Vibration Assessment of a New Danube Bridge at Komárom


Fig. 11 Velocity contours of the deck at construction stage Fig. 12



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Fig. 11 Velocity contours of the deck at construction stage
Fig. 12 Velocity contours of the completed deck
Table 1 Simulated aerodynamic parameters of the construction stage
model
I
mesh
c
D
c
y
'
St
kε
1%
mesh#1
1.190
0.108
0.100
kε
1%
mesh#2
1.190
0.105
0.106
kε
1%
mesh#3
1.166
0.108
0.106
kε
5%
mesh#1
1.239
0.067
0.094
kε
5%
mesh#2
1.229
0.069
0.099
k–ε
5%
mesh#3
1.236
0.068
0.100
DDES
1%
mesh#4
1.143
0.084
0.094
Table 2 Simulated aerodynamic parameters of the final stage
model
I
mesh
c
D
c
y
'
St
kε
1%
mesh#1
1.704
0.149
0.082
kε
1%
mesh#2
1.774
0.238
0.094
kε
1%
mesh#3
1.787
0.255
0.094
kε
5%
mesh#1
1.652
0.108
0.081
kε
5%
mesh#2
1.635
0.088
0.081
kε
5%
mesh#3
1.774
0.106
0.081
DDES
1%
mesh#4
1.724
0.251
0.088
Fig. 14 Distribution of the measured wind direction
Fig. 13 Spectrum of the measured mean wind speed


Szabó et al.
Period. Polytech. Civ. Eng.
|7
6 Validation to present monitoring data
In this section the numerical model of the Komárom 
Bridge was validated based on the results gained from the 
monitoring system dedicated to this particular structure. 
The relevant large amplitudes could be expected within the 
period of the longest cantilever stages. As was shown in 
Fig. 13, however, no wind velocities high enough to cause 
vortex induced resonance of the deck occurred; therefore, 
rather low vibration amplitudes could be observed only. 
The highest wind loading coincided with stage-11, the time 
series is shown in Fig. 15. The corresponding measured 
vertical acceleration of the TMD closest to the end of the 
cantilever can be seen in Fig. 16. Within approximately 20 
minutes, the deck and the TMD vibration was amplified by 
vortex shedding of the deck as the mean wind speed grew, 
which is highlighted with red rectangle. The mean wind 
speed was around 7m/s within this time range. Other than 
the relevant highlighted time range, the local growth of the 
wind speed and that of the bridge deck acceleration coin-
cides everywhere along the time axis, as a consequence of 
vortex shedding phenomenon (see Figs. 15 and 16).
The structural dynamics simulation was carried out 
according to model shown in Fig. 5. The dynamic load 
was a uniform vertical periodic excitation along the deck, 
except for the end of the cantilever (see Fig. 17). Due to 
the three-dimensional flow around the end of the deck, 
the excitation was assumed to be zero within a length of 
4D = 10.5 m [13]. The mean wind speed U was 7.0 m/s, 
with a horizontal skewness α of 141.8° (see Fig. 14); there-
fore, wind speed perpendicular to the deck U was 4.33 m/s. 
Based on the measured frequency, lock-in was assumed, 
thus the excitation frequency was set to 0.346 Hz. The sim-
ulated RMS of lift (c
y
' = 0.068) in case of high (5%) tur-
bulence intensity was used, which was related to the full-
scale width of the deck (B = 20.4 m). Considering the low 
vibration amplitudes (< 1 cm), the excitation force was 
constant, that is the aerodynamic forces were linear.
Within the wind speed time range marked in Fig. 15, 
the measured vertical acceleration of the structure and the 
TMD (at the position of the sensors) are shown in Fig. 18 
and Fig. 19 in detail. The RMS of the acceleration of the 
structure and the TMD were approximately 20 mm/s
2
and 
37 mm/s
2
, respectively. In Fig. 20 the simulated vertical 
accelerations of the corresponding point of the structure 
and the TMD are shown.
The calculated vibration accelerations of the deck and 
the TMD after the transient period are 45 mm/s
2
and 
95 mm/s
2
, respectively (see Fig. 20), which are roughly 2.5 
times higher than the corresponding measured values.
7 Conclusions
In this paper the vortex shedding excitation of the 
Komárom Bridge was investigated. The bridge struc-
ture was monitored during the most critical construc-
tion stages. The structural properties of the bridge were 
determined based on the free decay motion after a group 
of people excited periodically the end of the cantilever. 
The natural frequency of the bridge determined by the 
FEM model was well in line with the measurements. The 
measured damping of the steel structure was close to the 
value of steel bridges proposed by Eurocode. The damp-
ing effects of the TMD elements were also investigated by 

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