• Structural Engineering and Mechanics
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• 제41권1호
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• pp.139-155
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• 2012

Structural health monitoring systems are often installed on bridges to provide assessments of the need for structural maintenance and repair. Damage or deterioration may be detected by observation of changes in bridge characteristics evaluated from measured structural responses. However, construction materials such as concrete and steel cables exhibit certain time-dependent behaviour, which also results in changes in structural characteristics. If these are not accounted for properly, false alarms may arise. This paper proposes a systematic and efficient method to study the time-dependent effects on the dynamic properties of cable-stayed bridges. After establishing the finite element model of a cable-stayed bridge taking into account geometric nonlinearities and time-dependent behaviour, long-term time-dependent analysis is carried out by time integration. Then the dynamic properties of the bridge after a certain period can be obtained. The effects of time-dependent behaviour of construction materials on the dynamic properties of typical cable-stayed bridges are investigated in detail.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.198-203
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• 2004

Ocean developments gradually move to deep-sea in the 21 century. A deep-sea unmanned underwater vehicle is one of important tools for ocean resource survey. A marine cable plays an important role for the safe operation and signal transmission of a deep-sea unmanned underwater vehicle. The first cable of a deep-sea unmanned underwater vehicle is excited by surface vessel motion and shows non-linear dynamic behaviors. A ROV launcher is also excited by the 1st cable motion. A numerical method is necessary for analysing the dynamic behaviour of the first marine cable and the ROV launcher. In this study, a numerival program is appled to a 6,000m long cable for a deep-sea unmanned underwater vehicle to shaw shows the dynamic behaviour of the cable and the ROV launcher under combined excitations.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.123-130
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• 2004

Ocean developments gradually move to deep-sea in the 21 century. A deep-sea unmanned underwater vehicle is one of important tools for ocean resource survey. A marine cable plays an important role for the safe operation of a deep-sea unmanned underwater vehicle. The first cable of a deep-sea unmanned underwater vehicle is excited by surface vessel motion and shows non-linear dynamic behaviors. A numerical method is necessary for analysing the dynamic behaviour of the first marine cable. In this study, a numerical program is estabilished based on a finite difference method. The program is appled to a 6000m long cable for a deep-sea unmanned underwater vehicle and shows good reasonable results.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권1호
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• pp.9-19
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• 2012

A set of equations of motion is derived for vibratory motions of an underwater cable connected to a moving vehicle at one end and with drogues at the other end. From the static analysis, cable configurations are obtained for different vehicle speeds and towing pretensions are determined by fluid resistance of drogues. Also the dynamic analysis is required to predict its vibratory motion. Nonlinear fluid drag forces greatly influence the dynamic tension. In this study, a numerical analysis program was developed to find out the characteristic of cable behaviour. The motion is described in terms of space and time coordinates based on Chebyshev polynomial expansions. For the spatial integration the collocation method is employed and the Newmark method is applied for the time integration. Dynamic tensions, displacements, velocities, accelerations were predicted in the time domain while natural frequencies and transfer functions were obtained in the frequency domain.

• 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.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.157-173
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• 2020

In the finite element modelling of long-span cable-stayed bridges, there are a lot of uncertainties brought about by the complex structural configuration, material behaviour, boundary conditions, structural connections, etc. In order to reduce the discrepancies between the theoretical finite element model and the actual static and dynamic behaviour, updating is indispensable after establishment of the finite element model to provide a reliable baseline version for further analysis. Traditional sensitivity-based updating methods cannot support updating based on static and dynamic measurement data at the same time. The finite element model is required in every optimization iteration which limits the efficiency greatly. A convenient but accurate Kriging surrogate model for updating of the finite element model of cable-stayed bridge is proposed. First, a simple cable-stayed bridge is used to verify the method and the updating results of Kriging model are compared with those using the response surface model. Results show that Kriging model has higher accuracy than the response surface model. Then the method is utilized to update the model of a long-span cable-stayed bridge in Hong Kong. The natural frequencies are extracted using various methods from the ambient data collected by the Wind and Structural Health Monitoring System installed on the bridge. The maximum deflection records at two specific locations in the load test form the updating objective function. Finally, the fatigue lives of the structure at two cross sections are calculated with the finite element models before and after updating considering the mean stress effect. Results are compared with those calculated from the strain gauge data for verification.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.55-60
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• 2004

In this study, the configuration and tension of a towing cable for side-scan sonar are predicted in an ambient flow and at an unsteady towing condition. The governing equation of three-dimensional dynamic analysis for a flexible cable is solved using a finite difference method. We successfully predict the configuration and tension of a side-scan sonar and designed the towing system. It is found in static analyses that the side-scan sonar must be towed to keep a its stable depth at a reasonable speed. The study also reveals in the transient analyses that the dominant component affecting the top tension is the tangential drag force for the larger towing speed than the critical speed, and the self weight of a towed instrument for the smaller towing speed than. It should be maneuvered for a towing vessel with good consideration for the impact effect in a cable due to tension peak when a towing speed is suddenly increase. The developed program can be applicable for three-dimensional dynamic analysis of a towing system for various marine survey instruments.

• 대한토목학회논문집
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• 제9권3호
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• pp.1-12
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• 1989

사장교는 경간이 크기 때문에 발생하는 대변형 효과, 케이블의 현수 작용, 그리고 축력으로 인한 휨 강성 변화 등으로 비선형 거동이 나타난다. 사장교의 동적 거동은 구조물 안정성 검사를 위한 중요한 요소가 된다. 특히, 편재 이동하중이 작용하는 경우, 연직 변위와 비틂 변위는 복합될 뿐만 아니라 단면 좌우의 케이블 축력 변화도 중요한 동적 특성을 나타낸다. 본 연구에서는 편재 이동하중이 작용하는 사장교의 해석을 위한 이론적 연구와 유한 요소법을 제시하였고 이동 하중의 속도변화와 편심량의 크기에 따라 케이블의 장력과 절점 변위에 대한 동적 거동을 규명하였다. 본 연구에서 수행한 해석 결과에 따르면, 편재 이동 하중을 받는 사장교의 해석에서는 주형의 비틂과 이로 인한 케이블 축력 증가도 고려해야 할 것으로 사료된다.

• 대한조선학회논문집
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• 제39권1호
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• pp.28-37
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• 2002

본 연구에서는 저장력 예인케이블의 비선형 동적거동을 수치적으로 해석하였다. 고장력 케이블해석에서는 흔히 무시되는 굽힘강성의 효과가 저장력 케이블에서는 중요한 역할을 하므로 본 연구에서는 이를 고려하였다. 또한 저장력 케이블에서는 대변위가 발생하기 쉬우므로 기하학적인 비선형 및 유체 비선형 효과가 크므로 이를 고려하였다. 저장력 예인케이블에 대한 3차원 비선형 운동방정식을 수립하고 유한차분법을 적용하여 이산화 시켰다. 시간적분에 있어서 안정적인 해를 얻을 수 있는 음해법(implicit method)을 적용하였으며 비선형 해를 구하기 위하여 Newton-Raphson 반복법을 사용하였다. 케이블과 같이 양단경계조건을 갖고 대각선 주변 성분만 있는 행렬식을 계산하는 경우에는 Gauss-Jordan 방법 등과 같이 일반적인 방법 보다 블록삼중대각행렬 풀이법이 계산시간을 상당히 줄일 수 있음을 알 수 있었다. 몇 가지 예제해석을 수행하였으며 실해역 실험결과에 의해 이미 검증되어 있는 케이블 해석프로그램인 WHOI Cable 프로그램의 해석결과와 비교 검토한 결과 서로 잘 일치함을 알 수 있었다.

• 대한토목학회논문집
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• 제14권6호
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• pp.1299-1308
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• 1994

본 연구는 사장교의 차량하중에 의한 동적거동을 파악하고자 수치해석상 비교적 간단한 일본의 풍리(豊里)(Toyosato)대교(大橋)의 자료를 근거로하여 수치해석 대상모델을 구조형식별로, 여러가지 설계변수-즉, (1) 경간비, (2) 중앙경간장과 주탑높이와의 비, (3) 거어더의 강성, (4) 주탑의 강성, (5) 케이블의 강성-을 변화시켜 수치해석을 수행하여 동적거동을 파악하고, 그 결과를 가지고 설계변수의 영향 및 충격계수의 변화에 대하여 비교 분석하였다. 이때 변위 및 단면력의 영향선을 구하기 위한 해석은 전달행렬법을 이용하였으며, 동적해석에 있어서는 평면구조계의 집중질량계로 모델을 가정하여 차량과 교량의 운동방정식을 유도한 후 모드중첩법을 사용하여 각 질점에 대한 변위 및 단면력의 동적시간이력을 구하였다.