• Magazine of the Korea Concrete Institute
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• v.10 no.2
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• pp.137-146
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• 1998

본 연구에서는 콘크리트 속에서 인장과 전단을 받는 FRP 다우얼의 거동과 파괴를 예측할 수 잇는 수리적인 파괴 해석 모델을 개발하였다. 다우얼 파괴해석 모델은 다우얼 작용과 파괴기준에 대한 두 개의 하위 모델로 구성되어 있는데 이들을 수정, 결합하여 만들어졌다. 다우얼 작용에 대한 모델로는 BEF 모델을 기초로 하여 두가지의 지수를 새로이 정의, 사용하였는데 하나는 콘크리트지지 강성을 변화시키기 위한 변위 정도 지수이고 다른 하나는 긴장된 케이블의 반력을 고려하기 위한 인장 지수이다. 인장과 전단이 작용하는 FRP다우얼의파괴 모델로는 Tsai-Hill 파괴기준이 사용되었고 이 기준을 적용하기 위하여 파괴 계수를 정의하였다. 개발된 파괴 해석 모델은 긴장된 FRP다우얼의 극한 전단력과 극한 변위를 예측하는데 사용하였고, 해석결과는 여러 인장응력을 가진 FRP 다우얼의 시험결과와 비교하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.2 s.48
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• pp.1-10
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• 2006

Reinforced concrete bridge columns with relatively small aspect ratio show flexure-shear behavior, which is flexural behavior at initial and medium displacement stages and shear failure at final stage. Since the columns with flexure-shear failure have lower ductility than those with flexural failure, shear capacity curve models shall be applied as well as flexural capacity curve in order to determine ultimate displacement for seismic design or performance evaluation. In this paper, a modified shear capacity curve model is proposed and compared with the other models such as the CALTRANS model, Aschheim et al.'s model, and Priestley et al.'s model. Four shear capacity curve models are applied to the 4 full scale circular bridge column test results and the accuracy of each model is discussed. It may not be fully adequate to drive a final decision from the application to the limited number of test results, however the proposed model provides the better prediction of failure mode and ultimate displacement than the other models for the selected column test results.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.1-8
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• 2006

Nonseismic designed RC frame have a possibility of shear failure because of deficiencies of reinforcing details. To model the shear failure in numerical analysis, shear strength degradation models which Include Moehle's and ATC 40 are compared and applied to push-over analysis. For numerical analysis, three storied building frame is selected and designed according to Korean Concrete Design Code(2003). As results, It is shown that Moehle's shear strength degradation model estimates the shear strength lower than NZSEE model and has less variation than ATC 40 model and all the shear strengths of models are greater than the nominal shear strength of ACI 318. Also, from the numerical analysis, it is pointed out that there may be great difference in lateral drift capacity if a different shear strength model is used. And the capacity can be severely underestimated if the restraining model of plastic rotation of ATC 40 is used, compared to the use of shear spring model for shear degradation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.109-116
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• 2010

Three-dimensional finite element model for analysis of reinforced concrete members was developed in order to investigate the prediction of bending and shear failure of reinforced concrete beams. A failure surface of concrete in strain space was newly proposed in order to predict accurately the ductile response of concrete under multi-axial confining stresses. Cracking of concrete in triaxial state was incorporated with considering the tensile strain-softening behavior of cracked concrete as well as the cracked shear behavior on cracked surface of concrete caused by aggregate interlocking and, dowel action. By correlation study on failure types of bending and shear of beams, current finite element model was well simulated not only the type of ductile bending failure of under-reinforced beams but also the type of brittle shear failure of no-stirruped reinforced concrete beam.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.3
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• pp.35-44
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• 2000

전편의 실험적 연구에 이어서, 기 수행된 4개의 외부 접합부 시험체에 현존하는 여러 강도 예측식을 사용하여 콘크리트 기둥-강재 보 접합부의 내진 성능을 결정하는 패널 전단 및 지압 강도를 평가하였다. 또한, 접합부 패널지역의 변형특성을 묘사할 수 있는 일련의 스프링을 사용한 macro 형태의 해석모델이 논의되었으며, 이에 따라 Drain-2DX 및 IDARC 등의 상용프로그램을 사용하여 접합부의 패널전단 및 지압 파괴형태의 변형을 포함하는 단순해석이 수행되었다. 강도 예측결과에 의하면 본 연구에서 제시하는 수정된 내부 콘크리트 패널 전단 강도식을 포함하고 있는 ASCE 방법이 실험결과에 가장 근접한 것으로 나타났으며, 본 연구에서 검토된 패널지역 변형을 고려한 단순해석모델은 향후 전체 건물해석에 사용할수 있는 것으로 판단되었다.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.523-530
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• 2008

In structural design provision, maximum punching shear stress of slabs is prescribed as combined stress in direct shear occurred by gravity load and eccentric shear occurred by unbalanced moment. This means that the effect of unbalanced moment is considered to decide the punching shear stress. However, from the resistance capacity standpoint, the effect of unbalanced moment strength is not considered for deciding punching shear strength. In this paper, a model considering interrelation between unbalanced moment and punching shear was proposed. In the model, the relation between load effect and resistance capacity in unbalanced moment and punching shear was two-dimensionally expressed. Using the interrelation model, a method how unbalanced moment strength should be considered to decide the punching shear strength was proposed. Additionally, effective width enlargement factors for deciding the unbalanced moment strength of flat plates with shear reinforcements were proposed. The interrelation model proposed in this paper is very effective for the prediction of the behavior of slab-column connection because not only punching shear and unbalanced moment strengths but also failure modes of flat plates can be accurately predicted.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.6
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• pp.393-401
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• 2021

In this paper, we proposed a numerical model based on moment-curvature, to evaluate the resistance of reinforced concrete (RC) members subjected to blast loading. To consider the direct shear failure mode, we introduced a dimensionless spring element based on the empirical direct shear stress-slip relation. Based on the dynamic increase factor equations for materials, new dynamic increase factor equations were constructed in terms of the curvature rate for the section which could be directly applied to the moment-curvature relation. Additionally, equivalent bending stiffness was introduced in the plastic hinge region to consider the effect of bond-slip. To verify the validity of the proposed model, a comparative study was conducted against the experimental results, and the superiority of this numerical model was confirmed through comparison with the analytical results of the single-degree of freedom model. Pressure-impulse (P-I) diagrams were produced to evaluate the resistance of members against bending failure and direct shear failure, and additional parametric studies were conducted.

• Computational Structural Engineering
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• v.6 no.1
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• pp.44-49
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• 1993

이 글에서는 거시적 모델을 사용하여 전단벽체를 수치모델하는 방법에는 여러가지의 방법이 있으며 각기 그 모델들에는 장점과 단점을 지니고 있음을 보았다. 거시적 모델로 구조물을 해석하는 경우에는 전단벽체의 모델과 그에 맞는 반복이력모델의 선정에 주의하여야 한다. 이는 전단벽체의 파괴양상과 비선형거동 등의 복잡한 거동을 한개의 모델을 가지고 일률적으로 적용하지 못한다는 거시적 모델의 한계점 때문이다. 그러나 아직까지 계산기의 발전과 미시적 모델의 한계점을 고려한다면 구조물 비선형해석시 최선의 선택은 미시적 방법보다는 거시적 방법이라하겠다. 거시적 모델을 사용하여 구조물의 3차원 해석 프로그램을 개발한 예를 보았듯이, 3차원 비선형거동까지 고려한다면 거시적방법이 적당하리라고 판단된다.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.75-84
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• 2009

An analytical model for predicting the shear strength of prestressed concrete beams without shear reinforcement was developed, on the basis of the existing strain-based shear strength model. It was assumed that the compression zone of intact concrete in the cross-section primarily resisted the shear forces rather than the tension zone. The shear capacity of concrete was defined based on the material failure criteria of concrete. The shear capacity of the compression zone was evaluated along the inclined failure surface, considering the interaction with the compressive normal stress. Since the distribution of the normal stress varies with the flexural deformation of the beam, the shear capacity was defined as a function of the flexural deformation. The shear strength of a beam was determined at the intersection of the shear capacity curve and the shear demand curve. The result of the comparisons to existing test results showed that the proposed model accurately predicted the shear strength of the test specimens.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.519-526
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• 2000

강수량 변동에 따른 사면 내의 지하수유동과 사면의 안정성 변화를 동시에 분석.평가하기 위하여 하나의 완전 연동된 수리지질역학적 모델을 제시하였다. 이 모델은 변형성 지질매체 내에서의 지하수유동을 설명하는 일련의 지배식들과 Galerkin 유한요소법에 기초하여 개발되었다. 1990년부터 1999년까지의 서울지역의 건기 (1월) 및 우기 (8월) 강수량 하에 있는 토양 사면에 대해 개발된 모델을 적용하여 일련의 수치실험을 실시하였다. 수치실험의 결과는 강수량이 증가함에 따라 사면의 수리역학적 안정성이 전반적으로 악화됨을 보여준다. 즉 강수량이 증가할수록 공극수압이 증가하고 지하수면이 상승한다. 그 결과 불포화대가 축소되고 삼출면이 팽창되며 사면의 전단부를 따라 지하수유동속도가 증가하게 된다. 동시에 강수량이 증가할수록 사면 전단부를 향해 전반적인 변위량이 증가한다. 그 결과 안전율이 1 이하인 불안전한 지역이 사면 전단부에서 사면 상부 쪽으로 전파.팽창되며 그 두께도 증가한다. 수치실험의 결과는 또한 사면의 표면에서는 전단파괴와 더불어 인장파괴도 발생할 수 있음을 보여준다.