• Smart Structures and Systems
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• 제19권1호
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• pp.11-20
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• 2017

For structural damage detection of shear buildings, this paper proposes a new concept using structural element mass-stiffness vector (SEMV) based on special mass and stiffness distribution characteristics. A corresponding damage identification method is developed combining the SEMV with the cross-model cross-mode (CMCM) model updating algorithm. For a shear building, a model is assumed at the beginning based on the building's distribution characteristics. The model is updated into two models corresponding to the healthy and damaged conditions, respectively, using the CMCM method according to the modal parameters of actual structure identified from the measured acceleration signals. Subsequently, the structural SEMV for each condition can be calculated from the updated model using the corresponding stiffness and mass correction factors, and then is utilized to form a new feature vector in which each element is calculated by dividing one element of SEMV in health condition by the corresponding element of SEMV in damage condition. Thus this vector can be viewed as a damage detection feature for its ability to identify the mass or stiffness variation between the healthy and damaged conditions. Finally, a numerical simulation and the laboratory experimental data from a test-bed structure at the Los Alamos National Laboratory were analyzed to verify the effectiveness and reliability of the proposed method. Both simulated and experimental results show that the proposed approach is able to detect the presence of structural mass and stiffness variation and to quantify the level of such changes.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.327-330
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• 2003

In this paper, a viscoelastic structural analysis for the spent pressurized water reactor(PWR) nuclear fuel disposal canister is carried out to predict the collapse of the canister while the canister is stored in a deep repository for long time. There may exist some subterranean heat in a deep repository while the nuclear fuel disposal canister is stored for long time. Then, a time-dependent viscoelastic structural deformation may occur in the canister due to the subterrnean heat Hence, the viscoelastic stress variation according to time should be computed to predict the structural strength of the canister. A viscoelastic material model is adopted. Analysis results show that even though some subterrnean heat may exist for quite a long time, the canister structure still endures stresses below the yield strength of the canister. Hence, some subterranean heat cannot seriously affect the structural strength of the canister.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.805-810
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• 2000

The purpose of this study is to predict long-term structural safety on the Yonggwang Unit 3 prestressed concrete containment building. The aging-related degradations of its main structural materials are investigated and the effects of the property variation of time-dependent materials on the structural behavior of containment building are also assessed through the analysis on the ultimate pressure capacity. The nonlinear finite element analyses for both the design criteria condition a the present aging condition are conducted to assess the present structural capacity of the containment building As a result, it is verified that the structural capacity of the Yonggwang Unit 3 containment building under the present aging condition is judged to be still rugged. n addition, the sensitivity of the ultimate pressrue capacity of containment building according to th degradation levels of the structural materials are assessed. Finally, it is showed that the sensitivity levels are in the order of the tendon, rebar and concrete in case of individual material degradations, and the tendon-rebar, tendon-concrete and rebar-concrete in case of coupled material degradations.

• Structural Monitoring and Maintenance
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• 제9권2호
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• pp.157-177
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• 2022

In this paper, an innovative finite element updating method is presented based on the variation wavelet transform coefficients of Auto/cross-correlations function (WTCF). The Quasi-linear sensitivity of the wavelet coefficients of the WTCF concerning the structural parameters is evaluated based on incomplete measured structural responses. The proposed algorithm is used to estimate the structural parameters of truss and plate models. By the solution of the sensitivity equation through the least-squares method, the finite element model of the structure is updated for estimation of the location and severity of structural damages simultaneously. Several damage scenarios have been considered for the studied structure. The parameter estimation results prove the high accuracy of the method considering measurement and mass modeling errors.

• Composites Research
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• 제18권2호
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• pp.46-51
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• 2005

본 논문은 램파(Lamb waves)를 이용한 능동검사시스템을 구조 건전성 모니터링 시스템에 적용하기 위하여 램파의 특성연구를 수행하였다 연구는 보다 실제 구조물에 근접한 구조물을 고려하여 두께변화가 있는 준등방성 복합재 평판을 대상으로 PZT 탐촉자(transducer)를 표면에 부착하여 수행하였다. 본 연구에서는 두께변화로 인한 램파의 전파특성을 분석하기 위하여 간단하지만 새로운 기법을 적용하였다 본 연구의 결과는 램파의 전파특성은 상대적으로 얇은 구조물에 민감하였고 두께변화가 램파의 전파에 미치는 영향을 보여 주었다. 또한 본 연구에 사용한 분석기법은 램파를 이용한 구조 건전성 모니터링에 적용할 수 있는 가능성을 보여주었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.355-362
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• 2004

An efficient boundary-based technique is developed for addressing shape design sensitivity analysis in various problems. An analytical sensitivity formula in the form of a boundary integral is derived based on the continuum formulation for a general functional defined in problems. The formula, which is expressed in terms of the boundary solutions and shape variation vectors, can be conveniently used for gradient computation in a variety of shape design problems. While the sensitivity can be calculated independent of the analysis means, such as the finite element method (FEM) or the boundary element method (BEM), the FEM is used for the analysis in this study because of its popularity and easy-to-use features. The advantage of using a boundary-based method is that the shape variation vectors are needed only on the boundary, not over the whole domain. The boundary shape variation vectors are conveniently computed by using finite perturbations of the shape geometry instead of complex analytical differentiation of the geometry functions. The supercavitating flow problem and fillet problem are chosen to illustrate the efficiency of the proposed methodology. Implementation issues for the sensitivity analysis and optimization procedure are also addressed in these problems.

• 한국전기전자재료학회논문지
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• 제19권8호
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• pp.701-706
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• 2006

In addition to its similarity to genuine diamond film, diamond-like carbon (DLC) film has many advantages, including its wide band gap and variable refractive index. In this study, DLC films were prepared by the RF PECVD (Plasma Enhanced Chemical Vapor Deposition) method on silicon substrates using methane $(CH_4)$ and hydrogen $(H_2)$ gas. We examined the effects of the post annealing temperature on the structural variation of the DLC films. The films were annealed at temperatures ranging from 300 to $900^{\circ}C$ in steps of $200^{\circ}C$ using RTA equipment in nitrogen ambient. The thickness of the film and interface between film and substrate were observed by surface profiler, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), respectively. Raman and X-ray photoelectron spectroscopy (XPS) analysis showed that DLC films were graphitized ($I_D/I_G$, G-peak position and $sp^2/sp^3$ increased) ratio at higher annealing temperature. The variation of surface as a function of annealing treatment was verified by a AFM and contact angle method.

• 정보처리학회논문지D
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• 제18D권2호
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• pp.89-100
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• 2011

인간 유전체에 존재하는 유전적 구조 변이(genetic structural variation) 중 하나인 유전체 단위반복변이(Copy Number Variation, CNV)은 유전자의 기능 발현과 밀접한 관련이 있다. 특히 특정 유전 질병이 있는 사람들을 대상으로 CNV와 유전자발현의 관계를 밝히는 연구가 계속 진행되고 있지만, 정상인 유전체에 대한 CNV의 기능적 분석은 아직 활발히 이루어지고 있지 않다. 본 논문에서는 다수의 정상인 샘플에서 찾아낸 공통된 CNV에 대하여 유전자들과의 기능적 관계를 유전자의 분자적 위치와 상관없이 밝힐 수 있는 분석 방법을 제시한다. 이를 위해 서로 다른 이질적인 생물학데이터를 통합하는 방법을 제시하고 공통된 CNV와 유전자와의 연관성을 분자적 위치와 상관없이 계산할 수 있는 새로운 방법을 제시한다. 제안된 방법의 유의성을 보이기 위해서 유전자 온톨로지 (Gene Ontology) 데이터베이스를 이용한 다양한 검증 실험들을 수행하였다. 실험결과 새롭게 제안된 연관성 측정방법은 유의성이 있으며 공통된 CNV와 강한 연관성을 갖는 유전적 기능의 후보들을 시스템적으로 제시할 수 있는 것으로 나타났다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 가을 학술발표회 논문집
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• pp.145-151
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• 1994

Welded connections have been designed on basis of allowable stresses, wherein the response to loading is assumed to be totally elastic. This is the vector analysis method, which resolves the stresses determined from the direct stress formula and the torsion formula into a vector combination to obtain a solution. It has been known that this method gives conservative answers and typically a very high factor of safety. An analytical method based on the Instantaneous Center of Rotation has been developed which predicts the ultimate strength of an eccentically loaded fillet welded connection. The method of Instantaneous Center of Rotation results in weld resistance capacities greater than the vector analysis method, by recognizing the variation in fillet weld strength with respect to the direction of the applied loading and actual load-deformation response of elemental fillet welds. The procedure of numerical analysis is iterative and complex. The relations between vector analysis method and the method of Instantaneous Center of Rotation on eccentrical distance subjected to variation of load direction are presented in this paper. Considering of the effects on configuration of weld groups, the method of Instantaneous Center of Rotation are provided a more exact results of the numerical analysis.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1991년도 가을 학술발표회 논문집
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• pp.29-32
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• 1991

It is well known that the fatigue damage process in composite materials is very complicated due to complex failure mechanisms that comprise debounding, matrix cracking, delamination and fiber splitting of laminates. Therefore, the residual strength, instead of a single dominant crack length, is chosen to describe the criticality of the damage accumulated in the sublaminate. In this study, two models for residual strength degradation established by Yang-Liu and Tanimoto-Ishikawa that are capable of predicting the statistical distribution of both fatigue life and residual strength have been investigated and compared. Statistical methodologies for fatigue life prediction of composite materials have frequently been adopted. However, these are usually based on a simplified probabilistic approach considering only the variation of fatigue test data. The main object of this work is to propose a fatigue reliability analysis model which accounts for the effect of all sources of variation such as fabrication and workmanship, error in the fatigue model, load itself, etc. The proposed model is examined using the previous experimental data of GFRP and it is shown that it can be practically applied for fatigue problems in composite materials.