• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.239-244
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• 1999

The reduction phenomena of the compressive strength of concrete with respect to the size of specimens have been extensively investigated. However, adequate analysis technique have not been developed until now. Existing researches have shown that the larger member size, the smaller the strength. This indicated the necessity of nonlinear fracture mechanics theory in order to analyze the fracture behaviors of concrete. The are some models that predict the size effect of compressive strength of cylindrical specimens. Theses equations, however, are developed not considering the difference of fracturing mechanism which depends on both geometry of specimen and the strength level of concrete. In this paper, a model to predict compressive strength of cylindrical concrete specimens with respect to diameters, h/d ratios, and the strength level of concrete, is suggested. For this purpose, theoretical and statistical analyses are conducted. Experimental constants used in the model of new size effect are formulated in terms of strength levels of concrete based on existing experimental data.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.220-225
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• 1993

This paper is an experimental study on shear capacity of the high strength lightweight reinforced concrete beams with shear-depth ratio between 1.5 and 2.5. Thirteen T & rectangular beams were tested to determine their diagonal cracking and ultimate shear capacity. The major variables are shear span-depth ratio (a/d=1.5, 2.0, 2.5), concrete compressive strength(f'c=210, 24., 270㎏/㎠) and tensile steel ratio( =0.6, 1.2%). Based on results obtained from experiment of high strength lightweight reinforced concrete Beam & normal concrete, the following conclusions were drawn. (1) The shear capacity of high-strength lightweight concrete is less 15% than that of normal concrete under same condition. (2) As the results of Comparing this experimental datas with other various formulas. It is regarded that ACI 318-89 shear strength formula related tensile strength is proper to design formula of shear strength of high-strength lightweight reinforced concrete using lightweight concrete.

• Advances in concrete construction
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• 제5권2호
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• pp.173-182
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• 2017

This paper is aimed at determining the shear and impact strength of waste plastic fibre reinforced concrete. M30 grade of concrete is prepared with waste plastic door fibres cut into 5 mm width and aspect ratios of 30, 50, 70, 90 and 110. Fibres are used in a volume fraction of 0 to 1.5% with an increment of 0.25%. L shaped specimens are cast for shear strength tests and flat plates of size $250{\times}250{\times}30mm$ are used for impact tests. "Drop ball method" is used for checking the impact strength. Shear strength is checked with L shaped specimens under UTM with a special attachment. It was found that up to 1.25% of waste plastic fibres can be effectively used for better strength of concrete both in shear and impact. Shear and impact strength were found to be increasing up to a volume fraction of fibres of 1.25%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.399-404
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• 2000

This paper are the mechanical characteristics of eccentrically loaded normal strength and high strength reinforced concrete columns based on the test results. The columns are $120\times120$mmat the mid-section and are haunched at the ends to apply the eccentric loading and prevent premature failure. Variables are concrete strengths(361, 672, 974 kgf/$\textrm{cm}^2$), $\textrm{cm}^2$longitudinal reinforcement ratios (1.98, 3.54, 1 5.53%), spacing of lateral reinforcement (30, 60, 120mm), and eccentricities (24, 40mm). As a results, the main conclusions obtained from the comparison and analysis for the strength tendency, deformation and ductility of high strength reinforced concrete columns with variables are as follows; As the concrete compressive strength concrete and lateral reinforcement increases, the ductility index of high strength reinforced concrete columns decrease, but it increase with the increase of eccentricity and longitudinal reinforcement ratio. The confinement ratio must be greater than 20 percent in order for the level of ductility between high strength reinforced concrete columns and normal strength reinforced concrete columns to be almost equal.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.763-770
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• 1998

This paper deals with evaluation of bending fatigue strength in SCM415 carburized spur gears. The constant stress amplitude fatigue test is performed by using an electrohydraulic servo-controlled pulsating tester. The S-N curves are obtained and the enhanvement of fatigue strength due to carburized treatment is clarified. In this study the improvement of fatigue strength is assumed to be caused by an increase of both hardness and residual stress and experimental formula has been proposed for the estimation of bending fatigue strength of carburized gears. The effect of surface conditions on the fatigue strength is evaluated quantitatively and it is close to the relative surface condition factor used in the ISO strength rating formula.

• 펄프종이기술
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• 제29권1호
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• pp.7-12
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• 1997

This study was intended to investigate the proper shape and size of calcium carbonate for the improvement of paper properties and its end use performance. We loaded calcium carbonate of various shapes and size in the handsheet and measured their physical and optical properties. Results obtained from the study are summarized as follows : 1. Due to different particle shapes and sizes, precipitated calcium carbonate (PCC) contributed greater to bulk improvement than ground calcium carbonate (GCC). Scalenohedral form of PCC produced the bulkiest sheet, GCC made the sheet bulkier as average particle size increases. 2. Tensile strength increased as average particle size was increasing. GCC kept tensile strength more effectively than PCC. The effect of particle size on tensile strength was much more pronounced as filler addition level was increasing. 3. Over the average particle size of 6.99$\mu$m, GCC gave much higher burst strength and internal bond than PCC did. In the filler levels of 20% and 30%, GCC by using bigger size fillers showed 50~100% improvement in some cases than PCC at the same filler content. 4. Tear strength increased as average particle size was increasing. At the filler level of 30%, PCC decreased tear greatly. 5. Over the average particle size of 13.56$\mu$m, GCC kept bending stiffness greater than PCC. Due to its shape, Scalenohedral form of PCC showed higher stiffness than others at the same particle size. 6. Cubic and acicular form of PCC improved light scattering coefficient very effectively. Light scattering coefficient of GCC decreased as average particle size increased. 7. Both of particle shape and size of filler were important factor in developing optical properties and bending stiffness. Particle size was the only important factor in developing other strength properties

• 펄프종이기술
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• 제29권4호
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• pp.36-44
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• 1997

This experiment was mainly performed with a mechanical treatment using ultrasound. We got the following conclusions : At seven minutes-ultrasonic treatment using nonionic surfactant, yield, brightness and residual ink contents were superior to other treatment, but several strength properties were decreased. On the other hand anionic surfactant was considerably low ink removal efficiency. For ultrasonic treatment using nonionic surfactant, yield and brightness were dropped when temperature was over 4$0^{\circ}C$, but were observed to be insensitive to the pulp consistency and flotation time. In the case of nonionic surfactant, tensile and burst strength were improved when ultrasonic treatment was used comparing to non-treatment, and nonionic surfactant was generally better than anionic surfactant in terms of tensile and burst strength regardless of ultrasound conditions. Several properties were decreased when anionic surfactant was used in comparison with nonionic surfactant except yield, therefore, anionic surfactant. was not proper to be used in this condition.

• 펄프종이기술
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• 제40권3호
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• pp.9-14
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• 2008

Agar-agar extracted from red algae was used as a surface sizing material for paper after filtering, bleaching, and viscosity adjustment by oxidative depolymerization. Oxidized starches from corn and tapioca were compared to agar-based surface size in the respects of paper surface modification, strength improvement, and printability. Agar-based surface size showed high strength improvement and good printability as much as starch-based ones except film forming ability, which may be improved by adding additives, and demonstrated its great potential to be used as inexpensive and high quality surface size in future.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
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• pp.152-153
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• 2015

Recently, solar energy generation is one of the fastest growing industries for eco-friendly energy. Every year, solar energy generation industry grows to 42% on average. However, polysilicon sludge is generated from processing of polysilicon but, there is nothing to handle that. Therefore, we need research to recycle polysilicon sludge. Also, improved fire resistance efficiency of wall is required according to reinforced fire safety standards due to many cases of big fires in our country. This study focuses on density and strength properties according to the addition ratio of paper Ash for the lightweight composite panel core with polysilicon sludge. As a result of the test, adding paper ash 9% has the best density and strength properties.

• 펄프종이기술
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• 제33권3호
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• pp.44-51
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• 2001

Sedimentation characteristics such as SS, $BOD_5$, COD removal efficiency of waste water in the toilet paper mill using milk carton were examined. Optimum dosage of coagulant, rapid mixing time and slow mixing time were determined by turbidity, SS, COD, $BOD_5$ and then equation for treatment efficiency was suggested. Mechanical strength of floc was determined by turbidity. For the coagulant, polyacrylamide (PAM) is more efficient for removing pollution than the aluminium sulfate. Effective mixing ratios of PAM and aluminum sulfate to remove pollution are 70:30 and 30:70. The lowest turbidity was showed when rapid mixing at 300 rpm after coagulant injection was applied. That which indicates the highest point of flocs mechanical strength.