• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.109-116
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• 2014

The flexural behavior test of UHPC segmental box girder which has 160 MPa compressive strength and 15.4 m length was carried out. The effect of steel fibers in combination with reinforcing bars on improving the ductile performance of UHPC box girder was evaluated by comparing the flexural behavior of the UHPC segmental box girders made by the two kinds of mixing portion. The test variables are volume fraction of steel fibers and the arrangement of reinforcing bars. The behavior of UHPC box girder BF2 composed of 1% volume fraction of steel fibers and longitudinal reinforcing bars in web and upper flange with stirrup showed the similar ductile behavior with the girder BF1 composed of 2% volume fraction without stirrup in elastic stress region. But BF1 had the better stiffness and showed the more ductile behavior in inelastic stress region. Segmental interfaces of UHPC box girder have not any crack and slide until the final flexural collapse load.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.101-111
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• 1998

This study presents test results of RC beams strengthened by carbon fiber sheet(CFS), carbon fiber reinforced plastics(CFRP) or glass fiber reinforced plastics(GFRP) for increasing shear resistance. Nineteen specimens were tested, and the test was performed with different parameters including the type of strengthening materials(CFS, GFRP, CFRP), shear-strengthening methods(wing type, jacket type, strip type), strip-spacing, strengthening direction of FRP. The test results show that shear-damaged RC beams strengthened by FRP(CFS, GFRP, CFRP) have more improved the shear capacity. The mathematical model based on plastic theory was also developed to predict shear strength of shear-damaged RC beams strengthened by FRP. The predictions using the mathematical model. are agreed with the observations from the observed shear strengths for 19 test beams.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.835-838
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• 2008

This study presents the nonlinear finite element analysis to predict the behavior of reinforced concrete (RC) beams shear-strengthened with fiber-reinforced polymer laminates (FRP). In this paper, modeling concept for the FRP is introduced to enable the use of finite element methods for the shear analysis of RC beams shear-strengthened with FRP composites. The numerical techniques are used to represent the FRP composite, bond properties between the FRP and the concrete, and the RC beams. According to the proposed modeling methods, a finite element analysis is performed using a two-dimensional nonlinear finite element analysis program, VecTor2, based on the Disturbed Stress Field Model (DSFM). To verify the application of the DSFM for the prediction of the behavior of the shear-critical beams strengthened with FRP composites in shear, a detailed comparison between experimental and numerical results for the response of the RC beams is carried out.

• Magazine of the Korea Concrete Institute
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• v.9 no.4
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• pp.145-153
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• 1997

전단벽제 양단의 보강기둥은 비선형 휨거동에 주요 영향을 미치는 구조 요소이다. 본 연구에서는 전단 벽체에 일반적으로 사용되는 모델인 TVLEM에서, 수직 스프링 요소로 표현되는 보강기둥의 반복이력 모델을 제안하고 기존의 모델과 비교 검토하였다. 제안된 단순모델은 Vulcano의 모델 중 철근의 거동을 이중직선으로 가정하여 유도되었으며, 제안된 모델을 검증하기 위하여 Vulcano와 Kabeyasawa의 모델 사용시의 수치해석 값과 비교하였다. 비선형 해석은 자체 개발된 프로그램을 사용하였으며, Vallenas와 Bertero가 실험(1979)한 SP6의 모델에 대하여 수치해석을 수행하여 반복이력특성과 변위이력 및 발산에너지량을 비교하였다.

• Journal of Korean Society of Steel Construction
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• v.26 no.1
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• pp.21-30
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• 2014

In this study, an experimental study was performed to evaluate the shear resistance of cast-in-place(CIP) anchors reinforced with hairpin and stirrup bars under static and dynamic loads. The reinforcement was developed using D6 bars, and the anchors were installed with 20mm diameter and 120mm edge distance. Three tests were conducted for each type of reinforced anchor under static and dynamic shear load with a pulsating frequency of 1 Hz, respectively. It was found that the strength of hairpin-reinforced anchor was affected by the concrete cover and the dynamic tests showed no capacity reduction of anchors compared with static tests. The stirrup-reinforced anchor showed little increase of resistance compared with unreinforced anchor and the resistance under dynamic loading showed nearly same strength by static loading.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.211-214
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• 2010

플랫 플레이트 시스템은 기둥 주위의 국부적인 응력집중 현상으로 인한 뚫림전단 파괴에 대해 취약하다. 따라서 유한요소해석을 통해 이러한 플랫 플레이트 시스템의 뚫림전단 성능을 평가하고자 한다. 슬래브의 전단을 고려하기 위하여 Reissner-Mindlin 가정을 바탕으로 한 등매개변수 감절점 쉘 요소를 적용하였다. 콘크리트의 재료적 비선형 거동을 고려하기 위해 압축거동은 수정압축장 이론을 적용하였으며 인장강성효과 또한 콘크리트 재료모델에 반영하였다. 기존 실험결과와의 비교를 통해 타당성을 검증하고자 하였다. 비교 결과, 약 16%의 오차율을 보였으며 보강비가 낮은 실험체에 비해 보강비가 높은 실험체가 실험결과에 가까운 값을 예측하는 것으로 나타났다.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.193-202
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• 1994

In this study, an equation for modelling the shear strength of reinforced concrete member with web reinforcement is proposed. Although the general formulas for shear strength of reinforced concrete member with small a /d are obtained based on the experimental results, the proposed equation herein is derived from lower bound theorem of limit analysis. The proposed model takes into account arch mechanism and truss mechanism. And ir provides the values of divided shear strength ratio of each mechanism as well as visual understanding of the mechanism on how the given load is transfered to the support. Also, the model takes into account the effect of a /d. longitudinal reinforcement ratio, and web reiriforcement ratio quantitively. Based on the comparisons of the result of this model with previous, test results, it shows good agreements.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.446-449
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• 2009

본 연구에서는 강관말뚝과 기초와의 연결시 보강에 사용되는 관통형 말뚝두부보강에 대한 파괴거동을 파악하기 위한 구조해석을 수행하였다. 구조물의 관공부에 대한 해석에서 철근의 인장파괴시 발생하는 관통부의 응력을 검토하고 철근의 파괴형상과 실험에서 얻어진 철근의 파괴형상을 비교하였다. 대상구조물의 전체적인 파괴거동은 인장, 압축, 전단, 휨모멘트에 대하여 파괴가 발생할 때까지 변위를 증가시키고 이때 발생하는 반력과 구조물의 파괴거동을 파악하였다. 이 때 강재의 비선형 거동 및 충진콘크리트의 비선형및 균열거동이 고려되었다. 해석의 결과로 대상구조물의 파괴거동 및 극한하중 저항능력이 평가되었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.76-85
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• 2021

In this study, a shear experiment was conducted to evaluate the structural performance of RC members according to the shape of web opening reinforcement. For a total of 4 RC members specimens, the main variables were with or without web openings, with or without web opening reinforcement, and shape of web opening reinforcement, respectively. In this study, a spiral web opening reinforcement with a mixture of square and octagonal shapes was proposed and compared with the existing band type. As a result of the experiment, the specimen with the proposed web opening reinforcement showed that the shear capacity and the energy dissipation capacity increased compared to other specimens. It was confirmed that the web opening reinforcement proposed in this study had a positive effect on the shear performance and crack control of RC members with web openings.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.285-291
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• 2016

The purpose of this study was to evaluate the structural capacity of steel pipe pile specimens reinforced with hollow steel plate shear connectors by pull-out test. Compressive strength testing of concrete was conducted and yield forces, tensile strengths and elongation ratios of re-bars and hollow steel plate were investigated. A 2,000kN capacity UTM was used for the pull-out test with 0.01mm/sec velocity by displacement control method. Strain gauges were installed at the center of re-bars and hollow steel plates and LVDTs were also installed to measure the relative displacement between the loading plate and in-filled concrete pile specimens. The yield forces of the steel pipe pile specimens reinforced with hollow steel plate shear connectors were increased 1.44-fold and 1.53-fold compared to that of a control specimen, respectively. Limited state forces of steel pipe pile specimens reinforced with hollow steel plate shear connectors were increased 1.23-fold and 1.29-fold compared to that of a control specimen, respectively. Yield state displacement and limited state displacement of steel pipe pile specimens reinforced with hollow steel plate shear connector were decreased 0.61-fold and 0.42-fold compared to that of a control specimen, respectively.