• Journal of Ocean Engineering and Technology
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• v.26 no.1
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• pp.70-77
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• 2012

In this study, a numerical analysis of offshore installation using a floating crane with heave compensator is carried out in time domain. The motion analysis of crane vessels is based on floating body dynamics using convolution integral and the crane wire is treated as simple spring. The lifted structure is assumed as a rigid body with 3 degree-of-freedom translational motion. The heave compensator is numerically modelled by the generalized spring-damper system. Firstly, forced motion simulations of crane wire system are carried out to figure out the basic principle of heave compensator. The transfer function of crane wire system is obtained and effective wave period of heave compensator are found. Then, coupled analysis of crane vessel, crane wire, and lifted structure are performed in regular and irregular sea conditions. Two different crane vessels and two lifted structures (suction pile and manifold) are considered in this study. Through a series of numerical calculations, the effective zone of heave compensator is investigated with respect to wave period and crane wire length.

• Journal of Korean Association for Spatial Structures
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• v.4 no.1 s.11
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• pp.49-59
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• 2004

A previous study evaluated the seismic response of typical multi-span simply supported (MSSS) and multi-span continuous (MSC) steel-girder bridges in the central and southeastern United States. The results showed that the bridges were vulnerable to damage resulting from impact between decks, and large ductility demands on nonductile columns. Furthermore, fixed and expansion bearings were likely to fail during strong ground motion. In this paper, several retrofit measures to improve the seismic performance of typical multi-span simply supported and multi-span continuous steel girder bridges are evaluated, including the use of elastomeric bearings, lead-rubber bearings, and restrainer cables. It is determined that iead-rubber bearings are the most effective retrofit measure for reducing the seismic vulnerability of typical bridges. While isolation provided by elastomeric bearings limits the forces into the columns, the added flexibility results in pounding between decks in the MSSS steel-girder bridge. Restrainer cables, which are becoming a common retrofit measure, are only moderately effective in reducing the seismic vulnerability of MSSS and MSC steel girder bridges.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.9-20
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• 2014

Steel intermediate moment frames (IMFs) have been generally used as seismic load resisting systems (SLRSs) of a building to provide resistances against strong ground shaking. However, most of low and mid-rise steel buildings in Korea were constructed during pre-seismic code era or before the introduction of well-organized current seismic codes. It has been recognized that the seismic performance of these steel IMFs is still questionable. In order to respond to such a question, this study quantitatively investigates the seismic capacities of steel IMFs. Prototype models are built according to the number of stories, the levels of elastic seismic design base shear and the ductilities of structural components. Also, the other prototype models employing hysteretic energy dissipating devices (HEDDs) are considered. The collapse mechanism and the seismic performance of the prototype models are then described based on the results obtained from nonlinear-static and incremental-dynamic analyses. The seismic performance of the prototype models is assessed from collapse margin ratio (CMR) and collapse probability. From the assessment, the prototype model representing new steel IMFs has enough seismic capacities while, the prototype models representing existing steel IMFs provide higher collapse probabilities. From the analytic results of the prototype models retrofitted with HEDDs, the HEDDs enhance the seismic performance and collapse capacity of the existing steel IMFs. This is due to the energy dissipating capacity of the HEDDs and the redistribution of plastic hinges.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.2039-2046
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• 2003

Storage tank filled with fluid has unique dynamic characteristics compared to general structures, due to the interaction between fluid and structure. The oscillation of the fluid surface caused by external forces is called sloshing, which occurs in moving vehicles with contained liquid masses, such as trucks, railroad cars, aircrafts, and liquid missles. In this study, the evaluation method for the reduction of sloshing, the optimized size and location of wing and diaphragm baffles are suggested based on the experimental results. The experimental device can simulate the translation motion. A rectangular tank and various baffles are fabricated to study on the sloshing characteristics. The forces measured using the load cell at tank wall and those are compared with each other through the Fourier transformation for various conditions. The study of the sloshing of the rectangular tank equipped with baffles is conducted under the same conditions with non-baffled rectangular tank experiment. From the experimental results, the sloshing reduction effect by the baffles is observed. In conclusion in case of diaphragm baffles, the optimized size ratio of the width of baffle to the water height is 0.44 and the installation location has no effect to the damping of sloshing. In case of wing baffles, the optimized size ratio of the width of baffle to the length of a rectangular tank is 0.1 and the optimized location ratio of the baffle to the water height is 0.9.

• Journal of KSNVE
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• v.5 no.3
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• pp.275-283
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• 1995

본 글에서는 지능구조물의 개념설명과 더불어 ERF의 특성, ERF를 함유란 함유 한 지능구조물 시스템의 구성, 동적 모델링과 진동제어 그리고 그 응용성에 관한 연구 현황과 방향에 대해 살펴보았다. 설명한 바와 같이 지능구조물은 새로운 차원의 신생 하는 첨단분야로서, 소음 및 진동에 관련된 무한한 잠재력과 다양한 응용성으로 미루 어 볼때 아주 매력적인 연구 분야이다. 그러나, 여러 응용 시스템의 상품화 단계로의 도약에 있어서 각 시스템 구성 요소 분야별 해결해야할 연구 사항들이 있다. 먼저, 액추에이팅을 수행하는 ERF 자체의 내구성 문제로서 고온에서 ERF의 효과 하락과 장시간 사용시 ERF에 의한 마멸, 고체 입자의 침전에 의한 초기 상태 불안정 등이 있다. 아울러 기존의 장치의 성능을 능가하기 위해 보다 큰 효과를 나타내는 새로운 차원의 ERF개발이 요구된다. 그리고 센서기술 분야에서는 호스트 재료에 보다 쉽게 결합이 되고 여러가지 형태의 요구조건을 만족시킬 수 있으며 외부 환경조건에 강건 하고 다양한 센서 개발이 요구된다. 또한, 보다 일번적인 동적 모델링을 통해 적용 시스템에 적합하고 강건한 제어기에 대한 연구가 진행되어야 한다. 마지막으로 능동 제어기를 실제로 구현하기 위한 호스트 재료 각 요소마다 센서의 설치, 페회로 피드백 시스템 장착, 상호간의 인터페이스 등의 기술 발전이 요구되며, 아울러 보다 효율적 인 시스템의 성능 특성을 실현할 수 있는 호스트 재료와 기계 메카니즘이 필요로 된다. 이상의 설명에서 알 수 있듯이 지능구조물에 대한 연구는 어느 한 분야에서만 아니라 기계, 전기전자, 토목, 물리, 재료과학 등 통합형식에 의한 접근 방향으로 추진되어야 할 것이다.서 세탁기의 진동 소음을 저감시키기 위해 진동 소음원에 대해 논술하고, 진동해석을 위해 컴퓨터 시뮬레이션 결과를 이용한 저진동 기술 개발에 대하여 기술하고자 한다.rotary piston)식 압축기는 약 20여년 전 부터 냉방용 압축기에서부터 널리 쓰이게 되었다. 약 10여년전부터 상용화 된 스크롤(scroll) 형 압축기도 현재 상대적으로 용량이 큰 가정용 냉방기를 중심으로 많이 쓰이고 있다. 스크류형 압축기는 보통 중대형 상업용에 주로 쓰인다. 해결하려 하였고, 수치해석은 피스톤의 운동을 배제한 단순화한 흡배기계의 정상상태 유동해석이 주를 이루어왔다. Taghaui and Dupont 등[5]은 KIVA코드를 사용하여 흡기포트와 연소실 그리고 밸브의 움직임을 동시에 고려한 수치해석을 도입하였다. 하지만 이들이 밸브의 운동을 고려하기 위해 사용한 이동격자는 격자점은 시간에 따라 변화하지만 그 격자의 수가 일정하게 유지되어 있어서 밸브의 완전개폐를 해석할 수가 없다. 강희정[6]은 단일 실린더와 단일 배기밸브를 갖는 문제로 단순화하여 피스톤과 밸브의 움직임을 고려하므로써 배기행정 후 소음이 어떻게 전파해 나가는가를 연구하였다. 본 연구에서도 최소밸브간격과 최대밸브간격 사이에서만 계산이 가능하나 흡기의 경우는 밸브가 닫힐 때 생기는 압력파가 중요하므로 실린더와 밸브사이에 벽면조건을 주어 밸브의 개폐를 모사하였다.술을 보유하고자 한다. 이용한 해마의 부피측정은 해마경화증 환자의 진단에 있어 육안적인 MR 진단이 어려운 제한된 경우에만 실제적 도움을 줄 수 있는 보조적인 방법으로 생각된다.ofile whereas relaxivity at high field is not affected by τS.

• Journal of the Korea Society for Simulation
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• v.15 no.4
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• pp.119-128
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• 2006

A turnout system which permits trains to pass from one track to another is a combination of the switch, the crossing, lead rails which are necessary to connect the switch and the crossing, two guard rails and a switch machine for operating the switch. A turnout is the sole moving part among the railway components and has complex configuration, so the safety has always been raised an issue. In Korea, it is planned to adopt the high speed tilting train, which operates at the maximum speed of 200km/h, at conventional lines by the year of 2010. However, for the application of the tilting train to conventional lines, it is prerequisite to establish a stable turnout system allowing the tilting train to pass through it without reducing speed. Therefore, the improved turnout system for the speed-up of conventional lines has been developed and the prototype of the turnout system has been constructed. In this study, simulation of noise and vibration around the improved turnout system was performed in order to predict the generation level of noise and vibration due to passing of the tilting train through the turnout system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1244-1251
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• 2022

Marine accidents due to a loss of stability, have been gradually increasing over the last decade. Measures must be taken on the roll reduction of a ship. Amongst the measures, building an anti-roll tank in a ship is recognized as the most simple and effective way to reduce the roll motion. Therefore, this study aims to develop a computational model for a U-tube type anti-roll tank and to validate it by experiment. In particular, to validate the developed computational model, the height of the free surface in the tank was measured in the experiment. To develop a computational model, the mesh dependency test was carried out. Further, the effects of a turbulence model, time step size, and the number of iterations on the numerical solution were analyzed. In summary, a U-tube type anti-roll tank simulation had to be performed accurately with conditions of a realizable k-𝜖 turbulence model, 10^-2s time step size, and 15 iterations. In validation, the two cases of measured data from the experiment were compared with the numerical results. In the present study, STAR-CCM+ (ver. 17.02), a RANS-based commercial solver was used.

• Journal of Navigation and Port Research
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• v.41 no.6
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• pp.365-372
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• 2017

The rolling motion of a floating body makes crews and passengers exhausted and/or applies forces to the structure to cause damage; it might even upset the body. Therefore, almost all ships are equipped with bilge keels for anti-rolling; in special cases, an anti-rolling tank(ART) or fin stabilizer or gyroscope could be installed. But an ART requires a large capacity to install it, and a fin stabilizer and gyroscope need great costs to install and also many expenses to operate. The authors suggest the use of an anti-rolling pendulum(ARP), and they showed that the ARP is effective to reduce rolling by experiments and via a Runge-Kutta analysis. This paper introduces the linearized 2 degrees of freedom with a viscous damping system for a ship equipped with ARP; it also shows the validation of the linearized analysis for the ship's roll motion. The paper proposes an optimum ARP on the basis of the justified model. The case of the 7.7kg model with ship 20g ARP of a mass ratio of 0.26%, is the most effective for reducing roll motion. The paper shows the ARPs with various mass ratios are effective for reducing the roll motion of a ship by free decaying roll experiments.