Reinforced concrete bridges - Computational Analysis and Design of Bridge Structures - page 117

Single-strip modeling

Figure 4.10 Example 1 skewed RC slab bridge computer rendering by Merlin - DASH.

12 0 . W

E = 84 0 1 44 . + . LW ≤ (4.5a)

j j

N

L

where:
E is the equivalent width (in)
L j is the modified span length, less than 60′ (22.6′ or 6.9 m in this case)
W j is the modified edge-to-edge width, less than 60′ (36′ or 11 m in
this case)
W is the physical edge-to-edge width of the bridge
N L is the number of design lanes (two lanes in this case)

In this example one lane of loading is distributed within the equivalent
width of 125.07″, 10.42′ (3.18 m). For skewed bridge, the longitudinal force
effect may be reduced by the factor r with a skew angle of θ in degrees
(42° in this case):

r = 1 05 0 25 . − . tan θ (4.5b)

This correction factor calculated is 0.825. Because the model is a one-foot
strip, the live load distribution factor within this one-foot strip can be con-
sidered as 0.0791 (=0.825 × 1′/10.42′) for this example.
The second model as shown in Figure 4.11 is a more sophisticated finite
element model, with the whole bridge, including its skewness, modeled by
CSiBridge ® . The bridge is a three-span skewed concrete slab bridge. It con-
sists of 16″ (406-mm) thick flat slab supported by abutments and bents.
The slab is connected at its bottom to the abutments and bents. Abutments
are supported by fixed foundation springs. Bents consist of bent caps and
columns. The column bases are fixed and moments are released at the top.