Approximate and refined analysis methods - Computational Analysis and Design of Bridge Structures - page 45

-1.3

0.8

2.2 MN m/m

0.9

(a) (b)

−1.1
−0.9

1.0

0.9

−0.9
−0.6

1.3 1.2

(c) (d)

(f )

(e)

Figure 2.29 (a-f) 2D frame structure modeled with soil springs.

where:
E is the equivalent width (mm)
L 1 is the modified span length taken equal to the lesser of the actual
span or 18,000 mm
W 1 is the modified edge-to-edge width of bridge taken equal to the
lesser of the actual width or 18,000 mm
W is the actual edge-to-edge width of bridge
L is the physical length of bridge
N is the number of design lanes

If a bridge is skewed, the longitudinal force effects may be reduced (AASHTO
2013). The simplified beam model yields reasonably good results for the
bridge design work.
If a refined model, such as grillage analogy method, is used, a bridge may
be divided into strips of equal widths, with idealized longitudinal beams
lined up as shown in Figure 2.13a. For each longitudinal beam, the assign-
ment of rigidities can be found using Equations 2.6 through 2.9.

2.5.3 Beam-slab bridge
Beam-slab bridge is the most popular bridge group and is well defined
in the AASHTO LRFD Specifications (2013). Section 2.2 describes the