• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제15권11호
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• pp.1232-1240
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• 2005

The purpose of this paper is that investigates the dynamic behavior characteristic of W.T.S (wind turbine system) and carries out the evaluation analysis during operating W.T.S. To investigate the dynamic behavior characteristic of W.T.S, the experiments to measure vibration of the blade from the attached accelerometer on the flap and edge section of the blade that is one of the most important elements of dynamic characteristic of W.T.S are performed. Natural frequency and mode shape are calculated with commercial program ( ANSYS) using the measured vibration acceleration that receives the signal with F.F.T Analyzer from the accelerometer For validation of these experiments, the finite element analysis is performed with commercial F.E.M program (ANSYS) on the basis of the natural frequency and mode shape. The results indicate that experimental values have good agreements with the finite element analysis.

• Journal of the Korean Society for Precision Engineering
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• 제17권7호
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• pp.203-208
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• 2000

The vibration of a mask degrades the color purity in CRT Therefore, a damping wire is put into contact with the mask to reduce the vibration in perfectly flat CRT. In this study, we analyzed the vibration of the mask contacting with the damping wire using FEM. First we calculated the natural frequencies and mode shapes of the mask by modal analysis, and compared them with the measured results to confirm our finite element model. The modal analysis of the wire was also performed to investigate resonance with the mask. Finally, the transient dynamic analysis of the mask contacting with the wire was performed. The vibration of the mask was measured to confirm our analysis, and the results are in good agreement with the analysis.

• Journal of the Korean Society for Railway
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• 제14권1호
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• pp.24-30
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• 2011

Conventional slope stability analysis is focused on calculating minimum factor of safety or maximum probability of failure. To minimize inherent uncertainty of soil properties and analytical model and to reflect various analytical models and its failure shape in slope stability analysis, slope stability analysis method considering simultaneous failure probability for multi failure mode was proposed. Linear programming recently introduced in system reliability analysis was used for calculation of simultaneous failure probability. System reliability analysis for various analytical models could be executed by this method. For application analysis for embankment, the results of this method shows that system stability of embankment calculate quantitatively.

• Structural Engineering and Mechanics
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• 제52권1호
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• pp.51-73
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• 2014

A three-dimensional finite element model for the Jiashao Bridge, the longest multi-span cable-stayed bridge in the world, is established using the commercial software package ANSYS. Dynamic characteristics of the bridge are analyzed and the effects of structural system measures including the rigid hinge, auxiliary piers and longitudinal constraints between the girders and side towers on the dynamic properties including modal frequency, mode shape and effective mass are studied by referring to the Jiashao Bridge. The analysis results reveal that: (i) the installation of the rigid hinge significantly reduces the modal frequency of the first symmetric lateral bending mode of bridge deck. Moreover, the rigid hinge significantly changes the mode shape and effective mass of the first symmetric torsional mode of bridge deck; (ii) the layout of the auxiliary piers in the side-spans has a limited effect on changing the modal frequencies, mode shapes and effective masses of global vibration modes; (iii) the employment of the longitudinal constraints significantly increases the modal frequencies of the vertical bending modes and lateral bending modes of bridge deck and have significant effects on changing the mode shapes of vertical bending modes and lateral bending modes of bridge deck. Moreover, the effective mass of the first anti-symmetric vertical bending of bridge deck in the longitudinal direction of the fully floating system is significantly larger than that of the partially constrained system and fully constrained system. The results obtained indicate that the structural system measures of the multi-span cable-stayed bridge have a great effect on the dynamic properties, which deserves special attention for seismic design and wind-resistant design of the multi-span cable-stayed bridge.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제28권5A호
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• pp.631-639
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• 2008

This paper reports the mode shapes of Seohae cable-stayed bridge extracted by TDD technique. In order to record total 72 acceleration points in the vertical direction of the bridge deck, a custom made data acquisition system with LAN communication has been especially developed and a set of ambient vibration tests has been conducted. For the measured acceleration responses, total twenty four mode shapes up to 2Hz has been extracted by TDD technique. The extracted mode shapes include many new modes that have not been identified in the current on-line health monitoring system installed in the bridge. It is confirmed that TDD technique is the most effective in extracting the high resolution mode shapes on a particularly long span bridge.

• Structural Engineering and Mechanics
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• 제57권3호
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• pp.543-567
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• 2016

This study attempts to address the buckling and free vibration characteristics of an isotropic cylindrical panel subjected to non-uniform temperature rise using numerical approach. Finite element analysis has been used in the present study. The approach involves three parts, in the first part non-uniform temperature field is obtained using heat transfer analysis, in the second part, the stress field is computed under the thermal load using static condition and, the last part, the buckling and pre-stressed modal analysis are carried out to compute critical buckling temperature as well as natural frequencies and associated mode shapes. In the present study, the effect of non-uniform temperature field, heat sink temperatures and in-plane boundary constraints are considered. The relation between buckling temperature under uniform and non-uniform temperature fields has been established. Results revealed that decrease (Case (ii)) type temperature variation field influences the fundamental buckling mode shape significantly. Further, it is observed that natural frequencies under free vibration state, decreases as temperature increases. However, the reduction is significantly higher for the lowest natural frequency. It is also found that, with an increase in temperature, nodal and anti-nodal positions of free vibration mode shapes is shifting towards the location where the intensity of the heat source is high and structural stiffness is low.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.840-840
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• 2003

Operational Modal Analysis (OMA) is a technique for identification of modal parameters by measurement of only the system's response. On many lightweight structures, such as load-speaker cones and disk drive read/write heads, is impossible or impractical to measure the input forces. Another characteristic of lightweight structure is their sensitivity to mass loading from sensors. The Scanning Laser Doppler Vibrometry(SLDV) allows response measurements to be taken without mass loading. One disadvantage of OMA testing compared to tradition input output modal testing is the OMA mode shapes are un-scaled. This means that the mode shape obtained from an OMA test can not used for analytical structural modification studies. However, the un-scaled mode shapes from an OMA test can be used to update a Finite Element Model (FEM). The updated FEM can then be used to analytically predict the effect of structural modifications. This paper will present the results of an OMA test performed on a simple plate and motor in operating conditions. The un-scaled mode shapes from this test will be used to update a FEM model of the system. The updated FEM model will be then be used to predict the effect of attaching a mass to the plate. The shapes predicted by the FEM for the modified system will be compared to a second OMA test on the modified system

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제17권10호
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• pp.946-949
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• 2007

This paper discusses the lateral vibration of a beam with boundary condition of one end fixed and the other end free. The uniform beam has a solution by summation of some simple exponential functions. But if its shape is not uniform, its solution could be by Bessel's function or mathematical solution could not exist. Even if the solution of Bessel's function exists, as Bessel function is a series function, we must get the solution by numerical method. Author had proposed the solution of the matrix method by Ritz's method and a new mode shape function, and had earned the good results for a wedge beam. Hereby a vibration analysis for the tapered beam with circle cross section was executed, and so good results were showed.

• Journal of Drive and Control
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• 제12권1호
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• pp.21-27
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• 2015

Pneumatic cylinders are classified into rod-type pneumatic cylinders and rodless pneumatic cylinders depending on the presence of the rod. Rodless cylinders have a constant area and have no deflection. Rodless cylinders are widely used in automatic systems requiring high-speed performance and high-precision transportation. However, the research of the pneumatic cylinder has been focused on the structure and life characteristics. In this research, aging characteristics and shape parameter analysis which are related to the lifetime were investigated. By conducting the lifetime tests with two different materials for the transfer plate, the failure mode and lifetime characteristics were analyzed. By the Anderson-Darling (A-D) verification based on the complete data set, the analysis results of lifetime distribution, shape parameter, and scale parameter were provided.

• Earthquakes and Structures
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• 제6권4호
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• pp.437-455
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• 2014

Some conventional lateral load patterns for pushover analysis, and proposing a new accurate pattern was investigated in present research. The new proposed load pattern has load distribution according weight and stiffness variation in height and mode shape of structure. The assessment of pushover application with mentioned pattern in X type braced steel frames and steel moment resisting frames, with stiffness and mass variation in height, was studied completely and the obtained results were compared with nonlinear dynamic analysis method (including time history analysis). The methods were compared from standpoints of some basic parameters such as displacement, drift and shape of lateral load pattern. It is concluded that proposed load pattern results are closer to nonlinear dynamic analysis (NDA) compared to other pushover load patterns especially in tall and medium-rise buildings having different stiffness and mass during the height.