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프리스트레스가 도입된 강섬유보강콘크리트의 균열면 전단거동
갈경완,황진하,이득행,김강수,최일섭 한국구조물진단유지관리공학회 2012 한국구조물진단유지관리공학회 논문집 Vol.16 No.1
일반적으로 콘크리트는 경제성이 뛰어나지만 낮은 인장강도로 인하여 구조성능상의 한계를 가지고 있기 때문에 콘크리트와 결합된 다양한 합성재료의 특성을 활용한 구조부재의 개발이 진행되고 있다. 강섬유 보강 콘크리트(SFRC)는 높은 인장강도로 인하여 콘크리트의 재료적 단점을 보완할 수 있는 우수한 합성재료로서 알려져 있고, 특히 고강도 콘크리트의 화재시 폭렬현상에 대한 대안으로 여겨지고 있다. 또한, 프리스트레스트콘크리트(PSC) 부재는 장경간 구조에 매우 유리하며 일반철근콘크리트(RC) 부재에 비해 높은 전단강도를 가진다. 따라서, 이 연구에서는 SFRC에 프리스트레스를 적용한 강섬유 보강 프리스트레스트 콘크리트(SFR-PSC)부재의 전단거동을 이해하기 위하여 총 22개의 직접전단실험체를 제작하여 실험을 수행하였다. 또한, 실험결과를 바탕으로 SFR-PSC부재의 균열면에서의 균열전달 구성방정식을 제안하였다. SFR-PSC의 거동특성을 반영하여 제안된 재료관계식은 실험결과와 잘 일치하는 것으로 나타났다. Although structural concrete is well known for its good economic efficiency, it has limits of structural performance due to the low tensile strength, for which new structural members utilizing various concrete composite materials have been developed. Steel Fiber-Reinforced Concrete(SFRC) has great tensile strength, which is the one of the excellent composite material to complement the weakness of concrete, and it is also considered as a good alternative to prevent the explosive failure of high strength concrete under fire. Also, prestressed concrete members are of great advantages to long span structures and have greater shear strength compared to conventional reinforced concrete members. In this research, thus, a total of 22 direct shear test specimens were fabricated and tested to understand the shear behavior of Steel Fiber-Reinforced Prestressed Concrete(SFR-PSC) members, in which SFRC members combined with prestressing method. Based on the test results, the constitutive equations of shear behavior at crack interfaces were proposed, which provided good estimation on the shear behavior of the SFR-PSC direct shear test specimens.
강섬유로 보강된 콘크리트 보의 전단강도에 관한 실험적 연구
갈경완,김강수,이득행,황진하,오영훈 한국구조물진단유지관리공학회 2010 한국구조물진단유지관리공학회 논문집 Vol.14 No.3
강섬유를 혼입한 콘크리트(Steel Fiber Reinforced Concrete, SFRC) 보는 강섬유의 우수한 인장강도로 인하여 일반 철근콘크리트 보에 비하여 높은 전단강도를 가진다. 이 연구에서는 강섬유 혼입율에 따른 SFRC 보의 전단거동을 규명하기 위하여 실험을 수행하였으며, 특히, 압축영역에서의 비균열 콘크리트 단면의 전단저항 분담율을 분석하였다. 또한, 이 연구의 실험결과 및 기존에 보고된 87개의 실험 데이터를 수집하여 SFRC보의 전단예측식들에 대한 정확도를 평가하였다. 강섬유의 혼입율이 증가할수록 전단강도는 증가하는 경향성을 나타내었다. 그러나, 강섬유 혼입율이 0.5%인 실험체는 사인장 균열 이후 갑작스럽게 파괴되었고, 강섬유의 혼입율이 2.0%인 실험체에서는 전단보강효율이 감소하는 것으로 관찰되어 최대 전단보강효율을 가질 수 있는 혼입율은 1~2% 사이에 있을 것으로 추정된다. 또한, 압축영역에서의 비균열 콘크리트 단면의 전단저항 분담율은 약 21% 이상으로 관찰되었으며, 이 연구에서 평가된 SFRC보의 전단강도에 대한 기존 제안식 중에서 오영훈 등이 제안한 식이 비교적 정확하게 전단강도를 예측하였다. Steel Fiber Reinforced Concrete (SFRC) beams has greater shear strength than typical reinforced concrete beams due to the high tensile strength of steel fibers. In this research, an experiment has been conducted to investigate the shear behavior of SFRC beams, and especially, the portion of shear resistance by uncracked compressive concrete section has been measured. Based on the test results in this study and 87 test data collected from literature, the accuracy of the existing equations for the estimation of shear strength has been evaluated. The shear strength of SFRC beams increased as more steel fibers were mixed. However, it is considered that the most efficient amount of steel fiber for enhancement of shear strength would be between 1% and 2% in that the specimen with 0.5% of steel fibers were abruptly failed after inclined cracking, and that the specimen with 2.0% of steel fibers showed a relatively low efficiency in increasing shear strength. The portion of shear resistance by the uncracked compressive concrete section was measured to be greater than 21%, and the equation proposed by Oh et al. provided the best accuracy on the estimation of shear strength of SFRC beams among the approaches evaluated in this study.
갈경완,황진하,이득행,박현철,김강수,최일섭,Karl, Kyoung-Wan,Hwang, Jin-Ha,Lee, Deuck-Hang,Park, Hyun-Chul,Kim, Kang-Su,Choi, Il-Sup 대한건축학회 2011 대한건축학회논문집 Vol.27 No.12
As social demand on the improved performance of concrete is consistently increased, the researches on fiber reinforced concrete have also been actively conducted till this moment. Especially, steel fibers are easy to produce, have homogeneous material properties, and can be easily mixed with concrete, on which many studies were forced. The steel fiber reinforced concrete(SFRC) has improved performance in tensile strength, crack control ability, and ductile failure modes, which leads to have the greater shear strength of flexural members. Most analysis or experimental studies on shear of SFRC beams, however, have been focussed on shear strength prediction, and few investigations on shear transfer mechanism of SFRC at crack surface is available. Thus, in this study, 15 SFRC direct shear specimens were fabricated and tested with primary parameters of compressive strength and steel fiber volume fraction. Based on the test results, the constitutive equations for shear behaviour of SFRC at crack surfaces were proposed, which showed good agreements to test results.
인공신경망을 이용한 강섬 유보강콘크리트 보의 전단강도 예측
갈경완 ( Kal Kyoung-wan ),이득행 ( Lee Deuck-hang ),김강수 ( Kim Kang Su ) 한국구조물진단유지관리공학회 2009 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.13 No.2
Steel fibers have recently been well recognized for good composite/strengthening materials, which also provide great improvement in shear strength. Consequently, many researchers proposed shear strength prediction models/equations. most of which, however, are based on regression analysis. This is because the shear mechanisms of steel fiber reinforced concrete(SFRC) members are very complicated. Neural network method is useful to predict the complicated shear strength of SFRC members, and is simpler and more accurate than regression analysis method. This paper, therefore, introduces the neural network approach and provides the prediction results of shear strength of 176 SFRC beams obtained from previous studies.
강섬유로 보강된 고강도 콘크리트 보의 전단강도에 관한 실험적 연구
갈경완(Karl Kyoung-Wan),김강수(Kim Kang-Su),이득행(Lee Deuck-Hang),황진하(Hwang Jin-Ha),주현진(Ju Hyun-Jin),서수연(Seo Soo-Yeon) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.10
It is generally known that the inclusion of steel fibers into concrete improves tensile strength, ductility, crack control ability, and shear strength of concrete beams. In this study, experiments on three high-strength steel fiber reinforced concrete(HSFRC) beams with 0.5 ~ 1.0 % volume fraction have been conducted to investigate the shear strength. The applicability of existing shear strength equations to HSFRC beams has been evaluated based on test results from both this experiment and previous researches, and an emperical equation for the evaluation of shear strength of HSFRC beams has been proposed. In addition, the portion of shear resistance by the uncracked compressive section of concrete has been obtained quantitatively, which led us to know the one by the cracked tensile section. Test results indicated that both of the initial diagonal cracking strength and the ultimate shear strength were increased as the compressive strength or the fiber volume fraction was increased. The portion of shear resistance by the uncracked compressive concrete section of HSFRC beams was measured approximately 20% on average. The proposed equation provided reasonably good estimation on the shear strengths of HSFRC beams examined in this paper.
갈경완(Karl, Kyoung-Wan),황진하(Hwang, Jin-Ha),이득행(Lee, Deuck-Hang),박현철(Park, Hyun-Chul),김강수(Kim, Kang-Su),최일섭(Choi, Il-Sup) 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.12
As social demand on the improved performance of concrete is consistently increased, the researches on fiber reinforced concrete have also been actively conducted till this moment. Especially, steel fibers are easy to produce, have homogeneous material properties, and can be easily mixed with concrete, on which many studies were forced. The steel fiber reinforced concrete(SFRC) has improved performance in tensile strength, crack control ability, and ductile failure modes, which leads to have the greater shear strength of flexural members. Most analysis or experimental studies on shear of SFRC beams, however, have been focussed on shear strength prediction, and few investigations on shear transfer mechanism of SFRC at crack surface is available. Thus, in this study, 15 SFRC direct shear specimens were fabricated and tested with primary parameters of compressive strength and steel fiber volume fraction. Based on the test results, the constitutive equations for shear behaviour of SFRC at crack surfaces were proposed, which showed good agreements to test results.
인공신경망을 이용한 강섬유보강콘크리트 보의 전단강도 예측
갈경완(Kal, Kyoung-Wan),이득행(Lee, Deuck-Hang),김강수(Kim, Kang Su) 한국구조물진단유지관리학회 2009 한국구조물진단학회 학술발표회논문집 Vol.2009 No.2
Steel fibers have recently been well recognized for good composite/strengthening materials, which also provide great improvement in shear strength. Consequently, many researchers proposed shear strength prediction models/equations, most of which, however, are based on regression analysis. This is because the shear mechanisms of steel fiber reinforced concrete(SFRC) members are very complicated. Neural network method is useful to predict the complicated shear strength of SFRC members, and is simpler and more accurate than regression analysis method. This paper, therefore, introduces the neural network approach and provides the prediction results of shear strength of 176 SFRC beams obtained from previous studies.