• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.352-355
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• 2010

본 논문에서는 내부 및 외부 긴장재로 보강된 PSC 거더의 가속도 응답 특성을 이용한 구조건전성 모니터링을 위해 실험 및 수치해석 결과를 비교 분석하는 연구를 수행하였다. 첫 번째로, 내부 및 외부 긴장재로 보강된 모형 PSC 거더를 제작하였다. 두 번째로, 모형 PSC 거더의 형상, 재료 및 경계조건과 긴장재의 배치를 고려하여 초기 유한요소모델을 설계하였다. 세 번째로, 다수의 내부 및 외부 긴장력 조건하의 모형 PSC 거더에 대한 동특성 추출 실험 및 수치해석을 수행하였다. 마지막으로, 실험결과와 수치해석 결과를 비교 분석하여 가속도 응답 특성을 이용한 내부 및 외부 긴장재로 보강된 PSC 거더의 구조건전성 모니터링에 대한 적용성을 검토하였다.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.404-410
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• 2011

For the simulation of one-dimensional unsteady flow, the Taylor-Galerkin finite element method was adopted to the discretization of the Saint Venant equation. The model was applied to the backwater problem in a single channel and the flood routing in dendritic channel networks. The numerical solutions were compared with previously published results of finite difference and finite element methods and good agreement was observed. The model solves the continuity and the momentum equations in a sequential manner and this leads to easy implementation. Since the final system of matrix is tri-diagonal with a few additional entry due to channel junctions, the tri-diagonal matrix solution algorithm can be used with minor modification. So it is fast and economical in terms of memory for storing matrices.

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.85-91
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• 2005

This paper investigates P-S (load-settlement) relationship for the end-bearing Pile in granular material using the CRISP FE Program with the laboratory 2D model pile load test. In order to simulate the effect of end-bearing pile problem in the FEA, the author adopts several forms of slip element around the pile length and the pile tip. Through this study it was found that e degree of non-associated Plastic flow rule incoporated into the Mohr-Coulomb model for the end-bearing pile with the slip elements was a dominant factor in terms of numerical solution convergence. In contrast, the roller boundary used along the pile shaft showed a smooth convergence with respect to the degree of non-associated plastic flow rule.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.69-78
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• 1991

This paper concentrates on the analysis of deflection of the reinforced concrete flexural members under monotonic loading. Concrete is treated as an orthotropic nonlinear material. The concept of equivalent strain and crack strain are used to establish independent stress-strain relationships in the directions of orthotropy. Steel is modeled as an elstoplastic material, and von Mises failure criterion is applied. The finite element computer program for the nonlinear analysis of the deflection of RC flexural members under monotonic loading is developed. The accuracy and reliability of the numerical procedure is demonstrated by the FEM analysis and experiments of the under reinforced concrete beams over the entire loading range up to failure.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.7-19
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• 2002

This paper presents the results of an investigation on the effect of foundation stiffness on the performance of soil-reinforced segmental retaining walls (SRWalls). Laboratory model tests were performed using a reduced-scale physical model to capture the fundamentals of the manner in which the foundation stiffness affects the behavior of SRWalls. A series of finite-element analyses were additionally performed on a prototype wall in order to supplement the findings from the model tests and to examine full-scale behavior of SRWalls encountered in the field. The results of the present investigation indicate that lateral wall displacements significantly increase with the decrease of the foundation stiffness. Also revealed is that the increase in wall displacements is likely to be caused by the rigid body movement of the reinforced soil mass with negligible internal deformation within the reinforced soil mass. The findings from this study support the current design approaches, in which the problem concerning the foundation condition are treated in the frame work of the external stability rather than the internal stability. The implications of the findings from this study to current design approaches are discussed in detail.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.5
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• pp.11-24
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• 2011

A real-time hybrid test of a 3 story-3 bay reinforced concrete frame which is divided into numerical and physical substructure models under uniaxial earthquake excitation was run using a fixed iteration implicit HHT time integration method. The first story inner non-ductile column was selected as the physical substructure model, and uniaxial earthquake excitation was applied to the numerical model until the specimen failed due to severe damage. A finite-element analysis program, Mercury, was newly developed and optimized for a real-time hybrid test. The drift ratio based on the top horizontal displacement of the physical substructure model was compared with the result of a numerical simulation by OpenSees and the result of a shaking table test. The experiment in this paper is one of the most complex real-time hybrid tests, and the description of the hardware, algorithm and models is presented in detail. If there is an improvement in the numerical model, the evaluation of the tangent stiffness matrix of the physical substructure model in the finite element analysis program and better software to reduce the computational time of the element state determination for the force-based beam-column element, then the comparison with the results of the real-time hybrid test and the shaking table test deserves to make a recommendation. In addition, for the goal of a "Numerical simulation of the complex structures under dynamic loading", the real time hybrid test has enough merit as an alternative to dynamic experiments of large and complex structures.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.1
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• pp.34-44
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• 1992

A numerical model using Hybrid Element Method(HEM) is presented for the prediction of wave agitations in a harbor which are induced by the intrusion and transformation of incident short-period waves. A linear mild-slope equation including bottom friction is used as the governing equation and a partial absorbing boundary condition is used on solid boundaries. Functional derived in the present paper is based on the Chen and Mei(1974)'s concept which uses finite element net in the inner region and analytical solution of Helmholtz equation in the outer region. Final simultaneous equations are solved using the Gaussian Elimination Method. The model appears to be reasonably good from the comparison of numerical calculation with hydraulic experimental results of short-wave diffraction through a breakwater gap(Pos and Kilner, 1987). The problem of requring large computational memory could be overcome using 8-noded isoparametric elements.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.2
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• pp.19-28
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• 1982

The development of unsteady, depth-averaged two dimensional sediment transport prediction model in estuaries and harbors by the Galerkin finite element technique is presented. The model consists of two submodels, flow induced circulation model and sediment transport model. The sediment transport submodel is formulated by incorporating sediment continuity equation and sediment diffusion equation. Numerical experiments of the model, which were carried out in one dimensional channel under different conditions for circulation and sediment transport, show the adaptability of the formulation for predicting the migration of both cohesive and noncohesive sediments. The model was applied to Busan harbor to simulate circulation and sediment transport for simplified conditions. Of the results by the model the flow pattern are shown to be similar to observed data.

• Journal of Korea Water Resources Association
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• v.35 no.3
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• pp.261-274
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• 2002

The purpose of this study was to develop two dimensional contaminant transport numerical model by finite element method. The developed model system was tested for water quality analysis when contaminants from tributaries and sewage treatment Plants flow into the main river. In this study, the model was to perform calibration for reasonable parameter production and verification for reliability and accuracy. And, the proposed model was applied on the downstream of Han river using calibrated parameters. These results represented real con taminant distribution profile along the channel, and produced the good agreement in comparing calculated vague with measured value.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1737-1741
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• 2008

하천 개수나 치수를 위한 기초 연구의 일환으로 수치모형을 이용한 검증 및 예측 과정이 요구되어 왔고, 고전적인 수치모의 방법으로 결과 산출이 용이한 1차원 모형을 적용시켜 왔다. 1차원 모형의 경우 모의영역을 쉽게 넓힐 수 있고, 입력 자료가 간단하다는 장점이 있지만, 수직적이고 수평적인 흐름특성 변화 및 난류 구조를 보이는 3차원적인 자연하천 흐름을 종방향의 1차원적인 모의 결과를 이용하여 평가한다는 점에서 비현실적이다. 하천을 가로질러 교각이나 보와 같은 구조물이 위치하고 있거나, 좌우 비대칭적인 형상의 수로를 모의할 경우 흐름특성의 공간적인 분포는 단순한 단면 평균적인 개념으로는 설명되기 힘들다. 최근에야 비로소 수공학 관련 실무자들에 의해서 최소한 2차원 수치모형을 기본적인 평가법으로 도입해야 한다는 분위기가 감지되고 있으며, 일반적으로 한강과 같은 대하천을 모의할 경우, 대다수의 실무자들과 연구자들이 축척을 문제 삼아 수로 내부에 위치한 교각을 생략하여 2차원 모의를 수행하기도 한다. 따라서 본 연구에서는 수로 내부에 위치한 교각을 2차원 모의하는 방법에 대한 비교 평가를 수행하고자 한다. 동일한 격자를 이용하여 교각을 고려하지 않았을 경우와 교각 형상을 모의 영역에서 삭제하여 경계처리를 하였을 경우, 마지막으로 교각이 위치하고 있는 영역에 항력을 적용하였을 경우에 대해서 비교 평가한다. 이를 위하여 2차원 천수방정식을 흐름방정식으로 하는 유한요소모형을 구축하였으며, 모형의 검증을 위해 교각이 수로에 위치할 경우에 대한 실내 실험 자료와 비교한다. 또한 검증된 모형을 이용하여 교각이 포함된 한강의 일부 구간을 선정하여, 교각 모의 방법에 대한 비교 평가를 수행한다. 본 연구에서 구축된 자료 및 제시된 수치모형은 하천복원, 치수관리 측면에서 매우 유용하게 사용될 것으로 기대된다.