• 벤처창업연구
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• 제7권3호
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• pp.133-141
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• 2012

글로벌 경쟁 상황에 처한 현대의 모든 기업들은 고객의 니즈를 충족시키고, 이를 통한 경쟁력을 강화하기 위한 방안으로서 서비스를 이해하기 시작하면서 서비스에 대한 관심이 날로 증가하고 있다. 기업들이 제공하는 제품이나 서비스의 가치는 주로 고객과 서비스 제공자 간의 관계에서 형성되는 만족도의 정도로 정의되는 서비스 신뢰도에 의해 크게 좌우된다. 본 연구에서는, 유형의 제품이나 시스템의 실패 유형과 영향을 평가하는데 널리 사용되는 FMEA를 서비스의 신뢰도 평가에 적용하였다. 이를 위해, 서비스의 설계와 서비스 기능과 실패 간의 관계를 용이하게 표현할 수 있는 사건중심 프로세스 모델을 이용하였다. 본 연구의 목적은 서비스 프로세스 관점에서의 서비스 신뢰도를 평가하는 방법을 제시하는 것으로서, 이를 위해 fuzzy FMEA와 grey 이론을 이용하였다. 제안된 방법은 자동차정비 프로세스 사례에 적용하여 평가하였다.

• Geomechanics and Engineering
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• 제12권6호
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• pp.983-1001
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• 2017

The extent by which economy and safety concerns can be addressed in earth retaining structure design depends on the accuracy of the assumed failure surface. Accordingly, this study attempts to investigate and quantify mechanical backfill properties that control failure surface geometry of cohesionless backfills at the active state for translational mode of wall movements. For this purpose, a small scale 1 g physical model study was conducted. The experimental setup simulated the conditions of a backfill behind a laterally translating vertical retaining wall in plane strain conditions. To monitor the influence of dilative behavior on failure surface geometry, model tests were conducted on backfills with different densities corresponding to different dilation angles. Failure surface geometries were identified using particle image velocimetry (PIV) method. Friction and dilation angles of the backfill are calculated as functions of failure stress state and relative density of the backfill using a well-known empirical equation, making it possible to quantify the influence of dilation angle on failure surface geometry. As a result, an empirical equation is proposed to predict active failure surface geometry for cohesionless backfills based on peak dilatancy angle. It is shown that the failure surface geometries calculated using the proposed equation are in good agreement with the identified failure surfaces.

• Structural Monitoring and Maintenance
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• 제5권3호
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• pp.345-361
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• 2018

The set of processes performed to determine the dynamic characteristics of the constructed structures is named experimental modal analysis. Using experimental modal analysis and interpreting its results, structural failure can be assessed and then it would be possible to plan for their repair and maintenance. The purpose of the experimental modal analysis is to determine the resonance frequencies, mode shapes and Mode damping for the structure. Diverse methods for determining the shape of the mode by various researchers have been presented. There are pros and cons for each of these methods. This paper presents a method for determining the mode shape of the structures using the response spectrum in the experimental modal analysis. In the first part, the principles of the proposed method are described. Then, to check the accuracy of the results obtained from the proposed method, single and multiple degrees of freedom models were numerically and experimentally investigated.

• 한국지진공학회논문집
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• 제10권2호
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• pp.1-10
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• 2006

형상비가 상대적으로 작은 철근콘크리트 교각에 지진작용으로 인한 반복 횡하중이 작용하면 초기단계와 중간단계의 변위에서는 휨 거동을 보이다가 최종변위단계에서는 전단에 의해 파괴되는 휨-전단 거동을 보인다. 휨-전단 파괴거동을 보이는 교각은 휨 파괴거동을 보이는 교각에 비하여 연성능력이 저하되므로, 내진설계 또는 내진성능평가에서 극한변위를 해석적으로 결정하기 위해서는 휨성능곡선과 함께 전단성능곡선 모델을 적용하여야 한다. 본 논문에서는 원형교각에 대한 기존 모델을 수정한 전단성능곡선 모델을 제안하였고, CALTRANS 모델, Aschheim등의 모델, Priestley 등의 모델, 제안모델의 특징을 비교하였다. 또 국내에서 수행된 실물크기 기둥 실험체를 대상으로 전단성능곡선 모델을 평가하였다. 제한된 범위의 소수 실험결과에 대한 적용으로서 일반화하기는 어려울 것이지만, 실험결과와 비교 검토한 결과 제안모델이 파괴형태의 예측과 변위성능 예측의 정확도에서 매우 우수한 것으로 평가되었다.

• 대한기계학회논문집A
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• 제23권6호
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• pp.1039-1047
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• 1999

It is necessary to evaluate the fatigue behavior of rail steel under the multi-axial stress state to assure the railway vehicle's safety. For this purpose, the stress analysis to investigate the crack initiation criteria, static failure and fatigue behavior under mixed-mode are performed. The stress analysis results show that the initiation of the transverse fissure depends on the maximum shear stress below the surface. For the mixed mode, the fatigue crack growth behavior which is represented by the projection crack length and comparative S.I.F, ${\Delta}K_v$, shows the more conservative results. Also, its rate is lower than that of the case of the mode I, and this difference decreases with increasing the stress ratio, R.

• 대한치과보철학회지
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• 제41권2호
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• pp.232-242
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• 2003

Statement of problem : Fiber-reinforced posts have lower modulus of elasticity than titanium post or cast post-core. With this similar elasticity to that of dentin, fiber-reinforced posts have been known to have a tendency to reduce the risk of root fracture. However, there were few studies on the teeth restored with fiber-reinforced posts under the condition of reduced periodontal support. Purpose : The purpose of this study was to evaluate the fracture strength and failure mode of endodontically treated teeth restored with fiber-reinforced posts and titanium posts under the condition of reduced periodontal support. Material and method : Extracted human maxillary incisor roots were divided into 3 groups (group 1 carbon fiber post, group 2 : glass fiber post, and group 3 : titanium alloy post). After coronectomy and endodontic treatment, teeth were restored with each post systems and resin core according to the manufacturer's recommendation. Then, teeth with simulated periodontal ligament were embedded in the acrylic resin blocks at the level of 4 mm below the cemento-enamel junction. Each specimen was exposed to $10^5$ load cycles with average 30 N force in $36.5^{\circ}C$ water using a computer-controlled chewing simulator. Loads were applied at $45^{\circ}$ angle to the long axis of the teeth. After cyclic loading, teeth were subjected a compressive load until failure at a crosshead speed of 0.5 mm/min. Fracture strength (N) and failure mode were examined. The fracture strength was analyzed with one-way ANOVA and the Scheffe adjustment at the 95% significance level. Results and conclusion : The results were as follows. 1. There was no statistically significant difference in the mean fracture strength among the groups (P<.05). 2. Carbon fiber post and glass fiber post group showed less root fracture tendency than control group. 3. All specimens with root fractures showed fracture lines above the level of acrylic resin block, except for only one specimen in group 3.

• 한국강구조학회 논문집
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• 제15권6호통권67호
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• pp.673-681
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• 2003

본 논문은 냉간성형 각형강관 T형 접합부의 최대내력에 관한 실험 연구이다. 새로운 접합부로 지관을 트러스 평면에 대해 $45{^{\circ}}$회전시켜서 주관에 용접하고 주관 웨브 측면에는 플레이트로 보강한 형상을 연구 대상으로 설정하였다. $16.7{\leq}2{\gamma}(B/T){\leq}33.3$이고 $0.63{\leq}{\beta}(b1/B){\leq}0.7$ 범위의 지관 $45{^{\circ}}$회전시킨 T형 접합부에 대하여, 기존 최대내력식과의 비교 검토를 통하여 웨브 측면 보강에 따른 내력증대 및 파괴모드의 변화 등에 대하여 실험을 통해 조사하고자 한다. 실험결과, 보강판 두께 증가에 따라 보강 실험체의 접합부 내력이 상승하는 것으로 나타났다. $2{\gamma}=33.3$이고 플레이트로 웨브 보강한 실험체는는 접합부 파괴모드가 플랜지 파괴(M2)에서 복합파괴(M3) 형태로 전환되었으며, $2{\gamma}=16.7$이고 플레이트로 웨브 보강한 실험체에서는 웨브파괴(M1)에서 플랜지파괴(M2)로 지배 파괴모드가 변화하는 것으로 나타났다.

• Steel and Composite Structures
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• 제39권2호
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• pp.201-213
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• 2021

Currently, there is a lack of research in the design approach to avoid column wall failure in the concrete filled double skin steel tubular (CFDST) column-beam connections. In this paper, a finite element model has been developed and verified by available experimental data to analyze the failure mechanism of CFDST column-beam connections. Various finite element models with different column hollow ratios (χ) were established. The simulation result revealed that with increasing χ the failure mode gradually changed from yielding of end plate, to local failure of the column wall. Detailed parametric analyses were performed to study the failure mechanism of column wall for the CFDST column-beam connection, in which the strength of sandwiched concrete and steel tube and thickness of steel tube were incorporated. An analytical model was proposed to predict the moment resistance of the assembled connection considering the failure of column wall. The simulation results indicate that the proposed analytical model can provided a conservative prediction of the moment resistance. Finally, an upper bound value of χ was recommend to avoid column wall failure for CFDST column-beam connections.

• 한국안전학회지
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• 제31권6호
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• pp.58-66
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• 2016

This study aims to estimate the failure probability of concrete gravity dams for their risk analysis under flood situation. To the end, failure modes of concrete gravity dams and their limit state functions are proposed based on numerous review of domestic and international literatures on the dam failure cases and design standards. Three failure modes are proposed: overturning, sliding, and overstress. Based on the failure modes the limit state functions, the failure probability is assessed for a weir section and a non-weir section of a dam in Korea. As water level is rising from operational condition to extreme flood condition, the failure probability is found to be raised up to the warning condition, especially for overturning mode at the non-weir section. The result can be used to reduce the risk of the dam by random environmental variables under possible flood situation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.511-518
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• 2000

Characteristics of joint orientation, length, spacing and their distribution are very important factors for slope stability, Especially, the effect of joint spacing is an essential factor of slope stability. This study is to analyze the effect of joint spacing in cases of sliding and toppling, which is a typical failure mode. Joint spacing can divided into vertical spacing(spacing) and horizontal spacing(gap). And then, the spacing/length ratio of joint directly affect rock slope failure. When the ratio is below 0.05, the possibility of failure is rapidly increased. In case of toppling, the possibility of failure depends on the ratio of spacing to height of slope ratio slope. As the ratio decreases, the possibility of toppling failure increased. The critical ratio of spacing to height of slope is determined by the dip angle of the slope and the orientation of joint sets.