• Wind and Structures
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• v.1 no.3
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• pp.225-241
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• 1998

The high-rise supporting towers of long-span suspension and cable-stayed bridges commonly comprise a pair of slender prisms of roughly square cross-section with a center-to-centre spacing of from perhaps 2 to 6 widths and connected by one or more cross-ties. The tower columns may have a constant spacing as common for suspension bridges or the spacing may reduce towards the top of the tower. The present paper is concerned with the aerodynamics of such towers and describes an experimental investigation of the overall aerodynamic forces acting on a pair of square cylinders in two-dimensional flow. Wind tunnel pressure measurements were carried out in smooth flow and with a longitudinal intensity of turbulence 0.10. Different angles of attack were considered between $0^{\circ}$ and $90^{\circ}$, and separations between the two columns from twice to 13 times the side width of the column. The mean values of the overall forces proved to be related to the bias introduced in the flow by the interaction between the two cylinders; the overall rms forces are related to the level of coherence between the shedding-induced forces on the two cylinders and to their phase. Plots showing the variation of the force coefficients and Strouhal number as a function of the separation, together with the force coefficients spectra and lift cross-correlation functions are presented in the paper.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.265-273
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• 2007

The most common structural system for apartment buildings in Korea is adopted to combine structural systems: for example, a moment-resisting frame will be used for lower stories and bearing wall system for the upper stories. This type of buildings have soft and/or weak stories in lower stories, and it may lead to collapse of those buildings during the large earthquake. Reversed cyclic load tests were conducted to estimate the performance and behavioral characteristics of deep beam and exterior column Joints. Experimental parameter is the amount of transverse reinforcement (designed by ACI code and Sheikh's procedure). The results of this study are as follows: (1) The required transverse reinforcement of column designed by Sheikh's procedure requires 2.9 times larger than that designed by ACI procedure. Large amount of transverse reinforcement increase the ductility of the column. (2) Most of the lateral drift in the column is due to the flexural deformation in the joint and plastic hinge region and up-lift rotation. (3) Transverse reinforcement in the exterior column shall be required not only in the hinge region but also in the joint.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.599-616
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• 2021

The semi-submersible with three circular columns is an original concept of efficient multifunctional platform, which can be used for marginal oil, gas field, and Floater of Wind Turbines (FOWT). However, under certain flow conditions, especially in uniform current with specific velocities, the eddies will alternatively form and drop behind columns, resulting in the fluctuating lift force and drag force. Consequently, the semi-submersible will subject to the Flow-Induced Motions (FIM). Based on the Detached Eddy Simulation (DES) method, the numerical studies were carried out to understand the FIM characteristics of the three-column semi-submersible at two different parameters, i.e., current incidences (0°, 30°, and 60°-incidences) and reduced velocities (4 ≤ U_r ≤ 14). The results indicate that the lock-in range of 6 ≤ U_r ≤ 10 for the transverse motions is presented, and the largest transverse non-dimensional nominal amplitude is observed at 60°-incidence, with a value of A_y/D = 0:481. The largest yaw amplitude A_yaw is around 3.0° at 0°-incidence in the range of 8 ≤ U_r ≤ 12. The motion magnitude is basically the same as that of a four-column semi-submersible. However, smaller responses are presented compared to those of the three-column systems revealing the mitigation effect of the pontoon on FIM.

• Journal of Environmental Science International
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• v.1 no.2
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• pp.105.1-113
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• 1992

The present study was performed to develop the removal system of the offensive gases, including hydrogen sulfide of acid gas, ammonia or amice of base gas, from the nightsoil treatment plant. In order to remove the offensive gases, the Fe-EDTA system liquid phase catalytic oxidation method with the bubble lift column reactor was employed. From the results obtained, it was confirmed that the offensive gases can be deodorized simultaneously and also hydrogen sulfide of acid gas, ammonia of base gas completely removed at pH 6.45. In addition, as input gases feed rate the efficiency of acid gas did not change but the efficiency of base gases decreased to approximately 90 % at pH 6, 0. From the result of particle size analyzer, it was found that the particle sizes including sulfur and other impurites grew up to $21{\mu}m$ over 72hour reaction time.

• KSBB Journal
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• v.25 no.5
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• pp.421-428
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• 2010

This paper reports on the experimental investigation carried out to evaluate the physical optimal conditions in the absorption column to remove odorous hydrogen sulfide gas. Hydrogen sulfide gas, as a highly undesirable contaminant, is most widely emitted from environmental treatment facilities. The absorbent mixed with natural second metabolites extracted from conifer trees and chemical absorbent of 2-aminoethanol was applied to remove it via chemical neutralization. The absorbent of natural second metabolites was achieved by a removal efficiency of 20-40% by itself depending on the treatment conditions, but the complex absorbent mixed with 0.1% amine chemical provides the removal efficiency of 98%. The optimal removal efficiencies have been examined against the two major parameters of temperature and pH. This study shows that the aqueous solution by natural second metabolites can be used as an appropriate absorbent in the column absorbed for the removal of hydrogen sulfide gas.

• Journal of Korean Association for Spatial Structures
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• v.16 no.4
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• pp.101-108
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• 2016

Lifting plan in the large spacial structure is an important factor influencing the efficiency and economy of the construction process. The purpose of this study was deriving the requirements for lifting techniques as the basic research in the double spoke wheel roof structure construction. In the lift up erection method, management plan of the interference error in the column and outer-ring was needed that occur during lifting roof structure. In the bent erection method, material usage reduction plan was required by the structural design of the temporary bent. In the hybrid erection method, lifting plan was needed that minimizes weather condition and crane usage. All lifting techniques were required Value Engineering model for reduction of cost and construction period.

• The Korean Journal of Mycology
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• v.34 no.1
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• pp.1-6
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• 2006

In order to select a suitable bioreactor type for the submerged cultivation of Ganoderma applanatum, both growth characteristics and polysaccharides production were compared among four different types of bioreactor. These include an external-loop type air-lift bioreactor (ETAB), a balloon type air bubble bioreactor (BTBB), a column type air bubble bioreactor (CTBB) and a stirrer type bioreactor (STB). The mycelial biomass produced from the reactors were in decreasing order: ETAB ($7\;g/{\ell}$) > BTBB ($6.2\;g/{\ell}$) > STB ($6\;g/{\ell}$) > CTBB ($5\;g/{\ell}$). Maximal soluble exopolysaccharides ($1\;g/{\ell}$) and endopolysaccharides (2.7%) were also obtained from ETAB. Thus, the ETAB was most suitable for submerged culture of G applanatum mycelium. Based on the results, ETAB was chosen for further detailed study. The most effective aeration rate for the mycelial growth in ETAB ranged from 0.05 to 0.1 vvm. For the maximal production, the mycelium at the initial growth stage needed low aeration rate to reduce cell damages by fluid flow. However, as the mycelia grew, the culture became viscous and thus needed higher aeration. The molecular weight of exopolysaccharides obtained from the culture grown in ETAB was higher than that from the culture grown in other bioreactors.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.95-104
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• 2007

Three types of high-rise RC building structures having irregularity in the lower two stories were selected as prototypes and were performed nonlinear static analysis by using OpenSees to verify the analysis technique and to investigate the seismic capacity of those buildings. The first one has a symmetrical moment resisting frame (Model 1), the second has an infilled shear wall in the central frame (Model 2), and the third has an infilled shear wall only in one of exterior frames (Model 3). Fiber model, which consists of concrete and reinforcing bar represented from stress-strain relationship, is adapted used for simulate the nonlinearity of members, and MVLEM(Multi vertical linear element model) is used for simulate the behavior of wall. The analytical results are simulate the behavior of piloti stories well, for example, the stiffness and yield farce of piloti stories, the up-lift of wall and the variation of lateral stiffness of column due to the variation of axial forces. Overstrength of Model 2 and Model 3 are about 2 times larger than that of Model 1. The reason of the high oversttrength and ductility of Model 2 and Model 3 is that the conservative design of Model 2 and Model 3, whose beam and column sections are the same as those of Model 1. The ductilities of Model 1 and Model 3 are slightly larger than that of Model 1 and Model 3. Model 1 and Model 3 reached mechanism condition, whereas Model 2 failed to the shear failure of shear wall and the large axial forces in columns due to large overturning moment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.1-10
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• 2021

In this study, a circular pipe can be installed by suction pressure for construction on soft ground with a low-water level. A series of laboratory-scale model tests were conducted in sandy ground to comprehend the suction pressure of the circular pipe in low-water levels. For repeated tests on saturated sandy soil, a container was mounted with three vibration generators on the floor. A repetitive vibration was applied using the vibration system for ground compaction. In the model tests, different diameters and thicknesses on saturated sandy soil with a water depth were considered. The result showed that the suction pressure increased with increasing penetration depth of the circular pipe. Moreover, the suction pressure required to penetrate the pipe decreased with increasing diameter. In the low-water level, the total suction pressure measured at the top lid increased because additional suction pressure is required to lift the water column. On the other hand, this led to a decrease in suction pressure to penetrate the circular pipe because the weight of the water column is applied as a dead load. Therefore, it is necessary to consider the water level to design the required suction pressure accurately.

• Journal of ILASS-Korea
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• v.13 no.4
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• pp.212-219
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• 2008

To develop the twin-fluid atomizer having the excellent performance of painting, the spray characteristics of how a wide area can be painted efficiently by one time spraying were studied in this paper. Spray phenomena are affected by the many factors determining the spray field such as the spraying pressure of gas, the spraying pressure and viscosity of liquid paints, the opening duration of needle valve, the design dimension of nozzle, and so on. As the results of experiments, these factors affecting on spray characteristics were suggested as followings; 1) The optimum spraying pressure of gas was $0.015{\sim}0.02\;kPa$, and the appropriate spraying pressure of liquid paint was 0.01kPa, In these situations, the setting up pressures must be compensated as much as the losing amount of pressure because a decompression occurred when operating valves. 2) The duration of opening the needle valve must be sustained for $1{\sim}2$ seconds to inject gas after spraying the liquid paint. This operating of the needle valve was necessary to avoid the affect on the changing of liquid column length, and to prevent the droplet deposit at the initial time of spraying. 3) The spray tip penetration was gained form the experimental equation, and the effective spraying angle was $85^{\circ}{\pm}5^{\circ}$ just at he appropriate spraying pressure of gas. The distribution of the area sprayed had the variation in $350{\pm}50\;mm$ because of the spraying pressure of gas, the its distance from the spray tip, and the lift of the needle valve.