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I형 휨 부재에서 균열 크기에 따른 변형률 측정 민감도 분석
박휘립(Park Philip),허용학(Huh Yong-Hak),김동진(Kim Dong-Jin),전대형(Jeon Dea-Hyoung),손병직(Son Byung Jik) 한국구조물진단유지관리학회 2004 한국구조물진단학회 학술발표회논문집 Vol.- No.-
Stram variations with various sizes of a crack in I-sectioned flexural member were investigated by finite element analysis and fatigue experiment As a parameter to estimate the crack in I-beam, a stram compliance were defined. In the section containing the crack, the strains at the positions of back face of the crack, compressive flange side, and tensile flange side were acquired during the fatigue experiment
I형 휨 부재에서 균열 크기에 따른 변형률 측정 민감도 분석
박휘립 ( Park Philip ),허용학 ( Huh Yong-hak ),김동진 ( Kim Dong-jin ),전대형 ( Jeon Dea-hyoung ),손병직 ( Son Byung Jik ) 한국구조물진단유지관리공학회 2004 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.8 No.2
Strain variations with various sizes of a crack in I-sectioned flexural member were investigated by finite element analysis and fatigue experiment. As a parameter to estimate the crack in I-beam, a strain compliance were defined. In the section containing the crack, the strains at the positions of back face of the crack, compressive flange side, and tensile flange side were acquired during the fatigue experiment. Measured back face strain(BFS) compliances and the strain compliances at compressive flange side(CFS) showed stable increment with crack growth and well agreed with finite element analysis result. From these results, a relationships between the crack size and BFS/CFS compliances were acquired by regression analysis. Sensitivity of the strain variation along longitudinal direction of the beam were also investigated and a relationship between the sensitivity and the distance from the cracked section were acquired. Those results show a possibility to estimate cracks in structural beams by monitoring the strain compliance and can be applied to structural health monitoring system.
유한요소 해석을 통한 Asphalt Plug Joint의 분석 방법에 대한 연구
문경태(Moon Kyoung-tae),박휘립(Park Philip),박상렬(Park Sang-yeol) 대한토목학회 2011 대한토목학회논문집 D Vol.31 No.2D
Asphalt Plug Joint(API)는 미국을 비롯한 유럽의 여러 국가에서 적용사례가 늘어가고 있는 새로운 형태의 신축이음장치이다. APJ는 시공 및 유지보수 비용이 저렴하고 시공이 간단하며, 우수한 평탄성을 확보한다는 장점을 가지고 있으나 조기 파손되는 문제점이 드러나 사용성을 방해하고 있다. 이러한 문제를 해결하기 위한 연구가 진행되어 왔고, 기존 연구 중 FEM 해석을 수행하였으나 FEM 해석시 재료를 너무 단순화하여 해석함으로써 해석의 신뢰성이 많이 떨어져 신축이음장치의 거동을 분석하는데 미흡하였다. 따라서 본 논문에서는 이러한 FEM 해석의 신뢰성을 높이기 위해 새로운 재료모델을 제안하고 실제 거동과 비교하여 유효성을 확인하였다. 본 연구에서 FEM 해석은 ABAQUS 전산 프로그램를 사용하였으며 재료모델은 Bramel et al.이 APJ 재료 시험한 결과를 근거로 탄소성모델과 점탄성모델을 제안하였다. 탄소성모델은 시간에 따른 변형속도를 반영하지 못하므로 시간독립해석으로 정의하였으며, 점소성 모델은 변형속도를 반영하므로 시간의존해석으로 정의하였다. 해석을 통해 APJ의 거동에 영향을 미치는 다양한 요소의 영향을 검토하였으며, 시간의존해석이 실제 실험결과와 비슷한 거동을 나타냄을 확인하였다. Asphalt Plug Joint(APJ) is a new type of expansion joint that it's application are increased in USA as well as several European countries. APJ's' advantages are cheap construction and maintenance costs, and simple construction and securing of excellent flatness. However, APJ's usability is hindered because it showed a problem of premature failure. Research for solving this problem has been progressed, and FEM analysis among existing researches was peformed. However, the behavior of APJ was insufficiently analyzed and the reliability of the analysis was much low, since the material showing complicated behavior was oversimplified, Therefore, a material model was proposed and its effectiveness was confirmed by comparing it with actual behavior in order to improve the reliability of FEM analysis in this paper. ABAQUS program was used for FEM analysis, and an elasto-plastic model and a viscous-plastic model as the material model of APJ were suggested on the base of experiment results of APJ material performed by Bramel et al. The elasto-plastic model was defined by time-independent analysis since it didn't consider time and strain rate, and the viscous-plastic model was defined by time-dependent analysis since it considered. Influence of various elements affecting the behavior of APJ was investigated, and it was confirmed that the time-dependent analysis showed better result closed to actual behavior than the time-independent analysis.
권일범 ( Kwon Il-bum ),박휘립 ( Park Philip ),허용학 ( Huh Yong-hak ),김동진 ( Kim Dong-jin ),이동춘 ( Lee Dong-chun ),홍성혁 ( Hong Sung-hyuk ),문한규 ( Moon Hahngue ) 한국구조물진단유지관리공학회 1999 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.3 No.1
Fiber optic sensors can be embedded in the structures to get the health information in the structures. The fiber sensor was constructed with 3x3 fiber couplers to sense the multi-point strains and failure instants. The 2 RC(reinforced concrete) beams were made to one of A type, one of B type beams. These beams were reinforced by the steel bars, and were experimented under the flexural loading. The behavior of the beams was simultaneously measured by the fiber optic sensors, electrical strain gages, and LVDT. The states of the beams were interpreted by these all signals. By these experiments, There were verified that the fiber optic sensors could measure the structural strains and failure instants of the RC beams. The fiber sensors were well operated until the failure of the beams. It was shown that the strains of the reinforcing steel bar can be used to monitor the health of the beams through the flexural test of RC beams. On the other words, the results were arrived that the two strains in the reinforcing bar measured at the same point can give the information of the structural health status. Also, the failure instants of beams were well detected from the fiber optic filtered signals.
피로균열 열림 및 닫힘에 따른 음향방출 신호 발생 특성 고찰
정중채(Jung-Chae Jeong),윤동진(Dong-Jin Yoon),박휘립(Philip Park),김기복(Ki-Bok Kim),이승석(Seung-Seok Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3
The objective of this study was to investigate the effect of crack opening and closure in the AE activities during fatigue test. Laboratory experiment using various materials and test conditions were carried out to identify AE characteristics of fatigue crack propagation. Compact tension specimens of SWS 4908 and Al 7075-T6 aluminum alloy were prepared for fatigue test. AE activities were analyzed based on the phase of the loading cycle. Generally, most of AE were generated at the time of early stage of crack opening and closure, whereas a few in the peak loading of cycle. Also the time of high occurrence of AE event was different with each specimen. However, in the same material, the trend of AE activity was not affected by the change of cyclic frequency (0.1, 0.2, 1 ㎐). It was found that AE activities during crack opening and closure depend on material properties such as micro-structure, yield strength and elongation.