• Journal of Navigation and Port Research
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• v.38 no.2
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• pp.97-103
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• 2014

In these days, the world has been increasing navy forces such as aircraft carriers and high-tech destroyers etc. and the importance of submarines is being emphasized. Therefore, accurate values of the derivatives in equations of motion are required to control motion of the submarines. Hydrodynamic derivatives were measured by the vertical planar motion mechanism(VPMM) model test. VPMM equipment gave pure heave and pitch motion respectively to the submarine model and the forces and moments were acquired by load cells. As a result, the hydrodynamic derivatives of the submarine are provided through the Fourier analysis of the forces and moments in this paper.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.117-118
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• 2013

In these days, the world have been increasing navy forces such as aircraft carriers and high-tech destroyers etc. and the importance of submarines is being emphasized. Therefore, accurate values of the derivatives in equations of motion are required to control motion of the submarines. Hydrodynamic coefficients were measured by the vertical planar motion mechanism(VPMM) model test. VPMM equipment gave pure heave and pitch motion respectively to the submarine model and the forces and moments were acquired by load cells. As a result, the hydrodynamic coefficients of the submarine are provided through the fourier analysis of the forces and moments in this paper.

• Journal of Korean Society of Steel Construction
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• v.28 no.2
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• pp.85-96
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• 2016

Double split tee connection has various strength, stiffness, and energy dissipation capacity according to changes of thickness of T-stub flange and gauge distance, number, and diameter of high-strength bolt. If the double split tee connection is applied to a low- or medium-rise steel structure, a shear tab can't be applied for supporting shear force because of geometrical limitation. So it is required to propose details of improved double split tee connection to support shear force as well as flexural force. This research was performed to see if enough rotational stiffness is found when the double split tee connection without shear tab which was obtained through analytic and experimental researches by Yang et al. is applied to a low- or medium-rise steel structure. Also, it was seen if the low- or medium-rise steel structure having double split tee connection without shear tab has safe structural behavior, as well as material saving effect.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.2
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• pp.129-138
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• 2012

This paper deals with geometrical non-linear analyses of the tapered variable-arc-length beam, subjected to the combined load with an end moment and a point load. The beam is supported by a hinged end and a frictionless sliding support so that the axial length of the deformed beam can be increased by its load. Cross sections of the beam whose flexural rigidities are functionally varied with the axial coordinate. The simultaneous differential equations governing the elastica of such beam are derived on the basis of the Bernoulli-Euler beam theory. These differential equations are numerically solved by the iteration technique for obtaining the elastica of the deformed beam. For validating theories developed herein, laboratory scaled experiments are conducted.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.73-81
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• 2012

Safety issue for offshore wind-turbine foundation becomes a crucial factor as offshore wind turbines have been scaled up. Correspondingly, there is a demand to understand the effect of soil-structure interaction on to system behavior in geotechnical engineering point of view. The p-y curve method researched in past few decades is one of the most appropriate methodology to analyze the problem. In this study, recently proposed p-y curve models for various rocks are calibrated to analyze the engineering characteristics of seabed of Jeju Island where it is known to be most suitable area for offshore wind energy farm. Step by step calibration process for p-y models is presented. Analysis results show that subgrade reaction generally increases as closer to seabed. It is also shown that the behavioral characteristics of foundation reflect well rock properties in terms of resultant moment, shear force, etc.

• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.483-492
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• 2007

Pre-Engineering Building (PEB) system is one of the most economical structural systems. Tapered members can resist a maximum stress at a single location, whereas stresses of the rest of the members are considerably low. This results in appreciable savings both in terms of materials and construction costs. However, it was appreciated that special consideration would be required for certain aspects of this structural form. In particular, because of their slenderness, webs would buckle laterally and torsionally under the combined action of excessive axial, bending and shear forces. In this study, a total of four large-scale rafters with simple ends were tested. The main parameters were the width-thickness ratio of the web, the stiffener, and the flange brace. The purpose of this experiment is to evaluate the structural stability and to offer back-data on PEB design.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.196-196
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• 2012

전 지구적으로 발생하고 있는 잦은 기상이변과 기후변화의 가속화로 자연재해 발생빈도 및 피해규모는 증가하는 추세로 나타나고 있다. 이러한 기상이변은 우리나라 또한 예외가 아니며 최근 한반도에서 발생한 적설로 인하여 많은 인명과 재산피해가 증가하고 있다. 본 연구에서는 기상청에서 제공하는 KMA-RCM 기후자료를 바탕으로 관측자료 및 시나리오의 온도, 강수, 적설량 간의 관계를 이용하여 기상청 산하 기상관측소 58개 대상 지점으로부터 목표기간별(목표 I:1979~2008년, 목표 II:2011~2040년, 목표 II:2041~2070년, 목표IV:2071~2100년) 적설량을 예측하였으며, 빈도별(20년, 30년, 50년, 80년, 100년, 200년) 확률적설량을 산정하고자 하였다. KMA-RCM 자료를 이용한 미래 적설량 예측은 기상인자들의 복잡한 비선형 조합으로 발생하기 때문에 적설량에 영향을 미치는 온도, 강수, 적설량의 비선형 과정들을 고려할 수 있는 신경망 모형을 이용하여 적설량 예측 모형을 구성하였고, 58개 대상 지점의 30년 이상 관측기상자료 중 온도, 강수, 적설량 자료를 이용하여 지점별로 훈련을 시켜 이를 기후변화 시나리오에 활용하였다. 확률적설량에서 매개변수 추정은 확률가중모멘트법(PWM)을 이용하였고 적정확률분포형으로는 시나리오적 방법 및 비시나리오적 방법에 대한 분포형 검정결과 가장 적합하다고 판정되는 Gumbel분포형을 선정하였다. 위의 방법론을 통하여 미래 목표기간별로 확률적설량을 확률적설량을 산정하였으며 본 연구결과는 기후변화 시나리오를 고려한 목표기간별 적설량 산정 및 관련 방재기준의 개선 방안 및 재설정 기준 마련에 기초자료로 활용될 수 있을 것으로 기대된다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1087-1094
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• 2012

This study deals with structural analysis and testing under loading conditions calculated by computational fluid dynamics for a small composite blade that is utilized in a dual rotor wind turbine system. First, the aerodynamic forces were analyzed at the rated and cutout wind speed to identify the bending moment distribution along the blade length in previous research. Then, full-scale structural tests were conducted according to IEC 61400-2 to evaluate the structural integrity of the composite blade. These results were compared with finite element analysis to identify the accuracy of the structural analysis. Based on these results, it was revealed that the existing blade has a very high safety margin. Then, the layup of the composite blade was redesigned and analyzed using finite element analysis to achieve structural integrity and economic efficiency.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.88-88
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• 2020

수심평균 2차원 혼합모형은 하천환경에서 다양한 용존성 오염물질의 혼합현상을 모의하기 위해 널리 활용되어왔다. 2차원 혼합모형에서 분산계수는 하천의 전단 흐름에 의해 야기되는 오염물질의 퍼짐 현상을 표현하는 중요한 인자로서 작용하기 때문에 정교한 오염물질 혼합거동을 모의하기 위해서는 적합한 분산계수를 산정하는 것이 필수적이다. 분산계수를 실험적으로 산정하는 방법으로는 크게 모멘트법과 추적법으로 나뉘며, 비정상상태의 혼합거동에 대해 종방향 및 횡방향 분산계수를 동시에 산정할 수 있는 방법은 추적법 계열의 2차원 유관추적법(2D STRP)이 유일하다. 본 연구에서는 하천에 유입된 오염물질의 2차원 혼합해석을 위한 수치모형을 개발하였으며, 개발된 모형의 수치해를 바탕으로 다양한 Peclet 수의 범위에 대해 기존연구에서 제시된 2D STRP의 적용범위 및 성능을 정량적으로 분석하였다. 분석된 정보를 바탕으로 기존 2D STRP의 한계를 극복하기 위한 개선된 2차원 유관추적법(2D STRP-i)을 개발하고, 사행하천을 모형화한 실규모 하천실험시설에서 검증하였다. 기존 2D STRP의 성능평가 결과, Peclet 수가 낮은 조건일수록 농도분포의 예측 정확도가 감소하는 경향을 보였으며, 하안 경계에 도달하는 농도가 증가할수록 부정확한 결과를 초래하는 것으로 나타났다. 본 연구에서는 기존 2D STRP의 한계를 보완하여 더욱 정확한 분산계수를 산정하고자 하안 경계면 조건을 고려한 2차원 유관추적법(2D STRP-i)을 개발하였다. 2D STRP-i는 직교-곡선좌표계 기반의 2차원 이송-분산 방정식을 바탕으로 횡방향 유속분포 및 하안 경계조건을 고려할 수 있도록 개선되었다. 2D STRP-i는 공간적으로 상이한 이송효과 및 하안경계 조건을 적절히 반영함으로써 농도분포의 예측 정확도를 개선 시키는 것으로 평가되었으며, 하안경계면에서 농도가 증가하는 구간에서 기존 2D STRP의 결과와 비교하여 더욱 정확한 농도분포 및 분산계수를 제공하는 것으로 밝혀졌다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6A
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• pp.641-650
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• 2009

This paper presents new equations for member forces in concrete floating structures under wave loadings. The currently adopted design equations for wave loadings disregard the effect of mismatch between design wave length and the length of the structure. In most cases, however, additional internal forces occur due to disequilibriating buoyancy caused by the difference between design wave length and the length of the structure. In this study, new design equations considering the influence of the disequlibriating buoyancy is proposed. In addition, finite element solutions are sought to demonstrate the adequacy of the proposed design formulae in estimating the actual internal forces considering the structure as either rigid or flexible. It has been found that member forces are decreased approximately to around 55% for flexible model when compared with the rigid one.