• Journal of the Korean Geosynthetics Society
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• v.3 no.4
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• pp.21-27
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• 2004

Stress relaxation behaviors of nonwoven geotextile and geomembrane which have protection, filtration and drainage, water barrier functions, respectively were analyzed. 'Theory of transition phenomena' was applied to interpretate the stress relaxation behaviors of two geosynthetics. The initial and later relaxation times for stress relaxation behaviors of geosynthetics were derived from the constitutive equations. The initial relaxation behaviors of these geosynthetics were dependent on the additional strains and were especially faster with temperature. Finally, both relaxation times of geosynthetics were shorter with additional strain and temperature.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.880-884
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• 2009

여름철 강우시 저수지로 유입하는 고탁도의 하천수는 저수지 주변 수체에 비해 낮은 수온과 높은 부유물질 농도(SS)로 인해 상대적으로 높은 밀도를 가지며, 저수지 내에서 동일 밀도층을 따라 분포하며 밀도류를 형성하게 된다. 탁수는 대부분 장기간 저수지에 체류하며 수질과 수생태계에 큰 영향을 주게 된다. 따라서 저수지로 유입한 탁수의 밀도류 거동특성을 파악하는 것은 저수지 운영, 수질관리 및 수생태계 보호를 위한 관리대책 수립에 있어서 중요한 요소이다. 본 연구의 목적은 횡방향 평균 2차원 수치모델을 이용하여 초기수위별 다양한 유량규모에서 소양호로 유입하는 밀도류의 거동특성(유입경계지점 수심($h_0$), 침강점 수심($d_p$)과 거리($X_p$), 분리점 수심($d_s$), 중층류 관입두께($h_i$), 댐 축 도달시간($t_a$), 희석율(${\beta}$))을 분석하여 저수지 수질관리를 위한 의사결정지원 기초정보를 제공하는데 있다. 밀도류의 거동분석을 위해 사용된 유량조건은 그동안 소양호에서 발생한 홍수크기를 바탕으로 7개의 등급으로 나누었으며, 각각의 유량조건별 수문곡선은 2007년 수문사상 중 7월 30일부터 8월 30일까지의 수문사상을 바탕으로 수정가우시안 공식을 사용하여 산정하였다. 탁수 거동 특성의 모의는 서로 다른 초기 수위 및 유량조건하에서의 탁수거동을 나타냈고, SS농도 25 mg/L 이상을 기준으로 하여 탁수층의 $d_p$, $X_p$, $d_s$, $h_i$, $t_a$, ${\beta}$를 산정하였다. 일반적으로 유량규모가 커질수록 $d_p$와 $d_s$는 증가하였고, $X_p$는 댐 축으로부터 가까워짐이 확인되었으나, 동일 유량규모에 대해 초기 수위가 증가함에 따라 $X_p$는 대체로 댐으로부터 멀어졌다. $h_i$는 유량규모가 증가함에 따라 완만하게 증가하는 경향을 보였고, $t_a$는 초기수위가 EL. 165 m일 때 유량이 2,000 CMS 미만인 경우 댐 앞까지 도달하지 못하는 것으로 나타났으며, 나머지 수위조건에서는 유량이 3,000 CMS 미만인 경우 댐 앞까지 도달하지 못하는 것으로 나타났다. 유량 규모에 따라 $X_p$가 0 km인 지점과 19 km인 지점에서의 ${\beta}$ 값을 산정한 결과 일반적으로 유량규모가 커질수록 유입수의 희석효과는 작아지며 초기수위가 커질수록 증가하는 경향을 나타냈다. 연구 결과는 탁수 발생 초기 저수지 운영 실무자들이 유량규모 및 초기 수위조건에 따른 밀도류의 거동특성을 신속히 예측하는 목적으로 사용될 수 있다.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.29-39
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• 1999

In this study, mathematical modelling for initial motion of test vehicle launched from sliding launcher is performed, and simulation results from this mathematical models are verified by comparing them with sea trial results. Especially, it is showed that models using strip method give better results than using empirical formulae and linear equations of motion. This mathematical model can give useful tools to design sliding launchers or test vehicles.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.4
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• pp.27-35
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• 2000

강한 지진 하에서 효율적으로 거동하도록 유도하는 연구중의 하나로서 개구부를 가진 합성보의 이력거동을 조사하고 있다. 직사각형 개구부를 가진 합성보에 대한 연구를 발전시켜 에너지 소산능력이 보다 큰 달걀형 개구부를 가진 합성보에 대한 연구를 수행하였다. 실험적 연구와 비선형 FEM 해석 연구 모두가 그러한 합성보의 연성도를 입증하였다. 본 연구는 달걀형 개구부를 가진 합성보의 강도와 초기강성도를 산정하는 약산식을 제시하였고, 그 결과를 실험 및 비선형 FEM 해석의 결과와 비교 분석하였다.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.2
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• pp.86-90
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• 1994

This paper attempts to incorporate the initial crack damage effect into the existing idealized plate unit. For this purpose, a new concept which indicates the equivalent, reduced material properties due to initial cracks at the structural unit level, not at he microscopic aspect, is suggested, and a simplified mechanical plate model for the initially cracked plate in axial tension is formulated as a function of initial crack length, based on the finite-element solutions obtained by crack propagation analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1A
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• pp.15-24
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• 2008

This paper presents the analytical method for the long-term behavior of simply supported composite beams with precast decks prestressed in the longitudinal direction. The objectives of time-dependent analysis are to estimate losses of prestress on the concrete slab and long-term deflection due to creep and shrinkage of concrete, relaxation of prestressing steel. Also, the time-dependent analysis was carried out using the presented analytical method to evaluate the effects of several parameters on the long-term behavior of composite bridge with precast deck, including geometrical shapes of composite beams, compressive strength of concrete and magnitude of initial prestress. The results of the analysis indicated that, in the effects of geometrical shapes of composite beams, the main parameters affecting the losses of prestress and the long-term deflection were the cross sectional area and the moment of inertia of steel beam, respectively. Finally, the determination method for the required initial prestress was proposed by evaluation of the loss characteristics due to shrinkage and creep of concrete.

• Journal of the Korean Geotechnical Society
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• v.34 no.2
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• pp.5-17
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• 2018

In this study, the in-situ stress, strength and stress-strain characteristics with shear parameters (UU, CU, ${\bar{CU}}$) are analytically evaluated and the stability analyses are carried out under loading/unloading conditions. The in-situ stress and the stress-strain behaviour may become different according to input shear parameters in finite element analyses with construction step, Especially, if the internal friction angle in Mohr-Coulomb model is set to zero, the in-situ stress and the stress-strain behaviour might not be properly predicted. The results from CU parameter of total stress analysis have no significant difference with the results from CU of effective stress analysis. Therefore, in the numerical analysis for soft ground, CU parameters can be applied to predict in-situ stress and stress-strain behaviors. In addition, the calculation method was proposed to determine the shear parameter of Mohr-Coulomb model, which is corresponding to the shear strength equivalent to that of in-situ soil.

• Journal of Energy Engineering
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• v.11 no.2
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• pp.122-129
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• 2002

The analytical models and algorithm of the SPIKE code, which has been developed by KAERI's KALIMER team to investigate the sodium-water reaction phenomena in the liquid metal reactor, were introduced with its verification calculation results. The sodium water reaction of KALIMER IHTS was evaluated. Early stage of the sodium-water reaction consists of wave and mass transfer regimes. The pressure variations were independent of specific design features in the wave transfer regime. However in the mass transfer regime, the pressure variations were strongly dependent on cover gas volume and rupture disk set pressure. The early stage SWR analysis showed that the KALIMER IHTS with an appropriate cover gas volume and rupture disk set pressure had enough margin to its design pressure.

• Composites Research
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• v.20 no.6
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• pp.15-20
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• 2007

In this work, the structural response of thin-walled, composite beams with built-in twist angles is analyzed using a mixed beam approach. The analytical model includes the effects of elastic couplings, shell wall thickness, and torsion warping. Reissner's semi-complimentary energy functional is used to describe the beam theory and also to deal with the mixed-nature in the beam kinematics. The bending and torsion related warpings introduced by the non-zero pretwist angles are derived in closed-form through the proposed beam formulation. The theory is validated with available literature and detailed finite element analysis results for rectangular solid section beams with elastic couplings. Very good correlation has been obtained for the cases considered.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.1
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• pp.13-20
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• 2005

Since High Tensile Steel has been widely used to thin plate on the steel structure and marine structure, It has increased possibility of buckling. Especially, initial deflection of ship structure is mainly caused by heat processing of welding or cutting etc. This initial deflection has negative effect to thin plate, which would incur a complicated nonlinear behavior accompanied with secondary buckling. If idealized initial deflection is considered in early marine structure design of secondary buckling, accuracy and reliability will be improved considerably. The measurement data of initial deflection from experiment is applied to finite element series analysis. For FEA(ANSYS), Applied nonlinear buckling analysis is used by Newton-Raphson method & Arc-length method included in this program.