Overall Conceptual Seismic Design and Local Seismic Capacity Design for Components of Bridges - Structural Seismic Design Optimization and Earthquake Engineering - page 285

Figure 13. Finite element model of the Jiubao Bridge

Table 8. Seismic response comparisons of the arch bridges with RC and SCC girders

Girder Southern approach Main bridge

Shear-PS6
(×10 3 kN)

Moment-PS6
(×10 3 kN.m)

Displacement of
bearing-PS2 (m)

Shear-PS1
(×10 3 kN)

Moment-PS1
(×10 3 kN.m)

Displacement of
bearing-PN1(m)

(i) RC 8.450 156.10 0.290 10.492 138.85 0.240

(ii) SCC 5.195 95.53 0.190 7.894 102.89 0.190

(ii)/(i) (%) 61.5 61.2 65.5 75.2 74.1 79.2

Solutions and Recommendations For a long span floating cable-stayed bridge,

a new-type spatial bridge tower is proposed to
replace the originally designed inverted Y shape
tower. Analysis results show that the longitudinal
seismic displacements can be reduced significantly
for a bridge with the spatial tower. The transverse
displacement at the midspan of the spatial tower
model is also reduced. Although the transverse
displacement of the tower top increases to some
extent, the magnitude of the displacement is
relatively small and practically acceptable for
the cable-stayed bridge. Moreover, the seismic
force demands in each column of the spatial tower
model are less than or almost equal to those of
the original model.

From the perspective of overall linear conceptual
seismic design, several new design strategies have
been presented. For a typical long span continuous
girder bridge, the forms of piers and the locations
of expansion joints are adjusted respectively for
different site conditions to improve the stiffness
distribution. Based on code design response
spectra, theoretical analyses and numerical simula-
tions show that both the displacement and stress
demands are greatly mitigated, and the demand
variations along the piers are decreased as well
after adopting the strategies.