• Geomechanics and Engineering
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• v.28 no.5
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• pp.455-461
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• 2022

Numerical assessment of the dynamic stability behavior of nonlocal beams rested on elastic foundation has been provided in the present research. The beam is made of fucntional graded (FG) porous material and is exposed to thermal and humid environments. It is also consiered that the beam is subjected to axial periodic mechanical load which especific exitation frequency leading to its instability behavior. Beam modeling has been performed via a two-variable theory developed for thick beams. Then, nonlocal elasticity has been used to establish the governing equation which are solved via Chebyshev-Ritz-Bolotin method. Temperature and moisture variation showed notable effects on stability boundaries of the beam. Also, the stability boundaries are affected by the amount of porosities inside the material.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.860-866
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• 2022

An accurate prediction of the pressure drop along the flow paths is crucial in the design of advanced passive systems cooled by heavy liquid metal coolants. To date, a generic pressure drop correlation over spacer grids by Rehme has been applied extensively, which was obtained from substantial experimental data with multiple types of components. However, a few experimental studies have reported that the correlation may give large discrepancies. To provide a more reliable correlation for ring-type spacer grids, the current numerical study aims at figuring out the most critical factor among four hypothetical parameters, namely the flow area blockage ratio, number of fuel rods, type of fluid, and thickness of the spacer grid in the flow direction. Through a set of computational fluid dynamics simulations, we observed that the flow area blockage ratio dominantly influences the pressure loss characteristics, and thus its dependence should be more emphasized, whereas the other parameters have little impact. Hence, we suggest a new correlation for the drag coefficient as C_B = C_ν,m/ε^2.7, where C_ν,m is formulated by a nonlinear fit of simulation data such that C_ν,m = -11.33 ln(0.02 ln(Re_b)).

• Wind and Structures
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• v.12 no.6
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• pp.519-540
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• 2009

This paper presents the results of a study into experimental and numerical methods for the identification of bridge deck flutter derivatives. Nine bridge deck sections were investigated in a water tunnel in order to create an empirical reference set for numerical investigations. The same sections, plus a wide range of further sections, were studied numerically using a commercially available CFD code. The experimental and numerical results were compared with respect to accuracy, sensitivity, and practical suitability. Furthermore, the relevance of the effective angle of attack, the possible assessment of non-critical vibrations, and the formulation of lateral vibrations were studied. Selected results are presented in this paper. The full set of raw data is available online to provide researchers and engineers with a comprehensive benchmarking tool.

• The Journal of Engineering Geology
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• v.19 no.1
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• pp.43-50
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• 2009

A 3-D numerical analysis was carried out to observe potential effects of orientation of inherent weak zones to tunnel behaviors and stress distributions during tunnel excavation. Weak zones used for the analysis were placed at the upper 1D part from crown, on the crown and on the center of face, using orientations derived from the 6th RMR parameter for assessment of joint orientation effect on tunnel. Mechanical properties of rock mass were derived through a in-situ displacement measurement-based back analysis. Finally, a classification chart for crown settlement with five ranks based on orientation and location of weak zones is suggested.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.83-90
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• 2002

There are few earthquake records in Korea and the Japanese or American representative earthquake records have been generally used in the seismic design. In this study, some earthquake records which the range of earthquake magnitudes varies from 5.3 to 7.9 were collected and analyzed to assess which record can rationally reflect Korean seismic characteristics. In this assessment, each seismic energy and acceleration spectrum were analyzed with the unified maximum ground acceleration. Several numerical analyses on Korean representative caisson structures were also carried out to compare each dynamic displacement. In these numerical analyses, soil conditions and the dimension of structure such as height and width were changed. Through this assessment, it is found that the compatible earthquake magnitude in Korea is lower than 7. From the result of numerical analyses, it is shown that horizontal dynamic displacements corresponding to earthquake magnitudes over than 7 are quite larger than those below earthquake magnitude 7. Based on this study, it is necessary that Korean seismic design guideline will refer earthquake magnitude criteria for the construction of the economical aseismic structure.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.132.2-132
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• 2001

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2682-2695
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• 2021

This paper aims to evaluate the structural dynamic responses and damage/failure of the nuclear fuel reprocessing plant under the free drop impact of spent fuel cask (SFC) and fuel assembly (FA) during the on-site transportation. At the present Part I of this paper, the large-scale SFC model free drop test and the corresponding numerical simulations are performed. Firstly, a composite target which is composed of the protective structure, i.e., a thin RC plate (representing the inverted U-shaped slab in the loading shaft) and/or an autoclaved aerated concrete (AAC) blocks sacrificial layer, as well as a thick RC plate (representing the bottom slab in the loading shaft) is designed and fabricated. Then, based on the large dropping tower, the free drop test of large-scale SFC model with the mass of 3 t is carried out from the height of 7 m-11 m. It indicates that the bottom slab in the loading shaft could not resist the free drop impact of SFC. The composite protective structure can effectively reduce the damage and vibrations of the bottom slab, and the inverted U-shaped slab could relieve the damage of the AAC blocks layer dramatically. Furthermore, based on the finite element (FE) program LS-DYNA, the corresponding refined numerical simulations are performed. By comparing the experimental and numerical damage and vibration accelerations of the composite structures, the present adopted numerical algorithms, constitutive models and parameters are validated, which will be applied in the further assessment of drop impact effects of full-scale SFC and FA on prototype nuclear fuel reprocessing plant in the next Part II of this paper.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.5
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• pp.95-101
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• 2023

Recent persistent coastal developments have expanded recreational areas and enhanced accessibility. However, this growth has also led to a rise in safety incidents. These accident factors can be divided into human-made and natural types. The latter is comprised of dynamic factors like waves, tides, sea fogs, and winds. While institutions like the Korea Meteorological Administration and the Korea Hydrographic and Oceanographic Agency already offer data on these dynamic factors, the resolution is often insufficient for a precise assessment of localized risks. In this study, to overcome these limitations, we utilized the dynamic information from existing open systems to construct a high-resolution numerical simulation. Through this, we developed an automated module to predict dynamic factors in localized coastal activity areas. Particularly during the module's construction, we compared and reviewed the numerical prediction results for waves with observed wave heights.

• Journal of Environmental Impact Assessment
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• v.4 no.1
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• pp.17-23
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• 1995

To assess preliminarily the contamination potential of water resources including groundwater owing to the hydrogeological characteristics of landfill site and the potential impact to humans and animals through contamination of water resources by leachate, "Landfill Site Preliminary Assessment Model(LASPAS)" was contrived. LASPAS could help them proritization of remediation of landfil sites by the convenient and relatively simple evaluation method of landfill site features. LASPAS was designd to aliot numerical ratings to landfill site related factors undermentioned; 1) hydrogeological factors such as hydraulic conductivity of aquifer, thickness of confining layer over aquifer, topographical slope, net recharge, and subsurface containment 2) water resources contamination factors of impacts on receptors such as proximity to drinking water supply, substitutability of drinking water supply, type of use of water resources, known impact on drinking water supply, and flood potential.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.144-147
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• 2003

This paper presents a nonlinear finite element analysis procedure for the seismic performance assessment of reinforced concrete bridge piers using damage indices. The accuracy and objectivity of the assessment process may be enhanced by the use of sophisticated nonlinear finite element analysis program. A computer program, named RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Damage indices aim to provide a means of quantifying numerically the damage reinforced concrete bridge piers sustained under earthquake loading. The proposed numerical method for the seismic performance assessment of reinforced concrete bridge piers is verified by comparison with the reliable experimental results.