Arch bridges - Computational Analysis and Design of Bridge Structures - page 276

Figure 9.10 Yajisha Bridge, China, 2000, a half-through steel tubular concrete arch
bridge with a main span of 360 m.
and finished in June 2000. What distinguishes the Yajisha Bridge is not its
truss-like steel tubular concrete main arch as shown in Figure 9.11, but its
combined construction method of vertical rotation and horizontal rotation.
Each of the two half arches is first assembled on shore at a lower vertical
position. After assembled on falsework, the half arch is vertically lifted to
the design elevation and then rotated horizontally to meet the bridge axis.
9.2.2.1 Cross section of the main arch
The main arch comprises six steel tubes, each with a diameter of 750 mm,
as shown in Figure 9.11. Three steel tubes are connected by steel plates,
horizontally forming an arch rib. Two ribs on the top and bottom are con-
nected by steel tubes with a diameter of 450 mm as vertical and diagonal
truss members, forming a composite arch cross section (Figures 9.11 and
9.12d). After closure, top and bottom ribs are filled with concrete. The
composited arch section varies from 4000 mm at crown to 8039 mm at
springing, while maintaining a constant width of 3450 mm.
9.2.2.2 Vertical rotation
Main arch is split into several segments, and each segment is fabricated off-
site. Each of the half arch is first assembled segment by segment with the
support of falsework on shore. The axis of the arch at this stage is almost per-
pendicular to the designed bridge axis. As shown in Figures 9.12a and 9.13,