Introduction - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 36

shown that the composite bridge service life results corroborated the impor-
tance of considering the roughness of the pavement surface and other design
parameters such as floor thickness, structural damping, and beam cross-
sectional geometric properties in the bridge dynamic and fatigue analyses.
The analysis methodology considered a vehicle structure mathematical
model, which included the interaction between their dynamic properties.
It was shown that the proposed methodology can be general and can be used
as a solution strategy on other highway bridge types such as multigirder brid-
ges, continuous multigirder bridges, cable-stayed bridges, and rigid-frame
bridges. The authors showed that the fatigue problemwas much more com-
plicated and was influenced by several highway bridge types. It was con-
cluded that the investigated composite (steel-concrete) highway bridge
can perform safely with an acceptable probability that indicated that failure
by fatigue cracking can be eliminated. It was also shown that when the
dynamic actions related to the vehicles moving on the bridge lateral track
path and two simultaneous lateral track paths were applied on the bridge
structure, it was observed that the service life values proposed by current
design codes were exceeded. Okamoto and Nakamura [ 1.67 ] proposed
and applied a new type of hybrid high tower to a multispan cable-stayed
bridge. The proposed type was a sandwich-type structure and consisted
of a steel double box section filled with concrete. The filled concrete
increased its strength due to the confined effect, and the steel plates increased
the resistance against local buckling because the deformation was restricted
by the filled concrete. The study showed that the hybrid tower can have
high bending and compressive strength and also a good ductile property.
In the study, static analysis was conducted for different live-load intensity
and distribution. The live loads distributed in alternate spans gave larger
bending moment of the towers than the live loads distributed in full spans.
The authors checked the safety of the tower using limit state design method.
Serviceability was not a major problem for the hybrid tower. Following the
static analysis, seismic analysis was performed for a multispan cable-stayed
bridge subjected to the medium and ultra-strong seismic waves. Three sup-
port conditions of the girder at the tower cross beams were considered,
which were movable, connection with linear springs and bilinear springs.
The study showed that bilinear springs were very effective in reducing
the dynamic displacements and bending moments of the towers. The study
also showed that a new steel-concrete hybrid tower was feasible for multi-
span cable-stayed bridges and most effective for seismic forces when the
girder was connected with bilinear springs.