Just wondering about the strength of a bridge on a small logging road.
The span is 30ft. The bridge is to be constructed of 10, 32ft I-Beams;
   I-BEAM - 32'X 12" // 26lb/ft // flange 6.5" // webbing 1/4"
The bridge will be 16ft wide, so the 10 I-beams will be placed within
the 16' width. 4x4 hemlock decking will be placed crossways on top of
the I-beams.

The load will be 3 rear truck axels (70,500lb distributed across 10ft) (7050lb/ft).

QUESTION: Will the I'Beams fail? If not what load (>70500lb) will cause it to fail??

This is actually a very tough problem because you are depending on the
4x4 decking to distribute the load. The beam loading depends on the
deflection in the 4x4's and how it is applied to the beams. The 10
beams should be placed 5 per side close to the wheel centers because
if you get an axle load at the center of the bridge you have a serious
problem. It would probably mean that the truck has left the bridge (or
very close to it). I could answer your question if we consider the
axle load as a point load divided equally between the 10 beams, but I
don't think that is what actually happens.