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南台科技大學 劉雲輝
Nature of environmental vibrations
劉雲輝
南台科技大學
機械工程系
電話﹕(06) 2533131 ext.3538
電郵﹕[email protected]
網頁﹕faculty.stut.edu.tw/~yhliu/
Dec 20 , 2005
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南台科技大學 劉雲輝
Nature of Environmental Vibrations

Ground motion
random 、 0.5-30 Hz.

Human activity
a decay free-vibration motion

Rotating equipment
multi-tone periodic vibration、10-500 Hz

Air pressure fluctuations
random 、 serious at resonant frequencies.
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南台科技大學 劉雲輝
Ground Motion (1)




traffic
wind
earthquake
other external sources
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南台科技大學 劉雲輝
Ground Motion (2)
Environmental vibration comparison between different storeys
1.4
Basement
Velocity (mm/s)
1.2
1-storey
1
2-storey
0.8
0.6
0.4
0.2
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
Frequency
The lower story instrument is housed,
the lower ground motion it suffers.
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南台科技大學 劉雲輝
Human Activity

The peak amplitude produced by footfall
rather than the complete history is of most
importance.
 It depends on magnitude of impact load, and
the ratio of the load duration and the period
of vibration.
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南台科技大學 劉雲輝
Rotating Equipment
 Due to unbalance of the rotor.
 Fundamental frequency almost is same as
rotary speed of rotor.
 The periodic vibrations can be easily reduced
by use of spring isolator on vibration source.
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南台科技大學 劉雲輝
Air Pressure Fluctuations
 Noise in most laboratory environments often
approaches the operative limits of the most
advanced technology instrument.
a 560 x 710 x 0.4 mm
thick steel panel
70dB (re 20 mpa)
31.5 to 125 Hz
75 dB
(ref. 1 minch/s)
 The air turbulence within large air ducts may
generate random vibrations transmitted to
their attachment points.
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