• 대한토목학회논문집
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• 제28권5A호
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• pp.657-664
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• 2008

사장교 케이블은 구조적으로 휨강성과 감쇠력이 작아 풍우에 의해 쉽게 유해진동이 발생한다. 이러한 풍우진동을 저감시키기 위한 효과적인 방법으로 부가댐퍼를 장착하여 케이블의 감쇠력을 증가시키는 제어시스템이 널리 사용되어왔다. 그러나 사장교의 장대화로 인해 구조적으로나 미적으로 충분한 감쇠력을 제공할 수 있는 위치에 부가댐퍼를 장착하기 어렵게 되었다. 최근 본 저자는 사장교의 미관을 해치지 않으면서 기존의 제어시스템보다 효과적으로 케이블의 진동을 저감시킬 수 있는 새로운 개념의 사장교 케이블 진동 제어시스템을 제안하였다. 본 논문에서는 기존의 연구를 확장하여 새그(Sag)를 고려한 Movable anchorage 시스템을 제안하였으며, 수치해석을 통한 제어성능을 평가하였다. 수치해석의 결과 제안된 시스템은 새그를 고려하였을 때에도 고려하지 않은 경우와 마찬가지로 베어링장치의 강성이 작을수록 기존의 비감쇠 시스템이나 일반적인 수동제어시스템보다 훨씬 좋은 성능을 나타내었다. 제안된 시스템에 있어서 최적의 제어성능을 제공하기 위해서는 새그의 크기를 고려해서 최적의 감쇠계수를 결정해야 할 것으로 사료된다.

• 대한토목학회논문집
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• 제26권5A호
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• pp.881-885
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• 2006

사장교 케이블은 구조적으로 휨강성과 감쇠력이 작아 풍우에 의해 쉽게 유해진동이 발생한다. 이러한 풍우진동을 저감시키기 위한 효과적인 방법으로 부가댐퍼를 장착하여 케이블의 감쇠력을 증가시키는 제어시스템이 널리 사용되어왔다. 그러나 사장교의 장대화로 인해 구조적으로나 미적으로 충분한 감쇠력을 제공할 수 있는 위치에 부가댐퍼를 장착하기 어렵게 되었다. 그러므로 본 논문은 사장교의 미관을 해치지 않으면서 기존의 제어시스템보다 효과적으로 케이블의 진동을 저감시킬 수 있는 새로운 개념의 제어시스템을 제안하였다. 제안된 시스템은 케이블 앵커리지에 적층고무베어링과 같은 유동이 가능한 장치와 내부댐퍼로 구성되었으며, 제어성능평가를 위해 해석모델을 개발하였다. 제안된 시스템의 제어성능 분석을 위해 수치해석을 수행하였으며 기존의 부가 댐퍼시스템과 진동 저감효과를 비교하였다. 제안된 제어시스템은 기존의 부가댐퍼 시스템 보다 효과적으로 진동을 저감시킬 수 있었으며 사장교 케이블의 풍우진동 저감을 위해 효과적인 시스템으로 사료된다.

• Structural Engineering and Mechanics
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• 제5권4호
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• pp.399-414
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• 1997

This paper presents an investigation into the seismic response characteristics of a proposed ligh-weight pedestrian cable-stayed bridge made entirely from Glass Fiber Reinforced Plastics(GFRP). The study employs three dimensional finite element models to study and compare the dynamic characteristics and the seismic response of the GFRP bridge to a conventional Steel-Concrete (SC) cable-stayed bridge alternative. The two bridges were subjected to three synthetic earthquakes that differ in the frequency content characteristics. The performance of the GFRP bridge was compared to that of the SC bridge by normalizing the live load and the seismic internal forces with respect to the dead load internal forces. The normalized seismically induced internal forces were compared to the normalized live load internal forces for each design alternative. The study shows that the design alternatives have different dynamic characteristics. The light GFRP alternative has more flexible deck motion in the lateral direction than the heavier SC alternative. While the SC alternative has more vertical deck modes than the GFRP alternative, it has less lateral deck modes than the GFRP alternative in the studied frequency range. The GFRP towers are more flexible in the lateral direction than the SC towers. The GFRP bridge tower attracted less normalized base shear force than the SC bridge towers. However, earthquakes, with peak acceleration of only 0.1 g, and with a variety of frequency content could induce high enough seismic internal forces at the tower bases of the GFRP cable-stayed bridge to govern the structural design of such bridge. Careful seismic analysis, design, and detailing of the tower connections are required to achieve satisfactory seismic performance of GFRP long span bridges.

• Smart Structures and Systems
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• 제15권3호
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• pp.505-522
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• 2015

Variation of temperature is a primary environmental factor that affects the behavior of structures. Therefore, understanding the mechanisms of normal temperature-induced variations of structural behavior would help in distinguishing them from anomalies. In this study, we used the structural health monitoring data of the Shanghai Yangtze River Bridge, a steel girder cable-stayed bridge, to investigate the mechanisms of thermally induced vertical deflection ($D_T$) at mid-span of such bridges. The $D_T$ results from a multisource combination of thermal expansion effects of the cable temperature ($T_{Cab}$), girder temperature ($T_{Gir}$), girder differential temperature ($T_{Dif}$), and tower temperature ($T_{Tow}$). It could be approximated by multiple linear superpositions under operational conditions. The sensitivities of $D_T$ of the Shanghai Yangtze River Bridge to the above temperatures were in the following order: $T_{Cab}$ > $T_{Gir}$ > $T_{Tow}$ > $T_{Dif}$. However, the direction of the effect of $T_{Cab}$ was observed to be opposite to that of the other three temperatures, and the magnitudes of the effects of $T_{Cab}$ and $T_{Gir}$ were found to be almost one order greater than those of $T_{Dif}$ and $T_{Tow}$. The mechanisms of the thermally induced vertical deflection variation at mid-span of a cable-stayed bridge as well as the analytical methodology adopted in this study could be applicable for other long-span cable-stayed bridges.

• 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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.344-345
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• 2011

A necessity to a superconducting cable in power transmission systems have been growing more and more due to high power density in urban areas and rapid increase of power demand. In view of these situation, it is a noteworthy fact that superconducting cable has remarkable advantages, such as lower power loss and 3-5 times higher power transmission capacity, compared with conventional power cable. For the last a few years, long-term reliability tests had been carried out in the KEPCO PT Center, and now it has been installed in KEPCO's real power grid for demonstrating commercial operation. This paper deals with the test results of dielectric properties performed at manufacturing factory for the joint box, termination and core of HTS cable system and whole system connected in real power grid.

• 한국기계가공학회지
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• 제16권3호
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• pp.138-145
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• 2017

With the increasing use of smart electronic devices, the size of the related I/O interface market is increasing rapidly. Demand is also growing for the continuous increase of data and video signals-such as faster data processing speed and data storage capacity-in the smart electronic device input/output interface market. Currently, the POF hybrid cable used in the smart electronic device input / output interface market cannot transmit over a long distance because the optical loss is too large, and the GOF hybrid cable is both vulnerable to bending and other sudden outside changes, and expensive. Therefore, in this study, the design and fabrication of a GOF hybrid cable and fiber guide were carried out in order to develop a cable which can easily withstand external impact, has low optical losses, and meets the demand for continuous data and video signal increase in the smart electronic device input / output interface market.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.191-196
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• 2002

The paper presents a numerical and experimental investigation on dynamic behaviors of a towed low tension cable. In the numerical study, an implicit finite difference algorithm is employed for three-dimensional cable equations. Fluid and geometric non-linearity and bending stiffness are considered and solved by Newton-Raphson iteration. Block tri-diagonal matrix method is applied for the fast calculation of the huge size of matrices. In order to verify the numerical results and to see real physical phenomena, an experiment is carried out for a 6m cable in a deep and long towing tank. The cable is towed in two different ways; one is towed at a constant speed and the other is towed at a constant speed with top end horizontal oscillations. Cable tension and shear forces are measured at the top end. Numerical and experimental results are compared with good agreements in most cases but with some differences in a few cases. The differences are due to drag coefficients caused by vortex shedding. In the numerical modeling, non-uniform element length needs to be employed to cope with the sharp variation of tension and shear forces at near top end.

• Smart Structures and Systems
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• 제18권3호
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• pp.585-599
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• 2016

Steel cables serve as the key structural components in long-span bridges, and the force state of the steel cable is deemed to be one of the most important determinant factors representing the safety condition of bridge structures. The disadvantages of traditional cable force measurement methods have been envisaged and development of an effective alternative is still desired. In the last decade, the vision-based sensing technology has been rapidly developed and broadly applied in the field of structural health monitoring (SHM). With the aid of vision-based multi-point structural displacement measurement method, monitoring of the tensile force of the steel cable can be realized. In this paper, a novel cable force monitoring system integrated with a multi-point pattern matching algorithm is developed. The feasibility and accuracy of the developed vision-based force monitoring system has been validated by conducting the uniaxial tensile tests of steel bars, steel wire ropes, and parallel strand cables on a universal testing machine (UTM) as well as a series of moving loading experiments on a scale arch bridge model. The comparative study of the experimental outcomes indicates that the results obtained by the vision-based system are consistent with those measured by the traditional method for cable force measurement.

• 한국초전도ㆍ저온공학회논문지
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• 제9권3호
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• pp.52-56
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• 2007

A high temperature superconducting (HTS) DC cable is ideal for transmitting large blocks of electrical power over a long distance. However, it must be designed to operate reliably within the constraints of the electrical systems. Therefore, a study of the electrical insulation is important to develop a HTS DC cable because it is operated in a cryogenic high voltage environment. This paper discusses the dielectric constructions of the cable and summarizes the experimental results on the DC and impulse dielectric characteristics of the insulation material. in sheet form and mini-model cable configuration. This shows how to design such insulation to be operated reliably. These studies are essential for the insulation design of a HTS DC cable operated in cryogenic environment.