• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.608-613
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• 2003

In this paper, the variability of modal properties caused by temperature effects is assessed to adjust modal data used for frequency-based damage detection in plate-girder bridges. First, experiments on model plate-girder bridges are described. Next, the relationship between temperature and natural frequencies is assessed and a set of empirical frequency-correction formula are analyzed for the test structure. Finally, a frequency-eased method is used to locate and estimate severity of damage in the test structure using experimental modal data which are adjusted by the frequency-correction formula. Here, local damage in beam-type structures is detected by using measured frequencies and analytical mode shapes.

• Structural Engineering and Mechanics
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• v.74 no.1
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• pp.121-128
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• 2020

This paper presents an experimental study on the dynamic characteristics of infilled reinforced concrete (RC) frames. A 1/3-scaled, one-bay, three-storey RC frame was produced and tested by using operational modal analysis (OMA). The experiments were performed on five specimens: one reference frame with no infill walls and four frames with infill walls. The RC frame systems included infill walls made of hollow clay brick, which were constructed in four different patterns. The dynamic characteristics of the patterns, including the frequency, mode shapes and damping ratios in the in-plane direction, were obtained by 6 accelerometers. Twenty-minute records under ambient vibration were collected for each model, and the dynamic characteristics were determined using the ambient vibration testing and modal identification software (ARTeMIS). The experimental studies showed that the infill walls significantly affected the frequency value, rigidity and damping ratio of the RC frame system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.323-326
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• 2004

In these days, gear whine noise of the axle and transmission is getting more important for reduction of vehicle noise, because major noise of vehicle was reduced. Therefore, in this paper, axle noise and vibration is measured, and then the modal analysis and running modal analysis is applied for reduction of axle gear whine noise.

• Structural Engineering and Mechanics
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• v.29 no.2
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• pp.171-186
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• 2008

The seismic response analysis of an existing bridge needs a mathematical model that can be calibrated with measured dynamic characteristics. These characteristics are the periods and the associated mode shapes of vibration and the modal damping coefficients. This paper deals with the measurements and the interpretation of the results of ambient vibration tests done on a newly erected cable stayed bridge across the Oued Dib River at Mila city in Algeria. The signal analysis of ambient vibration records will permit to determine the dynamic characteristics of the bridge. On the other hand, a 3-D model of the bridge is developed in order to assess the frequencies and the associated modes of vibration. This information will be necessary in the planning of the test on the site (locations of the sensors, frequencies to be measured and the associated mode shapes of vibration). The frequencies predicted by the finite element model are compared with those measured during full-scale ambient vibration measurements of the bridge. In the same way, the modal damping coefficients obtained by the random decrement method are compared to those of similar bridges.

• Smart Structures and Systems
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• v.6 no.8
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• pp.905-920
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• 2010

Changes in temperature, loads and boundary conditions may have effects on the dynamic properties of large civil structures. Taking the Run Yang Suspension Bridge as an example, modal properties obtained from ambient vibration tests and from the structural health monitoring system of the bridge are used to identify and evaluate the modal parameter variability. Comparisons of these modal parameters reveal that several low-order modes experience a significant change in frequency from the completion of the bridge to its operation. However, the correlation analysis between measured modal parameters and the temperature shows that temperature has a slight influence on the low-order modal frequencies. Therefore, this paper focuses on the effects of the boundary conditions on the dynamic behaviors of the suspension bridge. An analytical model is proposed to perform a sensitivity analysis on modal parameters of the bridge concerning the stiffness of expansion joints located at two ends of bridge girders. It is concluded that the boundary conditions have a significant influence on the low-order modal parameters of the suspension bridge. In addition, the influence of vehicle load on modal parameters is also investigated based on the proposed model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.933-939
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• 2000

In this paper we present an overview of the factors and techniques that must be considered in vibration measurements in the floor structures for microelectronics facilities. Normally narrowband vibration spectrum or equivalent signals are suggested as the guide indexes of site vibration phenomina. But it cannot support perfect informations in designing vibration control systems for the vibration sensitive equipment even though the spectrum serves to illustrate the fact that most real vibration environments are dominated by broadband energy as opposed to tonal energy. The major topics cover stiffness in frequency and time domain, acceleration level and modal characteristics from experimental modal analysis as well as narrowband spectrum. The combined signal analysis through the items mentioned above can give better solutions and would be positively recomended to solve the vibration problems on a sort of limited field.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.233-237
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• 1998

In this work, to identify the dynamic characteristics of disk-spindle system in hard disk drive, experimental modal analysis was performed. And an experimental analysis system including testing apparatus, precision sensors, and analysis software was established in order to perform the testing effectively. From the experimental results, coupled and uncoupled modal characteristics of 3-disk spindle system are clearly identified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.401.2-401
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• 2002

An unconstrained tuning fork with a 3-D model has been numerically analyzed by Finite Element Method (FEM) and Boundary Element Method (BEM). The first three natural frequencies were calculated by the FEM modal analysis. Then the change of the modal frequencies was examined with the variation of the tuning fork length and width. (omitted)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.361.1-361
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• 2002

Coupling adjacent steel frame using elastic dampers fer control of response to low and moderate dynamic event is investigated in this paper. The complex modal superposition method is first used to determine dynamic characteristic, mainly modal damping ratio and modal frequency, of damper linked linear adjacent steel frame for fractical use. Dynamic response of steel frame linked by hydraulic-excitation method. (omitted)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.470-476
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• 2002

We tested the natural frequency for the 1st moving blades of a steam turbine in general power plants, carried out the modal test of the blade groups each natural frequency. By this test results, we identified the resonance results largely in damaging the blades. We can predict damage probability for the blade groups and change state of material property by using the result of this study.