drilled shaft design

hi all, please help me.
struggling with AASHTO code and help with this site. i could finish the design of the super structure for AASHTO grider bridge. thanks a lot.

now i have to design drilled shaft under abutment. i could design capbeam using live load and dead load from superstructure and from abutment including stem wall and back wall..

i am very curious while i am designing for capbeam, i modelled the capbeal as simply supported beam. and i came up with reasonable reinforcement. but how can i find out the moment and axial load on drilled shaft? should i modell the capbeam and drilled shaft as fixed or pinned?
i mean if the capbeam and drilled shaft is fixed, then it will be just like frame. please help me, how to deal with this case....

and the drilled shaft does not have any foundation, that is, just pile foundation. i do not know how to model this shaft to find out the max. moment and axial load. could you please also tell me about how to deal with this pile foundation and capbeam to find the design moment?

thanks a lot

young