• Advances in concrete construction
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• 제4권3호
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• pp.161-172
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• 2016

An experimental investigation was carried out on the strength and behavior plain and fiber reinforced geopolymer concrete beam column joints and the results were compared with plain and steel fiber reinforced conventional concrete beam column joints. The volume fraction of fibers used was 0.5%. A total of six Geopolymer concrete joints and four conventional concrete joints were cast and tested under reversed cyclic loading to evaluate the performance of the joints. First crack load, ultimate load, energy absorption capacity, energy dissipation capacity stiffness degradation and moment-curvature relation were evaluated from the test results. The comparison of test results revealed that the strength and behavior of plain and fiber reinforced geopolymer concrete beam column joints are marginally better than corresponding conventional concrete beam column joints.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.231-236
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• 2001

A newly developed Advanced Indentation System (AIS), which is a portable and nondestructive system for evaluating tensile properties, was used to measure mechanical behavior of materials used under high temperature and pressure conditions. This test measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation and fracture. Aging effects of Cr-Mo and Cr-Mo-V steel at high temperature were simulated. Tensile properties including yield strength and tensile strength at various temperature are obtained from the test. For all test materials and conditions, the AIS-derived results were in good agreement with those from conventional standard test method. Examples of the test results ate given and potential applications of the AIS to assess the integrity of aging structures are briefly discussed.

• 한국의류학회지
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• 제20권5호
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• pp.905-914
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• 1996

To study the effect of the bleaching agents in detergents on the degradation of cotton fabrics, the carboxyl contents, copper numbers, degree of polymerization, the change of tensile strengths and fiber surfaces of cotton fabric before and after washing were examined. The results obtained were as follows: As the cycles and temperature of washing increased, the carboxyl content of washed cotton fabric changed little but the copper unmber of cotton fabric was increased. At 6$0^{\circ}C$ , 8$0^{\circ}C$ the copper number of cotton fabric washed with soidum perborate (PB) was higher than that of with sodium percarbonate (PC). The degree of polymeriazation and tensile strength of cotton fabric were decreased and at higher temperature those were more decreased but were less decreased when tetraacetyehylenediamine (TAED) was added. The degree of polymerization had negative relation with copper unmber but with tensile strength of cotton fabric had positive relation. Cotton fiber surface was more degraded by bleaching agents and hydrogen peroxide exhaustion was increased as the temperature of washing increased. And hydrogen peroxide exhaustion had negative relation with the degree of polymerization.

• 한국식품영양과학회지
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• 제28권2호
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• pp.417-422
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• 1999

Algin and chitosan are known as biodegradable natural polymers. PVA is useful for the production of water soluble packaging, paper, textile sizes. PVA/Algin and PVA/chitosan films were prepared by solution blends method in the weight ratio of chitosan, algin for the purpose of useful biodegradable films. Thermal and mechanical properties of blend films such as DSC, impact strength, tensile strength and morphology by SEM were determined. As a result, The ratio of 10.0wt% PVA/chitosan films were similar to PVA at thermal and mechanical properties. PVA/Algin films were found that phase separation was occured as more than 25wt% increasing the blend ratio of algin. PVA/Algin films were observed to be less partially compatibility than 10wt% increasing the blend ratio of algin by DSC, mechanical properties and SEM. Blend films were completely degraded pH 4.0 better than 7.0, 10.0 in the buffer solution. Also, they were rapidly degraded in the enzyme( glucosidase) solution better than pH solution by enzymolysis.

• 한국수소및신에너지학회논문집
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• 제10권2호
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• pp.81-89
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• 1999

Various characteristics - mechanical propertis, thermal cyclic hydriding characteristics and resistance to degradation by $H_2O$, CO in hydrogen - of hydrogen storage alloy powder compacts using PTFE and silicon sealant as a polymer binder were studied. Diametral tensile strength of 10wt% PTFE and 5wt% silicon sealant added compacts showed relatively high value of $4kg/cm^2$ and $10kg/cm^2$, respectively. Compacts show a good resistance to degradation by $H_2O$ in hydrogen. But hydrogen absorption rate and capacity of compacts were decreased by CO in hydrogen with the number of cycles. Cu coated and PTFE bonded compacts showed very small decrease of capacity and a good strength even after 1000 cycles of thermal hydriding and dehydriding.

• Structural Engineering and Mechanics
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• 제54권6호
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• pp.1111-1133
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• 2015

Rebar corrosion in concrete is one of the main causes of reduction of service life of reinforced concrete buildings. This paper presents the influence of rebar corrosion on the structural behavior of reinforced concrete (RC) buildings subjected to strong earthquake ground motion. Different levels of rebar corrosion scenarios were applied on a typical four story RC frame. The deteriorated conditions as a result of these scenarios include loss in cross-sectional area and loss of mechanical properties of the reinforcement bars, loss in bond strength, and loss in concrete strength and its modulus of elasticity. Dynamic analyses of the frame with different corrosion scenarios are performed with selected strong earthquake ground motion records. The influences of degradation in both concrete and reinforcement on structural behavior are investigated by comparing the various parameters of the frame under different corrosion scenarios with respect to each other. The results show that the progressive deterioration of the frame due to rebar corrosion causes serious structural behavior changes such as change in failure mode. The intensity, propagation time, and extensity of rebar corrosion have very important effects on the level of degradation of steel and concrete, as well as on the earthquake behavior of the structure.

• 대한전기학회논문지
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• 제41권7호
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• pp.802-808
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• 1992

To investigate degradation procedure and life time of the oxidized PE and the unoxidized PE, alternative voltage is applied to the CIGRE Method-II (CM-II) electrode system, which is loaded artificial void, and measures the distribution of partial discharging generation. From the results, the samples etched by oxidation had wide degradation area of dielectric strength. Furthermore, discharge starting voltage was shifted to low voltage, the discharge generation frequency was high and consequently, the quantity of mean charge becomes small. Also, life time of the oxdized sample is shortened according as the oxidation time is longer.

• 대한의용생체공학회:의공학회지
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• 제16권1호
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• pp.57-60
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• 1995

To develop an artificial bone substitute that is gradually degraded and replaced by the regenerated natural bone, the authors designed and produced a composite that is consisted of calcium phosphate and collagen. Human umbilical cord origin pepsin treated type I atelocollagen was used as the structural matrix, by which sintered or non-sintered carbonate apatite was encapsulated to form an inorganic-organic composite. With cross linking atelocollagen by UV ray irradiation, the resistance to both compressive and tensile strength was increased. Collagen degradation by the collagenase induced collagenolysis was also decreased.

• 한국안전학회지
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• 제16권2호
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• pp.27-35
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• 2001

For the purpose of healing the degradation part, $CO_2$ laser beam was irradiated with different irradiation condition (porer, diameter, velocity and beam type) to find out optimum irradiation condition. The test series of hardness, residual stress measurement, and fatigue were carried out after the irradiation. Experimental results show that micro-hardness values on the surface of the irradiated specimens m approximately 2.5 times higher than those of un-irradiated ones. Fatigue tests show that the fatigue life was improved by the compressive residual stress after laser beam irradiation. However, some specimens with different conditions show the shorter fatigue life. It means that laser beam irradiation with optimum irradiation condition and optimum absorb energy, Q can improve the fatigue strength.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall
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• pp.343-350
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• 1999

The purpose of this study is to compare the response of the high-strength concrete beam-column-slab subassembly with the response of a normal-strength concrete specimens. Four assemblies were designed 2/3 scale beam-column-slab joint(fc'=240kg/cm2 fc'=700kg/cm2) and tested to investigate seismic behaviour. From the test results 1) flexral cracks emerge to inside of bean deeply for high strength concrete member 2) the high-strength specimens represented stable hysteretic behaviour for the displacement ductility 5.5 but degradation in stiffness and strength and unstable hysteretic behaviors were observed owing to the brittleness of high-strength concrete beyond its range.