• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1023-1031
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• 1994

The closed forms of consistent mass matrix with rotational inertia matrix are developed for free vibration analysis in space sutructures containing linearly tapered members with cross section of thin-walled I-sections. The exact displacement functions are used for formulating mass matrices. The very small slopes of the tapered member are used in usual practice, such that the series expansion forms of these are also developed to avoid numerical failure in vibration analysis. Significant improvements of accuracy and efficiency of free vibation analysis are achieved by using the mass matrices developed in this study. Frequencies of free vibation of tapered members are compared with solutions based upon stepped representation of beam element in the ANSYS. The mass matrices presented in this study can be used for the free vibration analysis of tapered and prismatic members.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.10
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• pp.946-952
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• 2010

A method for the identification of structural characteristic parameters of a steel bar in the matrices form such as stiffness matrices and mass matrices from frequency response function(FRF) by genetic algorithm is proposed. As the method is based on the finite element method(FEM), the obtained matrices have perfect physical meanings if the FRFs got from the analysis and the FRFs from the experiments were well coincident each other. The identified characteristic matrices from the FRFs with maximun 40 % of random errors by the genetic algorithm are coincident with the characteristic matrices from exact FEM FRFs well each other. The fitted element diameters by using only 2 points experimental FRFs are similar to the actual diameters of the bar. The fitted FRFs are good accordance with the experimental FRFs on the graphs. FRFs of the rest 9 points not used for calculating could be fitted even well.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.363-374
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• 2000

An accurate method is presented for vibrations of rhombic plates having three different combinations of clamped, simply supported, and free edge conditions. A specific feature here is that the analysis explicitly considers the moment singularities that occur in the two opposite corners having obtuse angles of the rhombic plates. Stationary conditions of single-field Lagrangian functional are derived using the Ritz method. Convergence studies of frequencies show that the corner functions accelerate the convergence rate of solutions. In this paper, accurate frequencies and normalized contours of the vibratory transverse displacement are presented for highly skewed rhombic plates, so that a significant effect of corner stress singularities nay be understood.

• Journal of KSNVE
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• v.10 no.3
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• pp.536-550
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• 2000

Inversitgated in this study are the modal characteristics of the eccentric cylindrical shells with fluid-filled annulus. Theoretical method is developed to find the natural frequencies of the shell using the finite Fourier expansion and their results are compared with those of finite element method to verify the validation of the method developed. The effect of eccentricity on the modal characteristics of the shells is investigated using a finite element modeling.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.348-351
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• 2007

This paper investigates the natural modes of moduled floating structure with module unit connector. As an example structure, a floating parking place($120m{\times}60m$) is considered. In the evaluation of natural modes, numerical equations are formulated by FEM(Finite Element Method) and the natural modes are solved by the subspace iteration method. By comparing results for various stiffness of module unit connector, the effect of stiffness of unit connector is examined.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.3
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• pp.356-360
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• 2008

This paper investigates the natural modes of moduled floating structure with module unit connector. As an example structure, a floating parking place($120m\;{\times}\;60m$) is considered. In the evaluation of natural modes, numerical equations are formulated by FEM(finite element method) and the natural modes are solved by the subspace iteration method. By comparing results for various sizes of module unit, the effect of unit size is investigated. By comparing results for various stiffness of module unit connector, the effect of stiffness of unit connector is also examined.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.8-18
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• 2002

In this paper, wave energy absorption of OWC(oscillating water column) device is analyzed. The analytic model consists of a partially immersed circular vertical cylinder open at its end and an air turbine connected with the air chamber. The boundary value problem is decomposed into scattering problem related to scattering by an incident wave in the absence of a pressure variation and radiation problem describing the flow due to an oscillating pressure in the absence of an incident wave. By invoking the continuity of an air flow inside the chamber, the oscillating pressure in a chamber is derived. With oscillating pressure, the mean power absorbed by OWC device and the capture width are obtained. In numerical calculation, the induced volume flux across the internal free surface of the chamber in the scattering and radiation problem and the maximum capture width are compared with various design parameters such as radius and submergence depth of chamber and wave conditions. The maximum capture width obtained by choosing the optimal value of turbine constant occurs at the first resonant mode (Helmholtz mode) among the natural frequencies of a circular cylinder chamber.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.3
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• pp.191-200
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• 2021

This paper deals with the boundary conditions of the stress resultants at the mid-arc for free vibration analyses of the arch. The considered arch is a horseshoe symmetric elliptic arch. The work dealing with the boundary conditions of the deflection at both ends of the arch has already been reported in the open literature. This revisited paper aims to study the suitability of the boundary conditions of the stress resultants at the mid-arc to be replaced by the boundary condition at both ends. In this study, the boundary conditions of the stress resultants at the mid-arc are newly derived based on the theory of the previous work, and natural frequencies and mode shapes are obtained using the new boundary conditions of the stress resultants. The numerical results of this paper confirm that the new boundary conditions have been validated according to previous studies and results of finite element ADINA.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.189-195
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• 2002

This paper deals with the free vibration of horizontally curved beams with transition currie. Based on the dynamic equilibrium equations of a curved beam element subjected to the stress resultants and inertia forces, the governing differential equations are derived for the out-of-plane vibration of curved beam with variable curvature. These equations are applied to the beam having transition curve in which the clothiod curve is chosen in this study. The differential equations are solved by the numerical methods lot calculating the natural frequencies and mode shapes. For verifying theories developed herein, the frequency parameters obtained from this studs and ADINA are compared with each other. As the numerical results, the various parametric studies effecting on natural frequencies are investigated and those results are presented in tables and figures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.2
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• pp.144-152
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• 2010

This paper deals with free vibrations of the tapered circular arches with constant volume, whose cross sectional shape is the solid regular polygon. Volumes of the objective arches are always held constant regardless shape functions of the cross-sectional depth. The shape functions are chosen as the linear, parabolic and sinusoidal ones. Ordinary differential equations governing free vibrations of such arches are derived and solved numerically for determining the natural frequencies. In the numerical examples, hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered. As the numerical results, the relationships between non-dimensional frequency parameters and various arch parameters such as rise ratio, section ratio, side number, volume ratio and taper type are reported in tables and figures.