• Geomechanics and Engineering
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• 제23권5호
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• pp.467-480
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• 2020

The failure behavior and tensile strength of sandstone materials under different strain rates are greatly different, especially under static loads and impact loads. In order to clearly investigate the failure mechanism of sandstone materials under static and impact loads, a series of Brazilian disc samples were used by employing green sandstone, red sandstone and black sandstone to carry out static and impact loading splitting tensile tests, and the failure properties subjected to two different loading conditions were analyzed and discussed. Subsequently, the failure behavior of sandstone materials also were simulated by finite element code. The good agreement between simulation results and experimental results can obtain the following significantly conclusions: (1) The relationship of the tensile strength among sandstone materials is that green sandstone < red sandstone < black sandstone, and the variation of the tensile sensitivity of sandstone materials is that green sandstone > red sandstone > black sandstone; (2) The mainly cause for the difference of dynamic tensile strength of sandstone materials is that the strength of crystal particles in sandstone material, and the tensile strength of sandstone is proportional to the fractal dimension; (3) The dynamic failure behavior of sandstone is greatly different from that of static failure behavior, and the dynamic tensile failure rate in dynamic failure behavior is about 54.92%.

• Steel and Composite Structures
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• 제21권1호
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• pp.37-55
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• 2016

In this study, the influence of centrally placed circular and square cutouts on vibration and buckling characteristics of different ply-oriented laminated panels under the action of compressive and/or tensile types of non-uniform in-plane edge loads are investigated. The panels are inspected under the action of uniaxial compression, uniaxial tension and biaxial, compression-tension, loading configurations. Furthermore, the effects of different degrees of edge restraints and panel aspect ratios are also addressed in this work. Towards this, a nine-node heterosis plate element has been adopted which includes the effect of shear deformation and rotary inertia. According to the results, the tensile buckling loads are higher than that of compressive buckling loads. However, the tensile buckling load continuously reduces with the increased cutout sizes irrespective of ply-orientations. This is also true for compressive buckling loads except for some particular ply-orientations with higher sized cutouts.

• 대한기계학회논문집A
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• 제28권5호
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• pp.554-562
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• 2004

An empirical relationship between parameters from SP curves and tensile properties has been systematically investigated by experimental tests and FEM simulations. A series of SP and tensile tests were performed. SP tests were also simulated by FE analysis with various tensile properties. It was found that the yield loads(Py) and the maximum loads( $P_{MAX}$) in SP curves were linearly related with the yield strength($\sigma$$_{o}$) and the tensile strength($\sigma$$_{UTS}$), respectively. The yield loads defined from the intersection point of two lines tangent to the elastic bending region and plastic bending region showed better relation to the yield strength than those from offset line. The maximum loads in SP curves showing plastic instability region was linearly related with the tensile strengths. The slope of SP curves in simulation results had a close correlation with the hardening coefficient and hardening strength as well.l.l.l.

• 콘크리트학회논문집
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• 제19권4호
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• pp.449-456
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• 2007

본 연구는 줄눈콘크리트포장에 환경 하중과 차량하중이 작용할 때 콘크리트 슬래브의 상하부에 발생하는 최대 인장응력의 특성을 분석하기 위하여 수행되었다. 유한요소법을 이용한 줄눈콘크리트포장의 수치해석모형을 개발하여 우선 포장이 환경 하중 또는 차량하중 만을 받을 때의 응력 특성을 분석하였다. 그 후 환경 하중과 차량하중을 동시에 받을 때 슬래브 상하부의 응력 특성을 분석하였다. 연구 결과, 차량하중에 의한 슬래브 하부의 최대 인장응력은 하중이 어느 정도 줄눈부에서 멀어지면 위치에 관계없이 거의 같아지게 되는 젓을 알 수 있었다. 환경 하중에 의해 슬래브가 컬다운 되었을 때는 차량하중이 슬래브의 중앙에 작용할 때 슬래브 하부에 최대인장응력이 발생하며 슬래브가 컬업 되었을 때는 차량하중이 줄눈부에 작용할 때 슬래브의 상부에 최대인장응력이 발생한다. 슬래브 하부 최대인장응력은 컬다운 상태에서는 하부층 일반 스프링을 사용한 모델을 이용하여 환경 하중과 차량하중에 의한 각각의 최대응력을 더하여 구할 수 있으며, 컬업 상태에서는 차량 하중에 의한 최대 응력에서 온도 하중에 의한 최대 응력을 감하여 구할 수 있다. 반면에 슬래브 상부 최대인장응력은 컬업 상태에서 하부층 무인장 스프링을 이용한 모델을 사용하여 환경하중에 대한 최대응력과 차량하중이 줄눈부에 작용할 때 슬래브 중앙부의 최대응력을 더하여 구할 수 있으나 하부층을 일반 스프링으로 모델링하여 환경 하중에 대한 최대응력 만을 구하여 사용하는 실용적인 방법도 있었다.

• 대한토목학회논문집
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• 제5권2호
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• pp.59-66
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• 1985

동적(動的) 인장하중(引張荷重) 받는 콘크리트의 거동(擧動) 모델화(化)하기 위한 비선형(非線型) 구성이론(構成理論)이 제안(提案)되었다. 콘크리트의 정적(靜的) 인장거동(引張擧動)은 징세균열면처리론(徵細龜裂面處理論)에 의(依)하여 모델하고, 동적(動的) 인장하중(引張荷重)으로 인한 변형율속도효과(變形率速度效果)를 고려하기 위하여 유사변환을 이용(利用)하였다. 본(本) 모델의 결과(結果)를 현존하는 여러 동적(動的) 인장실험자료(引張實驗資料)와 비교하였다. 또한, 동적(動的) 인장하중(引張荷重)으로 인한 인장강도의 증가현상을 예측하기 위한 공식(公式)이 제안되었다. 본(本) 모델은 콘크리트구조물(構造物)의 좀 더 실제적인 동적(動的) 유한요소해석(有限要素解析)을 가능케 한다.

• 한국도로학회논문집
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• 제10권4호
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• pp.269-279
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• 2008

본 연구는 프리스트레스트 콘크리트 포장(PSCP)의 횡방향 긴장 설계방안을 구축하기 위하여 수행되었다. 우선 PSCP에 횡방향 긴장을 가했을 경우에 긴장간격에 따른 슬래브의 응력분포를 분석하였다. 또한 환경하중과 차륜하중이 PSCP슬래브에 작용할 때 슬래브에 발생하는 인장응력의 분포도 분석하였다. 이러한 환경 및 차륜하중 등의 설계하중과 긴장응력을 결정하는 기준인 슬래브의 허용인장응력을 합리적으로 선정하는 방법에 대하여 논의하였으며 이러한 기준의 선정이 횡방향 긴장 설계에 미치는 영향을 분석하였다. 연구결과, 긴장간격이 커질수록 긴장응력의 손실을 가져오는 범위가 넓어지며 특히 Shoulder부분에서의 응력손실이 급격하게 증가하는 것을 알 수 있었다. 따라서 횡방향 긴장 설계는 설계하중에 대한 슬래브의 응력을 산출한 후 슬래브가 허용인장응력 이내의 응력을 받도록 평균긴장응력을 산출하여 긴장간격 및 긴장량을 결정하면 되지만, 이때 Shoulder, Wheel Pass, 중앙부 등 슬래브의 여러 다른 위치에서의 응력 또한 반드시 검토하여 적절한 긴장간격을 선정하여야 한다.

• 한국의류학회지
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• 제20권6호
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• pp.975-982
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• 1996

This study was conducted to examine the fatigue phenomenon of mechanical properites in denim fabrics for slacks during repeated shear and tensile deformation by analysing the change in the basic dynamic properties of fabrics on the basic of experiments to obtain the basic data necessary to measure their fatigue. In addition, this study was carried out by allowing these denim fabrics at market to go through the repeated deformation under such different loads as 500 gf/cm2 and 1000 gf/cm2 by using a simulated fatigue tester, by calculating both dynamic properties and hand value (HV) of these fabrics with KES-F system and then by obtaining the THV through these calculated properties. The results are as follows: 1 The fatigue phenomenon of dynamic properties was remarkably shown by the repeated shear and tensile deformation, while the increase of hysterical plastic substances was also remarkable in these shearing and bending properties. 2. The elasticity values of tensile, bending and compression properties, such as, B and G were reduced: whereas RT and RC values increased. It was shown, then, that those fabrics lost their elasticity and became flexible and soft with the increase of fatigue. 3. The fatigue phenomenon of hand value also showed that those fabrics became soft in relation with the change of all dynamic properties, and that their performance was also change to flexible hand value. 4. TRhe degree of fatigue was also shown by the loads given to the repeated deformation. It was shown that the fatigue was higher for the tensile load of 1000 gf/cm3 than did the standard load of 500 gf/cm3 It is necessary, therefore, to consider the load in accordance with their usage when examining the fatigue phenomenon with respect to the dynamic properties of clothing materials. 5. The loads were nearly not influenced by the change in the general hand value tended to show a little of increase with the increase of fatigue, Based on those results, it seems that the fatigue phenomonon is related to the loads given to the repeated deformation.

• 한국농공학회지
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• 제30권4호
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• pp.94-108
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• 1988

The use of geotextile as reinforcing materials in soil structures has become widespread throughout the world. Geotextile reinforcement has been used in retaining walls, roadbed, embankment stabilization and especially reinforcement of soft foundation, and so on, In the past, however, its design and construction have been performed empirically. In this study, laboratory model tests were carried out in order to investigate the effects of geotextile rein- forcement on vertical and horizontal displacement and other characteristics in soft founda- tions. The experiments were executed in eight treatments ;no geotextile between embank - ment and subsoils, and seven geotextiles with different tensile strength. And such factors as the loading conditions, the tensile strength of geotextiles, the ingredient of geotextiles and the elapsed time were investigate in this study. And the analytical method were executed in order to study the stress and behavior of geotextile - reinforced soil structure by the nonlinear elasto - plastic finite element model. The following conclusions were drawn from this study. 1. Geotextile reinforcement reduced the effects of banking loads on subsoils more effectively with the increase of their tensile strength. 2. As the tensile strength of geotextiles was increase, the rate of the initial vertical disp - lacements of loading plate was reduced inverse proportional to loads, Rowever, the effect of loading was reduced when the loads exceed a certain limits, 3. The effect of reinforcement of nonwoven geotextile was 1.5-4.5 times larger than that of the woven geotextile with equivalent tensile strength. 4. The increased bearing capacity and the reduced settlement are proportioned as the tensile strength of geotextile. 5. The settlement at the long time loading were developed almost all, were completed after 10 days and the additional settlement were not developed since then. 6. The nonlinear elasto - plastic finite element method are accurate to predict the stresses and behayior of geotextile - reinforced soil structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.359-362
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• 2003

Carbon fiber sheet is attractive due to its good tensile strength, resistance to corrosion, and low weight. The strengthening of concrete structures with externally bonded carbon fiber sheets is increasingly being used for repair and rehabilitation of existing structures. However CFS strengthened beams break down under the service loads. As rupture strain is not reached ultimate value, reduction of the tensile strength is recommended. This study evaluate CFS tensile strength reduction factor which is required to analyze bending moment.

• Smart Structures and Systems
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• 제16권5호
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• pp.961-980
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• 2015

Magnetorheological (MR) fluids are capable of changing their rheological properties under the application of external fields. When MR fluids operate in the so-called squeeze mode, in which displacement levels are limited to a few millimetres but there are large forces, they have many potential applications in vibration isolation. This paper presents an experimental and a numerical investigation of the performance of an MR fluid under tensile and compressive loads and oscillatory squeeze-flow. The performance of the fluid was found to depend dramatically on the strain direction. The shape of the stress-strain hysteresis loops was affected by the strength of the applied field, particularly when the fluid was under tensile loading. In addition, the yield force of the fluid under the oscillatory squeeze-flow mode changed almost linearly with the applied electric or magnetic field. Finally, in order to shed further light on the mechanism of the MR fluid under squeeze operation, computational fluid dynamics analyses of non-Newtonian fluid behaviour using the Bingham-plastic model were carried out. The results confirmed superior fluid performance under compressive inputs.