OpenRoads Designer Earthwork

Best option is to stop corridors at structures.  Having a separate bridge corridor.  Then starting another corridor on the other side of the structure.  By doing this the bridge can be  turned off when doing quantities if needed. Having multiple corridors helps with grading around the abutments as well. Usually the finish grade surface wraps around the abutment .  Having one corridor over a bridge area causes issues with graphical filters as well.  The gap is ignored when selecting breaklines for finish grade.  

For the bridge elements, use a Feature Definition that is set to a Volume Option of None and it will be ignored during earthwork runs. Milling works in a similar manner, such that you are not quantifying cut of existing in those locations, because that is typically paid as its own item.