• Steel and Composite Structures
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• v.33 no.1
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• pp.67-79
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• 2019

Composite columns made of high strength materials have been used in high-rise construction owing to its excellent structural performance resulting in smaller cross-sectional sizes. However, due to the limited understanding of its structural response, current design codes do not allow the use of high strength materials beyond a certain strength limit. This paper reports additional test data, analytical and numerical studies leading to a new design method to predict the ultimate resistance of composite columns made of high strength steel and high strength concrete. Based on previous study on high strength concrete filled steel tubular members and ongoing work on high strength concrete encased steel columns, this paper provides new findings and presents the feasibility of using high strength steel and high strength concrete for general double symmetric composite columns. A nonlinear finite element model has been developed to capture the composite beam-column behavior. The Eurocode 4 approach of designing composite columns is examined by comparing the test data with results obtained from code's predictions and finite element analysis, from which the validities of the concrete confinement effect and plastic design method are discussed. Eurocode 4 method is found to overestimate the resistance of concrete encased composite columns when ultra-high strength steel is used. Finally, a strain compatibility method is proposed as a modification of existing Eurocode 4 method to give reasonable prediction of the ultimate strength of concrete encased beam-columns with steel strength up to 900 MPa and concrete strength up to 100 MPa.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.4
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• pp.76-80
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• 2015

In filler loaded paper, the size of the filler affects its strength, optical and surface properties. As the size of the filler increases, tensile strength and bulk usually increases, opacity decreases, and smoothness becomes worse. Pre-flocculation of GCC (grounded calcium carbonate) makes large diameter flocs at aqueous medium that consists of multiple GCC particles, but they collapse to 2-dimensional shape in dried paper and makes low bulk paper. The hybrid calcium carbonate (HCC) that was made by in-situ $CaCO_3$ formation between GCC in aqueous medium made high bulk paper without harming tensile strength, bulk, opacity, and smoothness. The GCC that has equivalent size as HCC failed to make high opacity and smoothness as much as HCC.

• Journal of the Korean Society of Clothing and Textiles
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• v.41 no.4
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• pp.633-645
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• 2017

This study examined the effects of the number of Dakji layer (a layer, two layers), the time of Jumchichigi (20, 40 and 60 minutes) and the type of Choji method making Dakji (Oebal-teugi, Ssangbal-teugi) on five strength properties of Jumchi-Hanji. As a result, the number of Dakji layer and the time of Jumchichigi influenced the five strength properties (tensile, wet tensile, tearing, bursting, and folding strengths). Jumchi-Hanjis made with two layers of Dakijis had higher properties than Jumchi-Hanjis with a layer of Dakji in the strength properties. The more the time for Jumchichigi is spent, the more the five strength properties of Jumchi-Hanji increased. The type of Choji was related to only three strength properties. The tearing strength of Jumchi-Hanjis with one and two layers, and the wet tensile and the folding strengths of Jumchi-Hanjis with two layers depended on the type of Choji. The differences of Jumchi-Hanji and Dakji were also identified in the strength properties. All Jumchi-Hanjis had low tensile and wet tensile strengths when compared to Dakjis. However, Jumchi-Hanjis, made by sixty minute Jumchchigi, had generally higher tearing, bursting, and folding strengths than the Dakjis. In conclusion, the strength properties of Jumchi-Hanji could be improved by controlling the number of Dakji layers and the time of Jumchichigi.

• Journal of Welding and Joining
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• v.18 no.4
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• pp.87-95
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• 2000

Residual stresses and deformations due to welding have effects on the strength of structures. In this paper, the compressive strength of basic welded structures is studied and the effects of the residual stresses and deformations on the compressive strength of beams, plates and shells are investigated,. Theoretical analysis for the basic structures is carried out and simplified methods to calculate the compressive strength are proposed. The proposed methods yield simple formulas to calculate the compressive strength, of which results are much helpful. The accuracy of the proposed method is revealed by comparison with experimental results.

• Journal of the Korean Geosynthetics Society
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• v.5 no.4
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• pp.27-33
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• 2006

Frictional properties between geostrip and sand paper interface were estimated considering soil particle size also the friction coefficients and angles were determined with normal stress. Three kinds of geostrips of design strength 50, 70, 100 KN/m were used and 5 sandpapers of P100, P220, P320, P400, P600 were used also. Shear strength between geostrip and sand paper interface with design strength showed big difference and this is due to the uniform surface pattern of each geostrip when contact to sandpaper without regard to design strength. Shear strength of geostrip was increased with design strength and geostrips/P100 sandpaper interface showed the biggest value. Finally, all of geostrips showed the decrease phenomena of post-peak strength and this is due to the abrasion of geostrip surface by shear test.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.4 s.107
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• pp.9-15
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• 2004

To increase paper strength, refining and wet pressing are performed. Many researches were carried out to identify the origin of paper strength. Since fracture toughness was governed by stress concentration, fracture toughness reflects microscopic paper strength. The aim of this paper is to analyze how paper strength was affected by changes of refining and wet-pressing. Fiber properties and structural, tensile and fracture properties of hand­sheets were evaluated. Especially, fracture toughness was evaluated by J-integral. As the refining proceeds, stock properties maybe divided into two stages such as fibers activation and fines activation according to freeness. In fibers activation stages, about 750-450 mL CSF, the fracture toughness increased with refining and wet pressing but in fines activation stages, about 450-250 mL CSF, the fracture toughness increased only with wet pressing. It is clear that fracture toughness was affected not only by fibers properties but also by fines properties in fines activation stages.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.4
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• pp.160-167
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• 2015

The reduction of energy consumption in papermaking process has been considered as one of the major issue in the paper technology. The energy efficiency of paper mill becomes more significant for the mill which manufacture the board grade products such as linerboard with recycled paper such as OCC. The application of lignocellulose spacer to the board grade paper stock would be the feasible solution by increasing the paper bulk and the drying efficiency. The major defects originated from the application of the lignocellulose spacer could be the loss of strength properties. In this study, the ways for improving the strength properties of the spacer-added linerboard were suggested and evaluated. The effects of the addition of various types polyelectrolytes were tested and the different methods of polyelectrolytes were applied for finding the efficient way. The pretreatments of lignocellulose spacer with the polyelectrolytes during wood spacer hydration resulted in the higher strength properties than the typical application method such as the addition to the mixed stock. Multilayer treatments of the spacer with polyelectrolytes were also evaluated and leaded to the higher strength properties with the similar bulk improvement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.100-103
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• 2003

The primary insulation system used in an oil-filled transformer is kraft paper, wood, porcelain and oil. Modern transformers use paper that is chemically treated to improve its tensile strength properties and resistance to aging caused by immersion in oil. But these insulation papers are mainly aged to thermal stress. Over the course of the insulation paper and oil's life it is exposed to high temperatures, oxygen and water. Its interaction with the steel of the tank and core plus the copper and aluminium of the windings will eventually cause the chemical properties of the oil to decay. High temperature have an effect on mechanical strength of cellulous paper using the layer insulation. We made two aging cell in which thermal aging tests of insulation papers and mineral oil are conducted. It is measured dielectric strength, number of acid, moisture, etc. of insulation paper and oil aged in the aging cells.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.2
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• pp.26-32
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• 2003

For the purpose of manufacturing water-resistant corrugated board boxes for agricultural products in the cold chain system, the effects of fiber types, wet strength agents and a moisture-proof chemical on the properties of the base papers were investigated first. PAE(polyamide amine epichlorohydrin) showed better performance than MF(melamine formalde-hyde) over broad stock pH ranges, which was prefered as wet strength agent for the paper grade. When short fibers(AOCC, KOCC) were mixed with long fiber(UKP) in certain ratios, some physical properties of the paper made with mixed fibers were similar to those of the paper made with UKP only. Paper containing AOCC showed the biggest increase in water resistance when PAE was added to the stock. Synergistic effects in moisture-proof and some mechanical properties of paper were appeared when PAR was added internally, together with the coating of a moisture proof chemical on the sheets.

• Journal of the Korea Safety Management & Science
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• v.9 no.4
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• pp.83-90
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• 2007

This study is to find out if it can be recycled for making better concrete. Therefore, waste paper as of newspaper and newspaper are added into concrete to see if waste paper-mixing concrete can have any particular characteristic. The test result of paper concrete was compared and analyzed through four kinds of tests such as compressive strength as of a fundamental one of concrete resistant capacity against heat. $200^{\circ}C,\;400^{\circ}C\;and\;600^{\circ}C$ heated concrete were compressively tested in order to find out concrete strength resistant to high temperature. heat capacity was also tested, based on the expectancy of its low conductivity. finally flexural strength test using four reinforced concrete beams with size of $20cm{\times}30cm{\times}160cm$ was made. And concrete property exposed to the temperature showed that there are almost not effect for the strength up to $400^{\circ}C$, but it was decreased down to 50% of the original condition. volume of paper mixed with concrete without relation to paper kinds of new and waste one.