bridge load distribution

[koo]

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!