• Earthquakes and Structures
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• 제11권4호
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• pp.649-664
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• 2016

A seismic damaged bridge may be hit again by a strong aftershock or another earthquake in a short interval before the repair work has been done. However, discussions about the impact of the unrepaired damages on the residual earthquake resistance of a steel bridge are very scarce at present. In this paper, nonlinear time-history analysis of a steel arch bridge was performed using multi-scale hybrid model. Two strong historical records of main shock-aftershock sequences were taken as the input ground motions during the dynamic analysis. The strain response, local deformation and the accumulation of plasticity of the bridge with and without unrepaired seismic damage were compared. Moreover, the effect of earthquake sequence on crack initiation caused by low-cycle fatigue of the steel bridge was investigated. The results show that seismic damage has little impact on the overall structural displacement response during the aftershock. The residual local deformation, strain response and the cumulative equivalent plastic strain are affected to some extent by the unrepaired damage. Low-cycle fatigue of the steel arch bridge is not induced by the earthquake sequences. Damage indexes of low-cycle fatigue predicted based on different theories are not exactly the same.

• Advances in concrete construction
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• 제8권2호
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• pp.77-90
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• 2019

This paper aims to investigate vibration frequency decrease (vibration period elongation) of reinforced concrete (RC) structure with unreinforced infill wall and reinforced infill wall exposed to progressively increased artificial earthquake load on shaking table. For this purpose, two shaking table experiments were selected as a case study. Shaking table experiments were carried on 1:1 scaled prototype one bay one storey RC structure with infill walls. The purpose of this shaking table experiment sequence is to assess local behavior and progressive collapse mechanism. Frequency decrease and eigen-vector evolution are directly related to in-plane and out-of-plane bearing capacities of infill wall enclosure with reinforced concrete frame. Firstly, frequency decrease-damage relationship was evaluated on the base of experiment results. Then, frequency decrease and stiffness degradation were evaluated with applied Peak Ground Acceleration (PGA) by considering strength deterioration. Lastly, eigenvector evolution-local damage and eigenvector evolution-frequency decrease relationship was investigated. Five modes were considered while evaluating damage and frequency decrease of the tested specimens. The relationship between frequency decrease, stiffness degradation and damage level were presented while comparing with Unreinforced Brick Infill (URB) and Reinforced Infill wall with Bed Joint Reinforcement (BJR) on the base of natural vibration frequency.

• 비파괴검사학회지
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• 제23권6호
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• pp.559-565
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• 2003

A spectral element model-based structural damage identification method (SDIM) was derived in the previous study by using the damage-induced changes in frequency response functions. However the previous SDIM often provides poor damage identification results because the nonlinear effect of damage magnitude was not taken into account. Thus, this paper improves the previous SDIM by taking into account the nonlinear effect of damage magnitude. Accordingly an iterative solution method is used in this study to solve the nonlinear matrix equation for local damages distribution. The present SDIM is evaluated through the numerically simulated damage identification tests.

• 한국재난정보학회 논문집
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• 제16권2호
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• pp.223-236
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• 2020

연구목적: 본 연구에서는 재난관리(예방-대비-대응-복구) 중 대비차원으로 활용하고자 강풍피해예측함수를 개발하였다. 연구방법: 본 연구에서 제안하는 강풍피해예측함수는 재해연보이력, 피해당시 기상자료 그리고 지역특성을 고려하였다. 기상자료는 기상청에서 관측한 풍속과 기온, 피해이력에 해당하는 통계자료는 재해연보, 그리고 지역특성을 반영하기 위한 요소로는 재해연보 상 수록된 복구비, 인구, 비닐하우스 면적, 농가수 등을 활용하였다. 연구결과: 본 연구에서 개발한 함수식은 과거에 발생한 강풍피해이력을 기반으로 예측되는 기상인자와 지역특성을 반영하였으며, 단시간에 피해규모를 예측할 수 있다. 결론: 본 연구에서 개발한 강풍피해예측함수는 정책결정자들의 의사결정, 비상인력 및 방재자원의 배치 등과 같은 효율적인 재난관리에 활용할 수 있을 것으로 판단된다.

• 한국구조물진단유지관리공학회 논문집
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• 제13권2호통권54호
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• pp.115-121
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• 2009

본 연구에서는 동적 가속도 데이터를 사용하는 신호기반 손상진단 알고리즘으로 ARX 모델을 제시하였다. ARX 모델은 구조물의 두 지점에서 계측된 가속도 데이터를 입력과 출력의 두 세트 신호로 보고, 두 세트 가속도 데이터의 상관관계를 설정한다. 구조물 손상은 계측한 데이터와 전달함수인 ARX 모델로 예측한 데이터의 차이인 시간이력 잔차를 사용하여 통계적으로 탐색하였다. 시간이력 잔차의 정규분포함수를 구하고, 그 통계적 특성치를 계산하여 손상 평가에 사용하였다. 손상 전후의 정규분포함수를 비교하여 손상을 탐색하기 위하여 세 가지 손상지수를 제시하였다. 손상지수의 통계적 평가를 위해 실내실험을 수행하였고, 제안한 알고리즘의 효율성을 검증하고 제한점을 검토하였다.

• 대한공간정보학회지
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• 제22권4호
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• pp.71-80
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• 2014

본 연구에서는 강원도를 대상으로 산사태로 인한 피해지역을 사전에 예측하였으며, 도로, 건물, 산림 등의 피해규모를 지자체별로 산정하였다. 산사태를 예측하기 위해서 기존의 연구 성과를 활용하여 산사태 취약성도, 발생가능성도, 위험지도 제작기법을 정립하였다. 도로, 건물, 산림의 산사태 피해규모는 누적강우량 100mm, 200mm, 300mm 발생시 각각의 산사태 위험지도를 제작하여 지자체별로 산정하였다. 그 결과 100mm~200mm 미만 누적강우량 발생시 도로피해는 홍천군, 건물피해는 정선군, 산림피해는 홍천군 순으로 나타났으며, 200mm~300mm 미만 누적강우량 발생시 도로피해는 춘천시, 건물피해는 평창군, 산림피해는 홍천군 순으로 나타났다. 특히, 300mm 이상 누적강우량 발생시 홍천군의 경우 도로, 건물, 산림피해가 다른 지자체에 비해서 가장 피해가 클 것으로 예측되었다. 이와 같이 지자체의 산사태 피해규모를 각각 산정함으로써 산사태 예방의 우선순위 결정뿐만 아니라 예산을 투입하는데 있어 의사결정의 기초자료가 될 수 있을 것으로 기대된다.

• Composites Research
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• 제15권5호
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• pp.7-13
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• 2002

압전필름센서는 복합재 구조물의 저속충격응답을 관측하기에 우수한 특성을 지니고 있다. 본 연구에서는 Gr/Ep 복합재 적층판이 손상이 발생할 수 있을 정도의 충격에너지를 받았을 때 압전필름센서 신호를 이용하여 충격거동을 모니터링할 수 있는 가능성에 대하여 고찰하였다. 손상이 발생하지 않는 저에너지 충격조건부터 국부적인 손상을 유발할 수 있는 충격조건까지 압전필름센서가 부착된 Gr/Ep 복합재 적층판에 대하여 16가지의 저속충격시험을 수행하였다. 세 가지 조거의 충격시험에서 기지균열 및 층간분리 등의 국부적인 손상이 발생하였으나, 충격력과, 변위, 변형률, 압전센서 신호와의 관계를 이용한 선형해석 모델을 사용하여 충격하중에 의한 복합재 적층판의 응답을 예측하는 정방향 문제와 압전센서 신호로부터 충격력을 복원하는 역방향 문제에서 시험과 해석 결과는 비교적 잘 일치하는 경향을 보였다. 복원된 충격력으로부터 국부적인 손상이 발생할 정도의 충격까지는 압전필름센서 신호를 이용하여 충격력을 정확히 복원할 수 있음을 확인하였다.

• 대한기계학회논문집A
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• 제30권4호
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• pp.393-401
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• 2006

The influences of stress triaxiality on ductile fracture have been investigated for various specimens and structures. With respect to a transferability issue, recently, the interests on local approaches reflecting micromechanical specifics are increased again due to rapid progress of computational environments. In this paper, the applicability of the local approaches has been examined through a series of finite element analyses incorporating modified GTN and Rousselier models as well as fracture toughness tests. The ductile crack growth of nuclear carbon steels is assessed to verify the transferability among compact tension (CT) specimens with different in-plane size. At first, the basic material constants were calibrated for standard CT specimens and used to predict fracture resistance (J-R) curves of larger CT specimens. Then, the in-plane size effects were examined by comparing the numerically estimated J-R curves with the experimentally determined ones. The assessment results showed that the in-plane size effect should be considered for realistic engineering application and the damage models might be used as useful tool for ductile fracture evaluation.

• 한국정밀공학회지
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• 제23권4호
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• pp.116-123
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• 2006

During the last two decades, many researchers investigated influences of stress triaxiality on ductile fracture for various specimens and structures. With respect to a transferability issue, the local approach reflecting micro-mechanical specifics is one of effective methods to predict constraint effects. In this paper, the applicability of the local approach was examined through a series of finite element analyses incorporating modified GTN (Gurson-Tvergaard-Needleman) and Rousselier models as well as fracture toughness tests. To achieve this goal, fracture resistance (J-R) curves of several types of compact tension (CT) specimens with various crack length, with various thickness and with/without 20% side- grooves were estimated. Then. the constraint effects were examined by comparing the numerically estimated J-R curves with experimentally determined ones. The assessment results showed that the damage models might be used as useful tool for fracture toughness estimation and both the crack length and thickness effects should be considered for realistic structural integrity evaluation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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• pp.125-126
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• 2019

This study aims to recognize damage indicators of typhoon and to develop damage function's indicators, using information derived from the actual loss of typhoon Maemi. As typhoons engender significant financial damage all over the world, governments and insurance companies, local or global, develop hurricane risk assessment models and use it in quantifying, avoiding, mitigating, or transferring the risks. For the reason, it is crucial to understand the importance of the risk assessment model for typhoons, and the importance of reflecting local vulnerabilities for more advanced evaluation. Although much previous research on the economic losses associated with natural disasters has identified the risk indicators that are indispensable, more comprehensive research addressing the relationship between vulnerability and economic loss are still called for. Hence this study utilizes and analyzes the actual loss record of the typhoon Maemi provided by insurance companies to fill such gaps. In this study, natural disaster indicators and basic building information indicators are used in order to generate the vulnerability functions; and the results and indicators suggest a practical approach to create the vulnerability functions for insurance companies and administrative tasks, while reflecting the financial loss and local vulnerability of the actual buildings.