• Computers and Concrete
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• 제20권4호
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• pp.469-481
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• 2017

This paper aims to analytically investigate the effect of shear stress at the concrete-steel interface on the mechanical behavior of the circular steel tube-confined concrete (STCC) stub columns with active and passive confinement subjected to axial compression. Nonlinear 3D finite element models divided into the four groups, i.e. circumferential-grooved, talc-coated, lubricated, and normal groups, with active and passive confinement were developed. An innovative method was used to simulate the actively-confined specimens, and then, the results of the finite element models were compared with those of the experiments previously conducted by the authors. It was revealed that both the predicted peak compressive strength and stress-strain curves have good agreement with the corresponding values measured for the confined columns. Then, the mechanical properties of the active and passive specimens such as the concrete-steel interaction, longitudinal and hoop stresses of the steel tube, confining pressure applied to the concrete core, and compressive stress-strain curves were analyzed. Furthermore, a parametric study was performed to explore the effects of the concrete compressive strength, steel tube diameter-to-wall thickness ratio, and prestressing level on the compressive behavior of the STCC columns. The results indicate that reducing or removing the interfacial shear stress in the active and passive specimens leads to an increase in the hoop stress and confining pressure, while the longitudinal stress along the steel tube height experiences a decrease. Moreover, prestressing via the presented method is capable of improving the compressive behavior of STCC columns.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.87-88
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• 2010

철근콘크리트 기둥은 횡보강철근으로 구속함으로써 부재의 강도 및 연성능력의 증진효과를 얻을 수 있다. 이에 횡보강철근으로 구속된 콘크리트의 응력-변형률 모델이 다양하게 제시되어왔다. 본 연구에서는 고강도 횡보강철근으로 구속한 원형실린더의 최대 횡구속 응력에 영향을 주는 요소를 파악하고 실험결과로부터 콘크리트와 횡보강철근 사이의 변형률을 분석하여 포아송비식을 제안하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.129-134
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• 2011

In this paper, the confined single slot jet impingement is investigated numerically. Although the geometry of the jet impingement is simple, the flow pattern of the jet impingement is complex and the numerical results of the jet impingement is affected much by numerical methods. The first goal of this study is to analyze the effects of Reynolds models and numerical spatial discretization schemes on the results of heat transfer performance and the flaw characteristics and to select the best method. Various versions of the low Reynolds number k-epsilon turbulence models are compared. Using the selected numerical method, the flow field and heat transfer characteristics of confined single slot jet impingement on a moving plate are analyzed.

• 대한조선학회논문집
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• 제48권4호
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• pp.317-324
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• 2011

When a ship proceeds in confined water, like canal, the water ahead of ship is pushed by hull. This pushed water returns to the side and under the hull, and this returned water will make fluid velocity higher at the side and under the hull, compared to the case in the infinite water depth. Due to the higher velocity, the pressure under the hull will decrease, resulting in the ship drop. This phenomenon is called "ship squat" and ship squat will result in various marine accidents. In this paper, for predicting ship squat, numerical calculation was carried out using commercial CFD code, FLUENT. To confirm wave pattern profile around the ship, VOF(Volume of Fluid) method was applied. The calculated results were compared with other paper's results and empirical methods.

• Structural Engineering and Mechanics
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• 제12권3호
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• pp.231-248
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• 2001

The three-dimensional behavior of confined concrete was investigated, including strength enhancement due to triaxial compressive stresses, lateral expansion, compression softening, cover spalling and post-peak ductility. A finite element program based on a nonlinear elasticity methodology was employed to evaluate the ability to model triaxial behavior of reinforced concrete (RC) by combining constitutive models proposed by several researchers. The capability of compression field based models to reproduce the softening behavior of lightly cracked confined concrete was also investigated. Data from tested specimens were used to evaluate the validity of the formulations. Good agreement with the experimental results was obtained.

• Steel and Composite Structures
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• 제11권4호
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• pp.325-340
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• 2011

Based on the experimental data presented in part I of these companion papers, a semi-empirical model is proposed for axial stress-strain curves of reinforced high-strength concrete square columns confined by aramid fiber reinforced polymer (FRP) jackets. Additionally, a three-dimensional finite element model is developed to simulate the mechanical behaviors of the columns. In the finite element model, both material nonlinear and contact nonlinear are taken into account. Moreover, the influence of contact nonlinear (i.e., the end friction on the contact surface between test machines and specimens) is investigated deeply. Predictions from both the semi-empirical model and the finite element model agree with the experimental results, and it is also demonstrated that the friction coefficient of end friction notably affect the properties of columns when it ranges from 0.00 to 0.25.

• 설비공학논문집
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• 제27권8호
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• pp.440-447
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• 2015

In the shipbuilding process, the confined work spaces of the ship are formed continuously; the ventilation method can therefore be limited to dilution ventilation due to the complex structure and limited opening of the confined space. Also, it is difficult to evaluate air-quality using measurement and an adequate ventilation method. CFD simulation methods are typically used in analyzing ventilation efficiency in these cases. In this study, a method is suggested to analyze the air quality of the complex enclosures in shipbuilding using CFD. Especially, among the conventional indices, the ventilation efficiency scales or indices, the supply air contribution (SVE4), and the age of the air (SVE3) (fit for the confined and complex enclosure) were applied.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.5-8
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• 2004

In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns in improving the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. A total of four one-half scale specimens are tested under repeated lateral loads. Specimens are tested to failure with increasing maximum lateral drifts while a vertical axial load was applied and maintained constant. The constant vertical axial stresses applied are 0, 0.84 and 1.80MPa, while the amount of reinforcements in horizontal and vertical directions are $0\%,\;0.08\%\;and\;0.18\%$ respectively. Test results obtained for each specimen include cracking patterns, load-deflection data, and strains in reinforcement and walls in critical locations. Analysis of test data showed that above parameters generate a considerable effect on the seismic performance of confined concrete block masonry walls.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.353-356
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• 2004

Nonlinear numerical analysis was performed to investigate the behavioral characteristics and failure mechanism of flexure -dominated structural walls with partially confined boundary elements. Based on the results, deformability of walls with partially confined boundary elements was evaluated, and a design method which can determine depth of confined boundary element according to given ductility demand, was developed. Also, effective details of laterally confining re-bars were proposed for boundary elements with rectangular cross-section. The design method can be used to choose the spacing of confining re-bars assuring the confining effect and constructability.

• Steel and Composite Structures
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• 제1권3호
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• pp.313-328
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• 2001

This paper presents a three-dimensional finite element analysis methodology for a quantitative evaluation of confinement in concrete-filled box-shaped unstiffened steel columns. The confinement effects of concrete in non-circular sections can be assessed in terms of maximum average lateral pressure. A brief review of a previous method adopted for the same purpose is also presented. The previous method is based on a two-dimensional finite element analysis method involving a concrete-steel interaction model. In both the present and previous methods, average lateral pressure on concrete is computed by means of the interaction forces present at the concrete-steel interface. Subsequently, the strength enhancement of confined concrete is empirically related to the maximum average lateral pressure. The results of the former and latter methods are then compared. It is found that the results of both methods are compatible in terms of confined concrete strengths, although the interaction model yields a somewhat overestimated estimation of confinement than those of the present method when relatively high strength concrete is used. Furthermore, the confinement in rectangular-shaped sections is investigated and the reliability of previously adopted simplifications in such cases is discussed.