• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.848-851
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• 2002

In this paper, an experimental method using a reference accelerometer has been developed to measure the in-plane vibration intensity of a beam. It has the advantages of reducing accelerometer phase error comparing with the cross spectral intensity measurement technique using an accelerometer array. It needs no measurement of the input force required in the frequency response method using the only one accelerometer This method has been used to measure the in-plane vibration intensity over the beam. The result has been compared with an input power and the vibration intensity obtained with other methods. It showed that the present experimental method can be effectively used to measure the structural in-plane vibration intensity.

• Computers and Concrete
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• v.12 no.1
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• pp.79-90
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• 2013

In this study, dynamic characteristics such as natural frequencies, mode shapes and damping ratios of RC frame is determined for different construction stages using Operational Modal Analyses method under ambient vibration. Full scaled, one bay and one story RC frames are selected as an application for different construction stages such as plane, brick in-filled and brick in-filled with plaster. The RC frame is vibrated by natural excitations with small impact effects and the response signals are measured using sensitive accelerometers during ambient vibration tests. Measurement time-frequency span and effective mode number are determined by considering similar studies in literature. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, output-only system identification technique is employed namely; Enhanced Frequency Domain Decomposition technique in the frequency domain. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of RC frames.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.390-393
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• 2005

In this study, examined heavy-weight floor impact sound to rahmen structure(steel reinforced concrete structure) and bearing-wall structure(box frame type structure) that have slab thickness of 4 form at a standard laboratory through noise and vibration measured. The results of ANSYS modeling of structures was predicted that the nature natural frequency increased according to change of thickness of each slab by finite element analysis, and acceleration value decreased. Rahmen structures compares with bearing-wall structure, nature frequency was predicted low. Measurement results of natural frequency and acceleration level for structures at a standard laboratory, tendency department such as ANSYS modeling appeared. Rahmen structures appeared that reduction effect is less in Acceleration level and heavy impact sound transmission level comparing with bearing-wall structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.184-188
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• 2001

Severe vibration was detected during test operation in motor frame of the Turbo Chiller (300RT). To identify the vibration problem, vibration measurement and modal test were carried out. From the test results, it is concluded that the severe vibration occurred due to the resonance between the motor frame horizontal mode and the motor excitation frequency. Therefore the horizontal mode of the frame could be controlled by the sensitivity analysis results for the length of the supporting plate.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.12
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• pp.1082-1089
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• 2013

3-Axis sensor measurement system is needed for measuring ride quality of elevator. But because 3-Axis piezoelectric accelerometer is expensive. We developed 3-Axis sensor system which is suitable for measuring ride quality of elevator using cheap MEMS sensor. There are two types of MEMS sensor that are piezoresistive and capacitive type. The excellence of piezoresistive type in characteristic of frequency response and noise is confirmed compare to capacitive type as a result of this paper's experiment and reference. 3-Axis system using MEMS sensor needs MEMS's proper frequency response characteristic. Additionally noise characteristic of sensor and circuit, stiffness of assembly are needed for deciding frequency range and accuracy of amplitude.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.5 s.110
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• pp.514-520
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• 2006

In this study, the performance of a digital pile rebounding and penetration monitoring system (DPRMS) is evaluated and the measurement precision of the DPRMS is improved. The DPRMS is a high speed line-scanning camera system to measure the rebound and penetration of a pile in a construction work. A main problem in the DPRMS is a measurement error, which is caused by a shock or vibration due to a hammer impact. The measurement error is investigated by analyzing vibration signals of the DPRMS during the impact. Moreover, the frequency response functions of the DPRMS are also analyzed. As a result, it is found that the tripod height has an influence on the DPRMS performance and a shorter tripod is better. One more founding in this study is that the DPRMS should be placed with a appropriate distance from a pile for improving the measurement precision.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.4
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• pp.75-81
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• 2012

In this study, vibration characteristics in according to the load type of cast resin transformer using vibration measurement device were compared. Measurement conditions are the same installation and operation of the three-phase cast resin transformer. If the load increases in transformer using the rotating machinery, the frequency is growing. In the transformer using the lighting and heating loads, it's detected the 55 [${\mu}m/s$] in or outside and 120 [${\mu}m/s$] or more at 60[Hz], the 30 [${\mu}m/s$] in or outside at 120[Hz], and the 70 [${\mu}m/s$] in or outside at 420[Hz]. When increases the loads, it's appeared the 60 [${\mu}m/s$] or less at 450[Hz] or more in rotating machinery, but the velocity of lighting and lighting loads are appeared from 5[${\mu}m/s$] to 115[${\mu}m/s$] inside the 420[Hz] in the same load condition of 20[%]. Through this study, it's verified that there are differences the internal vibration in according to the type of load in cast resin transformer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.930-933
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• 2005

Non-destructive inspection techniques using laser have been breading their application areas as well as growing their measurement skills together with the rapid development of circumferential technology like fiber optics. computer and image processing The ESPI technique is already on the stage of on-line testing with commercial products in developed country nations. Especially, this technique is expected to be applied to the nuclear industry, automobile and aerospace because it is proper for the vibration measurement and it can be applied to objects of a high temperature. This paper describes the use of the ESPI system for measuring vibration patterns on the reflecting objects. Using this system, high-quality Jo fringes for identifying mode shapes are displayed. A bias vibration is introduced into the reference beam to shift the Jo fringes so that fringe shift algorithms can be used to determine vibration amplitude. Using this method. amplitude fields for vibrating objects were obtained directly from the time-average interferometer recorded by the ESPI system.

• Journal of the Society of Disaster Information
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• v.11 no.1
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• pp.89-96
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• 2015

To reduce noise inside an elevated railroad station, the vibration of the station structure should be lowered, and to establish more effective anti-vibration measures it is required that, reflecting the track-bridge-structure interaction, the transfer characteristics of vibration induced by a train is well identified. In this paper, the current status of domestic railroad stations is classified, and the vibration transfer characteristics is analyzed via measurement data from representative elevated stations. From the analysis results on the measurement data, in transferring vibration from the track to the structure, remarkable vibration reduction in higher frequency range is observed, and, in some stations, amplified response characteristics in lower frequency range is identified. Also, for stations with floating track system or TPS type, relatively greater reduction in transferred vibration is observed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.1
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• pp.135-140
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• 2010

Vibration on the ship was generated mainly by main engine and propeller. The vibration which is generated from the ship has an effect on durability of ship's machinery and it also has an evil influence on the working conditions for crew. In this research, vibration measurement system to measure ship's vibration was built and vibration signals using acceleration sensors were measured from an accomodation space of training ship. An evaluation of vibration with regard to habitability was also discussed and the evaluation process followed the guidelines ISO6954:2000E.