• 한국구조물진단유지관리공학회 논문집
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• 제5권1호
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• pp.195-205
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• 2001

An analytical finite element approach to nonlinear behavior of reinforced concrete shear walls with opening under monotonic loading was presented in this paper. In order to achieve the objectives of present paper, the orthogonal anisotropic models for cracked reinforced concrete element based on smeared crack concept were used as the nonlinear material models of biaxial state of stress. The stiffness of cracked concrete was evaluated through the combined use of tension and compression stiffness models in and parallel directions of crack, respectively and shear transfer effect due to the aggregate interlocking at crack surface. The stress and strain of reinforcement in concrete was evaluated using the average stress and average strain relation with bond effect. based on smeared crack concept. The diagonal reinforcing bar was modeled using truss element with bond effect. A special significance of diagonal reinforcement near opening was given to the shear wall with opening and an effective distribution of diagonal reinforcement was presented in order to give an ultimate strength increment as well as a crack control.

• Geomechanics and Engineering
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• 제35권4호
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• pp.395-409
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• 2023

Long-span suspension bridges have tunnel anchor systems to maintain stable cables. More investigations are required to determine how closely tunnel excavation beneath the tunnel anchor impacts the stability of the tunnel anchor. In order to investigate the impact of the adjacent tunnel's excavation on the stability of the tunnel anchor, a large-span suspension bridge tunnel anchor is utilised as an example in a three-dimensional numerical simulation approach. In order to explore the deformation control mechanism, orthogonal tests are employed to pinpoint the major impacting elements. The construction of an advanced pipe shed, strengthening the primary support. Moreover, according to the findings the grouting reinforcement of the surrounding rock, have a significant control effect on the settlement of the tunnel vault and plug body. However, reducing the lag distance of the secondary lining does not have such big influence. The greatest way to control tunnel vault settling is to use the grout reinforcement, which increases the bearing capacity and strength of the surrounding rock. This greatly minimizes the size of the tunnel excavation disturbance area. Advanced pipe shed can not only increase the surrounding rock's bearing capacity at the pipe shed, but can also prevent the tunnel vault from connecting with the disturbance area at the bottom of the anchorage tunnel, reduce the range of shear failure area outside the anchorage tunnel, and have the best impact on the plug body's settlement control.

• 방송공학회논문지
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• 제27권2호
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• pp.244-247
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• 2022

본 논문에서는 고속 이동환경에서 강건성을 향상시킬 수 있는 OTFS(orthogonal time frequency space) 시스템에서 주파수 및 시간영역에서의 선형 MMSE(minimum mean squared error) 필터를 이용한 디코딩 알고리즘과 강화된 Gauss-Seidel 알고리즘을 이용한 디코딩 알고리즘의 성능을 비교한다. 강화된 Gauss-Seidel 알고리즘은 잡음 증폭을 억제함으로써 비트 오류율 성능을 개선할 수 있다. 전산 실험 결과를 통해 주파수 영역에서 MMSE 필터를 이용한 디코딩 알고리즘은 수신기의 이동 속도가 높아짐에 따라 성능 열화가 발생하는 것을 확인할 수 있고, 강화된 Gauss-Seidel 알고리즘을 이용한 디코딩 방법은 120km/h 속도와 500km/h 속도를 가지는 채널 환경에 대해 주파수 영역 및 시간 영역에서의 MMSE 필터 디코딩 알고리즘에 비해 우수한 성능을 나타내는 것을 확인할 수 있다.

• Earthquakes and Structures
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• 제11권4호
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• pp.723-740
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• 2016

Reinforced concrete corbels are generally used to transfer loads within a structural system, such as buildings, bridges, and facilities in general. They commonly present low aspect ratio, requiring an accurate model for shear strength prediction in order to promote flexural behavior. The model described here, originally developed for walls, was adapted for corbels. The model is based on a reinforced concrete panel, described by constitutive laws for concrete and steel and applied in a fixed direction. Equilibrium in the orthogonal direction to the shearing force allows for the estimation of the shear stress versus strain response. The original model yielded conservative results with important scatter, thus various modifications were implemented in order to improve strength predictions: 1) recalibration of the strut (crack) direction, capturing the absence of transverse reinforcement and axial load in most corbels, 2) inclusion of main (boundary) reinforcement in the equilibrium equation, capturing its participation in the mechanism, and 3) decrease in aspect ratio by considering the width of the loading plate in the formulation. To analyze the behavior of the theoretical model, a database of 109 specimens available in the literature was collected. The model yielded an average model-to-test shear strength ratio of 0.98 and a coefficient of variation of 0.16, showing also that most test variables are well captured with the model, and providing better results than the original model. The model strength prediction is compared with other models in the literature, resulting in one of the most accurate estimates.

• Steel and Composite Structures
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• 제42권2호
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• pp.173-190
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• 2022

With the development of spatial structures, the joints are becoming more and more complex to connect tubular members of spatial structures. In this study, an approach is proposed to establish high-efficiency finite element model of multiplanar KTX-joint with the weld geometries accurately simulated. Ultimate bearing capacity the KTX-joint is determined by the criterion of deformation limit and failure mechanism of chord wall buckling is studied. Size effect of fillet weld on the joint ultimate bearing capacity is preliminarily investigated. Based on the validated finite element model, a parametric study is performed to investigate the effects of geometric and loading parameters of KT-plane brace members on ultimate bearing capacity of the KTX-joint. The effect mechanism is revealed and several design suggestions are proposed. Several simple reinforcement methods are adopted to constrain the chord wall buckling. It is concluded that the finite element model established by proposed approach is capable of simulating static behaviors of multiplanar KTX-joint; chord wall buckling with large indentation is the typical failure mode of multiplanar KTX-joint, which also increases chord wall displacements in the axis directions of brace members in orthogonal plane; ultimate bearing capacity of the KTX-joint increases approximately linearly with the increase of fillet weld size within the allowed range; the effect mechanism of geometric and loading parameters are revealed by the assumption of restraint region and interaction between adjacent KT-plane brace members; relatively large diameter ratio, small overlapping ratio and small included angle are suggested for the KTX-joint to achieve larger ultimate bearing capacity; the adopted simple reinforcement methods can effectively constrain the chord wall buckling with the design of KTX-joint converted into design of uniplanar KT-joint.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.217-222
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• 2000

An iterative numerical computational algorithm is presented to design a plate or shell element subjected to membrance and flexural forces. Based on equilibrium consideration, equation for capacity of top and bottom reinforcements in two orthogonal directions have been derived. The amount of reinforcement is determined locally, I. e., for each integration point, from the equilibrium between applied and internal forces. Three cases of design are performed for slab element (used by Marti(1987)) and shell element (used by Kirscher and Collins(1986), by Polak and Vecchio(1993)) to verify the adequacy of the present design method for reinforced concrete shells. Based on nonlinear analyses performed, the analytically calculated ultimate load exceeded the design ultimate load. This shows the adequacy of the design method present in this study at least for slab and shell element case studied. To generalize the conclusion more design-analyses should be performed with different shell configurations.

• International Journal of Railway
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• 제4권4호
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• pp.86-92
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• 2011

Chloride ion diffusion at the corner of rectangular-shaped concrete structures is presented. At the corner of rectangular-shaped concrete, chloride ion diffusion is in two-dimensional process. Chloride ions accumulate from two orthogonal directions, so that corrosion-free life of concrete structures is significantly reduced. A numerical procedure based on finite element method is used to solve the two-dimensional diffusion process. Orthotropic property of diffusion coefficient of concrete is considered and chloride ion profile obtained from numerical analysis is used to produce transformed diffusion coefficient. Comparisons of experimental data are also carried out to show the reliability of proposed numerical analysis. As a result of two-dimensional chloride diffusion, corrosion-free life of concrete structure for railway is estimated using probability of corrosion initiation. In addition, monographs that produces transformed diffusion coefficient and corrosion-free life of concrete structure are made for maintenance purpose.

• KCI Concrete Journal
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• 제11권3호
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• pp.53-64
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• 1999

A theory is proposed to predict the response of the load-deformation relationship of the reinforced concrete structures under the service state after cracking. The crack direction and concrete strains through the loading history before failure can be estimated by this theory based on the rotating crack model, which considers equilibrium, compatibility conditions, and average stress-strain relationship. The proposed crack direction and deformation show good agreement with test results under service state. The behavior of a variety of concrete structures, such as shear walls, deep beams and the web of box girders, can be predicted by this proposed theory under service state.

• Journal of the Korean Wood Science and Technology
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• 제43권6호
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• pp.861-867
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• 2015

유리섬유 보강적층재의 파괴인성을 평가하기 위하여 Compact tension (CT)형 시험을 실시하였다. 보강재는 직물형 유리섬유와 시트형 유리섬유강화플라스틱을 사용하였으며, 보강적층재는 층재사이에 보강재를 삽입 적층하였다. ASTM D5045에 의거하여 CT형 시험편을 제작하였다. 시험편의 길이는 끝면거리를 고려하여 선정하였으며, 인위적인 노치 끝에 볼트구멍(12 mm, 16 mm, 20 mm)을 선공하였다. 시트형 유리섬유강화플라스틱 보강적층재의 파괴인성하중은 보강하지 않은 적층재보다 최대 33% 증가하였으며, 직물형 유리섬유 보강적층재는 최대 152% 증가하였다. 이중외팔보(Double Cantilever Beam)이론에 의한 응력확대계수는 시트형 유리섬유강화플라스틱 보강적층재의 경우 1.08~1.38이었으며, 직물형 유리섬유 보강적층재는 1.38~1.86이었다. 이는 직물형 유리섬유 보강적층재의 경우 유리섬유와 층재의 섬유배열방향이 직교하여 파괴하중으로 인한 목재의 할렬진행을 억제시켰기 때문이다.

• 콘크리트학회논문집
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• 제21권2호
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• pp.179-186
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• 2009

고강도콘크리트의 취약점으로 지적되고 있는 화재시의 폭렬현상에 대한 대책을 마련하기 위해 각 계의 노력이 활발한 현 상황에서 각종 폭렬 저감성 재료 및 새로운 개념의 소재에 대한 적정 혼입비율을 구명해야 하는 긴요한 상황이다. 본 연구에서는 메타카올린, 페타이어칩, 폴리프로필렌섬유 및 강섬유의 4가지 기능성 소재를 대상으로, 기본적인 품질 요건은 물론, 내화성능에 최적의 효과를 나타낼 수 있는 배합비를 실험적, 통계적으로 도출하고자 하였다. 여기서, 실험은 4인자 3수준의 직교배열표를 이용하여 최소실험법으로 계획하고, 통계적 분석은 반응표면분석 기법을 이용하였다. 그 결과, 80 MPa급 고강도콘크리트의 내화성능 보강인자로 선정된 기능성 소재간에는 복합 사용시 상호 보완적인 기여를 하는 것으로 확인되었다. 한편, 반응표면분석을 통해 도출한 내화성능 보강인자의 최적조건은 메타카올린을 실리카퓸 대신 80% 수준으로 용적치환하고, 폐타이어칩은 잔골재 대신 3% 수준으로 용적치환하는 경우와 폴리프로필렌 섬유를 전체용적에 대하여 0.2% 수준으로 첨가하는 한편, 강섬유를 혼입하지 않는 것이 고강도콘크리트의 기초 특성과 내화특성을 고루 만족할 수 있는 것으로 분석되었다.