• 한국지반신소재학회논문집
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• 제8권4호
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• pp.47-51
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• 2009

우리나라의 자연재해는 대부분 풍수해에 의해 발생하며, 강우시 산비탈이 갑작스럽게 붕괴되는 산사태로 인해 큰 재난을 겪고 있다. 사면파괴를 유발하는 요인은 다양하고 요인들이 서로 관련이 있기 때문에 어느 하나의 요인에 의하여 사면파괴의 발생을 설명할 수는 없으나, 외적요인 중 강우는 가장 중요한 외적요인이다. 따라서, 본 논문에서는 무보강된 일반사면과 친환경 호안구조물로 사면보호공법이 적용된 사면을 대상으로 실내 강우재현실험을 수행하였으며, 강우강도와 사면경사에 따른 유출량과 저류량을 분석하여 호안구조물의 침식에 대한 사면보호효과에 대하여 검토하였다.

• 한국기계가공학회지
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• 제19권2호
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• pp.81-88
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• 2020

The damping hinge of a built-in refrigerator was examined in terms of its stress and fatigue life. Analysis of the initial design showed that stress concentration occurred at the concave surface of the hinge lever, which was broken during the door opening-and-closing endurance test of the prototype. The maximum von Mises stress at this location exceeded the yield strength. In addition, Goodman fatigue analysis of the initial design showed that the fatigue life at this location was consistent with the failure observed during the endurance test. Based on these results, an improved design for the damping hinge was derived. Analysis of this improved design showed that the stress concentration in the hinge lever of the initial design was eliminated. In this case, the maximum stress occurred at the position where the hinge lever was in contact with the door stopping pin, and the maximum von Mises stress was smaller than the yield strength. Goodman fatigue analysis of the improved design indicated that the fatigue life of the entire damping hinge was infinite. It was therefore concluded that the improved design does not suffer from fatigue damage during the endurance test.

• Smart Structures and Systems
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• 제7권4호
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• pp.263-274
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• 2011

A reliability-based slope stability assessment method considering fluctuations in the monitored matric suction was proposed for real-time identification of slope risk. The assessment model was based on the limit equilibrium model for infinite slope failure. The first-order reliability method (FORM) was adopted to calculate the probability of slope failure, and results of the model were compared with Monte-Carlo Simulation (MCS) results to validate the accuracy and efficiency of the model. The analysis shows that a model based on Advanced First-Order Reliability Method (AFORM) generates results that are in relatively good agreement with those of the MCS, using a relatively small number of function calls. The contribution of random variables to the slope reliability index was also examined using sensitivity analysis. The results of sensitivity analysis indicate that the effective cohesion c' is a significant variable at low values of mean matric suction, whereas matric suction ($u_a-u_w$) is the most influential factor at high mean suction values. Finally, the reliability indices of an unsaturated model soil slope, which was monitored by a wireless matric suction measurement system, were illustrated as 2D images using the suggested probabilistic model.

• 대한토목학회논문집
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• 제42권3호
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• pp.359-369
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• 2022

산사태에 대한 비탈면 안정해석시, 산지 비탈면의 경사와 지형의 변화가 심한 경우에는 엄밀한 해석으로 안정성을 평가해야 한다. 본 연구에서는 불포화층에서 강우로 인한 침투 현상을 해석하여 간극수압의 변동을 고려한 산사태 안정성 분석을 수행하였다. 비탈면 안정해석 시 실제 산사태가 발생한 지역을 선정하여 3차원 비탈면 안정해석을 수행하였고 무한비탈면 해석결과와 비교하였다. 세밀한 지반정보를 기반하여 3차원 비탈면 안정해석으로 지형에 따라 변동하는 산사태의 발생위치와 규모를 예측할 수 있다고 판단되었다.

• 한국지반공학회논문집
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• 제21권6호
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• pp.137-146
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• 2005

본 연구에서는 전국의 299개 철도연변 사면에 대한 현장 조사를 통해 사면의 파괴 유형 및 보강 실태를 분석하고, 조사된 사면 중 절취 토사사면으로 분류된 14개의 사면에 대하여 강우의 영향을 고려한 안정성 해석을 수행하였다. 표층유실 형태의 얕은 파괴를 검토하기 위해 강우에 의해 지표에 임시적으로 형성되는 지하수위를 가정한 무한사면해석을 수행하였으며, 유한요소법을 적용한 침투해석 결과와 지하수위를 지표 근처로 가정하는 방법을 통해 강우를 고려한 한계평형해석을 수행하였다. 기존의 파괴 기록과 안정성 해석으로 예측된 파괴 형태를 비교함으로써 적용된 해석방법들의 적합성을 평가하였다. 철도연변의 절취 토사사면에서는 얕은 깊이의 표층파괴가 주로 발생하였으나, 한계평형해석법으로는 이를 적절히 예측할 수 없었다. 강우에 의한 표층파괴를 보다 합리적으로 예측하기 위해서는 강우에 의한 안정성 저하 효과로서 모관흡입력의 감소로 인한 간극수압의 증가뿐만 아니라, 지반의 침투능보다 큰 강우로 인해 발생하는 표면 유출수에 의한 침식을 고려할 수 있는 새로운 해석기법의 개발이 요구된다.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.133-138
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• 2007

Surface pitting is a major failure mode for gears. The contact fatigue life analysis of transmission gear considering running-in process is presented in this paper. Surface roughness change of rolling test is used in a life analysis. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions; the subsurface stress field is obtained using rectangular patch solutions. Mesoscopic multiaxial fatigue criterion which can yield satisfactory results for non-proportional loading is then applied to predict fatigue damage. Suitable counting method and damage rule were used to calculate the fatigue life of random loading caused by rough surface. The life analysis considering running-in is in good agreement with the experimental results.

• Structural Engineering and Mechanics
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• 제26권5호
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• pp.557-568
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• 2007

The elastic T-stress is increasingly being recognized as an important second parameter to the stress intensity factor for fracture and fatigue assessments. In this paper, the mutual or M-contour integral approach is employed in conjunction with the Boundary Element Method (BEM) to determine the numerical T-stress solutions for cracks in plates with multiple holes. The problems investigated include plates of infinite width with multiple holes at which single or double, symmetric cracks have grown from. Comparisons of these results are also made with the corresponding solutions of finite plates with a single hole. For completeness, stress intensity factor solutions for the cracked geometries analyzed are presented as well. These results will be useful for failure assessments using the two-parameter linear elastic fracture mechanics approach.

• Communications for Statistical Applications and Methods
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• 제6권1호
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• pp.99-106
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• 1999

This paper considers an imperfect repair model for which the repairable system is maintained preventively at periodic times and is replaced by a new system when a predetermined number of preventive maintenance has been applied. our main objective of this is to determine the optimal number of preventive maintenances before the system is replaced and the optimal length of interval between two consecutive preventive maintenances under a new repair model which is referred to as an ineffective preventive maintenance. Such a model assumes a periodic preventive maintenance in which the system is effectively maintained with a certain probability. Otherwise the system is not improved at all after each maintenance and thus the failure rate remains the same as before. The criteria to determine the optimal number of preventive maintenances and length of period is the expected cost rate per unit time for an infinite time span. We give the explicit expressions for the expected cost rate per unit time. Some numerical examples are presented for illustrative purposes.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.687-696
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• 2006

Slope failure triggered by rainfall produces severe effects on the serviceability and stability of railway. Therefore slope stability problem is one of the major concerns on the operation of railway. In this study we collected rainfall data when and where slope failures were observed. The collected data show that the range of cumulative rainfall is from 150 to 500mm and the rainfall duration is about 3 to 24 hours. By using the collected rainfall information, slope stability analysis considering infiltration was carried. The analyses employs multiple sliding surfaces to find the minimal factor of safety in the infinite slope condition. This approach show more reasonable results than the results from analysis following the design code which assumes that groundwater level and the slope surface are equal.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.262-267
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• 2001

In this study, the Reliability of degraded steam turbine blade was evaluated using the limited fatigue data. The statistical estimation of limited fatigue data implies that some unknown uncertainties which may be involved in fatigue reliability analysis. Therefore, an appropriate distribution in the fatigue strength was determined by the characteristic distribution - linear correlation coefficient, fatigue physics, error parameter. 3-parameter Weibull distribution is the most appropriate distribution to assume for infinite region. The load applied on the blade is mainly tensile. The maximum Von-Mises stress is 219.4 MPa at the steady state service condition. The failure probability($F_p$) derived from the strength-stress interference model using Monte carlo simulation under variable service condition is 0.25% at the 99.99% confidence level.