http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
CFRP 긴장재로 비부착 프리스트레스트된 콘크리트보의 휨 거동
이차돈,정상모,박상렬,이규현,허서영 한국구조물진단유지관리학회 2006 한국구조물진단학회 학술발표회논문집 Vol.10 No.1
Prestressed concrete beams with CFRP tensile materials are subjected to a tendency of brittle failure under the loads. In order to overcome this undesirable structural behavior, CFRP tendons are unbonded and part of compressive zone in a beam section is confined with stirrups with smaller spacings. Characteristics of load-deflection relations, crack patterns and failure mechanisms are described based on experimental observations on prestressed concrete beams with unbonded CFRP tendons. It has been shown that better ductile flexural behavior of unbonded prestressed concrete beams can be obtained with less prestressing force, and with confinement of concrete in a compressive zone in a section.
링 형태 강섬유와 양단갈고리 선형 강섬유 보강 콘크리트 패널의 휨성능
이차돈,조원택 한국구조물진단유지관리공학회 2009 한국구조물진단유지관리공학회 논문집 Vol.13 No.1
링 형태의 강섬유 (Ring-type steel fibers: 이하 RSF)는 원형의 폐곡선 형태를 갖는 강섬유로서 선형강섬유와는 다른 저항 메카니즘을 가지며 폐곡선으로 둘러싸인 평면에 대하여 동일한 방향성을 가지는 특성을 갖는다. 이 연구에서는 섬유의 단위투입량 15kg/㎥과 30kg/㎥의 RSF 및 선형 강섬유를 혼입한 콘크리트 패널의 휨인성을 실험, 비교하였다. 파단면에서의 RSF의 저항 형태를 규명하였으며 RSF를 혼입한 패널이 선형 강섬유를 혼입한 패널에 비하여 우수한 인성값을 나타냄이 관찰되었다. RSF에 대한 방향성을 제시하였으며 RSF를 혼입한 실험체의 경우, 보 실험체에 비하여 두께가 상대적으로 얇은 패널 실험체에서 RSF가 더 효율적으로 인성 증가에 기여함이 관찰되었다. Ring-type steel fibers (RSFs) of the closed circular shape, have different resistance mechanisms other than straight steel fibers. RSFs also maintain the same value of the orientation factor for the plane enclosed by the fiber ring perimeter. In this research, comparative studies were performed for the panels reinforced with RSFs and with straight steel fibers of 15kg/㎥ and 30kg/㎥ , respectively. Resisting mechanisms of RSFs were identified and higher toughness indices were experimentally observed for the concrete panels reinforced with RSFs than with straight steel fibers. Orientation factor for the RSF was suggested. It was found that RSFs were more effective in increasing toughness for the panel specimens with relatively thinner thickness than beam specimens.
Balanced Ratio of Concrete Beams Internally Prestressed with Unbonded CFRP Tendons
이차돈,신상민,이송희 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.1
The compression or tension-controlled failure mode of concrete beams prestressed with unbonded FRP tendons is governed by the relative amount of prestressing tendon to the balanced one. Explicit assessment to determine the balanced reinforcement ratio of a beam with unbonded tendons (qU pfb) is difficult because it requires a priori knowledge of the deformed beam geometry in order to evaluate the unbonded tendon strain. In this study, a theoretical evaluation of qU pfb is presented based on a concept of three equivalent rectangular curvature blocks for simply supported concrete beams internally prestressed with unbonded carbon-fiber-reinforced polymer (CFRP) tendons. The equivalent curvature blocks were iteratively refined to closely simulate beam rotations at the supports, mid-span beam deflection, and member-dependent strain of the unbonded tendon at the ultimate state. The model was verified by comparing its predictions with the test results. Parametric studies were performed to examine the effects of various parameters on qU pfb.
비선형 유한요소법에 의한 부착 및 비부착된 프리스트레스트 콘크리트 보의 휨 모델
이차돈,김민경,이재찬 중앙대학교 건설환경연구소 2001 環境科學硏究 Vol.12 No.2
본 연구에서는 기존의 이론 모델을 고찰하고 이들 모델의 단점을 수정, 보완하여 부착 및 비부착된 프리스트레스트보의 하중-처짐 관계를 예측할 수 있는 비선형 휨모델을 유한요소법에 근거하여 개발하는데 목적이 있다. 주어진 외력과 단면 내력간의 불균형력(unbalanced force)를 감소시키기 위하여 반복계산 형태의 수치해석 방법을 사용하게 되는데, 본 연구에서는 Newton-Raphson Method를 도입하여, 보의 하중-처짐 곡선을 예측할 수 있는 진보된 수치해석 모델을 개발하였다. 또한 비부착 프리스트레스보의 긴장재의 응력은 콘크리트와 긴장재가 부착되어 있지 않기 때분에 부재 전체길이의 변형을 고려한 해석이 이루어져야 하므로, 비부착된 프리스트레스트보의 휨 거동은 부재전체의 휨변형과 관계가 되므로 A.E Naaman이 제시한 부착감소계수(Ω)의 개념을 적용하였다. 개발된 모델은 임의의 텐돈위치와 profile, 임의 위치의 하중에 대해 적용할 수 있도록 개발되으며, 비교적 실험결과과 잘 일치하였다. In this research, various types of theoretical models and solution techniques suggested for predicting flexural behavior of prestressed concrete beam are reviewed. An analytical method based on the nonlinear layered finite element method is then developed to simulate overall load-deflection behavior of bonded and unbonded prestressed concrete beams. Emphasis is given to eveluate the stressed in unbonded tendons Based on the i¥A M ðR¿ n" Ω) suggested by A.E. naaman. The developed model can take into account various types of tendon profiles and loads. The developed model is found to predict experimental results reasonably well.
이차돈,정상모,박상렬,이규현 한국구조물진단유지관리공학회 2007 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.11 No.1
Tensile strength of rectangular FRP stirrups in the bent portion is significantly reduced than in the straight ones, because of stress concentrations to the bent portion of the stirrups. An attempt is made in this research to strengthen the bent portion of CFRP stirrups by the use of CFRP sheet or strip in order to enhance the tensile strength of FRP stirrups. Twelve specimens were tested. Stirrups in concrete were partially unbonded to induce stress concentrations at the bent portion. Test results showed that depending on the strengthening methods, tensile strength of stirrups at bent portion increased by about 20% to 50% of the stirrups without strengthening in bent portion.
Stochastic Simulated Annealing에 의한 평면 트러스 최적 설계
이차돈 中央大學校 建設環境硏究所 1992 環境科學硏究 Vol.3 No.-
Two dimensional truss optimization problems are solved based on combinatorial optimization technique known as stochastic simulated annealing(SSA). SSA is a recent approach to the solution of problems characterized by large number of interacting degrees of freedom. It simulates the degrees of freedom in a problem in a such a way that they are a collection of atoms slowly being coolded down into a ground state which would correspond to the stationary point of the problem. In this paper, for a randomly disturbed current design, SSA establishes a probabilistic criterion for acceptance or rejection of current design and iteratively improves it to arrive at a stationary point at which critical temperature is reached. Using SSA, tested are simple truss optimization problems which consider combinations of yielding and buckling strengths of truss members, multiple loading conditions, and linking members in group as their constraints. Satisfactory results are obtained and some discussions are given for the behavior of SSA on the tested truss structures.
CFRP 긴장재로 비부착 프리스트레스트된 콘크리트보의 휨 거동
이차돈,정상모,박상렬,이규현,허서영 한국구조물진단유지관리공학회 2006 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.10 No.1
Prestressed concrete beams with CFRP tensile materials are subjected to a tendency of brittle failure under the loads. In order to overcome this undesirable structural behavior, CFRP tendons are unbonded and part of compressive zone in a beam section is confined with stirrups with smaller spacings. Characteristics of load-deflection relations, crack patterns and failure mechanisms are described based on experimental observations on prestressed concrete beams with unbonded CFRP tendons. It has been shown that better ductile flexural behavior of unbonded prestressed concrete beams can be obtained with less prestressing force, and with confinement of concrete in a compressive zone in a section.