Integral bridges - Computational Analysis and Design of Bridge Structures - page 508

(SHELL181) of four nodes with six degrees of freedom per node. Cross brac-
ings were modeled using the one-dimensional beam element (BEAM188).
The concrete abutment and soil were modeled using a 3D solid element
(SOLID185) of 20 nodes with three degrees of freedom per node. SOLID185
has plasticity, hyperelasticity, stress stiffening, creep, large deflection, and
large strain capabilities and is used for 3D modeling of solid structures.
As described in Rasmi's work (Rasmi 2012; Rasmi et al. 2013), the
geometry of the quarter model and the boundary conditions are shown in
Figure 16.14. Symmetry boundary conditions are applied on the symmetry
planes: z = 0 on symmetry surface 1 and x = 0 on symmetry surface 2. The
bottom of the soil is fixed in the y - and z -directions to simulate the end-bear-
ing type pile. The soil thickness in the positive z -direction (backfill soil thick-
ness) is assumed to be 0.9 m (3′), and its thickness in the negative z -direction
behind the piles is assumed to be 3 m (10′). Assuming that these soil layers are
thick enough, the free surfaces of the soil are assumed to be stationary in the
z -direction as the piles move. Therefore, the displacements perpendicular to
these free areas (displacement in the z -direction) are assigned zero value as the
boundary condition. Gravity is applied in the y -direction (Figure 16.14). The
supports are provided in the y -direction underneath the slab at 15.2-m (50′)
distances. The y -displacement at these constraints is zero.
As for material properties, steel material used in piles, girders, and cross
bracings are modeled as elastic-plastic material with multilinear plastic
behavior using a MISO command in ANSYS and only the deviatoric stress is
assumed to cause yielding. Concrete, where it is only used for slab and abut-
ment, is assumed to behave only elastically. For soil, the material cannot stand

Symmetric surface 1

Symmetric surface 2

Y

X

Z

Figure 16.14 Geometry of the quarter model of the integral abutment bridge. (Data
from Rasmi, J., “Thermo - Mechanical Fatigue of Steel Piles in Integral Abutment
Bridges,” PhD Dissertation, Civil and Environmental Engineering, University
of Maryland, College Park, MD, 2012.)