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PVA 및 PE 섬유를 하이브리드한 고인성 섬유보강 시멘트 복합체의 성능평가
이영오(Lee Young-Oh),전에스더(Jeon Esther),김선우(Kim Sun-Woo),윤현도(Yun Hyun-Do) 대한건축학회 2007 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.27 No.1
It is well-known that high performance fiber-reinforced cement composite (HPFRCCs) show multiple cracks, hardened state and a limited damage tolerance capability due to the debonding of the fibers of the cement matrix. Fiber is an important ingredient in high performance fiber-reinforced cementitious composite (HPFRCC), which can control fracture of cementitious composite by bridging action. The properties of reinforcing fiber, as tensile strength, aspect ratio and elastic modulus, have great effect on the fracture behavior of HPFRCC. Therefore, a variety of experiments have being performed to access the performance of HPFRCC recently. The research emphasis is on the mechanical properties of hybrid- HPFRCC made in Polyvinyl alcohol (PVA) and Polyethylene (PE) fibers, and how this affects the composite property, and ultimately its strain-hardening performance. Compressive, tensile, and four-point bending tests on hybrid-HPFRCC are carried out. As the results of the test, hybrid-HPFRCC showed high strength and ductility. Hybrid-HPFRCC was, also, superior to that of single fibers. On the other hand, effect of sand volume fraction on hybrid-HPFRCC was insignificant.
CFRP로 보강된 RC보의 AE 신호특성 및 이를 활용한 정량적 손상 평가
이영오(Lee Young-Oh),윤현도(Yun Hyun-Do),서수현(Seo Soo-Yeon) 대한건축학회 2007 大韓建築學會論文集 : 構造系 Vol.23 No.11
CFRP(Carbon Fiber Reinforced Polymer) has been widely used for reinforcement and rehabilitation of damaged concrete structure, and that offer many advantages when compared to conventional steel. Reinforced concrete structure reinforced with CFRP is difficult to estimate for damage, but characterization of acoustic emission (AE) can be demonstrated the micro damage that was not discovered from visual observation and it become known to an advantage that was discriminated from the existing nondestructive technique method. This study was investigated the evolution of fracture damage of reinforced concrete (RC) beams strengthened in flexure with CFRP sheets using AE technique, and developed an AE monitoring strategy that can determine the structural integrity of RC beams strengthened by external bonding of CFRP sheets. In order to analysis the acoustic emission signal of concrete beams reinforced with CFRP, a total of 4 specimens were tested under four point bending. CFRP is reinforced a bottom, side 40% and side 100% of specimen. And AE sensor is attached a side of specimen by triangle method. The aim of this study was to examine the emission of acoustic signals from four CFRP reinforced concrete beams at cracking, failure processes and the failure mechanism of specimens. The AE signal of the RC beams strengthened with CFRP was evaluated using the AE parameters, such as AE counts, amplitude, hits, duration time, amplitude/rise time and b-value. The two-dimensional AE source location was successful in measuring crack initiation and propagation in the RC beams strengthened with CFRP.
이영오 ( Lee Young-oh ),김선우 ( Kim Sun-woo ),윤현도 ( Yun Hyun-do ),김규용 ( Kim Kyu-young ),최경렬 ( Choi Kuyng-yuel ),강선종 ( Kang Sun-jong ),김대중 ( Kim Dae-jung ) 한국구조물진단유지관리공학회 2005 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.9 No.2
The use of recycled concrete is increasing faster than the development of appropriate design recommendations. This paper reports limited experimental data on lap splice performance of reinforced concrete beams with recycled aggregates. Reinforced concrete beams with natural aggregate and recycled aggregate were tested to evaluate their failure modes and lap splice characteristics. Based on the experimental results, reinforced concrete beams with recycled aggregates are about equal strength and failure mode with natural concrete beams.
골재크기에 따른 섬유보강 시멘트 복합체의 거동 및 파괴특성
이영오(Lee Young-Oh),윤현도(Yun Hyun-Do) 대한건축학회 2007 大韓建築學會論文集 : 構造系 Vol.23 No.12
Fiber is an important ingredient in ductile fiber-reinforced cementitious composite (DFRCC), which can control fracture of cementitious composite by bridging action. Also in compliance with the action of the fiber and the aggregate size, it showed a different failure mechanism. For practical application, it is needed to investigate the fractural behavior of the DFRCC and to understand the micro-mechanism of cement matrix with reinforcing fiber. In order to clarify characteristics of fracture process in the DFRCC, acoustic emission (AE) technique is carried out the analysis and evaluation of DFRCC damage by acoustic emission technique under flexural, compressive loadings. The AE signals were monitored by AMSY4 AE instrumentation during the entire loading period. All the specimens are reinforced with 1.5%(by volume) PVA(Polyvinyl alcohol) fiber, silica, 0.6, 1.2 and 2.5㎜ aggregates. The fiber was used PVA. The damage progress with a stress stage was divided four levels under monotonic loading. The test results showed that the damage progress of the DFRCC was characteristic for the aggregate size. As a result of analyzing the felicity ratio (FR) values, it is shown that this values can be used for evaluating the degree of DFRCC damage. On the whole the felicity ratio values of DFRCC is shown between 0.7 and 0.9. And, the AE kaiser effect was existed in the all DFRCC. Also, the damage behavior and the microscopic fracture process of the DFRCC was evaluated using the AE parameters, such as hits, frequency, amplitude and felicity ratio. From the AE parameters, fracture process of the DFRCC was evaluated from the AE characteristic.
순환골재의 종류에 따른 철근콘크리트 보의 전단성능 평가
이영오(Lee Young-Oh),장광수(Jang Gwang-Su),윤현도(Yun Hyun-Do),최기선(Choi Ki-Sun),유영찬(You Young-Chan),김긍환(Kim Keung-Hwan) 대한건축학회 2009 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.29 No.1(구조계)
The construction of buildings and highway bridges has been increasing from the beginning of the past century. These infrastructures need to be replaced or repaired because their end of service life is reached or the original design no longer satisfies the needs dues to the growth in population. Large volumes of aggregates are required to rebuild and demolition wastes are generated. Recycling of waste concrete by converting not only saves landfill space but also reduces the demand for extraction of natural raw material for new construction activity. Various investigations have been carried out to study the mechanical properties of concrete and the structure behavior (under flexure condition, shear, bond, torsion, etc.) with recycled aggregates. However, few investigations have been carried out to study the shear behaviors with recycled aggregates such as low absorption of recycled aggregate and full-scale specimens. The aim of this study is to investigate the shear behavior in the reinforced concrete beams with replacement level of recycled aggregates. The correlation of experimental results with code predictions is essential in order to check the applicability of current design provisions for recycled concrete beams. In this study, eight reinforced concrete beams were tested to evaluate the effects of failure modes, shear strength, and shear behavior on the replacement level (0, 30, 60, and 100%) of recycled aggregate.