Examples of Finite Element Models of Steel-Concrete Composite Bridges - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 615

included portions of the bridge deck, bridge girder, stiffener plate, and cross
bracing. The effect of the location of the cutoff boundaries on the stress and
strain results was also investigated. This was accomplished by comparing the
results obtained from the submodel near the cut boundaries with those
obtained from the coarse model. The sensitivity study showed that including
a portion that is 25 in. (635 mm) long on each side of the stiffener would be
sufficient to accurately analyze the web gap region. The common size of the
elements used to idealize the components included in the submodel was
0.25 in. (6.35 mm) by 0.25 in. (6.35 mm). The total number of elements
in the submodel was about 50,000. Mesh sensitivity by considering smaller
element sizes was also examined; however, the differences in the results were
negligible.
Zhou et al. [ 7.24 , 7.25 ] investigated steel bridges for high-speed trains,
which may be vulnerable to excessive fatigue damage owing to stronger
dynamic effects induced by the increased train speed. In part I [ 7.24 ] , the
authors conducted dynamic tests on a composite railway bridge for high-
speed trains. In addition, a detailed finite element model of the bridge
was developed and validated against the dynamic test results. Six types of
structural details in the bridge were considered for fatigue evaluation.
The stress history of each concerned detail during a single train passage
was generated by the validated finite element model. The stress spectrum
was used to calculate the fatigue damage of each detail. Among various struc-
tural details, the load carrying fillet weld around the gusset plate of the diag-
onal bracing at the bridge bearing was predicted to be the most fatigue
critical detail. In the study, a general methodology for determination of
fatigue critical details was presented. In part II [ 7.25 ] , the authors investi-
gated fatigue assessment based on the dynamic stresses predicted by different
approaches, that is, static analysis considering dynamic amplification factor,
direct dynamic analysis with a moving load model, or a train-bridge inter-
action model. Due to the large size of the investigated bridge including seven
simply supported spans, the finite element model of the overall bridge would
result in a large computational cost. Therefore, a simplified model of a single
span was developed with appropriate boundary conditions on the rails and
the ballast to simulate the weak coupling between adjacent spans. The sec-
ond span from the bridge was modeled after the design drawings, by using
the general-purpose finite element software ABAQUS [1.29]. Due to sym-
metry, the span was divided into three types of segments, that is, segment A
at the bridge bearing, segment B1 in the external portion near the bearing,
and segment B2 in the internal portion close to the midspan. The segments