The most severe would be 60' overall length with two tandems and a steer axle, probably 40' interior bridge.  Theoretically heavier trucks have more axles and they will not weigh more then 85,500 but I think some margin of safety would be advisable.  Width of trucks will be 96" or 102"

Beams are 5" by 5" with 3/8" flanges.   Deck is 1/2" thick.