함정에 의해 예인되는 수중 케이블 거동을 해석하는데 적합하다. 수중 케이블은 절점 위치유한 요소법으로 차분한다. 이 수치기법은 기하학적 비선형성을 표현할 수 있기 때문에 대변형을 동반하는 수중 케이블의 거동 예측에 적합하다고 알려져 있다. 본 논문은 실제 역 실험에서 계측된 수중 예인케이블의 심도 정보를 활용하여 수치 기법의 타당성을 확보한다.

• 한국강구조학회 논문집
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• 제19권5호
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• pp.435-454
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• 2007

본 연구에서는 국내 내진 설계규정에서 고려하고 있지 않은 근거리지진의 특성을 규명하고, 사장교 구조물에 미치는 영향을 검토하고자 한다. 대표적인 근거리 및 원거리지진의 실측자료를 선정한 후, 탄성 및 비탄성응답스펙트럼을 작성하여 지진기록의 특성을 분석하였다. 세 가지 형식의 사장교 및 실제 사장교 구조물을 대상으로 지진특성에 따른 응답해석을 수행하여 주요부재에 대한 응답특성을 비교 분석하였다. 또한 지진응답해석 결과를 이용하여 신뢰성해석을 수행하였으며, 신뢰성지수 및 파괴확률을 검토함으로써 대상 사장교 구조물의 내진 안전성을 정량적으로 평가하였다. 응답스펙트럼, 지진응답해석 및 신뢰성해석 결과에 의하면 근거리지진이 사장교 응답에 대한 영향은 기존의 원거리지진과는 상이한 양상을 보이고 있으므로, 사장교 구조물 설계 시 중요한 인자로 고려해야 할 것을 제시하고자 한다.

• Structural Engineering and Mechanics
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• 제18권4호
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• pp.429-440
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• 2004

Remotely Operated Vehicle of 6000-meters is a new conceptual equipment made to replace the manned systems for investigating the deep-sea environment, and all of the ROV systems in operational condition strongly depend on the connecting cables. In this point of view dynamics of the ROV cable system is very important for operational and safety aspects as a cable generally encounters great tension. Researches have been executed on this problem, and most of papers have been mainly focused on the operational condition of ROV system in deep sea. This paper presents the dynamic cable response analysis during ROV launching condition rather than the operational one in order to provide the design guide of a ROV cable system in this circumstance, considering the coupling effects between cable and wave-induced ship motion. To obtain the variations of cable tensions during a ROV launching, a pre-stressed harmonic response analysis was carried out. Wave-induced tensions of the cable during ROV launching were obtained in real sea states using FE modeling, and the basic design guide of a ROV cable system was obtained.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.424-429
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• 2003

As a critical member of cable-stayed bridges, stay cables play an important role of supporting the entire structure. Traffic, wind or rain-wind induced vibrations of stay cables would be a major cause of degrading both safety and serviceability of the bridge. One of the effective alternatives to solve this problem is to employ the cable dampers. In order to design the cable damper optimally. it is necessary to exactly estimate the dynamic characteristics of the existing cables. Therefore, in this study, a cable exciting system (exciter) controlled digitally was developed. And to evaluate the performance of the cable exciter developed, a solution of the differential equation of cable motion considering the exciter was derived. Using the cable exciter. sine sweeping and resonance tests on a cable model were carried out to obtain the dynamic characteristics effectively.

• Structural Engineering and Mechanics
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• 제18권2호
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• pp.231-246
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• 2004

In this paper, a comparison of various random vibration and deterministic dynamic analyses of cable-stayed bridges subjected to asynchronous ground motion is presented. Different random vibration methods are included to determine the dynamic behaviour of a cable-stayed bridge for various ground motion wave velocities. As a numerical example the Jindo Bridge located in South Korea is chosen and a 413 DOF mathematical model is employed for this bridge. The results obtained from a spectral analysis approach are compared with those of two random vibration based response spectrum methods and a deterministic method. The analyses suggest that the structural responses usually show important amplifications depending on the decreasing ground motion wave velocities.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.61-68
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• 2008

A set of modal parameters of a stay-cable have been extracted from a moving picture captured by a digital camera supported by shaking hands. It is hard to identify the center of targets attached on the cable surface from the blurred cable motion image, because of the high speed motion of cable, low sampling frequency of camera, and the shaking effect of camera. This study proposes a multi-template matching algorithm to resolve such difficulties. In addition, a sensitivity-based system identification algorithm is introduced to extract the natural frequencies and damping ratios from the ambient cable vibration data. Three sets of vibration tests are conducted to examine the validity of the proposed algorithms. The results show that the proposed technique is pretty feasible for extracting modal parameters from the severely shaking motion pictures.

• 한국소음진동공학회논문집
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• 제18권12호
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• pp.1229-1236
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• 2008

A set of modal parameters of a stay-cable have been extracted fi:on a moving picture captured by a digital camera supported by shaking hands. It is hard to identify the center of targets attached on the cable surface from the blurred cable motion image, because of the high speed motion of cable, low sampling frequency of camera, and the shaking effect of camera. This study proposes a multi-template matching algorithm to resolve such difficulties. In addition, a sensitivity-based system identification algorithm is introduced to extract the natural frequencies and damping ratios from the ambient cable vibration data. Three sets of vibration tests are conducted to examine the validity of the proposed algorithms. The results show that the proposed technique is pretty feasible for extracting modal parameters from the severely shaking motion pictures.

• Wind and Structures
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• 제19권5호
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• pp.481-503
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• 2014

A new theoretical model on rain-wind induced vibration (RWIV) of a continuous stay cable is developed in this paper. Different from the existing theoretical analyses in which the cable was modeled as a segmental rigid element, the proposed scheme focuses on the in-plane and out-of-plane responses of a continuous stay cable, which is identical with the prototype cable on cable-stayed bridge. In order to simplify the complexities, the motion law of the rivulet on the cable surface is assumed as a sinusoidal way according to some results obtained from wind tunnel tests. Quasi-steady theory is utilized to determine the aerodynamic forces on the cable. Equations of motion of the cable are derived in a Cartesian Coordinate System and solved by using finite difference method to obtain the in-plane and out-of-plane responses of the cable. The results show that limited cable amplitudes are achieved within a limited range of wind velocity, which is a unique characteristic of RWIV of stay cable. It appears that the in-plane cable amplitude is much larger than the out-of-plane cable amplitude. Rivulet frequency, rivulet distribution along cable axis, and mean wind velocity profile, all have significant effects on the RWIV responses of the prototype stay cable. The effects of damping ratio on RWIVs of stay cables are carefully investigated, which suggests that damping ratio of 1% is needed to well mitigate RWIVs of prototype stay cables.