Examples of Finite Element Models of Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 610

of bar elements and the bearings by appropriate springs. Diaphragms and
stiffeners may also be taken into account. It was shown that, in comparison
to the grillage model, which was usually used for the analysis of bridges, the
proposed 3-D model allowed a reliable prediction of deformations, internal
forces, and stresses. In addition, it was shown that curved bridges displayed
unique behavior characteristics, and for this reason, a grillage analysis was not
always suitable. Therefore, the authors concluded that the proposed model-
ing of composite bridges, using a spatial system of beam-like structural ele-
ments, was applied in the study for the modeling of curved composite
bridges. Worked examples were provided to illustrate the setup procedure
of the proposed modeling and to compare its results with those of the cor-
responding finite element models. The authors mentioned that a bridge
analysis model should be based on the following: (1) The model should
reflect the structural response in terms of deformation, strength, and local
and global stability; (2) the model should include as many structural elements
and parts (cross frames, stiffeners, bearings, etc.) as possible and their possible
eccentric connections; (3) the model should cover all construction stages and
loading cases; (4) loads should be easily introduced; (5) the model should
allow the performance of dynamic analysis and include the most important
modes; and finally (6) the model should run with a common analysis and
design software. The authors also mentioned that the structural system must
reproduce the 3-D behavior of a bridge as accurately as possible. This was
achieved through the representation of the steel I-girders by equivalent
trusses. The deck slab was idealized by a grillage of concrete beams. The
main concept was based on the setup of a global model, which will be easy
to modify during the different construction stages, including stages of erec-
tion or deck concreting. The study showed that curved composite bridges
displayed unique behavior characteristics. The presence of curvature
affected the geometry and, as a consequence, the behavior of the structure.
Curved bridges were subjected to coupled torsion and bending because of
the curvature, and their analysis was more complex than that of straight
bridges.
Gara et al. [ 7.18 ] proposed a simplified method of analysis for the design
of twin girder and single-box steel-concrete composite bridge decks. The
method relied on the use of the real width of the slab for the whole bridge
length when performing the global analysis, that is, without modifying the
deck geometry based on the effective width method, and the ability to eval-
uate the normal longitudinal stress distribution on the slab by means of a
cross-sectional analysis considering the internal actions obtained from the