• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.4
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• pp.453-462
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• 2007

The purpose of this study is to predict the ratios of increase in lateral stiffness for preliminary structural design of tall buildings. For this, the basic models of tall buildings with 60 stories are generated. The basic models have typical floor plan of Box or T type. And the factors for increase in lateral stiffness are selected as follows; the addition of outriggers, increase in material strength, and increase in member size of core walls, outrigger columns, and outrigger walls. Then these factors are applied to the basic models and their effects are investigated using the results of structural analysis. Finally, based on the investigation, the ratios of increase in lateral stiffness for preliminary structural design of tall buildings are proposed and applied to examples of tall building for verification of the ratios.

• Journal of the Korea Concrete Institute
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• v.21 no.2
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• pp.159-168
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• 2009

In this study, strength, stiffness and confinement effect with stress-strain and stress-volumetric strain curves for improved uniaxial compressive behavior of RC circular columns laterally confined with prestressing aramid fiber strap were experimentally investigated. The test variables were the specimens with or without axial reinforcing bar and the number and spacing of strap, prestressing level, the types of reinforcing fiber (CFS, GFS). As a result, the failure type of the columns was very stable and strength increase rate was about 73% comparison with the general RC columns. Moreover, the strain increase rate is very small and the axial displacement confinement effect was very effective compared with existry methods (CFS, GFS), the initial and final lateral confinement effect was excellent.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.41-51
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• 2008

The load distribution and deformation of single piles which is embedded in Jumunjin sand and Kimhae clay are investigated, based on small scale model tests. Special attention is given to the consideration of flexural rigidity in laterally loaded piles. To consider the flexural rigidity of the pile, tests are performed with the aluminium piles of three different length under different relative densities and undrained shear strength. The test results indicate that the initial slope from the results of tests is proportional to the depth and pile-soil rigidity in both soils. But the increasing rate of the initial slope in the clay is less than in the sand. In addition, the soil resistance is more related to the depth and soil condition than the pile rigidity. Base on the test results, an empirical formula is proposed, which is good agreement with previously published small scale model test and field lateral load test.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.639-647
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• 2002

A simplified analytical procedure is presented to estimate the reduction of elastic lateral stiffness of steel moment frames arising from the radius-cut dogbone weakening. With the original radius-cut dogbone shape, it is almost impossible or too complicated to integrate analytically the mathematical expressions encountered when applying the conjugate beam method to compute the beam deflection component. In this study, the problem is circumvented by replacing the original radius-cut dogbone with an equivalent dogbone of constant width. The equivalence between the two is established by imposing an equal dogbone elongation criterion. This approach is justified by using a calibrated finite clement analysis. Then, the elastic lateral deflection components from the column, panel zone, and beam are derived for a typical beam-column subassembly. The derived results can be used to evaluate the reduction of the frame lateral stiffness. Case studies conducted within some practical ranges of frame configurations show that the reduction in frame lateral stiffness due to the presence of dogbone cut is on the order of 1 to 2 percent and is reasonably negligible in practical sense.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.35-43
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• 2016

In order to understand rotation behavior of high strength steel endplate connections under fire, this study is compared with existing studies conducted using FEA program. Eurocode 3 presents the three failure modes according to the prediction of bending resistance moment. The parameters of analysis model are temperature, thickness and steel materials of endplate. The rotation stiffness, and bending resistance moment are analyzed according to the parameters. The change of rotation stiffness and bending resistance moment are analyzed about the parameters, regression equations are suggested the change of high strength steel endplate connections. Consequently, the regression equations were proposed as the linear and quadratic equation. The moment ratio of high strength steel under fire was more reduced than the carbon steel, and was small effect about the thickness. When the high strength steel under fire was compared with at ambient temperature, the slope of initial rotation stiffness reduced, the increment ratio of moment was slow, and the change of plastic rotation stiffness wasn't effect by the thickness increase.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.535-542
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• 2010

Precise estimation of a structure's dynamic characteristics is indispensable for ensuring stable dynamic responses during lifetime especially for the structures which can experience resonance such as railway bridges. In this paper, the results of forced vibration tests of different excitation methods (vibration exciter and impact hammer) are compared to examine the differences and the cause of differences of extracted natural frequencies. Consequently a natural frequency modification method is suggested to eliminate effects of non-structural disturbance factors. Also, sequential forced vibration tests are performed before and after track construction according to the construction stage of a railway bridge, and the variation of natural frequencies are examined. Effect of added mass of vibration exciter and variation of support condition due to the level of excitation force are concluded as the major cause of natural frequency differences. Thus eliminating these effects can enhance the reliability of the extracted natural frequencies. Construction of track affects not only the mass of structure but also the stiffness of the structure. Also, the amount of increase in stiffness varies according to the level of structural deflection. Therefore, reasonable estimation of the level of structural response during operation is important for precise natural frequency calculation at design phase.

• Journal of Navigation and Port Research
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• v.31 no.5 s.121
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• pp.339-344
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• 2007

Shipwaves can cause beach erosion, seawall destruction and difficulty of cargo working due to rolling of ship. In addition, high speed operation of motor boat and passenger ship jeopardize sea bathers and anglers' safety. This study aims to investigate the characteristics of shipwaves which occurred and propagated in shallow water experimentally and theoretically. Shipwaves which occurred and propagated in shallow water depth represent large wave height increase.

• The korean journal of orthodontics
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• v.36 no.2 s.115
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• pp.145-152
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• 2006

The purpose of this study was to evaluate electroless plating as a method of increasing the diameter of an orthodontic wire in comparison with eletroplating. After pretreatment plating of the 0.016 inch stainless steel orthodontic wire, electroless plating was performed at $90^{\circ}C$ until the diameter of the wire was increased to 0.018 inch. During the process of electroless plating, the diameter of the wire was measured every 5 minutes to examine the increasing ratio of the wire's diameter per time unit. And to examine the uniformity, the diameter at 3 points on the electroless-plated orthodontic wire was measured. An X-ray diffraction test for analyzing the nature of the plated metal and a 3-point bending test for analyzing the physical property were performed. The electroless-plated wire group showed a increased tendency for stiffness, yield strength, and ultimate strength than the electroplated wire group. And there was a statistically significant difference between the two groups for stiffness and ultimate strength. In the electroless-plated wire group, the increasing ratio of the diameter was $0.00461{\pm}0.00003mm/5min$ (0.00092 mm/min). In the electroplated wire group, it was $0.00821{\pm}0.00015mm/min$. The results of the uniformity test showed a tendency for uniformity in both the plating methods. The results of this study suggest that electroless plating of the wire is closer to the ready-made wire than electroplating wire in terms of the physical property. However, the length of plating time needs further consideration for the clinical application of electroless plating.

• Food Science and Preservation
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• v.18 no.1
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• pp.1-6
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• 2011

Kochujang-gulbi, a Korean traditional food, was prepared with kochujang and freeze-dried gulbi slices. Kochujang-gulbi was treated with high hydrostatic pressure (200, 400 and 600 MPa) and gamma-irradiation (7, 10, 20 and 30 KGy) to improve its quality and shelf-life. The pH of high hydrostatic pressure and gamma-irradiation treated kochujang-gulbi samples did not significantly different compared to that of control. However, Hunter L value slightly increased, and Hunter a and b values decreased by high hydrostatic pressure and gamma-irradiation treatment. During storage, the pH and color of high hydrostatic pressure and gamma-irradiation treated kochujang-gulbi samples did not significantly changed. The VBN and TBA level decreased by the increase treatment of high hydrostatic pressure and then slowely increased during storage. The VBN and TBA level of kochujang-gulbi samples treated by the strong gamma ray emission slowely increased during storage. In particular, gamma-irradiation treatment was very effective to sterilize microorganisms when compared to that of high hydrostatic pressure in kochujang-gulbi products. In addition, the high hydrostatic pressure and gamma-irradiation treated kochujang-gulbi samples shown significantly lower total viable cell number than control for the 20 days of storage at room temperature with retort pouch packaging.

• Environmental and Resource Economics Review
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• v.32 no.2
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• pp.107-126
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• 2023

This study analyzes the financial efficiency of the early scappage support system using the benefit and cost analysis. To do so, we use comprehensive administrative data on the early scrappage of old diesel vehicles. The result shows that the benefit-cost ratio was greater than 1 before 2020, but it appeared to be less than 1 after 2020. This indicates that despite recent reforms to increase the subsidy of early scrappage of old diesel vehicles, the rate of the benefit of air quality improvement is not as fast as the increase in system operation cost of this system. The benefit of air quality improvement depends on how much the operating period is shortened due to early scrappage support system. The earlier this period is brought forward, the more likely it is that the benefits of early scrappage will exceed the costs. Upon examining the results of this study, it was found that when the scrappage timing is brought forward by 5 years, the B/C for 98% of the samples becomes 1, greatly securing financial efficiency. Therefore, it is important for the government to reform the system so that it can influence the decision of old diesel vehicle owners on the timing of scrappage.