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계측된 FRF 데이터로부터 추출된 POM 곡률의 평균값에 근거한 보 구조물의 손상탐지
은희창(Eun, Hee-Chang) 대한건축학회 2015 大韓建築學會論文集 : 構造系 Vol.31 No.4
This work presents an analytical method for detecting damage of flexural beam member without the baseline data at intact state. Utilizing FRF (frequency response function) data collected in the neighborhood of the resonance frequency, the POV (proper orthogonal value) and the corresponding POM (proper orthogonal mode) are extracted to use as a damage detection index. It is observed from the POM curvature curve that the damage coincides with the location to represent the abrupt change of the curve. The validity of the proposed method is illustrated in a numerical experiment. The sensitivity of the proposed method depending on the measurement data contaminated by the external noise, the resonance frequency region to collect the FRF data and the selected POV is investigated in a numerical experiment.
FRF 계측데이터의 통계수정에 의한 휨부재의 손상탐지에 관한 연구
은희창(Eun, Hee-Chang),김진봉(Kim, Jin-Bong) 대한건축학회 2014 大韓建築學會論文集 : 構造系 Vol.30 No.4
This work presents an analytical method for detecting damage of flexural beam member without the baseline data at intact state. Based on the statistical process of FRF (frequency response function) data collected in the neighborhood of the resonance frequency, the damage of the beam member is considered. Normalizing the FRF data set collected at each nodal point, and extracting their mean values and the central difference approximation, the curvature of the mean values can be obtained. It can be observed that the damage exists at the region to represent the abrupt change of the curvature. The proposed method is rarely affected by the external noise and its level. It is exhibited that the FRF data in the region of the first resonance frequency can be utilized more effectively rather than the ones in the second resonance frequency. The validity of the proposed method is illustrated in a numerical experiment of beam model.
은희창(Eun Hee-Chang),이민수(Lee Min-Su),최진(Choi Jin) 대한건축학회 2009 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.29 No.1(구조계)
Exact structural analysis may be carried out based on proper description of structural parameters. It is not easy to properly describe the physical parameter matrices of specimens or real structures for analytical analysis because of modelling and measurement errors, and damages. This study considers the correction of parameter matrices for modelling by minimizing cost functions of the difference between analytical and corrected parameter matrices. The validity of the proposed method is illustrated through an application and the analytical and numerical comparison with other methods.
구조 해석을 위한 유한 요소 분할 및 합성법에 대한 연구
은희창(Eun Hee-Chang),양근혁(Yang Keun-Heok),정헌수(Chung Heon-Soo) 대한건축학회 2003 大韓建築學會論文集 : 構造系 Vol.19 No.9
This paper presents an explicit equilibrium equation related to a finite element tearing and interconnection method for structural analysis. This method is based on a decomposition of the finite element model into substructures. Using the displacement compatibility at each interface between substructures and modifying the previous results provided by the authors this study determines the equilibrium equation of the global structure with floating substructures as substructures. The new method can explicitly determine the static displacements from the explicit form of equilibrium equation. But, it has a disadvantage not to be able to reduce the global number of degree of freedom due to the calculation of generalized inverse matrix. Also, several applications illustrated the validity and easiness of the proposed method.
장방형 개구부를 갖는 고강도 철근콘크리트 깊은 보의 전단거동
은희창(Eun Hee-Chang),양근혁(Yang Keun-Hyeok),정헌수(Chung Heon-Soo) 대한건축학회 2003 大韓建築學會論文集 : 構造系 Vol.19 No.8
This study is an experimental study to investigate the shear behavior of reinforced high-strength concrete deep beams with rectangular openings and presents an equation to determine the shear strength of those beams. Experimental parameters include shear span-to-overall depth ratio(a/h) as well as the width and depth of web opening. Test results indicate that the maximum crack width depended on shear span-to-overall depth ratio rather than size of web opening and the depth of opening had more influence on the shear strength of the beams than the width of opening. Based on Yang & Chung's equation which proposed to predict the shear strength of deep beams, an equation was established by the experimental results, fundamental theory of fracture mechanics, and multiple regression method. Through the comparison of experimental data and analytical results obtained from this and other studies, it was observed that the proposed equation properly estimates the ultimate shear strength of deep beams with rectangular openings.
추정된 물리적 특성변화에 의한 구조물의 손상탐지에 관한 연구
은희창(Eun Hee-Chang),정창용(Chung Chang-Yong) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.4
This study proposes the model-based damage detection method based on physical parameter matrices estimated from the measured response data. The physical parameters deviated by modelling and measurement errors as well as the damage should be corrected for structural design and analysis. The variation of the parameter matrices should be an important index to evaluate the occurrence of damage. Thus, this study firstly derives the mathematical formulations of physical parameter matrices to be updated and control force to be required for satisfying the measured responses. Taking the singular value decomposition of the variation of parameter matrices or the coefficient matrix of control force, this paper presents the methods to properly detect the damages. The validity of the proposed methods is illustrated in simple applications to detect the single and multiple damages.
은희창(Eun Hee-Chang),양근혁(Yang Keun-Heok),정헌수(Chung Heon-Soo) 대한건축학회 2003 大韓建築學會論文集 : 構造系 Vol.19 No.3
This paper determined the static equilibrium positions of linked bar structures. The static equilibrium positions are defined as the ones to minimize the variation of potential energy and can be obtained from the equation of motion at freezing time. Assuming each bar of the structure as a rigid body, the equation of motion for the structure must satisfy its rigid body condition. In order to combine both the equation of motion and the constraint equation, it is necessary to numerically calculate a weighting matrix to minimize the variation of potential energy and the generalized inverse method gives an explicit weighting matrix. Thus, with the modification of the generalized inverse method to explicitly describe the constrained motion, this paper presented a simple method to determine the equilibrium positions of linked bar structures, and the validity of the method was illustrated by two simple bar structures.