Civil Engineering Reference
In-Depth Information
c67 File 106 145Y [mm] INT(C43)
1.0
0.5
0.0
−
0.5
−
1.0
0
20
40
60
Time [s]
80
100
c57 File 106 202Z [mm] INT(C33)
1.0
0.5
0.0
−
0.5
−
1.0
0
20
40
60
Time [s]
80
100
c91 File 106 145Y [mm2s] PSD(C67)
c81 File 106 202Z [mm2s] PSD(C57)
B2
SL1
1.8
3.0
2.5
2.0
B1
1.5
1.0
0.5
0.0
0.1
0
2
4
6
8
10
Frequency [Hz]
Fig. 2.23
The jogger crossing the bridge, and back, at a little too high pace.
Red
: Long cable out-of-plane displacement at 0.4 L,
Black
: Bridge
vertical deflection at 0.33 L
fundamental frequency B1, f
2.73 Hz, we can notice this in
the vertical bridge response. As soon as the jogger stops, he was instructed to run over the bridge, wait for 30 s and run back,
the bridge goes in the B1-mood, f
¼
1.19 Hz. As long as the jogger is loading the bridge with f
¼
¼
1.19 Hz, it likes most. Just check the respective mode shapes to confirm this bridge-
state-of-mood-philosophy.
Secondly, it was simply a consequence of being stubborn and also having a look at the cable vibration signals that the
following fact was reckognized (Fig.
2.23
): The jogger running at a little bit too high pace excited the long cable
fundamental mode to a significant intensity. With a very slow decay after the jogger having left the bridge.
