• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.278-282
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• 2001

The purpose of this study is to introduce a new spacer damper for the bundle transmission lines network. It has the special design, the main characteristics and advantage of this new kind of spacer damper. An Existing spacer damper with bolted clamps, although widely used, is a method of connection with certain disadvantage both as regards assembly on the conductor and in the course of time. Even if tightening torque is correctly applied by using bolt with share head or torque wrench during working time, the aeolian vibration could involve untightening during life time, so the cable can move into the Jaws and wire's breakage appear. To salve this problems, France, Japan and other countries had developed a spacer damper with an automatic system through many years. This new spacer damper is an original automatic clamping device (beltless) which does not require special tool for its installation. This device prevents clamp unlocking problems, ensures a simple installation and ensures a reliable-tightening during life time. Therefore, it is necessary to localize this boltless spacer damper with automate clamping device.

• 한국전기전자재료학회논문지
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• 제17권12호
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• pp.1326-1331
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• 2004

In this paper, we have investigated thermal properties and Impurities content of specimens showing by changing the content of carbon black that is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens was measured by ICPAES(Inductively Coupled Plasma Atomic Emission Spectrometer). Heat capacity(ΔH) and melting temperature(Tm) were measured by DSC(Differential Scanning Calorimetry). The ranges of measurement temperature were from $0^{\circ}C$ to 20$0^{\circ}C$, and heating temperature was 4$^{\circ}C$/min. And then thermal diffusivity was measured by LFA 447. The measurement temperature was $25^{\circ}C$. Impurities content was highly measured according to increasing the content of carbon black from ICPAES results. And heat capacity and melting temperature from the DSC results were simultaneously decreased according to increasing the content of carbon black, while thermal diffusivity was increased according to increasing the content of carbon black. Because ionic impurities of carbon black containg Fe, Co, Mn, Al, and Zn were rapidly increasing kinetic energy by vibration of ionic impurities through the applied heat energy.

• Structural Monitoring and Maintenance
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• 제3권1호
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• pp.51-69
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• 2016

Monitoring the performance and estimating the remaining useful life of aging civil infrastructure in the United States has been identified as a major objective in the civil engineering community. Structural health monitoring has emerged as a central tool to fulfill this objective. This paper presents a review of the major structural monitoring programs that have been recently implemented in the United States, focusing on the integrity and performance assessment of large-scale structural systems. Applications where response data from a monitoring program have been used to detect and correct structural deficiencies are highlighted. These applications include (but are not limited to): i) Post-earthquake damage assessment of buildings and bridges; ii) Monitoring of cables vibration in cable-stayed bridges; iii) Evaluation of the effectiveness of technologies for retrofit and seismic protection, such as base isolation systems; and iv) Structural damage assessment of bridges after impact loads resulting from ship collisions. These and many other applications show that a structural health monitoring program is a powerful tool for structural damage and condition assessment, that can be used as part of a comprehensive decision-making process about possible actions that can be undertaken in a large-scale civil infrastructure system after potentially damaging events.

• 소음진동
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• 제9권3호
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• pp.535-543
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• 1999

The seismic qualification of the structures has been great concern in our engineering society with an effort to reduce the severe damages from an earthquake. However, on the contrary to the importance of the seismic qualification, the whole procedures are used to rely on the advanced countries who require various expenses for the qualification, which leads to the heavy loss of the foreign currency. In this study, the nuclear air conditioning system produced by LG Cable are adopted for the seismic qualification based on the guideline of NUREG, IEEE and ASME code. In order to confirm the validity of the present study, the results from the Ellis & Watts are compared with the present results and, also, the seismic qualification procedures and results mentioned herein are approved by KOPEC, which is a naitonal surveillance institute for the construction of nuclear power plant. From these results, the author confirmed the validity of the present seismic qualification procedures and results, which might be usefully applied to the other kind of seismic qualification of equipments.

• Wind and Structures
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• 제31권5호
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• pp.403-418
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• 2020

To investigate the effects of central buckles on the dynamic behavior and flutter stability of long-span suspension bridges, four different connection options between the main cable and the girder near the mid-span position of the Aizhai Bridge were studied. Based on the flutter derivatives obtained from wind tunnel tests, formulations of self-excited forces in the time domain were obtained using a nonlinear least square fitting method and a time-domain flutter analysis was realized. Subsequently, the influences of the central buckles on the critical flutter velocity, flutter frequency, and three-dimensional flutter states of the bridge were investigated. The results show that the central buckles can significantly increase the frequency of the longitudinal floating mode of the bridge and have greater influence on the frequencies of the asymmetric lateral bending mode and asymmetric torsion mode than on that of the symmetric ones. As such, the central buckles have small impact on the critical flutter velocity due to that the flutter mode of the Aizhai Bridge was essentially the symmetric torsion mode coupled with the symmetric vertical mode. However, the central buckles have certain impact on the flutter mode and the three-dimensional flutter states of the bridge. In addition, it is found that the phenomenon of complex beat vibrations (called intermittent flutter phenomenon) appeared in the flutter state of the bridge when the structural damping is 0 or very low.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권9호
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• pp.455-458
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• 2004

In this paper, we investigated impurities content and physical properties showing by changing the content of carbon black that is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens was measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer), and density of specimens were measured by density meter And then specific heat (Cp) was measured by DSC (Differential Scanning Calorimetry). A ranges of measurement temperature were from $0^{\circ}[C]$ to $200^{\circ}[C]$, and heating temperature was $4^{\circ}[C/min]$. Impurities content was highly measured according to increasing the content of carbon black from this experimental result, also density was increased according to these properties. Especially impurities content values of the Al and A2 of existing resins were measured more than 4000［ppm］. Specific heat from the DSC results was decreased according to increasing the content of carbon black. Because ionic impurities of carbon black having Fe, Co, Mn, Al and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.

• Structural Engineering and Mechanics
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• 제77권1호
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• pp.1-17
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• 2021

The influence of prestress force on the fundamental frequency and static deflection shape of uncracked Prestressed Concrete (PC) beams with a parabolic bonded tendon was examined in this paper. Due to the conflicts among existing theories, the analytical solutions for properly considering the dynamic and static behavior of these members is not straightforward. A series of experiments were conducted for a total period of approximately 2.5 months on a PC beam made with high strength concrete, subsequently and closely to the 28 days of age of concrete. Specifically, the simply supported PC member was short term subjected to free transverse vibration and three-point bending tests during its early-age. Subsequently, the experimental data were compared with a model that describes the dynamic behavior of PC girders as a combination of two substructures interconnected, i.e., a compressed Euler-Bernoulli beam and a tensioned parabolic cable. It was established that the fundamental frequency of uncracked PC beams with a parabolic bonded tendon is sensitive to the variation of the initial elastic modulus of concrete in the early-age curing. Furthermore, the small variation in experimental frequency with time makes doubtful its use in inverse problem identifications. Conversely, the relationship between prestress force and static deflection shape is well described by the magnification factor formula of the "compression-softening" theory by assuming the variation of the chord elastic modulus of concrete with time.

• Wind and Structures
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• 제32권1호
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• pp.71-80
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• 2021

In steel cable bridges, the use of magnetorheological (MR) dampers between butt cables is constantly increasing to dampen vibrations caused by rain and wind. The biggest problem in the actual applications of those devices is to launch a kind of appropriate algorithm that can effectively and efficiently suppress the perturbation of the tie through basic calculations and optimal solutions. This article discusses the optimal evolutionary design based on a linear and quadratic regulator (hereafter LQR) to lessen the perturbation of the bridges with cables. The control numerical algorithms are expected to effectively and efficiently decrease the possible risks of the structural response in amplification owing to the feedback force in the direction of the MR attenuator. In addition, these numerical algorithms approximate those optimal linear quadratic regulator control forces through the corresponding damping and stiffness, which significantly lessens the work of calculating the significant and optimal control forces. Therefore, it has been shown that it plays an important and significant role in the practical application design of semiactive MR control power systems. In the present proposed novel evolutionary parallel distributed compensator scheme, the vibrational control problem with a simulated demonstration is used to evaluate the numerical algorithmic performance and effectiveness. The results show that these semiactive MR control numerical algorithms which are present proposed in the present paper has better performance than the optimal and the passive control, which is almost reaching the levels of linear quadratic regulator controls with minimal feedback requirements.

• 대한토목학회논문집
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• 제33권1호
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• pp.71-80
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• 2013

설계를 위한 교량의 해석모델은 구조물의 안전성을 확보하기 위해 자중 및 외부하중은 되도록 크게, 구조물의 강성은 되도록 작게 평가하는 것이 일반적이다. 때문에 설계모델을 이용한 버페팅 응답은 실제 공용교량의 버페팅 응답과 차이를 나타낸다. 공용교량의 버페팅 응답을 정확하게 예측하기 위해서는 공용교량의 동적특성을 계측하여 해석모델이 계측값을 반영하도록 수정하여야 한다. 일반적으로, 실제교량과 동일한 고유진동수를 갖는 MBM(Measurement -based Model)을 구축하기 위해 설계모델의 다양한 물성치를 파라미터로 조정하며 계측된 고유진동수와 일치시키는 MTM(Manual Tuning Method)이 사용되고 있다. MTM은 파라미터의 초기치 설정에 따른 임의성이 높고 여러 수렴점을 가질 수 있어 분석에 상당한 노력이 소요된다. 본 연구는 버페팅해석에 널리 적용되고 있는 단일모드 주파수영역 해석법이 구조물의 모드형상, 고유진동수 및 감쇠비의 동적특성만을 이용하는 점에 착안하여 MTM과정 없이 설계모델의 버페팅 응답을 공용교량의 버페팅 응답으로 보정하는 BRCM(Buffeting Response Correction Method)을 제안하였다. BRCM은 설계모델의 모드형상 별 버페팅 응답을 공용교량의 고유진동수만으로 보정하는 방법이다. 공용교량의 고유진동수는 상시진동에 의한 계측 가속도로부터 산정하였다. BRCM의 적용성을 단순보 모델의 시간이력 버페팅해석을 수행하여 수치적으로 평가하였으며 공용교량모델을 이용한 버페팅해석결과, BRCM과 MTM의 응답 차이는 3% 이하로 나타났다. 공용교량의 실시간 계측시스템에 BRCM을 도입할 경우 사장교의 유지관리 효율성을 높일 수 있을 것으로 기대된다.

• 한국가스학회지
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• 제17권6호
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• pp.15-19
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• 2013

이 논문은 자동차 엔진룸에서 전기적인 접촉불량에 의한 단락현상과 엔진의 뜨거운 열에 의해 가연성 물질과 접촉하여 화재가 발생된 원인을 분석하고 연구하는 것이다. 첫째, 배터리에서 시동모터로 연결되어 있는 배터리 전원선이 자동변속기 상단에 배선을 고정시켜 주는 브래킷(Bracket) 볼트 이완으로 차체와의 단락 현상에 의해 화재가 발생된 것을 확인하였다. 둘째, 배터리에서 시동모터까지 가는 배선에 감은 절연테이프가 녹아 단락현상에 의해 화재를 일으킨 것을 확인하였다. 셋째, 냉각 팬 배선이 이완되어 과열된 엔진의 열에 의해 배선이 융착되어 화재가 발생된 것을 확인하였다 따라서, 엔진에 관련된 시스템의 화재는 엔진 및 각 시스템의 손상으로 자동차 탑승객을 위험에 처하게 하며, 화재 후 자동차는 재사용이 어렵게 되므로 시스템의 철저한 관리와 세심한 주의가 요구되어진다.