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Table 7. Seismic response comparisons of RC and SCC continuous girder bridges
Design
scheme
Superstructure
mass (×10
6
kg)
Pier area
(m
2
)
Pier stiffness
(×10
6
kN/m)
Period
(s)
Shear
(×10
3
kN)
Moment
(×10
3
kN.m)
Disp. (m)
(i) RC
3.900
4.050
0.199
0.880
3.430
24.00
0.017
(ii) SCC
2.118
2.200
0.189
0.670
2.470
17.30
0.013
(ii)/(i) (%)
54.3
54.3
95.0
76.1
72.0
72.1
76.5
cable stiffness increases. It is obvious that the
change of the system, namely the increase of the
bridge stiffness will cause a decrease of the fun-
damental period and an increase of the horizontal
brake force of the girder. The transformation of the
force transmission path is the main reason why the
seismic demands change along the curves shown
in Figure 10 to 12. For a floating cable-stayed
bridge without elastic cables under earthquakes,
the large horizontal forces produced by the girder,
whose acting point is usually at upper zones of
the tower, are all transmitted to the tower by the
stayed-cables. But the elastic cables can share
most of the seismic forces and transmit them to
lower zones of the tower for a cable-stayed bridge
installed with them.
with the same span and deck width has a lighter
superstructure, less pier stiffness and fundamental
period. The seismic shear force and bending mo-
ment at the pier bottom are 72.0% and 72.1% of
those from the initial reinforced concrete scheme.
Moreover, the pier top displacement is only 76.5%
of that in design scheme (i). The seismic potential
of the SCC bridge system is significant.
A major highway bridge located in the city of
Hangzhou, China, the Jiubao Bridge consists of
an SCC continuous girder system for the northern
approach (55 m, 85 m, 85 m, 90 m), an arch with
SCC girder system for the main bridge (three 210
m spans) and another SCC continuous girder
system for the southern approach (90 m, nine 85
m, 55 m). The SCC deck is a reinforced concrete
slab on top of steel box girders. The superstructure
is supported by sliding and pot bearings, both
types being fixed in the transverse direction. In
the longitudinal direction the bearings are designed
to be fixed at pier PN4, PS1, PS5, PS6 and PS7
as shown in the finite element model in Figure
13.
Seismic Potential and Performance
for Long Span SCC Bridges
To illustrate the advantage of steel-concrete com-
posite (SCC) system, a typical four span bridge
with spans of 25 m, 30 m, 30 m and 25 m, deck
18 m wide, and piers 7 m high was ever studied
(Turkington, Carr, Cooke, & Moss, 1989). In
this section, there are two design schemes for the
bridge: (i) a conventional reinforced concrete (RC)
continuous girder bridge supported by solid form
piers and (ii) an SCC continuous girder bridge sup-
ported by hollow form piers, all basic properties
being shown in Table 7. The seismic responses
of both design schemes from elastic response
spectrum analyses (Ministry of Transport of the
People's Republic of China, 2008) are also shown
in Table 7. It can be seen that the SCC scheme
It was suggested that the girders of the SCC
bridge might be replaced by equivalent concrete
girders with weight twice as heavy as the SCC
ones. Response spectrum analyses were performed
(Cao, 2009) and the results are shown in Table 8
for the bridge, and it is clear that the long span
SCC bridge has lower seismic force and displace-
ment demands than the RC one. Hence, the SCC
system has higher seismic potential and better
seismic performance.
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