• 한국농공학회지
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• 제34권1호
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• pp.78-86
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• 1992

This paper aims at investigating the effect of steel ratio and the magnitude of edge-ratio on the mechanical characteristics of reinforced concrete ring sector plate. The influence of steel bars was taken into account by coupling stiffness matrix of the steel bar element with that of the concrete plate element without dealing with separate element of steel bar and by establishing the composite stiffness matrix, which leads to the desirable result which does not increase th number of element could be obtained. Through case studies with 6 cases various steel ratios in ring sector plate supported at four edges and 4 cases with different open angles, the influence of the steel ratio was examined. A numerical analysis to find out the effect of the steel ratio d ue to above mentioned cases was carried out by 4 boundary conditions ; all edges clamped (B.C-1), all edges simply supported (B.C-2), curvilinear two edges clamped and other edges free (B.C-3) and curvilinear two edges simply supported and other edges free(B.C-4). The main results obtained are summarized as follows : 1. The effect of steel ratio on the magnitude of lateral deflection and x-directional bending moment at the center of sector plate and the midpoint of outer and inner curvilinear edges is almost the same up to $30^{\circ}$ of open angle. Beyond $30^{\circ}$ of the angle, the larger the angle, the greater the effect of ratio. 2. In design works using balanced steel ratio, the effect of steel bar can be ignored. But for larger open angles, especially greater than $90^{\circ}$, it proves desirable to consider the effect of steel bar. 3. The effect of the arc length of center circle/straight edge on lateral deflection and bending moment is remarkable in B.C-2. For larger open angle, the effect is also noted except for B.C-3 which turn out hardly affected. 4. The effect of the radius of curvature/straight side length on lateral deflection and x-directional bending moment is noted in B.C-2. As open angle increases, B.C-1 and B.C-3 almost agree and B.C-2 approaches B.C-4.

• 한국안전학회지
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• 제25권6호
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• pp.128-136
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• 2010

In according with concrete structural design standard, it is common designing flexure reinforcement concrete to induce tension failure. So reinforcing ratio is limited to inducing tension failure. And maximum reinforcing ratio is regulated to protecting concrete compression strength caused by over reinforced building. Minimum reinforcing ratio is also limited in designing standard to protecting brittle failure as extremely using less reinforcing bar. But in minimum reinforcing ratio it is extremely conservative or it is sometimes impossible to induce stable tension-failure because they are depending on yield failure and experienced method and concrete designing standard strength. Therefore the purpose of the present paper is to evaluate the flexural behavior of minimum steel ratio of reinforced concrete of beams and to propose the guide-line of equation of minimum steel ratio by performing static flexural test of 16 beams according to size effect, number of steel, yielding stress of steel, and concrete compressive strength which are presumed effective variables. From experimental results, the equation of minimum steel ratio was newly proposed considered size effect.

• 한국디지털건축인테리어학회논문집
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• 제11권2호
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• pp.31-39
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• 2011

Concrete-filled steel tube(CFT) columns have become popular for building construction due to not only composite effect of steel tube and infilled concrete, but also more economical. The purpose of this paper is to propose the applicable boundary formula of width-to-thickness ratio for rectangular steel tube as using CFT column. A parametric study was performed taking width-to-thickness ratio of rectangular steel tube and compressive strength of concrete as the main parameter. The strength of concrete are selected to 30, 60, 90MPa. The non-linear analysis was adopted in order to take into account the effect of concrete strength. Finally, from the test and analysis results, the effect of increasing strength according to concrete strength and width-to-thickness of steel tube and plastic behavior of specimens were verified distinctly.

• Steel and Composite Structures
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• 제11권6호
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• pp.469-488
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• 2011

This paper consists of two parts; the first part describes the laboratory work concerning the behavior of lightweight aggregate concrete filled steel tubes (LACFT). Based on eccentricity tests, fifty-four specimens with different slenderness ratios (L/D= 3, 7, and 14) were tested. The main parameters varied in the test are: load eccentricity; steel ratio; and slenderness ratio. The standard load-strain curves of LACFT columns under eccentric loading were summarized and significant parameters affecting LACFT column's bearing capacity, failure mechanism and failure mode such as confinement effect and bond strength were all studied and analyzed through the comparison with predicted strength of concrete filled steel tube columns (CFT) using the existing codes such as AISC-LRFD (1999), CHN DBJ 13-51-2003 (2003) and CHN CECS 28:90 (1990). The second part of this paper presents the results of parametric study and introduces a practical and accurate method for determination of the maximum compressive strength of confined concrete core ($f_{max}$), In addition to, the study of the effect of aspect-ratio and length-width ratio on the yield stress of steel tubes ( $f_{sy}$) under biaxial state of stress in CFT columns and the effect of these two factors on the ultimate load carrying capacity of axially loaded CFT/LACFT columns.

• 한국농공학회지
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• 제35권1호
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• pp.59-66
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• 1993

Ring Sector Plate Supported by Elastic Beam Although all the reinforced concrete circular ring sector plates are elastically supported, it is conventional to simplify their supporting conditions as fixed or simply-supported ones assuming that their supporting beam has infinite stiffness. However, in order to obtain a precise solution, it should be required to consider the stiffness of their supporting beam. As a methodological improvement to the precise analysis, "Reinforced Concrete Model" previously developed by the author was applied to the structural analysis of the reinforced concrete circular ring sector plates with elastically supported beam. The results of analysis in the cases under various conditions of open angle, steel ratio, relative stiffness(EI/DL) between plate and supporting beam were summarized as follows ; 1.Although the effect of relative stiffness between plate and supporting beam varies depending on the magnitude of open angle, in general, it shows the largest when not more than 5.0 and negligible when not less than 10.0. Therefore, it would be considered as fixed supporting condition :in the case of its open angle of 0$^{\circ}$rectangular plates), its stiffness ratio being not less than 10.0 and in the other case of its open angle of 30$^{\circ}$, its stiffness ratio being not less than 5.0. 2.In the rectangular plates, the effect of steel ratio is considerable in no supporting condition, but neglible in the supporting condition. So, the effect of steel ratio should be negligible in the case of the elastically supported circular ring sector plates. 3.However, the effect of steel ratio is much more considerable in the case of the fixed supported circular plates, especially, when steel ratio being not more than 1.0% and stiffness ratio being smaller. So, the effect of steel ratio should be considered in the analysis of reinforced concreate circular ring sector plates with fixed conditions. 4.The effect of open angle is greater in the case of without-supporting beam conditions. However, in the other case of with-supporting beam conditions, the effect is a little bit when open angle of not more than 300 and negligible when open angle of not more than 30$^{\circ}$.

• 소성∙가공
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• 제18권5호
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• pp.410-415
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• 2009

Experimental and numerical studies were performed to examine the effect of material temperature and reduction ratio on friction coefficient during hot flat rolling. We carried out a single pass pilot hot flat rolling test at the temperatures range of $900{\sim}1200^{\circ}C$ and measured the spread of deformed material while reduction ratio varied from 20% to 40%. Materials used in this study were a high carbon steel and two alloy steels. The dimension of specimen used in hot rolling experiment was $50mm{\times}50mm{\times}300mm$. We performed a series of finite element simulation of the hot rolling process to compute the friction coefficient change in terms of steel grade and reduction ratio. Results showed that temperature dependency of friction coefficient is not noteworthy but the effect of reduction ratio on friction coefficient is quite large. For high carbon steel, friction coefficient at reduction ratio of 30% is lower than that at that of 20%. Meanwhile friction coefficient at reduction ratio of 40% was one and half times large compared with that at that of 20%. The effect of steel grade on friction coefficient was significant when reduction ration was large, e.g., 40%.

• Journal of Mechanical Science and Technology
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• 제16권10호
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• pp.1246-1252
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• 2002

Ultrafine grained (UFG) low carbon (0.15 wt.% C) steel produced by equal channel angula. pressing (ECAP) was tested for investigating the effect of load ratio on the fatigue crack growth rate. Fatigue crack growth resistance and threshold of UFG steel were lower than that of asreceived coarse grained steel. It was attributed to the less tortuous crack path. The UFG steel exhibited slightly higher crack growth rates and a lower △Kth with an increase of R ratio. The R ratio effect on crack growth rates and △Kth was basically indistinguishable at lower load ratio (R >0.3), compared to other alloys, which indicates that contribution of the crack closure vanishes. The crack growth rate curve for UFG steel exhibited a longer linear extension to the lower growth rate regime than that for the coarse grained as-received steel.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.58-61
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• 2006

The effect of the steel ratio on the behavior of continuously reinforced concrete pavement (CRCP) under moving wheel loads and environmental loads were investigated in this study. The CRCP sections having different steel ratios of 0.6, 0.7, and 0.8% were considered: (1) to evaluate the load transfer efficiency (LTE) at transverse cracks; (2) to investigate strains in CRCP when the system is subjected to moving vehicle loads; (3) and to investigate the time histories of the crack spacing variations. The LTEs were obtained by conducting the falling weight deflectometer (FWD) tests. The strains in the concrete slab and the bond braker layer under moving vehicle loads were obtained using embedded strain gages. The results of this study show that the LTEs at transverse cracks are very high and not affected by the steel ratio. The strains in CRCP under vehicle loads become smaller as the vehicle speed increases or as the wandering distance increases; however, the strains are not clearly affected by the steel ratio. However, the changes in the crack spacings are affected by the steel ratio.

• 동력기계공학회지
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• 제13권3호
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• pp.47-52
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• 2009

The effect of forging start temperature, forging ratio on the microstructure and mechanical properties of B7B4 steel ware investigated. Microstructure of centrifugal casted B7B4 steel consisted of martensite and ferrite phase. The volume fraction of ferrite increased with increase of forging start temperature and decreased with increase of forging ratio. Tensile strength and hardness decreased with higher of forging start temperature, while impact value and elongation increased with higher of forging start temperature. With increase of forging ratio, tensile strength rapidly increased up to the forging ratio of 30%, and then slowly increased, but elongation was decreased. Hardness and impact value rapidly increased with increase of forging ratio.

• 한국해양공학회지
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• 제1권2호
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• pp.123-129
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• 1987

Corrosion fatigue fracture of dual phase steel(SS41) and raw material steel(SS41) were investigated in 3.5% NaCl aqueous solution at PH 4,6,9 and 11. The fatigue limit of dual phase steel is increased approximately 1.8 times larger than that of raw material in air. The corrosion fatigue life of dual phase steel is about 5-10 times larger than that of raw material in 3.5% NaCl aqueous solution. The reduction of fatigue life is larger for the acidsalt solution than for the alkali salt solution. The reduction of stress level on the reduction ratio of corrosion fatigue life is large as pH 6-11. The reduction ratio of corrosion fatigue life of dual phase steel and raw material is nearly coincided at pH 2. While at pH4-2 the reduction ratio of corrosion fatigue life only depends on the corrosion effect. It has been found that the corrosion resistance effect of dual phase steel is smaller than that of raw material in corrosion fatigue crack propagation rate. As pH below 6 is changed, it can be clearly observed from raw material that the brittle intergranular fracture is characterized, and from the above result, the influence of corrosion of dual phase steel is small.