• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.1091-1096
• /
• 2003

Pullout tests of single headed bars using plain concrete blocks indicate that the embedment depth of $10d_b$ is in general required for the headed bars to develop pullout strength equivalent to 125% of bar yield strength. In this experimental study, test results of multiple headed bars installed in reinforced concrete column sections are presented. Test variables included embedment depth, column main reinforcement ratio, and spacing of column ties. 2D29 bars were pulled out at one time from normal strength concrete. Test results indicated that the embedment depths, column tie spacings, and column main reinforcement ratios all influenced the pullout strengths of the headed bars. When the embedment depth was not sufficient, narrow tie spacings especially resulted in increased pullout strengths of the headed bars. Test results also indicated that the embedment depth of 15㏈ was sufficient for the closely spaced two headed bars (head-to-head spacing =$6d_b$) to develop pullout strength equivalent to 125% of the bar yield strength.

• Journal of Environmental Science International
• /
• v.20 no.8
• /
• pp.997-1009
• /
• 2011

In order to estimate volume transport by upwelling for single artificial seamount, same shape and size of artificial seamount already deployed was applied to numerical experiment. The result showed that strong upwelling appeared at front while took place downwelling at rear. The strongest upwelling existed at the top of the artificial seamount. Volume transport by upwelling was computed as 785 m3/s. Column arrangement was applied to two artificial seamount in three cases; case 1) no clearance, case 2) sixty-five meters of clearance as half of artificial seamount's length, and case 3) hundred-thirty meters of clearance as an artificial seamount's length. All cases of column arrangements showed more upwelling volume transport than that of single seamount. Particularly, the case of no clearance calculated as 106% and appeared the most upwelling effect comparing to two other cases. Row arrangement was also applied to two artificial seamount in three cases; case 4) no clearance, case 5) forty meters of clearance as an artificial seamount's width, and case 6) eighty meters of clearance as twice of artificial seamount's width. Upwelling volume transport in case 4 increased 48% than the case of single seamount. Other two cases of 5 and 6 were estimated as 97% increased and more effective than case 4. According to the case experiments, column arrangements show more upwelling volume transport than that of row arrangements. In cases of column arrangements, with decreasing clearance between two seamount, the effect increases while showing maximum value at clearance zero. In cases of row arrangements, on the contrary, with decreasing clearance between two seamount, the effect decreases while showing minimum value at clearance zero. Since simple barotropic condition was considered for this study, further study is necessary by considering baroclinic condition to get close to reality. In conclusion, in deploying artificial seamount, optimal arrangement should be well designed to enhance primary and secondary productivity and to increase the diversity of species as well as reducing time and space.

• Structural Engineering and Mechanics
• /
• v.26 no.6
• /
• pp.651-672
• /
• 2007

This study presents an improved method that uses the elastic and inelastic system buckling analyses for determining the K-factors of steel column members. The inelastic system buckling analysis is based on the tangent modulus theory for a single column and the application is extended to the frame structural system. The tangent modulus of an inelastic column is first derived as a function of nominal compressive stress from the column strength curve given in the design codes. The tangential stiffness matrix of a beam-column element is then formulated by using the so-called stability function or Hermitian interpolation functions. Two inelastic system buckling analysis procedures are newly proposed by utilizing nonlinear eigenvalue analysis algorithms. Finally, a practical method for determining the K-factors of individual members in a steel frame structure is proposed based on the inelastic and/or elastic system buckling analyses. The K-factors according to the proposed procedure are calculated for numerical examples and compared with other results in available references.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.7
• /
• pp.843-845
• /
• 1999

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.10 no.1
• /
• pp.47-54
• /
• 2004

Normally, the single wall(SW) corrugated board has more advantages than double wall (DW) corrugated board in terms of the cost of the materials and logistics. For instance, the SW corrugated board has 3 layer papers whereas the DW corrugated board has 5 layer papers. The thickness of the SW is about 5mm, but that of the DW is 8mm. Accordingly, the SW corrugated board is quite more used in the developed countries than the DW corrugated board. But in Korea, the DW corrugated board is quite more used. The reason why more DW corrugated board are used than the SW corrugated in Korea is that in order that the SW corrugated board has the same box compression strength as DW corrugated board, the cost of the SW corrugated board is higher than that of the DW corrugated board because the virgin kraft liners are all imported from overseas. In this study, the physical properties such as flat crush strength and column crush strength of typical SW corrugated board and single wall dual-layer medium corrugated board and their costs were analyzed. The analysis resulted in that single wall dual-layer medium corrugated board has the same thickness as the SW corrugated board but the more flat crush strength and column crush strength and the less cost than the SW corrugated board.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.1106-1116
• /
• 2008

Single-pole transmission structures which are supported by drilled shaft foundations are usually subjected to large overturning moments with modest vertical and lateral loads. To analyze the behavior of the drilled shaft under such loading conditions, an analytical model was developed based on beam-column and subgrade reaction methods. Field model tests were performed to calibrate the developed analytical model in which additional subgrade spring models were adopted. The field test results estimated from the calibrated analytical model were compared with those calculated by one spring model and other commercial program. According to the comparison study, the developed analytical model was proven to be a useful tool to analyze the laterally loaded behavior of foundations for single-pole structures.

• Journal of Korean Association for Spatial Structures
• /
• v.12 no.3
• /
• pp.71-78
• /
• 2012

The dynamic behavior of spatial structures is different depending on the aspect ration of arch structure, as the rise-span ratio or open-angle, and these spatial structures show differently the character of seismic response in accordance with stiffness and connection of the lower support structures that are directly influenced by earthquake. Therefore, in this paper, dynamic analysis is conducted for seismic response of single layer arch structures by the influence of column's stiffness and connection, to reflect the different vertical and horizontal vibration mode of single layer arch structures. The vertical response of single layer arch structures is more influence by lower columns and the influence of column's connection rotational stiffness is not large, except to the hinged connections.

• Journal of Ocean Engineering and Technology
• /
• v.36 no.2
• /
• pp.132-142
• /
• 2022

We investigate the performance of multi-body wave energy converters (WECs). This investigation considers multiple scattering of water waves by the buoys of a WEC under the generalized mode approach. Predominantly, the effect of a WEC's configuration on its energy extraction is studied in this research. First, single-row terminator and single-column attenuator arrays of vertical cylinders have been studied. The performance of these attenuator arrays shows that the wall effect induced by the periodic buoys influences the wave propagation and energy extraction in these WECs. Further studies show that a single-row terminator array of vertical cylinders performs better than the corresponding single-column attenuator array. Subsequently, multi-row terminator arrays of vertical cylinders are investigated by conducting a parametric study. This parametric study shows that the hydrodynamic property of three resonance phenomena makes energy extraction efficiency drop down, and the magnitude of energy extracted oscillates between the resonance points in these WECs. Finally, a 4×8 terminator array of vertical cylinders is studied to determine the effect of various d_x (x-directional distance between adjacent rows) within this WEC on its performance. In particular, this study enforces at least two equal d_x values within the 4×8 terminator array of vertical cylinders. It shows that a small value of this d_x leads to better energy extraction efficiency in some of these various d_x arrays than that of a corresponding regular array with the same d_x.

• Journal of Korean Society of Steel Construction
• /
• v.27 no.1
• /
• pp.119-129
• /
• 2015

Due to reduced self weight and alleviated wind effect, the multi-column wind towers that consist of a number of circular tubes as vertical members interconnected with horizontal brace members can be a substitute for the large-scale single cylinder wind towers. It is critical to guarantee strengths of tubular joints where vertical and horizontal members are structurally connected in order to make the whole multi-column system behave as a single tower structure. In this study, strength evaluation has been conducted for T-type tubular joints that are applicable in multi-column towers. Four of available design codes, i.e., AISC, Eurocode3, ISO 19902, CIDECT have been investigated and predictor equations in the considered design codes were validated and discussed through parametric numerical study on slenderness ratios of chords and braces at joints.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.2
• /
• pp.253-261
• /
• 1987

Thermoacoustic oscillation of an air column induced by heated wires is investigated analytically and experimentally. Acoustic power generation from a single heater wire is estimated based on the result of heat transfer analysis and expressed in terms of the efficiency factor indicating the conversion efficiency from heat to acoustic energy. It is shown that the efficiency factor becomes maximum when the wire radius is the order of the coustic boundary layer thickness and the flow velocity is close to the thermal diffusion velocity. Onset condition of the column oscillation is obtained by equating the acoustic power generation at the heater to the power loss due to thermoviscous dissipation at the tube wall and the convection and radiationloss at the open ends of the tube. In estimating the acoustic power generation, the heater is treated as a stretched single wire by correcting the flow velocity to take into account the interactions between adjacent heater wires. Experiment is performed by using a spiral heater of 1mm diameter in an air column of 37mm diameter. The heat input to drive the oscillation is measured and compared with the theoretical prediction. A good agreement is found between the theory and experiment, which is regarded as a substantial verification of the present analysis.