• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.2
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• pp.19-26
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• 2008

This study has been carried out to investigate the dynamic characteristics of RC slabs. For this purpose, the 20-node solid element has been used to discretize the RC slabs into two parts of concrete and rebar. The material non-linearity considering elasto-visco plastic model and the smeared crack model have been adopted in the finite element formulation. The applied load can handle step load, load intensity of harmonic load, area of distributed load and frequency. The frequency of harmonic load has an significant effect on dynamic behaviour in terms of displacement. As the frequency is increased, the effect of load amplitude is more serious. Especially, if the frequency of harmonic load exceeds 30 Hz, it is noted that the displacement by harmonic load is greater than that by step load. In case of harmonic load, the damping effect shows no certain tendency with respect to frequency of load. In details, the damping is effective when the frequency of harmonic load is 2 Hz, but there is no consistent tendency according to damping ratio. The dynamic response when the frequency of harmonic load is 3 Hz shows same result for undamped case as well as for damped case with 5% damping ratio. It is also noted that we can get the largest deflection for damped case with 1% damping ratio. However, there is not any damping effect when the frequency of harmonic load is greater than 4 Hz.

• Journal of Mechanical Science and Technology
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• v.19 no.7
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• pp.1405-1413
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• 2005

Malfunctions or critical fatigue problems often occur in mistuned periodic structural systems since their vibration responses may become much larger than those of perfectly tuned periodic systems. These are called vibration localization phenomena and it is of great importance to accurately predict the localization phenomena for safe and reliable designs of the periodic structural systems. In this study, a simple discrete system which represents periodic structural systems is employed to analyze the vibration localization phenomena. The statistical effects of mistuning, stiffness coupling, and damping on the vibration localization phenomena are investigated through Monte Carlo simulation. It is found that the probability of vibration localization was significantly influenced by the statistical properties except the standard deviation of coupling stiffness.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.585-594
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• 2013

In this study, laboratory experiments and numerical simulations were conducted to test the performance of resonance power buoy system proposed by Kweon et al.(2010). The system is composed of a linear generator and a mooring buoy. The mover of the linear generator mainly has heave motion driven by vertical oscillation of the buoy. In this system, the velocity discrepancy between the mover and the buoy makes electricity. However, ocean wave energy as a natural resource around Korean peninsula is comparatively small and the driving force for producing electricity is not enough for commercialization. Therefore, it is necessary that the buoy motion be amplified by using resonance characteristics. In order to verify the resonance effects on the test power buoy, the experimental investigations were conducted in the large wave flume (length of 110 m, width of 8 m, maximum depth of 6 m) equipped with regular and random plunger wave generator. The resonance draft of test power buoy is designed for the corresponding period of incident wave, 1.96 sec. Regular wave test results show that the heave response amplitude operator(RAO) by a test buoy has the amplification of 5.66 times higher compared to the wave amplitude at the resonance period. Test results of random waves show that the buoy has the largest spectrum area of 20.73 times higher at the point of not the resonance period but the shorter one of 1.85 sec. Therefore this study suggests the resonance power buoy for wave power generation for commercial application in the case of the coastal and oceanic area with smaller wave energy.