Stability - Computational Analysis and Design of Bridge Structures - page 458

Table 14.2 (Continued) Loading patterns and the critical loads in stability analysis
Loading patterns

Description Critical case

At S 2 plus W ,
increase C step
by step

To search the
construction load safety
factor with wind
interfering at maximum
single-cantilever stage

At 46 times of C , the vertical
displacement at the end of the
girder increased to over 100 m
accompanied with 42 m of lateral
displacements (Figure 14.22).

At 48 times of W , the lateral
displacement at the end of the
girder increased to over 100 m.

At S 2 , increase W
step by step

To search the static wind
load safety factor at
maximum single-
cantilever stage without
the consideration of the
construction load

S 0 , the ideal state at the service stage (the structural weight, cable tuning, and the superimposed dead
load); S 1 , the state at the maximum dual-cantilever stage (the structural weight and the cable tuning);
S 2 , the state at the maximum single-cantilever stage (the structural weight and the cable tuning); S , the
whole structure weight plus superimposed dead load; V , the live loads that cause the maximum verti-
cal displacement at the center of the main span; C , a 100-ton crane at one or two ends of the canti-
lever and 1 ton/meter of the other construction load; W , the lateral wind load.

1

0
0

1

0

18

2

0 0 6 10 12 14

0

0

0 0

30 63
110

0 0

0 0

42

35

24

14

6

0 0 0 0 0 1

Figure 14.22 The vertical (top) and the lateral (bottom) displacements (m) of the girder
when the construction loads are increased by 46 times of the normal
construction loads at the maximum single-cantilever stage.

46 times the earlier construction load, while the lateral wind load remains
unchanged. The stability analysis also shows that the structure at the stage
when its main span is ready to close is more vulnerable than at the stage when
its side span reaches the second auxiliary pier. Although the results of these
six loading patterns show that the structure has sufficient stability against
live loads, wind load, construction load, and the structural weight, the full
nonlinear ultimate analysis (Ren 1999), in which the material nonlinearity
is also considered, and the aerodynamic stability analysis are required.