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ECC로 보강한 조적벽체의 전단성능에 관한 실험적 연구
배백일(Bae Baek-Il),박병규(Park Byung-Kyu),최현기(Choi Hyun-Ki),최창식(Choi Chang-Sik) 대한건축학회 2009 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.29 No.1(구조계)
In order to performing remodeling or change the usage of building, URM walls which used commonly in apartment as non-structural element need to have reliable performance of buildings because removal of this types of wall could make more wastes in construction site and removal procedure may cause delay of construction. Using normal shotcrete, as retrofitting method, cannot improve ductility and may cause brittle failure of structure. However, recent study for new materials, such as ECC or UHPC, can solve these problems increasing ductility and toughness of retrofitting materials. In this study, we used sprayed ECCs for retrofitting URM wall. ECCs can be designed to work in conjunction with existing walls to increase both strength and ductility for in-plane behavior of the URM wall. And this may change non-structural masonry wall to structural wall. To ensure that this technique will perform its intended purpose, in-plane lateral loading test was performed. The results of lateral load test of two retrofitted URM compared to non-retrofitted one. Retrofitted walls are consisted of just sprayed and anchored to wall base, RTM-ECC and have wiremesh, same detail of others, RTM-ECC-WM. Retrofitted specimens show significant increase of strength, ductility and energy dissipation capacity compared to URM. RTM-ECC show stiff strength degradation however, RTM-ECC-WM show slow degradation of strength because of the load transferring effect of wiremesh.
전단철근으로 보강되지 않은 강섬유보강 초고강도콘크리트의 전단강도에 대한 실험적 연구
배백일(Bae, Baek-Il),최현기(Choi, Hyun-Ki),최창식(Choi, Chang-Sik) 대한건축학회 2017 大韓建築學會論文集 : 構造系 Vol.33 No.3
In this study, fiber reinforced ultra high strength concrete beams were tested defining the shear behavior of fiber reinforced ultra high strength concrete and evaluating the previously suggested equations for shear strength of concrete members. The main variables of test are compressive strength of concrete(100, 200 MPa), volume fraction of steel fiber(0, 2%), shear-span to depth ratio(3.4, 2.0). According to the test results, specimens without fiber experienced the abrupt shear failure. In the case of fiber reinforced specimen with shear span ratio of 3.4, failure mode of test specimen is changed into flexural failure. And specimen with shear span ratio 2.0 experienced shear-compression failure mode. However, shear strength increase caused by the increase of compressive strength of concrete is not higher than effect of steel fiber inclusion. In order to make safe design of fiber reinforced ultra high strength concrete under shear, shear strength estimation equations are evaluated. Comparing estimated value with test results, shear strength contribution of matrix is over-estimated and shear strength contribution of steel fiber is under-estimated. Among all equations, equation of AFGC-Setra is most accurate.
배백일,손종민,최창식,최현기,Bae, Baek-Il,Son, Jong-Min,Choi, Chang-Sik,Choi, Hyun-Ki 대한건축학회 2012 대한건축학회논문집 Vol.28 No.5
In this study, experiments on ultra-high-strength steel fiber reinforced concrete beams with 2% volume fraction of steel fiber had been conducted. Test was conducted by two point loading with 2,000kN actuator for slender beam specimen. Shear-span to depth ratio was 6 intending the flexural failure. For the flexural design of ultra-high strength fiber reinforced concrete member an empirical equation had been proposed. Improving accuracy of empirical equation, 9 possible stress distributions for concrete section was compared with test results. For the reliability of empirical equation, these models were compared with experiment results conducted with previous researches. As a results of comparative study, the most exact solution was the model that use the real stress distribution of ultra-high strength fiber reinforced concrete. However, more safer prediction was possible using stress block parameters that was proposed by the study results of ultra-high strength concrete and tensile stress distribution that was considered the debonding properties of fiber.
이음된 초고강도 강섬유보강콘크리트 보의 휨강도에 관한 실험적 연구
배백일 ( Baek-il Bae ),손동희 ( Dong-hee Son ),최현기 ( Hyun-ki Choi ),정형석 ( Hyung-suk Jung ),최창식 ( Chang-sik Choi ) 한국구조물진단유지관리공학회 2021 한국구조물진단유지관리공학회 논문집 Vol.25 No.6
본 연구에서는 이음된 초고강도 강섬유보강콘크리트 부재의 휨거동을 검토하고, 현행설계기준의 초고강도 강섬유보강콘크리트 구조물의 이음 설계에 대한 안전성을 평가하기 위해 총 6개의 보에 대한 가력 실험을 수행하였다. 주요 변수는 섬유의 혼입여부와 이음 길이로 설정하였다. 혼입된 섬유는 강섬유로 2%의 부피비로 결정하였으며, 이음길이는 8db와 16db로 결정하여 실험체를 제작하였다. 실험 결과 섬유로 보강되지 않은 실험체들은 이음부에서 급격한 하중지지능력을 상실하고 철근의 항복을 경험하지 못하였으나, 섬유로 보강된 경우 16db의 이음길이가 확보되면 주인장철근의 항복을 경험할 수 있으며, 적절한 휨강도를 발현할 수 있는 것으로 나타났다. 본 연구의 실험결과를 바탕으로 현행설계기준 및 초고강도콘크리트 구조설계지침의 이음길이 산정식들을 검토한 결과 모두 보수적인 평가를 하고 있는 것으로 나타났다. This study examines the bending behavior of lap-spliced ultra-high-strength fiber-reinforced concrete members and evaluates the safety of the design codes for ultra-high-strength fiber-reinforced concrete structures. An experiment on a total of six beams was performed. The main variables were the fiber-inclusion and the lap-spliced length at the center of the beams. The steel fibers in a volume fraction of 2% were used, and the lap-splice lengths were determined to be 8db and 16db. As a result of the test, the specimens not reinforced with fiber lost abrupt load-bearing capacity at the lap region and did not experience yielding of the reinforcing bar. In the case of fiber-reinforced concrete, if a lap-splice length of 16db is secured, the yielding of the main reinforcing bar can be experienced, and appropriate flexural strength can be expressed. Based on the experimental results of this study, as a result of reviewing the lap-splice length calculation formulas of the current design standards and the ultra-high-strength concrete structural design recommendations, it was found that all of them were evaluated conservatively.
철근콘크리트 부재의 전단강도 크기효과에 대한 강섬유 보강 효과
배백일 ( Bae Baek-il ),최창식 ( Choi Chang-sik ) 한국구조물진단유지관리공학회 2023 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.27 No.1
철근콘크리트 대형부재의 전단강도 산정에 있어서 크기효과의 영향을 검토하고, 강섬유의 크기효과에 미치는 영향을 검토하기 위하여 깊이가 950mm 인 부재에 대한 가력 실험을 수행하였다. 강섬유로 보강되지 않은 실험체와 강섬유로 보강된 실험체에 대한 4점 가력 실험 결과 강섬유로 보강하지 않은 보의 경우 KDS와 ACI 의 설계기준에 의거하여 계산한 공칭전단 강도에 도달하지 않는 것을 확인하였으며, 강섬유로 보강한 경우 ACI544에서 권고한 설계식을 적용한 경우의 설계강도에 비해 높은 강도를 나타내는 것을 확인할 수 있었다.
배백일(Bae Baek-Il),손종민(Son Jong-Min),최창식(Choi Chang-Sik),최현기(Choi Hyun-Ki) 대한건축학회 2012 大韓建築學會論文集 : 構造系 Vol.28 No.5
In this study, experiments on ultra-high-strength steel fiber reinforced concrete beams with 2% volume fraction of steel fiber had been conducted. Test was conducted by two point loading with 2,000kN actuator for slender beam specimen. Shear-span to depth ratio was 6 intending the flexural failure. For the flexural design of ultra-high strength fiber reinforced concrete member an empirical equation had been proposed. Improving accuracy of empirical equation, 9 possible stress distributions for concrete section was compared with test results. For the reliability of empirical equation, these models were compared with experiment results conducted with previous researches. As a results of comparative study, the most exact solution was the model that use the real stress distribution of ultra-high strength fiber reinforced concrete. However, more safer prediction was possible using stress block parameters that was proposed by the study results of ultra-high strength concrete and tensile stress distribution that was considered the debonding properties of fiber.