bridge load distribution

huangyhg

bridge load distribution
hi, everyone,
i'm a new member and looking for some advice.  i have a prestressed spread box girder bridge, and i am trying to determine the distribution factor for interior girders.
use eq. 3-33 in aashto give me 0.745 vs. 0.886 from s/7. (btw, 1.03 for exterior beam using simpe beam analysis.)
which one makes more sense?  is eq. 3-33 applicable in my case? it seems eq. 3-33 gives a lower factor, but what is the rationale? any reference?
thanks for any input!