• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.830-832
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• 2014

In this study, friction stick-slip vibration're interpretation of the phenomenon, we used a statistical model of friction. In a previous study using a definite friction factor, but to a dynamic simulation using a constantly changing during the integration time by a Monte Carlo simulation method, not the average coefficient of friction and the dynamic friction coefficient and a constant value in this study.

• 한국지진공학회논문집
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• 제11권4호
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• pp.25-31
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• 2007

For areas such as the Korean Peninsula, which have moderate seismic activity but no available records of strong ground motion, synthetic seismograms can be used to evaluate ground motion without waiting for a strong earthquake. Such seismograms represent the estimated ground motions expected from a set of possible earthquake scenarios. Local site effects are especially important in assessing the seismic hazard and possible ground motion scenarios for a specific fault. The earthquake source and rupture dynamics can be described as a two-step process of rupture initiation and front propagation controlled by a frictional sliding mechanism. The seismic wavefield propagates through heterogeneous geological media and finally undergoes near-surface modulations such as amplification or deamplification. This is a complex system in which various scales of physical phenomena are integrated. A unified approach incorporates multi-scale problems of dynamic rupture, radiated wave propagation, and site effects into an all-in-one model using a three-dimensional, fourth-order, staggered-grid, finite-difference method. The method explains strong ground motions as products of complex systems that can be modified according to a variety of fine-scale rupture scenarios and friction models. A series of such deterministic earthquake scenarios can shed light on the kind of damage that would result and where it would be located.

• Geomechanics and Engineering
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• 제15권4호
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• pp.937-945
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• 2018

A probabilistic study of a reinforced earth wall in a frictional soil using the surface response methodology (RSM) is presented. A deterministic model based on numerical simulations is used (Abdelouhab et al. 2011, 2012b) and the serviceability limit state (SLS) is considered in the analysis. The model computes the maximum horizontal displacement of the wall. The response surface methodology is utilized for the assessment of the Hasofer-Lind reliability index and is optimized by the use of a genetic algorithm. The soil friction angle and the unit weight are considered as random variables while studying the SLS. The assumption of non-normal distribution for the random variables has an important effect on the reliability index for the practical range of values of the wall horizontal displacement.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1998년도 터널.암반역학위원회 박사학위 논문집
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• pp.3-34
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• 1998

The stability condition of rock slopes is greatly affected by the geometry and strength parameters of discontinuities in the rock masses. Rock slopes Involving movement of rock blocks on discontinuities are failed by one or combination of the three basic failure modes-plane, wedge, and toppling. In rock mechanics, practically all the parameters such as the joint set characteristics, the rock strength properties, and the loading conditions are always subject to a degree of uncertainty. Therefore, a reasonable assessment of the rock slope stability has to include the excavation of the multi-failure modes, the consideration of uncertainties of discontinuity characteristics, and the decision on stabilization measures with favorable cost conditions. This study was performed to provide a new numerical model of the deterministic analysis, reliability analysis, and reliability-based optimization for rock slope stability. The sensitivity analysis was carried out to verify proposed method and developed program; the parameters needed for sensitivity analysis are design variables, the variability of discontinuity properties (orientation and strength of discontinuities), the loading conditions, and rock slope geometry properties. The design variables to be optimized by the reliability-based optimization include the cutting angle, the support pressure, and the slope direction. The variability in orientations and friction angle of discontinuities, which can not be considered in the deterministic analysis, has a greatly influenced on the rock slope stability. The stability of rock slopes considering three basic failure modes is more influenced by the selection of slope direction than any other design variables. When either plane or wedge failure is dominant, the support system is more useful than the excavation as a stabilization method. However, the excavation method is more suitable when toppling failure is dominant. The case study shows that the developed reliability-based optimization model can reasonably assess the stability of rock slopes and reduce the construction cost.

• 한국지반공학회논문집
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• 제15권6호
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• pp.3-16
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• 1999

본 논문은 새로 개발된 파괴형태를 고려한 암반사면의 신뢰도해석 모델의 검증을 위하여 예제를 통한 민감도해석을 수행하였고 그 결과를 수록하였다. 민감도분석에 이용된 매개변수는 암반 불연속면의 공학적 특성 (불연속면의 방향 및 강도),하중조건 및 암반사면의 기하학적 형상 등이다. 확률론적 해석에서 고려할 수 있는 불연속면의 방향 및 마찰각의 통계적 특성이 파괴형태를 고려한 암반사면의 안정에 큰 영향을 보였다. 암반사면의 안정은 굴착면의 방향에 가장 민감하였다. 예제분석을 통하여 개발된 파괴형태를 고려한 암반사면의 신뢰도모델은 암반사면의 안정성 조사에 성공적으로 적용할 수 있었다.

• 소음진동
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• 제9권4호
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• pp.643-651
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• 1999

A brief description of the current technology (contact-start-stop) employed in most of today's hard disk drive is presented. The dynamics and head/disk interactions during a start/stop process are very complicated and no one has been able to accurately model the interactions. Thus, the head/disk interface that meets the start/stop durability and stiction requirements are always developed statistically. In arriving at a solution. many sets of statistical tests are run by varying several parameters. such as, the carbon overcoat thickness. lubricant thickness. disk surface roughness, etc. Consequently, the cost associated III developing an interface could be significant since the outcome is difficult to predict. An alternative method known as Load/Unload technology alters the problem set. such that. the start/stop performance can be designed in a predictable manner. Although this techno¬logy offers superior performance and significantly reduces statistical testing time, it also has some potential problems. However. contrary to the CSS technology. most of the problems can be solved by design and not by trial and error. One critical problem is that of head/disk contacts during the loading and unloading processes. These contact can cause disk and slider damage because the contacts are likely to occur at high disk speeds resulting in large friction forces. Use of glass substrate disks also may present problems if not managed correctly. Due to the low thermal conductivity of glass substrates. any head/disk contacts may result in erasure due to frictional heating of the head/disk interface. In spite of these and other potential problems. the advantage with L/UL system is that these events can be understood. analyzed. and solved in a deterministic manner.

• 한국지반공학회지:지반
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• 제7권3호
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• pp.21-32
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• 1991

본 연구에서는 복합 zone을 가진 rockfill dam성토 재료의 강도정수들과 core zone에서의 간극 수압의 불확정성을 고려할 수 있도록, 성토 재료의 공간적인 변화의 불확실성, 시료수의 제한에 의 한 불확정성에 실험실 결과와 현장 결과와의 차이에 따른 model 오차의 영향을 고려한 종합적인 설계변수들의 불확정성을 규명하였으며 core zone의 간극수압과 rockfill zone의 내부 마찰각을 bayeg 이론을 이용하여 불확정성을 Updating할 수 있는 방법을 제시하였다. 사면 안정 해석에서 시공직후 상, 하류, 만수위 상, 하류 수위, 급강하 시의 2차원 사면안정해석 과 end effect 영향을 고려한 3차원사면 안정해석을 하였다. 본 목적을 위하여 복합 zone을 가진 rockfill dam의 사면 안정해석에서 end effect의 영향을 고려한 3차원 사면안정해석 Program인 "ESTABL"을 개발하였으며, 파괴 사면의 강도정수와 간극수압의 변동계수를 구하는 프로그램 "COV", 복합 zone사면 안전율의 변동계수를 구하는 프로그램 "PCOV"을 개발하였다. 사면안정해석 결과 3차원안전율이 2차원안전율보다 약 200A정도 크게 나타나므로 end restraint 효과가 상당히 큼을 알 수 있다. 3차원사면안정은 근본적으로 system reliability 문제이 므로 안전율의 평균간보다 그 불확정성이 더 큰 영향을 미침을 보여준다. 또한 기초설계 치로 설계 를 마친후 시공중 혹은 추가로 각종 계측치가 있을 때 updating 이론을 이용하여 신뢰도를 증가시 킬 수 있음을 보여주며 강도계수의 변화에 의한 파괴확률의 변화는 점착력의 불확정성이 내부마찰 각의 불확정성보다 민감하게 영향을 미침을 보여준다.찰 각의 불확정성보다 민감하게 영향을 미침을 보여준다.

• 한국방재안전학회논문집
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• 제12권2호
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• pp.65-72
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• 2019

한국은 국토의 64%이상이 산지로 구성되어 있어 산지재해에 취약한 지형적 특성을 가진다. 연구대상지역인 태백산국립공원 당골유역은 탐방로 대부분이 급경사지와 인접해 있어 집중호우 시 산사태와 토석류에 취약한 지역이다. 본 연구에서는 결정론적 분석방법인 사면안정성 모델을 이용하여 사면재해 발생예측 가능성을 검토하였다. 모델의 매개변수는 정밀토양도의 토양분류에 따라 토질의 단위중량, 유효점착력, 흙의 내부마찰각, 유효토심, 지표경사 등을 이용하였고 1 m격자의 DEM을 바탕으로 사면안정성 평가를 실시하였다. 사면안정성평가 분석결과 지하수/ 유효토심과의 비가 1.0에 가까워질수록 위험지역이 높게 나타났으며, 국립공원 하류지역의 민가와 상업시설 상당수가 위험에 노출된 것으로 나타났다.