Introduction - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 23

direction. It was also found that bearing movement constraints on the other
end introduced normal forces in the steel girders that were not considered in
deck designs. In addition, the study has shown that a nonlinear gradient
across the bridge width was developed, which resulted in additional stresses
found on diaphragm members at the outside girders.
Cheng and Li [ 1.38 ] performed a reliability analysis for a long-span steel
arch bridge against wind-induced stability failure during construction. An
algorithm was developed based on stochastic finite element method to eval-
uate the reliability analysis. The study has incorporated uncertainties in static
wind load-related parameters. The proposed algorithm integrated the finite
element method and the first-order reliability method. The authors per-
formed the analysis as an example on a long-span steel arch bridge with a
main span length of 550 m built in China. The reliability analysis was per-
formed in two different construction stages. The first construction stage
involved the construction process before closure of main arch ribs. On
the other hand, in the second construction stage, all the remaining parts
of the bridge have been completed except the stiffening girder of the main
span. Three components of wind loads (drag force, lift force, and pitch
moment) acting on both steel girder and arch ribs were considered in the
study [ 1.38 ] . The authors have concluded that the steel arch bridge during
the second construction stage was more vulnerable to wind-induced stability
failure than that during the first construction stage. The authors have per-
formed a parametric study to investigate the effects of the variations of wind
speed with height, drag force of wind loads, design wind speed at the bridge
site, and static aerodynamic coefficients on the probability of wind-induced
stability failure during the construction stages for the steel arch bridge. Yoo
and Choi [ 1.39 ] proposed an iterative system buckling analysis to determine
the effective lengths of girder and tower members of cable-stayed bridges.
The proposed technique included a fictitious axial force that was added
to the axial force of each member in the geometric stiffness matrix to rep-
resent an additional force for the individual buckling limit of the member.
The proposed method was initially used to analyze a three-story plane frame
under two different load cases. After that, it was applied to cable-stayed
bridge examples with several center span lengths and girder depths. The
effective lengths of the individual members in these example bridges were
computed using the proposed method and compared with those found using
system buckling analysis. The study has shown that the critical load expres-
sion in combination with system buckling analysis yields excessively large
effective length for members subjected to small axial forces. Also, it was