• 제목/요약/키워드: Stress influence coefficient

검색결과 228건 처리시간 0.025초

Experimental study on seepage characteristics of large size rock specimens under three-dimensional stress

  • Sun, Wenbin;Xue, Yanchao;Yin, Liming;Zhang, Junming
    • Geomechanics and Engineering
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    • 제18권6호
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    • pp.567-574
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    • 2019
  • In order to study the effect of stress and water pressure on the permeability of fractured rock mass under three-dimensional stress conditions, a single fracture triaxial stress-seepage coupling model was established; By using the stress-seepage coupling true triaxial test system, large-scale rock specimens were taken as the research object to carry out the coupling test of stress and seepage, the fitting formula of permeability coefficient was obtained. The influence of three-dimensional stress and water pressure on the permeability coefficient of fractured rock mass was discussed. The results show that the three-dimensional stress and water pressure have a significant effect on the fracture permeability coefficient, showing a negative exponential relationship. Under certain water pressure conditions, the permeability coefficient decreases with the increase of the three-dimensional stress, and the normal principal stress plays a dominant role in the permeability. Under certain stress conditions, the permeability coefficient increases when the water pressure increases. Further analysis shows that when the gob floor rock mass is changed from high stress to unloading state, the seepage characteristics of the cracked channels will be evidently strengthened.

Study on deformation law of surrounding rock of super long and deep buried sandstone tunnel

  • Ding, Lujun;Liu, Yuhong
    • Geomechanics and Engineering
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    • 제16권1호
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    • pp.97-104
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    • 2018
  • The finite difference software Flac3D is used to study the influence of tunnel burial depth, tunnel diameter and lateral pressure coefficient of original rock stress on the stress and deformation of tunnel surrounding rock under sandstone condition. The results show that the maximum shear stress, the radius of the plastic zone and the maximum displacement in the surrounding rock increase with the increase of the diameter of the tunnel. When the lateral pressure coefficient is 1, it is most favorable for surrounding rock and lining structure, with the increase or decrease of lateral pressure coefficient, the maximum principal stress, surrounding displacement and plastic zone range of surrounding rock and lining show a sharp increase trend, the plastic zone on the lining increases with the increase of buried depth.

Finite element modelling of reinforced concrete structures with laboratory verification

  • Cheng, Y.M.
    • Structural Engineering and Mechanics
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    • 제3권6호
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    • pp.593-609
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    • 1995
  • The presence of reinforcement has a significant influence on the stress-strain behaviour of reinforced concrete structures, expecially when the failure stage of the structures is approached. In the present paper, the constrained and non-constrained zones of concrete due to the presence of reinforcement is developed and the stress-stress-strain behaviour of concrete is enhanced by a reinforcement confinement coefficient, Furthermore, a flexible method for the modelling of reinforcement with arbitrary orientation and not passing the nodes of concrete element is also proposed. Numerical examples and laboratory tests have shown that the coefficient and the modelling technique proposed by the author are satisfactory.

대학생의 사회적지지 및 사회심리적 스트레스와 음주 후 문제행동과의 관련성 (Correlation between Social Support & Psychosocial Stress and Problem Behavior after Consuming Alcohol among College Students)

  • 윤미은;오현경;김형태;진경;현보람;천성수
    • 한국학교ㆍ지역보건교육학회지
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    • 제17권3호
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    • pp.1-10
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    • 2016
  • Objectives: The purpose of this study was to verify correlation between social support & psychosocial stress and drinking behavior after consuming alcohol among college students. Methods: This study surveyed by questionnaire 440 students who consumed alcohol regularly from 36 colleges around the country in 2014. Data were analyzed using the program SPSS 21. Results: The effects of social support on problem behavior after drinking and psychosocial stress had significant influence with each path coefficient -0.178(CR= -3.408, p<0.001) and -0.294(CR= -6.195, p<0.001). Also, the effects of psychosocial stress on problem behavior after drinking had significant influence with path coefficient -0.141(CR= -2.858, p<0.05). Social support had significant influence(p<0.001) on problem behavior after drinking through psychosocial stress, serving as a mediator variable, and social support had significant influence on problem behavior after drinking through psychosocial stress. Conclusions: Problem behavior after consuming alcohol held strong relevance in social support and psychosocial stress.

쇄빙연구선 ARAON호의 국부 빙하중 추정을 위한 영향계수행렬의 보완 (Enhanced Influence Coefficient Matrix for Estimation of Local Ice Load on the IBRV ARAON)

  • 조성록;최경식;손범식;정성엽;하정석
    • 대한조선학회논문집
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    • 제58권5호
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    • pp.330-338
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    • 2021
  • This paper focuses on the improvement of the influence coefficient matrix method for estimation of local ice load on the icebreaking research vessel ARAON. The influence coefficient matrix relates ice pressure on the hull plate to the measured/calculated hull strain/stress. Conventionally von Mises equivalent stresses representing hull stresses and ice pressure acting on the hull plate are utilized to assemble the influence coefficient matrix. Because of the three dimensional features of the ship-ice collision process, an enhanced method to assemble the influence coefficient matrix is derived considering ice loads in the X, Y, and Z direction simultaneously. Furthermore the location of ice loads acting on hull-plate may fall outside the measuring sensor area, and the enhanced influence coefficient matrix is modified to reduce the difference between the actual and the estimated ice loads by expanding the domain outward from the sensor area. The developed method for enhanced influence coefficient matrix is applied to IBRV ARAON during the 2019 Antarctic ice field test and the local ice loads in three directions are efficiently calculated compared to those by a conventional method.

접합재의 고온강도 특성 평가 (Evaluation of High Temperature Strength Characteric in Joint Metal)

  • 허선철;박영철;윤한기;박원조
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 춘계학술대회논문집A
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    • pp.103-108
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    • 2000
  • Since the ceramic/metal joint material is made at a high temperature, the residual stress development when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of $Si_3N_4/STS304$ joints quantitatively and to compare the strength of Joints. The difference of residual stress is measured when repeated thermal cycle is loaded under the conditions of the practical use of the ceramic/metal joint. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a residual it is known that the stress of joint decreases as the number of thermal cycle increases.

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영향계수를 이용한 원통용기 표면결함의 응력확대계수의 계산 (Stress Intensity Factor Calculation for the Semi-elliptical Surface Flaws on the Thin-Wall Cylinder using Influence Coefficients)

  • 장창희;문호림;정일석
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집A
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    • pp.280-285
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    • 2001
  • As an integral part of the probabilistic fracture mechanics analysis, stress intensity factor calculation scheme for semi-elliptical surface flaws in thin-walled cylinder has been introduced. The approximation solution utilizes the influence coefficients to calculate the stress intensity factor at the crack tip. This method has been compared with other solution methods including 3-D finite element analysis for cooldown boundary condition. The analysis results confirmed that the simplified methods provided sufficiently accurate stress intensity factor values for axial semi-elliptcal flaws on the surface of the reactor pressure vessel.

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잔류응력 완화에 미치는 상변태의 수치적 모델링 (N.M.for the Effect of P.T. on Resicual Stress Relaxation)

  • 장경복;손금렬;강성수
    • Journal of Welding and Joining
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    • 제17권6호
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    • pp.84-89
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    • 1999
  • Most of ferrous b.c.c weld materials may experience martensitic transformation during rapid cooling after welding. It is well known that volume expansion due to the phase transformation could influence on the relaxation of welding residual stress. To apply this effect practically, it is a prerequisite to establish a numerical model which is able to estimate the effect of phase transformation on residual stress relaxation quantitatively. For this purpose, the analysis is carried out in two regions. i.e., heating and cooling, because the variation of material properties following a phase transformation in cooling is different in comparison with the case in heating, even at the same temperature. The variation of material properties following phase transformation is considered by the adjustment of specific heat and thermal expansion coefficient, and the distribution of residual stress in analysis is compared with that of experiment by previous study. consequently, in this study, simplified numerical procedures considering phase transformation, which based on a commercial finite element package was established through comparing with the experimental data of residual stress distribution by other researcher. To consider the phase transformation effect on residual stress relaxation, the transition of mechanical and thermal property such as thermal expansion coefficient and specific heat capacity was found by try and error method in this analysis.

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Investigation of influences of mixing parameters on acoustoelastic coefficient of concrete using coda wave interferometry

  • Shin, Sung Woo;Lee, Jiyong;Kim, Jeong-Su;Shin, Joonwoo
    • Smart Structures and Systems
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    • 제17권1호
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    • pp.73-89
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    • 2016
  • The stress dependence of ultrasonic wave velocity is known as the acoustoelastic effect. This effect is useful for stress monitoring if the acoustoelastic coefficient of a subject medium is known. The acoustoelastic coefficients of metallic materials such as steel have been studied widely. However, the acoustoelastic coefficient of concrete has not been well understood yet. Basic constituents of concrete are water, cement, and aggregates. The mix proportion of those constituents greatly affects many mechanical and physical properties of concrete and so does the acoustoelastic coefficient of concrete. In this study, influence of the water-cement ratio (w/c ratio) and the fine-coarse aggregates ratio (fa/ta ratio) on the acoustoelastic coefficient of concrete was investigated. The w/c and the fa/ta ratios are important parameters in mix design and affect wave behaviors in concrete. Load-controlled uni-axial compression tests were performed on concrete specimens. Ultrasonic wave measurements were also performed during the compression tests. The stretching coda wave interferometry method was used to obtain the relative velocity change of ultrasonic waves with respect to the stress level of the specimens. From the experimental results, it was found that the w/c ratio greatly affects the acoustoelastic coefficient while the fa/ta ratio does not. The acoustoelastic coefficient increased from $0.003073MPa^{-1}$ to $0.005553MPa^{-1}$ when the w/c ratio was increased from 0.4 to 0.5. On the other hand, the acoustoelastic coefficient changed in small from $0.003606MPa^{-1}$ to $0.003801MPa^{-1}$ when the fa/ta ratio was increased from 0.3 to 0.5. Finally, it was also found that the relative velocity change has a linear relationship with the stress level of concrete.

비합리적 신념이 유치원 교사의 직무 스트레스에 미치는 영향 (Influence of Irrational Beliefs on Job Stress in Kindergarten Teachers)

  • 양연실;이희영;최태진
    • 수산해양교육연구
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    • 제28권4호
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    • pp.1089-1097
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    • 2016
  • The purpose of this study was to investigate the relationship between irrational beliefs and job stress in kindergarten teachers and explore specific irrational beliefs that influence kindergarten teachers' job stress. One hundred ninety one kindergarten teachers participated in the study and completed Job Stress Scale and General Attitude and Belief Scale. Collected data were analyzed using Pearson Correlation Coefficient Analysis and Multiple Regression Analysis. The major findings of the study were as follows: First, on the whole irrational beliefs were significantly positively related to job stress. Second, Although Self-Degradation and Demands for Fairness significantly predicted Kindergarten teachers' job stress, Self-Degradation were the most influential irrational belief. Finally the theoretical and practical implication of the results were discussed with the suggestion of future research.