• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.239-240
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• 2021

In this study, we conducted a study to evaluate the more accurate mechanical properties of concrete damaged by fire. In relation to this, in this study, the results of compressive strength and biaxial flexural strength were compared for concrete that received high temperature heat. As a result, both the compressive strength and the biaxial bending strength decreased as the heating temperature increased. As a result of examining the correlation between the compressive strength and the biaxial flexural strength, the biaxial flexural strength was smaller than the compressive strength.

• Land and Housing Review
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• v.2 no.1
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• pp.47-52
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• 2011

Recent advances of technology in materials science have made it easy to respond to user's needs on high performance steel in civil and building structures. The high-performance and high-strength steel are required for large scale structure and high-rise building to have high-strength, high fracture toughness and better weldability etc. Therefore development of 600MPa class steel for mega structure is necessary. high strength steels, however, may have mechanical properties that are significantly different from those of the conventional steels. The application of high-strength steels to building structures should be reviewed as to whether inelastic behavior equivalent to that of conventional steels can be attained or not. This study researched the structural behavior of high strength circular tubes compression and under flexure. Three column tests and three flexural tests were carried out. The suitability of existing design formulae(KBC 2009) and the structural behavior were investigated through these columns and beams with various types.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.481-488
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• 2010

Since existing constitutive models developed for confined normal strength concrete overestimate ductility when they are applied to confined high strength concrete, these models cannot be directly applied to confined high strength concrete. In an effort to solve this problem, an accurate stress-strain relationship of the hihg strength concrete needs to be formulated by examining the confinement effects due to increase of the concrete strength. In this study, a constitutive model is developed to express the stress-strain relationship of confined high strength concrete by carrying out regression analysis of the main parameters affection strength and ductile behavior of reinforced high strength concrete columns. Twenty-five test specimens were chosen from the reported experimental studies in the literature. The experimental results of stress-strain relationships of show a good agreement with results of the stress-strain relationships of suggested high strength concrete, covering a strength range between 60 and 124 MPa.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.165-170
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• 2008

New high strength bolts are required due to the development of the high strength steel, the ultra-thick steel plates, and the long-span bridge, though high strength bolts with tensile strength of 1,000 MPa are mainly used in construction site of every country. The high strength bolts are often subjected to a repeated tension-type of loading in which the fatigue failure is a major mode of failure. However, the theoretical and experimental study for the fatigue failure of tension bolt has not been well established in Korea. In this study, we performed a tensile fatigue test of F8T, F10T and F13T, F13T-N high strength bolts under tension. We proposed three fatigue strength specifications by performing 95% survival probability analysis for F8T, F10T, F13T, and F13T-N bolt under the $2{\times}10^6$ cycles of repeated loading. And the fatigue strength for the advanced screw thread shape bolt developed in this study are compared with the previous KS screw thread shape bolt.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.5
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• pp.827-831
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• 1994

Investigation on the extractability, Mg2+-, Ca2+ , EDTA-ATPase activity and solubility of actomyosin prepared from leg and breast muscle of silky fowol were as follows. The extractability of actomyosin in leg and breast muscle was 779mg/100g and 1, 318mg/100g respectively, breast muscle was higher than leg muscle . Mg2+-ATPase activity of actomyosin was high inionic strength 0.02-0.10 and Mg2+ATPase activity of low ionic strength was higher than high ionic strength not related to the part. Ca2+ ATPase activity was high in ionic strength 0.05-0.13, the activity of leg muscle was higher that breast muscle. And EDTA-ATPase activity showed low in low ionic strength and showed high in high ionic strength, and increased greatly depend ionic strength up to 0.4. The solubility of actomyosin was not different in leg and breast muscle , the solution started in KCI concentration of 0.3M and ended in DCI concentration of 0.4M.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.45-48
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• 2005

This study is basic experiment for estimating influence of strength by curing temperature of concrete's heat of hydration and estimate relationship of compressive strength development by initial curing temperature factor, and then asume temperature factor which influence compressive strength development and for showing basic document of qualify control. According to the result of cement mortar by the curing temperature factor high-curing temperature shows high strength on 3 day compare with low curing-temperature, shows higher strength than the piece of high curing temperature.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.37-40
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• 2005

Recently, in order to reduce the spalling of high strength concrete under fire, the addition of organic fibres to high strength concrete has been investigated. In this study, the effect of thermal characteristic of organic fibres on the spalling of high strength concrete was experimantally investigated. Two types of fibre, polypropylene(PP) and polyvinyl alcohol(PVA) fibres, were selected, and the strength level of concrete was correnponding to the design strength of 80MPa. As a result, it appears that when the remaining ratios(by weight) of fibre at 300$^{circ}C$ and 350$^{circ}C$ are less than 80$\%$ and 50$\%$, respectively, the spalling of high strength concrete is prevented.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.117-120
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• 2004

Up to now, many researches have been performed md verified that many properties of concrete can be improved by using mineral admixtures such as blast furnace slag, silica fume, and expansive admixture. But it is not clear whether there is any need for entraining air to make a high strength concrete using expansive admixture and mineral admixtures to insure enough freeze-thaw resistance. this paper presents the strength and durability properties of high strength concrete using expasive admixtures and industrial by-products. It was observed from the test results that very high strength concrete$(W/B=20\%)$ is not needed to be air entrained and high strength concrete$(W/B=30\%)$ using expansive admixture and mineral admixtures is needed to be entrained $2\~4\%$ air.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.115-116
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• 2013

Property of the compressive strength of high strength concrete was investigated in adiabatic temperature history considering hot-weather conditions. As a result, compressive strength of specimens subjected to high temperature history showed more than 120% at 3days of age compare to standard cured specimens. But, at 91days of age showed the incidence of strength less than 100%.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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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.