• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.233-240
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• 1999

A general procedure is presented here to develope seismic design and analysis method for cable-supported bridges like suspension bridges subjected to ground motion. For representing a numerical model of suspension bridges. a new approach which satisfy design conditions for the initial equilibrium state of suspension bridges. without any nonlinear iterations. is proposed. The dynamic behavior of that model is verified by free vibration analysis. This study uses the response spectrum analysis to determine the Peak response of a suspension bridge to earthquake-induced ground motion. The SRSS(Square Root of Sum of Square). modal combination rule, is adopted for each direction, longitudinal and transverse. To illustrate the potential applicability for the seismic design of suspension bridges, a numerical example is presented in which the dynamic response of the Nam-hae suspension bridge subjected to earthquake

• Kyungpook Mathematical Journal
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• v.56 no.3
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• pp.831-844
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• 2016

In this paper, we consider a discrete predator-prey system with Watt-type functional response and impulsive controls. First, we find sufficient conditions for stability of a prey-free positive periodic solution of the system by using the Floquet theory and then prove the boundedness of the system. In addition, a condition for the permanence of the system is also obtained. Finally, we illustrate some numerical examples to substantiate our theoretical results, and display bifurcation diagrams and trajectories of some solutions of the system via numerical simulations, which show that impulsive controls can give rise to various kinds of dynamic behaviors.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.11
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• pp.742-748
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• 2000

This paper presents a numerical method to analyze the electromechanical-coupled field in the spindle motor of a computer hard drive and investigates dynamic response due to the electromechanical excitation, i.e. unbalanced magnetic force and centrifugal force for the rotational asymmetric motor. Magnetic field is calculated from Maxwells equation and voltage equation by introducing nonlinear time-dependent finite element analysis. Mechanical motion of rotor is calculated by solving Newton-Euler equation. Electromechanical excitation and dynamic response are characterized by analyzing the free response of a rotating rotor and Fourier analysis of the excitation force and resulting vibration of a rotor. It shows that centrifugal force produces the unbalanced magnetic force even in the rotational symmetric motor. It also shows that resonance produces quite considerable vibration even when the high excitation frequency with small amplitude matches with the natural frequency of the spindle motor.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.04a
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• pp.89-94
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• 1994

Latticed domes take form a curved surface by arranged members with certain patterns. For this reason, it is possible for the characteristics of vibration to complicate by change of various parameters of dome; grid-pattern, boundary condition and ratio of radius-height etc. Therefore, it is important to clarify the effect by these parameters before generalized dynamic response analysis. So this study deals with free vibration analysis of latticed domes and makes clear an effect of shape coefficient, that is, geometrical characteristics of latticed domes, on the vibration characteristics.

• Structural Engineering and Mechanics
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• v.71 no.1
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• pp.13-22
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• 2019

In this paper, the static and dynamic responses of a tied-arch railway bridge under train load were studied through field tests. The deflection and stresses of the bridge were measured in different static loading scenarios. The dynamic load test of the bridge was carried out under the excitation of running train at different speeds. The dynamic properties of the bridge were investigated in terms of the free vibration characteristics, dynamic coefficients, accelerations, displacements and derailment coefficients. The results indicate that the tie of the measuring point has a significant effect on the vertical movement of the test section. The dynamic responses of arch bridge are insensitive to the number of trains. The derailment coefficients of locomotive and carriage increase with the train speed and symmetrically distributed double-line loads reduce the train derailment probability.

• Structural Engineering and Mechanics
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• v.7 no.2
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• pp.181-202
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• 1999

Dynamic response of axisymmetric arbitrary laminated composite cylindrical shell of finite length, using three-dimensional elasticity equations are studied. The shell is simply supported at both ends. The highly coupled partial differential equations are reduced to ordinary differential equations (ODE) with variable coefficients by means of trigonometric function expansion in axial direction. For cylindrical shell under dynamic load, the resulting differential equations are solved by Galerkin finite element method, In this solution, the continuity conditions between any two layer is satisfied. It is found that the difference between elasticity solution (ES) and higher order shear deformation theory (HSD) become higher for a symmetric laminations than their unsymmetric counterpart. That is due to the effect of bending-streching coupling. It is also found that due to the discontinuity of inplane stresses at the interface of the laminate, the slope of transverse normal and shear stresses aren't continuous across the interface. For free vibration analysis, through dividing each layer into thin laminas, the variable coefficients in ODE become constants and the resulting equations can be solved exactly. It is shown that the natural frequency of symmetric angle-ply are generally higher than their antisymmetric counterpart. Also the results are in good agreement with similar results found in literatures.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.1
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• pp.31-36
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• 2022

This paper presents the measuring process of dynamic properties of offshore wind power foundation and provides consideration of each step. This Guideline enables to maintain consistent measuring procedure and therefore increase the reliability of test results. Small scaled suction bucket foundation was fabricated to represent the commercial support structure installation mechanism and two cases(free-free, free-fixed) of dynamic tests were performed at workshop. From the tests, the importance of dynamic properties of connection part between suction bucket and tower was figured out. More over, types and configuration of measuring devices are recommended which can help find the natural frequency of wind turbine foundation correctly. In field test, it was found that the natural frequency of suction bucket foundation was increased linearly with the penetration depth due to the confining effect of ambient soil. Meanwhile, it was not easy to get an enough excitation force with normal impact hammer because the N.F of suction bucket model was in the lower range of 0 Hz ~ 5 Hz. Therefore, new excitation method which has enough force and can excite lower frequency range was devised. This study will help develop safety check procedure of suction bucket foundation in field at each installation stage using the N.F measurement.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.231-244
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• 2000

This paper presents a dynamic analysis technique for a 2-D soil-structure interaction problem in the frequency domain, which can directly be applied as an analysis tool for seismic response analyses of underground structures, tunnels, embankments, and so on. In this method, the structure and near-field soil is modeled by the standard finite elements, while the unbounded far-field soil is represented using the dynamic infinite elements in the frequency domain. The earthquake-input motion is regarded as traveling P and SV waves which are incident vertically from the far-field of underlying half-space to the near-field of layered medium. The equivalent earthquake forces are then calculated utilizing so-called fixed-exterior-boundary-method and the free-field responses including displacements and tractions. For the verification of the present study, seismic response analyses are carried out for a multi-layered half-space free-field soil medium and a cylindrical cavity embedded in a homogeneous half-space. Comparisons of the present results with solutions by other approaches indicate that the proposed methodology gives accurate estimates. Finally, an application example of seismic response analysis for a subway station is presented, which demonstrates the applicability of the present study.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.63-71
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• 2001

This paper introduces a method for calculation of dynamic stress occurring in flexible bodies of a moving multibody system by using commercial softwares DADS for dynamic analysis and MSC/NASTRAN for finite element analysis. Three methods for model transient response analysis of a flexible body are summarized. Elastic deformation of a flexible body can be described with normal modes and static modes composed of constraint modes and residual attachment modes. The deformation modes divided into fixed-interface modes and free-interface modes can be determined by using MSC/NASTRAN and selected for dynamic analysis. The dynamic results obtained from DADS are utilized to calculate dynamic stress by using mode-displacement method or mode-acceleration method of MSC/NASTRAN. As a numerical example of the analysis, we used a three dimensional slider-crank model with a flexible connecting rod.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.4
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• pp.243-254
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• 2021

In this study, the conservatism of the response displacement method (RDM) for the seismic response analysis of box-shaped power cable tunnels was evaluated. A total of 50 examples were used considering the cross-sections of 25 power cable tunnels and two soil conditions for each power cable tunnel. The following three methods were applied for the analysis by the RDM: (1) single cosine method, (2) double cosine method, and (3) dynamic free-field analysis method. A refined dynamic analysis method considering soil-structure interaction (SSI) was employed to compare the conservatism of the RDM. The double cosine method demonstrated the most conservative result, while the dynamic free-field analysis method yielded the least deviation. The soil stiffness reduction factor, C, for the double cosine method was recommended to be 0.9 and 0.7 for the operational performance and collapse prevention levels, respectively, to ensure a probability of at least 80% that the member force by the RDM is larger than that of dynamic SSI analysis.