Straight and curved steel box girder bridges - Computational Analysis and Design of Bridge Structures - page 250

elements. Shell elements were used to model the structural components
of the box girder bridges (webs, bottom flange, top flanges, and the solid
diaphragms), whereas truss and beam elements were used to model top
bracing trusses and cross frames:
1. Shell 63 (elastic shell). It is a four-node element that has both bending
and membrane capabilities. The element has five degrees of freedom at
each node; translations in x , y , and z directions; and rotations about
y and z axes (of the element's local coordinate system). Large deflec-
tion capabilities are included in the element. This type of element can
produce good results for a curved shell surface provided that each flat
element does not extend over more than a 15° arc.
2. Link 8 (3D spar). It is a two-node, 3D truss element. It is a uniaxial
tension-compression element with three translational degrees of
freedom at each node. The element used for bracing is a pin-jointed
structure with no bending capabilities. Plasticity and large deflec-
tion capabilities are included. The required inputs for this element
are material properties and cross-sectional area.
3. Beam 188 (3D linear finite strain beam) . It is a 3D linear (two-node) or
quadratic beam element. Beam 188 has six or seven degrees of freedom
at each node. These include three translations and three rotations in x ,
y , and z directions (of the element's local coordinate system). A seventh
degree of freedom (warping displacement) can also be considered. This
element is well-suited for linear, large rotation and/or large strain non-
linear applications. The beam elements are one-3D line elements.
4. Beam 4 (3D elastic beam). It is a uniaxial element with tension,
compression, torsion, and bending capabilities. The element used
for longitudinal stiffeners has six degrees of freedom at each node;
translations in x , y , and z directions; and rotations about x , y , and
z axes (of the element's local coordinate system). Stress stiffening
and large deflection capabilities are included. The required inputs
for this element are cross-sectional properties such as moment of
inertia, area, and torsional constant.
Results from the ANSYS finite element models can be used in understanding
the box bridge behavior. In addition, they can be used to compare the stress
profiles. Therefore, creating the same general construction of straight and
curved bridge models with same boundary conditions is required.
8.3.1 Straight box shell model (M1)
Straight box bridge model is made using Shell 63 elements for webs, the
top flange, and the bottom flange. Shell 63 elements are used as well to
model longitudinal and transverse stiffeners and solid diaphragms at the