• Computers and Concrete
• /
• 제21권1호
• /
• pp.55-66
• /
• 2018

A large main shock may consist of numerous aftershocks with a short period. The aftershocks induced by a large main shock can cause the collapse of a structure that has been already damaged by the preceding main shock. These aftershocks are important factors in structural damages. Furthermore, despite what is often assumed in seismic design codes, earthquakes do not usually occur as a single event, but as a series of strong aftershocks and even fore shocks. For this reason, this study investigates the effect and potential of consecutive earthquakes on the response and behavior of concrete structures. At first, six moment resisting concrete frames with 3, 5, 7, 10, 12 and 15 stories are designed and analyzed under two different records with seismic sequences from real and artificial cases. The damage states of the model frames were then measured by the Park and Ang's damage index. From the results of this investigation, it is observed that the sequences of ground motions can almost double the accumulated damage and increased response of structures. Therefore, it is certainly insufficient to ignore this effect in the design procedure of structures. Also, the use of artificial seismic sequences as design earthquake can lead to non-conservative prediction of behavior and damage of structures under real seismic sequences.

• 한국정밀공학회지
• /
• 제28권10호
• /
• pp.1166-1173
• /
• 2011

There have been many researches about SUGV (Small Unmanned Ground Vehicle) mechanism regarding off-road mobility and obstacle negotiation. This paper introduces an analysis of geometry parameters to enhance the vertical obstacle negotiation ability for the SUGV. Moreover, this paper proposes an anti-shock structure analysis of wheels to protect the main body of the SUGV when it falls off a vertical obstacle. Major system geometry parameters will be determined under certain constraints. The constraints and optimization problem for maximizing the ability of vertical obstacle negotiation will be presented and discussed. Dynamic simulation results and experiments with manufactured platform will also be presented to validate the analysis. Several types of wheel materials and structures will be compared to determine the best anti-shock wheel design through FEM (Finite Element Method) simulations.

• 한국수소및신에너지학회논문집
• /
• 제21권3호
• /
• pp.167-183
• /
• 2010

This paper analyzes the backgrounds of the standards for protection against electric shock in Global Technical Regulations (GTR) of Fuel Cell Vehicle (FCV). Targets on research were high voltage criteria, safety current, isolation and grounding resistance, time limitation, energy, adequate clearance, and test procedure. Based on human impedance and effect of current in IEC 60479-1, safety of human was examined. Then, isolation and grounding circuit model of FCV were analyzed theoretically. The results give several suggestions: touch voltage less than 25V, AC energy less than 0.0813J, separation considering middle finger length, grounding resistance less than $0.2\Omega$, maximum AC ground voltage of 1V (rms), and isolation resistance between earth and electrical chassis. In MATLAB/Simulink environment, error characteristics of isolation resistance measurement procedure using internal DC sources were analyzed under variations of internal resistance of voltmeter and isolation resistance.

• 한국군사과학기술학회지
• /
• 제24권6호
• /
• pp.569-576
• /
• 2021

Radar is a ground defense system that detects enemy aircraft and receives power from a mobile power supply in an emergency. Serious problems may occur if the equipment is damaged by impact during transportation for use. The US military standard MIL-STD-810H contains information on environmental tests such as shock and vibration applied to munitions. Therefore, in this study, the transient analysis of ANSYS 19.2 was performed using the impact data specified in MIL-STD-810H as an input value. Through this, the maximum stress generated in the impact environment of the mobile power supply container was derived, and the safety margin was calculated to confirm the reliability of the container.

• 전기학회논문지
• /
• 제60권4호
• /
• pp.885-891
• /
• 2011

In this paper, we studied dc leakage current properties analysis of LED lamps of road and landscape lighting when leakage current appeared in dc power line. Generally, converter of LED lighting is divides to insulated type and non-insulated type according to components. When electric leakage happened in AC power line, earth leakage breaker(ELB) senses leakage current and interrupts electric circuit. In dc power source, We need experimental verification about dc electric leakage for electricity safety. In normal wiring conditions and in the water, in case of using insulated type of converter, dc leakage current did not occur. However, in case of using non-insulated type of converter, dc leakage current occurred and passed through into the ground. We found that there is a hazard of electric shock by dc leakage current. We expect that the results of these studies would be helpful for electrical safety of LED lamps for road and landscape lighting.

• 조명전기설비학회논문지
• /
• 제28권12호
• /
• pp.13-17
• /
• 2014

In this paper, the risk of electric shock is analyzed through analysis for characterization of potential distribution analysis and ground fault current analysis near the area where there are occurred a ground fault at electric vehicle wireless charging system using 20kHz. Studies for electric vehicle wireless charging system are in the works for development of efficiency increase, pickup shape design and communication module as a fundamental research step. But the research related to electrical safety and is still scarce state so that more studies are necessary to commercialize. As a result of analysis, it is verified that induced voltage is arisen more up to 45V near the a area of accident during ground fault and fault current has been maintained continuously without clearing fault condition by operating characteristics for circuit breaker and inverter.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 추계학술대회 논문집
• /
• pp.196-201
• /
• 2008

In DC traction systems, a part of feedback current returning through rails becomes leakage current, illumination on a metal laid underground results from the leakage current to ground. To prevent the leakage current on rails, feedback rails almost have insulated with the ground. Insulation between rails and the ground causes that the earth method changes a isolated method in DC traction systems. the rail potential rise results in the isolated method. the rail potential rise causes an electric shock when a person touches the ground and rolling stock. To decrease the rail potential rise and leakage current, there are methods for reducing the feedback resistance and current of rails, increasing the leakage resistance, decreasing the distance between substations. But it are necessary to forecast and analyze the rail potential and amplitude of leakage current. In this paper, we modeled DC traction systems and feedback circuit to simulate the rail potential and amplitude of leakage current using PSCAD/EMTDC that is power analysis program, forecasted the rail potential and amplitude of leakage current about changing various parameters in the electric circuit. By using the simulation model, we easily will forecast the rail potential and amplitude of leakage current in case of a level of basic design and maintenance in electric railway systems, valuably use basic data in case of system selection.

• 조명전기설비학회논문지
• /
• 제16권2호
• /
• pp.121-129
• /
• 2002

본 논문에서는 효과적인 접지그리드 설치기법에 대하여 기술하였으며, 낙뢰나 지락고장서지, 개폐서지 등으로 부터 인체의 감전보호나 컴퓨터를 비롯한 전기·전자기기의 보호를 위한 접지그리드의 시설 및 배치방법에 따른 실험적인 평가를 수행하였다. 접지그리드의 배치에 따른 대지표면전위경도의 분석과 위험전압으로 작용하는 대지 표면전위상승의 억제에 주안점을 두고 실험용 모델접지전극을 시설한 후 임 펄스전류를 인가하였다. 기존의 등간격 접지그리드의 결점을 보완하기 위해 접지그리드에 경사를 가지는 보조접지그리드를 시설하였으며, 보조접지그리드를 시설한 접지시스템에서는 인체나 전기·전자기기에 위험전압으로 작용하는 대지표면전위경도를 최대 50%이상 완화시키는 효과를 얻었다.

• 화약ㆍ발파
• /
• 제30권2호
• /
• pp.9-20
• /
• 2012

최근 광업계는 지하개발이 주로 이루어지며, 대형 굴착장비의 보급으로 인해 갱도 및 채굴공동이 지하심 부화되고 있다. 채광설계 시 채굴공동의 붕락방지와 채광작업의 안전성 확보를 위해 채굴공동 및 광주의 설계가 매우 중요하게 대두되고 있다. 이에 본 연구는 지하채굴공동의 발파진동계측을 통한 발파진동 예측식 도출을 수행하였고, 채굴공동의 발파시 발생되는 비산석의 파쇄입도 분석과 비산거리 측정을 통하여 광주에 가해지는 이론적인 충격진동을 산정하였다. 지하채굴공동의 발파에 따른 광주의 영향을 검토하기 위하여 유한요소해석을 수행하여 발파진동 예측식과 비교하였으며, 채굴공동의 발파로 인해 발생되는 비산석이 광주에 충격이 가해졌을 때의 충격진동과 이론적인 충격진동을 비교, 분석하였다.

• 한국항공우주학회지
• /
• 제46권8호
• /
• pp.652-661
• /
• 2018

고속 고온 유동에서 나타나는 고온 기체 현상을 모사하기 위해서는 마하수뿐 아니라 절대속도도 재현할 수 있어야 한다. 이러한 유동을 초음속 유동과 구분하여 극고속 유동이라 부르며, 충격파 터널과 같은 고엔탈피 시험 장치를 통해 연구가 이루어지고 있다. 그러나 이러한 고엔탈피 시험 장비는 높은 온도와 압력 때문에 노즐에서 열화학적 비평형 현상을 경험하게 되며 기존의 이론적 방법으로 그 실험 조건을 규정하기 어렵다. 이에 본 연구에서는 알려진 비평형 노즐 코드의 단점들을 보완하고 충격파 터널의 운용 조건에서 시험부 유동 특성을 빠르게 예측하기 위하여 열화학적 비평형을 고려한 준 1차원 노즐 해석 코드를 개발하였다. 개발된 코드는 시험 결과 및 2차원 축대칭 해석 결과와 비교를 통하여 충격파 풍동 시험부 유동 조건 예측을 위한 활용성 및 한계를 살펴보았다.