Curved concrete bridges - Computational Analysis and Design of Bridge Structures - page 186

Cap beam element

Rigid link

3.38′

×20 ×20

Node (typical)

Superstructure
centroid

20.0′

Column element

Pinned at
column base

×10 ×10

3.5′

Footing
element

×100 ×100

Foundation
springs connected here

(b)

Figure 6.14 (Continued) Details of super- and substructural elements. (b) Details of bent
elements. (Data from FHWA 1996.)

earthquake analysis, the intermediate bent foundations were modeled with
equivalent spring stiffness for the spread footing to capture the soil effect. In
this grillage model, section properties, A x , A y , A z , I xx , I yy , and J , are calcu-
lated as described in the early section and later in Chapter 17 for verification
purpose. The superstructure has been modeled with four elements per span,
and the element axes are located along the centroid of the superstructure. The
bents are modeled with 3D frame elements that represent the cap beams and
individual columns. As columns are pinned to the column bases, two elements
were used to model each column between the top of footing and the soffit of
the box girder superstructure. A rigid link was used to model the connection
in between. The final model is shown in Figure 6.14a. Note that unlike what
is demonstrated in Chapter 17, no plastic hinge is modeled here.

6.5 3d finite eleMent Model illustrated
exaMPles —nChrP Case study Bridge

To demonstrate the 3D finite element model of curved concrete bridge, the
bridge example B-1 in the NCHRP study by Nutt and Valentine (2008) is
adopted. This fictitious bridge is a cast-in-site curve bridge with a curve