design of supported floor for aashto loading

huangyhg

design of supported floor for aashto loading
in the near future, i will be designing a county garage building on horrible soil conditions.  the building will need to be on piles, grade beams, etc.  the architect also wants to use precast floor members.
i believe the trucks will fall under the h-20 load conditions, but i'll have to check that.
i haven't worked much with aashto loadings in the past, but i basically know the procedure.  i don't think a high impact factor is warranted, since the trucks will be pulling in slowly and parking, but i'm unsure of a factor to use.  maybe, 20% to 25%?  also, is there some approximate equivalent uniform load to match aashto h-20 loading to check my design?  much of the space will not be heavily loaded, except in the parking stalls, but the middle is a traffic lane, and there are no live load reductions for such heavy loads.  i hate to penalize the number of piles required by considering a large, unreducible live load over the entire area, when much of the building is typically empty, (ie. the drive lane).
any thoughts or ideas?
confirm with your client that you do not have to support a fire truck inside the building. i very rarely need to use aashto so will let others more familiar with it comment on your other concerns.