직접 인발 시험을 이용한 에폭시 도막 철근의 부착 특성

김지상(Jee-Sang Kim),이상현(Sang-Hyun Lee) 한국건설순환자원학회 2017 한국건설순환자원학회 논문집 Vol.5 No.3

철근 콘크리트 구조물에 있어서 철근의 부식은 구조물의 내구성 측면에서 심각한 문제를 야기하고 있으며, 이에 대한 효율적인 대책의 하나로 에폭시 도막 철근의 사용이 제시되고 있으나, 철근 표면의 에폭시 도막으로 인하여 콘크리트와의 부착 성능이 저하되는 문제점이 발생하게 된다. 이를 정확히 평가하고 대안을 제시하기 위한 기초단계로 이 연구에서는 현재 국내에서 생산되는 에폭시 도막 철근의 직접 부착 실험을 수행하고 부착성능을 평가하였다. 에폭시 도막 철근의 부착 실험은 지름 10, 19, 29mm의 철근에 대하여 콘크리트 피복두께를 철근 지름의 1, 2, 3, 4.5배로 하여 수행되었다. 총 66개의 시편이 RILEM 시험법에 따라 실험이 진행 되었는데, 에폭시 도막 철근의 지름이 증가할수록 에폭시 도막 철근과 일반철근의 부착응력 차이가 증가하였으며, 도막두께의 영향은 뚜렷하지 않았다. 또한, 에폭시 도막 철근의 부착강도는 KS 표준에 제시된 제한값인 일반 철근 대비 85%의 부착성능을 나타내는 것을 확인할 수 있었다. 이 실험의 결과에 근거하여 평형방정식에 기초한 에폭시 도막 철근의 정착길이 증가계수를 수정한 새로운 산정식을 제안하였다. The corrosion of reinforcements embedded in concrete causes some durability problems in reinforced and prestressed concrete structures. The epoxy coated reinforcements are one of the effective and reliable methods to prevent corrosion of reinforcements. However, it has been known that the epoxy coating reduces the bond capacity of reinforcement to concrete. This paper investigates the bond behaviors of epoxy coated reinforcements experimentally using direct pull-out test. Bond behaviors of epoxy coated bars for various reinforcement diameters of 10, 19 and 29mm and thicknesses of cover concrete of 1, 2, 3, and 4.5c/db(ratio of cover to bar diameter) are examined. Total 66 specimens were manufactured and tested according to the RILEM standard method. As the diameters of the epoxy coated reinforcements increase, the difference of bond strength between epoxy coated reinforcements and uncoated bars also increases. Epoxy coated bars showed more than 85% bond performance compared to those of uncoated bars. A new formular for estimating basic development length of epoxy coated reinforcement based on equilibrium equation is proposed using this experimental result.

Quasi-isotropic 적층 보강재로 보강된 RC보의 휨 보강 설계에 관한 연구

지효선 ( Ji¸ Hyo-seon ) 한국복합신소재구조학회 2021 복합신소재구조학회논문집 Vol.12 No.5

본 논문은 준등방성 적층 섬유배열된 FRP보강재로 보강된 철근콘크리트보의 휨 보강 설계에 대하여 소개하고 있다. 본 논문에서는 첫 번째로 FRP보강재의 적층설계와 그 적층부재의 물성값 해석이 수행되었다. 마지막으로 여러 개의 준등방성 적층구조로 보강된 철근콘크리트보에 대한 휨 해석이 수행되었다. 그 결과값은 직교차 적층 구조를 갖는 RC보와 비교되었다. 따라서 본 연구가 준등방성 적층구조의 FRP보강재로 보강된 노후 RC보의 휨 설계의 지침서가 될 수 있을 것이다. This study presents the flexural design for deteriorated reinforced concrete beams strengthened with quasi-isotropic laminate structures’ fiber-reinforced polymer (FRP) reinforcements. First, the laminates for FRP reinforcements were designed and then their properties were analyzed. The flexural analysis demonstrated that the reinforced concrete (RC) beams strengthened with FRP reinforcements of several quasi-isotropic laminate structures prevented the coupling effect of the FRP reinforcements in this study. The results were analyzed and compared with the RC beams strengthened with cross-ply laminate structures. Thus, this study can serve as a flexural design guideline for RC beams strengthened with the FRP reinforcements of quasi-isotropic laminate structures.

Evaluation of Pullout and Drainage Properties of Geosynthetic Reinforcements in Weathered Granite Backfill Soils

Yoo, Han-Kyu,Kim, Hong-Taek,Jeon, Han-Yong The Korean Fiber Society 2007 Fibers and polymers Vol.8 No.6

The main aim of this research is to systematize the reinforced-earth wall system using the geosynthetic reinforcements in the weathered granite backfill soils containing relatively large amount of fines with low permeability. As a staged endeavor to accomplish this purpose, laboratory pullout tests and finite element modeling are carried out focusing on the analysis of friction characteristics associated with interaction behaviors of the geosynthetic reinforcements composed of geogrid with outstanding tensile resistance and geotextile with a sufficient drainage properties. In addition, drainage effects of the geotextile laid below the geogrid are examined based on the analysis of finite difference numerical modeling. From the present investigation, it is concluded that the geosynthetic reinforcements in the weathered granite backfills can be used to achieve combined effects of the reduction of deformations and the increase of tensile resistance, together with drainage effects.

전단철근에 의한 휨 구속 효과

김병호,은희창,서일교 제주대학교 산업기술연구소 2001 尖端技術硏究所論文集 Vol.12 No.1

The objective of this study is to present a design method of over-reinforced concrete beam confined by shear reinforcements. Fourteen reinforced concrete beams were tested with the variables of the amount of longitudinal bars, the spacing of shear reinforcements, and the shear-span ratio. It was observed that the confinement of core concrete by shear reinforcements led to the enhanced flexural capacity and ductility. Comparing the experimental and analytical results and grasping the confinement effects of shear reinforcements, this paper illustrated the validity of designing over-reinforced concrete beam.

전단철근에 의한 휨 구속 효과

김병호,은희창,서일교 濟州大學校 産業技術硏究所 2001 산업기술연구소논문집 Vol.12 No.1

The objective of this study is to present a design method of over-reinforced concrete beam confined by shear reinforcements. Fourteen reinforced concrete beams were tested with the variables of the amount of longitudinal bars. the spacing of shear reinforcements. and the shear-span ratio. It was observed that the confinement of core concrete by shear reinforcements led to the enhanced flexural capacity and ductility. Comparing the experimental and analytical results and grasping the confinement effects of shear reinforcements. this paper illustrated the validity of designing over-reinforced concrete beam.

鐵筋콘크리트 보에서 剪斷鐵筋이 휨耐力에 미치는 影響

고유신,기진호,김병호,은희창,서일교 제주대학교 산업기술연구소 2000 尖端技術硏究所論文集 Vol.11 No.2

Shear reinforcement has an important role to strengthen shear capacity of reinforced concrete beam. Although the flexural design corresponding to design code does not consider the effects of the shear reinforcement, its utilization in flexural region leads to the improved ductility and the enhanced strength by confining concrete. It allows to design the over-reinforcement beam. In this study, we considered the effects of the shear reinforcement on the flexural ductility and strength of reinforced concrete beam according to the spacing of shear reinforcement, steel ratio, and shear span ratio. The flexural capacity depends on the amount of longitudinal bars and the ductility the confinement degree by the shear reinforcement. The flexural analysis varies with the stress-strain relation of confined concrete. The analytical results based on the stress-strain relation presented by Chung almost corresponded to the experimental ones. It was observed that the proper design of shear reinforcement leads to utilize the over-reinforcement concrete beam.

고장력 철근이 적용된 철근콘크리트 보-기둥 접합부 파괴모드에 대한 실험적 연구

김대훈,박아론,이기학,Kim, Dae-Hoon,Park, Aa-Ron,Lee, Kihak 한국공간구조학회 2016 한국공간구조학회지 Vol.16 No.2

Behavior of RC(Reinforced-concrete) beam-column connections has been subjected to the earthquake loading has been determined by shear and attachment mechanism. However, since the shear and attachment are very fragile for cycle loadings. Through occurring plastic hinges at the beam, the column and the connection should remain elastic condition and the beam should dissipate the energy from the earthquake. This study was investigate on the seismic performance of 6 RC beam - column connections built with the high strength reinforcements (700MPa) based on design and detailing requirements in the ACI 318-05 Provision and KCI-07 appendix II. This is aimed to evaluate the effect of the high-strength reinforcements as used the beam-column connection members. The main comparisons were the seismic performance of the connections affect the seismic performance in terms of strength, stiffness and ductility, joint shear stress-strain. A total of 6 beam-column specimens were built with a 1/2 scale and subjected to the cyclic loadings. Main design considerations were the area of the longitudinal reinforcements of the beam and details of the beam-column joint designed based on the seismic code. Cyclic test results are given and recommendations for the usage of high strength reinforcements for the seismic design is provided.

집중하중을 받는 철근콘크리트 깊은 보의 전단거동에 관한 실험적 연구

이진섭,김상식,Lee, Jin-Seop,Kim, Sang-Sik 한국콘크리트학회 1999 콘크리트학회지 Vol.11 No.1

집중하중을 받는 단순지지 철근콘크리트 깊은 보를 대상으로 콘크리트의 압축강도, 전단스팬비, 웨브 수직 및 수평 보강철근비를 변수로 하여 깊은 보의 구조거동과 전단강도를 실험적으로 조사하였으며, 각 변수의 영향을 고찰하고 규준식 및 제안식 등과 비교, 검토하였다. 42개의 시험체를 실험한 결과, 모든 시험체는 전단스팬 내에서 콘크리트의 과도한 균열 및 압괴에 의해 파괴되었고, 시험체의 초기강성은 압축강도에 관계없이 전단 스팬비가 작을수록 크게 나타났으며, 경사균열 발생 이후 보의 강성이 점진적으로 감소되었다. 전단스팬비가 증가함에 따라 경사균열 및 최대하중은 일정하게 감소하며, 콘크리트 압축강도가 증가할수록 최대하중은 증가하나 경사균열 하중은 거의 변화가 없었고, 전단스팬비의 증가에 따라 콘크리트의 압축강도가 전단강도에 미치는 영향 또한 일정하게 감소하는 것으로 보인다. 웨브의 전단보강근 효과는 전단스팬비의 영향을 받으며, 전단스팬비가 작아지면 수평보강근의 효과가, 전단스팬비가 커지면 수직보강근의 효과가 상대적으로 커짐을 알 수 있었다. 실험결과와 비교하여, 이론식은 de Paiva의 제안식이, 규준식은 CIRIA guide가 실험결과에 가장 부합하는 것으로 나타났으며, 국내 규준식은 실험값에 비해 상당히 낮은 강도로 계산되고 있어 안전 측에 있는 것으로 판단된다. The shear behavior of simply supported reinforced concrete deep beams subject to concentrated loads has been scrutinized experimentally to verify the influence of the structural parameters such as concrete strength, shear span-depth ratio, and web reinforcements. A total of 42 reinforced concrete deep beams with compressive strengths of 250 kg/$cm^2$ and 500 kg/$cm^2$ has been tested at the laboratory under one or two-point top loading. The shear span-depth ratio have been taken as three types of 0.4, 0.8 and 1.2, and the horizontal and vertical shear reinforcements ratio, ranging from 0.0 to 0.57 percent respectively. In the tests, the effects of the shear span-depth ratio, concrete strength and web reinforcements on the shear strength and crack initiation and propagation have been carefully checked and analyzed. From the tests, it has been observed that the failures of all specimens were due to shear and the shear behaviors of specimens were greatly affected by inclined cracks from the load application points to the supports in shear span. The load bearing capacities have changed significantly depending on the shear span ratio, and the efficiency of horizontal shear reinforcements were increased as the shear span-depth ratio decreased. The test results have been analyzed and compared with the formulas proposed by previous researchers and the design equation from the code. While the shear strengths obtained from the tests showed around 1.4 and 1.9 times higher than the values calculated by CIRIA guide and the domestic code, they were closely coincident with the formulas given by de Paiva's equation.

보-기둥 접합부의 방폭성능에 관한 해석적 연구

임광모,윤영수,이주하 한국방재학회 2015 한국방재학회논문집 Vol.15 No.4

As the increase of explosive accidents and terrorism, demands of blast-resistant capacity in structures would be increased to prevent those situation. Therefore, various studies on blast-resistant structures should be performed. In this study, behavior of beam-column connections is investigated. Base specimen was designed according to the design criterion of beam-column connections. To determine the effects of reinforcement details, flexure, shear and diagonal bar were considered as variables. LS-DYNA, nonlinear finite element program, is selected to the numerical analysis of specimens. The analysis results included failure shape of specimens, deflection, support rotation and stress of reinforcements. In conclusion, specimen which was reinforced with additional flexure bars did not show significant differences as contrasted with base specimen. The diagonal reinforcements are more effective to resist the blast loads than additional flexure reinforcements because safety of connection was enhanced due to the transfer of plastic hinge region in case of reinforcing diagonal bars. In the specimen which is reinforced with additional shear bars, outstanding behavior was observed. In the structures subjected to blast loads, therefore, it is should be considered to not only flexural performance but also shear forces. 폭발사고나 테러 등이 증가함에 따라 구조물 방폭성능의 요구가 증가되고 있다. 국내에서도 폭발사고 등에 대비하기 위한 방폭구조물의 수요가 증가할 것이며, 이를 위해서는 다양한 측면의 관련 연구가 수행되어야 할 것이다. 본 연구에서는 철근상세가 보-기둥 접합부의 방폭성능에 미치는 영향에 대해 분석하였다. 표준 시험체는 보-기둥 설계매뉴얼을 바탕으로 정하중에 대해 설계되었으며 이 외에철근상세에 따른 영향을 분석하기 위해 휨, 전단, Diagonal철근 등이 보강된 시험체와 비교하였다. 접합부의 방폭성능을 평가하기 위해 유한요소해석 프로그램인 LS-DYNA에 의한 해석적 연구가 수행되었다. 해석결과는 시험체의 파괴형상, 변형, 지점회전각 그리고철근의 응력을 포함하고 있다. 추가적인 휨철근이 보강된 시험체의 방폭성능을 표준 시험체와 비교하여 큰 차이를 보이지 않았으나, Diagonal철근이 보강된 시험체는 보 영역에서 발생하는 소성힌지영역을 이동시켜 접합부의 안전성을 확보하는 등 방폭성능을 향상시켰다. 따라서 동일한 철근비에서 휨철근보다 Diagonal철근이 폭발하중에 더 효율적으로 저항하는 것을 확인하였다. 이에 더하여 전단철근이 배근된 시험체는 우수한 방폭성능을 보였으며, 이를 통해 폭발하중을 받는 콘크리트 구조에서 휨 성능과 함께 전단성능 역시중요한 고려사항임을 확인할 수 있었다.

탄화규소/7091알루미늄 복합재료의 부식거동

강우승 ( Woo Seung Kang ) 한국부식방식학회(구 한국부식학회) 2012 Corrosion Science and Technology Vol.11 No.4

The effects of volume fraction (15-30%) of SiC particulate reinforcements on the corrosion behavior of SiCp/7091 Al conposites in the 3.5% NaCl solution were studied by electrochemical techniques and scanning electron microscopy. The results showed that the amount of SiC particulate reinforcements did not cause much difference in the corrosion behavior of SiCp/7091 Al composites but the corrosion rate was proportional to the amount of SiCp reinforcement, And numerous pits and severe dissolution of the matrix was observed probably due to the discontinuities and galvanic effects between Al matrix and SiC reinforcements.