• 한국공간구조학회논문집
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• 제22권1호
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• pp.59-66
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• 2022

In this paper, the flexural capacity equation of FRP-bar reinforced concrete beams was verified by comparing the experimental results and flexural capacity obtained according to the ACI procedure. And, also the economic feasibility of FRP-bar reinforced concrete beams was analyzed by comparing nominal moment capacity of beams. The results of analysis were as follows, 1) GFRP concrete beams have lower flexural performance than reinforced concrete beams, whereas CFRP concrete beams have similar flexural performance to reinforced concrete beams under the same reinforcement ratio 2) Although the design moment increased as the compressive strength of concrete increased, the flexural performance of GFRP reinforced concrete beams was found to be lower than the reinforced concrete beams for all reinforcement ratios.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.87-90
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• 2001

In particle or short-fiber reinforced composites, cracking of the reinforcements is a significant damage mode because the broken reinforcements lose load carrying capacity. This paper deals with elastic stress distributions and load carrying capacity of intact and cracked ellipsoidal inhomogeneities. Three dimensional finite element analysis has been carried out on intact and broken ellipsoidal inhomogeneities in an infinite body under pure shear. For the intact inhomogeneity, as well known as Eshelby(1957) solution, the stress distribution is uniform in the inhomogeneity and non-uniform in the surrounding matrix. On the other hand, for the broken inhomogeneity, the stress in the region near crack surface is considerably released and the stress distribution becomes more complex. The average stress in the inhomogeneity represents its load carrying capacity, and the difference of average stresses between the intact and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The load carrying capacity of the broken inhomogeneity is expressed in terms of the average stress of the intact inhomogeneity and some coefficients. It is found that the broken inhomogeneity with higher aspect ratio still maintains higher load carrying capacity.

• Journal of electromagnetic engineering and science
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• 제1권2호
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• pp.120-125
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• 2001

The capacity improvement in the DS-CDMA system can be obtained by allowing spectrum-overlap between adjacent channels. In this paper, an analysis for capacity improvement is newly considered according to the various chip waveforms in the partial spectrum-overlapped DS-CDMA system. Optimum-overlapping ratio is numerically found to obtain maximum capacity improvement for each chip waveform. Assuming the bandwidth containing 95% of the total power, i.e., 95% power bandwidth, rectangular chip waveform has the largest capacity improvement in the considered chip waveforms and then the amount of improvement is 136.5% at overlapping ratio 1.5 for BER = $10^{-3}$TEX> . Furthermore, as the required BER becomes lower, the capacity improvement gets smaller for a1l of chip waveforms. For the unequal power channels, it is shown that the larger capacity improvement is achieved as the power of desired channel becomes larger than that of adjacent channels. And the capacity improvement can be obtained even though the desired channel power is lower than the adjacent channel power.

• Journal of Mechanical Science and Technology
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• 제15권6호
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• pp.709-719
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• 2001

In particle or short-fiber reinforced composites, cracking of reinforcements is a significant damage mode because the cracked reinforcements lose carrying capacity. This paper deals with elastic stress distributions and load carrying capacity of intact and cracked ellipsoidal inhomogeneities. Three dimensional finite element analysis has been carried out on intact and cracked ellipsoidal inhomogeneities in an infinite body under uniaxial tension and pure shear. For the intact inhomogeneity, as well known as Eshelbys solution, the stress distribution is uniform in the inhomogeneity and nonuniform in the surrounding matrix. On the other hand, for the cracked inhomogeneity, the stress in the region near the crack surface is considerably released and the stress distribution becomes more complex. The average stress in the inhomogeneity represents its load carrying capacity, and the difference between the average stresses of the intact and cracked inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The load carrying capacity of the cracked inhomogeneity is expressed in to cracking damage. The load carrying capacity of the cracked inhomogeneity is expressed in terms of the average stress of the intact inhomogeneity and some coefficients. It is found that a cracked inhomogeneity with high aspect ratio still maintains higher load carrying capacity.

• Steel and Composite Structures
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• 제30권2호
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• pp.123-140
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• 2019

This paper presents experimental study on effects of width-to-thickness ratio and loading history on cyclic rotational capacity of H-shaped steel beams subjected to pure bending. Eight Class 3 and 4 H-shaped beams with large width-to-thickness ratios were tested under four different loading histories. The coupling effect of local buckling and cracking on cyclic rotational capacity of the specimens was investigated. It was found that loss of the load-carrying capacity was mainly induced by local buckling, and ductile cracking was a secondary factor. The width-to-thickness ratio plays a dominant effect on the cyclic rotational capacity, and the loading history also plays an important role. The cyclic rotational capacity can decrease significantly due to premature elasto-plastic local buckling induced by a number of preceding plastic reversals with relative small strain amplitudes. This result is mainly correlated with the decreasing tangent modulus of the structural steel under cyclic plastic loading. In addition, a theoretical approach to evaluate the cyclic rotational capacity of H-shaped beams with different width-to-thickness ratios was also proposed, which compares well with the experimental results.

• 한국지반공학회논문집
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• 제18권4호
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• pp.189-197
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• 2002

개단말뚝의 지지력은 말뚝의 폐색정도에 영향을 받으며, 이러한 폐색정도는 관내토증분비인 IFR에 의하여 정량화 될 수 있다. 그러나 말뚝의 폐색정도가 말뚝의 지지력에 미치는 영향을 정확하게 고려하는 개단말뚝의 지지력 산정기준이 현재까지 없는 실정이다. 따라서 말뚝의 폐색정도가 지지력에 미치는 영향을 조사하기 위하여 계측기가 부착된 모형 개단말뚝과 가압토조를 이용해서 모형말뚝시험을 수행하였다. 시험결과 개단말뚝의 IFR은 말뚝의 관입깊이에 대한 관내토길이의 비로 정의되는 관내토길이비(PLR)로부터 예측이 가능함을 알 수 있었다. 그리고 개단말뚝의 선단 지지력과 주면마찰력은 말뚝의 IFR이 증가함에 따라 감소하는 경향을 보였다. 또한 이와 같은 모형말뚝시험의 결과에 근거하여 개단말뚝의 선단지지력과 주면마찰력을 산정할 수 있는 새로운 지지력산정식이 제안되었다.

• 한국건설순환자원학회논문집
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• 제4권1호
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• pp.47-54
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• 2016

본 연구에서는 섬유 보강 콘크리트 바닥슬래브의 주요 설계하중인 선반하중과 이동하중에 의한 휨 내력을 평가하였다. 설계기준을 바탕으로 각 하중의 크기와 작용면적을 정의하였으며, 그 관계를 분석하였다. 단일하중에 의해서는 슬래브 경계면에서 휨 내력이 평가되어야 하며, 슬래브 두께 180mm 이상, 콘크리트 강도 35MPa 이상일 때는 최소 등가 휨강도비로써 휨 내력을 충분히 만족하였다. 조합하중에 의해서는 선반하중간의 조합이 가장 큰 등가 휨강도비를 요구하였으며, 선반하중과 이동하중의 조합은 선반하중간의 조합에 비해서는 작게 평가되었고, 단일 하중에 비해서는 크게 평가되었다. 본 연구결과 섬유 보강 콘크리트 바닥슬래브의 휨 설계는 하중 조합에 의한 내력 평가가 필요함을 확인하였다.

• Journal of Ceramic Processing Research
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• 제23권6호
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• pp.766-769
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• 2022

A Battery capacitor was prepared by controlling the mixing ratio of positive materials of the positive electrode to optimize cellproperties. The positive electrode was made by mixing two types of LiNi0.6Mn0.6Co0.2O2 (NMC 622) and LiCoO2 (LCO), andthe electrode was fabricated by changing the ratio of the two positive materials. Increasing of the content of LCO, decreasedthe capacity, and the retention of discharge capacity as a function of current rates did not change remarkably with anincreasing of the content LCO on the mixing ratio of positive materials. The life characteristics showed the highest capacityretention rate compared to the initial period under the condition that the ratio of NCM and LCO was 66 to 20. These resultsclearly indicate that mixing ratio of positive materials affects the electrochemical performances of battery capacitor.

• Geomechanics and Engineering
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• 제11권3호
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• pp.385-400
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• 2016

Bearing capacity of open-ended piles depends largely on inner frictional resistance, which is influenced by the degree of soil plugging. While a fully-plugged open-ended pile produces a bearing capacity similar to a closed-ended pile, fully coring (or unplugged) pile produces a much smaller bearing capacity. In general, open-ended piles are driven under partially-plugged mode. The formation of soil plug may depend on many factors, including wall thickness at the pile tip (or inner pile diameter), sleeve height of the thickened wall at the pile tip and relative density. In this paper, we studied the effects of wall thickness at the pile base and sleeve height of the thickened wall at the pile tip on bearing capacity using laboratory model tests. The tests were conducted on a medium dense sandy ground. The model piles with different tip thicknesses and sleeve heights of thickened wall at the pile tip were tested. The results were also discussed using the incremental filling ratio and plug length ratio, which are generally used to describe the degree of soil plugging. The results showed that the bearing capacity increases with tip thickness. The bearing capacity of piles of smaller sleeve length (e.g., ${\leq}1D$; D is pile outer diameter) was found to be dependent on the sleeve length, while it is independent on the sleeve length of greater than a 1D length. We also found that the soil plug height is dependent on wall thickness at the pile base. The results on the incremental filling ratio revealed that the thinner walled piles produce higher degree of soil plugging at greater penetration depths. The results also revealed that the soil plug height is dependent on sleeve length of up to 2D length and independent beyond a 2D length. The piles of a smaller sleeve length (e.g., ${\leq}1D$) produce higher degree of soil plugging at shallow penetration depths while the piles of a larger sleeve length (e.g., ${\geq}2D$) produce higher degree of soil plugging at greater penetration depths.

• 한국지반공학회논문집
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• 제22권8호
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• pp.5-11
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• 2006

준설매립된 초연약지반의 표층처리공법 적용시 보강재로 이용되고 있는 대나무망 및 토목섬유로 보강된 준설매립지반의 지지력 특성을 파악하기 위하여 현장 대형평판재하시험을 실시하였다. 각 보강재별 지지력비(BCR) 산정결과 대나무망 보강의 경우 지지력비는 $.{\sim}6.03$, 토목섬유의 경우 $2.19{\sim}3.59$로서 대나무망 보강의 경우 $1.6{\sim}1.7$배 크게 측정되었고, 실험결과와 이론식에 의한 지지력 비교결과 기존 토목섬유 보강시의 지지력 평가식은 대나무망 보강시 지지력 평가에 있어 적용성이 떨어짐을 알 수 있었다. 대나무 망 보강시의 지지력 평가를 위한 변수들의 상관관계 분석결과, 시험에서 얻어진 지지력비(BCR)와 복토두께/대나무망 간격의 비(H/S)로 표현한 경우 좋은 상관관계 특성을 얻을 수 있었고, 이는 대나무망의 지지력특성 파악을 위한 기초 자료로서 활용할 수 있을 것으로 판단되었다.