• Journal of the Korean Society of Hazard Mitigation
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• v.2 no.4 s.7
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• pp.131-141
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• 2002

Precast concrete (PC) panels are often used as retaining walls to support soil pressure. In such a case, the panels should be connected at the location where PC panels meet with a buttress. However, it is not easy to provide enough development length for the reinforcing steels due to the limited width of the buttress. If it happens, the width of buttress should be increased as large enough although it is not desirable. The critical section required for providing the development length is always located where the flexural moment is maximum. Thus it is the place the buttress width ends. Also it is the place that the reinforcing steels stressed to maximum. However, it is possible to make differentiate between the maximum moment location and the most stressed location of reinforcing steels. It means that the most stressed location of reinforcing steels, the critical section, can be moved to the other place where the moment is not maximum. New critical location will have less moment than that of buttress width ends. In consequence, the development length would be longer than that of the typical way of construction. Debonding or cutting technique make it possible to reduce the moment strength of a section. Therefore reinforcing steels are debonded or cut to have a desired flexural strength at a desired place. In this study, five test specimens in full scale were erected to examine the effects of critical section movement in PC panel joints. Test parameters were the length variations of debonded and cut reinforcing steels. The test results showed that the debonding or cutting technique could be used to lengthen the development length in the joint of PC panels.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.143-153
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• 2003

New strengthening method based on Near Surface Mounted technique (NSM) is suggested, which can overcome the brittle nature of failure inherent to those reinforced concrete beams strengthened with FRP composite materials. The suggested technique secures ductile failure of reinforced concrete beams by having the strengthening Hybrid FRP rebars unbonded in parts. Experiments were performed in order to compare structural behaviors of strengthened beams with and without unbending along the Hybrid FRP rebars. Test results showed that only those beams strengthened by partially unbonded NSM failed in ductile manner. Theoretical expressions were derived for the minimum unbonded length of Hybrid FRP rebars with which ultimate strength of the reinforced concrete beam with partially unbonded NSM could be reached. The suggested partially unbonded NSM technique is expected to significantly improve the structural behavior of the strengthened beam with FRP composite materials.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.29-36
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• 2005

The purpose of this study is to investigate the inelastic behavior of reinforced concrete bridge columns with unbonding of main reinforcements at plastic hinge region. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. The effect of unbonding of main reinforcements at plastic hinge region has been also taken into account to model the concrete and reinforcing steel. The proposed numerical method for the inelastic behavior of reinforced concrete bridge columns with unbonding of main reinforcements at plastic hinge region is verified by comparison with reliable experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.10a
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• pp.90-96
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• 1992

경계면 요소를 이용하여 철근콘크리트 구조물의 접촉면 문제를 유한 요소법으로 해석하는 기법에 대하여 연구한다. 본 연구에서는 경계면 요소의 수치해석의 이론과정을 전개하고, 실험 관찰된 부착 시험체에 적용하여 이형철근과 콘크리트 부착기구의 접촉면을 해석한다. 경계면은 특별한 연결요소를 이용하여 재현하며 Mohr-Coulomb의 마찰 이론을 응응한다. 해석의 주요점으로 하중상태에 따라 변화되는 경계면의 접촉상태, 즉 고정(stick), 미끄러짐(slide), 분리(separation)를 묘사하여 경계면 재료의 비선형 거동을 관찰한다. 부착모델의 해석결과는 실험실의 결과와 대체로 일치되며 따라서 철근콘크리트 접촉면의 응력해석을 위해 경계면 요소가 활용될 수 있음을 보여준다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.201-202
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• 2009

The objective of this paper is to develop nonlinear analysis method using fiber element. The program is based on flexibility method and developed for analyzing bernoulli's beam element. Using fiber element, three dimensional effects, such as concrete confinement can be incorporated into the uniaxial stress-strain relationship. In addition, most appropriate modeling method is used for application of bond-slip and shear effects.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.639-642
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• 2011

이 연구에서는 완전 조립식 교량 하부구조의 비선형해석을 위한 전산플랫폼을 개발하였다. 완전 조립식 교량 하부구조의 비선형거동을 정확하게 파악하고 합리적이면서 경제적인 설계기준의 개발을 위한 자료를 제공하는데 그 목적이 있다. 재료적 비선형성에 대해서는 균열콘크리트에 대한 인장, 압축, 전단모델과 콘크리트 속에 있는 철근모델을 조합하여 고려하였다. 사용된 부착 또는 비부착 텐던요소는 유한요소법에 근거하며 프리스트레스트 콘크리트 부재의 콘크리트와 텐던의 상호작용을 구현할 수 있다. 그리고 접합면요소는 세그먼트 접합부의 비탄성거동을 예측할 수 있다. 제안된 해석기법은 수치예제에 대하여 비선형거동을 비교적 정확하게 예측하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.734-737
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• 2010

이 연구에서는 프리스트레스트 콘크리트 깊은 보의 비선형해석을 위한 전산플랫폼을 개발하였다. 프리스트레스트 콘크리트 깊은 보의 전단거동을 정확하게 파악하고 합리적이면서 경제적인 설계기준의 개발을 위한 자료를 제공하는데 그 목적이 있다. 재료적 비선형성에 대해서는 균열콘크리트에 대한 인장, 압축, 전단모델과 콘크리트 속에 있는 철근모델을 조합하여 고려하였다. 사용된 부착 또는 비부착 텐던요소는 유한요소법에 근거하며 프리스트레스트 콘크리트 부재의 콘크리트와 텐던의 상호작용을 구현할 수 있다. 이 연구에서는 프리스트레스트 콘크리트 깊은 보의 전단거동을 파악하기 위해 제안한 해석기법을 신뢰성 있는 연구자의 실험 결과와 비교하여 그 타당성을 검증하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.4
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• pp.39-49
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• 2001

In this paper, inelastic analysis procedures are presented for the seismic performance evaluation of RC bridge piers with premature termination of main reinforcement. The mechanical characteristic of cracked concrete and reinforcing bar in concrete has been modeled, considering the bond effect between reinforcing bars and concrete, the effect of aggregate interlocking at crack surface and the stiffness degradation after the crack. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, local discontinuous deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The increase of concrete strength due to the lateral confining reinforcement has been also taken into account to model the confined concrete. The proposed numerical method for seismic performance evaluation of RC bridge piers with premature termination of main reinforcement will be verified by comparison with reliable experimental results.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.55-66
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• 1999

This paper presents an analytical prediction of the hysteresis behavior of reinforced concrete long column with rectangular section under the cyclic loading state. The mechanical characteristic of cracked concrete and reinforcing bar in concrete has been modeled, considering the bond effect between reinforcing bar and concrete, the effect of aggregate interlocking at crack surface and the stiffness degradation after the crack has taken place. The strength increase of concrete due to the lateral confining reinforcement has been also taken into account to model the confined concrete. The formulation of these models for concrete and reinforcing bar has been based on the smeared crack concept that the stress-strain relationship of reinforced concrete element would be defined using the average values. In addition to the material nonlinear properties, the algorithm for large displacement problem that may give an additional deformation has been formulated using total Lagrangian formulation. The analytically predicted behavior was compared with test result and they showed good agreement in overall behavior.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.1 s.53
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• pp.79-87
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• 2007

This paper presents an analysis procedures of Joints in precast segmental prestressed concrete bridge piers. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. An unbended tendon element based on the finite element method, that can represent the interaction between tendon and concrete of prestressed concrete member, is used. A joint element is newly developed to predict the inelastic behaviors of segmental joints. The proposed numerical method for joints in precast segmental prestressed concrete bridge piers is verified by comparison with reliable experimental results.