• 한국터널지하공간학회 논문집
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• 제9권3호
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• pp.263-273
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• 2007

일반적으로 고심도에 건설되는 암반구조물의 경우 높은 현지응력과 공동의 굴착에 따른 유도응력으로 인하여 공동 경계면에서 스폴링(spatting)이나 슬래빙(slabbing)과 같은 취성파괴가 발생할 수 있다. Hoek-Brown과 Mohr-Coulomb 파괴기준과 같은 전통적인 파괴기준을 적용한 결과 취성파괴현상과 파괴심도 등을 예측할 수 없는 것으로 나타나 취성파괴를 예측하기 위한 여러 모델이 제안되었으며, 그 중 CWFS 모델이 적합한 것으로 알려져 있다. 본 연구에서는 모형실험에서 얻어진 원형공동주변의 취성파괴현상을 모델링하기위하여 CWFS 모델을 적용하였으며, 입력자료의 산정을 위해 암석의 손상정도와 손상에 따른 물성의 변화를 측정하는 손상제어시험을 수행하였다. CWFS 모델에 의해 예측된 파괴양상을 전통적인 파괴기준에 의한 해석결과 및 모형실험결과와 비교하여 취성파괴모델링의 적용성을 평가하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.434-443
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• 2009

Slope stability analysis is an essential part of rock slope design. For highly fractured rock, the limit equilibrium method (LEM) based slope stability analysis with a circular failure surface is often carried out assuming the rock mass behaves more or less as a continuum. This paper examines first, the applicability of the finite-element method (FEM) based shear strength reduction (SSR) technique for highly fractured rock slope, and second the use of Mohr-Coulomb (MC) failure criterion in conjunction with generalized Hoek-Brown (HB) failure criterion. The numerical results on a number of cases are compared in terms of the factor of safety (FS). The results indicated that the FEM-based SSR technique yields almost the same FSs from LEM, and that the MC and HB failure criteria yield almost identical FSs when the strength parameters for MC failure criterion are obtained based on the modified HB failure criterion if and only if value of the Hoek-Brown constant $m_i$ is smaller than 10 and slope angle is smaller than 1:1, otherwise MC failure criteria over-estimate the factor of safety.

• Structural Engineering and Mechanics
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• 제61권1호
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• pp.161-169
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• 2017

This study aimed to develop a simple and effective method to facilitate the experimental research on mechanical properties of masonry under biaxial compressive stress. A series of tests on full-scale brick masonry panels under biaxial compression have been performed in limited principal stress ratios oriented at various angles to the bed joints. Failure modes of tested panels were observed and failure features were analyzed to reveal the mechanical behavior of masonry under biaxial compression. Based on the experimental data, the failure curve in terms of two orthotropic principal stresses has been presented and the failure criterion of brick masonry in the form of the tensor polynomial has been established, which indicate that the anisotropy for masonry is closely related to the difference of applied stress as well as the orientation of bed joints. Further, compared with previous failure curves and criteria for masonry, it can be found that the relative strength of mortar and block has a considerable effect on the degree of anisotropy for masonry. The test results demonstrate the validity of the proposed experimental method for the approximation of masonry failure under biaxial compressive stress and provide valuable information used to establish experimentally based methodologies for the improvement of masonry failure criteria.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.107-110
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• 2004

In this paper, a new structural health monitoring technique for composite laminates through the use of embedded fiber Bragg grating (FBG) sensors is presented. The method traces the ply stress states of a laminate and compares them with failure criteria during the service time of structures. The ply stress state of every ply composing the composite laminate can be obtained using classical lamination theory by embedded FBG sensors in the laminate. Graphite/epoxy laminate specimens, embedded with three FBG sensors, were fabricated. Tension tests were performed to evaluate the ply stress states tracing technique. Experimental results show that laminates experience fracture when the ply stress states are over the boundaries of failure criteria. In this method, critical damage can be detected by the ply stress states which are close to the boundaries of the failure criteria.

• 한국신뢰성학회지:신뢰성응용연구
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• 제10권2호
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• pp.123-135
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• 2010

Failure mode and effects analysis (FMEA) is a widely used technique to assess or to improve reliability of products or processes at early stage of development. Traditionally, the prioritization of failures for corrective actions is performed by evaluating risk priority numbers (RPN). In practice, due to insufficient evaluation criteria specific to related products and processes, RPN is not always evaluated properly. This paper reestablishes an effective methodology for prioritization of failure modes in FMEA procedure. Revised evaluation criteria of RPN are devised and a refined FMEA sheet is introduced. To verify the proposed methodology, it is applied to inspection processes of PCB products.

• 대한기계학회논문집
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• 제14권5호
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• pp.1181-1185
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• 1990

본 연구에서는 정적파괴는 피로균열 진전의 최종과정에서 생기는 경우가 많다. 따라서 정적파괴의 경우의 파괴평가선도 및 피로파괴의 경우의 파괴평가선도가 얻어지 면 실제의 사용에 대해서 대단히 유용하다. 이와같은 관점에서 피로파괴에 대한 파 괴평가선도와 데이터베이스(data base)의 구축을 검토해 보고자 한다.

• 한국구조물진단유지관리공학회 논문집
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• 제23권3호
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• pp.51-55
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• 2019

저수지의 붕괴 발생 시 인명 및 재산피해의 예방 및 저감을 위하여 붕괴예보 시스템의 필요성은 대두되고 있는 상황이다. 붕괴 예보시스템의 효율적 활용을 위해서는 실시간 계측한 이상거동 및 붕괴징후에 따라 대응할 수 있는 관리기준은 가장 중요한 요소이다. 기 연구된 수위 관리기준의 검증을 위하여 저수량에 따라 10여개의 저수지를 선정하고 수위변화 자료를 분석하여 적정성을 검토하였다. 1년 동안의 수위계측 자료에서 가장 급격한 변화구간을 선정하여 가중치 및 추세선을 적용하여 분석한 결과 3분위로 수립된 관리기준값은 7%이내의 표준편차를 보여주었다. 이는 수립된 관리기준값은 적정하다고 판단된다.

• Steel and Composite Structures
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• 제1권4호
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• pp.411-426
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• 2001

This paper treats the failure analysis of prestressing steel wires with different kinds of localised damage in the form of a surface defect (crack or notch) or as a mechanical action (transverse loads). From the microscopical point of view, the micromechanisms of fracture are shear dimples (associated with localised plasticity) in the case of the transverse loads and cleavage-like (related to a weakest-link fracture micromechanism) in the case of cracked wires. In the notched geometries the microscopic modes of fracture range from the ductile micro-void coalescence to the brittle cleavage, depending on the stress triaxiality in the vicinity of the notch tip. From the macroscopical point of view, fracture criteria are proposed as design criteria in damage tolerance analyses. The transverse load situation is solved by using an upper bound theorem of limit analysis in plasticity. The case of the cracked wire may be treated using fracture criteria in the framework of linear elastic fracture mechanics on the basis of a previous finite element computation of the stress intensity factor in the cracked cylinder. Notched geometries require the use of elastic-plastic fracture mechanics and numerical analysis of the stress-strain state at the failure situation. A fracture criterion is formulated on the basis of the critical value of the effective or equivalent stress in the Von Mises sense.

• Nuclear Engineering and Technology
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• 제48권1호
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• pp.218-227
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• 2016

Background: Steam explosions may occur in nuclear power plants by molten fuel-coolant interactions when the external reactor vessel cooling strategy fails. Since this phenomenon can threaten structural barriers as well as major components, extensive integrity assessment research is necessary to ensure their safety. Method: In this study, the influence of yield criteria was investigated to predict the failure of a reactor cavity under a typical postulated condition through detailed parametric finite element analyses. Further analyses using a geometrically simplified equivalent model with homogeneous concrete properties were also performed to examine its effectiveness as an alternative to the detailed reinforcement concrete model. Results: By comparing finite element analysis results such as cracking, crushing, stresses, and displacements, the Willam-Warnke model was derived for practical use, and failure criteria applicable to the reactor cavity under the severe accident condition were discussed. Conclusion: It was proved that the reactor cavity sustained its intended function as a barrier to avoid release of radioactive materials, irrespective of the different yield criteria that were adopted. In addition, from a conservative viewpoint, it seems possible to employ the simplified equivalent model to determine the damage extent and weakest points during the preliminary evaluation stage.

• 한국방재학회 논문집
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• 제4권3호
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• pp.9-17
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• 2004

최근 발생하는 집중호우 및 태풍을 동반한 국지성 호우로 인한 사면붕괴가 자연재해 피해의 큰 부분을 차지하고 있으며, 사면붕괴로 인한 피해가 해마다 증가하는 추세에 있다. 본 연구에서는 사면붕괴를 예지하기 위하여 예 경보시스템 도입에 대한 검토를 다음 사항에 중점을 두어 수행하였다. (1) 사면붕괴의 유형과 원인을 분석한다. (2) 현재 많이 사용하고 있는 사면안정성 평가기준을 검토한다. (3) 사면의 지형적 지질학적 특성뿐 아니라 사면을 구성하는 물질들의 특성을 고려함으로써 사면의 안정성을 평가한다. 그리고 (4) 사면안정성에 영향을 미치는 가장 중요한 변수들을 결정한다. 사면 예 경보는 자동계측시스템을 이용하여 데이터를 수집하고 인터넷 기술을 이용하여 수집된 데이터를 전송하여 분석하면 관리 기준값과 비교를 통하여 예 경보가 이루어지는 시스템을 제안하였다. 이 연구에서 제안한 관리 기준값은 경보단 산정의 기준이 되는 1차, 2차 기준값으로 구분하였는데, 측정된 계측 데이터의 분석 및 연구를 통하여 기준값의 지속적인 수정 및 보완이 필요하다.