Dynamic/earthquake analysis - Computational Analysis and Design of Bridge Structures - page 537

43′ 0″

12′ 0″ 5′ 6″ 5′ 6″

L Bent

12′ 0″

4′ 0″ 1′ 0″ (TYP) 4′ 0″

1′ 6”

5

4′ 0″ Columns (TYP)

Concrete
hinge (TYP)

14′ 0″ × 14′ 0″
Square FTG (TYP)

11′ 3 1/8″ 11′ 3 1/8″

C Column C Column

1 Section

Figure 17.19 Cross-sectional view of illustration example 1. (Data from Mast et al. 1996.)

elevation views of illustration example 1. The superstructure is a cast-in-
place concrete box girder with two interior webs. The intermediate bents
have a crossbeam integral with the box girder and two round columns that
are pinned at the top of spread footing foundations. Figure 17.19 shows
the cross-sectional view.

17.4.1 foundation stiffness
The intermediate bent foundations were modeled with equivalent spring
stiffness for the spread footing. For this bridge, all of the intermediate bent
footings used the same foundation springs. Values of stiffness were devel-
oped for the local bent supports and transformed to global support when
input to SAP2000 (2007) program so as to have compatible results for the
MPA analysis and the NL-THA. Values of stiffness for foundation springs
provided by (Mast et al. 1996) are used in this study. The abutments were
modeled with a combination of full restraints (vertical translation and
superstructure torsional rotation) and equivalent spring stiffness (trans-
verse translation); other DOFs were all released.