Civil Engineering Reference
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bridge is composed of three parts, the central cable stayed section and two
side (approaching) parts made of pre-stressed RC beams that rest on elas-
tomeric bearings. The central section of the bridge is divided into three
spans of lengths 90 m, 215 m and 90 m, while the deck (of 13.50 m width)
is suspended with cables by the 90 m height pylons at M5 and M6. The
displacements of the deck along the longitudinal direction are permitted in
piers M4 and M7 while those in the transverse direction are restrained
(Lekidis
et al.
, 2005). The behavior of the Evripos cable-stayed bridge is
constantly monitored through a special accelerometer array installed by the
Institute of Engineering Seismology and Earthquake Engineering (ITSAK).
The network is composed by four triaxial accelerometers installed at the
base of the bridge on the pile caps of piers M5 and M6 and on soil surface
in areas adjacent to piers M4 and M7. There are also 31 additional uniaxial
accelerometers installed on the superstructure, for system identifi cation
purposes.
To study the spatial variation of earthquake ground motion, the bridge
response recorded at four locations of the accelerometer network during
the
M
s
5.9, 7 September 1999 Athens earthquake was utilized (Karakostas
et al.
, 2011). The records were fi ltered to remove inertial interaction effects
and their coherency was computed for all available record pairs as seen in
Fig. 22.8. A detailed FE model of the cable-stayed bridge was also devel-
oped and its response was computed using both the recorded motions and
four synchronous excitation scenarios.
For the particular bridge studied, spatial variability of seismic ground
motion has a generally favorable effect, at least on the pier base bending
moments and the displacements at the middle of the central span deck.
=
1
Calculated
Luco & Wong
a
0.9
0.8
10
-4
Luco & Wong
a
=2.5
×
0.7
10
-4
=0.5
×
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
8
10
f
[Hz]
22.8
Comparison between observed and predicted coherency loss for
different values of the Luco and Wong model (Luco and Wong, 1986).
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