• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.86-91
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• 2002

Glass/phenolic composite laminates have been used in the field of non-flammable light rail transit and their applications have expanded more widely. Low velocity impact tests have been used to evalute the effect of temperature and acceleration aging on low velocity impact response of phenolic matrix composites reinforced with woven E-glass fabric. The damage of matrix cracking and delamination are suddenly reduced the compressive strength after impact. The damage area increases with increasing temperature and impact energy. UT C-scan is used to determine damage areas by impact loading. Therefore, all this observations indicate reduced impact damage resistance and damage tolerance of the laminates at elevated temperature.

• 콘크리트학회논문집
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• 제18권1호
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• pp.37-46
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• 2006

재료구성관계의 범위에서의 강성 성능저하의 스펙트럼 특성을 기본 유한요소법을 이용하여 개별 유한요소와 그의 조합행렬에 대한 스펙트럼 분석을 상호 비교하여 수치적인 의미를 확인하고자 한다. 본 논문의 주 관심부분은 탄성 강성특성의 저하로 인한 콘크리트 재료의 손상정도를 다양한 스펙트럼 특성인 최소고유치의 변화, 유효계수의 변화 등의 시나리오를 가지고 해의 유일성 여부, 특이성의 표현 여부 그리고 변분유계와의 근접여부 등을 관찰하였다. 1차원 및 2차원 예제가 제시되었으며 강성이 서로 다른 혼입재를 가진 2상복합체의 형식으로 콘크리트의 골재, 매트릭스를 표현하고 상호연관성 및 기하학적 영향을 고려하였다. 더불어 2차원 탄성계면요소를 이용하여 골재와 매트릭스 사이에 존재하는 약한 고리인 계면을 묘사하고 이들 계면의 탄성계수의 성능저하로 인한 전체 구조계의 영향 등을 분석, 비교하였다.

• Structural Engineering and Mechanics
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• 제86권4호
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• pp.547-571
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• 2023

To deeply probe the actual earthquake level and fragility of typical reinforced concrete (RC) structures under multiple intensity grades, considering diachronic measurement building stock samples and actual observations of representative catastrophic earth shocks in China from 1990 to 2010, RC structures were divided into traditional RC structures (TRCs) and bottom reinforced concrete frame seismic wall masonry (BFM) structures, and the empirical damage characteristics and mechanisms were analysed. A great deal of statistics and induction were developed on the historical experience investigation data of 59 typical catastrophic earthquakes in 9 provinces of China. The database and fragility matrix prediction model were established with TRCs of 4,122.5284×104 m² and 5,844 buildings and BFMs of 5,872 buildings as empirical seismic damage samples. By employing the methods of structural damage probability and statistics, nonlinear prediction of seismic vulnerability, and numerical and applied functional analysis, the comparison matrix of actual fragility probability prediction of TRC and BFM in multiple intensity regions under the latest version of China's macrointensity standard was established. A novel nonlinear regression prediction model of seismic vulnerability was proposed, and prediction models considering the seismic damage ratio and transcendental probability parameters were constructed. The time-varying vulnerability comparative model of the sample database was developed according to the different periods of multiple earthquakes. The new calculation method of the average fragility prediction index (AFPI) matrix parameter model has been proposed to predict the seismic fragility of an areal RC structure.

• Smart Structures and Systems
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• 제17권6호
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• pp.1017-1030
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• 2016

This study focuses on the system identification of reinforced concrete bridges using vector autoregressive model (VAR). First, the time series output response from a bridge establishes the autoregressive (AR) models. AR models are one of the most accurate methods for stationary time series. Burg's algorithm estimates the autoregressive coefficients (ARCs) at p-lag by reducing the sum of the forward and the backward errors. The computed ARCs are assembled in the state system matrix and the eigen-system realization algorithm (ERA) computes: the eigenvector matrix that contains the vectors of the mode shapes, and the eigenvalue matrix that contains the associated natural frequencies. By taking advantage of the characteristic of the AR model with ERA (ARMERA), civil engineering can address problems related to damage detection. Operational modal analysis using ARMERA is applied to three experiments. One experiment is coupled with an artificial neural network algorithm and it can detect damage locations and extension. The neural network uses a specific number of ARCs as input and multiple submatrix scaling factors of the structural stiffness matrix as output to represent the damage.

• 한국인터넷방송통신학회논문지
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• 제18권5호
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• pp.209-214
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• 2018

본 논문에서는 대규모 재난이 발생할 경우 재난으로 인해 시설물에 가해지는 피해를 알아보고 그로 인해 발생 가능한 재난들을 매트릭스 형식으로 나타내었다. 대규모 재난으로 태풍을 선정하였으며 태풍으로 인해 발생 가능한 피해인 홍수피해를 주로 다뤘다. 홍수피해의 경우 주로 침수가 발생하게 되고 침수심과 유속에 따라 피해여부가 결정되게 되며 이를 저층시설물에 적용한 결과를 도출해 내었다. 또한 시설물 피해로 인한 재난 연계를 한눈에 알아보기 쉽도록 매트릭스 형식으로 재난 유형을 분류하는 방법을 적용시켜 결과를 도출시켰다. 본 논문에서 제시한 형식으로 지속적인 연구가 진행되었을 경우 재난 발생에 따른 추가적인 재난을 미리 알아보는데 도움이 될 것이다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.53-56
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• 2005

This paper investigates the effect of ductile deformation behavior of high performance hybrid fiber-reinforced cement composites (HPHFRCCs) on the shear behavior of coupling beams to lateral load reversals. The matrix ductility and the reinforcement layout were the main variables of the tests. Three short coupling beams with two different reinforcement arrangements and matrixes were tested. They were subjected to cyclic loading by a suitable experimental setup. All specimens were characterized by a shear span-depth ratio of 1.0. The reinforcement layouts consisted of a classical scheme and diagonal scheme without confining ties. The effects of matrix ductility on deflections, strains, crack widths, crack patterns, failure modes, and ultimate shear load of coupling beams have been examined. The combination of a ductile cementitious matrix and steel reinforcement is found to result in improved energy dissipation capacity, simplification of reinforcement details, and damage-tolerant inelastic deformation behavior. Test results showed that the HPFRCC coupling beams behaved better than normal reinforced concrete control beams. These results were produced by HPHFRCC's tensile deformation capacity, damage tolerance and tensile strength.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.42-45
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• 2003

Nondestructive damage sensing and mechanical properties for acid-treated carbon nanotube (CNT) and nanofiber (CNF)/epoxy composites were investigated using electro-micromechanical technique and acoustic emission (AE). Carbon black (CB) was used to compare to CNT and CNF. The results were compared to the untreated case. The fracture of carbon fiber was detected by nondestructive acoustic emission (AE) relating to electrical resistivity under double-matrix composites test. Sensing for fiber tension was performed by electro-pullout test under uniform cyclic strain. The sensitivity for fiber damage such as fiber fracture and fiber tension was the highest for CNT/epoxy composites. Reinforcing effect of CNT obtained from apparent modulus measurement was the highest in the same content. For surface treatment case, the damage sensitivity and reinforcing effect were higher than those of the untreated case. The results obtained from sensing fiber damage were correlated with the morphological observation of nano-scale structure using FE-SEM. The information on fiber damage and matrix deformation and reinforcing effect of carbon nanocomposites could be obtained from electrical resistivity measurement as a new concept of nondestructive evaluation.

• 한국생산제조학회지
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• 제8권2호
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• pp.80-85
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• 1999

The purpose of this work is to investigate fatigue damage of quasi-isotropic laminates under tensile loading in different directions. Low cycle fatigue tests of [0/-60/+60]a laminates and [+30/-30/90]s lamina tes were carried out. Material systems used are AS4/Epoxy and AS4/PEEK. The fatigue damage of [+30/-30/90]s is very different from that of [0/-60/+60]s. The position of delamination generated at AS4/Epoxy and AS$/PEEK laminates were differentiated by the matrix difference that is, we suppose, the value of both GIcr(critical energy release rate of mode-I) and GIIIcr(critical energy release rate of mode-III) difference.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.228-233
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• 2001

It is well known that composite laminates are easily damaged by low velocity impact. The damage of composite laminates subjected to impact loading are occurred matrix cracking, delamination, and fiber breakage. The damage of matrix cracking and delamination are reduced suddenly the compressive strength after impact. This study is to evaluate impact characteristics and the relationship between impact force and inside damage of composite laminates by low velocity impact loading. UT C-scan is used to determine impact damage areas by impact loading.

• 한국구조물진단유지관리공학회 논문집
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• 제8권4호
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• pp.247-256
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• 2004

하층충격에 의한 2층 전단건물의 손상곡선을 엄계변위를 발생시키는 하중최대치 비와 임펄스 비를 이용하여 작성하였다. 손상곡선 작성에 필요한 구조물의 거동파악은 하중과 임펄스 응답행렬의 합성곱을 이용하여 구하였으며, 합성곱에 필요한 임펄스응답행렬은 모드중첩법을 이용하여 구하였다. 작성된 손상곡선으로부터 하층충격에 의한 각층의 안전성은 상층은 하중의 최대치에 그리고 하층은 임펄스의 크기에 민감한 것으로 파악되었다.