• Structural Engineering and Mechanics
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• v.13 no.2
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• pp.211-230
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• 2002

The objective of this study is to investigate the dynamic behavior of elastic beams subjected to moving loads. Although analytical methods are available, they have limitations with respect to complicated structures. The use of computer technology in recent years is an effective way to solve the problem; thus using the latest technology this study establishes a finite-element solution procedure to investigate dynamic behaviors of a typical elastic beam having a set of constant geometric properties and various span lengths. Both the dead load of the beam and traffic load are applied in which the traffic load is considered a concentrated moving force with various traveling passage speeds on the beam. Dynamic behaviors including deflection, shear, and bending moment due to moving loads are obtained by both analytical and finite element methods; for simple structures, they have an excellent agreement. The numerical results show that based on analytical methods the fundamental mode is good enough to estimate the dynamic deflection along the beam, but is not sufficient to simulate the total response of the shear force or the bending moment. The linear dynamic behavior of the elastic beams subjected to multiple exciting loads can easily be found by linear superposition, and the geometric nonlinear results caused by large deformation and axial force of the beam are always underestimated with only a few exceptions which are indicated. In order to make the results useful, they have been nondimensionalized and presented in graphical form.

• The Journal of the Korea Contents Association
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• v.15 no.6
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• pp.539-546
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• 2015

In this study, we develop numerical model using the elliptic mild-slope equation for waves propagating around axis-symmetric topographies where the water depth varies arbitrarily having zero at the coastline. The entire region is divided into three regions. In the both of inner and outer regions, an existing analytical solutions are used. In the middle region, the finite element technique is applied to the governing equation. To get the solution, the methods of separation of variables, Frobenius series are used. Developed solution is validated by comparing with previously developed analytical solution. We also investigate various cases with different bottom topographies.

• Ocean Systems Engineering
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• v.3 no.2
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• pp.79-95
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• 2013

Suction anchors are widely adopted in mooring systems. However there are still challenges in predicting the failure mode and ultimate pullout capacity of the anchor. Previously published methods for predicting the inclined pullout capacity of suction anchors are mainly based on experimental data or the FEM analysis. In the present work, an analytical method that is capable of predicting the failure mode and ultimate pullout capacity of the suction anchor in clay under inclined loading is developed. This method is based on a rational mechanical model for suction anchors and the knowledge of the mechanism that the anchor fails in seabed soils. In order to examine the analytical model, the failure angle and pullout capacity of suction anchors from FEM simulation, numerical solution and laboratory tests in uniform and linear cohesive soils are employed to compare with the theoretical predictions and the agreement is satisfactory. An analytical method that can evaluate the optimal position of the attachment point is also proposed in the present study. The present work proves that the failure mode and pullout capacity of suction anchors can be reasonably determined by the developed analytical method.

• The Korean Journal of Applied Statistics
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• v.37 no.4
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• pp.445-453
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• 2024

For Markov processes whose stationary probabilities are difficult to obtain in the analytical form, approximate solutions can be considered using numerical methods such as a matrix operation method or an iterative calculation method. In this paper we perform the study to verify the accuracy of a numerical iteration formula which calculate the stationary probabilities of Markov chains or processes. Especially, the convergence and accuracy of the numerical method are investigated by using Markov models for system availability. We compare the values of the system availability based on the numerical calculation and those based on the complicated but analytical solutions. We also calculate the iteration numbers necessary for the convergence of the numerical solutions. The accuracy and usefulness of the numerical iterative calculation method can be ascertained through this study.

• Structural Engineering and Mechanics
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• v.28 no.2
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• pp.221-238
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• 2008

Numerical solution to buckling analysis of beams and columns are obtained by the method of differential quadrature (DQ) and harmonic differential quadrature (HDQ) for various support conditions considering the variation of flexural rigidity. The solution technique is applied to find the buckling load of fully or partially embedded columns such as piles. A simple semi- inverse method of DQ or HDQ is proposed for determining the flexural rigidities at various sections of non-prismatic column ( pile) partially and fully embedded given the buckling load, buckled shape and sub-grade reaction of the soil. The obtained results are compared with the existing solutions available from other numerical methods and analytical results. In addition, this paper also uses a recently developed technique, known as the differential transformation (DT) to determine the critical buckling load of fully or partially supported heavy prismatic piles as well as fully supported non-prismatic piles. In solving the problem, governing differential equation is converted to algebraic equations using differential transformation methods (DT) which must be solved together with applied boundary conditions. The symbolic programming package, Mathematica is ideally suitable to solve such recursive equations by considering fairly large number of terms.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.3
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• pp.3-10
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• 2018

It's not practical to collect all information at the entire degrees of freedom of finite element model. The incomplete measurements should be expanded for subsequent analysis and damage detection. This work presents the analytical methods to expand the incomplete static or dynamic response data. Using the expanded data, introducing the concept of residual force, and minimizing the performance index expressed as the stiffness matrix and its difference before and after damage, the variation in stiffness matrix is derived. Based on the difference in the stiffness matrix, the damage detection method of structures is also provided. The validity of the proposed methods is illustrated in a numerical application, the numerical results are analyzed for applications, and the applicability of both methods is investigated.

• Journal of the Korean GEO-environmental Society
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• v.13 no.12
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• pp.67-74
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• 2012

The arching effect of the active earth pressure acting on an excavation wall subjected to close excavation reduces lateral earth pressure acting on excavation wall. In this paper, the arching effect was estimated for varying width to excavation depth ratio and wall friction angle by analytical and numerical methods verified with centrifuge test results. The arching effect is significant when the width to excavation depth ratio and wall friction angle is decreased and increased, respectively. The analytical solution derived from the classical arching theory suggested by Handy(1985) shows good agreement with the numerical solution than the other solutions.

• ETRI Journal
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• v.37 no.5
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• pp.845-855
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• 2015

To enable the coexistence of Licensed Assisted Access (LAA) and Wi-Fi in 5 GHz unlicensed bands, a new channel access mechanism is proposed. Accounting for the fairness between LAA and Wi-Fi, the proposed mechanism finds the optimal transmission time ratio by adaptively adjusting the transmission durations for LAA and Wi-Fi. In addition, we propose a new analytical model for the distributed coordination function of IEEE 802.11 through some modifications of conventional analytical models for saturation and non-saturation loads. By computing the activity ratio of Wi-Fi, the proposed analytical model is able to control the time ratio between LAA and Wi-Fi, which is required for practical implementation of the proposed access mechanism. Through numerical simulations, the proposed channel access mechanism is compared with conventional methods in terms of throughput and utility.

• Steel and Composite Structures
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• v.50 no.2
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• pp.135-148
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• 2024

This paper analytically investigates the free vibration analysis of functionally graded-carbon nanotube reinforced composite (FG-CNTRC) plates by dynamic stiffness method (DSM). The properties of CNTRC are determined with the extended rule of mixture. The governing differential equations of motion based on the first-order shear deformation theory of CNTRC plate are derived using Hamilton's principle. The FG-CNTRC plates are studied for a uniform and two different distributions of carbon nanotubes (CNTs). The accuracy and performance of the DSM are compared with the results obtained from closed closed-form and semi-analytical solution methods in previous studies. In this study, the effects of boundary condition, distribution type of CNTs, plate aspect ratio, plate length to thickness ratio, and different values of CNTs volume fraction on the natural frequencies of the FG-CNTRC plates are investigated. Finally, various natural frequencies of the plates in different conditions are provided as a benchmark for comparing the accuracy and precision of the other analytical and numerical methods.

• Computers and Concrete
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• v.24 no.2
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• pp.117-123
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• 2019

Optimization is an important subject which is widely used in engineering problems. In this paper, an analytical method is developed for optimum design of reinforced concrete beams considering both flexural and shear effects. A closed-form formulation is derived for optimal height and rebar of beams. The total material cost of steel and concrete is considered as the objective function which is minimized during the optimization process. The ultimate flexural and shear capacities of the beam are considered as the main constraints. The ultimate limit state is considered for deriving the relations for flexural capacity of the beam. The design requirements are considered according to the item 9 of the Iranian National Building. Analytical formulas and some curves are proposed to be used for optimum design of RC beams. The proposed method can be used to perform the optimization of RC beams without the need of any prior knowledge in optimization. Also, the results of the studied numerical example show that the proposed method results in a better design comparing with the other methods.