Examples of Finite Element Models of Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 609

the extension of the model to skewed composite bridges. The presence of
skew made the analysis complicated, and for this reason, the grillage analysis
was not recommended. The authors showed that phenomenons like differ-
ential deflections of the main girders during concreting and lateral displace-
ments of the flanges could be adequately predicted using the proposed
model. The proposed models of composite bridges, using a spatial system
of beam-like structural elements, could be also used for stability analysis
of skewed bridges. Worked examples were provided to illustrate the setup
procedure of the proposed modeling and to compare the different ways of
analysis. To overcome the difficulties of the grillage and finite element
models, a 3-D truss model was proposed where the steel I-girders were
modeled by equivalent trusses [ 7.15 , 7.16 ] while the deck slab by a grillage
of concrete beams. The main intention was the set up of a global model,
which can be used during the erection stages and deck concreting and for
the serviceability and ultimate limit states. In the modeling of a composite
girder through the use of an equivalent truss, the flanges of the truss were
modeled as beam elements with cross section composed of the flange
and part (1/3) of the web of the steel girder. The flanges were connected
by a hybrid combination of truss and beam elements that represented the
web of the steel girder. The concrete section was represented by another
beam element connected with the upper flange of the truss through the
appropriate offset. In order to verify the validity of the proposed model,
numerical investigations for deformations, stresses, buckling, and dynam-
ical modes were performed for a simply supported beam with either steel
or composite cross sections. In the grillage analysis of the concrete slab of a
composite bridge, concrete slab can be represented by a grillage of in-
terconnected beams. The longitudinal stiffness of the slab was concentrated
in the longitudinal beams and the transverse stiffness in the transverse
beams. In order to show the differential deflections that occur on a skewed
bridge during concreting and to make a first comparison between the two
models, a skewed bridge was investigated using a 3-D finite element
analysis. The deck of a skewed bridge may be represented through a gril-
lage of beam-like elements. The bridge was simply supported at one edge
(hinged supports), while on the other edge, there was free translation along
the longitudinal axis.
Adamakos et al. [ 7.17 ] presented a modeling technique for steel compos-
ite bridges, which was previously detailed in Refs. [ 7.15 , 7.16 ]. The pro-
posed modeling technique was based on the representation of steel
I-girders by equivalent trusses. The concrete slab was represented by a set