• 국제지역연구
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• 제15권2호
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• pp.331-350
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• 2011

본 연구는 1989-2009년 기간 동안의 MTI 2단위, 56개 품목의 대일 수출입 시계열 패널자료를 사용하여 대일 상품수지 함수를 추정하였다. 대일 상품수지 함수는 정태패널 모형과 거래비용을 고려한 동태패널모형을 사용하여 추정하였으며 실증분석결과 정태패널모형보다는 거래비용을 고려한 동태패널모형이 모형의 안정성이 우수한 것으로 나타났다. 안정적인 대일 상품수지 함수의 추정의 의미는 비록 대일 상품수지 적자가 지속되고 있더라도 양국교역은 양국후생에 도움이 된다는 것을 의미한다. 동태패널 분석결과 균형 상품수지로의 조정속도는 0.0389로 매우 느린 것으로 나타났으며 이는 대일상품수지 균형으로의 조정에 필요한 비용이 현재 상품수지 적자로 인한 비용보다 크기 때문이다. 상품수지에 대한 일본실질소득 탄력성과 한국실질소득 탄력성은 각각 4.38168과 -0.835225로 이론에 부한하는 부호를 나타내며 유의한 것으로 나타나, 대일 수출상품은 사치재의 성격을 갖는 반면 수입상품은 필수재의 성격을 갖는 것으로 나타났다. 대일 상품수지의 환율탄력성(${\partial}TB/{\partial}ER$)은 0.478435로 비탄력적인 것으로 밝혀졌다. 이는 환율변동이 대일 상품수지에 미치는 영향이 작은 반면 대일 상품수지변동은 큰 폭의 원/엔 실질환율을 변동시킬 수 있음을 의미한다.

• Steel and Composite Structures
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• 제46권4호
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• pp.451-469
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• 2023

The use of precast hollow-core slabs (PCHCS) in civil construction has been increasing due to the speed of execution and reduction in the weight of flooring systems. However, in the literature there are no studies that present a finite element model (FEM) to predict the load-slip relationship behavior of pushout tests, considering headed stud shear connector and PCHCS placed at the upper flange of the downstand steel profile. Thus, the present paper aims to develop a FEM, which is based on tests to fill this gap. For this task, geometrical non-linear analyses are carried out in the ABAQUS software. The FEM is calibrated by sensitivity analyses, considering different types of analysis, the friction coefficient at the steel-concrete interface, as well as the constitutive model of the headed stud shear connector. Subsequently, a parametric study is performed to assess the influence of the number of connector lines, type of filling and height of the PCHCS. The results are compared with analytical models that predict the headed stud resistance. In total, 158 finite element models are processed. It was concluded that the dynamic implicit analysis (quasi-static) showed better convergence of the equilibrium trajectory when compared to the static analysis, such as arc-length method. The friction coefficient value of 0.5 was indicated to predict the load-slip relationship behavior of all models investigated. The headed stud shear connector rupture was verified for the constitutive model capable of representing the fracture in the stress-strain relationship. Regarding the number of connector lines, there was an average increase of 108% in the resistance of the structure for models with two lines of connectors compared to the use of only one. The type of filling of the hollow core slab that presented the best results was the partial filling. Finally, the greater the height of the PCHCS, the greater the resistance of the headed stud.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.212-213
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• 2005

The results of an experimental and analytical study of composite pressure hull on buckling pressure are presented for URN 300. We predicted the buckling and post buckling analysis of composite laminated cylindrical shell and panel under external compression by using ABAQUS/Standard[Ver 6.4]. To obtain nonlinear static equilibrium solutions for unstable problems, where the load-displacement response can exhibit the type of nonlinear buckling behavior, during periods of the response, the load and/or the displacement may decrease as the solution evolves, used the modified Riks method. Experiments were conducted to verify the validation of present analysis for cross-ply laminated shells. The shells considered in the study have four different lamination patterns, [${\pm}{\Theta}$/0/90]$_{14s}$,[${\pm}{\Theta}_{14}$/$0_{14}$/$90_{14}$],[${\pm}$45/0/90]$_{18s}$ and [/0/90]$_{18s}$. At the result of this study, the optimized ply orientation angle is $75^{\circ}$. The critical load from experiment is 69% of that of numerical analysis, because the fracture of matrix was generated before buckling. So URN 300 is not proper to use at the condition under high external pressure.

• Journal of Biosystems Engineering
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• 제27권3호
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• pp.219-226
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• 2002

Desorption equilibrium moisture contents of oak mushroom were measured by the static method using salt solutions at flour temperature levels of 35$\^{C}$, 45$\^{C}$, 55$\^{C}$ and 6$\^{C}$ and five relative humidity levels in the range from 11.0% to 90.8%. EMC data were fitted to the modified Henderson, Chung-Pfost, modified Halsey and modified Oswin models using nonlinear regression analysis. Drying tests far oak mushroom were conducted in an experimental dryer equipped with air conditioning unit. The drying test were performed in triplicate at flour air temperatures of 35$\^{C}$, 45$\^{C}$, 55$\^{C}$ and 65$\^{C}$ and three relative humidities of 30%, 50% and 70% respectively. Measured moisture ratio data were fitted to the selected four drying models(Lewis, Page, simplified diffusion and Thompson models) using stepwise multiple regression analysis. The results of comparing root mean square errors for EMC models showed that modified Halsey was the best model, and modified Oswin models could be available far oak mushroom. The results of comparing coefficients of determination and root mean square errors of moisture ratio for four drying models showed that Page model were found to fit adequately to all drying test data with a coefficient of determination of 0.9990 and root mean square error of moisture ratio of 0.00739.

• Structural Engineering and Mechanics
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• 제85권5호
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• pp.593-605
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• 2023

This work presents a comparison between analytical and finite element analysis for bending of porous sandwich functionally graded material (FGM) plates. The plate is rectangular and simply supported under static sinusoidal loading. Material properties of FGM are assumed to vary continuously across the face sheets thickness according to a power-law function in terms of the volume fractions of the constituents while the core is homogeneous. Four types of porosity are considered. A refined higher-order shear with normal deformation theory is used. The number of unknowns in this theory is five, as against six or more in other shear and normal deformation theories. This theory assumes the nonlinear variation of transverse shear stresses and satisfies its nullity in the top and bottom surfaces of the plate without the use of a shear correction factor. The governing equations of equilibrium are derived from the virtual work principle. The Navier approach is used to solve equilibrium equations. The constitutive law of the porous FGM sandwich plate is implemented for a 3D finite element through a subroutine in FORTRAN (UMAT) in Abaqus software. Results show good agreement between the finite element model and the analytical method for some results, but the analytical method keeps giving symmetric results even with the thickness stretching effect and load applied to the top surface of the sandwich.

• Structural Engineering and Mechanics
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• 제50권4호
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• pp.487-500
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• 2014

An analytical solution for the nonlinear in-plane free oscillations of the suspended cable which contains the quadratic and cubic nonlinearities is investigated via the homotopy analysis method (HAM). Different from the existing analytical technique, the HAM is indeed independent of the small parameter assumption in the nonlinear vibration equation. The nonlinear equation is established by using the extended Hamilton's principle, which takes into account the effects of the geometric nonlinearity and quasi-static stretching. A non-zero equilibrium position term is introduced due to the quadratic nonlinearity in order to guarantee the rule of the solution expression. Therefore, the mth-order analytic solutions of the corresponding equation are explicitly obtained via the HAM. Numerical results show that the approximate solutions obtained by using the HAM are in good agreement with the numerical integrations (i.e., Runge-Kutta method). Moreover, the HAM provides a simple way to adjust and control the convergent regions of the series solutions by means of an auxiliary parameter. Finally, the effects of initial conditions on the linear and nonlinear frequency ratio are investigated.

• Steel and Composite Structures
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• 제16권3호
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• pp.325-337
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• 2014

The strength and buckling problem of a five layer sandwich beam under axial compression or bending is presented. Two faces of the beam are thin aluminium sheets and the core is made of aluminium foam. Between the faces and the core there are two thin binding glue layers. In the paper a mathematical model of the field of displacements, which includes a share effect and a bending moment, is presented. The system of partial differential equations of equilibrium for the five layer sandwich beam is derived on the basis of the principle of stationary total potential energy. The equations are analytically solved and the critical load is obtained. For comparison reasons a finite element model of the beam is formulated. For the case of bended beam the static analysis has been performed to obtain the stress distribution across the height of the beam. For the axially compressed beam the buckling analysis was carried out to determine the buckling load and buckling shape. Moreover, experimental investigations are carried out for two beams. The comparison of the results obtained in the analytical and numerical (FEM) analysis is shown in graphs and figures. The main aim of the paper is to present an analytical model of the five layer beam and to compare the results of the theoretical, numerical and experimental analyses.

• Geomechanics and Engineering
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• 제24권5호
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• pp.491-503
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• 2021

Shallow tunnels are vulnerable to earthquakes, and shallow ground is usually inhomogeneous. Based on the limit equilibrium method and variational principle, a solution for the seismic collapse mechanism of shallow tunnel in inhomogeneous ground is presented. And the finite difference method is employed to compare with the analytical solution. It shows that the analytical results are conservative when the horizontal and vertical stresses equal the static earth pressure and zero at vault section, respectively. The safety factor of shallow tunnel changes greatly during an earthquake. Hence, the cyclic loading characteristics should be considered to evaluate tunnel stability. And the curve sliding surface agrees with the numerical simulation and previous studies. To save time and ensure accuracy, the curve sliding surface with 2 undetermined constants is a good choice to analyze shallow tunnel stability. Parameter analysis demonstrates that the horizontal semiaxis, acceleration, ground cohesion and homogeneity affect tunnel stability greatly, and the horizontal semiaxis, vertical semiaxis, tunnel depth and ground homogeneity have obvious influence on tunnel sliding surface. It concludes that the most applicable approaches to enhance tunnel stability are reducing the horizontal semiaxis, strengthening cohesion and setting the tunnel into good ground.

• 대한토목학회논문집
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• 제10권1호
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• pp.57-69
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• 1990

본(本) 연구(硏究)에서는 기하학적(幾何學的) 비선형성(非線形性)을 고려(考慮)하여 해저(海底)파이프라인을 설치(設置)하는 동안의 정적(靜的) 해석방법(解析方法)을 제시(提示)하였다. 해석(解析)방법(方法)으로는 유한요소법(有限要所法)을 사용(使用)하였으며, 기본방정식(基本方程式)은 최소위치(最少位置)에너지의 원리(原理)를 사용(使用)하여 유도(誘導)하였다. 평형방정식(平衡方程式)의 해(解)는 modified Newton-Raphson방법(方法)을 사용(使用)하여 구(求)하였다. 파이프라인요소(要素)의 유한변위(有限變位) 및 회전(回轉)과 축방향력(軸方向力)의 영향(影響)이 고려(考慮)되었고 경계조건(境界條件)은 스프링요소(要素)를 사용(使用)하여 모델화(化)하였다. 해석(解析) 적용례(適用例)에서는 다이아몬드형(形) 프레임, 곡선(曲線)외팔보와 해저(海底)파이프라인을 설치(設置)하는 동안의 정적(靜的) 해석례(解析例)를 다루었으며 다른 방법(方法)에 의(依)한 해석결과(解析結果)와 비교(比較)하여 본(本) 연구(硏究)의 정당성(正當性)을 입증(立證)하였다.

• Geomechanics and Engineering
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• 제31권5호
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• pp.439-452
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• 2022

A forecast of slope behavior during catastrophic events, such as earthquakes is crucial to recognize the risk of slope failure. This paper endeavors to eliminate the significant supposition of predefined slip surfaces in the slope stability analysis, which questions the relevance of simple conventional methods under seismic conditions. To overcome such limitations, a methodology dependent on the slip line hypothesis, which permits an automatic generation of slip surfaces, is embraced to trace the extreme slope face under static and seismic conditions. The effect of earthquakes is considered using the pseudo-static approach. The current outcomes developed from a parametric study endorse a non-linear slope surface as the extreme profile, which is in accordance with the geomorphological aspect of slopes. The proposed methodology is compared with the finite element limit analysis to ensure credibility. Through the design charts obtained from the current investigation, the stability of slopes can be assessed under seismic conditions. It can be observed that the extreme slope profile demands a flat configuration to endure the condition of the limiting equilibrium at a higher level of seismicity. However, a concurrent enhancement in the shear strength of the slope medium suppresses this tendency by offering greater resistance to the seismic inertial forces induced in the medium. Unlike the traditional linear slopes, the extreme slope profiles mostly exhibit a steeper layout over a significant part of the slope height, thus ensuring a more optimized solution to the slope stability problem. Further, the susceptibility of the Longnan slope failure in the Huining-Wudu seismic belt is predicted using the current plasticity approach, which is found to be in close agreement with a case study reported in the literature. Finally, the concept of equivalent single or multi-tiered planar slopes is explored through an example problem, which exhibits the appropriateness of the proposed non-linear slope geometry under actual field conditions.