Curved concrete bridges - Computational Analysis and Design of Bridge Structures - page 185

6.4 grillage Model illustrated
exaMPles —fhWa Bridge no. 4

This skewed bridge example as shown in Figure 6.14a is used to illustrate the
modeling technique. This monolithic concrete bridge is one of the FHWA
examples series (Mast et al. 1996) and is also used as an illustrated example
in Chapter 17. It consists of three spans. The total length is 97.5 m (320′), with
span lengths of 30.5, 36.6, and 30.5 m (100′, 120′, and 100′), respectively.
In the longitudinal direction, the intermediate bent columns are assumed
to resist the entire longitudinal force, whereas the seat-type abutments pro-
vide vertical but no longitudinal restraint. As shown in Figure 6.14a, all sub-
structure elements are oriented at a 30° skew from a line perpendicular to a
straight bridge centerline alignment. The superstructure is a cast-in-place con-
crete box girder with two interior webs. The intermediate bents have a cross-
beam integral with the box girder and two round columns that are pinned
at the top of spread footing foundations. Because this model was used for

C L Abutment B

C L Bent 2

C L Bent 1

C L Abutment A

30° Skew

30° Skew

Rigid link (typical)

Bent column
(typical)

Y

Support node
at abutment (typical)

X

Z

(a)

Figure 6.14 Details of super- and substructural elements. (a) Grid model. (Continued)