• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.1
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• pp.13-20
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• 1984

As the first step to the dynamic stress analysis of structures, transient responses of a Timoshenko beam with variable section subject to impact load are analyzed. According to the various characteristics of impact load, time histories of the transient response of Timoshenko beam with general boundary conditions are obtained and compared with those of one degree of freedom system. Numerical solutions of the governing equations of motion are calculated by adopting the equivalent lumped-mass system and the finite difference method. It is found that the dynamic responses of Timshenko beam depend on the effect of concentration and location of impact load. As a result, increasing tendency of fluctuation in dynamic response, especially in bending moment, is found according to the increase of load concentration factor in time and space.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1582-1589
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• 2004

The dynamic response of an eccentric Griffith crack in functionally graded piezoelectric ceramic strip under anti-plane shear impact loading is ana lysed using integral transform method. Laplace transform and Fourier transform are used to reduce the problem to two pairs of dual integral equations, which are then expressed to Fredholm integral equations of the second kind. We assume that the properties of the functionally graded piezoelectric material vary continuously along the thickness. The impermeable crack boundary condition is adopted. Numerical values on the dynamic stress intensity factors are presented for the functionally graded piezoelectric material to show the dependence of the gradient of material properties and electric loadings.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.3
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• pp.185-192
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• 2004

Vibration table is required to obtain high packing density in expendable pattern casting process. Packing density. which is an important manufacture factor, depends on the vibration pattern induced by vibration table. In general, circular vibration pattern is recognized as the best pattern. The existing vibration table is investigated to identify current vibration pattern and consider a countermeasure. Modal test is utilized to identify the dynamic characteristics of vibration table, and finite element method is used to propose the improved design. In simulation using finite element method, the position of stiffeners is obtained to satisfy the required dynamic characteristics.

• Journal of KSNVE
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• v.11 no.2
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• pp.346-353
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• 2001

In this study dynamic characteristic of catenary system that supplies electrical power to KTX Korean high-speed trains are investigated. A simulation program based on 3-span and 6-span finite element models of the catenary is developed. The influences of the various design parameters on the dynamic responses of the catenary are determined. The main design parameters include tension on the contact and messenger wires and the stiffness of the droppers connecting the two wires. The vibrational responses are primarily determined by the reflections of the propagating wave, and the dropper stiffness is found to be the dominant factor that influences overall dynamic characteristics of the catenary.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.328-333
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• 2002

When vehicle travelling along the track which has irregularity such as vertical profile, dynamic forces arise at the Wheel/Rail contact patch by wheel/rail interaction. In particular short wavelength irregularities on dipped joint and small stiffness of connecting rail bring about intense wheel/rail dynamic effects at higher speed. In the paper, a new model for dipped joint rail is developed to study dynamic behavior of track. A cusp behavior on dipped joint was defined by its amplitude and decay factor, which was presented by FRA track classes. The result of case study are presented, which show wheel rail contact force in each track classes, train operation speed and bending flexible rigidity ratio of fishplates which are connecting the rail.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.320-330
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• 2008

This paper presents an improved dynamic programming (IDP) approach to solve the economic power dispatch problem including transmission losses in power systems. A detailed mathematical derivation of recursive dynamic programming approach for the economic power dispatch problem with transmission losses is presented. The transmission losses are augmented with the objective function using price factor. The generalized expression for optimal scheduling of thermal generating units derived in this article can be implemented for the solution of the economic power dispatch problem of a large-scale system. Six-unit, fifteen-unit, and forty-unit sample systems with non-linear characteristics of the generator, such as ramp-rate limits and prohibited operating zones are considered to illustrate the effectiveness of the proposed method. The proposed method results have been compared with the results of genetic algorithm and particle swarm optimization methods reported in the literature. Test results show that the proposed IDP approach can obtain a higher quality solution with better performance.

• Computers and Concrete
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• v.14 no.2
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• pp.163-174
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• 2014

Damping as a material property plays an important role in decreasing dynamic response of structures. However, very little is known about the evaluation and application of the actual damping of Fiber Reinforced Polymer Confined Reinforced Concrete (FRP-C RC) material which is widely adopted in civil engineering at present. This paper first proposes a stress-dependent damping model for FRP-C RC material using a validated Finite Element Model (FEM), then based on this damping-stress relation, an iterative scheme is developed for the computations of the non-linear damping and dynamic response of FRP-C RC columns at any given harmonic exciting frequency. Numerical results show that at resonance, a considerable increase of the loss factor of the FRP-C RC columns effectively reduces the dynamic response of the columns, and the columns with lower concrete strength, FRP volume ratio and axial compression ratio or higher longitudinal reinforcement ratio have stronger damping values, and can relatively reduce the resonant response.

• Wind and Structures
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• v.8 no.3
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• pp.147-161
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• 2005

Two identical tall building models with square cross-sections are experimentally studied in a wind tunnel with high-frequency-force-balance (HFFB) technique to investigate the interference effects on wind loads and dynamic responses of the interfered building. Another wind tunnel test, in which the interfered model is an aeroelastic one, is also carried out to further study the interference effects. The results from the two kinds of tests are compared with each other. Then the influences of turbulence in oncoming wind on dynamic interference factors are analyzed. At last the artificial neural networks method is used to deal with the experimental data and the along-wind and across-wind dynamic interference factor $IF_{dx}$ & $IF_{dy}$ contour maps are obtained, which could be used as references for wind load codes of buildings.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.544-549
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• 2003

In this study, non-linear dynamic FE analysis of a tracked vehicle under the traveling load is performed by FE code ABAQUS. The stability of vehicle is examined using the structure analysis for the road wheel. The dynamic analysis is performed by traveling load. The traveling load include the 6 step loading spectrum about road wheel. The stress level around road wheel are 30 MPa ${\sim}$ 40 MPa. These value are indicated under modified fatigue strength 50.3 MPa. It takes about 3 second to be stable the structure after traveling load.

• Journal of the Korean Society for Railway
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• v.9 no.4 s.35
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• pp.401-411
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• 2006

The major objective of this study is to investigate the dynamic behaviors of track due to the deterioration characteristics of ballast for servicing tracks by the field test. The durability of ballast plays an important role in the track behaviour. To estimate the deterioration characteristics of ballast, several tests have been carried out by several scholars. The deterioration characteristics of ballast is one of the most important factor in the dynamic behaviour of track and its life. In this paper abrasion/breakage characteristics of ballast is studied to predict the effect of physical ballast characteristics on ballast track. To reveal deterioration characteristics of ballast, the field test were carried out. The deterioration characteristics, studied in this paper, is applied to the dynamic behaviour of track in various conditions.