Stability - Computational Analysis and Design of Bridge Structures - page 457

14.7 3D illuStratED ExaMplE with
nonlinEar StaBility analySiS of
a caBlE-StayED BriDgE, JiangSu,
pEoplE'S rEpuBlic of china

For the demonstration of nonlinear stability analysis, the same cable-stayed
bridge, Sutong Bridge, Jiangsu, China, in Chapter 11 is taken as an exam-
ple to illustrate issues. The typical cross section of the steel box girder, the
concrete pylon, and elevation profile are shown in Figures 12.23, 12.26,
and 12.29, respectively. As described in Chapter 11, the steel girder and
the pylon are modeled as a 3D frame, the diaphragm at the anchor posi-
tion is modeled as a rigid body, and the cable is modeled as a 3D truss.
Totally, the model is meshed with 1032 elements and 1035 nodes. VBDS is
employed in the analysis. ANSYS is also employed for checking some analy-
ses. Several different loading patterns are taken in the stability analysis of
this bridge. Table 14.2 lists the load patterns and critical load of the stability
analysis. In the six loading patterns, only the increment of the construction
load, which includes a 100-ton crane at the end of the girder and a uniform
load of 1 ton/m at the maximum single-cantilever stage, shows the cou-
pling of bending in vertical and lateral directions. Figure 14.22 shows the
vertical and lateral displacements when the construction loads increase to

Table 14.2 Loading patterns and the critical loads in stability analysis
Loading patterns

Description Critical case

At S 0 , increase V
step by step

To search the live load
safety factor without wind
interfering at service stage

When the live loads are increased by
40 times of the normal live load, the
vertical displacements at the center
of the main span abruptly reached
42 and 13 m at the top of the pylon.
The structure, however, still
maintains some degree of stiffness.
No lateral displacement significantly
increased.

At S 0 , increase S
step by step

To search the whole
structural weight safety
factor without wind
interference at service stage

At about three times of S , the
displacements increase abruptly. No
lateral displacement significantly
increased.

At S 1 plus W ,
increase C step
by step

To search the construction
load safety factor with wind
interference at maximum
dual-cantilever stage

When increased to 240 times of C ,
the displacements increase abruptly.
No lateral displacement significantly
increased.

At S 1 , increase W
step by step

To search the static wind
load safety factor at
maximum dual-cantilever
stage

Still remains in elastic even at
50 times of W , while the lateral
displacement at the end of the
girder reaches to 7 m.

( Continued )