• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.37-45
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• 2023

The purpose of this study is to prevent diagonal tension failure of existing conventional coupling beams, increase the shear strength of conventional coupling beams, and quantitatively evaluate the increase. Steel fibers can improve shear strength and partially change the failure mechanism, but this is the result of research on general RC beams and columns, and research on the shear strength enhancement of conventional coupling beams for steel fiber reinforced concrete is still lacking. Therefore, in order to confirm the increased shear strength caused by steel fiber and the resulting change in failure mechanism, three specimens were fabricated with the steel fiber volume fraction as a variable (0%, 1%, 2%) and repeated loading experiments were performed. As a result, the shear strength of the specimens reinforced with steel fibers (1%, 2%) increased as the shear resistance contribution of concrete increased after the maximum strength was developed compared to the specimens without it (0%).

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.154-163
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• 2006

This paper presents a nonlinear analysis method for the reinforced concrete beams strengthened by the external bonding of high strength, lightweight fiber sheets on the tension face of the beams. The method is based on the results of experimental studies. The experimental study involved tensile tests of 120 specimens to evaluate the tensile properties of fiber sheets(carbon, glass, and aramid fiber) and bending tests of 75 beams strengthened with various types of fiber sheets to evaluate the flexural capacities. Based on these experimental results, reasonable rupture strains of the fiber sheets were estimated. The nonlinear flexural analysis considered nonlinear flexural stresses as compressive and tensile stresses of concrete, load-deflection curves, and rupture strains of fiber sheets. The nonlinear flexural analysis accurately predicts the load-deflection response and the flexural behavior of the retrofitted beams.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.443-443
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• 2012

최근 지구 온난화 및 기후변화로 인하여 국지적 집중호우에 의한 농지 침수 및 유실 피해가 점차 증가 추세에 있으며 가뭄에 의한 물 부족 현상도 심화되고 있다. 이와 같은 홍수 및 가뭄 피해에 대비하기 위하여 농업용 저수지와 수문 그리고 농수로와 같은 농업수리시설물이 신축 운영되고 있으나 이들 시설물은 비교적 규모가 작은 대신에 그 수가 매우 많고 또한 지역적으로 널리 산재해 있기 때문에 관리자가 이들을 효율적으로 운영하고 관리하는데 한계가 있다는 특징이 있다. 더욱이 이들 시설물은 물과 항상 접하는 철근 콘크리트 구조물로 이루어져 있어서 시간이 경과함에 따라 균열발생과 철근부식과 같은 노후화 현상이 뚜렷하게 진전되어 정기적 안전점검이 필요한 실정이다. 이에 따라 농업수리시설을 보다 체계적으로 관리하고 농업용수를 보다 효율적으로 확보 운영하기 위하여 물관리 자동화 사업이 추진되어 많은 개선이 이루어졌으나 아직까지 현장업무가 관리자의 수작업에 의존하고 있으며 농촌 용수의 정확한 정보가 제때에 제공되지 못하는 등 농업수리시설에 대한 다양한 요구를 충족시키지 못하고 있다. 따라서, 농촌수자원의 효율적 관리를 위하여 농업수리시설 가운데 하나인 농수로의 수위 및 유량 정보를 자동으로 측정하며 농업수리시설물의 상태 정보를 입력하고 관리할 수 있는 모바일 App을 개발하였다. 안드로이드 OS 기반의 스마트폰을 활용하였으며 여기에는 시설물 고유정보가 포함된 QR코드 및 Active 태그를 통하여 시설물의 상태정보를 원격에 있는 서버 컴퓨터로 전송할 수 있는 원거리 무선통신 모듈이 구비되어 있다. 특히, 농업수리시설물 관리 어플리케이션은 현장관리자가 기존에 수기방식으로 시설물을 관리해 오던 것을 휴대단말 상에서 보다 효율적으로 관리를 함으로써 시설물 유지관리 업무의 효율성을 향상시키는 특징이 있다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.39-47
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• 2023

The demand for lightweight and high-strength materials is increasing. However, studies on the bond of concrete and reinforcing bars for high-strength lightweight concrete with a compressive strength of 120 MPa and a unit weight of 20 kN/m³ to structural members are lacking. Therefore, in this paper, 108 specimens of high-strength lightweight concrete with a compressive strength of 120 MPa and a unit weight of about 20 kN/m³ were fabricated, a direct pull-out test was performed, and the bond characteristics were evaluated by comparing the test results with design code. Compared to the decrease in unit weight, the solid bubble shows relatively little reduction in compressive strength and modulus of elasticity. It was f ound to have larger slip and parameter values than concrete with low compressive strength and unit weight.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.165-179
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• 2007

For the purpose of optimum design of reinforced concrete structures, pre-determined section database of column and beam are constructed and arranged in order of the resisting capacity. Then, regression equations representing the relation between section number and section resisting capacity are derived. In advance, effective optimization algorithms which search optimized solution quickly using direct search method from these database are proposed. In practice, from the fact that engineers conduct member design close to capacity optimization rather than cost optimization, both capacity and cost optimization using proposed algorithms are performed, and the review for the obtained results are followed. Moreover, the investigation for the applicability and effectiveness of the Introduced design procedure is conducted through correlation study for example structures. Because of no restriction in constructing objective functions with very simple optimization processes and fast convergence, the introduced method can effectively be used in the preliminary design stage. Especially, selected solutions from database are directly applicable in practice because these sections already satisfy all the requirements in design codes and practical restrictions.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.433-438
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• 1998

Design lateral strength calculated by current seismic design code is prescribed to be much lower than the force level required for a structure to respond elastically during design level earthquake ground motion. Present procedures for calculating seismic design forces are based on the use of elastic spectra reduced by a strength reduction factor known as "response modification factor, R". This factor accounts for the inherent ductility, overstrength, redundancy, and damping of a structural system. This study considers ductility and overstrength of the wall-type structure for investigating R factor. This means that R factor is determined from the product of "ductility-based R factor($R_$\mu$$) and overstrength factor($R_s$). $R_$\mu$$ factor is calibrated to attain the targer ductility ratio (system ductility capacity) and produced in the from of $R_$\mu$$ spectra considering the influence of target ductility, natural period, and hysteretic model. On the other hand, $R_s$ is more difficult to quantify, since it depends on both material and system-dependent uncertain parameters. In this study Rs factor was determined from the result of push-over analysis.-over analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.2
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• pp.15-27
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• 2009

The purpose of this study is to investigate the seismic behavior of precast segmental PSC bridge columns. For the analysis of reinforced concrete structures, a computer program named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) is used. To represent the interaction between tendon and concrete of a prestressed concrete member, a bonded or unbonded tendon element based on the finite element method is used. A joint element is modified to predict the inelastic behaviors of segmental joints. The solution of the equations of motion is obtained by numerical integration using Hilber-Hughes-Taylor (HHT) algorithm. The proposed numerical method gives a realistic prediction of seismic behavior throughout the input ground motions for numerical examples.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.521-526
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• 2001

The flexural behavior of a strengthened beam that is a reinforced concrete beam with externally bonded carbon fiber sheets, is theoretically and experimentally investigated. A rectangular beam having a width of 20cm depth of 30cm and effective depth of 25cm is chosen. In order to have a variety of beams analyzed, three reinforcement ratios are chosen for the analysis: 1)$\frac{1}{2}$$\rho$$_{max}$, which is the most suitable reinforcement ratio for deflection consideration and the highest reinforcement ratio for practical designing beams as well; 2)$\rho$$_{max}$, which is the lowest reinforcement ratio for design purposes; and 3)the reinforcement ratio halfway from 1) and 2). Carbon fiber sheets with width of 15cm are externally bonded at the bottom fiber of the beam. The effect of the amount of carbon fiber sheets varying from 1 to 4 plies on the flexural capacity of the strengthened beam are also examined. Yield loads, ultimate loads, and flexural rigidities of the strengthened beam from the experimental results are composed with theoretical ones.nes.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.85-88
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• 2008

The purpose of this study was to investigate the seismic behavior of precast concrete segmental bridge piers with shear resistance connecting structure. A model of precast concrete segmental bridge columns with shear resistance connecting structure was tested under a constant axial load and a cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. The proposed numerical method for the seismic behavior of precast concrete segmental bridge piers with shear resistance connecting structure is verified by comparison with reliable experimental results.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.5
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• pp.455-468
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• 2013

In recent, various types of steel pipe-roof methods, which is reinforced by mortar after propulsion of steel pipe into the ground, have been used for the construction of trenchless underpass. Integrated steel pipe-roof has flexural stiffness and can resist against overburden load and reduce the stress acting on the concrete underpass structures. Due to arching effect, vertical and horizontal stress distribution around the steel pipe-roof is changing. In this study, therefore, the characteristic of stress distribution around the underpass induced by the construction of integrated steel pipe-roof is investigated by using numerical method. To examine the soil-structure interaction, interface element is introduced. Results show that vertical stress acting on the concrete structure placing inside the steel pipe-roof is significantly reduced due to arching effect and flexural stiffness of integrated steel pipe-roof. Design load can be reduced and effective design of underpass will be available if the earth pressure reduction due to arching effect is considered in the design stage.