• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.87-88
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• 2010

The strength and ductile capacity of reinforced concrete column can be improved by confinement using transverse reinforcement. Variety stress-strain models about the reinforced concrete confined by transverse reinforcement has been proposed. In this paper, parameters which effect to the ultimate confinement stress of circular cylinder confined by high strength transverse steel is examined. And the possion's ratio equation is proposed by analysis of strain between concrete and transverse reinforcement.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.578-588
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• 2002

An experimental study was conducted to investigate the effectiveness of transverse reinforcement in reinforced concrete tied columns subjected to monotonically increasing axial compression. Eighteen large-scale columns(260$\times$260$\times$1200 mm) were tested. Effects of main variables such as the concrete compressive strength, the tie configuration, the transverse reinforcement ratio, the tie spacing, and the spatting of the concrete cover were considered. High-strength concrete columns under concentric axial loads show extremely brittle behavior unless the columns are confined with transverse reinforcement that can provide sufficiently high lateral confinement pressure There is a consistent decrease in deformability of column specimen with increasing concrete strength. Test results were compared with the previous confinement model such as modified Kent-Park, Sheikh-Uzumeri, Mander, and Saatcioglu-Razvi model. The comparison indicates that many previous models for confined concrete overestimate or underestimate the ductility of confined concrete.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5C
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• pp.183-190
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• 2009

It is necessary to predict the deformation and stresses on soils to establish the nonlinear stress-strain relationship of geomaterials at various strain levels. Especially, a need exists to establish the pre-failure nonlinear characteristic of cemented granular geomaterials used in road constructions. In this paper, therefore, conventional granular soils were mixed with various cementing materials, such as cement and fly ash from coal combustion by-products. Then, the normalized nonlinear behavior of cemented geomaterials was assessed using unconfined compression test. In addition, various constitutive models of soils were evaluated for estimating pre-failure non-linear behavior of cemented geomaterials from the test results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.409-416
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• 2019

An improved numerical model for non-linear analysis of reinforced concrete (RC) slabs subjected to blast loading is proposed. This approach considers a strain rate dependent orthotropic constitutive model that directly determines the stress state using the stress-strain relation acquired from the data obtained using the biaxial strength envelope. Moreover, the bond-slip between concrete and reinforcing steel is gradually enlarged after the occurrence of cracks and is concentrated in the plastic hinge region. The bond-slip model is introduced to consider the crack direction of the concrete under a biaxial stress state. Correlation studies between the numerical analysis and the experimental results were performed to evaluate the analytical model. The results show that the proposed model can effectively be used in dynamic analyses of reinforced concrete slab members subjected to explosive loading. Moreover, it was determined that it is important to consider biaxial behavior in the material model and the bond-slip effect.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.704-707
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• 2010

구조 건전성 모니터링에 사용되는 기존 센서들의 문제점을 극복하고 높은 분해능과 동특성 모니터링에 대한 이점을 지닌 FBG센서는 구조물 모니터링에 있어 큰 이점을 지니고 있다. FBG 센서는 점 센서라는 한계 때문에 구조물의 전체적인 변형률 및 응력 평가에 어려움이 있을 수 있다. 본 연구에서는 FBG 센서로부터 계측한 변형률 값들로부터 임의의 하중조건에서 철골 보의 변형률 분포를 추정하는 기법을 제시하였다. 임의의 개별 하중조건에 대해 FBG 센서로 계측된 값을 통해 센서의 부착 위치와 최소 필요 개수를 결정하고 변형률 추정식을 유도함으로써 FBG 센서의 계측 기법에 대한 기준을 세웠다. 나아가 임의의 조합 하중이 작용하는 실제의 경우를 고려하여 철골 보의 변형률 분포를 추정하는 보다 일반화된 수학적 모델을 제시하였다. 그리고 예제를 통하여 본 연구에서 제시한 변형률 분포 추정 모델을 검증하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.3
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• pp.67-80
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• 2009

The basic concept of seismic design is to attain the ductility required in a design earthquake. This ductility can be obtained by providing sufficient lateral confinements to the plastic hinge regions of columns. The most cost-effective design might be derived by determining the proper amount of lateral confinement using a stress-strain relationship for confined concrete. Korean bridge design code requires the same amount of lateral confinement regardless of target ductility, but Japanese design code provides the stress-strain relationship of the confined concrete to determine the amount of lateral confinement accordingly. While design based on material characteristics tends to make the design process more involved, it makes it possible to achieve cost-effectiveness, which is also compatible with the concept of performance-based design. In this study, specimens with different numbers of lateral confinements have been tested to investigate the characteristics of the stress-strain relationship. Test results were evaluated, using several empirical equations to quantify the effects.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.101-110
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• 2015

Recently, nine $1397{\times}1397{\times}178mm$ RC panels were tested under in-plane pure-shear monotonic loading condition using the Panel Element Tester by Hsu (1997, ACI). By combining the equilibrium, compatibility, and the softened stress-strain relationship of concrete in biaxial state, Modern Truss Model (MCFT, RA-STM) are capable of producing the nonlinear analysis of RC membrane panel through the complicated trial-and-error method with double loop. In this paper, an efficient algorithm with one loop is proposed for the refined Mohr compatibility Method based on the strut-tie failure criteria. This algorithm can be speedy calculated to analyze the shear history of RC membrane element using the results of Hsu test. The results indicate that the response of shear deformation energy at Big Bang of shear strain significantly influenced by the principal compressive stress-strain (crushing failure).

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.685-692
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• 2007

When the shear force governs the response of an RC element, as in the case of a low-rise shear wall, the effect of shear on the element's response is thought to be responsible for the 'pinching effect' in the hysteretic loops. However, it was recently shown that this undesirable pinching effect can be eliminated in the hysteretic load-deformation curves of a shear-dominant element if the steel grid orientation is properly aligned in the direction of the applied principal stresses. In this paper, the presence and absence of the pinching mechanism in the hysteretic loops of the shear stress-strain curves of RC elements was explained rationally using a compatibility aided truss model. The analytical results indicate that the pinching effect of the RC elements is strongly related to the direction of the steel arrangement. The area of the energy dissertation does not increase proportionally to the difference between the direction of the principal compressive stress and the direction of the steel arrangement.

• Geotechnical Engineering
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• v.12 no.2
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• pp.9-18
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• 1996

The results of a series of triaxial compression tests on remolded normally consolidated clay are compared with the predictions .by the isotropic single -hardening constitutive model, which incorporates eleven parameters. The parameters can be determined from undrained triaxial compression tests on isotropically consolidated specimens of remolded clay. The model with the determined parameters is applied to predict the stress-strain and pore pressure behaviors for untrained triaxial compresion tests on anisotropically consolidated specimens. Also the model is utilized to predict the stress strain and voltmetric strain behavior for drained triaxial compression tests on both isotropic and anisotropic specimens. The predicted response agrees well with the measured behavior for undrained triaxial compression tests on not only isotropically but also anisotroically but also anisotropically consolidated specimens. The initial volumetric strain is, however, predicted to be less than the measured value from drained triaxial compression tests, while the predicted volumetric strain close to failure is greater than the measured value. Nevertheless, it may be stated generally that overall acceptable predictions are produced. Therefore, the results of this study indicate that the applicability of the model on prediction of the behavior of normally consolidated clay is achieved sufficiently.

• Journal of Biomedical Engineering Research
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• v.21 no.2
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• pp.181-187
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• 2000

동맥의 일부분이 팽창하는 동맥류는 파열로 인한 높은 사망률을 야기한다. 동맥류의 발생 및 파열에는 혈관벽의 구조적 약화와 혈류에 의한 응력이 중요한 역할을 하며, 혈류에 의해 혈관벽에 가해지는 전단응력은 간접적으로 혈관벽 구조를 변화시키고, 직접적으로 혈관벽에 응력을 가하므로 동맥류 파열에 영향을 미치는 중요한 혈류역학적 인자이다. 동맥류가 자주 발생하는 복부대동맥류 모델을 제작하여 정상류와 맥동류 유동에서 광색성 염료를 이용한 유동가시화 방법으로 벽 전단변형률을 측정하였다. 벽전단변형률은 동맥류 내부에서 감소하여 음의 값을 가지며, 동맥류 최대확장부 후부에서 다시 증가하여 확장부가 끝나는 위치에서 동맥 벽에 비해 약 1.5배 정도의 큰 전단변형률 값을 가졌다. 동맥류 최대확장부 후부에서는 벽전단변형률의 방향의 바뀌며, 위치에 따른 전단변형률의 변화가 크게 나타났다. 맥동류 유동에서는 동맥류의 위치에 따라 시간에 따른 벽전단형률 파형이 측정되었다. 동맥류 내부에서는 전단변형률의 크기가 작고 그 방향이 시간에 따라 변화가 심하였으므로 혈관벽의 구조변화가 발생하기 쉬운 지역으로 지목된다. 동맥류 최대 확장부 후부는 위치 및 시간에 따른 전단변형률의 변화가 심하며, 혈관벽 응력이 최대값을 갖는 지역이므로 동맥류의 파열이 발생하기 쉬운 지역으로 예측된다.