• 콘크리트학회논문집
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• 제12권5호
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• pp.81-92
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• 2000

A fixed angle softened truss model has been developed in order to predict both shear strength and deformation of reinforced concrete members. The model takes into account the contribution of concrete by accuming the angle of cracks in the postcracking concrete that coincides with the reinforced concrete principal compressive angle determined by the applied stresses. Therefore, this model is capable of predicting the contribution of concrete from the govering equilibrium and compatibility equations including the shear stress and strain developed along concrete diagonal crack. However, the model has a limiting range to be applicable for reinforced concrete members. This research proposes a new algorthm of fixed angle softened truss model capable of removing the limitation of applicability. The proposed algorithm adopts a new conception of constitutive laws. The average normal stresses of concrete in the x- y- directions can be calculated by transforming the principal stresses of concrete. The proposed algorthm is verified by comparing to the test results.

• 콘크리트학회논문집
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• 제13권2호
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• pp.130-138
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• 2001

본 논문은 변환각 트러스 모델(TATM)에 의한 철근콘크리트 보의 전단거동 예측에 관한 연구이다. TATM은 주응력면에 대한 응력과 변형률을 균열면에서의 응력과 변형률로 변환시킴으로써 콘크리트 균열면에 대한 응력-변형률 관계를 구한다. 제안된 해석 방법은 고정각 연화트러스 모델(FA-STM)을 간략화시켰으며 그 적용 한계 또한 제거하였다. 변환각 트러스 모델을 이용하여 철근콘크리트 보의 전단강도와 전단변형률을 예측하였다. 제안된 해석 방법의 검증을 위하여, TATM에 의한 해석결과는 총 40개 철근콘크리트 보의 전단 실험결과에 대하여 FA-STM과 RA-STM의 해석결과와 비교되었다. TATM에 의한 해석결과는 실험결과에 대하여 모멘트 효과를 고려하지 않은 상태에서 평균 0.80, 표준편차 0.105, 변동계수 0.132로 비교적 만족스러운 결과를 보였다.

• Structural Engineering and Mechanics
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• 제5권5호
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• pp.599-608
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• 1997

The concrete stiffness matrices of membrane elements used in the finite element analysis of wall-type structures are reviewed and discussed. The behavior of cracked reinforced concrete membrane elements is first described by summarizing the constitutive laws of concrete and steel established for the two softened truss models (the rotating-angle softened-truss model and the fixed-angle softened-truss model). These constitutive laws are then related to the concrete stiffness matrices of the two existing cracking models (the rotating-crack model and the fixed-crack model). In view of the weakness in the existing models, a general model of the matrix is proposed. This general matrix includes two Poisson ratios which are not clearly understood at present. It is proposed that all five material properties in the general matrix should be established by new biaxial tests of panels using proportional loading and strain-control procedures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.595-600
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• 2000

The shear strength and strain of reinforced concrete beams are predicted by using the Transformated-Angle Truss-Model. This proposed analytical method simplified the fixed-angle softened-truss model (FA-STM) and removed the limitation of applicability of the FA-STM. The results of the proposed method for reinforced concrete beams were compared to those of the FA-STM.

• Computers and Concrete
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• 제13권1호
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• pp.49-70
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• 2014

Steel fiber-reinforced concrete (SFRC) is known as one of the efficient modern composites that can greatly enhance the material performance of cracked concrete in tension. Such improved tensile resistance mechanism at crack interfaces in SFRC members can be heavily influenced by methodologies of treatments of crack direction. While most existing studies have focused on developing the numerical analysis model with the rotating-angle theory, there are only few studies on finite element analysis models with the fixed-angle model approach. According to many existing experimental studies, the direction of principal stress rotated after the formation of initial fixed-cracks, but it was also observed that new cracks with completely different angles relative to the initial crack direction very rarely occurred. Therefore, this study introduced the direct tension force transfer model (DTFTM), in which tensile resistance of the fibers at the crack interface can be easily estimated, to the nonlinear finite element analysis algorithm with the fixed-angle theory, and the proposed model was also verified by comparing the analysis results to the SFRC shear panel test results. The secant modulus method adopted in this study for iterative calculations in nonlinear finite element analysis showed highly stable and fast convergence capability when it was applied to the fixed-angle theory. The deviation angle between the principal stress direction and the fixed-crack direction significantly increased as the tensile stresses in the steel fibers at crack interfaces increased, which implies that the deviation angle is very important in the estimation of the shear behavior of SFRC members.