• 한국지반공학회논문집
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• 제23권9호
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• pp.17-28
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• 2007

도심지 지하 터널은 주변 구조물의 존재 하에서 미고결성 저토피고 지반에 건설되는 경우가 많기 때문에 일반 산악 터널이나 대심도 암반층에 건설되는 지하공동과는 달리 터널 주변의 지반 변위, 지표면 침하와 기울기가 터널 설계의 주요인자가 된다. 본 논문은 도심지 NATM 터널의 변형거동에 대한 합리적 해석 방법의 확립을 위한 연구로서 변형률 연화 모델을 이용한 수치해석적인 방법을 통하여 굴착에 따른 지반 평가와 거동 예측을 수행하였다. 적용되어진 변형률 연화모델은 지반이 항복후 전단변형률의 증가에 따른 전단강성와 강도정수의 저하를 고려한 것이다. 현장 계측 결과는 시공중 설계물성치의 재설정에 이용되어졌다. 연화모델의 결과와 현장 계측값과의 비교에서 적용되어진 모델이 지표 침하, 기울기, 지중 침하 및 지중 수평변위의 변형 양상을 어느 정도 재현될 수 있음을 알 수 있었다. 본 논문에서 제안된 모델을 토대로 시공조건이 엄밀한 도심지 터널의 변형거동에 정량적인 평가 및 예측이 가능할 것으로 기대된다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.77-84
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• 2003

In this paper, the refined plastic-hinge analysis accounting for the effect of strain reversal caused by non-proportional loading is developed. This analysis accounts for material and geometric nonlinearities of the structural system and its component members. Moreover, the problem, conventional refined plastic-hinge analyses have underestimated the strength of structures subjected to non-proportional loading, is overcome. The modified stiffness degradation model approximating the effect of strain reversal is discussed in detail. The proposed analysis is verified by the comparison of the finite element analysis. A case study shows that the effect of strain reversal is a very crucial element to be considered in second-order plastic-hinge analysis. The proposed analysis is shown to be an efficient, reliable tool ready to be implemented into design practice.

• 대한기계학회논문집A
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• 제33권10호
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• pp.1054-1064
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• 2009

본 연구에서는 인장시험 및 유한요소해석으로 재료의 파단 진변형률을 구하고, 궁극적으로 재료의 진응력-진변형률을 얻는 방법을 제안했다. 먼저 인장시험으로 얻은 응력-변형률 선도를 네킹점에서 선형 외삽해, 초기 진응력-진변형률 곡선을 설정하고, 이를 유한요소해석에 채택했다. 유한요소해석 후 Bridgman 계수 및 평판 수정계수들을 사용해, 단축 상태의 하중-진변형률 선도를 얻어 파단진변형률을 실험-해석적으로 구했다. 이 예측 파단진변형률의 실험치 대비 오차는 3% 미만이다. 이렇게 구한 파단 진변형률과 이에 상응하는 파단진응력을 구해 파단점을 결정한다. 이어 네킹점과 결정한 파단점을 연결하는 네킹 후 진응력-진변형률 선형선도를 확보하고, 이를 네킹 전의 실험선도와 결합해 최종적으로 재료의 진응력-진변형률 선도를 완성했다. 본 연구에서 제시한 실험-해석적 진응력-진변형률 곡선 획득 방법은 SS400 평판시편과 같이 파단면적 측정이 어려운 경우, 그 유용함이 배가된다.

• Computers and Concrete
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• 제22권6호
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• pp.563-572
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• 2018

Uniaxial compressive strength test and uniaxial compression creep one were produced on four groups of twelve concrete specimens with different hole number by RLW-2000 rock triaxial rheology test system. The relationships between horizontal holes and instantaneous failure stress, the strain, and creep failure stress, the strain, and the relationships between stress level and instantaneous strain, creep strain were studied, and the relationship between horizontal holes and failure mode was determined. The results showed that: with horizontal hole number increasing, compressive strength of the specimens decreased whereas its peak strain increased, while both creep failure strength and its peak strain decreased. The relationships between horizontal holes and compressive strength of the specimens, the peak strain, were represented in quadratic polynomial, the relationships between horizontal holes and creep failure strength, the peak strain were represented in both linear and quadratic polynomial, respectively. Instantaneous strain decreased with stress level increasing, and the more holes in the blocks the less the damping of instantaneous strain were recorded. In the failure stress level, instantaneous strain reversally increased, creep strain showed three stages: decreasing, increasing, and sharp increasing; in same stress level, the less holes the less creep strain rate was recorded. The compressive-shear failure was produced along specimen diagonal line where the master surface of creep failure occurred, the more holes in a block, the higher chances of specimen failure and the more obvious master surface were.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.886-891
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• 2000

One of the domestic co-generation plants have undergone excessive vibration problems of turbine attributed to external force for years. The root cause of turbine vibration may be shan alignment problem which sometimes is changed by thermal expansion and external farce, even if turbine technicians perfectly performed it. To evaluate the alignment condition from plant start-up to full load, a strain measurement of turbine and main steam piping subjected to thermal loading is monitored by using strain gages. The strain gages are bonded on both bearing housing adjusting bolts and pipe stoppers which. installed in the x-direction of left-side main steam piping near the turbine inlet in order to monitor closely the effect of turbine under thermal deformation of turbine casing and main steam piping during plant full load. Also in situ load of constant support hangers in main steam piping system is measured by strain gages and its results are used to rebalance the hanger rod load. Consequently, the experimental stress analysis by using strain gages turns out to be very useful tool to diagnose the trouble and failures of not only to stationary components but to rotating machinery in power plants.

• 한국연소학회지
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• 제5권1호
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• pp.7-18
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• 2000

Numerical simulations of counterflow non-premixed $CH_4/C_2HCl_3/Air$ flames added 8%(by volume) C2HCl3 on the fuel side are conducted at atmospheric pressure using a detailed chemical reaction mechanism in order to understand the effect of strain rates. A detailed sensitivity analysis is also performed in order to assess the relative influence of each reaction on the flame established at a strain rate of 200s-1. The structure of flames (i.e., temperature, velocity, and concentration of species) established at both a strain rate of 150s-1 and 300s-1 are investigated. As the strain rate increases, the "flame zone" is restricted to a narrower range and the position of maximum temperature is shifted to the fuel side. The concentrations of major species, H2O, CO, H2, HCl, Cl2, and Cl are decreased with increased strain rate. The reaction involving chlorine, CH4 + Cl $\rightarrow$ CH3 + HCl, instead of the reaction, CH4 + H $\rightarrow$ CH3 + H2 influences the consumption of methane. C2HCl3 + OH $\rightarrow$ CHCl2 + CHOCl and HCl + OH $\rightarrow$ H2O + Cl, are major reactions, through which OH radicals are consumed.

• 산업기술연구
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• 제23권A호
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• pp.165-173
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• 2003

The purpose of this paper is to analysis of initial behavior of concrete pavement with initial measurement strain gauge for concrete pavement at field, and to investigate the field test results for field applicability testing. The early-age behaviors of concrete pavement slabs were measured using the strain gauges. From the slab depths and positions, the outputs from each gauges were recorded at initial curing period. The initial measurement of concrete pavement and check of crack at the joint were performed, the results could be summarized as follows. From the results of concrete strength, compressive strength and flexural strength were showed $271kgf/cm^2$, $43kgf/cm^2$ respectively. From the tests of early-age strain measurement, it was found that the strain varied at the maximum value of $150{\mu}{\varepsilon}$ and early behavior of concrete slab was showed a tensile strain. However, for long-term was showed a compressive strain due to dry-shrinkage.

• Journal of Microbiology
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• 제45권3호
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• pp.268-271
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• 2007

In Korea, the Mycobacterium tuberculosis K-strain is the most prevalent clinical isolates and belongs to the Beijing family. In this study, we conducted comparative porteomics of expressed proteins of clinical isolates of the K-strain with H37Rv, H37Ra as well as the vaccine strain of Mycobacterium bovis BCG following phagocytosis by the human monocytic cell line U-937. Proteins were analyzed by 2-D PAGE and MALDI-TOF-MS. Two proteins, Mb1363 (probable glycogen phosphorylase GlgP) and MT2656 (Haloalkane dehalogenase LinB) were most abundant after phagocytosis of M. tuberculosis K-strain. This approach provides a method to determine specific proteins that may have critical roles in tuberculosis pathogenesis.

• 한국구조물진단유지관리공학회 논문집
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• 제2권4호
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• pp.177-185
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• 1998

This paper deals with the flexural behaviors of R.C beams strengthened by carbon fiber sheets. The behaviors of strengthened beams which were preloaded up to 50%, 60% and 70% of the ultimate load of unstrengthened beam are compared with that of a beam which was not preloaded. The structural behaviors of strengthened beams are compared with analytical method in terms of load-strain of concrete, load-strain of steel bar, load-strain of CFS and falilure load. Four cases of analytical method are investigated according to cracked section or partially cracked section and including strain hardening effect of steel bar or not. Comparing the results of test and analysis, both are similar in terms of load-strain of concrete, and falilure load, the results of analytical method underestimate the failure load. But each results of load-strain of steel bar, load-strain of CFS near at failure is some different, thus near at failure the composite action between CFS and upper concrete is assumed to be disturbed. Consequently, the analytical method was proved to be efficient and accurate in estimating the flexural response of CFS strengthened RC beams.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.147-155
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• 2002

교량의 안전성과 사용성을 검토하기 위해서는 외적 하중에 대한 구조 부재의 거동 특성과 정확한 저항 능력 평가가 반드시 고려 되어야 한다. 구조 부재의 거동 특성과 저항능력을 평가하기 위해서는 구조물의 변형률과 변위가 반드시 측정 되어야 한다. 변형률 측정을 위해서 전기 저항식 변형률 게이지를 사용하는 것이 보통이다. 그러나 교량의 교각이 높고, 장지간을 갖는 경우 변형률 게이지 부착은 매우 어렵고 경제적이지 못하다. 또한 구조 부재에 균열이 많이 발생되어 있거나 습윤 상태라면 전기 저항식 변형률 게이지에 의한 변형률 계측은 추천할만한 방법이 못된다. 따라서 본 연구에서는 이러한 단점을 보완 할수 있도록 측정 변위를 이용한 변형률 해석 알고리즘을 제안 하였다.