• Magazine of the Korea Concrete Institute
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• v.10 no.1
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• pp.109-118
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• 1998

전단거동에 의해 지배되는 고강도 철근콘크리트 춤이 큰 보의 전단역학적 거동 및 전단강도특성을 고려한 이론식을 제시하고자 소성이론에 근거한 극한해석에서 상계치정리를 이용하여 이론적 전개를 하였으며, 고강도 R/C춤이 큰 보의 전단응력에 영향을 미치는 콘크리트 압축강도, 수직전단보강근 및 수평잔단보강근의 보강효과를 고려한 이론식을 제시하였으며, 수평철근 즉 주인장철근 및 수평전단보강근의 장부작용을 고려하였다. 실험결과와 비교할 때 제안식은 수직잔단보강근의 전단보강효과를 과대평가하고있으며, 수평전단보강근의 효과를 적절하게 평가하고 있음을 나타내었다. 또 전단스팬비가 0.5, 0.85인 경우에는 제안식에 의한 값이 다소 낮게 나타내, 전단스팬비가 낮은 경우는 다소 과소평가하는 것으로 나타났다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.125-131
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• 2003

This paper presents the characteristics of flexural behavior of RC beam strengthened with CFRP(Carbon Fiber Reinforced Polymer Plate). Experimental variables included the strengthening length, width, reinforcement ratio, end anchorage and preloading corresponding to 75 percent of ultimate capacity and the effects according to each experimental variables were analyzed. To study, a total 21 RC beams were constructed, tested and the response of the beams in terms of ultimate load, deflection, strain of CFRP, failure mode were examined.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.389-400
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• 2009

A compression lap splice can be calculated longer than a tension lap splice in high strength concrete according to current design codes. Including effects of transverse reinforcement, a compression splice becomes much longer than a tension splice. Effects of transverse reinforcement and bar size on strength and behavior of compression lap splice, which always exist in actual structures, have been investigated through experimental study of column tests with concrete strength of 40 and 60 MPa. The results of the tests with bar diameters of 22 and 29 mm show that there is no size effect of bar diameter on compression lap splice. Bond strength of small bar diameter may increase. However, large diameters of re-bars are used in compression member and the size effect of re-bars does not have to be considered in compression lap splice. Confined specimens have twice of calculated strengths by current design codes. New design equations for the compression lap splice including the effects of transverse reinforcement are required for practical purpose of ultra-high strength concrete. End bearing is enhanced by transverse reinforcement placed at ends of splice not by transverse reinforcement within splice length. As more transverse reinforcement are placed, the stresses developed by bond linearly increase. The transverse reinforcements at ends of splice a little improve the strength by bond. Because the stresses developed by bond in compression splice with transverse reinforcement are nearly identical to or less than those in tension splice with same transverse reinforcement, strength increment of compression splice is attributed to end bearing only.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.180-186
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• 2017

거의 모든 철근콘크리트 구조물의 보강 강재는 분할된 두개 이상의 철근으로 제작되며, 이러한 철근의 분할 부위를 평행한 두개의 철근으로 겹쳐 설치하는 것을 겹이음(Lap splice)이라고 부른다. 일반적으로 겹이음 설계는 무리없이 설계 강도를 만족시킬 뿐만 아니라 충분히 긴 수명을 가진다. 그러나 550MPa 이상의 항복 강도를 갖는 철근이나 인장 부재의 설계, 초고성능 섬유보강 콘크리트의 보강재 설계와 같은 경우, 현행 철근 겹이음 설계만으로는 그 한계가 발생한다. 따라서 현 겹이음 설계는 관련 기준의 추가와 구조적인 측면에서의 개선이 필요할 것으로 보여지며, 이를 위해 적절한 실험과 데이터 분석, 그리고 컴퓨터를 이용한 새로운 설계 모델의 개발 등의 과정이 필요할 것으로 여겨진다. 본 연구는 균질하지 않은 물성의 파괴를 다루는 RBSN(Rigid-Body-Spring Networks)을 통한 컴퓨터 시뮬레이션으로 더 효과적이고 정확한 겹이음 설계가 가능할 것으로 판단하고, 실제 모델링으로 그 가능성을 검증하였다.

• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.81-88
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• 1999

In order to properly evaluate the shear strength of reinforced concrete circular columns due to the transverse shear reinforcement, the average of fractions of forces generated along the circular transverse hoops across the shear failure plane in the loading direction is calculated. For this, the center-to-center diameter of circular transverse hoops. spacing and the crack angle measured to the column longitudinal axis are considered. Using these variables, an equation representing the effective section area of circular transverse shear steel is proposed. The study result shows that the constant parameter. used for the calculation of the effective section area of circular hoops over the last 10 years, should not universally be applied any more. The use of the constant parameter may not seriously do harm to the evaluation of shear strength for circular columns with non-seismically designed transverse hoop reinforcement, since it gives slightly conservative results. However. for well-confined circular columns with close spacing or circular steel jacketing. it gives about 20% overestimation of the shear capacity contributed by the transverse hoop steel.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.1
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• pp.45-55
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• 2022

Because boundary confinement details proposed in the current design standards are significantly inferior in workability and production quality, it is necessary to develop boundary confinement details of RC structural walls that are capable of ensuring seismic performance and workability. With the recent development of the wire rod manufacturing technology, various pre-fabricated continuous hoop details can be manufactured. In this study, an analysis was conducted on the moment-curvature relationship of RC structural walls to which the pre-fabricated continuous hoop details were applied. According to the nonlinear cross-section analysis, the RC structure wall to which the details of the pre-fabricated continuous hoop details are applied can ensure seismic performance as the area of the pre-fabricated continuous hoop increases. Based on these research results, when applying the pre-fabricated continuous hoop in detail, it is necessary to secure the area of the pre-fabricated continuous hoop as much as the area of the existing boundary confinement.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.173-176
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• 2008

The aim of this paper is to clarify the shear behavior of RC beams strengthened with channel-type Fiber Reinforced Polymer(FRP) plates. Fourteen RC beams were specifically designed. All the beams were tested under four point bending and extensively instrumented to monitor strains, cracking, load capacity and failure modes. The structural response of all beams is then critically analyzed in terms of deformability, strength and failure processes. It is shown that with channel-type Fiber Reinforced Polymer(FRP) plates, a brittle debonding failure of beams bonding FRP in the concrete surface can be transformed to an almost ductile failure with well-defined enhancement of structural performance in terms of both deformation and strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.409-412
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• 2008

This study were evaluated the corrosion threshold reached at steel reinforcement in latex modified concrete(LMC). Accelerated testing was accomplished to the evalate the diffusion coefficient of LMC mix, and the time dependent constants of diffusion. Also, average chloride diffusion coefficient was estimated. From the average chloride ion diffusion coefficient, the time which critical chloride contents at depth of reinforcement steel was estimated. Test results indicated that the corrosion threshold reached at reinforcement in LMC are effected on the mix proportion factor including latex content, and water-cement ratio.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.73-81
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• 2004

In this study, experimental research was carried out to improve earthquake-resistant performance for the retrofitting of reinforced concrete beam-column joints using carbon fiber materials in existing reinforced concrete building. Six reinforced concrete beam-column joints were constructed and tested to evaluate the retrofitting effect of test variables, such as the retrofitting materials and retrofitting region(plastic hinge, beam-column joint) under load reversals. Test results show that retrofitting specimen(RPC-CP2, RPC-CR, RJC-CP, RJC-CR), using new materials(carbon fiber plate, carbon fiber rod and carbon fiber sheet), designed by the improvement of earthquake-resistant performance and ductility, attained more load-carrying capacity and stable hysteretic behavior.

• 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.