• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.388-393
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• 1996

This study evaluated characteristics and performance of recycled concrete as a pavement which was constructed on a low volume road. The recycled concrete was prepared by replacing a half of coarse aggregate with recycled aggregate. Natural sand from a source was used as fine aggregate together with admixtures such as plasticizer and fly ash (0.8% and 5% by wt. of cement, respectively). The length, thickness and width of the pavement were 100mm, 20cm and 3m, respectively. From construction experience, it was found that workability and finishability of the recycled concrete mixture were relatively poor, but strengths were satisfactory. Flexural strength, compressive strength and elastic modulus at 28 days were approximately 45Kg/$\textrm{cm}^2$, 250Kg/$\textrm{cm}^2$, and 240,000 Kg/$\textrm{cm}^2$, respectively. The pavement could be constructed by hand without much difficulty. The surface was finished smoothy by wet fabric and only minor cracks were found on the surface.

• 건설안전기술
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• 통권49호
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• pp.84-91
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• 2009

By bond mechanism between the prestressing strand and the concrete surrounding it, the effective force of prestressing must be transferred to the concrete entirely. The distance required to transfer the effective force of prestressing is called the transfer length, and the development length is the bond length required to anchor the strand as it resists external loads on the member. Transfer length was determined from the concrete strain profile at the level of the strands at transfer and development length was determined from various external loading lengths and compared with current code equation. Through the test results, bond failure is predicted based on the distress caused by cracks when they propagate within the transfer zone of prestressing strand. The current code equation was found to be conservative in comparison with the measured value.

• 한국농공학회지
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• 제30권1호
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• pp.63-72
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• 1988

The primary objective of the study was to find the deformation characteristics of reinforced polymer concrete beams. A test program was carried out to compare the behavior in deformation of polyester and MMA concrete beams with cement concrete beams but with varying ratios of tensile reinforcement. From the results the following conclusions can be made. 1.The various strengths of polymer concrete ware very high compared to the strengths for cement concrete. Also, compared to conventional concrete beams, flexural strength of reinforced polymer concrete beams was distinctly higher for the same section and steel ratios. 2.The polymer concrete beams exhibit large deflections accompanied by relatively high strengths as compared to cement concrete beams. 3.The average ultimate strain at the extreme compression fiber of polymer concrete beams was 0.01 1 cm / cm, and this value was about three to four times as large as that of cement concrete beams, 4.The polymer concrete beams developed more cracks which were more wide crack distribution spacing than the cement concrete beams, and the beams failed in a more ductile manner. 5.The reinforcing steel ratio has a significant effect on the beam strength, load-deflection response, stress-strain curve, and crack pattern of polymer concrete beams.

• Structural Engineering and Mechanics
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• 제6권2호
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• pp.161-172
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• 1998

Reinforced concrete beams possess variable flexural and torsional stiffnesses due to formation of cracks in the tension area along the beam. In order to check the stability of the beam, it is thus more appropriate to divide the beam into a finite number of segments for which mean stiffnesses and also bending moments are calculated. The stability analysis is further simplified, by using these mean values for each segment. In this paper, an algorithm for calculating the critical lateral buckling slenderness ratio for a definite load level, in a reinforced concrete beam without lateral support at the flanges, is presented. By using this ratio, the lateral buckling safety level of a slender beam may be checked or estimated.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.677-680
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• 2006

Tensile as well as flexural strengths of concrete can be substantially increased by introducing closely spaced fibers that would obstruct the propagation of microcracks, therefore delaying the onset of tension cracks and increasing the tensile strength of the material. Fibers of various shapes and sizes produced from steel, plastic, glass and natural materials are being used. In this study, we used cellulose chip fiber to decrease the shrinkage crack in mortar and concrete. Specially, we have studied the dispersion characteristic of cellulose chip fiber. As a result, it was assumed that the slurry type of cellulose chip fiber is very effective to disperse the fiber in mortar and concrete.

• 한국안전학회지
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• 제23권6호
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• pp.115-121
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• 2008

By bond mechanism between the prestressing strand and the concrete surrounding it, the effective force of prestressing must be transferred to the concrete entirely. The distance required to transfer the effective force of prestressing is called the transfer length, and the development length is the bond length required to anchor the strand as it resists external loads on the member. Transfer length was determined from the concrete strain profile at the level of the strands at transfer and development length was determined from various external loading lengths and compared with current code equation. Through the test results, bond failure is predicted based on the distress caused by cracks when they propagate within the transfer zone of prestressing strand. The current code equation was found to be conservative in comparison with the measured value.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.107-118
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• 2002

The purpose of this study is to investigate the strengthening effect of RC beams with carbon fiber grid. Carbon fiber grid that is very lightweight and stronger than steel reinforcement does not rust or corrode and has a very high resistance to salt. In this study, five real size specimens which are strengthened with different types of carbon fiber grid are tested. With the results of this tests, we found the physical and mechanical properties of carbon fiber grid and polymer mortar which are used to strengthen the damaged or cracked reinforcement concrete beams. we also investigate the strengthening effect of carbon fiber grid on the five flexural test specimens that have cracks.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.181-188
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• 2002

The objective of this study is to determine crack depth located under steel reinforcement in concrete specimens using ultrasonic method. Experimental studies were performed on concrete specimens containing vertical and inclined surface-opening cracks with known depths. The other studies were carried out on specimens with flexural crack. Experimental results have shown that the crack depth is effectually measured when the distance between the probes is less than the crack depth. The effect of steel on crack depth estimation is studied through a model by considering P-waves diffaction at the tip of crack and steel. In addition, experimental results show that the ultrasonic method is one of useful methods to evaluate the crack depth in reinforced concrete.

• 한국해양공학회지
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• 제21권6호
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• pp.107-114
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• 2007

The main aim of this study was to evaluate the bending and torsional behaviors of representative regular type cap beams in elevated guideway structures. A1/2 scale model copping beam, excluding the column portion, was designed, constructed, and tested. The copping beam was subjected to horizontal monotonic and cyclic loads with a constant vertical load over the loading stage. The damage was very much dominated by torsion. Experiment results showed that the spiral confinement in the beam helped to restrain the opening of torsional cracks in the column zone. Hence, the torsional strength of the cap beam contributesgreatly to the confinement conditions of the column.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.408-420
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• 2023

Beryllium oxide (BeO) is being re-emphasized and utilized in Micro Modular Reactors (MMR) because of its prominent nuclear and high temperature properties in recent years. The implications of the research about effects of neutron irradiation on the microstructure and properties of BeO are significant. This article comprehensively reviews the effects of neutron irradiation on BeO and proposes the maximum permissible neutron doses at different temperatures for BeO without cracks in appearance according to the data in the previous literature. This maximum permissible neutron dose value has important reference significance for the experimental study of BeO. The effects of neutron irradiation on the thermal conductivity and flexural strength of BeO are also discussed. In addition, microstructure evolution of irradiated BeO during post-irradiation annealing is summarized. This review article has important implications for the application of BeO in MMR.