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
c D c y ' St k–ε 1%
k–ε 5% mesh#3 1.236 0.068 0.100 DDES
Table 2 Simulated aerodynamic parameters of the final stage
c D c y ' St k–ε 1%
Fig. 14 Distribution of the measured wind direction
Fig. 13 Spectrum of the measured mean wind speed
Szabó et al.
Period. Polytech. Civ. Eng.
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 . 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
, 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
, 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