Examples of Finite Element Models of Steel Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 561

considered to have a perfect elastoplastic behavior. Displacement constraints
were applied to these loaded nodes in the out-of-plane direction and all
rotations were restrained. The finite element analysis was performed using
the modified Riks method to properly trace the nonlinear path of the load-
displacement response of the girder. In order to model the initial geometric
imperfections, the authors performed a linear eigenvalue buckling analysis.
Dynamic and seismic assessment of a double-track railway bridge with
four discrete spans located in an earthquake-prone region was presented
by Caglayan et al. [ 6.17 ] . A 3D computer model of the bridge was generated
using a commercial general finite element analysis software COSMOS/M
[ 6.18 ] . Field measurements such as static and dynamic tests and material tests
were conducted on the bridge. The developed 3D finite element model of
the bridge structure was used for necessary calculations regarding structural
assessment and evaluation according to train loads and seismic loads. Addi-
tional members were proposed to transmit seismic loads to supports. The
fourth span, which had a permanent imperfection due to truck collision,
was studied in detail. The authors considered significant structural irregular-
ities and stiffness changes that existed on the bridge in the finite element. A
single span was modeled with beam and spring elements using COSMOS/
M[ 6.18 ] . Two riveted plate girders functioning as the main girder of each
span were simulated with beam elements located on the centroid line and
having the same torsional and flexural rigidities of actual main girder. Floor
beams were modeled by using beam elements in the transverse direction and
rigid bars were used to simulate center of gravity for floor beams and main
girders. Since the connections between the rigid bars and crossbeams were
semirigid rather than fixed, springs were used to simulate joint rotational
rigidities. Connections between the rigid bars and all of the line elements
were free to rotate in the longitudinal vertical plane. Also, the connections
between the stringers and crossbeams behave semirigidly; therefore, rota-
tional spring elements are used to simulate the rotational rigidities. Vertical,
transverse, and longitudinal spring elements for each main girder support
were included in the model to simulate the effective stiffness of the com-
bined bearing and pier or abutment structure and the longitudinal restraints
at the sliding bearings in each direction.
Altuni¸ik et al. [ 6.19 ] presented finite element modeling and operational
modal analysis of a full-scale arch-type steel highway bridges. The numerical
investigation was performed on a highway bridge, which has arch-type
structural system with a total length of 336 m. The 3D finite element model
was constructed using project drawings and an analytic modal analysis.