• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.372-376
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• 2005

본 연구에서는 다양한 유량 조건 하에서 수로의 만곡이 존재하고 하중토가 존재하는 비교적 복잡한 지형에 대한 수리모형실험에 LSPIV기법과 기존 점유속계(2차원 전자기유속계)를 함께 적용하고 그 결과를 비교하여 복잡한 흐름에 대한 LSPIV의 적용성을 검토하였다. LSPIV를 이용한 표면유속장과 2차원 전자기유속계를 이용하여 1점법으로 측정된 유속장을 비교할 때, 수로 만곡과 같은 지형적 특성으로 인한 유속분포의 특성이 유사하게 관측되었으며, 홍수시의 주변고수부지 및 하중도 침수로 인해 복잡한 흐름구조가 발생하는 경우에는 LSPIV를 이용한 표면유속장 측정을 통하여 흐름특성을 더욱 명확하게 관찰할 수 있었다. 측정된 유속자료 및 하도단면자료를 이용하여 홍수량을 산정해 본 결과 하도횡단면이 비교적 단순한 경우에는 표면유속과 점유속을 이용해 계산한 홍수량 간의 차가 크지 않았으나 하도단면이 복잡한 경우에는 계산된 홍수량 사이의 차가 크게 나타났다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2401-2409
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• 2013

Reliability analysis with response surface method (RSM) was peformed for a offshore wind turbine (OWT) monopile, which is one of mostly used foundations under 25m seawater depth in the world. The behaviors of a real OWT monopile installed into sandy soils subjected to offshore environmental loads such as wind and wave were analysed using reliability design program (HSRBD) developed in KIOST. Sensitivity analysis of design variables for a OWT monopile with 6m diameter showed that the larger in pile diameter the smaller in probability of failure ($P_f$) of a horizontal deflection and a rotational angle at a pile top, but at a greater than 7m of pile diameter, the reduction rate of $P_f$ was almost constant. It is a necessary that appropriate local design criteria should be designated as soon as possible because there were significant differences on horizontal deflections; $P_f$ was 60% at a minimum criteria 15mm deflection, however, 1.5% $P_f$ when 60mm deflection using 1% of pile diameter from local design criterion standard. Finally, friction angle of sand among many design variables was found most influential design factor in OWT monopile design, and a sensitivity analysis is found an important process to understand which design variables can mostly reduce $P_f$ with a optimum design for maintaining OWT stability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.57-63
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• 2002

지면효과를 받는 와류면의 2차원 비정상 전개를 이산와류법을 사용하여 연구하였다. 와류면이 말리는 정확한 형상을 얻기 위하여, 두 개의 평활기법을 비교하였다. 타원형 하중분포를 가지는 지면가까이에 있는 날개의 후류말림에 대하여 본 연구 방법을 적용하였다. 날개가 지면가까이 비행할 때, 지면효과로 인하여 와류가 날개길이방향으로 이동하였으며 날개익단부근에서 와류면의 늘림운동이 발생하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.1
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• pp.55-61
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• 2017

Recently several researches have been conducted to develop sliding track system in which friction between concrete track and bridge slab has been reduced. This paper investigated shear load carrying capacity of lateral supporting concrete block which should be implemented to resist lateral load due to train in sliding track system. In order to evaluate shear load carrying capacity of lateral supporting concrete block, analytical model has been developed considering concrete friction and rebar dowel action along construction joint. The proposed model predicted test results on the shear load carrying capacity from literature conservatively by 13~23% because effect of aggregate interlock along crack surface was neglected. Since construction joint status is ambiguous on construction site, it can be concluded that the proposed model can be used for reasonable design of lateral supporting concrete block. Based on the proposed model, design proposal for lateral supporting concrete block has been established.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.453-460
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• 2015

Since the Fukushima nuclear accident, several researchers are extensively studying the effect of torsion on the piping systems In nuclear power plants. Piping installations in power plants with a circumferential crack can be operated under combined loading conditions such as bending and torsion. ASME Code provides flaw evaluations for fully plastic fractures using limit load criteria for the structural integrity of the cracked pipes. According to the recent version of Code, combined loadings are provided only for the membrane and bending. Even though actual operating conditions have torsion loading, the methodology for evaluating torsion load is not established. This paper provides the results of limit load analyses by using finite element models for circumferentially cracked pipes under pure bending, pure torsion, and combined bending and torsion with tension. Theoretical limit load solutions based on net-section fully plastic criteria are suggested and verified with the results of finite element analyses.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1947-1955
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• 2013

The purpose of this paper is to present an photoelasticity technique for measuring the displacement and stress distribution in particle assembly subjected to shallow foundation loading. Photoelastic measurement technique was employed to visualize the force transmission of a particle assembly. A model assembly bounded by a steel frame was built by stacking bi-dimensional circular particles made of polycarbonate elastomer. Each particle was coated by a thin photoelastic sheet so that the force transmission represented by bright light stripes can be visualized. In a contacted particle, both magnitude and orientation of principal stress difference can also be measured via the photoelasticity technique. The different distributions of the contact stresses at the initial loading and near the failure were quantitatively compared. The photoelastic patterns and displacement fields observed in the pre-failure state disappears immediately after the buckling of confined force chains.

• Geotechnical Engineering
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• v.13 no.6
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• pp.61-70
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• 1997

Although the load -settlement curve characteristics of embedded piles are different from those of driven piles, for the determination of their allowable loads the same analysis method has been adopted without any considerations. According to the related domestic chi teria, the analysis methods of load-settlement curve have some conflicts among themselves and have several vague points in obtaining the allowable capacity from ultimate or yield capacity. In order to solve those problems, the relevant literatures were reviewed. And also the result of 106 pile load tests was analysed. Analysis result indicates that analysis met hods of the load-settlement curve based on single mathematical curve are not suitable for the general analysis method of load-settlement curves due to their various characteristics. As a result, the appropriate analysis methods and safety factors for the determination of allowable capacity of pile are suggested in this paper.

• Journal of Navigation and Port Research
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• v.31 no.1 s.117
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• pp.21-27
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• 2007

The wave load and its influence on the response of offshore structure have been well investigated through the statistical approach based on the linear theory. The linear approach has a limitation to apply the extreme condition such as extreme wave, which corresponds to extreme value of wave spectrum. The main topic of present study is to develop an efficient numerical method to predict wave load induced by extreme wave. As a numerical method, finite element method based on variational principle is adopted. The frequency-focusing method is applied to generate the extreme wave in the numerical wave tank. The wave load on the bottom mounted vertical cylinder is investigated. The hydroelastic response of the vertical cylinder is also investigated so as to compare the wave loads with the rigid body case in the extreme wave condition.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.83-90
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• 2007

Buildings become high and large. CFT(Concrete Filled steel Tube) columns have been developed to manage effectively that loads which columns support and cross sections of columns are increased. Because CFT column is the composite structure made of two different materials, many researches have been performed to look into mechanical behaviors. This study is an analytic study about bond stress on interface between concrete core and steel tube in circular and rectangular CFT columns. ABAQUS/Standard Version 5.8 is used to analyze bond stress by bond form and position of shear-connector, and improved analystic method about mechanical characters on interface is suggested.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.3
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• pp.417-426
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• 1999

The some papers which deal with the dynamic instability for shell-like structures under the step load have been published, but there are few papers which treat the essential phenomenon of the dynamic buckling using the phase plane for investigating occurrence of chaos. In nonlinear dynamics, examining the characteristics of attractor on the phase plane and investigating the dynamic buckling process are very important thing for understanding why unstable phenomena are sensitively originated by various initial conditions. In this study, the direct and the indirect snap-buckling of shallow arches considering geometrical nonlinearity are investigated numerically and compared with the static critical load.