• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.135-144
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• 2006

In performing a risk analysis of structures under earthquakes, it is imperative to identify the vulnerability of structures associated with various damage stages considering structural properties, soil-structure interactions, site condition, and so on. In this paper, the method to derive a representative fragility curve of seismic isolated LRB(lead rubber bearing) bridges is proposed. In which, the curve is assumed log-normally distribution with two parameters. The risk analysis of seismic isolated LRB bridges considering earthquake effects such as PGA, PGV, SA, SV, and SI is also performed to assure the earthquake resisting capability of the structures. An practical way for constructing the representative fragility curves is also recommended combining fragility curves of structures.

• Journal of the Society of Disaster Information
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• v.11 no.3
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• pp.406-412
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• 2015

Recently, frequent earthquakes can cause serious damage to the bridge. So newly constructed bridge is considered earthquake resistant design, and for the existing old bridge evaluation of damage state is needed. In this paper, replacement of US-artificial earthquakes which are used for the construction of fragility curve for evaluating damage state to Korean artificial earthquakes to meet the Korean specifications is studied. For the generation of artificial earthquakes, the fragility curves are constructed for the PGA, for the cases of having isolated bearing and not having that.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.247-256
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• 2004

The damage curves for the 2-story shear building to the impulsive rectangular loads were established with the peak load and Impulse ratio producing the critical displacement. The convolution integrations with the Impulse response matrix and the loads were used to find the responses of the building. The impulse response matrix required in the calculations of the convolution integration were found with the mode superposition method It is shown from the established damage curves that the responses of the top and bottom floor are sensitive to the magnitude and the impulse of the loads respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.145-152
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• 2009

In performing a risk analysis on structure for earthquake, it is imperative to identify the vulnerability of structures associated with various stages of damage. And the earthquake resisting capability is needed for structures like bridge. So the damage analysis of bridges with or without isolator for earthquake effects is necessary. In this paper, the risk analysis of seismic isolated LRB bridges considering earthquake effects such as PGA, PGV, SA, SV, and SI is performed using fragility curves to assure the earthquake resisting capability of the structures. And, the stability of fragility curve is investigated with respect to input earthquake.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.203-210
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• 2004

The fragility curves of seismic retrofitted bridges by steel jacketing at bridge columns and restrainers at expansion joints after the 1994 Northridge earthquake are developed. Fragility curves are represented by lognormal distribution functions with two parameters (median and log-standard deviation) and developed as a function of peak ground acceleration(PGA). Two parameters in the lognormal distribution are estimated by the maximum likelihood method. The sixty ground acceleration time histories for Los Angeles area developed for FEMA SAC project are used for the dynamic analysis of bridges. The comparison of fragility curves of the bridges before and after column retrofit demonstrates that the improvement of the bridges with steel jacketing on the seismic performance is excellent for the damage states defined in this study. The comparison of fragility curves of the bridges before and after the installation of restrainers at expansion joints also shows the improvement in the seismic performance of restrained bridges for the severe damage state.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.01a
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• pp.9-12
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• 2017

본 논문에서는 어깨 초음파 영상을 분석하여 인대 손상(Tear) 영역을 추출하는 방법을 제안한다. 제안된 방법은 초음파 영상에서 ROI(Region of Interest) 영역을 추출하고 추출된 ROI 영역에서 사다리꼴 형태의 소속 함수를 적용한 퍼지 스트레칭 기법을 이용하여 명암 대비를 높인다. 명암 대비가 조정된 ROI 영역에서 밝기 평균 이진화 기법을 적용하여 ROI 영역을 이진화한다. 이진화가 적용된 ROI 영역에서 워터쉐드 기법을 적용하여 연골과 힘줄의 후보 영역들을 추출한다. 추출된 연골과 힘줄의 후보 영역들 중에서 위에서 아래로 스캔하여 수평 너비가 가장 큰 영역에 해당하는 힘줄 영역의 상단 경계선을 추출한다. 그리고 아래에서 위로 스캔하여 수평 너비가 가장 큰 영역의 상단 경계에 스플라인 곡선을 적용하여 연골 영역의 상단 경계선을 추출한다. 힘줄 영역의 상단 경계선과 연골 영역의 상단 경계선 양 끝에 2차 함수 곡선을 적용하여 곡선 사이의 양자화할 영역을 추출한 후, SOM 기법을 적용하여 인대 손상 후보 영역을 양자화한다. 양자화된 인대 손상 후보 영역을 분석하여 어깨 힘줄의 손상 영역과 비손상 영역을 구분하고 인대 손상(Tear) 영역을 추출한다. 제안된 방법을 어깨 힘줄이 있는 초음파 영상을 대상으로 실험한 결과, 인대 손상(Tear) 영역이 비교적 정확히 추출되었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.175-182
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• 2008

In performing a risk analysis of structure for earthquake, it is imperative to identify the vulnerability of structures associated with various stages of damage. And the earthquake resisting capability is needed for structures like bridge. So the damage analysis of bridges with or without isolator for earthquake effects is necessary. In this paper, the risk analysis of seismic isolated LRB bridges considering earthquake effects such as PGA, PGV, SA, SV, and SI is performed using fragility curves to assure the earthquake resisting capability of the structures. And, the stability of fragility curve is investigated with respect to elastic modulus.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.239-246
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• 2004

The fixed ends beam is analyzed by the s d 0 f system with the rigid-plastic model. And the safety criteria of the fixed ends beam to the Impulsive loads are established with the peak-load ratio to the static collapse load and impulse ratio to the ideal impulse producing the critical displacement. It is shown that the impulse and the peak-load of the impulsive loads are the important factors for the damage of the structures. It is also shown that the damage curves with the peak-load and impulse ratio are useful method to estimate the damage of the structures due to the emphasis on the equivalent dynamic loads rather than the equivalent static loads in the process of deriving the curve.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.157-164
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• 2004

The safety criteria for the simple beam with a rigid-plastic model under the impulsive loadings are established with the peak-load ratio to the static collapse load and impulse ratio to the ideal impulse producing the plastic hinge at the mid-span. It is shown that the impulse and peak-load of the impulsive loadings are the important factors for the damage of the structures. It is also shown that the damage curves with the peak-load and impulse ratio may be useful method to estimate the damage of the structures due to the emphasis on the equivalent dynamic loads rather than the equivalent static loads in the process of deriving the curve.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.425-433
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• 2001

A correlation between fatigue damage and acousto-ultrasonic (AU) parameters has been obtained from signals acquired during fatigue loading of the single-lap joints of a carbon-fiber reinforced plastic (CFRP) laminates and A16061 plate. The correlation showed an analogy to those representing the stiffness reduction $(E/E_0)$ of polymer matrix composites by the accumulation of fatigue damage. This has been attributed to the transmission characteristics of acoustic wave energy through bonded joints with delamination-type defects and their influence on the change of spectral content of AU signals. Another correlation between fatigue cycles and the spectral magnitude of acoustic emission (AE) signals has also been found during the final stage of fatigue loading. Both AU and AE can be applied almost in real-time to monitor the evolution of damage during fatigue loading.