Civil Engineering Reference
In-Depth Information
150
Pulse duration
T= 10 ms
T= 1 ms
125
100
75
50
25
0
-50
-40
-30
-20
-10
0
10
20
30
40
50
Time (ms)
Figure 1.5
Time functions of rectangular pulses.
1.0
0.9
Ampl
.=100
T= 10 ms
T= 5 ms
T= 1 ms
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
10
100
1000
Frequency (Hz)
Figure 1.6
Modulus of the Fourier transforms of rectangular pulses.
B) The example above does not represent, for many reasons, an oscillatory motion
you will find in real life. It does, however, illustrate important relationships concerning
the form of a pulse and the corresponding frequency spectrum. The following example
uses a more realistic type of motion; the function used represents the amplitude
(displacement, velocity or acceleration) of a simple mass and spring system having a
