• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.195-200
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• 2007

System identification of real-scale structure is performed using forced vibration test. There exist various techniques available for identifying the dynamic characteristis of structures using dynamic and static measurements. In this study, The finite element(FE) model of the structure is analytically constructed using ANSYS and the model was updated using the results experimentally measured by the forced vibration test. forced vibration tests showed that Hybrid Mass Damper induced floor responses coincided with the earthquake induced ones which was numerically calculated based on the updated FE model.

• Journal of Biosystems Engineering
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• v.6 no.1
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• pp.1-14
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• 1981

A laboratory model test was carried out with a newly designed model to figure out the vibration characteristics of the vibratory tillage tool according to the method of forced vibration, i.e., horizontally and vertically forced vibrations. The results are summarized as follows: 1. The reduction ratios of the draft force of the vibratory blade were 14.2-42.6% for the case where the vibration was forced parallel to the travelling direction of the blade, and 15-54.5% for the vertically forced vibration. And it was thought that the method of vertically forced vibration was preferable to the reduction of the draft force. 2. The ratio of the draft force of a vibratory blade to that of a static one could be represented as a function of V/At. It was found to be possible to reduce the draft force by taking a lower value of (V/Af) and this meant that the effictiveness of tillage practice using the vibratory system would be limited. 3. The torque to the main rotating shaft to vibrate the model blade increased frequency and amplitude. This tendency varied according to the physical properties of tested soil. In case of horizontally forced vibration, the torque was 8~34% less than in case of vertically forced vibration. 4. With the increase of frequency, the total power requirement increased linearly, and also the portion of oscillating power requirement in the total power tended to increase. The magnitude of the total power requirement was 1.4-13 times greater than that of a static one for the case of horizontal vibration, and 1.5-15 times greater for the case of vertical vibration. It was thought that the horizontal vibration of the blade was preferable to the vertical vibration in view of the power requirement. 5. A linearity was found between the amplitude of moment oscillogram and magnitude of oscillating acceleration. Only positive values of moment occurred when the blade was forced to vibrate vertically, but negative values occurred in rarity in the case of amplitude A3 when the blade was forced to vibrate horizontally.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.13-18
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• 2001

This paper deals with finite element analysis for free vibration and forced sine vibration of Ka- and Ku- bend antenna structures using MSC/PATRAN/NASTRAN. The structures are designed to satisfy minimum resonance frequency requirement in order to decouple the dynamic interaction of the satellite with the spacecraft bus structure. From the forced sinusoidal vibration, we have observed output acceleration versus input in X-,Y- and Z- direction, based on base excitation using large mass method. The results of finite elements analysis can be used as the reference data for the experimental test of satellite antenna, resulting in the reduction of cost and time by predicting and complementing experimental data.

• Journal of KSNVE
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• v.7 no.5
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• pp.853-860
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• 1997

For this study, the multi-degree of freedom analysis model of torsional vibration was developed. This model is combined with mass moment of inertia and torsional spring in two wheel drive and four wheel drive vehicle. We compared and analyzed torsional vibration characteristics by natural frequencies and mode shapes which are obtained by free vibration analysis of this model. And we studied torsional vibration contribution of driveline elements by performing the forced vibration analysis of engine excitation torque. The validity of this model is demonstrated by the field test. The reduction effect of the torsional vibration along the driveline design factor is presented by the analytical results.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.6 s.52
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• pp.103-114
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• 2006

Forced vibration testing is important for correlating the mathematical model of a structure with the real one and for evaluating the performance of the real structure. There exist various techniques available for evaluating the seismic performance using dynamic and static measurements. In this paper, full scale forced vibration tests simulating earthquake response are implemented by using a hybrid mass damper. The finite element (FE) model of the structure was analytically constructed using ANSYS and the model was updated using the results experimentally measured by the forced vibration test. Pseudo-earthquake excitation tests showed that HMD induced floor responses coincided with the earthquake induced ones which were numerically calculated based on the updated FE model.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.27-38
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• 2007

A series of forced vibration tests and ambient vibration measurement was conducted on a four-story reinforced concrete building damaged in the 1994 Northridge earthquake. Both low amplitude broadband and moderate amplitude harmonic excitation were applied using a linear shaker and two eccentric mass shakers, respectively, and ambient vibrations were measured before and after each forced vibration test. Accelerations, interstory displacements, and curvature distributions were monitored using accelerometers, LVDTs and concrete strain gauges. Natural frequencies and the associated mode shapes fur the first 7 modes were identified. Fundamental frequencies determined from the eccentric mass shaker tests were 70% to 75% of the values determined using ambient vibration data, and 92% to 93% of the values determined using the linear shaker test data. Larger frequency drops were observed in the NS direction of the building, apparently due to damage that was induced during the Northridge earthquake.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1224-1230
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• 2007

In this study, a new modal test method is presented to evaluate vibration characteristic of the nano imprint stage system. Since it is difficult to measure vibration level without contacting the machine component, non contacting modal test method, laser scanning system is ultrared. Finite element analysis results are compared with the modal test results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.396.1-396
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• 2002

The AVT under traffic-induced vibrations was carried out on Namhae Suspension bridge in Korea. Mode shapes as well as natural frequencies up to the 15th mode were acquired exactly, and the effect of traffic mass and temperature on measured natural frequencies was investigated. The results from the AVT are compared with those from forced vibration test(FVT) and FE analysis. (omitted)

• Structural Engineering and Mechanics
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• v.82 no.5
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• pp.651-665
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• 2022

While the lateral confinement provided by an FRP jacket to a concrete column is passive in nature, confinement is activated when the concrete expands due to additional compression stresses or significant shear deformations. This characteristic of FRP jacketing theoretically leads to similar initial stiffness properties of FRP retrofitted buildings as the buildings without retrofit. In the current study, to validate this theoretical assumption, the initial stiffness characteristics, and thus, the potential seismic demands were investigated through forced vibration tests on two identical full-scale substandard reinforced concrete buildings with or without FRP retrofit. Power spectral density functions obtained using the acceleration response data captured through forced vibration tests were used to estimate the modal characteristics of these buildings. The test results clearly showed that the natural frequencies and the mode shapes of the buildings are quite similar. Since the seismic demand is controlled by the fundamental vibration modes, it is confirmed using vibration-based full-scale tests that the seismic demands of RC buildings remain unchanged after CFRP jacketing of columns. Furthermore, the damping characteristics were also found similar for both structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.97-102
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• 2000

The purpose of this study was performed to estimate the mechanical characteristics of curing concrete affected by forced vibration. The major variables of this test were vibration method, vibration velocity and duration of vibration, The compressive strength, slip, bending strength and displacement are measured for all the cylinder paper molds and beams. The results can be summarized as follows ; 1)According to vibration, velocity(RMS), the compressive strength, bending and displacement for continual vibration increased, but for immediate vibration decreased. 2) Immediate vibration effected on concrete compressive strength, slip than continual vibration. especially in vibration velocity 3.59mm/sec(RMS; 0.624mm/sec) slip secreased 15% in continual vibration, 20% in immediate vibration.