• Structural Engineering and Mechanics
• /
• 제82권1호
• /
• pp.81-92
• /
• 2022

Ultra-high performance fiber reinforced concrete (UHPFRC) is a composite building material with high ductility, fatigue resistance, fracture toughness, durability, and energy absorption capacity. The aim of this study is to develop a nonlinear finite element model that can simulate the response of the UHPFRC beam exposed to impact loads. A nonlinear finite element model was developed in ABAQUS to simulate the real response of UHPFRC beams. The numerical results showed that the model was highly successful to capture the experimental results of selected beams from the literature. A parametric study was carried out to investigate the effects of reinforcement ratio and impact velocity on the response of the UHPFRC beam in terms of midpoint displacement, impact load value, and residual load-carrying capacity. In the parametric study, the nonlinear analysis was performed in two steps for 12 different finite element models. In the first step, dynamic analysis was performed to monitor the response of the UHPFRC beam under impact loads. In the second step, static analysis was conducted to determine the residual load-carrying capacity of the beams. The parametric study has shown that the reinforcement ratio and the impact velocity affect maximum and residual displacement value substantially.

• 한국음향학회지
• /
• 제26권6호
• /
• pp.235-242
• /
• 2007

공동주택의 바닥충격음 측정 및 평가는 주로 입주 전에 이루어지고 있으나 실제 충격음 발생은 입주 후 커튼과 가구와 같은 중량물이 설치되어 있는 조건이므로 입주 전 후 음원세대(음원실)와 수음세대(수음실)의 상황은 다르다고 할 수 있다. 본 연구에서는 음원실에 가구 등과 같은 하중 설치에 따른 중량충격음 변화정도를 파악하기 위하여 바닥충격음 시험동과 현장에서 활하중($200kg/m^2$) 설치 전 후의 음원실 바닥슬래브 하부 진동가속도레벨 및 수음실 충격음레벨 변화를 측정하였다. 측정결과 하중설치를 통하여 진동가속도레벨 및 충격음레벨이 다소 저감되었으나 큰 영향은 받지 않는 것으로 나타났으며, 슬래브의 공진주파수도 변화하지 않았다.

• Journal of Electrical Engineering and Technology
• /
• 제10권3호
• /
• pp.859-864
• /
• 2015

This paper analyzes the impact of Plug-in Electric vehicles(PEVs) on power demand and voltage change when PEVs are connected to the domestic distribution system. Specifically, it assesses PEVs charging load by charging method in accordance with PEVs penetration scenarios, its percentage of total load, and voltage range under load conditions. Concretely, we develop EMTDC modelling to perform a voltage distribution analysis when the PEVs charging system by their charging scenario was connected to the distribution system under the load condition. Furthermore we present evaluation algorithm to determine whether it is possible to adjust it such that it is in the allowed range by applying ULTC when the voltage change rate by PEVs charging scenario exceed its allowed range. Also, detailed analysis of the impact of PEVs on power distribution system was carried out by calculating existing electric power load and additional PEVs charge load by each scenario on new-town in Korea to estimate total load increases, and also by interpreting the subsequent voltage range for system circuits and demonstrating conditions for countermeasures. It was concluded that total loads including PEVs charging load on new-town distribution system in Korea by PEVs penetration scenario increase significantly, and the voltage range when considering ULTC, is allowable in terms of voltage tolerance range up to a PEVs penetration of 20% by scenario. Finally, we propose the charging capacity of PEVs that can delay the reinforcement of power distribution system while satisfying the permitted voltage change rate conditions when PEVs charging load is connected to the power distribution system by their charging penetration scenario.

• International Journal of Ocean System Engineering
• /
• 제2권3호
• /
• pp.151-159
• /
• 2012

The characteristics of an impact load and pressure were experimentally investigated. Drop tests were carried out using a modified Wigley with CB = 0.56. The vertical force, pressures, and vertical accelerations were measured. A 6-component load cell was used to measure the forces, piezo-electric sensors were used to capture the impact pressure, and strain-gauge type accelerometers were used to measure the vertical accelerations. A 50-kHz sampling rate was applied to capture the peak values. The repeatability of the measured data was confirmed and the basic characteristics of the impact load and pressure such as the linearity to the falling height were observed for all of the measurements. A simple formula was derived to extract the physical impact load from the measured force based on a simple mass-sensor-mass diagram, which was validated by comparing impact forces with existing data using the mathematical model of Faltinsen and Chezhian (2005). The effects of the elasticity of the model and change in acceleration during the water entry were investigated. It is interesting to observe that the impact loads occurred and reached peak values at the same time duration after water entry for all drop heights.

• 환경영향평가
• /
• 제15권6호
• /
• pp.407-415
• /
• 2006

This study carried out submerged area due to Dam construction in the near future. It includes species classification of plant, survey of community structure, examination of pollutant load and assessment of water quality impact. The vascular plants of this area are listed 224 taxa; 64 families, 168 genera, 193 species, 30 varieties and 1 form. This study area is classified into total 21 communities, most community was consist of grass vegetation. Among the communities, Erigeron annuus ($869,286m^2$, 22%) community was dominant and Erigeron annuus-Avena fatua comminity (16%) was subdominant until May, and then Erigeron canadensis community occupied most area to $1,774,985m^2$ (32%) from May to July. For the evaluation of water quality impact due to submerged macrophyte, nutrient release test was conducted both dead body macrophyte and living body macrophyte. The results of release test show that T-N is not released at dead body macrophyte, but it is released at living body macrophyte, especially living body Artemisia priceps var. orientalis shows 1.436mgN/g. At release test of dead body macrophyte, T-P release rate of Erigeron annuus shows 0.500mgP/g at the top of them and it also shows 0.436mgP/g at Erigeron annuus of living body macrophyte. T-N load of submerged macrophyte shows 0.76% by comparison of total load on watershed and T-P load of that shows 3.61%. In case of removal macrophyte for reduction of pollutant load in submerged area, T-N load of submerged macrophyte changes from 0.76% to 0.15% by comparison of total load on watershed and T-P load of that changes from 3.61% to 0.72%.

• 대한조선학회논문집
• /
• 제36권4호
• /
• pp.87-94
• /
• 1999

선수 구조부의 파랑충격현상은 대단히 복잡한 현상을 나타내고 있고 정확하게 규명하기 어렵기 때문에 아직 경험적인 설계에 의존하고 있다. 파랑충격하중에 의한 선수 구조부의 손상은 주로 충격압력역적과 파랑충격하중의 면적에 의하여 크게 영향을 받는다. 본 연구에서는 두 번째 단계로서 파랑충격하중에 대한 선수 구조부 강도의 추정을 위하여 효율적인 부재치수의 결정 프로그램을 개발하고, 파랑충격하중의 면적을 추정하고자 한다. 동적 비선형 범용 프로그램 LS/DYNA3D를 이용하여 DWT 300,000급 VLCC의 선수 구조부를 이상화된 패널구조 모델의 중앙부에서의 최대 손상변형을 비교하여 추정하고자 한다. 이것은 다음 단계의 선수 구조부의 동적 구조해석의 검증에 사용될 것이다. 본 연구에서는 극치 6.5MPa, 후부높이 1.0MPa, 그리고 지속시간 5.0msec인 파랑충격압력 곡선 하에서, 강성이 작은 보강재로 보강된 경우 파랑충격하중의 면적은 $1.5s{\times}1.5s$ 보강재 간격(s), 강성이 큰 스트링거로 보강된 경우는 $2.5s{\times}2.5s$로 추정하였다.

• Carbon letters
• /
• 제16권2호
• /
• pp.107-115
• /
• 2015

Impact damages induced by a low-velocity impact load on carbon fiber reinforced polymer (CFRP) composite plates fabricated with various stacking sequences were studied experimentally. The impact responses of the CFRP composite plates were significantly affected by the laminate stacking sequences. Three types of specimens, specifically quasi-isotropic, unidirectional, and cross-ply, were tested by a constant impact carrying the same impact energy level. An impact load of 3.44 kg, corresponding to 23.62 J, was applied to the center of each plate supported at the boundaries. The unidirectional composite plate showed the worst impact resistance and broke completely into two parts; this was followed by the quasi-isotropic lay-up plate that was perforated by the impact. The cross-ply composite plate exhibited the best resistance to the low-velocity impact load; in this case, the impactor bounced back. Impact parameters such as the peak impact force and absorbed energy were evaluated and compared for the impact resistant characterization of the composites made by different stacking sequences.

• Journal of Electrical Engineering and Technology
• /
• 제8권2호
• /
• pp.244-251
• /
• 2013

This paper presents a study the change of the load profile on the power system by the charging impact of electric vehicles (EVs) in 2020. The impact of charging EVs on the load demand is determined not only by the number of EVs in usage pattern, but also by the number of EVs being charged at once. The charging load is determined on an hourly basis using the number of the EVs based on different scenarios considering battery size, model, the use of vehicles, charging at home or work, and the method of charging, which is either fast or slow. Focusing on the impact of future load profile in Korea with EVs reaching up 10 and 20 percentage, increased power demand by EVs charging is analyzed. Also, this paper analyzes the impact of a time-of-use (TOU) tariff system on the charging of EVs in Korea. The results demonstrate how the penetration of EVs increases the load profile and decreases charging demand by TOU tariff system on the future power system.

• 대한조선학회지
• /
• 제21권1호
• /
• pp.13-20
• /
• 1984

As the first step to the dynamic stress analysis of structures, transient responses of a Timoshenko beam with variable section subject to impact load are analyzed. According to the various characteristics of impact load, time histories of the transient response of Timoshenko beam with general boundary conditions are obtained and compared with those of one degree of freedom system. Numerical solutions of the governing equations of motion are calculated by adopting the equivalent lumped-mass system and the finite difference method. It is found that the dynamic responses of Timshenko beam depend on the effect of concentration and location of impact load. As a result, increasing tendency of fluctuation in dynamic response, especially in bending moment, is found according to the increase of load concentration factor in time and space.

• 전산구조공학
• /
• 제9권3호
• /
• pp.187-197
• /
• 1996

Explicit 직접적분법 알고리듬을 사용하여 Euler기둥의 동적 좌굴거동을 해석할 수 있는 수치해석법을 제시하였다. 평면뼈대 유한요소를 기하학적 비선형 거동과 전체좌굴의 영향을 고려할 수 있도록 보의 대변위 이론으로부터 유도하였고, central difference method를 바탕으로 해석 알고리듬을 개발하였다. 다양한 형상, 크기, 재하시간을 갖는 충격하중에 대하여 Euler기둥의 동적좌굴거동과 고유치 문제를 해석하였다. 수치해석 예제를 통하여 본 연구의 결과를 검증하였다.