• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.6
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• pp.523-531
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• 2008

In hole type CPTu equipment which combines the concepts of inhole test method and piezocone test method was newly developed in order to evaluate the dynamic properties of marine soils. It is possible to perform inhole type CPTu without any additional source device because the source and receiver are contained inside the cone rod, which is different from the conventional seismic cone system. In this study, laboratory tests using kaolinite as soft soil and numerical simulations using finite element method were carried out to investigate the effects of several parameters including test methods and soil conditions on the test results from inhole type CPTu and to find out the optimum test method. It was found that it is necessary to maintain the length of swing arm as well as the distance between source and receiver consistently to obtain the rigorous test results. The laboratory test and numerical results also reveal that contrary to the input wave frequency, the water content of soil layer and the disturbance due to the installation of swing arm apparently affect the shear wave velocity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.557-564
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• 2019

The characteristics of the torque and torque ripple of Interior Permanent Magnet Synchronous Motor(IPMSM) are influenced by the size and position of the rotor magnet and the size of the stator slot. This paper deals with the optimal design method for improving torque and torque ripplerate for IPMSM using Response Surface Methodology(RSM). Two objective functions of torque output and torque ripple were derived from the sensitivity analysis by Plackett-Burmann(PB) for the characteristic variables affecting torque and torque ripple. Secondary characteristic variables were selected from the derived objective function and RSM secondary regression model function was estimated by the experiment schedule and analysis results according to the Central Composite Design (CCD). The reliability of the secondary regression model was verified using ANOVA table. The analysis according to the experimental schedule was verified by JMAG(Ver. 18.0) which is Finite Element Method(FEM) software. The torque output of IPMSM applied with final characteristic variables was increased torque output by 11.5 % and the torque ripplerate was reduced by 9.1 %.

• Journal of Korean Association for Spatial Structures
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• v.11 no.3
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• pp.95-103
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• 2011

Among structural systems for complex-shaped tall buildings, diagrid system is widely used because of its structural efficiency and beauty of form. Recently, mega frame is favorably employed as a suitable structural system for skyscrapers because this structural system has sufficient stiffness against the lateral forces by combination of mega members which consist of many columns and girders. Diagrid mega frame system is expected to be promising structural system for future super tall buildings. However, it takes tremendous analysis times and engineer's efforts to predict the structural behavior of tall buildings applied with diagrid mega frame system because the diagrid mega frame structure has significant numbers of elements and nodes. Therefore, efficient analytical method for all buildings applied with diagrid mega frame system has been proposed in this study to reduce the efforts and time required for the analysis and design of diagrid mega frame structure. To this end, an efficient modelling technique using the characteristics of diagrid mega frame structures and an efficient analytical model using minimal DOFs by the matrix condensation method were proposed in this study. Based on the analysis of an example structure, the effectiveness and accuracy of the proposed method have been verified by the comparison between the results of the proposed method and the conventional method.

• Journal of the Korean Geotechnical Society
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• v.31 no.8
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• pp.5-15
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• 2015

One-dimensional rainfall laboratory tests using gneissic weathered soil were conducted to investigate effect of antecedent rainfall on infiltration characteristics. Experimental results using samples from Chuncheon and Chungju sites showed that rainfall onto the ground surface decreased initial negative pore water pressure of unsaturated soils, which recovered gradually after the end of rainfall. Rainfall intensity increases water infiltration rate, and infiltration rate during main rainfall is faster than that of the preceding rainfall. It is considered that higher water saturation after antecedent rainfall increases water infiltration rate during main rainfall. In particular, Chungju sample with higher clay content had slower recovery of negative pore water pressure and infiltration rate. Numerical results using finite element slope stability analysis showed that reduction of initial negative pore pressure due to rainfall infiltration deteriorates slope stability, and diffusion of pore water pressure after the end of rainfall further reduces FS of the slope in the short term. Main rainfall after prior rainfall further reduced factor of safety of the unsaturated slope. Pattern of antecedent rainfall has a significant impact on the magnitude and distribution of initial pore water pressure in unsaturated soils which are controlling factor to assess factor of safety of unsaturated slope during rainfall.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.1
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• pp.31-39
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• 1997

This paper is on the vibration control of access floor on the frames of reinforced structure. In this study, the horizontal anti-vibration system using precise spring damper was developed and modeling and vibration analysis of the RC structure was performed for the control of horizontal vibration coused by machinery and worker's moving. Experiment was done in three cases, no damper at the RC structures, dampers connecting pedestal to pedestal and pedestal to the structure, for the investigation of the effect of the system on disigned RC structure. For each experiment, the occeleration responses on slab and access floor after giving impact wave and external vibration were measured. It was shown that the magnitude of resonance response of the system with dampers are smaller than without damper and the resonance peak also partly moved to low-frequency range. Furthermore. It was shown that the acceleration components of the system with domoers decreased greatly in high-frequency range and the system was very much effective especially for external vibration. In order to verify the anti-vibration effect of the developed system, the vibration analysis was also done for the system by using the finite element modelling. The analysis results was in good agreement with experimental results. Thus, It is concluded that this study is useful for the design of precise anti-vibration system and micro-vibration control of concrete structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3B
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• pp.175-183
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• 2012

In this study, Galerkin scheme and SU/PG scheme of Petrov-Galerkin family were applied to the shallow water equations and a finite element model for shallow water flow was developed. Numerical simulations were conducted in several flumes with convection-dominated flow condition. Flow simulation of channel with slender structure in the water course revealed that Galerkin and SU/PG schemes showed similar results under very low Fr number and Re number condition. However, when the Fr number increased up to 1.58, Galerkin scheme did not converge while SU/PG scheme produced stable solutions after 5 iterations by Newton-Raphson method. For the transcritical flow simulation in diverging channel, the present model predicted the hydraulic jump accurately in terms of the jump location, the depth slope, and the flow depth after jump, and the numerical results showed good agreements with the hydraulic experiments carried out by Khalifa(1980). In the oblique hydraulic jump simulation, in which convection-dominated supercritical flow (Fr=2.74) evolves, Galerkin scheme blew up just after the first iteration of the initial time step. However, SU/PG scheme captured the boundary of oblique hydraulic jump accurately without numerical oscillation. The maximum errors quantified with exact solutions were less than 0.2% in water depth and velocity calculations, and thereby SU/PG scheme predicted the oblique hydraulic jump phenomena more accurately compared with the previous studies (Levin et al., 2006; Ricchiuto et al., 2007).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.34-42
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• 2011

It's been reported that the global warming effect has invoked the ever increasing typhoon intensity and long-term sea level rise which jointly cause severe wave overtopping over breakwaters or shore dykes. A simple measure to cope with this undesirable change may be just to increase the crest height of the dykes and breakwaters. This is surely effective to prevent wave overtopping, but it also decreases the seaward visibility of coastal waterfront. In this paper, a dynamic deformable rubber membrane parapet which not only reduces wave overtopping in storm period but also secures seascapes in normal days is presented. Several optimal configurations of the parapet are proposed. Through numerical analyses using a nonlinear finite element model and hydraulic experiments, the air controlled expansion and contraction of the parapets, their behavior against wave overtopping and structural stability are investigated.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.449-456
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• 2007

This research was conducted to analyze the features of the critical tensile stresses at the top and bottom of the concrete slab in the jointed concrete pavement (JCP) when subjected to both the environmental and vehicle loads. First, the stress distribution in JCP was analyzed when the system was subjected to only the environmental loads or the vehicle loads by using the finite element model of JCP. Then, the stresses were analyzed when the system was subjected to the environmental and vehicle loads at the same time. From this study, it was found that the critical tensile stresses at the slab bottom under the vehicle loads were almost constant regardless of the loading positions once the loads were applied at the positions having some distance from the transverse joint. The critical tensile stresses at the slab bottom could be obtained using the model consisting of normal springs for underlying layers by adding the critical stresses due to the environmental loads and the vehicle loads for the curled-down slab, and by subtracting the critical stress due to the environmental loads from that due to the vehicle loads for the curled-up slab. The critical tensile stresses at the top of the slab could be obtained using the model consisting of tensionless springs for underlying layers by adding the critical stress due to the environmental loads and the stress at the middle of the slab under the vehicle loads applied at the joint for the curled-up slab. An alternative to obtain the critical stresses at the top of the slab for the curled-up slab was to use the critical stresses under only the environmental loads obtained from the model having normal springs for underlying layers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.9-16
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• 1990

The safety of concrete nuclear containment structures should be secured against all kinds of loading due to various natural disasters or extraordinary accidental loads. The current design criteria of concrete containment structures are not based on the reliabillty-based design concept but rely on the conventional design concept. In this paper, a probabillty-based reliability analysis were proposed based on a FEM-based random vibration analysis and serviceability limit state of structures. The limit state model defined for the study is a serviceability limit state in terms of the more realistic crack failure that might cause the emission of radioactive materials, and the results are compared with those of the strength limit state. More accurate reliability analyses under various dynamic loads such as earthquake loads were made possible by incorporation the FEM and random vibration theory, which is different from the conventional reliability analysis method. The uncertainties in loads and resistance available in Korea and the refernces were adapted to the situation of Korea, and especially in the case of earthquake, the design earthquake was assessed based on the available re ports on probabilistic description of earthquake ground acceleration in the Korea peninsula.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2003.04a
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• pp.510-516
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• 2003

연안관리 정책을 결정하기 위해서는 다양한 정보의 수집과 이를 체계적으로 관리하고 분석할 수 있는 기법이 필요하다. 특히, 다양한 이해집단과 목적들이 상충하는 지역의 특성을 파악하기 위해서는 환경, 사회, 경제적인 기준 및 의사결정자의 가치체계가 반영될 수 있어야 하며, 선호도가 반영된 요소를 효율적으로 분석할 수 있어야 한다. 이에, 본 연구에서는 공간자료의 처리 및 분석이 용이한 GIS 환경에 다기준 분석법, 그 중에서도 AHP 모형을 결합하는 방법을 다루어 보았다. 분석과정을 살펴보면, 본 연구에서는 지역에 영향을 미치는 사회ㆍ경제적인 지표, 환경 지표를 정하였고, 이런 지표들의 데이터를 GIS라는 도구를 통하여 분석이 용이하도록 변환시켰다. 한편, 이 지역에 영향을 미치는 각 기준들의 중요성을 파악하여 의사결정자의 의견을 반영할 수 있도록 다기준 분석법의 하나인 AHP를 이용하여 가중치를 산정하였다. 다음으로, 다양한 출처의 자료를 표준화하여 GIS의 래스터 자료로 구축한 후, 가중치를 적용한 개별 레이어를 지도대수와 중첩분석을 이용하여 최종 결과 레이어를 생성하였다. 생성된 최종 결과 레이어 상의 공간의 대안인 각 셀 값을 비교ㆍ분석하였다. 이로 인한 결과는 연안의 유한한 자원과 공간의 다양한 이용상태를 관리하기 위한 해안과 육상의 정보를 제공할 수 있다. GIS와 다기준 분석을 통합함으로써 다양한 출처의 공간정보를 분석하고 연안의 현 상태를 밝힐 수 있다. 또한, 이것은 분석 결과가 단순하고 명확하게 설명되어 정책 결정자에게 유용한 정보를 제공할 뿐만 아니라, 이 정보를 이용하여 실질적인 연안관리계획을 수립하는데 도움이 된다.가능성 0.5이상의 면적은 59%를 차지하였다.퇴적이 우세한 것으로 관측되었다.보체계의 구축사업의 시각이 행정정보화, 생활정보화, 산업정보화 등 다양한 분야와 결합하여 보다 큰 시너지 효과와 사용자 중심의 서비스 개선을 창출할 수 있는 기반을 제공할 것을 기대해 본다.. 이상의 결과를 종합해볼 때, ${\beta}$-glucan은 고용량일 때 직접적으로 또는 $IFN-{\gamma}$ 존재시에는 저용량에서도 복강 큰 포식세로를 활성화시킬 뿐 아니라, 탐식효율도 높임으로써 면역기능을 증진 시키는 것으로 나타났고, 그 효과는 crude ${\beta}$-glucan의 추출조건에 따라 달라지는 것을 알 수 있었다.eveloped. Design concepts and control methods of a new crane will be introduced in this paper.and momentum balance was applied to the fluid field of bundle. while the movement of′ individual material was taken into account. The constitutive model relating the surface force and the deformation of bundle was introduced by considering a representative prodedure that stands for the bundle movement. Then a fundamental equations system could be sim