• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
• /
• pp.167-172
• /
• 1992

To analyze the effects compressive strength of concrete and longitudinal steel ratio on second-order moment of columns, 30tied rein reinforced concrete columns with hinged ends were tested. The 80mm square cross section was used and the amount of eccentricity was 24mm. The compressive strengths of column specimens with slenderness ratios of 10, 60, and 100were 250, 648 and 880kg/$\textrm{cm}^2$, and the longitudinal steel ratios were 1.98%(4-D6) and 3.95%(8-D6). The ratio of ultimate load capacity to that of short column with the same eccentricity (Pu/Pn) was much decreased at high slenderness ratio with increasing the compressive strength of concrete. And the lateral displacement of slender column at the ultimate load was decreased as the strength was increased. These are due to that at high slenderness ratio the load capacity and behavior of column are affected by flexural rigidity. And, it was also found that with increasing steel ratio, the value of Pu/Pn and the lateral displacement at the ultimate load were larger for the same slenderness ratio.

• 콘크리트학회논문집
• /
• 제17권5호
• /
• pp.843-852
• /
• 2005

Presently, test results and stress-strain models for poorly confined high-strength columns, more specifically for columns with a tie volumetric ratio smaller than $2.0\%$, are scarce. This paper presents test results loaded in axial direction for square reinforced concrete columns confined by various volumetric ratio lateral ties including low-volumetric ratio. Test variables include concrete compressive strength, tie yield strength, tie arrangement type, and tie volumetric ratio. Local strains measured using strain gages bonded to an acryl rod. For square RC columns confined by lateral ties, the confinement effect was efficiently improved by changing tie arrangement type from Type-A to Type-B. A method to compute the stress in lateral ties at the concrete peak strength and a new stress-strain model for the confined concrete are proposed. Over a wide range of confinement parameters, the model shows good agreement with stress-strain relationships established experimentally.

• Journal of Welding and Joining
• /
• 제23권3호
• /
• pp.54-60
• /
• 2005

Tungsten Inert Gas(TIG) welding is today one of the most popular arc welding process because of its high quality welds and low equipment costs. Even if welding productivity increases with welding speed and current, this strategy is limited by the appearance of defects such as undercut and humping bead due to the depressed molten metal. The purpose of this study investigates the effect of He mixing ratio on the characteristics with high current and speed in TIG welding. The conclusions obtained permit to explain the arc start characteristics quantitatively and the maximum welding speed on stable bead formation with He mixing ratio for high current and speed TIG welding observed in experiments. Also through the relation of the maximum arc pressure and surface depression depth at high current and speed TIG welding, it made clear the mechanism of unstable bead formation.

• 한국건축시공학회지
• /
• 제5권2호
• /
• pp.153-159
• /
• 2005

This study is to choose the optimal mixture and to analyze the sensibility properties of High strength concrete and mass concrete to apply the high rising building. The main experimental variables were water/binder ratio $39\%,\;33\%,\;35\%\;and\;37\%$, replacement ratio of fly ash $5\%,\;10\%\;and\;15\%$, in the high strength concrete and water/binder ratio $39\%,\;41\%\;and\;43\%$, replacement ratio of fly ash $10\%,\;20\%\;and\;30\%$, in the man concrete. According to the test results, the principal conclusions are summarized as follows. 1) The slump(or slump flow) and air content of fresh concrete were found to be the highest in the elapsed time 30 minutes. 2) The optimal mixture conditions are W/B $40\%$, FA $25\%$ in the mass concrete and W/B $33.4\%$, FA $15\%$ in the high strength concrete. 3) The ranges of sensibility are satisfied in the moisture content ${\pm}l\%\;and\;S/a\;{\pm}2\%$.

• 전기학회논문지P
• /
• 제57권2호
• /
• pp.121-126
• /
• 2008

This paper analyzes the losses of a Steinmetz connection three-phase induction motor which is supplied by a single-phase source. The T-type equivalent circuit which is taken no-load losses into account is used to determine phase converter capacitive reactances at starting and rated speed by using the condition of the minimum voltage unbalance. The starting and the operating capacitor are replaced at the slip of the same voltage unbalance factor points which are depicted using two capacitive reactances. The operation characteristics are investigated by comparing with those of three-phase balanced operation to find the feasibility of single-phase operation. To analyze the losses of this motor, the output power decrease factor(OPDF), the loss ratio(LR), the no load loss ratio(NLLR), the copper loss ratio(CLR), the stator copper loss ratio(SCLR), and the rotor copper loss ratio(RCLR) are defined and simulated in the whole slip range. The simulated results show that OPDF is maintained almost uniformly, LR is low at low speed and high at high speed, CLR is higher !ban NLLR, but CLR varies concavely and NLLR varies convexly at high speed, SCLR is low at low speed and high at high speed, but SCLR varies convexly at high speed, and RCLR is nearly opposite to SCLR.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2009년도 제33회 추계학술대회논문집
• /
• pp.3-8
• /
• 2009

Wall flush mounted injector with various orifice shape and injection conditions, were examined to enhance jet penetration and mixing in supersonic cross flow, in view of application to air-breathing accelerator vehicle. Orifice shapes with high aspect ratio were found to preferable for better penetration in the cold flow, and in the reacting flow for scramjet-mode combustion conditions. However, the effectiveness of the high aspect ratio was diminished in the dual-mode combustion conditions. Supersonic injection was applied to the high aspect ratio orifice, and further increase in penetration was observed in the cold and reactive flow for scramjet-mode combustion conditions, however, mixing enhancement due to mixing layer / pseudo-shock wave system interaction was dominant in the dual-mode combustion conditions. Difficulty in attaining ignition in the case with the high aspect ratio orifice was encountered during the combustion tests.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2006년도 춘계학술논문 발표대회 제6권1호
• /
• pp.89-92
• /
• 2006

To investigate the properties of high flowing and high strength concrete with crushed sand and fly ash for CFT structure, many batches were performed by a trial-error method. In the experiment W/B was set up three levels as 0.25, 0.30 and 0.35. Also the variables of the experiment were a substitution ratio of fly ash, a blend ratio of crushed sand and the ages of specimens(3, 7, 28 days). The results of this study are summarized as the follows; 1) The effect a substitution ratio of fly ash on the compressive strength was not consistent with age. For twenty-eight day compressive strength, the best result was come out when cement was substituted by 10% of fly ash. 2) The decrease of the water binder ratio, the increase of compressive strength and elastic modulus. Also the relationship is very similar to the case of a normal concrete

• 한국농촌건축학회논문집
• /
• 제12권1호
• /
• pp.57-64
• /
• 2010

This study is to clarify the actual conditions of high school of environment friendly architecture per ecological environment elements through extracting ecological environment elements which is possible to analyze in quantity certification standards of environment friendly architecture. As the method of the study, First, certification as an examination on certification system of environment-friendly architecture, summary of certification system of environment friendly architecture and certification high school, ecological environment elements which is possible for quantitative analysis of ecological environment certification standards were extracted. Second, actual condition of ecological environment elements per non-certification high school by collecting actual data of certification schools environment friendly architecture were analyzed and the results are as the follows. The average of ecological area ratio was 17.8 percent in case of non-certification school facilities it was analyzed that the natural based green area ratio was 17.5 percent, continuous green axis length ratio was 19.0 percent and roof green garden area ratio was 0 percent.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2022년도 봄 학술논문 발표대회
• /
• pp.148-149
• /
• 2022

The use of high-strength grout applied for facility foundations and bridges has recently been expanding in offshore wind farm. Wind farm in offshore require bearing capacity for horizontal loads such as wind, waves, and earthquakes. In order to improve the bearing force of the base part, sufficient fluidity and a certain strength should be ensured so that the high-strength grout is densely charged in the narrow space of the connection part. Therefore, in this study, changes in fluidity and strength according to the ratio of PC-based superplasticizer mixed in high-strength grout were measured. As a result, as the ratio of the superplasticizer increased, fluidity increased and strength decreased. However, the strength did not decrease when the ratio of superplasticizer was above a 0.005. Therefore, it was confirmed that the fluidity change was remarkable when a 0.005 ratio of PC-based superplasticizer were added.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.676-679
• /
• 2004

In this study, we considered the characteristic of drying shrinkage from age of high strength concrete with garnet minute powder to be industry by-product. The factors of experiment are unit water content$(160kg/m^3)$, water-binder ratio(30, $35\%$), fine aggregate ratio(40, 42, $44\%$), admixture replacement ratio(0, 10, $20\%$), admixture type(garnet minute powder, fly ash, blast-furnace slag). We make a comparative study of shrinkage about concrete with a passage of age(1, 3, 7, 14, 28, 56, 91 days). As a result of experiment, we reach a conclusion as follow. In the same mix condition, as unit water content and fine aggregate ratio go up, the drying shrinkage ratio increase. In the drying shrinkage ratio according to admixture replacement ratio, it goes up when admixture replacement Ratio increase in case of fly ash and blast-furnace slag. But, drying shrinkage ratio decrease when admixture replacement ratio increase in case of garnet minute powder.