• Title/Summary/Keyword: 준연속체

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Application of Nonlocal Anisotropic Damage Model for the Reinforced Concrete Structures (철근콘크리트 구조물에 대한 비국소 이방성 손상모델의 적용)

  • Woo, Sang Kyun;Kwon, Yong Gil;Han, Sang Hoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.3A
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    • pp.309-316
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    • 2010
  • This paper proposed a nonlocal anisotropic damage model to simulate the behavior of plain and reinforced concrete structures that are predominantly tensile and compressive load. This model based on continuum damage mechanics, used a symmetric second-order tensor as the damage variable. For quasi-brittle materials, such as concrete, the damage patterns were different in tension and in compression. These two damage states were modeled by damage evolution laws ensuring a damage tensor rate proportional to the total strain tensor in terms of principal components. To investigate the effectiveness of proposed model, the double edge notched specimen experimented by nooru-mohamed and reinforced concrete bending beam were analyzed using the implementation of the proposed model. As the results for the simulation, the nonlocal anisotropic damage model with an adequate control of rupture correctly represented the crack propagation for mixed mode fracture. In the structural failure of reinforced concrete bending beam, the proposed model can be showed up to a very high damage level and yielding of the reinforcements.

Wave-Induced Response of Unsaturated and Multi-layered Seabed; A Semi-analytical Method (파랑으로 인한 불포화된 다층 해저지반의 거동;준해석적 방법)

  • ;Rahman, M. S.
    • Journal of the Korean Geotechnical Society
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    • v.15 no.6
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    • pp.45-55
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    • 1999
  • Wave-induced response, liquefaction and stability of unsaturated seabed are studied. The unsaturated seabed is modeled as a fluid-filled polo-elastic medium. The coupled process of fluid flow and the deformation of soil skeleton is formulated in the framework of Biot's theory. The resulting governing equations are solved using a semi-analytical method to evaluate the stresses and pore water pressure of unsaturated and multi-layered seabed. The semi-analytical method can be applied to calculate a pore pressure and the stresses of in anisotropic inhomogeneous seabed. The results indicate that the degree of saturation influences mostly on the magnitudes of a pore pressure and the stresses of unsaturated and multi-layed seabed. Based on the pore pressure and stresses in seabed, the analysis on the possibilities of liquefaction and shear failure was performed. The results show that the maximum depth of shear failure occurrence is deeper than the maximum liquefaction depth.

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Peridynamic Modeling for Crack Propagation Analysis of Materials (페리다이나믹 이론 모델을 이용한 재료의 균열 진전 해석)

  • Chung, Won-Jun;Oterkus, Erkan;Lee, Jae-Myung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.31 no.2
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    • pp.105-114
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    • 2018
  • In this paper, the computer simulations are carried out by using the peridynamic theory model with various conditions including quasi-static loads, dynamic loads and crack propagation, branching crack pattern and isotropic materials, orthotropic materials. Three examples, a plate with a hole under quasi-static loading, a plate with a pre-existing crack under dynamic loading and a lamina with a pre-existing crack under quasi-static loading are analyzed by computational simulations. In order to simulate the quasi-static load, an adaptive dynamic relaxation technique is used. In the orthotropic material analysis, a homogenization method is used considering the strain energy density ratio between the classical continuum mechanics and the peridynamic. As a result, crack propagation and branching cracks are observed successfully and the direction and initiation of the crack are also captured within the peridynamic modeling. In case of applying peridynamic used homogenization method to a relatively complicated orthotropic material, it is also verified by comparing with experimental results.

Evaluation of Shear Capacity of Wide Beams Reinforced with GFRP and Steel Plates with Openings by Various Supporting Areas (지지부 조건에 따른 유공형 판으로 전단보강된 넓은 보의 전단성능 평가)

  • Kim, Heecheul;Ko, Myung Joon;Kim, Min Sook;Lee, Young Hak
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.29 no.3
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    • pp.269-275
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    • 2016
  • In this paper, shear performance of concrete wide beams was evaluated through shear failure tests. The specimens were designed to have two continuous spans with a column at the center of the wide beam. Also the specimens were reinforced with plates with openings as shear reinforcements. For the test, total eight specimens, including five specimens were reinforced with steel plates and the other three specimens were reinforced with GFRP plates were manufactured. And the shear strengths obtained from the tests were compared with ones from the equation provided by ACI 318. Support width of wide beam, support section of wide beam and shear reinforcement material were considered as variables. The results showed that the support width was proportional to the increase of shear strength. Also, regardless of material type of shear reinforcement, the shear reinforcing effect was similar when the amount of shear reinforcement was the same.

Prestressing Inducing Effect of Continuous Open-top Steel Box Girder Using Modular CFT Members (모듈형 CFT부재를 이용한 개구제형 연속 강박스 거더의 프리스트레싱 도입 효과)

  • Lee, Hak Joon;Kim, Ryeon-Hak;Cho, Kwang-Il;Ahn, Jin-Hee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.3
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    • pp.111-119
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    • 2022
  • The increasing sectional stiffness and inducing prestress method of continuous steel box girder using modular CFT members use the restoring force of the CFT module generated from removing the prestressing bars in the CFT module after integrating the prestressed CFT module with the lower steel plate of the steel box girders as a prestressing force. The integrated CFT module in the steel box girder can improve the sectional stiffness of the continuous steel box girder section. To examine the applicability of the introduction of prestressing to the integrated steel box girder using the CFT module, in this study, inducing prestressing tests were conducted using CFT modules for steel plate specimens simulating the lower steel plate of the continuous steel box girder, and FE analyses were conducted for inducing prestressing tests. In addition, to confirm the effect of inducing prestress to the actual steel box girder and increasing sectional stiffness by the CFT modules, FE analyses for the actually applicable continuous steel box section were carried out depending on prestressing force and sectional conditions of the CFT modules, FE analysis results were compared.

Solid Circulation Rate in a Viscous Liquid-Solid Circulating Fluidized Bed (점성유체 액/고 순환유동층에서 입자의 순환속도)

  • Hong, Sung Kyu;Jang, Hyung Ryun;Lim, Dae Ho;Yoo, Dong Jun;Kang, Yong
    • Korean Chemical Engineering Research
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    • v.54 no.5
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    • pp.706-711
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    • 2016
  • Characteristics of solid circulation rate in the liquid-solid circulating fluidized beds with viscous liquid medium were investigated. Effects of primary and secondary liquid velocities, particle size, liquid viscosity and height of solid particles piled up in the solid recycle device on the solid circulation rate were considered. The solid circulation rate increased with increasing primary and secondary liquid velocities, liquid viscosity and height of solid particles in the downcommer, but it decreased with increasing particle size. The particle rising velocity in the riser decreased with increasing the ratio of $U_{L1}/U_{L2}$ and particle size. The slip velocity of liquid and particle, $U_L/U_S$, decreased with increasing liquid viscosity but it increased with increasing particle size. The values of solid circulation rate were well correlated in terms of operating variables and dimensionless groups.

Development of Temperature Dependent Damage Model for Evaluating Material Performance under Cryogenic Environment (극저온 재료 성능분석을 위한 온도의존 손상모델 개발)

  • Lee, Kyoung-Joon;Kim, Tae-Woo;Yoo, Jea-Sin;Yoo, Seong-Won;Chun, Min-Sung;Lee, Jae-Myung
    • Journal of the Society of Naval Architects of Korea
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    • v.45 no.5
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    • pp.538-546
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    • 2008
  • In this paper, the constitutive equation is developed to analyze the characteristics of strain-induced plasticity in the range of low temperature of 316 stainless steel. The practical usefulness of the developed equations is evaluated by the comparison between experimental and numerical results. For 316 stainless steel, constitutive equations, which represent the characteristics of nonlinear material behavior under the cryogenic temperature environment, are developed using the Bodner's plasticity model. In order to predict the material behaviour such as damage accumulation, Bodner-Chan's damage model is implemented to the developed constitutive equations. Based on the developed constitutive equations, 3-D finite element analysis program is developed, and verified using experimental results.

An Equation of State to Meet the Boundary Conditions between Critical Point and Inversion Points (임계온도와 반전점들 사이의 경계조건에서 구한 기체의 상태방정식)

  • Seung-Hee Kim;Wonsoo Kim;Tong-Seek Chair
    • Journal of the Korean Chemical Society
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    • v.35 no.5
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    • pp.487-492
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    • 1991
  • $[P+a(b/v)^n]$ = RT / (V - b) Above equation of state had been derived from Roulette theory. Three parameters-a, b, n are estimated from the critical point and the inversion temperature. When it is applied to 52 materials and to the regions of high density such as dense gas and supercritical gas, the results are good.

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Characteristics of Continuous Preparation of ZnO Powder in a Micro Drop/bubble Fluidized React (마이크로 액적/기포 유동반응기에서 ZnO 입자의 연속제조 특성)

  • Lee, Seung Ho;Yang, Si Woo;Lim, Dae Ho;Yoo, Dong Jun;Lee, Chan Ki;Kang, Gyung Min;Kang, Yong
    • Korean Chemical Engineering Research
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    • v.53 no.5
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    • pp.597-602
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    • 2015
  • Characteristics of continuous preparation of ZnO powder were investigated in a micro drop/bubble fluidized reactor of which diameter and height were 0.03 m and 1.5 m, respectively. The flow rate of carrier gas for transportation of precursors to the reactor was 6.0 L/min and the concentration of Zn ion in the precursor solutions was 0.4 mol/L, respectively. Effects of reaction temperature (973 K~1,273 K) and flow rate of micro bubbles (0~0.4 L/min) on the pore characteristics of prepared ZnO powder were examined. The optimum reaction temperature for the maximum porosity in the ZnO powder was 1,073 K within this experimental condition. The mean size of ZnO powder prepared continuously in the reactor decreased but the surface of the powder became smooth, with increasing reaction temperature. The injection of micro bubbles into the reactor could enhance the formation of pores in the powder effectively, and thus the mean BET surface area could be increased by up to 58%. The mean size of prepared ZnO powder was in the range of $1.25{\sim}1.75{\mu}m$ depending on the reaction temperature.

Seismic Performance of Hollow Rectangular Precast Segmental Piers (프리캐스트 중공 사각형 철근콘크리트 교각의 내진성능)

  • Lee, Jae-Hoon;Park, Dong-Kyu;Choi, Jin-Ho;Shin, Sung-Jin
    • Journal of the Korea Concrete Institute
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    • v.24 no.6
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    • pp.705-714
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    • 2012
  • Precast reinforced concrete bridge columns with hollow rectangular section were tested under cyclic lateral load with constant axial force to investigate its seismic performance. After all the precast column segments were erected, longitudinal reinforcement was inserted in the sheath prefabricated in the segments, which were then mortar grouted. Main variables of the test series were column aspect ratio, longitudinal reinforcement ratio, amount of lateral reinforcement, and location of segment joints. The aspect ratios were 4.5 and 2.5, and the longitudinal steel ratios were 1.15% and 3.07%. The amount of lateral reinforcement were 95%, 55%, 50%, and 27% of the minimum amount for full ductility design requirements in the Korean Bridge Design Code. The locations of segment joints in plastic hinge region were 0.5 and 1.0 times of the section depth from the bottom column end. The test results of cracking and failure mode, axial-flexural strength, lateral load-displacement relationship, and displacement ductility are presented. Then, safety of the ductility demand based seismic design in the Korean Bridge Design Code is discussed. The column specimens showed larger ductility than expected, because buckling of longitudinal reinforcing bar was prevented due to confinement developed not only by transverse steel but also by sheath and infilling mortar.