• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.613-620
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• 2013

Concrete has been recognized as a material which is resistant to high temperatures, but chemicophysical property of concrete is changed by the high temperature. So, mechanical properties of concrete may be reduced. Because of this, standards and researches on the degradation of the mechanical properties of concrete at high temperatures have been presented. However, research data about the state that considering the loading condition and high-strength concrete is not much. Therefore, this study evaluated the high-temperature properties of high-strength concrete by loading condition and elevated temperature. The stress-strain, strain at peak stress, compressive strength, elastic modulus, thermal strain and the transient creep are evaluated under the non-loading and $0.25f_{cu}$ loading conditions on high strength concrete of W/B 12.5%, 14.5% and 20%. Result of the experiment, decrease in compressive strength due to high temperature becomes larger as the compressive strength increases, and residual rate of elastic modulus and compressive strength is high by the shrinkage caused by loading and thermal expansion due to high temperature are offset from each other, at a temperature above $500^{\circ}C$.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.97-104
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• 2010

The materials failure relation $\ddot{\Omega}=A{(\dot{\Omega})}^\alpha$ where $\Omega$ is a measurable quantity such as displacement and the dot superscript is the time derivative, may be used to analyze the accelerating creep of materials. Coefficients, A and $\alpha$, are determined by fitting given data sets. In this study, it is tried to predict the failure time of tunnel using the materials failure relation. Four fitting techniques of applying the materials failure relation are attempted to forecast a failure time. Log velocity versus log acceleration technique, log time versus log velocity technique, inverse velocity technique are based on the linear least squares fits and non-linear least squares technique utilizes the Levenberg-Marquardt algorithm. Since the log velocity versus log acceleration technique utilizes a logarithmic representation of the materials failure relation, it indicates the suitability of the materials failure relation applied to predict a failure time of tunnel. A linear correlation between log velocity and log acceleration appears satisfactory(R=0.84) and this represents that the materials failure relation is a suitable model for predicting a failure time of tunnel. Through comparing the real failure time of tunnel with the predicted failure times from four curve fittings, it is shown that the log time versus log velocity technique results in the best prediction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.91-97
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• 2016

Evaluation on the test of actual concrete member to confirm the fire resistance of the concrete member using ultra-high strength concrete is required. However, test equipment which has large loading capacity is needed to the actual member experiment. So, many researchers evaluated the fire performance through analytical studies using the material models. This study experimentally evaluated strain properties on ultra-high-strength concrete of 80, 130 and 180 MPa with heating and examined to apply the existing strain model about ultra-high-strength concrete. As a results, constants are drawn by method of least squares applying experimental values and calculated values by the existing strain model, it proposed strain model that can be applied to ultra-high-strength concrete.

• Journal of Korean Society of Forest Science
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• v.61 no.1
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• pp.45-52
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• 1983

This study was carried out to find the effect of heat treatment on the pitch content and the properties of the kraft pulp produced from Pinus koraiensis. In the results of this experiments, the heat treatment with $40^{\circ}C$ showed the best result in the yields and the pitch contents of kraft pulp of the woods from both artificial and natural stands. Other properties, however, were not improved. They were rather deteriorated with heat treatment. Therefore, it needs to select, the heat treatment conditions according to the properties of raw material, the pulping methods and the final use of pulp.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.194-202
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• 1996

Hot melt adhesive based on the polyamide resin was studied to improve the conventional hot melt adhesives such as ethylene-vinyl acetate which have inherent problems against creep and heat resistance. It was found that the terpolymer of nylons6, nylon66, and nylon12 or the nylon blend instead of nylon homopolymer was suitable base resin for hot melt adhesives, since the disruption of regularity in the polymer chains reduced the crystallinity, resulting in lower melting point and melt viscosity. Also, the rheological properties of the polyamide based hot melt adhesive could be controlled by the incorporation of terpene resin, butyl benzyl phthalate, and paraffin wax. The results of melt viscosities and tensile properties of adhesive itself indicated that the optimum adhesion properties could be obtained through the blending of CM831/843P resins with weight ratio 75/25~50/50. The adhesion between steel and steel was tested by using lap shear geometry. It was found that the surface roughness of steel affected the adhesion strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.253-256
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• 2008

Although researches on the beams strengthened with Fiber reinforced Polymers (FRPs) have recently been conducted around the world, there are few researches on the beams with FRPs under a sustained load. This paper presents the behavior of the beams with Carbon Fiber Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) under a sustained load during 300 days. Strains of steel and FRP reinforcement were measured in order to investigate the behavior of the beams. Additionally, Adjusted Effective Modulus Method (AEMM) and Ghali and Farve's method were used to predict increase in the stress and strain caused by creep and shrinkage. Through the experiment, it was found that the beam with CFRP is more effective than the beam with GFRP in terms of flexural strengthening. Compared with analytical results, it was indicated that strains of tension steels were overestimated, whereas strains of compression steels were underestimated.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.615-625
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• 2014

Excessive long-term slab deflection caused by construction load is a critical issue for the design of concrete slabs, as long span flat plates become popular for tall buildings. In the present study, the effect of construction load causing early slab cracking on the long-term deflection was theoretically studied. On the basis of the result, a numerical analysis method was developed to predict the long-term deflection of flat plates. In the proposed method, immediate deflection due to slab cracking and long-term effect of creep and shrinkage were considered. To verify the construction load effect, long-term slab deflections were measured in actual flat plate buildings under construction. The results showed that the immediate deflection due to the construction load increased significantly the long-term deflection. The proposed method was used to predict the deflections of the buildings. The results were compared with the measurement results. The predictions agree well with the long-term deflections of flat plate affected by construction load.

• Korean Journal of Poultry Science
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• v.4 no.1
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• pp.66-74
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• 1977

닭의 혈액상에 관한 발표는 많으나 아직 우리나라에서의 보고는 거의 없다. 이에 산난능력이 우수한 닭과 병계에 대한 앞으로의 혈액학적 연구를 위한 기초적자료를 얻고저 임상적으로 건강한 소위 한국 재내종(LCH)과 백색레그혼 (WLH)암탉의 정상 혈액학치 즉 적혈구, 백혈구, 혈색소, 헤마토크리프. 평균적혈구 용적, 평균 적혈구 혈색소량. 평균 적혈구 혈색소 농도 등을 조사하였다. 1 R.B.C.는 L.C.H.에서 3.18$\pm$0.10million per c$\mu$. mm였으며 W.L.H.는 3.23$\pm$0.05였다. 2. W.B.C.는 L.C.H에서 42.17$\pm$3.35, thousand per. c$\mu$mm였으며 W.L.H.는 35.64$\pm$2.89였다. 3. Hemoglobin치는 L.C.H.에서 11.24$\pm$0.30gm per 100$m\ell$였으며 WL.H.는 38.40$\pm$0.75였다. 4. Hematocrit치는 L.C.H.에서 34.00$\pm$0,98 percent였으며, W.L.H.는 33.40$\pm$0.75였다. 5. M.C.V.는 L.C.H에서 103.66$\pm$1.22 c$\mu$ 였으며, W.L.H.는 103.32$\pm$1.28이였다. 6. M.C.H,는 C.L.H.에서 34.19$\pm$0.41 $\mu$ $\mu\textrm{g}$9였으며. W.L.H,는 34.37$\pm$0.31이었다. 7. M.C.H.C는 L.C.H.에서 33.09$\pm$0.22 percent였으며, W.L.H.는 33.25$\pm$0.36 0.36이었다. (중략)

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.429-438
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• 2013

An object oriented numerical analysis program of axial-flexural elements and the step-by-step method (SSM) has been developed to analyze concrete long-term behaviors of structures constrained internally and externally. The results of the numerical analysis for simple and continuous prestressed (PS) concrete box and composite girders, pre-cast slab of continuous steel composite girder, and simple preflex composite girder show that the adjusting coefficient decreases by increasing constraint. The loss rates of pre-tension force were not sensitive but those of pre-compression force were increased rapidly by decreasing adjusting coefficient. This indicates that the design based on the loss rate of pre-tension can over-estimate the pre-compression force in a concrete section constrained internally and externally. The adjusting coefficients which satisfy results of the numerical analysis are 0.35~0.95, and it can be used as an index of constraint of concrete long-term deformation. The adjusting coefficient 0.5 of Bridge Design Specifications can under-estimate residual stress of PS concrete slab, and the coefficient 0.7 or 0.8 of LRFD Bridge Designing Specifications can under-estimate the loss rates of continuous PS concrete girders. The adjusting coefficient of hybrid structures should be less then 0.4.

• Journal of the Korean Institute of Gas
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• v.14 no.1
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• pp.47-54
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• 2010

In order to reduce the number of installation processes and the cost, a unified ball valve and polyethylene-steel pipe is proposed and tested. An integrated design approach is carried out such that a virtual manufacturing based on finite-element analysis is first performed in order to examine contact conditions under exaggerated temperature variations (${\Delta}T\;=\;60^{\circ}C$ and $-50^{\circ}C$ for summer and winter, respectively). From the final design configuration, it was predicted that the maximum contact pressures are 71 and 8.1 MPa for summer and winter, respectively, at relatively larger contact surface. Based on this observation, a prototype model is fabricated to go through an actual leakage test. The prototype pipe passed a hydrostatic strength test successfully, showing no leakage at even much higher (54 MPa) than the operational pressure (0.25 MPa).